JP2002097005A - Silicon nitride-based powder and its manufacturing method, silicon nitride-based sintered compact and its manufacturing method, and circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly thermal conductive-type silicon nitride-based sintered compact having an excellent mechanical strength and the enhanced thermal conductivity more than before without the anisotropy in the direction of thermal conduction. SOLUTION: For the method for manufacturing a silicon nitride-based power, the raw material contains oxygen in the range of >=0.02 wt.%, <2 wt.% in SiO2 conversion and has a specific surface area of >=0.5 m2/g, is characteristically heated above 1,400 degree C in the non-acidic atmosphere of nitrogen or nitrogen/hydrogen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a member for electronic parts such as a semiconductor substrate and a heat sink for a heating element, or a structural member such as a member for general machinery, a member for molten metal, or a member for a heat engine. High-strength, high-thermal-conductivity-rich silicon nitride-based sintered body and a method for producing the same, silicon nitride-based powder suitable for the production thereof, and a method for producing the same,
In addition, the present invention relates to a circuit board formed using the silicon nitride sintered body.

[0002]

2. Description of the Related Art Conventionally, silicon nitride sintered bodies have excellent heat resistance, low thermal expansion, thermal shock resistance, and corrosion resistance to metals, in addition to mechanical properties such as high-temperature strength characteristics and wear resistance. It is used for various structural members such as members for gas turbines, members for engines, mechanical members for steelmaking, and melt-resistant members of molten metal. In addition, it is used as an electrical insulating material by utilizing high insulating properties.

[0003] In recent years, with the development of semiconductor elements having a large amount of heat, such as high-frequency transistors and power ICs, the demand for ceramic substrates having a high thermal conductivity to obtain good heat dissipation characteristics in addition to electrical insulation has increased. ing. As such a ceramic substrate, an aluminum nitride substrate is used, but there is a problem that mechanical strength and fracture toughness are low, and cracks are generated by fastening in a process of assembling the substrate unit. Further, in a circuit board in which a Si semiconductor element is mounted on an aluminum nitride substrate, since the thermal expansion difference between Si and the aluminum nitride substrate is large, cracks and cracks occur in the aluminum nitride substrate due to thermal cycling, and the mounting reliability is reduced. There's a problem.

Accordingly, a substrate made of a silicon nitride sintered body having high thermal conductivity, which is inferior in thermal conductivity to an aluminum nitride substrate but has a coefficient of thermal expansion close to that of Si and is excellent in mechanical strength, fracture toughness and thermal fatigue resistance, has attracted attention. And various proposals have been made.

[0005] For example, Japanese Patent Application Laid-Open No. 4-175268 discloses that silicon and silicon are substantially composed of silicon nitride, the content of Al and oxygen both contained as impurities is not more than 3.5% by weight, and the density is 3.15 Mg / m3 (3.15 g / m3). cm3) or more, and a silicon nitride-based sintered body having a thermal conductivity of 40 w / (m · K) or more.

[0006] Japanese Patent Application Laid-Open No. 9-30866 describes that
85 to 99% by weight of β-type silicon nitride grains and the remainder are composed of an oxide or oxynitride grain boundary phase, and Mg, C
a, Sr, Ba, Y, La, Ce, Pr, Nd, Sm,
It contains at least one element selected from Gd, Dy, Ho, Er and Yb in an amount of 0.5 to 10% by weight, the content of Al element in the grain boundary phase is 1% by weight or less, and the porosity is 5% or less.
% Or less and a minor axis diameter of 5
A silicon nitride based sintered body in which the ratio of those having μm or more is 10 to 60% by volume is described.

[0007] Japanese Ceramics Association 1996 Annual Meeting Proceedings 1G11, 1G12, and JP-A-10-1
No. 94842 discloses a method in which columnar silicon nitride particles or whiskers are added in advance to a raw material powder, and a molded body in which the particles are two-dimensionally oriented is obtained by a doctor blade method or an extrusion molding method, and then fired. A silicon nitride-based sintered body in which the anisotropy is given to the heat conduction to increase the heat conductivity in a specific direction.

[0008] As a method for producing β powder used for improving the thermal conductivity of silicon nitride or for constructing a microstructure that achieves both bending strength and fracture toughness, silicon nitride raw material powder is prepared by adding a predetermined amount of Y ₂ O ₃ and SiO _{2. 2} is obtained by sintering the mixture in a non-oxidizing atmosphere such as nitrogen. Ce
ram. Soc. Japan., 101 [9] 1078-80 (1993).

Further, as a method for improving the β fraction of silicon nitride powder, a silicon nitride-based raw material powder having a specific surface area of 1 m ² / g or more and containing 2 to 5% by weight of oxygen as SiO ₂ , A method of performing heat treatment in a non-oxidizing atmosphere is described in JP-A-6-263410.

[0010]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open No. 4-17 / 1994
In Japanese Patent No. 5268, a thermal conductivity of 40 W / (m · K) or more is obtained. However, a material having higher thermal conductivity and excellent mechanical strength is desired. Further, in the methods described in JP-A-9-30866 and JP-A-10-194842, a seed crystal or a whisker serving as a growth nucleus is used in order to obtain huge columnar particles in a silicon nitride sintered body. , And baking in a nitrogen atmosphere of 2000 ° C. or more and 10.1 MPa (100 atm) or more is indispensable. Therefore, special high-temperature and high-pressure equipment such as a hot press or HIP is required, resulting in an increase in cost. In addition, since a molding process for obtaining a molded body in which silicon nitride particles are oriented is complicated, there is a problem that productivity is significantly reduced.

Further, the above-mentioned J.A. Ceram. Soc. Japan, 101
[9] In the method described in 1078-80 (1993), since the amount of Y ₂ O _{3 and the} amount of SiO ₂ used as slag are large, the resulting treated powder is strongly agglomerated and crushed in a crushing mortar or the like. It is essential. Further, a dissolution treatment with an acid for removing oxides attached to the particle surface and a classification treatment for adjusting the particle size are required, and the process becomes complicated.
Further, there is a problem that the used auxiliary component is dissolved in the obtained treated powder.

Further, the method described in the above-mentioned Japanese Patent Application Laid-Open No. 6-263410 makes it possible to industrially and inexpensively produce a silicon nitride powder having a β fraction of 95% or more. According to this, as a technique for improving the β fraction, Si
It contains 2 to 5% by weight of oxygen in terms of O ₂ and has a specific surface area of
It is characterized in that a silicon nitride-based powder of 1 m ² / g or more is heat-treated at a temperature of 1500 ° C. or more in a non-acidic atmosphere. The reason that the amount of oxygen contained in the silicon nitride powder used in the present invention is defined as 2 to 5 wt% in terms of SiO ₂ is that if the value is less than 2 wt%, the effect of increasing the β fraction of the silicon nitride powder is increased. And the β fraction tends to vary. On the other hand, when the value exceeds 5 wt%, SiO ₂ remains in the silicon nitride powder after the heat treatment, and the powder characteristics of the silicon nitride powder deteriorate. Regarding the particle size, in order to perform the treatment of the present invention uniformly and in a short time, it is preferable that the fine particles have a specific surface area of 1 m ² / g or more. However, in the example, the β fraction was 9
Although a processing powder of 5% or more is obtained, a silicon nitride raw material powder having an oxygen content of ₂ to 5 wt% in terms of SiO ₂ is used for the purpose of completing the processing at a low temperature and in a short time. Therefore, the amount of oxygen in the resulting powder is
It is 1.2 wt% or more. In addition, there is a problem in that SiO ₂ powder is added in advance to adjust the oxygen amount of the raw material powder to a predetermined amount, or heat treatment in an oxygen atmosphere is required. Furthermore, since the silicon nitride-based powder obtained by the method of the present invention is agglomerated by heat treatment,
In use, there is a drawback that a step of crushing using, for example, a ball mill or a roll crusher is required.

The present invention has been made in view of the above-described conventional problems, and does not require a high-cost and high-temperature sintering method of 2,000 ° C. or more and 10.1 MPa (100 atm) or more. It is an object of the present invention to provide a high thermal conductivity type silicon nitride sintered body which is excellent in heat conductivity and does not have anisotropy in the direction of heat conduction and has a higher thermal conductivity than conventional ones. Another object of the present invention is to provide a silicon nitride powder having a high thermal conductivity and a high strength by defining the β fraction, the oxygen content, the amount of impurities and the mixing ratio with the α-type silicon nitride powder. An object of the present invention is to provide a silicon-based sintered body and a method for producing the same. Another object of the present invention is to provide a silicon nitride powder used for developing high strength and high thermal conductivity and a method for producing the same. The object of the present invention is to provide the high strength
An object of the present invention is to provide a circuit board having good heat radiation properties, which is constituted by using a silicon nitride sintered body rich in high thermal conductivity.

[0014]

Means for Solving the Problems In order to achieve the above object, the present inventors define powder characteristics such as β fraction, oxygen content, impurities and mixing ratio with α powder of a silicon nitride powder to be used. As a result, it has been found that a silicon nitride sintered body having a thermal conductivity of 100 W / (m · K) or more and a sufficient bending strength can be obtained stably. Further, it is effective to improve the sinterability by using a sintering aid as an MgO group and to contain a specific amount of at least one element selected from rare earth elements (RE) containing La, Y and Yb. Discovered and led to the present invention.

The silicon nitride-based powder of the present invention is prepared, for example, by using a silicon nitride-based powder as a raw material obtained by a metal silicon direct nitridation method, a silica reduction method or a silicon imide decomposition method, at 1400 ° C. in a nitrogen or nitrogen / hydrogen mixed atmosphere. ~ 1950 ℃ × 5
It can be manufactured by heat treatment for up to 20 hours. Heat treatment conditions at 1800 ° C to achieve high β fraction and low oxygen
It is more preferable to set the temperature to 1900 ° C. × 5 to 20 hours. Note that the heat treatment at 1800 ° C. or more is preferably performed in a nitrogen or nitrogen / hydrogen atmosphere of 1.0 MPa (10 atm) or more to avoid decomposition of silicon nitride. In order to reduce the oxygen content after the heat treatment to 0.5 wt% or less, the initial oxygen content is set to Si.
It is preferable that the content be less than 2 wt% in terms of O ₂ . In order to minimize the amount of impurities such as Fe and Al, it is more preferable to use silicon nitride powder as a high-purity raw material by an imide decomposition method. The container used for charging the raw material powder may be made of carbon or BN. However, if a carbon heater and a heat treatment furnace with a carbon insulating material specification are used, B is used to suppress the action of an excessive CO reducing atmosphere.
It is desirable to use a product made of N.

The silicon nitride powder of the present invention uses Si powder which acts as an auxiliary agent because it uses a raw material powder having a low oxygen content.
O ₂ component is low and β-type silicon nitride powder
Phase transition to silicon nitride type powder is through gas phase, resulting in low oxygen content, no aggregation after heat treatment, no need for acid treatment step for grinding and removing surface oxides . Also, since oxides such as Y ₂ O ₃ are not used as sintering aids for particle growth, solid solution of these aid components in silicon nitride powder can be avoided.
That is, the silicon nitride powder of the present invention has a β fraction of 30 to 10
0%, the oxygen content is 0.5 wt% or less, and the average particle size is
0.2 to 10 μm, and the aspect ratio is 10 or less. Further, it is characterized in that the Fe content and the Al content are each 100 ppm or less.

In the method for producing a silicon nitride sintered body according to the present invention, the β fraction is 30 to 100%, and the oxygen content is 0.5 wt.
% Or less, an average particle diameter of 0.2 to 10 μm, an aspect ratio of 10 or less, 1 to 59 parts by weight of a silicon nitride powder, and an α-type silicon nitride powder 99 of an average particle diameter of 0.2 to 4 μm.
5050 parts by weight and sintering. When the β fraction of the silicon nitride-based powder is less than 30%, although it has an effect as a growth nucleus, it partially acts as a nucleus,
Abnormal grain growth occurs, and large particles cannot be uniformly dispersed in the microstructure of the finally obtained silicon nitride sintered body, and the bending strength decreases. Therefore, the β fraction of the silicon nitride powder is desirably 30% or more. When the average particle diameter of the silicon nitride powder is less than 0.2 μm, a silicon nitride sintered body having a microstructure in which columnar particles are uniformly developed cannot be obtained as described above, and the thermal conductivity and the bending strength may be increased. Have difficulty. The average particle size of the silicon nitride powder is 10μ.
If it is larger than m, densification of the silicon nitride of the sintered body is hindered. Therefore, the average particle size of the silicon nitride powder is 0.2
1010 μm is preferred. On the other hand, when the aspect ratio is more than 10, the densification of the silicon nitride sintered body is hindered, and as a result, the three-point bending strength at room temperature becomes less than 600 MPa. Therefore, it is preferable that the aspect ratio of the silicon nitride powder is 10 or less.

The silicon nitride sintered body of the present invention converts the contained Mg into magnesium oxide (MgO) and contains at least one element selected from the group consisting of rare earth elements (RE) containing La, Y and Yb. To oxide (RE _x O _y )
Converted, the sum of the content in terms of oxide is 0.6 to 7 wt.
%. If the total content in terms of oxide is less than 0.6 wt%, the densification effect during sintering becomes insufficient, and the relative density becomes less than 95%, which is not preferable.
In the case of more than one, the amount of the grain boundary phase having a low thermal conductivity, which is the second microstructure component of the silicon nitride sintered body, becomes excessive and the thermal conductivity of the sintered body becomes less than 100 W / (m · K). The total of these silicon nitride contents is more preferably 0.6 to 4% by weight. The silicon nitride-based sintered body has a thermal conductivity at room temperature of 100 to 300 W /
(M · K) and the three-point bending strength at room temperature is 600-150.
It is 0MPa and has high strength and high thermal conductivity. The silicon nitride-based sintered body converts Mg contained in magnesium oxide (MgO) and contains La, Y and Yb.
At least one selected from rare earth elements (RE) containing
The species elements are converted to oxides (RE _x O _y ), the total content of the oxides is 0.6 to 7 wt%, and MgO
When the weight ratio represented by / RExOy is 1 to 70, high strength and high thermal conductivity are particularly improved. (MgO / RE
_{When xOy} ) (weight ratio) is less than 1, the ratio of the rare earth oxide in the grain boundary phase increases, so that the liquidus temperature rises in the sintering process, the sintering becomes difficult, and a dense sintered body is obtained. Absent. (MgO /
If RE _x O _y ) (weight ratio) exceeds 70, the Mg
Cannot be suppressed, and color unevenness occurs on the surface of the sintered body. When the MgO / RExOy (weight ratio) is in the range of 1 to 70, the preform is fired at a sintering temperature of 1650 to 1850 ° C., and then a heat treatment at 1850 to 1900 ° C. makes high thermal conductivity remarkable. A silicon nitride sintered body exceeding 120 w / (m · K) can be obtained, which is particularly preferable. The increase in thermal conductivity due to this heat treatment is due to the combined effect of the growth of silicon nitride particles and the efficient vaporization of the MgO-based grain boundary phase component having a high vapor pressure out of the silicon nitride sintered body.

Further, the circuit board of the present invention converts the contained Mg into magnesium oxide (MgO), and the contained L
At least one element selected from the rare earth elements (RE) containing a, Y and Yb is converted into oxide (RE _x O _y ), and the total content of the oxides is 0.6 to 7 wt%. It is possible to provide a material which is constituted by using an elementary sintered body and has excellent heat resistance and heat dissipation as compared with the prior art.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The amount of oxygen in the silicon nitride powder is
The reason why the content is set to 0.5 wt% or less is that when the silicon nitride-based powder is used as a growth nucleus to form a silicon nitride-based sintered body, the solid solution forms in the silicon nitride-based particles constituting the silicon nitride-based sintered body. The amount of oxygen strongly depends on the amount of oxygen in the silicon nitride powder used as a growth nucleus, and the higher the amount of oxygen in the silicon nitride powder, the higher the amount of oxygen dissolved in the silicon nitride particles. Oxygen contained in the silicon nitride particles causes scattering of phonon, which is a heat conduction medium, and lowers the thermal conductivity of the silicon nitride sintered body. In order to express a high thermal conductivity that was not obtained with the conventional silicon nitride sintered body of 100 W / mK or more, the oxygen content of the silicon nitride powder was suppressed to 0.5 wt% or less and finally obtained. It is indispensable to reduce the oxygen content of the silicon nitride sintered body.

Fe Content in Silicon Nitride Powder and A
If the l content exceeds 100 ppm, F
e or Al remarkably forms a solid solution, and phonon, which is a heat conductive medium, is scattered at the solid solution portion, thereby lowering the thermal conductivity of the silicon nitride sintered body. Therefore, in order to obtain a thermal conductivity of 100 W / m · K or more, it is important to control the Fe content and the Al content in the silicon nitride powder to 100 ppm or less, respectively.

The ratio of the silicon nitride powder having a β fraction of 30 to 100% to the α-type silicon nitride powder is 1 to 50 wt%: 99
~ 50 wt% is preferred. When the ratio of the silicon nitride-based powder having a β fraction of 30 to 100% is less than 1 wt%, although there is an effect as a growth nucleus, the number of growth nuclei acting due to a small amount of addition is small, and abnormal grain growth occurs. Large particles cannot be uniformly dispersed in the microstructure, and the bending strength decreases. On the other hand, if the content exceeds 50 wt%, the number of growth nuclei increases, and in the process of grain growth, particles collide with each other, thereby inhibiting growth and maintaining strength. However, a silicon nitride sintered body composed of developed columnar particles can be maintained. Cannot be obtained, and it becomes difficult to realize a high thermal conductivity as compared with the related art.

Mg and Y are useful as sintering aids and are effective for densification of silicon nitride raw material powder. Since these elements have a low solid solubility in silicon nitride particles, which are the first microstructure component constituting the silicon nitride sintered body, the thermal conductivity of the silicon nitride particles, and thus the silicon nitride sintered body, is high. Can be kept.

Like Y, it has a small solid solubility in silicon nitride particles, and is useful as a sintering aid.
Ce, Nd, Pm, Sm, Eu, Gd, Dy, Ho, E
At least one rare earth element selected from the group consisting of r, Tm, Yb and Lu is included. Among them, La and C are preferred because they can be fired without excessively increasing the temperature and pressure.
At least one rare earth element selected from the group consisting of e, Gd, Dy and Yb is preferred.

The substrate made of the silicon nitride sintered body of the present invention takes advantage of the characteristics of high strength, high toughness and high thermal conductivity to make use of various substrates such as a substrate for a power semiconductor or a substrate for a multi-chip module, or It is suitable for electronic component members such as a heat transfer plate for a Peltier element or a heat sink for various heating elements.

When the silicon nitride sintered body of the present invention is used as a substrate for a semiconductor device, the occurrence of cracks in the substrate when subjected to repeated thermal cycles accompanying the operation of the semiconductor device can be suppressed, and the thermal shock resistance can be reduced. In addition, the heat cycle resistance is significantly improved, and the reliability is excellent. Further, even when a semiconductor element for high output and high integration is mounted, deterioration of the thermal resistance characteristics is small and excellent heat radiation characteristics are exhibited. In addition, the excellent mechanical properties allow not only the function as the original substrate material but also the structure itself to serve as a structural member, so that the structure of the substrate unit itself can be simplified.

Further, the silicon nitride sintered body of the present invention can be widely used for materials requiring heat resistance characteristics such as thermal shock and thermal fatigue in addition to the above-mentioned electronic component members. Structural members include various heat exchanger parts and heat engine parts, heater tubes used in the field of melting metals such as aluminum and zinc, Stokes, die-cast sleeves, propellers for molten metal agitation, ladles, thermocouple protection tubes, etc. Applicable to Further, by applying the present invention to a sink roll, a support roll, a bearing, a shaft, or the like used in a hot-dip metal plating line for aluminum, zinc, or the like, a member having excellent crack resistance against rapid heating and cooling can be obtained. Also,
In the field of steel or non-ferrous processing, when used for rolling rolls, squeeze rolls, guide rollers, drawing dies, or tool tips, etc., it has good heat dissipation when it comes into contact with the workpiece, so it can withstand heat fatigue and heat resistance. The impact resistance can be improved, thereby reducing abrasion and making thermal stress cracking less likely to occur.

Further, the present invention can be applied to a sputter target member, for example, forming an electric insulating film used for an MR head, a GMR head, or a TMR head of a magnetic recording apparatus, and abrasion resistance used for a thermal head of a thermal transfer printer. Suitable for forming a film. The film obtained by sputtering has inherently high thermal conductivity, a sufficiently high sputter rate, and a high electric breakdown voltage of the film. Therefore, an MR head, GMR head, or TM
Since the electrical insulating film for the R head has characteristics of high thermal conductivity and high withstand voltage, it is possible to increase the heat generation density of the element and to reduce the thickness of the insulating film. In addition, the wear-resistant coating for a thermal head formed by this sputter target has not only good wear resistance due to the inherent characteristics of silicon nitride, but also high thermal conductivity, so that thermal resistance can be reduced. Can be enhanced.

[0029]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. (Example 1) less than the oxygen content is 2.0 wt% in terms of SiO _2, a silicon nitride powder by the imide decomposition method with an average particle diameter 0.2~2.0μm was filled in a BN crucible and then atmospheric pressure to 1.
0 MPa 1 at 1400 ℃ ~1950 ℃ in N ₂ atmosphere (10 atm)
Heat treatment for ~ 20 hours was applied and then cooled to room temperature. The β fraction of the obtained silicon nitride-based powder was 90 to 100%, and the oxygen content was 0.2 to 0.4% by weight. FIG. 1 shows an SEM observation image of the obtained silicon nitride-based powder example. The β fraction of the powder is 100%, the amount of oxygen is 0.2% by weight, and the amounts of Fe and Al are 50 ppm and 40 ppm, respectively. Grooves are formed in the powder in parallel with the major axis direction of the particles, which is a feature when grain growth occurs through the gas phase, and it has been demonstrated that the smaller the amount of oxygen is, the more significant it becomes. Was. Following the powder, the obtained β-type Si ₃ N
₄ to 5 to 30 parts by weight of a silicon nitride-based powder having an oxygen content of 0.3 to 1.5 wt% and an average particle diameter of 0.5
μm α-type silicon nitride (Si 3 N 4) powder 99.5-66
Parts by weight and an average particle size of 0.
2 μm of MgO powder and RE _x O _y powder (sintering aid) described in Table 1 having an average particle diameter of 0.2 to 2.0 μm were blended,
Further, 2 wt% of a dispersant (Leoka-to-GP) was blended, charged into a ball mill container filled with ethanol, and then mixed. The resulting mixture is vacuum dried, and then has an aperture of 150 m.
And granulated through a sieve. Next, press machine to 20mm in diameter
A disk-shaped compact having a thickness of 10 mm, a diameter of 100 mm and a thickness of 15 mm was obtained by CIP molding under a pressure of 3 tons. Then 1750-1
The firing was performed for 5 hours in a nitrogen gas atmosphere at 900 ° C. and 0.9 MPa (9 atm). The impurities of Fe and Al in the obtained silicon nitride powder were analyzed by a plasma emission spectrometry (ICP).
The oxygen content was measured by an infrared heating absorption method.
The β fraction of the obtained silicon nitride powder was determined from the X-ray diffraction intensity ratio using Cu-Kα ray according to the formula (1). β fraction (%) = {(I _{β (101)} + I _{β (210)} ) / (I _{β (101)} + I
_{β (210)} + I _{α (102)} + I _{α (201)} )} × 100 (1) I _{β (101)} : (101) plane diffraction peak intensity of β-type Si ₃ N ₄ , I _{β (210 )} : (210) plane diffraction peak intensity of β-type Si ₃ N ₄ , I _{α (102)} : α-type Si ₃ N ₄ (102) plane diffraction peak intensity, I _{α (210)} : α type (210) plane diffraction peak intensity of Si ₃ N ₄ . The average particle diameter and average aspect ratio of the obtained silicon nitride-based powder were determined by using a SEM photograph obtained at an observation magnification of × 2000 by SEM observation, and a total of 500 nitrided particles within a visual area of 200 μm × 500 μm were used. The silicon particles were randomly selected, the minimum diameter and the maximum diameter were measured by an image analyzer, and the average value was obtained and evaluated. Next, from the obtained silicon nitride sintered body, a test piece having a diameter of 10 mm and a thickness of 3 mm for measuring thermal conductivity and density, and a bending test piece having a length of 3 mm, a width of 4 mm and a length of 40 mm were collected. The density was calculated by measuring the size with a micrometer and measuring the weight. The thermal conductivity was determined by measuring the specific heat and the thermal diffusivity at room temperature by the laser flash method and calculating the thermal conductivity. 3-point bending strength is JIS at room temperature
The measurement was performed according to R1606. The outlines of the above manufacturing conditions and the evaluation results are shown in Samples 1 to 11 in Tables 1 and 2.

Comparative Example 1 Silicon nitride powders having different β fractions were prepared in the same manner as in Example 1 except that the production conditions shown in Table 1 were used. Next, a silicon nitride-based sintered body was prepared using the obtained silicon nitride-based powder and evaluated. The outline of the above manufacturing conditions and the evaluation results are shown in Tables 1 and 2 for sample No. 3.
1 to 41.

[0031]

[Table 1]

[0032]

[Table 2]

The following findings were obtained from Sample Nos. 1 to 11 in Tables 1 and 2. The silicon nitride powder added as growth nuclei has a β fraction of 30% or more, an oxygen content of 0.5% by weight or less, an Fe content of 100 ppm or less, and A
l content is 100 ppm or less, the average particle size is 0.2 ~ 10μ
m, the aspect ratio is 10 or less, and the β-conversion rate is 30% or more. The silicon nitride-based sintered body obtained by mixing 1 to 50 wt% of the silicon nitride-based powder has a thermal conductivity of 10% at room temperature.
0 w / (m · K) or more, and the three-point bending strength at room temperature becomes 600 MPa or more. The thermal conductivity of the silicon nitride sintered body according to the prior art was about 40 w / (m · K), and the thermal conductivity could be dramatically increased. In addition, Mg as a sintering aid
In terms of magnesium oxide (MgO), Y, La, C
e, Dy, Gd and Yb are converted to oxides (RE _x O _y ), and the total content of the oxides is 0.6 to 7.0 wt%.
And (MgO / RE _x O _y ) (weight ratio) is 1 to 70
Has a thermal conductivity of 100 w / (mK) or more and a bending strength of 6
00MPa or more was obtained.

On the other hand, Sample N of Comparative Example 1 in Tables 1 and 2
o. The following findings were obtained from 31 to 41. In No. 31, when the β fraction of the silicon nitride particles is less than 30%, the bending strength is remarkably reduced to about 500 MPa. In No. 32, when the amount of oxygen inevitably contained in the silicon nitride-based powder exceeds 0.5 wt, the thermal conductivity is reduced to 70 w / (m · K) or less. No.33 and
In No. 34, the impurity F contained in the silicon nitride powder was
When the content of each of e and Al exceeds 100 ppm, the thermal conductivity decreases to 65 w / (m · K) or less. No.35 and N
In o.36, when the average particle diameter of the silicon nitride powder is less than 0.2 μm, the thermal conductivity is reduced to 60 w / (mK) or less, and when it is more than 10 μm, a dense sintered body cannot be obtained. Thermal conductivity is 60 w /
(m · K) or less, and the bending strength decreases to 600 MPa or less. In No. 37, when the aspect ratio of the silicon nitride-based powder was 10 or more, a dense sintered body was not obtained, and the bending strength was reduced to 600 MPa or less. In Nos. 38 and 39, the bending strength was 600 MPa when the addition amount of the silicon nitride powder was less than 1.0 wt%.
If it falls below 50 wt%, the thermal conductivity becomes
It decreased to 70 w / (m · K) or less. In Nos. 40 and 41, when the sintering aid component was less than 0.6 wt%, the density of the sintered body was reduced, and as a result, the thermal conductivity and the bending strength were significantly reduced. If the sintering aid component exceeds 7.0 wt%, a sufficient glass phase is generated during the firing process, so that the sintered body can be densified, but on the other hand, the grain boundary phase, which is a low thermal conductive phase, has been increased. Thermal conductivity dropped below 60 w / (m · K).

(Example 2) The β conversion rate produced in Example 1 was
3 wt% MgO, 1 wt% in 30% or more silicon nitride powder
A mixed powder to which a sintering aid of% Y ₂ O ₃ was added was prepared. Then, toluene containing 2 wt% of an amine-based dispersant was added.
The prepared mixed powder and a ball made of silicon nitride as a grinding medium were put into a resin pot of a ball mill filled with a butanol solution, and wet-mixed for 48 hours. Then, 15 parts by weight of a polyvinyl-based organic binder and 100 parts by weight of a plasticizer (dimethyl phthalate) were added to 100 parts by weight of the mixed powder in the pot.
G) was added thereto and wet-mixed for 48 hours to obtain a sheet forming slurry. After adjusting this molding slurry,
Green sheets were formed by a doctor blade method. Next, the formed green sheet is heated at 400 to 600 ° C in air for 2 hours.
By heating for ５5 hours, the organic binder component added in advance was sufficiently degreased (removed). Then defatted body 0.9M
The obtained silicon nitride-based sintering was performed by firing at 1850 ° C. × 5 hours in a nitrogen atmosphere of Pa (9 atm), then performing heat treatment at 1900 ° C. × 24 hours in the nitrogen atmosphere, and then cooled to room temperature. Machine processing is applied to the body sheet, length 50 mm × width 50 mm × thickness 0.
A 6 mm substrate for a semiconductor device was manufactured. A circuit board shown in FIG. 2 was produced using the silicon nitride sintered body substrate. In FIG. 2, the circuit board 1 has the length of 50 mm ×
A copper circuit board 3 is provided on the surface of a silicon nitride-based sintered body 2 having a size of 50 mm in width × 0.6 mm in thickness, and a copper plate 4 is joined to a back surface of the substrate 2 with a brazing material 5. This circuit board 1 was subjected to three-point bending strength evaluation and heat cycle test. As a result, the bending strength is as large as 600 MPa or more, and the frequency of occurrence of cracks due to tightening cracks in the mounting process of the circuit board 1 and thermal stress in the soldering process is hardly observed, and the semiconductor device using the circuit board 1 It has been demonstrated that the manufacturing yield can be significantly improved. In the heat cycle test, cooling at -40 was
10 minutes at room temperature and 20 minutes at 180 ° C.
The heating / cooling cycle as one minute was defined as one cycle, which was repeatedly applied, and the number of cycles until cracks or the like occurred in the substrate portion was measured. As a result, even after the lapse of 1000 cycles, there was no cracking of the silicon nitride sintered body substrate 2 or peeling of the copper circuit board 2, and it was confirmed that both the durability and the reliability were excellent. Further, even after 1000 cycles, the withstand voltage characteristics did not decrease.

[0036]

As described above, the silicon nitride sintered body of the present invention has a high thermal conductivity in addition to its inherent high strength / high toughness. Cracks are less likely to occur in the substrate due to repeated thermal cycles associated with the operation of the element, and the thermal shock resistance and the thermal cycle resistance can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a photograph of a representative silicon nitride powder of the present invention taken with a scanning electron microscope.

FIG. 2 is a sectional view of a main part of a circuit board according to the present invention.

[Explanation of symbols]

1 circuit board, 2 board, 3 copper circuit board, 4
Copper plate, 5 brazing material.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G001 BA06 BA08 BA09 BA10 BA11 BA32 BA71 BA73 BB06 BB08 BB09 BB10 BB11 BB32 BB71 BB73 BC52 BC54 BD03 BD14 BE33

Claims (8)

[Claims] 1. A SiO ₂ calculated as 0.02 wt% or more, 2
The method is characterized by heat-treating a silicon nitride powder raw material having a specific surface area of 0.5 m ² / g or more containing less than wt% oxygen at a temperature of 1400 ° C. or more in a non-acidic atmosphere of nitrogen or nitrogen / hydrogen. A method for producing silicon nitride-based powder. 2. The composition according to claim 1, wherein the β fraction is 30 to 100% and the oxygen content is 0.5%.
1 wt% or less, an average particle diameter of 0.2 to 10 µm, and an aspect ratio of 10 or less. 3. The method according to claim 1, wherein the Fe content and the Al content are respectively
3. The silicon nitride powder according to claim 2, wherein the content is 100 ppm or less. 4. A β-fraction of 30 to 100% and an oxygen content of 0.5
wt% or less, an average particle diameter of 0.2 to 10 μm, an aspect ratio of 10 or less, 1 to 50 parts by weight of silicon nitride powder, and an α-type silicon nitride powder 99 of average particle diameter of 0.2 to 4 μm.
To 50 parts by weight and sintering. 5. The method according to claim 5, wherein the Mg contained is magnesium oxide (Mg).
O), and at least one element selected from the rare earth elements (RE) containing La, Y and Yb contained therein is converted into oxides (RE _x O _y ), and the total of the contents in terms of oxides is A silicon nitride based sintered body characterized in that the content is 0.6 to 7% by weight. 6. The thermal conductivity at room temperature is 100 to 300 W / (m
・ K) and the three-point bending strength at room temperature is 600 ~ 1500MP
The silicon nitride-based sintered body according to claim 5, which is a, which is rich in high strength and high thermal conductivity. 7. A method according to claim 7, wherein the contained Mg is magnesium oxide (Mg).
O), and at least one element selected from the rare earth elements (RE) containing La, Y and Yb contained therein is converted into oxides (RE _x O _y ), and the total of the contents in terms of oxides is 0.6 to 7 wt%, and (MgO / RE _x
O _y) weight ratio expressed by the 1 to 70 claims 5 or silicon nitride sintered body according to 6. 8. A method according to claim 8, wherein the Mg contained is magnesium oxide (Mg).
O), and at least one element selected from the rare earth elements (RE) containing La, Y and Yb contained therein is converted into oxides (RE _x O _y ), and the total of the contents in terms of oxides is A circuit board having high strength and high thermal conductivity, characterized by being constituted by using a silicon nitride sintered body of 0.6 to 7 wt%.