JP7694615B2 - Manufacturing method of a substrate with through holes filled with conductor and substrate with through holes filled with conductor - Google Patents

Description

The present invention relates to a method for manufacturing a conductor-filled through-hole board and a conductor-filled through-hole board.

In recent years, in order to miniaturize, improve functionality, and integrate electronic devices or components, a method has been used in which through holes are formed in insulating substrates and a conductor is placed in the through holes to electrically connect both main surfaces of the substrate.

A known method for providing a conductor in a through hole is to provide an active metal layer on the wall surface of the through hole in an insulating substrate, and then fill the through hole with copper by copper plating. However, when the aspect ratio of the through hole increases due to a thinner insulating substrate and a smaller diameter through hole, voids and dimples are more likely to occur in the conductor. To prevent such problems, the following Patent Document 1 proposes a method for filling the through hole with copper by copper electroplating in a DC cycle that includes applying a high current density for a predetermined period and applying a low current density for a predetermined period.

JP 2017-147441 A

However, the method described in Patent Document 1 requires plating to be performed while suppressing the deposition rate of the copper coating, which lengthens the work time and poses a problem in terms of productivity.

On the other hand, conductor-filled through-hole boards, in which the through-holes are filled with conductor, are required to not only have sufficient conductivity, but also to have excellent connection reliability, in which resistance is unlikely to increase even when subjected to temperature changes.

Therefore, one aspect of the present invention aims to provide a method for efficiently manufacturing a conductor-filled through-hole board having sufficient conductivity and excellent connection reliability, and a conductor-filled through-hole board having sufficient conductivity and excellent connection reliability.

As a result of extensive research into achieving the above object, the inventors formed a copper sintered body having a porous structure in the through-hole of a through-hole board, impregnated the copper sintered body with a curable resin composition, and cured the composition to form a conductor comprising a copper sintered body whose pores are filled with a cured resin. The inventors then discovered that a conductor-filled through-hole board in which the through-hole is filled with such a conductor exhibits a sufficiently low initial resistance value and is also resistant to an increase in resistance value in a temperature cycle connection reliability test, which led to the completion of the present invention.

That is, one aspect of the present disclosure provides the following invention.
[1] A preparation step of preparing a through-hole board including an insulating base having through holes formed therein, the through holes communicating with both main surfaces;
A copper sintered body forming step of forming a copper sintered body having a porous structure so as to fill at least the through holes;
a resin impregnation step of impregnating the copper sintered body with a curable resin composition;
A resin curing step of curing the curable resin composition impregnated in the copper sintered body to form a conductor including the copper sintered body in which the pores are filled with a resin cured product;
A method for manufacturing a conductor-filled through-hole substrate, comprising:

[2] The method according to [1], wherein the filling rate of the cured resin in the conductor is 80 volume % or more based on the volume of the internal space of the porous material.
[3] The method according to [1] or [2], wherein the porosity of the copper sintered body is 1 to 15 volume % based on the volume of the copper sintered body.
[4] The method according to any one of [1] to [3], wherein in the copper sintered body forming step, the copper sintered body is formed so as to cover at least a portion of a main surface of the through-hole board.
[5] The method according to [4], further comprising a conductor removing step of removing at least a portion of the conductor formed on the main surface of the through-hole board.
[6] The method according to [5], wherein the removing means in the conductor removing step is one or more selected from the group consisting of etching, mechanical polishing, and chemical mechanical polishing.
[7] The method according to any one of [1] to [6], wherein the through-hole board has a metal coating provided on at least a wall surface of the through hole.
[8] The method according to any one of [1] to [7], wherein the ratio L/D of the hole length L to the hole diameter D of the through hole is 10 or more.

[9] The copper sintered body forming step comprises:
a copper paste filling step of filling the through holes of the through-hole board with a copper paste containing copper particles;
a copper paste firing step of firing the copper paste to form the copper sintered body;
The method according to any one of [1] to [8], comprising the steps of:
[10] The method according to [9], wherein the copper paste contains, as the copper particles, first copper particles having a particle size of 0.8 μm or more and second copper particles having a particle size of 0.5 μm or less.
[11] The method according to [10], wherein the first copper particles are flat.
[12] The method according to any one of [9] to [11], wherein the copper paste is fired under a pressure of 0.1 MPa or more.
[13] The method according to any one of [9] to [12], wherein the copper paste is fired in an atmosphere containing nitrogen or hydrogen.

Furthermore, one aspect of the present disclosure provides the following invention.
[14] A through-hole board including an insulating base having a through hole, the through hole communicating with both main surfaces, and a conductor filling the through hole,
The conductor-filled through-hole board includes a copper sintered body having a porous structure and a cured resin filled in the pores of the copper sintered body.

[15] The conductor-filled through-hole substrate according to [14], wherein a filling rate of the cured resin in the conductor is 80 volume % or more based on the volume of the internal space of the porous material.
[16] The conductor-filled through-hole board according to [14] or [15], wherein the through-hole board has a metal coating provided on at least a wall surface of the through hole.
[17] The board with a conductor-filled through-hole according to any one of [14] to [16], wherein the ratio L/D of the hole length L to the hole diameter D of the through hole is 10 or more.
[18] The conductor-filled through-hole board according to any one of [14] to [17], wherein the conductor covers at least a portion of a main surface of the through-hole board.

According to one aspect of the present invention, a method for efficiently manufacturing a conductor-filled through-hole substrate having sufficient conductivity and excellent connection reliability, and a conductor-filled through-hole substrate having sufficient conductivity and excellent connection reliability are provided.

The above method makes it possible to provide a conductor-filled through-hole substrate that is airtight and impermeable (resistant to liquid penetration).

1A to 1C are schematic diagrams illustrating a method for manufacturing a conductor-filled through-hole substrate according to one embodiment. 1A to 1C are schematic diagrams illustrating a method for manufacturing a conductor-filled through-hole substrate according to one embodiment. 1A to 1C are schematic diagrams illustrating a method for manufacturing a conductor-filled through-hole substrate according to one embodiment. 1A-1C are schematic diagrams illustrating a method for manufacturing a conductor-filled through-hole substrate according to an embodiment and a conductor-filled through-hole substrate according to an embodiment. 1 is a schematic diagram illustrating a semiconductor device according to an embodiment; 4 is a cross-sectional photograph of a copper sintered body formed in a through hole of a conductor-filled through-hole substrate obtained in Example 1. FIG. 2 is a schematic diagram showing a test piece.

Below, the embodiments for implementing the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and duplicate explanations will be omitted.

(Method of Manufacturing Conductor-Filled Through-Hole Boards)
1 to 4 are schematic diagrams showing a method for manufacturing a substrate having a through hole filled with conductor according to one embodiment.

The method for manufacturing a conductor-filled through-hole substrate according to the present embodiment includes a preparation step of preparing a through-hole substrate including an insulating base having through-holes formed therein and having the through-holes communicate with both main surfaces of the insulating base;
A copper sintered body forming step of forming a copper sintered body having a porous structure so as to fill at least the through holes;
a resin impregnation step of impregnating the copper sintered body with a curable resin composition;
A resin curing step of curing the curable resin composition impregnated in the copper sintered body to form a conductor including the copper sintered body in which the pores are filled with a resin cured product;
a conductor removing step of removing at least a portion of the conductor formed on the main surface of the through-hole board;
Equipped with.

<Through-hole board preparation process>
1(a), a through-hole substrate 40 can be prepared, which has an insulating substrate 1 with a through-hole 30 formed therein, and a metal coating 2 provided on the wall surface of the through-hole and on the surface of the insulating substrate 1. The through-hole 30 communicates with both main surfaces of the through-hole substrate 40.

Examples of the insulating substrate 1 include insulating substrates such as silicon substrates, glass substrates, ceramic substrates, and glass epoxy resin substrates. Figures 1 to 4 show an embodiment in which a silicon substrate is used as the insulating substrate 1.

The thickness of the insulating substrate 1 may be 100 μm or more, 200 μm or more, or 300 μm or more from the viewpoint of suppressing warping of the substrate after sintering, and may be 800 μm or less, 300 μm or less, 200 μm or less, or 100 μm or less from the viewpoint of reducing the weight and increasing the density of the substrate.

When the insulating substrate 1 is a silicon substrate, the upper limit of the diameter of the through hole 30 may be 200 μm or less, 100 μm or less, or 60 μm or less from the viewpoint of increasing the density of the resulting semiconductor device, and the lower limit of the diameter of the through hole 30 is not particularly limited, but may be 20 μm or more, or 50 μm or more.

From the viewpoint of increasing the density of the resulting semiconductor device, the ratio L/D of the hole length L to the hole diameter D of the through hole 30 may be 1 or more, 5 or more, or 10 or more, and the upper limit of the aspect ratio L/D of the through hole 30 is not particularly limited, but may be 15 or less, 10 or less, or 5 or less. The hole length L of the through hole 30 may be the thickness of the insulating substrate 1. In this case, the ratio T/D of the thickness T of the insulating substrate 1 to the hole diameter D of the through hole 30 may be in the above range.

When the insulating base 1 is a silicon substrate, the number of through holes 30 provided in the through-hole substrate may be 100 or more or 300 or more per 1 ^cm2 of the main surface of the substrate, from the viewpoint of achieving high density in the resulting semiconductor device.

The metal coating 2 may be provided on both main surfaces of the insulating substrate 1 and on the wall surface of the through hole 30, or on at least one main surface of the insulating substrate 1 and on the wall surface of the through hole 30, or may be provided only on the wall surface of the through hole 30, or may not be provided at all. In the embodiment shown in FIG. 1(a), the through-hole substrate 40 has a metal coating 2 on both main surfaces of the insulating substrate 1 and on the wall surface of the through hole 30.

Examples of the metal coating 2 include titanium, nickel, chromium, copper, aluminum, palladium, platinum, and gold. From the viewpoint of adhesion, the metal coating 2 is preferably a coating in which titanium, nickel, and copper are layered in this order. When the material of the main surface of the insulating substrate 1 is silicon, the surface of the insulating substrate 1 is oxidized to silicon oxide, and a titanium layer is formed on the silicon oxide, thereby improving adhesion. In addition, by providing a nickel layer on the titanium layer and a copper layer on top of that, it is possible to suppress the diffusion of copper into the insulating substrate 1 compared to the case where a copper layer is directly provided on the titanium layer. Furthermore, by providing a copper layer on the surface, adhesion between the copper sintered body formed in the copper sintered body forming process described below and the through-hole board is improved.

<Copper sintered body forming process>
In this step, a copper sintered body having a porous structure is formed so as to fill at least the through-holes. In this embodiment, the copper sintered body may be formed so as to cover at least a part of the main surface of the through-hole board. In this case, a conductor is formed to fill the through-holes of the through-hole board, and a conductor can also be provided on the main surface of the through-hole board. The conductor provided on the main surface of the through-hole board can form wiring and electrodes.

The copper sintered body forming process may include a copper paste filling process in which a copper paste containing copper particles is filled into the through holes of the through-hole board, and a copper paste firing process in which the copper paste is fired to form the copper sintered body. When the copper sintered body is formed on the main surface of the through-hole board, a layer of copper paste can be provided on both main surfaces of the through-hole board 40 during or after the copper paste filling process.

As the copper sintered body forming process, for example, as shown in FIG. 1(b), a copper paste 3 containing copper particles is applied to a through-hole board 40, and the copper paste 3 is filled into the through-holes 30, and a layer of the copper paste 3 is also provided on both main surfaces of the through-hole board 40. Details of the copper paste 3 will be described later.

Methods for applying the copper paste 3 to the through-hole board 40 include, for example, screen printing, transfer printing, offset printing, jet printing, a dispenser, a jet dispenser, a needle dispenser, a comma coater, a slit coater, a die coater, a gravure coater, a slit coat, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, a bar coat, an applicator, a particle deposition method, a spray coater, a spin coater, a dip coater, etc.

When the copper paste is also applied onto the main surface of the through-hole board, the thickness of the copper paste layer may be 1 μm or more, 2 μm or more, 3 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more, and may be 3000 μm or less, 1000 μm or less, 500 μm or less, 300 μm or less, 250 μm or less, 200 μm or less, 150 μm or less, or 100 μm or less.

The copper paste 3 may be dried as appropriate from the viewpoint of suppressing the flow of copper particles during sintering of the copper paste 3 and the generation of voids in the copper sintered body. When drying the copper paste 3, the atmosphere during drying may be an oxygen-free atmosphere such as nitrogen and rare gas, or a reducing atmosphere such as hydrogen and formic acid.

The drying method may be drying at room temperature, drying by heating, or drying under reduced pressure. For example, a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, a steam heating furnace, a hot plate press device, etc. can be used for drying by heating or drying under reduced pressure. The drying temperature and time may be appropriately adjusted according to the type and amount of the dispersion medium used. The drying temperature may be, for example, 50°C or higher and 180°C or lower. The drying time may be, for example, 1 minute or more and 120 minutes or less.

After the copper paste filling step, the copper paste 3 is fired to sinter the copper particles contained in the copper paste 3. In this way, as shown in FIG. 2(a), a copper sintered body-filled through-hole board 50 is obtained in which the through-hole 30 is filled with a copper sintered body 5 having a porous structure, i.e., a pore 4, as shown in FIG. 2(a). In this embodiment, a copper sintered body-filled through-hole board 50 is obtained in which a copper sintered body 5 is provided on both main surfaces of the through-hole board 40. Details of the copper sintered body 5 formed will be described later.

The firing can be carried out by a heat treatment. For the heat treatment, a heating means such as a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, or a steam heating furnace can be used.

The atmosphere during firing is preferably an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the copper sintered body, and more preferably a reducing atmosphere from the viewpoint of removing the surface oxide of the copper particles in the copper paste 3. Examples of the oxygen-free atmosphere include the introduction of an oxygen-free gas such as nitrogen or a rare gas, or under a vacuum. Examples of the reducing atmosphere include pure hydrogen gas, a mixed gas of hydrogen and nitrogen represented by forming gas, nitrogen containing formic acid gas, a mixed gas of hydrogen and a rare gas, and a rare gas containing formic acid gas. When the copper paste 3 is sintered by heating without pressurization as described below, it is preferable to use pure hydrogen gas or a mixed gas of hydrogen and nitrogen represented by forming gas, and more preferably pure hydrogen gas. By heating in pure hydrogen gas, it is possible to lower the sintering temperature of the copper particles. When pure hydrogen gas is used, even if the thickness of the substrate is as thick as 500 μm and the diameter of the through hole 30 is as small as 20 μm, the gas reaches the center of the through hole 30, making it easy to obtain the copper sintered body 5.

The maximum temperature reached during the heat treatment may be 150°C or higher, and may be 350°C or lower, 300°C or lower, or 260°C or lower, from the viewpoint of reducing thermal damage to each component and improving yield. If the maximum temperature reached is 150°C or higher, sintering tends to proceed sufficiently when the maximum temperature is held for 60 minutes or less. From the viewpoint of volatilizing all the dispersion medium and improving yield, the maximum temperature held for may be 1 minute or more, and may be 60 minutes or less, 40 minutes or less, or 30 minutes or less.

The copper paste may be fired under pressure. In this case, in an atmosphere containing pure hydrogen gas, the pressure may be 0.05 MPa or more, 0.1 MPa or more, or 0.3 MPa, and 20 MPa or less, 15 MPa or less, or 10 MPa or less. In an atmosphere containing nitrogen gas, the pressure may be 1 MPa or more, or 3 MPa, and 20 MPa or less, 15 MPa or less, or 10 MPa or less.

By setting the pressure to 0.05 MPa or more when pure hydrogen gas is used, and 1 MPa or more when nitrogen gas is used, it becomes easier to suppress the generation of voids in the copper sintered body 5 formed in the center of the through hole 30, and it becomes easier to obtain a copper sintered body with good conductivity. In addition, by setting the pressure to the above-mentioned lower limit value or more, when the through-hole board has a metal coating 2, it becomes easier to improve the bonding strength between the metal coating 2 and the copper sintered body 5. Furthermore, as shown in FIG. 1 (b), when the through-hole board 40 provided with a copper paste layer is pressed by sandwiching it from above and below with the pressure jig A, by setting the pressure applied to the pressure jig A to the above-mentioned lower limit value or more, it becomes easier to smooth the surface of the copper sintered body formed on the main surface of the through-hole board 40. If the surface of the copper sintered body is smooth, there is an advantage that fine wiring is easily formed when wiring is formed by etching or the like in a later process. The pressure jig A is not particularly limited, but may be a commercially available one, and may also be made using a metal member having a flat portion. For example, a pressure jig having two or more of the above-mentioned metal members can apply pressure to a through-hole board by sandwiching the through-hole board between the metal members arranged so that the flat portions face each other. Pressure jig A may have a mechanism for adjusting the pressure applied to the through-hole board. A spring or the like can be used as the pressure adjustment means.

If the pressure is 20 MPa or less, warping of the through-hole board 40 is easily suppressed. The inventors speculate that the reason for this effect is as follows. First, when the pressure is increased, the sintered density of the copper paste (particularly the density of the side in contact with the pressure jig A) increases, and the thermal expansion coefficient of the formed copper sintered body approaches the thermal expansion coefficient of 16.5 μm/(m·K) of general copper at 25°C. On the other hand, for example, the thermal expansion coefficient of silicon at 25°C is 2.6 μm/(m·K). Therefore, as the density of the copper sintered body increases, the difference in the thermal expansion coefficient between the copper sintered body and silicon increases, and warping is likely to occur. In this embodiment, by setting the pressure to 20 MPa or less, the increase in the density of the copper sintered body is appropriately suppressed, and as a result, the difference in the thermal expansion coefficient between the copper sintered body and silicon becomes smaller, and warping is suppressed.

In addition, if the pressure applied during firing is within the above range, no special pressure device is required, and the yield is not compromised, and voids can be reduced and the bonding strength and connection reliability can be further improved. Methods for applying pressure to a through-hole board coated with copper paste include, for example, placing a weight on it, applying pressure using a pressure device, and applying pressure using a fixed jig for applying pressure.

From the viewpoint of reducing the volume resistivity of the copper sintered body 5, the porosity of the copper sintered body formed on the main surface of the through-hole board may be 15 volume % or less, 14 volume % or less, 12 volume % or less, or 9 volume % or less, based on the total volume including the porous structure of the copper sintered body. Also, from the viewpoint of suppressing cracking and warping of the through-hole board 40, the porosity of the copper sintered body 5 may be 1 volume % or more, 3 volume % or more, or 5 volume % or more.

By having the copper sintered body formed on the main surface of the through-hole board have the above-mentioned porous structure, it is possible to lower the thermal expansion coefficient, reduce the difference in thermal expansion coefficient with an insulating substrate such as a silicon substrate, and suppress cracking and warping of the insulating substrate.

From the viewpoint of reducing the volume resistivity of the copper sintered body 5, the porosity of the copper sintered body filled in the through holes may be 15 volume % or less, 14 volume % or less, 12 volume % or less, or 9 volume % or less based on the total volume including the porous structure of the copper sintered body. Also, from the viewpoint of reducing the volume resistivity of the copper sintered body 5, the porosity of the copper sintered body 5 may be 1 volume % or more, 3 volume % or more, or 5 volume % or more.

The copper sintered body filled in the through holes has the above-mentioned porous structure, which makes it possible to prevent breaks in the copper sintered body due to cracks after sintering.

The porosity of the copper sintered body is calculated by the following procedure.
(i) A cross section of the copper sintered body of the copper sintered body-filled through-hole substrate (a cut surface in the thickness direction of the substrate) is exposed by a focused ion beam.
(ii) A cross-sectional image (within a range of 10 μm in the thickness direction of the substrate and 10 μm in a direction perpendicular to the thickness direction of the substrate) of the exposed cross section is photographed using a scanning electron microscope.
(iii) The cross-sectional image obtained is binarized so that the sintered copper portion and the porous portion are separated.
(iv) From the binarized cross-sectional image, the ratio of the area of the porous portion to the total area of the cross-section of the copper sintered body is determined as the porosity of the copper sintered body.
When calculating the porosity of the copper sintered body filled in the through hole, in the above (i), the cross section of the central part of the copper sintered body filled in the through hole is exposed. When calculating the porosity of the central part of the copper sintered body filled in the through hole, a range of ±5 μm in the thickness direction of the substrate and ±5 μm in the direction perpendicular to the thickness direction of the substrate is observed from the central part of the copper sintered body filled in the through hole. When calculating the porosity of the copper sintered body formed on the main surface of the copper sintered body filled through hole substrate, in the above (i), the cross section of the copper sintered body on the main surface is exposed. When calculating the porosity of the copper sintered body formed on the main surface of the copper sintered body filled through hole substrate, a region up to 5 μm from the surface of the copper sintered body formed on the main surface is observed.
When calculating the porosity of the copper sintered body used to calculate the filling rate of the resin cured material in the conductor described below, the observation points of the copper sintered body can be appropriately set to be the same as the observation points of the conductor.

In addition, if the pressure applied during firing is within the above range, no special pressure device is required, and the yield is not compromised, and voids can be reduced and the bonding strength and connection reliability can be further improved. Methods for applying pressure to a through-hole board coated with copper paste include, for example, placing a weight on it, applying pressure using a pressure device, and applying pressure using a fixture for applying pressure.

The proportion of copper element in the constituent elements of the copper sintered body, excluding light elements, may be 95% by mass or more, 97% by mass or more, 98% by mass or more, or even 100% by mass. If the proportion of copper element in the copper sintered body is within the above range, the formation of intermetallic compounds or the precipitation of different elements at the metallic copper crystal boundaries can be suppressed, the properties of the metallic copper that constitutes the copper sintered body are likely to be strengthened, and even better connection reliability is likely to be obtained.

In the copper sintered body forming process, the copper paste may be heated and fired without applying pressure. In this case, the porosity of the copper sintered body formed on the main surface of the through-hole board tends to increase, and the thermal expansion coefficient of the copper sintered body decreases, making the through-hole board less likely to crack or warp.

<Resin impregnation process>
In this step, for example, the copper sintered body 5 can be impregnated with the curable resin composition by applying the curable resin composition to the copper sintered body filled through-hole substrate 50 obtained through the copper sintered body forming step. In this embodiment, the copper sintered body 5 filling the through hole 30 and the copper sintered body 5 formed on both main surfaces of the through-hole substrate 40 are impregnated with the curable resin composition. It is preferable that the pores 4 of the copper sintered body 5 are sufficiently filled with the impregnated curable resin composition.

(Curable resin composition)
The components constituting the curable resin composition include a thermosetting compound. Examples of the thermosetting compound include an oxetane compound, an epoxy compound, an episulfide compound, a (meth)acrylic compound, a phenol compound, an amino compound, an unsaturated polyester compound, a polyurethane compound, a silicone compound, and a polyimide compound. Among them, an epoxy compound may be used in order to further improve the curability and viscosity of the curable resin composition and improve the characteristics and insulation reliability when left at high temperatures.

The curable resin composition may further include a heat curing agent. Examples of heat curing agents include imidazole curing agents, amine curing agents, phenol curing agents, polythiol curing agents, acid anhydrides, thermal cationic initiators, and thermal radical generators. These may be used alone or in combination of two or more. Among these, imidazole curing agents, polythiol curing agents, and amine curing agents are preferred because they can be cured quickly at low temperatures. In addition, latent curing agents are preferred because they have high storage stability when the thermosetting compound and the heat curing agent are mixed. The latent curing agent is preferably a latent imidazole curing agent, a latent polythiol curing agent, or a latent amine curing agent. The heat curing agent may be coated with a polymeric substance such as a polyurethane resin or a polyester resin.

The imidazole curing agent is not particularly limited, and examples thereof include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, and 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct.

The polythiol curing agent is not particularly limited, and examples thereof include trimethylolpropane tris-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, and dipentaerythritol hexa-3-mercaptopropionate. The solubility parameter of the polythiol curing agent is preferably 9.5 or more, and preferably 12 or less. The solubility parameter is calculated by the Fedors method. For example, the solubility parameter of trimethylolpropane tris-3-mercaptopropionate is 9.6, and the solubility parameter of dipentaerythritol hexa-3-mercaptopropionate is 11.4.

The above amine curing agent is not particularly limited, and examples thereof include hexamethylenediamine, octamethylenediamine, decamethylenediamine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraspiro[5.5]undecane, bis(4-aminocyclohexyl)methane, metaphenylenediamine, and diaminodiphenylsulfone.

The above-mentioned thermal cationic curing agents include iodonium cationic curing agents, oxonium cationic curing agents, and sulfonium cationic curing agents. The above-mentioned iodonium cationic curing agents include bis(4-tert-butylphenyl)iodonium hexafluorophosphate. The above-mentioned oxonium cationic curing agents include trimethyloxonium tetrafluoroborate. The above-mentioned sulfonium cationic curing agents include tri-p-tolylsulfonium hexafluorophosphate.

The thermal radical generator is not particularly limited, and examples thereof include azo compounds and organic peroxides. Examples of the azo compounds include azobisisobutyronitrile (AIBN). Examples of the organic peroxides include di-tert-butyl peroxide and methyl ethyl ketone peroxide.

Methods for applying the curable resin composition include screen printing, transfer printing, offset printing, jet printing, dispenser, jet dispenser, needle dispenser, comma coater, slit coater, die coater, gravure coater, slit coat, letterpress printing, intaglio printing, gravure printing, stencil printing, soft lithography, bar coat, applicator, particle deposition method, spray coater, spin coater, dip coater, etc.

The curable resin composition may be applied to one of the main surfaces of the copper sintered body filled through-hole board 50, or may be applied to a portion of the main surface. When applying the resin composition to both sides of the copper sintered body filled through-hole board 50, the resin composition may be applied to one of the main surfaces of the copper sintered body filled through-hole board 50, the resin composition may be allowed to penetrate to the main surface side of the copper sintered body filled through-hole board 50 to which the resin composition has not been applied, and then the resin composition may be applied to the main surface to which the resin composition has not been applied. This allows the resin composition to permeate the porous 4.

The copper sintered body filled through-hole substrate 50 coated with the curable resin composition can be left in a reduced pressure environment to improve the impregnation of the curable resin composition into the pores 4 of the copper sintered body 5.

In the resin impregnation step, it is preferable to impregnate the copper sintered body with the cured resin composition so that the filling rate of the cured resin in the conductor formed through the resin curing step falls within the preferred range described below.

<Resin curing process>
In this step, as shown in Fig. 2(d), the curable resin composition impregnated into the copper sintered body 5 (the curable resin composition filled in the holes 4) is cured to form a conductor 35 including the copper sintered body 5 with the holes 4 filled with the cured resin 6, thereby obtaining a conductor-filled through-hole substrate 51 in which at least the through-holes 30 are filled with the conductor 35. In the case of this embodiment, the conductor 35 including the copper sintered body 5 with the holes 4 filled with the cured resin 6 is provided on both main surfaces of the through-hole substrate 40.

The curable resin composition can be cured by a heat treatment. For the heat treatment, a heating means such as a hot plate, a hot air dryer, a hot air heating furnace, a nitrogen dryer, an infrared dryer, an infrared heating furnace, a far-infrared heating furnace, a microwave heating device, a laser heating device, an electromagnetic heating device, a heater heating device, or a steam heating furnace can be used.

The atmosphere in the resin curing step may be an oxygen-free atmosphere from the viewpoint of suppressing oxidation of the copper sintered body 5, or a reducing atmosphere from the viewpoint of removing surface oxides of the copper sintered body 5. Examples of the oxygen-free atmosphere include the introduction of an oxygen-free gas such as nitrogen or a rare gas, or a vacuum. Examples of the reducing atmosphere include a pure hydrogen gas atmosphere, a mixed gas of hydrogen and nitrogen such as forming gas, nitrogen containing formic acid gas, a mixed gas of hydrogen and a rare gas, and a rare gas containing formic acid gas.

The maximum temperature reached during the heat treatment in the resin curing process may be 150°C or higher, and may be 350°C or lower, 300°C or lower, or 260°C or lower, from the viewpoint of reducing thermal damage to each component and improving yield. If the maximum temperature reached is 150°C or higher, the curing of the resin composition tends to proceed sufficiently when the maximum temperature is held for 60 minutes or less.

The conductor 35 formed in the resin curing step (the conductor before the conductor removing step) may have a filling rate of the cured resin 6 that satisfies the following condition.
(Through-hole conductor)
(a) In a region extending from a point S1 at a depth of 10 μm from a line L1 that passes through a central portion C of the through hole 30 (the center of the hole length L and the center of the hole diameter D there) and that extends in the thickness direction of the substrate to the surface of the conductor 35, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the copper sintered body.
(b) In the region from point S1 to a depth of 10 to 20 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.
(c) In the region from point S1 to a depth of 20 to 30 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.
(d) Within a range of ±5 μm from the center C of the through hole 30 in the thickness direction of the substrate and in a direction perpendicular to the thickness direction of the substrate, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the copper sintered body.

(Conductors on the main surface of the substrate)
(e) In the region from the surface S2 of the conductor 35 formed on the main surface of the substrate to a depth of 5 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the porous 4 of the copper sintered body 5.
(f) In the region from the surface S2 of the conductor 35 formed on the main surface of the substrate to a depth of 10 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the porous 4 of the copper sintered body 5.
(g) In a region 10 to 20 μm deep from the surface S2, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.
(h) In the region 20 to 30 μm deep from the surface S2, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.

The filling rate of the cured resin 6 in the conductor 35 is calculated by the following procedure.
(i) A cross section of the conductor of a conductor-filled through-hole substrate (a cut surface in the thickness direction of the substrate) is exposed by a focused ion beam.
(ii) A cross-sectional image (within a range of 10 μm in the thickness direction of the substrate and 10 μm in a direction perpendicular to the thickness direction of the substrate) of the exposed cross section is photographed using a scanning electron microscope.
(iii) The cross-sectional image obtained is binarized so that the sintered copper portion and the cured resin portion are separated from the porous portion not filled with the cured resin.
(iv) From the binarized cross-sectional image, the ratio of the area of the porous portion not filled with the cured resin to the total area of the cross-section of the conductor is calculated, and this is regarded as the porosity of the conductor.
(v) The filling rate of the cured resin in the conductor is calculated by substituting the porosity of the copper sintered body before impregnation with the curable resin composition and the porosity of the conductor into the following formula (1).
Filling rate (%) of cured resin in conductor=[(B−A)/B]×100 Equation (1)
[In formula (1), A represents the porosity (%) of the conductor, and B represents the porosity (%) of the copper sintered body.]
When calculating the porosity of the conductor filled in the through hole, a cross section of the central part of the conductor in the through hole is exposed in the above (i).When calculating the porosity of the conductor formed on the main surface of the conductor-filled through-hole substrate, a cross section of the conductor on the main surface is exposed in the above (i).

<Conductor removal process>
In this step, at least a portion of the conductor 35 formed on the main surface of the through-hole board 40 can be removed. Methods for removing the conductor include chemical polishing, mechanical polishing, chemical mechanical polishing, fly-cut processing, plasma processing, etc. Fly-cut processing refers to cutting and flattening using a surface planer.

In this embodiment, from the viewpoint of being a common technique and being easily applicable, it is preferable that the removal means is one or more selected from the group consisting of etching, mechanical polishing, and chemical mechanical polishing, but is not limited thereto.

The manufacturing method for the conductor-filled through-hole substrate of this embodiment includes a conductor removal process, which, for example, makes the surface of the conductor 35 formed on the main surface of the through-hole substrate 40 flat, making it easier to form wiring.

In this embodiment, the filling rate of the cured resin 6 in the conductor 35 after the conductor removing step may satisfy the following condition. The filling rate can be calculated in the same manner as above.
(Through-hole conductor)
(a) In a region extending from a point S3 at a depth of 10 μm, where a line L1 passing through a central portion C of the through hole 30 (the center of the hole length L and the center of the hole diameter D there) and extending in the thickness direction of the substrate intersects with the surface of the conductor 35, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the copper sintered body.
(b) In the region from point S3 to a depth of 10 to 20 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.
(c) In the region from point S3 to a depth of 20 to 30 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.
(d) Within a range of ±5 μm from the center C of the through hole 30 in the thickness direction of the substrate and in a direction perpendicular to the thickness direction of the substrate, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the copper sintered body.
(Conductors on the main surface of the substrate)
(e) In the region from the surface S4 of the conductor 35 formed on the main surface of the substrate to a depth of 5 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the porous 4 of the copper sintered body 5.
(f) In the region from the surface S4 of the conductor 35 formed on the main surface of the substrate to a depth of 10 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the porous 4 of the copper sintered body 5.
(g) In a region 10 to 20 μm deep from the surface S4, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.
(h) In the region 20 to 30 μm deep from the surface S4, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.

The method for manufacturing a conductor-filled through-hole substrate of this embodiment may further include a wiring formation process. The wiring formation process may include a resist formation process, an etching process, and a resist removal process, which are described below.

<Resist Forming Process>
In the resist formation step, as shown in FIG. 3( f ), an etching resist 8 is formed on the conductor 35 formed on the main surface of the through-hole board 40 .

Methods for forming the etching resist 8 include, for example, silk screen printing resist ink, or laminating a negative photosensitive dry film for etching resist onto copper foil, placing a light-transmitting photomask on top of it in the shape of the wiring, exposing it to ultraviolet light, and removing the unexposed areas with a developer.

<Etching process>
In the etching step, as shown in Fig. 4(g), the conductor 35 in the portion not covered with the etching resist 8 is removed by etching. In this embodiment, a part of the metal coating 2 provided on each of the main surfaces of the insulating substrate 1 is removed by etching.

Examples of etching methods include those using chemical etching solutions typically used for wiring boards, such as a solution of cupric chloride and hydrochloric acid, a solution of ferric chloride, a solution of sulfuric acid and hydrogen peroxide, or an ammonium persulfate solution.

<Resist Removal Process>
In the resist removal step, the etching resist 8 formed on the conductor 35 is removed.

The manufacturing method of the through-hole board according to this embodiment further includes a wiring formation process having the above steps, so that wiring 9 including conductor 35 can be formed on the main surface of the through-hole board 40.

(Conductor-filled through-hole board)
Fig. 4(h) is a cross-sectional view showing one embodiment of a conductor-filled through-hole board that can be manufactured by the method according to the above-mentioned embodiment. The conductor-filled through-hole board 52 shown in Fig. 4(h) includes an insulating base 1 having a through-hole 30, a through-hole board 40 having the through-hole 30 on both main surfaces, and a conductor 35 filling the through-hole 30, the conductor 35 including a copper sintered body 5 having a porous structure and a resin cured material 6 filling the pores 4 of the copper sintered body 5.

The conductor-filled through-hole board 52 shown in FIG. 4(h) has a metal coating 2 on both main surfaces of the insulating substrate 1 and on the wall surface of the through-hole, but the metal coating 2 does not have to be provided on the main surfaces, it may be provided only on one main surface, or it may not be provided on the wall surface of the through-hole. Also, the conductor-filled through-hole board 52 has wiring 9 including the metal coating 2 and conductor 35 provided on both main surfaces of the through-hole board 40, but the wiring 9 may be provided on one main surface of the through-hole board 40.

Conductor-filled through-hole substrate 52 may be one in which the filling rate of cured resin 6 in conductor 35 satisfies the following condition. The filling rate can be calculated in the same manner as above.
(Through-hole conductor)
(a) In a region extending from a point S5 at a depth of 10 μm from a line L1 passing through a central portion C of the through hole 30 (the center of the hole length L and the center of the hole diameter D there) where the line L1 extending in the thickness direction of the substrate intersects with the surface of the conductor 35, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the copper sintered body.
(b) In the region from point S5 to a depth of 10 to 20 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.
(c) In the region from point S5 to a depth of 20 to 30 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.
(d) Within a range of ±5 μm from the center C of the through hole 30 in the thickness direction of the substrate and in a direction perpendicular to the thickness direction of the substrate, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the copper sintered body.
(Conductors on the main surface of the substrate)
(e) In the region from the surface S6 of the conductor 35 formed on the main surface of the substrate to a depth of 5 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the porous 4 of the copper sintered body 5.
(f) In the region from the surface S6 of the conductor 35 formed on the main surface of the substrate to a depth of 10 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the internal space of the porous 4 of the copper sintered body 5.
(g) In the region 10 to 20 μm deep from the surface S6, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.
(h) In the region 20 to 30 μm deep from the surface S6, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.

(Semiconductor device)
A semiconductor device manufactured using the conductor-filled through-hole substrate of this embodiment will be specifically described with reference to FIG. 5. FIG. 5 is a schematic cross-sectional view showing one embodiment of the semiconductor device of the present invention, which is a semiconductor device using TSV (Through-Silicon-Via) technology. In the semiconductor device 100 shown in FIG. 5(a), the wiring 27 on the interposer substrate 25 is directly connected to the conductor 35 of the conductor-filled through-hole substrate 51, thereby flip-chip connecting the interposer substrate 25 and the conductor-filled through-hole substrate 51. The gap between the interposer substrate 25 and the conductor-filled through-hole substrate 51 is filled with the cured adhesive 20 without any gaps and sealed. On the main surface of the conductor-filled through-hole substrate 51 opposite to the interposer substrate 25, the conductor-filled through-hole substrates 51 are repeatedly stacked. The conductor-filled through-hole substrates 51 are connected to each other by the conductor 35. The gaps between the conductor-filled through-hole substrates 51 are filled with the cured adhesive 20 without leaving any gaps, thereby sealing them.

The semiconductor device 100 may be obtained, for example, by the following method. That is, the conductor-filled through-hole substrates 51 are laminated via an adhesive to obtain a laminate. The adhesive may be cured during the lamination. The obtained laminate and the interposer substrate 25 are electrically connected by pressure bonding, forming a connection body in which the laminate and the interposer substrate 25 are electrically connected. A dicing tape is attached to the surface of the formed connection body opposite to the surface on which the interposer substrate 25 is provided, and dicing is performed along the dicing lines to obtain the semiconductor device 100.

In the semiconductor device 200 shown in FIG. 5(b), the wiring 27 on the interposer substrate 25 and the conductor 35 of the conductor-filled through-hole substrate 51 are connected via the fine bumps 15, so that the interposer substrate 25 and the conductor-filled through-hole substrate 51 are flip-chip connected. The gap between the interposer substrate 25 and the conductor-filled through-hole substrate 51 is filled with the cured adhesive 20 without any gaps, and is sealed. On the main surface of the conductor-filled through-hole substrate 51 opposite the interposer substrate 25, the conductor-filled through-hole substrates 51 are repeatedly stacked via the fine bumps 15. The gap between the conductor-filled through-hole substrates 51 is filled with the cured adhesive 20 without any gaps, and is sealed.

The semiconductor device 200 may be obtained, for example, by the following method. That is, a conductor-filled through-hole substrate 51 having fine bumps 15 on one main surface is laminated via an adhesive to obtain a laminate. The adhesive may be cured during lamination. The obtained laminate and the interposer substrate 25 are electrically connected by pressure bonding, forming a connection body in which the laminate and the interposer substrate 25 are electrically connected. A dicing tape is attached to the surface of the formed connection body opposite to the surface on which the interposer substrate 25 is provided, and dicing is performed along the dicing lines to obtain the semiconductor device 200.

In the semiconductor device 100 or 200, the filling rate of the cured resin 6 in the conductor 35 may satisfy the following condition. The filling rate can be calculated in the same manner as above.
(Through-hole conductor)
(A) Within a range of ±5 μm from the center C of the through hole 30 in the thickness direction of the substrate and in a direction perpendicular to the thickness direction of the substrate, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the copper sintered body.
(B) In a region extending from a point S7, which passes through a central portion C of the through hole 30 (the center of the hole length L and the center of the hole diameter D there), where a line L1 extending in the thickness direction of the substrate intersects with a surface S10 including the main surface of the insulating substrate, to a depth of 10 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal space of the copper sintered body.
(C) In the region from point S7 to a depth of 10 to 20 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.
(D) In the region from point S7 to a depth of 20 to 30 μm, the filling rate of the cured resin may be 80 vol. % or more, 90 vol. % or more, or 95 vol. % or more, based on the total volume of the porous internal spaces of the copper sintered body.

(Copper paste)
The copper paste containing copper particles used in the method for producing a conductor-filled through-hole board of this embodiment will be described.

The copper paste may contain, as copper particles, first copper particles having a particle size (maximum diameter) of 0.8 μm or more.

The particle size (maximum diameter) of the first copper particles may be 1.2 μm or more. The particle size (maximum diameter) of the first copper particles may be 10 μm or less, or 8.0 μm or less.

The average particle size (average maximum diameter) of the first copper particles contained in the copper paste may be 0.5 μm or more, 0.8 μm or more, or 1.2 μm or more, and may be 20 μm or less, 10 μm or less, or 8 μm or less, from the viewpoint of improving the sintering density in the through holes and suppressing the generation of voids in the through holes.

The particle size (maximum diameter) and average particle size (average maximum diameter) of the first copper particles can be determined, for example, from an SEM image of the particles. An example of a method for calculating the particle size (maximum diameter) of the first copper particles from an SEM image is shown below. A powder of the first copper particles is placed on a carbon tape for SEM with a spatula to prepare a sample for SEM. This sample for SEM is observed at 5000 times magnification with an SEM device. A rectangle circumscribing the first copper particle in the SEM image is drawn using image processing software, and the long side of the rectangle is taken as the particle size (maximum diameter) of the particle. This measurement is performed on 50 or more first copper particles using multiple SEM images, and the average particle size (average maximum diameter) is calculated.

The shape of the first copper particles may be, for example, spherical, clumpy, needle-like, flat (flake-like), approximately spherical, etc. The first copper particles may be an agglomerate of copper particles having these shapes.

The first copper particles are preferably flat (flake-like) with an aspect ratio (long diameter/thickness) of 4 or more. In this case, the first copper particles are oriented approximately parallel to the surface to which the copper paste is applied, which suppresses volumetric shrinkage when the copper particles in the copper paste are sintered, making it easier to suppress voids that occur in the through-holes. In addition, by suppressing volumetric shrinkage when the copper particles in the copper paste are sintered, it is possible to suppress cracks in the copper sintered body formed on at least one of the main surfaces of the through-hole board.

The aspect ratio of the first copper particles is preferably 4 or more, more preferably 5 or more, and even more preferably 6 or more. If the aspect ratio is within the above range, the first copper particles in the copper paste are more likely to be oriented parallel to the surface of the copper paste applied, and the volume shrinkage when the copper particles in the copper paste are sintered can be suppressed. This makes it possible to further suppress breakage of the wiring due to thermal stress when wiring is formed from the conductor provided on the main surface of the through-hole board. In addition, the adhesion between the copper sintered body and the metal coating formed on the insulating substrate can be improved. The aspect ratio (major axis/thickness) of the copper particles in the copper paste can be determined, for example, by observing an SEM image of the particles and measuring the major axis and thickness.

The copper paste preferably contains first copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of 4 or more. By containing such first copper particles in the copper paste, the volumetric shrinkage when the copper particles in the copper paste are sintered can be sufficiently reduced, and it becomes easy to form a copper sintered body in the through hole having a porous structure and a sufficiently formed conductive network. As a result, it is possible to suppress the generation of voids in the through hole, and to form a copper sintered body on the main surface of the through-hole board that is less likely to crack, and when wiring is formed from a conductor containing this copper sintered body, it is possible to further suppress breakage of the wiring due to thermal stress.

The copper paste may contain copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of less than 2, but the content of the copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of less than 2 may be 50 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, 10 parts by mass or less, or 0 parts by mass, per 100 parts by mass of the first copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of 4 or more. By limiting the content of the copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of less than 2, it is possible to form a copper sintered body in the through hole having a porous structure while sufficiently forming a conductive network, while suppressing the generation of voids in the through hole by the first copper particles in the copper paste. Furthermore, on the main surface of the through-hole board, the first copper particles tend to be oriented approximately parallel to the surface to which the copper paste is applied, and by more effectively suppressing volumetric shrinkage, a copper sintered body that is less susceptible to cracking can be formed. When wiring is formed from a conductor containing this copper sintered body, breaks in the wiring due to thermal stress can be further suppressed.

The content of the first copper particles in the copper paste may be 15% by mass or more, 20% by mass or more, or 50% by mass or more, and may be 85% by mass or less, 70% by mass or less, or 50% by mass or less, based on the total mass of the metal particles contained in the copper paste. If the content of the first copper particles is within the above range, the above-mentioned effects are more easily obtained.

The first copper particles may be treated with a surface treatment agent from the viewpoint of dispersion stability and oxidation resistance. The surface treatment agent may be one that is removed during wiring formation (when sintering the copper particles). Examples of such surface treatment agents include aliphatic carboxylic acids such as palmitic acid, stearic acid, arachidic acid, and oleic acid; aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, and o-phenoxybenzoic acid; aliphatic alcohols such as cetyl alcohol, stearyl alcohol, isobornylcyclohexanol, and tetraethylene glycol; aromatic alcohols such as p-phenylphenol; alkylamines such as octylamine, dodecylamine, and stearylamine; aliphatic nitriles such as stearonitrile and decanenitrile; silane coupling agents such as alkylalkoxysilanes; and polymer treatment agents such as polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, and silicone oligomers. One type of surface treatment agent may be used alone, or two or more types may be used in combination.

The amount of the surface treatment agent may be an amount equal to or greater than one molecular layer on the particle surface. The amount of such a surface treatment agent varies depending on the specific surface area of the first copper particles, the molecular weight of the surface treatment agent, and the minimum coverage area of the surface treatment agent. The amount of the surface treatment agent is usually 0.001% by mass or more.

The amount of the surface treatment agent can be calculated from the number of molecular layers (n) attached to the surface of the first copper particle, the specific surface area (A _p ) (unit: m ² /g) of the first copper particle, the molecular weight (M _s ) (unit: g/mol) of the surface treatment agent, the minimum coverage area (S _S ) (unit: m ² /piece) of the surface treatment agent, and the Avogadro's number (N _A ) (6.02 × 10 ²³ pieces). Specifically, the amount of the surface treatment agent is calculated according to the formula: amount of surface treatment agent (mass%) = {(n·A _p ·M _s ) / (S _S ·N _A + n·A _p ·M _s )} × 100%.

The specific surface area of the first copper particles can be calculated by measuring the dried copper particles by the BET specific surface area measurement method. The minimum coverage area of the surface treatment agent is 2.05×10 ⁻¹⁹ m ² /1 molecule when the surface treatment agent is a linear saturated fatty acid. In the case of other surface treatment agents, the surface treatment agent can be measured, for example, by calculation from a molecular model or by the method described in "Chemistry and Education" (Katsuhiro Ueda, Sumio Inafuku, Iwao Mori, 40 (2), 1992, pp. 114-117). An example of a method for quantifying the surface treatment agent is shown below. The surface treatment agent can be identified by a thermal desorption gas/gas chromatograph mass spectrometer of the dried powder obtained by removing the dispersion medium from the copper paste, and the carbon number and molecular weight of the surface treatment agent can be determined. The carbon content of the surface treatment agent can be analyzed by carbon content analysis. Examples of carbon content analysis methods include high-frequency induction heating furnace combustion/infrared absorption method. The amount of the surface treatment agent can be calculated from the carbon number, molecular weight and carbon content of the identified surface treatment agent according to the above formula.

Commercially available first copper particles can be used. Examples of commercially available first copper particles include MA-C025 (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size 4.1 μm), 3L3 (manufactured by Fukuda Metal Foil & Powder Co., Ltd., average particle size 7.3 μm), 1110F (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size 5.8 μm), and 2L3 (manufactured by Fukuda Metal Foil & Powder Co., Ltd., average particle size 9 μm).

When manufacturing the copper paste, copper particles can be used that contain first copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of 4 or more, and that contain copper particles having a particle size (maximum diameter) of 0.8 μm or more and 10 μm or less and an aspect ratio of less than 2 within the above-mentioned range. A commercially available product made of such copper particles can be selected and used.

The ratio of the pore size of the through holes to the particle size (maximum diameter) of the first copper particles [pore size (μm)/particle size (μm)] may be 4 or more, 8 or more, or 10 or more, and may be 150 or less, 100 or less, or 50 or less, from the viewpoint of suppressing volumetric shrinkage and forming a copper sintered body that is less susceptible to cracking.

In one embodiment, the copper paste may include the first copper particles described above and second copper particles having a particle size (maximum diameter) of 0.5 μm or less. In this case, when the copper particles are sintered, the second copper particles are present between the first copper particles, which tends to improve the conductivity of the resulting wiring. That is, it is preferable to use the first copper particles and the second copper particles in combination. When the copper paste is prepared only from the second copper particles, the volume shrinkage and sintering shrinkage caused by drying the dispersion medium are large, so that when the copper particles are sintered, the sintered body is easily peeled off from the metal coating provided on the insulating base, making it difficult to obtain sufficient airtightness and connection reliability. However, by using the first copper particles and the second copper particles in combination, the volume shrinkage when the copper paste is sintered is suppressed, and the adhesion between the copper sintered body formed in the through hole and the metal coating formed on the wall surface of the through hole can be improved. As a result, the copper sintered body in the through hole is less likely to break due to thermal stress, and the airtightness and connection reliability against thermal stress are further improved.

The second copper particles can act as copper particles that suitably bond the first copper particles together. In addition, the second copper particles have better sinterability than the first copper particles and can promote the sintering of the copper particles. For example, it is possible to sinter the copper particles at a lower temperature than when the first copper particles are used alone. In addition, when preparing a copper paste from only the second copper particles, the volume shrinkage and sintering shrinkage caused by drying the dispersion medium are large, so that the copper sintered body formed inside the through hole is likely to shrink in volume and cause voids inside the through hole. In particular, by using the flat first copper particles and the second copper particles in combination, the flat first copper particles act as copper particles that are suitably bonded by the second copper particles, which makes it easy to form a copper sintered body having a porous structure while suppressing the generation of voids inside the through hole.

The average particle size (average maximum diameter) of the second copper particles contained in the copper paste may be 0.01 μm or more, 0.03 μm or more, 0.05 μm or more, 0.08 μm or more, 0.1 μm or more, or 0.2 μm or more, and may be 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, or 0.2 μm or less.

If the average particle size (average maximum diameter) of the second copper particles is 0.01 μm or more, it is easy to obtain effects such as reducing the synthesis cost of the second copper particles, good dispersibility, and reducing the amount of surface treatment agent used. If the average particle size (average maximum diameter) of the second copper particles is 0.5 μm or less, it is easy to obtain effects such as excellent sintering properties of the second copper particles.

The second copper particles may contain 20% by mass or more of copper particles having a particle size (maximum diameter) of 0.01 μm or more and 0.5 μm or less. From the viewpoint of the sinterability of the copper paste, the second copper particles may contain 30% by mass or more, 50% by mass or more, or 85% by mass or less of copper particles having a particle size (maximum diameter) of 0.01 μm or more and 0.5 μm or less. When the content ratio of copper particles having a particle size (maximum diameter) of 0.01 μm or more and 0.5 μm or less in the second copper particles is 20% by mass or more, the dispersibility of the copper particles is further improved, and the increase in viscosity and the decrease in paste concentration can be further suppressed.

The content of the second copper particles in the copper paste may be 20% by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more, and 85% by mass or less, 80% by mass or less, or 75% by mass or less, based on the total mass of the metal particles contained in the copper paste. If the content of the second copper particles is within the above range, it is easy to form a copper sintered body that has excellent adhesion to the metal coating provided on the through-hole board while suppressing the generation of voids in the through holes, and a copper sintered body that is less likely to crack on the main surface of the through-hole board can be formed, and when wiring is formed from a conductor containing this copper sintered body, breakage of the wiring due to thermal stress can be further suppressed.

The content of the second copper particles in the copper paste may be 20% by mass or more and 85% by mass or less, based on the sum of the mass of the first copper particles and the mass of the second copper particles. If the content of the second copper particles is 20% by mass or more, the spaces between the first copper particles can be sufficiently filled, and a copper sintered body that is less likely to crack can be formed, and the wiring formed from the conductor containing this copper sintered body is less likely to break due to thermal stress. If the content of the second copper particles is 85% by mass or less, the volumetric shrinkage when the copper particles are sintered can be sufficiently suppressed, so that the generation of voids in the through holes can be suppressed and a copper sintered body that is less likely to crack can be formed, and the wiring formed from the conductor containing this copper sintered body is less likely to break due to thermal stress.

From the viewpoint of making the above-mentioned effect more easily obtainable, the content of the second copper particles may be 20 parts by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more, based on the total mass of the first copper particles and the second copper particles, and may be 85% by mass or less, or 80% by mass or less.

The shape of the second copper particles may be, for example, spherical, clumpy, needle-like, flat (flake-like), approximately spherical, etc. The second copper particles may be an aggregate of copper particles having these shapes. From the viewpoint of dispersibility and packing ability, the shape of the second copper particles may be spherical, approximately spherical, or flat (flake-like), and from the viewpoint of combustibility and mixability with the first copper particles, etc., the shape of the second copper particles may be spherical or approximately spherical.

The aspect ratio of the second copper particles may be 5 or less, 4 or less, or 3 or less from the viewpoints of dispersibility, packing ability, and mixability with the first copper particles.

The second copper particles may be treated with a specific surface treatment agent. Examples of specific surface treatment agents include organic acids having 8 to 16 carbon atoms. Examples of organic acids having 8 to 16 carbon atoms include caprylic acid, methylheptanoic acid, ethylhexanoic acid, propylpentanoic acid, pelargonic acid, methyloctanoic acid, ethylheptanoic acid, propylhexanoic acid, capric acid, methylnonanoic acid, ethyloctanoic acid, propylheptanoic acid, butylhexanoic acid, undecanoic acid, methyldecanoic acid, ethylnonanoic acid, propyloctanoic acid, butylheptanoic acid, lauric acid, methylundecanoic acid, ethyldecanoic acid, propylnonanoic acid, butyloctanoic acid, Saturated fatty acids such as pentylheptanoic acid, tridecanoic acid, methyldodecanoic acid, ethylundecanoic acid, propyldecanoic acid, butylnonanoic acid, pentyloctanoic acid, myristic acid, methyltridecanoic acid, ethyldodecanoic acid, propylundecanoic acid, butyldecanoic acid, pentylnonanoic acid, hexyloctanoic acid, pentadecanoic acid, methyltetradecanoic acid, ethyltridecanoic acid, propyldodecanoic acid, butylundecanoic acid, pentyldecanoic acid, hexylnonanoic acid, palmitic acid, methylpentadecanoic acid, ethyltetradecanoic acid, propyltridecanoic acid, butyldodecanoic acid, pentylundecanoic acid, hexyldecanoic acid, heptylnonanoic acid, methylcyclohexanecarboxylic acid, ethylcyclohexanecarboxylic acid, propylcyclohexanecarboxylic acid, butylcyclohexanecarboxylic acid, pentylcyclohexanecarboxylic acid, hexylcyclohexanecarboxylic acid, heptylcyclohexanecarboxylic acid, octylcyclohexanecarboxylic acid, and nonylcyclohexanecarboxylic acid; octene Examples of the organic acid include unsaturated fatty acids such as benzoic acid, nonenoic acid, methylnonenoic acid, decenoic acid, undecenoic acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, myristoleic acid, pentadecenoic acid, hexadecenoic acid, palmitoleic acid, and sabienoic acid; and aromatic carboxylic acids such as terephthalic acid, pyromellitic acid, o-phenoxybenzoic acid, methylbenzoic acid, ethylbenzoic acid, propylbenzoic acid, butylbenzoic acid, pentylbenzoic acid, hexylbenzoic acid, heptylbenzoic acid, octylbenzoic acid, and nonylbenzoic acid. The organic acid may be used alone or in combination of two or more. By combining such an organic acid with the second copper particles, it is possible to achieve both the dispersibility of the second copper particles and the detachment of the organic acid during sintering.

The amount of the surface treatment agent may be an amount that adheres to the surface of the second copper particles in a monolayer to trilayer form. The amount of the surface treatment agent may be 0.07% by mass or more, 0.10% by mass or more, or 0.2% by mass or more, and may be 2.1% by mass or less, 1.6% by mass or less, or 1.1% by mass or less. The amount of the surface treatment agent of the second copper particles can be calculated by the method described above for the first copper particles. The same applies to the specific surface area, the molecular weight of the surface treatment agent, and the minimum coverage area of the surface treatment agent.

The second copper particles can be synthetic or commercially available.

The sum of the content of the first copper particles and the content of the second copper particles in the copper paste may be 90% by mass or more based on the total mass of the metal particles contained in the copper paste. If the sum of the content of the first copper particles and the content of the second copper particles is within the above range, it is easier to suppress the generation of voids in the through holes. From the viewpoint of making such an effect even easier to obtain, the sum of the content of the first copper particles and the content of the second copper particles may be 95% by mass or more, or may be 100% by mass, based on the total mass of the metal particles.

The copper paste may further contain other metal particles other than copper particles. Examples of other metal particles include nickel, silver, gold, palladium, platinum, and the like. The average particle size (maximum diameter) of the other metal particles may be 0.01 μm or more or 0.05 μm or more, and may be 5 μm or less, 3.0 μm or less, or 2.0 μm or less. When other metal particles are contained, the content thereof may be less than 20 mass% and may be 10 mass% or less based on the total mass of the metal particles contained in the copper paste from the viewpoint of obtaining sufficient bonding properties. Other metal particles may not be contained. The shape of the other metal particles is not particularly limited.

The dispersion medium contained in the copper paste is not particularly limited, and may be, for example, a volatile one. Examples of volatile dispersion media include monohydric and polyhydric alcohols such as pentanol, hexanol, heptanol, octanol, decanol, ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, α-terpineol, and isobornylcyclohexanol (MTPH); ethylene glycol butyl ether, ethylene glycol phenyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, diethylene glycol hexyl ether, triethylene glycol methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl ether, diethylene glycol isopropyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol butyl ether, propylene glycol propyl ether, and dipropylene glycol. Examples of the esters include methyl ether, dipropylene glycol ethyl ether, dipropylene glycol propyl ether, dipropylene glycol butyl ether, dipropylene glycol dimethyl ether, tripropylene glycol methyl ether, and tripropylene glycol dimethyl ether; esters such as ethylene glycol ethyl ether acetate, ethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol butyl ether acetate, dipropylene glycol methyl ether acetate (DPMA), ethyl lactate, butyl lactate, γ-butyrolactone, and propylene carbonate; acid amides such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, and N,N-dimethylformamide; aliphatic hydrocarbons such as cyclohexane, octane, nonane, decane, and undecane; aromatic hydrocarbons such as benzene, toluene, and xylene; mercaptans having an alkyl group having 1 to 18 carbon atoms; and mercaptans having a cycloalkyl group having 5 to 7 carbon atoms. Examples of mercaptans having an alkyl group with 1 to 18 carbon atoms include ethyl mercaptan, n-propyl mercaptan, i-propyl mercaptan, n-butyl mercaptan, i-butyl mercaptan, t-butyl mercaptan, pentyl mercaptan, hexyl mercaptan, and dodecyl mercaptan. Examples of mercaptans having a cycloalkyl group with 5 to 7 carbon atoms include cyclopentyl mercaptan, cyclohexyl mercaptan, and cycloheptyl mercaptan.

The content of the dispersion medium may be 3 parts by mass or more, 4 parts by mass or more, or 5 parts by mass or more, and may be 20 parts by mass or less, 16 parts by mass or less, or 12 parts by mass or less, assuming that the total mass of the metal particles contained in the copper paste is 100 parts by mass. If the content of the dispersion medium is within the above range, the viscosity of the copper paste can be adjusted to a more appropriate value, and it is also easier to suppress the occurrence of voids in the through holes.

If necessary, the copper paste may contain appropriate additives such as wetting improvers, such as nonionic surfactants and fluorosurfactants; antifoaming agents, such as silicone oil; and ion trapping agents, such as inorganic ion exchangers.

The above-mentioned copper paste can be prepared by mixing copper particles and any components (additives, other metal particles, etc.) in a dispersion medium. After mixing the components, a stirring process may be performed. The maximum diameter of the dispersion may be adjusted by a classification operation.

The copper paste may be prepared by mixing the second copper particles, the surface treatment agent, and the dispersion medium in advance, carrying out a dispersion process to prepare a dispersion of the second copper particles, and then mixing the first copper particles, other metal particles, and any additives. This procedure improves the dispersibility of the second copper particles, improving their mixability with the first copper particles, and further improving the performance of the copper paste. The dispersion of the second copper particles may be subjected to a classification operation to remove agglomerates.

The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the following examples.

(Synthesis of second copper particles)
[Synthesis of copper nonanoate]
150 mL of 1-propanol (Kanto Chemical Co., Ltd., special grade) was added to 91.5 g (0.94 mol) of copper hydroxide (Kanto Chemical Co., Ltd., special grade) and stirred, and 370.9 g (2.34 mol) of nonanoic acid (Kanto Chemical Co., Ltd., 90% or more) was added to the mixture. The resulting mixture was heated and stirred at 90°C for 30 minutes in a separable flask. The resulting solution was filtered while still heated to remove undissolved matter. It was then allowed to cool, and the resulting copper nonanoate was suction filtered and washed with hexane until the washing liquid became transparent. The resulting powder was dried in an explosion-proof oven at 50°C for 3 hours to obtain copper nonanoate (II). The yield was 340 g (yield 96% by mass).

[Synthesis of second copper particles]
15.01 g (0.040 mol) of copper (II) nonanoate obtained above and 7.21 g (0.040 mol) of copper (II) acetate anhydride (Kanto Chemical Co., Ltd., special grade) were placed in a separable flask, 22 mL of 1-propanol and 32.1 g (0.32 mol) of hexylamine (Tokyo Chemical Industry Co., Ltd., purity 99%) were added, and the mixture was heated and stirred at 80 ° C. in an oil bath to dissolve. The mixture was transferred to an ice bath and cooled to an internal temperature of 5 ° C., and then 7.72 mL (0.16 mol) of hydrazine monohydrate (Kanto Chemical Co., Ltd., special grade) was stirred in the ice bath. The molar ratio of copper:hexylamine was 1:4. The mixture was then heated and stirred at 90 ° C. in an oil bath. At that time, a reduction reaction accompanied by foaming proceeded, and the reaction was completed within 30 minutes. The inner wall of the separable flask exhibited a copper luster, and the solution turned dark red. Centrifugation was carried out at 9000 rpm (revolutions per minute) for 1 minute to obtain a solid matter. The process of washing the solid matter with 15 mL of hexane was repeated three times to remove acid residues, and a powder of copper particles having a copper luster (second copper particles) was obtained.

The copper particles synthesized above were observed with a transmission electron microscope (manufactured by JEOL Ltd., product name: JEM-2100F). The average major axis length of 200 randomly selected copper particles was 104 nm. The shape of the second particles was spherical.

(Preparation of copper paste)
<Examples 1 to 73>
The raw materials shown below were mixed in the ratios shown in Tables 1 to 8 to prepare copper pastes.

[First copper particles]
Flat 1.4 μm: 1100YP (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size 1.4 μm (D50), product name)
Flat 3.1 μm: 1200YP (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size 3.1 μm (D50), product name)
Flat 5.8 μm: MA-C05KP (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size 5.8 μm (D50), product name)
Flat 7.3 μm: MA-C05KFD (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size 7.3 μm (D50), product name)

[Second copper particles]
Spherical 100 nm: Copper particles synthesized above Spherical 250 nm: CH0200 (manufactured by Mitsui Mining & Smelting Co., Ltd., D50 250 nm, product name)
[others]
Diethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

<Comparative Example 1>
A copper paste was prepared by mixing 70 parts by mass of 1100YP (manufactured by Mitsui Mining & Smelting Co., Ltd., average particle size 1.4 μm (D50), trade name) as the first copper particles, 30 parts by mass of the copper particles synthesized above as the second copper particles, 5 parts by mass of diethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 5 parts by mass of a resin component. As the resin component, a mixture of an acrylic resin as an organic binder and a mixture of carbitol and terpineol as organic solvents (the mass ratio of carbitol and terpineol in the mixture is carbitol:terpineol = 1:1) in a mass ratio of 1:2 was used.

(Through-hole board preparation process)
<Examples 1 to 73 and Comparative Example 1>
A silicon substrate having a through hole and having a titanium layer, a nickel layer, and a copper layer formed in that order on both main surfaces and on the wall surface of the through hole was prepared as a through-hole substrate. The silicon substrate had a diameter of 6 inches and a thickness of 500 μm. The diameters of the through holes in the silicon substrate are shown in Tables 1 to 8. The titanium layer, nickel layer, and copper layer were formed in that order by sputtering.

(Copper sintered body forming process)
<Examples 1 to 8, 12 to 21, 24 to 43, 48 to 73 and Comparative Example 1>
The prepared copper paste was applied to both main surfaces of a silicon substrate with a metal spatula, and the copper paste was filled into the through holes. After application, the copper paste was dried in the air at 90° C. for 10 minutes. After drying, a copper paste layer having a thickness of 30 μm was formed on the silicon substrate.

The silicon substrate on which the copper paste layer was formed was pressurized from both sides with a pressurizing tool. The pressure applied to the silicon substrate was set to the pressures listed in Tables 1 to 8. The pressurizing tool was equipped with a flat aluminum plate and a spring, and the pressure applied during pressurization could be adjusted. The silicon substrate pressurized by the pressurizing tool was placed in a tube furnace (manufactured by AVC Co., Ltd.), and argon gas was flowed at 1 L/min to replace the air in the tube furnace with argon gas. The copper paste was then sintered by sintering under the conditions of heating for 10 minutes and at 300°C for 60 minutes while flowing hydrogen gas at 300 mL/min. The argon gas was then changed to 0.3 L/min, cooled, and removed into the air at 50°C or less to obtain a copper sintered body-filled through-hole substrate. The thickness of the copper sintered body formed on both main surfaces of the sintered silicon substrate was 25 μm.

<Examples 9 to 11>
Except for not pressing the silicon substrate with a pressing jig, a copper sintered body filled through-hole substrate was obtained in the same manner as in Example 1. The thickness of the copper sintered body formed on both main surfaces of the silicon substrate after sintering was 35 μm.

<Examples 22 and 23>
Except for flowing nitrogen gas instead of hydrogen gas during the sintering process, a copper sintered body filled through-hole substrate was obtained in the same manner as in Example 1. The thickness of the copper sintered body formed on both main surfaces of the silicon substrate after sintering was 30 μm.

<Examples 44 to 47>
A copper sintered body filled through-hole substrate was obtained in the same manner as in Example 1, except that the temperature rise time was 10 minutes and the sintering treatment was performed under conditions of 60 minutes at 225° C. The thickness of the copper sintered body formed on both main surfaces of the silicon substrate after sintering was 30 μm.

(Measurement of porosity of sintered copper body)
<Examples 1 to 73 and Comparative Example 1>
Using a focused ion beam processing observation device (manufactured by Hitachi High-Technologies Corporation, product name: MI4050), the cross section of the center of the through hole of the silicon substrate in the copper sintered body filled through-hole substrate and the cross section of the copper sintered body provided on the main surface of the silicon substrate were exposed by the focused ion beam, and the cross sections were observed. When observing the cross section of the center of the through hole, a range of ±5 μm in the thickness direction of the silicon substrate and ±5 μm in the direction perpendicular to the thickness direction of the silicon substrate from the center of the copper sintered body filled in the through hole was observed. When observing the cross section of the copper sintered body provided on the main surface of the silicon substrate, a range of 10 μm in the thickness direction of the silicon substrate and 10 μm in the direction perpendicular to the thickness direction of the silicon substrate was observed in the region up to 5 μm from the surface of the copper sintered body formed on the main surface of the silicon substrate.
For the observation, a scanning electron microscope (Hitachi High-Technologies Corporation, product name: S-3700N) was used at a magnification of 10,000 times, and a cross-sectional image (about 10 μm square) of the copper sintered body was taken. Five observation points were taken. The obtained cross-sectional image was binarized using image analysis software (Adobe Photoshop (registered trademark) Elements) so that the sintered copper part and the porous part were separated. The binarized cross-sectional image is shown in FIG. 6. For each of the five observation points, the ratio of the area of the porous part to the total area of the copper sintered body cross section was taken as the porosity. The average value of the porosity of the five observation points was taken as the porosity of the copper sintered body. The results are shown in Tables 1 to 8.

(Resin impregnation process)
<Examples 1 to 73>
The curable resin composition shown below was applied to one side of the copper sintered body-filled through-hole board by a roll coater. Next, the copper sintered body-filled through-hole board was placed in a container, and the inside of the container was sucked to a gauge pressure of 100 KPa to create a vacuum state. The copper sintered body-filled through-hole board was held in a vacuum state for 10 minutes, and then the copper sintered body-filled through-hole board was taken out of the container. It was confirmed that the copper sintered body in the through-hole was impregnated with the curable resin composition, and the curable resin composition reached the opposite side of the copper sintered body in the through-hole to the side to which the curable resin composition was applied. The curable resin composition remaining on the applied surface of the copper sintered body-filled through-hole board was removed with a rubber spatula. Next, the curable resin composition was applied to the opposite side to the side to which the curable resin composition was applied by a roll coater, and the curable resin composition remaining on the surface of the copper sintered body-filled through-hole board was removed as much as possible with a rubber spatula.

[Curable resin composition]
YDF-170 (trade name of bisphenol F type epoxy resin, manufactured by Tohto Kasei Co., Ltd., epoxy equivalent = 170): 95 parts by mass 2PZ-CN (trade name of imidazole compound, manufactured by Shikoku Kasei Co., Ltd.): 5 parts by mass

<Comparative Example 1>
No resin impregnation step was performed.

(Resin curing process)
<Examples 1 to 73>
The through-hole substrate, in which the copper sintered body was impregnated with the curable resin composition, was held in a nitrogen atmosphere at 180° C. for 1 hour to obtain a conductor-filled through-hole substrate.

<Comparative Example 1>
No resin curing step was performed.

(Conductor removal process)
<Examples 1 to 73 and Comparative Example 1>
Both sides of the conductor-filled through-hole board were mechanically polished until the thickness of the copper sintered body on both sides of the conductor-filled through-hole board was 20 μm. A ceramic jig (manufactured by Kemet Japan Co., Ltd.) was used as a sample stage for attaching the conductor-filled through-hole board, and Alcowax (manufactured by Nikka Seiko Co., Ltd.) was used as a material for attaching the conductor-filled through-hole board to the sample stage. In addition, DP-Suspension P-3 μm, 1 μm, and 1/4 μm (manufactured by Struers) were used in this order as a polishing agent.

[Filling rate of cured resin in conductor]
<Examples 1 to 73 and Comparative Example 1>
The conductor-filled through-hole substrate that had been subjected to mechanical polishing was cut in the thickness direction, and the cross section of the center of the through-hole of the silicon substrate and the cross section of the conductor provided on the main surface of the silicon substrate were exposed by a focused ion beam, and these cross sections were observed. When observing the cross section of the center of the through-hole of the silicon substrate, a range of ±5 μm from the center of the through-hole in the thickness direction of the silicon substrate and ±5 μm in the direction perpendicular to the thickness direction of the silicon substrate was observed. When observing the cross section of the conductor provided on the main surface of the silicon substrate, a range of 10 μm in the thickness direction of the silicon substrate and 10 μm in the direction perpendicular to the thickness direction of the silicon substrate was observed in a region from the surface of the conductor provided on the main surface of the silicon substrate to 5 μm.
A focused ion beam processing observation device (manufactured by Hitachi High-Technologies Corporation, product name: MI4050) was used. For the observation, a scanning electron microscope (manufactured by Hitachi High-Technologies Corporation, product name: S-3700N) was used at a magnification of 10,000 times, and a cross-sectional image (about 10 μm square) of the conductor was taken. Five observation points were used. The obtained cross-sectional image was binarized using image analysis software (Adobe Photoshop (registered trademark) Elements) so that the sintered copper part and the resin cured part were separated from the space in the porous part that was not filled by the resin cured product. For each of the five observation points, the ratio of the area of the space in the porous part that was not filled by the resin cured product to the total area of the conductor cross section was obtained, and this was taken as the porosity. The average value of the porosity of the five observation points was taken as the porosity of the conductor. The filling rate of the cured resin in the conductor was calculated by substituting the porosity of the copper sintered body and the porosity of the conductor into the following formula (1).
Filling rate (%) of cured resin in conductor=[(B−A)/B]×100 Equation (1)
[In formula (1), A represents the porosity (%) of the conductor, and B represents the porosity (%) of the copper sintered body.]

(Wiring formation process (resist formation, etching, and resist removal))
<Examples 1 to 73 and Comparative Example 1>
A dry film for ultraviolet-curable etching resist H-W425 (trade name, manufactured by Hitachi Chemical Co., Ltd.) was pressure-bonded by a laminator to the surfaces of the copper sintered body on both sides of the conductor-filled through-hole board that had been subjected to mechanical polishing treatment. Thereafter, a photomask was aligned to expose a wiring pattern, and wiring was formed through resist development, etching of the copper sintered body, and removal of the resist, to obtain a conductor-filled through-hole board (test piece 55) shown in FIG. 7. In the obtained conductor-filled through-hole board (test piece 55), the conductor filled in the through-hole is electrically connected by the conductor (wiring) provided on the board surface.

(Initial resistance value)
<Examples 1 to 73 and Comparative Example 1>
The interconnection resistance was measured as the initial resistance of the conductor-filled through-hole substrate (test piece 55). When the through-hole diameter of the silicon substrate was 20 μm, the resistance of 20 interconnected through-holes was measured; when the through-hole diameter of the silicon substrate was 30 μm, the resistance of 30 interconnected through-holes was measured; when the through-hole diameter of the silicon substrate was 50 μm, the resistance of 30 interconnected through-holes was measured; when the through-hole diameter of the silicon substrate was 100 μm, the resistance of 100 interconnected through-holes was measured; and when the through-hole diameter of the silicon substrate was 200 μm, the resistance of 200 interconnected through-holes was measured. The measured interconnection resistance was evaluated according to the following criteria. Evaluations of B or higher were judged to be good. The results are shown in Tables 1 to 8.
A: Resistance value is less than 10 mΩ B: Resistance value is 10 mΩ or more but less than 30 mΩ C: Resistance value is 30 mΩ or more but less than 100 mΩ D: Resistance value is 100 mΩ or more but less than 500 mΩ E: Resistance value is 500 mΩ or more

(Temperature cycle connectivity test)
<Examples 1 to 73 and Comparative Example 1>
Conductor-filled through-hole board (test piece 55) was set in a temperature cycle tester (TSA-72SE-W, manufactured by Espec Corporation), and a temperature cycle connection reliability test was carried out under the following conditions: low temperature side: -40°C, 15 minutes, room temperature: 2 minutes, high temperature side: 125°C, 15 minutes, defrost cycle: automatic, number of cycles: 50, 100, 300, 500 cycles. When the diameter of the through-hole of the silicon substrate was 20 μm, the resistance value of 20 through-holes connected together was measured; when the diameter of the through-hole of the silicon substrate was 30 μm, the resistance value of 30 through-holes connected together was measured; when the diameter of the through-hole of the silicon substrate was 50 μm, the resistance value of 30 through-holes connected together was measured; when the diameter of the through-hole of the silicon substrate was 100 μm, the resistance value of 100 through-holes connected together was measured; and when the diameter of the through-hole of the silicon substrate was 200 μm, the resistance value of 200 through-holes connected together was measured. The measured connection resistance was evaluated according to the following criteria. Those that were evaluated as B or higher after 500 cycles of the temperature cycle test were judged to be good. The results are shown in Tables 1 to 8.
A: The rate of resistance change is less than 1% of the initial resistance value. B: The rate of resistance change is 1% or more and less than 3% of the initial resistance value. C: The rate of resistance change is 3% or more and less than 5% of the initial resistance value. D: The rate of resistance change is 5% or more and less than 10% of the initial resistance value. E: The rate of resistance change is 10% or more and less than 20% of the initial resistance value. F: The rate of resistance change is 20% or more of the initial resistance value.

(Cracks in the board)
<Examples 1 to 73 and Comparative Example 1>
The conductive material-filled through-hole substrate (test piece 55) was visually inspected to confirm the presence or absence of cracks in the silicon substrate. The absence of cracks was evaluated as ◯, and the presence of even partial cracks was evaluated as ×. The results are shown in Tables 1 to 8.

(airtightness)
<Examples 1 to 73 and Comparative Example 1>
The airtightness of the conductor-filled through-hole board (test piece 55) was evaluated. The evaluation was performed using a helium leak detector (UL200 manufactured by LEYBOLD). Specifically, the conductor-filled through-hole board was set on a jig, and a vacuum was drawn until the inlet pressure of the measuring device reached 5 Pa. When the inlet pressure reached 5 Pa, He pressure (0.1 MPa) was applied for 30 seconds, after which the amount of leakage was measured and evaluated according to the following criteria. The results are shown in Tables 1 to 8.
A: Leakage amount is less than 1x10 ^-11 Pa.m ³ /sec B: Leakage amount is 1x10 ^-11 or more and less than 1x10 ^-10 Pa.m ³ /sec C: Leakage amount is 1x10 ^-10 or more and less than 1x10 ^-9 Pa.m ³ /sec D: Leakage amount is 1x10 ^-9 or more and less than 1x10 ^-8 Pa.m ³ /sec E: Leakage amount is 1x10 ^-8 or more and less than 1x10 ^-6 Pa.m ³ /sec F: Leakage amount is 1x10 ^-6 Pa.m ³ /sec or more.

(Wiring adhesion - pull strength)
<Examples 1 to 73 and Comparative Example 1>
A stud pin with a tip area of 1 ^mm2 was soldered vertically to a conductor-filled through-hole board obtained in the same manner except that a 2 mm x 2 mm wiring pattern was formed in the wiring formation process, and used as a test piece. The test piece was fixed, the stud pin was held by the chuck of a tensile tester, and pulled vertically upward at an ascending speed of 50 mm/min, and the fracture load was measured when the copper sintered body on the main surface of the silicon substrate peeled off from the silicon substrate. Then, the adhesion strength was calculated using the following formula from the measured fracture load and the fracture area of the copper sintered layer. The measured value was the average of 10 points and was evaluated according to the following criteria. The results are shown in Tables 1 to 8.

Adhesion strength (MPa)=breakage load (kgf)/breakage area (mm ² )×9.8 (N/kgf).
A: Adhesion strength (MPa) is 50 MPa or more B: Adhesion strength (MPa) is 40 MPa or more and less than 50 MPa C: Adhesion strength (MPa) is 30 MPa or more and less than 40 MPa D: Adhesion strength (MPa) is 20 MPa or more and less than 30 MPa E: Adhesion strength (MPa) is 5 MPa or more and less than 20 MPa F: Adhesion strength (MPa) is less than 5 MPa

(Wiring formability - presence or absence of cracks -)
<Examples 1 to 73 and Comparative Example 1>
Conductor-filled through-hole boards were obtained in the same manner except that five wiring patterns of 2 mm x 2 mm were formed in the wiring formation process. The wiring patterns were inspected with an optical microscope to check for cracks (length 0.5 mm or more). The magnification was 500 times, and the evaluation was based on the following criteria. The results are shown in Tables 1 to 8.
A: No cracks B: 1 or more but less than 2 cracks C: 2 or more but less than 5 cracks D: 5 or more but less than 10 cracks E: 10 or more but less than 20 cracks F: 20 or more cracks

(Volume Resistivity)
<Examples 1 to 73 and Comparative Example 1>
The volume resistivity of the conductor formed on the silicon substrate was measured. The volume resistivity was calculated from the sheet resistance measured with a four-point needle sheet resistance meter (manufactured by Mitsubishi Analytech, product name: Loresta GP) and the film thickness obtained with a non-contact surface/layer cross-sectional shape measurement system (VertScan, Ryoka Systems Co., Ltd.). The results are shown in Tables 1 to 8.

1...insulating substrate, 2...metal coating, 3...copper paste, 4...porous, 5...copper sintered body, 6...resin hardened product, 8...etching resist, 9...wiring, 15...fine bump, 20...hardened adhesive, 25...interposer substrate, 27...wiring, 30...through hole, 35...conductor, 40...through-hole substrate, 50...copper sintered body filled through-hole substrate, 51, 52...conductor filled through-hole substrate, 55...test piece, 100, 200...semiconductor device, A...pressure jig

Claims (19)

a preparation step of preparing a through-hole board including an insulating base having through holes formed therein, the through holes communicating with both main surfaces;
A copper sintered body forming step of forming a copper sintered body having a porous structure so as to fill at least the through holes;
a resin impregnation step of impregnating the copper sintered body with a curable resin composition;
A resin curing step of forming a conductor including the copper sintered body in which pores are filled with a resin cured product by curing the curable resin composition impregnated in the copper sintered body;
Equipped with
The method for manufacturing a substrate with a conductor-filled through hole, wherein the porosity of the copper sintered body is 15 volume % or less based on the volume of the copper sintered body. The method according to claim 1, wherein the filling rate of the cured resin in the conductor is 80 volume % or more based on the volume of the internal space of the porous material. The method according to claim 1 or 2, wherein the porosity of the copper sintered body is 1% by volume or more based on the volume of the copper sintered body. The method according to any one of claims 1 to 3, wherein in the copper sintered body forming step, the copper sintered body is formed so as to cover at least a portion of the main surface of the through-hole board. The method according to claim 4, further comprising a conductor removal step of removing at least a portion of the conductor formed on the main surface of the through-hole substrate. The method according to claim 5, wherein the removing means in the conductor removing step is one or more selected from the group consisting of etching, mechanical polishing, and chemical mechanical polishing. The method according to any one of claims 1 to 6, wherein the through-hole substrate has a metal coating provided on at least the wall surface of the through hole. The method according to any one of claims 1 to 7, wherein the ratio L/D of the hole length L to the hole diameter D of the through hole is 10 or more. The copper sintered body forming step comprises:
a copper paste filling step of filling the through holes of the through-hole board with a copper paste containing copper particles ;
a copper paste firing step of firing the copper paste to form the copper sintered body;
The method according to any one of claims 1 to 8, comprising: The method according to claim 9, wherein the copper paste contains, as the copper particles, first copper particles having a particle size of 0.8 μm or more and second copper particles having a particle size of 0.5 μm or less. The method according to claim 10, wherein the content of the second copper particles is 35 mass% or more based on the sum of the mass of the first copper particles and the mass of the second copper particles. The method according to claim 10 or 11 , wherein the first copper particles are flat. The method according to any one of claims 9 to 12 , wherein the copper paste is fired under a pressure of 0.1 MPa or more. The method according to any one of claims 9 to 13 , wherein the copper paste is fired in an atmosphere containing nitrogen or hydrogen. A through-hole board including an insulating base having a through hole, the through hole communicating with both main surfaces, and a conductor filling the through hole,
The conductor includes a copper sintered body having a porous structure and a cured resin filled in the pores of the copper sintered body,
A conductor-filled through-hole board, wherein the porosity of the copper sintered body is 15 volume % or less based on the volume of the copper sintered body. 16. The circuit board according to claim 15 , wherein a filling rate of the cured resin in the conductor is 80 volume % or more based on the volume of the internal space of the porous material. 17. The conductor filled through-hole board of claim 15 or 16 , wherein the through-hole board comprises a metal coating provided on at least the wall surface of the through hole. 18. The board according to claim 15 , wherein a ratio L/D of a hole length L to a hole diameter D of the through hole is 10 or more. The conductor-filled through-hole board of claim 15 , wherein the conductor covers at least a portion of a main surface of the through-hole board.

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