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Research Papers

Vacuum Venting Enhances the Replication of Nano/Microfeatures in Micro-Injection Molding Process

[+] Author and Article Information
Seong Ying Choi

School of Mechanical and Materials Engineering,
University College Dublin,
Belfield, Dublin 4, Ireland
e-mail: seong.choi@ucd.ie

Nan Zhang

School of Mechanical and Materials Engineering,
University College Dublin,
Belfield, Dublin 4, Ireland
e-mail: nan.zhang@ucd.ie

J. P. Toner

School of Mechanical and Materials Engineering,
University College Dublin,
Belfield, Dublin 4, Ireland
e-mail: jp.toner@ucdconnect.ie

G. Dunne

School of Mechanical and Materials Engineering,
University College Dublin,
Belfield, Dublin 4, Ireland
e-mail: garreth.dunne@ucdconnect.ie

Michael D. Gilchrist

Professor
Mem. ASME
School of Mechanical and Materials Engineering,
University College Dublin,
Belfield, Dublin 4, Ireland
e-mail: michael.gilchrist@ucd.ie

1Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO- AND NANO-MANUFACTURING. Manuscript received July 22, 2015; final manuscript received February 25, 2016; published online March 24, 2016. Assoc. Editor: Martin Jun.

J. Micro Nano-Manuf 4(2), 021005 (Mar 24, 2016) (7 pages) Paper No: JMNM-15-1054; doi: 10.1115/1.4032891 History: Received July 22, 2015; Revised February 25, 2016

Vacuum venting is a method proposed to improve feature replication in microparts that are fabricated using micro-injection molding (MIM). A qualitative and quantitative study has been carried out to investigate the effect of vacuum venting on the nano/microfeature replication in MIM. Anodized aluminum oxide (AAO) containing nanofeatures and a bulk metallic glass (BMG) tool mold containing microfeatures were used as mold inserts. The effect of vacuum pressure at constant vacuum time, and of vacuum time at constant vacuum pressure on the replication of these features is investigated. It is found that vacuum venting qualitatively enhances the nanoscale feature definition as well as increases the area of feature replication. In the quantitative study, higher aspect ratio (AR) features can be replicated more effectively using vacuum venting. Increasing both vacuum pressure and vacuum time are found to improve the depth of replication, with the vacuum pressure having more influence. Feature orientation and final sample shape could affect the absolute depth of replication of a particular feature within the sample.

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Figures

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Fig. 1

(a) Cassette mold showing AAO mold template (arrow, left) and BMG mold strips (right); (b) cassette mold connected to vacuum pump; (c) illustration of mold cross section; and (d) sample shape (front view) and feature location for quantitative analysis

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Fig. 2

SEM images of (a) AAO template, (b) COC samples under no vacuum, (c) COC sample under ∼−33.25 kPa for 3 s, (d) COC sample under ∼−65 kPa for 3 s, (e) COC sample under ∼−33.25 kPa for 10 s; and (f) COC sample under ∼−65 kPa for 10 s (scale bar: 1 μm)

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Fig. 3

SEM image of FIB features on BMG: (a) position of features (scale bar: 300 μm), (b) horizontal channels (scale bar: 50 μm), (c) vertical channels (scale bar: 40 μm), and (d) 45 deg channels (scale bar: 50 μm). The arrow represents direction of gate from the microfeatures.

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Fig. 4

Depth replication (%) as a function of maximum vacuum gauge pressure applied for (a) horizontal channels, (b) vertical channels, and (c) 45 deg channels, at constant vacuum time 2 s for channels 1–7 (n = 3)

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Fig. 5

Depth replication (%) as a function of vacuum time applied for (a) horizontal channels, (b) vertical channels, and (c) 45 deg channels, at constant vacuum gauge pressure of ∼45 kPa for channels 1–7 (n = 3)

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Fig. 6

Effect of different channel directions on depth of replication at (a) control condition (no vacuum applied), (b) maximum vacuum gauge pressure of ∼−45 kPa at 2 s vacuum time; (c) maximum vacuum gauge pressure ∼−65 kPa at 2 s vacuum time; and (d) vacuum gauge pressure of vacuum time of ∼−45 kPa at 2 s vacuum time. Note: comparison of (b) and (c) for different vacuum gauge pressures and comparison of (b) and (d) for different vacuum time.

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