Two-layer beams (i.e., bimaterials) under thermomechanical stress are prone to peeling or delamination at the free edges. The self-equilibrating peeling stress gives rise to a peeling moment close to the free ends. A simple and exact formula for is presented in which the sign of indicates whether the beam is prone or resistant to delamination. The effect on both the sign and magnitude of of the flexural rigidities of both layers is examined. As the stiffness of one layer becomes dominant, the magnitude of the differential rigidity converges to one-half the thickness of the opposite layer.
Issue Section:
Brief Notes
1.
Moore
, T. D.
, and Jarvis
, J. L.
, 2003
, “A Simple and Fundamental Design Rule for Resisting Delamination in Bimaterial Structures
,” Microelectron. Reliab.
, 43
(3
), pp. 487
–494
.2.
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, S.
, 1925
, “Analysis of Bi-metal Thermostats
,” J. Opt. Soc. Am.
, 11
(Sept.
), pp. 233
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.3.
Suhir
, E.
, 1986
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,” ASME J. Appl. Mech.
, 53
, pp. 657
–660
.4.
Suhir
, E.
, 1989
, “Interfacial Stresses in Bi-metal Thermostats
,” ASME J. Appl. Mech.
, 56
, pp. 595
–600
.5.
Ru
, C. Q.
, 2002
, “Interfacial Thermal Stresses in Bimaterial Beams: Modified Beam Models Revisited
,” ASME J. Electron. Packag.
, 124
, pp. 141
–146
.6.
Moore
, T. D.
, and Jarvis
, J. L.
, 2001
, “Failure Analysis and Stress Simulation in Small Multichip BGAs
,” IEEE Trans. Adv. Packag.
, 24
(2
), pp. 216
–223
.Copyright © 2004
by ASME
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