JPH04314397A - Manufacture of multi-layer printed wiring board - Google Patents

Abstract

PURPOSE:To eliminate the lowering of connection reliability or the generation of defective connection between the plating copper in through-holes and the internal layer copper when the circuit is formed through electroless plating. CONSTITUTION:In one production step for printed wiring boards, a resin substrate provided with an adhesive layer including catalyst is drilled for interlayer connection, a smear processing is carried out on it, a resist is printed, and the adhesive layer is roughed by using a roughing solution to form a circuit through electroless copper plating. On the other hand, in the other production step for printed wiring boards, a resin substrate provided with an adhesive layer is drilled for interlayer connection, the adhesive layer is roughed by using a roughing solution and catalyzed thereafter, and a resist is printed to form a circuit through electroless copper plating. In the above both production steps for the printed wiring boards, a metallic film is formed on the internal layer copper walls exposed in the through-holes after drilling processing and before roughing processing.

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 multilayer printed wiring board, and more particularly to a method for manufacturing a multilayer printed wiring board in which circuits are formed by electroless copper plating.

0002

2. Description of the Related Art In recent years, in response to the increasing density of printed wiring boards and changes in mounting methods, a method of manufacturing multilayer printed wiring boards using a so-called full additive method has been attracting attention.

[0003] This involves punching or drilling holes in a resin substrate with a catalyst-containing adhesive layer, then smearing the resin substrate, printing a resist, then roughening the adhesive layer with a roughening liquid, and applying electroless copper plating to the circuit. Alternatively, after punching or drilling holes in a resin substrate with an adhesive layer, roughen the adhesive layer with a roughening liquid, perform catalytic treatment, print a resist, and then form a circuit with electroless copper plating. The method is to form.

0004

[Problems to be Solved by the Invention] However, in the method of manufacturing multilayer printed wiring boards using the conventional fully additive method as described above, most of the roughening liquid used in the roughening process is a strong acid oxidizer. It is a liquid and copper is relatively easily attacked by it, so when the inner layer copper is etched back and a circuit is formed using electroless copper plating, the connection reliability between the plated copper inside the through hole and the inner layer copper may be reduced or there may be a connection failure. There was a problem that occurred.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a manufacturing method using a fully additive method, and moreover, which eliminates the etch-back of the inner layer copper in the roughening process. It is an object of the present invention to provide a method for manufacturing a multilayer printed wiring board that can suppress the above problems.

[0006]

[Means for Solving the Problems] The method of suppressing etchback of inner layer copper of the present invention is to protect inner layer copper with a metal film,
Metal coatings include Ni, Au, Pd, Sn, Cu, and C.
o, Pb, Cr, Zn, Ag, Rh, Pt, Re, In
It is characterized by being an alloy containing one or more of these metals.

The metal coating used in the present invention may be of any type other than those mentioned above as long as it is resistant to attack by the roughening solution. Further, the reason why Cu is also used as the metal film is that by forming a protective copper metal film on the inner layer copper wall, the copper metal film is first etched, thereby suppressing the amount of etchback of the inner layer copper.

[0008] The metal film is formed after drilling and before the roughening step. Electroless plating is the preferred method for forming the metal film. Further, the formation of the metal film may require one or more plating steps. Furthermore, since the purpose is achieved if the metal coating is formed on the inner layer copper wall, it does not matter whether the entire inside of the through hole is covered with the metal coating or only the inner layer copper wall is covered. Note that a metal plating layer is not formed on the surface of the substrate by electroless plating unless it is subjected to a roughening process. Therefore, the metal film for protecting the inner layer copper is formed only within the through hole.

[0009]

[Operation] By performing metal coating after drilling and before the roughening process, etchback of the inner copper layer during the roughening process does not occur at all or is considerably suppressed. Therefore,
When forming a circuit using electroless copper plating, no connection failure occurs between the plated copper inside the through-hole and the inner layer copper, and connection reliability is also improved.

0010

EXAMPLES The present invention will be explained below based on examples. (Example 1) After punching or drilling holes in a multilayer substrate with a catalyst-containing adhesive layer, smearing was performed, and then P was replaced.
d plating was performed at room temperature for 3 to 5 minutes, and after washing with water, electroless Ni plating was performed at 75 to 80° C. for 5 minutes. After printing the resist, the adhesive layer was roughened using a chromic acid/sulfuric acid mixed roughening solution at 36°C for 5 minutes, and after further neutralization and plating pretreatment, the circuit was formed using electroless copper plating. A multilayer printed wiring board was fabricated. The resistance between the inner layer copper and the through-hole copper was measured, and the number of cycles of the hot oil test (260° C. for 5 seconds, water for 5 seconds) until disconnection occurred was determined. The results are shown in the table. (Example 2) A multilayer substrate with a catalyst-containing adhesive layer was punched or drilled, smeared, and electroless Ni plated at 75 to 80°C for 5 minutes. Next, after printing the resist, use a roughening solution of chromic acid/sulfuric acid mixture to
After roughening the adhesive layer at ℃ for 5 minutes, performing neutralization and pre-plating treatment, a circuit was formed by electroless copper plating to create a multilayer printed wiring board. The resistance between the inner layer copper and the through-hole copper was measured, and a hot oil test (26
The number of cycles (5 seconds at 0°C, 5 seconds at water) was determined. The results are shown in the table. (Example 3) A multilayer substrate with a catalyst-containing adhesive layer was punched or drilled, then smeared and electroless Au plating was performed. Next, after printing the resist, the adhesive layer was roughened using a chromic acid/sulfuric acid mixed roughening solution at 36°C for 5 minutes, neutralized and pre-plated, and then the circuit was formed using electroless copper plating. A multilayer printed wiring board was fabricated. Measure the resistance between the inner layer copper and through-hole copper, and conduct a hot oil test (260°C for 5 seconds, water for 5 seconds) until disconnection occurs.
The number of cycles was calculated. The results are shown in the table. (Example 4) A multilayer substrate with a catalyst-containing adhesive layer was punched or drilled, then smeared, a resist was printed, and electroless Ni plating was performed at 75 to 80° C. for 5 minutes. Next, a roughening solution of chromic acid/sulfuric acid mixture was used at 36°C.
The adhesive layer was roughened for 5 minutes, neutralized and pre-plated, and a circuit was formed by electroless copper plating to create a multilayer printed wiring board. The resistance between the inner layer copper and the through-hole copper was measured, and a hot oil test (260
The number of cycles (5 seconds at °C, 5 seconds at water) was determined. The results are shown in the table. (Example 5) After punching or drilling holes in a multilayer substrate with an adhesive layer, smearing is performed, followed by displacement Pd plating at room temperature for 3 to 5 minutes, and then electroless Ni plating after washing with water at 75 to 80°C. I did it for 5 minutes. Then, the adhesive layer was roughened using a chromic acid/sulfuric acid mixture roughening solution at 36° C. for 5 minutes to perform neutralization. Next, perform catalytic treatment,
After printing the resist, a circuit was formed by electroless copper plating to create a multilayer printed wiring board. The resistance between the inner layer copper and the through-hole copper was measured, and the number of cycles of the hot oil test (260° C. for 5 seconds, water for 5 seconds) until disconnection occurred was determined. The results are shown in the table. (Comparative Example) A multilayer substrate with a catalyst-containing adhesive layer was punched or drilled, and then smeared. After printing the resist, the adhesive layer is roughened using a chromic acid/sulfuric acid mixed roughening solution at 36°C for 5 minutes, neutralized and pre-plated, and a circuit is formed by electroless copper plating. Then, a multilayer printed wiring board was created. The resistance between the inner layer copper and through-hole copper is measured, and a hot oil test (
The number of cycles (5 seconds at 260°C, 5 seconds at water) was determined. The results are shown in the table. (Hereafter, margin)

[0011]

[Table 1]

0012

[Effects of the Invention] As explained above, in the present invention,
This method has the effect that a high-quality multilayer printed wiring board can be obtained, with no inner layer connection failure occurring at all, and connection reliability being significantly improved.

Claims (6)

[Claims] Claim 1: After drilling holes in a resin base plate with a catalyst-containing adhesive layer for interlayer connection, smearing is performed, a resist is printed, the adhesive layer is roughened with a roughening liquid, and electroless copper plating is applied. In the process of forming a circuit, or after drilling holes in a resin substrate with an adhesive layer for interlayer connection, the adhesive layer is roughened with a roughening liquid, catalyzed, and after printing a resist, electroless copper plating is performed. A method for manufacturing a multilayer printed wiring board comprising a step of forming a circuit, which comprises forming a metal film on at least the inner layer copper wall exposed in the through-holes after the hole-drilling step and before the roughening step. Production method. [Claim 2] The metal film is Ni, Au, Pd, Sn, C.
u, Co, Pb, Cr, Zn, Ag, Rh, Pt, Re
, In, or an alloy containing one or more of these metals. [Claim 3] The metal film is Ni, Au, Pd, Sn, C.
u, Co, Pb, Cr, Zn, Ag, Rh, Pt, Re
, In, or an alloy containing one or more of these metals, and is formed by electroless plating. Claim 4: The metal film is made of Ni or Ni alloy,
2. The method of manufacturing a multilayer printed wiring board according to claim 1, wherein the multilayer printed wiring board is formed by electroless Ni plating after the catalytic treatment. 5. The catalytic treatment in claim 4 comprises substituted Pd
The method for manufacturing a multilayer printed wiring board according to claim 1, characterized in that the method is a plating method. [Claim 6] The metal film is made of Au, and the metal film is made of N on the inner layer copper wall.
2. The method of manufacturing a multilayer printed wiring board according to claim 1, wherein after coating the layer i, the layer is formed by electroless Au plating.