JPS6036695A - Silver plating method of stainless steel wire for electronic parts - Google Patents

Abstract

PURPOSE:To obtain a lead wire which is inexpensive and has high tensile strength and excellent electrical characteristic and solderability by plating directly silver to the stainless steel wire which is chemically polished and electrolytically activated in a specifically composed acidic activating bath and cathodic electrolyzing bath. CONSTITUTION:A stainless steel wire is defatted and is then passed, under irradiation of an ultrasonic wave thereto, through a bath compounded with 15- 25vol% 35% hydrochloric acid, 5-15vol% 85% sulfuric acid, 5-15wt% citric acid powder, 0.5-1.5vol% 90% acetic acid, 4-6vol% 68% nitric acid, 0.1-0.3 wt% nonionic or amphoteric surface active agent and 0.0-0.15wt% amine corrosion inhibitor to remove oxide and impurities from the surface. A bath compounded with 5-15vol% 85% phosphoric acid, 5-15wt% 85% sulfuric acid, 5- 15wt% citric acid powder, 0.5-15wt% 90% acetic acid, 0.1-0.3wt% nonionic or amphoteric surface active agent and 0.05-0.15wt% amine corrosion inhibitor is heated and negative current is conducted to said steel wire to activate the surface thereof. The steel wire is subjected to silver strike plating after neutralization.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for silver plating stainless steel wire for electrical components, which is less expensive than conventional lead wires, and
Moreover, the present invention relates to a novel silver plating method for stainless steel wire for electrical components, which has high strength, excellent electrical properties and solderability.

Conventionally, lead wires for electrical components have been made of gold wire for high-performance equipment, and generally have been made of copper wire plated with tin or solder.

Further, relatively thick lead wires such as nickel wires or 42 nickel alloy wires are used for lead wires of electrical components such as automobiles and machines that require earthquake resistance.

Gold wire is most preferred due to its superior properties, but has the drawback of being very expensive, and copper wire has drawbacks in corrosion resistance and tensile strength. In addition, nickel wire and 42 nickel alloy wire have poor solderability, and when soldering is difficult, use hydrofluoric acid,
Soldering cannot be done without using flux such as nitric acid or hydrochloric acid.

If these fluxes are used for soldering, acid will remain after soldering and cause corrosion, so they are not preferred as lead wires for electrical components.

Therefore, nickel wire and 42 nickel alloy wire have the disadvantage that they cannot be welded except by spot welding or the like.

In order to provide a lead wire that is inexpensive, has high tensile strength, and has excellent electrical properties and solderability required as a lead wire for electrical components, the inventor has conducted research over a long period of time and developed a silver-plated stainless steel lead wire. The inventors discovered that steel wire has a much better fit than gold wire, copper wire, and old nickel wire, and based on this knowledge, they completed the present invention. That is, the gist of the present invention is a silver plating method for obtaining a silver-plated stainless steel wire.

The stainless steel wire to be silver plated according to the present invention has a diameter of 0.02 rmhl to 5 mm, preferably 0.03 rmhl to 2 mm.
rtar+, and the thickness of silver plating is 0.11tm~5
μm1 is preferably in the range 05 μm = 311 m.

Generally, when silver plating is performed, the material to be plated is first degreased, and then the surface is cleaned and activated using an acid bath.

In particular, it is necessary to completely remove the strong passivation film formed on the surface of stainless steel wire, but care must be taken not to erode the base of the stainless steel wire itself.

The present invention will be described below with reference to Examples, but the present invention is not limited to the Examples.

Example 1 Stainless steel (18
The Cr 8Ni ) wire was sequentially passed through the following steps (1) to (2) to be continuously silver plated.

■ Degreasing process A commercially available alkaline degreasing liquid for iron is heated to 70 to 80°C in a stainless steel tank, and the stainless steel wire is passed through this tank sequentially from the bobbin winding to perform primary degreasing. Next, DC electrolytic degreasing was performed in an alkaline bath at a temperature of 40 to 60 DEG C., using the stainless steel plate as an anode and the stainless steel wire as a cathode, and applying a voltage of 100 volts.

■Chemical polishing process The stainless steel wire is then polished with 20 volumes of hydrochloric acid (35% solution), 10 volumes of sulfuric acid (85% solution), 100% citric acid (powder), 1 volume of acetic acid (90φ solution), and nitric acid. (
68 solution) A mixed acid consisting of 5 parts, 0.2% by weight of a nonionic or amphoteric surfactant of amino acids such as polyethylene glycol alkyl ether or polyethylene glycol fatty acid ester, and an amine type (for example, Armohib 28 manufactured by Lion Armor) ) The stainless steel wire was passed through a bath containing 0.1% by weight of a corrosion inhibitor while being irradiated with ultrasonic waves of 600 W and 26 KHz to remove oxides and impurities on the surface of the stainless steel wire.

■Electrolytic activation process Add 10% by volume of phosphoric acid (85% solution), 100% by weight of sulfuric acid (85% solution), 100% by weight of citric acid (powder), 1% by weight of acetic acid (90% solution). Alternatively, a solution containing 02% by weight of an amphoteric surfactant and 11% by weight of a corrosion inhibitor is heated to 60°C, and a (-) current is passed through the stainless steel wire and a (+) current is passed through the titanium platinum plated plate to a voltage of 4 volts. The surface of the stainless steel wire was activated by passing it through the bath.

(2) Alkali neutralization process Alkali neutralization was carried out by passing through a 5% by weight solution of potassium cyanide (powder).

■Silver strike plating process In a plating solution containing 5% by weight of silver cyanide, 15% by weight of copper cyanide, and 100% by weight of potassium cyanide, the temperature of the solution was kept at 25℃ for 7 seconds. (+
) A current was passed through the sample, and a strike plate (6) was applied continuously for 10 seconds at a current density of 5 A,/dm''.

■Silver plating 7 "Cyanide IJ 120,!9 / 1% potassium carbonate 259/e, potassium hydroxide 160g/l plating bath, keeping the liquid temperature at 40°C, at a current density of 7A/dm2. Silver plating was performed continuously for 5 minutes by applying a (-) current to the stainless steel wire and a (''-) current to the silver plate.

As a result, a silver plating layer with a thickness of about 3 μm was formed on the surface of the stainless steel wire, and a silver-plated stainless steel wire was obtained.

Example 2 Wire diameter: 0.5 +n+n length: 30 [A 10 m stainless steel (18Cr 12Ni 2Mo) wire was silver plated through the same process as in Example 1.

The results of the performance tests of the silver-plated stainless steel wire obtained through the above steps are shown below. ) As a result of a rapid cooling test after heating at 400° C. for 10 minutes, no peeling of the silver plating layer from the stainless steel wire was observed in all three methods.

Solderability test) (a) Test results using a solder test machine showed that the solder wettability was extremely good, and there was almost no upward movement of the solder due to the surface tension of the solder at the initial stage of solder immersion.

(b) Solder was melted at 230°C, and a silver-plated stainless steel wire was dipped into the solder, taken out after 10 seconds, and inspected for solderability. As a result, over 98% of the immersed area was found to have adhered solder. .

(c) A silver-plated stainless steel wire is placed in an electric furnace set at 500°C, taken out after 2 minutes, allowed to cool in the atmosphere, and then immersed in solder melted at 260°C for 10 seconds.
] The sex was tested. As a result, there were no blisters at all, and the solder adhered evenly over the entire surface of the stainless steel wire, with no areas of poor adhesion found.

Compared to electrically conductive nickel wire or .42 nickel wire, it was found to have more than twice the electrical conductivity.

A uniform silver plating layer is formed on the stainless steel wire]
Therefore, the uniformity of the wire diameter was maintained.

Tensile Strength Test Comparing the tensile strength of a gold wire with a wire diameter of 0.05 bleached wire and a silver-plated stainless steel wire, the strength of the stainless steel wire is approximately twice that of the gold wire, and even compared to copper wire. , the stainless steel wire exhibited approximately twice the tensile strength.

As the above performance test results show, the silver plating method of the present invention achieves high performance! Compared to gold wire, stainless steel is superior in price and strength: 1. Compared to copper wire, 1. has superior corrosion resistance and strength; 2. Compared to Nokel wire,
It is understood that the industrial effects of the present invention are extremely remarkable, and the electrical characteristics are incomparable. Be it...),,
(9)

Claims (1)

[Claims] Hydrochloric acid (55% solution) 15-25 volume, sulfuric acid (85 solution) 5-15 volume, citric acid powder 5-15 weight, acetic acid (90% solution) 05-15 volume , nitric acid (68 volume solution) 4-6 volume ratio, non-ionic or amphoteric surfactant 01-
A chemical polishing process in which stainless steel wire is immersed in an acidic activation bath containing 0.3% by weight and an amine-based corrosion inhibitor 005 to 0.15% by weight, and phosphoric acid (85% solution) from 5% to 15 parts by weight, sulfuric acid (85 parts solution) 5 to 15 parts by weight, citric acid powder 5 to 15 parts by weight, acetic acid (90 parts solution) 05 to 155 to 15 parts by weight Still amphoteric surfactant 01 to 031 to 03 Weight related corrosion inhibitor 0.
an electrolytic activation step of activating the stainless steel wire using a cathode electrolytic bath containing 05 to 015 weight factor; and a step of directly silver plating the stainless steel wire with an acidic silver plating bath. A method for silver plating stainless steel wire for electrical parts, characterized by: