Dear Mr.  Choe,

  Normally eutectic AuSn 80/20, should melt around 282-286.  Depending on your
bonding atmosphere and volume of solder, there should be very little need for
pressure.  Normally you should reflow the solder in an inert environment (ie N2,
N2H2, Flux, ect) to prevent oxidation on the solder layer.  Only slight pressure
should be applied in order to promote wetting along the entire surface of the
device.  Depending on the size of your part that could be from a few grams to a
few hundred grams.  Please feel free to contact me directly to discuss your
process in more detail, I would be happy to give you some suggestions.

Best Regards,

Brian Douglas
Suss Microtec Inc.
Applications Engineer - Bonders
Phone: (802) 244 - 5181 x202
Fax:  (802) 560 - 0001