JP2014031484A - Insulation properties heat conduction filler dispersion composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulation properties heat conduction filler dispersion composition that can combine thermal conductivity and insulation properties, and to provide a production method of an insulation properties heat conduction polyimide resin composition in which the insulation properties heat conduction filler dispersion composition is used, and thereby high breakdown voltage can be obtained; an insulation film; a metal radiator plate; and a metal base circuit board.SOLUTION: An insulation properties heat conduction filler dispersion composition includes: a polyamic acid; an insulation properties heat conduction filler; and a solvent, wherein the polyamic acid is obtained by reacting biphenyltetracarboxylic acid dianhydride and diaminodiphenyl ether, the insulation properties heat conduction filler comprises aluminium nitride in which a surface is coated by aluminium nitride or aluminum oxide, a specific surface is 1.5-5 m/g, a content of the insulation properties heat conduction filler is 35-70 vol.%, and the insulation properties heat conduction filler is subjected to homogeneous dispersion so that a volume average particle diameter may become 1-8 μm, dmay become at least 0.5 μm and dmay become at most 15 μm.

Description

The present invention relates to an insulating thermally conductive filler dispersion composition capable of achieving both thermal conductivity and insulating properties. Moreover, it is related with the manufacturing method of an insulating heat conductive polyimide resin composition which can obtain a high dielectric breakdown voltage using this insulating heat conductive filler dispersion composition, an insulating film, a metal heat sink, and a metal base circuit board.

In recent years, output energy required for power conversion devices has increased, and reduction of energy loss when converting and controlling electric energy has become an important issue in the future.
Inverter circuit boards are often used not only for general-purpose units and inverters, but also for hybrid vehicles that are spreading as environmentally-friendly vehicles, electric vehicles that are next-generation environmentally friendly, and fuel cells. In various fields such as the liquid crystal field and the lighting field, the use of a high power LED substrate or the like is being studied.

Along with high-density mounting, circuit boards used in these applications need to have high thermal conductivity and excellent electrical insulation characteristics against high voltages in order to improve the heat dissipation of the heat generated from the element. It is said that.
For this reason, attempts have been made to use a high thermal conductive material in which a high thermal conductive filler is dispersed in polyimide having stable physical properties even under high temperature conditions as a metal base printed circuit board application that is widespread in the electronics industry.

However, even with such a high thermal conductivity material, the level of the required conduction characteristics in recent years (thermal conductivity: 1.0 W / (m · k), thermal diffusivity conversion with polyimide: 4 × 10 ⁻⁷ In order to obtain (m ² / S)), it is necessary to add 35% by volume or more of a high thermal conductive filler. As a result, the strength of the product obtained by using such a high thermal conductive material and the insulation are reduced. Also, when used as a sheet as well as when used as a circuit board, in addition to the load and strain at the time of circuit formation, there is a problem that the resin material is destroyed due to dielectric breakdown due to drive voltage at the time of actual use. It was happening.

On the other hand, materials for achieving both thermal conductivity and insulation have been studied. For example, Patent Document 1 discloses a heat transistor such as a power transistor, a thyristor, a rectifier, a transformer, and a power MOS FET. As a heat-dissipating fin or an insulating heat-dissipating sheet to be attached to the heat-dissipating plate, a cured product obtained by mixing a highly heat-conductive material in a silicone rubber that has insulating properties and high heat resistance is used. When used under these high temperature conditions, the silicone rubber deteriorates due to the influence of impurities in the high heat conductive material, and there is a drawback that the insulating properties are impaired over time.

Patent Document 2 describes that a polyimide composition excellent in thermal conductivity is obtained by containing 60% by weight or more of a boron nitride filler of 1.0 μm or less. In addition, in order to solve the problem of dispersibility and filler crystallinity, it is described that a boron nitride filler having a specific surface area of ² to 50 m ² / g is used.
However, in the method described in Patent Document 2, since volume change due to an imidization reaction during molding and a strain relaxation effect during operation are small, a decrease in withstand voltage physical properties and strength due to interfacial peeling between filler resins becomes a problem. .
Furthermore, when the filler described in Patent Document 2 is used, a sufficient heat conduction path and a physically stable interface cannot be secured, and a large amount is required to obtain the required level of heat conductivity. It was necessary to add the filler. As a result, the interface between the filler and the resin increases, and the probability of occurrence of interfacial peeling increases, so that there is a problem that sufficient electrical insulation cannot be realized.

Patent Document 3 describes an adhesive composition containing a filler as a material having both adhesive strength and thermal conductivity, and describes that an aluminum nitride-containing material is used as an example of the filler. Yes.
However, the epoxy resin and acrylyl resin described in Patent Document 3 have a problem in durability under a high temperature condition of 200 ° C. or more, and in general polyimide, the interface between the polyimide resin and the filler becomes unstable. There is a problem in that the electrical insulation is lowered.

Patent Document 4 describes a heat conductive polyimide film material in which a heat conductive filler is dispersed in various polyimide resins, and in the examples, it was possible to realize insulation exceeding 197 kV / mm as a dielectric strength. Have been described.
However, even the configuration of Patent Document 4 has a problem that the required thermal conductivity and sufficient electrical insulation cannot be obtained.

Japanese Patent Publication No. 7-7605 JP-A-10-87990 JP 2003-206469 A JP 2006-169534 A

In view of the above-mentioned present situation, the present invention is to provide an insulating heat conductive filler dispersion composition capable of achieving both heat conductivity and insulating properties. Also provided are a method for producing an insulating heat conductive polyimide resin composition capable of obtaining a high dielectric breakdown voltage, an insulating film, a metal heat sink, and a metal base circuit board using the insulating heat conductive filler dispersion composition. For the purpose.

The present invention is an insulating heat conductive filler dispersion composition comprising a polyamic acid, an insulating heat conductive filler, and a solvent, wherein the polyamic acid reacts with biphenyltetracarboxylic dianhydride and diaminodiphenyl ether. The insulating heat conductive filler is made of aluminum nitride or aluminum nitride whose surface is coated with aluminum oxide, and has a specific surface area of 1.5 to ⁵ m ² / g, and the insulating heat conductive filler The insulating heat conductive filler is uniform so that the volume average particle diameter is ₁ to 8 μm, d ₁₀ is 0.5 μm or more, and d ₉₀ is 15 μm or less. It is the insulating heat conductive filler dispersion composition currently disperse | distributed.
The present invention is described in detail below.

As a result of intensive studies, the present inventors have used a specific polyamic acid as a polyimide resin as a matrix constituting the insulating heat conductive filler dispersion composition and using an insulating heat conductive filler having a specific shape. The present invention has found that an insulating thermal conductive filler dispersion composition that can suppress interfacial delamination between matrix and filler, and as a result, can achieve high thermal conductivity and sufficient electrical insulation at the same time. The invention has been completed.

The insulating thermally conductive filler dispersion composition of the present invention contains a polyamic acid obtained by reacting biphenyltetracarboxylic dianhydride with diaminodiphenyl ether.
Since the polyimide resin obtained by the polyamic acid is non-thermoplastic, there is little change in physical properties when used at high temperatures. In addition, the volume change during dehydration condensation during the imidization reaction of the polyamic acid is small, and the crystalline structure has a flexible bond in the molecular structure, so that the shrinkage stress during molding accompanied by the imidization reaction is also small.
By having these characteristics, it becomes possible to absorb the stress at the time of molding by a flexible bond in the molecular structure, and since the strain acting on the interface between the resin and the filler is reduced, the interface peeling is suppressed, It is considered that excellent withstand voltage physical properties (electrical insulation) can be realized.

Examples of the biphenyltetracarboxylic dianhydride include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (s-BPDA) and 2,3,3 ′, 4′-biphenyltetracarboxylic acid. Dianhydride (a-BPDA), 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride (i-BPDA), biphenyltetracarboxylic dianhydride blended with two or more of the above Can be used.

Specific examples of the diaminodiphenyl ether include 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, and 3,4′-diaminodiphenyl ether.
Since these diaminodiphenyl ethers have two phenylene rings connected by an ether bond, there is little volume reduction due to dehydration reaction at the time of imidization with respect to a constant molecular weight. It is difficult to occur and high withstand voltage characteristics can be realized.
In addition, since the strain can be flexibly absorbed by the ether bond in the molecule, the interfacial peeling between the resin and the filler can be effectively suppressed.

The mixing ratio of the biphenyltetracarboxylic dianhydride and diaminodiphenyl ether in the reaction may be approximately equimolar. Here, “substantially equimolar” specifically means that 0.8 to 1.2 mol of diaminodiphenyl ether is used per 1 mol of biphenyltetracarboxylic dianhydride. Preferably 0.9 to 1.1 mol, more preferably 0.99 to 1.01 mol is used.

Examples of the reaction between the biphenyltetracarboxylic dianhydride and diaminodiphenyl ether include a polycondensation reaction.
As the polycondensation reaction, a known method can be employed, for example, a solution containing diaminodiphenyl ether and amidated by adding biphenyltetracarboxylic dianhydride at room temperature (about 15 to 30 ° C.). The method of preparing an acid solution is mentioned.

The polyimide resin is particularly preferably obtained by reacting biphenyltetracarboxylic dianhydride and diaminodiphenyl ether in an organic polar solvent.

The organic polar solvent is preferably an aprotic organic polar solvent such as N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”), N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, hexamethylphosphoamide, 1,3-dimethyl-2-imidazolidinone and the like are used. One or two or more of these solvents may be used. In particular, NMP is preferable.

The polyamic acid preferably has a weight average molecular weight of 3000 to 30000.
When the weight average molecular weight is less than 3,000, oligomeric molecules do not have an entanglement effect with internal molecules, resulting in the formation of a fragile layer on the surface of the thermally conductive polyimide composition. When the weight average molecular weight exceeds 30000, the molecular chain is entangled and the viscosity becomes high. As a result, a large amount of solvent is required to adjust the viscosity so that the filler can be dispersed, and the molding cost may increase. More preferably, it is 6000-25000.
In addition, adjustment of the weight average molecular weight of the said polyamic acid can be performed by a well-known method.
The weight average molecular weight can be measured by the GPC method (solvent: NMP, converted to polyethylene oxide).

The insulating heat conductive filler dispersion composition of the present invention contains a predetermined insulating heat conductive filler.
By using such an insulative heat conductive filler, the physical interaction (anchor effect) between the polyimide resin and the insulative heat conductive filler is increased, and molding shrinkage strain during imidization reaction and bending during use -Interfacial peeling can be suppressed against compressive strain. As a result, it is presumed that an insulating heat conductive filler dispersion composition having both excellent heat conductivity and insulating properties can be obtained.

The insulating heat conductive filler is made of aluminum nitride whose surface is coated with aluminum nitride or aluminum oxide.
As a commercial item of the insulating heat conductive filler which consists of said aluminum nitride, Shapepal (made by TOKYAMA), TOYALNITE (made by Toyo Aluminum Co., Ltd.) etc. are mentioned, for example.

Examples of the aluminum nitride whose surface is coated with the aluminum oxide include H grade and F grade of Shapel (manufactured by TOKYAMA).
In addition, as a commercial item of the said aluminum oxide, the Nippon Steel Materials company make, the Micron company make, the electrochemical industry company thing, etc. can be used, for example.

The insulating heat conductive filler is aluminum nitride having a Si—Al—O—N layer formed on the surface, or aluminum nitride surface-treated with an organosilicon coupling agent or a titanate and aluminate coupling agent. It is preferable that

Examples of aluminum nitride on which the Si—Al—O—N layer is formed include TOYALNITE Super FL series (manufactured by Toyo Aluminum Co., Ltd.).

Aluminum nitride surface-treated with the above organosilicon coupling agent or titanate and aluminate coupling agent includes, for example, aminosilane coupling agents (trade names: KBM503, KBE903, etc., manufactured by Shin-Etsu Chemical Co., Ltd.), aluminate It is obtained by treating the surface by a known method using a system coupling agent (trade name: Preneact, manufactured by Ajinomoto Fine Techno Co., Ltd.) and a titanate coupling agent.

The insulating heat conductive filler has a specific surface area of 1.5 to ⁵ m ² / g.
When the specific surface area is less than 1.5 m ² / g, it is confirmed that the dielectric breakdown voltage decreases. This is because the physical interaction between the filler and the polyimide interface is weak. This is presumably because fine voids are generated at the filler-polyimide interface due to residual stress due to sedimentation of the resin and shrinkage of the imidization reaction.
On the other hand, even when the specific surface area exceeds 5 m ² / g, it has been confirmed that the dielectric breakdown voltage decreases. This is because the irregularities on the filler surface are fine and large, and therefore the insulating heat conductive filler dispersion composition. This is probably because sufficient wetting between the filler interface and the polyamic acid solution cannot be obtained, and as a result, many voids are generated at the filler-imide interface in the insulating resin after imidization.
The specific surface area of the insulating heat conductive filler is preferably ^{2 to} 4.5 m ² / g. By setting it in this range, the filler and imide interface in the imidization process becomes a strong continuous layer due to the physical interaction such as the anchor effect, and the uneven distribution of filler due to sedimentation is also reduced. A heat transfer network can be formed.
In addition, the said specific surface area can be measured by the specific surface area measurement principle by BET method. Examples of the measuring apparatus include SA3100 (manufactured by Beckman Coulter), Flowsorb (manufactured by Shimadzu Corporation), and the like.

The insulating heat conductive filler preferably has a volume average particle diameter of 1 to 8 μm.
When the volume average particle size is less than 1 μm, the dielectric breakdown voltage is lowered, and it is difficult to form a heat transfer network using an insulating heat conductive filler, so that it is difficult to obtain sufficient heat conduction characteristics. May be.
When the volume average particle diameter exceeds 8 μm, the precipitation in the polyamic acid is severe, and the dielectric breakdown voltage decreases due to the uneven distribution of the filler in the thickness direction. In the polyimide film after the imidation reaction, the free surface However, it may be difficult to make full use of the thermal conductivity characteristics of the polyamic acid.
In addition, the said volume average particle diameter can be measured with a commercially available particle size distribution measuring apparatus (The Nikkiso Co., Ltd. make, Nanotrac UPA series, MP3000II series etc.).

Since the relationship between the volume average particle diameter and the specific surface area is a shape close to a perfect sphere when the relationship of the following formula (1) is satisfied, in order to obtain a material having an isotropic heat conduction direction, the following formula ( It is preferable to select a heat conductive filler close to the relational expression 1).
In the formula (1), Sv represents a specific surface area (m ² / g), D represents a diameter (m), and ρ represents a density (g / m ³ ).
Sv = 6 / (D · ρ) (1)

Content of the said insulating heat conductive filler in the insulating heat conductive filler dispersion composition of this invention is 35-70 volume%.
If the content is less than 35% by volume, the thermal conductivity required as a heat dissipation material cannot be obtained, and if it exceeds 70% by volume, sufficient insulation cannot be obtained and the dielectric breakdown voltage decreases.
Preferably it is 35-65 volume%, More preferably, it is 35-60 volume%.
In addition, since the heat conductivity is obtained by a heat transfer network between fillers, the content is defined by the volume fraction.

In the insulating heat conductive filler dispersion composition of the present invention, the insulating heat conductive filler is uniformly dispersed so that the volume average particle diameter is ₁ to 8 μm, d ₁₀ is 0.5 μm or more, and d ₉₀ is 15 μm or less. ing. This eliminates the problems caused by the presence of insulating thermal conductive fillers in the range where the center particle size is within the specified range, which is far outside the specified range. Insulating properties with both insulating properties and high thermal conductivity It becomes a heat conductive filler dispersion composition.

The insulating heat conductive filler is uniformly dispersed with a volume average particle diameter of 1 to 8 μm. By being uniformly dispersed with such a volume average particle diameter, the filler is evenly dispersed in the matrix. Since a heat conduction network can be formed, an insulating / high heat conduction film having both insulation and heat conductivity is obtained.
When the volume average particle diameter is less than 1 μm, the dielectric breakdown voltage is lowered, and it is difficult to form a heat transfer network with an insulating heat conductive filler, and it is difficult to obtain sufficient heat conduction characteristics. In addition, since an air gap is generated between the filler and the matrix, the insulating property is also lowered.
Even when the volume average particle diameter exceeds 8 μm, the dielectric breakdown voltage decreases, the unevenness of the free surface is severe, the contact resistance with the heat radiation partner material increases, and the heat conduction characteristics of the polyamic acid can be fully utilized. It becomes difficult.
Moreover, it is preferable that it is uniformly dispersed by 2-7 micrometers.
In addition, the said volume average particle diameter can be measured with a commercially available particle size distribution measuring apparatus (The Nikkiso Co., Ltd. make, Nanotrac UPA series, MP3000II series etc.).

The insulating thermally conductive filler is a _{d 10} is 0.5μm or more is a particle size of 10 vol% in the particle size distribution, and, _{d 90} is 15μm or less a particle size of 90% by volume.
When the d ₁₀ is less than 0.5 [mu] m, the variation of the breakdown voltage can be obtained a stable insulating material for greater difficult.
On the other hand, when the d ₉₀ exceeds 15 μm, the dielectric breakdown voltage decreases.
The d ₁₀ is preferably 0.5 to 1 μm. Further, the _{d 90} is preferably 12～15Myuemu.
Incidentally, the _{d 10} and _{d 90} may be measured by commercially available particle size distribution measuring apparatus similar to the volume average particle diameter (manufactured by Nikkiso Co., Ltd., Nano Truck UPA series and MP3000II series, etc.).

The insulating heat conductive filler dispersion composition of the present invention preferably has a viscosity of 0.5 to 35 Pa · s measured at 25 ° C. using a rotational viscometer. In addition, the said viscosity can be measured, for example in TVE-33H using 3 degrees xR9.7 cone rotor (made by Toki Sangyo Co., Ltd.).
When the viscosity is less than 0.5 Pa · s, a heat conduction network in the thickness direction is not partially formed because the filler settles in the course of the heat treatment after coating, or the heat conductivity is impaired, or the sedimentation part. By increasing the filler density at, the probability of occurrence of fine voids between the polyimide resin and the filler increases, and the insulating property may decrease.
Further, when the viscosity exceeds 35 Pa · s, the fluidity is remarkably lowered, so that it is difficult to form a thin film by coating, and the variation in the film thickness increases the variation in thermal conductivity and voltage resistance of the entire material. Insulation may be reduced due to increase in the number of fine voids generated between the polyimide resin and the filler due to shear during molding.

Examples of the method for producing the insulating heat conductive filler dispersion composition of the present invention include a method in which the polyamic acid, the insulating heat conductive filler, and the solvent are mixed using a ball mill, a jet mill, a bead mill, a medialess dispersion, or the like. Is mentioned. Among these, a method using medialess dispersion is preferable.
In particular, since the particles are uniformly dispersed in the above-mentioned volume average particle diameter, d ₁₀ , d ₉₀ , the conditions are such that the insulating heat conductive filler is not crushed by the collision energy of the media but the aggregate is dissociated by shearing force. Alternatively, it is preferable to use a method.
Specifically, a method of dispersing the filler dispersion liquid by the effect of compression, shearing, and turbulent flow when passing through the slit of 30 to 300 μm at a high pressure of 20 to 200 MPa is preferable.

After applying the insulating heat conductive filler dispersion composition of the present invention, the polyamic acid is imidized by performing a heat treatment step, and an insulating heat conductive polyimide resin composition is obtained. The insulating film thus obtained is also one aspect of the present invention.
Although the manufacturing method of the said insulating heat conductive polyimide resin composition is not specifically limited, For example, after apply | coating the insulating heat conductive filler dispersion composition of this invention on a metal plate or a glass plate, the method of heat-processing etc. are mentioned. It is done.
Examples of the coating method include known coating methods and apparatuses such as a comma coater, a knife coater, a roll coater, a reverse coater, a die coater, a gravure coater, and a wire bar.
Examples of the heat treatment method include a method of heating by a known method such as hot air, hot nitrogen, far infrared rays, and high frequency induction heating.

A metal heat radiating plate is obtained by combining an insulating layer made of the insulating thermally conductive polyimide resin composition of the present invention and a metal plate.
The method for producing the metal heat radiating plate is not particularly limited. For example, the insulating heat conductive filler dispersion composition of the present invention is applied to the surface of the metal plate with a uniform thickness, and then a heat treatment step is performed. Methods and the like.
As a method for the coating and heat treatment, the same method as the method for producing the insulating heat conductive polyimide resin composition can be used.
In addition, when performing coating, it is preferable to remove previously attached volatile components such as cutting oil. Moreover, when performing the said coating, the adhesiveness of a polyimide resin and a metal plate can be improved by an anchor effect by etching the surface of a metal plate previously, and giving a fine unevenness | corrugation. Examples of the etching method include a method of etching using Mec Almat AR-1200 (manufactured by Mec Co., Ltd.) or the like when the metal plate is made of aluminum.

The metal base circuit board which has the insulating layer which consists of the insulating heat conductive polyimide resin composition of this invention, and the metal foil for circuits is also one of this invention.

The thickness of the metal foil for circuit is preferably 3 to 175 μm, more preferably 17.5 to 175 μm. For the metal foil (plate) for the base substrate, those having a thickness of 50 to 3000 μm are preferably used.
As the circuit metal foil, a single-sided or double-sided surface-treated copper foil coated with an inorganic substance such as a single metal or its oxide on the surface or treated with a coupling agent such as aminosilane or epoxysilane is used. It is preferable.
As the metal foil for circuit, it is more preferable to use a surface-treated foil having higher corrosion resistance or to take measures such as making the atmosphere during heating inactive.

As a method for producing the metal base circuit board of the present invention, for example, the insulating heat conductive filler dispersion composition of the present invention is coated on the surface of the circuit metal foil to a uniform thickness and then subjected to a heat treatment step. Methods and the like.
Note that the metal base circuit board may be a single-sided circuit board, and a known method such as providing a metal layer on the insulating resin layer by electroless plating or providing a metal foil via an adhesive. It is good also as a double-sided metal base circuit board.

In the insulating film, metal heat sink and metal base circuit board of the present invention, the thermal diffusivity of the insulating layer is preferably 4 × 10 ⁻⁷ W / (m · k) or more, and the dielectric breakdown voltage is 50 kV / mm or more. It is preferable that

ADVANTAGE OF THE INVENTION According to this invention, the insulating heat conductive filler dispersion composition which can make heat conductivity and insulation compatible is provided. In addition, by using the insulating heat conductive filler dispersion composition, a method for producing an insulating heat conductive polyimide resin composition capable of obtaining a high dielectric breakdown voltage, an insulating film, a metal heat sink, and a metal base circuit board can be provided. .

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
Under a nitrogen flow, 47.6 g of 4,4′-diaminodiphenyl ether was added to 488 g of N-methylpyrrolidone (NMP), kept at 50 ° C., stirred, and completely dissolved. By gradually adding 70 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride to this solution, 605.6 g of a polyamic acid solution was obtained.
The resulting polyamic acid solution had a viscosity of 3 Pa · s and a solid content concentration of 18.0% by weight. The viscosity was measured using TVE-33H at 25 ° C. with 3 ° × R9.7 cone rotor (manufactured by Toki Sangyo Co., Ltd.).

41.5 g of aluminum nitride particles (specific surface area = 2.5 m ² / g, volume average particle diameter 1.2 μm) and 5.2 g of NMP are added to 99.0 g of the obtained polyamic acid solution, and a pressure-type wet dispersion apparatus is added. The aluminum nitride dispersed polyamic acid solution was obtained by uniformly dispersing the aluminum nitride particles by passing the filler dispersion at 100 MPa through a 150 μm slit.
In addition, when the dispersion state of the aluminum nitride-dispersed polyamic acid solution was confirmed using a particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., MT3300), the volume average particle diameter including secondary particles of aluminum nitride particles was 5 μm, and d ₁₀ was 1 μm and d ₉₀ were 13 μm.
The aluminum nitride-dispersed polyamic acid solution had a solid content concentration of 41% by weight and a viscosity at 25 ° C. of 18.5 Pa · s.

A formed metal plate having a width of 300 mm and a length of 450 mm (the surface was mirror-finished) was prepared and installed in a sufficiently horizontal coating apparatus (PI1210 automatic coating apparatus manufactured by Tester Sangyo Co., Ltd.).
Next, 16.5 g of the obtained aluminum nitride-dispersed polyamic acid solution was collected, and a doctor blade adjusted so that the coating solution film thickness was 180 μm was formed on the molded metal plate at a stroke speed of 10 mm / sec. By moving the top, a liquid coating film having a uniform coating thickness was obtained.
Further, the coated molded metal plate is placed on a holding plate having a width of 400 mm and a length of 550 mm which is horizontally adjusted to a raised floor at a position 100 mm from the inner floor of the hot air drying furnace, and has a width of 350 mm, a length of 500 mm, and a height. A stainless steel cover having a thickness of 150 mm was placed so as to cover the molded metal plate, and the temperature was gradually raised to 320 ° C. for 1 hour, and heating was continued at that temperature for 1 hour.
After this heating was completed and the temperature reached room temperature, the polyimide film was obtained by peeling from the molded metal plate.
In addition, it was confirmed by infrared spectroscopic analysis that N-methylpyrrolidone remaining in a trace amount by heat treatment was completely removed and imidized.
The thickness of the obtained polyimide film was 50 μm ± 2 μm, and the roughness of the front and back surfaces was 3.2 μm and 1.6 μm in terms of Rz (10-point average roughness). A part of the film was cut and the cross section was enlarged with a scanning electron microscope (hereinafter referred to as SEM) to observe the dispersion state of the aluminum nitride powder. From the front surface to the back surface (molded from the free surface) It was also confirmed that large aluminum nitride particles gradually increased and dispersed in a continuous inclined state as a volume fraction toward the interface with the metal plate.

(Example 2)
In Example 1, except that 27.6 g of aluminum nitride particles (specific surface area = 2.5 m ² / g, volume average particle diameter 1.2 μm) and NMP 5.2 g were added to 99.0 g of the polyamic acid solution. In the same manner as in Example 1, an aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained. The resulting aluminum nitride-dispersed polyamic acid solution had a viscosity of 8.0 Pa · s. Further, the dispersion state of the aluminum nitride-dispersed polyamic acid solution was confirmed by the same method as in Example 1.

(Example 3)
In Example 1, except that 96.8 g of aluminum nitride particles (specific surface area = 2.5 m ² / g, volume average particle diameter 1.2 μm) and NMP 5.2 g were added to 99.0 g of the polyamic acid solution. In the same manner as in Example 1, an aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained. In addition, the viscosity of the obtained aluminum nitride-dispersed polyamic acid solution was 24.0 Pa · s. Further, the dispersion state of the aluminum nitride-dispersed polyamic acid solution was confirmed by the same method as in Example 1.

Example 4
Instead of the molded metal plate, an aluminum plate (A5052) having a width of 300 mm, a length of 450 mm, and a thickness of 2 mm was used as a heat sink, and a metal heat sink was obtained in the same manner as in Example 1 except that peeling was not performed.
A heating element (transistor: 2SC4058) was provided on the metal heat dissipation plate thus obtained and compared with the element temperature. As a result, it was confirmed that the temperature of the element opposite surface of the metal heat sink was low, and it was found that the metal heat sink has sufficient performance as a heat sink corresponding to the power transistor.

(Example 5)
Peeling is performed using a single-side treated copper foil (Furukawa Electric Co., Ltd., electrolytic copper foil GTS-STD, thickness 175 μm) having a width of 300 mm, a length of 450 mm, and a thickness of 2 mm as a metal circuit board material instead of a molded metal plate. A copper circuit board material was obtained in the same manner as in Example 1 except that there was no.
The copper circuit board material obtained in this way was left as it was for 3 minutes in an environment test at 260 ° C. for 3 minutes, and then was left in a 160 ° C. environment for 500 hours to confirm thermal conductivity and insulation. As a result, it was confirmed that there was no change in insulation performance and heat conduction performance before and after the environmental test, and the performance as a circuit board material was obtained.
Therefore, it is possible to obtain a circuit board by forming a wiring by etching the copper foil of the copper circuit board material by a known method.

(Example 6)
In Example 1, aluminum nitride particles having a volume average particle diameter of 4.2 μm and a specific surface area of 4.5 m ² / g were used, and a filler dispersion liquid was applied to a 150 μm slit using a pressure-type wet dispersion apparatus. An aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained in the same manner as in Example 1 except that the aluminum nitride particles were uniformly dispersed by passing at 100 MPa. Obtained aluminum nitride dispersed polyamic acid solution has a volume average particle diameter of 3.5 [mu] _{m, d 10} is 1.0 _{.mu.m, d 90} was 9.0 .mu.m. Moreover, the viscosity of the obtained aluminum nitride-dispersed polyamic acid solution was 22.0 Pa · s.
Further, the dispersion state of the aluminum nitride-dispersed polyamic acid solution was confirmed by the same method as in Example 1.

(Example 7)
In Example 1, aluminum nitride particles having a volume average particle diameter of 7.5 μm and a specific surface area of 2.0 m ² / g were used, and a filler dispersion liquid was applied to a 150 μm slit using a pressurized wet dispersion apparatus. An aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained in the same manner as in Example 1 except that the aluminum nitride particles were uniformly dispersed by passing at 100 MPa. Obtained aluminum nitride dispersed polyamic acid solution has a volume average particle diameter of 7.0 _{.mu.m, d 10} is 3.5 [mu] _{m, d 90} was 14 [mu] m. In addition, the viscosity of the obtained aluminum nitride-dispersed polyamic acid solution was 14.5 Pa · s. Further, the dispersion state of the aluminum nitride-dispersed polyamic acid solution was confirmed by the same method as in Example 1.

(Example 8)
In Example 1, after adding aluminum nitride particles and passing the filler dispersion at 100 MPa through a 150 μm slit using a pressurized wet dispersion apparatus, the aluminum nitride particles were uniformly dispersed, and then the silane coupling agent. An aluminum nitride-dispersed polyamic acid solution and a polyimide film were dropped in the same manner as in Example 1 except that 0.24 g (manufactured by Shin-Etsu Silicone Co., Ltd., KBM903) was added dropwise, stirred for 30 minutes with a simple stirrer, and subjected to coupling treatment. Got. The viscosity of the obtained aluminum nitride-dispersed polyamic acid solution was 19.5 Pa · s. Further, the dispersion state of the aluminum nitride-dispersed polyamic acid solution was confirmed by the same method as in Example 1.

Example 9
In Example 1, except that 35.4 g of aluminum nitride particles (specific surface area = 2.5 m ² / g, volume average particle diameter 1.2 μm) and NMP 77.6 g were added to 99.0 g of the polyamic acid solution. In the same manner as in Example 1, an aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained.
The filler concentration of the aluminum nitride-dispersed polyamic acid solution was 35% by volume, and the viscosity measured at 25 ° C. was 0.7 Pa · s. Further, the dispersion state of the aluminum nitride-dispersed polyamic acid solution was confirmed by the same method as in Example 1.

(Example 10)
In Example 1, except that 197.1 g of aluminum nitride particles (specific surface area = 2.5 m ² / g, volume average particle diameter 1.2 μm) and 50.5 g of NMP were added to 99.0 g of the polyamic acid solution. In the same manner as in Example 1, an aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained.
The filler concentration of the aluminum nitride-dispersed polyamic acid solution was 70% by volume, and the viscosity measured at 25 ° C. was 28 Pa · s. Further, the dispersion state of the aluminum nitride-dispersed polyamic acid solution was confirmed by the same method as in Example 1.

(Comparative Example 1)
Under nitrogen flow, 47.6 g of paraphenylenediamine (PPD) was added to 488 g of N-methylpyrrolidone (NMP), and the mixture was kept at 50 ° C. and stirred to completely dissolve. By gradually adding 70 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride to this solution, 605.6 g of a polyamic acid solution was obtained.
Similar to Example 1, except that an aluminum nitride-dispersed polyamic acid solution was used, and a film-forming mold was used to take 1 hour to 430 ° C., the temperature was gradually raised, and heating was continued at that temperature for 1 hour. Thus, a polyimide film was obtained.

(Comparative Example 2)
In Example 1, except that 17.8 g of aluminum nitride particles (specific surface area = 2.5 m ² / g, volume average particle diameter 1.2 μm) and NMP 5.2 g were added to 99.0 g of the polyamic acid solution. In the same manner as in Example 1, an aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained.

(Comparative Example 3)
In Example 1, except that 124.5 g of aluminum nitride particles (specific surface area = 2.5 m ² / g, volume average particle diameter 1.2 μm) and NMP 5.2 g were added to 99.0 g of the polyamic acid solution. In the same manner as in Example 1, an aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained.

(Comparative Example 4)
In Example 1, except that 27.6 g of aluminum nitride particles (specific surface area = 0.9 m ² / g, volume average particle diameter 7.0 μm) and NMP 5.2 g were added to 99.0 g of the polyamic acid solution. In the same manner as in Example 1, an aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained.

(Comparative Example 5)
In Example 1, except that 96.8 g of aluminum nitride particles (specific surface area = 0.9 m ² / g, volume average particle diameter 7.0 μm) and NMP 5.2 g were added to 99.0 g of the polyamic acid solution. In the same manner as in Example 1, an aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained.

(Comparative Example 6)
In Example 1, except that 27.6 g of aluminum nitride particles (specific surface area = 7.0 m ² / g, volume average particle diameter 1.5 μm) and NMP 5.2 g were added to 99.0 g of the polyamic acid solution. In the same manner as in Example 1, an aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained.

(Comparative Example 7)
In Example 1, except that 96.8 g of aluminum nitride particles (specific surface area = 7.0 m ² / g, volume average particle diameter 7.5 μm) and 5.2 g of NMP were added to 99.0 g of the polyamic acid solution. In the same manner as in Example 1, an aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained.

(Comparative Example 8)
In Example 1, an aluminum nitride filler was crushed and dispersed using a bead mill which is a media collision type dispersing machine, and the dispersion state of the aluminum nitride-dispersed polyamic acid solution was measured using a particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd., MT3300). confirmed. As a result, the volume average particle diameter comprising secondary particles of aluminum nitride particles was obtained 4 [mu] _{m, d 10} is 0.4 _{.mu.m, d 90} is an aluminum nitride dispersed polyamic acid solution to be 10.5 [mu] m.
The aluminum nitride-dispersed polyamic acid solution had a solid content concentration of 41% by weight and a viscosity at 25 ° C. of 19.0 Pa · s.

(Comparative Example 9)
In Example 1, the volume average particle size including secondary particles of aluminum nitride particles is 6 μm, and d ₁₀ is 1 by passing the filler dispersion liquid at 30 MPa through a 300 μm slit using a pressurized wet dispersion apparatus. An aluminum nitride-dispersed polyamic acid solution and a polyimide film were obtained in the same manner as in Example 1 except that an aluminum nitride-dispersed polyamic acid solution having a thickness of 0.5 μm and d ₉₀ of 17 μm was obtained.

(Evaluation)
About the polyimide film obtained by the Example and the comparative example, it evaluated by the following method. The results are shown in Table 1.

(1) Thermal diffusivity Thermal diffusivity was measured by temperature wave thermal analysis. Moreover, thermal conductivity was calculated more as a reference value from the following formula (2) and specific heat and density measured separately.
In the formula, K is thermal conductivity [W / (m · k)], α is thermal diffusivity [W / (m · k)], Cp is specific heat [J / (kg · k)], and ρ is It represents density [kg / m ³ ].

K = α · Cp · ρ (2)

(2) Dielectric breakdown voltage In accordance with the air test method of JIS C 2110, the dielectric breakdown voltage was measured using the standard electrode-1.

ADVANTAGE OF THE INVENTION According to this invention, the insulating heat conductive filler dispersion composition which can make heat conductivity and insulation compatible is provided. Also provided are a method for producing an insulating heat conductive polyimide resin composition capable of obtaining a high dielectric breakdown voltage, an insulating film, a metal heat sink, and a metal base circuit board using the insulating heat conductive filler dispersion composition. be able to.
In addition, the insulating heat conductive filler dispersion composition of the present invention is used in inverter boards, motor parts, high-density / high-brightness LED mounting boards, mobile phones, portable terminals, communication system bases for hybrid cars and fuel cell cars. It can be used for heat dissipation and heat diffusion of station equipment, personal computers / servers, semiconductor manufacturing equipment, etc.

Claims (10)

An insulating heat conductive filler dispersion composition containing a polyamic acid, an insulating heat conductive filler, and a solvent,
The polyamic acid is obtained by reacting biphenyltetracarboxylic dianhydride with diaminodiphenyl ether,
The insulating heat conductive filler is made of aluminum nitride or aluminum nitride whose surface is coated with aluminum oxide, and has a specific surface area of 1.5 to ⁵ m ² / g,
The content of the insulating heat conductive filler is 35 to 70% by volume, and
The insulating heat conductive filler is dispersed uniformly so that the volume average particle diameter is ₁ to 8 μm, d ₁₀ is 0.5 μm or more, and d ₉₀ is 15 μm or less. Composition. The insulating heat conductive filler is made of aluminum nitride having a Si—Al—O—N layer formed on the surface, or aluminum nitride surface-treated with an organosilicon coupling agent or a titanate and aluminate coupling agent. The insulating heat conductive filler dispersion composition according to claim 1, wherein Solvents are N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, hexamethylphosphoamide and 1,3-dimethyl- The insulating thermal conductive filler dispersion composition according to claim 1 or 2, wherein the dispersion composition is an at least one organic polar solvent selected from the group consisting of 2-imidazolidinone. The insulating heat conductive filler dispersion composition according to claim 1, 2 or 3, wherein the content of the insulating heat conductive filler is 35 to 60% by volume. 5. The insulating thermally conductive filler dispersion composition according to claim 1, wherein the viscosity measured at 25 ° C. using a rotational viscometer is 0.5 to 35 Pa · s. A method for producing an insulating thermally conductive polyimide resin composition comprising a step of heat-treating after applying the insulating thermally conductive filler dispersion composition according to claim 1, 2, 3, 4 or 5. It manufactures with the manufacturing method of the insulating heat conductive polyimide resin composition of Claim 6. The insulating heat conductive polyimide resin composition characterized by the above-mentioned. An insulating film comprising the insulating thermally conductive polyimide resin composition according to claim 7. A metal heat radiating plate comprising an insulating layer made of the insulating heat conductive polyimide resin composition according to claim 7 and a metal plate. A metal base circuit board comprising an insulating layer made of the insulating thermally conductive polyimide resin composition according to claim 7 and a circuit metal foil.