Doug,
	I guess the first thing to look at is if you are working under some 
specification that addresses the issue of Burn-In.  If no regulating document, 
then I'd take this approach:

1)  Failure due to nonelectrical material or system.
	a)  Repair with no additional burn-in.  Develop corrective action if 
necessary.
2)  Failure due to component attach.
	a)  Replace component and reburn-in.
3)  Failure due to component.
	a)  Replace and reburn-in if component supplier has no screening 
process.
	b)  Replace with no additional burn-in if component supplier has 
effective screening process.

	It sounds like you're in number 3) and you definitely want to avoid a 
reburn-in process.  If you choose to not perform reburn-in, I suggest you 
document your justification and monitor the product.  You might also want to 
analyze all failures (at bench and in the field) before settling in on a 
reburn-in process to look for trends and the overall effectiveness of the 
initial burn-in.

Glenn Pelkey
Quality/Reliability Engineer
Maxtek Components Corp.


[log in to unmask] (Doug McKean) Wrote:
| 
| Thought I had sent this out once before. 
| Sorry if this is a repeat ... 
| 
| We have a product requires thermal testing -
| 
|  50 degrees C
|  Power ON
|  full functional setup
|  total high temp time = 72 hours
| 
| PRIOR to electronic bench testing. We do this to weed out
| an infant mortality with board assembly, bad chips, etc...
| 
| Now, if the bench test discovers or as indicated by front
| panel leds some failure and some rather large ICs
| need to be replaced, does the entire assembly go back
| through full cycle temp testing?
| 
| This could have a major impact on stock and ship 
| quantities.
| Plus only so many products can go in the chamber. Any
| retest knocks out *new* products coming through in the
| regular flow.
| 
| Comments, thoughts, even speculations welcome.

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