Using Sn60/Pb40 on Sn63/Pb37 Rework

Lead and tin form a eutectic solution. So no to that one, as to breaking some rule or other other people who are far more knowledgeable than me on "the rules" could pipe in. Also tin/lead eutectics don't grow tin whiskers like a lot of the replacements based around a 97% tin content. It is by far preferable if you want to build high reliability, long lived products.

sarason

reply »

In both cases you will be close to the eutectic composition(61.9%Sn), so I expect joint to be intact and uniform.

reply »

Here is a site with a graph to visualize and explain if you might have an issue. Basically, it's not entirely eutectic. You'll have a small percentage chance of unequal flow mix due to uneven melting and solidifying points. https://www.pcbdirectory.com/community/what-is-eutectic-solder

reply »