High performance electronic interconnect materials characterization-techniques & challenges

High-power and LED devices generate significant heat that, if not efficiently removed from the assembly, leads to lower operating efficiency and / or lower luminous flux and shorter lifetime. Because the majority of heat is transported through the device interconnect layer, the thermal resistance of the heat path significantly impacts overall device performance. Higher thermal conductivity interconnect materials significantly decrease the thermal resistance of the stack. The effects of high performance interconnect materials are easy to observe and affect end user performance and reliability (e.g. by increasing total luminous flux, efficiency, and color stability). These effects become more pronounced as these devices are over driven and are particularly important in power electronics and UV LED applications. In this study, a series of interconnect materials, including sintered nano-silver, SAC305 and a hybrid silver sintering epoxy, were used to assemble high-power AlGaInP/Si LEDs for laboratory testing. Junction temperature, thermal resistance, thermal conductivity, total luminous flux, peak wavelength, and efficiency were measured according to JESD51-1 and LM-79-08. In this paper we discuss the technical and design challenges associated with making accurate thermal resistance measurements across a multi-layered stack. The results of this laboratory study show the comparative performance of identical devices assembled with a variety of interconnect materials. A field example showing enhanced UV LED device performance with high thermal interconnect material is presented.