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Research Papers

Analysis of Solderless Press-Fit Interconnections During the Assembly Process

[+] Author and Article Information
Hironori Tohmyoh

Department of Nanomechanics, Tohoku University, Aoba 6-6-01, Aramaki, Aoba-ku, Sendai 980-8579, Japantohmyoh@ism.mech.tohoku.ac.jp

Kiichiro Yamanobe, Masumi Saka

Department of Nanomechanics, Tohoku University, Aoba 6-6-01, Aramaki, Aoba-ku, Sendai 980-8579, Japan

Jiro Utsunomiya, Takeshi Nakamura

 Keihin Corporation, Houshakuji 2021-8, Takanezawa, Shioya, Tochigi 329-1233, Japan

Yoshikatsu Nakano

Institute of Fluid Science, Tohoku University, Katahira 2-2-1, Aoba-ku, Sendai 980-8577, Japan

J. Electron. Packag 130(3), 031007 (Jul 30, 2008) (6 pages) doi:10.1115/1.2957330 History: Received November 16, 2007; Revised February 01, 2008; Published July 30, 2008

This paper deals with typical mechanical problems that are encountered in a solderless press-fit assembly process. First, the elastic-plastic properties of two types of press-fit pins and the friction coefficients of the pins in thin plated through holes are determined both experimentally and by three-dimensional finite element analysis. The elastic-plastic properties of the press-fit pins are determined by small-scale testing under three-point bending. The coefficients of friction of the pins in the through holes are successfully determined from the load-displacement relationships of the pins during press-fit assembly processes. The validity of the parameters that are determined is clarified by inserting the press-fit pins into holes of different diameters. By comparing the damaged areas of the printed circuit boards after assembly and the numerically obtained stress distributions, the failure stress of the boards is determined. Finally, both the retention force of the pins and the degree of damage to the printed circuit boards after assembly are predicted by numerical analysis.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

An example of a compliant press-fit interconnection: (a) cross-sectional photograph and (b) photograph of the A-A section

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Figure 2

Flowchart for determining the linear-hardening elastic-plastic properties of press-fit pins. Step I is for the determination of E and Step II is for the determination of σY and E′.

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Figure 3

Details of the two types of compliant press-fit pins used in this study. (a) shows the top and side views of Pin A and (b) shows those of Pin B.

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Figure 4

Photographs of the three-point bending test. (a) shows the test setup before loading and (b) shows the press-fit pin after loading.

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Figure 6

Stress-strain relationships of the printed circuit board

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Figure 7

Geometrical model of the press-fit assembly for determining μ

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Figure 8

Load-displacement relationships of the loading tip obtained by three-point bending tests for the cases of (a) Pin A and (b) Pin B

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Figure 12

Retention forces for Pin A (a) and Pin B (b) against the diameter of the THs

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Figure 5

FE models of the press-fit assembly for Pin A (a) and Pin B (b)

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Figure 9

Load-displacement relationships of Pin A (a) and Pin B (b) obtained by the press-fit assembly processes, together with the values of F1 obtained by the FEA

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Figure 10

Relationships between A and P (a). The values of μ for Pin A and Pin B against p (b).

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Figure 11

Load-displacement relationships of Pin A during press-fit assembly trials for THs with diameters of 0.94mm and 1.09mm are shown in (a) and (b), respectively. Equivalent values for Pin B are shown in (c) and (d), respectively.

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Figure 13

Cross-sectional photographs obtained at a depth of 0.05mm from the surface of printed circuit boards with Pin A. (a) shows the case for TH with diameters of 0.94mm, (b) 1.01mm, and (c) 1.09mm, respectively. The contour plots of the equivalent von Mises stress (MPa) are shown in the photographs.

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Figure 14

Relationships between the damaged area of the PCB and the diameter of THs for Pin A (a) and Pin B (b)

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