Progress in atmospheric pressure sintering process of ITO target

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In the early 1990s, a new target sintering method, atmospheric pressure sintering, was developed By controlling the factors in the sintering process, the growth of ITO green grain can be effectively controlled, so as to achieve the uniform distribution and high densification of the target. This method has high requirements for the sintering activity of the powder and the control of the target deformation.

Generally, the larger the target size, the less the seam on the plate, and the higher the value. Foreign countries can make a single target with a width of 1200 mm and a length of nearly 3000 mm, while in China, only those with a width of no more than 800 mm can be manufactured.

Preparation process of ITO in Japan

1. Tosoh Corp

According to the patent of toko company of Japan, ITO powder with particle size less than 1 μ m is put into a ball mill with steel core nylon ball. After milling for 60 h, the blank is pressed by cold isostatic pressing and die pressing, and then sintered under normal pressure. After sintering, the final target density is 7.06 g / cm3. In the problem of target material deformation, the traditional atmospheric pressure sintering is that the prepared blank is directly sintered on the corundum plate in the furnace. Because of the friction between the corundum plate and the bottom surface of ITO blank, the shrinkage of the upper and lower contact surfaces is inconsistent, which leads to the deformation of the sample. According to the patent of Dongcao company of Japan, a layer of alumina powder is laid on the corundum plate, and then the blank is placed on the powder. The sintering temperature is 1590 ℃, the sintering time is 5h, and the sintering atmosphere is oxygen. After sintering, the target density can reach 99.5%, thus solving the problem of target deformation.

2. Mitsui Metal Co., Ltd

Ultra high density ITO target was prepared by MMF (filter forming die).

(1) Embryo molding

The raw material powder, ion-exchange water and 5mm zirconia ball mixed with indium tin oxide were put into the tank made of resin, and then milled and mixed for 20 hours; organic additives (polycarboxylic acid dispersant) were added for mixing for 1 hour; after 1 hour, appropriate wax binder was added, and ball milling mixing was conducted for 19 hours. The formed slurry is injected into a filter type forming die composed of non water soluble materials to obtain a body by decompressing and draining water from the ceramic raw material, and the water in the slurry is reduced and drained to form a body, and the formed body is dried and degreased.

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Plate forming die

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Concave convex shape forming die

1. Slurry 2. Upper molding frame 3. Lower molding frame 4. Filter membrane (wet filter cloth) 5. Filling material 6. Drainage hole

Schematic diagram of Mitsui mmf-ito forming device


(2) Sintering

The mixture of indium oxide and tin oxide is made into shape by filter forming die method, dried and degreased (400 ℃ - 600 ℃), and the obtained formed body is heated to the highest sintering temperature of 1580 ℃ - 1700 ℃ (preferably 1600 ℃ - 1650 ℃), and the holding time of the highest sintering temperature is set to less than 300 seconds, and then it is cooled to the second sintering temperature of 1400 ℃ - 1 The method is characterized in that the holding time of the second sintering temperature is set to be 3 to 18 hours, and then the temperature is cooled to room temperature, which is characterized in that the holding time of the second sintering temperature is set as a non oxidizing gas environment at a time point of at least 1 to 4 hours (preferably 2 to 3 hours), and comprises the steps of setting the holding time of the second sintering temperature as a non oxidizing gas environment at an average cooling rate of 10 ℃ - 100 ℃ / min When the sintering temperature is lowered to 400 ℃ (the parent phase of In2O3 and the fine particles of in2sn3o12 will not grow up), the high density ITO sintered body is obtained.

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Mitsui Metal Corporation ITO strip, whole piece ceramic target


By selecting the specific surface area of indium oxide and tin oxide raw materials in a proper range, the forming method of filter type forming die invented by Mitsui Metal Mining Co., Ltd. can obtain large-scale high-density ITO sinter without defects such as uneven density and composition; the pressure of the forming die and decompression drainage is only applied to the filtration Therefore, the material with lower strength can be used as the lower die for forming. Even if the forming size is increased, the material cost can be kept low.

Domestic ITO manufacturers

At present, there are more than 20 domestic ITO target materials enterprises. After years of development, they have gradually evolved from small-scale production to large-scale production. The main enterprises are Jinglian optoelectronic (Longhua Technology), ashchuang, Xianxian rare materials, Zhuzhou Smelter Group, Yina optoelectronics, medium target new materials, metallurgical science and technology, etc.

1. Guangxi Jinglian photoelectric material Co., Ltd

Its patent The normal pressure sintering method of TFT grade ITO target material: select ultra-high activity ITO nano powder, press the granulating ITO powder through molding, the molding pressure is 25-80 MPa, holding time is 15-300 seconds; then, it is reinforced by cold isostatic pressing, the isostatic pressure is 180-300 MPa, and the holding time is 300-1200 seconds; then, it is directly put into the sintering furnace, the atmosphere is introduced and the temperature is raised in several stages at a certain heating rate At a certain rate, the sintering is completed by cooling to room temperature.


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2. Guangdong Xianfeng thin material Co., Ltd

Its patent The preparation method of high-purity and high-density ITO target: making homemade ITO powder and pure water into slurry, then adding dispersant, grinding in the sand mill, then adding binders and defoamers for ball milling, and then spraying granulation to obtain ITO granulating powder. The ITO granulation powder is loaded into the mould to preform the ITO initial billet, and the resulting ITO initial blank is formed on the cold isostatic pressing machine to get ITO. The ITO target with high purity and high density can be obtained by debinding the ITO blank in a degreasing furnace and then sintering in an oxygen atmosphere sintering furnace.

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According to the market demand, Haoyue technology has continuously developed and improved its technology. It has launched ITO target sintering furnace with excellent performance to assist the domestic high-end target market, providing large-scale flat plate sintering furnace (square meter target) and tube target sintering furnace (rotating target), providing perfect heat treatment solutions for domestic target manufacturers.

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Haoyue Technology is a high-tech enterprise integrating R & D, production and sales of electric furnace. The company has been focusing on advanced ceramics and composite materials, semiconductor materials, carbon materials, lithium batteries and new energy materials equipment four major fields, has rich industry experience and professional technology, wholeheartedly serves customers and provides perfect integrated industrial solutions.

 





Updated date: 2020-11-02

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