Jim,

In my previous job, I had a number of years experience of assembling onto
flex circuits. We had carriers manufactured as you suggested with a top and
a bottom plate. These were made out of CDM material (composite delmat
material I believe) which is manufactured by Von Roll Isola. This material
is extremely thermally stable and designed for multiple reflows (there is a
static dissipative version of the material which is dark grey / black).

We did try using stainless carriers but found that if too thin, they warped
/ distorted as they passed down the reflow oven (components popped off /
moved) or if made thicker, were of too great a thermal mass.

Regards,

Martin



===== Original Message from [log in to unmask] (TechNet E-Mail Forum.) at
28/09/00 12:56
>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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