Hi Charles -  see comments below:

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.)

** Pl/Pt/Au - this must be a virus running around the industry this time of
year! We just went through an experience of making a Pl/Pt finish (no gold
in our case) useable. My understanding is that the Pl/Pt/Au finish was a
common finish for components/pwbs in the past but quickly disappeared due
to solderability issues. Although Pl/Pt/Au are noble metals there are
several oxide reactions that result in solderability issues so I would
recommend the use of a very active flux. We solved our issue by putting
together a detailed retinning procedure (very active flux, strictly
controlled cleaning steps) that made the components useable.

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.)

** Soldering to copper is one of those activities most everyone likes to
do. Your standard process materials should work for you providing there are
no temperature issues.

2. What about suggested fluxes? (I don't believe the solder we are getting
is cored.)

**Make sure your flux activity can do the job - the Pl/Pt/Au is going to be
tough. You could also look at using solder paste instead of a flux cored
wire to get initial wetting/ pad coverage.

Good Luck.

Dave Hillman
Rockwell Collins
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[log in to unmask] on 11/05/97 03:35:48 PM

Please respond to [log in to unmask]; Please respond to [log in to unmask]

To:   [log in to unmask]
cc:    (bcc: David D Hillman/CedarRapids/Collins/Rockwell)
Subject:  [TN] Assy: Hi Temp Soldering to pads on Ceramic substrate




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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