Experimental stress analysis for flip chip BGA packages using strain gauge

The application of a flip chip ball grid array (BGA) package with organic substrate in electronic devices has significantly grown during the past few years. However, potential package reliability problems can still occur, for example die cracks, underfill cracks, and solder joint cracks. An experimental stress analysis which is to measure the stress distribution at the flip chip BGA package using strain gauge and finite element analysis were performed to predict the susceptibility of die cracking during thermal cyclic loading. The experimental stress analysis which is the in-situ stress measurement technique was applied for different variables such as chip thickness, organic substrate and underfill materials. The stress distribution was measured on four kinds of flip chip BGA packages. These results were also compared with the reliability data of package level in order to verify its effectiveness. From the above results, we can find that the strain behavior of the flip chip BGA package with temperature is nonlinear. It also reveals that the strain measured at the lowest temperature is not the maximum. Finally, we can conclude that the experimental stress analysis is a very useful method to predict the susceptibility of die tracking during the thermal cyclic loading in flip chip BGA packages.