An Investigation of Stresses Induced by Temperature Variation in Integrated Circuit Molding Process

[+] Author and Article Information
Zone-Ching Lin1

Department of Mechanical Engineering,  National Taiwan University of Science and Technology, 43 Keelung Road, Section 4, Taipei, Taiwan, R.O.C.zclin@mail.ntust.edu.tw

Chang-Cheng Chen

Department of Mechanical Engineering,  Northern Taiwan Institute of Science and Technology, 2 Xueyuan Road, Beitou, 112 Taipei, Taiwan, R.O.C.ccchen@mail.ntist.edu.tw


Corresponding author.

J. Electron. Packag 129(1), 19-27 (Sep 20, 2006) (9 pages) doi:10.1115/1.2429705 History: Received February 24, 2004; Revised September 20, 2006

A molding model is established in this study based on a real integrated circuit for simulating the molding process. This paper presents both the temperature distribution and the thermal stress field of the molding model while the simulation proceeded along the molding time. In addition, the concept of strain energy density is incorporated under the acquisition of thermal stress field of the molding model in order to analyze possible positions of the onset of yield or damage in the molding model. The simulation results also include the extent of deformation in the package body. The results provide references to the subsequent process for determining whether the strips were affected by such deformation while being loaded in the magazine after the molding process. Besides, the displacement of internal lead position could also be derived through the simulation for reference in the design of bonding wire length. The results derived in this paper help in the constructive estimations of the molding design in the integrated packaging process and help designers to avoid the defect caused by the thermal effect during the molding process.

Copyright © 2007 by American Society of Mechanical Engineers
Topics: Temperature , Stress , Molding
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Figure 1

(a) The procedure of simulated molding process used in one of Taiwan IC packaging company in this study; and (b) the back end process of a general IC packaging

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Figure 2

The molding model of SOJ-28L type IC (unit: mm)

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Figure 3

Finite element grid of the molding model (unit: mm)

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Figure 4

(a) A hexahedron element containing two types of materials is divided into six CST elements; and (b) A hexahedron element containing only one material is divided into five CST elements

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Figure 5

(a) An experimental device; and (b) the temperature distribution of the experimental results and the simulation results of the specimen heated on the furnace

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Figure 6

Temperature variation on axis Y(X=0.0) on the Z=1.0mm surface, upper surface of the lead frame, of the molding model

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Figure 7

Distribution of equivalent stress curves on the contact surface of the plastic molding compound between the plastic molding compound and the die’s (a) back surface; (b) upper surface; and (c) right surface (unit: MPa).

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Figure 8

Distribution of equivalent stress on the interface between the die and the die pad at the molding process was completely simulated: (a) on the surface of the die; and (b) on the surface of the die pad (unit: MPa).

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Figure 9

Distribution of the strain energy density curves of the plastic molding compound after its temperature is decreased to room temperature (a) on Z=1.55mm surface; and (b) on Z=1.0mm surface (unit: MPa)

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Figure 10

The characteristics of curve surface on the upper surface of the plastic molding compound due to the thermal deformation in decrease after the molding process

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Figure 11

Position of bonding wire between the seven internal leads and the die inside the molding model



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