JP2008088022A - Method of manufacturing aluminum nitride substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a low cost aluminum nitride substrate capable of preventing occurrence of stain using an inexpensive setter having high durability and small glass absorption. <P>SOLUTION: The method of manufacturing the aluminum nitride substrate 10 by firing the laminated body 11 of a green sheet containing a sintering assistant to form a degreased body 15 and sintering to form the sintered compact includes: a step of placing the laminated body 11 on an Mo plate 12, covering the outer periphery with an Mo spacer 13 and the Mo plate 12 and firing the body 11 to form a degreased body 15; a step of holding the both side surfaces of the degreased body 15 with the aluminum nitride setters 16 formed by powder-press-molding granulated power comprising aluminum nitride powder having ≥99.5% purity and substantially containing no sintering assistant and firing to sinter at 1,850-1,950°C for 10-15 hr by a normal pressure firing method; and a step for placing the degreased body 15 on the Mo plate 12, covering the outer periphery with the Mo spacer 13 and the Mo plate 12 and firing to obtain the sintered compact. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing an aluminum nitride substrate having high substrate strength, excellent chemical resistance, high thermal conductivity, and high electrical insulation.

  An aluminum nitride substrate is used as a heat-resistant material because it has high substrate strength from a room temperature to a high temperature range and excellent chemical resistance. In addition, the aluminum nitride substrate is mounted with a light emitting element such as a light emitting diode (hereinafter referred to as an LED) as a heat dissipation material for generating heat from the semiconductor element by utilizing high thermal conductivity and high electrical insulation. It is used as a light emitting element storage package for storage. The aluminum nitride substrate used in this manner is normally used as a sintered body because aluminum nitride itself does not have a melting point and decomposes at a high temperature of about 2200 ° C. or higher. Since this aluminum nitride sintered body has poor sinterability when an aluminum nitride powder is used alone, it is difficult to produce a high-density sintered body other than sintering by a hot press method. ing. In order to sinter the sintered body at normal pressure, a sintering aid such as rare earth oxide or alkaline earth metal oxide is added to the aluminum nitride powder and fired at a high temperature of about 1700 to 1850 ° C. This makes it possible to produce a sintered body having a considerably high density and high thermal conductivity.

As shown in FIG. 4, the aluminum nitride substrate 50 made of this sintered body is usually formed by superposing a plurality of sheets by forming a conductor wiring pattern on a sheet-like ceramic green sheet of aluminum nitride containing a sintering aid. After the laminated body 51 is formed by applying temperature and pressure, a ceramic green sheet and a conductor wiring pattern are simultaneously fired to form a degreased body, and further fired to produce a sintered body. In order to produce a degreased body and a sintered body from the laminate 51, the laminate 51 is placed on a refractory metal plate 52 such as molybdenum (Mo), and the refractory metal around the laminate 51 is placed. A spacer 53 made of a metal block of Mo is placed on the plate 52 so as to close the laminated body 52, and a plurality of layers in this state are stacked, and the uppermost layer is further covered with a refractory metal plate 52. The assembly 54 is closed. Then, the assembly 54 is, after degreasing was 4-6 hours firing 1300-1400 ° C. in a _N 2 / _{H 2} atmosphere metal firing furnace made of Mo furnace wall, of the same metal sintering furnace _{N 2} The aluminum nitride substrate 50 is fabricated by firing and sintering at 1650 to 1750 ° C. for 5 to 7 hours in a / H ₂ atmosphere.

However, when the laminate 51 is degreased and then directly placed on the refractory metal plate 52 such as molybdenum (Mo) and sintered, the glass from the sintering aid in the laminate 51 is used. The components are extracted into the refractory metal plate 52 and scratches are generated on the surface of the aluminum nitride substrate 50. Therefore, as shown in FIG. 5, when the degreased body 55 is sintered, the degreased body 55 is sandwiched from both sides by a setter 56 made of aluminum nitride. Further, the sandwiched material is placed on a high melting point metal plate 52 such as Mo, surrounded by a spacer 53 made of a metal block of Mo, a plurality of layers in this state are stacked, and the uppermost layer has a higher melting point. The metal plate 52 is covered with a lid. The degreased body 55 is fired at 1650 to 1750 ° C. for 5 to 7 hours in an N ₂ / H ₂ atmosphere of a metal firing furnace made of a Mo furnace wall to produce a sintered aluminum nitride substrate 50. .

As a conventional method of manufacturing an aluminum nitride substrate, a method using a setter obtained by sintering a ceramic green sheet of aluminum nitride by a hot press method has been proposed (for example, see Patent Document 1).
Further, as a conventional setter, one using an aluminum nitride sintered body that does not use a sintering aid has been proposed (for example, see Patent Document 2).
Furthermore, a conventional setter has been proposed that uses a sintered body of aluminum nitride containing a sintering aid for hexagonal boron nitride (see, for example, Patent Document 3).

JP-A-5-105526 JP-A-6-199573 JP 2003-246675 A

However, the conventional method for manufacturing an aluminum nitride substrate as described above has the following problems.
(1) When a degreased body of an aluminum nitride substrate containing a sintering aid is sandwiched between aluminum nitride setters and sintered, the glass component to be diffused from the degreased body to the aluminum nitride setter side is glass in the aluminum nitride setter. If it is absorptive, spots are generated on the surface of the aluminum nitride substrate, resulting in a deterioration in quality on appearance.
(2) When the setter is made of aluminum nitride containing a sintering aid such as hexagonal boron nitride in order to prevent the generation of spots on the aluminum nitride substrate surface, a normal pressure firing method at a relatively low temperature Although the setter can be made cheaper by sintering with glass, and the glass absorbability can be made smaller, the strength of the setter is reduced, so deformation is likely to occur with repeated use and the life is shortened. It has become.
(3) When an aluminum nitride setter that does not use a sintering aid is sintered by high-temperature hot pressing or the like, the setter has high strength and can withstand repeated use of the setter. This increases the cost of the aluminum nitride substrate.
The present invention has been made in view of such circumstances, and provides an inexpensive aluminum nitride substrate manufacturing method that prevents the occurrence of spots using an inexpensive setter having high durability and low glass absorbability. With the goal.

  The method for manufacturing an aluminum nitride substrate according to the present invention in accordance with the above object is to degrease and fire a laminated body of aluminum nitride green sheets containing a sintering aid to form a degreased body, and then sinter the sintered body. In the method for manufacturing an aluminum nitride substrate to be formed, a step of forming a degreased body by placing the laminate on a molybdenum plate and degreasing and firing so as to close the outer periphery with a molybdenum spacer and a molybdenum plate; After a granulated powder composed of 99.5% or more aluminum nitride powder substantially containing no sintering aid is powder press-molded, it is sintered by a normal pressure firing method at 1850 to 1950 ° C. for 10 to 15 hours. A process of sandwiching both surfaces with an aluminum nitride setter, and placing a degreased body sandwiched between aluminum nitride setters on a molybdenum plate with a molybdenum spacer and a molybdenum plate. A step of forming a sintered body by sintering so as to block the periphery.

  Here, in the above method for manufacturing an aluminum nitride substrate, the aluminum nitride setter preferably has an aluminum nitride average particle diameter of 20 to 30 μm and a flat surface whose surface is ground.

  The method of manufacturing an aluminum nitride substrate according to claim 1 or claim 2 dependent thereon, wherein the laminate is placed on a molybdenum plate and degreased and fired so as to block the outer periphery with a molybdenum spacer and a molybdenum plate. And then forming a degreased body by powder press-molding a granulated powder composed of 99.5% or more of aluminum nitride powder substantially containing no sintering aid, followed by 1850-1950 ° C., 10 A process of sandwiching both surfaces with an aluminum nitride setter that is sintered by an atmospheric pressure firing method for 15 hours, and a degreased body sandwiched between aluminum nitride setters is placed on a molybdenum plate, and is removed with a molybdenum spacer and a molybdenum plate. Since it has a step of forming a sintered body by sintering so as to close the periphery, it is contained in a ceramic green sheet using a dense, highly durable and inexpensive setter. It is possible to provide a manufacturing method of an inexpensive aluminum nitride substrate to prevent ingestion stain occurrence of prevention to an aluminum nitride substrate surface after sintering to setter sintering aid.

  In particular, in the method for manufacturing an aluminum nitride substrate according to claim 2, since the aluminum nitride setter has an aluminum nitride average particle size of 20 to 30 μm and a flat surface whose surface is ground, the ceramic green sheet of the aluminum nitride substrate This prevents the sintering aid contained in the setter from sucking into the setter and prevents the surface of the aluminum nitride substrate from being stained after sintering. A manufacturing method can be provided.

Subsequently, the best mode for carrying out the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention.
1A to 1C are explanatory views of a method of manufacturing an aluminum nitride substrate according to an embodiment of the present invention, FIG. 2 is a manufacturing process diagram of the aluminum nitride substrate, and FIG. It is a manufacturing process figure of the setter used with the manufacturing method of an aluminum substrate.

  The aluminum nitride substrate manufactured by the method for manufacturing an aluminum nitride substrate according to one embodiment of the present invention has various forms for mounting a semiconductor element or the like. For example, a light-emitting element storage package for mounting a light-emitting element such as an LED has a polygonal inner periphery on a flat plate-shaped aluminum nitride substrate having a rectangular shape, a polygonal shape, a circular shape, or the like in plan view. In addition, the frame is made of a window frame-shaped ceramic made of a round shape or the like, a rectangular shape, a polygonal shape, a circular shape, or the like, or a frame made of a metal, a resin, or the like. In this light emitting element storage package, the light emitting element can be mounted on the cavity formed by the upper surface of the aluminum nitride substrate exposed from the opening of the frame and the wall surface of the opening of the frame. This aluminum nitride substrate is fired by a normal pressure sintering method at a firing temperature of about 1700 ° C. to 1800 ° C., and the heat conductivity after sintering can be extremely high as 160 to 180 W / mK. Heat generated from the light emitting element to be stored can be efficiently transferred and radiated to the outside.

  In order to form the substrate with high thermal conductivity and high translucency, aluminum nitride for forming the above aluminum nitride substrate may employ a hot press method for more complete sintering. is there. However, the sintering by the hot press method increases the cost of the aluminum nitride substrate because of the large equipment and lack of mass productivity. Therefore, in order to form an inexpensive aluminum nitride substrate, it is necessary to use a normal pressure sintering method. By this atmospheric pressure sintering method, an aluminum nitride substrate can be manufactured with a high productivity and an inexpensive substrate.

Next, a method for manufacturing the aluminum nitride substrate 10 will be described with reference to FIGS. 1 (A) to 1 (C), FIG. 2 and FIG.
As shown in FIGS. 1A to 1C, a method for manufacturing an aluminum nitride substrate 10 according to an embodiment of the present invention includes stacking a plurality of ceramic green sheets before the aluminum nitride substrate 10 is sintered. A laminated body 11 is used. A method for manufacturing the aluminum nitride substrate 10 from the production of the ceramic green sheet to the sintering of the laminate 11 will be described below with reference to the manufacturing process diagram shown in FIG.

(1) Ceramic Green Sheet Manufacturing Step For the aluminum nitride substrate 10, a ceramic green sheet made of aluminum nitride before sintering is used. This ceramic green sheet is obtained by adding a sintering aid such as yttria (Y ₂ O ₃ ), calcia (CaO), alumina (Al ₂ O ₃ ), etc. to an aluminum nitride powder raw material, for example, a binder such as butyral resin Add a plasticizer such as dioctyl phthalate, a dispersant, and a solvent such as toluene, xylene, butanol, etc., knead thoroughly with a resin ball mill, adjust the viscosity, and vacuum defoam to form a slurry. ing. And from the slurry, the ceramic green sheet dried into the sheet form of thickness about 0.2 mm is formed by the doctor blade method etc., for example. Furthermore, the ceramic green sheet for the aluminum nitride substrate 10 is produced by cutting the sheet-like ceramic green sheet into an appropriate size.

(2) Conductor printed pattern forming step Next, if necessary, through holes for vias and the like for making the upper and lower layers electrically conductive are punched in one or more ceramic green sheets. After drilling using a die or punching machine, for example, screen printing using a conductive paste made of a high melting point metal such as tungsten or molybdenum, for vias, for conductor wiring patterns, and various connection terminals A conductor print pattern for pads or the like is formed.

(3) Laminate Forming Step Next, the plurality of ceramic green sheets on which the conductor print pattern is formed are overlapped with each other and bonded by applying temperature and pressure to form the laminate 11.

(4) Degreasing step Next, the laminated body 11 is placed on a molybdenum (Mo) plate 12 which is a high melting point metal having high heat resistance and little deformation, and is surrounded by a molybdenum spacer 13 and a molybdenum plate 12. To block. In addition, each molybdenum plate 12 on which this laminate 11 is placed is stacked in multiple stages with a molybdenum spacer 13 interposed therebetween in order to improve firing efficiency, and the uppermost portion is covered with the molybdenum plate 12. Thus, an assembly 14 is obtained (see FIG. 1A). The assembly 14 is placed in a metal firing furnace in which the heating element is made of metal such as molybdenum, tungsten, or platinum rhodium, and the furnace wall is made of molybdenum or the like. In this firing furnace, the temperature in the furnace is raised as a non-oxidizing atmosphere of nitrogen and hydrogen. The laminated body 11 in the firing furnace is passed through a temperature of about 1300 to 1400 ° C. for about 2 to 10 hours and degreased to remove the binder in the ceramic green sheet to form a degreased body 15.

(5) Sintering Step Next, the degreased body 15 that has been degreased from the laminate 11 is taken out of the assembly 14 and formed again in the assembly 14a for sintering (FIG. 1B). reference). That is, the assembly 14 a is formed by first placing the aluminum nitride setter 16 on the molybdenum plate 12, placing the degreased body 15 on the aluminum nitride setter 16, and further placing the aluminum nitride setter 16 on the degreased body 15. The both surfaces of the degreased body 15 are sandwiched between the aluminum nitride setters 16. Further, the degreased body 15 sandwiched between the aluminum nitride setters 16 is stacked in multiple stages so as to close the outer periphery with the molybdenum spacer 13 and the molybdenum plate 12, and the uppermost part is covered with the molybdenum plate 12. An assembly 14a is provided. The assembly 14a is placed in a metal firing furnace in which, for example, a heating element similar to the firing furnace in which the degreased body 15 is produced is made of a metal such as molybdenum, tungsten, or platinum rhodium, and the furnace wall is made of molybdenum or the like. is doing. In this firing furnace, the temperature in the furnace is raised as a non-oxidizing atmosphere of nitrogen and hydrogen. The degreased body 15 in the firing furnace produces the aluminum nitride substrate 10 made of a sintered body by a normal pressure firing method in which the temperature is passed to about 1700 to 1800 ° C. for about 2 to 8 hours (see FIG. 1C). ).

Here, a manufacturing method of the aluminum nitride setter 16 used in the above-described sintering process will be described according to the manufacturing process diagram shown in FIG.
(1) Aluminum nitride powder preparation process As an aluminum nitride powder raw material for producing the aluminum nitride setter 16, the thing with an average particle diameter of about 5-10 micrometers is prepared.
(2) Granulated powder preparation step Next, 99.5% or more aluminum nitride powder substantially containing no sintering aid is mixed with a resin, a solvent, a plasticizer and the like, and then sprayed. A granulated powder having an average particle size of about 80 μm is produced by drying with a dryer.
(3) Powder press molding process Next, the granulated powder is formed into a plate-shaped molded body using a powder press molding machine comprising an upper die, a die, and a lower die.
(4) Sintering process Next, the molded body is put into a metal firing furnace in which a heating element is made of a metal such as molybdenum, tungsten, or platinum rhodium, and a furnace wall is made of molybdenum or the like. In this firing furnace, the temperature in the furnace is raised as a non-oxidizing atmosphere of nitrogen and hydrogen. The formed body in the firing furnace is made into an aluminum nitride setter 16 made of a sintered body by sintering at a temperature of about 1850 to 1950 ° C. for about 10 to 15 hours and sintering. The aluminum nitride setter 16 produced in this way is formed by dense powder press-molding of aluminum nitride substantially free of sintering aid, at a high temperature of 1850 to 1950 ° C., for a long time of 10 to 15 hours, Since sintering is performed by a normal pressure firing method, the sintered aluminum nitride setter 16 can have an average aluminum nitride particle size of 20 to 30 μm, and is dense and has low glass absorbency and high bending strength. Thus, an inexpensive aluminum nitride setter 16 can be obtained. Therefore, the aluminum nitride substrate 10 manufactured using this can be an inexpensive substrate that prevents the occurrence of spots.
(5) Surface Grinding Step The above-mentioned fired body is produced in an aluminum nitride setter 16 that is ground with a surface grinder as necessary to make both surfaces planar. Thereby, the aluminum nitride substrate 10 with less warpage can be easily manufactured.

  Note that the aluminum nitride setter 16 described above becomes difficult to obtain a dense setter due to insufficient grain growth if the firing temperature falls below 1850 ° C. or the firing time falls below 10 hours. Further, when the firing temperature of the aluminum nitride setter 16 exceeds 1950 ° C. or the firing time exceeds 15 hours, the firing furnace deteriorates quickly and it becomes difficult to obtain an inexpensive setter. Furthermore, the aluminum nitride powder of the aluminum nitride setter 16 is 99.5% or more because it contains substantially no sintering aid and the sintering aid as an impurity of less than 0.5%. Even if it is contained, it represents an acceptable range.

  The aluminum nitride substrate manufactured by the method for manufacturing an aluminum nitride substrate of the present invention can be used for illumination, a display, or the like by mounting a light emitting element such as an LED. The aluminum nitride substrate produced by the method for producing an aluminum nitride substrate of the present invention can also be applied to a package for mounting electronic components that require high heat dissipation characteristics and high reflectivity.

(A)-(C) are explanatory drawings of the manufacturing method of the aluminum nitride board | substrate which concerns on one embodiment of this invention, respectively. It is a manufacturing process figure of the aluminum nitride substrate. It is a manufacturing process figure of the setter used with the manufacturing method of the aluminum nitride substrate. It is explanatory drawing of the manufacturing method of the conventional aluminum nitride board | substrate. It is explanatory drawing of the other manufacturing method of the conventional aluminum nitride board | substrate.

Explanation of symbols

  10: Aluminum nitride substrate, 11: Laminated body, 12: Molybdenum plate, 13: Molybdenum spacer, 14, 14a: Assembly, 15: Degreased body, 16: Aluminum nitride setter

Claims (2)

In the method of manufacturing an aluminum nitride substrate in which a laminated body of aluminum nitride green sheets containing a sintering aid is degreased and fired to form a degreased body, and then sintered to form a sintered body.
Placing the laminate on a molybdenum plate and closing the outer periphery with a molybdenum spacer and the molybdenum plate to form the degreased body by degreasing and firing;
The degreased body is powder-press-molded with a granulated powder composed of 99.5% or more aluminum nitride powder substantially containing no sintering aid, and then subjected to atmospheric pressure firing at 1850 to 1950 ° C. for 10 to 15 hours. Sandwiching both sides with an aluminum nitride setter sintered at
A step of placing the degreased body sandwiched between the aluminum nitride setters on the molybdenum plate and sintering the outer periphery with the molybdenum spacer and the molybdenum plate to form the sintered body. A method for producing an aluminum nitride substrate, comprising:   2. The method of manufacturing an aluminum nitride substrate according to claim 1, wherein the aluminum nitride setter has an average aluminum nitride particle size of 20 to 30 [mu] m and a flat surface whose surface is ground. Method.

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