Silicon nitride ceramic substrates play a pivotal role in Active Metal Brazing (AMB) substrates for power modules whose applications include inverters for electric vehicle (EV) and hybrid electric vehicle (HEV) motor control. These substrates have a function of heat dissipation during operation of power semiconductor module. Meanwhile, the thinner the substrate and higher its thermal diffusivity, the greater the operational efficiency of the power semiconductor module.
Image Credit: NGK Insulators LTD.
Increasing adoption of EVs and HEVs is driving greater use of power semiconductor modules designed for high power, thereby culminating in rising demand for thinner substrates that feature substantial thermal dissipation performance. However, a lack of definitive methods for evaluating thermal diffusivity of substrates thinner than 0.5 millimeters has given rise to challenges with respect to ensuring consistency of measurement results. This joint research enlists AIST and its extensive knowledge of evaluation methods along with NGK and its advanced ceramic substrate technologies in efforts to collect data for quantifying the preliminary process, which affects measurement of thermal diffusivity of substrates. This will enable us to verify methods for evaluating high-performance thin substrates that are even thinner than 0.5 millimeters, such that are not yet defined under existing Japanese Industrial Standards (JIS), thereby contributing to high accuracy of measurement data and future standardization of evaluation methods.
Through this joint research, AIST seeks to help bring about standardization of evaluation methods in this sector while further enhancing competitive strengths of Japanese industry by proposing solutions to industry in the form of highly precise and reproducible methods for measuring thermal diffusivity of thin substrates.
NGK will engage in this joint research with the aims of enhancing reliability of AMB substrates for power modules and helping to address societal challenges by providing its proprietary ceramics technologies and products.
Silicon Nitride Ceramic Substrates
Silicon nitride (Si3N4) is widely used in bearings and structural components and materials that require heat resistance given its exceptional properties particularly in terms of its heat resistance, corrosion resistance, substantial hardness, and high thermal conductivity. Demand for silicon nitride has been mounting in recent years for use in AMB substrates for power modules in harnessing properties that include its high thermal conductivity along with its exceptional insulation performance and toughness.
AMB Substrates for Power Modules
AMB substrates for power modules consist of a silicon nitride ceramic substrate and two copper plates. The AMB circuit substrates for power semiconductor modules of NGK have proprietary advanced bonding technology to create an extremely thin bonding layer of just a few microns or less between the ceramic substrate and copper plates. This greatly reduces thermal resistance and internal strain in the bonding layer, resulting in exceptional thermal dissipation properties.