JPH0692739A - Aluminum nitride sintered compact - Google Patents

Abstract

PURPOSE:To obtain an AlN sintered compact having high strength and high heat conductivity, inhibiting exfoliation at the interface between the base material of a circuit board and a metal layer when used as the base material and enhancing the reliability of the circuit board by allowing SiC to enter into solid soln. in AlN crystal lattices. CONSTITUTION:This AlN sintered compact contains 0.01-0.5wt.% SiC allowed to enter into solid soln. in the AlN crystal lattices. In the case of 0.01wt.% SiC, a high strength AlN sintered compact cannot be obtd. In the case of >0.5wt.% SiC, the heat conductivity of the resulting AlN sintered compact is reduced. When this AIN sintered compact is produced, starting material prepd. by adding SiC and a sintering aid to AlN powder is compacted to form a compact and this compact is fired at 1,800-2,000 deg.C for >=1hr in a nonoxidizing atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride (AlN) sintered body used as a base material for circuit boards.

[0002]

2. Description of the Related Art An AlN sintered body is used as a heat-radiating substrate for semiconductor mounting because it has a higher thermal conductivity than alumina and a thermal expansion coefficient close to that of silicon (Si). Further, since it has properties such as high strength at high temperature and poor reactivity with molten metal, its application to other fields is expanding.

In recent years, research on increasing the thermal conductivity of AlN sintered bodies has progressed, and 200 W / m · K grade materials have been obtained everywhere. When the AlN sintered body is used as a circuit board, it is necessary to metallize the surface of the base material made of the AlN sintered body. As for the metallizing method, an improved method has been introduced based on the technique built on the conventional alumina base material. A fundamental technical problem in the metallization of a base material made of an AlN sintered body is mismatch of thermal expansion coefficients. Al
The coefficient of thermal expansion of the N sintered body is about 4.5 × 10 ⁻⁶ / ° C.,
It is about half that of the alumina sintered body. Moreover, the thermal expansion coefficient of most metals is larger than that of the AlN sintered body. As a result, a larger stress is generated on the base material side near the interface between the base material made of the AlN sintered body and the metallized layer than when the alumina sintered body is used as the base material. Therefore, in most cases except when the joining method itself is inadequate, the peeling from the metal layer is caused by the destruction of the base material side made of the AlN sintered body. Further, the stress concentration at the bonding interface leads to a reduction in reliability of the element mounted on the circuit board due to peeling of the bonding surface.

[0004]

DISCLOSURE OF THE INVENTION The present invention has high strength and high thermal conductivity, and when applied to the base material of a circuit board, suppresses the occurrence of peeling at the interface with the metal layer, thereby suppressing the occurrence of peeling of the circuit board. It is intended to provide an AlN sintered body which can improve reliability.

[0005]

In the AlN sintered body according to the present invention, SiC is 0.01 to 0.5 in the AlN crystal lattice.
It is characterized in that it forms a solid solution by weight percent.

The solid solution amount (0.01 to 0.5% by weight) of the SiC in the AlN crystal lattice is 3.1111 to 3.1116 on the a-axis and 4.10 on the C-axis according to the measurement of the lattice constant. 9
This is equivalent to 803/10 ^{-10 m to} 4.9809 / 10 ^{-10 m} .

SiC dissolved in the AlN crystal lattice
The reason for limiting the amount is as follows.
If the amount of SiC is less than 0.01% by weight, a high-strength AlN sintered body cannot be obtained. On the other hand, the S
If the iC amount exceeds 0.5% by weight, the thermal conductivity of the AlN sintered body decreases. A more preferable solid solution amount of SiC is
0.02 to 0.3% by weight.

Although it is necessary for the SiC to form a solid solution in the AlN crystal lattice, it is allowed to exist not only in the crystal lattice but also as a grain boundary phase. However, the amount of SiC existing as the grain boundary phase is preferably 0.2% by weight or less.

The AlN sintered body is allowed to contain 0.01 to 10% by weight of a grain boundary phase derived from a sintering aid.
Examples of the sintering aid include alkaline earth metals such as Ca, Ba and Sr and oxides thereof, rare earth elements such as Y, La and Ce and oxides thereof.

The AlN sintered body may contain 0.01 to 2% by weight of a transition metal and its compound. Examples of the transition metal include Ti, W, Mo, Ta, N
b etc. can be mentioned.

The AlN sintered body according to the present invention is manufactured, for example, by the following method.

First, a raw material obtained by adding SiC and a sintering aid to AlN powder is molded to produce a molded body. Continuing,
The molded body is heated at 1800 to 2000 ° C. in a non-oxidizing atmosphere.
The AlN sintered body is manufactured by firing at 1 hour or more.

The AlN powder has an impurity oxygen content of 0.1 to 2.5% by weight, more preferably 0.4 to 1.5.
It is desirable to use those having an amount of 1 wt% and an average primary particle diameter of 1.5 μm or less, more preferably 0.05 to 1.2 μm.

As the sintering aid, oxides, carbides, fluorides and carbonates of alkaline earth metals such as Ca, Ba and Sr and / or rare earth elements such as Y, La and Ce,
Oxalate, nitrate, alkoxide and the like can be used. The mixing amount of these sintering aids is preferably in the range of 0.5 to 10% by weight.

In producing the molded body, the AlN
In addition to powders, SiC and sintering aids, oxides, carbides, fluorides, carbonates, etc. of transition metals such as Ti, W, Mo, Ta, and Nb for coloring and strengthening, if necessary, It is allowed to mix oxalate and nitrate in the range of 0.01 to 3% by weight. Further, in order to reduce the sintering temperature, an aluminum compound such as aluminum oxide or aluminum fluoride or a silicon compound such as silicon oxide or silicon nitride is allowed to be blended in a range of 1% by weight or less.

The AlN sintered body according to the present invention is manufactured by hot pressing a raw material obtained by adding SiC and a sintering aid to the AlN powder, in addition to the above-mentioned pressureless sintering method.

[0017]

According to the present invention, by solid-solving SiC in the AlN crystal lattice in the range of 0.01 to 0.5% by weight, an AlN sintered body having high thermal conductivity and high strength can be obtained. be able to. Although the mechanism for increasing the strength of the AlN sintered body is not clear, it is possible to form a solid solution of the SiC in the AlN crystal lattice to form a solid solution of Al.
It is presumed that this is because the bond strength between N crystal grains changes.

Therefore, when the high-strength AlN sintered body is applied to the base material of the circuit board, the occurrence of peeling at the interface with the metal layer can be suppressed, so that a highly reliable circuit board can be realized.

[0019]

EXAMPLES Examples of the present invention will be described in detail below.

Example 1 First, with respect to 100 parts by weight of AlN powder having an amount of impurity oxygen of 1.0% by weight and an average primary particle size of 0.6 μm, an additive has an average particle size of 0.1 μm and a purity of 99.9%. Of Y ₂ O ₃
3 parts by weight of powder and 99% pure SiC (impurity oxygen content 0.
(8 wt%) 0.45 part by weight was added, and the mixture was pulverized and mixed using a ball mill to prepare a raw material powder. Subsequently, 5% by weight of an acrylic binder was added to the raw material powder and granulated, and the granulated powder was molded under a uniaxial pressure of 500 kg / cm ² to obtain a green compact. Subsequently, the green compact was heated to 700 ° C. in a nitrogen gas atmosphere to remove the acrylic binder. Next, the green compact was set in an h-BN container and fired in a graphite heater furnace at 1 atm in a nitrogen gas atmosphere at 1900 ° C. for 3 hours to produce an AlN sintered body.

The obtained AlN sintered body of Example 1 was white in color.

The density of the AlN sintered body was measured by the Archimedes method. As a result, it was sufficiently densified to 3.28 g / cm ³ .

A disk having a diameter of 10 mm and a thickness of 3 mm was cut out from the AlN sintered body, and the thermal conductivity was measured by a laser flash method at room temperature of 21 ° C. ± 2 ° C. as a result,
It was confirmed to have a high thermal conductivity of 210 W / m · K.

After crushing one piece of the AlN sintered body, X
The constituent phases were investigated by line diffraction. As a result, the constituent phases other than AlN were Y ₂ O ₃ , Y ₄ Al ₂ O ₉ and a trace amount of unknown phase.

The above-mentioned AlN sintered body and NB which were similarly crushed
Using standard Si manufactured by S, the lattice constant of the AlN sintered body was measured by the internal standard method. As a result, the a-axis is 3.111.
2 、 c-axis is 4.9808 / 10 ^-10 m, the normal A
It was confirmed that the c-axis length was longer and the a-axis length was shorter than the lattice constant of the 1N sintered body, and that SiC was a solid solution in the AlN crystal lattice. In addition, the above-mentioned Al by the IPC method
The amount of Si in the N sintered body was analyzed. As a result, it was 0.25% by weight.

Further, 3 mm × 4 from the AlN sintered body
A square bar of mm × 40 mm was cut out and the strength was measured by three-point bending. As a result, the average of 10 measurements is 55k.
It was confirmed that the strength was higher than the average strength of 45 kg / mm ² of the conventional AlN sintered body in which g / mm ² and SiC were not solid-dissolved in the crystal lattice.

Example 2 The compounding amount of SiC (impurity oxygen amount 0.8% by weight) was 0.1.
Using the same raw material powder as in Example 1 except for the parts by weight,
An AlN sintered body was manufactured by the same procedure as in Example 1.

With respect to the obtained AlN sintered body of Example 2, the thermal conductivity, constituent phase, lattice constant and three-point bending strength were evaluated in the same manner as in Example 1. As a result, the thermal conductivity was 215 W / mK, the constituent phases other than AlN were Y ₂ O ₃ ,
Y ₄ Al ₂ O ₉ , the lattice constant is 3.1113 on the a-axis, 4.9807 / 10 ^-10 m on the c-axis, and the 3-point bending strength is 48 kg.
/ Mm ² .

Example 3 The compounding amount of SiC (impurity oxygen amount 0.8% by weight) was 0.0
An AlN sintered body was manufactured by using the same raw material powder as in Example 1 except that the amount was 1 part by weight and following the same procedure as in Example 1.

With respect to the obtained AlN sintered body of Example 3, the thermal conductivity, constituent phase, lattice constant and three-point bending strength were evaluated in the same manner as in Example 1. As a result, the thermal conductivity was 213 W / mK, the constituent phases other than AlN were Y ₂ O ₃ ,
Y ₄ Al ₂ O ₉ , the lattice constant is 3.1113 on the a-axis, 4.9807 / 10 ^-10 m on the c-axis, and the 3-point bending strength is 48 kg.
/ Mm ² .

Example 4 The same raw material powder as in Example 1 was subjected to 180 ° C. in a nitrogen gas atmosphere.
An AlN sintered body was manufactured by hot pressing at 0 ° C. for 2 hours under a pressure of 500 kg / cm ² .

With respect to the obtained AlN sintered body of Example 4, the thermal conductivity, constituent phase, lattice constant and three-point bending strength were evaluated in the same manner as in Example 1. As a result, the thermal conductivity was 180 W / m · K, the constituent phases other than AlN were a small amount of unknown phase, and the lattice constants were 3.1113 on the a-axis and 4.980 on the c-axis.
6/10 ⁻¹⁰ m, 3-point bending strength was 56 kg / mm ² .

[0033]

As described above in detail, according to the aluminum nitride sintered body of the present invention, it has high strength and high thermal conductivity, and when it is applied to the base material of the circuit board, it is formed at the interface with the metal layer. There is a remarkable effect such that the occurrence of peeling can be suppressed and the reliability of the circuit board can be improved.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Katsuyoshi Oishi 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Research Institute Ltd. (72) Inventor Akihiko Tsuge, Komukai-Toshiba, Kawasaki-shi, Kanagawa 1-City, Ltd. In Toshiba Research Laboratories, Inc. (72) Inventor Shun Kadoma, 4-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture In-house Research Laboratories, Keihin Works, Toshiba Corp. (72) Takashi Takahashi, Tsurumi, Yokohama-shi, Kanagawa Prefecture 2-4 Suehiro-cho, Tokyo Inside Keihin Office of Toshiba Corporation

Claims (1)

[Claims] 1. An aluminum nitride sintered body characterized in that 0.01 to 0.5% by weight of SiC is solid-solved in an aluminum nitride crystal lattice.