The technology of contactless energy transfer is emerging for application in implantable medical device. High transfer efficiency and high quality factor are specific design requirements for micro-inductors which are key component of contactless energy transfer micro-modules. Thermal stress analysis and electrical analysis of an inductor are sequentially performed to elucidate the effect of thermal strain on the electrical properties of a micro-inductor. Three dimensional finite element models of an inductor were generated by the commercial stress analysis software, ANSYS, to calculate the thermal stress and thermal strain. The deformed model of the inductor was then imported to the commercial electrical property analysis software, ANSOFT, to calculate changes of the electrical properties, such as the inductance, the quality factor and the electrical resistance. The investigation shows that the thermal stress is concentrated at the four corners of the inductor with SU8 support, and that the inductor without SU8 support is twisted without substrate warpage. The electrical properties of inductors do not change dramatically under thermal loading caused by a temperature change from −40°C to 125°C.
Thermal stress analysis for a cusp-type crack problem under remote thermal loading
