Investigation of Sn‐Zn‐Bi solders – Part II: wetting measurements on Sn‐Zn7Bi solders on copper and on PCBs with lead‐free finishes by means of the wetting balance method

K. Bukat (Tele and Radio Research Institute, Warsaw, Poland)
J. Sitek (Tele and Radio Research Institute, Warsaw, Poland)
and
M. Kościelski (Tele and Radio Research Institute, Warsaw, Poland)
Z. Moser (Polish Academy of Sciences, Institute of Metallurgy and Materials Science, Cracow, Poland)
W. Gąsior (Polish Academy of Sciences, Institute of Metallurgy and Materials Science, Cracow, Poland)
J. Pstruś (Polish Academy of Sciences, Institute of Metallurgy and Materials Science, Cracow, Poland)

Soldering & Surface Mount Technology

ISSN: 0954-0911

Publication date: 21 September 2010

Abstract

Purpose

The purpose of this paper is to investigate the influence of Bi additions on the wetting properties of SnZn7Bi alloys (Bi=1 and 3 per cent by mass) on a copper substrate and printed circuit boards (PCBs) with lead‐free finishes (SnCu, immersion Sn, Ni/Au, organic solderability preservative) in the presence of fluxes. The practical implications of the results is the main purpose of these investigations.

Design/methodology/approach

A wetting balance method was used for wetting measurements at 230 and 250°C in nitrogen and air atmospheres in the presence of ORM0‐ or ROL0‐type fluxes. The PCBs were investigated ‘as received’ and after accelerated aging. The analysis of variance (ANOVA) analysis was performed in order to explain how the main factors of the experiments (the Bi content in the alloy (1 or 3 per cent), the test temperature and the test atmosphere) influenced the wetting ability of SnZn7Bi on Cu substrates.

Findings

As expected, a higher temperature and a higher Bi content in the alloy favoured the wetting of the copper substrate in the presence of the ORM0‐type flux in a nitrogen atmosphere. These results were confirmed by ANOVA analysis. Very good results were also obtained for the SnZn7Bi3 alloy's wettability on “tin coatings” on PCBs (SnCu and immersion Sn) both “as received” and after aging, in the presence of the ORM0‐type flux, for all the applied testing conditions (in both temperatures and N2 and air atmospheres). The less active flux (ROL0) caused a worsening of the alloy's wettability properties; however, the PCBs with SnCu and immersion Sn finishes maintained their wettability, even after aging, at very good and good levels, respectively.

Research limitations/implications

It is suggested that further studies are necessary for confirmation of the practical application, but they should be limited to the soldering of SnZnBi3 on PCBs with “tin coatings” and the quality of the solder joint performance.

Practical implications

The best SnZn7Bi3 wetting results on PCBs with “tin coatings” (SnCu and immersion Sn) at 230 and 250°C and in N2 and air atmospheres suggest the possibility of a practical usage of the tin‐zinc‐bismuth alloys for soldering in electronics using both the ORM0‐type flux and the even less active ROL0‐type flux, which are currently used in industrial lead‐free soldering processes.

Originality/value

The wetting balance method, combined with ANOVA was used as the quickest way to determine the wettability properties of SnZn7Bi on Cu substrates. Wettability measurements were also performed on the SnZn7 and SnZn7Bi alloys with different lead‐free finishes, in different experimental conditions.

Keywords

Citation

Bukat, K., Sitek, J., Kościelski, M., Moser, Z., Gąsior, W. and Pstruś, J. (2010), "Investigation of Sn‐Zn‐Bi solders – Part II: wetting measurements on Sn‐Zn7Bi solders on copper and on PCBs with lead‐free finishes by means of the wetting balance method", Soldering & Surface Mount Technology, Vol. 22 No. 4, pp. 13-19. https://doi.org/10.1108/09540911011076844

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Publisher

:

Emerald Group Publishing Limited

Copyright © 2010, Emerald Group Publishing Limited

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