Study On System-in-Package Technology Of MEMS Air Pressure Sensor

With the development of MEMS technology, more and more MEMS products turn to be true. MEMS pressure sensor is one of the important applications in the MEMS technology .At present, MEMS pressure sensor is applied in the field of automobile electronics, but the packaging cost generally covers 50%-80% of the whole cost of a functional device or system. So the research on the technology of MEMS package is very significant.At first the theory of pressure sensor was present in the paper. Based on the piezo-resistance theory the sensitivity of pressure sensor was calculated by the software of ANSYS .About package structure design the lead frame design and the choice of the epoxy molding compound are discussed in the paper. By designing the structure of lead frame we achieve successfully the System-in-Package between ASIC and pressure sensor.Parylene is investigated for its applications to the package of air pressure transducers The changes of key characteristics of pressure transducers are discussed by experiments as the sensitivity of pressure sensor, temperature characteristics, hysteresis and the strength of wire bonding .The cause of changes is analyzed in the paper. Compared with the silicon gel the protection performance of parylene is excellent under hash environments.It is important to choose the gel and to design the thickness of silicon gel in the package of air pressure transducers. The paper investigates the effect of the thermal stress which is caused by the difference of coefficients of thermal expansion (CTE) among the material on the performance of pressure transducers. The Von Mises stress is defined as the objective function. The relation of the thickness of silicon gel and the Von Mises stress of the membrane is discussed.Furthermore, we take into account various parameters of bond wire such as the diameter and height of bond-wire, the span of the squashed bond pad .The simulation results show that sensor's reliability is high enough when suitable parameters of bond wire are selected.