Electromigration of SnBi Solder for Second-Level Interconnect
Section: Board Assembly

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Project Leaders

Project Leader
Prabjit Singh, IBM

Raiyo Aspandiar, Intel

Hemant M. Shah, Intel 

Statement of Work & Project Statement



The low melting temperature of 138°C makes SnBi alloys attractive for assembling thermally warpage-prone high-density microelectronic packaging. However, Bi has a high propensity for electromigration and segregation at the anode under high current density conditions. This can lead to potentially brittle solder joints with high electrical resistance over time in the field. There is need to explore ways to mitigate such shortcoming and develop SnBi solder joints that maintain their performance and reliability over the product life. This iNEMI project plans to explore the potential to reduce electromigration in low height solder joints by taking advantage of mechanical and/or chemical back stresses. 



The overall project objective is to determine the boundaries of the envelope formed by joint height, temperature, current density and PCB finishes within which the solder joint will operate reliably over the product life. 

The project has multiple phases planned. The first phase will:

  • Establish an appropriate test vehicle for electromigration study of solder joints, including a convenient means of achieving various joint heights.
  • Investigate the role of back pressure in reducing electromigration in eutectic SnBi solder joints by determining the rate of electromigration of SnBi solder joints with and without diffusion barriers as a function of current density, temperature and joint height.



LTS Tech Topic Series: Electromigration in Tin-Bismuth Planar Solder Joints, Prabjit Singh, PhD (IBM), October 17/18, 2023 

Comparison of Electromigration in Tin-Bismuth Planar and Bottom Terminated Component Solder Joints,” Prabjit Singh, Ph.D., IBM Corporation, SMTA International 2023, Session LTS3: Electromigration, Shear and Drop Shock Assessment of Low Temperature Sn-Bi Solder Joints, October 11, 2023; Minneapolis, Minnesota. (Originally published in the proceedings of the SMTA International, October 9 - October 12, 2023).
NOTE: This paper received Honorable Mention for the “Best of Proceedings” Award from the 2023 SMTA International Conference.

Presentation: Call-for-Participation Webinar (January 11 & 13, 2022)


Haley Fu