On thermo-mechanical reliability of plated-through-hole (PTH)

The mechanical properties of plated copper in plated-through-hole (PTH) were investigated experimentally by a thermo-mechanical analyzer, a nano-indenter, and an acoustic emission instrument. Coefficients of fatigue life prediction models for plated copper have been determined by different failure criteria. Afterwards thermal fatigue test of PTH at three different diameters were performed, and Weibull statistics was employed to evaluate the fatigue life of samples under different failure criteria. Finally, the strain variation of PTH during thermal cycle has been simulated by the finite element analysis (FEA) so as to predict its fatigue life by the selected models. From the comparison of the estimated fatigue life and its experimental results, it is found that the error can be minimized to be within 100%, provided that the drifting of electrical resistance by 20% is used as failure criteria and total strain amplitude is used as control variable in fatigue life prediction model. Based on these findings, design of PTH in printed circuit board (PCB) can be optimized by FEA. It is concluded that fatigue life of PTH will increase with lesser PCB layers, smaller depth-to-diameter ratio, higher PTH density and thicker plated copper.