JPS6126798A - Electrodeposition hard gold plating bath and method - 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 Field of Application] The present invention includes potassium potassium cyanide, malic acid, and potassium hydroxide in an aqueous solution. The present invention relates to an acid cyanide bath for electrodepositing hard gold plating of electrical contact members, and a method of using this bath to electrodeposit hard gold plating of electrical contact members.

BACKGROUND OF THE INVENTION Fully electrodeposited materials are distinguished by their excellent corrosion resistance and very good electrical properties, both of which are particularly useful in plug-in connections, relay and switchgear contacts, and similar components. It is of great significance in electrical contact components, since in these components the electrically deposited gold layer must protect the support material from corrosion and transmit energy without loss. In this case, a constant and low contact resistance of 1 m/l'7c is most important.In addition, the mechanical stress of the contact member (1) The hardness and wear resistance of the gold layer are extremely important. Corresponding wear-resistant hard metals are often produced from plating baths containing so-called hardeners, in which metals such as cobalt or nickel are used as hardeners in the acidic baths.Cobalt The hardness of the precipitate can be increased as desired by alloying base metals such as C and nickel, but may be influenced by other properties of the co-deposited layer.

Especially when contact parts are placed in high temperature areas.

The base metals leach onto the surface of the deposited layer, which leads to an undesirable increase in contact resistance.

The present invention uses ferric potassium cyanide as a gold source,
Malic acid as a conductive salt, nitrilotriacetic acid as a complexing agent, cobalt sulfate as a hardener, and p
Contains potassium hydroxide to adjust the H value to 3.8-4.7. The starting point is the acid cyanide bath known from DE 31 21 509.

The metal deposited from this bath is hard and wear resistant.

From European Patent Application No. 0 025 220, a so-called additive-free bath for electrodeposition hard gold plating is known, which uses alkali gold nine cyanide, in particular ferric potassium cyanide, as the gold source.

It contains potassium dihydrogen phosphate and optionally potassium hydroxide as a buffer system and hydrazine hydrate as a reducing agent. This document states that additive-free baths may contain no hardening additives, such as cobalt or nickel, or only in very small amounts of less than +om9/l. Despite the hardness of the gold layer deposited from this additive-free bath, so-called sticky friction occurs in electrical contact parts such as plug-in connections and similar parts. When two gold layers of this type rub, they fuse together, which leads to corresponding wear.

“Chemical Abst + Shoes J (Chemical A
bs-tracts) Volume 90, Al (1, 1979
Acidic cyanide gold baths are known from March 5, 2013, p. 418, 78466J, in which gold is used as sodium gold cyanide or potassium potassium cyanide, and cobalt or nickel is used as a water-soluble salt of an oxycarboxylic acid. in the form of and 2
It contains a mixture of different oxycarboxylic acids, such as citric acid and trihydroxyglutamic acid or malic acid and tetrahydroxyadipic acid. When the pH value is 38-6o and the bath temperature is 20-50℃, 0.5A
A bright gold layer is deposited at a current density of 7 dm". However, for electrodeposited hard gold plating of hot production parts such as electrical contact parts, higher current densities as well as faster rates are required for economical processing. Deposition speed is required.

U.S. Pat. No. 4,075,065 discloses that an alkali gold cyanide, such as potassium potassium cyanide or sodium gold cyanide, and an alkali gold cyanide, such as quinaldic acid or with weak Lewis acids such as boric acid.

Weakly water-soluble polyfunctional fatty acids, such as citric acid or malic acid; 1 non-precipitable metal compounds, such as aluminum, barium or magnesium compounds, and cobalt, nickel, in the form of water-soluble salts as hardening additives; Acid cyanide baths for electrodeposited hard gold plating containing metals such as cadmium, silver, copper, iron or platinum are known. When the pH value is 3.7-48 and the bath temperature is 30-50°C,
The hard gold layer has a thickness of 0.05 to 2. Deposition occurs at a current density of 1A/dm''.

However, in order to economically electrodeposit hard gold plate electrical contact members, it is desirable to achieve baths of simpler composition and higher current densities.

[Problem that the invention seeks to solve]

The present invention provides a method for electrodeposition hard gold-plating of contact elements which has a simple composition and which makes it possible to economically deposit a gold layer which is hard and wear-resistant and has a particularly low contact resistance which is constant over time. The purpose is to create a bath.

[Means for solving problems]

The purpose of this is to prepare a bath of the type first described in which the aqueous solution contains a) 5 to 45 g/g of gold as potassium cyanide.
l, b) Malic acid 50-3oog/lrC) pH (
Potassium hydroxide to adjust the iH from 3,8 to 50, d) cobalt or nickel in the form of water-soluble salts θ ~ 300 mg/
The inclusion of l is achieved by C2.

The present invention provides that in the bath known from DE 31 21 509, the nitrilotriacetic acid used as a complexing agent is omitted without being replaced by the other components, as long as the other components of the bath maintain the concentrations specified in 1. It is based on the recognition that it is possible. According to this understanding, the malic acid contained in Bath C2 according to the invention acts simultaneously as a conducting salt, as a buffering agent and as a complexing agent. This gives baths of very simple composition, containing only aric potassium cyanide, malic acid, potassium hydroxide and, in case C, cobalt or nickel in the form of water-soluble salts. The gold layer deposited from this bath is hard and wear-resistant and has low contact resistance. Since cobalt or nickel as a hardening additive is present in only a small amount, and other additives (7) D can be omitted, the hardening additive will not cause contact even when hard gold-plated contact members are used at high temperatures. No increase in resistance could be detected. The highly advantageous mechanical and electrical characteristics of this hard gold plating are due to the simple bath composition and the omission of conventional bath components.

In the case of the bath according to the invention, the aqueous solution does not necessarily require curing additives. In this case, it is hard and wear resistant and also has special C
2. A dull precipitate is deposited, exhibiting low contact resistance with good temporal invariance.

However, in the baths according to the invention, the aqueous solution contains cobalt as hardening additive from 30 to z5 onhgg/l, preferably 4
0-100 mg//, and optimally about 50 mL)/l, or 50-300 increments/l of nickel. The optimum C2 may contain about 1008 to 9//. A shiny precipitate is deposited in this case, which is hard and wear-resistant and exhibits a low contact resistance that is constant over time. Furthermore, the current density window in which acceptable precipitation is obtained is significantly larger in this case than in additive-free baths.

In baths with hardening additives, the aqueous solution contains cobalt, especially in the form of cobalt sulfate, or nickel in the form of nickel sulfate.

According to another advantageous embodiment of the invention, the aqueous solution contains gold at Iθ
It contains ~25g/l, and the optimal effect is gold 1.
5'j/l.

Furthermore, it is advantageous for the aqueous solution to contain 150 to 250 g/9y golic acid. The best quality of the precipitate is obtained when the aqueous solution contains about 200 Q/l malic acid.

Regarding the quality of the deposited precipitate, the aqueous solution has a pH value of 4
Amounts to adjust the pH between 2 and 47, advantageously around 45.
It is particularly advantageous to contain potassium hydroxide in a value-adjusting amount.

Further, the present invention provides an improved method for electrodeposition hard gold plating of electrical contact members using the additive-free bath according to the present invention. In this case, the hard gold plating is carried out in a spray plating apparatus at a current density of 2 to 20 A/drn'' and an aqueous solution injection speed of 1 to IO m/s. The current density 2
˜13 A/dm”.

Furthermore, the present invention provides an improved method for electrodeposited hard gold plating of C2 electrical contact elements using a bath according to the invention containing cobalt or nickel as a hardening agent. In this case, hard gold plating is carried out in a spray plating device at a current density of 2 to 45 A/d m2 and an aqueous solution spray rate of 1 to 1
Perform with Om/S. Particularly good quality of the deposited layer is obtained when hard gold plating is carried out at current densities of 2 to 35 A/dm2 (1).

The best effects are obtained when hard gold plating is carried out at an aqueous spray velocity of approximately 2 m/s in baths without additives and in baths C containing cobalt or nickel as hardening additives. In both cases, the hard gold plating was heated to a bath temperature of 40 to 65
It is particularly advantageous to carry out C1 preferably at 50 to 60°C, with a bath temperature of approximately 55°C being considered optimal.

[Example〕 The present invention will be further described in detail based on the following examples.

In order to electrodeposit hard gold on the plug-in contact member using the clay spray plating equipment, the following ingredients are added to the aqueous solution in the form of ferric potassium cyanide, 15 g/l of pure gold, and goric acid.
200 liters/l of rat potassium hydroxide is required to adjust the pH value to 4.5.

A bath containing no additives was charged.

The spray plating device was operated (the bath temperature was adjusted to 55° C.) and the aqueous bath solution was sprayed through the spray nozzle of the spray plating device at a spray speed of approximately 2 m/s to deposit the electrodeposition area of the plug-in contact member. C
Two spraying, plating process with current density 2~13A/d”
It was carried out in The current efficiency of the cathode was 90-95%. A dull hard gold layer was deposited with a layer thickness of approximately 25 μm,
It had very good abrasion resistance, significant degree of elongation and low contact resistance. After this plug-in contact member was placed in a hot location several times, no noticeable increase in contact resistance was observed.

In a Bitkers hardness test of the precipitated hard gold layer using an indentation body weighing 50 g, the hardness Hv (so) was normally C2l.
There were two Cs within the range of 70 to 180 K p/1111''.

%J 2 Spray plating equipment (-1 For electrodeposition hard gold plating of plug-in contact members, pure gold 15 g/l malic acid in the form of ferric potassium cyanide containing the following ingredients in an aqueous solution)
20og/l potassium cobalt in the form of cobalt sulfate.

A bath containing

When operating the spray plating apparatus, the bath temperature was adjusted to 55"C and the spray speed was adjusted to about 2 m/s. In the current density range 2~:'+5 A/dm2, the cathode current efficiency was 40.
At ~70%, a shiny hard gold layer was deposited with a layer thickness of about 25 μm, which had very good abrasion resistance, good degree of stretching and low contact resistance. After placing this plug-in contact member on a high-temperature stage, no increase in contact resistance was observed.The hardness measured by the Bitker's hardness test) TV (50) was always reduced to 120. It was within the range of 80 Kp/-.

Example 3 In order to electro-deposit hard gold plate the insertion contact member in the injection plating device,
Pure gold in the form of potassium cyanide containing the following ingredients in an aqueous solution: 15 g/l malic acid
zoOLi/1lium.

A bath containing

Electrodeposition of a bright, hard gold layer was obtained with the values stated in Example 2. The effects described in Example 5 with respect to the wear resistance, elongation, contact resistance, and hardness (1) of the hard gold layer were almost achieved.

Each of the baths described in Examples 1.2 and 3 did not contain any other ingredients or additives other than those listed. In the case of the baths described in Examples 2 and 3, similar good results were obtained if the cobalt or nickel used as hardening additive was added in the form of other water-soluble salts, for example in the form of cobalt chloride or nickel chloride. I was able to get

Claims (1)

[Scope of Claims] 1) In an acid cyanide bath for electrodeposition hard gold plating of electrical contact members, the aqueous solution contains a) potassium cyanide, malic acid, and potassium hydroxide; Electrodeposition hard gold plating bath characterized in that it contains 5-45 g/l of gold as potassium gold cyanide b) 50-300 g/l of malic acid c) Potassium hydroxide to adjust the pH value to 3.8-5.0 . 2) In an acidic cyanide bath for electrodeposition hard gold plating of electrical contact members, the aqueous solution contains a) potassium cyanide containing 5 to 50 gold as potassium cyanide; 45 g/l b) Malic acid 50-300 g/l c) Potassium hydroxide to adjust the pH value to 3.8-5.0 d) Contains not more than 300 mg/l of cobalt or nickel in the form of water-soluble salts An electrodeposited hard gold plating bath characterized by: 3) Cobalt as a curing additive in aqueous solution from 30 to 250
3. The bath according to claim 2, characterized in that it contains 0.1 mg/l. 4) The bath according to claim 3, wherein the aqueous solution contains 40 to 100 mg/l of cobalt. 5) Bath according to claim 3 or 4, characterized in that the aqueous solution contains about 50 mg/l of cobalt. 6) Bath according to any one of claims 2 to 5, characterized in that the aqueous solution contains cobalt in the form of cobalt sulfate. 7) Aqueous solution containing 50-300 nickel as hardening additive
3. A bath according to claim 2, characterized in that it has a concentration of 1.0 mg/l. 8) Approximately 100 mg of nickel is added to the aqueous solution as a hardening additive.
Claim 7, characterized in that it contains /l
Bath as described in section. 9) A bath according to any one of claims 2 and 7 to 8, characterized in that the aqueous solution contains nickel in the form of nickel sulfate. 10) The bath according to any one of claims 2 to 9, characterized in that the aqueous solution contains 10 to 25 g/l of gold. 11) Bath according to claim 10, characterized in that the aqueous solution contains about 15 g/l of gold. 12) The bath according to any one of claims 2 to 11, characterized in that the aqueous solution contains 150 to 250 g/l of malic acid. 13) Bath according to claim 12, characterized in that the aqueous solution contains about 200 g/l of malic acid. 14) The bath according to any one of claims 2 to 13, characterized in that the aqueous solution contains potassium hydroxide which adjusts the pH value to 4.2 to 4.7. 15) Bath according to claim 14, characterized in that the aqueous solution contains potassium hydroxide which adjusts the pH value to approximately 4.5. 16) a) 5 to 45 g of gold as potassium potassium cyanide
/l b) Malic acid 50-300 g/l c) In a method for electrodeposition hard gold plating of electrical contact members using an acid cyanide bath containing potassium hydroxide, adjusting the pH value to 3.8-5.0. , current density 2-20A/
1. A method for electrodeposition hard gold plating of electrical contact members, characterized in that hard gold plating is carried out using a spray plating device with a jetting speed of 1 to 10 m/s of dm^2 and an aqueous solution. 17) The method according to claim 16, characterized in that the hard gold plating is carried out at a current density of 2 to 13 A/dm^2. 18) a) 5 to 45 g of gold as potassium potassium cyanide
/l b) Malic acid 50-300 g/l c) Potassium hydroxide to adjust the pH value to 3.8-5.0 d) Acid cyanide bath containing up to 300 mg/l of cobalt or nickel in the form of water-soluble salts In a method of electroplating hard gold on electrical contact members using a current density of 2 to 45 A/
1. A method for electrodeposition hard gold plating of electrical contact members, characterized in that hard gold plating is carried out using a spray plating device with a jetting speed of 1 to 10 m/s of dm^2 and an aqueous solution. 19) The method according to claim 18, characterized in that the hard gold plating is carried out at a current density of 2 to 35 A/dm^2. 20) The method according to claim 18 or 19, characterized in that the hard gold plating is performed at an aqueous solution spraying speed of about 2 m/s. 21) The method according to any one of claims 18 to 20, characterized in that the hard gold plating is carried out at a bath temperature of 40 to 65°C. 22) The method according to claim 21, characterized in that the hard gold plating is carried out at a bath temperature of 50 to 60°C. 23) A method according to claim 22, characterized in that the hard gold plating is carried out at a bath temperature of about 55°C.