JPH10329294A - Laminated sheet for printed wiring board according to additive method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the adhesion of electroless copper plating to a through hole by a method wherein a plating catalyst used for a laminated sheet for a printed wiring board according to an additive method is interposed sufficiently also in a gap between reinforcing bases of the laminated sheet. SOLUTION: This laminated sheet for a printed wiring board is obtained by a method wherein reinforcing fiber bases are impregnated with the epoxy resin varnish containing epoxy resin, an epoxy resin hardener, an electroless plating catalyst and an organic solvent at least and are dried and prepregs thus obtained are laminated in appropriate numbers and heated, pressed and formed. In this case, the epoxy resin hardener is the triazine phenol novolac resin of a nitrogen content of 5 wt.% or above and the triazine phenol novolac resin is compounded so that the number of the phenolic hydroxyl groups thereof is in the ratio of 0.6-1.6 equivalent weight to the epoxy resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminate which can be suitably used for forming a wiring pattern by an additive method.

[0002]

2. Description of the Related Art Electroless copper plating is generally used as a means for selectively forming a printed wiring pattern on a laminate by an additive method. As the laminate, a laminate containing an electroless plating catalyst dispersed therein for forming a printed wiring pattern by electroless copper plating is used. As an electroless plating catalyst,
No. 1B of the periodic table of elements described in JP-A-31276.
Inactive fine solid particles of a basic exchangeable substance obtained by chemisorption of a cation by base exchange with a cation of a metal selected from the genus and genus 8, and the elements described in JP-B-50-1424. Those selected from metal organic compounds of metals selected from Groups 1B and 8 of the periodic table are generally used. These electroless plating catalysts are dispersed and contained in an epoxy resin varnish.The laminate for additive printed circuit boards is equipped with electroless copper plating when the wiring pattern is selectively printed by electroless plating. Places with excellent properties (for example, the front and back of the laminate)
It is known that there is an inferior place (for example, an inner wall surface of a through hole). If the adjustment of the activity of the electroless plating solution is adjusted according to the place where the plating property is poor, the place where the plating property is excellent (for example, the front and back surfaces of the laminate)
In such a case, there is a problem that plated copper often precipitates (copper drops) on an insulating portion and causes insulation failure. Conversely, if the activity of the electroless plating solution is lowered and adjusted to such an extent that the copper drop phenomenon does not occur in a place having excellent plating properties (for example, the front and back surfaces of the laminate), a place having poor plating properties (for example, the inner wall surface of a through hole) In (2), there is a problem that the non-uniformity of the electroless copper plating film of the wiring pattern selectively formed by printing and plating voids often occur, which causes poor conduction. The problem of poor insulation due to the copper falling phenomenon, the problem of non-uniformity of the electroless copper plating film, and the problem of poor conduction due to the occurrence of plating voids are caused by the increased density of printed wiring patterns accompanying the reduction in size and weight of electronic devices. If required, it may be necessary to take further measures. While examining the causes of the non-uniformity of the electroless copper plating film and the occurrence of plating voids on the inner wall surface of the through hole, the inventors found that the electroless plating catalyst dispersed and contained in the matrix resin of the laminate was used. Since there will be no cut surface of the reinforcing fiber base material exposed on the inner wall of the through hole, we thought that the inner wall of the through hole was inferior in electroless copper plating, in addition to that, It was discovered that the gap between the reinforcing fibers in the laminate did not allow the electroless plating catalyst, which had been dispersed and contained in advance, to enter the specified ratio due to its particle size, and the penetration ratio of the matrix resin increased. This has led to the invention.

[0003]

According to the present invention, in order to solve the above problems, a reinforcing fiber base material is impregnated with an epoxy resin varnish containing at least an epoxy resin, an epoxy resin curing agent, an electroless plating catalyst and an organic solvent. In a laminated board for an additive method printed wiring board obtained by heating, pressing and molding a suitable number of prepregs obtained by drying, the epoxy resin curing agent is a triazine phenol novolak resin having a nitrogen content of 5% by weight or more. The number of phenolic hydroxyl groups of the triazine phenol novolak resin is set to be 0.6 to 1.6 equivalents to the epoxy groups of the epoxy resin.

The reinforcing fiber substrate used in the present invention includes, but is not limited to, paper, glass fiber nonwoven fabric and woven fabric.

[0005] The epoxy resin used in the present invention is not particularly limited, but examples thereof include bisphenol A type epoxy resin, novolak type epoxy resin, cresol novolak type epoxy resin, and dimer acid modified epoxy resin. In addition, a brominated epoxy resin can be used to impart flame retardancy to these epoxy resins. These epoxy resins can be used alone or in combination of two or more.

The epoxy resin curing agent used in the present invention comprises:
A triazine phenol novolak resin having a nitrogen content of 5% by weight or more, wherein the number of phenolic hydroxyl groups of the triazine phenol novolak resin is 0.6 to 1.6 equivalents to the epoxy groups of the epoxy resin.
The epoxy resin and its curing agent, a triazine phenol novolak resin having a nitrogen content of 5% by weight or more,
In the process of pressing and molding, the phenolic hydroxyl group of the triazine phenol novolak resin reacts preferentially with the functional group of the epoxy resin, so that the triazine component remains in a state of maintaining a highly reducing nitrogen group. Since the highly reducing nitrogen group of the triazine component is impregnated around the reinforcing fiber base material and in the gaps between the reinforcing fiber base materials, it is used for an additive method printed wiring board obtained by heating, pressing and molding. The laminate exchanges ions with electroless copper ions during electroless copper plating to reduce the electroless copper ions, and the nitrogen content in the triazine component is 5% by weight.
As described above, the effect of improving the property of attaching the electroless copper plating on the inner wall surface of the through hole is observed. The number of phenolic hydroxyl groups contained in the phenol novolak component of the triazine phenol novolak resin is condensed with the epoxy group of the epoxy resin, crosslinking proceeds, and the number of phenolic hydroxyl groups is 0.6 to 0.6 with respect to the epoxy group of the epoxy resin. 1.
Mix in a ratio of 6 equivalents. If the number of phenolic hydroxyl groups is less than 0.6 equivalents relative to the epoxy groups of the epoxy resin, the epoxy resin will be insufficiently cured, failing to provide sufficient mechanical strength as a printed wiring board, and 1.6. If the equivalent weight is exceeded, the printed wiring board will have mechanical strength but will not be satisfactory in terms of heat resistance and dimensional stability.

The electroless plating catalyst used in the present invention is not particularly limited, but a cation obtained by base exchange with a cation of a metal selected from Groups 1B and 8 of the periodic table is chemically adsorbed. Inactive fine solid particles of the basic exchangeable substance or a metal organic compound of a metal selected from Groups 1B and 8 can be used. These electroless copper plating catalysts are subjected to ion exchange with electroless copper ions and exhibit strong reducing properties for electroless copper ions. As the inert fine solid particles of the basic exchangeable substance, Japanese Patent Publication No. 50-3127
No. 6 can be used, and those described in JP-B-50-1424 can be used as the metal organic compound.

The organic solvent used in the present invention is not particularly limited. Examples thereof include ketones such as acetone and methyl ethyl ketone, ethers such as ethylene glycol monoethyl ether and diethylene glycol monobutyl ether, and aromatic compounds such as benzene, toluene and xylene. N, N-dimethylformamide and the like can be used.

[0010]

[Function / Effect] Since a phenol novolak resin having a triazine component having a nitrogen content of 5% by weight or more which is not directly involved in the curing reaction with the epoxy resin is used as the epoxy resin curing agent, there is no gap between the reinforcing fiber substrates. It is considered that a proper amount of a nitrogen group that has a reducing action on electrolytic copper ions can be present, and that the inner wall surface of the through hole has improved electroless copper plating adherence.

[0011]

Example 1 First, 100 parts by weight of a solid content of brominated bisphenol A epoxy resin (trade name: DER514, epoxy equivalent: 485, manufactured by Dow Chemical Co.), triazine phenol novolak resin (trade name: Fenolite LA, manufactured by Dainippon Ink and Chemicals, Inc.) -7051, hydroxyl equivalent 124, nitrogen content 5% by weight) solids 15.3 parts (note: this amount is equivalent to 0.6 equivalent to the epoxy group of the above brominated bisphenol A type epoxy resin). ) And 0.24 in
Electroless plating catalyst 1 containing weight percent palladium
2.5 parts by weight of methyl ethyl ketone as a solvent and N,
N-dimethylformamide was added to prepare an epoxy resin varnish having a resin solid content of 60%. Next, this epoxy resin varnish was impregnated and applied to a plain woven glass cloth (trade name: WEA7628H257N, manufactured by Nitto Bo) with a thickness of 0.18 mm, and dried by heating to obtain a prepreg sheet having a resin amount of about 45%. Next, six prepreg sheets were stacked, and a plurality of the stacked bodies were stacked in a plurality of stages via a release sheet therebetween, and heated and pressed by a hot plate from both sides to react and harden to form an integrated thickness 1. A 2 mm laminate was obtained. A predetermined interval was provided in this laminated plate, and 100 through-holes were drilled by drilling.
After roughening with a sodium fluoride-based roughening solution, an electroless copper plating solution for an additive method (plating speed 1.8 μm / h)
r) for 3 hours to form electroless copper plating on the inner wall surface of 100 through-holes. The occurrence of pinholes was examined by observing 100 through-hole platings under a microscope. The results are shown in Table 1.

[0012]

Comparative Example 1 Instead of triazine phenol novolak resin, phenol novolak resin (Phenolite TD-2093, trade name, manufactured by Dainippon Ink and Chemicals, Inc., hydroxyl equivalent: 104) solids 12.9 parts (Note: bromine of Example 1) With respect to the epoxy group of the functionalized bisphenol A type epoxy resin.
Example 1 except that 6 equivalents were used.
The same was done.

[0013]

Comparative Example 2 2.6 parts by weight of dicyandiamide instead of triazine phenol novolak resin (Note: equivalent to 0.6 equivalents to the epoxy group of the brominated bisphenol A type epoxy resin of Example 1) And the procedure of Example 1 was repeated except that 0.1 part by weight of 2-ethyl-4-methylimidazole was used.

[0014]

[Table 1]

[0013]

The laminate for an additive-processed printed wiring board according to the present invention comprises a triazine phenol novolak resin of 5% or more as a curing agent for an epoxy resin, wherein the number of phenolic hydroxyl groups is greater than the number of epoxy groups in the epoxy resin. 0.6 to 1.6 equivalents, the phenol novolak component undergoes a crosslinking reaction by a condensation reaction between a phenolic hydroxyl group and an epoxy group of an epoxy resin to provide mechanical strength characteristics as a printed wiring board. In addition, it has adhesive strength characteristics, and the triazine component is impregnated between the reinforcing fibers and taken in, and the nitrogen groups of the triazine component exposed on the through-hole wall are ion-exchanged with copper ions during electroless copper plating and reduced. Thus, the surrounding performance with electroless copper plating can be improved. By improving the perimeter of the through-hole wall with the electroless copper plating, the activity of the electroless plating solution can be adjusted to a lower value, and thus the copper drop in places with good plating can be reduced. Therefore, it can be said that the additive method can contribute to higher density of the printed wiring pattern.

Claims (1)

[Claims] 1. A suitable number of prepregs obtained by impregnating and drying an epoxy resin varnish containing at least an epoxy resin, an epoxy resin curing agent, an electroless plating catalyst, and an organic solvent on a reinforcing fiber base material and laminating them are heated and pressed. In the additive method printed wiring board laminate obtained by molding,
The epoxy resin curing agent is a triazine phenol novolak resin having a nitrogen content of 5% by weight or more, and the number of phenolic hydroxyl groups of the triazine phenol novolak resin is 0.6 to 1.6 equivalents to the epoxy group of the epoxy resin. A laminate for an additive method printed wiring board characterized by being blended in the following ratio.