James,
I performed a similar feat at a prior job incarnation. We manufactured very
thin (.008") teflon rf boards. The previous method of assembly was to mount
the bare board to it's fixture. The fixture was aluminum and a HUGE heat
sink. The built assy was ran through an IR oven at gargantuan temps
(450-500C) to overcome the sinking. My first fix was to machine blank pieces
of FR4 to the depth of the of the board and securing with a window pane
style top piece. The FR4 would deform immensely after 2 or so runs, so I
procured some fo the now "outlawed" Arlon 35N ( I think that was the
material). This gave me more runs per panel. I purchased 6 3'x6' panels, so
that gave me 72 pieces. I panelized the boards at around 12 per panel. This
worked like gangbusters and I was able to run the panels through our dinky
Heller 4 zone oven (I've always hated IR anyway). Hope this helps.

Jason Gregory
Manufacturing Supervisor
ACT Manufacturing
Corinth, MS. 38834
(662)287-3771 x470
[log in to unmask]

> -----Original Message-----
> From: Marsico, James [SMTP:[log in to unmask]]
> Sent: Thursday, September 28, 2000 6:57 AM
> To:   [log in to unmask]
> Subject:      [TN] DENSE ASSEMBLY (PART II)
>
> I want to thank those who responded to my request for suggestions
> regarding
> the assembly of my dense board.  If you recall, it is 6002 Duroid, .005"
> thick, 1.5" x 2", with 270 0402s on it.  The direction I'm leading to is
> to
> panelize the boards (6" x 9").  The panel will be placed on a solid plate
> (.050"?) and held in place with another plate (window frame) on top.  This
> would allow me to go through pick & place and reflow by handling the
> fixture
> only.  How does this approach sound?  Would you suggest the fixture be
> made
> of stainless steel or should I consider a more thermally stable material
> like graphite?
>
> Second question...  This assembly is being used for a high frequency RF
> application, so solder coating the boards will effect performance.  (Just
> try and HASL this board!)  The RF guys like bare copper, gold, silver,
> maybe
> even nickel or tin plating.  Does anyone have any recommendations
> regarding
> surface finish for this assembly?  (from a board fabrication and assembly
> process perspective... I'll deal with the RF guys).
>
> Thanks again,
> Jim M.
>
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