JPH08139451A - Manufacturing method of printed-wiring board - Google Patents

Abstract

PURPOSE: To provide the title manufacturing method of printed-wiring board having excellent bond properties between inner layer copper foils, outer layer copper foils and an electroplating copper while avoiding a decline in precipitation of manganese oxide on an insulator surface on a through hole inner wall, especially on a glass cloth, thereby improving the conductivity on the through hole inner wall part. CONSTITUTION: The title manufacturing method of pronted-wiring board is composed of the four steps as follows, i.e., the first step of treating a perforated and cleaned printed-wiring board with a solution containing neutral permanganate, the second step of pickling the printed-wiring board, the third step of coating the printed-wiring board inner wall part with organic monomer and the fourth step of immersing the printed-wiring board in an acid solution for making an organic monomer into conductive polymer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a double-sided and multilayer printed wiring board having through holes for connecting front and back wiring patterns.

[0002]

2. Description of the Related Art When electroplating an inner wall of a through hole of a printed wiring board, as a means for imparting conductivity to the inner wall of the through hole in advance, it is disclosed in Japanese Patent Publication No. H05-506125.
As disclosed in Japanese Patent Laid-Open No. 4-188696 and Japanese Patent Laid-Open No. 4-188696, a treatment liquid containing an organic monomer that forms a conductive polymer by oxidative polymerization and a solvent or a solubilizing agent, instead of conventional electroless plating, For example, pyrrole monomer and N
-Proposed a method of forming a conductive polymer film on the surface of the insulating material such as epoxy resin and glass cloth exposed on the inner wall of the through hole using a mixed solution with methyl-2-pyrrolidone and then performing electroplating. Has been done. That is,
For example, drill a hole in the printed wiring board at a predetermined location,
Then, after a cleaning activation step (desmear step) including polishing, washing, etc., and further a soft etching step, a permanganate step, an organic monomer applying step, an acid polymerization step, direct electrolytic copper plating is performed, and then a printed wiring board Through holes were formed. In this case, an alkaline permanganate solution is used to form manganese oxide, which is a polymerization catalyst for the organic monomer, to obtain an acid polymerization type conductive polymer film on the inner wall of the through hole. However, since an alkaline permanganate solution containing 10 to 30 g / l of sodium hydroxide is used, the amount of manganese oxide deposited on the glass cloth is remarkably reduced, the conductivity is deteriorated, and electrolytic copper plating is performed. Will be extremely disadvantageous. Furthermore, since the polyimide base material and the like are more vulnerable to alkalis than the glass epoxy base material, it is difficult to perform permanganate treatment under the same conditions by the above conventional method, which is not preferable in terms of work.

[0003]

In order to solve the above-mentioned conventional problems, the present inventors have proposed that the precipitation of manganese oxide on the inner wall of the through hole of the printed wiring board be changed to the conventional alkaline permanganate solution. However, it was proposed to do this by using a neutral permanganate solution. However, although this method can improve the conductivity and plating depositability of the conductive polymer coating, it facilitates the formation of a trace amount of a metal oxide coating on the copper foil, and thus the copper foil and the electroplated copper are separated from each other. There is a problem that a conductive polymer intervenes in the above, causing poor adhesion, and that a boundary is seen at the connecting portion.

The present invention prevents a decrease in the amount of manganese oxide deposited on the surface of the insulator of the inner wall of the through hole, particularly on the glass cloth, thereby improving the conductivity of the inner wall of the through hole and forming an inner layer copper foil. Provided is a method for producing a printed wiring board having excellent adhesion between an outer layer copper foil and electroplated copper.

[0005]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention uses a neutral permanganate solution to deposit a manganese oxide layer on the inner wall of a through hole and then performs pickling. Thus, the metal oxide coating on the copper foil is removed to solve the above problems. That is, the present invention includes (1) a step of treating a printed wiring board that has been perforated and washed with a solution containing a neutral permanganate, and (2)
A step of pickling the printed wiring board, (3) a step of applying an organic monomer to the inner wall of the through hole, and (4) a step of immersing the printed wiring board in an acid solution to conduct the organic monomer. The present invention provides a method for producing a printed wiring board, characterized in that a base for direct electrolytic copper plating is formed by a step including a step of forming a conductive polymer.

In this case, sulfuric acid can be used as the acid used in the step (2), and the concentration of the aqueous solution contains, for example, 5 to 10% and the treatment temperature is 1%.
0-30 degreeC is preferable.

[0007]

By treating the step (1) of treating with permanganate with a neutral solution, the decrease in the amount of manganese oxide deposited on the glass cloth, which is observed in the conventional alkaline solution, can be eliminated. Further, it is possible to improve the deposition of plating on the glass cloth and stabilize the quality of the product. further,
No boundary is seen between the copper foil and the electroplated copper, and the thermal shock test improves the reliability of the through hole.

[0008]

【Example】

Example 1 A through hole having a diameter of 0.6 mm was formed with a drill at a predetermined position of a multilayer printed wiring board (6 layers, board thickness 1.6 mm). Then, after removing burrs by surface polishing, permanganate desmear treatment was performed. Next, an oxidizer brushed DMA (trade name, manufactured by Brasberg) 80 g / l,
Using an etching solution consisting of 20 g / l of concentrated sulfuric acid, 30
Soft etching was performed for 3 minutes at ℃. Then, as a conditioner, a solution containing 15 ml / l of the surfactant Brasolit DMS2 Part 1 (Brasberg, trade name) and 30 ml / l of the surfactant Brasolit DMS2 Part 2 (Brasberg, trade name). make use of,
It was treated at 60 ° C. for 5 minutes. Furthermore, potassium permanganate treatment was performed at 90 ° C. for 5 minutes using a neutral solution containing 60 g / l of potassium permanganate. Next, it was treated for 1 minute at room temperature with a pickling solution containing concentrated sulfuric acid at 100 ml / l. The manganese oxide on the copper foil and the glass cloth before and after the pickling treatment was measured, but no decrease in the amount of precipitation was observed. After that, the organic monomer agent catalyst DM
Immerse S2 (Brasberg Co., trade name) in an aqueous solution containing 400 ml / l for 1 minute at room temperature to deposit an organic monomer, and then to dilute sulfuric acid (concentrated sulfuric acid 100 ml / l) 1
It was immersed for a minute, and the monomer was oxidatively polymerized to form a conductive polymer on the inner wall of the through hole. Next, as a copper sulfate plating bath, copper sulfate pentahydrate 70 g / l, concentrated sulfuric acid 180 g
/ L and an additive, Caprostar LP-1 (Brasberg, trade name) 4 ml / l, 2 A / dm
As a result of conducting electroplating at ² for 5 minutes and conducting a light transmission test of the through hole, the entire through hole was completely covered with plated copper. Further, when electroplating was performed at 2 A / dm ² for 60 minutes and the through hole cross section of the wiring board in which the copper plating film having a thickness of 25 μm was formed on the inner wall of the through hole was observed, the outer copper foil and the inner copper foil and the plated copper were No boundary was found at the connection. Using the wiring board prepared as described above, a solder dip test and a thermal shock test were conducted, but no abnormality was recognized at all.

Example 2 The same procedure as in Example 1 was carried out except that 50 ml / l of concentrated sulfuric acid was used as the pickling solution after the treatment with potassium permanganate and the treatment was carried out at room temperature for 1 minute. Similar results to Example 1 were obtained.

Comparative Example 1 In Example 1, a potassium permanganate solution was treated with potassium permanganate containing 10 g / l of sodium hydroxide at 90 ° C. for 5 minutes to deposit an organic monomer without pickling. Then, the same treatment as in Example 1 was performed except that a conductive polymer was formed on the inner wall of the through hole. as a result,
The amount of manganese oxide deposited on the copper foil is 0.01 mg / dm
^Although it was ² or less, the amount of manganese oxide deposited on the glass cloth decreased by 90%, and most of the glass cloth was plated in the through hole light transmission test 5 minutes after electroplating. It was not precipitated.

Comparative Example 2 The same treatment as in Example 1 was carried out except that no pickling was carried out after the treatment with potassium permanganate. As a result, no reduction in the amount of manganese oxide deposited on the glass cloth was observed, but about 0.2 mg / d on the copper foil.
Precipitation of m ² of manganese oxide was observed. Also, in the light transmission test of the through hole after 5 minutes of electroplating,
The entire through-hole was completely covered with plated copper and showed good plating depositability, but the cross-section of the through-hole after forming the copper plating film with a thickness of 25 μm was observed. Boundary and peeling were observed at the connection part of.

[0012]

As described above, according to the present invention, in the permanganate treatment step, the precipitation amount of manganese oxide is not lowered by making the pH of the bath neutral, so that the through It is possible to obtain a uniform and highly conductive polymer film in the hole. Further, by pickling after the permanganate treatment, since the metal oxide on the copper foil is removed, it is possible to prevent the occurrence of a boundary between the inner layer copper foil and the outer layer copper foil, and thereby the copper foil. The adhesion of the plated copper is improved, and the quality of the product can be stabilized.

Claims (1)

[Claims] 1. A step of: (1) treating a printed wiring board that has been perforated and washed with a neutral permanganate solution to deposit a manganese oxide layer on an insulator portion of an inner wall portion of a through hole; ) A step of pickling the printed wiring board from (1) above, and (3) a step of depositing an organic monomer capable of forming a conductive polymer on the printed wiring board from above (2) by oxidative polymerization. 4) Next, a step of immersing the printed wiring board from the above step (3) in an acidic solution to form a conductive polymer film on the insulator surface of the inner wall of the through hole. A method for manufacturing a printed wiring board, which comprises forming an underlayer for electrolytic copper plating.