Electro- and thermomigration induced Cu3Sn and Cu6Sn5 formation in SnAg3.0Cu0.5 bumps

For the general prediction of the migration induced IMC formation the related material parameters are needed. Against this background the Cu3Sn and Cu6Sn5 formation was observed during temperature storage tests on Amkor® Package-on-Package packages (12 × 12 mm) with SnAg3.0Cu0.5 ball grid arrays. A mathematical model was developed to calculate the average mass flux of Sn and Cu during the stress tests. Based on the mass flux values the activation energies and diffusion constants for Cu and Sn in Cu3Sn and Cu6Sn5 were determined. Afterwards the temperature storage was combined with an AC and a DC current load to investigate thermo- and electromigration-related phenomena. Based on the IMC formation speed during the AC and the DC tests the heat of transport Q* and the effective charge of the moving ion Z* were calculated. An interpretation of the material parameters is given in consideration of the high defect density in Cu3Sn and Cu6Sn5.