JP4489899B2 - Method for manufacturing double-sided circuit board for multilayer printed wiring board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a multilayer printed wiring board.Face turnThe present invention relates to a method for manufacturing a road substrate.
[0002]
[Prior art]
Recently, a multilayer printed wiring board having an interstitial via-hole structure (hereinafter referred to as “IVH structure”) that can easily cope with high-density wiring in response to demands for miniaturization, light weight, high speed, and high functionality of electronic devices. Proposed.
The multilayer printed wiring board having the IVH structure is a structure in which a plurality of circuit boards are stacked, and a via hole (believe electrically connecting between inner layer conductor circuits or between an inner layer conductor circuit and an outer layer conductor circuit). Via holes or blind via holes). Therefore, such a multilayer printed wiring board having an IVH structure does not require a special region for forming a through hole, and each interlayer connection can be made only with a minute via hole. High density and high speed signal propagation can be easily realized.
[0003]
[Problems to be solved by the invention]
When manufacturing the multilayer printed wiring board, a plurality of circuit boards are manufactured in advance, and they are laminated and integrated by a heat press or the like, but in order to efficiently provide a large number of via holes in each circuit board, It has been proposed to provide an opening for forming a via hole by intermittently irradiating a laser on the surface of an insulating substrate.
However, since resin residues are likely to remain in the openings formed by laser processing, it is necessary to perform a desmear process for cleaning the openings from the viewpoint of securing connection reliability.
[0004]
As such a conventional desmear treatment method, a method using potassium permanganate or chromic acid (wet process) or a method using plasma or UV ozone (dry desmear) is known. All of the desmear treatment methods have the following problems.
[0005]
That is, when the former wet process method is adopted when manufacturing a circuit board for a multilayer printed wiring board, a B-stage resin adhesive provided on the surface of each circuit board is used for the purpose of bonding a plurality of circuit boards to each other. When the latter dry desmear method is used, the entire circuit board is heated in the plasma, so the resin adhesive softens. Thus, the shape of the non-through hole is distorted, and the PET film attached on the adhesive layer for protecting the resin adhesive layer is softened and easily peeled off from the circuit board.
[0006]
The present invention has been made in view of the above problems of the conventional desmear treatment method, and its main purpose is that the adhesive layer and the PET film provided on the laminated circuit board are not thermally damaged. Another object of the present invention is to propose a method of manufacturing a circuit board for a multilayer printed wiring board capable of efficiently forming a via hole of uniform quality.
[0007]
[Means for Solving the Problems]
  As a result of diligent research to realize the above-mentioned object, the inventors formed a fine non-through hole for forming a via hole by carbon dioxide laser irradiation, and then irradiated with an ultraviolet laser or an excimer laser in the non-through hole. It has been found that the resin residue remaining in the non-through holes can be effectively cleaned by carrying out the process, and the present inventors have arrived at the present invention having the following contents as a gist configuration.
[0008]
IeFor the multilayer printed wiring board of the present inventionBoth sidesThe circuit board manufacturing method is
  For multilayer printed wiring boards having a conductive circuit pattern on both surfaces of a hard insulating substrate, and via holes are formed in the insulating substrate to electrically connect the conductor circuits.Both sidesIn manufacturing a circuit board, during the manufacturing process, at least the following steps (1) to (5):
(1) On the other surface of the insulating base material on which copper foil is pasted on one side,A semi-cured adhesive layer is formed on the adhesive layer.After sticking the protective film, irradiate the carbon dioxide laser from the protective film,Through the adhesive layer and the protective filmForming a non-through hole reaching the copper foil;
(2) A step of desmearing the resin residue remaining in the non-through hole by irradiating the non-through hole with an ultraviolet laser or an excimer laser,
(3) A step of filling the desmeared non-through holes with a conductive paste using the protective film as a printing mask,
(4) After peeling off the protective film from the surface of the insulating substrate, the conductive paste exposed from the other surface of the insulating substrate is covered with a copper foil,Curing the semi-cured adhesive layer;Forming a filled via hole for electrically connecting the conductive paste and the copper foil;
(5) A step of etching the copper foil attached to the insulating base material to form a conductor circuit on both surfaces of the insulating base material,
  It is characterized by including.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the method for manufacturing a circuit board according to the present invention, a non-through hole is provided in a hard insulating base material constituting the circuit board by carbon dioxide laser irradiation, and a resin residue remaining in the non-through hole is irradiated with an ultraviolet laser or an excimer laser. After the desmear treatment is performed, the filling via hole is formed by filling and curing the conductive paste in the desmeared non-through hole.
[0011]
  Ie, Paste copper foil on one side of hard insulating base material, and on the other side of the insulating base materialIn addition to forming a semi-cured adhesive layer and sticking a protective film on the adhesive layer, carbon dioxide laser irradiation is performed from above the protective film to penetrate the adhesive layer and the protective film.Non-through hole reaching copper foilShapeThe non-through hole is irradiated with an ultraviolet laser or an excimer laser to desmear the resin residue remaining in the non-through hole, and the desmeared non-through hole is filled with a conductive paste. Cover the conductive paste exposed from the other side of the insulating substrate and heat-press the copper foilTo cure the semi-cured adhesive layer,After forming the filled via hole that electrically connects the conductive paste and the copper foil, the conductive foil pattern is etched on both sides of the insulating base material by etching the copper foil pasted on both sides of the insulating base material. It is characterized by manufacturing a double-sided circuit board having the same.
[0012]
According to such a configuration, by performing carbon dioxide gas laser irradiation on the surface of the insulating substrate, a non-through hole for forming a via hole can be formed quickly and accurately, and an ultraviolet laser or a laser beam can be formed in the non-through hole. By performing the excimer laser irradiation, the resin residue that may remain in the non-through hole due to the carbon dioxide laser irradiation can be accurately processed without heating the entire insulating substrate. Uniform quality via holes can be efficiently formed without causing thermal damage to the resin adhesive layer or PET film provided on the material.
[0013]
The insulating base material used in the circuit board manufacturing method of the present invention is not a semi-cured prepreg as in the prior art, but a hard insulating base material formed from a completely cured resin material. By using a simple material, the final thickness of the insulating substrate due to the pressing pressure is eliminated when the copper foil is crimped onto the insulating substrate with a hot press, minimizing misalignment of via holes. By suppressing, the via land diameter can be reduced. Therefore, the wiring pitch can be reduced and the wiring density can be improved. In addition, since the thickness of the substrate can be kept substantially constant, when the non-through hole for forming the filled via hole is formed by laser processing, the laser irradiation conditions can be easily set.
[0014]
As the insulating substrate, a glass cloth epoxy substrate having a thickness of 20 to 600 μm is preferably used. The reason is that when the thickness is less than 20 μm, the strength is reduced and handling becomes difficult, and the reliability with respect to the electrical insulation is reduced. When the thickness exceeds 600 μm, formation of fine via holes and filling of conductive paste are performed. This is because the thickness of the substrate itself is increased.
[0015]
It is desirable that a copper foil is attached to one surface of the insulating base material via an appropriate resin adhesive, and a conductor circuit pattern is formed in advance by an etching process. Instead of sticking the copper foil on such an insulating substrate, a single-sided copper clad laminate in which the copper foil is previously stuck on the insulating substrate can also be used.
As for the thickness of the said copper foil, 5-18 micrometers is desirable. The reason is that when the thickness is less than 5 μm, a hole is also formed in this copper foil when forming a through hole for forming a via hole in an insulating substrate using laser processing as will be described later. On the contrary, if the thickness is larger than 18 μm, a conductor circuit pattern having a fine line width cannot be formed.
[0016]
When producing a double-sided circuit board according to the present invention, first, a protective film is adhered to the surface opposite to the surface of the insulating base material to which the copper foil is attached via a semi-cured resin adhesive layer. Then, carbon dioxide laser irradiation is performed from above the protective film to form a non-through hole that reaches the copper foil on which the conductor circuit pattern is to be formed. After conducting the etching process to form a conductor circuit pattern, a protective film is adhered to the surface opposite to the surface of the insulating substrate on which the conductor circuit pattern is formed via a semi-cured resin adhesive layer. It is desirable to form a non-through hole by irradiating a carbon dioxide laser from the protective film.
As will be described later, the resin adhesive is for bonding a copper foil to the surface of an insulating substrate. For example, the resin adhesive is formed from a bisphenol A type epoxy resin, and the thickness is preferably in the range of 10 to 50 μm.
[0017]
In addition, the protective film affixed on the resin adhesive layer also functions as a printing mask that fills the conductive paste into the non-through holes reaching the copper foil from the surface of the insulating base material. After the non-through hole is formed, the adhesive layer is peeled off from the adhesive layer. This protective film is preferably formed from, for example, a PET film having a pressure-sensitive adhesive layer thickness of 1 to 20 μm and a film thickness of 10 to 50 μm.
The reason is that, depending on the thickness of the PET film, the amount of protrusion of the conductive paste from the surface of the insulating substrate is determined. Therefore, if the thickness is less than 10 μm, the amount of protrusion is too small and connection failure tends to occur. If the thickness exceeds 50 μm, the melted conductive paste spreads too much at the connection interface, so that a conductor circuit pattern having a fine line width cannot be formed.
[0018]
The diameter (via diameter) at the opening end of the non-through hole formed on the glass epoxy substrate having the thickness in the above range is desirably in the range of 50 to 250 μm, in order to form such a non-through hole. The irradiation conditions of the carbon dioxide laser are desirably such that the pulse energy is 0.5 to 100 mJ, the pulse width is 1 to 100 μs, the pulse interval is 0.5 ms or more, and the number of shots is 3 to 50.
The reason why the via diameter is preferably in the range of 50 to 250 μm is that if it is less than 50 μm, it becomes difficult to fill the conductive paste in the non-through holes and the connection reliability is lowered. This is because densification becomes difficult.
[0019]
Furthermore, before filling the non-through hole with the conductive paste, it is essential from the viewpoint of securing connection reliability to perform a desmear process for removing the resin residue remaining on the inner wall surface of the non-through hole. This desmear treatment is preferably performed by irradiating the non-through hole with an ultraviolet laser or an excimer laser.
[0020]
The conditions for performing the desmear process are as follows:
(1) In the case of ultraviolet laser irradiation using YAG third harmonic, the transmission frequency is 3 to 15 KHz, and the pulse energy density is 0.1 to 5 mJ / cm.²It is desirable that the number of shots is 10 to 30.
(2) In the case of excimer laser irradiation, the energy density is 0.5-1 J / cm.²The number of shots is desirably 20 to 100.
[0021]
Further, when the laser beam is irradiated toward the non-through hole, when the beam diameter is made larger than the via diameter, the beam is irradiated to the entire region including the side surface and the bottom surface of the non-through hole. Although it is suitable for cleaning the remaining resin residue over time, the resin adhesive layer is also irradiated with laser through the PET film, so that the range of laser irradiation conditions is limited.
[0022]
On the other hand, when the beam diameter is smaller than the via diameter, the beam is concentrated and irradiated on the bottom surface of the non-through hole, so there is no thermal effect on the periphery of the opening end of the non-through hole, and the beam remains on the bottom surface. It is suitable for cleaning the resin residue. In this case, depending on the accuracy of alignment, it is not suitable for cleaning the resin residue over the entire non-through hole.
[0023]
According to the desmear treatment, it is possible to effectively remove the resin residue in the non-through holes by preventing the positional deviation of the opening due to the softening of the resin adhesive and the peeling of the PET film.
[0024]
After the desmear treatment for the non-through holes of the insulating base material, the conductive paste is filled into the non-through holes. The filling of the conductive paste is preferably performed by a vacuum pressure defoaming method, which is suitable for reducing the manufacturing cost and improving the yield.
As the conductive paste, a conductive paste containing at least one metal particle selected from silver, copper, gold, nickel, and solder can be used.
[0025]
In addition, as the metal particle, a metal particle whose surface is coated with a different metal can be used. Specifically, the metal particle which coat | covered the noble metal chosen from gold | metal | money and silver on the surface of a copper particle can be used.
As the conductive paste, an organic conductive paste in which metal particles are added with a thermosetting resin such as an epoxy resin or a phenol resin, or a thermoplastic resin such as polyphenylene sulfide (PPS) can be used.
Such filling of the conductive paste into the non-through holes can be performed by any method such as a printing method using a metal mask or a method using a squeegee or a dispenser.
[0026]
The decompression condition and the pressure to be applied are determined according to the viscosity of the conductive paste, the type and amount of the solvent, the via diameter and the depth, and the pressure application to the conductive paste under such an appropriate condition is For example, it can be performed using a known press apparatus or a vacuum laminator for forming a dry film.
Furthermore, if necessary, the time for eliminating bubbles can be shortened by heating the conductive paste filled in the non-through holes to increase the fluidity thereof.
[0027]
When manufacturing a single-sided circuit board for multilayer printed wiring boards, after filling the non-through holes of the insulating base material with conductive paste, the protective film is peeled off from the resin adhesive layer, resulting in a semi-cured state. The exposed resin adhesive is exposed on the surface of the insulating substrate. A circuit board in which such a conductor circuit pattern is formed on one side of an insulating base material is suitable as a circuit board for laminating, and a predetermined amount of conductive paste filled in via holes is exposed from the substrate surface. It is preferable to form a protruding conductor for connection.
[0028]
Further, when manufacturing a double-sided circuit board, a semi-cured resin adhesive remaining on the insulating substrate by heating press after filling the non-through holes of the insulating substrate with a conductive paste Copper foil is affixed through the layers.
The thickness of the copper foil is desirably 5 to 18 μm, and the heating press is performed under an appropriate temperature and pressure. More preferably, the conventional prepreg is used because the copper foil can be firmly bonded to the insulating substrate by performing only heat-pressing under reduced pressure and curing only the semi-cured resin adhesive layer. Manufacturing time is shortened compared to conventional circuit boards.
[0029]
As described above, the copper foil attached to one surface of the insulating base material is subjected to an appropriate etching treatment together with the copper foil previously attached to the other surface of the insulating base material, Desired conductor circuit patterns are formed on both sides.
[0030]
Thus, the circuit board in which the conductor circuit pattern is formed on both surfaces of the insulating base material is suitable as a core board when forming the multilayer printed wiring board, but on the board surface corresponding to each via hole, In a preferred embodiment, the via land (pad) as a part of the conductor circuit pattern is formed in a diameter of 50 to 250 μm.
[0031]
Hereinafter, an example of a method for producing a circuit board for a multilayer printed wiring board according to the present invention will be specifically described with reference to FIG.
{Circle around (1)} In manufacturing a circuit board for a multilayer printed wiring board according to the present invention, a material in which a copper foil 12 is stuck on one side of an insulating substrate 10 is used as a starting material (see FIG. 1 (a)).
The insulating base material 10 is, for example, a glass cloth epoxy resin base material, a glass cloth bismaleimide triazine resin base material, a glass cloth polyphenylene ether resin base material, an aramid nonwoven fabric-epoxy resin base material, an aramid nonwoven fabric-polyimide resin base material. Although a rigid (hard) laminate substrate may be used, a glass cloth epoxy resin substrate is most preferred.
[0032]
As for the thickness of the said insulating base material 10, 20-600 micrometers is desirable. The reason is that when the thickness is less than 20 μm, the strength is reduced and handling becomes difficult, and the reliability with respect to the electrical insulation is reduced. When the thickness exceeds 600 μm, formation of fine via holes and filling of conductive paste are performed. This is because the thickness of the substrate itself is increased.
[0033]
Moreover, as for the thickness of the copper foil 12, 5-18 micrometers is desirable. The reason is that, when laser processing as described later is used to form a non-through hole for forming a via hole in an insulating base material, if it is too thin, it penetrates. This is because it is difficult to form a conductor circuit pattern having a fine line width.
[0034]
As the insulating base material 10 and the copper foil 12, in particular, a single-sided copper-clad laminate obtained by laminating an epoxy resin into a glass cloth to form a B stage and laminating a copper foil and heating and pressing. It is preferable to use a plate. The reason is that the position of the wiring pattern and the via hole is not shifted during handling after the copper foil 12 is etched as will be described later, and the positional accuracy is excellent.
[0035]
(2) Next, when manufacturing a double-sided circuit board, a semi-cured adhesive, that is, a B stage, is formed on the surface opposite to the surface on which the copper foil 12 of the insulating base material 10 is attached. The adhesive layer 14 is provided, and a protective film 16 is attached on the adhesive layer 14 (see FIG. 1B).
[0036]
The adhesive 14 is for bonding a copper foil on which a conductor circuit pattern is formed. For example, an epoxy resin varnish is used, and the layer thickness is preferably in the range of 10 to 50 μm.
This protective film 16 is used as a mask for printing a conductive paste described later, and for example, a polyethylene terephthalate (PET) film having an adhesive layer on the surface can be used.
The PET film 16 is such that the pressure-sensitive adhesive layer has a thickness of 1 to 20 μm and the film itself has a thickness of 10 to 50 μm.
[0037]
(3) Next, carbon dioxide laser irradiation is performed from above the PET film 16 affixed on the insulating base material 10, penetrating the PET film 16 and the adhesive layer 14, and copper foil from the surface of the insulating base material 10. A non-through hole 18 reaching 12 (or a conductor circuit pattern) is formed (see FIG. 1C).
This laser processing is performed by a pulse oscillation type carbon dioxide laser processing apparatus. The processing conditions are as follows: the pulse energy is 0.5 to 100 mJ, the pulse width is 1 to 100 μs, the pulse interval is 0.5 ms or more, and the number of shots is 3 It is desirable to be within the range of ˜50.
The via diameter that can be formed under such processing conditions is preferably 50 to 250 μm.
[0038]
(4) A desmear process is performed to remove the resin residue remaining on the side and bottom surfaces of the non-through holes 18 formed in the step (3). This desmear treatment is preferably performed by irradiating the non-through hole with an ultraviolet laser or an excimer laser from the viewpoint of securing connection reliability.
[0039]
The laser irradiation conditions when this desmear treatment is performed by, for example, ultraviolet laser irradiation using the YAG third harmonic are as follows: the transmission frequency is 3 to 15 KHz, and the pulse energy is 0.1 to 5 mJ / cm.²A range of 10 to 30 shots is desirable.
[0040]
(5) Next, the conductive paste 20 is filled into the non-through-hole 18 subjected to desmearing treatment using the PET film 16 as a printing mask (see FIG. 1 (d)).
Thereafter, the entire substrate is fixed on a stage in a vacuum chamber (not shown), and 1 × 10³~ 5x10³Under a reduced pressure of Pa, the exposed side surface of the conductive paste 20 of the insulating substrate 10 is pressurized for several minutes by an appropriate press device (not shown).
[0041]
(6) Thereafter, after the PET film 16 is peeled off from the surface of the adhesive layer 14 (see FIG. 1 (e)), the copper foil 24 is heated and pressed on one side of the insulating substrate 10 via the adhesive layer 14 The adhesive layer 14 is cured by pressure bonding (see FIG. 1 (f)). At that time, the copper foil 24 is bonded to the insulating substrate 10 through the cured adhesive layer 14, and the conductive paste 20 and the copper foil 24 are electrically connected. As for the thickness of this copper foil 24, 5-18 micrometers is desirable.
[0042]
(7) Next, an etching protective film is applied to each of the copper foils 12 and 24 applied to both surfaces of the insulating base material 10 and is shown with a mask having a predetermined circuit pattern. Conductor circuits 26 and 28 (including via lands) are formed (see FIG. 1 (g)).
[0043]
In this processing step, first, a photosensitive dry film resist is applied to the surfaces of the copper foils 12 and 24, and then an etching resist is formed by exposing and developing along a predetermined circuit pattern. The metal layer is etched to form conductor circuit patterns 26 and 28 including via lands.
The etching solution is preferably at least one aqueous solution selected from an aqueous solution of sulfuric acid monohydrogen peroxide, persulfate, cupric chloride, and ferric chloride.
[0044]
As a pretreatment for etching the copper foils 12 and 24 to form the conductor circuits 26 and 28, in order to facilitate the formation of a fine pattern, the entire surface of the copper foil is etched in advance to a thickness of 1 to 10 μm. Preferably, the thickness can be reduced to about 2 to 8 μm.
The via land as a part of the conductor circuit has an inner diameter that is substantially the same as the via hole diameter, but the outer diameter is preferably in the range of 50 to 250 μm.
[0045]
(8) Next, the surfaces of the conductor circuits 26 and 28 formed in the step (7) are roughened (the display of the roughened layer is omitted) to form the double-sided circuit board 30 for the core.
This roughening treatment is to improve adhesion with the adhesive layer and prevent peeling (delamination) when multilayering.
Examples of the roughening treatment method include soft etching treatment, blackening (oxidation) one-reduction treatment, formation of needle-like alloy plating made of copper-nickel-phosphorus (made by Sugawara Eugleite: trade name Interplate), manufactured by MEC There is surface roughening with an etchant named “MEC Etch Bond”.
[0046]
In this embodiment, the roughening layer is preferably formed using an etching solution. For example, the surface of the conductor circuit is etched using an etching solution from a mixed aqueous solution of a cupric complex and an organic acid. It can be formed by processing. Such an etching solution can dissolve the copper conductor circuit pattern under oxygen coexistence conditions such as spraying and bubbling, and the reaction is assumed to proceed as follows.
Cu + Cu (II) A_n  → 2Cu (I) A_{n / 2}
2Cu (I) A_{n / 2}  + N / 4O₂  + NAH (Aeration)
→ 2Cu (II) A_n  + N / 2H₂O
In the formula, A represents a complexing agent (acts as a chelating agent), and n represents a coordination number.
[0047]
As shown in the above formula, the generated cuprous complex is dissolved by the action of an acid, is combined with oxygen to form a cupric complex, and again contributes to the oxidation of copper. The cupric complex used in the present invention is preferably an azole cupric complex. The etching solution comprising the organic acid-cupric complex can be prepared by dissolving a cupric complex of an azole and an organic acid (halogen ions as required) in water.
Such an etching solution is formed, for example, from an aqueous solution in which 10 parts by weight of imidazole copper (II) complex, 7 parts by weight of glycolic acid, and 5 parts by weight of potassium chloride are mixed.
The double-sided circuit board for a multilayer printed wiring board according to the present invention is manufactured according to the above steps (1) to (8), and is suitable as a core circuit board for the multilayer printed wiring board.
[0048]
Next, a method of manufacturing a single-sided circuit board that is laminated on the front and back surfaces of such a double-sided circuit board will be described with reference to FIG.
(1) First, an etching protective film is pasted on the copper foil 12 stuck on one surface of the insulating base material 10, and is covered with a mask having a predetermined circuit pattern. (Including via land) is formed (see FIG. 2B).
In this processing step, first, a photosensitive dry film resist is applied to the surface of the copper foil 12, and then exposed and developed along a predetermined circuit pattern to form an etching resist. The layer is etched to form a conductor circuit pattern 34 including via lands.
The etching solution is preferably at least one aqueous solution selected from an aqueous solution of sulfuric acid monohydrogen peroxide, persulfate, cupric chloride, and ferric chloride.
As a pretreatment for forming the conductor circuit 34 by etching the copper foil 12, the entire surface of the copper foil is etched in advance to have a thickness of 1 to 10 μm, more preferably 2 to 2 to facilitate the formation of a fine pattern. The thickness can be reduced to about 8 μm.
[0049]
(2) After the conductor circuit 34 is formed on one side of the insulating substrate 10, the processing according to the steps (2) to (5) of the double-sided circuit board is performed (FIGS. 2 (c) to 2 (e). After that, when the PET film 16 is peeled off from the surface of the adhesive layer 14, a single-sided circuit board 40 having a conductor circuit 34 on one side of the insulating substrate 10 is manufactured (see FIG. 2 (f)). .
[0050]
In the state where the PET film 16 is peeled off, the conductive paste 20 filled in the non-through holes 18 is obtained by adding approximately the thickness of the adhesive layer 14 and the thickness of the PET film 16 from the surface of the insulating substrate 10. The height of the protruding portion 36 (hereinafter referred to as “protruding conductor”) is preferably in the range of 5 to 30 μm.
The reason is that if the thickness is less than 5 μm, poor connection is likely to occur, and if the thickness exceeds 30 μm, the resistance value becomes high, and when the protruding conductors 36 are thermally deformed in the hot press process, they extend too much along the surface of the insulating substrate. This is because a fine pattern cannot be formed.
[0051]
Further, it is desirable that the protruding conductor 36 formed from the conductive paste 20 is in a pre-cured state. The reason is that the protruding conductor 36 is hard even in a semi-cured state, and its tip protrudes from the adhesive layer 14. Therefore, before the adhesive layer 14 is softened at the stage of the lamination press, another circuit board is laminated. This is because electrical contact with the conductor circuit (conductor pad) is possible. In addition to deformation during hot pressing, the contact area increases and the conduction resistance can be lowered, as well as variations in the height of the protruding conductors 36 can be corrected.
[0052]
As described above, the single-sided circuit having the conductor circuit 34 on one surface of the insulating base material 10 and the protruding conductor 36 formed by exposing a part of the conductive paste on the other surface. The board 40 is laminated on the core circuit board 30 manufactured in advance to be multilayered.
[0053]
FIG. 3 shows that a four-layer board in which three single-sided circuit boards 40, 42 and 44 are laminated on both sides of a core double-sided circuit board 30 has a heating temperature of 150 to 200 ° C. and a pressure of 1 M to 4 MPa. Originally, a multilayer printed wiring board integrated by one press forming is shown.
Thus, by heating simultaneously with pressurization, the adhesive layer 14 of each single-sided circuit board is cured, and strong adhesion is performed between adjacent single-sided circuit boards. Note that a vacuum hot press is preferably used as the hot press.
[0054]
In addition, instead of the adhesive layer 14 formed in advance on the surface of the insulating base material, after each single-sided circuit board is manufactured, in the stage of multilayering, the entire surface on the protruding conductor side of the insulating base material and Alternatively, an adhesive may be applied to the entire surface on the conductor circuit side and formed as an adhesive layer made of an uncured resin in a dried state. The adhesive layer is preferably pre-cured for easy handling, and the thickness is preferably in the range of 5 to 50 μm.
[0055]
In the above-described embodiment, the double-sided circuit board for core and the three-sided single-sided circuit board are used to form a multi-layered structure with four layers.
[0056]
【Example】
Example 1
(1) A single-sided copper-clad laminate obtained by laminating an epoxy resin in a glass cloth to form a B stage and laminating a copper foil and hot pressing was used as a substrate. The thickness of the insulating substrate 10 was 75 μm, and the thickness of the copper foil 12 was 12 μm.
[0057]
(2) An adhesive layer 14 having a thickness of 25 μm made of a B-stage epoxy resin is provided on the surface opposite to the surface on which the copper foil 12 of the insulating base material 10 is pasted, and the adhesive A PET film 16 having a thickness of 11 μm is pasted on the layer 14. The PET film 16 includes a pressure-sensitive adhesive layer having a thickness of 5 μm and a PET film base having a thickness of 6 μm.
[0058]
(3) Next, laser irradiation using a pulse oscillation type carbon dioxide laser oscillator (Mitsubishi Electric 5100U) is performed on the PET film 16 under the following laser processing conditions to form a non-through hole for forming a via hole having a diameter of 100 μm. 18 is formed.
[Laser processing conditions]
Pulse energy 2.0mJ
Pulse width 15μs
Pulse interval 2ms or more
5 shots
[0059]
(4) Further, in order to remove the resin residue remaining on the side surface and the bottom surface of the non-through hole 18, a desmear treatment is performed by performing laser irradiation using an ultraviolet laser oscillator (Mitsubishi Electric GT605LDX) under the following conditions. Was given.
[Ultraviolet laser irradiation conditions]
Oscillation frequency: 5KHz
Pulse energy: 0.3mJ / cm²
Number of shots: 20
Mask aperture: 1.8mm
The diameter of the non-through hole 18 formed by the carbon dioxide laser irradiation, that is, the via diameter is 100 μm (the maximum via bottom diameter is 80 μm), and the diameter on the PET film surface is 120 μm. It processed by the mask imagining method using the mask of.
[0060]
(5) Next, the conductive paste 20 is filled into the through hole 18 using the PET film 16 as a printing mask to form a filled via hole 22 having a diameter of 100 μmφ. At that time, vacuum depressurization is performed under the following conditions.
[Vacuum pressure defoaming conditions]
Degree of vacuum: 2.5 × 10³Pa
Applied pressure: 2 MPa
[0061]
(6) After peeling the PET film 16 from the adhesive layer 14, a copper foil 24 having a thickness of 12 μm is heated and pressed on the adhesive layer 14 under the following conditions.
[Heat press conditions]
Heating temperature: 180 ° C
Heating time: 70 minutes
Pressure: 2MPa
Degree of vacuum: 2.5 × 10³Pa
Thereafter, the copper foils 12 and 24 were appropriately etched to form conductor circuit patterns 26 and 28 (including via lands), and the double-sided circuit board 30 was produced. Finally, the double-sided circuit board 30 was patterned and the via resistance was measured. As a result, a good via resistance value was obtained, and it was confirmed that the resin residue in the non-through hole was sufficiently removed.
[0062]
(Example 2)
A double-sided circuit board was manufactured by carrying out substantially the same treatment as in Example 1 except that the irradiation conditions of the ultraviolet laser in the desmear treatment step (4) of Example 1 were as follows.
[Ultraviolet laser irradiation conditions]
Oscillation frequency: 5KHz
Pulse energy: 0.5mJ / cm²
Number of shots: 15
Mask aperture: 1.8mm
[0063]
(Example 3)
A double-sided circuit board was manufactured by carrying out substantially the same treatment as in Example 1 except that the irradiation conditions of the ultraviolet laser in the desmear treatment step (4) of Example 1 were as follows.
[Ultraviolet laser irradiation conditions]
Oscillation frequency: 5KHz
Pulse energy: 0.8mJ / cm²
Number of shots: 10
Mask aperture: 1.8mm
[0064]
Example 4
After the step (1) of the first embodiment, the copper foil 12 attached to one surface of the insulating base material 10 is subjected to an appropriate etching process to form a conductor circuit 34 (including via land).
(2) Next, substantially the same processing as in the steps (2) to (5) of the first embodiment is performed, and the conductive paste 20 is filled in the inside of the non-through hole 18 and cured, and the via A filled via hole 22 having a diameter of 100 μmφ was formed, and the PET film 16 was peeled from the adhesive layer 14 to produce a single-sided circuit board 40.
[0065]
With respect to each of the double-sided circuit board manufactured according to Examples 1 to 3 and the single-sided circuit board manufactured according to Example 4, the presence or absence of resin residue remaining in the non-through hole, the surface of the insulating base around the non-through hole As a result of observing the presence or absence of thermal damage with a scanning electron microscope (SEM), no resin residue in the non-through holes or thermal damage on the substrate surface was observed in any of the examples. Further, neither peeling of the PET film nor softening of the resin adhesive was observed.
[0066]
【The invention's effect】
As described above, according to the present invention, non-through holes for forming via holes are precisely and efficiently formed by carbon dioxide laser irradiation, and before filling the conductive paste into these non-through holes, Since cleaning in the non-through hole can be performed accurately and effectively by irradiation with an ultraviolet laser or an excimer laser, the resin residue remaining in the non-through hole without causing thermal damage to the PET film or the resin adhesive Can be removed quickly and effectively, and a circuit board for a multilayer printed wiring board having a uniform quality via hole having a stable interlayer connection resistance can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram showing a part of a manufacturing process of a double-sided circuit board for a multilayer printed wiring board according to the present invention.
FIG. 2 is a diagram showing a part of a manufacturing process of a single-sided circuit board for a multilayer printed wiring board according to the present invention.
FIG. 3 is a view showing a four-layer wiring board in which a double-sided circuit board and a single-sided circuit board according to the present invention are laminated.
[Explanation of symbols]
10 Insulating substrate
12 Copper foil
14 Resin adhesive
16 PET film
18 Non-through hole
20 Conductive paste
22 Filled via hole
24 Copper foil
26, 28 conductor circuit
30 Double-sided circuit board for core
34 Conductor circuit
36 Protruding conductor
40, 42, 44 Single-sided circuit board for lamination

Claims (1)

In producing a circuit board for a multilayer printed wiring board having conductor circuits on both surfaces of a hard insulating substrate, and via holes are formed in the insulating substrate to electrically connect the conductor circuits. During the production process, at least the following steps (1) to (5):
(1) A semi-cured adhesive layer is formed on the other surface of the insulating base material with a copper foil attached to one surface, and a protective film is adhered on the adhesive layer, and then the protective film Carbon dioxide laser irradiation from above, forming a non-through hole that reaches the copper foil through the adhesive layer and the protective film ,
(2) A step of desmearing the resin residue remaining in the non-through hole by irradiating the non-through hole with an ultraviolet laser or an excimer laser,
(3) A step of filling the desmeared non-through holes with a conductive paste using the protective film as a printing mask,
(4) After peeling off the protective film from the surface of the insulating base material, the conductive paste exposed from the other surface of the insulating base material is covered with a copper foil, and the semi-cured state is obtained. Curing the adhesive layer and forming a filled via hole for electrically connecting the conductive paste and the copper foil;
(5) A step of etching the copper foil attached to the insulating base material to form a conductor circuit on both surfaces of the insulating base material,
A method for producing a double-sided circuit board for a multilayer printed wiring board, comprising:

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