Characterization of hermetic wafer-level Cu-Sn SLID bonding
conference paper
A flux-less copper-tin (Cu-Sn) solid-liquid inter-diffusion (SLID) bonding process, providing a cost-effective hermetic vacuum sealing at wafer-level, has been investigated. Observations have been made indicating that the storage time of Cu-Sn plated wafers before bonding is critical with regard to voiding. Growth of the intermediately formed intermetallic compound (IMC), Cu 6Sn5, was investigated as a possible cause. Room temperature aging of Cu-Sn plated wafers prior to bonding was performed as well as annealing of un-bonded Cu-Sn plated wafers. The presence of large Cu 6Sn5 and Cu3Sn crystallites which nearly depleted the Sn was observed by optical microscopy after annealing. If large Cu6Sn5 grains from opposite contact planes meet at the bond interface, voids are predicted to be formed during the subsequent stages of liquid inter-diffusion and solidification. Implications on the Cu-Sn bonding strategy based on the results are presented.
Topics
TNO Identifier
507172
ISBN
9781467346450
Publisher
IEEE Computer Society
Article nr.
6542150
Source title
2012 4th Electronic System-Integration Technology Conference, ESTC 2012, 17 September 2012 through 20 September 2012, Amsterdam
Files
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