JPH0450397B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a silver plating solution, more specifically, a matte high-speed silver plating solution suitable for electrodepositing a matte silver film. .

(Prior Art) Silver plating technology is widely used for silver plating electronic components such as lead frames and connectors, or electrical components. When silver plating these parts, high-speed plating is advantageous from an economic point of view and is the mainstream.

There are two main types of silver plating: glossy silver plating and matte silver plating. Matte silver plating is used because of its characteristics.

It is known that it is effective to increase the speed of silver plating by increasing the current density, increasing the liquid temperature, increasing the metal ion concentration, and increasing the flow rate of the plating solution. Furthermore, in silver plating for bright silver plating, it is known that by adding appropriate organic and inorganic additives to the plating solution, it is possible to increase gloss and speed. .

(Problems to be Solved by the Invention) However, when forming a matte (matte) precipitated silver film by matte silver plating, conventional silver plating solutions are capable of forming a matte precipitated silver film at a low current density (approx.
30A/dm ² or less) and lacked high speed. Attempts have been made to increase the current density by adding metal salts as inorganic additives to plating solutions for matte silver plating.
Addition of metal salts increased the glossiness of the plating, making it impossible to obtain the required matteness.
Further, even when a matte precipitated silver film is obtained by adding a metal salt, there are problems such as a narrow current density range, poor adhesion due to glare, and discoloration.

An object of the present invention is to provide a matte high-speed silver plating solution that can produce a matte precipitated silver film with excellent bonding and soldering properties at a high current density.

SUMMARY OF THE INVENTION The present invention is directed to a matte high speed silver plating solution containing organic and inorganic additives and substantially free of free cyanide. The plating solution of the present invention contains a naphthalene sulfonic acid formalin condensate as an organic additive of 5 mg/ to 5 g/, and a selenium salt as an inorganic additive of 0.05 g based on selenium.
mg/ to 10g/contains.

Naphthalene sulfonic acid formalin condensates are obtained as a mixture of isomers with different condensation degrees and structures, and the naphthalene ring may have a hydrocarbon group, and alkylated naphthalene sulfonic acid formalin condensates are also included. . These condensates are often commercially available as sodium salts, but can also be used as acid forms, other soluble salts, or mixtures thereof.

Selenium is usually preferably added in the form of a soluble salt, such as a sodium or potassium salt of cyanated selenic acid, selenic acid or selenite.

The components of the silver plating solution of the present invention can be any low cyanide bath that is substantially free of free cyanide and is obvious to those skilled in the art. For example, the main ingredients are silver compounds such as silver potassium cyanide and silver sodium cyanide, and conductive salt components such as phosphates, pyrophosphates, sulfates, nitrates, and sulfamates, and other buffering agents and chelating reagents. Examples include low cyanide baths that can contain PH adjusters and the like.

(Function) The inventor has discovered that by adding a metal salt that contributes to high current density but also has the property of originally imparting luster to the silver film, it is possible to achieve high current density and reduce the amount of deposited silver. We conducted extensive research to develop a silver plating solution that does not lose its matte finish. As a result, by using a selenium salt as the metal salt and a naphthalene sulfonic acid formalin condensate as the organic additive, a silver plating solution that can achieve high current density and maintain matteness. I found out. Although it is known that selenium contributes to high current density, it is not precisely known why mattness can be maintained by combining selenium and naphthalene sulfonic acid formalin condensate. Although it is a speculation, it is thought that the naphthalene sulfonic acid formalin condensate suppresses the function of selenium to impart luster to the silver coating.

According to research, as the amount of naphthalene sulfonic acid formalin condensate added decreases to less than 5 mg, it becomes increasingly difficult to obtain a silver film with no silver plating, and as the amount exceeds 5 g, the precipitated silver film tends to discolor. At the same time, it turned out to be economically disadvantageous.

In addition, when the amount of naphthalene sulfonic acid formalin condensate added is within the above range, if the amount of selenium is less than 0.05 mg/, the effect of adding selenium (current density improvement effect) cannot be expected substantially. However, it was found that as the amount of selenium exceeds 10 g/min, the physical properties such as heat resistance of the deposited silver film gradually deteriorate due to eutectoid selenium.

(Examples and Comparative Examples) Hereinafter, the present invention will be described with reference to Examples thereof, and comparative examples conducted in connection with the present invention will also be described.

Example 1 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 5 mg of naphthalene sulfonic acid formalin condensate (sodium salt), and 0.1 mg of potassium cyanide selenate (as selenium),
High-speed plating (jet plating) was performed using a tightening solution with a pH of 8.2 and a temperature of 65°C using a pH adjustment reagent, and a platinum plate as an anode.

A good matte silver film was obtained at a current density in the range of 60 to 130 A/dm ² . The obtained silver film had good physical properties such as bonding properties, soldering properties, and heat resistance.

Example 2 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 10 mg of naphthalene sulfonic acid formalin condensate (sodium salt), and 0.5 mg of potassium cyanide selenate (as selenium),
High-speed plating (jet plating) was performed using a phishing solution with a PH of 8.2 and a temperature of 65° C. using a PH adjustment reagent, and a platinum plate as an anode.

A good matte silver film was obtained at a current density in the range of 60 to 140 A/dm ² . The obtained silver film had good physical properties such as bonding properties, soldering properties, and heat resistance.

Example 3 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 100 mg of naphthalene sulfonic acid formalin condensate (sodium salt), and 0.05 mg of potassium cyanide selenate (as selenium), and the pH was adjusted using a PH adjusting reagent. 8.2, high-speed plating (jet plating) was performed using a tightening solution at a temperature of 65°C and a platinum plate as an anode.

A good matte silver film was obtained at a current density in the range of 60 to 130 A/dm ² . The obtained silver film had good physical properties such as bonding properties, soldering properties, and heat resistance.

Example 4 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 300 mg of naphthalene sulfonic acid formalin condensate (sodium salt), and 10 g of potassium cyanide selenate (as selenium), and adjusted the pH using a PH adjusting reagent. 8.2. High-speed plating (jet plating) was performed using a tamping solution at a temperature of 65°C and a platinum plate as an anode.

A good matte silver film was obtained at a current density in the range of 60 to 150 A/dm ² . The obtained silver film had good physical properties such as bonding properties, soldering properties, and heat resistance.

Example 5 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 700 mg of naphthalene sulfonic acid formalin condensate (sodium salt), and 1 mg of potassium cyanide selenate (as selenium), and adjusted the pH using a PH adjusting reagent. 8.2. High-speed plating (jet plating) was performed using a tamping solution at a temperature of 65°C and a platinum plate as an anode.

A good matte silver film was obtained at a current density in the range of 60 to 140 A/dm ² . The obtained silver film had good physical properties such as bonding properties, soldering properties, and heat resistance.

Example 6 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 1 g of naphthalene sulfonic acid formalin condensate (sodium salt), and 5 g of potassium selenite (as selenium), and adjusted the pH to 8.2 using a PH adjusting reagent. High-speed plating (jet plating) was carried out using a tightening solution at a temperature of 65°C and using a platinum plate as an anode.

A good matte silver film was obtained at a current density in the range of 60 to 160 A/dm ² . The obtained silver film had good physical properties such as bonding properties, soldering properties, and heat resistance.

Example 7 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 3 g of naphthalene sulfonic acid formalin condensate (sodium salt), and 100 mg of potassium cyanide selenate (as selenium),
High-speed plating (jet plating) was performed using a phishing solution with a PH of 8.2 and a temperature of 65° C. using a PH adjustment reagent, and a platinum plate as an anode.

A good matte silver film was obtained at a current density in the range of 60 to 150 A/dm ² . The obtained silver film had good physical properties such as bonding properties, soldering properties, and heat resistance.

Example 8 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 5 g of naphthalene sulfonic acid formalin condensate (sodium salt), and 7 g of potassium cyanide selenate (as selenium),
Adjust the pH to 8.2 and the temperature to 65℃ using the pH adjustment reagent.
High-speed plating (jet plating) was carried out using a tight plating solution and a platinum plate as an anode.

A good matte silver film was obtained at a current density in the range of 60 to 140 A/dm ² . The obtained silver film had good physical properties such as bonding properties, soldering properties, and heat resistance.

Example 9 Potassium silver cyanide 120g/, potassium phosphate 40g/, naphthalene sulfonic acid formalin condensate (sodium salt) 500mg/, antimonyl potassium tartrate 500mg/(as antimony)
Contains 1 mg/potassium cyanoselenate
Contains selenium (as selenium) and adjusts the pH using a pH adjustment reagent.
8.2. High-speed plating (jet plating) using a tightening solution at a temperature of 65℃ and using a platinum plate as an anode.
I went there. In this example, potassium antimonyl tartrate is added as a new additive.

A good matte silver film was obtained at a current density in the range of 60 to 130 A/dm ² . In this example, antimony salt was added in addition to selenium salt as an inorganic additive, and the resulting silver film had good physical properties such as bonding properties, soldering properties, and heat resistance. Ta. Therefore, it is understood that in the present invention, a predetermined amount of a metal salt may be added in addition to the selenium salt.

Comparative Example 1 Contains 120g/potassium cyanide and 40g/potassium phosphate, and the pH was adjusted to 8.2 with a PH adjusting reagent.
High-speed plating (jet plating) was performed using a tightening solution at a temperature of 65°C and a platinum plate as an anode.

A matte silver film was obtained at a current density in the range of 10 to 30 A/dm ² . However, Examples 1 to 9
In comparison, the current density range in which a matte silver film can be obtained is extremely narrow and the current density is low, making it impossible to use at high current densities and clearly inferior in high-speed performance.

Comparative Example 2 A tightening solution containing 120 g of potassium cyanide, 40 g of potassium phosphate, and 1 g of naphthalene sulfonic acid formalin condensate (sodium salt) was used, and the pH was adjusted to 8.2 and the temperature was adjusted to 65°C using a pH adjustment reagent. Then, high-speed plating (jet plating) was performed using a platinum plate as an anode.

Matte silver coatings were obtained at current densities ranging from 50 to 90 A/dm ² . However, Examples 1 to 9
Compared to the previous method, the current density range in which a matte silver film could be obtained was narrower, and the high current density could not be used, and the high speed performance was clearly inferior.

Comparative Example 3 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 3 mg of naphthalene sulfonic acid formalin condensate (sodium salt), and 1 mg of potassium cyanide selenate (as selenium),
High-speed plating (jet plating) was performed using a phishing solution with a PH of 8.2 and a temperature of 65° C. using a PH adjustment reagent, and a platinum plate as an anode.

A bright silver film was obtained at a current density in the range of 50 to 100 A/dm ² .

Comparative Example 4 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 7 g of naphthalene sulfonic acid formalin condensate (sodium salt), and 1 mg of potassium cyanide selenate (as selenium),
High-speed plating (jet plating) was performed using a phishing solution with a PH of 8.2 and a temperature of 65° C. using a PH adjustment reagent, and a platinum plate as an anode.

Matte silver coatings were obtained at current densities ranging from 60 to 130 A/dm ² . However, the obtained silver film was slightly reddish, and swelling (poor adhesion) was observed during heat resistance.

Comparative Example 5 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 100 mg of naphthalene sulfonic acid formalin condensate (sodium salt), and 0.03 mg of potassium cyanide selenate (as selenium), and the pH was adjusted using a PH adjusting reagent. 8.2, high-speed plating (jet plating) was performed using a tightening solution at a temperature of 65°C and a platinum plate as an anode.

Matte silver coatings were obtained at current densities ranging from 50 to 90 A/dm ² . However, compared to Examples 1 to 9, the current density range in which a matte silver film could be obtained was narrower, and it could not be used at high current densities, and the high speed performance was clearly inferior.

Comparative Example 6 Contains 120 g of potassium cyanide, 40 g of potassium phosphate, 100 mg of naphthalene sulfonic acid formalin condensate (sodium salt), and 15 g of potassium cyanide selenate (as selenium), and the pH was adjusted using a PH adjusting reagent. 8.2. High-speed plating (jet plating) was performed using a tamping solution at a temperature of 65°C and a platinum plate as an anode.

Matte silver coatings were obtained at current densities ranging from 60 to 130 A/dm ² . However, compared to Examples 1 to 9, the obtained silver films were inferior in bonding and soldering properties, and swelling (poor adhesion) and black spots were observed during heat resistance, resulting in poor adhesion. There has occurred.

(Effect) If the silver plating liquid of the present invention is used, the
A matte precipitated silver film can be obtained at high current densities over a wide range of dm ² , allowing for faster speeds, and the precipitated silver film has excellent physical properties such as bondability, solderability, and heat resistance. can be obtained.

Claims (1)

[Scope of Claims] 1. A matte high-speed silver plating solution containing an organic additive and an inorganic additive and substantially free of free cyanide, which comprises a naphthalene sulfonic acid formalin condensate as the organic additive. A matte high-speed silver plating solution, characterized in that the inorganic additive contains a selenium salt of 0.05 mg/to 10 g/based on selenium.