Stress Distributions Around an Interference-Fit Pin Connection in a Plated Through Hole

ln our applications with interference fit pins in plated through holes, we find it necessary to determine regions of high stress. The regions of high stress may be a source of cracks in the plated copper or land regions. In order to understand the source of these high stress regions, two analyses were performed. First, a thermal stress analysis of an interference fit pin connection is carried out with an assumed temperature rise of 70°C. Secondly, an analysis of the process of the insertion of a pin into a PTH is considered. The process is modeled by considering a series of shear and normal loads applied to the inside of the PTH. Inertia effects arc not considered in this analysis. The finite element method is used to determine the solutions to both analyses. The results of the thermal stress study show high stresses in the barrel of the PTH only, thereby implying that cracks in the copper of the land area are unlikely to occur due to a temperature rise of 70°C. Shear stress set up at this interface is not large enough to cause cracking either. The results of the pin insertion process show that the interface goes through a rather severe change in stress history during insertion. It is estimated that the interface stress changes from 18 000 lbf/in2 (compression) to 7860 lbf/in2(tension) during in- sertion.