Member formed with coating film having tin as its main component, coating film forming method and soldering method

a technology of coating film and main component, applied in the direction of core/yokes, manufacturing tools, solventing apparatus, etc., can solve the problem of insufficient effect of this, and achieve the effect of preventing the wettability of solder from being lowered and suppressing the generation of whiskers

Inactive Publication Date: 2011-10-06
FUJITSU LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

As the intermetallic compound is formed along the crystalline grain boundaries of the coating film, a migration of a tin atom through the grain boundaries is restricted. It is therefore possible to suppress whisker generation. Before solder is put, a heat treatment is performed to move the intermetallic compound to the base member side. It is therefore possible to prevent solder wettability from being lowered by the influence of the intermetallic compound.

Problems solved by technology

However, although generation of whiskers can be suppressed to some extent, the effects of this cannot be said sufficient.

Method used

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  • Member formed with coating film having tin as its main component, coating film forming method and soldering method
  • Member formed with coating film having tin as its main component, coating film forming method and soldering method
  • Member formed with coating film having tin as its main component, coating film forming method and soldering method

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Embodiment Construction

With reference to FIGS. 1A to 1C, description will be made on a coating film forming method according to an embodiment.

As shown in FIG. 1A, a base member 1 on which a coating film is formed is prepared. The base member 1 used in the embodiment is a 28-pin connector terminal member made of phosphor bronze. First, as a plating pre-process, a cathode electrolytic degreasing process is executed for the base member 1. Electrolytic degreasing agent may be Cleaner 160 manufactured by Meltex Inc. For example, a process temperature is 65° C., a current density is 2.5 A / dm2, and a process time is 30 seconds. After the electrolytic degreasing process, the base member 1 is water-washed.

Next, the base member is subject to chemical polishing. Polishing chemicals may be 50% CPB40 manufactured by Mitsubishi Gas Chemical Company Inc. For example, a temperature of chemicals is set to approximately the room temperature, and an immersion time is set to 20 seconds. After chemical polishing, the base mem...

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Abstract

A member having a coating film capable of suppressing whisker generation is provided. The coating film (3) including a plurality of crystalline grains (3a) made of tin or tin alloy is formed above the surface of the base member (1). An intermetallic compound (3b) of tin and the first metal is being formed along the crystalline grain boundaries of the coating film.

Description

TECHNICAL FIELDThe present invention relates to a member formed with a coating film having tin as its main component, and more particularly to a member plated by using a material as a substitute for tin-lead plating. The present invention relates also to a method of forming a coating film and a soldering method for the member.BACKGROUNDTin-lead solder plating has been conducted conventionally for connector terminals, semiconductor integrated circuit lead frames and the like. For the recent viewpoint of environmental protection, studies have been made on usage of tin (Sn) plating, tin-copper (Sn—Cu) alloy plating, tin-bismuth (Sn—Bi) alloy plating, tin-silver (Sn—Ag) alloy plating and the like not containing lead, as a substitute for tin-lead solder plating. A technique of Sn—Cu alloy plating is disclosed in Patent Document 1 described below.If a coating film is made of the above-described alloy not containing lead, needle-like tin crystals called whiskers are likely to be generated....

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B23K31/02B32B15/04B32B5/16
CPCB23K35/262Y10T428/12076C22C13/00C23C2/08C23C26/00C23C30/00C25D3/12C25D5/12C25D5/50C25D7/00H01R13/03C25D7/12Y10T428/12715Y10T428/12708B32B15/01Y10T428/31678
Inventor SAKUYAMA, SEIKI
Owner FUJITSU LTD
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