JPH0614591B2 - Manufacturing method of printed wiring board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a printed wiring board for forming a conductor circuit of the printed wiring board by electroless copper plating.

(Prior Art) Conventionally, as a method of manufacturing a printed wiring board by electroless copper plating, (1) a step of forming an adhesive layer of a plating film containing synthetic rubber and phenol resin on the surface of an insulating substrate, and (2) The step of roughening the surface of the adhesive layer, (3) the step of activating with a catalytic solution for electroplating, (4) the step of masking parts other than the circuit formation part (resist forming step), and (5) the electroless plating There is a method for manufacturing a printed wiring board, which is characterized by forming a circuit.

Further, in order to improve the adhesion between the plating film and the adhesive layer of the printed wiring board obtained by the above method, a manufacturing method of a printed wiring board characterized by including an alkaline aqueous solution treatment step after the roughening step of the adhesive surface. There is a method (JP-A-55-22841).

(Problems to be Solved by the Invention) In these methods, a catalyst is applied to the adhesive surface of the circuit part in order to perform the resist forming step after the activation step. A catalyst layer is formed.
Therefore, the plating property of the surface of the adhesive is good, but there is a drawback that the insulation resistance between the circuits decreases when the circuit interval becomes narrow.

In addition, special consideration is required for handling after the activation step and before immersion in the electroless copper plating solution. That is, since the catalyst layer of electroless copper plating formed by activation is formed only on the surface of the substrate, when a part of the device or a finger or the like makes strong contact with the surface, the catalyst adheres to them and further adheres to them. The catalyst has a defect that it is transferred to the plating resist surface of another substrate, and that even if it is a small scratch, the catalyst is lacking, and that part has a defect of a circuit or disconnection.

INDUSTRIAL APPLICABILITY The present invention has excellent insulation resistance characteristics between circuits, does not have the drawback of transfer to another catalyst and redeposition on the substrate, which is a problem at the time of manufacture, and the circuit at that portion is not damaged even if scratched. It is intended to provide a method for manufacturing a printed wiring board that does not cause disconnection.

(Means for Solving Problems) The present invention relates to a method for producing a printed wiring board by electroless copper plating using an insulating substrate having an adhesive containing a catalyst for electroless copper plating applied on the surface thereof. A step of forming a through hole in the substrate; a step of roughening the surface of the adhesive with a chemical roughening solution; a step of applying a catalyst with a solution that becomes a catalyst for electroless copper plating; and an adhesive generated by roughening. A printed wiring board comprising: a step of removing a fragile layer on a roughened surface; a step of forming a plating resist on a portion other than a circuit forming portion; and a step of forming a circuit by f electroless copper plating in this order. It is a manufacturing method.

The adhesive is intended to improve the adhesion with plated copper and to have a catalytic ability for electroless copper plating, and is generally composed of synthetic rubber-thermosetting resin-filler-catalyst for electroless copper plating. Is used. As the catalyst, those obtained by adsorbing a metal such as palladium or a metal salt, an oxide or the like on a carrier such as Al ₂ O ₃ —SiO ₂ and those dispersed in an epoxy resin are used.

The insulating substrate may be a phenol type laminated plate, an epoxy type laminated plate, a polyimide type laminated plate or the like, and can be used even when an electroless copper plating catalyst is contained. Punching and drilling can be used to open through holes. The roughening is performed using a chemical roughening solution.

Chromic acid-sulfuric acid system, dichromate-
Borohydrofluoric acid type can be used. For applying a catalyst for electroless copper plating, a usual palladium-tin-hydrochloric acid type catalyst can be used.

To remove the brittle layer, an alkaline aqueous solution treatment, an acid treatment, an ultrasonic cleaning treatment, a high-pressure water washing treatment, and the like are used.
An alkaline solution having a pH of 11 or higher can be used for the alkaline solution treatment. The treatment condition is effective soaking at 70 ° C. for 5 minutes or more. Acid solutions other than sulfuric acid having a pH of 1 or less can be used for the acid treatment.

As the alkaline aqueous solution, the following aqueous solutions are used. Sodium hydrogen phosphate and sodium hydroxide, sodium carbonate and hydrochloric acid, phosphoric acid and boric acid and acetic acid and sodium hydroxide, sodium carbonate and sodium hydrogen carbonate, glycine and sodium chloride and sodium hydroxide, borax and sodium hydroxide, water Sodium oxide, potassium hydroxide,
At least one of aliphatic amines such as ammonia, monomethyl ammonia and dimethyl ammonia, sodium carbonate, calcium hydroxide, guanidine and hydrochloric acid.

A surfactant can be mixed in the above aqueous solution.

As the acid treatment, an aqueous solution of sulfuric acid or borofluoric acid is used.

The ultrasonic cleaning and the high-pressure water cleaning treatment can be performed using a commercially available device under general use conditions. In addition, a soft organic sponge or the like is used for sweeping. The sponge may be rolled into a conveyor for processing.

Here, the brittle layer is a porous layer in which gaps are formed in the roughened surface layer when the insulating substrate with the adhesive is chemically roughened. Since the brittle layer has an effect of impeding the firm adhesion between the circuit obtained by plating and the substrate, it is originally desirable that it is less.

In this fragile layer removal, the larger the amount of the fragile layer removed, the more the amount of the catalyst applied in the activation step is removed.

Therefore, the amount of the fragile layer removed is precious and expressed as 1
200 mg / m ² or more preferably is 500 mg / m ² or more.

The catalyst applied to the through holes remains without being removed by these treatments. Therefore, the through-hole plating property is good.

Next, the plating resist needs to be alkali resistant,
Thermosetting ink, UV curable ink, dry film, etc. can be used. For example, the following can be used as the electroless copper plating solution.

Copper sulfate (pentahydrate) = 10 g / ethylene sodium diamine tetraacetate = 40 g / 37% formalin = 4 ml / sodium cyanide = 50 mg / pH = 12.0 Temperature = 70 ° C. (action) The present invention is applied to the adhesive surface. It does not depend on activation (catalyst application) by a catalyst solution as a means for performing electroless copper plating. Instead, an insulating substrate with an adhesive in which a catalyst for electroless copper plating is dispersed in the adhesive is used. After the catalyst application step for activating the through holes, the catalyst layer applied in the activation step, which is unnecessary and poses a problem on the roughened surface of the adhesive, is removed. The removal method is performed at the same time as removing the brittle layer caused by the chemical roughening of the adhesive.

In the method of the present invention, the active layer having such a high concentration that the insulation resistance between the circuits is lowered is removed together with the brittle layer.

Further, even in the case of scratches on the roughened surface of the adhesive, in the present invention, since the adhesive is catalytically added, it is possible to prevent chipping or disconnection of the circuit.

Furthermore, since the fragile layer has been removed, during the plating process,
A small piece of the roughening adhesive adheres to the plating resist, and plating deposition occurs at that portion. That is, the phenomenon of pretending to be copper does not occur.

Example 1 Through holes were made in an insulating substrate of paper epoxy provided with an adhesive layer containing an acrylonitrile rubber, a phenol resin, an epoxy resin, a filler and a catalyst for electroless copper plating.

Next, the surface of the adhesive was roughened by immersing it in a chemical roughening liquid.

Next, a catalyst was applied with a catalyst solution for palladium-tin-hydrochloric acid based electroless copper plating.

Then, as an alkaline aqueous solution treatment, pH 12.3, 0.1M
Hydrogen phosphate = 7 in sodium / sodium hydroxide solution
Immersion was performed at 0 ° C. for 3 hours, washed with water, and dried at 110 ° C. for 30 minutes.

Next, alkali-resistant drive film (SR manufactured by Hitachi Chemical
-3000) was used to form a plating resist.

Next, the printed wiring board was obtained by immersing in an electroless copper plating solution and plating until the plating thickness became 35 μm.

Example 2 Instead of the alkaline aqueous solution treatment in Example 1, an organic sponge was used to sweep the roughened surface after the activation treatment. A printed wiring board was obtained in the same manner as in Example 1 except for the above.

Comparative Example 1 A printed wiring board was obtained in the same manner as in Example 1 except that the catalyst-free adhesive was used.

Comparative Example 2 A printed wiring board was obtained in the same manner as in Comparative Example 1 except that roughening was followed by alkaline aqueous solution treatment and then activation (catalyst application).

Regarding the above Examples and Comparative Examples, the through hole plating property, the circuit (adhesive surface) plating property, the presence or absence of transfer of the activated catalyst, the scratching part plating property, and the insulation resistance between circuits Is shown in the table.

(Effects of the Invention) As described above, according to the present invention, there is no transfer of the catalyst after the catalyst is applied, and even if the circuit portion is scratched before the plating solution is introduced, the plating chipping or the circuit disconnection does not occur. A printed wiring board having excellent insulation resistance between circuits can be obtained.

Claims (2)

[Claims] 1. A step of forming a through hole in an insulating substrate coated with an adhesive containing a catalyst for electroless copper plating, a step of roughening the surface of the adhesive with a chemical roughening solution, and a C electroless By the step of activating with a copper plating catalyst solution, the step of removing the fragile layer on the adhesive surface caused by the D roughening, the step of forming a plating resist on a portion other than the E circuit forming portion, and the F electroless copper plating. A method of manufacturing a printed wiring board, which comprises sequentially forming a circuit other than a resist forming portion. 2. The method for producing a printed wiring board according to claim 1, wherein 100 mg / m ² or more of the brittle layer is removed in step D.