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RESEARCH PAPERS

Prediction of Wire Sweep During the Encapsulation of IC Packaging With Wire Density Effect

[+] Author and Article Information
Chien-Chang Pei

Department of Mechanical Engineering,  National Cheng Kung University, Tainan, Taiwan

Sheng-Jye Hwang

Department of Mechanical Engineering,  National Cheng Kung University, Tainan, Taiwanjimppl@mail.ncku.edu.tw

J. Electron. Packag 127(3), 335-339 (Nov 03, 2004) (5 pages) doi:10.1115/1.1939028 History: Received July 14, 2004; Revised November 03, 2004

More wires in a package and smaller wire gaps are the trend in the integrated circuit (IC) packaging industry. The effect of wire density is becoming increasingly apparent, especially on the flow pattern of the epoxy molding compound during the molding process and, hence, on the amount of wire sweep. In most mold flow simulations, the wire density effect is ignored. In order to consider the wire density effect on the predicted amount of wire sweep in the analysis, several indirect approaches were used by researchers before. But those approaches were not general enough to be applied to all cases. This paper presents a more direct and convenient approach to consider wire density effect by including wires in the mesh model for three-dimensional (3D) mold-filling analysis. A thin small outline package (TSOP) with 53 wires is used as the demonstration example, and all the wires are modeled in the 3D mesh. By comparison with experimental results, it is shown that this approach can accurately describe the wire density effect. When the wires are included in the mesh model, the predicted wire sweep results are better than those without considering the wire density effect.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

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Figure 1

Flowchart of wire sweep analysis

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Figure 2

Outline of TSOP II 40∕44L and wire locations

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Figure 3

Illustration of element extrusion. The left panel shows the original 2D mesh and the extruded 3D mesh is shown in right panel.

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Figure 4

Mesh is refined around the projected area containing wires

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Figure 5

Outlines of the mesh models for mold-filling analysis

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Figure 6

Melt front of mold-filling analysis with and without accounting for wire density effect. Deeper color lines indicate the results from the simulation that accounts for the wire density effect, and the lighter color lines indicate the results from the simulation that does not account for the wire density effect.

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Figure 7

Illustration of extraction of mold-filling results

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Figure 8

Comparison of the wire sweep indices between computational and experimental results

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