5. Conclusions
Designing suitable glasses for the sealing/joining of
SiC ceramics for high temperature electronic packaging
applications is a challenge. The glass must wet the ceramic,
have a matched CTE, and be unreactive. Furthermore,
the glass must be able to be processed at
temperatures that do not affect the die and other package
materials and provide hermeticity during the life of the
component. Thermodynamic calculations have shown
that a number of common constituents of oxide glasses
are unstable in contact with SiC. Reactions that occur
will result in the production of CO, which manifests itself
in the form on bubbles in the glass. The pressure of CO
can be determined and has been shown to depend on
the concentration of a particular oxide in the glass formulation.
Temperature also plays an important role
through its effect on the free energy of reaction and on
glass viscosity. The results presented here give selection
criteria for possible glass constituents for use with SiC.