โ Scribed by K. Kitamura; K. Nagata; M. Shibui; T. Fuse; N. Tachikawa; M. Akiba; M. Araki; M. Seki
No coin nor oath required. For personal study only.
Residual stresses that developed during cooling of the tungsten-copper duplex structure were measured by the strain gauge method and compared with those by thermoelastic-plastic analyses. Good agreement was obtained for both residual stress and displacement, even when the creep effect of the copper heat sink was neglected in the analyses. The residual stress on the tungsten top surface decreased with increase in the ratio of copper thickness (t c) to tungsten diameter (D).
The effect of tc/D on the residual stress was large in the range of t c/D < 1, and small for t c/D > 1. The effective thickness of the plastic region in the copper heat sink was reduced in the same manner as the residual stress. The copper heat sink plastic region developed first from the bonding interface and then from the center part of the bottom surface. The calculated edge stresses on the tungsten side surface were quite sensitive to the finite element mesh size near the interface edge, while stress on the tungsten top surface did not depend so much on the mesh size.
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