Sorry, Mike I have to disagree with you on this.  It would be very uncommon
to see 1 oz copper at 1.3 mils in a finished board.

Almost everyone uses foil that is at the thin end of the spec.  Why?
Because copper is sold by weight and thinner foil weighs and costs less.
IPC 4562 says that ED foils can be 10% below the listed nominal (nominal for
1 oz is 34.3 um or 1.35 mils).  Foil more commonly comes in at 1.30 mils or
less.  Processing does reduce this down to 1.2 or thinner.  Remember on the
finished board, the copper thickness only needs to be 1.0 mils.

Mike McMaster
RF Product Engineer
Merix Corporation
503-992-4263



> ----------
> From:         Barmuta, Mike[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;Barmuta, Mike
> Sent:         Tuesday, June 03, 2003 7:19 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] (2) Micro-inch to copper weight conversion...
>
> Robert: Fascinating story about ivory PCB's, never heard that one before.
>
> I think there needs to be some clarification on the thickness of 1oz Cu
> foil. It may start out at 1.4 mils but it ends up at about 1.3 mils due to
> processing steps such as deburring and microetch. So in the real world,
> the
> boards Steve was questioning that were fabricated using 1oz foil should
> have
> a FINISHED Cu foil thickness of 1.3 mils after conventional processing.
>
>
> Regards
>
> Michael Barmuta
>
> Staff Engineer
>
> Fluke Corp.
>
> Everett Wa
>
> 425-446-6076
>
>
>
> -----Original Message-----
> From: Robert Tarzwell [mailto:[log in to unmask]]
> Sent: Monday, June 02, 2003 4:37 PM
> To: [log in to unmask]
> Subject: Re: [TN] Micro-inch to copper weight conversion...
>
>
> This just goes to show how old I am but when we first started to
> manufacture
> printed circuit boards the only copper you could buy was a very thin sheet
> the roofers used to solder flashes around wondows and stuff it was 2 oz
> copper and thats how it was sold by the oz. then the lamianted manufatures
> started to make laminate I think GE was first, or thats who we got, So
> even
> though theres lots of replies  it all started  with the available copper
> of
> the day. early 1960's
> Not realy connected but my grandfather told me about making a sort of
> printed board in the 20's by using IVORY and drawing lines between copper
> rivets with carbon black in wavy lines to make resistors.
> Robert tarzwell
> PS some replies have the thickness of 1 oz of copper incorect it is closer
> to 1.39 mils. not 1.3
>
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