Leland, I would like to have Werner Engelmaier comment on cooling  rates.  
Seems to me I heard him say at IPC Midwest 2 months ago, that more  damage is 
done to the board (not just the solder joint) in fast cooling.   Someone asked 
why reflow ovens have four heat-up zones, and only one cooling  zone.  I think 
I saw Werner shrug and say that no one knows how damaging  fast cooling is to 
the board.  This was in a forum on "lead-free effects in  board fabrication" 
for a proposed White Paper from the IPC.  
 
Denny Fritz
MacDermid. 
 
In a message dated 12/5/2007 10:19:45 A.M. Eastern Standard Time,  
[log in to unmask] writes:

Good  morning, everyone!

Lately we've had a slight issue with one of our  reflow ovens.  We have
set our temp parameter for the last zone at 150  degrees C.  When we
first received this oven we had no problem with  maintaining this zone as
prescribed.

I assume we have an insulation  barrier that's breaking down and causing
this situation.

Anyway, how  critical is this cooling zone?  If the oven is no longer
able to  maintain the current setpoint, would it harm anything for this
zone to move  up in the 160 to 170 degree range?

We're running a pb-free process  here, just in case it makes any
difference...

Thanks in advance for  your help.

Leland Woodall


 



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