JP2003020282A - Aluminum nitride sintered compact, production method therefor and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum nitride sintered compact which has remarkably increased deflective strength and improved thermal impact resistance while maintaining its densiness and high thermal conductivity equal to or above those of the conventional one, to provide its production method, and to provide a circuit board using the aluminum nitride sintered compact as an aluminum nitride board. SOLUTION: In the aluminum nitride sintered compact, a samarium(Sm) yttrium(Y) aluminum(Al) based multiple oxide is present in an intergranular phase, and the density of the compact is >=3.1 g/cm<3> , and the three point bending strength of the compact is >=400 MPa. The method for producing an aluminum nitride sintered compact can be applied to the production of the aluminum nitride sintered compact. The circuit board uses the aluminum nitride sintered compact as an aluminum nitride board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride sintered body having excellent mechanical properties and high thermal conductivity, a method for producing the same, and uses thereof.

[0002]

2. Description of the Related Art Conventionally, a conductive metal circuit layer is joined to the surface of a semiconductor mounting ceramic substrate with a brazing material,
Further, a circuit board having a semiconductor element mounted at a predetermined position on the metal circuit layer is used. In order for the circuit board to operate with high reliability, it is important to dissipate the heat generated by the semiconductor element so that the temperature of the semiconductor element does not become excessive. In addition, high thermal conductivity is required so as to exhibit excellent heat dissipation characteristics. In recent years, with the miniaturization of circuit boards and the higher output of power modules,
Aluminum nitride substrates are receiving attention.

An aluminum nitride sintered body which is an aluminum nitride substrate is generally manufactured by the following method.
That is, aluminum nitride powder is mixed with an appropriate amount of a sintering aid, an organic binder, and additives such as a plasticizer and a dispersant, and the mixture is molded into a thin plate or sheet by extrusion molding or a doctor blade method. . In the case of a thick plate or a large size, press molding is performed. Then, the molded body is air, nitrogen,
After removing (degreasing) the organic binder component by heating to 350 to 600 ° C. in an atmosphere of an inert gas or the like, 4-1 at a sintering temperature of 1800 to 2000 ° C. in a non-oxidizing atmosphere of nitrogen or the like.
It is manufactured by holding it for 0 hours, turning off the power of the firing furnace and allowing it to cool.

Since aluminum nitride has a strong covalent bond and is difficult to sinter, the sintering aid is calcium oxide (CaO) based on rare earth oxides such as yttrium oxide (Y ₂ O ₃ ). Various compounds such as alkaline earth metal oxides have been investigated (for example, JP-A-60-127).
267, JP-A-61-10071, JP-A-60-71575).

The function of the sintering aid is to react with oxygen contained in the aluminum nitride raw material powder to generate a liquid phase, to densify the aluminum nitride sintered body, and to prevent oxygen and Fe from interfering with thermal conductivity. High thermal conductivity is achieved by fixing cation metal components such as Ca and Ca in the grain boundary phase.

For example, yttrium oxide (Y ₂ O ₃ )
Reacts with oxygen in the aluminum nitride raw material powder and aluminum oxide on the surface of the aluminum nitride particles to produce yttrium-aluminum-garnet (3Y ₂ O ₃ .5Al ₂
O ₃₎ (hereinafter, "YAG" hereinafter.), Yttria-alumina compound _{(Y 2 O 3 · Al 2} O 3) ( hereinafter, "YAL"
Say. ), Yttria-alumina-metal compound (2Y
₂ O ₃ · Al ₂ O ₃ · M _x O _y ) (hereinafter referred to as “YAM”) is formed to promote densification and high thermal conductivity. Further, these composite oxides, while forming a liquid phase around the aluminum nitride particles during sintering, remain glassy or crystalline in the grain boundary phase of the aluminum nitride crystal grains after sintering, It is a constituent of the aluminum nitride sintered body.

[0007]

Thus, the use of sintering aids, especially those based on rare earth oxides,
Although the aluminum nitride sintered body was able to be highly densified and achieve high thermal conductivity, its mechanical properties, particularly bending strength, were still insufficient. If the bending strength is small,
When a semiconductor element is mounted on the metal circuit layer provided on the surface of the aluminum nitride substrate, the element is damaged, or due to repeated thermal cycles associated with the operation of the semiconductor element, a crack occurs in the aluminum nitride substrate near the junction of the metal circuit layer. Therefore, there is a problem that heat resistance cycle characteristics and reliability are not improved. Especially recently, in ceramic substrates for power modules and jigs for semiconductor manufacturing equipment,
Since it is increasingly used under heat cycles that are more severe than before, there is an urgent need to improve the thermal shock resistance and thus the bending strength.

An object of the present invention is to provide an aluminum nitride sintered body having a significantly improved bending strength and thermal shock resistance while maintaining a compactness and a high thermal conductivity equal to or higher than those of conventional ones, and a method for producing the same. It is to provide a circuit board.

[0009]

That is, according to the present invention, a samarium (Sm) -yttrium (Y) -aluminum (Al) -based composite oxide is present in the grain boundary phase and has a density of 3.1.
The aluminum nitride sintered body is characterized by having a three-point bending strength of 400 MPa or more and a g / cm ³ or more. In this case, the samarium (Sm) -yttrium (Y) -aluminum (Al) -based compound oxide present at the triple points of the aluminum nitride crystal structure has an atomic ratio of Y / Sm of 3 or less, and the aluminum nitride crystal structure is (Sm) and yttrium (Y) existing at the interface between two particles
The Y / Sm atomic ratio of the aluminum (Al) -based composite oxide is preferably larger than 3.

Further, according to the present invention, the amount of oxygen is 3% by mass or less,
For aluminum nitride raw material powder having an average particle size of 5 μm or less,
Aluminum oxide 0.02 to 2% by mass, samarium or a compound thereof and yttrium or a compound thereof in an amount of 0.1 to 10% by mass in terms of oxide, and Sm ₂ O ₃
/ (Sm ₂ O ₃ + Y ₂ O ₃ ) in a molar ratio of 0.05 to 0.9, and the sintering temperature is set to 1500 ° C. or higher in a non-oxidizing atmosphere at 1 ° C./min or less. 1600-190
A method for producing an aluminum nitride sintered body, which comprises raising the temperature to 0 ° C., maintaining the sintering temperature for 0.2 to 2 hours, and then cooling. Furthermore, the present invention is a circuit board characterized in that the aluminum nitride sintered body is used as an aluminum nitride substrate, and a metal circuit is formed on the surface thereof.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below.

The characteristics of the aluminum nitride sintered body of the present invention are that when its crystal structure is microscopically observed, it is samarium (Sm) / yttrium (Y) / aluminum (Al).
-Based complex oxide (hereinafter referred to as "Sm / Y / Al complex oxide")
Say. ) Is formed in the grain boundary phase, which means that the density can be 3.1 g / cm ³ or more and the three-point bending strength can be 400 MPa or more. This is a yttrium (Y) component and samarium (S) as a sintering aid.
This can only be realized by using component m) together with sintering under specific conditions, and differs from the conventional technique using Y ₂ O ₃ or the like in the sintering aid component and the sintering conditions. .

A further feature is that the composition of the Sm.Y.Al complex oxide existing at the triple point composed of aluminum nitride crystal grains and at the interface between the two grains of the aluminum nitride crystal is different. That is, FIG. 1 is a schematic diagram of the structure of the aluminum nitride sintered body of the present invention, but Sm · existing at the triple points (2) of the aluminum nitride crystal grains (1).
The composition of the Y / Al complex oxide has a Y / Sm atomic ratio of 3 or less, whereas that existing at the two-grain interface (3) of the aluminum nitride crystal has a Y / Sm atomic ratio of greater than 3. That's what it means.

In the present invention, the triple point (2) of aluminum nitride crystal grains is formed by being sandwiched between three aluminum nitride particles when the polishing fracture surface of the aluminum nitride sintered body is observed with a scanning electron microscope or the like. The grain boundary phase, and the two-grain interface (3) means a grain boundary phase formed between the faces of two grains of aluminum nitride facing each other. Also, Sm ・ Y
The Y / Sm atomic ratio of the Al composite oxide can be calculated from the peak values of Y and Sm detected on the polished fracture surface using EDS-SEM.

There are many unclear points about the reason why the strength characteristics are improved by taking such a crystal structure. However, in the conventional aluminum nitride sintered body, the grain boundary phase has only three points. The size is 1 to 5 μm, but in the aluminum nitride sintered body of the present invention, a grain boundary phase exists not only at the triple point but also at the grain boundary of two grains, and these grain boundary phases are relatively minute. In particular, the maximum diameter of the grain boundary phase at the interface between the two grains is related to the fact that most of the grain boundary phase is 1 μm or less, which can be explained as follows.

In general, the mechanical properties of ceramics are strongly influenced by microstructural factors, and the morphology of the grain boundary phase has a large effect on the bonding force of crystal grains. In a structure in which a coarse grain boundary phase coagulated and segregated at three points exists, the bonding force between the crystal grains is small because the contact area between the crystal grains and the grain boundary phase is small.
In addition, the grain boundary phase itself has a small strength due to strain and residual stress caused by the difference in thermal expansion between the crystal grain and the grain boundary phase at the grain boundary segregation portion, resulting in low strength characteristics.
On the other hand, when the grain boundary phase exists at the interface between the two particles, the contact area between the crystal grain and the grain boundary phase increases, so that the bonding force between the crystal grains is strengthened.

In the present invention, the size of the grain boundary phase at the triple point and two grain interfaces is preferably as small as possible within the range of the maximum diameter of 3 μm or less. The grain boundary phase having such a size can be adjusted by the amount of the sintering aid and the firing conditions. A compound of yttrium (Y) and samarium (Sm) is added in a total amount of 0.1 to 10% by mass in terms of oxide.
And the grain boundary portion is densified by firing so that the relative density of the aluminum nitride sintered body becomes 90% or more, the grain boundary phase at the triple point and the two grain interfaces tends to be small.

In the aluminum nitride sintered body of the present invention, the composition of the grain boundary phase existing at the triple point or double grain interface is
It is not always necessary that 100% is the Sm.Y.Al composite oxide, and if the existing ratio is 50% or more, a remarkable improvement in bending strength is recognized. The remaining components of the grain boundary phase are
YAG, detected by Cu-Kα X-ray diffraction analysis,
YAL, YAM, Samaria-alumina composite oxide (Sm
₂ O ₃ · Al ₂ O ₃ ) and the like. However, in all of these complex oxides, the lattice constant is changed, and not a pure crystal structure but a crystal structure in which some elements are replaced with other elements. When analyzed together with the EDS analysis results,
It is highly possible that Y and Sm are mutually substituted crystal structures, and in particular, both the Sm ₂ O ₃ .Al ₂ O ₃ phase and the Y ₂ O ₃ .Al ₂ O ₃ phase belong to the perovskite type structure, so that they are mutually substituted. Is believed to be happening. The structural formula in that case is Y _1-x
The composition of the crystal phase represented by Sm _x Al ₂ O ₃ and existing at the triple points of the aluminum nitride crystal is x ≧ 0.25 from the relation of the above Y / Sm atomic ratio, and the crystal existing at the interface between two particles is The composition of the phases is x <0.25.

In the present invention, the composition of the grain boundary phase present at three points has a Y / Sm atomic ratio of 3 or less, more preferably 2
And the composition of the grain boundary phase at the interface between the two grains is Y.
The atomic ratio of / Sm is larger than 3, more preferably 4
The characteristic is that it is -10. The composition of the grain boundary phase does not necessarily have to be 100% in such an atomic ratio range, and the existence ratio thereof may be 70% or more. As for the composition of the grain boundary phase, a plurality of composition phases may exist as long as the atomic ratio is within the above range.
And 9 (in the above structural formula, Y _0.8 Sm _0.2 Al ₂ O ₃ and Y _0.9 Sm _0.1 Al ₂ O ₃ ), the same level of strength improving effect can be obtained even if the grain boundary phases having the composition are mixed.

The formation mechanism of the Sm.Y.Al composite oxide in the present invention is based on Sm ₂ O ₃ .Al ₂ O ₃ or Y ₂
Different from the mechanism that O ₃ · Al ₂ O ₃ is generated, yttrium (Y) component and samarium (Sm) are used as sintering aids.
This is related to the fact that the sintering temperature is lowered while using the components together. In the present invention, since the coarse grain boundary phase aggregated and segregated at three points is reduced, the composition of the grain boundary phase becomes Y / Sm (atomic ratio)> 3 during firing,
It can be presumed that a liquid phase having a low melting point and a low viscosity is generated and the wettability with the aluminum nitride crystal particles is improved. Therefore, a grain boundary phase is also formed at the fine two-grain interface in the aluminum nitride sintered body, which contributes to a remarkable improvement in bending strength.

Next, a method for manufacturing the aluminum nitride sintered body of the present invention will be described. The production method of the present invention can be applied to the production of the aluminum nitride sintered body of the present invention.

As the aluminum nitride raw material powder, a powder produced by a known method such as a direct nitriding method or an alumina reduction method can be used, but the amount of oxygen is 3% by mass or less and the average particle size is 5 μm or less. desirable. If the amount of oxygen exceeds 3% by mass, the thermal conductivity of the aluminum nitride sintered body may decrease. On the other hand, if the average particle size exceeds 5 μm, the density of the sintered body may decrease, and the thermal conductivity and strength characteristics may decrease. Further, as impurities other than oxygen, F excluding Al is used.
0.1 mass% or less of cation impurities such as e and Ca, carbon 1
It is preferably 000 ppm or less. If the amount of these impurities is exceeded, the sinterability will be impaired and the thermal conductivity and strength properties may be adversely affected.

In the present invention, samarium or a compound thereof and yttrium or a compound thereof are used together as a sintering aid, and the total oxide of both is 0.1 to 10% by mass (based on the aluminum nitride powder). It is compounded so that the molar ratio of Sm ₂ O ₃ / (Sm ₂ O ₃ + Y ₂ O ₃ ) is 0.05 to 0.9. If the total amount of the sintering aids in terms of oxide is less than 0.1% by mass, densification does not proceed and it becomes difficult to manufacture an aluminum nitride sintered body having a density of 3.1 g / cm ³ or more. On the other hand, if the content exceeds 10% by mass, the sinterability is deteriorated, so that the three-point bending strength is 40%.
Achieving 0 MPa or more becomes difficult, and thermal conductivity is 100 W
/ M · K or less. Sm ₂ O ₃ / (Sm ₂
When the molar ratio of (O ₃ + Y ₂ O ₃ ) is other than 0.05 to 0.9,
Formation of grain boundary phase at the interface between two particles by using samarium (compound) and yttrium (compound) together (Y / Sm
Since the grain boundary phase (atomic ratio> 3) is reduced, a remarkable effect of improving strength cannot be obtained.

Further, as a sintering aid, aluminum oxide is mixed so as to be contained in an amount of 0.05 to 2% by mass.
This ratio is determined in consideration of the amount of aluminum oxide originally present in the aluminum nitride raw material powder. Aluminum oxide plays a role of sufficiently generating Sm · Y · Al composite oxide, and when it is less than 0.05% by mass, Sm · Y.
The amount of Y / Al complex oxide produced is insufficient, and the effect of improving the strength cannot be obtained. If it exceeds 2% by mass, the thermal conductivity of the aluminum nitride sintered body decreases, and it is 130 W / m · K or more, especially 1
It will be difficult to achieve 50 W / mK or more.

As the samarium compound and the yttrium compound, one or more of fluorides, nitrides, carbides and the like are used in addition to the oxides thereof. An oxide is preferable in view of easy handling and cost. Also,
Examples of aluminum oxides include α-Al ₂ O ₃ and γ-Al.
Al ₂ O ₃ such as ₂ O ₃ or precursors which become these oxides during firing are used. The purity of samarium or its compound, yttrium or its compound, and aluminum oxide is preferably 99.5% or more, more preferably 99.
It is 9% or more. The average particle size is 5μ.
m or less, and more preferably 1 μm or less. If the average particle size is more than 5 μm, the reaction becomes non-uniform, the structure may vary, and the strength may decrease.

Explaining an example of the procedure of the manufacturing method, first, a predetermined amount of a sintering aid is mixed with aluminum nitride raw material powder and mixed by a ball mill or the like. Then, an organic binder and, if necessary, various additives are added to the mixed powder, and the mixture is subjected to treatments such as granulation, granulation and kneading, and then molded. As the molding method, a method suitable for the desired shape is selected from die press molding, hydrostatic press molding, doctor blade method, extrusion molding and the like. Subsequently, the molded body is heated at a temperature of 350 ° C. to 600 ° C. in a non-oxidizing atmosphere such as nitrogen gas.
The organic binder is removed by heating at ℃ for 1 to 5 hours.

Then, the degreased molded body is placed in a firing container and sintered at a predetermined temperature in a non-oxidizing atmosphere. For sintering, an atmospheric pressure sintering method, a hot press sintering method, or the like can be adopted. The firing atmosphere is a nitrogen gas or a non-oxidizing atmosphere containing nitrogen gas. As the non-oxidizing gas, H ₂ gas or CO gas may be used. Note that the sintering is performed by any one or a plurality selected from vacuum (including a slight non-oxidizing atmosphere), reduced pressure, increased pressure and normal pressure.

What is important in the present invention is to raise the rate of temperature increase from 1500 ° C. or higher at which the amount of liquid phase is generated by the reaction of the sintering aid to 1 ° C./min or less to the sintering temperature. The temperature rising rate is preferably 0.5 ° C./min or less,
More preferably, it is 0.3 ° C./min or less. Temperature rising rate is 1
If the temperature exceeds ° C / min, the reaction of the sintering aid proceeds nonuniformly, the structure of the grain boundary phase varies, and the strength may decrease.

In the present invention, the sintering proceeds at a lower temperature than the conventional Y ₂ O ₃ or the like, or a samarium compound alone. The sintering temperature is 1600 to 1900 ° C., and sintering is performed by holding this temperature for 0.2 to 2 hours. If the sintering temperature exceeds 1900 ° C., the vapor pressure of aluminum nitride in the sintering furnace will be high, making it difficult to densify, and if the holding time exceeds 2 hours, the grain growth of aluminum nitride particles will be excessive. There is a risk of being accelerated, forming coarse defects and deteriorating the strength characteristics. If the sintering temperature is less than 1600 ° C. or the holding time is less than 0.2 hours, sintering will be insufficient and it will be difficult to manufacture an aluminum nitride sintered body having a density of 3.1 g / cm ³ or more. A particularly preferable sintering temperature is 1700 to 1800 ° C., and a holding time is 0.
5 to 1 hour.

The aluminum nitride sintered body of the present invention is excellent in mechanical properties and has a high thermal conductivity inherent to aluminum nitride, and therefore is suitable for a circuit board used under severe usage conditions, for example, a circuit board for a power module. It is a material.

The circuit board of the present invention is a circuit board in which a metal circuit is formed on one surface of a ceramic substrate and a heat-dissipating metal plate is formed on the other surface of the ceramic substrate, and the ceramic substrate is the aluminum nitride of the present invention. This is an aluminum nitride substrate made of a sintered body. That is, the circuit board of the present invention is one in which a metal circuit for mounting a semiconductor element is formed on one surface of an aluminum nitride substrate, and a metal heat dissipation plate is formed on the opposite surface thereof as needed.

There are various thicknesses of aluminum nitride substrates,
About 0.3 to 1.0 mm if heat dissipation characteristics are important, and 1 to 3 mm if you want to significantly increase the dielectric strength under high voltage.
Something is used.

The materials of the metal circuit and the metal heat sink are Al and C.
It is preferably u or an Al-Cu alloy. These are used in the form of a single body or a laminated body such as a clad including the single layer. Al has a smaller yield stress than Cu, is rich in plastic deformation, and can significantly reduce the thermal stress applied to the ceramic substrate during thermal stress load such as heat cycle. Therefore, Al is generated in the aluminum nitride substrate rather than Cu. It becomes possible to suppress cracks, resulting in a highly reliable module.

The thickness of the metal circuit is preferably 0.4 to 0.5 mm for the Al circuit and 0.3 to 0.5 mm for the Cu circuit from the viewpoint of electrical and thermal characteristics. on the other hand,
The thickness of the metal heat dissipation plate is determined so as not to cause warpage during soldering. Specifically, 0.1 to 0.4 mm for Al heat sinks and 0.15 to 0.4 m for Cu heat sinks.
It is preferably m.

In the circuit board of the present invention, a plate-shaped aluminum nitride sintered body or a plate-shaped aluminum nitride sintered body processed by grinding or the like is used as an aluminum nitride substrate, which is joined to a metal plate and then etched or the like. Can be used to form a metal circuit. Further, it can also be manufactured by mounting a metal plate on which a circuit is formed beforehand by punching or the like on an aluminum nitride substrate and bonding them. For joining the aluminum nitride substrate and the metal circuit, etc., Ag, Cu, or an Ag-Cu alloy and T
A brazing material containing an active metal component such as i, Zr or Hf may be interposed between the aluminum nitride substrate and the metal plate and heated in an inert gas or vacuum atmosphere (active metal method) or the like.

[0036]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples.

Example 1 Oxygen content 1.0% (mass%, the same applies hereinafter), average particle size 1.8
Aluminum nitride powder of μm, average particle size 1.2 μm
Of Sm ₂ O ₃ and Y ₂ O ₃ having an average particle size of 1.1 μm are 5.0% in total, and the Sm ₂ O ₃ / (Sm ₂ O ₃ + Y ₂ O ₃ ) molar ratio is 0.33 (Sm ₂ O ₃ and Y ₂ O ₃ are mixed in a molar ratio of 1: 2), and α-Al ₂ O _{3 having an} average particle size of 1.5 μm is further added.
0.6% and 3% of an organic binder (acrylic resin) were added and mixed for 2 hours by a wet ball mill using methanol as a dispersion medium. Table 1 shows the blending ratio of the mixed powder, the blending amount, the firing temperature, the firing time, and the heating rate of 1500 ° C or more.
It was shown to.

This mixed powder is filtered and dried, then 30MP
Press-molding with a pressure of a to form a 50 × 50 × 5 mm molded body, which is filled in a boron nitride (BN) crucible,
After heating in air at 500 ° C. for 3 hours to degrease, it was heated in an electric furnace of a carbon heater at 1750 ° C. for 30 minutes to carry out atmospheric pressure sintering. The heating rate during heating is from room temperature to 1
10 ° C / min up to 500 ° C, 1500 ° C to 1750 ° C
Was 0.3 ° C./min.

About the obtained aluminum nitride sintered body, the density, the thermal conductivity and the room temperature 3 according to the Archimedes method were measured.
The point bending strength was measured, and the average value of 10 measurements was obtained.
Further, the powder obtained by crushing the sintered body in a mortar was analyzed by an X-ray diffraction method to identify grain boundary phase crystals. Furthermore, after the fracture surface of each sintered body is mirror-polished, each element of Sm, Y, and Al of the Sm / Y / Al complex oxide existing at the triple point of the aluminum nitride crystal and at the interface between the two grains is analyzed by SEM-EDS. Was analyzed to determine the Y / Sm atomic number ratio. The thermal conductivity and bending strength are obtained by grinding an aluminum nitride sintered body and measuring the thermal conductivity with a diameter of 10 mm x 3 mm.
The disc and the strength test body were prepared according to JIS-R1601, and the thermal conductivity was measured by the laser flash method. The obtained results are shown in Table 2 together with the results of XRD analysis.

Examples 2 to 14 Aluminum nitride compacts were prepared in the same manner as in Example 1 except that the type of aluminum nitride powder, the type of sintering aid and the compounding ratio thereof were variously changed as shown in Table 1. Molded, Table 1
The aluminum nitride sintered body was manufactured by firing under various firing conditions shown in.

Comparative Examples 1 to 3 Sm ₂ O ₃ and Al ₂ O ₃ were used without using Y ₂ O ₃ as a sintering aid.
Example 1, except that the compounding ratio was changed to that shown in Table 1.
Aluminum nitride sintered bodies were manufactured in the same manner as in Nos. 4 and 5.

Comparative Examples 4 to 6 Y ₂ O ₃ and Al ₂ O ₃ were used without using Sm ₂ O ₃ as a sintering aid.
Example 1, except that the compounding ratio was changed to that shown in Table 1.
Aluminum nitride sintered bodies were manufactured in the same manner as in Nos. 4 and 5.

Example 15 Comparative Example 7 To the aluminum nitride powder used in Example 1, Y (N
O₃)₃・ 6H₂O and Sm (NO₃)₃・ 6H₂O for each
Re Y₂O₃, Sm₂O₃6 mass% and 12 mass in total
%, Sm₂O₃And Y₂O₃Sm converted to₂O₃/ (Sm₂O₃
+ Y₂O₃) The molar ratio is 0.33 (Sm₂O₃And Y₂
O₃To give a molar ratio of 1: 2)
Γ-Al with a particle size of 1.0 μm₂O₃0.4 mass% is added
By a wet ball mill using methanol as the dispersion medium.
Mixed for hours. Note that Y (NO₃)₃・ 6H ₂O and Sm
(NO₃)₃・ 6H₂O dissolved in n-butanol is used
It was In Comparative Example 7, Sm (NO₃)₃・ 6H₂O and γ-A
l₂O₃Was used as a sintering aid.

Then, in accordance with Example 1, this mixed powder was press-molded, and under a nitrogen gas atmosphere, 1770 ° C., 1
It was heated for 2 minutes and sintered under normal pressure. The rate of temperature increase during heating is from room temperature to 1500 ° C at 10 ° C / min and 1500 ° C.
To 1750 ° C. was 0.25 ° C./min.

[0045]

[Table 1]

[0046]

[Table 2]

As can be seen from the table, the aluminum nitride sintered body of the present invention has a thermal conductivity of 150 W / m · K or more and a density of 3.1 g / cm ³ or more and a three-point bending strength of 400.
It turns out that it is above MPa.

Example 16 The aluminum nitride sintered body of Example 2 was ground to give an aluminum nitride substrate (dimensions: 40 × 40 × 0.63).
5 mm). On the back surface of this aluminum nitride substrate, through a bonding material (Al-9.5% Si-1% Mg alloy foil), Al
An Al plate for circuit formation and an Al heat dissipation plate formation (thickness 0.5
mm, Al purity 99.9%) were stacked, sandwiched between graphite plates, and heated at 580 ° C. in vacuum while applying pressure from the vertical direction of the aluminum nitride substrate. The obtained joined body was magnified 3 times using soft X-rays and inspected for joining defects, but it was not observed (detection lower limit diameter: 0.3 mm). Then, 2 mm around each Al plate on the back surface was etched with an aqueous solution of ferric chloride, and electroless Ni—P plating was performed to 3 μm to produce a circuit board.

About this circuit board, the lower span is 30 m
When the three-point bending strength was measured at m, it was 780 MPa. In addition, when a heat cycle test was performed for a total of 3000 cycles, with holding at -40 ° C for 10 minutes and then heating at 125 ° C for 10 minutes as one cycle, a three-point bending strength of the circuit board after the heat cycle was obtained. Is 7
It was 65 MPa, and cracks of the substrate and peeling of the circuit were not recognized even after the heat cycle test.

Example 17 The powder obtained by mixing the aluminum nitride powder and the sintering aid shown in Example 1 was mixed with a molding binder (water-soluble cellulose type).
10 parts by mass and 8 parts by mass of pure water were added and mixed, and a sheet having a sheet width of 90 mm and a sheet thickness of 0.75 mm was produced by an extruder. The obtained sheet was cut into a size of 50 mm × 70 mm, BN was applied to the surface, and 20 sheets were laminated,
Degreasing was performed in the air at 500 ° C. for 3 hours. The obtained degreased body was filled in a BN container, heated in an electric furnace of a carbon heater under the firing conditions shown in Example 1 to produce a sintered body, and then wet-honed using # 400 alumina abrasive grains. The surface BN and the altered layer were removed to obtain an aluminum nitride substrate.

An active metal-containing brazing material (with a mass ratio of Ag: Cu: Ti of 80: 1) was formed on both surfaces of the aluminum nitride substrate.
5: 5) is screen-printed with a thickness of 30 μm, and a Cu plate (thickness 0.25 mm, purity 99.9%) is placed on each of the circuit side and the heat radiating side, and in a vacuum atmosphere of about 10 ⁻³ Pa. It was heated at 850 ° C. for 30 minutes to obtain a joined body. Then, 2 mm around the Cu plate on each of the back surfaces was etched with an aqueous solution of ferric chloride, and electroless Ni—P plating was performed to 3 μm to produce a circuit board.

The obtained circuit board was subjected to three-point bending strength measurement and heat cycle test in the same manner as in Example 18. The three-point bending strength was 880 MPa, and the three-point bending strength after 3000 heat cycles was 865 MPa. Met. Further, even after the heat cycle test, neither cracking of the substrate nor peeling of the circuit was observed.

[0053]

EFFECTS OF THE INVENTION According to the present invention, there is provided an aluminum nitride sintered body having significantly improved transverse rupture strength and improved thermal shock resistance while maintaining compactness and high thermal conductivity equal to or higher than conventional ones. It

Further, according to the method for producing an aluminum nitride sintered body of the present invention, the transverse rupture strength is remarkably increased while maintaining the same denseness or higher thermal conductivity as the conventional one,
It is possible to easily manufacture an aluminum nitride sintered body having improved thermal shock resistance.

The aluminum nitride sintered body of the present invention can be used as a highly reliable structural material. In particular, it is suitable as an electronic component such as a ceramics substrate for mounting semiconductors and a heat sink.

[0056]

[Brief description of drawings]

FIG. 1 is a schematic view of the structure of an aluminum nitride sintered body of the present invention.

[Explanation of symbols]

1 Aluminum nitride crystal grains 2 Triple points of aluminum nitride crystal grains 3 Two-grain interface of aluminum nitride crystal

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G001 BA03 BA08 BA09 BA36 BA73                       BC11 BC13 BC51 BC52 BC54                       BD03 BD14 BD23 BE31

Claims (4)

[Claims] 1. A samarium (Sm) -yttrium (Y) -aluminum (Al) -based composite oxide is present in the grain boundary phase and has a density of 3.1 g / cm ³ or more and a three-point bending strength of 40.
An aluminum nitride sintered body having a pressure of 0 MPa or more. 2. The samarium (Sm) -yttrium (Y) -aluminum (Al) -based composite oxide present at the triple points of the aluminum nitride crystal structure has an atomic ratio of Y / Sm of 3 or less, and an aluminum nitride crystal. Samarium (Sm), yttrium (Y), present at the interface between two particles of tissue
The aluminum nitride sintered body according to claim 1, wherein the atomic ratio of Y / Sm of the aluminum (Al) -based composite oxide is larger than 3. 3. The amount of oxygen is 3% by mass or less, and the average particle size is 5 μm.
In the aluminum nitride raw material powder of m or less, 0.02 to 2 mass% of aluminum oxide, 0.1 to 10 mass% of samarium or its compound and yttrium or its compound in terms of oxide, and Sm ₂ O ₃ / (Sm ₂ O ₃ +
Y ₂ O ₃ ) is present in a molar ratio of 0.05 to 0.9,
In a non-oxidizing atmosphere, increase the temperature rise rate of 1500 ° C or more to 1 ° C /
In less than a minute, the sintering temperature is increased to 1600 to 1900 ° C,
A method for producing an aluminum nitride sintered body, which comprises holding the sintering temperature for 0.2 to 2 hours and then cooling. 4. A circuit board comprising the aluminum nitride sintered body according to claim 1 or 2 as an aluminum nitride substrate, and a metal circuit formed on the surface thereof.