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November 1999

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Subject:
From:
Carey Pico <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 4 Nov 1999 11:20:02 -0800
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text/plain (114 lines)
Chicco,

I have had similar experience- although the "edge" effects of where the
metal line's edge is defined creates a problem if you don't want to damage
the dielectric.  The process becomes very slow.  Also, the 30 mils down is
just too deep for material to be
removed during laser ablation.

In terms of PWB circuitry repair, the market is not there to develop a
machine.

There has been much discussion about using the laser to vary buried
resistors (laser trimming is routine on ceramic and Si).  And one doesn't
have
to have much imagination as to what else.  The key is when is the market
ready to pay for such a machine.

Carey

-----Original Message-----
From: Adeodato Vigano <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Wednesday, November 03, 1999 4:24 PM
Subject: Re: [TN] Cutting through an inner trace


>Matt,
>
>We have experimented with laser with mixed results: on one occasion we were
>attempting to cut a connection approximately 5 mils under the surface of
the
>board (FR4 material), that worked out very well.
>
>Another time we were trying something a little more daring, cut out a
>clearance from a power plane 6 layers under the surface, approximately 30
>mils down. That one didn't go that well, the 1 mil laser beam that we were
>using was able to cut to the required depth but the 30:1 aspect ratio of
the
>cut caused, I think, a carbon re-deposition along the walls of the cut.
>That gave us a high resistance short that was impossible to remove.
>
>I would like to add that both times we were performing the operation under
>the direction of our customer to fix a design problem, I'd like to stress
>that because I'm pretty sure that this kind of "repair" would not be
>permissible without proper authorization.
>
>Chicco Vigano
>Compunetics, Inc.
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]]On Behalf Of Matt Cirineo
>Sent: Wednesday, November 03, 1999 5:28 PM
>To: [log in to unmask]
>Subject: [TN] Cutting through an inner trace
>
>
>Other than drilling, has anyone used an alternative method of cutting
>through an inner layer trace?  I'm thinking of methods such as laser, water
>cutting,...
>
>Your comments and suggestions would be greatly appreciated.
>Matthew Cirineo
>Operations Engineering
>Primex Aerospace Company
>phone: 425-885-5010 x4855
>fax: 425-895-4310
>
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