Werner -

Virtually all military, aerospace, and space OEM's require etchback.  They
call it out because they have test data (probably from the 70's and 80's)
that shows tha etchback is better than  no etchback.  I don't think it was
until the early 90's that plating developed to a point that would change the
data.  Since then everyone has reduced their engineering staffs and the
research into to etchback or not etchback is not funded.  Because of this I
would expect the etchback requirement to never go away.

Just my 2 cents worth...

Pete

>From: [log in to unmask]
>To: [log in to unmask], [log in to unmask]
>Subject: Re: [TN] Concentrated Sulfuric etchback
>Date: Fri, 29 Apr 2005 06:38:05 -0400
>
>Rob,
>Why would anybody in today's world require positive etchback?
>Werner Engelmaier
>
>-----Original Message-----
>From: Pete menuez <[log in to unmask]>
>To: [log in to unmask]
>Sent: Mon, 25 Apr 2005 11:49:44 -0400
>Subject: Re: [TN] Concentrated Sulfuric etchback
>
>
>Rob,
>You may find the board shop very reluctant to process through concentrated
>sulphuric acid. Plasma is the way to go.
>
>You should require the board shop or the plasma service bureau to do a
>cross
>section to evaluate etchback. If they just stick your panels into a
>"standard" etchback cycle there may be attributes on your panel that will
>not plasma etch properly. (Number of holes, diameter of holes, copper
>weights etc>)
>
>Also keep in mind plasma may not be even across the entire panel.
>
>Good luck,
>
>pete
>
> >From: Robert Coburn <[log in to unmask]>
> >Reply-To: TechNet E-Mail Forum <[log in to unmask]>,
> >[log in to unmask]
> >To: [log in to unmask]
> >Subject: [TN] Concentrated Sulfuric etchback
> >Date: Thu, 21 Apr 2005 08:55:21 -0400
> >
> >Hi T'Netters:
> >
> >One of our divisions has a design that requires positive etchback on a
>four
> >layer PCB (FR4 resin system).
> >The board shop that had previously provided these boards subcontracted to
>a
> >Plasma service.
> >The etchback does not meet requirements.
> >
> >Does anyone have a contact that can provide a concentrated Sulfuric acid,
> >Ammonium Biflouride etchback?
> >
> >TIA,
> >Regards,
> >Rob
> >
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