In a message dated 7/30/00 10:47:05 PM US Eastern Standard Time,
[log in to unmask] writes:

<< time
 Can anyone tell me how to get good solder perfomance when wave soldering
SOT23 packages >>

Since the problem I always had with SOT23's is solder skips (unsoldered
leads), I will tell you what I learned there.  SOT23 packages tend to collect
liquid flux under to component body, just enough to cause an air bubble to
form and push away the solder.  I have witnessed this effect by placing
SOT23's on a glass plate and watching for the wave flow dynamics as the
"board" hit the solder.  I was expecting to see some eddy pattern that would
explain how the solder sometimes hit and sometimes missed the pads, but it
was the bubbles that revealed the answer.  Long narrow pads will often cure
this problem, but there is another available solution.  If a small hole is
drilled under the SOT body to allow the gas to escape as the bubble tries to
form, then the solder is able to contact the pads without hindrance.  This
assumes that your design, internal and external latyers, allows room for the
hole.  In any case, knowing the cause will help in eliminating the defects.

Jon Moore

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