Electromigration in Sn-Cu intermetallic compounds

Abstract

As the shrinking in bump size continues, the effect of intermetallic compounds (IMCs) on electromigration becomes more pronounced. Electromigration in Sn-Cu intermetallic compounds was examined using edge displacement method. It was found that Cu(6)Sn(5) compounds are more susceptible to electromigration than Cu(3)Sn compounds. The lower solidus temperature and higher resistivity of the Cu(6)Sn(5) IMCs are responsible for its higher electromigration rate. Length-dependent electromigration behavior was found in the stripes of various lengths and the critical length was determined to be between 5 and 10 mu m at 225 degrees C, which corresponded to a critical product between 2.5 and 5 A/cm. Furthermore, the Sn-Cu compounds were proven to have better electromigration resistance than eutectic SnAgCu solder.