Duplex glass preforms for hermetic glass-to-metal compression sealing

A hermetic glass-to-metal compression sealed package for microcircuit chips, comprising:

• a duplex glass preform, said duplex glass preform further comprising:
• a soft glass matrix having a coefficient of thermal expansion mismatched with respect to coefficients of thermal expansion of metals used to form said hermetic glass-to-metal compression sealed package, a peripheral interfacing surface and at least one terminal bore therethrough substantially parallel to said peripheral interfacing surface, said terminal bore having an interfacing surface;
• a dispersion zone in at least one end of said soft glass matrix, said dispersion zone extending inwardly from a surface of said at least one end into said soft glass matrix for a predetermined depth;
• a first essentially ceramic-free zone intermediate said dispersion zone and said peripheral interfacing surface;
• a second essentially ceramic-free zone intermediate said dispersion zone and said terminal bore interfacing surface, and
• a plurality of ceramic particles selectively distributed in said dispersion zone of said soft glass matrix to form a ceramic particle density gradient therein, and wherein said ceramic particle density has a maximum value at said surface of said at least one end and gradually decreases to a zero value at said predetermined depth;
• a metallic terminal pin correspondingly disposed in said at least one terminal bore and hermetically sealed thereto by compressive stresses, said compressive stresses arising from a mismatch in coefficients of thermal expansion between said duplex glass preform and said metallic terminal pin;
• and
• a metallic body having at least one aperture therein which receives said duplex glass preform, and wherein said duplex glass preform is hermetically sealed in said body by compressive stresses, said compressive stresses arising from a mismatch in coefficients of thermal expansion between said duplex glass preform and said metallic body.