### Abstract

Extensive failure analysis was performed on identical, isothermally cycled wafer-level chip scale packages with. Sn3.8wt%0.7wt%Ag (SAC387) solder joints. Packages were periodically removed during the cycling process to observe crack front progression. The packages were dipped in liquid nitrogen to reduce solder ductility and then pried apart. The crack areas were observed under an optical microscope. The average crack areas on the corner and mid-edge joints of the package were measured using an image processing software. 50 packages were characterized from 240 to 7200 cycles at every 240 cycles. An average of 20 solder joints per cycle was observed to estimate the crack length and area. A finite element model of this package was constructed in ABAQUS. The solder interconnects of the model were given full plastic and creep properties. Using the failure analysis data and the finite element model, the material constant value in a previously developed hierarchal fracture model was calibrated for SAC387. The ability of the model to predict nonintuitive failure initiation sites due to the under bump metallurgy (UBM) geometry is demonstrated. The hierarchal fracture process model was inspired by information theory and continuum thermodynamics. It was earlier proposed to capture the length-scale and temporal hierarchy inherent in quasi-static fracture processes. This single parameter model allows for a non-empirical, geometry independent approach to predicting crack growth by relating equivalent inelastic dissipations and a material constant to the probability of fracture at a material point.

Original language | English (US) |
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Title of host publication | Proceedings of the ASME InterPack Conference 2009, IPACK2009 |

Pages | 199-205 |

Number of pages | 7 |

Volume | 2 |

DOIs | |

State | Published - Jun 30 2010 |

Externally published | Yes |

Event | 2009 ASME InterPack Conference, IPACK2009 - San Francisco, CA, United States Duration: Jul 19 2009 → Jul 23 2009 |

### Other

Other | 2009 ASME InterPack Conference, IPACK2009 |
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Country | United States |

City | San Francisco, CA |

Period | 7/19/09 → 7/23/09 |

### Fingerprint

### ASJC Scopus subject areas

- Hardware and Architecture
- Electrical and Electronic Engineering

### Cite this

*Proceedings of the ASME InterPack Conference 2009, IPACK2009*(Vol. 2, pp. 199-205) https://doi.org/10.1115/InterPACK2009-89402

**Characterization of crack fronts in a WLCSP package : Experiments and models for application of a multiscale fracture theory.** / Chan, Dennis; Bhate, Dhruv; Subbarayan, Ganesh; Nguyen, Luu.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*Proceedings of the ASME InterPack Conference 2009, IPACK2009.*vol. 2, pp. 199-205, 2009 ASME InterPack Conference, IPACK2009, San Francisco, CA, United States, 7/19/09. https://doi.org/10.1115/InterPACK2009-89402

}

TY - GEN

T1 - Characterization of crack fronts in a WLCSP package

T2 - Experiments and models for application of a multiscale fracture theory

AU - Chan, Dennis

AU - Bhate, Dhruv

AU - Subbarayan, Ganesh

AU - Nguyen, Luu

PY - 2010/6/30

Y1 - 2010/6/30

N2 - Extensive failure analysis was performed on identical, isothermally cycled wafer-level chip scale packages with. Sn3.8wt%0.7wt%Ag (SAC387) solder joints. Packages were periodically removed during the cycling process to observe crack front progression. The packages were dipped in liquid nitrogen to reduce solder ductility and then pried apart. The crack areas were observed under an optical microscope. The average crack areas on the corner and mid-edge joints of the package were measured using an image processing software. 50 packages were characterized from 240 to 7200 cycles at every 240 cycles. An average of 20 solder joints per cycle was observed to estimate the crack length and area. A finite element model of this package was constructed in ABAQUS. The solder interconnects of the model were given full plastic and creep properties. Using the failure analysis data and the finite element model, the material constant value in a previously developed hierarchal fracture model was calibrated for SAC387. The ability of the model to predict nonintuitive failure initiation sites due to the under bump metallurgy (UBM) geometry is demonstrated. The hierarchal fracture process model was inspired by information theory and continuum thermodynamics. It was earlier proposed to capture the length-scale and temporal hierarchy inherent in quasi-static fracture processes. This single parameter model allows for a non-empirical, geometry independent approach to predicting crack growth by relating equivalent inelastic dissipations and a material constant to the probability of fracture at a material point.

AB - Extensive failure analysis was performed on identical, isothermally cycled wafer-level chip scale packages with. Sn3.8wt%0.7wt%Ag (SAC387) solder joints. Packages were periodically removed during the cycling process to observe crack front progression. The packages were dipped in liquid nitrogen to reduce solder ductility and then pried apart. The crack areas were observed under an optical microscope. The average crack areas on the corner and mid-edge joints of the package were measured using an image processing software. 50 packages were characterized from 240 to 7200 cycles at every 240 cycles. An average of 20 solder joints per cycle was observed to estimate the crack length and area. A finite element model of this package was constructed in ABAQUS. The solder interconnects of the model were given full plastic and creep properties. Using the failure analysis data and the finite element model, the material constant value in a previously developed hierarchal fracture model was calibrated for SAC387. The ability of the model to predict nonintuitive failure initiation sites due to the under bump metallurgy (UBM) geometry is demonstrated. The hierarchal fracture process model was inspired by information theory and continuum thermodynamics. It was earlier proposed to capture the length-scale and temporal hierarchy inherent in quasi-static fracture processes. This single parameter model allows for a non-empirical, geometry independent approach to predicting crack growth by relating equivalent inelastic dissipations and a material constant to the probability of fracture at a material point.

UR - http://www.scopus.com/inward/record.url?scp=77953944569&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77953944569&partnerID=8YFLogxK

U2 - 10.1115/InterPACK2009-89402

DO - 10.1115/InterPACK2009-89402

M3 - Conference contribution

AN - SCOPUS:77953944569

SN - 9780791843604

VL - 2

SP - 199

EP - 205

BT - Proceedings of the ASME InterPack Conference 2009, IPACK2009

ER -