JPS5921948B2 - Indium plating method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a completely new indium plating method.

In recent years, various plating methods have been proposed as the demand for plating powder increases, and among these plating methods, the substitution plating method is widely used because of its ease of operation. The displacement plating method, which is conventionally known as a powder plating method, involves adding a plating metal-containing solution to a mixed powder of a powder to be plated and a metal powder for reduction, or to the mixing process of the mixed powder while stirring the mixed powder. Alternatively, the powder to be plated and the reducing metal powder are added together or separately into a solution containing the plating metal under stirring.

However, in the above-mentioned substitution plating method, the basic reaction is to reduce the metal to be plated with metal powder that is less noble, so the standard electrode potential of gold, platinum, palladium, silver, etc. Both reduction efficiency and plating finish are good when plating powders targeting very noble metals, but when plating metal powders with base electrode potentials such as zinc, tin, nickel, cobalt, and indium, Both the reduction efficiency and the plating finish are poor, making it impractical.

However, recently, as a countermeasure for this problem, when plating nickel, cobalt, zinc, etc., chloride crystal powder of the plating metal is added in the process of mixing the object to be plated with powder of a reducing metal such as magnesium or aluminum, or a mixture of both. A plating method has been proposed in which a small amount of water and/or hydrochloric acid is added after the reaction has started.

However, in any of the above-mentioned plating methods, the reducing metal powder must be more base than the plating metal, so the two metals are necessarily different types, and the treatment of the liquid after plating is therefore difficult. It becomes a problem.

For example, when zinc plating copper powder, when plating is performed by adding crystals of zinc chloride and water or dilute hydrochloric acid to a mixture of copper powder and aluminum powder, a solution containing aluminum chloride and zinc chloride is produced as a solution after plating according to the following reaction formula. You will get it.

Cu+Al+ZnCl2→Cu-Zn-1-AlCl3
+ZnCl2, that is, the above-mentioned post-plating solution, cannot be reused as it is as a solution for galvanizing copper powder, so its treatment becomes a problem, and there are also drawbacks such as a low reduction rate of zinc.

As a result of various studies regarding powder plating, the present inventor discovered a completely new method different from conventional substitution methods.

That is, the present invention uses metal powder for plating medium (because plating progresses by adding metal powder, metal powder of the same type as the metal ion component in the plating solution is referred to as metal powder for plating medium), which is the same as the plating metal. The object of the present invention is to provide a completely new and advantageous indium plating method by using the following metal.

The present invention will be explained in detail below. The object to be plated in the present invention contains a metal whose standard electrode potential is nobler than that of indium, such as gold, silver, platinum, copper, lead, nickel, cobalt, and molybdenum, or one or more of these metals. In addition to the alloys mentioned above, it also includes carbonaceous substances, metal carbides, metal oxides, metal sulfides, nitrides, etc. that have been coated in advance with the above metals or alloys.

Note that known techniques such as metal thin layer vapor deposition and palladium precipitation can be applied to this coating treatment. There are no particular restrictions on the shape of these objects to be plated, and powders, wires, plates, etc. may be used as appropriate depending on the purpose and use. The particle size of the indium powder used as the metal powder for the plating medium in the present invention can be selected in consideration of the type and size of the object to be plated, and the thickness of the plating thereto.

For example, using copper powder with an average particle size of 40μ as the object to be plated,
When plating 30% by weight, the particle size of the indium is suitably on the order of several microns.

The amount of indium powder used is 1.0 to 1.0 of the required amount of metal.
It may be 5 times (weight). The aqueous solution containing indium ions used in the present invention is preferably an aqueous solution of hydrochloric acid, sulfuric acid, or nitric acid with a pH of 1 to 3, and the amount used is such that the amount of indium in the aqueous solution is in excess of the amount required for plating. You may want to adjust it. In the present invention, indium plating is performed by heat-treating the above-mentioned object to be plated in the presence of an aqueous solution containing indium powder and indium ions. For example, when using powder as the object to be plated, It is preferable to add the above aqueous solution during the process of mixing the indium powder to the object to be plated, or after mixing the indium powder to the object to be plated, and heat the mixture with stirring to uniformly carry out the plating reaction.

The plating reaction is completed by adding an aqueous solution containing indium ions and heating for several minutes.

Note that heating may be performed at a temperature of about 80 to 100°C. After the reaction, the plating product is filtered through P to remove the liquid and then washed to recover the indium plating powder.

Since the liquid obtained by the above-mentioned filtration is an aqueous solution containing indium ions, it can be recycled as it is to the plating process and reused.

In the indium plating powder obtained as described above according to the present invention, indium is not deposited on the powder to be plated in the form of particles, and a coating having a substantially uniform thickness is formed.

Although the case where the object to be plated has the shape of powder has been described above, the same can be said of the object to be plated which has the shape of a wire or a plate.

However, in the case of a plate, the plate to be plated is immersed in an aqueous solution containing indium ions in which indium powder is suspended before the heat treatment, and ▲ filtration is not required after the reaction is completed. The case is different. Although the reaction mechanism in the plating method of the present invention is not yet clear, it is presumed that the indium powder is once dissolved during the reaction process, and the indium ions in the aqueous solution are precipitated on the surface of the object to be plated.

As described above, according to the present invention, the liquid after the plating process can be directly recycled to the plating process and reused, so the above-mentioned problems found in the conventional method can be solved.

The present invention will be described in more detail below by way of examples. Example 1 Copper powder 109 having an average particle size of 40 μ, indium powder 49 having an average particle size of several μ, and indium concentration 509/t
Pour 200 d of indium chloride aqueous solution into the plating tank (
The pH of the charging solution is 2 to 3), and the mixture is heated at 90° C. for 5 minutes with stirring to react.

The obtained reaction product is separated, washed with dilute sulfuric acid of pH 2 to 3 until the presence of chloride ions is no longer recognized, washed with water, and then dried. As a result, 13.989 indium plating powder was obtained.

This indium plating powder had the white luster of indium, and when observed under a microscope, it resembled the powder shape of the copper powder before plating, and no fine powder that was thought to be the indium powder itself was observed. Since the p liquid obtained by the above-mentioned filtration is an aqueous indium chloride solution, it is circulated to the plating tank and reused for the plating reaction.

Example 2 200 d of indium nitrate aqueous solution with a concentration of 2009/t and 5 f of indium powder with an average particle size of several microns! Twenty nickel wires each having a diameter of 21L1L and a length of 4mm were placed in a plating tank as objects to be plated, heated to 85°C with stirring, and plated for 5 minutes.

Thereafter, the same operations as in Example 1 were performed. The resulting plating body had a beautiful indium plating surface with no nickel base surface visible even under a microscope with a magnification of 400 times. Example 3 Indium powder 209 with an average particle size of several micrometers was added to 250 ml of an indium sulfate aqueous solution with a concentration of 2009/t, heated to 80°C, and stirred. Indium plating was performed by dipping for 5 minutes.

The obtained indium-plated copper plate had a uniform plating surface, and the copper base surface was not visible at all even under a microscope. The average plating thickness measured by an electronic film thickness meter was approximately 0.1 μm. Example 4 The body to be plated was coated with 325 mesh under one brass powder (C
The same operation as in Example 1 was carried out except that u8O arc Zn2O%) was used.

As a result, indium plating brass powder with a weight of 13.59 was obtained. When this plating powder was observed under a microscope with a magnification of 400 times, the surface was uniformly coated with indium and no brassy color was observed.

Claims (1)

[Claims] 1. An indium plating method characterized by heat-treating an object to be plated in the presence of an aqueous solution containing indium powder and indium ions.