Difference between tin-lead and tin-bismuth?++++
I'm working in an electronics company. We are using Tin bismuth plating solution. I just want to know the difference between tin-lead and tin-bismuth and what special characteristic does they have (if any)?Jay Balingit
Operator - Tarlac, Philippines
Your question can only be answered in general terms because you do not give any details about the exact compositions of your tin-lead and tin-bismuth alloys. The first simple answer is that one contains lead and the other bismuth. Seriously, though, it has long been the desire of the electronics industry and many others, to eliminate lead from their product range (especially solders) as it is very toxic and can cause the industry's workers many long term health problems. One safe common substitute for lead is silver, but this is expensive. Another one is bismuth, which is cheaper but not so widely available. Bismuth and tin will produce usable solders and alloys, but they may well have slightly different characteristics to tin-lead; for instance, the ratio of bismuth to tin will be different to that for lead and tin for any given melting point alloy. It will also have different surface tension and viscosity characteristics. You may also see a difference in its tendency to form whiskers.
R&D practical scientist
Chesham, Bucks, UK
Tin Bismuth as a plating material is interesting. However, there are concerns when soldering these things with Ti- Lead solder since this forms an alloy that melts at 96 °C. I heard something that less than 3 % Bi is no problem. Does anyone have literature regarding this item? I am especially interested in platings with low Bi- content and the effect of local concentration build up leading to areas with more than 3% Bi concentration.Guenter Grossmann
EMPA - Uebendorf, Switzerland