JPS62296492A - Manufacture of printed wiring board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method of manufacturing a printed wiring board by electroless plating.

(Prior Art) Connecting electronic components to a printed wiring board is accomplished by inserting lead wires of the components into holes and then dipping them with solder. Therefore, the quality of the solder flowing through the hole is one of the factors that determines the connection state of the parts.

By the way, fully additive wiring boards manufactured by electroless plating, for example, have a paper-based base material that easily absorbs moisture and has the disadvantage that it is difficult for solder to build up inside the holes even when heated and dried for a long time. be. Therefore, cedar is usually attached to the inside of the hole to make the plating inside the hole dense.

(Problem to be solved by the invention) However, in the conventional manufacturing method, after adhering the seeder to the hole, the seeder is dipped in sulfuric acid or the like to activate it, and then the adhesive layer is subjected to roughening treatment, etc. are doing. For this reason, cedar activated with sulfuric acid or the like is likely to be inactivated by roughening treatment, resulting in a disadvantage that its effectiveness as a plating catalyst is reduced.

An object of the present invention is to provide a method for manufacturing a printed wiring board that can improve the above-mentioned drawbacks, improve the efficiency of the action of the plating catalyst, and improve the formation of plating inside the holes.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides holes for through holes in an insulating substrate whose surface is coated with an adhesive containing a plating catalyst, and performs plating in the holes. In a printed wiring board manufacturing method in which a catalyst is attached, a plating resist layer is then formed, an adhesive layer is roughened, and a circuit is formed by electroless plating, an insulating substrate is placed in an acidic solution after the roughening treatment. The present invention provides an H2 method for a printed wiring board, which is characterized by performing a treatment of dipping the printed wiring board.

(Function) According to the present invention, after roughening the adhesive layer, the seeder is activated by dipping it in an acidic solution such as fi acid, phosphoric acid, hydrochloric acid, or 1M hydrofluoric acid. When electroless plating is performed after that, the plating precipitation inside the holes is improved.

In addition, as the refractory solution, a hydrotetrafluoric acid aqueous solution is preferable, the concentration thereof is 1 to 5 wt%, and the treatment temperature is 20 to 5 wt%.
The treatment time is preferably about 5 seconds to 10 minutes at 50°C.

(Example) Hereinafter, the present invention will be explained based on examples.

As the insulating substrate, a plating catalyst-containing paper-based phenol resin laminate or a paper-based epoxy resin laminate whose surface is coated with an adhesive containing a plating catalyst is used.

To manufacture a printed wiring board using this insulating substrate, first, holes for through holes are formed using a bunch or a drill, and a plating catalyst is applied to the surface of the adhesive layer and the inner surface of the hole by seeding. As the plating catalyst, for example, a mixture of palladium chloride and tin chloride is used.

Next, plating resist ink is printed on the surface of the insulating substrate by screen printing to form a feeding pattern, and then hardened.

After curing the plating resist ink, chromic anhydride, 1iI
The insulating substrate is immersed in an acid-based roughening solution to soften the surface of the adhesive layer.

After roughening the adhesive layer, the insulating substrate is dipped in an acidic solution such as an aqueous solution of sulfuric acid, borohydrofluoric acid, etc., to form metallic palladium and remove tin, thereby activating the plating catalyst.

After dipping in an acidic solution, the insulating substrate is immersed in a plating solution and subjected to electroless plating to form a predetermined circuit.

Next, regarding the examples of the present invention, the plating precipitation inside the holes, the blowhole occurrence rate, and the solder scattering were measured, and the results shown in the table were obtained. The manufacturing conditions for each example are as follows.

Example 1) Insulating substrate: Epoxy resin laminate coated with adhesive containing plating catalyst (ACL-E-144 manufactured by Hitachi Chemical Co., Ltd.) Plating catalyst: Hitachi Chemical Co., Ltd. 1j HS-101
B: Plating catalyst roughening treatment: Roughen the surface of the adhesive layer by immersing it in an anhydrous chromic acid/sulfuric acid roughening solution at a temperature of 40° C. for 10 minutes.

Acidic solution treatment: A plate is immersed for 10 minutes in a 2 wt % aqueous solution of hydrofluoric acid at a temperature of 30°C.

Electroless copper plating treatment: Electroless steel plating with a thickness of 30 μm is deposited.

Example 2) In Example 1), the acidic solution treatment is for 2 minutes. Example 3) In Example 1), the hydrofluoric acid concentration is 4%. Example 4) In Example 1), the The temperature of the hydrochloric acid solution is set to 40°C.

Further, in the conventional example, the acidic solution treatment of Example 1) was performed between the seeding treatment and the roughening treatment.

In addition, the plating precipitation inside the hole is the time until the inner peripheral surface of the hole becomes copper-colored due to plating, and the blowhole occurrence rate is the time required for the inner peripheral surface of the hole to become copper-colored.
The blowhole occurrence rate and solder scattering were measured when the sample was dipped in solder for 4 seconds, and the solder scattering was measured when the same treatment as blowholes was applied.

As is clear from the table, according to the present invention, the time for depositing in-holes was shortened to 1/4 of that of the conventional example, the blowhole occurrence rate was reduced to about 1/8, and almost no solder scattering was observed.

In the above examples, the acidic solution treatment was performed only after the roughening treatment, but it may be further performed between the seeder treatment and the roughening treatment.

(Effects of the Invention) As described above, according to the present invention, since the acidic solution treatment is performed after the pelletization, the plating catalyst can be activated to improve the precipitation properties of the plating inside the pores, and the blowhole generation rate can be reduced. A method of manufacturing a printed wiring board that can be improved, has less solder scattering, and is highly reliable is provided.

Claims (2)

[Claims] (1) A hole for a through hole is provided in an insulating substrate whose surface is coated with an adhesive containing a plating catalyst, a plating catalyst is adhered to the inside of the hole, and then a plating resist layer is formed and the adhesive layer is roughened. A method for manufacturing a printed wiring board in which a circuit is formed by electroless plating, the method comprising: immersing the insulating substrate in an acidic solution after roughening treatment. (2) The method for manufacturing a printed wiring board according to claim 1, wherein the acidic solution is an aqueous borofluoric acid solution.