I am interested in information and experience with solder for high
temperature applications for a program I am researching.  For this specific
example, the unit is a ceramic substrate with silver palladium pads.
Temperature conditions are as follows:

--Blob top cure is 3 hours at 130?C for three hours
--Thermal Shock:  Un-powered temperature cycling from -40?C to 140?C, 30
minutes at each temperature, with a 10second transition time (goal is 1000
cycles)
--Powered temp. cycling, 95% humidity, from -40?C to 105?C with one hour
transition time, 3 hour dwell time for 1000 hours.

Units that were built previously used a solder paste with a 179?C eutectic
temperature.  The solder joints failed over time in testing.

What is the best solder paste to use for this application (reflow process,
standard components)?

Some documentation recommends a high tin content (95%) but discussions have
suggested that at these temperatures the tin becomes brittle over time.
High lead content solders (88%) have been suggested, but these have such a
high reflow temperature (>300?C) that standard SMT components (SOIC's)
cannot stand these temperatures.

I appreciate any suggestions and information

Ed Holton
Hella Electronics
313-414-0944
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