Role of Bismuth in Lead-free Electronics - SMTA Webtorial

Bismuth (Bi), which is introduced either through the supply chain or by design, is becoming an inevitable element in lead-free electronic products. With the deliberation of all relevant parameters, theoretical and practical, Bi plays a “potent” role in electronic solder systems, which impact the performance and reliability of electronic package and assembly including solder joint performance, tin whisker mitigation, among others. The proper use of Bi can profoundly benefit the performance and reliability, and the improper use could degrade the performance and reliability. An adequate understanding of the property parameters of Bi is critical to product reliability. This webtorial will discuss the relevant aspects of Bi to help dispel misconceptions and to demonstrate performance criteria related to Bi. The webtorial will also highlight the distinction between Sn-based-Bi-containing alloys and Bi-based alloys. The goal is to help achieve the desired level of performance and product reliability. Your questions and issues for solutions and discussions are welcome.

Main Topics for Part 1:

• Your issues & concerns related to Bi
• Bi - characteristics, resources, safety data
• Bi effects in 63Sn37Pb solder joint
       Physical properties
       Mechanical behavior
• Effects of Bi from component coating and PCB surface finish
       Dissolving into solder joint
       Estimation of concentration of Bi in solder joint
       Effect of compositional change
• Bi effects in SAC solder joint (SnAgCuBi)
       Compositional change
       Stress vs. strain
       Fatigue behavior
• Bi effects in other Pb-free alloys (SnCu, SnAg, SnAgIn)
       Stress vs. strain
       Fatigue performance

Main Topics for Part 2:

• Historically established Bi-containing electronic solder alloys
       Pb-containing
       Pb-free
• Bi-containing Pb-free solder alloys
       Melting temperature range
       Compositional control level
       Physical, mechanical properties
       BGA thermal fatigue performance
• Distincion between Sn-based-Bi-containing alloys and Bi-based alloys
• Case study - PCB through-hole fillet-lifting vs. Bi
       Causes
       Solutions
• Low temperature BiPbSn phase
       Presence or absence
       Thermograms
       Detectable or non-detectable effects
       General guidelines
• Design limit in Pb-free solder joints vs. solder joint reliability
• Concluding points

Who Should Attend:
The webtorial provides a working knowledge to all who are involved with or interested in solder joint reliability and system integrity with and without the presence of Bi and related issues in electronic packages and assemblies including designers, engineers, researchers, managers and business decision makers; also is designed for those who desire the broad-based information on the subject.