Luke says:

May 30, 2019 at 10:16 am

The bismuth based solders would be nice, but they tend to be rare as hens’ teeth and expensive when you do find them from a local supplier. Also, the low melting point of 139 C is a little bit too close for comfort for some components like high power high temperature FETs that may run up to 150-200 C.

Report comment

Reply

Luke says:

May 30, 2019 at 10:24 am

Apparently, if there’s any lead involved, such as with pre-tinned wires or leads, the combination of Bi58Sn42 and the lead can lower the melting point to 95 C and create very weak and brittle joints that can be pried apart with a toothpick.

And in general bismuth solders have inferior mechanical properties, being somewhat brittle and stiff even when there’s no lead involved.

AMS says:
May 30, 2019 at 8:10 pm

Having tried quite a few, SN100C (It’s .7%cu, .05%Ni, .009%Ge Balance Sn) is about the best you’ll get other than 37/63 SnPb stuff. Yeah it’s higher temp but it wets well, is eutectic, and shiny, and doesn’t get all dross filled when soldering big stuff like 97/3 SnCu or SAC305.

All from

https://hackaday.com/2019/05/30/the-fascinating-world-of-solder-alloys-and-metallurgy/#comments

--