Hello,
        I use an automatic grinding and polishing unit and a special coupon
     with tooling holes. We routinely get to center hole on 60 coupons with
     drill diameter of 12.5 mils. Depending on the coupon artwork this can
     be over 600 holes. This takes about 45 minutes. For microvias, the
     coupon artwork has a row of them tightly spaced diagonally across the
     axis.
        This proves to be good for process control. I feel confident that
     it represents the boards as well. Nevertheless some of my customers
     also request a board sample.
     Rich
------------------------------------------------------------------
     Richard Olsen                Telephone (602)-232-9154
     Continental Circuits Corp.   Main      (602)-268-3461
     3502 East Roeser Road        Fax       (602)-268-0208
     Phoenix Arizona              Pager     (602)-310-6245
     85040-2905                   Internet  [log in to unmask]
     USA                    I make circuit boards,what do you do?
------------------------------------------------------------------



______________________________ Reply Separator _________________________________
Subject: Re: [TN] Microsections
Author:  [log in to unmask]>          Gabriela Bogdan <[log in to unmask] at
internet
Date:    2/25/98 11:38 AM


BOB HAYNES wrote:

> Ladies and Gentlemen,
>
> I have been asked by our Purchased Material Inspection (PMI)
> department to find out how other people are doing the required
> microsection on small holes. The "B" Coupon as required by Para..7.3.5 >
> of IPC-D-275, has holes of the smallest diameter on the printed
> wiring board. These are  vias which are now 10 mils and below and it
> is reported that these are very difficult to do a good microsection
> on.
>
> Has anyone else experienced the same problem and if so what was
> your solution? Any feed back and suggestions would be greatly
> appreciated.
>
> Thanks in advance,
>
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   Dear Technetters!
I am also looking for a reliable method to cross section small holes.
Until now I didn't use automatic equipment due to the fact that I
usually
don't trust test coupons, and I check holes on the real circuit after
reflow
and wave soldering on random locations,checking also the plugging or
tenting.
Am I wrong?
Gaby

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