Something the company I work for has done, on occasion, has been to place a
'DAISY CHAIN' coupon on the waste area of our processed panel (we call it a
master).  Basically, a series of the smallest hole on the board, with
alternating connections on the comp & ckt sides of the pcb (forces current
through the vias).  Place an ohm/continuity meter on the start and end
points and check for a connection.  If a failure is found it is very easy
to locate the offending hole, cross-section and determine a reason.  Qty of
vias on the board vs qty of vias on the coupon must be evalutated (10000
vias, you don't want a 5 hole coupon.)

If a substantial problem exisits, try putting a DC coupon on the waste rail
of your array, will cost more but may be worth it...

JOE SENDZ.....

----------
> From: Bogdan Gaby <[log in to unmask]>
> To: [log in to unmask]
> Subject: [TN] Plating integrity in small vias
> Date: Monday, November 24, 1997 7:11 PM
>
> Hello,Technetters!
> Skipping the horror story,I have a question to printed circuit
> manufacturers:
> How do you ensure the integrity of the plating in small vias?
> We require the manufacturer's cross sections as a proof of test
> for our circuits.Very seldom,they contain small vias.
> But,anyway,the failures found recently in our line are in random places
> on the boards.
> Are there other tests on bare boards which can detect reliability
> problems ?
>
> Thank you
> Gaby
>
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