Finite Element Analysis of a high voltage semiconductor polymeric package design using a Taguchi based experimental design

Plastic packaging has made successful progress in replacing ceramic and metal packages in many high reliability electronics applications where hermetic packaging has traditionally been used, e.g. military and aerospace semiconductors. However for high voltage/high current power devices, such as the thyristors and diodes used in High Voltage Direct Current (HVDC) power transmission applications, hermetic packaging is still the dominant technology. With increasing energy demands from large and rapidly developing countries, such as China, India, Brazil, etc., HVDC transmission is expected to play a significant role in meeting future current/voltage requirements and is consequently pushing suppliers to use larger semiconductor wafer diameters, thus requiring bigger, more fragile and more expensive packages. A switch from the present ceramic packaging to polymer packaging is expected to achieve a robust, low cost and low weight device. This paper reports a study of the design and electrical performance of a polymer package for high voltage devices using Finite Element Analysis (FEA) when blocking a high DC voltage. Following on from preliminary simulation studies where a number of design parameters were observed to influence the electrical field distribution within the package, the Taguchi Method of Experimental Design (TMED) has been used to systematically investigate the influence of design parameters on the electrical performance of the housing using a series of FEA simulations. For this work, the interactions between different design parameters were first identified and then used with the appropriate design factors to determine the optimum design settings, and to identify the contribution of the design factors towards the electric field variation. From the investigations, the copper pole piece diameter and package thickness were seen to have little effect on the electric field magnitude inside the housing, while factors such as the position and depth of the metal in- ert in the housing and the number of convolutes around the package, had a significant influence on the electrical stress magnitude.