Frik Koch wrote:
>
> We have to solder gold plated components with 80/20 Sn/Au preforms
> in  a forming gas of 10% H2 in N2. The eutectic melting point is 280 C.
> Can  somebody tell from experience what the minimum soldering
> temperature and the maximum dew point of the gas should be?  We are
> using a normal vacuum deposition system to solder the components on
> a hotplate and do not have any fancy gas handling or drying systems.
> We need the forming gas not only for its reducing properties but to get
> sufficient thermal conductivity between the hot plate and the
> components. At present the preforms come out oxidized. Any good
> ideas about cheaply handling and  drying the gas to the desired dew
> point would by useful as well.
> Thank you, Frik Koch
>
>
I have mounted silicon die to gold plated packages with those materials.
We used forming gas 85:15:: N2:H2 with better results. The gas was from
a gas cylinder lab grade.  Temperature was peaked at 325 degrees
centigrade for about 15 seconds.  It is very important to heat in an
inert or reducing ambient.  A good way is to use a Hughes Aircraft strip
heater where the parts are placed on a graphite susceptor and heated in
a bell jar filled with gas, where outside air has been purged.
Scientific Sealing in Texas also makes some more sophisticated
equipment. If you need phone numbers let me know.  I hope this helps.