JP5755170B2 - 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, a circuit board using the same, and an electronic device.

  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 electronic components, for example, a circuit member mainly composed of copper and a heat radiating member are bonded to the main surfaces on both sides of a support substrate made of an insulating ceramic sintered body. As a ceramic sintered body used for the support substrate, a silicon nitride-based sintered body has attracted attention.

As a silicon nitride sintered body used for such a circuit board, for example, in Patent Document 1, a rare earth element is converted to an oxide of 2.0 to 17.5% by weight, and Mg is converted to an oxide of 0.3 to 3.0% by weight. %, Al, Li, Na, K, Fe, Ba, Mn, B as impurity cation elements in total containing 0.3% by weight or less, consisting of a silicon nitride crystal and a grain boundary phase, and a crystalline compound in the grain boundary phase A highly thermally conductive silicon nitride sintered body in which the ratio of the phase to the whole grain boundary phase is 20% or more has been 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 a large number of gaps are generated in the grain boundary phase, and there is a problem 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 contains silicon nitride as a main component, and magnesium, rare earth element, and aluminum are 2% by mass to 6% by mass, 4% by mass to 10% by mass, and 0.1% by mass, respectively. And a grain boundary phase containing a component having a composition formula of RE ₄ Si ₂ N ₂ O ₇ (RE is a rare earth element), and a main crystal phase comprising β-Si ₃ N ₄ RE ₄ Si ₂ N ₂ 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. O ₇
The ratio (I ₁ / I ₀ ) of the first peak intensity I ₁ is 20% or less (excluding 0%).

  In the circuit board of the present invention, a circuit member is provided on the first main surface side of the support substrate made of the silicon nitride sintered body having the above structure, and a heat radiating member is provided on the second main surface side facing the first main surface. It is characterized by being provided.

  An electronic device according to the present invention is characterized in that an electronic component is mounted on a circuit member in the circuit board having the above-described configuration.

According to the silicon nitride sintered body of the present invention, the volume shrinkage accompanying the crystallization of RE ₄ Si ₂ N ₂ O ₇ is small, and it is difficult to form a gap in the grain boundary phase. A silicon nitride-based sintered body having heat dissipation characteristics and mechanical characteristics can be obtained.

  In addition, according to the circuit board of the present invention, since the support substrate is made of the silicon nitride sintered body having the above-described configuration, it has high dielectric strength and has excellent heat dissipation characteristics and mechanical characteristics. A highly 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 in the circuit board having the above-described configuration, the electronic device can be highly durable and reliable.

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. 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 elements and aluminum are 2% by mass to 6% by mass, 4% by mass to 10% by mass, 0.1% in terms of oxides, respectively. A silicon nitride-based sintered body containing from mass% to 0.5 mass%.

  In general, silicon nitride as a main component in a silicon nitride-based sintered body has a strong covalent bond, a low diffusion coefficient, and it is difficult to sinter silicon nitride alone. By adding the 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 a silicon nitride-based sintered body excellent in heat dissipation characteristics and mechanical characteristics is obtained.

  In particular, when a rare earth element oxide having a high affinity with oxygen is added as a sintering aid, a large amount of oxygen is taken into the liquid phase and the amount of oxygen contained in the silicon nitride powder along with the growth of silicon nitride grains. Can be further reduced.

However, in order to reduce the amount of oxygen contained in the silicon nitride powder, simply increasing the addition amount of the sintering aid will relatively increase the abundance ratio of the grain boundary phase that is not excellent in heat dissipation characteristics,
It becomes difficult to obtain a silicon nitride sintered body having excellent heat dissipation characteristics.

  Under such circumstances, the present inventors have obtained a silicon nitride 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) The present inventors have found that it is important to contain 4% by mass to 10% by mass, 0.1% by mass to 0.5% by mass or less.

The main component in this embodiment is 100% by mass of all components constituting the silicon nitride sintered body.
The component which occupies 83 mass% or more is said. And each content which converted silicon nitride, magnesium, rare earth elements (RE), and aluminum into an oxide is determined by fluorescent X-ray analysis, ICP (Inductively Coupled Plasma) emission analysis, or energy dispersive X-ray spectroscopy. The contents of Si, Mg, RE, and Al can be obtained, and these contents can be obtained by converting Si to Si ₃ N ₄ and the others to MgO, RE ₂ O ₃ , and Al ₂ O _3. .

  Since 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 by the sintering promoting action of the magnesium oxide, so that excellent mechanical properties can be obtained. It can be set as a silicon nitride sintered body. On the other hand, if the content of magnesium in terms of oxide is less than 2% by mass, the sintering promoting action is small, and if it exceeds 6% by mass, the occupancy of the grain boundary phase becomes high and the heat dissipation characteristics can be improved. Disappear. 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 rare earth elements in terms of oxide is 4% by mass or more and 10% by mass or less, a large amount of oxygen between silicon nitride powders is taken into the liquid phase due to high affinity with oxygen, Since grain growth of silicon nitride is promoted, a silicon nitride sintered body having excellent heat dissipation characteristics can be obtained. The content of the rare earth element in terms of oxide is preferably 5% by mass or more and 9% 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.

The silicon nitride sintered body according to the present embodiment satisfies the above-described composition range and has 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 For 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 RE ₄ Si ₂ N ₂ O _{7 at} a diffraction angle of 30 ° to 35 ° is 20% or less (excluding 0%). It is.

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 element oxide are combined, silicon nitride-based sintering excellent in 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 by a powder X-ray diffraction method.

Here, the rare earth element constituting the component represented by the composition formula RE ₄ Si ₂ N ₂ O ₇ is yttrium (Y), lanthanoid metal (La, Ce, Pr, Nd, Sm, Tb, Dy).
, Tm, Er, Yb, Lu). Among them, at least one of erbium (Er), ytterbium (Yb), and lutetium (Lu) is preferable.

Erbium (Er), ytterbium (Yb), and lutetium (Lu) are elements having a small ionic radius among the Group 3 elements of the periodic table. Therefore, Si, O, Since the bond with N is strong, the transmission of phonons is good and the thermal conductivity can be increased. 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 element 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 element 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 suitable for reducing the manufacturing cost.

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 it is difficult for gaps to occur 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 includes a component whose composition formula is shown as RE ₄ Si ₂ N ₂ O ₇ (RE is a rare earth element), 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%. For the following (excluding 0%), the maximum temperature, the holding time thereof, and the rate of temperature decrease from the maximum temperature are important in firing using the raw materials satisfying the above composition range.

In the silicon nitride sintered body in the present embodiment, it is preferable that the above-described peak intensity ratio (I ₁ / I ₀ ) is 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 intensity of the highest peak 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 Diffraction angle 30 when collated with the cards indicated by -1215, 00-034-1268, 00-055-1090, 00-032-1354, 00-031-0505, 00-051-0340, 00-033-0847 It is the intensity of the highest peak between ° and 35 °.

In calculating the ratio (I ₁ / I ₀ ), the first peak intensity I ₀ of β-Si ₃ N _{4 at} a diffraction angle of 27 ° to 28 °, and RE ₄ Si ₂ at a diffraction angle of 30 ° to 35 °. For the first peak intensity I _{1 of} N ₂ O ₇ , a value obtained by removing the background intensity from the diffraction intensity curve obtained by the powder X-ray diffraction method is used.

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

  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. As shown in the schematic diagram of FIG. 1, the silicon nitride sintered body of the present embodiment has a main crystal phase 1 made of β-Si ₃ N ₄ and a composition formula of RE ₄ Si ₂ N ₂ O _7. And a grain boundary phase 3 including the component 2. The grain boundary phase 3 includes a first metal silicide 4 made of at least one of iron and copper, and a second metal silicide 5 made of at least one of molybdenum, chromium, nickel, manganese and tungsten. It is preferable that these are included.

Here, 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 at least one of the components represented as CuSi ₃ .

Further, the silicide 5 of the second metal, composition _{formula, MoSi, MoSi 2, MoSi 3} , Mo 2 Si 3, Mo 5 Si 3, CrSi, CrSi 2, CrSi 3, Cr 2 Si 3, Cr 5 Si 3 _{, NiSi, NiSi 2, NiSi 3} , Ni 2 Si 3, Ni 5 Si 3, MnSi, MnSi 2, MnSi 3, Mn 2 Si 3, Mn 5 Si 3, WSi, WSi 2, WSi 3, W 2 Si 3 and It is at least any one of the components represented as W ₅ Si ₃ .

Since the first metal silicide 4 can sinter β-Si ₃ N ₄ at a lower temperature, the abnormal grain growth of β-Si ₃ N ₄ can be reduced. In addition, the silicide 5 of the second metal can control the solidification of the grain boundary phase 3 to enhance the mechanical characteristics at high temperature, and the color tone of the silicon nitride sintered body is blackened, and the silicon nitride sintered The color tone difference on the surface of the body 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 this way, when the first metal silicide 4 and the second metal silicide 5 are in contact with each other in the grain boundary phase 3, the first metal silicide 4 is a source of fracture in a high-temperature environment. Since the stress concentrated on the silicide 5 of the second metal that is likely to be dispersed 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. The first metal is iron,
When 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.

Further, the first metal silicide 4 is a component whose composition formula is expressed as FeSi ₂ , and the second metal silicide 5 is expressed as at least one of MoSi ₂ and WSi _2. Preferably it is a component. This is because the components whose composition formulas are expressed as FeSi ₂ , MoSi ₂ , and WSi ₂ are both thermodynamically stable components, and the crystal structures of the two are approximated. This is because the impact property 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 5 made of at least one of molybdenum, chromium, nickel, manganese and tungsten, Can be observed using energy dispersive X-ray spectroscopy. Specifically, an area having a cross-sectional area of 0.01 mm ² is irradiated with an electron beam using an X-ray microanalyzer. Thus, the element can be identified by detecting characteristic X-rays generated from each element in this region, and can be confirmed by mapping according to the intensity of the characteristic X-ray.

  Further, in the grain boundary phase 3, a solid solution 6a or an intermetallic compound 6b made of the first metal and silicon or the second metal and silicon may exist. The presence of the solid solution 6a and the intermetallic compound 6b in the grain boundary phase 3 improves the fracture toughness of the grain boundary phase 3, and even if fine cracks occur 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, according to the silicon nitride based sintered body of the present embodiment, it is preferable that white spots including calcium are present in the grain boundary phase. Thus, when the white spots containing 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 observing in a dark field at a magnification of 50 to 100 times using an optical microscope.

  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 the confirmation using the X-ray microanalyzer, magnesium, rare earth elements and aluminum 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 image taken with a CCD camera is captured in the range where the length in the vertical direction is 0.909 mm), and analyzed by a technique called particle analysis using image analysis software “A Image-kun” (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.). That's fine. Here, as setting conditions of this method, for example, 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 value in the image. The peak value of the histogram indicating the brightness of each point (each pixel) is 0.8 times or more and 2 times or less.

  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 sintered body can be evaluated by the strength of dielectric breakdown (MV / m) measured according to JIS C 2141-1992 (IEC 72-2 (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 5 MPam ^1/2 or more. By having the mechanical characteristics described above, the joining member obtained by joining the silicon nitride sintered body of this embodiment and the metal member particularly improves creep resistance and durability against heat cycle. Therefore, it is possible to obtain high reliability and use over a long period of 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 characteristics of the silicon nitride sintered body as described above are such that the volume resistivity is 10 ^{14 at} room temperature.
It is preferably Ω · cm or more, and preferably 10 ¹² Ω · cm or more at 300 ° C. 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 a second main surface in which circuit members 12a and 12b are opposed to the first main surface on the first main surface side of the support substrate 11 made of the silicon nitride sintered body of this embodiment. 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 application, it is preferably 0.2 mm or more and 1.0 mm or less in order to have a high withstand voltage 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.

  Further, the circuit members 12a and 12b and the heat radiating member 13 may be bonded to the bonding layers 14a and 14b via a copper material, respectively. Thus, the temperature when the circuit members 12a, 12b and the heat radiating member 13 are joined via the joining layers 14a, 14b is 800 to 900 ° C., but the circuit members 12a, 12b and Since the bonding between the copper material and between the heat dissipating member 13 and the copper material can be performed at a relatively low temperature of about 300 to 500 ° C. by diffusion of copper as the respective constituent components, the support substrate 11 The warp that occurs 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.

2 shows an example in which circuit members 12a and 12b having different dimensions are provided. If circuit members 12a and 12b having the same size are arranged on the first main surface side of the support substrate 11, the circuit members are provided. Since the stress bias generated in the support substrate 11 after joining 12a and 12b is reduced, 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. In addition, when the copper content increases, the yield stress is low, and plastic deformation is likely to occur when heated. Therefore, the adhesion of the circuit members 12a and 12b and the copper material, the heat dissipation member 13 and the copper material is increased, and the reliability is further improved. Becomes higher.

  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 containing at least one selected from titanium, zirconium, hafnium and niobium. The thickness of the bonding layers 14a and 14b is, for example, not less than 5 μm and not more than 20 μm.

  Further, the copper material interposed between the circuit members 12a and 12b and the bonding layer 14a, and the heat radiation member 13 and the bonding layer 14b is any one of oxygen-free copper, tough pitch copper and phosphorous deoxidized copper having a high copper content. In particular, the oxygen-free copper is composed of any one of linear crystalline oxygen-free copper, single-crystal high-purity oxygen-free copper, and vacuum-melted copper having a copper content of 99.995% by mass or more. The thickness is, for example, not less than 0.1 mm and not more than 0.6 mm.

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, and joining layer 14a, 14b by an etching etc.

  Next, FIG. 3 shows an example of the electronic device of this embodiment, (a) is a plan view, (b) is a cross-sectional view taken along line BB ′ in (a), and (c). Is a bottom view.

  The electronic device S of the example shown in FIG. 3 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 this embodiment. , 17 are electrically connected to each other by a conductor (not shown). The circuit member 12 and the heat radiating member 13 are bonded to the bonding layers 14a and 14b via copper materials 15a and 15b, respectively. 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. 3, for example, are 4 mm or more and 40 mm or less in length (X direction shown in FIG. 3), and 5 mm in width (Y direction shown in FIG. 3). 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. 3, 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 circuit board and the electronic device of the present embodiment, since the support substrate has high dielectric strength and excellent heat dissipation characteristics and mechanical characteristics, it is difficult to warp and cracks are generated even when heat is repeatedly applied. Since it does not easily occur, a highly reliable circuit board and electronic device can be obtained.

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

First, silicon nitride powder having a β conversion rate of 20% or less, magnesium oxide (MgO) as an additive component, rare earth element oxide (for example, Y ₂ O ₃ , La ₂ O ₃ , Ce ₂ O ₃ , Pr ₆ O ₁₁ , Nd ₂ O ₃ , Sm ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Tm ₂ O ₃ , Er 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 ) powders are wet-mixed with water using a mixing device such as a barrel mill, a rotating mill, a vibration mill, a bead mill, a sand mill, an agitator mill, or the like. To prepare a slurry.

And a silicon nitride sintered body containing magnesium, rare earth element and aluminum in terms of oxides of 2% by mass to 6% by mass, 4% by mass to 10% by mass, and 0.1% by mass to 0.5% by mass, respectively. To achieve this, the total of the silicon nitride powder and the total of these additive component powders is 100% by mass, and the additive component magnesium oxide (MgO) powder is 2 to 6% by mass, rare earth element oxide. The powder may be weighed so that 4 to 10% by mass of the powder, 0.1 to 0.5% by mass of the powder of aluminum oxide (Al ₂ O ₃ ), and the remaining 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 can be adjusted by the outer diameter of the ball, the amount of the ball, 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 slag bowl made of a silicon nitride sintered body. 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 oxides of rare earth elements is arranged 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. Then, the temperature is further raised and maintained at 1560 ° C. or higher and 1640 ° C. or lower for longer than 4 hours and 6 hours or shorter, and then the temperature is further raised and held at 1740 ° C. or higher and lower than 1800 ° C. for 4 hours or longer and 10 hours or shorter. Thereafter, by cooling at a temperature lowering rate of 500 ° C./hour or more, silicon nitride is the main component, and magnesium, rare earth element and aluminum are 2% by mass to 6% by mass and 4% by mass to 10% by mass in terms of oxides, respectively. % Or less, 0.1 mass% or more and 0.5 mass% or less, 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 element) RE 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 °, which is determined by an X-ray diffraction method. ₄ Si ₂ N ₂ O _{7 having} a first peak intensity I ₁ ratio (I ₁ / I ₀ ) of 20% or less (excluding 0%) is obtained in this embodiment. be able to.

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 sintered body of this 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 powder constituting the silicon nitride powder and the additive component Then, a powder consisting of at least one of each metal, oxide, silicide and the like, which becomes a first metal silicide and a second metal silicide after firing, is added, and water is added using a mixing device. The slurry may be prepared by wet mixing and pulverization. And after producing a slurry, by producing by the same method as the above-mentioned method, at least any one of the silicide of the 1st metal which consists of at least 1 sort of iron and copper, molybdenum, chromium, nickel, manganese, and tungsten It is possible to obtain the silicon nitride sintered body of the present embodiment including the first metal silicide and the second metal silicide.

Further, in order to obtain the silicon nitride-based sintered body of the present embodiment in which white spots including calcium are present in the grain boundary phase, calcium oxide is added to each of the above 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.

  Further, when a copper material is interposed between the circuit members 12a and 12b and the bonding layer 14a and between the heat dissipation member 13 and the bonding layer 14b, a thin copper material is disposed on the brazing material to be the bonding layers 14a and 14b, respectively. . Then, it heats at 800 degreeC or more and 900 degrees C or less, and joins a copper material via the joining layers 14a and 14b to the 1st main surface side and 2nd main surface side of the support substrate 11, respectively.

  Then, after polishing the surfaces of the copper material 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 arranged on the copper material. 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. It is possible to obtain the circuit board 10 in which 12a and 12b are joined to the second main surface side through the heat dissipation member 13 through the joining layers 14a and 14b and the copper material, respectively.

  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 additive component, rare earth element oxide and aluminum oxide (Al ₂ ) shown in Table 1 Each powder of O ₃ ) is weighed to have the content shown in Table 1, wet-mixed using a rotary mill, and pulverized until the particle size (D ₉₀ ) is 1 μm or less. did.

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 element oxide is placed around the silicon nitride-based molded body in an amount of 6% by mass with respect 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. 1-44 were obtained.

And content of each oxide of magnesium, rare earth elements, and aluminum was calculated | required by the energy dispersive X-ray spectroscopy. Table 1 shows the content of each oxide. Moreover, the component whose composition formula is represented by RE ₄ Si ₂ N ₂ O ₇ was identified by a powder X-ray diffraction method.

Then, based on the result obtained by the X-ray diffraction method, β-Si ₃ N ₄ at a diffraction angle of 27 ° to 28 ° is collated with a card represented by PDF (registered trademark) Number: 00-033-1160. Was defined as the first peak intensity I ₀ . 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. 2,4,6,8-12,14,16,19,21,23,25-29,31,33,35-44 are mainly composed of silicon nitride, oxide of magnesium, rare earth elements and aluminum Each containing 2% by mass to 6% by mass, 4% by mass to 10% by mass, 0.1% by mass to 0.5% by mass, a main crystal phase composed of β-Si ₃ N _4, and a composition formula of RE ₄
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, which is composed of a grain boundary phase containing a component shown as Si ₂ N ₂ O _7. The ratio of the first peak intensity I ₁ of RE ₄ Si ₂ N ₂ O ₇ at a diffraction angle of 30 ° to 35 ° (I ₁ / I ₀ ) is 20% or less (excluding 0%) Therefore, the strength of dielectric breakdown was 18 MV / m or more, the thermal conductivity was 50 W / (m · K) or more, and the three-point bending strength was 735 MPa or more. From this result, the silicon nitride based sintered body of the present embodiment has a high dielectric strength because the volume shrinkage accompanying the crystallization of RE ₄ Si ₂ N ₂ O ₇ is small and a gap is not easily generated in the grain boundary phase. It was found that the silicon nitride sintered body has excellent heat dissipation characteristics and mechanical characteristics.

  Sample No. 2,4,6,8-12,14,16,19,21,23,25-29,31-33,35-44 using a silicon nitride sintered body as a support substrate, through a brazing material When a circuit board is prepared by providing a circuit member on the first main surface side of the support substrate and a heat dissipation member on the second main surface side facing the first main surface, the support substrate has high dielectric strength and is excellent. It has been found that a highly reliable circuit board can be obtained because of its heat dissipation characteristics and mechanical characteristics.

  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 8-11 and 25-28 held at 1500 ° C. in an air atmosphere. The measured values are shown in Table 2.

As shown in Table 2, Sample No. 8 to 10, 25 to 27, since the ratio (I ₁ / I ₀ ) is 4% or more, a component having a high melting point and a composition formula of 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 element oxides shown in Table 3, aluminum oxide (Al ₂ O ₃ ), a first metal silicide powder comprising at least one of iron and copper shown in Table 3, and a second metal comprising at least one of molybdenum, chromium, nickel, manganese and tungsten shown in Table 3. Each of the silicide powders 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% in terms of oxides, respectively, for magnesium, rare earth element and aluminum in the silicon nitride sintered body.
In addition, the total content of the first metal and the total content of the second metal were weighed so as to be 0.4% by mass and 5% by mass in terms of silicide, respectively. However, sample No.
. In Nos. 45 and 63, the second metal silicide powder is not added.

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. 45-80 were obtained. The temperature decreasing rate was 500 ° C./hour.

  And magnesium, rare earth element, aluminum oxide, first metal silicide consisting of at least one of iron and copper, second metal consisting of at least one of molybdenum, chromium, nickel, manganese and tungsten. About the silicide, while identifying using a 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 elements and aluminum were calculated and confirmed as MgO, RE ₂ O ₃ and Al 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. 46 to 62 and 64 to 80 are the first metal silicide consisting 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 silicide of the first metal and the silicide of the second metal are in contact with each other, the silicide of the first metal may become a source of destruction in a high-temperature environment. Since the stress concentrated on a certain second metal silicide can be dispersed and relaxed, sample No. 1 in which the first metal silicide is not in contact with the second metal silicide. It was found that the thermal shock resistance was higher than 45 and 63.

In particular, sample no. 46, 50, 51, 52, 57, 58, 62, 64, 68, 69, 75, 76, 80, the first metal and the second metal are any one of iron, molybdenum and tungsten, respectively, It has been found that the thermal shock resistance can be further increased by increasing the probability of contact because the crystal structure of the silicide of this is close.

Sample No. of Example 3 A silicon nitride sintered body having the same additive component composition as 46 and different amounts of calcium oxide was prepared in the same manner as in Example 3. The amount of calcium oxide added is the same as that of sample No. 82 = 0.25 mass%, sample No. 83 = 0.50 mass%, sample No. 84 = 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 including calcium were observed in 82 to 84.

  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. 82 to 84, since white spots containing calcium are present in the grain boundary phase, sample Nos. 8 in which white spots containing calcium do not exist are shown. It was found that the thermal conductivity was higher than that of 81, and the heat dissipation characteristics could be improved.

  Sample No. of Example 3 The same additive component composition as that of No. 64, the addition amount of calcium oxide being 0.25% by mass, and the mixing / pulverization time by the mixing apparatus as the time shown in Table 5 were used. 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, and the CCD
Images in this range were captured with a camera, 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. 86 to 88 were obtained with high insulation resistance values and high thermal conductivity, and it was found that silicon nitride sintered bodies with high dielectric strength and improved heat dissipation characteristics could 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 element) 3: Grain boundary phase 4: Silicide of the first metal 5: Silicide of the 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
16, 17: Electronic parts

Claims (7)

Containing silicon nitride as the main component and containing magnesium, rare earth element and aluminum in an amount of 2% to 6%, 4% to 10%, 0.1% to 0.5% by weight in terms of oxides, respectively. X-ray diffraction comprising 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 (RE is a rare earth element) The first peak 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 β-Si ₃ N _{4 at} a diffraction angle of 27 ° to 28 ° determined by the method A silicon nitride-based sintered body having a ratio of strength I ₁ (I ₁ / I ₀ ) of 20% or less (excluding 0%). The silicon nitride based sintered body according to claim 1, wherein the ratio (I ₁ / I ₀ ) is 4% or more. The grain boundary phase includes 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. 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, and a circuit member is disposed on a first main surface side of the support substrate, and a second main surface facing the first main surface. A circuit board characterized in that a heat dissipation member is provided on each side. An electronic device, wherein an electronic component is mounted on the circuit member in the circuit board according to claim 6.

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