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Strain Measurements in A Thermally-Cycled Flip-Chip PBGA Solderball



Elizabeth S. Drexler


The mismatch between the coefficients of thermal expansion of the silicon chip and the organic substrate has been mitigated through the practice of using underfill in flip-chip packages. Yet solder fatigue and package failures still occur. This is particularly true for flip-chips on organic substrates that are thermally cycled between low (-55 C) and high temperatures (125 C). In this study we used electron-beam moire to measure displacements and calculate strains in a solderball contained in a flip-chip-on-board package. A crossed-line grating with a pitch of 450 nm was used to allow detailed measurements of the displacements from the Ņ-field images. Elastic displacements were observed and measured, and the out-of-plane displacements were more significant than the shear or in-plane displacements. Larger out-of-plane displacements were measured near the center of the Si chip than at the edge of the chip.
Journal of the Materials Research Society


electron-beam moire, flip chip, flip-chip-on-board, moire, solderball, strain, thermal cycling, underfill


Drexler, E. (1999), Strain Measurements in A Thermally-Cycled Flip-Chip PBGA Solderball, Journal of the Materials Research Society (Accessed May 26, 2024)


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Created March 1, 1999, Updated February 17, 2017