We also manufacture military electronics and we do not use any preheat when 
removing chip capacitors.  This practice doesn't seem to be a problem.

Jim Marsico
(516) 595-5879
[log in to unmask]
		
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Dear Technet,

We are a military assembly house that employs preheating 
plates for ceramic chip rework to reduce the risk of 
internal chip delamination from thermal shock. 
This has been done per IPC recommendations.   However, this step in the 
rework process is time consuming and cumbersome.  We have done 
minor and informal tests to determine the real value of this 
practice and found that it really is not needed if the operators take 
care in their soldering.  If the tip size and heating time is 
controlled, there doesn't seem to be an immediate effect or a 
temperature cycling effect on the chips.

I am interested to see how widespread the use of preheating
plates actually is.  I would like to hear from anyone having
any experience indicating that the process is actually necessary.
(or not necessary)

Thank you in advance for any input.

Jason Spera
Manufacturing Engineering
General Atronics Corporation


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