THREE-DIMENSIONAL CAE OF WIRE-SWEEP IN MICROCHIP ENCAPSULATION

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THREE-DIMENSIONAL CAE OF WIRE-SWEEP IN MICROCHIP ENCAPSULATION

Wen-Hsien Yang*, David C.Hsu and Venny Yang CoreTech System Co.,Ltd., HsinChu, Taiwan, ROC
Rong-Yeu Chang
National Tsing-Hua University, HsinChu, Taiwan, ROC
Francis Su
eCAD Technologies Inc., Tainan, Taiwan, ROC
Sheng-Jye Huang
National Chen Kung University, Tainan, Taiwan, ROC

Abstract
Wire Sweep is a common molding problem encountered in microchip encapsulation. The resin melt flow will exert drag force on wires and hence causes deformation of wires. In this paper, an integrated CAE of wire sweep is proposed to help engineer to evaluate and ptimize the encapsulation process. The resin flow is calculated by a true 3D thermal flow solver based on a highly flexible prismatic element generation technique. Thanks to the efficiency of the proposed methodology in terms of CPU time and memory requirement, the industrial packages with complex geometry and high pin count can be analyzed with minimum model simplification. Furthermore, a user-friendly integrated environment is also developed to link the flow analysis with structure analysis to provide the total solution for wire sweep assessment. The developed approach proved from numerical experiments to be a cost-effective method for true 3D simulation of wire sweep in microchip encapsulation

Introduction
The demands for lighter, thinner and smaller of electronic products have driven the IC packaging toward the high I/O technology. For the IC packages, high I/O means that the numbers of connectors are increasing and hence the distances between wires become much smaller. Accordingly, the influence of wire sweep becomes more critical in high-density packages. Wire sweep is one of the most common problems in IC packaging. The resin melt flow will exert drag force on wires and hence causes deformation of wires. The amount of wire sweep during encapsulation is affected by the wire properties, package dimension and process conditions. If the deformation of wires exceeds the limit, it can cause adjacent wire touching with each other or wire breakage, and the package will fail. Conventionally, the 2.5D CAE analysis is used to simulate the mold filling and predict the wire sweep [1-2]. However, the model simplification inherent in the 2.5D analysis neglect some detail flow phenomena especially that in the gapwise direction. To improve the prediction accuracy, this paper proposes an integrated 3D CAE tool for predicting the mold filling and wire sweep.

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