Resumen
Steinberg?s theory, which is based on the fatigue failure theory, has been widely used for predicting the structural safety of solder joints in aerospace electronic units under vibration during launches. However, theoretical limitations are encountered when evaluating the structural safety of highly integrated electronic packages mounted on printed circuit boards (PCBs) under various boundary conditions. Therefore, in our previous study, a PCB-strain-based methodology was proposed to overcome the technical limitations of the conventional Steinberg theory, and its effectiveness was validated by conducting fatigue life tests on various types of specimens, such as the ball grid array, column grid array, and quad flat package. In this study, the aim was to increase its completeness and reliability by targeting small outline packages (SOPs) that have not yet been considered. The finite element (FE) model of the SOP was proposed to guarantee the reliable prediction of the structural safety of the solder joints used in the PCB-strain-based methodology. The proposed modeling technique contributes to enable the rapid construction of an FE model for the electronic unit because it was greatly simplified into a zero-dimensional lumped mass and rigid link element to simulate the package mass and solder joint, respectively. The effectiveness of the methodology was validated by performing fatigue life tests on PCB specimens under various boundary conditions. Those experimental and analytical results indicated that the proposed methodology was much more effective in predicting the structural safety of a solder joint for various cases of tested specimens compared with the Steinberg?s theory. The simplified FE model of SOP with the rigid link element connected to six points on the package mounting area of the PCB was effective for estimating margin of safety of solder joint. The results of this study would contribute to increase the availability of the proposed methodology for rapid mechanical design of electronic units in aerospace industries.