A finite element model and experimental analysis of PTH reliability in rigid-flex printed circuits using the Taguchi method

The primary reliability concern in complex RFPC construction is PTH integrity as a result of thermo-mechanical deformation due to significant CTE mismatch between the copper and surrounding dielectric material. In this paper, a finite element model was developed to determine the maximum strain, by which the fatigue life could then be predicted and compared with the experimental thermal cyclic test results. The FEM results show that the maximum strain in the PTH of an RFPC depends on the varying properties of the dielectric materials. A Taguchi analysis indicated that higher fatigue life can be achieved by using high Tg and low CTE bonding material, increasing the plating thickness, reducing the board thickness and increasing the drill hole size. The results show a good agreement between the experimental data and the FEM analysis.