JPS624396A - Manufacture of printed wiring board by tin alloy through hole plating - 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 Field of Application The present invention relates to an improved method of manufacturing printed wiring boards by through-hole plating. More specifically, the present invention relates to a method for manufacturing printed wiring boards using tin alloy through-hole plating, which improves the drawbacks of solder through-hole plating.

Printed wiring boards are essential parts for electronic devices as they are used to mount semiconductor elements.

(Conventional technology) Through-hole plating wiring boards have gold through-holes using metal as etching resist, solder through-holes, etc.
There are also steel through-holes whose circuit parts are made of steel and are etched using organic resist.

The present invention relates to improvements in solder through-hole printed wiring boards that are widely and generally used, and the solder through-holes will be explained.

First, a general manufacturing process for solder through-hole wiring boards will be explained. That is, this wiring board is manufactured using a copper-clad laminate made of Siplastics through the steps shown in the drawings.

Next, this process will be explained.

(1) Drilling.

(2) Electroless steel plating: A plating film having a thickness of υ0.2 to 0.5μ is formed by chemical plating.

(3) - Secondary steel electroplating; A primary copper electroplating film having a thickness of 15 to 20 μm is formed on the plated film by electrolysis.

(4) Form a resist film on the necessary portions.

(5) Secondary steel plating: A secondary electrolytic steel plating film with a thickness of 15 to 20 μm is formed on the areas where there is no resist film.

(6) Solder plating.

(7) Remove the resist film by melting only the resist film and not melting the solder.

(8) Etching; Melt the copper in the area where the resist film was removed.

(9) Aging: The rough solder surface is smoothed by raising the temperature to the melting point of the solder.

Mask the area other than the αG terminal, for example, 19 parts of glacial acetic acid, 3
Treat with a mixed acid containing 1 part of ON perchloric acid to remove the solder.

En: Gold or nickel plating is applied to the terminals after removing the solder to ensure good electrical contact with the connector.

This process has the following drawbacks, for example:

The process is generally complicated, and in order to make good contact between the terminal and the connector, it is necessary to apply solder to only this part, and then perform plating after the soldering process. Furthermore, a borosilicate bath is commonly used for solder plating.
In these treatments, it is necessary to take care not to cause pollution in the wastewater, etc. Toxic gas is generated when soldering or soldering, but due consideration must be given to occupational hygiene.

For the reasons mentioned above, there is a strong desire to simplify this process and develop a treatment method that does not cause pollution.

(Problems to be Solved by the Present Invention) As a result of various studies for the purpose of developing a method for manufacturing printed wiring boards that meets this demand, the present inventors have found that tin alloy plating can be used instead of the solder plating process in the above process. The present invention was completed after confirming that all the drawbacks of the solder through-hole plating method described above can be overcome by adding an additional process.

(Means for Solving the Problems) That is, the present invention provides printed wiring using tin alloy through holes, characterized in that tin alloy plating is performed after secondary copper electroplating in the through hole plating process of printed wiring boards. Concerning the manufacturing method of boards.

The applicant previously filed a patent application for an invention related to a tin alloy electroplating bath composition, and patent No. 102729 was filed.
2, No. 1166434, and No. 1180236 were established. The composition of Patent No. 1027292 contains tin,
Cobalt or tin and nickel chlorides, sulfates or sulfamic acid salts with 1-hydroxyethane 1,
1 The secondary phosphoric acid compound contains its salt, conductivity salt, aldehyde, and betaine, Patent No. 11664
The compositions of No. 34 and No. 1180236 contain a chloride or sulfate of tin and nickel or tin and cobalt, a conductive salt, tartaric acid or a salt thereof, and glyfur ether, respectively. In the production of the printed wiring board of the present invention, it is possible to use the plating bath compositions of the above-mentioned patents in the tin alloy plating performed after the secondary copper electroplating, but it is not limited to them. Any material that can form a tin alloy plating film on a copper film may be used.

Next, each component and content of the plating bath composition preferably used in the present invention will be described.

(a) As an alloy film forming agent, tin, nickel, or a chloride or sulfate of each of tin and cobalt is used as metal tin, metal nickel, and metal cobalt, and 15.
0? μ~22.0 f/l.

15 f/L M-10 f/L, 2. ．． 5-10
Danger (6) Conductive salt 100 fμ ~ 200 f/L Furthermore, as a complexing agent, 1-hydroxyethane 1.1 secondary phosphate ester 30 ~ 55 f/L: Organic acid such as tartaric acid, citric acid, etc. 50 f/L ~70 f/L nigericolic acid 30 t/L ~ 40 f/L of 111 or more are allowed to coexist.

Note that the above-mentioned complexing agents include salts of IJum, potassium, and the like.

In addition, a small amount of surfactant, such as sodium fluorobenzenesulfonate, is added to the plating solution to reduce the surface tension of the plating solution and prevent the plating solution from adhering to the object to be plated and being discharged out of the plating tank. It is preferable to mix vμ to 0.01f/.

Although known plating conditions may be used, a bath temperature of 30 DEG C. to 60 DEG C. is particularly preferred, and a carbon or ferrite electrode is used as the anode. And the current density is 0.5A/d
- to 2174 m'' is preferred.

(Effects of the Invention) When a printed wiring board is manufactured by carrying out tin alloy plating as in the present invention, there are the following advantages over the solder through-hole method.

In other words, there is no need for as many as 7 second inserts as in the case of a chipped through hole. Also, in the case of solder through-holes, it is necessary to use solder foil for the terminal part in order to make good electrical contact between the terminal and the connector. However, in the present invention, since the terminal portion is coated with a tin alloy plating film, there is no need for multiple masking treatments.

Furthermore, in the solder plating process and solder plating process, there is no need to consider the pollution problem that occurs when multiple processes are performed in the present invention.

(Example) Next, the present invention will be explained with reference to examples.

Example 1 After drilling a hole with a diameter of 1 in a copper-clad laminate in which a 35 μm copper foil was attached to both sides of a base material with a thickness of 1.6 sm, first a hole with a diameter of 0.0 mm was made.
A 5μ electroless steel plating layer is applied on both sides, and then a 2μ thick electroless steel plating layer is applied on both sides.
A 5μ secondary plating layer was applied on each side. Next, a dry 7-kilometre resist film was formed on the necessary parts of the secondary steel plating layer. Next, the printed wiring board on which this resist film was formed was treated with the following plating bath composition as an electrolytic bath. Plating treatment was performed under the conditions shown.

Plating bath composition (1) Compound for tin alloy film; stannic chloride pentahydrate 60 f/L, nickel chloride hexahydrate 13 fμ (2)
NH40L 200φ (3) Sodium citrate and gelcholic acid 35
tμ Plating conditions Anode Material name: Carbon, Current density: 1.0μ Bath temperature: 3
As a result of electrolysis at 5 DEG C. for 10 minutes or more, a tin-nickel alloy film having a thickness of 2 microns and containing 70 weight tin and 30 weight Niracle was formed on the secondary steel plating layer.

Next, the resist film was removed using an NaOH solution with a concentration of 3 to 5%, and then treated with an etching solution, which is an ammoniacal aqueous solution with a pH of &5 containing sodium chlorite and ammonium bicarbonate, to remove the resist film. I removed the copper from the part.

The terminal portion of this treated plate is coated with a tin-nickel alloy film with the same thickness of 2μ as the through-hole portion, and is plated with gold without having to undergo multiple treatments as in the case of solder through-holes. I was able to do this.

Further, necessary processing was performed to obtain a printed wiring board.

During the tin alloy plating process and other processes, no effluent that caused any pollution was generated. That is, according to this embodiment, the process of the present invention is simplified compared to the conventional method of manufacturing printed wiring boards by solder through-hole plating,
It is clear that the results are excellent, as there is no pollution problem.Examples 2 to 8 All of the methods used in Example I except that the plating conditions for the printed wiring board on which the resist film was formed were as shown in Table 1. The treatment was carried out under the same conditions as in Example 1. As a result, a tin alloy coating shown in Table 2 was formed on the secondary steel plating layer. Next, a printed wiring board was manufactured using the same process as in Example 1, and the process was simplified compared to solder through-hole plating, and no pollution problems occurred. . Table 3 shows the results of measuring the solder wettability of the tin alloy film produced by this method using the wet balance method specified in the Japan Tin Center's soldering guide.

Table 3 As the flux, Zersin 2010 was used.

[Brief explanation of drawings]

The drawing shows the general manufacturing process for through-hole wiring boards.

Claims (3)

[Claims] (1) A method for producing a printed wiring board by tin alloy through-hole plating, which comprises performing tin alloy plating after secondary copper electroplating in the through-hole plating process of the printed wiring board. (2) The method for manufacturing a printed wiring board according to claim 1, wherein the tin alloy plating is tin-cobalt alloy plating. (3) The method for manufacturing a printed wiring board according to claim 1, wherein the tin alloy plating is tin-nickel alloy plating.