Microstructure and strength of bump joints in photodiode packages

Abstract

The joint strength and fracture surfaces of Sn-Pb and Au stud bumps for photodiode packages after isothermal aging were studied experimentally. Aluminum/gold stud bumps and Cu/Sn-Pb solders were adopted and aged for up to 900 h to analyze the effect of intermetallic compound (IMC) formation. The joint strength decreased with aging time. The diffraction patterns of Cu6Sn5, scallop-shaped IMCs, and planar-shaped Cu3Sn were characterized by transmission electron microscopy (TEM). The IMCs between Au stud bumps and Al pads was identified as AlAu2. The formation of Kirkendall voids and the growth of IMCs at the solder joint were found to be a possible mechanism for joint strength reduction.

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Kim, K., Kim, N., Yu, C. et al. Microstructure and strength of bump joints in photodiode packages. Journal of Elec Materi 33, 70–75 (2004). https://doi.org/10.1007/s11664-004-0296-2

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Key words

  • Solder bump
  • stud bump
  • photo-diode
  • thermal aging
  • intermetallic compound