Thermo-Mechanical Analysis and Optimization of PCBs : A Study on Strain Reduction in Automotive Camera Assemblies

Sammanfattning

A printed circuit board (PCB) mounted inside of a housing will experience more thermal strain when subjected to temperature compared to a non-mounted PCBs. This is due to a mismatch of the coefficient of thermal expansion (CTE) between the aluminium housing and FR-4 used in the PCB. This is a common problem in the automotive industry as the temperature intervals the PCB is expected to endure are large. In this report, f inite element analysis was used for simulating how the strain induced by CTE-mismatch spreads in the PCB relative to its temperature cycle. The concept of using slots were investigated further as a way to reduce the strains. Different slot designs were analysed using multi-disciplinary design optimization and then simulated to verify their effectiveness. It was discovered that the optimization algorithm favours slots that separates the PCB corner as much as possible from the rest of the PCB. Each slot was then analysed further, by incorporating each design into the created finite element model, and using different metrics, determine which slot preforms the best and why. The conclusions were that optimization could be a useful tool to investigate different slot designs, where some design parameters were favoured more than others. Furthermore, the use of slots indicated that strain can be significantly reduced, upwards of 27% near corner screw holes, depending on measurement.