Electromigration tests were performed for solder joints with various Si dies thickness and area. For the electro-migration in flip-chip solder joints with a 60, 100.250 and 760 mu m thick Si die, it is found that Si-die thickness has profound influence on electro-migration lifetime. The average failure time was 1608.0 h for joints with a 760-mu m-thick die when they are stressed by 1.0 A at 100 degrees C. However, it decreased significantly to 0.6 h for joints with a 60-mu m-thick die. According to the temperature measured by infrared microscopy, solder joints with a thinner die has a higher Joule heating effect, which results in a shorter electromigration lifetime. In addition, the die area has a considerable influence on the electromigration failure time. The electromigration failure time decreases as the die area decreases. The average failure time is 1608.0,28.0, 10.6,5.0 and 0.3 h for the solder joints with die area of 5350 x 4350 mu m(2), 5350 x 3600 mu m(2), 5350 x 3000 mu m(2), 5350 x 2000 mu m(2) and 5350 x 1000 mu m(2), respectively. The Joule heating effect becomes more serious in smaller dies, which causes a shorter electromigration lifetime. (C) 2011 Elsevier B.V. All rights reserved.