An accelerated thermal cycling test for RF MEMS switches
Thermal cycling tests are an important part of the standard space qualification procedure for RF MEMS devices. Standardized tests are rather demanding in terms of equipment, sample preparation and experimental time. In this paper, we present a fast thermal cycling test aimed at obtaining a rapid selection among different switch geometries in terms of thermal cycling resistance. Seven different switch typologies are examined and tested, evidencing that the most important source of deterioration is the mechanical deformation of the movable membrane due to changes in internal stresses. For this reason, the clamping typology is the most important design parameter to take into account in order to achieve a good thermal cycling resistance. Contrarily to expectations, the cantilever structure is not the most promising switch typology, because while the main part of the movable membrane is stress free, the anchoring part of the structure is on the contrary heavily stressed and modifies with the temperature change. The most promising structure is a four anchored switch with a flexural clamping structure that allows the thermal expansions in the horizontal direction, while the data for all the clamped clamped structures investigated are similar and their differences can be interpreted in terms of different distribution of the thermal strain over the whole membrane.