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Pb-free Solder Joint ReliabilityAnalysis Lab |
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Authored By:Joe Smetana, Alcatel-Lucent, Plano, TX Richard Coyle, Alcatel-Lucent, Murray Hill, NJ Thilo Sack, Celestica, Toronto, Canada Ahmer Syed, Amkor, Chandler, AZ David Love, Oracle, Santa Clara, CA Danny Tu, Huawei, China Steve Kummerl, Texas Instruments, Dallas TX TranscriptThis paper covers two different temperature cycling profiles that were used to compare the thermal fatigue reliability of lead free and tin/lead solder joints in 16 different, high strain surface mount packages. In some applications, high strain lead free components are expected to fail earlier than the equivalent tin/lead version. In this program, test results were compared for a 0-100 C thermal cycle, often used for evaluating high reliability applications, to those of a comparatively mild accelerated thermal cycle condition of 20-80 C. Over 6900 cycles were completed in the 0-100 C testing, and over 9700 cycles were completed in the 20-80 C thermal cycling. The program was completed over more than two years of elapsed test time. The results indicate that the tin/silver/copper components that create a high strain in thermal cycling tend to perform worse in 0-100 C testing than identical tin/lead soldered components. However, when the strain is reduced by testing with the reduced delta T in the 20-80 C cycle, the tin/silver/copper thermal fatigue performance is equal to, or better than, that of identical tin/lead soldered components. The encouraging tin/silver/copper performance in the 20-80 C cycle tends to mitigate lead free reliability concerns because the lower strain test conditions are closer to actual service conditions. SummaryTwo different temperature cycling profiles were used to compare the thermal fatigue reliability of Pb free and SnPb solder joints in 16 different, high strain surface mount (SMT) packages. In some applications, high strain Pb free (SnAgCu) components are expected to fail earlier than the equivalent SnPb version. In this program, test results were compared for a 0-100°C thermal cycle used often for evaluating high reliability applications to those of a comparatively mild accelerated thermal cycle condition of 20-80°C. A total of 6957 cycles was completed in the 0-100°C testing and a total of 9792 cycles was completed in the 20-80°C thermal cycling. The program was completed after over more than two years of elapsed test time. Weibull analysis, acceleration factors between the tests and failure analysis are included. The results indicate that the SnAgCu (SAC) components that create a high strain in thermal cycling tend to perform worse in 0-100°C testing than identical SnPb soldered components. However, when the strain is reduced by testing with the reduced ΔT in the 20-80°C cycle, the SAC thermal fatigue performance is equal to or better than that of identical SnPb soldered components. The encouraging SAC performance in the 20-80°C cycle tends to mitigate Pb free reliability concerns because the lower strain test conditions are closer to actual service conditions. ConclusionsThe following specific conclusions can be drawn from the results of the thermal cycling study:
Initially Published in the IPC Proceedings |
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