A SiC die with Os and/or W/WC/TiC contacts and metal conductors is encapsulated
either alone or on a ceramic substrate using a borosilicate (BSG) glass that is
formed at a temperature well below upper device operating temperature limits but
serves as a stable protective layer above the operating temperature (over 1000
C., preferably 1200 C.). The glass is preferably 30-50% B2O3/70-50%
SiO2, formed by reacting a mixed powder, slurry or paste of the components
at 460-1000 C. preferably about 700 C. The die can be mounted
on the ceramic substrate using the BSG as an adhesive. Metal conductors on the
ceramic substrate are also protected by the BSG. The preferred ceramic substrate
is AlN but SiC/AlN or Al2O3 can be used.
