Optimal Support Locations for a Printed Circuit Board Loaded With Heavy Components

[+] Author and Article Information
Kun-Nan Chen

Department of Mechanical Engineering, Tung Nan Institute of Technology, No. 152, Sec. 3, Beishen Rd., Shenkeng, Taipei, 222, Taiwan, R.O.C.knchen@mail.tnit.edu.tw

J. Electron. Packag 128(4), 449-455 (Feb 15, 2006) (7 pages) doi:10.1115/1.2353281 History: Received October 09, 2005; Revised February 15, 2006

In the design of printed circuit boards (PCBs), it is preferable to increase their fundamental frequency so as to reduce the effects of the dynamic loading on them. The dynamic characteristics of a PCB carrying various electronic components and modules are most significantly affected by the geometrical and material properties of the bare board and by the boundary conditions supporting the loaded PCB. In this research, a PCB carrying a heavy CPU cooling fan and supported by six fastening screws is investigated by the modal testing and analyzed by the finite element method. After the finite element model of the PCB is verified by the experimental results, the locations of the six supporting screws are optimized to achieve a maximum fundamental frequency for the loaded PCB. The position of each fastening screw can be determined by two design variables, i.e., x and y coordinates. Two cases are studied: the symmetric case (six design parameters) with the symmetric constraint on the support locations imposed, and the asymmetric case (12 design parameters) without the constraint imposed. Finally, verification experiments are performed on the two PCBs supported by screws located at the optimal positions. Although relatively large differences between the calculated, optimized fundamental frequencies and the experimental values are observed, the experiments confirm a very significant improvement in frequency for both cases.

Copyright © 2006 by American Society of Mechanical Engineers
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Figure 1

Schematic flow chart of the research procedure

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Figure 2

Locations of the supporting screws for the original PCB

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Figure 3

Experimental setup for modal testing of the original PCB

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Figure 4

(a) Test grid. (b)–(e) Measured mode shapes of the original PCB.

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Figure 5

(a) Finite element mesh. (b)–(f) FEA mode shapes of the original PCB.

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Figure 6

Feasible domain for the design parameters

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Figure 7

Iteration history of the six design parameters and the fundamental frequency for the symmetric case

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Figure 8

Iteration history of the 12 design parameters and the fundamental frequency for the asymmetric case

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Figure 9

Experimental setup for verification of the optimal support locations for the symmetric case

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Figure 10

Typical frequency response function of the PCB supported at the optimal locations for the symmetric case




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