Martin:
- The IPC definitions (IPC-T-50F, pages 22 and 46) of dewetting/nonwetting you
requested are:
- Dewetting - A condition that results when molten solder coats a surface and
then recedes to leave irregularly-shaped mounds of solder that are separated
by areas that are covered with a thin film of solder and with the basis metal
not exposed.
- Nonwetting - The partial adherence of molten solder to a surface that it has
contacted and basis metal remains exposed.

- I have always concluded from the above that with "dewetting" an
intermetallic has been formed (fragile though it may be) and that with
"nonwetting" No intermetallic has been formed and the "adherence" is strictly
mechanical in nature.  I think I can chip nonwetted solder off of the surface
with my thumb-nail, but I can't remove dewetted solder that way.
- By the way, there is a color photo of nonwetted/dewetted solder on page 38
of the April issue of Circuits Assembly magazine that might help with visual
identification.
  Jim Moffitt

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