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Research Papers

Microcutting and Forming of Thin Aluminium Foils for MEMS

[+] Author and Article Information
Christian D. Damsgaard

Department of Micro- and Nanotechnology,  Technical University of Denmark, DTU Nanotech building 345E, DK-2800 Lyngby, Denmarkchristian.damsgaard@nanotech.dtu.dk

Dennis Mortensen

Pirmin Rombach

EPCOS AG, Filial af EPCOS AG, Tyskland, A Group Company of TDK-EPC Corporation, SAW WT MEMS MICR DK Diplomvej 372, DK-2800 Kgs. Lyngby, Denmarkpirmin.rombach@epcos.com

Ole Hansen1

Department of Micro- and Nanotechnology,  Technical University of Denmark, DTU Nanotech building 345E, DK-2800 Lyngby, Denmarkole.hansen@nanotech.dtu.dk

1

Also at Center for Individual Nanoparticle Functionality (CINF), Technical University of Denmark, Denmark.

J. Manuf. Sci. Eng 133(6), 061015 (Dec 09, 2011) (6 pages) doi:10.1115/1.4003810 History: Received May 17, 2010; Revised February 21, 2011; Published December 09, 2011; Online December 09, 2011

This paper presents a simple procedure for simultaneous cutting and forming of thin Al foils for use in MEMS components. The procedure makes use of scaled down macroscopic sheet forming and cutting techniques by using a hydraulic press, a soft counterpart, and a microfabricated stamp tool. The relation between applied pressure and forming and cutting features has been characterized for a specific set of stamp geometries and boundary conditions. The results show that 10 μm forming features can be transferred to 4 μm thick Al foils, which simultaneously can be cut into products by 25 μm wide cut lines. Using the procedure presented in this paper scaled to full 4–8 in. silicon wafer stamp tools, a fast and adequate method for high volume production of MEMS components is obtained.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Sketch of setup. The Al foil is positioned between a Si stamp tool and a soft stamp counterpart and processed in a hydraulic press

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Figure 2

Schematic overview of the investigated parameters on the stamp tool and formed and cut Al foil. Upper case symbols denote dimensions on the stamp tool, whereas dimensions on the foil product are denoted by lower case symbols

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Figure 3

Schematic of the fabrication process for Si stamp tool. The process consists of two DRIE steps defining the forming and cutting structures, respectively. The stamps are completed by a final FDTS antistiction coating and diced into 1.2 × 1.2 cm2 pieces.

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Figure 4

(a) SEM-image of a used Si stamp tool with 1.95 ± 0.1 μm forming structures (protrusions), surrounded by a 28 ± 1.4 μm deep and 50 μm wide cut structure. Al residues are observed in the cut structures. (b) and (c) show some of the forming structures at higher magnification.

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Figure 5

Optical profilometer topography plot of a Si stamp tool with 1.94 ± 0.05 μm forming structures (protrusions), surrounded by a 7.52 ± 0.05 μm deep and 150 μm wide cut structure

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Figure 6

(a) SEM-image of the stamp counterpart side of an Al foil product fabricated at 48.6 MPa with forming structures (protrusions), surrounded by a 50 μm wide cut-out. (b) and (c) SEM-images of the stamp counterpart side of an Al foil product at higher magnification.

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Figure 7

Minimum cut width versus stamping pressure for a stamp tool with a 28 ± 1.4 μm deep cut structure. The bold line shows the best linear fit. The dashed lines indicate regions in which the foils products either were not cut or had severe adhesion to the stamp tool, respectively.

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Figure 8

Overall minimum cut width versus cut structure depth. The dashed lines indicate regions in which the foils products were either not cut or had nonuniform cutting and severe adhesion to the stamp tool, respectively.

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Figure 9

SEM-images of the cut-edge of an Al foil product fabricated at 46 MPa with a stamp tool cut depth of 28 ± 1.4 μm: (a) is taken along the stamp side toward the edge and (b) is taken from the front of the edge

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Figure 10

SEM-image of the cut-edge of an Al foil product fabricated at 20.8 MPa with a stamp tool cut depth of 28 ± 1.4 μm. The inset shows an incomplete cut-out.

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Figure 11

Optical profilometer topography scan of an Al foil product fabricated at 48.6 MPa overlaid on a SEM image. The SEM-image is scaled to the plot and shows another Al foil product also fabricated at 48.6 MPa. The circular line indicates the contour of the stamp structure used. The dashed lines indicate the fully formed structure width and foil forming line width.

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Figure 12

Optical profilometer topography plot of the stamp counterpart side of an Al foil product fabricated at 41.7 MPa with forming structures (protrusions), surrounded by a 50 μm wide cut-out. The white pixels are areas which the profilometer cannot resolve either due to steep slopes or lack of foil material.

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Figure 13

Foil forming line width and forming height versus stamping pressure for a stamp tool with a forming height of 1.95 ± 0.1 μm. The error bars are defined by the standard deviation of five separate measurements. The dashed lines indicate regions in which the foils were either not cut or had severe adhesion to the stamp tool, respectively.

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