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Research Papers

Vibration Durability Assessment of Sn3.0Ag0.5Cu and Sn37Pb Solders Under Harmonic Excitation

[+] Author and Article Information
Y. Zhou, M. Al-Bassyiouni

CALCE Electronic Products and Systems Center, and Department of Mechanical Engineering, University of Maryland, College Park, MD 20742

A. Dasgupta1

CALCE Electronic Products and Systems Center, and Department of Mechanical Engineering, University of Maryland, College Park, MD 20742dasgupta@umd.edu

1

Corresponding author.

J. Electron. Packag 131(1), 011016 (Feb 25, 2009) (9 pages) doi:10.1115/1.3078195 History: Received October 29, 2007; Revised December 05, 2008; Published February 25, 2009

In this paper, the vibration durability of both SAC305 and Sn37Pb interconnects are investigated with narrow-band harmonic vibration tests conducted at the first natural frequency of the test, printed wiring board, using constant-amplitude excitation. A time-domain approach, reported by Upadhyayula and Dasgupta (1998, “Guidelines for Physics-of-Failure Based Accelerated Stress Test,” Proceedings, Reliability and Maintainability Symposium, pp. 345–357), was adapted in this study for the fatigue analysis. The test board consists of daisy-chained components, to facilitate real-time failure monitoring. The response of the test specimens was characterized, and accelerated fatigue tests were conducted at different loading amplitudes to obtain a mix of low-cycle fatigue (LCF) and high-cycle fatigue data points. The SAC305 interconnects were found to have lower fatigue durability than comparable Sn37Pb interconnects, under the narrow-band harmonic excitation levels used in this study. This trend is consistent with most results from broadband vibration tests by Zhou (2006, “Vibration Durability Comparison of Sn37Pb vs. SnAgCu Solders,” Proceedings of ASME International Mechanical Engineering Congress and Exposition, Chicago, IL, Paper No. 13555), Zhou and Dasgupta (2006, “Vibration Durability Investigation for SnPb and SnAgCu Solders With Accelerated Testing and Modeling,” IEEE-TC7 Conference on Accelerated Stress Testing & Reliability, San Francisco, CA), and Woodrow (2005, “JCAA/JG-PP No-Lead Solder Project: Vibration Test,” Boeing Electronics Materials and Processes Technical Report) and from repetitive mechanical shock tests by Zhang (2005, “Isothermal Mechanical Durability of Three Selected Pb-Free Solders: Sn3.9Ag0.6Cu, Sn3.5Ag and Sn0.7Cu,” ASME J. Electron. Packag., 127, pp. 512–522), but counter to findings from quasistatic, LCF, and mechanical cycling studies by Cuddalorepatta and Dasgupta (2005, “Cyclic Mechanical Durability of Sn3.0Ag0.5Cu Pb-Free Solder Alloy,” Proceedings of the ASME International Mechanical Engineering Congress and Exposition, Orlando, FL, Paper No. 81171). Failure analysis revealed two competing failure modes, one in the solder and another in the copper trace under the component. Thus solder fatigue properties extracted with the help of finite element simulation of the test article should be treated as lower-bound estimates of the actual fatigue curves.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 2

Vibration durability test setup

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Figure 3

Frequency response from accelerometer modal test

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Figure 4

Strain gauge attachment

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Figure 5

Characteristic strain time history

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Figure 6

Strain amplitude

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Figure 7

Membrane strain results at the center of the PCB

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Figure 8

Resistor location on the test board

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Figure 9

Crack in LCR solder joint

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Figure 10

Crack in neck of BGA solder ball

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Figure 11

Copper trace crack for BGA component

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Figure 12

Copper trace crack for LCR component

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Figure 13

Durability plot for SAC305 LCR interconnects

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Figure 14

Durability plot for Sn37Pb LCR interconnects

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Figure 15

Local 2D model for resistor component

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Figure 16

LCR component on the FEA

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Figure 17

Detailed mesh for LCR component

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Figure 18

Normalized displacement at the center of the PCB for first mode

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Figure 19

Stress-strain material properties from literature (11)

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Figure 20

Local area used for averaging the strain in the critical solder joint

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Figure 21

Strain transfer function for center resistor

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Figure 22

Strain transfer function for edge resistor

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Figure 23

Plastic strain-life curves for SAC305 and Sn37Pb (15)

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Figure 24

Elastic strain-life curves for SAC305 and Sn37Pb solder materials

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Figure 25

Durability curves and experiment data points for SAC305 material

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Figure 26

Durability curves and experiment data points for Sn37Pb material

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Figure 27

Fatigue curve for both SAC305 and Sn37Pb solder materials

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Figure 1

Time domain approach for harmonic vibration durability test

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