JP2005306718A - Inorganic powder, resin composition filled with the powder, and use thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition which has thermal conductivity and can be used as a heat radiating member in the circuit board of an electronic component required to have electrical insulating property and heat radiating performance, and which has high withstand voltage characteristics even when a thin film-like insulative composition is formed, and to provide a thermally conducting inorganic powder useful as a filler for a heat radiating member, which can be filled in the resin composition at a high density large enough to enhance the heat radiating characteristics of the resin composition and can provide the thin film-like insulative resin composition having excellent withstand voltage characteristics. <P>SOLUTION: The inorganic powder has a frequency particle size distribution with multiple peaks and frequency peaks are present at least in particle size regions of 0.2-2 μm and 2-63 μm, and preferably it has the maximum particle size being ≤63 μm, the average particle size in a range of 4-30 μm, and the most frequent size in a range of 2-35 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  INDUSTRIAL APPLICABILITY The present invention relates to a resin composition having thermal conductivity useful as a heat radiating member in applications such as circuit boards for electronic components that require electrical insulation and heat dissipation performance, and its use, and as a heat conductive filler for resin components. The present invention relates to an inorganic powder having high thermal conductivity to be filled.

  In recent years, circuit boards equipped with electronic components such as semiconductor elements have been used in electronic control devices in various fields such as home appliances and automotive electrical equipment. The demand for higher integration and higher functionality is increasing. As a result, the amount of heat generated locally on the circuit or the like tends to increase. Since heat generation and heat storage adversely affect the durability of circuits, etc., circuit boards are required to have higher heat dissipation performance in addition to electrical reliability such as electrical insulation. In addition, improvements to heat dissipation performance and heat transfer / heat dissipation methods have been studied up to members such as insulating adhesive layers.

  The heat dissipation method is generally a method in which heat is transmitted and dissipated by assembling a metal fin or heat radiating plate having high thermal conductivity and a circuit board in contact with each other. However, if current is applied or short-circuited at both contact points, the circuit will be destroyed. Therefore, it is common to insulate by sandwiching a resin composition layer made of a known organic polymer composition having high electrical insulation between them. Is. However, generally only an organic polymer composition has low thermal conductivity, and its performance as a heat radiating member is low.

  As a method for adding thermal conductivity to a resin material made of an organic polymer composition or the like, a technique for filling an inorganic powder having high thermal conductivity as a thermal conductive filler has been known. The inorganic powder also serves as a filler that adds functions such as flame retardancy and electrical insulation. Here, in particular, spherical inorganic powders are excellent in terms of fillability and fluidity, and thus have already been put into practical use as heat dissipation members for circuit boards and filling materials for semiconductor encapsulants. For example, spherical aluminum oxide powder having high thermal conductivity is used as a heat dissipating filler, and spherical silica powder is used as a semiconductor encapsulant filler due to its high purity.

  As an example of a method for obtaining a spherical inorganic powder, a technique is known in which an inorganic powder as a raw material or a slurry thereof is introduced into a high-temperature flame to be in a molten state and spheroidized by surface tension (for example, patents). Document 1: Japanese Patent Laid-Open No. 2001-19425). Alternatively, a metal may be used as a raw material, and in this case, high-temperature oxidation of the metal and melt spheroidization occur simultaneously (for example, Patent Document 2; Japanese Patent Laid-Open No. 5-139908).

  The so-called high sphericity spherical inorganic powder having a good spherical state has a low viscosity (hereinafter referred to as a resin compound viscosity) when filled in a resin compound, which is an index of high filling property and fluidity. Less likely to cause resin defects such as voids. This is an advantage, and it is used as a filler that can be expected to improve the heat dissipation performance of the resin compound even if it is expensive. However, a relatively inexpensive inorganic powder with low sphericity or crushed powder, such as crushed powder, has a relatively high resin compound viscosity. Particularly, the resin has a markedly poor flow when the compound is thermally cured and highly viscous. Defects are likely to occur. When there are many resin defects, the strength against the dielectric breakdown voltage (hereinafter referred to as dielectric breakdown strength), which is an index of electrical reliability and withstand voltage characteristics, tends to decrease.

  In addition, since inorganic powders generally have a hydrophilic surface, they have low affinity with organic polymer compositions and silicone polymer compositions typified by epoxy resins as compounds. Since the surface is smooth, the bondability and adhesiveness are weak, so that interface breakdown is likely to occur, and the dielectric breakdown strength is likely to decrease. Even in such a case, a technique for improving the adhesiveness with the resin component by surface-treating the powder with a silane coupling agent or the like to make it hydrophobic is generally known. (For example, Patent Document 3; JP-A-5-335446, Patent Document 4; JP-A-2001-240771, Non-Patent Document 1; NUC Silane Coupling Agent Catalog manufactured by Nihon Unicar Co., Ltd.)

  The resin composition used for the heat dissipation member of the circuit board is required to have high heat dissipation performance while maintaining the flexibility and withstand voltage characteristics inherent in the organic polymerization composition. In order to obtain high heat dissipation performance, high filling with inorganic powder with high thermal conductivity leads to deterioration of withstand voltage characteristics due to the occurrence of interfacial breakage and resin defects, and flexibility reduction. In other words, expensive, highly spherical spherical inorganic powders having a low resin compound viscosity and high filling properties are selected and used. Furthermore, the technique used after implementing the improvement of the adhesiveness etc. by additional processing, such as special particle size distribution and particle property by classification and mixing process, and surface treatment (for example, patent document 5; JP 2001-139725 A, Patent Document 6; JP 2003-137627 A).

  That is, in the prior art, inorganic powders that are relatively poor in fluidity (that is, high resin compound viscosity) such as crushed powder and low sphericity powder that can be obtained and manufactured at a relatively low cost are difficult to achieve high filling. Furthermore, since the withstand voltage characteristics are remarkably deteriorated due to the occurrence of a resin defect or the like, it cannot be used. As a result, a resin composition having heat dissipation performance and high withstand voltage characteristics cannot be obtained.

Japanese Patent Laid-Open No. 2001-19425 JP-A-5-193908 JP-A-5-335446 JP 2001-240771 A JP 2001-139725 A JP 2003-137627 A Catalog of NUC silane coupling agent manufactured by Nihon Unicar Co., Ltd.

  In the present invention, it is possible to form a thin-film insulating resin composition (hereinafter referred to as a thin-film resin sheet) that can be filled so high that the heat dissipation performance can be improved in the resin material and that has a high withstand voltage characteristic. An object of the present invention is to provide a resin composition that can be used as a heat radiating member such as a circuit board that requires electrical insulation and heat dissipation performance.

  As a result of diligent research in view of the above situation, the present inventors have a specific particle size distribution, and more preferably by using a thermally conductive inorganic powder that has been subjected to a surface hydrophobization treatment in advance. Despite being a low sphericity powder with a high resin compound viscosity, it can be highly filled into resin materials, exhibits high thermal conductivity, and provides high dielectric breakdown strength during thin film resin sheet deposition As a result, the present invention was reached.

That is, the present invention includes the following embodiments.
1. An inorganic powder which is a powder having a multimodal frequency particle size distribution and having a frequency peak in a particle size range of at least 0.2 to 2 μm and 2 to 63 μm.
2. 2. The inorganic powder as described in 1 above, wherein the maximum particle size is 63 μm or less, the average particle size is in the range of 4 to 30 μm, and the mode diameter is in the range of 2 to 35 μm.
3. 2. The inorganic powder according to 1 above, wherein the proportion of particles having a particle diameter of less than 2 μm is 0 to 20% by mass, and the mode diameter of particles having a particle diameter of less than 2 μm is in the range of 0.25 to 1.5 μm.
4). 2. The inorganic powder as described in 1 above, wherein the proportion of particles having a particle size of 8 μm or more is 44 to 90% by mass.
5). 2. The inorganic powder according to 1 above, wherein the proportion of particles having a particle size range of 2 to 8 μm is 0 to 15% by mass.
6). 2. The inorganic powder as described in 1 above, wherein the proportion of particles having a particle size range of 2 to 8 μm is 32 to 45 mass%.
7). 2. The inorganic powder as described in 1 above, having a sphericity of 0.68 to 0.95 and a spheroidization ratio of 0.63 to 0.95.
8). 2. The inorganic powder as described in 1 above, wherein the particles having a particle diameter of less than 2 μm have a sphericity of 0.5 to 0.95 and a spheroidization ratio of 0 to 0.9.
9. 2. The inorganic powder according to 1 above, wherein the particles having a particle diameter of 8 μm or more have a sphericity of 0.7 to 0.95 and a spheroidization ratio of 0.7 to 0.95.
10. 2. The inorganic powder as described in 1 above, wherein the thermal conductivity of the inorganic powder is 30 W / m · K or more at the time of single crystal.
11. 11. The inorganic powder as described in 1 to 10 above, wherein the inorganic powder is an alumina powder.
12 12. The inorganic powder as described in 11 above, wherein the α-alumina crystal phase fraction is in the range of 30 to 75% by mass.
13. The inorganic powder as described in 11 above, wherein the α-alumina crystal phase fraction of particles less than 13.2 μm is in the range of 90 to 100% by mass.
12. The inorganic powder as described in 11 above, wherein the α alumina crystal phase fraction of particles of 14.8 μm or more is in the range of 30 to 70% by mass.
15. 2. The inorganic powder as described in 1 above, wherein the content of metal Al is 0.05% by mass or less.
16. 2. The inorganic powder as described in 1 above, wherein the sulfate ion content is 15 ppm or less.
17. 2. The inorganic powder as described in 1 above, wherein the chloride ion content is 15 ppm or less.
18. _2. The inorganic powder as described in 1 above, wherein the content of Fe ₂ O ₃ is 0.03% by mass or less.
19. The inorganic powder as described in 1 above, which does not substantially contain particles of less than 50 nm.
20. 2. The inorganic powder according to 1 above, wherein the surface is hydrophobized with a surface treatment agent selected from a silane coupling agent and a titanate coupling agent.
21. 21. A resin composition filled with the inorganic powder according to any one of 1 to 20 above.
22. 22. The resin composition as described in 21 above, which is filled with 50 to 90% by mass of inorganic powder.
23. When the resin composition is a thin film insulating resin composition having a thickness of 40 to 90 μm, the dielectric breakdown strength measured by a dielectric breakdown voltage test specified in JIS C2110 is 39 kV / mm or more 21 or 22. The resin composition according to 22.
24. 24. A circuit board for mounting on an automobile, wherein the resin composition according to any one of 21 to 23 is used.
25. 24. A circuit board for mounting on electronic equipment using the resin composition according to any one of 21 to 23.
26. 24. A heat dissipating member installed inside an electronic device using the resin composition according to any one of 21 to 23.
27. 24. A heat dissipating member for electronic parts using the resin composition according to any one of 21 to 23.
28. 28. The heat radiating member according to 26 or 27, which is in the form of a sheet.
29. 28. The heat dissipation member as described in 26 or 27 above, which is in a paste form or a gel form.
30. 28. The heat dissipating member according to the above 26 or 27, which is an underfill agent type member.
31. 28. The heat radiating member according to 26 or 27, wherein the heat radiating member is a type of heat radiating member applied to a heat generating portion of the element portion.
32. 24. A metal base circuit board, a metal core type circuit board, or a structure using these boards, wherein the resin composition according to any one of 21 to 23 is used as a heat dissipation member that also serves as an insulating adhesive layer.
33. 32. A heat dissipation metal member-integrated electronic component structure in which a heat generating electronic component and a heat dissipation metal member are bonded using the heat dissipation member according to any one of 26 to 31.
34. 32. An LED circuit board on which the heat dissipating member according to any one of 26 to 31 is used.
35. An automobile using the circuit board according to 32 or 34 or the structure according to 32 or 33.
36. 34. An electrical product using the circuit board according to 32 or 34 or the structure according to 32 or 33.
37. 34. A signal illuminator using the circuit board according to 32 or 34 or the structure according to 32 or 33.
38. A display using the circuit board according to 32 or 34 or the structure according to 32 or 33.

The inorganic powder according to a preferred embodiment of the present invention can be filled in the resin material at a high density even when the sphericity and spheroidization ratio are low, thereby improving the heat dissipation performance and dielectric breakdown strength of the resin composition. It is possible.
Furthermore, since the resin thin film sheet using the inorganic powder in a preferred embodiment of the present invention has high withstand voltage characteristics, the resin composition, the resin thin film sheet having excellent heat conductivity, heat dissipation characteristics, and withstand voltage characteristics, It is also possible to provide a circuit board and a structure using them as heat dissipation members.
That is, the inorganic powder in a preferred embodiment of the present invention has a specific particle size distribution, is preferably controlled to an impurity concentration within a certain range, and more preferably is a powder subjected to surface hydrophobization treatment. In addition, it has the advantage that even a powder with low sphericity and high resin compound viscosity can be filled in a resin material, and by using this inorganic powder as one of the components, it has excellent thermal conductivity, And the resin composition which shows the outstanding withstand voltage characteristic at the time of film-forming of the thin film resin sheet of thickness 40-90 micrometers is obtained.

Therefore, if the resin composition according to a preferred embodiment of the present invention is used, a circuit board for mounting on an automobile, a circuit board for mounting on an electronic device, a heat dissipation member inside the electronic device, and an electronic component having excellent heat dissipation characteristics and withstand voltage characteristics The heat radiating member is obtained. In this case, the heat radiation member for the electronic component may be a sheet-like member that can also serve as an insulating adhesive layer.
In addition, if the resin composition according to a preferred embodiment of the present invention is used, when used as a heat radiating member that also serves as an insulating adhesive layer or the like, in a metal base circuit board, a metal core type circuit board, and a structure thereof. Also exhibits excellent functionality.

  Further, the resin composition filled with the inorganic powder in a preferred embodiment of the present invention is made into a paste or gel, and a heat radiation sealing material or heat radiation underlayer for an electronic component having a heat generating element portion found in an LED or the like. By applying it as a filling agent, etc., for example, LED circuit boards for indoor lighting, LED circuit boards for meter lighting and their structures, other electronic devices such as personal computers, DVDs and color printers, homes such as TVs, etc. Electronic devices, mobile electronic devices such as PDAs, mobile phones, large full-color display equipment for outdoor installation, signal lighting equipment, home lighting equipment, optical communication equipment, LED circuit boards used for medical / measuring equipment, and their Even when used in structures, it exhibits excellent functionality in terms of thermal conductivity and insulation. In particular, when applied to a heat dissipation / cooling application of a high-brightness LED substrate in which LED elements are integrated at high density, it exhibits excellent functionality and can be used effectively with a surface emitting sign. Thus, the heat radiating member in this invention contributes to the brightness improvement of a LED board.

  Using these heat radiating members, it is possible to form a heat radiating metal member-integrated electronic component structure in which a heat-generating electronic component and a heat radiating metal member are bonded, thereby improving the performance of various electronic devices. Can contribute.

Hereinafter, embodiments of the present invention will be described in detail.
The inorganic powder according to a preferred embodiment of the present invention has a specific particle size distribution, so that the resin material can be highly filled.

The inorganic powder in a preferred embodiment of the present invention preferably has a maximum particle size of 63 μm or less and an average particle size of 4 to 30 μm, more preferably 4 to 16 μm, and a mode diameter of 2 ˜35 μm is preferable, more preferably in the range of 7 to 20 μm, and the powder is preferably multimodal (that is, having two or more peaks) in the frequency particle size distribution. That is, it is preferable that the frequency particle size distribution has multimodality having peaks in the particle size ranges of at least 0.2 to 2 μm and 2 to 63 μm. The sphericity is preferably 0.68 to 0.95, more preferably 0.68 to 0.80, and the spheroidization ratio is preferably 0.63 to 0.95, more preferably 0. .63 to 0.77.
By making it multimodal, it is thought that more fine particles slide into the voids of coarse particles and the close packing is accelerated, and further, the close packing is promoted by having a frequency peak in the above particle size range. Is done.

  The particle component contained in the particle size range of 0.2 to 2 μm is preferably 0 to 25% by mass, more preferably 0 to 25% by mass, when the inorganic powder is 100% by mass. Is 0 to 11% by mass or 13 to 25% by mass, and the mode diameter is preferably in the range of 0.25 to 1.5 μm. The sphericity is preferably 0.5 to 0.95, more preferably 0.8 to 0.85, and the spheroidization rate is preferably 0 to 0.9, more preferably 0 to 0. .5.

  As a feature of the particle component contained in the particle size range of 2 to 63 μm, the ratio of particles having a particle diameter of 8 μm or more is preferably 44 to 90% by mass, and more preferably 48 to 86% by mass. The sphericity is preferably 0.7 to 0.95, more preferably 0.7 to 0.8, still more preferably 0.7 to 0.78, and the spheroidization ratio is preferably 0.7 to 0.9. More preferably, it is 0.7-0.75.

Furthermore, the ratio of the particles contained in the particle size range of 2 to 8 μm is preferably 0 to 15% by mass or 32 to 45% by mass, and more preferably 4 to 15% by mass or 34 to 45% by mass.
By mixing the inorganic powder so as to have such a particle size distribution, it is possible to obtain an inorganic powder having a high degree of filling even if the sphericity of the powder is low.

Examples of inorganic powders include aluminum oxide, aluminum nitride, crystalline silica, magnesia, boron nitride, silicon nitride, beryllia, silicon carbide, boron carbide, titanium carbide, diamond, etc. An inorganic powder having both conductivity (thermal conductivity) and insulation (volume resistivity) is used. Particularly preferably, an inorganic powder having a thermal conductivity of 30 W / m · K or more and a volume resistivity of 1 × 10 ¹⁴ Ω · cm or more in the case of a single crystal is used.
For example, aluminum oxide, aluminum nitride, magnesia, boron nitride, beryllia and the like can be employed as particularly preferable inorganic powders.

  In consideration of moisture resistance, chemical stability, and use safety, aluminum oxide and aluminum nitride are most preferable as the inorganic powder of the present invention, but aluminum oxide is preferable in consideration of economy. The inorganic powder can be used alone or as a mixture.

  As the aluminum oxide powder, spherical aluminum oxide powder obtained by sintering or electromelting Bayer method aluminum hydroxide as a raw material and passing through the spheroidizing step of the flame melting method, or Bayer method water is used. Low-soda fine aluminum oxide powder produced from aluminum oxide, ammonia alum pyrolysis method or aluminum alkoxide hydrolysis method, aluminum underwater discharge method, or high purity fine aluminum oxide powder produced by other methods are preferred, In particular, it is not limited to these.

The aluminum nitride powder is preferably an aluminum nitride powder produced by a method such as a direct nitriding method or a reduction nitriding method, but is not particularly limited thereto.
These aluminum oxides and aluminum nitrides can be used alone or as a mixture. Furthermore, a plurality of aluminum oxides and aluminum nitrides obtained by various manufacturing methods can be used in combination.

  The inorganic powder in a preferred embodiment of the present invention is preferably an alumina powder having an α-alumina crystal phase fraction measured by X-ray diffraction analysis of 30 to 75% by mass, more preferably in the range of 30 to 67% by mass. An alumina powder.

Furthermore, the inorganic powder in a preferred embodiment of the present invention is preferably an alumina powder having an α-alumina crystal phase fraction of 90 to 100% by mass, more preferably 95 to 99% by mass, in a powder having a particle size range of less than 2 μm. In addition, an alumina powder having an α-alumina crystal phase fraction of a powder having a particle size range of 8 μm or more is preferably 30 to 70% by mass, and more preferably 35 to 60% by mass.
By adjusting the α-alumina crystallization rate in such a range, it is possible to obtain an inorganic powder (alumina powder) having high thermal conductivity.

  The particle size distribution of the inorganic powder according to a preferred embodiment of the present invention can be obtained using a known particle size distribution measuring apparatus. For example, it is preferable to use a laser diffraction / scattering particle size measuring device, and the particle size distribution measuring device is measured by, for example, Microtrac HRA (manufactured by Nikkiso Co., Ltd.) or SALD-2000J (manufactured by Shimadzu Corporation). be able to. The refractive index of water is 1.33. For example, when the inorganic powder is an aluminum oxide powder, a value in the range of 1.77 to 1.8 may be used as the refractive index of the powder.

  The maximum particle size referred to in the present invention is a cumulative particle size of 100% in the cumulative particle size distribution of the inorganic powder, and the average particle size is the median size, and the cumulative value in the cumulative particle size distribution of the inorganic powder. 50% particle size. The mode diameter is the particle diameter showing the highest frequency value among the peaks in the frequency particle size distribution of the inorganic powder.

The sphericity referred to in the present invention indicates an average sphericity and can be determined by the following method. Particle images taken with a stereomicroscope or a scanning electron microscope are taken into an image analyzer or the like, and the projected area (a) and contour circumference L _(a) of an arbitrary particle are measured from a photograph, and L _(a) When the area of a perfect circle having the same contour circumference is (b),
(B) = π × (L _(a) / 2π) ²
It can be expressed as. Therefore, the sphericity can be calculated by the following formula.
Sphericality = (a) / (b) = (a) × 4π / (L _(a) ) ²
In this way, the sphericity of a certain number of particles can be obtained, and the average value can be used as the average sphericity. In this case, it is preferable to calculate using 200 or more particles.

In addition, as a method for measuring sphericity other than the above, from the circularity of individual particles quantitatively automatically measured by a particle image analyzer, for example, “FPIA-2100” (manufactured by Sysmex Corporation), etc. The sphericity can also be obtained by conversion using the following equation.
Sphericality = (roundness) ²

  The spheroidization rate referred to in the present invention is the number frequency ratio of sphericity 1.0 in so-called sphericity distribution. This can be obtained from the number frequency integration of the circularity of the particles quantitatively automatically measured by the above-described particle image analyzer or the like.

In addition to the above, as a method for obtaining the spheroidization rate, 5 μm or more in one field of view taken with a scanning electron microscope at a predetermined magnification (an arbitrary magnification of 150 to 1000 times) according to the size of the powder particles The total number of particles and the number of non-spherical particles can be counted and calculated by the following formula.
Spheroidization rate = (total number−number of non-spherical particles) / total number As for the counting method of non-spherical particles, a visual method for comparison using a judgment sample prepared in advance, a counting method using a known image analysis device, etc. Any method may be used.

The measurement of the α-alumina crystal phase fraction in the inorganic powder (alumina powder) is not particularly limited, and can be measured with a known powder X-ray diffractometer. The slit is 0.3 mm with CuKα rays, the scan speed is 1 degree / X-ray diffraction analysis was performed under the condition of a scan range of 2θ = 65 to 70 °, and the obtained 2θ = 68.2 ° peak (α alumina) height was set to A, 2θ = 67.3 ° peak ( Intermediate alumina) B is the height, C is the baseline value of 2θ = 69.5 degrees as the background,
α alumina crystal phase fraction = (AC) / ((AC) + (BC)) × 100
Can be obtained.

  The concentration of the metal aluminum component contained in the inorganic powder in a preferred embodiment of the present invention is preferably 0.05% by mass or less, more preferably 0 to 0.01% by mass. When an inorganic powder containing a large amount of metal aluminum component in the powder is used as a heat dissipation filler for an insulating layer, for example, a short circuit (dielectric breakdown) occurs between the circuit copper foil and the substrate when a high voltage is applied. This is because the possibility of being easily generated increases and the risk of destroying the circuit or device increases.

  The method for measuring the concentration of the metal aluminum component contained in the inorganic powder in a preferred embodiment of the present invention is not particularly limited and can be measured by any known inorganic analysis method, but the inorganic powder is acidified with hydrochloric acid. After the heat extraction treatment, it is preferable to measure hydrochloric acid-soluble components contained in the filtrate with an ICP (high frequency inductively coupled plasma) emission spectroscopic analyzer. The analyzer can be measured using, for example, ICPS-7500 (manufactured by Shimadzu Corporation).

  In the inorganic powder according to a preferred embodiment of the present invention, the concentration of sulfate ions contained in the powder is preferably 15 ppm or less, more preferably 5 ppm or less. For example, when using inorganic powder surface-treated with a silane coupling agent as a filler or when using a silicone-based material as an insulating resin compound, a siloxane bond is formed around the silanol group on the powder surface or on the silicone resin itself. This is because, as the concentration of sulfate ions in the powder is higher, the acid component promotes the breaking of the siloxane bond and the gas of low molecular siloxane is more likely to be generated. The splitting of the siloxane bond may cause a decrease in flexibility of the resin composition itself and a decrease in the strength of the bonding interface with the particles, and the low molecular weight siloxane is volatilized at a high temperature and in a sealed environment such as in a device. In some cases, the surface of the contact terminal is recrystallized as silica crystals. As a result, since this crystal becomes an electrical insulator and increases the possibility of causing problems such as contact failure, it is desirable that the amount of sulfate ion contained is as small as possible.

  In the inorganic powder according to a preferred embodiment of the present invention, the concentration of chlorine ions contained in the powder is preferably 15 ppm or less, more preferably 10 ppm or less. As with the above-mentioned sulfate ion, chlorine ion may cause degradation of resin characteristics and circuit contact failure due to siloxane bond breakage in the resin composition, and the acid component may cause corrosion damage to the insulating layer resin. In view of ensuring the reliability of the insulating resin compound and the circuit board, it is desirable that the chlorine ion concentration is as low as possible.

  The method for measuring the concentration of sulfate ion and chloride ion contained in the inorganic powder in the present invention is not particularly limited as long as it is a known separation analysis method effective for measuring the concentration of trace amounts of inorganic anions / cations and organic acids. Although it can be measured by either method, it is preferable to measure the water-soluble component in the solution by ion chromatography after boiling and extracting the inorganic powder with pure water. The analyzer can be measured using, for example, Shodex (manufactured by Showa Denko KK).

  The existence form of sulfate ions and chloride ions is not particularly limited, and it is assumed that some ions exist in a non-ion state, but sulfate ions and chloride ions in the present invention are extracted by boiling heating of inorganic powder with pure water. It can be defined as a component that is detected as sulfate ion or chloride ion by ion chromatography.

In the inorganic powder according to a preferred embodiment of the present invention, the concentration of the Fe ₂ O ₃ component contained in the powder is preferably 0.03% by mass or less, more preferably 0.005 to 0.015% by mass. The higher the content concentration of the Fe ₂ O ₃ component present in the powder, the higher the possibility of a short circuit between the circuit copper foil and the substrate as in the case of the metal Al described above. In order to ensure reliability, it is desirable that the concentration be as low as possible.

The method for measuring the concentration of the Fe ₂ O ₃ component contained in the inorganic powder in a preferred embodiment of the present invention is not particularly limited and can be measured by any known inorganic analysis method, but phosphoric acid is added to the inorganic powder sample. After the addition, it is preferable to measure the components contained in the solution subjected to the decomposition treatment with the microwave acid decomposition apparatus with an ICP emission spectroscopic analysis apparatus. The analyzer can be measured using, for example, ICPS-7500 (manufactured by Shimadzu Corporation) in the same manner as the metal aluminum component.
The inorganic powder in a preferred embodiment of the present invention preferably contains substantially no particles of less than 50 nm. When the fine particles of less than 50 nm are present more than necessary, when the inorganic powder is filled, the viscosity of the resin compound is remarkably increased, which may impair the characteristics of the inorganic powder having a high filling degree. In that sense, it is preferable that the inorganic powder in a preferred embodiment of the present invention does not contain such fine particles.

  The fact that particles of less than 50 nm are not substantially contained in the inorganic powder means that the number of particles less than 50 nm is counted in an arbitrary photograph of 100 or more fields taken at a magnification of 50,000 times with a scanning electron microscope, It means that the value converted as an average value per view of a photograph is less than about 50. The number of particles of less than 50 nm is preferably smaller, but when the average number of particles is 50 or more, the effect of the present invention is not lost suddenly. It is a value.

  The inorganic powder used in a preferred embodiment of the present invention is preferably a powder subjected to a surface hydrophobization treatment with a silane coupling agent or a titanate coupling agent, and the method for performing the surface hydrophobization treatment is particularly limited. However, there are known methods such as a dry method using a stirring mixer having a shearing force, a wet slurry method in which a dispersion treatment is performed in an aqueous or organic solvent system, and a spray method using a fluid nozzle.

  In carrying out these surface hydrophobizing treatments, care should be taken so that the shape of the powder does not break in the case of a method involving a stirring force, and the conditions such as the stirring time are applied to the surface hydrophobizing treatment. What is necessary is just to determine suitably according to the particle size of powder, the kind of silane coupling agent or titanate coupling agent, and the target characteristic of powder.

  Although it does not specifically limit about the silane coupling agent used for the surface hydrophobization process, For example, epoxy-type silanes, such as (beta)-(3,4-epoxycyclohexyl) ethyltrimethoxysilane, (gamma) -glycidoxypropyl trimethoxysilane, Amino-based silanes such as γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, and ureidopropyltriethoxysilane are preferable, Or it can be used in plural. What is necessary is just to select in consideration of the adhesiveness and dispersibility of the resin component which comprises an insulating layer etc., and inorganic powder.

  Similarly, the titanate coupling agent is not particularly limited. For example, tetra (2,2-diallyloxymethyl-1-butyl) -bis (ditridecyl-phosphite) titanate, tetraoctyl-bis (ditridecyl-phosphite). Titanate, tetraisopropyl-bis (ditridecyl-phosphite) titanate, bis (dioctyl pyrophosphate) -oxyacetate titanate, isopropyltri (N-aminoethylaminoethyl) titanate, isopropyltriisostearoyl titanate, isopropyltri-i- Dodecylbenzene-sulfonyl titanate, isopropyl tri-n-dodecylbenzene-sulfonyl titanate, isopropyl-tri (dioctyl pyro-dioctyl pyro-phosphate) Titanate, bis (dioctyl pyrophosphate) -ethylene titanate, isopropyl tricumylphenyl titanate, dicumylphenyloxyacetate titanate, etc. are preferable, considering the adhesiveness and dispersibility of the resin component constituting the insulating layer and the inorganic powder. To be selected.

  Specific examples of the organic polymer (resin) used as the matrix of the resin composition filled with the inorganic powder in a preferred embodiment of the present invention include epoxy resin, polyimide resin, silicone resin, polyethylene, polypropylene, polystyrene, and the like. Polyolefin, melamine resin, urea resin, phenolic resin, polyethylene terephthalate, polyester such as unsaturated polyester, nylon 6, nylon 66, polyamide such as aramid, polybutadiene, polyester, polyvinyl chloride, polyvinylidene chloride, polyethylene oxide, polyethylene glycol, Polyvinyl alcohol, vinyl acetal resin, polyacetate, ABS resin, vinyl acetate resin, cellulose, rayon and other cellulose derivatives, polyurethane, Polycarbonate, urea resin, fluororesin, polyvinylidene fluoride, celluloid, chitin, starch sheet, acrylic resin, known resins such as alkyd resins, and mixtures thereof are preferred, not particularly limited thereto. These can be used alone or in plural.

  Among these, it is particularly preferable to use an epoxy resin or a polyimide resin that has a relatively strong adhesive force with a metal plate or metal foil and a relatively high affinity with the inorganic powder. Moreover, a hardening accelerator etc. can also be used for the above-mentioned resin composition as needed.

  The curing accelerator is not particularly limited as long as it can be cured by reacting with a resin to be used. For example, known accelerators that react and cure with an epoxy resin include phenol, cresol, imidazole, xylenol, resorcinol, Chlorophenol, t-butylphenol, nonylphenol, isopropylphenol, bisphenol compounds such as bisphenol A and bisphenol S, and acid anhydrides such as maleic anhydride are preferred, and may be selected in consideration of reactivity with the resin material used. .

  The kneading / filling method of the resin composition in the present invention is not particularly limited, but it is preferable to uniformly knead using a centrifugal kneader, a revolutionary rotary kneader, a roll mill, a Banbury mixer, a kneader, or the like. It is more preferable to knead while removing bubbles in the resin composition using an apparatus to which a defoaming effect is added.

  The film formation method of the resin composition in a preferred embodiment of the present invention is not particularly limited, but it is preferable to use a doctor blade method, an extrusion method, a press method, a calender roll method, or the like depending on the resin compound viscosity.

  The evaluation of the resin compound viscosity, which is an index indicating the fluidity of the inorganic powder in a preferred embodiment of the present invention, and the withstand voltage characteristic evaluation of the resin composition filled with the powder and formed into a thin film sheet are described in the examples. It can be performed by an evaluation method.

  The inorganic powder in a preferred embodiment of the present invention has a specific particle size distribution, and more preferably a powder having low sphericity and high resin compound viscosity due to the effect of being subjected to surface hydrophobization treatment. Even so, the resin component can be highly filled. By using such an inorganic powder as one of the components, a resin composition having excellent heat resistance and excellent withstand voltage characteristics when a thin film resin sheet having a thickness of 40 to 90 μm is formed can be obtained. It is done.

  Furthermore, if the resin composition using the inorganic powder in a preferred embodiment of the present invention is used, a circuit board for mounting on an automobile, a circuit board for mounting on an electronic device, a heat radiating member inside the electronic device, an electronic component by a known method It becomes possible to make it a heat radiating member. Further, the heat dissipation member for the electronic component may be a sheet-like member that can also serve as an insulating adhesive layer, and may be a metal base circuit board, a metal core type circuit board, or a structure thereof. (For example, electronic technology special issue in December 1985, pages 39-50, Circuit Technology, Vol. 5, No. 2, pages 96-103 (1990)).

Moreover, it is also possible to employ a known method to obtain a structure of a heat dissipation metal member integrated electronic component in which the heat generating electronic component and the heat dissipation metal member are bonded.
Further, the resin composition filled with the inorganic powder in a preferred embodiment of the present invention is made into a paste or gel, and a heat radiation sealing material or heat radiation underfill for an electronic component having a heat generating element portion found in an LED or the like. By applying as an agent, it is also possible to make LED circuit boards and their structures.

  In this case, for example, a vehicle-mounted indoor lighting LED circuit board, a meter lighting LED circuit board and their structures, other electronic devices such as personal computers, DVDs, color printers, household electronic devices such as TVs, PDAs, Used for mobile electronic devices such as mobile phones, large full-color display equipment for outdoor installation, signal lighting equipment, home lighting equipment, optical communication equipment, LED circuit boards and their structures used in medical and measuring equipment applications, etc. For example, it exhibits excellent functionality in terms of thermal conductivity and insulation, and is useful for improving the performance of electronic devices. In particular, when applied to a heat dissipation / cooling application of a high-intensity LED substrate in which LED elements are integrated at a high density, it exhibits excellent functionality and can be used effectively with a surface emitting sign. Thus, the heat radiating member in the preferable embodiment of the present invention can contribute to the improvement of the luminance of the LED substrate.

  In addition, it is possible to form a heat dissipation metal member-integrated electronic component structure in which a heat-generating electronic component and a heat dissipation metal member are bonded by using the heat dissipation member in a preferred embodiment of the present invention. It can contribute to high performance of equipment.

  Hereinafter, although an example and a comparative example explain the present invention concretely, the present invention is not limited to these examples.

Examples 1-8:
Aluminum oxide having a particle size distribution condition adjusted as shown in Table 1 after surface hydrophobization treatment in advance using γ-glycidoxypropyltrimethoxysilane (A-187; manufactured by Nihon Unicar Co., Ltd.) as a silane coupling agent Powders A, B, C, D, E, F, G, and H were prepared.
After kneading and filling the resin composition under predetermined conditions, a film was formed by a doctor blade method so that the film thickness after drying and curing was about 60 μm or less.
With respect to the thin film resin sheet dried and cured under predetermined drying conditions, each dielectric breakdown strength was measured. The dielectric breakdown strength was measured based on the dielectric breakdown voltage test method specified in JISC2110. The epoxy resin viscosity was measured as the resin compound viscosity evaluation for the aluminum oxide powders listed in Table 1.
As shown in Table 1, in the case of a sphericity powder having an average sphericity of less than 0.89, the viscosity of the epoxy resin is 1000 to 1400 P, and the dielectric breakdown strength is 67 to 93 kV / mm at a film thickness of 45 to 55 μm. (Examples 5 to 8), even when the low sphericity powder having a sphericity of less than 0.81 and the viscosity becomes higher as the epoxy resin viscosity becomes 5000 P or more, the film thickness 44 is increased. A dielectric breakdown strength of 39 to 78 kV / mm could be obtained at ˜53 μm (Examples 1 to 4).

  The powder and resin component kneading / filling conditions, film forming / drying conditions, sheet withstand voltage measuring method, and epoxy resin viscosity measuring method in preparing the thin film resin sheet are shown below.

(1) Kneading and filling conditions of powder and resin component Powder: 25 g
Resin: Epoxy resin compound 10g
Curing agent: 0.1 g of imidazole
The above mixture was kneaded using a revolutionary rotation mixing type defoaming kneader (AR-250, manufactured by Shinky Corporation) under conditions of kneading time of 5 minutes and defoaming time of 1 minute.

(2) Film formation / drying conditions The kneaded slurry is formed by the doctor blade method using an automatic film applicator (manufactured by Sepro Co., Ltd.) and a blade edge (75 μm), then immediately in a constant temperature and constant temperature drier. After drying at 40 to 50 ° C. for 30 or more, it was dried in three stages of 120 ° C. for 15 minutes and 180 ° C. for 30 minutes.

(3) Dielectric breakdown strength measurement method Using a withstand voltage tester (TOS-8870A type, manufactured by Kikusui Electronics Co., Ltd.), the dielectric breakdown voltage described in JIS C2110 is applied to the thin film resin sheet obtained by drying. It measured by the method based on the test method.

(4) Method for measuring viscosity of epoxy resin After kneading 250 parts by mass of powder and 100 parts by mass of epoxy resin (epoxy resin AER-250 manufactured by Asahi Kasei Co., Ltd.) and adjusting the temperature to 25 ° C. in a constant temperature water bath. The viscosity was measured with a BH viscometer.
(5) Concentration measurement of metallic aluminum component After the inorganic powder was subjected to an acid heating extraction treatment with hydrochloric acid, the hydrochloric acid-soluble component contained in the filtrate was measured with an ICP (high frequency inductively coupled plasma) emission spectroscopic analyzer. As an analyzer, ICPS-7500 (manufactured by Shimadzu Corporation) was used.
(6) Concentration measurement of sulfate ion and chloride ion After subjecting the inorganic powder to boiling heat extraction treatment with pure water, the water-soluble component in the solution was measured by ion chromatography. As the analyzer, Shodex (manufactured by Showa Denko KK) was used.
(7) After addition of phosphoric acid to the concentration measuring inorganic powder sample of Fe ₂ O ₃ component was measured component contained in the solution were decomposed with microwave acid decomposition apparatus by ICP emission spectrophotometer. The analyzer was measured using ICPS-7500 (manufactured by Shimadzu Corporation) in the same manner as the metal aluminum component.

Comparative Examples 1-4:
After filling the aluminum oxide powders I, J, K, and L shown in Table 2 into the resin components in the same procedure and conditions as in the examples, a thin film resin sheet was formed and the dielectric breakdown strength was measured. The epoxy resin viscosity was measured for each powder.
As shown in Table 2, the film thickness was 47 to 50 μm and the dielectric breakdown strength was 28 to 32 kV / mm.

Reference example 1:
As an example when the aluminum oxide powder has a very high sphericity, 20 masses of aluminum oxide powder I (manufactured by Admatechs, spherical aluminum oxide “Admafine (registered trademark) AO-502” shown in Table 3) %, “Admafine (registered trademark) AO-509” mixed at a ratio of 80 mass%).
After forming a thin film resin sheet by the same method as in the examples, the dielectric breakdown strength was measured, and the epoxy resin viscosity of the powder was measured.
As shown in Table 3, in the case of commercially available high sphericity powder, the epoxy resin viscosity was as low as 1080 P, and it was confirmed that a dielectric breakdown strength of 39 kV / mm was obtained at a film thickness of 55 μm.

Claims (38)

  An inorganic powder which is a powder having a multimodal frequency particle size distribution and having a frequency peak in a particle size range of at least 0.2 to 2 μm and 2 to 63 μm.   The inorganic powder according to claim 1, wherein the maximum particle size is 63 µm or less, the average particle size is in the range of 4 to 30 µm, and the mode diameter is in the range of 2 to 35 µm.   The inorganic powder according to claim 1, wherein the proportion of particles having a particle diameter of less than 2 µm is 0 to 20% by mass, and the mode diameter of particles having a particle diameter of less than 2 µm is in the range of 0.25 to 1.5 µm.   The inorganic powder according to claim 1, wherein the proportion of particles having a particle diameter of 8 µm or more is 44 to 90 mass%.   The inorganic powder according to claim 1, wherein the proportion of particles having a particle size range of 2 to 8 μm is 0 to 15% by mass.   The inorganic powder according to claim 1, wherein the proportion of particles having a particle size range of 2 to 8 µm is 32 to 45 mass%.   The inorganic powder according to claim 1, having a sphericity of 0.68 to 0.95 and a spheroidization ratio of 0.63 to 0.95.   The inorganic powder according to claim 1, wherein the particles having a particle diameter of less than 2 µm have a sphericity of 0.5 to 0.95 and a spheroidization ratio of 0 to 0.9.   2. The inorganic powder according to claim 1, wherein particles having a particle diameter of 8 μm or more have a sphericity of 0.7 to 0.95 and a spheroidization ratio of 0.7 to 0.95.   The inorganic powder according to claim 1, wherein the thermal conductivity of the inorganic powder is 30 W / m · K or more in the single crystal state.   The inorganic powder according to claim 1, wherein the inorganic powder is an alumina powder.   The inorganic powder according to claim 11, wherein the α-alumina crystal phase fraction is in the range of 30 to 75 mass%.   The inorganic powder according to claim 11, wherein the α-alumina crystal phase fraction of particles less than 2 μm is in the range of 90 to 100 mass%.   The inorganic powder according to claim 11, wherein the α-alumina crystal phase fraction of particles of 8 μm or more is in the range of 30 to 70 mass%.   The inorganic powder according to claim 1, wherein the content of metal Al is 0.05% by mass or less.   The inorganic powder according to claim 1, wherein the content of sulfate ions is 15 ppm or less.   The inorganic powder according to claim 1, wherein the chloride ion content is 15 ppm or less. The inorganic powder according to claim 1, wherein the content of Fe ₂ O ₃ is 0.03% by mass or less.   The inorganic powder according to claim 1, which contains substantially no particles of less than 50 nm.   The inorganic powder according to claim 1, wherein the surface is hydrophobized with a surface treatment agent selected from a silane coupling agent and a titanate coupling agent.   The resin composition with which the inorganic powder of any one of Claims 1 thru | or 20 is filled.   The resin composition according to claim 21, wherein the inorganic powder is filled in an amount of 50 to 90% by mass.   The dielectric breakdown strength measured by a dielectric breakdown voltage test specified in JIS C2110 is 39 kV / mm or more when the resin composition is a thin-film insulating resin composition having a film thickness of 40 to 90 μm. Or the resin composition of 22.   24. A circuit board for mounting on an automobile using the resin composition according to any one of claims 21 to 23.   24. A circuit board for mounting on electronic equipment using the resin composition according to any one of claims 21 to 23.   24. A heat dissipating member installed inside an electronic device, using the resin composition according to any one of claims 21 to 23.   A heat dissipating member for electronic parts using the resin composition according to any one of claims 21 to 23.   The heat dissipating member according to claim 26 or 27, wherein the heat dissipating member is in a sheet form.   The heat dissipating member according to claim 26 or 27, which is in a paste form or a gel form.   28. The heat dissipating member according to claim 26 or 27, which is an underfill agent type member.   28. The heat radiating member according to claim 26 or 27, wherein the heat radiating member is a type of heat radiating member applied to a heat generating portion of the element portion.   A metal base circuit board, a metal core type circuit board, or a structure using these boards, wherein the resin composition according to any one of claims 21 to 23 is used as a heat radiating member also serving as an insulating adhesive layer. .   A heat dissipation metal member-integrated electronic component structure in which a heat-generating electronic component and a heat dissipation metal member are bonded using the heat dissipation member according to any one of claims 26 to 31.   An LED circuit board on which the heat dissipating member according to any one of claims 26 to 31 is used.   An automobile using the circuit board according to claim 32 or 34 or the structure according to claim 32 or 33.   An electrical product using the circuit board according to claim 32 or 34 or the structure according to claim 32 or 33.   A signal illuminator using the circuit board according to claim 32 or 34, or the structure according to claim 32 or 33. A display using the circuit board according to claim 32 or 34 or the structure according to claim 32 or 33.