Advanced Packaging

Glass-Frit Bonding

One of the industrially most used processes for encapsulating MEMS structures in the past decade was based on glass-frit pastes, applied by screen printing to form sealing frames. The process is relatively robust and in principle it can be compared to soldering. However, to allow melting the glass paste already at around 425°C, it contains leadoxides as an additive. A somewhat higher melting (ca. 440°C) lead free glass frit system is available to reduce the environmental footprint of electronic packaging materials. The process technology requires about 200 µm wide seal frames that may be deposited on 300 µm wide silicon frames on the cap wafer.

As an alternative, ISIT developed metal-based soldering and bonding methods like eutectic gold-silicon bonding. The advantage of these is that they work at lower temperatures and are compliant to vacuum processing.