Hi all

I know I am swimming against the current (maybe that's wrong in English
but at least Werner will understand) but already in the last century we
found that joints after soldering have a fine grained structure in the
lead phase. The tin phase was always coarse. It's a question of
metallographic preparation to see that. After thermal cycling  the lead
phase is coarsening but the tin phase  is refining. For those who are
interested we published that 1996 in the proceedings of the  IEMT
Symposium in Austin. In lead free soldering (SnAgCu) we also observed
that the tin rich phase solidifies as dendrites. The globular, round
structure of the tin phase one also sees in SnAgCu solderings is due to
the fact that the dendrites are cut perpendicular to the "trunk".


Have a great day

Guenter



EMPA
Swiss Federal Laboratories  for Materials Testing and Research
Centre for Reliability
Guenter Grossmann,  Senior Engineer

8600 Duebendorf
Switzerland

Phone: xx41 1 823 4279
Fax :     xx41 1 823 4054
mail:     [log in to unmask]

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