Constitutive modeling of Sn/Ag and Sn/Ag/Cu solder alloys

Pei Min, Qu Jianmin

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

Solders are used extensively as electrical interconnects in microelectronics packaging. Lead-based alloys have been the de facto solder materials due to their low melting temperature, high ductility and good wetting to other metals. Because of environmental concerns, lead-based solders are being replaced by Sn/Ag and Sn/Ag/Cu based solder materials. Since the thermomechanical reliability of modern electronic devices depends on, to a large extent, the fatigue and creep behavior of the solder joints, it is imperative to understand the fatigue and creep behavior of these new lead-free solders. Several existing elastic-plastic, viscoplastic and creep models have been used extensively in the past to describe the thermomechanical behavior of lead-based solders. These constitutive models are also being used for Sn/Ag and Sn/Ag/Cu based solder alloys. However, the suitability of these existing constitutive models for lead-free solders has not been firmed established. Furthermore, unlike the lead-based solder alloys, there is a lack of experimental database on the thermomechanical fatigue and creep properties of lead-free solders. In this paper, we report some results from a recent study on developing constitutive laws suitable for Sn/Ag and Sn/Ag/Cu based solder materials. Extensive thermomechanical testing has been conducted on these lead-free solder alloys under various temperature (-55C ∼ 150C) and strain rate (10-7/s ∼ 10-1/s), subjected to both monotonic and cyclic loading. The experimental data are then used to develop a viscoplastic constitutive model to describe the thermomechanical behavior. In addition, a neural network based computational tool has been developed and trained. The tool can be used to extract the various parameters in the constitutive model based on the experimental data. The validity and accuracy of this tool have been verified by using the Anand model on Sn/Pb eutectic solder alloy. Once trained, the tool is capable of extracting all 11 parameters in the Anand model using the experimentally obtained stressstrain curves. These parameters can then be used directly in commercial finite element software such as ANSYS or ABAQUS for solder joint reliability analysis. Using this tool, we have obtained all 11 parameters in the Anand model for Sn/Ag and Sn/Ag/Cu based solder materials.

Original languageEnglish
Title of host publicationIEEE 11th International Symposium and Exhibition on Advanced Packaging Materials Processes, Properties and Interfaces
Pages118
Number of pages1
StatePublished - 2007
EventIEEE 11th International Symposium and Exhibition on Advanced Packaging Materials Processes, Properties and Interfaces - Atlanta, GA, United States
Duration: 15 Mar 200617 Mar 2007

Publication series

NameProceedings of the International Symposium and Exhibition on Advanced Packaging Materials Processes, Properties and Interfaces
Volume2007

Conference

ConferenceIEEE 11th International Symposium and Exhibition on Advanced Packaging Materials Processes, Properties and Interfaces
Country/TerritoryUnited States
CityAtlanta, GA
Period15/03/0617/03/07

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