JPS63222497A - Manufacture of printed wiring board by applying double-layer nickel-tin alloy plating to through-hole - 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 <Industrial Application Field> 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 include gold through-holes using metal in etching resist, solder through-holes, etc.
There are also copper through-holes in which the circuit parts are made of copper and are etched using organic resist.

The present invention relates to an improvement of a solder through-hole printed wiring board that is widely and generally used, and the solder through-hole will be explained.

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

Next, this process will be explained.

1. Drilling.

2. Electroless copper plating: A plating film with a thickness of 0.2 to 0.5 pots is formed by chemical plating.

3.-Blow-out electroplating; A primary copper electroplating film having a thickness of 15 to 20 W is formed on the above-mentioned plating film by electrolysis.

4. Form a resist film on the necessary areas.

5. Form a secondary electrolytic copper plating film with a thickness of 15 to 20 μl on the area where there is no secondary steel plating resist film.

6. Perform 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. Fusing: Raise the temperature to the melting point of the solder to smooth out the rough surface of the solder.

10. Mask the area other than the terminal part, for example, 19 parts of glacial acetic acid, 3
The solder is removed by treatment with a mixed acid consisting of 1 part of 0% perchloric acid.

11. Gold plating, nickel plating, etc. are applied to the terminal parts from which the solder has been removed in order to make good electrical contact with the connector.

This process has some drawbacks, such as:

The process is generally complicated, and in order to make good contact between the terminal and the connector, it is necessary to peel off the solder only in this area and then perform plating treatment after peeling. Furthermore, borofluoride baths are generally used for solder plating, and care must be taken to prevent pollution from occurring in waste water and the like during these treatments. Also, due to the possibility of toxic gas being generated during solder stripping, due consideration must be given to occupational hygiene.

For the reasons mentioned above, there is a strong demand for the development of a treatment method that simplifies this process and does not cause pollution.

As a result of various researches aimed at developing a manufacturing method for printed wiring boards that meets this demand, the inventors of the present invention have found that by providing a tin alloy plating process in place of the solder plating process in the above process, the solder through-hole plating method described above has been developed. Confirming that the drawbacks of the invention would be resolved, he filed Japanese Patent Application No. 142,610/1983.

<Problems to be Solved by the Invention> However, in the invention according to the above-mentioned application, the tin alloy film produced by the tin alloy plating process is prone to cracking when coated thickly.

If the etching process is performed with cracks present in the coating, the etching solution will reach the surface of the copper and corrode the copper.

Also, due to side etching, the tin alloy film on the copper film may protrude from the copper film due to lateral force, but in this case, the protruding portion is likely to be damaged.

The present inventors have conducted various studies to solve the above-mentioned drawbacks of the tin alloy coating, and found that by first performing nickel plating after secondary steel plating, and then performing tin alloy plating to provide a two-layer plating coating, The present invention was completed after confirming that the above-mentioned drawbacks were resolved.

<Means for solving the problem> That is, the present invention is characterized in that in the through-hole plating process of printed wiring boards, after secondary copper electroplating, nickel plating is first performed, and then tin alloy plating is performed. This invention relates to a method for manufacturing printed wiring boards using tin alloy through holes.

The applicant previously filed a patent application for an invention relating to a tin alloy electroplating bath composition, and patented ':51027.
292, No. 1166434, and No. 1180236 were established. The composition of Patent No. 1027292 contains tin, cobalt, or respective chlorides of tin and nickel;
It contains 1-hydroxyethane 1.1 secondary phosphate or its salt, conductivity salt, aldehyde, betaine in sulfate or sulfamic acid salt, and is disclosed in Patent No. 116.
The compositions of No. 6434 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 glycol ether, respectively. In the production of the printed wiring board of the present invention, is it possible to use the plating bath compositions of the above-mentioned patents in the tin alloy plating performed subsequent to the nickel plating after the secondary copper electroplating, or is it limited to them? It may be any material that can be formed on a copper film such as a tin alloy plating film.

Further, nickel plating is performed by known means.

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

1. First, let's talk about the composition of the nickel plating bath.

(a) Contains 20 g/I to 150 g/I of nickel salt as a nickel film forming agent as metal nickel (b) 15 to 50 g/I of boric acid as a pH adjuster.

Plating conditions are (1) pH 3.5-4.5 (2) Temperature 30-55℃ (3) Cathode current density: 1 to 5 A/d+*''.

2. Describe the composition of tin alloy plating bath.

(a) As an alloy film forming agent, tin, nickel, or a chloride or sulfate of tin or cobalt is used as metal tin, metal nickel, or metal cobalt, and 10.
0 g/l ~: 15. Og/l, 1.5 g/I~10
g/I, 2.0 g/l to 10 g/1 (b) conductive salt 100 g/l to 200 g/l and 1-hydroxyethane as a complexing agent. 1 Second phosphoric acid ester 30-55 g/I; Organic acids such as tartaric acid and citric acid 50 g/l-70 g/I; Glycolic acid: 10 g
/l to 40g/l of one or more types are allowed to coexist. Note that salts of sodium, potassium, etc. can also be used for the above-mentioned complexing agents.

In addition, in order 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, a small amount of surfactant such as sodium fluorobenzenesulfonate (0.005 g/ml) is added to the plating solution. I~0.01 g/
It is best to mix about 1.

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 0.5 A
A range of 2 to 2 A/d/d is preferable.

In addition, in the present invention, the thickness of the nickel plating film is 0.5~
3IL, the thickness of the tin alloy plating film is preferably 0.5 to Ig. The reason for this is described next.

The purpose of tin alloy plating is to create an etching resist, and due to its good corrosion resistance against this alloy etching solution, there is no need to make the film thicker than necessary.
is sufficient to achieve the purpose.

The purpose of nickel plating is to prevent the tin alloy on the sleeve from falling off due to overetching, and for this reason a thickness of 0.5 to 3p is required.

Furthermore, the copper is coated with tin-nickel or tin-cobalt for corrosion protection.

<Effects of the Invention> When nickel plating is first performed after double-blow plating and then tin alloy plating is performed according to the present invention, the produced film has the following advantages.

That is, even if the plating film is thick, there is no risk of the clutch engaging, and therefore there is no risk of corrosion of the copper layer.

Furthermore, even if the copper layer is side-etched, there is no risk of damage to the alloy itself on the copper layer. And the above-mentioned patent application in Showa 6
The following characteristics when manufacturing a printed wiring board by performing tin alloy plating according to No. 0-142610 are maintained as they are.

That is, there is no need for a fusing process as in the case of solder through holes. In addition, in the case of solder through-holes, it is necessary to strip the solder from the terminal part in order to make good electrical contact between the terminal and the connector, and this stripping process requires masking the area other than the terminal part so that the solder on other parts does not peel off. However, in the present invention, since the terminal portion is covered with a tin alloy plating film, there is no need for peeling treatment.

Furthermore, in the present invention, there is no need to consider the pollution problem that occurs during solder plating processing and solder plating film peeling processing.

<Example> Next, the present invention will be explained with reference to examples.

Examples 1 to 6 After drilling a hole with a diameter of 1 sm in a copper-clad laminate with a 35w copper foil pasted on both sides of a base material with a thickness of 1.6 mars, first, a hole with a diameter of 1 sm was made using electroless copper with a thickness of 0.5 mars. A plating layer was applied on both sides, followed by a 25 IL thick secondary phase plating layer on each side. Then, a dry film resist film was provided on the necessary portions of the secondary phase plating layer. A total of 6 samples were prepared in the same manner.

Next, each sample, which is a printed wiring board provided with this resist film, was first formed with a nickel film, and then a tin alloy film was formed thereon.

Nickel film formation plating bath composition and plating conditions.

The thickness of the produced nickel plating film is shown in Table 1, and the plating bath composition, plating conditions, plating film composition, and thickness of the produced tin alloy film are shown in Table 2.

As shown in Table 1 and Table 2 above, a plating film consisting of a nickel plating layer and a tin alloy layer could be formed on the secondary phase plating layer.

Next, the resist film was removed using a NaOH solution with a concentration of 3 to 5%, and then treated with an etching solution that is an ammoniacal aqueous solution containing sodium chlorite and ammonium bicarbonate with a pH of 8.5 to remove the resist film. The copper in the exposed area was peeled off.

Next, a tin alloy plating treatment was performed to protect the copper sleeve portion created by etching.

The terminal portion of this treated plate has a tin alloy coating formed on the nickel coating, similar to the through-hole portion, and can be plated with gold as is, without having to be peeled off like in the case of solder through-holes. was completed.

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

Plating with nickel and tin alloys and other treatments did not produce any waste fluid that could cause pollution.

Furthermore, there was no fear that the tin alloy would cause clutching or damage to the plating film, unlike in the case of only a plating film.

Next, Table 3 shows the results of measuring the solder wettability of the two-layer coating made of nickel and tin alloy according to the method of the present invention using the wet balance method specified in the Japan Tin Center's soldering manual.

Table 3 As the flux, Zersin 201O was used.

[Brief explanation of drawings]

The drawings show a general manufacturing process for through-hole wiring boards.

Claims (3)

[Claims] (1) A method for manufacturing a printed wiring board by tin alloy through-hole plating, characterized in that in the through-hole plating process of the printed wiring board, after secondary copper electroplating, nickel plating is first performed, and then tin alloy plating is performed. (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.