Advancing Manufacturing Technology

BiSn-Based Low-Temperature Soldering Process and Reliability


Project Leaders

Raiyo Aspandiar and Scott Mokler (Intel) 

Statement of Work and Project Statement


Recently there have been some drivers from most ODMs and some OEMs to adopt low-temperature soldering for the assembly of consumer electronic products, such as cell phones, tablets and mobile computers. The motivations for these drivers have been three fold: environmental, economic and technical.

Solders in the BiSn system, particular compositions close to the eutectic (58wt% Bi) are prone to brittle fractures at high strain rates. This leads to a high risk of brittle fracture of BiSn-based solder joints under mechanical shock and drop conditions for electronic products. To mitigate this risk, solder paste manufacturers have explored two pathways. One is through the development of a more ductile metallurgy within the BiSn solder system, by reducing the bismuth content, and addition of elemental dopants, both of which enhance the solder bulk mechanical properties by modifying its microstructure. The other is through the incorporation of polymer resins in the solder paste, that, during the reflow soldering process, cures after the solder wets to the metallic surfaces of the board and the component, and forms a polymeric reinforcement around the solder joint after the assembly cools down. There is a sparse independent assessment of these two pathways, both in terms of the processibility of these new solder pastes and the reliability of the solder joints thus formed by their use.


The purpose of this project is to assess the surface mount processibility and reliability of the solder joints formed when enhanced BiSn-based solder pastes are used for assembling electronic components on printed circuit boards.

Steps for Joining the Project
Please note:  iNEMI membership is required to participate in this project.  Sign up by January 29, 2016.  After that date, you must be approved by majority of team members.  Steps for joining the project follow.

For iNEMI members:

  • Complete and sign the project statement
  • Fax the completed statement(s) to +1 (703) 834-2735 or scan and email to
For non-members:


Presentation and Paper:  iNEMI Project on Process Development of BiSn-Based Low Temperature Solder Pastes — Part III: mechanical shock tests on PoP BGA assemblies, Jagadeesh Radhakrishna (Intel), presented at ICEP-IAAC 2018 (April 19, 2018; Kuwana, Mie, Japan) (iNEMI members only)

iNEMI Project on Process Development of BiSn-Based Low-Temperature Solder Pastes - Part II: Characterization of Mixed Alloy BGA Solder Joints; Raiyo Aspandiar (Intel); Pan Pacific Microelectronics Symposium (February 6, 2018; Big Island, Hawaii) iNEMI Project on Process Development of BiSn-Based Low-Temperature Solder Pastes; Raiyo Aspandiar (Intel); SMTAI  (September 20, 2017; Rosemont, Illinois, USA)

For Additional Information

Haley Fu