Hi Mike: I agree with you, my point was that the foil on the processed
original board in question is not 1.4 mils as stated by others. As you and I
are both saying, processing reduces it by about 0.1 mils or more. I
probably should have stated "nominally" 1.1-1.3 mils for finished foil
thickness but I didn't want to confuse those unfamiliar with bare board
fabrication any further.
Anyway we've probably beat this topic to death.
Regards
Mike Barmuta
Staff Engineer
Fluke Corp.
425-446-6076
-----Original Message-----
From: Mcmaster, Michael [mailto:[log in to unmask]]
Sent: Tuesday, June 03, 2003 9:40 AM
To: TechNet E-Mail Forum.; Barmuta, Mike
Subject: RE: [TN] (2) Micro-inch to copper weight conversion...
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]
<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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