Thermal Fatigue Life of Ceramic Based BGA Solder Joints After Reflux Warping

In the reflow process, warpage occurs in electronic packaging devices because of the thermal expansion coefficient of different materials is unmatched, and large deformation can negatively affect the reliability of components. To study the thermal reliability of ceramic based packaging after reflux warping, The thermal expansion coefficient of substrate and PCB was obtained by testing, and the reflow process of BGA was simulated by finite element simulation software. In order to be close to the real appearance, the copper wires on the PCB are imported into the model for calculation. At the same time, the shadow moiré method was used to carry out prototype experiment of reflux warping, and the simulation results were compared. Furthermore, thermal fatigue simulation was carried out for BGA after reflow, and the Darveaux model was used to calculate the solder joint life. The influence of ceramic substrate and organic substrate on the solder joint thermal fatigue life was compared. The results showed that:(1)In the reflow process, the warpage value of BGA and PCB varies with the temperature change. The warpage deformation is the largest in the corners of BGA package, and the solder joints in this area is easy to become open circuit. On PCB, the warpage in the center area which contact with BGA is the largest. The warpage of the center area in contact with BGA reaches the maximum at peak temperature (BGA is 121.2ȝm, PCB is 98.6ȝm). The simulation value of warpage is consistent with the measured value, which proves that the simulation model is reasonable.(2)After thermal cycle, the solder joint with largest stress is not in the corner, but is located in the center of the four sides device because of it is added underfill in the corners of BGA package. Extracting the maximum stress of solder joint life calculation, can get ceramic based BGA thermal fatigue life of 847 cycles, and the organic based BGA to 1237 cycles. The thermal suitability of the PCB to ceramic substrate is lower than that of organic substrate.