摘要(英) |
In this study, the finite element method is used to analyze flip chip solder joints under electromigration. Current input, environment temperature and element size are the three important factors for such electromigration simulation. We will discuss the sensitivity of flip chip solder joints under electromigration by analyzing current density distribution and temperature distribution under different current input and element size. We will also determine the critical current input for different environment temperature and element size. In addition, we investigate the void propagation in the case of high current input. It is found that the maximum temperature is within the Al trace. The location where electrons enter UBM from Al trace exist rather high current density. The solder next to the IMC also exist rather high current density and temperature. These two locations are both important and easily be damaged. For the same element size and environment temperature, resistance will increase much more when current input increases, and the effect of Joule heating will be more severe. Even though we consider temperature coefficient of resistance, current input is the major factor for the effect of Joule heating. For void nucleation and propagation issue, we use simulation to predict the path which void may propagate, and analyze the effect of Joule heating. In the case of high current input, void nucleation begins at the maximum current density region after incubation time, and then spreads along the contact area of IMC and solder. When 99.9% of the contact window is covered by the void, solder will reach its melting point and then fail by the effect of Joule heating. Furthermore, we will also analysis the influence of heat dissipation by heat conduction ability and location of heat source. |
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