JPH03146689A - Solder and tin plating solution - Google Patents

Abstract

PURPOSE:To improve the throwing power of plating and to reduce the rate of rejects by regulating the concn. of alcohol in a solder and tin plating soln. contg. a brightener as an org. acid bath to a specified range. CONSTITUTION:A brightener is dissolved in alcohol, mixed with a surfactant and added to a plating soln. as a liq. The concn. of the alcohol in the resulting solder and tin plating soln. contg. the brightener as an org. acid bath is regulated to a low level of 0-15ml/l. When the plating soln. is used, throwing power of plating is improved and ununiformity in thickness of plating on a body to be plated can be reduced in spite of its complex shape. In case of barrel plating, bodies to be plated can be prevented from sticking to each other and getting entangled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solder plating solution and a tin plating solution used when carrying out half-day or tin plating using a wet electroplating method among surface treatments.

It is necessary to add a brightener to the plating solution for tin and solder plating using the conventional two-skin electroplating method. Since the brightener does not dissolve in the plating solution as it is, it is dissolved in alcohol, a surfactant is added, and the liquid is poured into the plating solution.

Conventionally, standards have been set and managed for the concentration of the brightener itself in the plating solution, but there are no clear regulations regarding the alcohol that enters the plating solution, and the concentration is between 60 and 80%.
WL1/! It fluctuated between.

However, with conventional plating solutions, uniform electrodeposition of plating is poor depending on the shape and size of the objects to be plated, and in barrel plating, objects to be plated often stick together due to plating. For example, as shown in Fig. 3, such a tendency is noticeable in the case of an airtight terminal for a watch crystal oscillator, in which two leads 1, 1 are sealed to an eyelet 2 through a glass 3. Met. Furthermore, these problems were highly variable and suddenly worsened when the plating solution was prepared or adjusted.

As a result of a thorough investigation into the variable factor 2, it was found that the cause of the problem was the alcohol in the plating solution.

Based on this knowledge, this invention aims to solve the above problems by increasing the alcohol concentration in the plating solution from 0 to 1.
5w1/no.

The method is as follows: (1) When the brightener is dissolved in alcohol, it is dissolved to 80 to 90% of the saturation amount.

■After adding the surfactant, alcohol is no longer needed, so volatilize the alcohol by aerating the solution. After that, it is added to the plating solution.

■ If you use a plating solution with the alcohol concentration specified above,
Uniform electrodeposition is improved, and variations in plating thickness due to different parts of the plated object can be reduced even when the plated object has a complex shape. etc. can be reduced.

夾胤旌 This invention will be explained using the drawings.

Figure 3 shows an airtight terminal for a crystal oscillator which is to be plated, for example, φD"2-m, φd=0.2mm, L=8+a
It is about m. After the leads 1 and eyelets 2, which are metal, are sealed with glass 3, the metal parts are plated with solder. Figure 1 shows that this hermetic terminal was heated in an alkanol sulfonic acid bath at an average current density IA/dt/ for 60 minutes at
This figure shows the relationship between the plating thickness of the inner lead 1a and the eyelet 2 and the alcohol concentration when barrel plating is performed with n:Pb=5:95. FIG. 2 shows the change in defect rate when plating solutions were prepared with varying alcohol concentrations.

According to this example, the alcohol concentration in the plating solution is 1
If it is reduced to 5 d/J, sufficient uniformity of plating thickness can be obtained, and variations in plating thickness between objects to be plated are also reduced, which has the advantage that defects such as sticking and tangling are significantly reduced. This is because by reducing the concentration, the alcohol will not interfere with the brightener as much.
We were able to improve uniform electrodeposition, which is the original function of brighteners, and the brighteners worked well, resulting in dense plating, reducing friction between airtight terminals, and improving movement within the barrel. It is presumed that sticking and tangles have been reduced.

In addition, this airtight terminal requires that both the inner lead 1a and the eyelet 2 satisfy the plating thickness standard, as required when manufacturing the crystal resonator, but from Fig. 2,
This can be achieved if the alcohol concentration is 15wL1/1 or less.

Further, with respect to the 5N100% tin plating solution, good results were obtained when the alcohol concentration was set to 15id# or less, as in FIGS. 1 and 2.

As explained above, in the present invention, by specifying the alcohol concentration in the plating solution to 0 to 15 d#, it is possible to improve the uniform electrodeposition of plating and reduce the defective rate. Furthermore, by regulating the alcohol concentration to a smaller value, fluctuations in concentration due to alcohol volatilization are also reduced, making it possible to obtain products of stable quality.

In addition, a conventional method for improving uniform electrodeposition was to reduce the plating current density, but this required a longer plating time. If the above-mentioned plating solution is used, the current density does not need to be reduced, and workability is improved.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between the alcohol concentration and the plating thickness of the inner lead 1a and the eyelet 2 when the airtight terminal is plated. Figure 2 shows the plating solution prepared by changing the alcohol concentration.
FIG. 3 is a graph showing the change in defective rate when plating airtight terminals. Figure 3 is a perspective view of an airtight terminal for a crystal resonator used as an object to be plated when this invention was put into practice.

Claims (1)

[Scope of Claims] 1. A solder plating solution in an organic acid bath containing a brightener, characterized in that the alcohol concentration is regulated to 0 to 15 ml/l. 2. An organic acid bath tin plating solution containing a brightener, characterized in that the alcohol concentration is regulated to 0 to 15 ml/l.