SMTA International Conference Proceedings

Next Generation No-Clean Lead Free Solder Paste Evaluation For Fine Pitch Applications

Authors: Fei Xie, Ph.D., Daniel F. Baldwin, Ph.D., Paul N. Houston, Brian J. Lewis, Han Wu
Company: Engent, Inc.
Date Published: 10/13/2013   Conference: SMTA International

Abstract: Interest in using fine pitch SMT components (0.4/0.3 mm pitch WLCSP, WLQFN, 0201, 01005 components, and smaller) has increased greatly in recent years due to the growth of portable, hand held electronics and due to miniaturization trends in consumer and industrial electronics markets. Many studies have shown that there is a strong correlation between fine-pitch SMT defects and solder paste materials and print quality. More than 60% of the end of line defects in fine-pitch SMT assembly can be traced to solder paste and the printing process. Reflow adds another 15%. Therefore, having a good solder paste material is very critical for having high yields and reliable products during those fine-pitch SMT component assemblies.

This paper presents the evaluation process and results for thirteen next generation No Clean Lead-Free solder pastes from various solder paste vendors. The study centers on fine-pitch SMT component assembly applications using 0402 and 0201 components. Seven criteria were investigated which included the stencil releasing capability, variation of the printed volumes, wetting capability, flux residue cleaning capability, number of defects after placement and reflow, the intermetallic layer (IML) formation, and the IML thickness growth. The results for each study are presented in this paper. The solder paste with the best performance was chosen and has been implemented in our fine pitch component assembly process.

Key Words: 

No-Clean, Solder paste evaluation, Fine pitch component assembly

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