Low temperature hermertic packaging with Ag sintering process

MEMS devices often require to be hermetically packaged under a certain environment. In particular, hermetic packaging provides protection of MEMS structure from dust, humidity, corrosion, etc, isolation from thermo-mechanical stress on the package (during handling, die bonding, during operation. Some MEMS devices is sensitive to the related process temperature. The Hermetic packaging can be realized with soldering, electrode or laser welding, etc. However, local process temperature for welding temperature can up to more than 1000 °C, the soldering process is also more than 300 °C, some temperature sensitive MEMS device can not stand the process temperature more than 200-250 °C. This paper introduces lowcost and low temperature hermetic sealing process. During the sintering process, the sintering material is heated to a temperature below the melting point, the atoms in the powder particles diffuse across the boundaries of the particles, fusing the particles together and creating one solid piece Ag. The final Sintered Ag Structure is with uniform microstructure with typically 85% densification, even pure silver. This paper also introduces real-time dynamic insert control technology to control precisely pressure applied on the sintering Ag paste or film. With the dynamic insert, each device is applied the same pressure independent on the large tolerance.