Title :
Reliability evaluations of under bump metallurgy in two solder systems
Author :
Guo, Yifan ; Kuo, Shun-Meen ; Zhang, Charles
Author_Institution :
Semicond. Products Sector, Motorola Inc., Tempe, AZ, USA
fDate :
12/1/2001 12:00:00 AM
Abstract :
Under bump metallurgy (UBM) reliability is one of the critical issues in the total reliability of a flip-chip bumping technology. Since the UBM materials and structures vary for different bumping technologies, the UBM strength and reliability need to be determined for each design and process. In addition, the stress that a UBM experiences during thermal cycles depends on the solder alloy used in the interconnect. Different solder alloys require different UBM structures and strengths to achieve good reliability in thermal cycling. In this study, a simplified stress model is developed to determine the UBM stress during thermal cycling. A simplified stress model for the UBM strength is also developed. These models are used to predict the stress and strength of the UBM under the die pull test and the thermal cycle conditions for both eutectic and high lead solder systems. A methodology for using the pull test results to evaluate UBM reliability is also discussed. This methodology can be extended to the studies of UBM´s with other solder systems such as lead free solder systems
Keywords :
failure analysis; flip-chip devices; integrated circuit interconnections; integrated circuit metallisation; integrated circuit packaging; integrated circuit reliability; mechanical strength; soldering; stress analysis; UBM materials; UBM strength prediction; UBM stress prediction; die pull test; electronic packaging; eutectic solder systems; flip-chip bumping technology; high lead solder systems; interconnection failures; lead free solder systems; reliability evaluations; solder alloy; stress model; thermal cycles; under bump metallurgy reliability; Environmentally friendly manufacturing techniques; Lead; Materials reliability; Packaging; Predictive models; Process design; Soldering; System testing; Tensile stress; Thermal stresses;
Journal_Title :
Components and Packaging Technologies, IEEE Transactions on
DOI :
10.1109/6144.974957
