Analysis of packaging effects on wire bonder made microtransformer chips

Abstract

We present the fabrication and characterization of microtransformer chips, based on wire bonded microcoils which are encapsulated in a Polydimethylsiloxane (PDMS) package. Our investigations focused on the degradation in electrical performance due to the higher dielectric constant of PDMS compared to air. We further studied the thermo-mechanical induced strain on the system due to thermal expansion of the package at temperatures up to 250°C. According to the measurements, encapsulating the chips decreased the resonance frequency and the quality factor near the resonance. However, both the maximum quality factor and the power efficiency were not affected by the encapsulation. Furthermore, induced thermo-mechanical strains due to the mismatched coefficients of thermal expansion of the chip and the packaging materials did not decrease the mechanical integrity of the SU-8 post and the coil itself. © Published under licence by IOP Publishing Ltd.