JPS62260071A - Surface treatment of tin or tin alloy plated material - Google Patents

Abstract

PURPOSE:To protect the Sn (alloy) plated surface of a substrate for a long period and to well maintain the solderability for a long period by sticking a phosphonium salt represented by a prescribed formula to the plated surface. CONSTITUTION:A substrate is plated with Sn (alloy) and a phosphonium salt represented by a formula (HOCH2)4P-X (where X is 1/2SO4<2-> or Cl<->) is adsorbed or stuck to the Sn (alloy) plated surface. Thus, the plated surface is protected for a long period and the solderability is well maintained for a long period.

Description

Detailed Description of the Invention (Technical Field) The present invention relates to surface treatment of tin or tin alloy plated materials, and in particular, to maintain the corrosion resistance and solderability of the plated tin or tin alloy surface for a long period of time. It is for the purpose of

(Prior art and its problems) 8n or 5n-P
b 1Sn-Sb, 5n-Zn, 5n-A
Electroplating Sn alloys such as s-Ca and 5n-In,
Tin or tin alloy plating materials coated by methods such as electroless plating, hot dip plating, and vapor phase plating (vacuum deposition) (hereinafter referred to as plating) are widely used in various electronic materials and can materials. . The superior soldering properties of Sn and Sn alloys are due to their properties and electrical connectivity; for example, copper-clad steel wire plated with Sn f about 10 μm in thickness is used in large quantities for electrolytic capacitor lead wires. has been done.

Since the lead wires are soldered to circuits within electronic equipment, good solderability must be ensured over a long period of time until the capacitor is on the market and in the hands of the end user.

Also, strips, pins, etc. made of copper or copper alloy plated with Sn or 5n-Pb several microns thick are used as various connector materials.

Good solderability is required for soldering in circuits as well as lead wires.

Sn and Sn alloys are thought to exhibit corrosion resistance comparable to precious metals, but O! , moisture (humidity), heat, S
(Due to the effects of arsenic compounds, NOx,... rogens, etc., a thick film of oxides and sulfides is likely to form on the surface, and as a result, soldering performance, such as soldering properties, is greatly reduced.

For this reason, attempts have been made to coat the lead wires and connector materials with higher fatty acids or lard (fats and oils), but these efforts are not only insufficiently effective, but also have disadvantages such as contamination of electronic equipment. In addition, immersion treatment in an aqueous solution of inorganic chromic acid or sodium phosphate has been carried out to form a specific film on the surface, but although it is effective in preventing corrosion, it significantly reduces soldering properties. There are drawbacks that reduce it.

(Means for solving the problem and its effects) In view of this, the present invention has developed a surface treatment method that can maintain the corrosion resistance and solderability of tin or tin alloy plated materials in a good state for a long period of time as a result of various studies. It is characterized in that a phosphonium salt represented by the following structural formula is adsorbed or attached to the surface of tin or tin alloy plated on a substrate.

((HOCHri4P −X :l (X; +
So, '-, CL-) That is, in the present invention, after plating Sn or Sn alloy on a substrate, the Sn or S of the plating material is
A phosphonium salt represented by the above structural formula is adsorbed or adhered to the surface of Sn or Sn alloy by dipping or coating, and although the method is not clear, the derivative is strongly fixed to the surface of Sn or Sn alloy, forming a film on the order of molecules. Form.

As a result, corrosion from the external environment is inhibited on the Sn or Sn alloy surface, and although it is not clear whether this is because the coating is thin or because the coating itself has a flux effect, it is possible to solder without impairing properties at all. All of the phosphonium salts represented by the above structural formulas are water-soluble.

Therefore, immediately after the Sn or Sn alloy plating process, it is common to carry out an immersion process using an aqueous solution of the phosphonium salt represented by the above structural formula. It is. Even if this treatment is followed by washing with water or hot water, the film adsorbed or attached on the order of molecules will not be removed.

The present invention will be explained in more detail below using Examples and Comparative Examples.

Examples (1), (2), Comparative Examples (1), (2) Thickness 0.
Using a tin sulfate bath containing a commercially available brightening agent, a 1 μ thick pure Sn layer was brightly electroplated on a third copper plate using a conventional method, and after washing with water,
This was immersed for 5 seconds in an α2% aqueous solution of the phosphonium salt shown in Table 1, washed with water, and then dried. This temperature is 60
The solder wettability and the amount of surface oxidation were examined after being kept in a constant temperature and humidity chamber at a relative humidity of 98 degrees Celsius for 100 hours. The result f:
It is also listed in Table 1.

The solder wettability was determined by cutting a tin-plated copper plate into a 10°C width, applying rosin flux, dipping it in a eutectic solder bath at 230°C for 2 seconds, and then pulling it up to determine the solder-wetted area, which was expressed in x.

The amount of surface oxidation was determined by electrolyzing the sample in a solution of 0.1NKC at a current density of 0.1 mA/7 using the sample as a cathode, and measuring the amount of electricity required to reduce the surface oxide. I asked for

As can be seen from Table 1, the solder wettability and the amount of surface oxidation of Sn-plated copper plates of the products treated with the phosphonium salt 02 aqueous solution and the amount of surface oxidation of the products treated with the phosphonium salt 02 aqueous solution were significantly lower than that of the untreated and conventional 5% sodium phosphate aqueous solution. Compared to the treated comparative example, it is much more immersive.

Table 1 Example (3), (i), Comparative example (3), 0) Diameter 0.5
A +++m copper wire was plated with a 10μ thick Sn-pb alloy (10% Pb) using borofluoride using a conventional method, washed with water and dried, and then plated with 0.1% of the phosphonium salt shown in Table 2.
% aqueous solution for 5 seconds and then dried. After heating this in the air to a temperature of 100°C for 100 hours, Example (1)
), the solder wettability and the amount of oxidation were measured. The results are also listed in Table 2.

As can be seen from Table 2, all of the products treated by the treatment method of the present invention are far superior in semi-uniform wettability and amount of surface oxidation compared to the comparative examples that were untreated or treated with stearic acid. .

Table 2 As shown in Table 2, the treatment method of the present invention is industrially remarkable because it can stably protect the surface of Sn or Sn alloy plated materials over a long period of time, and it does not inhibit the original functions of the plating such as soldering properties at all. It has the following effects.

Claims (1)

[Scope of Claims] A method for surface treatment of tin or tin alloy plated materials, which comprises adsorbing or adhering a phosphonium salt represented by the following structural formula to the surface of tin or tin alloy plated on a substrate. [(HOCH_2)_4P-X] (in the formula ×; 1/2 SO
^3^-_4, Cl^-)