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Research Papers

A General Methodology to Predict Fatigue Life in Lead-Free Solder Alloy Interconnects

[+] Author and Article Information
David M. Pierce1

Department of Mechanical Engineering, Stanford University, Stanford, CA 94305

Sheri D. Sheppard

Department of Mechanical Engineering, Stanford University, Stanford, CA 94305

Paul T. Vianco

 Sandia National Laboratories, Albuquerque, NM 87185

1

Corresponding author.

J. Electron. Packag 131(1), 011008 (Feb 13, 2009) (11 pages) doi:10.1115/1.3068313 History: Received August 08, 2007; Revised August 09, 2008; Published February 13, 2009

The ubiquitous eutectic tin-lead (Sn–Pb) solder alloys are soon to be replaced with lead-free alternatives. In light of this transition, new computational tools for predicting the fatigue life of lead-free solders are required. A fatigue life prediction methodology was developed, based on stress-strain, creep, and isothermal fatigue data; the latter generated using a double lap-shear (DLS) test assembly. The proposed fatigue life prediction methodology builds on current practices in fatigue prediction for solder alloys, particularly the concepts of unpartitioned energy methods in finite element analysis (FEA) and continuum damage mechanics. As such, the current state of these fields is briefly discussed. Next, the global and local FEA simulations of the DLS test assembly are detailed. A correlation is then made between the empirical data and the FEA simulations. A general fatigue life prediction methodology is next described in detail. Finally, this methodology is tested and verified against the empirical data.

Copyright © 2009 by American Society of Mechanical Engineers
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References

Figures

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Figure 16

Predicted versus measured cycle number to a specified crack length for DLS crack propagation at 25°C(a0=35 μm). The crack length is specified in millimeters next to each data point.

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Figure 17

Predicted versus measured cycle number to a specified crack length (95.5Sn–3.9Ag–0.6Cu solder alloy) for DLS crack propagation at 100°C(a0=35 μm)

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Figure 18

Predicted versus measured cycle number to a specified crack length (95.5Sn–3.9Ag–0.6Cu solder alloy) for DLS crack propagation at 160°C(a0=35 μm)

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Figure 1

DLS test assembly, and edge and face views

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Figure 2

Sample of pad array crack length template

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Figure 3

Schematic of the data analysis approach

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Figure 4

Crack growth rate versus crack length at 25°C (95.5Sn–3.9Ag–0.6Cu solder alloy)

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Figure 5

Crack growth rate versus crack length at 100°C (95.5Sn–3.9Ag–0.6Cu solder alloy)

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Figure 6

Crack growth rate versus crack length at 160°C (95.5Sn–3.9Ag–0.6Cu solder alloy)

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Figure 7

DLS full model with submodel cut-boundary outline

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Figure 8

Submodel geometry and mesh

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Figure 9

Damage contour for a solder joint corresponding to TLS B-40 (81 cycles)

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Figure 10

Crack growth rate per viscoplastic strain-energy density increment versus crack length at 25°C (95.5Sn–3.9Ag–0.6Cu solder alloy)

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Figure 11

Crack growth rate per viscoplastic strain-energy density increment versus crack length at 100°C (95.5Sn–3.9Ag–0.6Cu solder alloy)

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Figure 12

Crack growth rate per viscoplastic strain-energy density increment versus crack length at 160°C (95.5Sn–3.9Ag–0.6Cu solder alloy)

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Figure 13

Parameter C1 as a function of temperature (95.5Sn–3.9Ag–0.6Cu solder alloy)

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Figure 14

Parameter C2 as a function of temperature (95.5Sn–3.9Ag–0.6Cu solder alloy)

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Figure 15

Numerical integration template

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