Investigation of viscoelastic effect of moulding compound on the warpage and stresses of a power plastic package
by Jianjun Wang, Daqing Zou, Sheng Liu
International Journal of Vehicle Design (IJVD), Vol. 21, No. 4/5, 1999

Abstract: In this paper, the creep deformation behaviour of a plastic power package under a thermal load condition was investigated by using a non-linear finite element technique coupled with a high-density laser moiré interferometry. The real-time moiré interferometry technique was used to monitor and measure the time-dependent deformation of the plastic power package during the test, while the finite element method was adapted to analyse the variation of stresses at the edges of all interfaces with time due to the viscoelastic properties of the molding compound. The results show that there does exist the obvious time-dependent deformation in the plastic power package under the thermal load due to the creep behaviour of the molding compound. The maximum steady state U-displacement is reduced by up to 21% compared with the maximum initial one. Likewise, the maximum steady state V-displacement is also reduced by up to 20% compared with the maximum initial state V-displacement. The creep deformation in the molding compound weakens the warpage situation of the plastic power package. In particular, such deformation greatly relieves part of the stresses at the edges of all interfaces and thereby effectively prevents interfaces from cracking. In addition, the predicted deformations of the plastic power package obtained from the finite element analysis were compared with the test data obtained from the laser moiré interferometry technique. It is shown that the deformations of the plastic power package predicted from the finite element analysis are in a fair agreement with those obtained from the test when the viscoelastic behaviour of the molding compound was considered.

Online publication date: Thu, 21-Oct-2004

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