Polarity effect of interfacial intermetallic compounds of BGA structure Cu/Sn–52In/Cu solder joints during electromigration

Sn–52In eutectic solder has gradually attracted much attention due to the feature of low melting temperature in recent years. However, Sn–52In solder may occur melting due to the severe Joule heating and causes serious reliability problems. This study mainly investigated the interfacial reaction of ball grid array (BGA) structure Cu/Sn–52In/Cu solder joints during electromigration with current densities of 0.5 × 104 A/cm2, 1.0 × 104 A/cm2 and 1.5 × 104 A/cm2 at 70 °C, 115 °C and 140 °C, respectively. Results show that during the solid-solid (S–S) electromigration and liquid-solid (L-S) electromigration process, respectively, both the In and Cu atoms on the cathode side diffuse to the anode side to participate in the interfacial reaction to form the intermetallic compounds (IMCs), which not only causes the dissolution of the Cu substrate on the cathode side, but also leads to the polarity effect in the growth of interfacial IMCs, i.e., the interfacial IMCs on the anode side is much thicker than that on the cathode side, and the higher the current density and temperature, the more obvious the polarity effect. In addition, with the increase of current density and temperature, the type of interfacial IMCs on the anode side changes from the initial Cu6(Sn,In)5 and Cu2In3Sn to Cu6(Sn,In)5 during S–S electromigration, while that changes from the initial Cu6(Sn,In)5 and Cu2In3Sn to the composition of Cu6(Sn,In)5 and Cu3(In,Sn) for L-S electromigration.