JPH0891935A - Sintered material of aluminum nitride, its production and circuit substrate - Google Patents

Abstract

PURPOSE: To obtain a sintered material of aluminum nitride having high thermal conductivity, high strength, excellent wetting properties of metallized layer and improved bond strength, comprising AlN particles having an average particle diameter of equal to or less than a fixed value, by covering a fixed % of the surface of AlN particles positioned on the surface with a grain boundary layer. CONSTITUTION: This sintered material of aluminum nitride comprises AlN particles having <=2μm, preferably 0.7-2.0μm average particle diameter. 5-100%, preferably 50-100% of the surface of AlN particles positioned at the surface is covered with a grain boundary layer. In production of the sintered material of aluminum nitride, a raw material containing AlN powder and a sintering auxiliary is molded, the molded article is sintered in a nonoxidizing atmosphere under 0.5-10 atmospheric pressure at <=1,600 deg.C, preferably <=1,550 deg.C. For example, an oxide or a carbide of an alkaline earth metal such as Ca, Ba or Sr is used as the sintering auxiliary and the amount of the sintering auxiliary added is 0.5-2 pts.wt. based on 100 pts.wt. of AlN powder. The grain boundary layer means the sintering auxiliary, a reaction product of the sintering auxiliary and AlN or a reaction product of the sintering auxiliaries.

Description

Detailed Description of the Invention

[0001]

The present invention relates to aluminum nitride (A
1N) A sintered body, a method for manufacturing an AlN sintered body, and a circuit board.

[0002]

2. Description of the Related Art Conventionally, alumina-based ceramics have been generally used as a base material in circuit boards for semiconductors.
However, when a high-power semiconductor element is mounted on the circuit board or when a semiconductor element having a high integration density is mounted, thermal conductivity is not always sufficient with a base material made of an alumina-based ceramic, and the semiconductor element It was difficult to sufficiently release the generated heat.

From the above, A having excellent thermal conductivity
Circuit boards having an 1N sintered body as a base material have been developed and come into use. Further researches on the AlN sintered body have revealed that, for example, JP-A-61-84037.
As disclosed in No. 3, the data on the surface condition such as the surface roughness of the substrate made of the AlN sintered body has been accumulated, and the manufacturing method and the technology for the metallized substrate have been advanced.

When the AlN sintered body is used as a metallized base material, since the wettability between the AlN sintered body and the metallized metal is poor, the AlN sintered body is oxidized in air before metallization. It is necessary to newly generate alumina (Al ₂ O ₃ ) having good wettability on the surface by the treatment. However, in the method of oxidizing the surface of the AlN sintered body, Al ₂ O _{3 is} formed on the surface of the AlN sintered body.
Are formed into islands or have a sufficient thickness of Al ₂ O
_{Since 3} is not formed, there is a problem in that the metal film (for example, a copper foil) and the AlN sintered body are separated from each other at the bonding interface to cause a decrease in reliability.

Therefore, Japanese Patent Laid-Open No. 2-9766 discloses A
A method is disclosed in which the grain boundary phase in the 1N sintered body is unevenly distributed on the surface and the grain boundary phase is utilized to strengthen the bond with the metallized layer. However, since the AlN sintered body is sintered at a high temperature (1800 ° C. or higher),
Growth of crystal grains occurs, resulting in a problem that mechanical strength decreases. This reduction in mechanical strength is fatal when applied as a semiconductor circuit board.

[0006]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide A having high mechanical strength and good wettability with a metallized layer.
It is intended to provide an IN sintered body and a method for manufacturing the same.

Another object of the present invention is to provide a circuit board in which a metal (circuit pattern) is firmly adhered to a base material composed of the AlN sintered body.

[0008]

Means and Actions for Solving the Problems An AlN sintered body according to the present invention has AlN particles having an average particle diameter of 2 μm or less, and 5 to 100% of the surface of the AlN particles is a grain boundary phase. It is characterized by being covered.

The AlN sintered body according to the present invention has a high thermal conductivity and an average grain size of 2 μm or less, and thus exhibits higher strength than the conventional sintered body and has a surface. Since the surface of the AlN particles located in the area is covered with the grain boundary phase, the wettability with the metallized layer is improved and the bonding strength is also improved. Further, since the grain boundary phase inside the sintered body is transferred to the surface side, scattering of phonons due to the grain boundary phase is suppressed, so that the decrease in thermal conductivity due to this grain boundary phase is improved.

The average particle size of the AlN particles is defined because if the average particle size exceeds 2 μm, an AlN sintered body having high mechanical strength cannot be obtained. The more preferable average particle diameter of the AlN particles is 0.7 to 2.0 μm.

The grain boundary phase is a compound such as alkaline earth or rare earth added as a sintering aid of AlN, a reaction product of the sintering aid and AlN, or a reaction between the sintering aids. Means product.

The area ratio of the grain boundary phase covering the surface of the AlN particles located on the surface is defined. If the area ratio is less than 5%, the wettability with the metallized layer cannot be improved. A more preferable area ratio of the grain boundary phase covering the surface of the AlN particles is 50 to 100%.

Next, a preferred manufacturing method (first method or second method) of the AlN sintered body according to the present invention will be described.

1) First Method In this method, a raw material containing AlN powder and a sintering aid is molded, and then the molded body is subjected to a pressure of 1600 in a non-oxidizing atmosphere of 0.1 to 0.9 atm. ℃ or less, preferably 1550
It is a method of sintering at ℃ or less.

That is, first, a sintering aid is added to AlN powder, mixed with a ball mill or the like, and if necessary, a binder or the like is added to knead and granulate to prepare a raw material, and then the raw material is molded. By doing so, a molded body is produced.

The AlN powder has an average primary particle size of 0.0
It is preferable that the amount of impurity oxygen is 3 to 1.2 μm and the amount of impurity oxygen is 0.2 to 3.5% by weight.

The reason why the average primary particle size of the AlN powder is limited to the above range is as follows. A
If the average primary particle size of the 1N powder is less than 0.03 μm, handling of the powder may be difficult and molding of the powder may be difficult. On the other hand, the average primary particle size of AlN powder is 1.
If it exceeds 2 μm, low-temperature sintering at 1600 ° C. or less, particularly 1550 ° C. or less may become difficult, and the particle size after sintering may exceed 2 μm and mechanical strength may decrease.
The more preferable average primary particle diameter of the AlN powder is 0.05 to
It is 1.0 μm.

The oxygen amount of impurities in the AlN powder means the amount that effectively contributes to the sintering immediately before the sintering. The reason for limiting the amount of impurity oxygen to the above range is as follows. When the amount of impurity oxygen is less than 0.2% by weight, it becomes difficult to sinter at 1600 ° C. or less, particularly 1550 ° C. or less, or the AlN sintered body is deteriorated at the handling stage of mixing or molding before sintering. There is a risk of
On the other hand, if the amount of impurity oxygen exceeds 3.5% by weight, it may not be possible to obtain an AlN sintered body having high thermal conductivity. A more preferable impurity oxygen amount is 0.5 to 2% by weight.

Examples of the sintering aid include Ca, B
Alkaline earth metal oxides such as a and Sr, carbides, carbonates, oxalates, nitrates, alkoxides, rare earth element oxides including Sc and Y, carbides, carbonates, oxalates,
One or more selected from nitrates and alkoxides can be used. Further, the addition amount of the sintering aid is 0.5 to 1 in terms of alkaline earth metal and / or rare earth element based on 100 parts by weight of the AlN powder.
It is desirable to set it in the range of 0 parts by weight.

The raw material composed of the AlN powder and the sintering aid is allowed to contain the AlN powder having a particle size larger than the average particle size (0.03 to 1.2 μm). Further, in the above raw materials, oxides, carbides, fluorides, carbonates, oxalates of transition metals such as Ti, W, Mo, Ta, Nb, and Mn are added to the raw materials for coloring and strengthening, if necessary. The nitrate may be added to the AlN powder in the range of 0.05 to 1% by weight in terms of transition metal. further,
Aluminum compounds such as Al ₂ O ₃ and AlF ₃ effective for lowering the sintering temperature, phosphorus compounds, boron compounds, silicon oxide (SiO ₂ ), and silicon nitride (Si ₃ N ₄ ) for improving mechanical strength. ) And other silicon compounds are allowed to be blended in the range of 1% by weight or less with respect to the AlN powder.

Examples of the molding method include a die press,
Hydrostatic pressing or sheet molding can be adopted.

Next, the molded body is heated in a non-oxidizing atmosphere such as a nitrogen gas stream to remove the binder, and then in a non-oxidizing atmosphere at a reduced pressure of 0.1 to 0.9 atm.
An AlN sintered body is manufactured by sintering at 600 ° C. or lower, preferably 1550 ° C. or lower. In the step of removing the binder, an atmosphere containing oxygen or an atmosphere containing water vapor can be used by appropriately selecting the maximum temperature for heating while paying attention to the oxidation of AlN.

It is preferable that the sintering step is carried out for 10 minutes to 90 hours in an atmosphere of the nitrogen gas or the like having the above-mentioned pressure by storing the molded body in an AlN container or the like.

The pressure of the atmosphere in the sintering process is limited to the above range for the following reason.
When the pressure of the atmosphere is less than 0.1 atm, the evaporation of AlN from the molded body and the AlN container and the like and the evaporation of the sintering aid component from the molded body become unfavorable. On the other hand, when the pressure of the atmosphere exceeds 0.9 atm, the effect of depressurization becomes small and it becomes difficult to transfer the internal grain boundary phase to the surface of the AlN particles located on the surface.
The surface of the AlN particles located on the surface of the sintered body cannot be covered with the grain boundary phase. A preferable atmosphere pressure is 0.1 to 0.5 atm.

According to the first method as described above, AlN
The growth of AlN particles can be suppressed by adding a sintering aid to the particles and then sintering at 1600 ° C. or lower in a non-oxidizing atmosphere of 0.1 to 0.9 atm under reduced pressure. As a result, it is possible to manufacture an AlN sintered body having AlN particles having an average particle diameter of 2 μm or less, having high thermal conductivity and having improved strength by miniaturizing the AlN particles. The mechanism by which the thermal conductivity is improved is that Al added by the sintering aid added in the sintering process.
This is a trap effect of oxygen impurities in N powder. The sintering aid reacts with impurity oxygen (Al ₂ O ₃ ) contained in AlN to form a rare earth-Al-O system or an alkaline earth-Al- system.
Since the impurity oxygen is moved to the grain boundaries of the AlN sintered body in the form of an O-based compound or the like, solid solution of oxygen in the AlN lattice is prevented. It is considered that this can improve the thermal conductivity.

Further, in the above-mentioned sintering step, the grain boundary phase caused by the internal sintering aid can be transferred to the surface of the AlN particles located on the surface thereof. This mechanism is based on the generated rare earth-Al-O system or alkaline earth-A system.
The l-O-based compound becomes a liquid phase having a reduced viscosity in the sintering step, and easily migrates to the surface side under the reduced pressure to cause AlN.
It is considered to cover the particle surface. As a result, it is possible to manufacture an AlN sintered body in which the surface of the AlN particles located on the surface is covered with the grain boundary phase at an area ratio of 5 to 100%. Examples of the grain boundary phase include Y ₂ O ₃ and Y ₃ Al ₅ when Y ₂ O ₃ that is a rare earth oxide is added as a sintering aid.
O ₁₂ , YAlO ₃ , Y ₄ Al ₂ O _{9 and the} like can be mentioned. CaC which is an alkaline earth carbon salt as a sintering aid
When O ₃ is added, Ca ₃ Al ₂ O ₆ and Ca ₁₂ A
l ₁₄ O ₃₃ , CaAl ₂ O ₄ , CaAl ₄ O ₇ , CaAl
₁₂ O _{19 and the} like can be mentioned. Also, the area ratio of the grain boundary phase covering these surfaces should be controlled by appropriately selecting the addition amount of the sintering aid, the holding time at the maximum temperature during sintering, the pressure, the rate of temperature increase and decrease, etc. Is possible.

Therefore, Al having an average particle size of 2 μm or less
By having N particles, high thermal conductivity is achieved, and strength is improved by refining AlN particles.
By coating the N particle surface with an area ratio of 5 to 100%, an AlN sintered body having improved wettability with the metallized layer can be manufactured.

2) Second Method In this method, a raw material containing AlN powder and a sintering aid containing halogen is molded, and then the molded body is subjected to 0.5 to
This is a method of sintering at 1600 ° C. or lower, preferably 1550 ° C. or lower in a non-oxidizing atmosphere of 10 atm.

That is, first, a sintering aid containing halogen is added to AlN powder and mixed by a method such as a ball mill,
If necessary, a binder or the like is added, kneading and granulation are performed to prepare a raw material, and then the raw material is molded to produce a molded body.

The AlN powder preferably has the same particle size and the same amount of impurity oxygen as those described in the first method.

As the halogen-containing sintering aid, for example, at least one selected from an alkaline earth metal halide, an acid halide, a rare earth element halide containing Sc, Y, and an acid halide is used. You can

The addition amount of the sintering aid is preferably in the range of 0.5 to 10 parts by weight in terms of alkaline earth metal and / or rare earth element based on 100 parts by weight of the AlN powder. It is also permissible to partially replace the sintering aid with an oxide of an alkaline earth metal and / or an oxide of a rare earth element.

In the raw material consisting of the AlN powder and the sintering aid, the AlN powder having a particle size larger than the average particle size (0.03 to 1.2 μm) is further added as in the first method described above. Allowed to be included. Further, if necessary, Ti, W, Mo, T may be added for coloring and strengthening.
a, Nb, Mn and other transition metal oxides, carbides, fluorides, carbonates, oxalates, and nitrates are mixed in the range of 0.05 to 1% by weight in terms of transition metal with respect to the AlN powder. Good. Furthermore, Al that is effective in lowering the sintering temperature
Aluminum compounds such as ₂ O ₃ and AlF ₃ , phosphorus compounds, boron compounds and silicon compounds such as silicon oxide (SiO ₂ ) and silicon nitride (Si ₃ N ₄ ) for improving mechanical strength are converted into AlN powder. On the other hand, it is allowed to be compounded in the range of 1% by weight or less.

As the molding method, for example, a die press, a hydrostatic press or a sheet molding can be adopted.

Then, the molded body is heated in a non-oxidizing atmosphere such as a nitrogen gas stream to remove the binder, and then at 1600 ° C. in a non-oxidizing atmosphere of 0.5 to 10 atm.
Hereinafter, the AlN sintered body is manufactured by sintering at preferably 1550 ° C. or lower. In the step of removing the binder, an atmosphere containing oxygen or an atmosphere containing water vapor can be used by appropriately selecting the maximum temperature for heating while paying attention to the oxidation of AlN.

It is desirable that the sintering step is carried out for 10 minutes to 90 hours in an atmosphere of nitrogen gas or the like having the above-mentioned pressure, with the molded body being housed in an AlN container or the like.

The reason why the pressure of the atmosphere in the sintering process is limited to the above range is as follows. When the pressure of the atmosphere is less than 0.5 atm, it is not preferable because evaporation of the halide which is the sintering aid from the molded body or decomposition of the acid halide becomes severe and the sinterability is significantly deteriorated. On the other hand, when the pressure of the atmosphere exceeds 10 atm, it becomes difficult to transfer the internal grain boundary phase to the surface of the AlN particles located on the surface, and the surface of the AlN particles located on the surface of the sintered body is coated with the grain boundary phase. Can not do. The preferable pressure range of the atmosphere is 0.7 to
It is 5 atm.

According to the second method as described above, AlN particles having a predetermined average primary particle diameter and impurity oxygen content are added to an alkaline earth metal halide, an acid halide,
After adding a rare earth element halide containing Sc, Y, at least one kind of sintering aid selected from acid halides, and a specific sintering aid containing halogen, a non-volatile material of 0.5 to 0.9 atm is added. By sintering at 1600 ° C. or lower in an oxidizing atmosphere, growth of AlN particles can be suppressed. as a result,
AlN having AlN particles with an average particle diameter of 2 μm or less, having high thermal conductivity and having improved strength by refining AlN particles
A sintered body can be manufactured. The mechanism by which the thermal conductivity is improved is A due to the sintering aid added in the sintering process.
This is a trap effect of impurity oxygen of 1N powder. The sintering aid reacts with impurity oxygen (Al ₂ O ₃ ) contained in AlN to form a rare earth-Al-O system or an alkaline earth-Al- system.
Since the impurity oxygen is moved to the grain boundaries of the AlN sintered body in the form of an O-based compound or the like, solid solution of oxygen in the AlN lattice is prevented. It is considered that this can improve the thermal conductivity.

Further, in the above-mentioned sintering step, the grain boundary phase caused by the internal sintering aid can be transferred to the surface of the AlN particles located on the surface thereof. The mechanism is that the rare earth-Al-O-based or alkaline earth-Al-O-based compound containing the generated halogen becomes a liquid phase in which the viscosity is lowered in the sintering process. It is considered that the concentration on the surface decreases due to the easy evaporation, and as a result, the concentration gradient is relaxed, and thus the particles easily move from the inside of the sintered body to the surface. Therefore, in the second method in which the sintering aid containing halogen is added, the grain boundary phase is easily located on the surface of the sintered body even if the pressure in the sintering step is slightly higher than that in the first method described above. It is presumed that the surface of the AlN particles is covered. As a result, the surface of the AlN particles located on the surface is 5
An AlN sintered body coated with an area ratio of ˜100% can be produced. As the grain boundary phase, for example, when YF ₃ which is a fluoride of a rare earth element is added as a sintering aid, Y
₂ O ₃ , Y ₃ Al ₅ O ₁₂ , YAlO ₃ , Y ₄ Al
₂ O ₉ , YOF and the like can be mentioned. Further, the area ratio of the grain boundary phase covering these surfaces can be controlled by appropriately selecting the addition amount of the sintering aid, the holding time at the maximum temperature during sintering, the pressure, the rate of temperature increase and decrease, etc. It is a thing.

Therefore, Al having an average particle size of 2 μm or less
By having N particles, high thermal conductivity is achieved, and strength is improved by refining AlN particles.
AlN in which the wettability with the metallized layer is improved by coating the N particle surface with an area ratio of 0.05 to 100%
A sintered body can be manufactured.

The circuit board according to the present invention is the above-mentioned Al.
It has a structure in which a metal is joined to a base material made of N sintered body.

The metal is directly bonded to the base material by, for example, a metallizing method.

Since the base material made of the AlN sintered body, in which the surface of the AlN particles located on the above-mentioned surface is covered with the grain boundary phase containing halogen, has high wettability with respect to the metallized layer, the metallized layer is applied to the base material. By joining the layers (conductor circuits), it is possible to obtain a circuit board in which the conductor circuits are firmly joined to the base material.

Further, when the AlN sintered body having the surface of the AlN particles located on the surface covered with the grain boundary phase containing halogen is used as the base material, the dielectric constant of the grain boundary phase is such that the grain boundary phase containing no halogen is present. Slightly lower than. Such AlN
When a conductor circuit is formed on a base material made of a sintered body by a metallizing method or the like, the signal transmission of the conductor circuit can be accelerated due to the decrease in the dielectric constant.

[0045]

EXAMPLES The present invention will be described in more detail below with reference to examples. Note that these examples are described for the purpose of facilitating the understanding of the present invention, and do not particularly limit the present invention.

Example 1 Y ₂ O ₃ powder having an average particle size of 0.1 μm and a purity of 99.9% was added to AlN powder having an average primary particle size of 0.2 μm and an impurity oxygen content of 1.8% by weight. 5% by weight
And WO ₃ having an average particle size of 0.1 μm and a purity of 99.9%
0.3% by weight of conversion was added, and an acrylic binder was added together with an organic solvent to mix and defoam using a ball mill, and then a 0.7 mm-thick sheet was formed by a tape casting method. Subsequently, after cutting the above-mentioned sheets, three sheets are laminated and thermocompression-bonded to obtain 100 × 100.
A molded body of × 2.1 mm ³ was produced. Subsequently, the molded body was heated in nitrogen to a maximum temperature of 700 ° C. to remove the binder.

Next, the molded body after degreasing is placed in an AlN container, the container is set in a carbon heater furnace, and the atmosphere is nitrogen gas at 0.6 atm, 1600 ° C., 12
Sintering was performed for a time to produce an AlN sintered body.

(Comparative Example 1) The same degreased molded body as in Example 1 was placed in an AlN container, and the container was set in a carbon heater furnace.
Sintering was performed at 800 ° C. for 12 hours to produce an AlN sintered body.

(Comparative Example 2) The same degreased molded body as in Example 1 was placed in an AlN container, and the container was set in a carbon heater furnace.
Sintering was performed at 0 ° C. for 8 hours to produce an AlN sintered body.

(Example 2) Average primary particle size is 0.08 μm
And AlC powder with an impurity oxygen content of 2.8% by weight was added to CaC with a sintering aid having an average particle size of 0.2 μm and a purity of 99.9%.
O ₃ was added in an amount of 1% by weight in terms of CaO, an acrylic binder was added together with an organic solvent, and the mixture was defoamed using a ball mill and defoamed.
A 7 mm sheet was molded. After this sheet was cut and laminated, it was degreased in the same manner as in Example 1, and the molded body after degreasing was placed in a container made of AlN, and this container was set in a heater furnace made of carbon, and nitrogen gas 0.9 Under atmospheric pressure, 1
Sintering was performed at 550 ° C. for 12 hours to produce an AlN sintered body.

Example 3 The average primary particle size is 0.2 μm,
Dy ₂ O having an average particle size of 0.1 μm and a purity of 99.9% as a sintering aid in AlN powder having an impurity oxygen content of 1.5 wt%.
₃ % by weight, average particle size 0.2 μm, purity 99.9% CaCO ₃ in terms of CaO 1% by weight and average particle size 0.
Titanium oxide (TiO ₂ ) powder having a particle size of 1 μm and a purity of 99.9% was added in an amount of 0.3% by weight in terms of Ti. Further, an acrylic binder was added together with an organic solvent and mixed using a ball mill, followed by defoaming by tape casting method. Thickness 0.
A 7 mm sheet was molded. After this sheet was cut and laminated, it was degreased in the same manner as in Example 1, and the molded body after degreasing was placed in an AlN container, and this container was set in a carbon heater furnace and nitrogen gas 0.1 Under atmospheric pressure, 1
Sintering was performed at 500 ° C. for 10 hours to produce an AlN sintered body.

Example 4 The average primary particle size is 0.6 μm,
3% by weight of YF ₃ having an average particle size of 0.2 μm and a purity of 99.9% was used as a sintering aid in AlN powder having an amount of impurity oxygen of 0.8% by weight, and an average particle size of 1.0 μm and a purity of 99. 9% A
n-Butanol was added to a mixture containing 0.5% by weight of 1 ₂ O ₃ and 0.3% by weight of WO ₃ having an average particle size of 0.1 μm and a purity of 99.9% in terms of W, and the mixture was dissolved by a wet ball mill. After crushing and mixing, n-butanol was removed to obtain a raw material powder. Subsequently, 5% by weight of an acrylic binder was added to this raw material powder together with an organic solvent for granulation, and then 50
A molded body was produced by uniaxially pressing with a pressure of MPa. This molded body is placed in a container made of an AlN sintered body, the container is set in a graphite heater furnace, and sintered at 1550 ° C. for 8 hours in an atmosphere of nitrogen gas at 1 atm to obtain an AlN sintered body. Manufactured.

Obtained Examples 1-4 and Comparative Examples 1-2
About the AlN sintered body of, density, thermal conductivity, average particle size,
The mechanical strength and the coverage of the surface of the sintered body with the grain boundary phase were measured. The density was measured by the Archimedes method, and the thermal conductivity was measured by the laser flash method according to JIS-R1611. The average particle size was obtained by observing the fracture surface of the sintered body with an SEM and by an intercept method. The mechanical strength was measured by the 4-point bending method according to JIS-R1601. The surface coverage of the grain boundary phase was determined by reading a low-magnification SEM photograph of the surface of the sintered body or an optical microscope photograph with a scanner and analyzing the image to determine the area percentage of the grain boundary phase. The results are shown in Table 1 below.

Further, SEM photographs of fracture surfaces near the surface of the sintered bodies obtained in Example 4 and Comparative Example 2 are shown in FIGS. 1 and 2, respectively.

Further, oxygen is added to each of the AlN sintered bodies at 40%.
A 35 × 35 mm ² copper plate containing 0 ppm is contacted,
In a nitrogen gas atmosphere containing 7 ppm of oxygen, the product was stored at a maximum temperature of 1070 ° C. for 3 minutes, the sintered body and the copper plate were joined, and the peel strength was measured. The peel strength was measured using an Instron strength tester with a crosshead of 50 mm.
It was determined by measuring the peel strength of the copper plate at a speed of / min. The results are also shown in Table 1 below.

Further, the circuit board 1 shown in FIGS. 3 and 4 was manufactured by selectively etching the copper plate bonded to the base material made of the AlN sintered body of Example 4. The circuit board 1 of FIGS. 3 and 4 has a base material 2 made of an AlN sintered body, and the copper circuit pattern 4 is eutectic liquid phase on the grain boundary phase 3 exuded on the surface of the base material 2. It has a structure in which it is joined via the solidified layer 5.

[0057]

[Table 1] (Examples 5 to 12) AlN powders and additives shown in Table 2 below were used, and 8 kinds of materials were prepared in the same manner as in Example 1 except that the sintering conditions were set to the temperature, time and pressure shown in Table 2 below. An AlN sintered body was manufactured. In Example 6, Y ₂ O
₃ was added by dissolving _{Y (NO 3) 3 · 6H} 2 O to n- butanol.

With respect to the obtained AlN sintered bodies of Examples 5 to 12, the density, thermal conductivity, average grain size, mechanical strength, and coverage of the surface of the sintered body with the grain boundary phase were the same as in Example 1. It was measured by the method. Further, a peel strength was measured by bonding a copper plate to each AlN sintered body under the same conditions as in Example 1. The results are shown in Table 3 below.

[0059]

[Table 2]

[0060]

[Table 3] (Examples 13 to 21) Nine kinds of samples were prepared in the same manner as in Example 1 except that the AlN powder and the additives shown in Table 4 below were used and the sintering conditions were the temperature, time and pressure shown in Table 4 below. An AlN sintered body was manufactured.

Regarding the obtained AlN sintered bodies of Examples 13 to 21, the density, the thermal conductivity, the average particle size, the mechanical strength and the coverage of the surface of the sintered body with the grain boundary phase were the same as in Example 1. It was measured by the method. Further, a peel strength was measured by bonding a copper plate to each AlN sintered body under the same conditions as in Example 1. The results are shown in Table 5 below.

[0062]

[Table 4]

[0063]

[Table 5] (Comparative Example 3) The same composition as in Example 4 was sintered under the same conditions, except that the pressure was 0.2 atm and 1550 ° C for 8 hours. However, the density was 3.24 g · cm ⁻³ , which was not completely densified.

Comparative Example 4 The same composition as in Example 4 was sintered under the same conditions, except that the pressure was 12 atm and the temperature was 1550 ° C. for 8 hours. Although the density was sufficiently densified as 3.31 g · cm ⁻³ , almost no grain boundary phase was observed on the surface, and an attempt was made to join the steel sheets by the same method as in Examples 1 to 4,
I couldn't join.

Example 22 The same composition as in Example 4 was sintered under the same conditions to obtain an AlN sintered body. Mo on this surface
A metallizing paste with a mixing ratio of TiN and TiN of 1: 2 (weight ratio) was applied by a screen printing method. In a nitrogen gas atmosphere, this sintered body had a maximum temperature of 1700 ° C. and a holding time of 1 hour,
The surface of the sintered body was metallized by heat treatment at a pressure of 1.2 atm. The obtained metallized AlN circuit board had practically no peeling or color unevenness and could be sufficiently put into practical use.

[0066]

As described above in detail, according to the present invention, AlN has high mechanical strength due to its small average grain size and has good wettability with metallized metal without oxidation treatment. A sintered body can be provided.

By directly bonding the metallized metal using the AlN sintered body as the base material, it is possible to provide a highly reliable circuit board in which the occurrence of peeling at the interface between the base material and the metallized metal is suppressed.

[Brief description of drawings]

FIG. 1 is an SEM photograph showing a cross-sectional structure in the vicinity of an AlN sintered body obtained in Example 4 of the present invention.

FIG. 2 is an SEM photograph showing a cross-sectional structure near the surface of an AlN sintered body obtained in Comparative Example 2.

FIG. 3 is a cross-sectional view of a circuit board having a base material made of an AlN sintered body obtained according to Example 4 of the present invention.

FIG. 4 is a plan view of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Circuit board, 2 ... Base material consisting of AlN sintered body, 3 ... Grain boundary phase, 4 ... Copper circuit pattern, 5 ... Solidified layer of eutectic liquid phase

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuo Kazo 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Inside the Toshiba Research and Development Center (72) Inventor Fumio Ueno Komukai-Toshiba, Kawasaki-shi, Kanagawa Town No. 1 Toshiba Corporation Research & Development Center

Claims (5)

[Claims] 1. Aluminum nitride sinter characterized in that it has aluminum nitride particles having an average particle diameter of 2 μm or less, and 5 to 100% of the surface of the aluminum nitride particles is covered with a grain boundary phase. body. 2. The aluminum nitride sintered body according to claim 1, wherein the grain boundary phase covering the surface of the aluminum nitride particles contains halogen. 3. In the production of an aluminum nitride sintered body, which comprises aluminum nitride particles having an average particle diameter of 2 μm or less, and 5 to 100% of the surface of the aluminum nitride particles is covered with a grain boundary phase, After molding the raw material containing the aluminum nitride powder and the sintering aid,
1600 ° C in a non-oxidizing atmosphere at a reduced pressure of 1 to 0.9 atm
A method for producing an aluminum nitride sintered body, which comprises the following sintering. 4. In the production of an aluminum nitride sintered body, which comprises aluminum nitride particles having an average particle diameter of 2 μm or less, and 5 to 100% of the surface of the aluminum nitride particles is covered with a grain boundary phase, After molding a raw material containing aluminum nitride powder and a sintering aid containing halogen,
This molded body was placed in a non-oxidizing atmosphere of 0.5 to 10 atm for 1
A method for producing an aluminum nitride sintered body, which comprises sintering at 600 ° C. or lower. 5. A circuit board, wherein a metal is bonded to a base material made of the aluminum nitride sintered body according to claim 1 or 2.