Fixture design and sequence analysis for low stress assembly of precision miniature devices without disturbance

The importance of fixturing is often underestimated in the development of precision assembly system for miniature products. A 5-part component of a micro accelerometer is selected as an example in this paper. The sensitive structure that influences the performance of accelerometer most is the flexible beam on one part. A fixture with flexible fastening mechanism was proposed for assembly these miniature parts. The key mechanism is a flexible part, which is with two contacted points and metal flexible linkages. The thermal stress of the component after curing was studied using finite element model (FEM). The simulation results revealed that the height difference was the main cause to the stress on the flexible beam. The assembly sequence and strategy were optimized. The maximum stress was reduced to 72% of the original one while the height difference reached 15 μm. This study implies that an optimized fixture design and assembly sequence can also reduce the assembly stress remarkably.