JPH0220717B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to surface treatment of tin or tin alloy plated copper materials, and in particular, to maintain the corrosion resistance and solderability of the plated tin or tin alloy surface in good condition for a long period of time. Sn or Sn-Pb, Sn-Sb, Sn-Zn, Sn-As-Cd, Sn
-Electroplating, electroless plating, Sn alloy such as In
BACKGROUND OF THE INVENTION Tin or tin alloy plated copper-based materials coated by methods such as hot-dip plating and vapor-phase plating (vacuum deposition) (hereinafter abbreviated as plating) are widely used in various electronic materials. All of these are Sn or
This is due to the excellent solderability and electrical connectivity of Sn alloys; for example, copper-clad steel wire plated with Sn to a thickness of about 10 μm is widely used in electrolytic capacitor lead wires. Since the lead wires are soldered to circuits within electronic equipment, good solderability must be ensured for a long period of time until the capacitors are on the market and in the hands of end users. Sn and Sn alloys are thought to exhibit corrosion resistance comparable to precious metals, _but
Due to the effects of heat, S compounds, NOx, halogens, etc., a thick film of oxides and sulfides tends to form on the surface, which significantly reduces performance such as solderability. For this reason, with something like the lead wire mentioned above,
Attempts have been made to apply higher fatty acids or lard (fats and oils), but these methods 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 substances such as chromic acid or sodium phosphate has been carried out to form a film of these compounds on the surface, but although it is effective for corrosion prevention, it has the disadvantage of significantly reducing solderability. There is. In view of this, and as a result of various studies, the present invention has developed a surface treatment method that can maintain the corrosion resistance and solderability of tin or tin alloy plating surfaces in good condition for a long period of time. Or, it is characterized by adsorbing or adhering the following phosphoric acid derivative to the surface of the tin alloy. However, at least one of X, Y, and Z is a polyalkylene chain represented by (-CmH ₂ m-O-) _o A, where m and n are integers, A represents hydrogen or a hydrocarbon, and the remainder is hydrogen, Indicates an alkali metal, amine, ammonia or aliphatic group. That is, in the present invention, after plating Sn or Sn alloy on a copper-based material, the above-mentioned phosphoric acid derivative (hereinafter abbreviated as derivative) is adsorbed or adhered to the surface of the Sn or Sn alloy of the plating material by dipping or coating. Something,
Although the manner is not clear, the derivative is strongly fixed to the surface of Sn or Sn alloy, forming a film on the order of molecules. As a result, corrosion from the external environment is inhibited on the Sn or Sn alloy surface, and it is not clear whether this is because the coating is thin or because the coating itself has a flux effect, but it can be used for a long time without impairing solderability. Keep in good condition. At least one of X, Y, and Z of the derivative is represented by (-CmH ₂ m-O-) _o A, for example, m=2
is polyoxyethylene, m=3 is polyoxypropylene, and there are also copolymerized block polymers of both. Further, n is the degree of polymerization, which is greatly related to solubility, and the larger n is, the more hydrophilic it becomes, but if it is a large value of 20 to 30 or more, it becomes solid at room temperature. Further, A is hydrogen or a hydrocarbon group, and an alkyl group or alkylbenzene group having 6 or more carbon atoms has a particularly remarkable surface activating effect. Said X,
Among Y and Z, the remaining groups are hydrogen, alkali metals, ammonia, and amines, and amines include not only various alkylamines but also diethanolamine, triethanolamine, propanolamine, and the like. In particular, these amine salts exhibit weak alkalinity as an aqueous solution and are convenient for treatment, and the sodium salts can also be used industrially at low cost. Such derivatives are water-soluble due to the action of the polyalkylene chain, but when m is large, n is small, and the hydrocarbon group of A has a high molecular weight, they tend to become oil-soluble and can be processed as an aqueous solution. However, it can also be treated by dissolving it in an organic solvent such as toluene, benzine, trichloroethylene, or methyl ethyl ketone. In the method of the present invention, immediately after the Sn or Sn alloy plating step, a treatment step with an aqueous solution or organic solution of the derivative of the Sn or Sn alloy plating material is generally provided, and the solution is about 0.1% It is fully effective in dilute solution. Even if this treatment is followed by a treatment such as washing with water or hot water, the adsorbed or adhered derivatives on the order of molecules will not be removed. The method of the present invention will be described below with reference to Examples. Example 1 A copper wire with a diameter of 0.8 mm was electroplated with pure Sn to a thickness of 12μ using a tin sulfate bath in a conventional manner. After washing with water, the wire was immersed in a 0.2% aqueous solution of the derivative shown in Table 1 for 5 seconds. , washed with water and then dried. This was kept in a constant temperature and humidity chamber at a temperature of 60°C and a relative humidity of 98% for 500 hours, and then its solder wettability was examined. The results are also listed in Table 1. Solder wettability is achieved by attaching rosin flux.
The sample was immersed in a eutectic solder bath at 235°C for 2 seconds and then pulled out, and the solder wetted area was determined and expressed in %.

[Table] As can be seen from Table 1, the solder wettability of Sn-plated copper wires treated with a 0.2% aqueous solution of a derivative according to the present invention is lower than that of untreated copper wires or conventional 5% aqueous sodium phosphate solution. Much better than processed ones. Example 2 Copper-clad steel wire (conductivity 30% IACS) with a diameter of 0.6 mm was coated with a 10μ thick Sn-
After plating with Pb alloy (Pb5%), washing with water and drying,
It was immersed in a 0.1% toluene solution of the derivative shown in the table for 2 seconds and then dried. After heating this in the air at a temperature of 150° C. for 100 hours, the solder wettability was measured in the same manner as in Example 1. The results are also listed in Table 2.

【table】

[Table] As can be seen from Table 2, the products treated by the treatment method of the present invention have much better solder wettability than those treated with stearic acid or those not treated. As described above, the treatment method of the present invention is industrially remarkable, as it stably protects the surface of Sn or Sn alloy plated copper materials for a long period of time, and does not impede the original functions of plating such as solderability at all. This has the following effects.

Claims (1)

[Scope of Claims] 1. A method for surface treatment of a tin or tin alloy plated copper-based material, which comprises adsorbing or adhering the following phosphoric acid derivative to the surface of tin or tin alloy plated on the copper-based material. However, at least one of X, Y, and Z is a polyalkylene chain represented by (-CmH ₂ m-O-) _o A, where m and n are integers, A represents hydrogen or a hydrocarbon group, and the remainder is hydrogen. , alkali metals, amines,
Indicates ammonia or an aliphatic group.