Vol.1 No.2 2008

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Research paper : The aerosol deposition method (J. Akedo et al.)−127 Synthesiology - English edition Vol.1 No.2 (2008) a manufacturing system using forming and processing technologies for functional material with immediate demand which includes the AD method, laser process, and ink jet method, that allows speed and diversity of mechanical processing as shown in Figure 9. We aimed for a manufacturing process that can handle multi-product variable production masklessly even though the manufacturing process was for electronic functional devices. Below are described the results of these investigations. Due to simplicity of its principle, the AD method holds potential of shifting the scale of device from role-to-role to desktop. Figure 10 shows some AD device prototypes at various scales. Currently, the largest size is a device with coating surface of 50 cm square, while the smallest is less than 1 cm2 in size. A small AD device has performed successfully in trial coating in zero gravity aircraft for potential use in a space station.For the equipment that includes AD created as prototype for manufacturing of aforementioned metal base optical scanner (Figure 9), the chamber size was optimized so as a single device would fit into 2 cm square area. In the actual production system, as shown in Figure 11, since mechanisms for automatic delivery and automatic alignment of sample must be added, the sample holder was installed in the chamber lid to enable reduction of tact time for transfer and positioning of the samples. The chamber lid with holder can be moved vertically by piston cylinder driven by compressed air. This allows the conveyor arm to set the sample, the lid to close, and vacuuming to start in less than 0.2 sec. The prototype system seem to be advantageous since high vacuum level is not required for coating using the AD method; and evacuation and vacuum leak time of the coating chamber are significantly reduced by down-scaling the coating device.Since the vacuum level necessary in AD method was about 100 Pa (during coating), high-speed evacuation at low vacuum range was necessary. By designing the whole chamber volume (up to gate valve) at extremely small scale, about 75 cm3, to match the sample size, coating became possible in about 3 sec after using a single small size rotary pump with 15~20 m3/min throughput to achieve 2 Pa. Atmospheric pressure after AD deposition was reached in 0.7 sec from about 0.1 Pa. Coating speed depends on the performance of the aerosol chamber. Although it is not satisfactory at this point, a coating rate of around 1 µm/sec can be achieved under current conditions.In the above design, for coating PZT thick film of 3 micrometers on 5 mm square surface area, time required for the processes of substrate insertion → evacuation → coating → vacuum leak → substrate retrieval was reduced dramatically to about 10 sec, as shown in Figure 12. This revolutionizes the conventional understanding that vacuum process must be done as a batch process, and is a major point in achieving on-demand production.In the punching process for forming the scanner body structure, 4 progressive divisions were set for mirror, torsion beam, entire scanner frame formation, and positioning holes. 4 micro-press mechanisms punched out the stainless steel ・High speed coating is possible : Reduction in actual coating time ~6 s・Room temperature impact consolidation : Heating of sample is unnecessary ~0 s・Coating on necessary parts only : Chamber size is reduced →Reduction in vacuuming/leak time ~2 s each →Time needed for sample removal (into atmosphere) is sped up ~1.5 sTotal time (time required from sample insertion to removal)~10 sSputter coating deviceHigh vacuum necessary (10-5 ~ 10-6 Pa)TMP usedLow coating speed (20 nm/min or less)Long tact time (3~5 hrs)High substrate temperature (550~600 °C)Chamber volume : ~1/2000Low vacuum : One rotary pumpFig. 11 Improvement of tact time by downsizing.-1012345678Time elapsed (sec) Vacuum level (Pa)1000010001001010.1-0.50.51.52.5Time elapsed (sec) Vacuum level (Pa)10000100000010001001010.1(Evacuation time)(Leak time)Fig. 12 Speed required to reach vacuum level where coating is possible, and leak time in a small AD device.(55)−

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