Hi Mark,
I have done this kind of design before. There are mechanical, thermal,
RF and electrical implications. Working with engineers in these other
disciplines this is what we did:
-cutout- Signal1
=Teflon dielectric
-GND
..Grease (Thermally and electrically conductive)
]] Heatsink
If you can connect directly to the heatsink you can eliminate the copper
plate.
The PCB already has a ground plane, you do not need the copper for that.
If you want or need the copper for heat transfer then you can add it
with another layer of grease above the heatsink.
If the thermal issue is most important, then lamination and sweat
soldering may not be necessary.
I am not sure if those RF transistors would survive being soldered to a
2mm copper plate.
My 2 cents worth. By all means call me if you have any questions.
Best regards,
Roy
Roy H. Beckman, C.E.T., C.I.D.
RHB DESIGNS INC.
Contractor
Harris Stratex Networks
Phone: 403-516-1829
Fax: 321-674-2575
email: [log in to unmask]
www.harrisstratex.com
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Mark
Koitmaa
Sent: Tuesday, August 28, 2007 5:31 PM
To: [log in to unmask]
Subject: Re: [DC] Lamination to Copper Plate
The primary side has a high power RF transistor mounted in a cutout in
the
PCB so that the transistor can be sweat-soldered to the copper plate.
There are a few other passive components and input/output microstrips on
the primary side connecting the transistor.
The secondary side is a solid GND plane which needs to conduct through
to
the 2mm copper plate. The 2mm copper is a solid plate, not plated. It is
laminated to the secondary side of the PCB after PCB fabrication using a
conductive laminate (solder?).
The copper plate serves as a GND plane, and most importantly it
transfers
heat from the high power transistors to a heatsink. The PCB cutouts
allow
sweat-soldering of the transistors to the copper plate. The copper plate
side of the board is then attached directly to a heatsink.
------- cutout ------- Primary Side Copper
======= ======= RO4350B Dielectric
------- ------- Secondary Side GND Plane
...................... Conductive Laminate (solder?)
////////////////////// 2mm Copper Plate
]]]]]]]]]]]]]]]]]]]]]] Heatsink
Hope this clarifies the application.
Mark
On Tue, August 28, 2007 4:00 pm, George Patrick wrote:
> So...
>
> You want a .031 [1.2] substrate with .079 [2.0] of copper plating on
the
> secondary side... What is on the primary side? Is the ~11 oz plating
> on the secondary side etched or just a solid copper surface?
>
> Methinks there has to be more to this story :)
>
> --
> George Patrick
> Tektronix, Inc.
> Central Engineering, EDS Applications Support
> P.O. Box 500, M/S 39-512
> Beaverton, OR 97077-0001
> * 503-627-5272 (voice) * 503-627-5587 (fax)
> http://www.tektronix.com http://www.pcb-designer.com
>
> "Off-Grid and Proud of it!"
>
>
> -----Original Message-----
> From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of
Mark
> Koitmaa
> Sent: Monday, August 27, 2007 15:41
> To: [log in to unmask]
> Subject: [DC] Lamination to Copper Plate
>
>
> Can anyone recommend a fab house that is able to laminate a 1-2mm
thick
> copper plate to the seconday side of a two layer Rogers RO4350B .031"
> PCB?
>
> Thanks in advance,
> Mark Koitmaa
>
>
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