I have done this and used the following steps: 

1) QA Survey and audit confirming quality system is evident and effective.
Also include process control of critical manufacturing parameters. 
2) PPAP run including all critical to function dimensions and part to
documentation/procurement agreement. 
3) Pre-acceptance run used to qualify that the PCB will function just like
or better than the previous part does. I typically would run 20-50 boards
through the entire process to confirm this keeping detailed records of each
process step. 
4) Forward to customer if needed for any additional qualification testing
and approvals. 

I then would maintain one of the PCB's as a historical sample with the
reports that support the acceptance/rejection of the new supplier. 

Sounds painful and you can cut corners if you choose to but to me I found
that I was asked to look at new vendors for a few main reasons: 

1) purchasing got a quote with a great deal. To stop the constant switching
and maintain better suppliers the process to change shouldn't be a simple
cake walk or you may find yourself constantly jumping depending on the new
suppliers delivering lower costs. 
2) to make the initial decision have more weight and to provide a motivation
to be better at original sourcing and not just run around for cost savings. 

Kat

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jack Olson
Sent: Friday, February 22, 2008 9:00 AM
To: [log in to unmask]
Subject: [TN] FAB Vendor Verification? Validation?

FAB: Vendor Verification? Validation?

It seems like I have leaned on Technet too often lately,
and I hope I'm not wearing out my welcome....

...but I am having to address this question:
"If you switch bare board manufacturers, what should you
do to verify that the new boards are just as good or better
than the old ones were?"

I can say a lot about how to CHOOSE a bare board vendor
and how to SPECIFY minimum levels of acceptability, but
from a technical point of view, is there more that should be
done than typical visual inspection, dimensional checks and
cross sections of the boards themselves?

Do any of you periodically monitor your bare board vendor
by asking for process control reports and stuff like that?

Have any of you ever been asked to re-validate a product
(reliability testing) on products just for changing the bare
board vendor?

Maybe I have just had a fortunate career by always getting
good boards, but lately I've been stung a few times in this
brave new world.

have a good day,
Jack

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