Effect of Environmental and Testing Conditions on Board Level Vibration

In this paper, the factors affecting the stability of the board level vibration testing are investigated by means of experimental testing combined with simulations. Environmental conditions and test parameters may affect the dynamic response of the PCB and thus the stress on the product. As the goal of the test is to predict solder joint reliability, the translation from test of surface mounted products on PCBs and field life once build in the final application unit becomes difficult. The natural frequency and the peak-to-peak displacement of the PCB are evaluated with an accelerometer, which is shown to have a similar impact on the dynamic behavior as large BGA packages. The influence of the PCB stack-up is also highlighted. Then, the temperature is varied between 17 degrees C and 47 degrees C, and the relative humidity between 30% and 60%. The temperature is shown to have a large impact on the displacement and the frequency, while the humidity is confirmed to have no influence. Next, increasing the acceleration from 1G to 10G is shown to increase the stress on the component and can potentially lead to faster test results. Nevertheless, it is observed to have a negative impact on the test stability since the frequency and displacement of the PCB are shifting during the test and the board is permanently damaged. The cables, used for the in-situ monitoring of daisy chains during the test in order to capture the intermittent contacts during the bending of the board, are shown to have an influence on the natural frequencies of the board, but predominantly on the higher order resonances. With the fixed environmental conditions and test parameters, a BGA package is tested and the failure distribution as well as the different failure modes observed are reported and discussed.