Simulation driven design of novel integrated circuits - Part 1: Selection of the materials based on the Virtual DoE

Abstract

The new age product development demands rolling out effective & efficient designs in short time span and reduced costs in the view of increased competition from market players. This requires the time conventionally needed for conceptualization and validation of new designs has to be significantly reduced without having to compromise on the quality. In order to determine the optimized variant, it is necessary to evaluate its thermal, thermo-mechanical, static response under varying material properties. This also helps in ascertaining the sensitive material parameters which influences the critical response. Finite element based simulation plays a crucial role here in predicting system behavior under varying parameters. This method proves to be useful in delivering credible results within a short time span thereby accelerating the design stage. Virtual Design of Experiment (Virtual DoE) is an automated simulation methodology wherein the design space is composed of the range of properties for a particular material which are available in the market. A suitable model is considered for which the range of the properties to be evaluated are defined as design space using central composite faced (CCF) plan. Numerical simulation results for the defined points in the design space are input to obtain the response surface of the considered model. The response surface such as deformation, stress, strain & strain energy helps in determining the effect of each parameter. The degree to which each parameter affects the response determines the critical material parameters of the system. From this information a judicious decision can be taken regarding the material property for the components in a timely & cost effective manner. In the present paper an example is taken up to illustrate the selection of the molding compound for simplified DPAK model. Five parameters: coefficient of thermal expansion below and above glass transition temperature (Tg), glass transition temperature, modulus of elasticity and thermal conductivity; are investigated. Using CCF DoE plan, 52 simulation legs are defmed. This covers the entire range of the molding compounds available in the market. The results of the 52 simulation cases are evaluated and later on regression analysis is conducted. Finally an Excel tool is created that is distributed among the process team and allows being used by everyone, without any prior knowledge of ANSYS or DoE software Cornerstone. The graphical representation of simulation and DoE results in the Excel tool enables them to obtain a better understanding of the implications of the varying material properties on the design.