Charles Barker@IO-US
11/05/97 03:35 PM

     We have been asked to run some tests to establish procedures for
attaching leads (24-28 AWG, teflon insul. tinned CU, stranded) to ceramic
substrate material 0.025" thick. We have a few sample pieces of ceramic
with the two different "pads" on them to test with.  I do not want to start
out down the wrong path and destroy the samples.
     The following is information I have received from the Engineer in
charge of this project:
1. The first substrates have a Pl/Pt/Au metal, about 0.001" - 0.003" thick.
(Looks dull as all get-out to me and quite thin-closer to the .001"
thickness.) (Small pads on my samples, about 0.063" square.)
2. The second substrates have a thick film metal covered with 0.005" thk
Cu, with 150 microinches typ of Ni, covered with 5 - 10 microinches of Au.
I don't think that the type of thick film metal matters because of the
copper.  (Large, roomy surfaces to solder to on the samples.)
3. The solder spec calls out a 5% Sn, 94% Pb, 1% Ag for the high
temperature solder (HMP).  (Liquidus around 300 deg C.)

For any of you that have worked with this type of material before:
1. Any recommendations or suggestions about soldering iron temperatures,
dwell time, etc.
2. What about suggested fluxes? (I don't believe the solder we are getting
is cored.)
3.  Any special tricks or techniques?
4. Should we try to pre-heat the ceramic? (This may not be possible with
the finished product.)
5.  Does anyone have any pull-strength data they might be able and willing
to share?

Many TIA's

Charlie B.

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