A fluxless bonding process using AuSn or Indium for a miniaturized hermetic package

In the field of high speed data transmissions or in the industrialisation of MEMS devices a hermetic package is often required. However this technological achievement represents an important part of the package price and usually limits the freedom of design and miniaturization. In this paper we propose a localized hermetic sealing method adapted to batch process, that uses either Eutectic AuSn (AuSn20) or pure Indium for the seal ring. A novel fluxless controlled thermocompression process is developed to achieve simultaneously a hermetic bonding and interconnection of I/Os located within the sealing ring through the capping part. Different designs are tested using a standard He aspersion leak test and additionally some reliability tests are performed. Leak rate <5.10^-8 mbar l/s are obtained with both AuSn20 and In seal rings.