Bismuth

For reflowed solder joints, Bi bearing solder has been reported to exhibit superior fatigue resistance. It also provides better wetting than many other alternatives, including SnAgCu systems. In my opinion, it may be the choice once all Pb can be phased out of the interconnect area, mainly due to a better potential in yield.

For wave soldering, Bi bearing alloys tends to have fillet lifting. Although studies indicate that the reliability is still very good, industry may need more data to confirm that fillet lifting is not a concern.

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