Mike,
        Do you know of a good reference for PCB layout rules for RF circuits?

Fred Watt
Finley Design Services

-----Original Message-----
From:   Mcmaster, Michael [SMTP:[log in to unmask]]
Sent:   Wednesday, April 19, 2000 11:17 AM
To:     [log in to unmask]
Subject:        Re: [TN] 8 Thou tracks in 2oz Copper

Mark

First let me make sure that when you refer to 8 thou you mean 0.008"?
That's what I'm basing my comments on.

8 mil trace/space on 2 oz copper should not be a problem for most board
manufacturers who regularly process 2 oz copper.  Our capability for 2 oz
layers at Merix extends down to 6 mil trace/space.  I would consider 8/8 a
comfortable design.

I don't see a reason why the inner layers couldn't be plated up to 2 oz
copper thickness, but I also don't see a reason to do it.  I suppose 2 oz
clad materials might not be as common as 1 oz and therefore a little harder
to obtain, especially for very short lead-time parts.  With a little
planning you should be able to get your boards built "properly" with 2 oz
foil.

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


        ----------
        From:  Mark Holmes [SMTP:[log in to unmask]]
        Sent:  Tuesday, April 11, 2000 3:23 AM
        To:  [log in to unmask]
        Subject:  [TN] 8 Thou tracks in 2oz Copper

        Hello all,

        I have a question for all you board manufacturers (and PCB
designers) out
        there. I have been working on an unusual 4-layer board which has 2oz
copper
        on all layers. The majority for the tracking is on the inner layers,
and the
        outer layers are effectively solid planes of copper. Many of the
tracks on
        the inner layers have to carry a lot of current, but there is also
some
        control circuitry which requires a clearance of 6.5mm from the high
power
        area. Here lies my problem. Due to the space limitations and
clearance
        required, I have tracked in a connector using 8th tracks which
travel almost
        the length of the board (around 110mm) along one edge. These 3
tracks are on
        their own, 6.5 mm from the rest of the tracking, adjacent to each
other with
        8th gaps.

        My question is - is this achievable? how much of a problem would
this cause
        the manufacture? The inner layers MUST be 2oz copper.

        My second question is - If 2oz of copper was specified for all
layers, is it
        acceptable to plate up the inner layers from 1oz copper foil?
        A manufacture told me they had done this (although in fact they had
not!)
        but I have never heard of this practice for inner layers before.

        This is a hot issue for me a the moment and I would appreciate any
advice or
        comments.

        Best Regards,

        Mark Holmes

        [log in to unmask]

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