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. 2018 Jan 19;11(1):160.
doi: 10.3390/ma11010160.

Quadrilateral Micro-Hole Array Machining on Invar Thin Film: Wet Etching and Electrochemical Fusion Machining

Woong-Kirl Choi  1 , Seong-Hyun Kim  2 , Seung-Geon Choi  3 , Eun-Sang Lee  4
Affiliations

Quadrilateral Micro-Hole Array Machining on Invar Thin Film: Wet Etching and Electrochemical Fusion Machining

Woong-Kirl Choi et al. Materials (Basel). .

Abstract

Ultra-precision products which contain a micro-hole array have recently shown remarkable demand growth in many fields, especially in the semiconductor and display industries. Photoresist etching and electrochemical machining are widely known as precision methods for machining micro-holes with no residual stress and lower surface roughness on the fabricated products. The Invar shadow masks used for organic light-emitting diodes (OLEDs) contain numerous micro-holes and are currently machined by a photoresist etching method. However, this method has several problems, such as uncontrollable hole machining accuracy, non-etched areas, and overcutting. To solve these problems, a machining method that combines photoresist etching and electrochemical machining can be applied. In this study, negative photoresist with a quadrilateral hole array pattern was dry coated onto 30-µm-thick Invar thin film, and then exposure and development were carried out. After that, photoresist single-side wet etching and a fusion method of wet etching-electrochemical machining were used to machine micro-holes on the Invar. The hole machining geometry, surface quality, and overcutting characteristics of the methods were studied. Wet etching and electrochemical fusion machining can improve the accuracy and surface quality. The overcutting phenomenon can also be controlled by the fusion machining. Experimental results show that the proposed method is promising for the fabrication of Invar film shadow masks.

Keywords: Invar film; electrochemical machining; fusion machining; micro-hole array; wet etching.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
SEM image of DFR (Dry Film Resist) -coated Invar thin film.
Figure 2
Figure 2
Sectional SEM image of DFR coated Invar thin film.
Figure 3
Figure 3
Invar film wet etching isotropic characteristics.
Figure 4
Figure 4
Principle of the electrochemical machining (ECM) process.
Figure 5
Figure 5
Schematic diagram of wet etching system.
Figure 6
Figure 6
Invar film single side wet etching material removal rate.
Figure 7
Figure 7
SEM images of Invar thin film after wet etching (photoresist coating face etching) for 5 min.
Figure 8
Figure 8
SEM images of Invar thin film after wet etching (photoresist coating face etching) for 10 min.
Figure 9
Figure 9
SEM images of Invar thin film after wet etching (photoresist coating face etching) for 15 min.
Figure 10
Figure 10
Schematic diagram of the electrochemical machining system.
Figure 11
Figure 11
SEM images of Invar film machined surface produced by (a) wet etching, (b) electrochemical machining.
Figure 12
Figure 12
Wet etching and electrochemical fusion machining (photoresist coating face etching).
Figure 13
Figure 13
SEM images of Invar thin film after wet etching for 2 min (photoresist coating face etching).
Figure 14
Figure 14
SEM images of 30 min electrochemical machined Invar thin film after wet etching (photoresist coating face etching) for 2 min.
Figure 15
Figure 15
Wet etching and electrochemical fusion machining (photoresist coating opposite face etching).
Figure 16
Figure 16
SEM images of 30 min electrochemical machined Invar thin film after wet etching (photoresist coating opposite face etching) for 2 min.
Figure 17
Figure 17
SEM images of 15 min electrochemical machined Invar thin film after wet etching (photoresist coating opposite face etching) for 5 min.
Figure 18
Figure 18
SEM images of 5 min electrochemical machined Invar thin film after wet etching (photoresist coating opposite face etching) for 10 min.
See this image and copyright information in PMC

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