Parameters Investigation and Heat Transfer Path Optimization of IGBT Baseplate in Photovoltaic Inverters

The issue of carbon emission is driving an increasing growth of the photovoltaic industry. Consequently the cost, efficiency, and safety of power devices become focal points in the field of photovoltaic inverters spontaneously. In response, semiconductor manufactures have introduced baseplate-free IGBT devices, with representative products such as the EASY 3B/4B package devices, to achieve lower thermal resistance and cost. However, in practical applications, the junction temperature of baseplate-free IGBT devices is unintentionally higher than that of the traditional IGBT devices with baseplate instead. To investigate the phenomenon, first a model of the coupled heat transfer mechanism of IGBT devices in photovoltaic inverter is conducted. Then the cause of higher junction temperature of baseplate-free IGBT devices is analyzed on the basis of the model. It is indicated that temperature deviation originates from the larger interface thermal resistance at the bottom of the device, leading to enhanced lateral heat spreading in the heat transfer path of the device baseplate, which reduces thermal resistance more than the longitudinal conduction. Through finite element simulation and experiments, the temperature rise of baseplate-free IGBT devices is 21.4% higher than that of IGBTs with baseplate on average, under the current mainstream product supply chain of photovoltaic inverters of 225kW and above.