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Research Papers

Experimental and Modeling of the Stress-Strain Behavior of a BGA Interconnect Due to Thermal Load

[+] Author and Article Information
Yan Zhang

Key Laboratory of Advanced Display and System Applications, Ministry of Education and SMIT Center, School of Mechatronics Engineering and Automation, Shanghai University, Shanghai, 200072, P.R.C.; Department of Applied Mechanics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden

Johan Liu

Key Laboratory of Advanced Display and System Applications, Ministry of Education and SMIT Center, School of Mechatronics Engineering and Automation, Shanghai University, Shanghai, 200072, P.R.C.; SMIT Center and Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden

Ragnar Larsson

Department of Applied Mechanics, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden

J. Electron. Packag 130(2), 021010 (May 15, 2008) (7 pages) doi:10.1115/1.2912183 History: Received February 16, 2007; Revised September 07, 2007; Published May 15, 2008

A plastic ball grid array component interconnect has been experimentally investigated and modeled on the basis of micropolar theory. The experimental results were analyzed, and the data also provided the verification for the micropolar interface model. Two different interconnect cross sections, namely, one near the component boundary and the other in the center region beneath the chip, have been measured. The effects of thermal cycling on the interconnect deformation have been considered. The deformation fields, due to the mismatch of the material properties of the constituents in the assembly system, have been observed by means of a multifunction macro-micro-moiré interferometer, whereby the displacement distributions have been obtained and analyzed for the different specimens. The interconnect layer is usually of smaller size as compared to the neighboring component, and there are even finer internal structures included in the interconnect. The scale difference makes conventional methods time consuming and of low efficiency. An interface model based on the micropolar theory has been developed, cf. Zhang, Y., and Larsson, R., 2007, “Interface Modelling of ACA Flip-Chip Interconnects Using Micropolar Theory and Discontinuous Approximation  ,” Comput. Struct., 85, pp. 1500–1513, Larsson, R., and Zhang, Y., 2007, “Homogenization of Microsystem Interconnects Based on Micropolar Theory and Discontinuous Kinematics  ,” J. Mech. Phys. Solids, 55, pp. 819–841, aiming at predicting the interconnect behavior under thermal load, especially when there exist internal structures in the interface and the component/structure sizes vary in a wide range. Numerical simulations, using the micropolar interface model, show a fairly good agreement between the experimental data and the numerical simulations.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Photo of the 4M interferometer

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Figure 2

Configurations of the PBGA component: (1) photo of the top view (die side) and (2) sketch of the ball array distribution on the bottom

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Figure 3

Photo of the cross section of PBGA (edge specimen)

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Figure 4

Photo of the cross section of PBGA (center specimen)

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Figure 5

Temperature profile of thermal cycling

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Figure 6

Fringe pattern of edge specimen after thermal loading: (1) the image before the moiré fringe is produced and (2) the fringe pattern of this edge specimen

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Figure 7

Fringe pattern of the center specimen after thermal loading

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Figure 8

Fringe pattern of the center specimen after thermal cycling

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Figure 9

Displacement of the edge specimen after thermal loading

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Figure 10

Displacement of the center specimen

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Figure 11

Relative displacement of the interconnect

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Figure 12

Sketch map of the considered geometry

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Figure 13

The microstructure in the interconnect

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Figure 14

FE modeling using LST triangles of the considered microsystem specimen. The thick line denotes the location of the BGA interconnect.

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Figure 15

Displacement along the interconnect after the thermal loading

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Figure 16

Distribution of stresses along the interface after the thermal loading.

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