Chip scale packaging of a MEMS accelerometer

Accelerometers fabricated with MEMS technology are widely used in automotive crash detection and vehicle dynamic control systems. Recently, there has been increased interest in the use of MEMS accelerometers in smart handheld devices. The most demanding new requirement for this application is package size. This paper details the fabrication a 2 axis accelerometer in a 4 mm×4 mm×1.5 mm thick lead frame chip scale package. The fabrication of the device depends on three technologies: (1) an integrated MEMS technology that yields the MEMS structure and all associated signal processing circuitry on a single die; (2) the development of a wafer scale capping process that provides protection for the MEMS sensor and renders it suitable for transfer molding; and (3) modifications to the standard lead frame chip scale package (LFCSP) assembly process to accommodate the capped MEMS sensor. The performance of the accelerometer is assessed and compared to the same device in a leadless chip carrier.