We are developing a new bonding process for MEMS that is ideal for packaging motors, protective covers, SMD parts or unpackaged IC dies, thin-film batteries, and other components (all of which our group uses) on the same substrate, but is also likely applicable to microfluidics, optoelectronics, and other devices. The process uses an on-chip heater trace to melt microfabricated solder. This approach limits heating to a local area on a chip (an approach first proposed by Liwei Lin twenty years ago that has seen little development since), which, unlike flip chip bonding, allows us to heat only part of a chip at a time for a multi-step assembly process or to package extremely temperature sensitive components (e.g., liquid thin-film battery chemistries that must remain below 60°C). We expect to achieve electrically conductive bonding of multiple dies and SMD components on a single substrate with sub-100μm pitch and minimal tooling (e.g., no externally applied pressure or temperature), assembly of 3D MEMS structures from multiple chips, and vacuum-tight hermetic seals (when minimizing or removing flux usage). So far, we have demonstrated thermal control and initial solder manipulation.
August 24, 2021
BSAC Project Materials (Current)
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