JP2006159654A - Method for producing ceramic sheet, ceramic substrate using it, and its application - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a ceramic sheet which solves the following problem: for example, a ceramic sintered body after baking is deformed to cause the defective printing of a circuit pattern or the defective joining to a metal circuit board or a radiation board by a defective appearance or quality lowering by the mixing of impurities, a production method of a long lead time, and the lowering or nonuniformity of the density of the molded sheet caused by insufficient kneading. <P>SOLUTION: In the method for producing the ceramic sheet good in production efficiency, quality equivalent or superior to conventional quality is obtained by using raw material powder by spray nitriding method and an extruder in which a twin-screw extruder having a strong kneading function and a single-screw extruder having molding stability are combined. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a method for producing a ceramic sheet using a nitride ceramic powder produced using a spray nitriding method, a ceramic substrate using the same, and a use thereof.

The ceramic circuit board is obtained by forming a conductive metal circuit on the ceramic board, and a semiconductor element or the like is mounted at a predetermined position of the metal circuit. In order to maintain high reliability of the ceramic circuit board, it is necessary to dissipate the heat generated by the semiconductor element so that the temperature of the semiconductor element does not rise excessively. Therefore, excellent heat dissipation characteristics are required.
In recent years, as ceramic circuit boards have become smaller and power modules have increased in output, aluminum nitride (hereinafter referred to as AlN) sintered bodies having high electrical insulation and high thermal conductivity are used for small and light modules. A ceramic circuit board and a ceramic circuit board in which a metal circuit is formed on the main surface of an AlN substrate have attracted attention.

A ceramic sintered body to be a ceramic substrate is generally manufactured by the following method. For example, in the case of an AlN sintered body, an appropriate amount of additives such as a sintering aid, an organic binder, a plasticizer, a dispersant, and a release agent are mixed with the AlN powder, and this is formed into a thin plate or sheet by extrusion molding or tape molding. To form. On the other hand, in the case of a thick plate shape or a large shape, it is formed by extrusion molding or pressing (in the present invention, a thickness of less than 1 mm is a thin plate, and a thickness of 1 mm or more is a thick plate). Subsequently, after heating a molded object in air or inert gas atmosphere, such as nitrogen, to 450-650 degreeC and removing an organic binder (degreasing | defatting process), it is 1600-600 in non-oxidizing atmosphere, such as nitrogen. It is manufactured by holding at 1900 ° C. for 0.5 to 10 hours (firing step).

In general, when an extrusion molding method is used, there is no limitation on the molding thickness, and thin and thick ceramic sheets can be molded. For example, the following methods are known. A mixed powder composed of ceramic powder, a sintering aid, and an organic powder binder, which have been surface-treated with oleic acid in advance, is prepared using a universal mixer, a laika machine, a mixer, a vibration sieve machine, or the like. Spray a mixed liquid consisting of water, organic liquid binder, mold release agent, plasticizer, etc. on this mixed powder, and produce a granular moisture raw material using a universal mixer, lykai machine, mixer, vibration sieve machine, etc. (Granulation process). Next, in order to adjust the ceramic powder treated with oleic acid and the aqueous binder solution, the wet powder is allowed to stand at a low temperature for 2 to 3 days (laying process). After this raw material is introduced into the raw material supply port of the kneader to prepare the dough (kneading step), it is left at a low temperature for 2 to 3 days to lower the kneading viscosity. This kneaded clay is put into a raw material supply section of a single screw extrusion molding machine provided with a die and molded into a thick plate shape or a sheet shape.
JP-A-2-248358 JP-A-2-283672 JP-A-2-083265

The manufacturing method is a production method with a long lead time that requires the laying process following the granulation process or leaving the dough under low temperature. Furthermore, since the kneading is insufficient in the single screw extruder, there is a problem that the density of the formed sheet is reduced or becomes non-uniform, and the sintered ceramic body after firing is deformed. An object of the present invention is to provide a method for producing a ceramic sheet that has a quality equivalent to or better than that of the prior art and that has good production efficiency, and a ceramic substrate, a ceramic circuit board, and a module using the same. is there.

That is, the present invention uses a nitride ceramic powder produced by spray nitriding as a raw material, and uses an extrusion molding machine in which a discharge port of a twin screw extruder and a raw material supply port of a single screw molding machine are connected. Is a method for producing a ceramic sheet characterized by forming a ceramic sheet having a thickness of 0.2 to 10 mm. 1) A mixed powder comprising a nitride ceramic powder, a sintering aid and an organic binder powder is mixed in a twin-screw extruder. (2) A mixed liquid composed of a liquid organic binder, a release agent and a plasticizer is supplied from a liquid supply unit of a twin screw extruder, and (3) in a kneading unit in the twin screw extruder. (4) A method for producing a ceramic sheet comprising kneading a mixed powder and a mixed liquid and (4) forming a sheet with a uniaxial molding machine equipped with a sheet die, and having a purity of 99.95% by mass or more and an oxygen content 0. To 1.1 wt%, average particle size of the manufacturing method of the ceramic sheet, characterized by the use of a nitride ceramic powder is 1.0 to 2.0 [mu] m.

Furthermore, it is a ceramic substrate obtained by subjecting the ceramic sheet produced by the above method to degreasing and sintering, forming a metal circuit on one main surface of the ceramic substrate, and joining a heat sink to the other main surface. The ceramic circuit board is a module using the ceramic circuit board.

  According to the present invention, a method for producing a ceramic sheet having a quality equal to or higher than that of the conventional method and having good production efficiency is provided, and the production of a ceramic substrate and a ceramic circuit substrate and application to a module are possible. is there.

The raw material powder according to the present invention is preferably a nitride ceramic powder produced by spray nitriding, and particularly preferably AlN or silicon nitride (hereinafter referred to as Si ₃ N ₄ ) powder. This is AlN and Si ₃ N ₄ powder obtained by spray nitriding metal aluminum or metal silicon powder in a high-temperature furnace in a nitrogen atmosphere. For example, a specific method for producing AlN is as follows. From the top of a vertical quartz furnace with a diameter of 1 m and a height of 3 m heated to 1800 to 2100 ° C. or higher, non-oxidized metal aluminum (hereinafter referred to as Al) powder with a purity of 99.97 mass% or more such as nitrogen or argon gas 10-50 g / min is sprayed using a sex gas as a carrier gas. When nitrogen gas is used as the carrier gas, the nitrogen gas amount as the reaction gas is supplied in a total amount of 150 to 300 l / min with the carrier gas, and the outer diameter of the quartz tube is 0.5 m lower than the top. Install a heater to surround The synthesis furnace is not particularly limited, and either a vertical type or a horizontal type can be used. The synthesized AlN powder is sucked from the lower part of the furnace body with a blower and collected by a bag filter, whereby the AlN powder can be obtained.

When the heating temperature of the reaction tube is lower than 1800 ° C., the reaction rate at which the metal aluminum powder is nitrided decreases, and unreacted metal aluminum may remain in the center of the AlN particles, thereby reducing the purity. On the other hand, if the temperature exceeds 2100 ° C., the reaction tube may be deteriorated at high temperature, and the lifetime of the production apparatus may be shortened.
If the spray amount of the metal aluminum powder on the reaction tube is less than 10 g / min, the AlN particles may be columnar and formability may be deteriorated. On the other hand, if it exceeds 50 g / min, the reaction rate at which the metal aluminum powder is nitrided decreases, and unreacted metal aluminum may remain at the center of the AlN particles, which may lower the purity.
When the total amount of the reaction gas and the carrier gas is less than 150 l / min, the reaction rate at which the metal aluminum powder is nitrided decreases, and unreacted metal aluminum may remain at the center of the AlN particles, which may reduce the purity. On the other hand, if it exceeds 300 l / min, the gas used for the reaction may convect in the reaction tube, and the synthesized AlN particles may become columnar and formability may deteriorate.

AlN powder produced by conventional alumina reduction method or direct nitridation method, Si ₃ N ₄ powder produced by reaction nitridation method, silica reduction method, etc., is the particle size of AlN or Si ₃ N ₄ powder according to the present invention. A small amount of the preparation material can be used in combination, but the purity is lowered by the carbon residue in the alumina reduction method or the silica reduction method. On the other hand, since the direct nitriding method and the reactive nitriding method go through a crushing process, the oxygen content in the AlN or Si ₃ N ₄ powder becomes high, which may cause problems in the sintering process and cannot be used.

The characteristics of the nitride ceramic powder obtained by the spray nitriding method are that the purity is 99.95% by mass or more, the oxygen content is 0.6 to 1.1% by mass, and the average particle size is 1.0 to 2.0 μm. It is. When the purity of the nitride ceramic powder is less than 99.95% by mass, the fired ceramic sintered body may deteriorate over time due to breakdown voltage.

When the oxygen content of the nitride ceramic powder is less than 0.6% by mass, the liquid phase is not sufficiently generated during sintering, the progress of the sintering reaction is delayed, densification is hindered, and the thermal conductivity is lowered. There is a case. On the other hand, if it exceeds 1.1% by mass, oxygen present in the ceramic crystal grains may inhibit the phonon path in the sintering reaction process, and the thermal conductivity may be lowered.

For the particle size distribution measurement of the nitride ceramic powder according to the present invention, it is preferable to use an apparatus capable of measuring the volume distribution frequency and cumulative value by laser diffraction. The nitride ceramic powder according to the present invention preferably has an average particle size (D50 μm) of 1.0 to 2.0 μm.

If the average particle size exceeds 2.0 μm, the sinterability may be adversely affected and the thermal conductivity may not be improved. On the other hand, if the average particle size is less than 1.0 μm, the sinterability is good but the shrinkage rate during sintering is low. It is large and deforms greatly as it shrinks, so the dimensional accuracy may deteriorate.

Depending on the type of the nitride ceramic powder, it is preferable to perform a surface treatment with stearic acid, oleic acid, phosphoric acid or the like in order to prevent hydrolysis. The surface treatment agent is preferably oleic acid, and the amount used is preferably 0.5 to 3 parts by mass with respect to 100 parts by mass of the ceramic powder. If the amount used exceeds 3 parts by mass, the fluidity of the dough may be reduced due to the water repellent action of oleic acid, and the moldability may be impaired. On the other hand, if the amount is less than 0.5 parts by mass, the surface treatment effect is insufficient. There are cases. The surface treatment is preferably performed for 30 to 60 minutes using a ball ton mill or a reiki machine in a non-oxidizing atmosphere.

As the sintering aid for the nitride ceramic powder according to the present invention, rare earth metals, alkaline earth metals, aluminum oxides, fluorides, chlorides, nitrates, sulfates, and the like can be used. Among these, rare earth oxides such as yttrium oxide are common. In the present invention, it is more preferable to use aluminum oxide in addition to the rare earth oxide to lower the firing temperature. The amount of the sintering aid used is preferably 1 to 5 parts by mass with respect to 100 parts by mass of the ceramic powder. If the amount used is less than 1 part by mass or exceeds 5 parts by mass, sintering may be difficult and a high-density sintered body may not be obtained. When using aluminum oxide together, the amount used is preferably 1 to 5 parts by mass with respect to 100 parts by mass of the nitride ceramic powder. If the amount used is less than 1 part by mass or exceeds 5 parts by mass, the thermal conductivity of the ceramic sintered body may not be improved.

As the liquid organic binder according to the present invention, a liquid organic binder containing a polymer obtained by polymerizing one or more monomers selected from the group consisting of acrylic ester, methacrylic ester, acrylic acid and methacrylic acid may be used. preferable. The reason for using this organic liquid binder is that, in the degreasing treatment in an inert gas atmosphere such as nitrogen, the thermal decomposability is better than other binders, and the residual carbon content can be easily controlled. The degreasing treatment is preferably performed in a non-oxidizing atmosphere. For example, when AlN and Si3N4 are degreased in an oxidizing atmosphere, the amount of oxygen in the AlN degreased body increases, and oxygen may be dissolved in the AlN lattice during sintering to lower the thermal conductivity. . The glass transition temperature of the polymer is preferably -50 to 0 ° C. If the glass transition temperature of the polymer is lower than −50 ° C., sufficient molded body strength may not be obtained and molding may be difficult. On the other hand, if the glass transition temperature is higher than 0 ° C., the molded body becomes hard and brittle. Cracks are likely to occur.

  The addition ratio of the liquid organic binder is preferably 0.5 to 30% by mass, more preferably 1 to 10% by mass, based on the nitride ceramic powder. If the addition ratio is less than 0.5% by mass, sufficient molded body strength may not be obtained and cracking may occur. On the other hand, if it exceeds 30% by mass, degreasing treatment takes a lot of time and degreasing. The amount of residual carbon in the body increases, and color unevenness may occur in the sintered body.

The organic binder powder according to the present invention is not particularly limited, but methylcellulose-based or acrylic-based materials are preferably used. As for the usage-amount of organic binder powder, 1-5 mass parts is preferable with respect to 100 mass parts of nitride ceramic powder. If the amount used is less than 1 part by mass, sufficient molded body strength may not be obtained and cracking may occur. On the other hand, if it exceeds 5 parts by mass, the density of the molded body will be reduced during binder removal during degreasing. In some cases, the shrinkage rate during sintering increases, resulting in dimensional defects and deformation.

In the present invention, the carbon content after the heat degreasing treatment of the molded body is preferably 2.0% by mass or less. If the residual carbon content exceeds 2.0% by mass, sintering may be inhibited and a dense sintered body may not be obtained.

As the plasticizer according to the present invention, purified glycerin, glycerin trioleate, diethylene glycol and the like can be used, and the amount used is preferably 2 to 5 parts by mass with respect to 100 parts by mass of the nitride ceramic powder. If the amount used is less than 2 parts by mass, the molded sheet is insufficiently flexible, so that the molded body becomes brittle during press molding, and the sheet may be easily cracked. On the other hand, when the amount exceeds 5 parts by mass, the viscosity of the kneaded clay is lowered and it is difficult to maintain the sheet shape.

  The release agent according to the present invention is not particularly limited, but stearic acid type or silicon type can be used, and the amount used is preferably 2 to 5 parts by mass with respect to 100 parts by mass of the nitride ceramic powder. If the amount used is less than 2 parts by mass, not only will it adhere to the kneaded clay kneader installed between the twin-screw extruder and the single-screw molding machine, which will hinder the supply of the clay and reduce productivity, There may be a case where unevenness of the sheet thickness is caused due to deterioration of the kneaded properties. On the other hand, when the amount exceeds 5 parts by mass, the kneaded clay viscosity decreases and it becomes difficult to maintain the sheet shape, and thus thickness unevenness in the sheet width direction may occur.

In the present invention, a dispersant may be further used as necessary.

As the solvent according to the present invention, ethanol, toluene or the like can be used, but ion-exchanged water or pure water is generally used in consideration of the global environment and explosion-proof equipment. The amount used is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the nitride ceramic powder. If the amount used is less than 1 part by mass, the fluidity of the clay viscosity is poor, which may hinder sheet molding. On the other hand, when the amount exceeds 15 parts by mass, the kneaded clay viscosity decreases and it becomes difficult to maintain the sheet shape, and thus thickness unevenness in the sheet width direction may occur.

The present inventor examined a doctor blade method, an extrusion molding method, a dry press method, an injection molding method, and a slip casting method in order to produce a ceramic sheet.

In the dry press method and the injection molding method, the amount of binder increases, so the shrinkage rate during firing increases, the dimensional accuracy cannot be obtained, and the sintered body must be polished. The slip casting method is suitable for small-sized shaped products and is inferior in mass productivity, and a thick molded body tends to have thickness unevenness in the width direction and the flow direction.

The doctor blade method can be used for molded products with a thickness of 0.5 to 1 mm, but if the thickness exceeds about 1 mm, the thickness unevenness will increase, and the thickness difference between the end and the center may be 40 μm or more. In some cases, large warping may occur after firing. Further, when the organic solvent is dried and removed after sheet molding, the surface of the thicker one may be roughened or pinholes may be generated due to the evaporated organic solvent.

On the other hand, the extrusion molding method can easily form a thick sheet only by increasing the clearance of the die, and the molding pressure can be increased to 5 to 10 MPa. The dimensional accuracy during firing is good.

FIG. 1 shows an extrusion molding machine combining a twin screw extruder and a single screw molding machine according to the present invention.

The kneading part of the twin screw extruder preferably occupies 30 to 70% by volume of the twin screw extruder. If the kneading part is less than 30% by volume, kneading shortage may occur and ceramic sheet density variation may be induced. On the other hand, if the kneading part exceeds 70% by volume, heat generation of the kneaded clay will be significant due to excessive kneading. There is a case where fluidity is lowered due to displacement or moisture evaporation, and a sheet having a stable quality cannot be obtained.

Although the screw rotation speed is related to the screw shape and cannot be determined strictly, it is generally preferably about 50 to 200 rpm, more preferably 70 to 150 rpm. If the rotational speed is less than 50 rpm, kneading may be insufficient. On the other hand, if it exceeds 200 rpm, heat generation of the kneaded clay becomes significant, and fluidity is reduced due to evaporation of the binder solution, so that the sheet quality may not be stable. . In order to eliminate the air bubbles mixed in the kneaded clay by kneading in the twin-screw extruder, vacuuming is performed between the kneading part and the strand dies. At this time, the degree of vacuum is maintained in a vacuum atmosphere of 1300 Pa or less in terms of absolute pressure. The twin-screw extruder is connected to a cooling chiller unit, and the discharge temperature from the twin-screw extruder is adjusted to 5 to 15 ° C.

The features of the twin screw extruder according to the present invention are as follows: (1) The twin screw can rotate in the same direction or in different directions, and the meshing portion between the two screw can be loaded with higher shear stress than the single screw molding machine. Thus, a kneaded clay uniformly kneaded in a short time can be obtained. (2) The biaxial screw is composed of a plurality of parts and is recombined according to the material, so that the degree of freedom of kneading is large. When a green sheet produced based on such a kneaded clay is fired, an isotropic shrinkage performance independent of the extrusion direction is exhibited, so that the size and deformation defect of the ceramic sintered body can be reduced.

When the components of the dough are uniform and good moldability is obtained, the viscosity of the dough is 4000 to 5000 Pa · s when the shear stress is 0.3 MPa with a descending flow tester, and the contour of the sheet cross section The shape is flat. When the viscosity is less than 4000 Pa · s, thickness unevenness occurs in the sheet width direction, which may cause dimensional defects or deformation of the fired ceramic substrate. On the other hand, when the viscosity exceeds 5000 Pa · s, the contour shape of the sheet cross section becomes flat, but a flow mark appears in the flow direction of the sheet surface, and thus the appearance of the surface of the ceramic substrate after firing may be impaired.

Although there is no restriction | limiting in particular regarding the screw diameter D and screw length L of a uniaxial molding machine, It is preferable that the screw diameter D of a uniaxial molding machine shall be more than the screw diameter of a biaxial extruder. Since the screw rotation speed of the uniaxial molding machine is proportional to the discharge amount, about 30 to 150 rpm is preferable. If the screw rotation speed is less than 30 rpm, the desired discharge amount may not be obtained and the productivity may decrease. On the other hand, if the screw rotation speed exceeds 150 rpm, exothermic heat of the dough becomes significant, and fluidity decreases due to evaporation of moisture in the solution. Therefore, a stable quality sheet may not be obtained. The kneading part of the single-shaft forming machine is unnecessary because the dough has already been kneaded sufficiently by the twin-screw extruder. The uniaxial molding machine is connected to a cooling chiller unit, and the temperature of discharged material from the uniaxial molding machine is adjusted to 5 to 15 ° C.

The connection part of the discharge port of a biaxial extruder and the raw material supply part of a uniaxial molding machine is installed as shown in FIG. The material of the box-like container (vacuum chamber) is not limited, but a transparent container is preferable in order to monitor the flow state of the kneaded clay during operation, and it is necessary not to break even under high vacuum. The inside of the container is kept at a vacuum of 1300 Pa or less in terms of absolute pressure so that bubbles do not enter the surface of the kneaded clay and cause a decrease in density. Sealing materials such as resin and rubber packing are used so that vacuum leakage does not occur at the interface between the biaxial extruder and uniaxial molding machine and the container. The clay discharged from the discharge port of the biaxial extruder is conveyed into the single screw molding machine by a kneader installed at the clay supply port of the single screw molding machine.

The feature of the uniaxial molding machine according to the present invention is that the pressure fluctuation caused by the raw material supply system is smaller than that of the biaxial extruder, and the thickness variation in the sheet flow direction of the biaxial extruder is R> 5 μm. In the machine, R ≦ 5 μm and the discharge stability is excellent. When the thickness variation in the sheet flow direction is R> 5 μm, the amount of warpage in the width direction of the ceramic substrate after firing becomes large, which may cause a problem in joining on the metal circuit board side and the metal heat sink side.

In the present invention, the reason why the twin-screw extruder and the single-screw molding machine are combined is to compensate for the disadvantages of both machines and take advantage of the excellent features. As shown in FIG. 1, the raw material supply section of the twin-screw extruder consists of two places for powder and liquid. The powder supply unit uses a mixed powder obtained by mixing ceramic powder, sintering aid powder, and organic binder powder with a mixer, and the liquid supply unit contains a mixed liquid such as a liquid organic binder, plasticizer liquid, mold release agent, and solvent. Use. It is preferable to use a weight loss type powder feeder and a weight loss type monopump or weight loss type tube pump with less discharge pulsation. What is important here is that the powder and liquid feed variations are controlled within │ ± R% │≤1, and the discharge of the powder feeder and the liquid addition pump is synchronized. Here, ± R% is calculated from the equations (1) and (2).

ここで、Ｘｉは３０秒間隔でi回（少なくとも１０回以上）測定したときの吐出量である。

Here, Xi is a discharge amount when measured i times (at least 10 times or more) at intervals of 30 seconds.

If the variation is outside of ±± R% | ≦ 1, the mixing ratio of the powder and the liquid is shifted, resulting in a variation in the density of the green sheet. Therefore, the sintered ceramic body after firing may be deformed.

The sheet is dried by passing the sheet through a drying zone, for example, by using a belt dryer or the like so that the moisture content of the sheet is 1.5 to 3.5% by mass, and then using a die press molding machine. To form a molded sheet. Next, in order to remove the organic binder and the like contained in the molded sheet, a degreasing treatment is performed by holding at a temperature of 400 to 700 ° C. for 1 to 20 hours in a non-oxidizing atmosphere such as nitrogen gas. The obtained degreased body is housed in a firing container made of boron nitride and fired in a non-oxidizing atmosphere at 1600 to 1850 ° C. for 0.5 to 10 hours. Firing can be performed under vacuum, reduced pressure, and increased pressure, but it is generally performed under normal pressure.

The ceramic sintered body produced by the present invention, especially the AlN sintered body, is excellent in mechanical properties and has high thermal conductivity. Therefore, a circuit board used under severe conditions such as a circuit board for power modules. It is a suitable material. The ceramic circuit board of the present invention is formed by forming a metal circuit on one main surface of a ceramic substrate and bonding a heat sink to the other main surface.

The thickness of the ceramic substrate according to the present invention is not particularly limited. For example, when the heat radiation characteristics are important, the thickness is about 0.2 to 1.0 mm, and when the dielectric strength under high voltage is to be increased, the thickness is 1.0. It is common to use a thing of about 10 mm.

The material of the metal circuit and the metal heat sink is preferably Al, Cu, or Al-Cu alloy. These can be used in the form of a single layer or a laminate such as a clad including the same. Among them, Al has a lower yield stress than Cu, and thus is easily plastically deformed. When a thermal stress load such as a heat cycle is applied, the thermal stress applied to the ceramic substrate can be greatly reduced. Therefore, Al is less prone to generate horizontal cracks between the metal circuit and the ceramic substrate than when Cu is used, and a more reliable module can be produced.

The thickness of the metal circuit is not particularly limited, but it is generally 0.1 to 0.5 mm for both the Al circuit and the Cu circuit because of electrical and thermal specifications. On the other hand, the heat dissipation plate needs to have a thickness that does not warp during soldering. For example, the Al heat dissipation plate and the Cu circuit are generally 0.1 to 0.5 mm.

The ceramic circuit board according to the present invention uses a plate-shaped ceramic sintered body or a ceramic sintered body processed into a plate shape by grinding to form a circuit by a method such as etching after joining a metal plate. Alternatively, it can be manufactured by bonding a pre-formed metal circuit to a ceramic substrate. Bonding between the ceramic substrate and the metal plate or metal circuit is inactive, for example, by interposing a brazing material containing an active metal component such as Al-Cu, Ag, Cu, or Ag-Cu alloy and Ti, Zr, Hf, etc. It is possible by a method of heating in a gas or vacuum atmosphere (active metal method).

<Synthesis of AlN powder by spray nitriding method>
From the top of a vertical reaction tube having a diameter of 400 mm and a length of 3000 mm maintained at 1950 ° C., metal aluminum powder was sprayed at 2 kg / hr using nitrogen gas as a carrier gas. The amount of nitrogen gas as the reaction gas was 200 l / min in total with the amount of nitrogen gas as the carrier gas, and an AlN powder was synthesized. The AlN powder was sucked from the lower part of the furnace body with a blower and collected by a bag filter.

AlN was classified by a centrifugal air classifier, and the powder was adjusted so that the average particle size (D50 μm) was 1.5 μm. The obtained AlN powder had a purity of 99.97% by mass, an iron content of 20 ppm, and a silicon content of 50 ppm.

<Sheet molding>
The surface treatment was performed by adding 1.5 parts by mass of oleic acid to 100 parts by mass of the AlN powder and mixing the ball ton mill for 45 minutes in a nitrogen atmosphere. Next, 100 parts by mass of the AlN powder surface-treated with oleic acid, 3 parts by mass of the organic binder powder, ₂ parts by mass of Al ₂ O ₃ , and 4 parts by mass of Y ₂ O ₃ were dry-mixed by a Bourton mixer, 13.4 kg / h was supplied to a powder supply port of a strong kneading type molding machine combining an extruder and a single screw molding machine using a quantitative powder feeder (supply variation <1%) (89% of the dough was powder) . Also, with 100 parts by mass of AlN powder, 3 parts by mass of plasticizer, 2 parts by mass of release agent, 4 parts by mass of ion exchange water, and 7% by mass of organic binder liquid are mixed and stirred. 1.6 kg / h of the obtained liquid was supplied to the liquid supply port of the extruder using a metered liquid monopump (supply variation <1%) (11% of the dough was liquid). The twin screw extruder was D = 46 mm, L = 1840 mm (L / D = 40), the kneading part was 50% by volume, the screw rotation speed was 100 rpm, and the degree of vacuum was 666.6 Pa in absolute pressure. The degree of vacuum in the vacuum chamber between the twin screw extruder and the single screw molding machine was 666.6 Pa. The uniaxial molding machine uses an apparatus consisting of D = 70 mm and L = 700 mm, and under a driving condition of a screw rotation speed of 60 rpm (discharge amount 30 kg / h), using a sheet die, a strip shape of width 80 mm × thickness 1.174 mm The sheet was molded. Table 1 shows the molding conditions, and Table 2 shows the physical properties of the molded sheets.

<AlN sintered body>
The formed green sheet was dried using a belt dryer until the sheet moisture content became 2%, and then adjusted to a size of 70 × 50 mm × 1.174 mm by a press machine with a mold. This was filled in a boron nitride crucible, degreased by holding at 500 ° C. in a nitrogen atmosphere for 4 hours under normal pressure, and then using a carbon heater electric furnace in a nitrogen atmosphere with an absolute pressure of 0.1 MPa. An AlN sintered body was produced by firing at 1800 ° C. for 2 hours. Table 2 shows the physical properties of the obtained AlN sintered body.

In order to evaluate the performance of the obtained AlN sintered body as a circuit board, an aluminum plate was joined as a metal circuit and a metal heat sink by the following method to form a circuit pattern.

A 70 × 50 mm × 0.2 mmt brazing alloy foil is pasted on both sides of the AlN sintered body, and a 70 × 50 mm × 0.2 mmt aluminum plate is sandwiched from both sides, and a laminate of 10 sheets is used as a carbon jig. After installation by tightening with carbon screws, the AlN sintered body and the aluminum plate were joined by holding at 620 ° C. for 2 hours. In order to form a circuit pattern of a predetermined shape on one main surface of the joined body and a heat sink pattern on the other main surface, a UV curable resist ink is screen-printed and then irradiated with a UV lamp to form a resist film. Was cured. Next, after etching the portion other than the resist-coated portion with an aqueous sodium hydroxide solution, the resist was peeled off with an aqueous ammonium fluoride solution to produce an aluminum circuit AlN substrate as shown in FIG.

  In order to evaluate the reliability of the obtained ceramic circuit board, a thermal history impact test was conducted. 1) Presence of printed pattern deviation, 2) Presence of occurrence of joint cracks between the circuit surface and heat sink surface and AlN substrate by cross-sectional observation. 3) After dissolving the circuit and the heat sink, it was confirmed whether or not the AlN substrate was cracked by an ink test. The results are shown in Table 3. Here, the presence / absence of occurrence of a joint crack is determined by performing a thermal hysteresis impact test, symbol 1 when the joint crack occurs in less than 2000 cycles, symbol 2 and 3000 when the joint crack occurs in 2000 to 3000 cycles. The case where no joint crack occurred even in the cycle was designated as symbol 3. The circuit board is preferably 2 or more.

<Materials used for AlN ceramics>
Metal aluminum powder: purity 99.97% by mass, average particle size 0.7 μm.
· _Al 2 _{O 3:} Admatechs Co., Ltd., trade name "AO-500", a powder particle size 1.0μm of D50, 99.9% purity.
Y ₂ O ₃ : manufactured by Shin-Etsu Chemical Co., Ltd., trade name “Yttrium Oxide”, D50 powder particle size 1.0 μm, purity 99.9%.
Organic liquid binder: Yuken Kogyo Co., Ltd., trade name “Cerander”, main component acrylic acid ester, glass transition temperature −20 ° C.
Organic binder powder: manufactured by Daicel Chemical Industries, Ltd., trade name “CMC Daicel”, main component carboxymethylcellulose.
・ Plasticizer: Kao Corporation, trade name “Exepearl”, main component glycerin.
Mold release agent: manufactured by San Nopco, trade name “Nopco Sera LU-6418”, main component stearic acid.
Aluminum plate: Mitsubishi Aluminum Co., Ltd., trade name “1085 material” (corresponding JIS number).
-Wax alloy foil: manufactured by Toyo Seiki Co., Ltd., trade name "A2017R-H alloy foil" (corresponding JIS number).
UV curable resist ink: trade name “PER-27B-6” manufactured by Kyoyo Chemical Co., Ltd.

<Measuring method>
・ Particle size distribution measurement: Laser diffraction scattering measurement device (“LS-230” manufactured by Beckman Coulter, Inc.), measurable range is 0.04 to 2000 μm, measurement principle is to irradiate powder with laser light, and size of particles from scattering pattern The particle size is measured from the intensity of scattering.
-Oxygen measurement: An oxygen / nitrogen simultaneous analyzer manufactured by HORIBA was used. The AlN powder is exposed to 3000 ° C., and the gasified oxygen is quantitatively evaluated.
-Dough viscosity: Viscosity at a shear stress of 0.3 MPa was measured with a descending flow tester.
Sheet thickness variation R: Using a micrometer, the thickness was measured at intervals of 5 mm from the end to the other end in the sheet width direction, and obtained from the formula (3).

ここで、ｙ_ｉはi回測定したときのシート厚みである。
・シート密度：金型プレス後の成形体を用いて（４）式より求めた。

Here, y _i is the sheet thickness when measured i times.
-Sheet density: It calculated | required from (4) Formula using the molded object after metal mold | die press.

ここで、W_sheetは成形体重量、W_liquedは１００℃、１時間乾燥後の含水除去した成形体重量、lはシート長手方向距離、wは短手方向距離、t成形体厚み。
・焼結体の収縮率：（５）式より求めた。

Here, W _sheet is the weight of the molded body, W _liqued is the weight of the molded body after moisture removal at 100 ° C. for 1 hour, l is the sheet longitudinal direction distance, w is the lateral direction distance, and t molded body thickness.
-Shrinkage of sintered body: determined from equation (5).

ここで、SはL方向の収縮率（％）、ｌsheetは成形体の長手方向長さ、lsintered bodyは焼結体の長手方向長さ。

Here, S is the shrinkage rate (%) in the L direction, lsheet is the longitudinal length of the molded body, and lsintered body is the longitudinal length of the sintered body.

The breakdown of the number of days until sheeting is shown below. Number of days required for preparation of powder and liquid: 0.5 days, number of days required for mixed preparation of powder and liquid: 0.5 days, number of days required for laying mixed product: 3 days, number of days required for kneading mixed product: 1 day The number of days required for laying the kneaded product was set to 3 days.
-L direction and W direction deformation rate of sintered body: determined from equation (6).

ここで、l_{yeilded rate}は長手方向の変形量であり、＋符号の場合は長手方向中央部が端部より長く、−符号の場合は長手方向中央部が端部より短い、l_centerは長手方向中央部の長さ、l_endは長手方向端部の長さ。W方向変形率は同式を用いて算出する。
・焼結体密度：アルキメデス法により（７）式から算出した。

_Here, l yeilded _rate is the deformation amount in the longitudinal direction, + longitudinal center if the sign is longer than the end, - in the case of code longitudinally central portion is shorter than the end portion, l _center longitudinal The length of the center, l _end is the length of the _end in the longitudinal direction. The W direction deformation rate is calculated using the same equation.
-Sintered body density: It calculated from Formula (7) by the Archimedes method.

ここで、rは嵩密度，W₁は空気中での焼結体の質量，W₂は焼結体の開気孔にブタノールが含浸したときの空気中における焼結体の質量，W₃はブタノール中での焼結体質量，r_Eは密度測定時（２５℃）のブタノールの密度：０．８０４８ｇ／ｃｍ３である。
・焼結体の抗折強度：下部スパン３０ｍｍ、クロスヘッド速度０．５ｍｍ／分の条件にて3点曲げ試験（JIS R1601）を行い、その破壊荷重を（８）式により求めた（ｎ＝１０）。

Where r is the bulk density, W ₁ is the mass of the sintered body in the air, W ₂ is the mass of the sintered body in the air when the open pores of the sintered body are impregnated with butanol, and W ₃ is the butanol The mass of the sintered body, r _E, is the density of butanol at the time of density measurement (25 ° C.): 0.8048 g / cm 3.
-Fracture strength of the sintered body: A three-point bending test (JIS R1601) was performed under the conditions of a lower span of 30 mm and a crosshead speed of 0.5 mm / min, and the breaking load was obtained from equation (8) (n = 10).

ここで、σ_fは抗折強度、P_fは破壊荷重，bは試験片の幅，hは試験片の厚さ，Lは下部スパン長さである．
・焼結体の熱伝導率：ＡｌＮ基板表面にカーボンスプレー処理を施し、レーザーフラッシュ法にて測定した。
・焼結体の反り量：株式会社東京精密社製触針式輪郭測定器『CONTOURECORD １６００D』を用いて測定した。
・熱履歴衝撃試験：（−２５℃、１０分→室温、１０分→１２５℃、１０分→室温、１０分）を１サイクルとして、３０００サイクルのヒートサイクルに供試体を晒す試験。
・セラミック基板の外観検査：蛍光灯にかざし、目視にてセラミック基板内の異物混入判定を行う試験。

Where σ _f is the bending strength, P _f is the breaking load, b is the width of the test piece, h is the thickness of the test piece, and L is the length of the lower span.
-Thermal conductivity of sintered body: The AlN substrate surface was subjected to carbon spray treatment and measured by a laser flash method.
-Warpage amount of sintered body: Measured using a stylus type contour measuring instrument "CONTOURECORD 1600D" manufactured by Tokyo Seimitsu Co., Ltd.
Thermal history impact test: A test in which a specimen is exposed to a heat cycle of 3000 cycles, with (−25 ° C., 10 minutes → room temperature, 10 minutes → 125 ° C., 10 minutes → room temperature, 10 minutes) as one cycle.
・ Appearance inspection of ceramic substrate: A test in which a foreign object in the ceramic substrate is visually checked by holding it over a fluorescent lamp.

Experiment No. 12 was performed in the same manner as in Example 1 except that Si ₃ N ₄ was used for the ceramic substrate and the metal circuit and the metal heat dissipation plate were made of an Al circuit substrate. The results are shown in Tables 1-3.

<Si ₃ N ₄ sintered body>
This was performed in the same manner as in Example 1 except that Si ₃ N ₄ was used as the raw material powder, 4 parts by mass of Y ₂ O ₃ was used as a sintering aid, and the pressure during firing was in a nitrogen atmosphere of 9.5 MPa. . The results are shown in Tables 2 and 3.
<Materials used for Si ₃ N ₄ ceramics>
Metallic silicon powder: purity 99.97% by mass, average particle size 0.7 μm.
Y ₂ O ₃ : manufactured by Shin-Etsu Chemical Co., Ltd., trade name “Yttrium Oxide”, D50 powder particle size 1.0 μm, purity 99.9%.
<Sintering of Si ₃ N ₄ ceramic>
-An Si ₃ N ₄ sintered body was produced by firing at 1800 ° C. for 2 hours in a pressurized nitrogen atmosphere with an absolute pressure of 9.5 MPa.

Experiment No. No. 13 was performed in the same manner as in Example 1 except that AlN was used for the ceramic substrate and the metal circuit and the metal heat dissipation plate were Cu circuit substrates. The results are shown in Tables 1-3.

A mixed powder composed of 85% by mass of Ag, 10% by mass of Cu, 2% by mass of Zr, and 3% by mass of TiH and a paste-like mixed liquid composed of 30% by mass of terpineol was applied to both sides of the AlN sintered body, and 3 inches on each side. X2 inch x 0.02 inch thick oxygen-free copper plate was pasted, and 14 laminated layers were installed on a carbon jig by tightening carbon screws, and then held at 850 ° C. for 2 hours to obtain an AlN sintered body The joined body which pinched | interposed between the copper plates was produced. In order to form a circuit pattern of a predetermined shape on one main surface of the joined body and a heat sink pattern on the other main surface, a UV curable resist ink is screen-printed and then irradiated with a UV lamp to form a resist film. Was cured. Next, after etching the portion other than the resist-coated portion with a cupric chloride solution, the resist was peeled off with an aqueous ammonium fluoride solution to produce a copper circuit AlN substrate.

<Materials used>
Oxygen-free copper plate: Product name “3100 series” (corresponding JIS number), manufactured by Sumitomo Metal Mining Copper Co.

Experiment No. No. 14 was performed in the same manner as in Example 2 except that Si ₃ N ₄ was used for the ceramic substrate and the metal circuit and the metal heat dissipation plate were made of copper plates. The results are shown in Tables 1-3.

Extruder according to the present invention combining a twin screw extruder and a single screw machine Screws for twin screw extruder and single screw machine Metal circuit ceramic substrate

Explanation of symbols

[Figure 1]
DESCRIPTION OF SYMBOLS 1 Powder supply port 2 Liquid supply port 3 Twin screw extruder 4 Vent port 5 Strand die 6 Vacuum chamber 7 Kneader 8 Sheet die 9 Single screw molding machine

[Figure 2]
1 Kneading screw 2 Conveying screw

[Fig. 3]
1 Circuit side metal plate 2 Heat dissipation side metal plate 3 AlN or Si ₃ N ₄ substrate

Claims (6)

Using a nitride ceramic powder produced by spray nitriding as a raw material, and using an extrusion molding machine in which the discharge port of a twin screw extruder and the raw material supply port of a single screw molding machine are connected, the thickness is 0.2 to 10 mm. A method for producing a ceramic sheet, comprising molding the ceramic sheet. (1) A mixed powder composed of a nitride ceramic powder, a sintering aid and an organic binder powder is supplied from a powder supply section of a twin screw extruder, and (2) a mixture composed of a liquid organic binder, a release agent and a plasticizer. The liquid is supplied from the liquid supply part of the twin screw extruder, (3) the mixed powder and the mixed liquid are kneaded in the kneading part in the twin screw extruder, and (4) the sheet is formed by the single screw molding machine equipped with a sheet die. The method for producing a ceramic sheet according to claim 1, wherein:     A nitride ceramic powder having a purity of 99.95% by mass or more, an oxygen content of 0.6 to 1.1% by mass, and an average particle size of 1.0 to 2.0 μm is used. 2. A method for producing a ceramic sheet according to 2. A ceramic substrate obtained by subjecting a ceramic sheet produced by the method according to claim 1 to degreasing and sintering. 5. A ceramic circuit board formed by forming a metal circuit on one main surface of the ceramic substrate according to claim 4 and bonding a heat sink to the other main surface. A module comprising the ceramic circuit board according to claim 5.

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