JP2001019576A - Substrate and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aluminum nitride substrate having a high thermal conductivity, a sufficiently high adhesion strength of an electroconductive layer formed on the surface to an aluminum nitride sintered compact and a slight warpage of the whole substrate. SOLUTION: This aluminum nitride substrate has an electroconductive layer comprising a high-melting metal such as tungsten on the surface of an aluminum nitride sintered compact and >=190 W/mK thermal conductivity of the substrate and >=5.0 kgf adhesion strength of the electroconductive layer to the aluminum nitride sintered compact. The method for producing the aluminum nitride substrate comprises degreasing an electroconductive paste formed compact prepared by forming a layer of the electroconductive paste comprising 100 pts.wt. of the high-melting metal powder having 0.8-5 μm average particle diameter and 11-20 pts.wt. of an aluminum nitride powder on the surface of an aluminum nitride formed compact comprising an aluminum nitride powder, a sintering aid and an organic binder within the range of 800-2,500 pm residual carbon ratio, then baking the resultant formed compact at 1,200-1,700 deg.C temperature and subsequently baking the obtained compact at 1,800-1,900 deg.C temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aluminum nitride sintered body having a conductive layer and a method for producing the same. Particularly, the present invention relates to an aluminum nitride sintered body having high thermal conductivity, good adhesion between the conductive layer and the aluminum nitride sintered body, high density of the conductive layer, and small warpage of the substrate, and a method for producing the same.

[0002]

2. Description of the Related Art Aluminum nitride sintered bodies have excellent properties such as high thermal conductivity, good electrical insulation, and substantially the same coefficient of thermal expansion as silicon (Si) forming integrated circuits. Therefore, it is used as a substrate for semiconductor circuit components.

In order to use an aluminum nitride sintered body as a semiconductor substrate, it is necessary to form a conductive layer of a conductive metal on the surface (hereinafter, also referred to as metallization).
A co-firing method has been used as one of the methods for performing metallization. The simultaneous firing method is a method in which the firing of the conductive layer and the sintering of the substrate are simultaneously performed in one firing, and has an advantageous aspect that the number of steps is smaller than the method of performing metallization after firing the substrate. However, in the conventional co-firing method, the thermal conductivity of the obtained sintered body is at most 17 ° C. at 25 ° C. due to the restriction caused by simultaneous firing of the conductive layer and firing of the substrate.
It was about 0 W / mK.

[0004] On the other hand, as one of the methods for producing an aluminum nitride sintered body having no conductive layer, a two-stage sintering method is performed (Japanese Patent Laid-Open No. 5-105525). In this method, the thermal conductivity of the obtained sintered body is 200 W / m at 25 ° C.
It is about K, and an aluminum nitride sintered body having high thermal conductivity can be obtained.

[0005]

However, when an aluminum nitride sintered body having a conductive layer is manufactured by the two-stage firing method, the surface of the conductive layer formed by the high melting point metal powder paste to which aluminum nitride powder is added is nitrided. A phenomenon occurs in which discoloration due to the aluminum powder easily occurs. In addition, a phenomenon occurs in which discoloration occurs due to exudation of the sintering aid. Therefore, when an electrode such as a Si chip or a pin is to be joined to the surface of the conductive layer by soldering or brazing, the following problem occurs. That is, when plating the surface of the conductive layer with Ni or the like in order to improve the wettability between the conductive layer made of the high melting point metal and the solder, the discolored portion is such that aluminum nitride powder or the like precipitates on the surface of the conductive layer. Therefore, plating is difficult to apply, and sufficient bonding strength cannot be obtained even if plating is applied. Furthermore, when an aluminum nitride sintered body having a conductive layer is manufactured by the two-stage firing method, it is difficult to obtain a sufficiently high adhesion strength between the aluminum nitride sintered body and the conductive layer, and a certain degree of adhesion strength is obtained. However, there is a problem that the variation in adhesion strength is large. Another problem is that the substrate of the aluminum nitride sintered body having the conductive layer has a large warp.

Therefore, it has a high thermal conductivity, an excellent adhesion strength between the conductive layer and the aluminum nitride sintered body and an excellent bonding strength between the conductive layer and the plating, and a small warpage having a highly dense conductive layer. Development of an aluminum nitride substrate has been desired.

[0007]

As a result of repeated studies to solve the above problems, the present inventor has found that discoloration due to the above-mentioned aluminum nitride powder, discoloration due to exudation of the sintering aid, substrate That the increase in warpage of the molded article is caused by the action of carbon after degreasing, and by controlling the residual carbon ratio of the degreased body of the molded body to a specific range, the surface of the conductive layer formed on the aluminum nitride substrate surface Occurrence of discoloration,
It has been found that an increase in the warpage of the substrate can be suppressed. Further, by controlling the residual carbon ratio of the degreased body, the amount of aluminum nitride powder added to the conductive paste, and the temperature range of the two-stage firing method to specific ranges, the aluminum nitride sintered body and the conductive It has been found that the adhesive strength with the layer is sufficiently strong and can be stabilized, and that the thermal conductivity of the aluminum nitride sintered body having the conductive layer can be sufficiently increased, and the present invention has been proposed here. .

That is, the present invention relates to a substrate having a conductive layer formed on the surface of an aluminum nitride sintered body, wherein the aluminum nitride sintered body has a thermal conductivity of 190 W / mK or more, and A substrate having an adhesion strength of 5.0 kgf or more with the conductive layer. Further, the present invention provides an aluminum nitride compact comprising an aluminum nitride powder, a sintering aid and an organic binder, on a surface thereof, 100 parts by weight of a high melting point metal powder having an average particle size of 0.8 to 5 μm and aluminum nitride powder 11 to 20 parts. A conductive paste layer consisting of parts by weight is formed, degreased so that the residual carbon ratio in the aluminum nitride molded product is in the range of 800 to 2500 ppm, and baked at a temperature of 1200 to 1700 ° C., and then 1800 to 1900 ° C. And a method for manufacturing a substrate characterized by firing at a temperature of

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a substrate having a conductive layer formed on the surface of an aluminum nitride sintered body is a so-called metallized substrate, and the thickness of the conductive layer is not particularly limited. The ratio of the area of the conductive layer to the area of one surface on which the conductive layer of the aluminum nitride sintered body is formed is not particularly limited, but is usually 10 to 10
0%.

The material constituting the conductive layer is not particularly limited as long as it is a high melting point metal, but is usually tungsten, molybdenum, etc., and particularly, 5 to 15 parts by weight of aluminum nitride relative to 100 parts by weight of the high melting point metal. It preferably contains a powder.

The thermal conductivity of the aluminum nitride sintered body in the present invention refers to the thermal conductivity of the aluminum nitride sintered body obtained by removing the conductive layer formed on the surface by grinding or the like.
If there is a through hole or a via, the thermal conductivity is measured while avoiding the portion. In the present invention,
The above thermal conductivity is a thermal conductivity measured at 25 ° C.

Further, the adhesion strength between the aluminum nitride sintered body and the conductive layer in the present invention is as follows: after forming a Ni plating layer having a thickness of 2 to 15 μm on the entire surface of the conductive layer, a width of 3.0 mm;
After a lead made of Kovar having a length of 33.0 mm and a thickness of 0.1 mm was brazed to the end surface of the conductive layer, the lead was bent at 90 ° to an aluminum nitride substrate to have a length of 2 mm.
The strength measured as the breaking strength when only pulled.

Conventionally, it has been difficult to achieve both high thermal conductivity of the aluminum nitride sintered body and high adhesion strength between the aluminum nitride sintered body and the conductive layer. But,
In the substrate of the present invention, the aluminum nitride sintered body has a thermal conductivity of 190 W / mK or more, and the adhesion strength between the aluminum nitride sintered body and the conductive layer is 5.0 kgf or more. It is an excellent substrate that achieves both high adhesion strength of the conductive layer. Further, if the manufacturing conditions are more suitably selected, a substrate having an adhesion strength between the aluminum nitride sintered body and the conductive layer of 7.5 kgf or more, and further, 10.0 kgf or more can be obtained.

Next, a method for manufacturing an aluminum nitride substrate of the present invention will be described.

In the present invention, the aluminum nitride powder constituting the aluminum nitride compact is not particularly limited, and any known aluminum nitride powder can be used. In particular, powders having an average particle size of 5 μm or less, as measured by the sedimentation method, are preferably used, more preferably 3 μm or less, and most preferably 0.5 to 2 μm. Aluminum nitride powder whose average particle diameter D1 calculated from the specific surface area and average particle diameter D2 measured by the sedimentation method satisfy the following expression: 0.2 μm ≦ D1 ≦ 1.5 μm D2 / D1 ≦ 2.60 Linear shrinkage at the time can be reduced, which not only improves the dimensional stability of the sintered body, but also approaches the linear shrinkage of the conductive paste layer, so that the adhesion strength between the aluminum nitride sintered body and the conductive layer is further improved. Since it can be increased, it is preferably used in the present invention.

Further, the aluminum nitride powder has an oxygen content of 3.0% by weight or less, and a cation impurity contained in an aluminum nitride composition of AlN of 0.5% by weight or less, particularly, an oxygen content of 0% or less. 0.4 to 1.0% by weight, and the content of cationic impurities is 0.2% by weight or less, and among the cationic impurities, Fe, Ca, S
Aluminum nitride powder having a total content of i and C of 0.17% by weight or less is preferred. When such an aluminum nitride powder is used, it is preferably used in the present invention because the resulting aluminum nitride sintered body has a large improvement in thermal conductivity.

As the sintering aid used in the present invention, known ones are used without any particular limitation. Specifically, an alkaline earth metal compound, for example, an oxide such as calcium oxide, a compound composed of yttrium or a lanthanide element, for example, an oxide such as yttrium oxide is preferably used.

The organic binder used in the present invention may be any known one without any particular limitation. Specifically, acrylic resins such as polyacrylates and polymethacrylates; cellulose resins such as methylcellulose, hydroxymethylcellulose, nitrocellulose, and cellulose acetate butyrate; and vinyl groups such as polyvinylbutyral, polyvinyl alcohol, and polyvinyl chloride Resin-containing resins, hydrocarbon resins such as polyolefins, oxygen-containing resins such as polyethylene oxide, and the like are used alone or in combination of two or more. Among them, acrylic resin is preferably used because it has good degreasing properties and can reduce the resistance of the conductive layer. Other known components such as a solvent, a dispersant, and a plasticizer may be used without any particular limitation.

In the present invention, known proportions of the above components constituting the aluminum nitride molded body are not particularly limited and are employed. For example, aluminum nitride powder 1
The sintering aid is preferably 0.01 to 10 parts by weight and the organic binder is preferably 0.1 to 30 parts by weight with respect to 00 parts by weight. In particular, it is preferable to mix the sintering aid in a ratio of 2 to 7 parts by weight, because it is advantageous for increasing the thermal conductivity.

The shape of the aluminum nitride molded body constituted by these components is not particularly limited, such as a column, a plate, a box, a tube, and a sheet. Further, the method of producing the molded body is not particularly limited, but generally, the molding material is filled in a mold and is subjected to pressure molding as a so-called pressed body. Alternatively, the green sheet is formed by a doctor blade method. This green sheet may be used alone or a plurality of green sheets may be stacked.

In the present invention, the high melting point metal powder constituting the conductive paste is not particularly limited as long as it has a melting point higher than the sintering temperature of the aluminum nitride compact.
Specifically, metals such as tungsten and molybdenum are preferably used. The average particle size of the high melting point metal powder needs to be 0.8 to 5 μm as measured by the Fischer method, preferably 0.8 to 4 μm,
Most preferably, it is μm. 0.8μ average particle size
If it is smaller than m, the shrinkage ratio during firing of the conductive layer is too large than the shrinkage ratio of the aluminum nitride molded body,
The conductive layer is cracked, and the adhesion strength between the aluminum nitride sintered body and the conductive layer is reduced. The average particle size is 5μ.
When the diameter is larger than m, the sinterability of the high melting point metal powder deteriorates, and the gap between the high melting point metal particles after sintering becomes large, so that the aluminum nitride powder and the sintering aid easily precipitate on the surface of the conductive layer. As a result, the adhesion strength between the conductive layer and the plating layer is reduced as described above, and the object of the present invention cannot be achieved.

As the aluminum nitride powder used for the conductive paste, known ones are used without any particular limitation. In particular, the aluminum nitride powder having properties suitable for use in the above-described aluminum nitride compact has good sinterability with a high melting point metal and is effective in improving the adhesion of the conductive layer. Also, the presence of the aluminum nitride powder in the conductive paste reduces the difference in shrinkage between the aluminum nitride portion and the conductive layer portion, and improves the dimensional stability of the sintered body.

In the present invention, the conductive paste has a composition in which 11 to 20 parts by weight of aluminum nitride powder is blended with 100 parts by weight of the high melting point metal powder. In the composition of the conductive paste, when the proportion of the aluminum nitride powder is less than 11 parts by weight, the adhesion between the conductive layer and the aluminum nitride sintered body is deteriorated and the adhesion strength is reduced, or the aluminum nitride portion and the conductive layer portion A phenomenon is observed in which a difference in shrinkage rate causes a crack to occur at the joint interface. In addition, when the amount of aluminum nitride is more than 20 parts by weight, the viscosity of the conductive paste increases and the printability deteriorates. As a result, the adhesion strength between the conductive layer and the aluminum nitride sintered body is low due to printing unevenness and blurring. In addition, discoloration due to exudation of the sintering aid and discoloration due to aluminum nitride powder easily occur on the conductive layer surface. For this reason, plating becomes difficult to apply, and the resistance of the conductive layer increases. Even if plating is applied, uniform and sufficient adhesion strength between the plating layer and the conductive layer cannot be obtained.
When aluminum nitride is more than 20 parts by weight,
Since the storage stability of the conductive paste itself deteriorates, when a conductive paste that has been used for several days after preparation is used, the viscosity of the conductive paste increases and the printability deteriorates, and as a result, the conductive layer becomes uneven due to print unevenness and blurring. And the aluminum nitride sintered body has low adhesion strength. The amount of the aluminum nitride powder is preferably 12 to 15 parts by weight from the viewpoint of the storage stability of the paste.

An organic binder and an organic solvent are mixed with the mixture of the high melting point metal powder and the aluminum nitride powder to prepare a paste having an appropriate viscosity, generally from 80,000 to 120,000 centipoise (cps).
Examples of the organic binder include acrylic resins such as polyacrylates and polymethacrylates, cellulose resins such as methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, nitrocellulose, and cellulose acetate butyrate, polyvinyl butyral, polyvinyl alcohol, and polyvinyl chloride. And the like. Examples of the organic solvent include di-n-butyl phthalate and diethylene glycol mono-.
Examples thereof include n-hexyl ether, 2- (2-butoxyethoxy) ethyl acetate, and terpineol.

In the present invention, the conductive paste layer is formed on the surface of the aluminum nitride molded body. As a method for forming the conductive paste layer on the surface of the aluminum nitride molded body, a known method is employed without particular limitation. Generally,
A method of applying the conductive paste by screen printing or the like is preferably used. In the present invention, the thickness of the conductive paste layer is not particularly limited, but is usually 5 to 6
0 μm.

In the present invention, the molded body having the conductive paste layer has a residual carbon ratio in the aluminum nitride molded body of 800 to 2500 ppm, preferably 800 to 23 ppm.
It is necessary to degrease so as to be in the range of 00 ppm. That is, when the residual carbon ratio is less than 800 ppm,
Even if the other conditions are satisfied, the thermal conductivity of the aluminum nitride sintered body becomes lower than 190 W / mK, and the object of the present invention cannot be achieved. In addition, the residual carbon ratio is 25
If it exceeds 00 ppm, the sinterability of the high melting point metal powder deteriorates, so that uniform and sufficient adhesion strength between the aluminum nitride sintered body and the conductive layer cannot be obtained. Also,
Discoloration due to bleeding of aluminum nitride or a sintering aid tends to occur on the surface of the formed conductive layer, so that a uniform and sufficient bonding strength between the plating layer and the conductive layer cannot be obtained. When the residual carbon ratio exceeds 2500 ppm, not only is it not possible to obtain a uniform and sufficient adhesion strength between the aluminum nitride sintered body and the conductive layer, but also the substrate of the aluminum nitride sintered body becomes large in warp. The object of the invention cannot be achieved.

The residual carbon ratio in the aluminum nitride compact of the aluminum nitride compact having the conductive layer is 800 to
The method of degreasing to 2500 ppm is not particularly limited, and a known method can be employed. The degreasing atmosphere is not particularly limited, except for an oxidizing atmosphere such as air that may oxidize the high melting point metal. Specifically, an inert gas atmosphere such as nitrogen, argon, and helium,
Atmosphere of reducing gas such as hydrogen, their mixed gas atmosphere,
A humidified gas atmosphere, vacuum or the like is preferably used.

The above degreasing temperature is appropriately selected, but is usually 500 to 1200 ° C., preferably 700 to 90 ° C.
A temperature of 0 ° C. is employed. The rate of temperature rise to such a temperature is not particularly limited, but is generally 10 ° C. /
Minutes or less is preferred.

Further, the degreasing time may be set to a time at which the residual carbon ratio of the molded body after degreasing becomes 800 to 2500 ppm or less. Since the time varies somewhat depending on the thickness of the molded product, the density of the molded product, the ratio of the conductive layer, the degreasing temperature, and the like, it cannot be specified unconditionally.
It is determined in the range of 00 minutes.

In the present invention, an aluminum nitride molded article having a conductive paste layer (hereinafter referred to as a “degreased article”) having a conductive carbon layer in which the residual carbon ratio in the degreased aluminum nitride molded article is in the range of 800 to 2500 ppm is then converted to a non-degreased product. The firing is performed in an oxidizing atmosphere or a dry reducing gas atmosphere. As the non-oxidizing atmosphere, for example, an atmosphere composed of a gas such as nitrogen, argon, and helium alone or a mixed gas, or a vacuum (or reduced pressure) atmosphere is used. As a dry reducing gas atmosphere, hydrogen or a mixed atmosphere of hydrogen and an inert gas is used. In addition, the firing temperature conditions are 1200 to 1700 ° C. for the first stage, preferably 1500 to 1700 ° C.
Firing at 650 ° C, then the second stage is 1800 to 1900
C., preferably at 1820 to 1880.degree.

If the firing temperature of the first stage is lower than 1200 ° C., the reduction reaction of oxygen in aluminum nitride by carbon remaining in the degreased body becomes difficult to proceed, and the thermal conductivity of the aluminum nitride sintered body is 190 W / MK, and the object of the present invention cannot be achieved. on the other hand,
If the first-stage sintering temperature exceeds 1700 ° C., sintering of aluminum nitride proceeds before the reduction and removal reaction of oxygen in aluminum nitride by residual carbon sufficiently proceeds, and as a result, oxygen is reduced to aluminum nitride. It diffuses into the solid solution and inhibits the high thermal conductivity of the aluminum nitride sintered body, so that the object of the present invention cannot be achieved. When the firing temperature in the first stage is 1500 to 1650 ° C., the reduction and removal reaction of oxygen proceeds effectively, which is preferable in increasing the thermal conductivity of the sintered body.

If the firing temperature of the second step is lower than 1800 ° C., aluminum nitride cannot be sufficiently sintered, and the thermal conductivity of the aluminum nitride sintered body is 190 W
/ MK, and the object of the present invention cannot be achieved. If the second-stage sintering temperature exceeds 1900 ° C., discoloration occurs due to the exudation of aluminum nitride or a sintering material on the surface of the conductive layer, or the adhesion strength between the conductive layer and the substrate is reduced. Therefore, the warpage of the sintered body becomes larger than 50 μm, and the object of the present invention cannot be achieved. The firing temperature in the second stage is 1820 ° C. to 18 ° C.
In the case of 80 ° C., the thermal conductivity of the aluminum nitride sintered body is preferably higher than 195 W / mK without impairing the adhesion strength between the conductive layer and the substrate, the appearance of the sintered body, and the value of the warpage.

The rate of temperature rise to such a temperature is not particularly limited, but is generally 1 to 40 ° C./min. Further, the holding time of the above temperature is not particularly limited, but it is preferable that the first stage is set in a range of 30 minutes to 10 hours, and the second stage is set in a range of 1 minute to 20 hours. Further, the first and second baking may be performed in a single baking without lowering the temperature in the middle, or the temperature may be reduced between the first and second stages and divided into two bakings. Is also good. However, in consideration of time and energy efficiency, it is preferable to perform the baking only once without lowering the temperature in the middle.

When an electrode such as a Si chip or a pin is to be joined by soldering or brazing to the surface of the conductive layer of the substrate obtained by the method of the present invention, it is necessary to improve the solder wettability of the refractory metal. Usually, the conductive layer is plated with Ni or the like. As a method for forming the plating layer, a known method is employed without particular limitation. For example, a metal such as nickel and gold is generally used as a material for plating, and electroplating, electroplating, or a combination thereof may be used without limitation.

[0035]

As will be understood from the above description, the substrate of the present invention has a thermal conductivity at 25 ° C. of 190 W / mK or more and an adhesion strength between the aluminum nitride sintered body and the conductive layer of 5. 0 kgf or more, strong enough, and substrate warpage is 50
μm or less, and its industrial value is extremely large. Since the aluminum nitride substrate according to the present invention has the above characteristics, it is used as a relay base for mobile communication by joining a metal lead to one side and a metal flange to the other side by brazing or the like. It can be suitably used for electronic and semiconductor equipment parts such as high frequency band device packages.

[0036]

EXAMPLES The present invention will now be specifically illustrated by way of examples, but the present invention is not limited to these examples.

In the examples and comparative examples, the residual carbon ratio was measured by a non-dispersive infrared absorption carbon analyzer (EMIA-11).
0, manufactured by Horiba, Ltd.).

The average particle size D1 determined from the specific surface area was calculated by the following equation.

D1 (μm) = 6 / (S × 3.26) [S: Specific surface area of AlN powder (m ² / g)] The average particle size D2 by the sedimentation method is a centrifugal method manufactured by Horiba, Ltd. It measured with the particle size distribution measuring device CAPA5000.

The appearance of the aluminum nitride sintered body was inspected visually and by observation with a stereoscopic microscope (× 40). The warpage of the aluminum nitride sintered body was measured with a micrometer equipped with a surface plate manufactured by Mitutoyo Corporation.

The adhesion strength between the aluminum nitride sintered body and the conductive layer was measured as follows. First, after a Ni plating layer having a thickness of 2 to 15 μm is formed on the entire surface of the conductive layer, a lead made of Kovar is brought into contact with the end surface of the conductive layer at a temperature of 720 ° C. for 10 minutes in a dry nitrogen / hydrogen mixed gas atmosphere. Attached. The lead is 3.0mm wide, 33.0mm long,
The thickness is 0.1 mm, the brazing material is Ag 72% by weight, C
u 28% by weight. This was set on a strobe M2 manufactured by Toyo Seiki Seisaku-sho, Ltd., and the breaking strength when the lead was pulled vertically by 2 mm in length was measured. The pulling speed was 10 mm / min. In the peeling mode, the fracture surfaces of the pin and the sintered body after the test were measured by using a stereo microscope (× 40), a metal microscope (× 400),
It was examined by observing with a line microanalyzer.

Example 1 The average particle size by the sedimentation method was 1.50 μm, the specific surface area was 2.50 m ² / g (the average particle size calculated from the specific surface area was 0.74 μm), and the oxygen content was 0.1 μm. 100 parts by weight of aluminum nitride powder having the composition shown in Table 1 at 85%, 5 parts by weight of yttria, 1 part by weight of hexaglycerin monooleate as a surfactant, 5 parts by weight of n-butyl methacrylate as an organic binder, and 100 parts by weight of toluene as a solvent Parts were weighed, put into a ball mill pot, and sufficiently mixed using a nylon ball to obtain white slurry. The slurry thus obtained was granulated by a spray dryer method. Using the obtained granules, a molding pressure of 1.0
Pressure at t / cm ² , diameter φ10mm, thickness 1.5m
m was prepared. Next, with respect to 100 parts by weight of tungsten powder having an average particle size of 2.6 μm measured by a Fischer method, 13.0 parts by weight of the aluminum nitride powder, 0.5 parts by weight of ethyl cellulose as an organic binder,
15.0 parts by weight of terpineol as a solvent, a plasticizer and a dispersant were sufficiently kneaded with an automatic mortar and subsequently a three-roll mill to form a paste, and a tungsten paste was printed on both sides of the aluminum nitride molded article by a printing method. .
The printed film thickness was about 25 μm.

The aluminum nitride compact having the conductive layer thus produced was heated and degreased at 800 ° C. for 2 hours while flowing dry nitrogen gas at 5 L / min. The heating rate was 2.5 ° C./min. When the residual carbon ratio of the test sample heated and degreased at the same time was examined, it was 2100 ppm. After degreasing, the degreased body was placed in a container made of aluminum nitride, heated in a nitrogen atmosphere at 1580 ° C. for 6 hours (first stage firing), and further heated at 1855 ° C. for 10 hours (second stage firing). The conductive layer surface of the obtained aluminum nitride substrate was not discolored and was a uniform surface. The warpage of the substrate was 20 μm. Subsequently, electroless Ni-B plating was performed on the surface of the conductive layer of the substrate. There was no plating non-precipitation, and the plating surface had a uniform color tone. The measured adhesion strength of the conductive layer of the plating layer was 10.1 kgf. In each of the peeling modes of the sample, the fracture was within the brazing material.

Next, the thermal conductivity of a test sample (substrate thickness 0.9 mm) in which the conductive layer portion of the aluminum nitride substrate having a conductive layer was removed with a surface grinder was measured by a laser flash method and found to be 215 W / mK. Was.

[0045]

[Table 1]

Examples 2 to 10 and Comparative Examples 1 to 7 In Example 1, except that the particle size of the tungsten powder in the conductive paste shown in Table 2 and the amount of aluminum nitride powder added to the conductive paste were changed. It was the same as in Example 1. Table 2 shows the results.

Example 11 The aluminum nitride compact having the conductive layer prepared in Example 1 was treated with a dry nitrogen gas at a flow rate of 4.2 L / min.
An aluminum nitride substrate was obtained in the same manner as in Example 1, except that degreasing by heating was performed at 00 ° C. for 2 hours. The surface of the conductive layer of the aluminum nitride substrate was not discolored, had a uniform surface, and had a uniform color tone without plating non-precipitation. The results are shown in Table 2.

Example 12 An aluminum nitride molded article having a conductive layer prepared in Example 1 was treated with a dry nitrogen gas at a flow rate of 8 L / min.
An aluminum nitride substrate was obtained in the same manner as in Example 1 except that heating and degreasing were performed at 2 ° C. for 2 hours. The surface of the conductive layer of the aluminum nitride substrate was not discolored, had a uniform surface, and had a uniform color tone without plating non-precipitation. The results are shown in Table 2.

Example 13 An aluminum nitride molded article having a conductive layer prepared in Example 1 was mixed with 5 l of a dry nitrogen / hydrogen mixed gas (hydrogen 10%).
An aluminum nitride substrate was obtained in the same manner as in Example 1, except that degreasing by heating was performed at 800 ° C. for 2 hours while flowing at a flow rate of / min. The surface of the conductive layer of the aluminum nitride substrate was not discolored, had a uniform surface, and had a uniform color tone without plating non-precipitation. The results are shown in Table 2.

Example 14 An aluminum nitride molded article having a conductive layer prepared in Example 1 was mixed with 7 l of dry nitrogen / hydrogen mixed gas (hydrogen 10%).
An aluminum nitride substrate was obtained in the same manner as in Example 1, except that degreasing by heating was performed at 800 ° C. for 2 hours while flowing at a flow rate of / min. The surface of the conductive layer of the aluminum nitride substrate was not discolored, had a uniform surface, and had a uniform color tone without plating non-precipitation. The results are shown in Table 2.

COMPARATIVE EXAMPLE 8 An aluminum nitride molded article having a conductive layer prepared in Example 1 was treated with 800 L of dry hydrogen gas at a flow rate of 5 L / min.
An aluminum nitride substrate was obtained in the same manner as in Example 1 except that heating and degreasing were performed at 2 ° C. for 2 hours. At the same time, the residual carbon ratio of the test sample heated and degreased was determined to be 450 pp.
m. The results are shown in Table 2.

COMPARATIVE EXAMPLE 9 An aluminum nitride molded article having a conductive layer prepared in Example 1 was mixed with a dry nitrogen gas at a flow rate of 3 L / min.
An aluminum nitride substrate was obtained in the same manner as in Example 1 except that heating and degreasing were performed at 2 ° C. for 2 hours. At the same time, the residual carbon ratio of the test sample heated and degreased was determined to be 2900p
pm. Discoloration occurred on the surface of the conductive layer of the obtained aluminum nitride substrate. Subsequently, when electroless Ni plating was performed on the surface of the conductive layer of the sintered body, plating non-precipitation occurred on a part of the conductive layer surface where discoloration had occurred before plating. The results are shown in Table 2.

Examples 15 to 19 and Comparative Examples 10 and 11 The procedure of Example 1 was repeated except that the firing temperature of the first stage shown in Table 2 was changed. Table 2 shows the results.

Examples 20 to 23 and Comparative Examples 12 and 13 The procedure of Example 1 was repeated except that the firing temperature in the second stage shown in Table 2 was changed. Table 2 shows the results.

Example 24 The aluminum nitride molded article having the conductive layer prepared in Example 1 was degreased, placed in a container made of aluminum nitride, heated in a nitrogen atmosphere at 1580 ° C. for 6 hours (first-stage firing), and cooled. . When the residual carbon ratio of the sample fired at the same time was examined, it was 160 ppm. After the first stage firing, the substrate was heated again at 1855 ° C. for 10 hours in a nitrogen atmosphere (second stage firing). The surface of the conductive layer of the aluminum nitride substrate was not discolored, had a uniform surface, and had a uniform color tone without plating non-precipitation. The results are shown in Table 2.

COMPARATIVE EXAMPLE 14 An aluminum nitride molded article having a conductive layer prepared in Example 1 was passed through a dry nitrogen gas at a flow rate of 1.5 L / min.
Heat degreasing was performed at 0 ° C. for 2 hours. The heating rate is 2.5 ° C /
Minutes. At the same time, the residual carbon ratio of the test sample heated and degreased was 4100 ppm. After degreasing,
The degreased body was placed in a container made of aluminum nitride, heated in a nitrogen atmosphere at 1580 ° C. for 6 hours (first-stage baking), and cooled. When the residual carbon ratio of the sample fired at the same time was examined, it was 770 ppm. After the first-stage firing, the substrate was heated again at 1855 ° C. for 10 hours in a nitrogen atmosphere (second-stage firing). Discoloration occurred on the surface of the conductive layer of the obtained aluminum nitride substrate. Subsequently, when electroless Ni plating was applied to the surface of the conductive layer of the sintered body, plating non-precipitation occurred in a part of the conductive layer surface where discoloration had occurred before plating. The results are shown in Table 2.

Example 25 100 parts by weight of the same aluminum nitride powder as used in Example 1, 5 parts by weight of yttria, and n-type dispersant
2 parts by weight of butyl methacrylate, 11 parts by weight of polybutyl acrylate as a binder, 7 parts by weight of dioctyl phthalate as a plasticizer, and 50 parts by weight of a mixed solvent of toluene and isopropyl alcohol are put into a ball mill pot, and nylon balls are used. And mixed well. The obtained slurry was applied to a defoaming apparatus, and the viscosity was 200
After setting the pressure to 00 cps, the sheet was formed on a polypropylene film using a doctor blade type sheet forming machine to produce an aluminum nitride green sheet having a thickness of about 0.5 mm. 65x65m above green sheet
m. Subsequently, three aluminum nitride green sheets were laminated. The laminating pressure is 50 kgf / cm
^{2. The} lamination temperature was 80 ° C. and the lamination time was 20 minutes.

On the aluminum nitride compact thus produced, the tungsten paste produced in Example 1 was printed on both surfaces of the compact. The printed film thickness was about 20 μm each.

The aluminum nitride compact having the conductive layer prepared as described above was heated and degreased at 800 ° C. for 2 hours while flowing dry nitrogen gas at 10 L / min. The heating rate was 2.5 ° C./min. When the residual carbon ratio of the test sample heated and degreased at the same time was examined, it was 2200 ppm.
Met. After degreasing, the degreased body was placed in a container made of aluminum nitride and heated in a nitrogen atmosphere at 1550 ° C. for 4 hours (first stage firing), and further heated at 1870 ° C. for 8 hours (second stage firing). The conductive layer surface of the aluminum nitride sintered body of the obtained substrate was not discolored and was a uniform surface.
The warpage of the substrate was 30 μm. Subsequently, electroless Ni-B plating was applied to the surface of the conductive layer of the sintered body. There was no plating non-precipitation, and the plating surface had a uniform color tone. The measured adhesion strength of the conductive layer was 11.2 kgf. In each of the peeling modes of the samples, the fracture was within the brazing material.

Next, the thermal conductivity of the test sample (substrate thickness 0.9 mm) simultaneously degreased and fired was 220 W / mK when measured by the laser flash method.

Examples 26 to 34 and Comparative Examples 15 to 18 The same procedures as in Example 25 were carried out except that the particle size of the tungsten powder in the conductive paste shown in Table 2 and the amount of the aluminum nitride powder added to the paste were changed. Same as 25. Table 2 shows the results.

Example 35 The aluminum nitride molded article having the conductive layer prepared in Example 25 was mixed with a dry nitrogen gas at a flow rate of 7 L / min.
An aluminum nitride substrate was obtained in the same manner as in Example 25 except that degreasing by heating was performed at 0 ° C. for 2 hours. The surface of the conductive layer of the aluminum nitride substrate was not discolored, had a uniform surface, and had a uniform color tone without plating non-precipitation. The results are shown in Table 2.

Example 36 An aluminum nitride molded article having a conductive layer prepared in Example 25 was treated with a dry nitrogen gas at a flow rate of 23 L / min.
Example 25 except that heat degreasing was performed at 00 ° C. for 2 hours.
In the same manner as described above, an aluminum nitride substrate was obtained. The surface of the conductive layer of the aluminum nitride substrate was not discolored, had a uniform surface, and had a uniform color tone without plating non-precipitation. The results are shown in Table 2.

Example 37 An aluminum nitride molded article having a conductive layer prepared in Example 25 was mixed with a dry nitrogen / hydrogen mixed gas (20% hydrogen) for 5 minutes.
An aluminum nitride substrate was obtained in the same manner as in Example 25 except that heating and degreasing were performed at 800 ° C. for 2 hours while flowing at L / min. The surface of the conductive layer of the aluminum nitride substrate was not discolored, had a uniform surface, and had a uniform color tone without plating non-precipitation. The results are shown in Table 2.

Example 38 An aluminum nitride compact having a conductive layer prepared in Example 25 was treated with a dry nitrogen / hydrogen mixed gas (20% hydrogen) in 7
An aluminum nitride substrate was obtained in the same manner as in Example 25, except that degreasing by heating was performed at 800 ° C. for 2 hours while flowing at L / min. The surface of the conductive layer of the aluminum nitride substrate was not discolored, had a uniform surface, and had a uniform color tone without plating non-precipitation. The results are shown in Table 2.

COMPARATIVE EXAMPLE 19 An aluminum nitride molded article having a conductive layer prepared in Example 25 was treated with a dry hydrogen gas at a flow rate of 10 L / min.
Heat degreasing was performed at 00 ° C. for 2 hours. 2.5 ° C heating rate
/ Min, and an aluminum nitride substrate was obtained in the same manner as in Example 25. At the same time, the residual carbon ratio of the test sample heated and degreased was 450 ppm.
The results are shown in Table 2.

Comparative Example 20 An aluminum nitride molded article having a conductive layer prepared in Example 25 was mixed with a dry nitrogen gas at a flow rate of 5 L / min.
An aluminum nitride substrate was obtained in the same manner as in Example 25 except that degreasing by heating was performed at 0 ° C. for 2 hours. At the same time, the residual carbon ratio of the test sample heated and degreased was determined to be 3300p
pm. The results are shown in Table 2.

Examples 39 to 43 and Comparative Examples 21 and 22 The same procedures as in Example 25 were performed except that the firing temperature in the first stage shown in Table 2 was changed. Table 2 shows the results.

Examples 44 to 47 and Comparative Examples 23 and 24 The same procedures as in Example 25 were carried out except that the firing temperature in the second stage shown in Table 2 was changed. Table 2 shows the results.

Example 48 The aluminum nitride molded article having the conductive layer prepared in Example 25 was degreased, put in a container made of aluminum nitride, and heated at 1550 ° C. for 4 hours in a nitrogen atmosphere (first-stage firing).
The temperature has dropped. When the residual carbon ratio of the sample fired at the same time was examined, it was 320 ppm. After the first firing,
Heating was performed at 1870 ° C. for 8 hours in a nitrogen atmosphere (second stage firing). The surface of the conductive layer of the aluminum nitride substrate was not discolored, had a uniform surface, and had a uniform color tone without plating non-precipitation. The results are shown in Table 2.

Comparative Example 25 The same procedure as in Example 25 was carried out except that the aluminum nitride molded article having the conductive layer produced in Example 25 was heated and degreased at 800 ° C. for 2 hours while flowing dry nitrogen gas at 1.2 L / min. Similarly, an aluminum nitride substrate was obtained. At the same time, the residual carbon ratio of the test sample heated and degreased was determined to be 490
It was 0 ppm. The results are shown in Table 2.

[0072]

[Table 2]

[0073]

[Table 3]

[0074]

[Table 4]

[0075]

[Table 5]

[0076]

[Table 6]

[0077]

[Table 7]

[0078]

[Table 8]

[0079]

[Table 9]

Claims (2)

[Claims] 1. A substrate having a conductive layer formed on the surface of an aluminum nitride sintered body, wherein the aluminum nitride sintered body has a thermal conductivity of 190 W / mK or more, and the aluminum nitride sintered body and the conductive layer Adhesion strength of 5.0kgf
A substrate characterized by the above. 2. 100 parts by weight of a high melting point metal powder having an average particle size of 0.8 to 5 μm and aluminum nitride powder 11 to 20 A conductive paste layer consisting of parts by weight is formed, degreased so that the residual carbon ratio in the aluminum nitride molded product is in the range of 800 to 2500 ppm, and baked at a temperature of 1200 to 1700 ° C., and then 1800 to 1900 ° C. 2. The method for manufacturing a substrate according to claim 1, wherein the substrate is fired at a temperature.