JPS6265979A - Production of aluminum nitride sintered plate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a sintered aluminum nitride plate. l (@Next technology and 7 problems') In recent years, electronic components have become significantly smaller and more highly integrated, and as a result, the amount of heat generated per unit area of these components continues to increase. How to release these heat waves is an important point in design, and it is desired to develop a single substrate made of a material with high thermal conductivity.

For this purpose, a silicon carbide sintered body or an aluminum nitride sintered body substrate has been proposed as an alternative to the conventionally widely used alumina substrate.

However, although silicon carbide has high thermal conductivity, it has poor electrical insulation properties, and the increasingly dense I/C requires hot breathability, so its field of use is limited. On the other hand, sintered aluminum nitride has a thermal conductivity that is 2 to 5 times that of alumina, although it is inferior to silicon carbide, and its electrical insulation properties are comparable to that of alumina, and it can be densified by pressureless sintering. 1. It is a highly versatile paulownia material.

The aluminum nitride sintered body is usually molded using aluminum nitride powder using a cold 7''less method, a doctor blade method, or the like, and then fired and bent in an inert atmosphere such as nitrogen.

The aluminum nitride sintered body is processed into a thin plate shape and coated with 24-electric paste, resistance paste, or dielectric paste) on a cedar board.
It is generally used for baked hybrid circuit boards or discrete electronic components, and it is expected that it will also be used for ceramic packages in the near future.Basically, it needs to be in a plate shape, so it cannot be used for general purposes. A low-cost sintered plate is required for this purpose.

Currently, in the case of the most commonly used alumina substrate, alumina powder, organic binder, organic dispersant, etc.
The blended and dispersed mixture of plasticizer A method has been adopted in which the substrate is made of alumina. In the case of alumina substrates, the history is long (more than 20 years have passed), so the type and amount of organic substances used have been optimized, and organic solvents are currently not recommended for safety and economic reasons. It is so advanced that attempts are being made to make slurry 2 in a water system without using it.

(Problem to be solved by the invention) On the other hand, in the case of aluminum nitride sintered bodies, it may be considered that forming sheets by the doctor blade method is the most advantageous economically.
It has a short history (it is currently at the trial and error stage without any conditions).The reason for this is that aluminum nitride has various problems compared to alumina.First of all, aluminum nitride This is something that can be easily overlooked.

For example, after producing the green sheet Y, the surface of the aluminum nitride powder may be oxidized during the organic matter removal process or raw material crushing process. When oxidized, an alumina field is formed on the surface, and the resulting aluminum nitride sintered body has poor thermal conductivity, and the properties of aluminum nitride are lost. Second, aluminum nitride powder is susceptible to hydrolysis. If the type of solvent used in the slurry IJ manufacturing process and the water content in the solvent are not controlled, the same problems as when the particles are subjected to hydrolysis and glueing will occur. Third, metal impurities in aluminum nitride If impurities such as silicon, iron, chromium, etc. are mixed into the glaze, the thermal conductivity of aluminum nitride will be similarly lost. kotv, l: 5
Kg-aluminum oxide has several problems that alumina does not have, and therefore, in the slurry training process for grinding with a doctor blade, it is necessary to consider conditions and formulations suitable for aluminum nitride, such as the subsequent organic matter removal (debinding) process. is necessary.

The present invention solves these problems by using sintered aluminum nitride, which has uniform and high thermal conductivity, has no stains, uneven color, or cracks, and has a smooth surface, and is inexpensive and has a high yield in manufacturing. The purpose of the present invention is to provide an excellent manufacturing method for a highly thermally conductive ceramic sintered plate consisting of a ceramic body.

(Means for solving the problems) That is, the present invention provides aluminum nitride powder, a sintering aid,
: 'i low caking agent, '5] plasticizer, dispersant and one solvent are mixed, molded, binder removed, and then fired in a non-oxidizing atmosphere to produce an aluminum nitride sintered plate. For 100ml of aluminum powder, 4 to 12 parts of polyvinyl butyral as an organic binder, 2 to 101 parts of dibutyl phthalate and/or dioctyl phthalate as a plasticizer, and 1 to 61 parts of aliphatic ester as a dispersant.
chlorine-based, ketone-based, aromatic-based,
In a mixed solvent of two or more selected from alcohol-based and paraffin-based solvents, they are mixed using a pot made of organic polymer and a negative zirconia ball, and then formed into a sheet using a doctor blade method. After that, the binder is removed and the material is fired in a non-melting atmosphere to achieve a relative density of 95% or more.The present invention will be described in more detail below.

First, in order to obtain a high-density sintered body by pressureless sintering of aluminum nitride powder, it is necessary to make the aluminum nitride powder a fine powder with an average particle size of 6 μm or less to prevent contamination with impurities. Since the average particle size of commonly available commercial products is about 7 to 8 microns, they must be pulverized. It has been found that a wet ball mill using a combined pot and a zirconia precious ball Z is effective in terms of efficiency (as a grinding method with less contamination of impurities).

Furthermore, since aluminum nitride itself is difficult to sinter, it is necessary to add a sintering aid. There is no limit to the percentage of the type of sintering aid, but using a cerium oxide-yttrium oxide compound or a mixture of two or more selected from cerium oxide, yttrium oxide, and lanthanum oxide will improve yield (and improve color). It is suitable for the present invention because it produces an aluminum nitride sintered plate with unevenness and warpage (and good thermal conductivity).The mixing state of the sintering aid and aluminum nitride powder has a subtle effect on sintering, so In order to obtain a sufficient mixing state, it is desirable to mix the sintering aid at the same time as the wet grinding in the aluminum nitride powder ball mill. It depends, but it may be appropriate to use about 4 to 20 parts of aluminum nitride powder per 8 parts of 100 m of aluminum nitride powder.

It is essential that the green sheet obtained by forming the slurry into a sheet using a doctor blade device has flexibility and stiffness necessary for handling such as punching in subsequent steps.

For this purpose, organic binders such as polyvinyl butyral, poval, acrylic polymers, etc. are used in the case of alumina substrates. In the case of aluminum nitride, an organic binder is also required, or in the present invention, polyvinyl butyral,
Among them, it has been found that polyvinyl butyral having two or more molecular weight distributions with different degrees of unity is suitable. A mixture of about 300 and 1700 degrees or 600 and 1700 degrees
The mixture has excellent flexibility and stiffness. Polyvinyl butyral has superior film-forming properties compared to other single binders, and can produce crack-free sheets.

Since polyvinyl butyral is a resin that is difficult to dissolve in organic solvents, it is not preferable to add the resin itself during wet mixing and pulverization of aluminum nitride powder and sintering aid. It is preferable to prepare a solution Z which has been bathed in an organic solvent together with a plasticizer in advance, and to mix this solution. The ma of polyvinyl butyral for organic solvents is 10-451
It is preferable that the amount is 1% in terms of ease of dissolution and handling. The blended amount of the mixed tower solution of polyvinyl butyral and plasticizer is 4 to 121 parts of polyvinyl butyral and 2 to 1 t parts of aluminum nitride powder.
Weigh and mix to obtain ~1 part of plasticizer. It should be noted that if a bath liquid containing only polyvinyl butyral is added during the crushing and mixing process of aluminum nitride powder, the viscosity of the slurry during crushing will increase, resulting in poor crushability, so it is not preferable. It is said to be compatible with dibutyl phthalate and/or
Or dioctyl phthalate can be used.

If the amount of polyvinyl butyral is less than 4 ml/t parts, a crack-free sheet cannot be obtained; The shrinkage during sintering becomes thick. Also, if the amount of plasticizer is less than 2 parts, the aforementioned slurry thinning effect cannot be obtained, and the advantage of adding more than 10:3 parts of plasticizer is do not have.

The aliphatic ester yarn dispersant used in the case of alumina to improve the dispersibility of the powder is also used in the case of aluminum nitride powder. As the aliphatic ester, for example, triolein is preferred, but other aliphatic esters can also be used.

The blending amount of the dispersant was 100% aluminum nitride powder. The amount is about 1 to 6 N parts per m parts. Further, it is preferable to add the aluminum nitride powder when the aluminum nitride powder and the sintering aid 1 are wet-pulverized and mixed, since this improves the dispersibility.

The viscosity of the slurry 'J-41) completed as described above is 50 to 5 [100 cps, and until now, when sheet-formed using a doctor blade device, it has been applied to a polyethylene phthalate film as a carrier film and dried. During this process, the slurry flows and a green sheet of uniform thickness cannot be obtained. Also, make holes in the green sheet to trap air and other bubbles in the slurry.
Problems such as this may arise. So the viscosity is 50~5000 cp
sura'J-(1) Pour into a defoaming machine to remove the solvent and remove the trapped air bubbles. Usually 0.01~0.
Defoaming is performed under a vacuum of 1 atm, and the final viscosity is 1 to 6.
Added 10,000 cps of slug IJ-(II).

The slurry is applied onto a polyethylene terephthalate film using a doctor blade device using this slurry (II) Y, and dried at room temperature to 120°C to remove the organic solvent to form a green sheet with abrasion of 0.5 to 1.51). . Since it is undesirable if bumping occurs during drying, it is preferable to use an organic solvent that does not have a very low boiling point and is capable of dissolving organic binders, plasticizers, and dispersants. Therefore, it is usually difficult to use a single solvent and mixed solvents are used. That is, in the present invention, 102 or more solvents are selected from chlorine-based solvents such as trichloroethane, ketone-based solvents such as acetone, aromatic solvents such as toluene, alcohol-based solvents, and paraffin-based solvents. Specific examples include sulfur, trichlorethylene/tetrachlorethylene/phthanol/chlorocene, toluene/ethanol/butanol, and toluene/isozolopanol/butanol. As mentioned above, does aluminum nitride contain moisture? Therefore, when using organic solvents, care must be taken to control the water content to 500 ppm or less, preferably 100 ppm or less.

The amount of mixed solvent used is usually about 1 g#1 times the amount of aluminum nitride powder.

After punching Green Zeaton into a predetermined shape, the temperature is 40℃.
After heating in an oxidizing atmosphere at 0 to 600°C for about 0.5 to 2 hours to depine (remove organic matter), heat to 1700 to 190°C in an inert gas atmosphere such as nitrogen or argon.
By performing sintering under normal pressure at a temperature range of 0° C., a sintered body Y having a relative density of 95% or more can be obtained.

The thermal conductivity of the aluminum nitride sintered plate produced by this process is 1oOW/mk or more. The original properties of aluminum chloride can be maintained, and stains and
It is possible to produce a good sintered board with no cracks and no problems in practical use.

(Example) This will be explained in more detail below using examples.

Example 1 A 1:1 combination of cerium oxide and yttrium oxide IF2QO5 was made by baking 3 kg of commercially available aluminum nitride powder with an average particle size of 7μ for 1400'03 hours.
' and Triolein 52g 'aj weighed 10! loaded into a nylon ball millbot. Place Zorconia Rapole with a length of 10 φ in a 20~pot, then add it to a mixed solvent 2.4 consisting of 60:24:16 trichlorethylene:butanol:tetrachloroethylene at a ratio of 1fii, and after sealing it, turn it at 80 rpm. The mixture was mixed and pulverized for 24 hours under the following conditions to obtain an aluminum nitride powder slurry (1) with an average particle size of 2.0μ.

On the other hand, a mixture of polyvinyl butyral with a kt ratio of 300 and 1700 at a kt ratio of 6:2, 300 g of wv and 150 g of sibutyl phthalate was dissolved in the above mixed solvent 1.5/cgK, and the total solution was made into a 800 gt sluice IJ-II). The mixture was then mixed for another 24 hours in the above-mentioned colander mill until the viscosity was 200.
cps slurry (II).

The slurry IJ-(II) was taken out from the komaru mill and defoamed using a vacuum defoaming machine to form a slurry Ym with a viscosity of 15,000 cp. After that, use a pipe doctor blade device to cut the width to 33
01) On the polyethylene terephthalate film of 1) with a clearance of 2.2 mm, during coating 2501) Slurning under the conditions of 1) IJ -'k! : Clothed. The drying zone is 15 m long and has a temperature gradient from room temperature to 120'C.

A green sheet was created under the conditions that the film feeding speed was IQ cm/min. The resulting green sheet has a tensile strength of 2CJkg/CIrL2 and a thickness of 1.1)1)
There was a lot of flexibility, and there were no occurrences of cranks, etc.

Is this a Green Geeton punching die? It was punched out into a 59y+i square. The cross section of the punched sheet was clear and no cracks were observed.

Next, 50 sheets of 50 square meters were placed in a graphite tray and treated at 450°C for 1 hour under air circulation to remove organic substances (organic binders, dispersants, and plasticizers). The amount of carbon remaining after removing organic matter was 0.3 M%, and it was confirmed that the amount of carbon remained was reduced to carbon i in the raw material aluminum nitride powder.

Thereafter, the green sheet t together with the graphite plate was set in a large sintering furnace, and fired for 1850°01) hours at normal pressure in a nitrogen atmosphere. The dimensions of the 50 aluminum nitride sintered plates were 4.
At 0 mm angle, their relative densities were all 9576 or higher, and the warpage was <0.1) 1/251) 1 or lower. In addition, when the thermal conductivity was measured using a radar flash method manufactured by Shinku Riko, it was 130 W/mk on average.
Ivy at W/mk.

Example 2 Sintering aid 'P! : A mixture of lanthanum chloride, cerium oxide, and yttrium chloride, each in a volume ratio of 1:
An aluminum nitride sintered plate was prepared in the same manner as in Example 1 and S except that the ratio was changed to 1:2. However, the sintering temperature was 1800°C. The obtained green sheet had no abnormalities such as cracks, and the relative density and warpage of the sintered body were the same as in Example 1.

The Hayabusa power rating of 1+' was 125W/mk.

Example 6 In Example 1, one filter mixed bath agent in slurry 1,1-(1) was reduced to 1.27 Cg, and the particle size of the aluminum nitride powder was 2.8μ, which was slightly coarse. Therefore, the pulverization and mixing time was increased by 10 hours to a value of 2.1μ.

The expected results were almost the same as in Example 1.

Implementation IJ 4 to 10 Comparative Examples 1 to 3 The types of sintering aids, dispersants, plasticizers, and pre-made binders in Example 1 were changed and the amount of type a was changed.
The average values of relative density and thermal conductivity of 50 sintered plates were determined. Seven knots JA and L are shown in the table.

(Effect of the invention) According to the present invention, the following effects can be achieved.

II Low content of group m impurities and aluminum nitride powder is not oxidized or hydrolyzed! Since it is possible to sinter under conditions that do not undergo IY, the high thermal conductivity of aluminum nitride can be demonstrated.

(2) There is no occurrence of cracks or other breaks in the green sheet, which improves the product yield. Further, even when the green sheet is punched out, no cracks or the like occur.

(3) In particular, when a pyrolyte-based solvent is used, the danger of explosion, etc. is reduced, which is advantageous in terms of equipment.

Claims (1)

[Claims] (1) Mix aluminum nitride powder, sintering aid, organic binder, plasticizer, dispersant, and organic solvent, mold, remove binder, and then bake in a non-oxidizing atmosphere to produce a sintered aluminum nitride plate. For production, 100 parts by weight of aluminum nitride powder is mixed with 4 to 12 parts by weight of polyvinyl butyral as an organic binder, 2 to 10 parts by weight of dibutyl phthalate and/or dioctyl phthalate as a plasticizer, and 1 part by weight of an aliphatic ester as a dispersant. ~3 parts by weight of an organic polymer is mixed with a sintering aid in a mixed solvent of two or more selected from chlorine, ketone, aromatic, alcohol, and paraffin organic solvents. A product with a relative density of 95% or more and a thermal conductivity of 100 W/1, which is characterized by mixing using a pot and a zirconia pole, forming it into a sheet using a doctor blade method, removing the binder, and firing it in a non-oxidizing atmosphere. A method for manufacturing aluminum nitride sintered plates of mk or higher.