Low-softening-point glass-frit bonding and chemical durability of metal/glass/ceramic heterojunctions

초록

Because conventional metal-ceramic bonding relies on high processing temperatures in systems with a large mismatch in thermal expansion coefficients, the resulting large temperature drop (triangle T) during cooling induces differential thermal strain between the metal and ceramic and consequently generates high residual stresses at the interface while also promoting oxidation of the metal substrate. This limitation can be alleviated by using glass-based interlayers, which soften and flow at the bonding temperature so that finely milled frits conform to both surfaces and infiltrate microvoids to form dense, uniform joints, while low-softening-point glasses further lower the bonding temperature and thus triangle T, thereby directly reducing the thermally induced strain. However, in applications that require such low-softening-point glasses, systematic data on their chemical durability remain limited. In this study, a low-softening-point tin-phosphate glass frit was developed as a bonding interlayer to minimize thermal stress and metal oxidation below 300 degrees C. The frit was finely milled to a median particle size of D-50 approximate to 1.15 mu m, and differential scanning calorimetry (DSC) revealed a glass transition temperature (T-g) of 128 degrees C and a softening temperature (T-s) of 252 degrees C. Cross-sectional analysis confirmed the formation of a dense and continuous glass interlayer, yielding a well-bonded Fe/glass/Al2O3 interface. Chemical-durability tests showed negligible mass loss except in strong alkalis. These results demonstrate that tin-phosphate glass frits provide a viable route to chemically stable, low-temperature metal-ceramic bonding with reduced thermal stress and suppressed metal oxidation.

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