Rheology and Wetting Characterizations of Flux and Solder Paste for Bga PackagesAuthors: Jinlin Wang, Ph.D.
Company: Intel Corporation
Date Published: 10/14/2018 Conference: SMTA International
The solder wetting balance test is one of the most common methods for solder wetting evaluation. This method can be used for flux, solder, and surface finish evaluations. The method with a molten solder pot, however, cannot be used for solder paste evaluation since the paste is a mixture of solder and flux.
In this paper, we will discuss a solder paste wetting method. A high resolution solder wetting balance was used for the solder paste wettability analysis. Solder wetting analysis for solder balls and solder paste with different pre-test conditions provide useful information for material selection and reflow process optimization studies. The effects of solder surface oxidation and paste aging on the solder-paste wetting interactions were investigated.
Wetting balance tests were performed for the characterization of paste and solder ball wetting behaviors. In addition, the understanding of the effect of solder ball reflow in relation to paste wetting was also analyzed in this work. In general, wetting test results showed that paste aging and improper paste used in SMT resulted in significant reduction in the wetting force. For the case of a multiple-reflowed solder ball, a decreasing trend in the wetting force was observed. The high resolution solder wetting balance was proven to be a useful technique in supporting the development of SMT paste materials.
flux, solder paste, rheology, solder wetting, materials process
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