JP6376802B2 - Metal bonding material - Google Patents

Description

  The present invention uses a metal bonding material containing metal particles and an organic solvent, more specifically, a known printing method such as a screen printing method or an ink jet printing method on a substrate, or a known ejection method such as a dispenser method. The present invention relates to a metal bonding material capable of bonding an electronic component onto the substrate by heat treatment at a low temperature (for example, about 200 ° C.) by coating.

  In the field of mounting electronic components on a substrate, lead-free solder, for example, tin-silver solder, tin-copper solder, tin-silver-copper solder is mainly used for electrical joining (Patent Document 1). . However, lead-free solder has a high melting point, and the mounting temperature is as high as 250 ° C. or higher. Therefore, the electronic component or the substrate may be thermally damaged, and it cannot be applied to all the electronic components and the substrate. Therefore, when using a substrate with poor heat resistance, such as PET, or when it must be bonded at a low temperature due to the heat resistance problem of the module, etc., bismuth and indium alloys that can be electrically bonded at a relatively low temperature Was used. However, bismuth has a problem in bonding strength and alloy brittleness, and an indium alloy has a problem in that it is expensive.

  On the other hand, silver paste that can be electrically joined at a relatively low temperature is used for mounting electronic components and modules that are unsuitable for soldering in terms of heat resistance, in order to prevent an increase in conduction resistance. Addition of a low melting point metal, a conductive filler, or metal nanoparticles to the silver paste is performed. Since metal nanoparticles have a large specific surface area and high reaction activity, they have the characteristic of low-temperature sintering that fuses at a low temperature compared to metal bulk. For example, in the case of silver nanoparticles, it is known that a fusion-bonding phenomenon occurs by heat treatment at about 200 ° C., which is much lower than the original melting point of 964 ° C., and exhibits the same level of conductivity as a metal bulk. However, there is a problem that conductivity and bonding strength are insufficient.

  In recent years, in order to cope with further downsizing of electronic components and thermal damage due to heat generated by electronic components, metal bonding materials are sintered by heat treatment at about 200 ° C. (hereinafter, referred to as “low temperature sintering”). In addition to the above, a bonding material having high heat dissipation is required. In addition, for high heat dissipation, it is also required to control the thickness of the metal bonding material to be thin during coating, and therefore, it is possible to deal with coating with a limited supply amount, for example, dispensing a small amount by a dispenser. Is also required. When dispensing (coating) a very small amount, if the dispersibility of the metal particles in the metal bonding material is low, solid-liquid separation occurs in the syringe, causing clogging at the nozzle opening of the syringe and unstable supply of the metal bonding material. There has been a problem that ejection (coating) defects such as conversion are likely to occur. In particular, when the supply amount of the metal bonding material is excessive, the metal bonding material may protrude from the side surface of the electronic component and a short circuit may occur.

  Therefore, in order to prevent solid-liquid separation when a small amount is discharged (applied), a metal bonding material in which a dispersing agent that is an acrylic copolymer is added to metal particles such as silver particles that are high heat dissipation materials is used. An electronic component is also mounted on a substrate.

  However, solid-liquid separation still tends to occur in the metal bonding material, and the clogging prevention at the nozzle opening of the syringe, stabilization of the supply amount of the metal bonding material, and the like are insufficient. In addition, the dispersant hindered the fusion bonding phenomenon during the heat treatment, and sufficient bonding strength was not obtained.

JP 2013-258399 A

  In view of the above circumstances, the present invention is excellent in the electrical conductivity of the joint and the bonding strength after sintering, and further prevents the occurrence of solid-liquid separation, and discharge (coating) even at the time of small amount (coating). ) It is an object to provide a metal bonding material capable of suppressing defects.

  An aspect of the present invention is a metal bonding material containing (A) metal particles, (B) a solvent composed of an organic solvent, and (C) a fluorine-based dispersant.

（式中、R^１、R^２、R^３、R^４は、それぞれ、独立に、Ｆ、ＣＦ_３、ＣＦ＝ＣＦ−ＣＦ _３ 、Ｃ_３Ｆ_７を表す。）で表される化合物、前記一般式（Ｉ）で表される化合物のオリゴマー、または前記一般式（I）で表される化合物のオリゴマーを主骨格とする化合物である金属接合材料である。上記「一般式（Ｉ）で表される化合物オリゴマー」とは、一般式（Ｉ）で表される化合物が２〜１００個結合した重合体を意味する。 In an embodiment of the present invention, the (C) fluorine-based dispersant is represented by the following general formula (I):

(Wherein R ¹ , R ² , R ³ and R ⁴ each independently represents F, CF ₃ , CF═CF—CF ₃ , or C ₃ F ₇ ); A metal bonding material which is a compound having a main skeleton of an oligomer of a compound represented by the formula (I) or an oligomer of a compound represented by the general formula (I). The “compound oligomer represented by the general formula (I)” means a polymer in which 2 to 100 compounds represented by the general formula (I) are bonded.

  An aspect of the present invention is a metal bonding material in which the compound represented by the general formula (I) is hexafluoropropene or hexafluoropropene trimer.

  In the aspect of the present invention, the (A) metal particles have (A1) first metal particles having an average primary particle size particle size distribution in the range of 100 nm to 6000 nm and (A2) an average primary particle size particle size distribution of 0. A metal bonding material comprising second metal particles in the range of 5 μm to 10 μm.

  An aspect of the present invention is a metal bonding material in which the (A1) first metal particles and the (A2) second metal particles are silver, a silver alloy, or copper coated with silver or a silver alloy.

  An aspect of the present invention is a metal bonding material in which (A1) the mass of the first metal particles: (A2) the mass of the second metal particles is 3: 7 to 7: 3.

  An aspect of the present invention is an electronic component assembly in which an electronic component is mounted on a substrate using the metal bonding material.

  An aspect of the present invention is an electronic component assembly in which the electronic component is an LED element or a power device.

  According to the aspect of the present invention, the blending of the fluorine-based dispersant not only provides excellent electrical conductivity and bonding strength, but also prevents solid-liquid separation and can be performed during a small amount of discharge (application). Even so, ejection (application) defects can be suppressed.

  According to the aspect of the present invention, the fluorine-based dispersant of the general formula (I) can reliably prevent solid-liquid separation, particularly, solid-liquid separation even in a fine syringe.

  According to an aspect of the present invention, (A) the metal particles are (A1) the first primary metal particles having an average primary particle size distribution in the range of 100 nm to 6000 nm and (A2) the average primary particle size distribution is By comprising the second metal particles in the range of 0.5 μm to 10 μm, the fusion bonding phenomenon occurs by heat treatment at about 200 ° C. with surely having mechanical bonding strength.

It is a figure explaining the temperature profile of the substrate surface which is a test piece.

  Next, the metal bonding material of the present invention will be described. The metal bonding material of the present invention contains (A) metal particles, (B) a solvent composed of an organic solvent, and (C) a fluorine-based dispersant.

(A) Metal particles The metal particles are not particularly limited in terms of type and particle diameter as long as the particles are conductive powder. As a metal seed | species, the metal simple substance used for solder, such as gold | metal | money, silver, copper, platinum, palladium, nickel, bismuth, lead, indium, tin, zinc, titanium, aluminum, and antimony, and the said metal seed | species are contained, for example. Mention may be made of metal alloys. Among the above metal species, silver, a silver alloy, or copper coated with silver or a silver alloy is preferable from the viewpoint of conductivity and high heat dissipation. The said metal may be used individually and may be used in mixture of 2 or more types.

  The particle diameter of the metal particles is, for example, an average primary particle diameter of 10 nm to 10 μm, and since the specific surface area is large and the reaction activity on the particle surface is high, the electronic component is boarded at a heating temperature much lower than the original melting point of the metal. It is preferable to include metal particles having an average primary particle size of nano-order (that is, an average primary particle size of 10 nm or more and less than 1000 μm) from the point of being able to be electrically bonded to the metal, and good mechanical bonding strength by suppressing generation of voids. (A1) first metal particles having an average primary particle size distribution in the range of 100 nm to 6000 nm and (A2) particles having an average primary particle size distribution in the range of 0.5 μm to 10 μm. Particularly preferred are metal particles comprising 2 metal particles.

  In addition, the maximum peak primary particle diameter of each of the (A1) first metal particles and the (A2) second metal particles is not particularly limited. From the viewpoint of obtaining an excellent metal joint, (A1) the maximum peak primary particle diameter of the first metal particles is preferably 200 nm to 800 nm, and (A2) the maximum peak primary particle diameter of the second metal particles is 500 nm to 2200 nm is preferable. Further, (A1) Mass of the first metal particles: (A2) The mass of the second metal particles is not particularly limited, but it is 3: 7 from the viewpoint of forming a high-density joint by widening the particle size distribution. ~ 7: 3 is preferred.

  Further, the blending ratio of the metal particles as the component (A) can be appropriately selected. For example, the lower limit is 80% by mass in the metal bonding material from the viewpoint of obtaining a bonded portion having good conductivity. It is preferably included, and 90% by mass is particularly preferable. On the other hand, the upper limit of the blending ratio is preferably 96% by weight, particularly preferably 95% by weight, from the viewpoint of blending the organic solvent which is the component (B).

(B) Organic solvent By mix | blending an organic solvent, the viscosity of a metal joining material is adjusted, for example, it can be made paste-like, and the applicability | paintability of a metal joining material can be improved. The organic solvent also functions as a lubricant when the metal particles move in the conductive material paste during sintering.

  The organic solvent is not particularly limited, and examples thereof include saturated or unsaturated aliphatic hydrocarbons such as decane, tetradecane, octadecane, and naphthene, ketones such as methyl ethyl ketone and cyclohexanone, and aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene. , Esters such as glycol ethers such as diethylene glycol monohexyl ether, ethyl acetate, butyl acetate, cellosolve acetate and esterified products of the above glycol ethers; nonan-1-ol, 2-ethyl-1,3-hexanediol, Examples thereof include alcohols such as terpineol and terpineol.

  Among these, in using the metal bonding material of the present invention for bonding between metals, the boiling point is 243 ° C. to 275 ° C. and 25 ° C. because the bonding strength is excellent and the thickness of the bonding portion can be controlled thinly. An organic solvent having a vapor pressure at 0 ° C. of 0.010 Pa to 4.0 Pa is preferable. Since the organic solvent is less volatile at room temperature, after the metal bonding material is applied to the substrate or the like performed at room temperature, the metal bonding material can be maintained in a paste state for a long time at room temperature. This is considered to be because the applied metal bonding material can be adjusted to a desired thickness by applying a predetermined load when mounted on the substrate. Further, the bonding strength is excellent when the heat treatment (for example, about 200 ° C.) is performed in a state where the metal bonding material is maintained in a paste state when bonding an electronic component or the like to the substrate. This is thought to be due to volatilization smoothly.

Examples of the organic solvent having a boiling point of 243 ° C. to 275 ° C. and a vapor pressure of 0.010 Pa to 4.0 Pa at 25 ° C. include, for example, compounds having a hydroxyl group, an ester bond and / or an ether structure. As a compound having a hydroxyl group, C _{8 to} C ₁₄ glycol ethers such as diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monoethyl hexyl ether, nonan-1-ol, dodecane-1-ol, tetradecane-1-ol, and the like. C ₉ -C ₁₄ acyclic aliphatic monoalcohols such as all, C ₅ -C ₇ straight chain aliphatic dialcohols such as pentanediol, hexanediol and heptanediol, 2-ethyl-1,3 -Branched chains such as hexanediol and 2,5-dimethyl-2,5-hexanediol And acyclic C ₆ -C ₉ aliphatic dialcohols having the formula: In addition, examples of the compound having no hydroxyl group include esters such as diethylene glycol monobutyl ether acetate and esters of the above glycol ethers with acrylic acid or methacrylic acid. These compounds may be used alone or in combination of two or more.

  The blending ratio of the organic solvent having a boiling point of 243 ° C. to 275 ° C. and a vapor pressure of 25 ° C. of 0.010 Pa to 4.0 Pa can be selected as appropriate. For example, the lower limit value provides good paste properties. From the viewpoint, it is preferable that 4.0% by mass is contained in the metal bonding material, and 5.0% by mass is particularly preferable. On the other hand, the upper limit of the blending ratio is preferably 10% by mass and particularly preferably 8.0% by mass from the viewpoint of ensuring good dispensing properties.

(C) Fluorine-based dispersant By blending a fluorine-based dispersant, it is possible to prevent separation of the metal particles and the organic solvent in the metal bonding material without impairing the low-temperature sinterability. It is possible to suppress clogging of the metal bonding material and uneven application amount.

  Although it is not particularly limited as long as it is a fluorine-based dispersant, the separation of the metal particles and the organic solvent is surely prevented, and clogging in the nozzle is prevented even with a nozzle having a nozzle diameter of 100 to 200 μm such as a dispenser. In addition, since the coating amount of the metal particles can be made uniform even with a minute supply amount, the following general formula (I)

(Wherein R ¹ , R ² , R ³ and R ⁴ each independently represents F, CF ₃ , CF═CF—CF ₃ , or C ₃ F ₇ ); A compound having a main skeleton of an oligomer of a compound represented by formula (I) or an oligomer of a compound represented by general formula (I) is preferred, and the compound represented by general formula (I) is hexafluoro Propene or hexafluoropropene trimer is particularly preferred. The “compound oligomer represented by the general formula (I)” means a polymer in which 2 to 100 compounds represented by the general formula (I) are bonded. These compounds may be used alone or in combination of two or more.

  The mixing ratio of the dispersing agent can be selected as appropriate. For example, the lower limit value is 0.3% by mass in the metal bonding material from the viewpoint of suppressing clogging of the metal bonding material and uneven application amount. It is preferably 0.4% by mass. On the other hand, the upper limit of the blending ratio is preferably 2.0% by mass, and particularly preferably 1.0% by mass from the viewpoint of preventing deterioration of characteristics due to excessive dispersant.

  In the metal bonding material of the present invention, a conventional additive may be appropriately blended depending on the application. Examples of the additive include a gloss imparting agent, a metal corrosion inhibitor, a stabilizer, a fluidity improver, a thickener, a viscosity modifier, a moisturizer, an antifoaming agent, a disinfectant, and a filler. . These additives may be used alone or in combination of two or more.

  Next, the manufacturing method of the metal joining material of this invention is demonstrated. The method for producing the metal bonding material of the present invention is not particularly limited. For example, after blending the above components (A) to (C) and other components at a predetermined ratio as necessary, a three-roll roll at room temperature. And kneading or mixing with a kneading means such as a ball mill or a sand mill, or a stirring means such as a super mixer or a planetary mixer.

  Next, application examples of the metal bonding material of the present invention will be described. The metal bonding material of the present invention can be widely used as a material for metal bonding between parts. For example, a high-brightness LED that is required to be mounted at a low temperature of 200 ° C. or lower and requires fine bonding is mounted on a substrate. It can be used as a conductive bonding material for electrically and physically bonding electronic components to a wiring board, such as a material for bonding or a power device to a substrate.

  Next, usage examples of the metal bonding material of the present invention will be described. When the metal bonding material of the present invention is used as a conductive bonding material, for example, a predetermined amount of the metal bonding material of the present invention is applied to a position where an electronic component (semiconductor, etc.) on the substrate is bonded. After placing the electronic component on the material, the electronic component is bonded onto the substrate by baking. The method for applying the metal bonding material is not particularly limited, and examples thereof include a screen printing method, a dispenser method, and an ink jet method. The application amount of the metal bonding material can be selected as appropriate, and for example, it is applied with a thickness of 1 to 20 μm and a width of 100 to 1000 μm. The firing temperature is not particularly limited as long as the metal particles are fused to each other and sintered. For example, the metal particles include metal particles having an average primary particle diameter of nano-order, and the metal species is copper. Or in the case of silver, it is 180-230 degreeC, Preferably it is 190-210 degreeC. Moreover, baking time can be selected suitably and is 30 to 120 minutes, for example.

  Next, the metal bonding material of the present invention will be described in more detail using examples. However, the metal bonding material of the present invention is not limited to the embodiments shown below.

Examples 1-5, Comparative Examples 1-6
Each component shown in the following Table 1 is blended at a blending ratio shown in the following Table 1, mixed and dispersed by three rolls, and used in Examples 1 to 5 and Comparative Examples 1 to 6 in a paste-like metal joint. The material was prepared. And the prepared metal joining material was apply | coated to the board | substrate as follows, and the test piece was produced. In addition, the numerical value of the mixture ratio in Table 1 shows a mass part, and the "-" part of a mixture ratio means 0 mass part.

Firing conditions Firing: 200 ° C., 60 min, heating rate 0.8 ° C./min
The substrate surface temperature was baked with the reflow simulator “SMT Scope SK-5000” manufactured by Sanyo Seiko under the temperature condition of the profile shown in FIG.

Evaluation (1) Volume resistivity On the slide glass, the paste of the metal bonding material prepared as described above was applied in the form of a thin film by screen printing on an area of 5 cm × 1 cm using a 50 μm-thick metal mask, and the above firing was performed. The thin film was fired under the conditions, and the obtained fired thin film was subjected to a four-probe method according to JIS K 7194, and “Lorestar GP” manufactured by Mitsubishi Chemical Analytech Co., Ltd. Was measured.

(2) Joint shear strength Using a Nordson EFD dispenser device “DISPENSER ULTIMUS V 100PSI” on a 10 mm × 10 mm × 1 mm thick Au / Ni plated Cu substrate degreased with ethyl acetate, the diameter is 150 to 250 μm, and the mass is 8 A metal bonding material was applied (discharged) to ˜12 μg, and a 1 mm × 1 mm Au / Ni plated Si dummy chip was mounted using a chip mounter “YV100Xg” manufactured by YAMAHA. Next, after firing under the above firing conditions, the shear strength was measured at a rate of 83.3 μm / sec (5 mm / min) using a bond tester “DAGE4000” manufactured by Nordson DAGE.
The results were evaluated in three stages: ◯: chip shear strength of 40 MPa or more, Δ: chip shear strength of 20 MPa or more and less than 40 MPa, and X: chip shear strength of less than 20 MPa.

(3) Bonding shear strength after drying in the air (drying property)
After applying (discharging) the metal bonding material in (2) above and before mounting the dummy chip, it is left for 1 hour in an environment of 25 ° C. and 55% humidity, and then the same process as in (2) above Then, the shear strength was measured in the same manner as in the above (2) for the sample that was mounted with a dummy chip and fired.
The results were evaluated in three stages: ◯: chip shear strength of 40 MPa or more, Δ: chip shear strength of 20 MPa or more and less than 40 MPa, and X: chip shear strength of less than 20 MPa.

(4) Separability About 2 g of metal bonding material was measured in a 10 cc glass bottle, centrifuged at 2000 rpm for 1 min, and it was visually confirmed whether solid-liquid separation had occurred.
The results are as follows: ○: no liquid floating is observed, no separation occurs, Δ: liquid is floating on the surface, x: liquid is separated so that the liquid that floats when it is tilted 3 Rated by stage.

(5) Continuous discharge (number of dots)
The Nordic EFD Air Dispenser “ULTIMUS” uses a 10cc syringe equipped with a precision nozzle of φ0.15mm to continuously discharge metal bonding material onto a flat glass slide and measure the number of points until just before clogging occurs. did.

(6) Solid-liquid separation during continuous discharge During the test of (5) above, it was visually confirmed whether solid-liquid separation of the metal bonding material was confirmed in the 10 cc syringe.
The results were evaluated in two stages: ○: solid-liquid separation not observed, x: solid-liquid separation.

  Each evaluation result about Examples 1-5 and Comparative Examples 1-6 is shown in the following Table 1. For reference, the boiling points of the organic solvents used in the examples and the vapor pressure at 25 ° C. are shown in Table 2 below.

  As shown in Tables 1 and 2, in Examples 1 to 5 using a fluorine-based dispersant, the value of volume resistivity is reduced to 5.0 Ω · cm or less, that is, without continuous loss without impairing conductivity. The solid-liquid separation can be suppressed, and the solid-liquid separation can be prevented from occurring in the metal bonding material even under severe centrifugal conditions. Further, in Examples 1 to 5 using a fluorine-based dispersant, clogging in the nozzle does not occur up to 10000 points even when the nozzle is continuously discharged with a small nozzle diameter of 0.15 mm, The clogging could be suppressed. Furthermore, in Examples 1 to 5 in which solid-liquid separation could be suppressed, both the joint shear strength and the joint shear strength after being left in the atmosphere were as good as 40 MPa or more, and even after firing immediately after coating, firing after the passage of time. However, in both cases, it was possible to form a joint having excellent mechanical strength.

  From Example 1 and Example 3, when a glycol ether system having a boiling point of 243 ° C. to 272 ° C. and a vapor pressure of 25 ° C. in the range of 0.013 Pa to 3.9 Pa is used as the organic solvent, the conductivity is increased. There was a tendency to improve.

  On the other hand, from Comparative Examples 1 to 5, if a dispersant other than the fluorine-based dispersant is used or a dispersant is not used, solid-liquid separation of the metal bonding material at the time of continuous discharge cannot be suppressed, and the metal bonding material even under centrifugal conditions Solid-liquid separation occurred. Further, in Comparative Examples 1 to 5, when the nozzles were continuously discharged at a minute nozzle diameter of 0.15 mm, the nozzles were clogged at 6000 points or less. Further, when a sorbitol-based dispersant is used from Comparative Example 6, it is possible to prevent solid-liquid separation from occurring even during continuous discharge or under centrifugal conditions, and even when discharged continuously with a very small nozzle diameter of 0.15 mm. Although clogging in the nozzle did not occur up to 10,000 points, both the joint shear strength and the joint shear strength after standing in the air decreased to less than 20 MPa, and the joint strength was not obtained.

  Since the metal bonding material of the present invention is excellent in the electrical conductivity of the bonded portion and the bonding strength after sintering, it is widely used as a bonding agent for intermetallic bonding, for example, mounting of semiconductor components such as LED elements and power devices on a substrate. In addition, the metal bonding material of the present invention can prevent solid-liquid separation and suppress discharge failure even during a small amount of discharge. Can be used in the field of high-brightness LED devices.

Claims (8)

A metal bonding material containing (A) metal particles, (B) a solvent composed of an organic solvent, and (C) a fluorine-based dispersant,
The (A) metal particles are (A1) first metal particles having an average primary particle size distribution in a range of 100 nm to 6000 nm and (A2) a particle size distribution of an average primary particle size in a range of 0.5 μm to 10 μm. The second metal particles in
(B) The metal joining material containing the organic solvent whose solvent consisting of the organic solvent has a boiling point of 243 ° C. to 275 ° C. and a vapor pressure of 0.010 Pa to 4.0 Pa at 25 ° C. The (C) fluorine-based dispersant is represented by the following general formula (I)

(Wherein R ¹ , R ² , R ³ and R ⁴ each independently represents F, CF ₃ , CF═CF—CF ₃ , or C ₃ F ₇ ), the above general formula The metal bonding material according to claim 1, which is a compound having a main skeleton of an oligomer of a compound represented by the formula (I) or an oligomer of a compound represented by the general formula (I).   The metal bonding material according to claim 2, wherein the compound represented by the general formula (I) is hexafluoropropene or hexafluoropropene trimer.   The metal bonding material according to claim 1, which is used for a dispenser.   The metal bonding material according to claim 1, wherein the (A1) first metal particles and the (A2) second metal particles are silver, a silver alloy, or copper coated with silver or a silver alloy.   The metal bonding material according to claim 1 or 5, wherein (A1) mass of the first metal particles: (A2) mass of the second metal particles is 3: 7 to 7: 3. A predetermined amount of the metal bonding material according to any one of claims 1 to 6 is applied to a position where the electronic component on the substrate is bonded, and after placing the electronic component on the applied metal bonding material, and sintering treatment, a method of manufacturing an electronic component joined body, which comprises mounting the electronic component on the substrate. The method of manufacturing an electronic component assembly according to claim 7, wherein the electronic component is an LED element or a power device.

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