Phil Bavaro is the master of this type stuff in our assembly area.  I don't
know what we'd do without our benchtop bead blast cabinet.  We've had a lot
of success removing mask and PTF (e.g. carbon ink) with walnut shell blast
media.  When it's tight quarters and precision is needed it's simple to
fabricate a metal stencil and overlay.  When it's real tight or high volume
then we've sent out and tool for removal on a laser.  We've done on the
order of 10,000 pieces when needed to implement ECO on the fly (e.g
component substitution due to shortages or tuning).

In the same vein, you can cut metal and/or dielectric using a stencil with
bicarbonate of soda as the blast media is effective.  We've successfully
blasted out 3 mil traces several layers down for ECO modifications.

cheers,
Dwight



>----- Original Message -----
>From: "Mike Sewell" <[log in to unmask]>
>To: <[log in to unmask]>
>Sent: Wednesday, June 30, 2004 10:22 AM
>Subject: Re: [TN] Soldermask on PTH pad???
>
>
> > We did something similar...had a stencil vendor cut aperatures for the
>
> > features we wanted to remove then used a Dremel with the abrasive
> > rubber tips.  Something about putting RF flags on traces for tuning
> > the assembly. Slow but it worked.
> >
> > Regards,
> > Mike Sewell
> >
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