Entrapped hydrogen? We had this problem with GaAs chips as well as
hybrid packages. When we soldered glass feedtrues, we got numerous voids
or bubbles in the solder joint. After heat treatment before soldering
there were no bubbles at all. There is a lot written about hydrogen in
nickel plated parts, some baths give no entrapped hydrogen at all,
others do. The below lines may cast some light on the topic. Finally,
minor bubbles from hydrogen should not cause any problems, voids are not
a catastroph, we have compared perfect solder joints with joints having
bubbles. There was no difference.
 
 
Ingemar Hernefjord
Ericsson Microwave Systems
 

 
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Gervascio, Thomas
Skickat: den 16 november 2005 14:49
Till: [log in to unmask]
Ämne: [TN] Snap ,crack and pop
 
We have been seeing solder fines all over some PCMCIA boards we have
build. We checked the degree of cure on the PCB, paste volume and paste
oxidation and slump and checked the oven profile (tried both a ramp-soak
and ramp to spike profile with 1 C/sec ramp rates). We then found that
it only happened when certain resistors were used. All I know right now
is that it is a RoHS (tin plated over nickel) on ceramic part- 0603.
 
We put some boards on a hot plate and heard a sizzle and popping of the
paste on a board that had these parts (didn't see the same on a printed
bare board).
What could be outgassing from the part terminations that would interact
with the paste that would cause this explosive phenomena? Could the
parts be tin plated and then fused? could it be some sort of organic
material (brightener) that is remaining and outgassing?
 
 
 
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