Electromigration in flip chip solder joints under extra high current density

Electromigration in flip chip solder joints under extra high current density (4.5×104 A/cm2) is studied. At such a high current density level, due to Joule heating, the chip temperature is strongly coupled to the applied current density. Accordingly, it is highly desirable to have the capability to decouple the chip temperature and the current density. Two experimental setups were used in this study, one with a cooling module to keep the chip temperature constant and the other one without a cooling module. Without the cooling module, the temperature increased rapidly with the applied current. When the current density reached 4.5×104 A/cm2, a rapid failure caused by excessive Joule heating was observed only after 10 min of current stressing. With the cooling module attached, the joint exhibited a much longer life (935 h) under 4.5×104 A/cm2. It was successfully demonstrated that the cooling module was able to decouple the applied current density and the chip temperature.

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