The influence of ceramic microstructure on metal-ceramic seal formation

The metal-ceramic seals have recently been more and more widely applied in high vacuum technology (feed-throughs, high vacuum tubes), modern electronics and optoelectronics. Seals between two types of debased aluminas and the MoMn metallizing layer have been studied. The reaction between ceramics and the metallizing layer at high temperature metallization is possible only in the presence of liquid phase. The metallizing layer in strong and vacuum tight seals (ASTM tensile strength > 70 MN m −2 and vacuum tightness down to the 10 −15 mbar I s −1) consists of a dense metal/glass composite layer. The metallizing layer in weak seals contains comparatively little glass and is porous. It was found that bond quality is stronly affected by the microstructure of the ceramics.