JP2857546B2 - Pretreatment method for nickel surface during printed wiring board manufacture - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a printed wiring board, particularly a rigid board such as an IC module and a wiring board such as a flexible board, by applying an electrolytic gloss to the surface of nickel plated by electrolysis or electroless. The present invention relates to a pretreatment method for performing solder plating or solder leveling such as solder plating, electrolytic matte solder plating, and electroless solder plating.

[0002]

2. Description of the Related Art In recent years, soldering has been performed on a nickel surface of a rigid board such as an IC module and a wiring board such as a flexible board by solder plating or a solder leveler. The surface of a nickel film formed by nickel plating or electrolytic nickel plating is not immediately soldered or soldered by a solder leveler, and it is difficult to install a series of directly connected lines. Therefore, after the nickel film is formed on the wiring board, it is often left unattended before solder plating or solder leveling. For this reason, conventionally, before solder plating or solder leveling, the nickel surface is treated with a diluted solution such as sulfuric acid, hydrochloric acid, borofluoric acid, or a persulfate or organic acid solution that is thought to dissolve nickel. Was processing. However, it is difficult to completely remove the oxide film of nickel by this pretreatment method for the nickel surface, and it is unstable because nickel is melted or not melted. Insufficient wettability caused the solder to stick and the plate thickness to become non-uniform, the solder to peel off, the nickel surface to be exposed at the time of component mounting, and deterioration due to oxidation of nickel.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for pretreating a nickel surface capable of completely removing a nickel oxide film.

[0004]

According to the present invention, there is provided a method for pretreating a nickel surface at the time of manufacturing a printed wiring board, which comprises the steps of: In plating or solder leveling, the nickel surface is treated with a mixed solution of hydrogen peroxide and sulfuric acid.

[0005]

As described above, in the method for pretreating a nickel surface during the manufacture of a printed wiring board according to the present invention, the nickel surface is treated with a mixed solution of hydrogen peroxide and sulfuric acid, that is, treated with an oxidizing agent. Is completely removed, and the nickel itself is melted to reveal a clean nickel surface.

[0006]

Embedded image

[0007] If the clean nickel surface is plated with solder or a solder leveler, the wettability of the solder is good, the solder does not stick, and the thickness becomes uniform. In addition, the adhesion of the solder is good, and there is no peeling of the solder, no exposure of the nickel surface at the time of component mounting, and no deterioration due to oxidation of nickel.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a method for pretreating a nickel surface at the time of manufacturing a printed wiring board according to the present invention will be described. The wiring board was subjected to electroless nickel plating at 5 μm, washed with water, and dried. Then, the wiring board was immersed in a mixed solution of hydrogen peroxide and sulfuric acid for 1 minute to dissolve the nickel surface at 0.3 μm to form a clean nickel surface. . Thereafter, washing with water, sulfuric acid treatment, washing with water, borofluoric acid treatment, and washing with water were performed, and a 5 μm electrolytic bright solder plating was applied, followed by washing with water, washing with hot water, and drying.

Next, a second embodiment will be described. After applying 5μm electrolytic nickel plating to the wiring board, washing with water and drying, the wiring board is passed through a spray tank of a mixed solution of hydrogen peroxide and sulfuric acid over a period of 0.5 minutes using a conveyor system to dissolve the nickel surface by 0.3μm. And a clean nickel surface. After that, it was washed with water, dried, and solder leveled to adhere 5 μm of solder, washed with hot water, washed with water, and dried.

A description will be given of a conventional example 1 with respect to the first embodiment. After electroless nickel plating was applied to the wiring board at 3 μm, washed with water and dried, the wiring board was immersed in a dilute solution of ammonium persulfate for 1 minute to treat the nickel surface.
Thereafter, washing with water, drying, treatment with borofluoric acid, and washing with water were performed, 5 μm of electrolytic glossy solder plating was applied, washing with water, washing with hot water, and drying were performed.

A description will be given of a second conventional example with respect to the second embodiment. Apply 5 μm electrolytic nickel to the wiring board and wash with water,
After drying, the wiring board was passed through a spray tank of a 10% dilute sulfuric acid solution for 0.5 minute by a conveyor system to treat the nickel surface. After that, it was washed with water, dried, and solder leveled to adhere 5 μm of solder, washed with hot water, washed with water, and dried.

The first and second embodiments and the conventional examples 1 and 2
As a result of a peel test of the adhesion of the solder in the first and second examples, while the solder was partially peeled in the conventional examples 1 and 2,
In the example, there was no peeling of the solder.

When the wettability of the solder was evaluated by leaving it at a high temperature, in the conventional examples 1 and 2, the sink of nickel and the solder was partially generated. The solder was completely wet in minutes.

Further, when the wettability was evaluated using a reflow furnace, the conventional examples 1 and 2 partially suffered sink marks of nickel and solder, whereas the first and second examples exhibited soldering at 240 ° C. for 15 seconds. Was completely wet.

[0015]

As described above, according to the method for pretreating a nickel surface at the time of manufacturing a printed wiring board according to the present invention, a nickel oxide film is completely removed, and nickel itself is dissolved to produce a clean nickel surface. . Therefore, when the clean nickel surface is plated with solder or a solder leveler, the wettability of the solder is good, the solder does not stick, and the thickness becomes uniform. In addition, the adhesion of the solder is good, the solder does not peel off, and the nickel surface is not exposed at the time of mounting components, there is no deterioration due to oxidation of nickel, and the reliability is improved.

Claims (1)

(57) [Claims] 1. A method of manufacturing a printed wiring board, wherein, when solder plating or solder leveling is performed on a nickel surface plated on the wiring board, the nickel surface is treated with a mixed solution of hydrogen peroxide and sulfuric acid. Pretreatment method of nickel surface at the time of plate manufacturing.