The eutectic combination of tin and lead is 63% tin, 37% lead. 60/40 has
a slightly higher melting point, and unlike the eutectic alloy, has a
plastic stage between liquid and solid. Consequently, 63/37 is a better
choice for solder.

Roy Lewallen, W7EL

Hal Rosser wrote:

plain old 60-40 rosin-core electrical solder has worked well for me - got
mine at a hamfest on a half-pound roll.
the silver stuff (I believe) melts at higher temperatures - and higher
temperatures are not good for electronics.
eutectic (if my memory serves) just means it's either solid or liquid - and
won't just 'soften' - like ice and water.
hth
Hal w4pmj