JP5743830B2 - Silicon nitride sintered body, circuit board and electronic device using the same - Google Patents

Description

  The present invention relates to a silicon nitride sintered body used for a heat dissipation member, a support substrate for a circuit member, and the like. Further, a circuit board in which a circuit member is provided on the first main surface side of the support substrate made of the silicon nitride-based sintered body, and a heat dissipation member is provided on the second main surface side facing the first main surface, and the circuit board The present invention relates to an electronic device in which an electronic component is mounted on a circuit member.

  In recent years, insulated gate bipolar transistor (IGBT) devices, metal oxide field effect transistor (MOSFET) devices, light emitting diode (LED) devices, freewheeling diode (FWD) devices, giant transistor (GTR) devices, etc. 2. Description of the Related Art An electronic device in which various electronic components such as a semiconductor element, a sublimation thermal printer head element, a thermal ink jet printer head element, and a Peltier element are mounted on a circuit member of a circuit board is used.

  As a circuit board provided with a circuit member for mounting an electronic component, for example, a circuit member mainly composed of copper and a heat dissipation member are respectively provided on both main surfaces of a support substrate made of an insulating ceramic sintered body. What is joined is used, and a silicon nitride sintered body has attracted attention as a ceramic sintered body used for a support substrate.

And as a silicon nitride sintered body used for such a circuit board, for example, in Patent Document 1, a rare earth metal is converted to an oxide in an amount of 2.0 to 17.5% by weight, and Mg is converted into an oxide in an amount of 0.3 to 3.0% by weight, Al, Li, Na, K, Fe, Ba, Mn, B as impurity cation elements
A high thermal conductivity silicon nitride sintered body comprising a total of 0.3% by weight of silicon nitride crystal and a grain boundary phase, and the ratio of the crystalline compound phase in the grain boundary phase to the whole grain boundary phase being 20% or more. Proposed.

JP 2000-34172 A

  However, the highly thermally conductive silicon nitride sintered body proposed in Patent Document 1 has a high ratio of the crystalline compound phase in the grain boundary phase to the entire grain boundary phase of 20% or more. Due to the volume shrinkage in the process of forming, there is a high possibility that many gaps are generated in the grain boundary phase. As described above, when many gaps are generated in the grain boundary phase, there is a problem in that the dielectric strength is reduced due to fouling caused by dust entering the gaps and adsorption of moisture.

  The present invention has been devised in view of the above problems, and has a silicon nitride sintered body having high dielectric strength, excellent heat dissipation characteristics and mechanical characteristics, and a circuit board and an electronic device using the same. It is intended to provide.

The silicon nitride based sintered body of the present invention is mainly composed of silicon nitride, and magnesium, rare earth metal, aluminum and boron are 2% by mass or more and 6% by mass or less, 12% by mass or more and 16% by mass or less, respectively, in terms of oxides. A main crystal phase composed of β-Si ₃ N ₄ and a composition formula of RE ₄ Si ₂ N ₂ O ₇ (RE is a rare earth metal), comprising 0.1% by mass to 0.5% by mass and 0.06% by mass to 0.32% by mass. ) With respect to the first peak intensity I ₀ of β-Si ₃ N _{4 at} a diffraction angle of 27 ° to 28 ° determined by an X-ray diffraction method. The ratio (I ₁ / I ₀ ) of the first peak intensity I ₁ of RE ₄ Si ₂ N ₂ O ₇ at ° to 35 ° is 20% or less (excluding 0%) It is.

  Further, the circuit board of the present invention radiates the circuit member on the first main surface side of the support substrate made of the silicon nitride sintered body of the present invention having the above-described configuration, and radiates heat on the second main surface side facing the first main surface. Each member is provided.

  The electronic device of the present invention is characterized in that an electronic component is mounted on the circuit member of the circuit board of the present invention having the above-described configuration.

According to the silicon nitride sintered body of the present invention, silicon nitride is the main component, and magnesium, rare earth metal, aluminum, and boron are 2% by mass to 6% by mass and 12% by mass to 16% by mass, respectively, in terms of oxides. In the following, 0.1 to 0.5% by mass, 0.06 to 0.32% by mass, a main crystal phase composed of β-Si ₃ N ₄ and a composition formula of RE ₄ Si ₂ N ₂ O ₇ (RE is And a grain boundary phase containing a component represented as (rare earth metal), and obtained with respect to the first peak intensity I ₀ of β-Si ₃ N _{4 at} a diffraction angle of 27 ° to 28 ° determined by an X-ray diffraction method. Since the ratio (I ₁ / I ₀ ) of the first peak intensity I ₁ of RE ₄ Si ₂ N ₂ O ₇ at the folding angle of 30 ° to 35 ° is 20% or less (excluding 0%), RE ₄ volume due to crystallization shrinkage of Si ₂ N ₂ O ₇ is small , Since the less likely a gap in the grain boundary phase in the can dielectric strength is high, the silicon nitride sintered body having excellent heat dissipation properties and mechanical properties.

  According to the circuit board of the present invention, the circuit member is disposed on the first main surface side of the support substrate made of the silicon nitride sintered body of the present invention having the above-described configuration, and the second main surface side facing the first main surface. Since the heat dissipating members are respectively provided on the supporting substrate, the support substrate has a high dielectric strength, and has excellent heat dissipating characteristics and mechanical characteristics, whereby a highly reliable circuit board can be obtained.

  In addition, according to the electronic device of the present invention, since the electronic component is mounted on the circuit member of the circuit board of the present invention having the above-described configuration, a highly durable and reliable electronic device can be obtained. .

It is a schematic diagram which shows an example of the cross section of the silicon nitride based sintered compact of this embodiment. An example of the circuit board of this embodiment is shown, (a) is a plan view, (b) is a sectional view taken along line A-A 'in (a), and (c) is a bottom view. The other example of the circuit board of this embodiment is shown, (a) is a top view, (b) is sectional drawing in the BB 'line | wire of (a), (c) is a bottom view. . The other example of the circuit board of this embodiment is shown, (a) is a top view, (b) is sectional drawing in CC 'line of (a), (c) is a bottom view. . An example of the electronic device of the present embodiment is shown, in which (a) is a plan view, (b) is a sectional view taken along line D-D 'in (a), and (c) is a bottom view.

  Hereinafter, an example of the silicon nitride sintered body of the present embodiment, a circuit board using the same, and an electronic device will be described.

The silicon nitride based sintered body of the present embodiment is mainly composed of silicon nitride, and magnesium, rare earth metal, aluminum and boron are 2% by mass to 6% by mass and 12% by mass, respectively, in terms of oxides.
A silicon nitride sintered body comprising 16% by mass or less, 0.1% by mass or more and 0.5% by mass or less, 0.06% by mass or more and 0.32% by mass or less.

  Generally, in silicon nitride-based sintered bodies, silicon nitride, which is the main component, has a strong covalent bond and a small diffusion coefficient, so that it is difficult to sinter silicon nitride alone. By adding an auxiliary agent, a grain boundary phase is formed and densified. Specifically, the added sintering aid reacts with oxygen contained in silicon nitride and silicon nitride powder to generate an oxynitride liquid phase, thereby reducing oxygen contained in the silicon nitride powder. As a result, grain growth of silicon nitride is promoted and densification proceeds, and the obtained silicon nitride-based sintered body is excellent in heat dissipation characteristics and mechanical characteristics.

  In particular, when a rare earth metal oxide having a high affinity for oxygen is added as a sintering aid, a large amount of oxygen is taken into the liquid phase, and silicon nitride grows and the oxygen contained in the silicon nitride powder. The amount can be further reduced.

  However, in order to reduce the amount of oxygen contained in the silicon nitride powder, simply increasing the amount of sintering aid increases the abundance ratio of the grain boundary phase having low heat dissipation characteristics. It becomes difficult to obtain a silicon nitride sintered body having excellent characteristics.

  For this reason, various trials and errors have been made regarding the type and content of the sintering aid in order to obtain a silicon nitride-based sintered body having both excellent heat dissipation characteristics and mechanical characteristics. In order to improve heat dissipation characteristics and mechanical characteristics, a crystalline compound phase is also present in the grain boundary phase. This crystalline compound phase is contained in the grain boundary phase by volume shrinkage in the process of formation. When gaps are likely to be generated and many gaps are generated in the grain boundary phase, the dielectric strength is reduced due to contamination caused by dust entering the gaps and moisture adsorption.

Under these circumstances, the present inventors have obtained a silicon nitride-based sintered body having high dielectric strength and excellent heat dissipation characteristics and mechanical characteristics. (At least one of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), aluminum and boron in oxide conversion It has been found that it is important to contain 2% by mass to 6% by mass, 12% by mass to 16% by mass, 0.1% by mass to 0.5% by mass, and 0.06% by mass to 0.32% by mass, respectively.

The main component in this embodiment is 100% by mass of all components constituting the silicon nitride sintered body.
The component which occupies 77 mass% or more is said. Each content of silicon nitride, magnesium, rare earth metal (RE), aluminum and boron in terms of oxide is determined by X-ray fluorescence analysis, ICP (Inductively Coupled Plasma) emission analysis, or energy dispersive X-ray spectroscopy. Thus, the contents of Si, Mg, RE, Al, B are obtained, and these contents are Si ₃ N ₄ for Si, and MgO, RE ₂ O ₃ , Al ₂ O ₃ , B ₂ O ₃ for the others. It can be obtained by converting to.

  When the content of magnesium oxide in terms of oxide is 2% by mass or more and 6% by mass or less, densification can be achieved even at a low firing temperature by the sintering promoting action of the magnesium oxide. A silicon nitride sintered body having excellent mechanical characteristics can be obtained. In addition, it is preferable that content in conversion of the oxide of magnesium is 3 mass% or more and 5 mass% or less.

In addition, since the content of the rare earth metal oxide in terms of oxide is 12% by mass or more and 16% by mass or less, due to the high affinity with oxygen, a large amount of oxygen is taken in between the silicon nitride powders in the liquid phase,
Since grain growth of silicon nitride is promoted, a silicon nitride sintered body having excellent heat dissipation characteristics can be obtained. In addition, the content of the rare earth metal in terms of oxide is preferably 13% by mass or more and 15% by mass or less.

  In addition, since the content of aluminum in terms of oxide is 0.1% by mass or more and 0.5% by mass or less, the amorphization of the grain boundary phase is promoted, and it is difficult for gaps to form in the grain boundary phase. It is possible to obtain a silicon nitride-based sintered body having a high thickness. The content of aluminum in terms of oxide is preferably 0.2% by mass or more and 0.4% by mass or less.

  Further, since the content of boron in terms of oxide is 0.06% by mass or more and 0.32% by mass or less, in addition to the effect of suppressing the expression of ionic conductivity in the grain boundary phase possessed by the boron oxide, the grain boundary phase Since the amorphization is promoted, it is difficult to form a gap in the grain boundary phase, and a silicon nitride-based sintered body having a high dielectric strength can be obtained. The content of boron in terms of oxide is preferably 0.15% by mass or more and 0.25% by mass or less. The total content of aluminum and boron in terms of oxides is preferably more than 0.3% by mass and less than 0.6% by mass.

The silicon nitride-based sintered body in the present embodiment includes a main crystal phase composed of β-Si ₃ N ₄ and a component whose composition formula is shown as RE ₄ Si ₂ N ₂ O ₇ (RE is a rare earth metal). RE ₄ at a diffraction angle of 30 ° to 35 ° with respect to the first peak intensity I ₀ of β-Si ₃ N _{4 at} a diffraction angle of 27 ° to 28 ° determined by an X-ray diffraction method. It is important that the ratio (I ₁ / I ₀ ) of the first peak intensity I ₁ of Si ₂ N ₂ O ₇ is 20% or less (excluding 0%).

Since the grain boundary phase contains a component shown as RE ₄ Si ₂ N ₂ O ₇ in which elements constituting silicon nitride and rare earth metal oxide are combined, silicon nitride-based sintering having excellent heat dissipation characteristics and mechanical characteristics It can be a body. Note that β-Si ₃ N ₄ which is the main crystal phase and components whose composition formula is shown as RE ₄ Si ₂ N ₂ O ₇ can be identified using a powder X-ray diffraction method.

Here, the rare earth metal constituting the component represented by the composition formula RE ₄ Si ₂ N ₂ O ₇ is a lanthanoid metal (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho. , Er, Tm, Yb, Lu). Among them, at least one of erbium (Er), ytterbium (Yb), and lutetium (Lu) is preferable. The reason is that erbium (Er), ytterbium (Yb) and lutetium (Lu) are other atoms constituting the above composition formula because they are elements having a small ionic radius among the Group 3 elements of the periodic table. This is because the strong coupling with Si, O, and N facilitates phonon transmission and increases the thermal conductivity. In addition, erbium (Er), ytterbium (Yb), and lutetium (Lu) have a strong bond with Si, O, and N, so that lattice vibration due to thermal energy is small and volume expansion due to temperature change is small. The coefficient can be reduced, and the thermal shock resistance can be increased. By making the rare earth metal constituting the above component at least one of erbium (Er), ytterbium (Yb) and lutetium (Lu), for example, the thermal expansion coefficient at room temperature is further reduced to 1.35 × 10 ⁻⁶ / K or less. The thermal conductivity can be increased to 51 W / (m · K) or higher.

Further, when the rare earth metal constituting the above component is erbium (Er), erbium oxide (Er ₂ O ₃ ) added to precipitate Er ₄ Si ₂ O ₇ N ₂ in the grain boundary phase is relatively inexpensive. In addition, since it can be sintered at a lower temperature than when ytterbium oxide (Yb ₂ O ₃ ) or lutetium oxide (Lu ₂ O ₃ ) is added, it is more preferable.

Then, RE ₄ Si ₂ N ₂ O _{7 at} a diffraction angle of 30 ° to 35 ° with respect to the first peak intensity I ₀ of β-Si ₃ N _{4 at} a diffraction angle of 27 ° to 28 ° determined by the X-ray diffraction method. When the ratio of the first peak intensity I ₁ (I ₁ / I ₀ ) is 20% or less (excluding 0%), the volume shrinkage due to crystallization of RE ₄ Si ₂ N ₂ O ₇ is Since it is small and a gap is not easily generated in the grain boundary phase, a silicon nitride sintered body having high dielectric strength and excellent heat dissipation characteristics and mechanical characteristics can be obtained.

As described above, the grain boundary phase contains a component whose composition formula is shown as RE ₄ Si ₂ N ₂ O ₇ (RE is a rare earth metal), and is obtained by the X-ray diffraction method. The ratio (I ₁ / I ₀ ) of the first peak intensity I ₁ of RE ₄ Si ₂ N ₂ O _{7 at} a diffraction angle of 30 ° to 35 ° with respect to the first peak intensity I ₀ of Si ₃ N ₄ is 20%. In order to make the following (excluding 0%), the maximum temperature, the holding time, and the temperature lowering rate are important in firing using the raw materials satisfying the above composition range.

In addition, the silicon nitride sintered body in this embodiment preferably has a ratio (I ₁ / I ₀ ) of 4% or more. When the ratio (I ₁ / I ₀ ) is 4% or more, the ratio of the component shown as RE ₄ Si ₂ N ₂ O ₇ having a high melting point to the grain boundary phase is increased, so that mechanical properties at high temperatures are increased. The characteristics can be increased. In particular, the ratio (I ₁ / I ₀ ) is more preferably 6% or more.

Here, the first peak intensity I ₀ of β-Si ₃ N ₄ at a diffraction angle of 27 ° to 28 ° is PDF (
It is the highest peak intensity at a diffraction angle of 27 ° to 28 ° when compared with a card represented by (registered trademark) Number: 00-033-1160. The first peak intensity I ₁ of RE ₄ Si ₂ N ₂ O ₇ at a diffraction angle of 30 ° to 35 ° is such that RE is, for example, Y, La, Ce, Pr, Nd, Sm, Tb, Dy, Tm, When Er, Yb, and Lu, PDF (registered trademark) Number: 00-032
-1451, 01-072-7716, 00-031-0339, 00-032-087, 00-031-085, 00-031-1215, 00-034-1268, 00-055-1090, 00-032-1354 , 00-031-0505, 00-051-0340, 00-033-0847, the highest peak intensity at a diffraction angle of 30 ° to 35 ° when collated with the card.

The first peak intensity of _β-Si 3 _{N 4} at a diffraction angle of 27 ° ~28 ° _{I 0,} the first peak intensity of the _RE 4 _Si 2 _N 2 _{O 7} in the diffraction angle of 30 ° to 35 ° _{I 1} together The value obtained by removing the background intensity from the diffraction intensity curve obtained by the powder X-ray diffraction method, and the ratio (I ₁ / I ₀ ) can be calculated using this value.

  Further, according to the silicon nitride sintered body of the present embodiment, the first metal silicide composed of at least one of iron and copper, molybdenum, chromium, nickel, manganese and tungsten are included in the grain boundary phase. It is preferable that the silicide of the first metal and the silicide of the second metal are in contact with each other.

  Here, the state in which the silicide of the first metal and the silicide of the second metal are in contact with each other will be specifically described with reference to FIG.

FIG. 1 is a schematic view showing an example of a cross section of the silicon nitride sintered body of the present embodiment. In the schematic diagram of the cross section of the silicon nitride sintered body of the example shown in FIG. 1, a main crystal phase 1 made of β-Si ₃ N ₄ and a component 2 whose composition formula is shown as RE ₄ Si ₂ N ₂ O ₇ are shown. The grain boundary phase 3 is included. The grain boundary phase 3 includes a silicide 4 of a first metal made of at least one of iron and copper, and a second metal made of at least one of molybdenum, chromium, nickel, manganese and tungsten. Contains silicide 5.

Since the first metal silicide 4 can sinter β-Si ₃ N ₄ at a lower temperature, β
It is possible to reduce the abnormal grain growth of -Si ₃ N _4. In addition, the silicide 5 of the second metal controls the solidification of the grain boundary phase 3 to improve the mechanical characteristics at high temperature, and blackens the color tone of the silicon nitride sintered body. The color tone difference can be reduced.

  In the silicon nitride sintered body of the present embodiment, the first metal silicide 4 and the second metal silicide 5 are preferably in contact with each other. As a form in which the first metal silicide 4 and the second metal silicide 5 are in contact with each other, for example, as shown in FIG. 1, the first metal silicide 4a and the second metal silicide are used. There is a form in which the first metal silicide 4b surrounds the second metal silicide 5b.

  In the grain boundary phase 3, a first metal silicide 4 made of at least one of iron and copper, and a second metal silicide made of at least one of molybdenum, chromium, nickel, manganese and tungsten. When the first metal silicide 4 and the second metal silicide 5 are in contact with each other, the first metal silicide 4 may be a source of destruction in a high-temperature environment. Since the stress concentrated on the bimetallic silicide 5 is dispersed and relaxed, the thermal shock resistance can be increased.

  In particular, it is preferable that the first metal is iron and the second metal is tungsten. When the first metal is iron and the second metal is tungsten, each silicide has an approximate crystal structure, so that the probability of contact increases, so that the thermal shock resistance can be further improved.

The silicide 4 of the first metal has a composition formula of FeSi ₃ , FeSi ₂ , FeSi, Fe ₂ Si ₃ , Fe ₃ Si, Fe ₃ Si ₂ , Fe ₃ Si ₄ , Fe ₃ Si ₇ , Fe ₅ Si _2. , Fe ₅ Si ₃ , Cu ₂ Si, CuSi, CuSi ₂ and CuSi ₃ .

Further, the silicide 5 of the second metal, composition formula _WSi, as _{WSi 2, WSi 3, W 2} Si 3, W 5 Si 3, MoSi, MoSi 2, MoSi 3, Mo 2 Si 3 and _Mo 5 Si ₃ It is at least any one of the components represented.

In particular, the first metal silicide 4 is a component whose composition formula is expressed as FeSi ₂ , and the second metal silicide 5 is a component whose composition formula is expressed as WSi _2. . This is because the components whose composition formulas are expressed as FeSi ₂ and WSi ₂ are both thermodynamically stable components, and the crystal structures of the two are close to each other. This is because it can be further improved.

In the grain boundary phase 3, a first metal silicide 4 made of at least one of iron and copper, and a second metal silicide made of at least one of molybdenum, chromium, nickel, manganese and tungsten. 5 can be observed using energy dispersive X-ray spectroscopy. Specifically, an electron beam is applied to a region having a cross-sectional area of 0.01 mm ² using an X-ray microanalyzer. By irradiating and detecting characteristic X-rays generated from each element in this region, the elements can be identified and confirmed by mapping according to the intensity of the characteristic X-rays.

  Further, the first metal and silicon or the second metal and silicon may form at least one of the solid solution 6a and the intermetallic compound 6b. By forming at least one of the solid solution 6a and the intermetallic compound 6b, the fracture toughness of the grain boundary phase 3 is improved, and even if a fine crack occurs in the grain boundary phase 3, the progress is suppressed. Therefore, the thermal shock resistance can be increased.

  The presence of each of the solid solution 6a and the intermetallic compound 6b can be observed using energy dispersive X-ray spectroscopy, and the composition formula of the intermetallic compound 6b should be identified using a powder X-ray diffraction method. Can do.

  Moreover, it is preferable that the silicon nitride sintered body of the present embodiment has white spots including calcium in the grain boundary phase. Thus, when white spots including calcium are present in the grain boundary phase, the thermal conductivity of the silicon nitride-based sintered body can be improved, so that the heat dissipation characteristics can be improved.

Here, white spots existing in the grain boundary phase can be confirmed by an image observed in a dark field at a magnification of 50 to 100 times using an optical microscope. Specifically, an observation image is taken in and analyzed by a technique called particle analysis using image analysis software “A image-kun” (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.). Here, as setting conditions of this method, the brightness is dark, the binarization method is manual, the small figure removal area is 5 μm ² , and a threshold value that is an index indicating the brightness of the image is set to each point ( What is necessary is just to set 0.8 times or more and 2 times or less of the peak value of the histogram indicating the brightness of each pixel).

  Further, whether or not white spots contain calcium can be confirmed using an X-ray microanalyzer. Specifically, the same region as the region where white spots were observed using an optical microscope is irradiated with an electron beam using an X-ray microanalyzer, and information on the wavelength inherent to calcium generated from this region and the intensity of this wavelength Can be confirmed by collating the mapping recorded in the XY coordinates with the position of white spots observed with an optical microscope.

  In confirmation using an X-ray microanalyzer, magnesium, rare earth metal, aluminum, and boron, which are components constituting the grain boundary phase, have a small amount of white spots.

Further, according to the silicon nitride-based sintered body of the present embodiment, it is preferable that there are 550 or more and 1650 or less white spots containing calcium having an equivalent circle diameter of 2 μm or more and 50 μm or less per 1 mm ^2. It is. When there are 550 or more and 1650 or less white spots containing calcium having an equivalent circle diameter of 2 μm or more and 50 μm or less per 1 mm ² , a silicon nitride sintered body with high dielectric strength and improved heat dissipation characteristics It can be.

Here, the number of white spots having an equivalent circle diameter of 2 μm or more and 50 μm or less per 1 mm ² is 100 × magnification using an optical microscope, for example, the area is 1.125 mm ² (the lateral length is 1.238 mm).
The range is set so that the length in the vertical direction is 0.909 mm), and an image in this range is captured with a CCD camera. The above-mentioned image analysis software “A Image-kun” (registered trademark, manufactured by Asahi Kasei Engineering Corp.) And confirming under the same conditions as described above.

  Moreover, it is preferable that content of the calcium contained in a white spot is 0.14 mass% or more and 0.36 mass% or less. The content of calcium contained in white spots is calculated by calculating the area ratio of calcium present at the positions of white spots that are collated with mapping and an image observed with an optical microscope, using the mapping described above. It is a value obtained by multiplying the area ratio of calcium present in the spots by the calcium content in the silicon nitride sintered body. The calcium content in the silicon nitride sintered body can be determined by fluorescent X-ray analysis, ICP emission analysis, or energy dispersive X-ray spectroscopy.

The dielectric strength of the silicon nitride based sintered body can be evaluated by the strength of dielectric breakdown (MV / m) measured according to JIS C 2141-1992 (IEC 672-2 (1980)). The silicon nitride sintered body of this embodiment has a dielectric breakdown strength of 18 MV / m or more.

In addition, the mechanical properties of the silicon nitride sintered body include a three-point bending strength of 740 MPa or more, a dynamic elastic modulus of 300 GPa or more, a Vickers hardness (Hv) of 13 GPa or more, and a fracture toughness (K _1C ) Is preferably 5 MPam ^1/2 or more. Because these mechanical properties are in the above range, the joined member obtained by joining the silicon nitride sintered body and the member made of metal can particularly improve creep resistance and durability against heat cycle. High reliability can be obtained and it can be used for a long time.

For the three-point bending strength, JIS R 1601-2008 (ISO 17565: 2003 (M
OD)). However, when the thickness of the silicon nitride sintered body is thin and the thickness of the test piece cut out from the silicon nitride sintered body cannot be 3 mm, the thickness of the silicon nitride sintered body is not changed. The thickness is evaluated, and it is preferable that the result satisfies the above numerical value.

  The dynamic modulus of elasticity may be measured in accordance with the ultrasonic pulse method specified in JIS R 1602-1995. However, if the thickness of the silicon nitride sintered body is thin and the thickness of the test piece cut out from the silicon nitride sintered body cannot be 10 mm, the cantilever resonance method is used for evaluation. It is preferable that the result satisfies the above numerical value.

Furthermore, regarding Vickers hardness (Hv) and fracture toughness (K _1C ), JIS R 1610-2003 (ISO 14705: 2000 (MOD)) and JIS R 1607-1995, respectively.
Measurement may be performed in accordance with the indenter press-fitting method (IF method) defined in 1. The thickness of the silicon nitride sintered body is thin, and the thickness of the test piece cut out from the silicon nitride sintered body is defined by the indenter press-in method (IF method) of JIS R 1610-2003 and JIS R 1607-1995, respectively. When the thickness cannot be 0.5 mm or 3 mm, it is preferable that the thickness of the silicon nitride sintered body is evaluated as it is as the thickness of the test piece, and the result satisfies the above numerical value. However, when the thickness of the silicon nitride sintered body is so thin that it is not possible to satisfy the above numerical value by evaluating the thickness as it is, for example, when the thickness is 0.2 mm or more and less than 0.5 mm, the test applied to the silicon nitride sintered body Force and indentation load are both 0.245N, and the time to hold the test force and indentation load is 15
What is necessary is _just to measure Vickers hardness (Hv) and fracture toughness (K1C) as second.

The electrical properties of the silicon nitride sintered body as described above, the volume resistivity, a is at normal temperature 10 ¹⁴ Ω · cm or more and 300 ° C. at 10 ¹² Ω · cm or more. This volume resistivity may be measured according to JIS C 2141-1992. However, if the silicon nitride sintered body is small and the silicon nitride sintered body cannot be sized in accordance with JIS C 2141-1992, the two-terminal method shall be used for evaluation. It is preferable to satisfy the above numerical values.

  2A and 2B show an example of the circuit board of the present embodiment, in which FIG. 2A is a plan view, FIG. 2B is a cross-sectional view taken along line AA ′ in FIG. 2A, and FIG. It is.

  The circuit board 10 of the example shown in FIG. 2 has circuit members 12a and 12b on the first main surface side of the support substrate 11 made of the silicon nitride sintered body of the present embodiment, and a second main surface facing the first main surface. The circuit board 10 is provided with a heat dissipation member 13 on the surface side, and the support substrate 11, the circuit members 12a and 12b, and the heat dissipation member 13 are bonded to each other through bonding layers 14a and 14b, respectively.

  Since such a circuit board 10 uses the support substrate 11 made of the silicon nitride-based sintered body of the present embodiment having high dielectric strength and excellent heat dissipation characteristics and mechanical characteristics, a highly reliable circuit board Can be 10.

The support substrate 11 made of a silicon nitride-based sintered body constituting the circuit board 10 of the present embodiment has a flat plate shape. For example, the length (X direction shown in FIG. 2) is 20 mm or more and 200 mm or less, and the width (FIG. 2 in the Y direction) is 10 mm or more and 120 mm or less. Although the thickness of the support substrate 11 varies depending on the use, it is preferably 0.2 mm or more and 1.0 mm or less in order to achieve high dielectric strength and excellent durability.

The circuit member 12a constituting the circuit board 10 of the present embodiment has, for example, a length (X direction shown in FIG. 2) of 15 mm or more and 155 mm or less, and a width (Y direction shown in FIG. 2) of 8 mm or more and 100 mm. It is as follows. The circuit member 12b has, for example, a length (X direction shown in FIG. 2) of 1 mm or more and 10 mm or less, and a width (Y direction shown in FIG. 2) of 8 mm or more and 100 mm or less. Circuit member 12
The thicknesses of a and 12b are determined by the magnitude of current flowing through the circuit members 12a and 12b and the amount of heat generated by electronic components (not shown) mounted on the circuit members 12a and 12b.
m or less.

  Further, the heat dissipating member 13 constituting the circuit board 10 of the present embodiment has a function of releasing heat from a heated electronic component (not shown), and has a length (X direction shown in FIG. 2) of 18 mm or more, for example. It is 190 mm or less, the width (Y direction shown in FIG. 2) is 8 mm or more and 100 mm or less, and the thickness is 0.5 mm or more and 5 mm or less.

  Next, FIG. 3 shows another example of the circuit board of the present embodiment, (a) is a plan view, (b) is a sectional view taken along line BB ′ of (a), ( c) is a bottom view.

  The circuit board 10 in the example shown in FIG. 3 includes circuit members 12a and 12b mainly composed of copper on the first main surface side of the support substrate 11 made of the silicon nitride sintered body of the present embodiment. Is a circuit board 10 in which a heat radiating member 13 mainly composed of copper is provided on the second main surface side opposite to the side of the support board 11 and joined from the support board 11 side through the joining layers 14a and 14b and the copper materials 15a and 15b, respectively. Has been.

  The circuit board 10 of the example shown in FIG. 3 can also obtain the same effects as the circuit board 10 of the example shown in FIG. Further, in the circuit board 10 of the example shown in FIG. 2, the temperature when the circuit members 12a, 12b and the heat radiating member 13 are joined to the support substrate 11 is 800 to 900 ° C., but the copper materials 15a, 15b are interposed. As a result, the bonding between the circuit members 12a and 12b and the copper material 15a and between the heat radiation member 13 and the copper material 15b are relatively low temperatures of about 300 to 500 ° C. due to the diffusion of copper as the respective constituent components. Therefore, the warp generated in the support substrate 11 can be suppressed. As a result, since the stress generated in the support substrate 11 is small, cracks hardly occur even when heat is repeatedly applied. In addition, since at least one of the circuit members 12a and 12b and the heat radiating member 13 can be thickened, the heat dissipation characteristics of the circuit board 10 can be enhanced.

  Next, FIG. 4 shows another example of the circuit board of the present embodiment, (a) is a plan view, (b) is a sectional view taken along the line CC ′ of (a), ( c) is a bottom view.

  The circuit board 10 in the example shown in FIG. 4 includes circuit members 12a and 12b mainly composed of copper on the first main surface side of the support substrate 11 made of the silicon nitride sintered body of the present embodiment. Is a circuit board 10 in which a heat radiating member 13 mainly composed of copper is provided on the second main surface side opposite to the side of the support board 11 and joined from the support board 11 side through the joining layers 14a and 14b and the copper materials 15a and 15b, respectively. Has been.

Further, the support substrate 11 and the heat dissipation member 13 in the example shown in FIG. 4 have the same dimensions as the support substrate 11 and the heat dissipation member 13 in the example shown in FIG. The circuit members 12a and 12b have the same dimensions, and the configuration of the heat dissipation member 13 provided on the second main surface is the same as that of the heat dissipation member 13 in the circuit board 10 of the example shown in FIG. 4 are, for example, a length (X direction shown in FIG. 4) of 7 mm to 85 mm and a width (Y direction shown in FIG. 4) of 7 mm to 85 mm. Yes, thickness is 0.5mm or more 5mm
It is as follows.

  When the circuit members 12a and 12b having the same size are arranged on the first main surface side of the support substrate 11 as in the example shown in FIG. 4, the circuit members 12a and 12b having different sizes shown in FIG. Since the bias of stress generated in the support substrate 11 can be reduced after the circuit members 12a and 12b are bonded to each other than the circuit substrate 10 to which is bonded, the warp generated in the support substrate 11 can be reduced.

  In addition, the content of copper, which is the main component of the circuit members 12a and 12b and the heat radiating member 13, is 90% by mass or more, and any of oxygen-free copper, tough pitch copper and phosphorous deoxidized copper with a large copper content. In particular, the oxygen-free copper is made of any of linear crystalline oxygen-free copper, single-crystal high-purity oxygen-free copper, and vacuum-dissolved copper having a copper content of 99.995% by mass or more. Is preferred. As described above, the circuit members 12a and 12b and the heat radiating member 13 each have a low electrical resistance and a high thermal conductivity when the copper content is increased. Therefore, the heat radiation characteristics are improved, and the circuit members 12a and 12b The circuit characteristics (characteristics for suppressing heat generation and reducing power loss of electronic components mounted on the circuit members 12a and 12b) are also improved. Further, when the copper content is increased, the yield stress is low, and plastic deformation tends to occur when heated. Therefore, the adhesion of each of the circuit members 12a and 12b and the copper material 15a, the heat radiation member 13 and the copper material 15b is increased, and more Increased reliability.

  The brazing material to be the bonding layers 14a and 14b is preferably composed of at least one of silver and copper as a main component and at least one selected from titanium, zirconium, hafnium and niobium. The thickness is, for example, 5 μm or more and 20 μm or less.

  Further, the copper materials 15a and 15b are preferably made of any one of oxygen-free copper, tough pitch copper, and phosphorus-deoxidized copper having a high copper content. It is preferable that the amount is 99.995% by mass or more of linear crystalline oxygen-free copper, single-crystal high-purity oxygen-free copper, and vacuum-melted copper, and the thickness thereof is, for example, 0.1 mm or more and 0.6 mm or less .

The three-point bending strength, dynamic elastic modulus, Vickers hardness (H _v ) and fracture toughness (K _1C ) of the support substrate 11 made of the silicon nitride substrate constituting the circuit substrate 10 are determined from the circuit substrate 10 to the circuit member. What is necessary is just to obtain | require by the method mentioned above, after removing 12a, 12b, the thermal radiation member 13, bonding layer 14a, 14b, and copper material 15a, 15b by an etching etc.

  Next, FIG. 5 shows an example of the electronic device of this embodiment, (a) is a plan view, (b) is a sectional view taken along line DD ′ in (a), and (c). Is a bottom view.

  The electronic device S of the example shown in FIG. 5 is one in which one or more electronic components 16 and 17 such as semiconductor elements are mounted on the circuit member 12 of the circuit board 10 of the present embodiment. , 17 are electrically connected to each other by a conductor (not shown). According to the electronic device S of the present embodiment, since the electronic components 16 and 17 are mounted on the circuit member 12 in the circuit board 10 of the present embodiment, even if the electronic components 16 and 17 repeatedly generate heat, the support substrate 11 Since the circuit member 12 and the heat radiating member 13 are not easily separated, the electronic device S having high durability can be obtained.

  The dimensions of the circuit member 12 and the heat dissipation member 13 in the example shown in FIG. 5, for example, are 4 mm or more and 40 mm or less in length (X direction shown in FIG. 5), and 5 mm in width (Y direction shown in FIG. 5). The thickness is 50 mm or less and the thickness is 0.5 mm or more and 5 mm or less.

  And as the example shown in FIG. 5, it is suitable for the circuit member 12 and the heat radiating member 13 to be arrange | positioned at multiple rows and multiple columns, respectively, by planar view. As described above, the circuit member 12 and the heat dissipation member 13 are arranged in a plurality of rows and columns in a plan view, so that the stress generated in the support substrate 11 when the circuit member 12 and the heat dissipation member 13 are joined to the support substrate 11. Can be easily dispersed, so that warpage occurring in the support substrate 11 can be reduced. In particular, the circuit member 12 and the heat radiating member 13 are preferably arranged at equal intervals in a plurality of rows and a plurality of columns, respectively, in plan view, as in the example shown in FIG.

  According to the example circuit board 10 shown in FIGS. 2 to 4 and the example electronic device S shown in FIG. 5, the support substrate 11 has high dielectric strength and has excellent heat dissipation characteristics and mechanical characteristics. In addition, since it is difficult for warping to occur and cracks are hardly generated even when heat is repeatedly applied, the circuit board 10 and the electronic device S with high reliability can be obtained.

  Next, a method for manufacturing the silicon nitride sintered body of this embodiment will be described.

First, powder of silicon nitride having a β conversion rate of 20% or less, magnesium oxide (MgO) as an additive component, rare earth metal oxide (for example, Sc ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , Ce) ₂ O ₃ , Pr ₆ O ₁₁ , Nd ₂ O ₃ , Pm ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er Each powder of ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ) and boric acid (H ₃ BO ₃ ), Using a mixing device such as a rotary mill, a vibration mill, a bead mill, a sand mill, an agitator mill, etc., wet mixing with water and pulverization produce a slurry.

By the way, there are two types of silicon nitride, α-type and β-type, due to the difference in crystal structure of silicon nitride. The α type is stable at low temperatures, the β type is stable at high temperatures, and the phase transition from α type to β type occurs irreversibly at 1400 ° C or higher. Here, the β conversion rate is α (102 obtained by the X-ray diffraction method.
) The sum of the peak intensities of the diffraction lines and α (210) diffraction lines is I _α , β (101) diffraction lines and β (210)
This is a value calculated by the following equation, where I _β is the sum of peak intensities with diffraction lines. β conversion rate = {I _β / (I _α + I _β )} × 100 (%)
The β conversion rate of the silicon nitride powder affects the strength and fracture toughness value of the silicon nitride sintered body containing silicon nitride as a main component. The reason why silicon nitride powder having a β conversion ratio of 20% or less is used is that both strength and fracture toughness values can be increased. Silicon nitride powder having a β conversion ratio of more than 20% becomes the core of grain growth in the firing step, tends to be coarse and have a small aspect ratio, and there is a risk that both strength and fracture toughness values will decrease. Therefore, it is particularly preferable to use silicon nitride powder having a β conversion rate of 10% or less.

Magnesium, rare earth metal, aluminum and boron are converted into oxides in an amount of 2% to 6%, 12% to 16%, 0.1% to 0.5%, 0.06% to 0.32%, respectively. In order to obtain a silicon nitride-based sintered body comprising the following, when the sum of the silicon nitride powder and the total of these additive component powders is 100% by mass, the additive component magnesium oxide (MgO) powder is added. 2 to 6 mass%, 12 to 16 mass% of rare earth metal oxide powder, 0.1 to 0.5 mass% of aluminum oxide (Al ₂ O ₃ ) powder, and 0.05 to 0.28 of boric acid (H ₃ BO ₃ ) powder What is necessary is just to weigh so that the mass% and the remainder may be silicon nitride.

Balls used for pulverization of silicon nitride and additive component powders are preferably balls made of a material in which impurities are hardly mixed or a silicon nitride sintered body having the same material composition. The silicon nitride and additive component powders are pulverized until the particle size (D ₉₀ ) is ₉₀ μm or less when the total volume of the particle size distribution curve is 100%. Is preferable from the viewpoint of improving the sinterability. The particle size distribution obtained by grinding is as follows: ball outer diameter, ball quantity,
It can be adjusted by the viscosity of the slurry, the grinding time, and the like.

Further, to perform in a short time or grinding, it is preferred that the particle size in advance at a cumulative volume _50% (D ₅₀₎ less is used powder 1 [mu] m. In addition, it is preferable for the moldability that the organic binder is mixed in the slurry at 1% by mass or more and 10% by mass or less with respect to the total of 100% by mass of the silicon nitride powder and the sintering aid powder. Furthermore, it is preferable to add a dispersant in order to improve dispersibility.

Next, the obtained slurry was passed through a mesh having a particle size number of 200 described in ASTM E 11-61 or a sieve having a finer mesh than this mesh, and then dried to obtain granules containing silicon nitride as a main component (hereinafter referred to as “silicone nitride”). , Referred to as silicon nitride granules). Drying may be performed by a spray dryer, and there is no problem even if other methods are used. Then, a silicon nitride granule is formed into a sheet by using a powder rolling method to form a ceramic green sheet, and the ceramic green sheet is cut into a predetermined length to form a molded body containing silicon nitride as a main component (hereinafter referred to as nitriding). This is referred to as a silicon-like molded body). Alternatively, instead of the powder rolling method, a pressure molding method is used, and a silicon nitride granule is filled in a mold and then pressed, so that the shape is, for example, a prismatic shape, a square plate shape, a cylindrical shape, or a disk shape. A silicon nitride-like molded body having a shape is obtained.

  Next, the obtained molded body is put into a mortar made of a silicon nitride sintered body having a relative density of 55% or more and 95% or less. At this time, in order to suppress volatilization of the components contained in the silicon nitride-based molded body, a co-material containing components such as magnesium oxide and rare earth metal oxide is disposed around the silicon nitride-based molded body, It is fired in a firing furnace in which a graphite resistance heating element is installed. The amount of the common material is preferably 2% by mass or more and less than 10% by mass with respect to the total mass of the silicon nitride-based molded body.

Moreover, about baking conditions, it heats up in a vacuum atmosphere from room temperature to 300-1000 degreeC, Then, nitrogen gas is introduce | transduced and nitrogen partial pressure is maintained at 15-900 kPa. Further, by further increasing the temperature, the additive component forms a liquid phase component in the vicinity of 1000 to 1400 ° C through a solid phase reaction, and the phase transition of silicon nitride from α-type to β-type in the temperature range of 1400 ° C or higher Happens irreversibly.

And after raising the temperature in the firing furnace and keeping it at 1560 ° C. or more and 1640 ° C. or less for 2 hours or more and 4 hours or less, further raising the temperature and keeping it at 1740 ° C. or more and less than 1800 ° C. for 4 hours or more and 10 hours or less, By cooling at a rate of temperature decrease of ℃ / hour or more, silicon nitride is the main component, and magnesium, rare earth metal, aluminum, and boron are 2% by mass to 6% by mass and 12% by mass to 16% by mass in terms of oxides, respectively. In the following, 0.1 to 0.5% by mass, 0.06 to 0.32% by mass, a main crystal phase composed of β-Si ₃ N ₄ and a composition formula of RE ₄ Si ₂ N ₂ O ₇ (RE is And a grain boundary phase containing a component represented as (rare earth metal), and obtained with respect to the first peak intensity I ₀ of β-Si ₃ N _{4 at} a diffraction angle of 27 ° to 28 ° determined by an X-ray diffraction method. much trouble RE at 30 ° ~35 ° Si ₂ N ₂ O ₇ first ratio _(I 1 / _{I 0)} of the peak intensity _{I 1} of 20% or less (excluding 0%) to obtain a silicon nitride sintered body of the present embodiment is Can do.

In addition, in order to obtain the silicon nitride sintered body of this embodiment in which the ratio (I ₁ / I ₀ ) is 4% or more, the temperature decreasing rate after maintaining the maximum temperature is 500 ° C./hour or more and 550 ° C./hour. What is necessary is just to cool below.

Further, in the grain boundary phase, a first metal silicide composed of at least one of iron and copper, and a second metal silicide composed of at least one of molybdenum, chromium, nickel, manganese and tungsten. In order to obtain the silicon nitride-based sintered body of the present embodiment in which the silicide of the first metal and the silicide of the second metal are in contact with each other, the above-mentioned respective components constituting the silicon nitride powder and additive components A powder is added to the powder, which is a silicide of a first metal and a silicide of a second metal after firing, and is made of at least one of each metal, oxide, silicide, etc. Then, it may be wet-mixed with water and pulverized to prepare a slurry. And after producing the slurry, by producing the same method as described above, the silicide of the first metal composed of at least one of iron and copper, molybdenum, chromium, nickel, manganese and tungsten. It is possible to obtain a silicon nitride-based sintered body of the present embodiment including at least one of the second metal silicides, wherein the first metal silicide and the second metal silicide are in contact with each other. it can.

Further, in order to obtain the silicon nitride-based sintered body of the present embodiment in which white spots containing calcium are present in the grain boundary phase, calcium oxide is added to each of the powders constituting the silicon nitride powder and the additive component. Add, for example, 0.25 wt% or more and 0.6 wt% or less, using a mixing device,
What is necessary is just to wet-mix with water and grind | pulverize and to produce a slurry. And after producing a slurry, the silicon nitride sintered body in which the white spot containing calcium exists in the grain boundary phase can be obtained by producing by the same method as described above.

In addition, white spots with an equivalent circle diameter of 2 μm or more and 50 μm or less are 550 or more 1650 per 1 mm ^2.
In order to obtain a silicon nitride sintered body having less than one, the mixing / pulverization time by the mixing device may be set to, for example, 24 hours or more and 72 hours or less.

  Next, a method for manufacturing the circuit board 10 of the present embodiment will be described.

To obtain the circuit board 10 of the example shown in FIG. 2, first, the length in the X direction is 20 mm to 200 mm, the length in the Y direction is 10 mm to 120 mm, and the thickness is 0.2 mm to 1.0 mm. The support substrate 11 is prepared by the manufacturing method described above. Next, a paste of a silver (Ag) -copper (Cu) alloy containing at least one selected from titanium, zirconium, hafnium and niobium, which becomes the bonding layers 14a and 14b, on both main surfaces of the support substrate 11. The brazing filler metal is applied by any one of the screen printing method, the roll coater method, the brush coating method, etc., and the circuit members 12a and 12b mainly composed of copper are provided on the first main surface side, and the second main surface side is provided. A heat dissipating member 13 mainly composed of copper is disposed. The pasty brazing material may contain one or more selected from molybdenum, tantalum, osmium, rhenium and tungsten. Thereafter, heating is performed in a vacuum atmosphere at 800 ° C. or more and 900 ° C. or less, and at the same time, a pressure of 30 MPa or more is applied. It is possible to obtain the circuit board 10 formed by joining the members 13 via the brazing materials 14a and 14b, respectively.

  In order to obtain the circuit board 10 shown in FIGS. 3 and 4, first, the support board 11 having the above-described size is prepared. Next, a paste of a silver (Ag) -copper (Cu) alloy containing at least one selected from titanium, zirconium, hafnium and niobium, which becomes the bonding layers 14a and 14b, on both main surfaces of the support substrate 11. The brazing filler metal is applied by any one of a screen printing method, a roll coater method and a brush coating method. The pasty brazing material may also contain one or more selected from molybdenum, tantalum, osmium, rhenium and tungsten. And thin copper material 15a, 15b is each arrange | positioned on a brazing material. Thereafter, heating is performed at 800 ° C. or more and 900 ° C. or less, and the copper material 15a is provided on the first main surface side of the support substrate 11 via the bonding layer 14a, and the copper material 15b is provided on the second main surface side via the bonding layer 14b. Join.

Then, after polishing the surfaces of the copper members 15a and 15b facing the circuit members 12a and 12b and the heat radiating member 13, respectively, the circuit members 12a and 12b and the heat radiating member 13 are disposed on the copper materials 15a and 15b, respectively. Then, heating is performed at 300 ° C. or more and 500 ° C. or less in an atmosphere selected from hydrogen, nitrogen, neon, and argon, and at the same time, a pressure of 30 MPa or more is applied to the circuit board member on the first main surface side of the support substrate 11. 12a and 12b, and the heat dissipating member 13 on the second main surface side, respectively, the bonding layer 14a
, 14b and the copper materials 15a, 15b can be sequentially joined to obtain the circuit board 10.

  Examples of the present embodiment will be specifically described below, but the present embodiment is not limited to these examples.

First, silicon nitride powder having a β conversion rate of 10% (that is, an α conversion rate of 90%), magnesium oxide (MgO) as an additional component, rare earth metal oxides shown in Table 1, aluminum oxide (Al ₂ Each powder of O ₃ ) and boric acid (H ₃ BO ₃ ) was weighed so as to have the content shown in Table 1, wet-mixed using a rotary mill, and the particle size (D ₉₀ ) was 1 μm or less It grind | pulverized until it became, and it was set as the slurry.

Next, after adding an organic binder to the obtained slurry, it is passed through a sieve having a mesh size of 250 described in ASTM E 11-61, and then dried using a spray dryer, thereby obtaining silicon nitride. Granules were obtained. Then, using a powder rolling method, the silicon nitride granule was formed into a sheet shape to form a ceramic green sheet, and the ceramic green sheet was cut into a predetermined length to obtain a flat silicon nitride molded body.

  Next, the obtained silicon nitride-based molded body was placed in a mortar made of a silicon nitride-based sintered body having a relative density of 75%. At this time, the co-material containing components such as magnesium oxide and rare earth metal oxide is placed around the silicon nitride-based molded body in an amount of 6% by mass relative to the total mass of the silicon nitride-based molded body. In the arranged state, it was fired in a firing furnace provided with a graphite resistance heating element.

Regarding the firing conditions, the temperature was raised in a vacuum atmosphere from room temperature to 500 ° C., and then nitrogen gas was introduced to maintain the nitrogen partial pressure at 100 kPa. Then raise the temperature in the firing furnace to 1580
After holding at 4 ° C. for 4 hours, the temperature was further raised to 1750 ° C. and held for 5 hours. Then, by cooling at a temperature lowering rate shown in Table 1, sample No. 1 which is a silicon nitride sintered body having a length of 60 mm, a width of 30 mm, and a thickness of 0.32 mm. 1-52 were obtained.

The content of each oxide of magnesium, rare earth metal, aluminum and boron was determined by energy dispersive X-ray spectroscopy. Table 1 shows the content of each oxide. Moreover, the component represented by the composition formula RE ₄ Si ₂ N ₂ O ₇ was identified using a powder X-ray diffraction method.

Based on the results obtained by the X-ray diffraction method _, PDF (registered trademark) Number: 00-033
The highest intensity of β-Si ₃ N _{4 at} a diffraction angle of 27 ° to 28 ° was set as the first peak intensity I _{0 in} comparison with the card indicated by −1160. Further, the highest intensity of RE ₄ Si ₂ N ₂ O _{7 at} the diffraction angle of 30 ° to 35 ° is compared with the card indicated by PDF (Registered Trademark) Number described in Table 1 as the first peak intensity I _1. It was. The first peak intensity _{I 1} of the _RE 4 _Si 2 _N 2 _{O 7} in _β-Si 3 _N first peak intensity _{I 0} and the diffraction angle of 30 ° to 35 ° of ₄ at a diffraction angle of 27 ° ~ 28 ° is The value obtained by removing the background intensity from the diffraction intensity curve obtained by the powder X-ray diffraction method. The first peak intensity of the _RE 4 _Si 2 _N 2 _{O 7} in respect to the first peak intensity _{I 0} of _β-Si 3 _{N 4} at a diffraction angle of 27 ° ~ 28 °, the diffraction angle 30 ° to 35 ° _{I 1} Were used to calculate the ratio (I ₁ / I ₀ ), and the calculated values are shown in Table 1.

In addition, the thermal diffusivity α in the thickness direction of each sample is suggested by using a thermal constant measuring device (TC-7000 manufactured by ULVAC-RIKO, Inc.) by a two-dimensional method using laser flash, and the specific heat capacity C of each sample is suggested. Using an ultrasensitive differential scanning calorimeter (DSC-6200, manufactured by Seiko Instruments Inc.) by scanning calorimetry (DSC method), the bulk density ρ (kg / m ³ ) of each sample was measured according to JIS R 1634. -Measured according to -1998. Then, the values obtained by these methods are substituted into the following equations to calculate the thermal conductivity κ (W / (m · K)) in the thickness direction of each sample, and the values are shown in Table 1. It was.
κ = α ・ C ・ ρ
In addition, in order to evaluate the dielectric strength of each sample, the dielectric breakdown strength (MV / m) of each sample was measured in accordance with JIS C 2141-1992 (IEC 672-2 (1980)), and the value Are shown in Table 1. In addition, the material of the electrode formed in each sample was brass, and silicone oil was used as the surrounding medium of each sample.

In addition, in order to evaluate the mechanical properties of the silicon nitride sintered body, the silicon nitride granules used for the preparation of each sample were formed into a prismatic shape by a dry pressure forming method, and then fired under the above-described firing conditions. In accordance with JIS R 1601-2008 (ISO 17565: 2003 (MOD)), the length is 36 mm,
The three-point bending strength (MPa) of a prismatic body having a width of 4 mm and a thickness of 3 mm was measured, and the values are shown in Table 1.

As shown in Table 1, Sample No. 2, 4, 6, 8, 10 to 14, 16, 18, 20, 21, 22, 23, 25, 27, 29, 31 to 35, 37, 39, 41, 43 to 52 are mainly composed of silicon nitride And magnesium, rare earth metal, aluminum and boron in terms of oxides of 2% to 6%, 12% to 16%, 0.1% to 0.5%, 0.06% to 0.32%, respectively. It is composed of a main crystal phase composed of β-Si ₃ N ₄ and a grain boundary phase containing a component whose composition formula is shown as RE ₄ Si ₂ N ₂ O ₇ , and is determined by an X-ray diffraction method. , for the first peak intensity _{I 0} of _β-Si 3 _{N 4} at a diffraction angle of 27 ° ~ 28 °, the first peak intensity _{I 1} of the _RE 4 _Si 2 _N 2 _{O 7} in the diffraction angle of 30 ° to 35 ° ratio _(I 1 / _{I 0)} is 20% or less (excluding 0%) because it is the strength of the dielectric breakdown 18 MV / m or more There, the thermal conductivity is at 50W / (m · K) or more, three-point bending strength was more than 740MPa. from this result,
The silicon nitride sintered body according to the present embodiment has a small volume shrinkage due to crystallization of RE ₄ Si ₂ N ₂ O ₇ and is less likely to cause a gap in the grain boundary phase. It was found to be a silicon nitride-based sintered body having properties and mechanical properties.

  Sample No. 2, 4, 6, 8, 10-14, 16, 18, 20, 21, 22, 23, 25, 27, 29, 31-35, 37, 39, 41, 43-52 Is used as a support substrate, and a circuit board is produced by providing a circuit member on the first main surface side of the support substrate and a heat dissipating member on the second main surface side facing the first main surface through a brazing material. As a result, it was found that since the dielectric strength of the support substrate is high and it has excellent heat dissipation characteristics and mechanical characteristics, a highly reliable circuit board can be obtained.

  Moreover, it was found that when an electronic component was mounted on the circuit member of the circuit board according to the present embodiment that was excellent in this way, a highly reliable electronic device could be obtained.

Sample No. 1 prepared in Example 1 was used. Three-point bending strength was measured in accordance with JIS R 1604-2008 with 10-13 and 31-34 held at 1500 ° C. in an air atmosphere. The measured values are shown in Table 2.

As shown in Table 2, Sample No. 10 to 12 and 31 to 33 have a ratio (I ₁ / I ₀ ) of 4% or more. Therefore, a component having a high melting point and a composition formula represented by RE ₄ Si ₂ N ₂ O ₇ is present in the grain boundary phase. It was found that the occupying ratio increased, the value of the three-point bending strength at high temperature was high, and the silicon nitride sintered body having excellent mechanical characteristics was obtained.

First, silicon nitride powder having a β conversion rate of 10% (that is, an α conversion rate of 90%), magnesium oxide (MgO) as an additive component, rare earth metal oxides shown in Table 3, aluminum oxide (Al ₂ O ₃ ), boric acid (H ₃ BO ₃ ), a first metal silicide powder comprising at least one of iron and copper shown in Table 3, and molybdenum, chromium, nickel, manganese and tungsten shown in Table 3 Each powder of the silicide of the second metal composed of at least one kind was wet mixed using a rotary mill, and pulverized until the particle size (D ₉₀ ) became 1 μm or less to obtain a slurry.

Here, the content of each of the above powders is 4 mass%, 14 mass%, and 0.3 mass, respectively, in terms of oxides of magnesium, rare earth metal, aluminum, and boron in the silicon nitride sintered body.
Weighing is performed so that the total content of the first metal and the total content of the second metal are 0.4% by mass and 5% by mass in terms of silicide, respectively. did. However, Sample No. 53 and 71 do not add silicide powder of the second metal.

Next, an organic binder is added to the obtained slurry, and after passing through a sieve having a particle size number of 250 described in ASTM E 11-61, the slurry is dried using a spray dryer. Granules were obtained. Then, a cylindrical silicon nitride-based molded body having a conical tip portion was produced from the silicon nitride-based granule using a dry pressure molding method.

As a subsequent manufacturing method, the same method as in Example 1 was performed, so that sample No. 1 which was a cylindrical silicon nitride sintered body having a length of 75 mm and a diameter of 7.5 mm was obtained. 53-88 were obtained. The temperature decreasing rate was 500 ° C./hour.

  And magnesium, rare earth metal, aluminum, boron oxide, first metal silicide consisting of at least one of iron and copper, molybdenum, chromium, nickel, manganese and tungsten. About the silicide of the 2nd metal, while identifying using the powder X-ray diffraction method, it confirmed that the component composition and content at the time of addition were the same by energy dispersive X-ray spectroscopy.

The oxides of magnesium, rare earth metal, aluminum and boron were calculated and confirmed as MgO, RE ₂ O ₃ , Al ₂ O ₃ and B ₂ O ₃ , respectively. The silicide of the first metal was calculated and confirmed as FeSi ₂ when the first metal was iron and CuSi ₂ when it was copper. In addition, when the second metal is molybdenum, chromium, nickel, manganese, or tungsten, the second metal silicide was calculated and confirmed as MoSi ₂ , CrSi ₂ , NiSi ₂ , MnSi ₂ , or WSi ₂ , respectively. .

Further, when the silicide of the first metal and the silicide of the second metal are in contact with each other, an area having a cross-sectional area of 0.01 mm ² is irradiated with an electron beam using an X-ray microanalyzer. By detecting characteristic X-rays generated from each element in the element, the element is identified and confirmed by mapping according to the intensity of the characteristic X-ray, and the first metal silicide and the second metal silicide Table 3 shows that the samples are found to be in contact with each other, and Table 3 shows that the samples where the first metal silicide and the second metal silicide are not found to be in contact with each other.

  And the thermal shock resistance of each sample was evaluated using the test apparatus and instrument described in JIS R 1648-2002, and Table 3 shows the temperature difference from the water temperature when cracks were confirmed in the sample. The presence or absence of cracks was confirmed before and after the thermal shock test according to JIS Z 2343-1-2001.

As shown in Table 3, Sample No. 54 to 70 and 72 to 88 include a first metal silicide composed of at least one of iron and copper and at least one of molybdenum, chromium, nickel, manganese and tungsten in the grain boundary phase. Since the first metal silicide and the second metal silicide are in contact with each other, the first metal silicide becomes a failure source in a high-temperature environment. Since the stress concentrated on the second metal silicide, which is likely to be dispersed, can be dispersed and relaxed, sample No. 1 in which the first metal silicide and the second metal silicide are not in contact with each other can be relaxed.
It was found that the thermal shock resistance was higher than 53 and 71.

  In particular, sample no. 58, 59, 65, 70, 76, 77, 83, and 88, the first metal and the second metal are iron and tungsten, respectively, and the probability of contact is due to the approximate crystal structure of each silicide. It was found that the thermal shock resistance can be further increased by increasing the thermal shock resistance.

Sample No. of Example 3 A silicon nitride-based sintered body having the same additive component composition as 54 and different amounts of calcium oxide added was produced in the same manner as in Example 3. The amount of calcium oxide added is the same as that of sample No. 90 = 0.25 mass%, sample No. 91 = 0.50 mass%, sample no. 92 = 0.6 mass%
It was.

  Each sample is observed in the dark field at a magnification of 50 times using an optical microscope, and the same region as that observed using the optical microscope is irradiated with an electron beam using an X-ray microanalyzer. By collating the mapping in which the information about the wavelength specific to calcium generated from the region and the intensity of this wavelength is recorded in the XY coordinates with the position of the white spot observed with the optical microscope, the sample No. White spots containing calcium were confirmed in 90-92.

  Next, the calcium content in the silicon nitride sintered body was determined by ICP emission analysis. In addition, using the mapping described above, the area ratio of calcium present at the position of white spots collated with the mapping and the image observed with an optical microscope is calculated, and the area ratio of calcium present at the white spots is calculated based on silicon nitride. By multiplying the content of calcium in the sintered body, the content of calcium contained in white spots was determined, and the value is shown in Table 4.

  Then, the thermal conductivity κ (W / (m · K)) in the thickness direction of each sample was calculated by the same method as shown in Example 1, and the values are shown in Table 4.

  As shown in Table 4, Sample No. In Nos. 90 to 92, since white spots including calcium are present in the grain boundary phase, sample No. No. It was found that the thermal conductivity was higher than that of 89, and the heat dissipation characteristics could be improved.

  Sample No. of Example 3 The same additive composition as 72, the addition amount of calcium oxide is 0.25% by mass, and the mixing / pulverization time by the mixing apparatus is the time shown in Table 5. A sintered body was produced.

Then, for each sample, the circle equivalent diameter is confirmed the number of 1 mm ² per 50μm following confessed spots than 2 [mu] m. First, using an optical microscope, set the range so that the area is 1.125 mm ² (the horizontal length is 1.238 mm and the vertical length is 0.909 mm) at a magnification of 100 times. The image of the range was taken in and analyzed by a technique called particle analysis using image analysis software “A image-kun” (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.). At this time, as setting conditions, the brightness is dark, the binarization method is manual, the small figure removal area is 5 μm ² , and a threshold value that is an index indicating the brightness of the image is set to each point (each pixel) in the image. Table 5 shows the results obtained by setting the peak value of the histogram indicating brightness of 0.8 to 0.8 to 2 times.

  Further, the thermal conductivity κ (W / (m · K)) in the thickness direction of each sample was calculated by the same method as shown in Example 1, and the values are shown in Table 5.

Further, in order to evaluate the insulation resistance of each sample, a paste-like brazing material of silver (Ag) -copper (Cu) alloy containing titanium and molybdenum is formed on both main surfaces of each sample by a screen printing method. The thin copper material was placed on the brazing material. Then, in a vacuum atmosphere, 840
The copper material was joined to both main surfaces of each sample through the joining layer which consists of a brazing material, heating at degreeC. Then, using this copper material as an electrode, the insulation resistance of each sample was measured, and the results are shown in Table 5.

As shown in Table 5, Sample No. 1 has white spots of 550 or more and 1650 or less per 1 mm ² containing calcium having an equivalent circle diameter of 2 μm or more and 50 μm or less. Nos. 94 to 96 have obtained high results of insulation resistance and thermal conductivity, and it was found that silicon nitride sintered bodies having high dielectric strength and improved heat dissipation characteristics can be obtained.

1: Main crystal phase 2: Component whose composition formula is shown as RE ₄ Si ₂ N ₂ O ₇ (RE is a rare earth metal) 3: Grain boundary phase 4: Silicide of first metal 5: Silicide of second metal 6a : Solid solution 6b: Intermetallic compound
10: Circuit board
11: Support substrate (silicon nitride sintered body)
12a, 12b: Circuit members
13: Heat dissipation member
14a, 14b: bonding layer
15a, 15b: Copper material
16, 17: Electronic parts

Claims (7)

Mainly silicon nitride, magnesium, rare earth metal, aluminum and boron in terms of oxides of 2% to 6% by mass, 12% to 16% by mass, 0.1% to 0.5% by mass, respectively. In the following, the main crystal phase comprising 0.06 mass% to 0.32 mass% and composed of β-Si ₃ N ₄ and the composition formula shown as RE ₄ Si ₂ N ₂ O ₇ (RE is a rare earth metal) And a diffraction angle of 30 ° to 35 with respect to the first peak intensity I ₀ of β-Si ₃ N _{4 at} a diffraction angle of 27 ° to 28 ° determined by an X-ray diffraction method. The ratio of the first peak intensity I ₁ (I ₁ / I ₀ ) of RE ₄ Si ₂ N ₂ O ₇ at ₂₀ ° C. is 20% or less (however, excluding 0%). Union. The silicon nitride based sintered body according to claim 1, wherein the ratio (I ₁ / I ₀ ) is 4% or more. In the grain boundary phase, a silicide of a first metal made of at least one of iron and copper, and a silicide of a second metal made of at least one of molybdenum, chromium, nickel, manganese and tungsten, The silicon nitride sintered body according to claim 1, wherein the silicide of the first metal and the silicide of the second metal are in contact with each other. 2. The silicon nitride based sintered body according to claim 1, wherein white spots including calcium are present in the grain boundary phase. 5. The silicon nitride based sintered body according to claim 4, wherein 550 or more and 1650 or less of white spots having an equivalent circle diameter of 2 μm or more and 50 μm or less are present per 1 mm ² . A silicon nitride sintered body according to any one of claims 1 to 5 is used as a support substrate, a circuit member is provided on the first main surface side of the support substrate, and a second main surface facing the first main surface. A circuit board comprising a heat dissipation member on each side. An electronic device in which an electronic component is mounted on the circuit member in the circuit board according to claim 6.

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