Electroless Ni-Cu-P barrier between Si/Ti/Al pad and Sn-Pb flip-chip solder bumps

Chun Jen Chen, Kwang Lung Lin

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


This work investigates the barrier effect of the electroless Ni-Cu-P deposit between Al conductor and Sn-Pb solder bump, as well as the interfacial reaction with the Sn-Pb solder. For the Ni-Cu-P/63Sn-37Pb system, a (Ni, Cu)3Sn4 compound with three different morphologies: fine-grain, whisker, and polygon are formed at the Ni-Cu-P/63Sn-37Pb interface after reflow at 220 °C for 15 s. These (Ni, Cu)3Sn4 crystals transform into polygon shape with smooth appearance during 150 °C aging. For the Ni-Cu-P/95Pb-5Sn system, equiaxial (Ni, Cu)3 Sn4 crystals are formed at the Ni-Cu-P/95Pb-5Sn interface after reflow at 350 °C for 15 s, and they also transform into polygon shape during 150 °C aging. In addition, the Ni-Cu-P deposit will crystallize to form Ni5 P2 during 350 °C reflow. The growth of the (Ni, Cu)3 Sn4 compound by solid state reaction is a diffusion controlled process for both Ni-Cu-P/63Sn-37Pb and Ni-Cu-P/95Pb-5Sn systems. A 4 μm Ni-Cu-P deposit can provide adequate barrier function between an Al conductor and two Sn-Pb solders under 150 °C aging for 1000 h.

Original languageEnglish
Pages (from-to)691-697
Number of pages7
JournalIEEE Transactions on Components and Packaging Technologies
Issue number4
Publication statusPublished - 2001 Dec

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


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