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Method for forming a displacement tin alloy plated film, displacement tin alloy plating bath and method for maintaining a plating performance

a technology of displacement tin alloy and plating bath, which is applied in the direction of liquid/solution decomposition chemical coating, coating, printed circuit manufacturing, etc., can solve the problems of lowering solderability, lead-free solders are inferior in solderability to tin-lead alloys, and adverse influence on solder bondability, etc., to achieve excellent uniformity, maintain the plating performance of the plating bath, and good solderability

Inactive Publication Date: 2008-07-24
C UYEMURA & CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0008]Under these circumstances, the present invention has for its object the provision of a method for forming a displacement tin alloy plated film being inhibited a whisker formation in such a way that the tin alloy plated film can be formed as a film having excellent uniformity ensuring good solder

Problems solved by technology

In this connection, with the formation of a tin alloy plated film to which second and third metallic components are added to tin is formed on a substrate such as of copper or the like, if a plated film of a given thickness necessary for practical application is formed, the thickness distribution of the film varies and a uniform thickness cannot be obtained, resulting in an adverse influence on solder bondability.
Lead-free solders are inferior in solderability to tin-lead alloys.
However, a tin alloy plated film of a non-uniform thickness causes the lowering of solderability.

Method used

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Examples

Experimental program
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Effect test

examples

[0054]Examples and Comparative Examples are shown to more particularly illustrate the present invention, which should not be construed as limited to the following Examples.

experimental examples 1 to 3

[0058]A displacement tin alloy plating bath having the following bath composition 4 was provided and used both for a low temperature bath and a high temperature bath. As a test piece, there was used a rolled copper sheet on which a copper film having a thickness of about 10 μm had been formed by copper sulfate electroplating. The test piece was subjected to degreasing and acid cleaning, followed by immersion (one minute) in a low temperature displacement tin alloy plating bath (30° C.) and subsequent immersion (15 minutes) in a high temperature displacement tin alloy plating bath (60° C.).

[0059]This plating operation was repeated, under which thiourea and silver methansulfonate were, respectively, added to make such concentrations as indicated in Tables 3 to 5 in every increment of 1 g / L of a copper concentration in the low temperature displacement tin alloy plating bath and the high temperature displacement tin alloy bath. In Experimental Example 1, the concentrations of thiourea a...

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Abstract

Disclosed herein is a method for forming a displacement tin alloy plated film, on a copper or a copper alloy on a substrate, a tin alloy plated film containing at least one additive metal selected from silver, bismuth, palladium, indium, zinc and antimony, the method including the steps of: forming an under layer on the copper or copper alloy in a low temperature displacement tin alloy plating bath at a temperature of 10 to 50° C.; and forming an upper layer on the under layer in a high temperature tin alloy plating bath at a temperature of 40 to 80° C. to form the displacement tin alloy plated film formed of the under layer and the upper layer.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2007-011175 filed in Japan on Jan. 22, 2007, the entire contents of which are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to a method for forming a displacement tin alloy plated film suited as a final surface treatment of printed circuit boards and electronic parts, a displacement tin alloy plating bath used in the method and a method for maintaining a plating performance of a plating bath in the above-mentioned method.[0004]2. Description of the Related Art[0005]Various types of lead-free solders have been proposed as a substitute for tin-lead alloy solders. Where a lead-free solder is applied onto portions to be soldered of different types of substrates, a tin plated film formed on the portion to be soldered as an underlying film is required not only to have ...

Claims

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Application Information

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IPC IPC(8): C25D3/60
CPCC23C18/54H05K3/244H05K2203/1476H05K2203/1105H05K2203/073C23C18/16C23C18/31
Inventor KISO, MASAYUKIMAEDA, TSUYOSHIKAMITAMARI, TOHRU
Owner C UYEMURA & CO LTD