Insulated Metal Substrate for High-Temperature Power Electronics Packaging

摘要

Direct bond copper substrates (DBC) are commonly used in power electronics packages and modules. The thick copper layer bonded to the ceramic substrate provides high current handling capacity while the ceramic has a higher thermal conductivity (e.g.,AlN) than a glass or glass-ceramic. Early failure of the DBC substrate was observed during relatively aggressive temperature cycling tests (−55°C to 250°C),raising concerns regarding its reliability and suitability for high-temperature power packages. An insulated metal substrate consisting of a cordierite-base glass-ceramic sintered on a molybdenum substrate that was developed for other applications is being investigated as a potential alternative to DBC. The glass-ceramic has a slightly lower coefficient of thermal expansion (CTE) of 4.1 ppm/°C than the molybdenum such that it is under compression below the processing temperature making the coating stable. A potential advantage seen with this substrate is that the molybdenum can simultaneously serve as the baseplate for the module and heat spreader/heat sink,thus eliminating several interfaces from the heat dissipation path. The adhesion of the coating is excellent and the interfacial fracture toughness obtained from indentation tests ranged from 10 to 19 J/mm~2 or higher. The insulator/metal interface of the substrate has significantly outlasted the DBC substrate,with no visual evidence of incipient failure of the insulating layer after 300 cycles (−50°C to 250°C). It is matched only by an AlN direct bonded aluminum (DAB) substrate.