Lower Temperature Solder Joint Encapsulant
The strength of solder joints is enhanced by several times, and thermal cycling performance is significantly improved.
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Authored By:
Dr. Mary Liu and Dr. Wusheng Yin
YINCAE Advanced Materials, LLC
Albany, NY
Summary
The electronic industry is currently very interested in low temperature soldering processes such as using Sn/Bi alloy to improve process yield, eliminate the head-in-pillow effect, and enhance rework yield. However, Sn/Bi alloy is not strong enough to replace lead-free (SAC) and eutectic Sn/Pb alloys in most applications. In order to improve the strength of Sn/Bi solder joints, enhance mechanical performance, and improve reliability properties such as thermal cycling performance of soldered electronic devices, the company has developed a low temperature solder joint encapsulant for Sn/Bi soldering applications.
This low temperature solder joint encapsulant can be dipped, dispensed, or printed. After reflow with Sn/Bi solder paste or alloy, solder joint encapsulant encapsulates the solder joint. As a result, the strength of solder joints is enhanced by several times, and thermal cycling performance is significantly improved. All details will be discussed in this paper.
Conclusions
A new low temperature solder joint encapsulant adhesive, which is good for low temperature solders such as Sn/Bi has been successfully developed. Low temperature solder joint encapsulant solder paste has demonstrated excellent solder wetting and room temperature stability, which is good for mass production processes. Compared to using traditional Sn/Bi solder paste, using low temperature solder joint encapsulant dramatically improved drop test performance by over 10 times. There was no first failure observed before 1000 cycles, much better than the performance using Sn/Bi solder paste.
Initially Published in the IPC Proceedings
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