Abstract

The trend towards electrification of the powertrain requires the development of electronic components that can withstand various types of mechanical loads, e.g., harmonic and stochastic vibrations or mechanical shocks. In the automotive sector, electronic components must be tested according to the mechanical requirements of relevant standards, e.g., to the VW80000. A major challenge in this context is the fatigue strength of solder joints, for which these loads are usually considered to be an undesirable condition. In this talk, a comprehensive simulation process for assessing the fatigue strength of solder joints is presented. In a nutshell, first, a modal-based frequency response analysis is performed for the finite element model (FE-model) of an electronic component containing a printed circuit board (PCB) equipped with substitute FE-models of surface mount devices (SMDs), in whose pins the nodal displacements are measured as a function of frequency. These nodal displacements of each single pin are then scaled by static analyses of a corresponding solder-joint sub-model to retrieve the solder-joint stresses and the solder-joint damage or safety factor is finally calculated in FEMFAT max, FEMFAT spectral, or FEMFAT break for harmonic, random, or shock loads, respectively. Since the number of SMDs on a single PCB can be very large and the simulation process requires substitute FE-models for each SMD and an individual solder-joint sub-model for each solder-joint footprint, it was essential to develop and implement algorithms, which build the substitute FE-models for the SMDs and sub-models for the solder joints automatically. Therefore, the proposed process consists of three core technologies: semi-automatic generation of substitute FE-models for SMDs, automatic placement of these substitute FE-models on FE-models of PCBs and automatic generation of solder-joint sub-models, for which the geometry is calculated based on pin dimensions of the SMD, the pad dimensions on the PCB, solder volume, surface tension and gravitation.