Size effect on electromigration reliability of pb-free flip chip solder bump

To understand for size effect on electromigration behavior in flip chip Pb-free solder bump, electromigration tests were performed with change of pad open size and solder bump height at 140degC, 4.6times10
⁴
A/cm
²
. Electromigration lifetime increases with pad open size and bump height decreasing. In pad open size change, electromigration lifetime increase with pad open size increasing because applied current decrease with pad open size decreasing. In bump height change, electromigration resistance increase with bump height decreasing due to thermal gradient induced thermomigration effect decreasing. It seems to that electromigration resistance increase with size of solder bump decreasing.