Simulation Driven Design of Novel Integrated Circuits - Part 4: Method of Validation of Coupled Thermal and Thermo-mechanical Simulation

We present the fourth and final step of simulation driven design: validation. The goal of this paper is to validate FEM model of test vehicle of the overmolded electronic control units (ECUs) using the displacement fields of the ECU as well as the stress state of the silicon die embedded in the ECU. Two techniques are employed for the validations: (1) moiré interferometry to investigate the displacement field of a test vehicle and (2) a piezoresistive stress sensor called “iForce” to measure the internal stress. For moiré interferometry, the full-field displacement fields obtained from passive and active temperature cycling testes are used to correlate a compressive numerical model. The stresses measured by the stress sensor enables us to compare a direct, damage relevant quantity such as mechanical stresses at the silicon die. As the sensor provides quantitative information about the stress state inside the IC package, validation using the sensor data becomes a final step, from which the accuracy of the simulation driven approach is confirmed. Our experience suggests that the simulation driven design can accelerate the design process of automotive ECUs by quantitative predictions of the deformation and stress state of actual products.