Adsorption Property of Alumina Porous Ceramics“NPP-3D”for Vacuum Chucks
アルミナ系多孔質セラミックス NPP-3D を用いた
真空チャックの吸着特性
Ryuichi MASUMOTO

増本Toshikazu YASUKOCHI龍一

安河内利一

Key words; alumina porous ceramics, vacuum, adsorption property
キーワード ; 多孔質アルミナセラミックス、真空吸着、吸着特性
Abstract
We have previously reported a method to produce a high purity and high strength ceramic material
with micropores without any pore-forming agent which we named “NPP-3D”. In the present study, weevaluated the adsorption property of NPP-3D vacuum chucks and confirmed that NPP-3D vacuum chuckplates and rolls have a “partial adsorption property”. This permits a variety of work sizes with only asingle NPP-3D vacuum chuck plate, and allows flexibility in manufacturing processes using NPP-3Dvacuum chuck rolls.
過去の報告において、造孔剤等の添加物を使用しない一般的な焼結工程で、高純度且つ高強度な多孔質セラミックス（NPP-3D）を製造する方法と、その機械的性質について報告した。
本研究では NPP-3D を用いて製作した真空チャックの吸着特性について評価した。その結果、NPP-3D を用いた真空チャックは高い「部分吸着性」を有し、多様なワークに 1 個の真空チャックで対応可能である事を見出した。NPP-3D を用いることで、従来の真空チャックと比較して、より柔軟にワークの変化に対応する工程設計が可能となると考える。

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1. Introduction
Porous ceramics are commonly used as catalyst carriers or filters, and have recently been used asvacuum carriers or vacuum chucks. We previously developed a high purity and high strength material for
semiconductor-related fields, which we named “NPP-3D”.[1] We showed that NPP-3D has high bending
strength (90 MPa vs. 29 MPa for competing materials) and small pores (0.5 µm vs. 10 µm for competingproducts). In the present study, we evaluate the adsorption property of a vacuum chuck plate and avacuum chuck roll.
Table 1 Mechanical and thermal properties of porous materials [1]2. Experimental
2.1 Vacuum chuck plate
As industrial machines, vacuum chucks are used for fixing or conveyance of various products. In thepresent study, we made a square chuck plate from NPP-3D with an adsorption area of 10,000 mm2 (100mm × 100 mm) and evaluated its adsorption property.
Fig. 1 shows a schematic diagram of the experimental apparatus. We compared the change in internal
vacuum degree with the ratio of work area to adsorption area. We changed the work size from 100 mm2
to 10,000 mm2, maintaining a gap between the work area and the adsorption area to prevent sealing. As
air flows into the vacuum chuck through the gap, the vacuum degree is expected to lower. We used aDA-60D (ULVAC, Inc.) vacuum pump (Pumping speed: 72 L/min, Ultimate vacuum: 3.32×103 Pa).

Fig.1 Schematic of the test chuck plate– 13 –

Nippon Tungsten Review Vol.41 (2017)

Generally, the equation of an adsorption power of a vacuum chuck is expressed byAdsorption power is proportional the vacuum degree and to the porosity of the chuck, and isindependent of pore size of the chuck. However, as shown in Fig. 2, as the ratio of work area toadsorption area decreases, the NPP-3D vacuum chuck prevents the vacuum degree from decreasing.
This is due to the micropores in the NPP-3D; even if there are gaps between work and adsorption area,
the chuck maintains the adsorption ability. We call this “partial adsorption property”.

Fig. 2 Ratio of work area to adsorption area and vacuum degree
Fig.3 shows calculation results using the difference between electrode weights before and after thedischarge as consumption. In Fig. 3, W means Pure-W, and Traditional Th-W and Traditional Ce-W mean
conventional products. The consumption became lower when adding 5 vol% Nd2O3, Sm2O3 and La2O3,
respectively, and NEO-TUN has a wear resistance equivalent to thoriated tungsten.
2.2 Vacuum chuck roll
A manufacturing method called “roll to roll” is commonly used in fields including the manufacture ofrechargeable batteries. Functional films are processed and conveyed by numerous rolls; vacuum chuckrolls are often used. Therefore, we prepared an NPP-3D vacuum chuck roll and evaluated the adsorption
property (Fig. 3).

Nippon Tungsten Review Vol.41 (2017)– 14 –Fig. 3 Appearance of a vacuum chuck roll of the NPP-3D
Conventional vacuum chuck rolls require additional parts to prevent air leakage. In contrast, owing tothe partial adsorption property, NPP-3D vacuum chuck rolls can have a very simple design and still
maintain vacuum power (Fig. 4).

Fig. 4 Benefits of NPP-3D vacuum chuck rolls owing to the partial adsorption property
To evaluate adsorption power of the vacuum chuck roll, a film was adsorbed onto the vacuum roll andpulled in a tangential direction by a spring balancer (Fig. 5). The load was measured when the film wasstripped from the vacuum chuck roll. Measurements were taken at five points, 20, 85, 150, 215 and 280
mm from the end of the vacuum chuck roll (points 1, 2, 3, 4 and 5, respectively), and in directions 0°,90°, 180° and 270° from the vertical (directions A, B, C and D, respectively), as shown in Fig. 6. The
results are shown in Table 2.

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Fig. 5 Experiment to evaluate adsorption power of vacuum chuck rolls
Table 2 Adsorption power (×10-3N/mm2) at each point on roll chuck

Fig. 6 Measuring points of adsorption power on a vacuum chuck roll
We confirmed that the adsorption power required to detach the film in the tangential direction wasapproximately 5.5×10-3N/mm2 and the dispersion was small across all measurement points.

Nippon Tungsten Review Vol.41 (2017)– 16 –3. Conclusion
The adsorption property of NPP-3D vacuum chuck plates and vacuum chuck roll (new porous alumina
ceramics with micropores) were investigated and the following advantages against conventional chuckwere found.
3.1 Vacuum chuck plate
Using a conventional vacuum chuck plate, many chuck plates are required and an appropriate sizemust be selected according to the work size. NPP-3D vacuum chuck plates can maintain a high vacuum
degree of about 90% of the maximum, even if no work is adsorbed, owing to the size of the micropores.
Therefore, even when the area was smaller than adsorption area, the chuck adsorbs the work.
Consequently only one NPP-3D vacuum chuck plate is required for various sizes of work.
3.2 Vacuum chuck roll
The internal structure design of a NPP-3D vacuum chuck roll is simpler than a conventional vacuum
chuck roll. In addition, NPP-3D vacuum chuck rolls are more versatile, because the roll can vacuum
works anywhere on the surface owing to the partial adsorption property.
(a) Vacuum angle
The vacuum angle of a conventional vacuum chuck roll must be decided at the design stage, whereas,
NPP-3D vacuum chuck rolls can change the angle freely owing to the partial adsorption property (Fig. 7).

Fig. 7 Vacuum roll angle for a manufacturing process of films(b) Gaps between the work and the ends of the chuck roll
Even if the work is narrower than the adsorption area of a chuck roll, NPP-3D chuck rolls can adsorb
the work sufficiently without requiring the gaps to be sealed (Fig. 8).

Fig. 8 Gaps between the work and the ends of the chuck roll, such as for narrow films– 17 –

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(c) Adsorption of unique shape of works
NPP-3D vacuum chuck rolls can adsorb and carry uniquely shaped works, such those with holes,
owing to the partial absorption property.

Fig. 9 Uniquely shaped of films for absorption

References[1] T. Yasukochi, M. Takasu, M.Nagano, and S.Sakaguchi:”Mechanical properties of high-purity, highstrength porous alumina ceramics”, Nippon Tungsten Review, 35(2003)19-23

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