Measurement of deformation and strain in flip chip on BGA (FC-BGA)

Kehoe, L.; Guenebaut, V.; Kelly, P.V.

doi:10.1109/ectc.2004.1319324

Cited by 2 publications

(1 citation statement)

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“…Besides residual stress, strain measurement is also essential for evaluating mechanical properties, instability behaviors, and crack initiation and propagation of materials and structures. At present, the full-field, non-contact and nondestructive deformation measurement techniques mainly include the moiré methods [2,3], the digital image correlation (DIC) method [4], geometric phase analysis (GPA) [5,6], the Fourier transform (FT) method, electronic speckle pattern interferometry (ESPI) [7]. Among these techniques, the DIC method is simple but powerless against noise because the deformation carrier is speckle, GPA and FT are weak for complex deformation measurement as multiple frequencies exist, and ESPI is highly sensitive to vibration.…”

Section: Introductionmentioning

confidence: 99%

Residual Thermal Strain Distribution Measurement of Underfills in Flip Chip Electronic Packages by an Inverse Approach Based on the Sampling Moiré Method

Wang

Enomoto³

2020

Exp Mech

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Residual deformation evaluation of underfill (UF) materials in flip chips is crucial to improve the reliability of electronic packages. In this study, we propose to evaluate the residual thermal strain distributions using an inverse method based on the sampling moiré technique. Even if a grid pattern is fabricated on the specimen at room temperature, the residual strain distributions at an arbitrary temperature relative to the specimen formation temperature can be successfully calculated. The residual strain distributions relative to the free contraction state at an arbitrary temperature can also be measured when the coefficient of thermal expansion is available. A thermal chamber for flip chips was designed under a laser scanning microscope. Using the proposed method, the normal, shear and principal internal strain distributions and deformation characteristics of two kinds of UFs in flip chips were investigated relative to 150 °C. The strains of the UF with low glass transition temperature (UF-A) concentrate near the die material, especially at the die corner, while the strain concentration of the underfill with high glass transition temperature (UF-B) mainly occurs at the die corner and the buffer layer. The maximum principal strain of UF-A is greater than that of UF-B around the die corner. The residual maximum principal strain distributions relative to the free contraction state at 25 °C were compared with the simulation results by the finite element method. The residual strain distribution trends from experiments are consistent with those from simulations.

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