JPH0680475A - Method for manufacturing light-shielding aluminum nitride sintered body - Google Patents

Abstract

(57) [Abstract] [Purpose] To minimize the amount of titanium element that impairs the thermal conductivity and insulation resistance, while uniformly dispersing the titanium element as a blackening material in the AlN sintered body. By doing so, the translucency is almost completely eliminated. [Structure] A titanate-based coupling agent 1 is added to and mixed with aluminum nitride raw material powder 3, the obtained raw material mixture is molded to form a molded body having a predetermined shape, and the obtained molded body is fired. Is characterized by. Further, the addition amount of the titanate coupling agent 1 is set to 0.1 to 1% by weight in terms of Ti element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a light-shielding aluminum nitride sintered body, and particularly, to reduce the content of titanium which hinders heat transfer characteristics as much as possible to satisfy both high thermal conductivity and light-shielding characteristics. The present invention relates to a method for producing a light-shielding aluminum nitride sintered body.

[0002]

2. Description of the Related Art In recent years, demands for miniaturization and improvement of functions of electronic devices and semiconductor devices have become extremely high, and semiconductors are required to have higher integration density, higher functionality, higher speed, higher output and higher reliability. It is making rapid progress. In particular, the amount of heat generated from the semiconductor is greatly increased in response to higher integration and higher output, and there is a demand for a substrate material having more excellent heat dissipation, which replaces the conventional Al ₂ O ₃ substrate.

As such a material having excellent heat dissipation,
BACKGROUND ART Aluminum nitride (AlN) sintered bodies, which have remarkably high thermal conductivity and electrical insulating properties and whose thermal expansion coefficient is similar to that of silicon which constitutes a semiconductor element, are widely used.

[0004]

However, among the electrically insulating high heat dissipation aluminum nitride substrates on which semiconductor elements are mounted, those having high heat dissipation with a thermal conductivity of 150 w / m · k or more are used in the visible light range. Some are translucent. In this case, in particular, there is a problem that the probability that the semiconductor element malfunctions due to visible light entering from the surface of the substrate increases and the operation reliability of the semiconductor device decreases.

As a countermeasure, a method of adding another element to color the aluminum nitride sintered body to prevent the transmission of visible light is also adopted. In particular, by including titanium oxide powder in the sintered body, the light transmittance is remarkably eliminated, and an AlN sintered body colored almost black is obtained.

However, when a large amount of titanium oxide is added, the thermal conductivity and the withstand voltage of the AlN sintered body are liable to decrease, and the high heat dissipation characteristics cannot be sufficiently exhibited,
There has been a problem that the function as an insulating substrate material is significantly reduced.

The present invention has been made in order to solve the above-mentioned problems, and reduces the amount of titanium element which impairs thermal conductivity and insulation resistance as much as possible, while at the same time, as a blackening material. It is an object of the present invention to provide a method for producing a light-shielding aluminum nitride sintered body, which is capable of almost completely eliminating translucency by uniformly dispersing titanium element in an AlN sintered body.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present inventors continued the experimental research to uniformly disperse the titanium element in the AlN sintered body. As a result, in place of the titanium oxide powder as the blackening material, when the titanate-based coupling agent was added to the aluminum nitride raw material powder, the coupling agent was firmly bonded to the entire surface of each aluminum nitride raw material powder, As a result, a raw material system in which titanium element is uniformly dispersed throughout the aluminum nitride raw material powder is obtained, and when this raw material system is processed according to the usual molding method and sintering method, high conductivity, high insulation resistance and light-shielding property are obtained. It was confirmed for the first time that an aluminum nitride sintered body satisfying the above conditions was obtained.

The present invention has been completed based on the above findings. That is, the method for producing a light-shielding aluminum nitride sintered body according to the present invention is a method of adding a titanate coupling agent to an aluminum nitride raw material powder, and molding the obtained raw material mixture to obtain a molded body having a predetermined shape. To form
It is characterized in that the obtained molded body is fired.

Further, the addition amount of the titanate coupling agent to the aluminum nitride raw material powder is preferably set to 0.1 to 1% by weight in terms of Ti element.

The titanate coupling agent is composed of a hydrocarbon compound containing a Ti element, and is bonded to the surface of the AlN raw material powder by its affinity with the hydroxyl group bonded to the surface of the AlN raw material powder. As a result, titanium element is uniformly dispersed and arranged on the entire surface of the AlN raw material powder. This titanate-based coupling agent has a function of coloring the AlN sintered body black by the contained Ti element, and is added to the aluminum nitride raw material powder in an amount of 0.1 to 1% by weight in terms of Ti metal. When the addition amount is less than 0.1% by weight, the effect of uniformly dispersing the Ti element on the surface and the periphery of the AlN raw material powder is small, and it is difficult to secure the perfect light shielding property of the AlN sintered body. Become. On the other hand, if the amount added is too much over 1% by weight, the oxygen component contained in the coupling agent will increase and the thermal conductivity will decrease. In addition, excessive TiN is generated and A
The insulation resistance of 1N is deteriorated.

As the preferred examples of the titanate coupling agent, those shown in Tables 1 and 2 below are adopted.

[0013]

[Table 1]

[Table 2]

A predetermined amount of the titanate-based coupling agent, the sintering aid, the solvent and the binder are added to and mixed with the aluminum nitride raw material powder to prepare a uniform raw material mixture, and the obtained raw material mixture is formed into a predetermined shape. A light-shielding aluminum nitride sintered body is obtained by molding the obtained molded body under degreasing sintering under predetermined conditions.

The aluminum nitride (AlN) powder used in the method of the present invention, which is the main component of the sintered body, has an impurity oxygen content suppressed to 3% by weight or less in consideration of sinterability and thermal conductivity. The average particle size is about 0.05 to 5 μm, preferably 3 μm or less.

As a sintering aid, rare earth elements (Y, Sc,
Ce, Dy, etc.) oxides, nitrides, oxides of alkaline earth metals (Ca), or substances that become these compounds by a sintering operation are used, particularly yttrium oxide (Y
₂ O ₃ ) and calcium oxide (CaO) are preferred. The addition amount of the sintering aid is adjusted within the range of 0.5 to 10% by weight. If the addition amount is less than 0.5% by weight, the effect of improving the sinterability is not sufficiently exerted, the sintered body is not densified and a low-strength sintered body is formed, or oxygen is not contained in the AlN crystal. However, it cannot form a sintered body having a high thermal conductivity. On the other hand, if the addition amount exceeds 10 wt%, the grain boundary phase remains in the sintered body, or the volume of the grain boundary phase removed by the heat treatment becomes large, so that pores remain in the sintered body. As a result, the shrinkage rate increases and deformation is likely to occur.

As the solvent, alcohols such as ethanol and methanol, and ordinary solvents such as ethers and esters are used. As the binder, a general-purpose organic binder such as an acrylic type, a wax or an emulsion type is suitable.

As a molding method of the AlN raw material mixture, a general-purpose die pressing method, isostatic pressing method, sheet molding method such as slurry casting method or doctor blade method can be applied, and a molded body having a predetermined shape is formed.

The obtained molded body is heated to 350 to 450 ° C. in a non-oxidizing atmosphere, for example, a nitrogen gas atmosphere, and the organic binder added in advance is sufficiently removed.

Next, the degreased compact is subjected to a sintering operation. The sintering operation is performed by heating the compact at a temperature of 1700 to 2000 ° C. for about 2 to 10 hours in a non-oxidizing atmosphere such as nitrogen gas. The sintering atmosphere is nitrogen gas or a reducing atmosphere containing nitrogen gas. H ₂ gas or CO gas may be used as the reducing gas. The sintering may be performed in an atmosphere including vacuum (including a slight reducing atmosphere), reduced pressure, increased pressure and normal pressure. Sintering temperature is 170
When fired at a low temperature of less than 0 ° C, it is difficult to obtain a dense sintered body although it depends on the particle size of the raw material powder and the amount of oxygen contained, but when fired at a temperature higher than 2000 ° C, the vapor of AlN itself in the firing furnace The sintering temperature is set in the above range because the pressure may increase and densification may become difficult.

[0021]

According to the method for manufacturing a light-shielding aluminum nitride sintered body having the above-mentioned structure, since the titanium-based coupling agent is added to the aluminum nitride raw material powder as a blackening material, the coupling agent is aluminum nitride. Bond to the entire surface of the raw material powder. Therefore, titanium element is uniformly dispersed and arranged in the entire aluminum nitride raw material powder,
By adding the minimum amount of titanium element, it is possible to obtain an aluminum nitride sintered body having excellent light-shielding properties without impairing high thermal conductivity and high insulation resistance.

[0022]

EXAMPLES The effects of the method for producing a light-shielding aluminum nitride sintered body according to the present invention will be described more specifically with reference to the following examples.

Example 1 Tetra (2,2-diallyloxymethyl-1-butyl) bis (ditridecyl) was added to aluminum nitride raw material powder having an average particle size of 1.5 μm produced by an oxide reduction method.
Coupling agent consisting of phosphite titanate was added to Ti
0.15% by weight in terms of elements, Y ₂ O as a sintering aid
₃ % by weight of yttrium oxide and 3% by weight of an acrylic binder as an organic binder were added and wet mixed in ethyl alcohol for 24 hours to prepare a slurry, and then a granulated powder formed from this slurry Are packed in a molding die of a press molding machine and compression-molded at a pressure of 1000 kg / cm ² to prepare a large number of disk-shaped molded bodies, and subsequently each molded body is heated to 700 ° C. in a nitrogen gas atmosphere. 2 at ℃
It was heated and degreased for an hour. Next, the degreased molded body was held in a nitrogen gas atmosphere at a temperature of 1850 ° C. for 3 hours and sintered to obtain a light-shielding aluminum nitride sintered body according to Example 1.

Example 2 Raw material under the same conditions as in Example 1 except that isopropyltriisostearoyl titanate was used in place of tetra (2,2-diallyloxymethyl) bis (ditridecyl) phosphite titanate as a titanate coupling agent. The mixture was prepared, molded, degreased and sintered to produce a large number of light-shielding aluminum nitride sintered bodies according to Example 2 having the same dimensions.

Comparative Example 1 Molding, degreasing and sintering were carried out under the same conditions as in Example 1 except that titanium oxide powder was added in an amount of 0.5% by weight in terms of Ti in the same manner as in the conventional method, instead of the titanate coupling agent. Thus, a conventional light-shielding aluminum nitride sintered body according to Comparative Example 1 was manufactured.

Comparative Example 2 An example was carried out except that titanium oxide powder was added in place of the titanate type coupling agent so as to have the same Ti element content (0.15% by weight in terms of Ti) as in Example 1. 1
A light-shielding aluminum nitride sintered body according to Comparative Example 2 was manufactured by molding and sintering under the same conditions.

Then, in order to evaluate the characteristics of each of the obtained AlN sintered bodies according to Examples 1 and 2 and Comparative Examples 1 and 2, the density, thermal conductivity and total transmittance of visible light were measured, and the following table is given. The results shown in 3 were obtained. The thermal conductivity was measured by a laser flash method after performing a flat grinding process so that each sample had a thickness of 2 mm. The total transmittance of visible light was calculated by irradiating each sample with visible light having a wavelength of 596 nm and calculating the ratio of the amount of transmitted light to the amount of incident light.

[0028]

[Table 3]

As is clear from the results shown in Table 3, in the light-shielding AlN sintered bodies according to Examples 1 and 2, since the titanate coupling agent was added as the blackening material, each sintered The Ti element is uniformly dispersed and arranged in the body, and it is uniformly colored by the addition of a trace amount of the titanium element, and the sintered body has an excellent light shielding property. The thermal conductivity is also 17
High as 8 to 180 w / m · k and density of 3.30 to 3.3
It has a high value of 1 and has high heat dissipation and mechanical strength.

Here, the action of the titanate coupling agent will be described with reference to FIG. That is, the titanate-based coupling agent 1 is composed of a Ti element 2 and various hydrocarbon groups R bonded to the Ti element 2, and the affinity with the hydroxyl group 4 bonded to the surface of the aluminum nitride powder 3 causes AlN raw material powder. 3 Bond to the surface. As a result,
As shown in the state after addition on the right side of, the Ti element 2 contained in the coupling agent is uniformly dispersed and arranged on the entire surface of the aluminum nitride powder 3. Therefore, by adding a small amount of titanium element 2, an AlN sintered body that is uniformly colored and has a high light-shielding property can be obtained, and the thermal conductivity and the withstand voltage characteristics are less likely to be impaired.

On the other hand, in Comparative Example 1, since titanium oxide powder having a lower dispersibility is used as the blackening material as compared with the coupling agent, in order to secure the same light-shielding property as in Example 1, Ti is used. It was necessary to add a large amount of 0.3% by weight in terms of conversion, and it was confirmed that addition of a large amount of this titanium oxide powder tended to slightly lower the thermal conductivity as compared with Examples 1 and 2.

In Comparative Example 2, Ti powder was added to the same extent as in Examples 1 and 2, but it was found that the light-shielding property was deteriorated because it was difficult to uniformly disperse the Ti powder.

[0033]

As described above, according to the method for manufacturing a light-shielding aluminum nitride sintered body of the present invention, the titanium-based coupling agent is added to the aluminum nitride raw material powder as a blackening material. The coupling agent binds to the entire surface of the aluminum nitride raw material powder. For this reason, titanium element is uniformly dispersed and arranged in the entire aluminum nitride raw material powder. Therefore, by adding a minimum amount of titanium element, an aluminum nitride sintered body excellent in light shielding property without impairing high thermal conductivity and high insulation resistance. Can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing the action of a titanate coupling agent used in the method of the present invention on inorganic particles (AlN raw material powder).

[Explanation of symbols]

 1 Titanate Coupling Agent 2 Ti Element 3 Aluminum Nitride Powder 4 Hydroxyl Group R Hydrocarbon Group

Claims (2)

[Claims] 1. A titanate-based coupling agent is added to and mixed with an aluminum nitride raw material powder, and the obtained raw material mixture is molded to form a molded body having a predetermined shape, and the molded body is fired. A method of manufacturing a light-shielding aluminum nitride sintered body, comprising: 2. A titanate-based coupling agent added to an aluminum nitride raw material powder in an amount of 0.1% in terms of Ti element.
The method for producing a light-shielding aluminum nitride sintered body according to claim 1, wherein the amount is set to 1 to 1% by weight.