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Research Papers

Effect of Shield-Can on Dynamic Response of Board-Level Assembly

[+] Author and Article Information
Da Yu, Jae Kwak, Soonwan Chung, Ji-Young Yoon

 Mechanical Engineering Department, State University of New York at Binghamton, Binghamton, NY 13905 Mechatronics and Manufacturing Technology Center, Samsung Electronics Co., LTD., Suwon, 443-803, South Korea

Seungbae Park1

 Mechanical Engineering Department, State University of New York at Binghamton, Binghamton, NY 13905 Mechatronics and Manufacturing Technology Center, Samsung Electronics Co., LTD., Suwon, 443-803, South Korea

1

Corresponding author.

J. Electron. Packag 134(3), 031010 (Jul 23, 2012) (8 pages) doi:10.1115/1.4007118 History: Received October 25, 2011; Revised June 20, 2012; Published July 23, 2012; Online July 23, 2012

In order to protect the electronic components of electronic devices on a printed circuit board (PCB) against electromagnetic radiation, a conductive shield-can or box is normally attached to the PCB covering the electronic components. In particular, handheld electronic devices are prone to be subjected to drop impact. This means that the products would experience a significant amount of out-of-plane deformation along the PCB, which may cause stresses eventually resulting in solder joint failures. The attached shield-can could provide additional mechanical strength and minimize the out-of-plane deformation, especially where the electronic package is located. In this study, both the dynamic responses of the PCB and the characteristic life of solder joints with different shield-can designs were investigated, which are seldom explored by other researchers. In the board-level drop tests, a noncontact full-field optical measurement technique, digital image correlation (DIC) with images taken by stereo-high-speed cameras, was used to obtain full-field displacement data showing the dynamic responses of the PCB during the drop impact. PCBs with a fine ball grid array (FBGA) package were prepared with various types of shield-can attached. From the experimental results the effects of different shield-can types, varying in shape and size on the dynamic responses of the PCB, were analyzed. In addition, the number of drops to failure for each shield-can was also recorded by an event detector. Using ANSYS/LS-DYNA, an accurately validated finite element model has been developed. Then the stress analysis could be performed in order to study the failure mechanism by finding the maximum tensile stress of the solder joints during the drop impact and correlate the stress results with the characteristic life of solder joint.

Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Experimental setup: drop test facility and the DIC measurement system

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Figure 2

Half–sine input pulse for the shock table

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Figure 3

Images from stereo-cameras showing the correlation facet

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Figure 4

(a) Test vehicles with two different connecting methods: (b) test vehicles with different shield-can sizes and shapes

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Figure 5

Sketch of the washer and shield-can

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Figure 6

Out-of-plane displacement of the maximum deformation point for different connection type shield-cans

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Figure 7

(a) Out-of-plane displacement of the maximum deformation point for a large polygon shaped shield-can, (b) out-of-plane displacement of the maximum deformation point for a small polygon shaped shield-can, (c) out-of-plane displacement of the maximum deformation point for a large square shaped shield-can, and (d) out-of-plane displacement of the maximum deformation point for a small square shaped shield-can

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Figure 8

(a) Out-of-plane displacement comparison of the maximum deformation point for a polygon shaped shield-can; (b) out-of-plane displacement comparison of the maximum deformation point for a square shaped shield-can

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Figure 9

Daisy chained circuits for the 332FBGA

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Figure 10

Weibull distribution of drop failures for different shield-cans

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Figure 11

Finite element model of the PCB assembly

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Figure 12

Elastic–plastic–model for the SAC405 [14]

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Figure 13

Define the boundary conditions and contact pairs

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Figure 14

Define the fictitious bonding material

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Figure 15

(a) Simulation results for a large square shaped shield-can; (b) simulation results for a small square shaped shield-can

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Figure 16

Peeling stress distributions of the solder joints

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Figure 17

Cross-section of the typical failed solder joint

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Figure 18

The maximum peeling stress of critical solder joints in the FEA model

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Figure 19

Sketch of local and global out-of-plane deformation of the PCB

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Figure 20

(a) Global and local out-of-plane deformation of a large square shield-can; (b) global and local out-of-plane deformation of a small square shield-can

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Figure 21

Correlation of the impact life and maximum peeling stress

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