JPS5934229B2 - Electroless plating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for electroless plating of tin using trivalent titanium ions as a reducing agent. The present invention relates to an electroless plating method characterized by using an organic sulfonate as a soluble salt.

In a system where a metal capable of assuming multiple oxidation states, such as titanium, exists in a lower oxidation state in an aqueous solution,
When ions of other metals are added, they themselves undergo oxidation,
It is a well-known fact that while reaching a high oxidation state, it can reduce the added metal ions to the metallic state, and Ti3+ can reduce Cu2+, Pb2+, Sn2+,
Due to their ability to reduce Ni2+, Co2+, etc. to their metallic state, these systems can be used as electroless plating methods.

However, due to the following limitations, the electroless plating method using such a system has not yet been put into practical use.

That is, in electroplating or electroless plating baths using formalin, hypophosphites, borohydrides, various amineboranes, hydrazine, etc. as reducing agents, the metal to be deposited and the base metal, The condition is that it is composed of components that do not form insoluble or hydrophobic compounds. The reason why it is not appropriate to include components that form resistant or poorly soluble compounds with the base metal is that when the object to be plated is immersed in the plating solution, resistant or poorly soluble compounds are formed on the base metal. This is because it causes serious defects such as poor adhesion or poor solderability. Furthermore, as in the present invention, in an electroless plating solution using a metal in a low oxidation state as a reducing agent, the above-mentioned two
In other words, in addition to the metal to be precipitated and the base metal, ions in a low oxidation state of the metal used as a reducing agent and ions in a high oxidation state generated after being used as a reducing agent are also dissolved, and insoluble and refractory ions are dissolved. The condition is that it is composed of components that do not form compounds. Therefore, when sulfates and chlorides, which are most often used in the preparation of plating solutions, are used, the sulfate radicals form a poorly soluble compound with Ti3+, and the chlorine ions adhere to the substrate containing copper or lead. This is not preferable because it forms a poorly soluble compound that causes defects and poor solderability. Tin plating is often applied to provide good solderability to light electrical and electronic components, and is therefore applied to copper substrates or partially pre-soldered substrates. Therefore, the inclusion of components that form poorly soluble compounds on these base surfaces is a fundamental defect and a problem that should be avoided at all costs.

The present invention was invented in view of the above-mentioned problems, and includes:
By using organic sulfonic acids that form hydrophilic salts with many metals, three
The object of the present invention is to provide a method for electroless plating using titanium titanium as a reducing agent.

The configuration of the present invention will be described below.

The plating baths used in the present invention are as follows (a) to (c)
), a salt of an organic sulfonic acid selected from the group consisting of trivalent titanium ions used as a reducing agent, and a salt of divalent tin as the metal to be deposited.

(a) Hydroxyalkanesulfonic acid represented by the general formula (b) General formula (c) General formula '--10~ (in the formula, ○〉 represents a benzene ring, x is a substituent,
Benzenesulfonic acid or its derivatives represented by H or 0H).

Some important examples of the organic sulfonic acids mentioned in (a) to (c) above are listed in the following table. Examples of the present invention using the above-mentioned matting bath will be described below.

Example 1 (1) Divalent tin ion (added as an aqueous solution of tin methanesulfonate 8): 0.04 mol/t (2)
Trivalent titanium ion (added as an aqueous solution of titanium methanesulfonate) (adjusted with aqueous ammonia to the specified pH) (added as an aqueous solution of tin 2-hydroxypropylsulfonate) Do) \υノFjReJL! V9V (Adjust with ammonia water to reach the specified pH)
Copper plate, mild steel plate, solder-plated mild steel plate, surface-polished cast lead, commercially available pre-treatment agent for electroless nickel plating using the plating bath composition and plating conditions shown in the above examples. As a result of plating each activated polypropylene plate, a good tin plating film was obtained in all cases.

In addition, in the bath of the present invention, EDTA2l. The ratio of Sn2+ and the ratio of NTA to Ti3+ affect the stability of the bath, but the molar ratio of EDTA/Sn2+ is 1.1 or more,
When the molar ratio of TA/Ti3+ was 3.5 or more, an electroless plated film could be obtained without causing suspended precipitation in the bath.

Claims (1)

[Scope of Claims] 1. A salt of an organic sulfonic acid selected from the group consisting of the following (a) to (c) and a trivalent titanium ion used as a reducing agent, and a divalent titanium ion which is the metal to be precipitated. An electroless plating method characterized by using a plating solution containing salt with tin. (a) General formula CnH_2n+_i-CH(OH)-CmH_2m-S
A hydroxyalkanesulfonic acid represented by O_3H (in the formula, n is a number of 0 to 2, and m is a number of 1 to 3). (b) Alkanesulfonic acid represented by the general formula CnH_2n+_1SO_3H (in the formula, n represents the number 1 or 2). (c) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ indicates a benzene ring, x is a substituent, and represents H or OH) benzenesulfonic acid or its derivatives.