JPH04254475A - Heat radiating plate - Google Patents

Abstract

PURPOSE:To provide a heat radiating plate having superior heat radiating property and made of an AlN sintered body having high heat conductivity. CONSTITUTION:Aluminum nitride contg. 0.001-7wt.% oxygen is mixed with 0.002-15wt.% (expressed in terms of alkaline earth metals) one or more kinds of alkaline earth metals or alkaline earth metal compds. converted finally into oxides, the resulting mixture is sintered to obtain an aluminum nitride sintered body and a heat radiating plate is made of this sintered body.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat sink made of a highly thermally conductive aluminum nitride sintered body.

0002

[Prior Art] Aluminum nitride (AlN) has high strength from room temperature to high temperature (the bending strength of a sintered body is usually 50
kg/mm2 or more), and has excellent chemical resistance, so it is used as a heat-resistant material, and its high thermal conductivity and high electrical insulation properties make it a promising material for heat sinks in semiconductor devices. Such AlN usually does not have a melting point and decomposes at high temperatures of 2200° C. or higher, so it is used as a sintered body except for applications such as thin films.

Incidentally, AlN sintered bodies have conventionally been manufactured by a cold sintering method or a hot pressing method. In the hot press method, AlN powder alone or A with an auxiliary agent added is used.
Sintering is performed under high temperature and high pressure using IN powder. However, with the hot press method, it is difficult to produce a sintered body with a complicated shape, and the productivity is low, resulting in high costs.

On the other hand, in the pressureless sintering method, a raw material in which silicon oxide or the like is added as a sintering aid to AlN powder is used for the purpose of increasing the density. Although this pressureless sintering method can solve the problems of the hot press method mentioned above,
The thermal conductivity of the obtained AlN sintered body is at most 40 W/m, whereas the theoretical thermal conductivity of AlN is 320 W/m・K.
・As low as K. For this reason, when the AlN sintered body is used as a heat sink material of the semiconductor device, there is a problem that good heat dissipation cannot necessarily be exhibited. Note that even the AlN sintered body manufactured by the hot pressing method (using AlN powder to which an auxiliary agent is added as a raw material) has a low thermal conductivity of about 40 W/m·K.

[0005]

Problem to be Solved by the Invention The present invention was made to solve the problems of the prior art, and it is an object of the present invention to solve the problems of the conventional method.
The present invention aims to provide a heat dissipation plate made of N sintered body and having excellent heat dissipation properties.

[0006]

[Means for Solving the Problems] The heat sink according to the present invention is made of aluminum nitride containing 0.001 to 7% by weight of oxygen, and one kind selected from alkaline earth metals and their compounds that ultimately become oxides. The above is 0.0 in terms of alkaline earth metals.
It is characterized by being made of an aluminum nitride sintered body formed by mixing and sintering aluminum nitride in an amount of 0.02 to 15% by weight.

The reason why the amount of oxygen in the AlN is limited is as follows. The amount of oxygen is 0.00
If it is less than 1% by weight, the sinterability cannot be improved and dense A
It becomes difficult to obtain an IN sintered body. On the other hand, if the amount of oxygen exceeds 7% by weight, the oxygen in AlN is not transferred to the grain boundaries and remains, resulting in a decrease in thermal conductivity. However, when adopting the pressureless sintering method as the sintering method, the amount of oxygen in the AlN is 0.05 to 5% by weight, more preferably 0.05% by weight.
It is desirable that the content be in the range of ~1% by weight. When using the hot press method, the amount of oxygen in the AlN is set to 0.0.
It is desirable that the content be in the range of 1 to 3% by weight, more preferably 0.001 to 1% by weight.

[0008] The alkaline earth metals include Ca, S
Examples of the alkaline earth metal compounds include oxides, carbonates, oxalates, sulfates, and nitrates. Such alkaline earth metals or compounds thereof may be used alone or in a mixture of two or more.

The reason why the mixing amount (in terms of alkaline earth metal) of the alkaline earth metal and its compound is limited is as follows. If the mixing amount is less than 0.002% by weight, sinterability cannot be improved and dense AlN
It becomes difficult to obtain a sintered body. On the other hand, the mixing amount is 1
When it exceeds 5% by weight, the absolute amount of AlN decreases, and Al
Not only the heat resistance and high strength, which are the inherent properties of the N sintered body, are impaired, but also the high thermal conductivity is reduced. In addition, when mixing these alkaline earth metals and their compounds, Al
When the amount of oxygen contained in the N raw material is large, the above range (0.0
It is desirable to increase the content within the range of 0.02 to 15% by weight. Further, when a pressureless sintering method is employed as the sintering method, it is desirable that the amount of the alkaline earth metal etc. mixed is 0.1 to 15% by weight. The heat sink according to the present invention allows a circuit pattern made of copper or the like to be formed on its surface. Furthermore, a heat sink may be connected to the heat sink. Next, a method for manufacturing an AlN sintered body constituting the heat sink of the present invention using (1) an atmospheric pressure sintering method and (2) a hot pressing method will be described.

(1) First, Al containing a predetermined amount of oxygen
Adding alkaline earth metals and their compounds to N powder,
After mixing using a ball mill or the like, a binder is added, kneading, granulation, and sizing are performed, and a molded body is produced by molding, isostatic pressing, or sheet molding. Subsequently, the molded body is heated at around 700° C. in a N2 gas stream to remove the binder. Next, the molded body was set in a graphite or aluminum nitride container, and heated for 16 hours in a N2 gas atmosphere.
An AlN sintered body is produced by pressureless sintering at 00 to 1900°C. At this time, relatively low temperature (1000 to 1300℃
), an alkaline earth metal/aluminum composite oxide, which will be described later, is produced, further melted at a high temperature, and pressureless sintered by the liquid phase sintering mechanism.

(2) An AlN sintered body is produced by adding alkaline earth metals and their compounds to AlN powder containing a predetermined amount of oxygen, and hot pressing the mixed raw materials using a ball mill or the like at 1600 to 1900°C. Manufacture.

0012

[Operation] The present inventors have discovered that AlN used as a heat sink
As a result of various studies on the low thermal conductivity of sintered bodies (including auxiliary agents) produced using conventional methods, it was found that the low thermal conductivity is due to the amount of auxiliary agents in the AlN sintered body as well as the oxygen content, which is involved in sinterability. It was determined that this was caused by In the AlN raw material,
It is necessary to contain oxygen in order to improve sinterability and obtain a dense AlN sintered body, but it was found that too much oxygen becomes a factor that inhibits high thermal conductivity.

[0013] Therefore, the inventors of the present invention conducted extensive research based on the above investigation results, and found that alkaline earth metals and their compounds that eventually become oxides in aluminum nitride containing 0.001 to 7% by weight of oxygen. By mixing 0.002 to 15% by weight of one or more selected from the following in alkaline earth metal terms and sintering, an aluminum nitride sintered body with extremely high thermal conductivity compared to conventional aluminum nitride sintered bodies is produced. I discovered a heat sink. It is presumed that the reason why the aluminum nitride sintered body constituting the heat sink of the present invention exhibits high thermal conductivity is due to the structure described below.

[0014] When an oxygen-containing AlN raw material to which an alkaline earth metal or a compound thereof is added is shaped and sintered, the alkaline earth metal reacts with the oxygen (usually present as aluminum oxide) in the AlN. , composition formula 6Al2
O3 -MeO, 2Al2 O3・MeO, 3Al2
Several forms of alkaline earth metal/aluminum composite oxides expressed in the form of O3 ・5MeO, Al2 O3 ・MeO [where Me is an alkaline earth metal] are produced, and the composite oxide is It promotes sintering and ultimately gathers at grain boundaries of AlN to fix oxygen in AlN. Which of the alkaline earth metal/aluminum composite oxides is produced depends on the amount of oxygen in AlN, the amount of alkaline earth metal added, and the sintering conditions.

[0015] In the sintering process, Al containing a large amount of oxygen
When a N raw material is used, oxygen that cannot be incorporated into the alkaline earth metal/aluminum composite oxide remains, and the oxygen diffuses into the AlN particles as a solid solution. The thermal conductivity of an insulator is controlled by the diffusion of elastic waves (phonons), but Al containing AlN particles in which oxygen is diffused as a solid solution
In the N sintered body, phonons are scattered in the solid solution diffused region,
As a result, thermal conductivity decreases.

For this reason, the amount of oxygen in the AlN raw material that fully contributes to the production of alkaline earth metal/aluminum composite oxide (0.001 to 7% by weight) should be adjusted in balance with the amount of alkaline earth metal added. ) and immobilized with AlN
It is presumed that by inhibiting solid solution diffusion into the AlN sintered body, phonon scattering is reduced, resulting in an AlN sintered body with improved thermal conductivity. The heat sink made of the AlN sintered body as described above has good heat dissipation characteristics due to its excellent thermal conductivity, and therefore can be used for mounting substrates of semiconductor devices, etc.

[0017]

EXAMPLES Examples of the present invention will be described in detail below. Example 1

First, 3% by weight of strontium oxalate powder (average particle size: 1 μm) was added to aluminum nitride powder (average particle size: 1 μm) containing 0.87% by weight of oxygen, and the mixture was ground and mixed using a ball mill. The raw material was prepared. Subsequently, this raw material was filled into a carbon mold with a diameter of 10 mm, and hot-pressed for 1 hour at a pressure of 300 kg/cm 2 and a temperature of 1800° C. to produce an AlN sintered body. Thereafter, the AlN sintered body was processed into predetermined dimensions to produce a heat sink. Comparative example 1

An AlN sintered body was produced in the same manner as in Example 1, except that aluminum nitride powder (average particle size 1 μm) containing 3% by weight of oxygen was used as the raw material, and further processed to form a heat sink. was produced. Comparative example 2

A raw material was prepared by adding 3% by weight of strontium oxalate powder (average particle size: 1 μm) to aluminum nitride powder (average particle size: 1 μm) containing 10% by weight of oxygen, and grinding and mixing using a ball mill. did. Continuing,
This raw material was hot pressed in the same manner as in Example 1, and A
A 1N sintered body was manufactured and further processed into predetermined dimensions to produce a heat sink.

Each of the heat sinks obtained in Example 1 and Comparative Examples 1 and 2 was polished to a thickness of about 3.5 mm, and then the thermal conductivity at room temperature was measured by a laser flash method. As a result, the heat sink of Example 1 had a power of 106 W/m.
・While it was 36W/K for the heat sink of Comparative Example 1,
m·K, and in the case of the heat sink of Comparative Example 2, it was 32 W/m·K.

Furthermore, the constituent phases of the AlN sintered body, which is the material of each of the heat sinks of Example 1 and Comparative Examples 1 and 2, were investigated by X-ray diffraction. As a result, in the AlN sintered body of Example 1, an AlN phase, an Al2O3 ・SrO phase, and a 2Al2
The O3 ・SrO phase is Al in the AlN sintered body of Comparative Example 1.
In addition to the N phase, a considerable amount of oxynitride phase was present in the Al of Comparative Example 2.
In addition to the AlN phase, a considerable amount of oxynitride phases were detected in the N sintered body. Example 2

[0023] Raw materials were prepared in the same manner as in Example 1, except that calcium carbonate powder was used instead of strontium oxalate powder, and this was hot-pressed to produce an AlN sintered body, which was further processed to predetermined dimensions. I made a heat sink.

After polishing the obtained heat sink to a thickness of about 3.5 mm, the thermal conductivity at room temperature was measured by the laser flash method, and it showed an extremely high thermal conductivity of 120 W/m·K. Ta. Furthermore, the constituent phases of the AlN sintered body, which is the material of the heat sink, were investigated by X-ray diffraction. the result,
AlN phase and Al2O3・CaO phase, 2Al2O
3.CaO phase was detected. Examples 3-8

First, calcium carbonate powder (average particle size 1 μm) was added to aluminum nitride powder (average particle size 1 μm) containing 0.95 weight % oxygen and 0.1% by weight, respectively.
Adding 5% by weight, 1% by weight, 3% by weight and 5% by weight,
Grind and mix using a ball mill to make 5 pieces weighing 200g.
Seed raw material was prepared. Next, 7% by weight of paraffin was added to each of these raw materials, and after granulation, the pressure was 300%.
Cold-formed at kg/cm2 to 37mm x 37mm x 6
It was made into a plate shape with a size of cm. Next, these plate-shaped bodies were heated to 700°C in a nitrogen gas atmosphere, held for 10 hours to degrease them, placed in an aluminum nitride container, and sintered at 1800°C in a nitrogen gas atmosphere for 20 hours under normal pressure. Six types of AlN sintered bodies were manufactured. Thereafter, these sintered bodies were processed into predetermined dimensions to produce a heat sink.

The density and thermal conductivity of each of the heat sinks of Examples 3 to 8 were examined. The results are shown in Table 1 below. In addition, Table 1 shows heat sinks produced by manufacturing AlN sintered bodies in the same manner as in Example 3, except that aluminum nitride powder itself without adding calcium carbonate was used as the raw material, and processed into predetermined dimensions. It is also listed as Comparative Example 3.
Table 1
Addition amount of CaCO3
degree thermal conductivity
(wt%) (g/c
m3) (W/m・K) Comparative example 3
0 2.
03 8 Example 3
0.1 3.
07 65 Example 4
0.5 3.1
9 81 Example 5
1 3.
23 110 Example 6
2 3.
20 105 Example 7
3 3.
21 110 Example 8
5 3.
21 105

Furthermore, the constituent phases of the AlN sintered body, which is the material of each of the heat sinks of Examples 3 to 7, were investigated. As a result, both AlN phase and 6Al2
O3 ・CaO phase, 2Al2 O3 ・CaO phase, 3A
l2 O3 ・5CaO phase, Al2 O3 ・CaO phase and a slight oxynitride phase were detected, but CaCO3
As the amount of addition increased, the oxynitride phase decreased and the alkaline earth metal/aluminum composite oxide phase increased. Furthermore, among the composite oxide phases, as the amount of CaCO3 added increased, the proportion of the oxide phase with a high CaO/Al2 O3 ratio increased. Examples 9-11

CaCO having an average particle size of 1 μm was added to aluminum nitride powder (average particle size 1 μm) containing 1% by weight of oxygen.
3, SrCO3 and BaCO3 at 3% by weight each
The mixture was added, ground using a ball mill, and mixed to prepare three types of raw materials. Subsequently, these raw materials were subjected to pressureless sintering in the same manner as in Example 3 to produce three types of AlN sintered bodies. Thereafter, these sintered bodies were processed into predetermined dimensions to produce a heat sink.

The thermal conductivity of each of the heat sinks of Examples 9 to 11 was examined. The results are shown in Table 2 below. In addition, Table 2 also lists as a reference example a heat sink produced by hot pressing aluminum nitride powder itself at 1800°C to produce an AlN sintered body and processing it to a predetermined size using aluminum nitride powder as a raw material without adding any auxiliary agent. did.
Table 2
additive auxiliary agent
Thermal conductivity

(W/m・K)
Example 9 CaCO3
105 Example 1
0 SrCO3 90
Example 11 Ba
CO3 80
Reference example No additives
50 Furthermore, each of the heat sinks of Examples 9 to 11 had a density of 3.2 g/cm 3 or more. Examples 12-15

[0030] Ca(NO3)2 was added to aluminum nitride powder (average particle size 1.1 μm) containing 3.5% by weight of oxygen.
- 15% by weight of 4H2O was added. Example 3
Four types of AlN sintered bodies were produced by pressureless sintering under the same conditions as (however, the sintering conditions were as shown in Table 3 below). Thereafter, these sintered bodies were processed into predetermined dimensions to produce a heat sink. The thermal conductivity of each of the heat sinks of Examples 12 to 15 was examined. The results are also listed in Table 3.
Table 3
Sintered strip
Thermal conductivity
temperature
Time (W/m・K)
Example 12 1750°C 2hr
62 Example 13
1800℃ 2hr 66
Example 14 1850°C 8
hr 70 Example 15 1800℃ 2hr
95

Further, each of the heat sinks of Examples 12 to 15 had a density of 3.2 g/cm 3 or more, and was sufficiently densified. According to the X-ray diffraction results of the AlN sintered body which is the material of each of the heat sinks of Examples 2 to 15, in addition to the AlN phase, 2Al2O3 ・CaO phase, Al2
O3 ・CaO phase, 12Al2 O3 ・7CaO phase,
An Al2O3.3CaO phase was detected. Examples 16-19

[0032] Ca having an average particle size of 1 μm was added to aluminum nitride powder (average particle size 0.7 μm) containing 5% by weight of oxygen.
10% by weight of CO3, 5% by weight of SrCO3, 10% by weight of SrCO3
% by weight and 10% by weight of BaCO3 were added, and the mixture was ground and mixed using a ball mill to prepare three types of raw materials. These raw materials were pressureless sintered under the same conditions as in Example 3 (however, the sintering conditions were as shown in Table 4 below) to produce four types of AlN sintered bodies. Thereafter, these sintered bodies were processed into predetermined dimensions to produce a heat sink. The thermal conductivity of each of the heat sinks of Examples 16 to 19 was examined. The results are also listed in Table 4.
Table 4
Added aids Sintering
Conditions Thermal conductivity
Type Addition amount
temperature time
(wt%)
(℃) (hr) (W/m・K) Example 16 CaCO3 10 180
0 2 62 Example 17
CaCO3 5 1800
2 58 Example 18 S
rCO3 10 1800 2
62 Example 19 BaCO3
10 1800 2
59 Furthermore, each of the heat sinks of Examples 16 to 19 had a density of 3.2 g/cm 3 or more, and was sufficiently densified.

[0033]

As detailed above, according to the present invention, it is possible to provide a heat sink that is made of a highly thermally conductive AlN sintered body, has excellent heat dissipation properties, and is useful for mounting boards of semiconductor devices, etc. Can be done.

Claims (1)

[Claims] Claim 1: Aluminum nitride containing 0.001 to 7% by weight of oxygen, and one or more selected from alkaline earth metals and their compounds, which will eventually become oxides, in an amount of 0.002 to 7% in terms of alkaline earth metal. 1. A heat dissipation plate comprising a sintered body of aluminum nitride mixed with 15% by weight of aluminum nitride and sintered.