JP4556260B2 - Additive insulation film for printed wiring boards - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an insulating film used for an additive printed wiring board 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.
[0003]
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.
[0004]
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.
[0005]
[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.
[0006]
Needless to say, the thinner the wire, the more advantageous the adhesive strength with the plated copper.
[0007]
In addition, as the cost of electronic equipment has been reduced, the manufacturing process can be simplified and the process can be shortened. Filming the additive adhesive and laminating it on the inner layer substrate can be used for complicated processes such as curtain coating. Even without this, a process capable of forming an insulating layer has been studied.
An object of the present invention is to provide an insulating film for an additive method wiring board that is excellent in adhesive strength with plated copper without impairing the insulating properties and can form an insulating layer by lamination.
[0008]
[Means for Solving the Problems]
The present invention relates to the following.
(1) An insulating film is laminated on an insulating substrate, the surface of the adhesive is chemically roughened, and used for printed wiring boards obtained by an additive method in which only necessary portions are formed by electroless plating. An insulating film for an additive method printed wiring board, comprising a resin curing agent, a curing accelerator, and a core-shell type crosslinked rubber.
(2) The insulating film for an additive method printed wiring board according to item (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 film composition.
(3) The insulating film for an additive method printed wiring board according to item (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 acrylic resin.
(4) The insulating film for an additive method printed wiring board according to item (1) or (2), wherein the core layer of the core-shell structure crosslinked rubber is crosslinked polybutadiene and the shell layer is crosslinked polymethyl methacrylate.
[0009]
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.
[0010]
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.
[0011]
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.
[0012]
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 polybutadiene, cross-linked polyisoprene and the like are effective for the core layer, and cross-linked polymethyl methacrylate and cross-linked polystyrene 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. Further, since the core-shell structure crosslinked rubber tends to aggregate when its particle size is too small, the average particle size is preferably 0.1 μm or more. The addition amount of the core-shell structure crosslinked rubber is 0.5 with respect to the total resin content of the insulating film (epoxy resin, epoxy resin curing agent, curing accelerator, core-shell crosslinked rubber, and total amount of rubber other than the core-shell crosslinked rubber). -50% by weight is preferred. 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.
[0013]
The insulating film of this invention produces an insulating film by varnishing resin using a solvent, apply | coating and drying on a release film. The solvent used here may be any solvent that dissolves the epoxy resin composition and rubber, but in particular acetone, methyl ethyl ketone, methyl butyl ketone, toluene, xylene, ethyl acetate, N, N-dimethylformamide. , N, N-dimethylacetamide, ethanol, ethylene glycol monomethyl ether and the like are preferable because they are excellent in solubility of the epoxy resin composition and rubber and have a relatively low boiling point. The amount of these solvents may be any amount as long as the resin dissolves, but is preferably in the range of 5 to 300 parts by weight, and in the range of 50 to 250 parts by weight with respect to 100 parts by weight of the resin. Further preferred. Further, these may be used in combination. [0014]
The release film used in the present invention may be any film as long as the insulating film varnish can be applied and dried, but is easy to release after lamination and has sufficient strength at the drying temperature. Is preferred. Examples of such a release film include a polyethylene terephthalate film and a polyimide film.
In this invention, the plating catalyst used as the precipitation nucleus of electroless copper plating can be contained in an insulating film. 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.
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.
Further, a silane coupling agent may be added, or a filler may be blended.
[0015]
As the inner layer substrate using the insulating film of 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 insulating film of the present invention is laminated on the inner layer substrate, and the release film is peeled off, followed by heat curing at a temperature of 140 ° C. to 190 ° C. for 30 minutes to 60 minutes.
[0016]
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. An aqueous solution containing an alkali metal hydroxide such as sodium or potassium hydroxide, a borofluoric acid-bichromic acid mixture, or the like can be used.
[0017]
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.
[0018]
[Action]
The core-shell structured crosslinked rubber contained in the insulating film of the present invention is a fine particle, and the core-shell structured crosslinked rubber dissolves in the roughening liquid, whereby a fine uneven shape suitable for the insulating resin 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. Furthermore, since the insulating layer can be formed by forming the insulating resin into a film and laminating the inner layer plate, the manufacturing process can be simplified.
[0019]
【Example】
Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited thereto.
[0020]
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 (palladium chloride resin mixture, 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.
[0021]
This varnish was applied to a release film (polyethylene terephthalate film, manufactured by Toray, trade name: PUREX A-63, 50 μm thick) so as to be 50 μm after drying, and dried at 100 ° C. for 15 minutes. An insulating film was obtained.
This insulating film was laminated on a glass cloth epoxy laminate (Hitachi Chemical Industry Co., Ltd., trade name: LE-168) using a press at 150 ° C., 2 MPa for 2 minutes, and the release film was peeled off at 160 ° C. Dry and cure for 60 minutes.
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 chromic acid-concentrated sulfuric acid-sodium fluoride mixture (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 2.0 kN / m.
[0022]
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 Butadiene-shell cross-linked polymethyl methacrylate core-shell structure cross-linked rubber (Paraloid EXL2655) 40 parts by weight, acrylonitrile butadiene rubber (Nippon Zeon Co., Ltd., trade name Nipol 1031) 20 parts by weight, filler (zirconium silicate) 10 parts by weight, An additive printed wiring board was produced in the same manner as in Example 1 except that 4 parts by weight of electroless plating catalyst (PEC-8) and 200 parts by weight of methyl ethyl ketone were used.
[0023]
The resulting additive printed wiring board had good solder heat resistance at 288 ° C. without causing swelling or the like for 180 seconds or more, and the copper peel strength was 2.1 kN / m.
[0024]
Example 3
40 parts by weight of bisphenol A type epoxy resin (Epicoat 828), 10 parts by weight of cresol novolak type epoxy resin (ESCN-190-3), phenol novolak resin (Hitachi Chemical Co., Ltd., trade name HP-850N, phenolic hydroxyl group equivalent 106) 30 Parts by weight, 0.5 parts by weight of 2-ethyl-4-methylimidazole, 20 parts by weight of core-shell structure crosslinked rubber (paraloid EXL2655) of core crosslinked butadiene-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.
[0025]
The obtained 288 ° C. solder heat resistance of the obtained double-sided copper-plated insulating resin cured product was good without causing swelling or the like for 180 seconds or more, and the copper peel strength was 1.9 kN / m. .
[0026]
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 printed wiring board at 288 ° C., swelling occurred in 125 seconds, and the copper peel strength was 1.5 kN / m.
[0027]
【The invention's effect】
As described above, by using a core-shell structure cross-linked rubber in an insulating resin composition, an insulating film for an additive method printed wiring board capable of improving the adhesive strength with plated copper without impairing insulation and heat resistance is provided. be able to.

Claims (3)

Adhesiveness for producing printed wiring boards obtained by the additive method of laminating an insulating film with adhesive properties on an insulating substrate, chemically roughening the surface of the insulating film , and forming a circuit only by electroless plating at the required location The insulating film contains an epoxy resin, an epoxy resin curing agent, a curing accelerator , and a core- shell type crosslinked rubber in which the core layer is a crosslinked polybutadiene and the shell layer is a crosslinked acrylic resin. Additive method insulation film for printed wiring boards. The insulating film 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 insulating film composition. The insulating film for an additive method printed wiring board according to claim 1 or 2, wherein the crosslinked acrylic resin of the shell layer of the core-shell structured crosslinked rubber is crosslinked polymethyl methacrylate .