Creep Prediction of a Printed Wiring Board For Separable Land Grid Array Connector

[+] Author and Article Information
J. Cepeda-Rizo

Department of Mechanical and Aerospace Engineering,  California State University, Long Beach, CA

Hsien-Yang Yeh1

Department of Mechanical and Aerospace Engineering,  California State University, Long Beach, CAhyyeh@esulb.edu


To whom correspondence should be addressed.

J. Electron. Packag 127(2), 185-188 (Oct 01, 2004) (4 pages) doi:10.1115/1.1899164 History: Received September 16, 2003; Revised October 01, 2004

The paper presents a study of creep behavior of a printed wiring board caused by the mechanical fastening of separable connector, known as a land grid array. Time-temperature superposition method was employed to predict the lifetime creep behavior. A low-cost testing method based on the ASTM D790 three-point bending procedure was developed to predict and characterize creep of polymeric materials under low temperature, low stress, and large elapsed times.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 2

Module/LGA/PWB system. LGA pins behave like small springs sandwiched between module and PWB components.

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Figure 3

Modeled out of plane displacement of PWB after module assembly. The center of the PWB has a positive displacement while the front and back edges have a negative displacement relative the unperturbed neutral axis of the PWB (see Ref. 3).

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Figure 4

Three-point bending apparatus per ASTM D790

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Figure 5

Flexure modulus measurements obtained from three-point bending test

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Figure 6

Result of 1h creep compliance tests performed for 16 different temperatures

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Figure 7

TTSP overlapped master curve. This curve was obtained by horizontally shifting the 16 individual creep curves obtained in Fig. 7.

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Figure 8

Shift factor plot, composed of the log of the horizontal time shift of each of the 16 curves done in obtaining the master curve. WLF is plotted and shows good agreement.

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Figure 9

Master curve compared to the theoretical Findley equation

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Figure 1

(a) Module mechanical stack-up; (b) side profile of module stack-up. Notice curvature of the stiffener plate that flattens upon fastening.




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