Function-based assembly: an application of MEMS-based assembly of rate gyroscopes

The assembly of MEMS-based devices in certain applications requires alignment within tolerances better than ±1μm. This standard has proven to be difficult to achieve consistently due to manufacturing and assembly errors. This article describes an active alignment process which incorporates the actual geometric parameters of the microelements as well as geometric constraints in order to determine the optimal location of the microelements in the assembly. The determination of this location guarantees optimal functionality of the device and helps achieve tight alignment tolerances without compromising the device design. The effectiveness of this approach is demonstrated in a micromachined vibrating rate gyroscope assembly. Simulation and measurements taken of the assembled rate gyroscope confirmed an assembly accuracy of better than ±1μm.