JP4556261B2 - Additive adhesive for printed wiring boards - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an additive printed circuit board adhesive suitable for high-density wiring.
[0002]
[Prior art]
As is well known, an additive printed wiring board forms a necessary wiring pattern on an adhesive insulating base material by electroless plating.
For example, an adhesive layer containing a plating catalyst is formed on an insulating substrate containing a plating catalyst or the like, and the adhesive layer is formed using dip coating or curtain coating. Next, drying is performed at a temperature of 100 ° C. to 150 ° C. for 10 minutes to 60 minutes to evaporate the solvent contained in the adhesive, and at the same time, the adhesive is temporarily cured. Furthermore, it is cured by heating at a temperature of 140 ° C. to 190 ° C. for 20 minutes to 90 minutes.
Next, the surface other than the circuit formation part is masked with a plating resist, and the adhesive surface of the circuit formation part is selectively used with an oxidizing etching solution such as chromium-sulfuric acid as a pretreatment for improving the adhesion with the electroless plating copper. Chemical roughening.
Thereafter, the substrate is immersed in an electroless plating solution through neutralization and water washing steps, and copper is deposited on the circuit portion to form a wiring pattern.
[0003]
As an adhesive for such an additive method printed wiring board, generally an acrylonitrile butadiene rubber having good adhesion to plated copper is used as a main component, and an epoxy resin is blended in order to ensure electrical characteristics.
Furthermore, an adhesive containing an inorganic filler or the like has been proposed in order to reinforce the adhesive film or increase the unevenness of the adhesive during chemical roughening.
Japanese Patent Publication No. 48-24250, Japanese Patent Publication No. 45-9843, Japanese Patent Publication No. 55-16391, Japanese Patent Publication No. 1-53910, etc. are disclosed as techniques relating to such an adhesive.
[0004]
[Problems to be solved by the invention]
By the way, in recent years, with the downsizing and multi-functionalization of electronic devices, it is necessary to increase the wiring density of printed wiring boards, and the wiring width has been rapidly reduced. Against this background, insulation is becoming an important characteristic for adhesives that support circuit conductors.
For this reason, generally, the blending amount of the acrylonitrile butadiene rubber whose insulation is inferior to that of the epoxy resin or the like is reduced and the blending amount of the epoxy resin is increased. However, in this case, since the epoxy resin whose roughening solution solubility is remarkably lower than that of acrylonitrile butadiene rubber is increased, the roughening unevenness is reduced and the adhesive strength with the plated copper is lowered.
Needless to say, the thinner the wire, the more advantageous the adhesive strength with the plated copper.
An object of this invention is to provide the composition of the adhesive for additive method wiring boards excellent in the adhesive force with plated copper, without impairing insulation.
[0005]
[Means for Solving the Problems]
The present invention relates to the following.
(1) Adhesive is applied to an insulating substrate, the surface of the adhesive is chemically roughened, and the adhesive is used for an additive printed wiring board in which a circuit is formed by electroless plating only at a necessary portion, and is a core-shell type cross-linking An additive adhesive for printed wiring boards, characterized by containing rubber.
(2) The adhesive for an additive method printed wiring board according to claim 1, wherein the core-shell type crosslinked rubber is contained in an amount of 0.5 to 50% by weight based on the total resin content in the adhesive composition. .
(3) The adhesive for an additive method printed wiring board according to claim 1 or 2, wherein the core layer of the core-shell structured crosslinked rubber is a crosslinked polybutadiene and the shell layer is a crosslinked acrylic resin.
(4) The adhesive for an additive method printed wiring board according to claim 1 or 2, wherein the core layer of the core-shell structure crosslinked rubber is a crosslinked polybutadiene and the shell layer is a crosslinked polymethyl methacrylate.
[0006]
The core-shell structure cross-linked rubber used in the present invention has a two-layer or three-layer structure, the core layer is a cross-linked rubber exhibiting rubber elasticity, and any structure can be used as long as the core layer is covered with a cross-linked polymer that does not exhibit rubber elasticity. Something like that. Cross-linked butadiene rubber and cross-linked isoprene rubber are effective for the core layer, and cross-linked polymethyl methacrylate, cross-linked polystyrene and the like are preferable for the shell layer. The average particle diameter of the core-shell structure crosslinked rubber is preferably 1 μm or less. When the average particle diameter is larger than 1 μm, the insulation reliability for the printed wiring board tends to decrease. The addition amount of the core-shell structure crosslinked rubber is preferably 0.5 to 50% by weight with respect to the total amount of the adhesive resin. When the amount is less than 0.5% by weight, the effect of the core-shell structure crosslinked rubber is not seen, and there is a tendency that the heat resistance and the copper adhesion are not improved. There is a tendency that characteristics as an insulating resin for printed wiring boards cannot be obtained.
[0007]
The basic resin composition containing the core-shell structure crosslinked rubber is not particularly limited, and a general resin composition used for an additive method wiring board can be applied. Preferably, in consideration of plating solution resistance, coating film forming property, roughening property, etc., rubber other than core-shell structure crosslinked rubber such as epoxy resin, epoxy resin curing agent, acrylonitrile butadiene rubber, curing accelerator, inorganic filler Etc. is good.
[0008]
The epoxy resin used in the present invention may be any compound as long as it has two or more epoxy groups in the molecule. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, Aliphatic chain epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, epoxidized polybutadiene, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, etc., especially bisphenol A type epoxy resin and cresol novolac type epoxy resin A mixture with a polyfunctional epoxy resin such as is preferred for improving the inner layer circuit filling property and heat resistance. These compounds may have any molecular weight, and several types can be used in combination.
[0009]
The epoxy resin curing agent used in the present invention may be any one as long as it is usually used as a curing agent for epoxy resins, and examples thereof include amines, phenols, acid anhydrides, and imidazoles. Among these, dicyandiamide, which is an amine, and phenol novolac resin, which is a phenol, are preferable for improving heat resistance. Several kinds of these compounds can be used in combination. The ratio of the epoxy resin curing agent to the epoxy resin is preferably in the range of 2 to 100 parts by weight with respect to 100 parts by weight of the epoxy resin. When the amount of the epoxy resin curing agent is less than 2 parts by weight, the curing of the epoxy resin tends to be insufficient and the heat resistance tends to decrease. When the amount is more than 100 parts by weight, the curing agent becomes excessive and becomes a plasticizer. It functions and tends to decrease heat resistance.
The curing accelerator used in the present invention may be any as long as it normally accelerates the curing reaction of the epoxy resin, such as imidazoles, organophosphorus compounds, tertiary amines, quaternary ammonium salts and the like. . The ratio of the curing accelerator to the epoxy resin is preferably in the range of 0.01 to 10 parts by weight with respect to 100 parts by weight of the epoxy resin. When the amount of the curing accelerator is less than 0.01 parts by weight, the epoxy resin is not sufficiently cured and the heat resistance is lowered. When the amount is more than 10 parts by weight, the curing accelerator is excessive and the heat resistance is lowered.
[0010]
In the present invention, rubbers other than the following core-shell structure crosslinked rubber may be used. As such, acrylonitrile butadiene rubber (which may contain an epoxy group or a carboxyl group) having good adhesion to plated copper is preferable. Such rubber is preferably used so that the total amount of the epoxy resin and the epoxy resin curing agent / rubber is in the range of 97/3 to 50/50 by weight. If the amount of such rubber used is too small, the resin tends to ooze out during lamination molding, and if it is too large, the filling property to the inner layer circuit and the insulation reliability tend to decrease.
[0011]
In this invention, the adhesive agent can contain the plating catalyst used as the precipitation nucleus of electroless copper plating. As the plating catalyst, salts or oxides of metals of Groups VIII, 1B and 2B of the Periodic Table of Elements can be used.
For example, a metal compound such as platinum, palladium, and tin can be used, and can be mixed into the adhesive in a liquid state so that it is dissolved in solid particles or an organic solvent or dissolved and dispersed together with other resins.
[0012]
If the amount of the plating catalyst in the adhesive is in the range of 2 to 15% by weight, copper is deposited by electroless plating.
Each component of the adhesive is kneaded and mixed in an organic solvent to prepare a solution mixture. Examples of the organic solvent to be used include toluene, methyl ethyl ketone, acetone, methyl isobutyl ketone, xylene, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether. A single or mixed system of acetate, ethyl ethoxypropiolate, propylene glycol monomethyl ether or the like can be used.
[0013]
As an insulating substrate using the adhesive according to the present invention, a substrate made of a phenol resin, an epoxy resin, an inorganic or organic composite, or the like can be used.
The adhesive is applied to an insulating substrate by 10 μm to 50 μm, and is heated and cured at a temperature of 140 ° C. to 190 ° C. for 30 minutes to 60 minutes.
[0014]
When depositing electroless plating, the surface of the adhesive is chemically roughened to a shape suitable for bonding.
Roughening solutions used for chemical roughening include chromic acid-concentrated sulfuric acid mixture, chromic acid-concentrated sulfuric acid-sodium fluoride mixture, potassium permanganate such as potassium permanganate, sodium permanganate and hydroxylation. Examples thereof include an aqueous solution containing an alkali metal hydroxide such as sodium and potassium hydroxide, and a borohydride-dichromate mixture.
The pattern is formed by screen-printing a plating resist or ultraviolet-curing and developing a photomask. These plating resists are performed before or after the chemical roughening treatment step.
[0015]
[Action]
By dissolving the core-shell structure crosslinked rubber of the present invention in the roughening solution, a fine uneven shape suitable for the adhesive surface can be formed. Further, since it is a cross-linked rubber having a core-shell structure, there is no deterioration in insulation proportional to the blending amount. In particular, this effect is remarkable when the core-shell structure crosslinked rubber of the present invention is a fine particle.
[0016]
【Example】
Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited thereto.
[0017]
Example 1
40 parts by weight of bisphenol A type epoxy resin (Oilized Shell Epoxy Co., Ltd. trade name Epicoat 828, epoxy equivalent 190), cresol novolac type epoxy resin (Sumitomo Chemical Co., Ltd. trade name ESCN-190-3, epoxy equivalent 190) 10 weights Parts, 2 parts by weight of dicyandiamide, 0.5 parts by weight of 2-ethyl-4-methylimidazole, core layer: cross-linked polybutadiene-shell layer: cross-linked polymethyl methacrylate core-shell structure cross-linked rubber (Kureha Chemical Industries, Ltd., trade name: Paraloid) EXL2655, particle size 200 nm 20 parts by weight, acrylonitrile butadiene rubber (Nippon Zeon Corporation trade name: Nipol 1031) 20 parts by weight, filler (zirconium silicate) 10 parts by weight, electroless plating catalyst (resin mixture of palladium chloride) , Hitachi Chemical Co., Ltd. Product Name: PEC-8) 4 parts by weight, were weighed and methyl ethyl ketone 200 parts by weight, to obtain a varnish and stirred.
This varnish is applied to a glass cloth epoxy laminate (Hitachi Chemical Co., Ltd., trade name: LE-168) by a dip coating method, applied to a film thickness of 25 μm, dried at 160 ° C. for 60 minutes and cured.
Furthermore, a resist for plating (trade name: Hitachi Chemical Co., Ltd .: SR-3000) was laminated, exposed to ultraviolet rays through a photomask for circuit formation, and developed.
Next, the adhesive was immersed in a roughening solution composed of a mixture of chromic acid-concentrated sulfuric acid-sodium fluoride (chromic acid 40 g / l, concentrated sulfuric acid 300 ml / l, sodium fluoride 10 g / l) at 40 ° C. for 5 minutes. Only the exposed portion was selectively chemically roughened, then neutralized and washed with water.
Furthermore, it is put into an electroless copper plating solution (manufactured by Hitachi Chemical Co., Ltd., trade name: CC-41 solution) to deposit 35 μm of plated copper, and then annealed at 160 ° C. for 60 minutes to produce an additive method print. A wiring board was produced. The resulting additive-processed printed wiring board had good solder heat resistance at 288 ° C. without swelling for 180 seconds or more, and the peel strength of the plated copper was 2.1 kN / m.
[0018]
Example 2
40 parts by weight of bisphenol A type epoxy resin (Epicoat 828), 10 parts by weight of cresol novolac type epoxy resin (ESCN-190-3), 2 parts by weight of dicyandiamide, 0.5 part by weight of 2-ethyl-4-methylimidazole, core crosslinking Polybutadiene-shell cross-linked polymethyl methacrylate core-shell structure cross-linked rubber (Paraloid EXL2655) 40 parts by weight, acrylonitrile butadiene rubber (manufactured by Nippon Zeon, trade name Nipol 1031), filler (zirconium silicate) 10 parts by weight, none An additive printed wiring board was produced in the same manner as in Example 1 except that 4 parts by weight of an electroplating catalyst (PEC-8) and 200 parts by weight of methyl ethyl ketone were used.
The resulting additive-processed printed wiring board had good solder heat resistance at 288 ° C. with no swelling for 180 seconds or more, and the copper peel strength was 2.2 kN / m.
[0019]
Example 3
40 parts by weight of a bisphenol A type epoxy resin (Epicoat 828), 10 parts by weight of a cresol novolak type epoxy resin (ESCN-190-3), a phenol novolak resin (manufactured by Hitachi Chemical, trade name HP-850N, phenolic hydroxyl group equivalent 106) 30 Part by weight, 0.5 part by weight of 2-ethyl-4-methylimidazole, 20 parts by weight of core-shell structure crosslinked rubber (paraloid EXL2655) of core-crosslinked polybutadiene-shell crosslinked polymethyl methacrylate, 10 parts by weight of filler (zirconium silicate) An additive printed wiring board was produced in the same manner as in Example 1 except that 200 parts by weight of methyl ethyl ketone was used.
The obtained heat-resisted cured resin with double-sided copper paste had good solder heat resistance at 288 ° C. without causing swelling or the like for 180 seconds or more, and the peel strength of copper was 2.0 kN / m. .
[0020]
Comparative Example An additive printed wiring board was produced in the same manner as in Example 1 except that the core-shell structure crosslinked rubber was not added. As for the solder heat resistance of the resulting additive-method printed wiring board at 288 ° C., swelling occurred in 125 seconds, and the copper peel strength was 1.6 kN / m.
[0021]
【The invention's effect】
As described above, by using a core-shell structure cross-linked rubber in an adhesive composition, an additive method for an adhesive for printed wiring boards that can improve the adhesive strength with plated copper without impairing insulation and heat resistance is provided. be able to.

Claims (3)

The adhesive is applied to the insulating substrate, an adhesive for the adhesive surface chemically crude However, making a additive process printed wiring board which is the circuit formed by electroless plating only where necessary, the adhesive An additive-based adhesive for printed wiring boards, wherein the agent contains a core-shell type crosslinked rubber in which the core layer is a crosslinked polybutadiene and the shell layer is a crosslinked acrylic resin . The core-shell type crosslinked rubber is an additive method for a printed wiring board adhesive of claim 1 wherein, characterized in that it contains 0.5 to 50 wt% relative to the resin component total amount in the adhesive composition. The adhesive for an additive method printed wiring board according to claim 1 or 2, wherein the cross-linked acrylic resin of the shell layer of the core-shell structure cross-linked rubber is cross-linked polymethyl methacrylate .