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RESEARCH PAPERS

Shorter Field Life in Power Cycling for Organic Packages

[+] Author and Article Information
S. B. Park

Department of Mechanical Engineering, State University of New York at Binghamton, Binghamton, NY 13902sbpark@binghamton.edu

Izhar Z. Ahmed

Department of Mechanical Engineering, State University of New York at Binghamton, Binghamton, NY 13902

J. Electron. Packag 129(1), 28-34 (May 01, 2006) (7 pages) doi:10.1115/1.2429706 History: Received March 23, 2005; Revised May 01, 2006

The importance of power cycling as a mean of reliability assessment was revisited for flip chip plastic ball grid array (FC-PBGA) packages. Conventionally, reliability was addressed empirically through accelerated thermal cycling (ATC) because of its simplicity and conservative nature of life prediction. It was well accepted and served its role effectively for ceramic packages. In reality, an assembly is subjected to a power cycling, i.e., nonuniform temperature distribution with a chip as the only heat source and other components as heat dissipaters. This non-uniform temperature distribution and different coefficient of thermal expansion (CTE) of each component make the package deform differently than the case of uniform temperature in ATC. Higher substrate CTE in a plastic package generates double curvature in the package deformation and transfers higher stresses to the solder interconnects at the end of die. This mechanism makes the solder interconnects near the end of die edge fail earlier than those of the highest distance to neutral point. This phenomenon makes the interconnect fail earlier in power cycling than ATC. Apparently, we do not see this effect (the die shadow effect) in ceramic packages. In this work, a proper power cycling analysis procedure was proposed and conducted to predict solder fatigue life. An effort was made for FC-PBGA to show the possibility of shorter fatigue life in power cycling than the one of ATC. The procedure involves computational fluid dynamics (CFD) and finite element analyses (FEA). CFD analysis was used to extract transient heat transfer coefficients while subsequent FEA–thermal and FEA–structural analyses were used to calculate temperature distribution and strain energy density, respectively.

Copyright © 2007 by American Society of Mechanical Engineers
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References

Figures

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Figure 2

119 (7×7) BGA I/O FC-PBGA—front view and top view

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Figure 3

Schematic outline to predict solder life through power cycling

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Figure 4

Chip power cycle load

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Figure 5

Complete assembly in ICEPAK

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Figure 6

Temperature contour profile of simulated package using CFD

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Figure 7

Quarter symmetry model of flip chip PBGA package in ANSYS

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Figure 8

Temperature profile in the cross section of the assembly

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Figure 9

Temperature profile at the top surface of the assembly

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Figure 10

Temperature profile of reference points

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Figure 11

Warpage distribution at the midplane of chip, substrate, and PCB for power cycling

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Figure 12

Warpage distribution at the midplane of chip, substrate, and PCB for ATC

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Figure 13

Two layers of 1.0mil thickness on the top and bottom surface of the solder joint

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Figure 14

Top view schematic of the quarter symmetry assembly

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Figure 15

Power cycling—maximum accumulated plastic work/cycle (PSI) for solder interconnects

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Figure 16

ATC—maximum accumulated plastic work/cycle (PSI) for solder interconnects

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Figure 17

Power cycling—characteristic life of solder interconnects

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Figure 18

ATC—characteristic life of solder interconnects

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Figure 1

Typical FC-PBGA package

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