0
Research Papers

Validation of a General Fatigue Life Prediction Methodology for Sn–Ag–Cu 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, Jerome A. Regent, J. Mark Grazier

 Sandia National Laboratories, Albuquerque, NM 87185

1

Corresponding author.

J. Electron. Packag 130(1), 011003 (Jan 31, 2008) (12 pages) doi:10.1115/1.2837515 History: Received October 13, 2006; Revised July 19, 2007; Published January 31, 2008

A general fatigue life prediction methodology, based on a unified creep plasticity damage (UCPD) model, was developed for predicting fatigue cracks in 95.5Sn–3.9Ag–0.6Cu (wt %) solder interconnects. The methodology was developed from isothermal fatigue tests using a double-lap-shear specimen. Finite element analysis model geometries, mesh densities, and assumptions were detailed for both a full model (an octant-symmetry slice of the entire ball grid array (BGA) assembly) and a submodel (the solder joint deemed most likely to fail and the surrounding package layers) to facilitate fatigue prediction. Model validation was based on the thermal mechanical fatigue of plastic BGA solder joints (250–4000 thermal cycles, 55°Cto125°C, and 10°Cmin). Metallographic cross sections were used to quantitatively measure crack development. The methodology generally underpredicted the crack lengths but, nonetheless, captured the measured crack lengths within a ±2X error band. Possible shortcomings in the methodology, including inaccurate materials properties and part geometries, as well as computational techniques, are discussed in terms of improving both the UCPD constitutive model and the fatigue life prediction methodology fidelity and decreasing the solution time.

Copyright © 2008 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 2

FR-4 substrate PC board with a mounted component

Grahic Jump Location
Figure 3

Plastic BGA cross section map and numbering scheme (13)

Grahic Jump Location
Figure 4

Thermal mechanically fatigued plastic BGA joint image (2500 thermal cycles)

Grahic Jump Location
Figure 5

BGA model joint numbering scheme

Grahic Jump Location
Figure 6

Package side empirical crack length data for Joint 6

Grahic Jump Location
Figure 7

PC board side empirical crack length data for Joint 6

Grahic Jump Location
Figure 8

Perspective view of full BGA assembly (76,265 nodes)

Grahic Jump Location
Figure 9

Top view (a) and side view (b) of full BGA assembly with material labels

Grahic Jump Location
Figure 10

BGA package and solder joint cross-section mesh (a), parameter values (b), and representative photograph (c)

Grahic Jump Location
Figure 11

Full model thermal profile, simulation substeps, and results of file generation

Grahic Jump Location
Figure 12

von Mises stress (S,eqv) in the solder array at the maximum temperature of the thermal cycle (125°C)

Grahic Jump Location
Figure 13

Perspective view of the BGA submodel geometry and solder joint mesh (note interface element layers, three elements of 0.0127mm thickness per element)

Grahic Jump Location
Figure 14

Predicted crack length numerical estimate versus cycle number for 200cycles

Grahic Jump Location
Figure 15

Accumulated plastic work per cycle versus cycle number for 200cycles

Grahic Jump Location
Figure 16

Extrapolated crack length numerical estimate versus cycle number for 7500cycles

Grahic Jump Location
Figure 17

PC board side predicted versus measured number of cycles to a specific crack length

Grahic Jump Location
Figure 18

Package side predicted versus measured number of cycles to a specific crack length

Grahic Jump Location
Figure 19

Board side empirical data and predicted crack length versus thermal cycle number for Joint 6

Grahic Jump Location
Figure 20

Package side empirical data and predicted crack length versus thermal cycle number for Joint 6

Grahic Jump Location
Figure 1

Plastic BGA 169 component

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In