Stress-Compensating MEMS Sensor Assembly

In this work, a system assembly technology will be presented that allows an effective mechanical decoupling of the MEMS element from the environment while maintaining minimal package footprint and cost. It utilizes a Si interposer with planar spring structures for an independent suspension of all interconnects to the MEMS element. The design of the planar springs was optimized for maximum stability and effectiveness using finite element analysis. The MEMS die is arranged below the interposer for mechanical protection during assembly and operation. The required clearance to the substrate is provided only by industry standard solder balls. The interposer is manufactured on a temporary carrier wafer by deep reactiveion etching, the interconnect to the MEMS die is realized by thermo-compression bonding. The effectiveness of this approach is demonstrated through the example of a high accuracy pressure sensor, although beyond that it has the potential to provide a functional package platform for MEMS sensors in a multitude of applications.