JPS5924559B2 - Base material for printed wiring boards - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in substrates used in the manufacture of double-sided through-hole printed wiring boards.

Conventionally, the manufacturing method for double-sided through-hole printed wiring boards is as follows:
Two methods are known: one method is to manufacture by etching using a double-sided copper-clad laminate as a starting substrate, and the other is to manufacture by electroless plating, etc., using an insulating board coated with an adhesive layer for electroless plating on both sides as a starting substrate. .

However, these double-sided copper-clad laminates and double-sided through-hole printed wiring boards made from base materials having adhesive layers on both sides have their own merits and demerits. The present invention was developed in view of the above circumstances, and it is possible to form a high-density circuit pattern by having copper foil on one side, and by having an adhesive layer for electroless plating on the other side. The object of the present invention is to provide a base material for a printed wiring board that can reduce the amount of etching waste liquid and reduce the load cost. That is, the present invention is characterized in that an adhesive layer for electroless plating comprising a thermosetting resin in which rubber particles are uniformly dispersed is adhered to the non-copper foil surface of a single-sided copper-clad insulating board. It is something. In the present invention, examples of the insulating board having copper foil adhered to one side include a paper-layer phenolic resin laminate, a paper-layer epoxy resin laminate, a glass fiber-containing phenol resin laminate, a glass fiber-containing epoxy resin laminate, and a phenol resin laminate. Examples include laminates, resin laminates such as epoxy resin laminates and polyester resin laminates, and ceramic plates such as alumina plates.

The adhesive layer for electroless plating in the present invention serves as a base for firmly adhering the electroless copper plating layer to the insulating plate.

Examples of rubber particles that are a component of such an adhesive include those made of one type or a mixture of two or more types selected from natural rubber or synthetic rubber such as acrylonitrile rubber, putadiene rubber, and acrylonitrile-ptadiene rubber. . However, from the viewpoint of contributing to roughening of the adhesive layer during treatment with a chromic acid-sulfuric acid mixture, etc., it is necessary that the rubber particles are not unevenly distributed in the adhesive layer but are uniformly dispersed. In addition, thermosetting resins that are other constituents of the adhesive include, for example, phenolic resins such as novolak type phenolic resin, resol type phenolic resin, and xylene resin, polycondensates of epichlorohydrin and bisphenol, and alicyclic epoxy resins. Resin Examples include one or a mixture of two or more epoxy resins such as epoxidized polyptadiene resins, and it is particularly desirable to use a mixture of a phenol resin and an epoxy resin. The blending ratio of each component in the adhesive is preferably in the range of 25 to 60% by weight of rubber particles and 75% by weight or less of thermosetting resin. In addition to the above two components, the adhesive may optionally contain inorganic fine powder such as colloidal silica to improve coating properties and adhesion, sulfur as a vulcanizing agent for rubber particles, and mercaptan as an accelerator. Additives such as system compounds may be used in combination. However, since the base material for printed wiring boards of the present invention has a structure in which an adhesive layer for electroless plating is adhered to the non-copper foil surface of a single-sided copper-clad insulating board, it is difficult to selectively etch one of the copper foils. This enables formation of high-density circuit patterns.

Further, by processing the other adhesive layer by electroless copper plating or the like using a so-called additive method, a circuit pattern can be formed without producing a large amount of copper etching waste liquid. Furthermore, if the circuit pattern side formed by selective etching of the copper foil is designed to be the soldering side, the circuit pattern on the opposite side is formed via an adhesive layer, so thermal shock during soldering can be avoided. can be absorbed by the adhesive layer, thereby preventing cracks from occurring in the circuit pattern on the side opposite to the soldering surface. Therefore, by using the base material of the present invention, it is possible to obtain a highly reliable, high-density double-sided through-hole printed wiring board that has the features of selective etching of the copper foil and the features of electroless plating on the adhesive layer. I can do it. Next, an example in which the base material of the present invention is applied to manufacturing a double-sided through-hole printed wiring Z board will be described with reference to the drawings.

Example (i) First, as shown in FIG. 1, a copper foil 2 with a thickness of 35 μm was adhered to one side of a paper-epoxy resin laminate 1.
On the non-copper foil side of a so-called single-sided copper-clad laminate, 40 parts by weight of acrylonitrile rubber, 20 parts by weight of resol-type phenolic resin, 20 parts by weight of bisphenol-type epoxy resin, and 10 parts by weight of silica gel were dissolved in a mixed solvent of methyl ethyl ketone and butyl cellosolve. Apply electrolytic plating adhesive,
The adhesive layer 3 was dried at 170° C. for 40 minutes to form an adhesive layer 3 having a thickness of about 30 μm, thereby producing a substrate for a printed wiring board.

(11) Next, after providing an ink mask for forming a circuit pattern on the surface of the copper foil 2 of the base material by screen printing, the copper foil portion exposed from the mask is removed by etching, and the ink mask is further dissolved. Remove copper foil circuit pattern 4
was formed (as shown in Figure 2).

The copper foil circuit pattern 4 thus formed had an extremely high density because only the copper foil 2 was selectively etched. Subsequently, a solder resist film 5 (product name: S-20 manufactured by Taiyo Ink Co., Ltd.) was applied to the portion of the copper foil circuit pattern 4 excluding the land portion 4' by screen printing (third
(Illustrated) Subsequently, an alkali-soluble coating 6 (trade name: X-JMoV, manufactured by Taiyo Ink Co., Ltd.) was applied to the entire surface of the copper foil circuit pattern 4 side using a roller coater method (as shown in Figure 4). [1] Next, as shown in FIG. 5, a hole 7 penetrating the adhesive layer 3 was punched from the center of the land portion 4' by press punching.

Subsequently, the surface of the adhesive layer 3 was roughened by treatment for 7 minutes in a mixed solution of 5009/1 chromic acid and 2509/l sulfuric acid (liquid temperature 4'C), and then electroless plating made by Shitsupre Co., Ltd. in the United States was applied. A palladium catalyst layer 8 was deposited on the surface according to the process typified by (FIG. 6).

At this time, the catalyst layer 8 adhered not only to the surface of the adhesive layer 3 but also to the walls of the holes 7 and the surface of the alkali-soluble secret film 6. Subsequently, while moving the starting substrate on a conveyor, a caustic potassium aqueous solution was sprayed on the alkali-soluble coating 6 for 2 minutes to dissolve and remove the coating 6, and at the same time remove the palladium catalyst layer 8 on the surface. It was treated with an electroless copper bath (trade name: 9027). At this time, as shown in FIG. 7, a thickness of 1 to 3 μm is applied to the surface of the adhesive layer 3 and the wall surface of the hole 7 to which the palladium catalyst layer (hereinafter omitted) is attached.
The electroless copper plating film 9 was selectively deposited, and no deposit was made on other solder resist films 5 and the like. Also,
Since the coating 6 is dissolved and removed using a caustic potassium aqueous solution,
Corrosion of the exposed land portion 4' of the copper foil circuit pattern 4 does not occur. ) Next, as shown in FIG. 8, an ink mask 10 is formed on the adhesive layer 3 other than the area where the circuit pattern is to be formed on the electroless copper plating film 9 by a screen printing method, and then the ink mask 10 is formed in a copper sulfate plating bath. Land portion 4' is treated with electrolytic copper plating.
, a copper plating film 11 with a thickness of 30 ttm is deposited on the exposed portion of the electroless copper plating film 9 on the adhesive layer 3 side and on the electroless copper plating film 9 in the hole 7, and further in a tin sulfuric acid plating bath. A tin-plated film 12 having a thickness of 8 μm was deposited on the copper-plated film 11 by electro-tinning.

Next, the ink mask 10 is dissolved and removed by spraying a 5% caustic potassium aqueous solution for 2 minutes while moving it on a conveyor so that the adhesive layer 3 side is the top surface (as shown in Figure 10).
After that, add ammonium alkaline copper etching solution (
The exposed electroless copper plating film 9 is etched away by spraying the exposed electroless copper plating film 9 by spraying for 1 minute with A process liquid manufactured by SCC Corporation in the United States, and the circuit board protected by the tin plating film 12 on the adhesive layer 3 side is removed. A double-sided through-hole printed wiring board was manufactured by forming holes 13 (as shown in FIG. 11). The obtained double-sided through-hole printed wiring board has a high-density copper foil circuit pattern 4 on one side, and the circuit pattern 13 on the other side is formed by a so-called additive method, so the burden cost of etching waste liquid is lower than that of a double-sided copper-clad laminate. This was significantly reduced compared to when using .

In addition, copper foil circuit pattern 4 of double-sided through-hole printed wiring board
When the side was subjected to flow solder treatment, no solder bridging occurred at all, similar to the copper sulfo printed wiring board of the same specifications, and no cracks occurred in the circuit pattern 13 on the opposite side.

Furthermore, there was no peeling or swelling of the solder resistor film 5 on the soldering surface. Furthermore, the soldering properties after long-term storage were comparable to those of conventional solder through-hole printed wiring boards. As detailed above, the present invention has the following features: It is possible to form a detailed circuit pattern by selectively etching the copper foil on one side, and the waste liquid load caused by electroless plating on the adhesive layer for electroless plating. It is possible to provide a base material for a printed wiring board, which has the feature that a circuit pattern can be formed at reduced cost and is useful for manufacturing a highly reliable, high-density double-sided through-hole printed wiring board.

[Brief explanation of the drawing]

1 to 11 are cross-sectional views showing the steps of manufacturing a double-sided through-hole printed wiring board from the substrate for printed wiring boards of the present invention. 1...Paper-phenol resin board, 2...
Copper foil, 3...Adhesive darkening for electroless plating, 4,4
t... Copper foil circuit pattern, 5... Solder resist film, 9... Electroless copper plating film, 11
......Copper plating film, 12...Tin plating film, 13
・−・・・Circuit pattern.

Claims (1)

[Claims] 1. A base material for a printed wiring board, characterized in that an adhesive layer for electroless plating, the main component of which is a thermosetting resin in which rubber particles are uniformly dispersed, is adhered to the non-copper foil surface of a single-sided copper-clad insulating board. .