Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.




Bismuth | 24 August, 2000

Hi Dr. Lee,

Besides the requirement of a PB free surface finish on PCBs, could you tell me what the pros and cons of a Bismuth bearing solder are?

Thanks, Jon Kervin

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Dr. Ning-Cheng Lee


Re: Bismuth | 24 August, 2000

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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