Hi Ed (and everybody else),

When you look for a cause of a problem first determine ALL the things that
changed prior to the problem manifesting itself.
Don't jump on the first change you come across and SAFELY assume it is the
culprit!!!
Sometimes the culprit is the big one that stands out (like in this case?),
many times it is the little one hidden under all the denials: I did not
touch it!

Have fun,
Ahne.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ed Popielarski
Sent: Wednesday, 01 November, 2006 07:55
To: [log in to unmask]
Subject: Re: [TN] Bizzare Phenomena...

Steve (and the rest of Technet),



LTNS! I've been extraordinarily busy lately. Good thing, I suppose.



Since you said "and we have never seen solderballs like this until we ran
the lead-free boards with the SAC 305 paste" then one can safely assume it
is related to the change, i.e., the lead-free paste. I would venture a guess
that the surface tension (much lower in LF alloys) plays a part in possibly
large areas of paste going liquidus then sluffing off in droplets. If you
could identify a particular assembly this happens consistently with, then
perhaps you could affix an inexpensive, i.e., "disposable" video cam to
watch it happen in the reflow zone. Even if you only get to see it once, it
would verify your suspicions. Another idea that struck me is to try a
competitor's paste and see if the symptom goes away, or tech support from
the original supplier gets smart suddenly?!



Regards,



Ed Popielarski

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