Compositions: ceramic – Ceramic compositions – Refractory
Patent
1995-12-07
1998-04-28
Marcheschi, Michael
Compositions: ceramic
Ceramic compositions
Refractory
501 986, 501 984, 501152, 428698, 428704, 428901, 4273833, 264 61, 264 65, C04B 35581, C04B 35582
Patent
active
057444110
DESCRIPTION:
BRIEF SUMMARY
This application is made under 35 United States Code section 371 of international application number PCT/US94/04256, filed Apr. 18, 1994.
BACKGROUND OF THE INVENTION
The invention relates to a sintered body of aluminum nitride (AIN) with high thermal conductivity and a process for preparing the sintered body at a relatively low sintering temperature. The invention relates more particularly to ternary sintering aid combinations that enable preparation of the sintered body at temperatures of 1850.degree. Centigrade (.degree.C.) or less, preferably 1650.degree. C. or less. The sintered body is suitable for use in a variety of known applications including integrated circuit substrates, integrated circuit heat sinks and packaging components or multichip module components. The sintered body may also be used in structural applications such as crucibles and components of armor.
AIN is an excellent material having a high thermal conductivity, insulation resistance and a low thermal expansion coefficient among its desirable properties. However, since AIN is a covalent bonding compound, it is quite difficult to produce a pure AIN sintered product without using sintering aids or a hot-press sintering method.
Sintered AIN bodies are typically prepared by heating an admixture of AIN powder and one or more sintering aids to a temperature within a range of from 1500.degree. C. to as high as 2100.degree. C. in an atmosphere that promotes sintering. The sintering aids typically include one or more oxides of alkaline earth metals or oxides of rare earth metals. Kasori et al. (U.S. Pat. No. 4,746,637) use a sintering aid combination of yttrium oxide (Y.sub.2 O.sub.3) and calcium oxide (CaO) to sinter AIN powder at a temperature of 1650.degree. C. or above. Other sintering aids may be used in place of, or in addition to, the alkaline earth metal oxides and rare earth metal oxides. Okuno et al. (U.S. Pat. No. 4,877,760) use at least one boride, carbide or nitride of titanium, zirconium, hafnium, vanadium, niobium or tantalum or boride or carbide of chromium, molybdenum or tungsten and, optionally, other sintering additives such as alkaline earth metal oxides and rare earth metal oxides. The sintering aids, including optional sintering aids, should not exceed 5 parts by weight per 100 parts by weight of AIN.
JP H03-146471 discloses mixtures of at least one oxide of yttrium, scandium or a lanthanide and at least one of lanthanum hexaboride (LaB.sub.6), magnesium hexaboride and calcium hexaboride as sintering aids. JP H03-197366 discloses mixtures of calcium oxide and LaB.sub.6 as sintering aids. These combinations of sintering aids lead to AIN sintered products that show a high thermal conductivity, but prefer a sintering temperature of 1900.degree. C. or above. Such temperatures make it necessary to use an expensive high temperature sintering furnace and fittings, such as a setter, capable of use at those temperatures. In addition, such temperatures result in high energy costs.
JP H04-130064 discloses sintering aids that are mixtures of a boron based compound such as boron nitride, boron carbide, boron oxide or boron fluoride, at least one oxide, carbide, nitride, or boride of titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, zirconium, molybdenum, cadmium, tin or tungsten and at least one alkaline earth metal oxide or rare earth metal oxide.
SUMMARY OF THE INVENTION
A first aspect of the invention is a process for producing an aluminum nitride (AIN) sintered product with a high thermal conductivity at a relatively low sintering temperature. For this aspect, an AIN powder having a specific surface area in a range of about 3 to 8 m.sup.2 /g, and preferably 4.5 to 7.5 m.sup.2 /g, and an oxygen content between 0.5 and 1.8 wt %, is used. Optimum amounts of sintering aids are combined with the AIN powder. The sintering aids substantially constitute a combination of three sintering aids (I), (II) and (III). Sintering aid (I) is at least one selected from the group consisting of rare earth oxides and rare earth c
REFERENCES:
patent: 4711861 (1987-12-01), Sawamura et al.
patent: 4877760 (1989-10-01), Okuno et al.
patent: 5242872 (1993-09-01), Taniguchi et al.
patent: 5314850 (1994-05-01), Miyahara
patent: 5330692 (1994-07-01), Hashimoto et al.
patent: 5424261 (1995-06-01), Harris et al.
Chiao Yi-Hung
Guiton Theresa A.
Hashimoto Noboru
Kajita Susumu
Rafaniello William
Marcheschi Michael
The Dow Chemical Company
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