Fluxless Flip Chip Interconnects for MEMS Devices for Heterogeneous Integration

Flip chip technologies (FC) is an enabling technology for heterogeneous integration of MEMS devices. FC reduces the package dimension, improves performance as well as enable scaling up of MEMS chips through 3-D packaging. This paper provide an overview of FC technologies for MEMS and identify the interconnect challenges for MEMS packaging. The paper shares an innovative fluxless FC bonding technique known as solid liquid interdiffusion by compressive force (SLICF) for MEMS packaging.The instantaneous SLICF bonding utilizes a mechanical force to break the Sn oxide layer and allows the submerged body to interact with fresh molten solders to form bonds through solid liquid inter-diffusion. This remove the need of flux and ideal for MEMS packaging for heterogeneous integration. The JIV plugged molten solder in via on flex substrate to enable a fluxless FC bonding for MEMS integration. The fine pitch design rule and foldable of flex substrate enable ease of heterogeneous integration. The bonding architecture enable fluxless FC bonding for heterogeneous integration of MEMS devices to reduce packaging cost and provide a high throughput for heterogeneous integration.