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