The effect of board stiffness on the solder-joint reliability of HVQFN-packages

In this work the results of thermal cycling tests on HVQFN-packages mounted on printed circuit boards are evaluated. The emphasis is on the fatigue life of the soldered interconnections as it is influenced by the printed circuit board, rather than that by the package or the solder. Data from different experimental set-ups are compared: panel thickness and stand-off height of the packages. New in this respect is inclusion of the base material of the panels as parameter. The test load was set to cycling at -40degC/+125degC and -20degC/+100degC. The results prove that the essential physical properties governing the fatigue life are the stiffness of the complete assembly and the thermal expansion mismatch between the parts. Numerical simulations support this.