Concur fully with Jon's comments but in addition was able to achieve
acceptable results with incorporation of Hot Plates for both assemblies and
components combined with a soldering iron and reduced tip temperatures.  It
would be nice if producers made one that ramped to a profile because hot air
is technique dependent also.  Tried turning the iron (brand name) off and on
to let the power up stage preheat but that was seriously difficult to
manage.

Mel Parrish

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Jon Moore
Sent: Friday, August 17, 2001 1:53 PM
To: [log in to unmask]
Subject: Re: [TN] To wave or not to wave, that is the question...


Kevin,
     Our FEA study concluded that the most likely source of thermal stress
resulting in a crack was the cooldown / reheating between the waves of a
dual
wave solder system.  If the temperature shock upon entering the first wave
is
less than 100C and the temperature drop between waves was kept to less than
62C, then the data predicted no cracking would occur.  We were able to
consistently create cracked capacitors by performing solder joint touch up
with a solder iron.  Only hot-air touch up would allow the right ramp rates
for crack-free caps.

Jon Moore

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