JPH0210237B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrolytic pretreatment agent suitable for plating iron and nickel alloys.

Iron (e.g. stainless steel), nickel alloy (e.g. 42% Ni alloy with the remainder Fe,
"Kovar" with 29% Ni, 17% Kovar, and the balance of Fe
etc.), it has conventionally been considered essential to perform strike plating before main plating. This is to improve the adhesion of plating (for example, silver plating) to the base material beforehand, and conventionally, it has been common practice to perform degreasing, activation, and strike treatments, and then apply the final plating. Plating of iron and nickel alloys is performed through processes such as peeling off unnecessary strike plating.

However, the strike plating process, like the main plating process, requires careful handling and is expensive (for example, in the case of gold strikes and silver strikes).
Since a stripping step is required (for example, stripping the copper strike in the case of copper strike-silver plating), there are many advantages in various plating processes if this can be omitted.

The present invention focuses on this point and aims to provide an electrolytic pretreatment agent that can omit the strike treatment and strike step that are essential to conventional plating treatment. Specifically, the electrolytic pretreatment agent for iron and nickel alloys according to the present invention contains various conductive salts, an anode activator, and potassium gold cyanide.

First, this electrolytic pretreatment agent selectively contains the following as various conductive salts.

Potassium cyanide 5-150g / Sodium cyanide 10-250g / Organic acid (e.g. salts such as citric acid, oxalic acid, tartaric acid, etc.) 20-200g / Sulfamic acid (e.g. sulfamic acid and salts) 10-250g / Next, this electrolytic pretreatment The agent contains an anode activator. As this anode activator, metal complexes such as nickel and cobalt are suitable, and 0.5
~50g/approximately.

Further, the electrolytic pretreatment agent contains gold potassium cyanide. The content may be a trace amount, for example, about 5 to 200 ppm (0.05 to 2 g/) as gold metal.

To pre-treat iron and nickel alloys after degreasing and activating them with such an electrolytic pre-treatment agent, a solution using an electrolytic pre-treatment agent (hereinafter referred to as "electrolytic pre-treatment agent") is required.
is operated under the following conditions.

PH 3.0 or higher Voltage 1~8V Time 5-120 seconds Temperature Room temperature ~ 70℃ Next, an example will be described.

Example 1 Electrolytic pretreatment liquid composition Potassium cyanide 50g / Potassium carbonate 20g / Potassium nickel cyanide 10g / Potassium gold cyanide
0.1g/(as gold metal) Operating conditions Voltage 6V Time 20sec Temperature 35°C or above, the Kovar IC lead frame is degreased and activated, followed by electrolytic pretreatment, and directly silver plated to 3μ without strike plating. did.
A peel test was then performed using cellophane tape (trade name), but the silver plating did not peel off, confirming that the adhesion had improved. We also conducted a heat resistance test at 380℃ for 5 minutes, but no discoloration or blistering was found.

Example 2 Pretreatment liquid composition Potassium citrate 100g/ Potassium phosphate 10g/ Potassium cobalt cyanide 10g/ Potassium gold cyanide
0.2g/(as gold metal) Operating conditions PH 6.8 Voltage 4V Time 20sec Temperature 60°C or above, the lead wire of the 42 alloy semiconductor is degreased and activated, followed by electrolytic pretreatment, and directly applied without strike plating. 3μ silver plating was applied.
When this lead wire was subjected to a bending test, no peeling of the silver plating was observed, and a heat resistance test at 380°C for 5 minutes was also performed, but no discoloration or blistering occurred.

As explained above, according to the present invention, since various conductive salts are combined with an anode activator and a trace amount of gold potassium cyanide is used, iron,
Direct plating is performed on the nickel alloy substrate by simply performing electrolytic pretreatment using this electrolytic pretreatment agent following degreasing and activation without performing strike plating treatment such as nickel strike, gold strike, silver strike, or copper strike. This simplifies the plating process, which was indispensable for conventional strikes, and contributes to cost reductions.It can also be expected to improve adhesion to the same level as conventional strikes, and requires weakly acidic alkali treatment instead of strong acid. Therefore, corrosion resistance is improved, and in addition, in conventional plating treatments such as copper strike-silver plating, copper comes out on the surface of precipitates by a so-called diffusion phenomenon and tends to generate oxides. Use of the pretreatment agent of the invention eliminates the need for copper strikes, which has the effect of completely eliminating such problems and contributing to improved electrical characteristics. Furthermore, since the peeling process can be omitted, it is also economical and has many advantages over conventional plating processes.

Claims (1)

[Claims] 1. An electrolytic pretreatment agent for iron and nickel alloys containing 5 to 250 g of various conductive salts, 0.5 to 50 g of an anode activator, and 0.05 to 2 g of gold potassium cyanide as gold metal. . 2. The electrolytic pretreatment agent for iron and nickel alloys according to claim 1, wherein the anode activator is a metal complex of nickel and cobalt.