If it's too late to get 100% solder on this board, one possible solution 
could be addressed in design.  I wonder if your designers use thermal 
pads for GND/PWR connections!

I've had similar problems with an 11X11" board until we used thermal 
pads vs. direct connections to the layer.  We had three layers of GND 
and we could never achieve the 100% flow.

Good luck,
bilal 
 


______________________________ Reply Separator 
_________________________________
Subject: ASSM:  Top fillet formation
Author:  [log in to unmask] at SMTPGATE
Date:    12/20/96 6:34 PM


Hello Technetters,

I need some advises. I have a  6- layers board. I try to wave solder it,
the solder
at the ground point is not able to flow up to the top side of the board, 
in
fact, it
doesn't flow above 75%.

We have tried using a solder-iron and set to temperature to 450 deg. 
cel. and
hopefully able to force the solder through the PTH. Too bad, it didn't 
work
anyway
and it in fact has caused some lifted pads.

We use full blow Nitrogeneous wave-solder machine, and the flux we use 
is
only 1.2% solid content. And if the preheat temperature set to high, the 
flux
gets degraded before it even reaches the wave..

I would like to know if anyone could advise me how wave-solder such a 
board
with a great heavy thermal mass.

Thanks in Advance..



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