Jason,

When I used this Taconic material, we brush gold plated the contacts and left the
remainder bare copper.  The bare copper was not left alone however.  Later on in the
process the copper was all sealed up, but that is a different secret.  Think we were at
around 10 Gigs.

What is probably happening is your tin is so thin that the copper intermetalic has made
it to the surface of the board, and oxidized beyond your fluxes ability to remove the
oxide (i.e. the oxygen is bonded really tightly to the Cu(x)-Sn(y) alloy.)

Have you tried organic coatings?  Immersion nickel/gold?  A thicker immersion tin
plate?

There are some other more exotic metal coatings out there now also with the rush for
non lead based soldering.  (May the gods watch over your soul if you use them, cause
you will be all alone going where few have gone before.)


George Franck
"My Opinions are just that"

jason gregory wrote:

> Hello all you technetters,
>
> Question for all the "high-freq" guys out there.
> We have been building PTFE boards quite some tme and a long-running problem
> has been the solderability of these boards. They are .018" thick and are
> used for high frequency applications. The spec is for tin immersion plating.
> No matter what reflow profiles I use, there are non-wetting signs all over
> the board. The solder just won't flow properly on the pads. It looks as
> though the solder flows, then stops. I've eliminated surface contamination
> by washing the boards prior to build and still the same problem. Are there
> any other platings available that will promote flow and won't affect high
> freq reliability. Please help. Thanks.
>
> Jason Gregory
> Process Tech
> Tadiran Microwave Networks
> (281)263-6671
> [log in to unmask]
>
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