Wafer-Level Packaged Accelerometer With Solderable SMT Terminals

Miniaturization of devices is driving replacement of electronic components with surface mount technology (SMT) equivalent parts, including any embedded sensing devices. In many cases the size of the sensor is restricted by the minimum size of the package rather than by the die. Other solutions to preserve real-estate involve manual mounting of the die onto substrates that have gone through an SMT assembly process. The +/-2g accelerometer presented here is wafer-level packaged and has solderable terminals allowing the silicon die to be mounted directly onto a substrate in a standard SMT process and without the need for stress-isolating interposers. With its small footprint and ceiling requirements (2.1times .9 times 0.8 mm³), and robustness and high performance it is the smallest commercially-available wafer-level packaged accelerometer suitable for medical applications where these characteristics are critical. Device performance is unaffected by the SMT assembly process. Preliminary results show that the solder mounted device is also able to withstand thermal cycling over a wide temperature range (-55 to 125degC).