WO2010021408A1

WO2010021408A1 - Method for producing thermally conductive resin molding

Info

Publication number: WO2010021408A1
Application number: PCT/JP2009/064903
Authority: WO
Inventors: 河合智之; 今岡功; 木下恭一; 谷澤元治
Original assignee: 株式会社豊田自動織機
Priority date: 2008-08-21
Filing date: 2009-08-20
Publication date: 2010-02-25
Also published as: JPWO2010021408A1

Abstract

Disclosed is a method for producing a thermally conductive resin molding containing binder resin (18), and thermally conductive inorganic filler powder (19) dispersed into the binder resin (18) while containing flat particles having anisotropy in thermal conductivity wherein thermal conductivity can be improved sharply in an arbitrary direction, e.g. the thickness direction of the molding, and increase in cost can be restrained. A molding is obtained via a step for preparing a mixture (P) by mixing uncured binder resin (18) and inorganic filler powder (19), a step for exhausting air in the molding cavity (17) of a molding die (12), a step for injecting the mixture (P) into the molding cavity (17) from an injection opening (16) communicating with the molding cavity (17), and a step for curing the mixture (P) injected into the molding cavity (17).

Description

Method for producing thermally conductive resin molding

This invention relates to a method for producing a thermally conductive resin molding.

In the prior art disclosed in Japanese Patent Application Laid-Open No. 2008-101227 (hereinafter abbreviated as “Patent Document”, particularly, see pages 4 to 6 and FIG. 1), an inorganic filler is added to the thermosetting resin as the binder resin. A thermally conductive resin sheet having an insulating property to which is added is disclosed. This resin sheet is formed on a substrate by applying a mixture containing a thermosetting resin and an inorganic filler to the substrate surface by a doctor blade method. Two types of fillers are used as the inorganic filler: an inorganic filler made of a flat plate powder and an inorganic filler made of a substantially spherical powder.
When the inorganic filler is composed only of a flat powder, the inorganic filler is oriented parallel to the surface of the resin sheet. At this time, since a large amount of binder resin exists between the flat particles, the thermal conductivity in the thickness direction of the resin sheet is not so large. On the other hand, when the inorganic filler consists only of a substantially spherical powder, the inorganic filler is uniformly dispersed in the resin. At this time, since a large amount of binder resin is interposed between the substantially spherical particles, the thermal conductivity in the thickness direction of the resin sheet is not so large.
When two types of powders, a flat powder and a substantially spherical powder, are mixed and used as an inorganic filler as in the patent document, the flat particles are made of the resin sheet by the substantially spherical particles. Orientation parallel to the surface is impeded. Furthermore, since the tabular particles play a role of joining the substantially spherical particles, they form a heat conduction path in which inorganic fillers are connected in the thickness direction of the resin sheet. For this reason, it is supposed that the thermal conductivity in the thickness direction of the resin sheet is improved.

However, in the prior art disclosed in the patent document, it is necessary to use two kinds of powders of a flat shape and a substantially spherical shape as the inorganic filler, and there is a problem that the raw material cost becomes high. In addition, in order to uniformly disperse two types of powders having different shapes and particle sizes in the resin, it is necessary to sufficiently mix them, and accordingly, the manufacturing time becomes longer and the manufacturing cost may be increased. .
Moreover, in the prior art disclosed by patent document, in order to form in a sheet form, the application system by a doctor blade method is used. In the case of such a coating method, there is an advantage that it can be formed into a sheet shape by a simple operation. However, the plate-like particles are affected by buoyancy in the resin before curing or affected by the coating direction, and are oriented parallel to the sheet surface, improving the thermal conductivity in the thickness direction of the sheet. There is a problem that becomes difficult.
The present invention has been made in view of the above-described problems, and an object of the present invention is to greatly improve the thermal conductivity in an arbitrary direction such as the thickness direction of the resin molded body and to suppress an increase in cost. The present invention provides a method for producing a thermally conductive resin molded body that can be used.
The method for producing the thermally conductive resin molded body of the present invention for achieving the above-described object is as follows.
A method for producing a thermally conductive resin molded article comprising: a binder resin; and a thermally conductive inorganic filler powder containing particles having a flat shape and anisotropy in thermal conductivity and dispersed in the binder resin. And
A preparation step of preparing a mixture by mixing at least the uncured binder resin and the inorganic filler powder;
A pair of mold members arranged to face each other with a gap, a seal portion that seals a peripheral portion of the mold member and defines a molding cavity together with the mold member, and an injection port that communicates with the molding cavity An exhaust process for exhausting the molding cavity of the mold;
An injection step of injecting the mixture into the molding cavity from the injection port;
A curing step of curing the mixture injected into the molding cavity;
A molded product is obtained through
Here, the “flat shape” means that the thickness is thin, and for example, it can be said to be a shape in which particles such as a sphere or a lump are crushed in one direction. “Flat shape” includes those referred to as plate, flake, and scale.
In general, when the inorganic filler powder dispersed in the binder resin contains particles having a flat shape and anisotropy in thermal conductivity (flat particles), heat conduction is caused by the orientation of the inorganic filler powder in the binder resin. The rate changes greatly. For example, in a sheet-like resin molded body, when flat particles are oriented perpendicularly to the thickness direction, the thermal conductivity in the thickness direction of the molded body is not so improved. On the other hand, when the flat particles are oriented in parallel with respect to the thickness direction, the thermal conductivity in the thickness direction of the compact is greatly improved. In addition, when the flat particles are oriented at random in the middle of parallel and perpendicular to the thickness direction, a heat conduction path is easily formed in the thickness direction of the molded body, and the thickness direction of the molded body The thermal conductivity of is improved.
According to the method for producing a thermally conductive resin molded body of the present invention, after the molding cavity is exhausted, the mixture is injected into the molding cavity from the injection port and molded. Therefore, the flat particles contained in the inorganic filler powder are randomly oriented by the liquid flow when injected into the molding cavity. Since the binder resin is cured in this random orientation state, in the obtained resin molded body, the flat particles are randomly oriented in the resin molded body. Therefore, a heat conduction path is easily formed in an arbitrary direction such as the thickness direction of the resin molded body, and the thermal conductivity in an arbitrary direction of the resin molded body is improved. Moreover, since it is not necessary to use two types of inorganic filler powders as in the prior art and only one type is required, raw material costs and manufacturing costs can be reduced. Furthermore, since the injection is performed under vacuum, it is possible to reduce the generation of bubbles in the resin molded body that contributes to characteristic variation.
Although the reason why the inorganic filler powder containing flat particles is randomly oriented by the production method of the present invention is not clear, the inorganic filler powder is disturbed when the mixture is injected into the molding cavity in the injection step. It is thought that.
The method for producing a thermally conductive resin molded body of the present invention further includes a step of storing the molding die and a resin reservoir containing the mixture in an injection chamber before the exhausting step,
The exhausting step is a step of exhausting the molding cavity by exhausting the injection chamber,
The injection step is preferably a step of injecting the mixture into the molding cavity by increasing the pressure in the injection chamber after the injection port is immersed in the mixture in the resin reservoir.
After the pressure of the molding cavity is evacuated, the injection port of the mold is immersed in the mixture and the pressure in the injection chamber is increased, so that the mixture can be reliably injected into the molding cavity.
The method for producing a thermally conductive resin molded body of the present invention may further include a step of removing the molded body from the mold after the curing step. Since the resin molded body is removed from the mold, the mold can be reused.
The inorganic filler powder may contain hexagonal boron nitride. Hexagonal boron nitride (hereinafter referred to as “h-BN”) has a layered crystal structure, has a flat particle shape, and has anisotropy in thermal conductivity due to the crystal structure. . The thermal conductivity in the direction (a-axis direction) parallel to the flat surface of the h-BN particles is several tens of times the thermal conductivity in the direction (c-axis direction) perpendicular to the flat surface of the h-BN particles. . Utilizing this characteristic, the thermal conductivity of the resin molding can be improved by randomly orienting the flat surfaces of the h-BN particles in the resin molding.
The molded body may be a sheet-like thermally conductive resin sheet. If the thermally conductive resin molding is a thermally conductive resin sheet, it can be widely used for circuit boards and the like. The sheet shape is assumed to have a thickness of 10 to 1000 μm, for example.
Moreover, in the method for producing a thermally conductive resin molded body of the present invention, the mixture contains a diluting solvent, and the curing step is a step of curing the mixture while pressing the mold member from the outside of the mold. Is desirable.
The viscosity of the mixture increases with an increase in the content of the flat inorganic filler powder, but the addition of a diluting solvent can lower the viscosity of the mixture and facilitate injection. In addition, since the mold member is pressurized from the outside during curing, even if the diluted solvent in the mixture injected into the molding cavity evaporates and shrinks in volume, it can be compensated by reducing the volume of the resin sheet.
That is, according to the method for manufacturing a thermally conductive resin molded body of the present invention, the mixture is injected after the molding cavity is evacuated to produce the resin molded body. Therefore, heat in any direction such as the thickness direction of the resin molded body is produced. The conductivity can be greatly improved, and an increase in cost can be suppressed.

FIG. 1 is a schematic view schematically showing the main configuration of a vacuum injection apparatus used in the method for producing a thermally conductive resin molded body of the present invention.
FIG. 2 is a flowchart showing a manufacturing process of a heat conductive resin sheet which is an embodiment of the method for manufacturing a heat conductive resin molded body of the present invention.
3A, 3B, 3C, and 3D are schematic views for explaining an injection process in the manufacturing process of the heat conductive resin sheet shown in FIG. 2, and (1-1) a mold and an injection chamber The resin reservoir is installed, (1-2) the mold is immersed in the mixture of the resin reservoir, (1-3) the mixture is injected into the molding cavity, and (1-4) the injection is completed.
FIG. 4A is a schematic diagram schematically showing a cross-sectional configuration of a resin sheet obtained by the manufacturing process of the heat conductive resin sheet shown in FIG. 2. FIG. 4B is a schematic diagram schematically showing a cross-sectional configuration of a resin sheet obtained by a coating method as a comparative example.
FIG. 5 shows an electron micrograph of the heat conductive resin sheet obtained by the manufacturing process of the heat conductive resin sheet shown in FIG.
6A and 6B show an X-ray diffraction method (θ-2θ method) of a heat conductive resin sheet obtained by the manufacturing process of the heat conductive resin sheet shown in FIG. 2 and a resin sheet obtained by a coating method as a comparative example. ) Shows the measurement results.
FIG. 7 is a schematic view schematically showing the main configuration of a heating furnace used in another embodiment of the method for producing a thermally conductive resin molded body of the present invention.
FIG. 8 is a flowchart showing a manufacturing process of a heat conductive resin sheet, which is another embodiment of the method for manufacturing a heat conductive resin molded body of the present invention.
9A and 9B are schematic views for explaining a heating step in the manufacturing process of the heat conductive resin sheet shown in FIG. 8, and (2-1) the mold into which the mixture is injected is placed in the heating furnace. It shows the state of installation and pressurization, (2-2) the state after curing by heating.
FIG. 10A, FIG. 10B, and FIG. 10C are schematic diagrams for explaining a method for producing a thermally conductive resin molded body, which is another embodiment of the method for producing a thermally conductive resin molded body of the present invention. FIG. 4 is a perspective view of a molding die, (b) a cross-sectional view showing an injection process into a molding cavity, and (c) a perspective view of an obtained resin molding.
FIG. 11A and FIG. 11B are schematic diagrams for explaining a method of manufacturing a thermally conductive resin molded body according to another embodiment, and FIG. 11A is a cross-sectional view illustrating an injection process into a molding cavity, and FIG. It is a perspective view of the obtained resin molding.
Drawing 12 is a mimetic diagram for explaining the manufacturing method of the heat conductive resin fabrication object concerning other embodiments.

Below, the best form for implementing the manufacturing method of the heat conductive resin molding of this invention is demonstrated.
<First Embodiment>
Hereinafter, the manufacturing method of the heat conductive resin sheet which concerns on 1st Embodiment is demonstrated using figures.
As shown in FIG. 1, a vacuum injection apparatus 10 used in the present embodiment includes a mold 12 having a pair of mold members 11 arranged facing each other with a predetermined gap, a binder resin 18 and inorganic filling. A resin reservoir 13 for containing the mixture P with the material powder 19; an injection chamber 14 for storing the mold 12 and the resin reservoir 13 containing the mixture P and injecting the mixture P into the mold 12; It has.
The mold 12 includes a pair of mold members 11, a seal portion 15 that seals a peripheral portion of the mold member 11, and an injection port 16. The mold member 11 is formed of a rectangular plate-like body, and is disposed to face each other with a constant gap interval t0. The seal part 15 seals the peripheral part of the mold member 11 and partitions the molding cavity 17 together with the mold member 11. The sealing portion 15 is provided with an inlet 16 for injecting the mixture P. That is, in the molding die 12, the inside of the gap in the molding die 12 is sealed from the outside except for the injection port 16, and the molding cavity 17 is formed, and the injection port 16 that connects the molding cavity 17 and the outside is formed. ing.
The injection chamber 14 is provided with an exhaust port 21 for evacuating the injection chamber 14, and the exhaust port 21 is connected to a vacuum pump (not shown) via a valve 22 for opening and closing the exhaust port 21. .
The manufacturing method of the heat conductive resin sheet using the vacuum injection apparatus 10 which has the above structures is demonstrated based on FIG. 2, FIG. 3A and FIG. 3B.
First, in S101, the binder resin main component and the curing agent and the inorganic filler powder containing flat particles are sufficiently mixed by the mixing means. As a result, in S102, a liquid mixture P is obtained.
Next, in S103, the molding cavity 17 is formed by having a pair of mold members 11 opposed to each other and sealing the periphery of the mold member 11 other than the injection port 16 by the seal portion 15. A mold 12 is prepared.
Next, in S104, as shown in FIG. 3A (1-1), the resin reservoir 13 and the mold 12 containing the mixture P are placed in the injection chamber 14, and the mold is placed above the resin reservoir 13. Twelve inlets 16 are arranged vertically downward. That is, the mold is arranged so that the thickness direction of the resin sheet is horizontal.
Next, in S105, the valve 22 of the exhaust port 21 is opened and the vacuum pump is driven, whereby the injection chamber 14 is evacuated. At this time, the molding cavity 17 in the mold 12 is similarly evacuated through the inlet 16.
Next, in S106, as shown in FIG. 3B (1-2), when the inside of the injection chamber 14 and the molding cavity 17 are in a predetermined vacuum state, the driving of the vacuum pump is stopped and the valve 22 of the exhaust port 21 is closed. . And although not shown in figure, the shaping | molding die 12 is moved below using an actuator etc., and the injection port 16 is immersed in the mixture P of the resin reservoir 13.
Next, in S107 and S108, as shown in FIG. 3C (1-3), the valve 22 of the exhaust port 21 is opened to introduce air into the injection chamber 14, and the pressure in the injection chamber 14 increases. As a result, a pressure difference occurs between the pressure in the molding cavity 17 in the mold 12 and the pressure in the injection chamber 14, and the mixture P is injected into the molding cavity 17 through the inlet 16.
Next, in S109, as shown in FIG. 3D (1-4), the injection of the mixture P into the gap space 17 is completed by returning the inside of the injection chamber 14 to atmospheric pressure.
By the way, as shown to FIG. 3D (1-4), since flat particle | grains are disturbed by the liquid flow of the mixture P at the time of inject | pouring into the shaping | molding cavity 17, the state in which the direction of the flat surface was orientated at random It is in.
When the injection of the mixture P is completed, the mold 12 is moved upward, but the mixture P injected into the mold 12 is held inside the mold 12 by the atmospheric pressure and the viscosity of the uncured resin.
Next, in S110, the mold 12 is taken out from the injection chamber 14, and the mixture P injected into the mold 12 is cured by a curing means (not shown). At this time, the direction of the molding die 12 remains with the injection work 16 directed downward in the vertical direction.
Next, in S111, the mold is removed by removing at least the seal portion 15. In S112, the resin sheet 23 as a resin molded body having a predetermined thickness is completed.
FIG. 4A (a) shows a cross-sectional configuration of the resin sheet 23 at this time, and only one mold member 11 of the mold member 11 is removed. In the resin sheet 23, the inorganic filler powder 19 containing flat particles is randomly oriented in the binder resin 18, and a heat conduction path is easily formed in the thickness direction of the resin sheet 23. The thermal conductivity in the vertical direction is improved.
FIG. 4B (b) shows a cross-sectional structure of the resin sheet when the mixture P is applied to the surface of the mold member by the application method and cured as a comparative example. In this case, the inorganic filler powder 19 containing flat particles is oriented parallel to the sheet surface. Therefore, the thermal conductivity in the thickness direction of the resin sheet of the comparative example is lower than the thermal conductivity in the thickness direction of the resin sheet 23.
<Preparation of thermal conductive resin sheet S1>
A heat conductive resin sheet was produced according to the above procedure. Epoxy resin (NM-108A (main agent) and NM-111B (curing agent) manufactured by Pernox Co., Ltd.) as a thermosetting resin as the binder resin 18, and hexagonal boron nitride (UHP manufactured by Showa Denko KK) as the inorganic filler powder 19 -2; hereinafter abbreviated as “h-BN”). The maximum length of the used h-BN particles in the direction parallel to the flat surface is about 10 μm. An epoxy resin and h-BN powder were blended so as to have a mass ratio of 70:30, and were sufficiently mixed together with a curing agent by a mixing means (not shown) to obtain a liquid mixture P. This mixture P was placed in a resin reservoir 13 having a certain depth.
The mold member 11 of the mold 12 is made of glass (Matsunami Glass Industry Co., Ltd.) whose surface is covered with a Teflon seal (Chuko Kasei Kogyo Co., Ltd.), and the seal part 15 is molded with double-sided tape (Sumitomo 3M Co., Ltd.) The cavity 17 was 76 mm × 26 mm × thickness 1 mm, and the injection port 16 was a 10 mm × 1 mm rectangular shape formed on the 26 mm × 1 mm surface of the molding cavity 17.
In the exhaust process, the injection chamber was evacuated until the molding cavity 17 could be filled with the mixture P in the next injection process, and in the injection process, the injection chamber was returned to atmospheric pressure. In the curing step, the mold 12 filled with the mixture P was left at 25 ° C. for 24 hours to cure the epoxy resin. Thereafter, the mold 12 was removed by removing the mold member 11 and the seal portion 15 to obtain a heat conductive resin sheet S1 (abbreviated as “sheet S1”) having a thickness of 1 mm.
FIG. 5 is an electron micrograph of the sheet S1 obtained by the above manufacturing method. In FIG. 5, the horizontal axis direction is the sheet surface direction parallel to the molding surface of the mold member, and the vertical axis direction is the sheet thickness direction. As apparent from the electron micrograph shown in FIG. 5, in the sheet S <b> 1, the flat h-BN particles in the epoxy resin 18 are in a state where the flat surfaces are oriented in random directions.
6A and 6B show X of a sheet S1 and a comparative resin sheet S2 (abbreviated as “sheet S2”) prepared by a conventional application method using a mixture P having the same material and the same blending ratio as the sheet S1. The line diffraction results are shown.
FIG. 6A (a) shows that the surface of the resin sheet is irradiated with X-rays at an angle θ, and the diffracted light is at the position of angle 2θ while continuously changing the irradiation angle (θ) and the detection angle (2θ). 6 is a graph showing the relationship between an angle 2θ when detected by a detector and the intensity of diffracted light. The solid line indicates the characteristic of the sheet S1, and the broken line indicates the characteristic of the sheet S2.
From this characteristic, for example, if the diffraction intensity at the diffraction peak (004) is I (004) and the diffraction intensity at the diffraction peak (100) is I (100), the diffraction intensities of I (004) and I (100) From the ratio, the orientation of boron nitride in the resin can be determined. That is, when the diffraction intensity ratio I (004) / I (100)> 0.4, boron nitride is oriented parallel to the measurement surface (sheet surface direction), and the diffraction intensity ratio I (004) / I (100 ) If <0.4, boron nitride is oriented perpendicular to the measurement surface (sheet surface direction), and if the diffraction intensity ratio I (004) / I (100) ≈0.4, boron nitride is randomly It can be seen that it is oriented. The fact that the diffraction intensity ratio in the case of random orientation is about 0.4 is based on the ICDD card.
FIG. 6B (b) reads the diffraction intensities I (004) and I (100) from the characteristic graph of the sheet S1 and the sheet S2 in FIG. 6A (a), respectively, and calculates the diffraction intensity ratio I (004) / I (100). It is what I have sought.
In the sheet S2 produced by coating, the diffraction intensity ratio is 1.0, which corresponds to the case where the diffraction intensity ratio I (004) / I (100)> 0.4, and is flat with respect to the sheet surface direction. It was found that the h-BN particles were oriented in parallel. On the other hand, in the sheet S1 produced by vacuum injection, the diffraction intensity ratio is 0.4, which corresponds to the case where the diffraction intensity ratio I (004) / I (100) ≈0.4, and flat h-BN particles Was randomly oriented.
As described above, in the sheet S1 produced by using the manufacturing method according to the present embodiment, the flat h-BN particles are randomly oriented in the epoxy resin, so that heat conduction is performed in the thickness direction of the resin sheet 23. A path is easily formed. As a result, the thermal conductivity in the thickness direction of the resin sheet 23 is improved.
According to the manufacturing method of the heat conductive resin sheet which concerns on this embodiment, there exist the following effects.
(1) After the injection chamber 14 is evacuated and the molding cavity 17 in the mold 12 is evacuated, the injection port 16 of the mold 12 is immersed in the mixture P of the resin reservoir 13 and the pressure in the injection chamber 14 is increased. And the mixture P is injected into the molding cavity 17 from the injection port 16 to produce the resin sheet 23. Therefore, the flat h-BN particles are in a state in which the flat surfaces are randomly oriented due to the liquid flow of the mixture P when injected into the molding cavity 17. Since the resin sheet 23 is produced by being cured by heating in this random orientation state, in the obtained resin sheet 23, the flat h-BN particles are randomly oriented in the epoxy resin, and the thickness of the resin sheet 23 is increased. A heat conduction path is easily formed in the vertical direction, and the thermal conductivity in the thickness direction of the resin sheet 23 is improved.
(2) The molding cavity 17 in the molding die 12 is evacuated, and the pressure in the injection chamber 14 is increased to create a pressure difference between the pressure in the molding die 12 and the pressure in the injection chamber 14, and based on this pressure difference. The mixture P is injected into the molding cavity 17 through the injection port 16. Therefore, the mixture P can be reliably injected into the mold 12. Moreover, since the injection is performed under vacuum, the generation of bubbles in the resin sheet 23 that contributes to the characteristic variation can be reduced.
(3) Since it is not necessary to use two types of inorganic filler powders as in the prior art and only one type of h-BN particles is required, raw material costs and manufacturing costs can be reduced.
(4) Since h-BN particles are used as the inorganic filler powder, it can be used by taking advantage of the anisotropy in the thermal conductivity of the h-BN particles. That is, it is possible to improve the thermal conductivity in the thickness direction of the sheet by randomly orienting the flat surface of the h-BN particles with respect to the sheet surface of the thermally conductive resin sheet 23. Further, since the h-BN particles are insulating particles, the heat conductive resin sheet 23 can be used as an insulating member of an electronic device.
(5) Since the resin sheet 23 is removed from the mold 12 after curing, the mold 12 can be reused.
<Second Embodiment>
Next, the manufacturing method of the heat conductive resin sheet which concerns on 2nd Embodiment is demonstrated based on FIG. 7, FIG. 8, FIG. 9A and FIG. 9B.
In this embodiment, the raw material composition of the mixture in the above embodiment and the treatment conditions at the time of heat curing are changed, and other configurations and manufacturing steps are common.
Therefore, here, for convenience of explanation, some of the reference numerals used in the previous explanation are used in common, explanations of common configurations and steps are omitted, and only the changed parts are explained.
The raw material of the mixture Q in this embodiment is obtained by adding a dilution solvent to the raw material of the mixture P in the above embodiment. The viscosity of the mixture Q can be reduced by adding a diluting solvent.
As for the vacuum injection apparatus, the vacuum injection apparatus 10 in the above embodiment can be used as it is. FIG. 7 shows a state where the injection of the mixture Q into the mold 12 is completed and the mold 12 moved upward is installed in a heating furnace 31 as a curing means. A heater 32 is installed in the heating furnace 31, and the set temperature and set time in the furnace can be controlled by control means (not shown).
Further, the pair of mold members 11 are arranged so as to be pressurized by a pressing means (not shown) in a direction inside both sides.
The manufacturing method of the heat conductive resin sheet using the vacuum injection apparatus 10 and the heating furnace 31 which have the above structures is demonstrated based on FIG. 8, FIG. 9A and FIG. 9B.
First, in S201, the thermosetting resin main component and the curing agent as the binder resin 18, the inorganic filler powder 19 containing flat particles, and the diluting solvent are sufficiently mixed by the mixing means. As a result, in S202, a liquid mixture Q is obtained.
Next, the steps from S203 to S209 are the same as the steps of S103 to S109 (see FIG. 2) in the first embodiment except that the mixture Q is used instead of the mixture P, and the description thereof is omitted. To do. In addition, since the viscosity of the mixture Q is reduced by adding methyl ethyl ketone, the mixture Q is easily injected into the mold 12.
Next, in S210, the mold 12 is taken out from the injection chamber 14 and installed in the heating furnace 31 as a curing means. At this time, as shown to FIG. 9A (2-1), the type | mold member 11 is pressurized with a fixed pressure in the direction inside the both sides with a pressurizing means. In addition, the clearance gap between the mold members 11 at this time is t1. Then, by heating for a predetermined time at a predetermined temperature in a pressurized state, the methyl ethyl ketone in the mixture Q evaporates and the mixture Q injected into the mold 12 is cured.
By the way, when the methyl ethyl ketone in the mixture Q evaporates, the volume of the mixture Q contracts. However, since the mold member 11 is pressurized in the inner direction from both sides, the mold members 11 move closer to each other in the inner direction in response to volume shrinkage. FIG. 9B (2-2) shows a state after curing, and the gap interval between the mold members 11 is t2 (t2 <t1). That is, when the gap interval t1 between the mold members 11 is reduced to t2, the volume shrinkage is compensated, and it is possible to prevent the occurrence of a problem associated with the volume shrinkage.
Next, in S211, the mold member 11 is removed, and in S212, the resin sheet 33 as a resin molded body having a predetermined thickness t2 is completed.
In the present embodiment, an epoxy resin which is a thermosetting resin is suitably used as the binder resin 18, h-BN particles as the inorganic filler powder 19, and methyl ethyl ketone as the diluent solvent. By producing a resin molded body according to the procedure shown in FIG. 8, a heat conductive resin sheet in which h-BN powders are randomly oriented, similar to the sheet S1 shown in FIG. 5, is obtained.
According to the manufacturing method of the heat conductive resin sheet which concerns on this embodiment, there exist the following effects. The effects (1) to (5) in the above embodiment are the same, and other effects will be described.
(6) Since the viscosity of the mixture Q can be reduced by adding a diluent solvent, the mixture Q can be easily injected into the mold 12.
(7) Since the mold member 11 is pressurized at the time of curing, the gap interval t1 between the mold members 11 is reduced to t2 even if methyl ethyl ketone in the mixture Q injected between the mold members 11 evaporates and shrinks in volume. By doing so, it is possible to prevent the occurrence of problems associated with volume shrinkage.
<Third Embodiment>
Next, the manufacturing method of the heat conductive resin molding which concerns on 3rd Embodiment is demonstrated based on FIG. 10A, FIG. 10B, and FIG. 10C.
In this embodiment, the shape of the mold 12 in the first embodiment is changed, and other configurations and manufacturing processes are common.
Therefore, here, for convenience of explanation, some of the reference numerals used in the previous explanation are used in common, explanations of common configurations and steps are omitted, and only the changed parts are explained.
As shown in FIGS. 10A (a) and 10B (b), the molding die 40 of this embodiment is composed of a cylindrical inner mold member 41 and an outer mold member 42, and around the inner mold member 41. The outer mold members 42 are arranged so as to face each other with a predetermined gap interval so as to surround them.
Seals 43 are provided at both opening end portions of the inner mold member 41 and the outer mold member 42, and a plurality of injection ports 44 for injecting the mixture P are provided at one opening end portion. The molding die 40 is in a state where the inside of the gap in the molding die 40 is sealed except for the injection port 44 and a cylindrical gap space 45 having a rectangular cross section is formed.
As shown in FIG. 10B (b), the mold 40 is immersed in a resin reservoir 46 in which the mixture P is placed in the injection chamber, and the mixture P enters the gap space 45 in the mold 40 through the injection port 44. Do the injection. After injection of the mixture P, the mold 40 is heated and cured in a heating furnace. Then, the inner mold member 41 and the outer mold member 42 are removed.
FIG. 10C (c) shows the cylindrical resin molded body 47 obtained as a result.
The operational effects in this embodiment are the same as the operational effects in the first embodiment except that the obtained resin molded body is not a sheet but a cylinder, and the description thereof is omitted.
<Other embodiments>
The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the gist of the invention. For example, the following modifications may be made.
In each of the above embodiments, the thermosetting epoxy resin is used as the binder resin and h-BN particles (hexagonal boron nitride) are used as the inorganic filler powder. However, as the binder resin, other unsaturated polyesters are also used. Thermosetting resins such as resins, phenol resins, melamine resins, silicone resins, and polyimide resins, or thermoplastic resins such as synthetic rubber resins, acrylic resins, and olefin resins may be used. In addition, as the inorganic filler powder, aluminum oxide (alumina), silicon carbide, graphite powder, or the like may be used. In addition, when using a heat conductive resin sheet as an insulating member, it is desirable to use insulating inorganic filler powder.
In each of the above embodiments, only the h-BN particles are used as the inorganic filler powder, but a powder further including particles having a shape different from the flat particles may be used. The particles having different shapes are preferably substantially spherical, but may be pulverized and polygonal. Examples of the material include alumina, silica, silicon nitride, aluminum nitride, silicon carbide, boron nitride and the like. By using together powders having different shapes, the thermal conductivity in the thickness direction of the molded body is further improved.
In the production of the heat conductive resin sheet S1, the epoxy resin and the h-BN powder were blended so as to have a mass ratio of 70:30. Increasing the blending ratio of the inorganic filler powder to the binder resin can increase the thermal conductivity of the resin sheet as a resin molded body. However, if the blending ratio is too high, the resin sheet becomes brittle and cracks are likely to occur. Become. A preferable mixing ratio is a mass ratio of binder resin: inorganic filler powder = 20: 80 to 80:20, or 65:35 to 75:25.
In the second embodiment, it has been described that methyl ethyl ketone is used as a diluent solvent. However, other common organic solvents such as acetone and toluene may be used, and it is desirable to select in consideration of compatibility with the binder resin. From the viewpoint that the filled mixture is easily held in the mold, the viscosity of the mixture is preferably 1 to 500 Pa · s, more preferably 50 to 200 Pa · s.
In the second embodiment, how much pressure is applied to the mold member by the pressurizing means depends on the amount of the solvent, but the pressure applied to the mixture is 1 × 10. ⁵ Pa ~ 1000 × 10 ⁵ It is desirable that the pressure is Pa or 1.5 to 10 Pa. 1000x10 ⁵ If it exceeds Pa, the matrix resin may be damaged, which is not desirable.
In each of the embodiments described above, a thermosetting epoxy resin is used as the binder resin and a heating furnace is used as the curing means to cure by heating. However, the binder resin may be cured by natural drying without being heated. Further, when the binder resin is a thermoplastic resin, curing by cooling may be performed as a curing means for the mixture in a high temperature state. Further, when a photocurable resin is used as the binder resin and the mold member is formed of a transparent material, a photocuring method by light irradiation may be used as the curing means.
In the production of the heat conductive resin sheet S1, one mold member was not removed. However, all mold members may be removed or only the seal part may be removed. For example, it is possible to form a resin molded body using a heat dissipation substrate as a mold member and then use it as a heat dissipation material while being in close contact with the surface of the heat dissipation substrate.
In each of the embodiments described above, the flat h-BN particles 19 have been described as being randomly oriented in the mixture P or Q injected into the

mold

12 or 40. However, by controlling injection conditions such as the injection port shape, injection speed and raw material viscosity, curing time, selection of binder resin, etc., the h-BN particles 19 are changed in the thickness direction of the resin sheet and the resin molded body sheet and the molded body. It is possible to orient it so that it may approach parallel more. As a result, the thermal conductivity in the thickness direction of the sheet and the molded body can be further improved.
In each of the embodiments described above, the injection chamber after exhausting is pressurized and the mixture is injected into the molding cavity, but the method of injecting the mixture is not limited. For example, in the injection chamber after evacuation, even if the mold is arranged so that the injection port is vertically upward and the mixture is poured from the injection port into the molding cavity by gravity, the flat particles are likely to be randomly oriented. Further, the mixture may be injected while the molding cavity is exhausted. That is, even if the exhaust process and the injection process are performed simultaneously in the manufacturing method of the present invention, the object of the present invention is achieved. Specifically, the molding cavity is exhausted from an opening (exhaust port) different from the injection port communicating with the molding cavity with the injection port immersed in the mixture.
The raw material viscosity is preferably 1 to 500 Pa · s, more preferably 1 to 200 Pa · s, and within this range, the flat particles are likely to be randomly oriented.
In the production of the heat conductive resin sheet S1, the injection chamber (that is, the molding cavity) is evacuated in the evacuation step, and then the pressure is increased to atmospheric pressure. If the degree of vacuum is too low, it will be difficult to store the mixture in a resin reservoir. On the other hand, if the exhaust is insufficient, the mixture is not sufficiently injected into the molding cavity depending on the dimensions of the molding cavity. Further, when the pressure in the injection chamber (that is, the molding cavity) is returned to atmospheric pressure, the pressure in the injection chamber may be adjusted so that the liquid level of the mixture filled in the molding cavity increases at 0.01 to 1 m / sec. If the degree of vacuum and the rising speed of the liquid level are in the above ranges, the flat particles are likely to be randomly oriented.
In the third embodiment, it has been described that the cylindrical resin molded body 47 is formed using the molding die 40 including the inner mold member 41 and the outer mold member 42. By devising the shape of each mold member, it is possible to form a resin molded body having an L shape, a U shape, a corrugated plate shape, or any other shape.
The material of the mold member is not particularly limited, but may be selected from glass, plastic, metal and the like according to the curing means of the binder resin. Further, if the mold member is released from the resin molded body after the curing step, a release agent may be applied to the surface of the mold member in advance.
There is no particular limitation on the material of the seal portion, and a general seal material may be used. Specific examples include epoxy adhesives, acrylic adhesives, polyester adhesives, and rubber adhesives such as silicone and urethane. In particular, when the mold member is pressurized by the pressing means as in the second embodiment, the seal portion is preferably made of a rubber-based adhesive such as a silicone-based adhesive.
There are no particular limitations on the formation position, size, shape, and number of the inlets, but if the inlet is too small, it is not preferable because the flat particles tend to be oriented in one direction. On the other hand, when the inlet is too large, it is difficult to hold the mixture in the molding cavity with the viscosity when the inlet is located below the mold. For this reason, it is preferable that one injection port has such a size as to fit within a circle having a diameter in the range of 0.1 to 10 mm, further 0.2 to 0.5 mm.
As shown in FIG. 11A and FIG. 11B, a resin having a non-uniform thickness is obtained by using a molding die 50 including a flat mold member 51b and a mold member 51a partially protruding outward. It is also possible to form the molded body 52.
In each of the above-described embodiments, the resin sheet 23 is manufactured using the pair of mold members 11. However, at least a pair of mold members may be used. That is, as shown in FIG. 12, a plurality of resin sheets may be formed simultaneously using a mold 60 in which a plurality of mold members 61 are laminated at a predetermined interval. In this case, as the spacer and seal material 62 for holding the mold member 61, a soft material such as silicone resin coated with polytetrafluoroethylene (PTFE) may be used. In FIG. 12, the three molds used in the first embodiment are arranged at a predetermined interval. However, a gap space 67 between adjacent molds may be used as a molding cavity.
That is, it is also possible to use both surfaces of a flat plate-shaped mold member as a molding surface.

Claims

A method for producing a thermally conductive resin molded article comprising: a binder resin; and a thermally conductive inorganic filler powder containing particles having a flat shape and anisotropy in thermal conductivity and dispersed in the binder resin. And
A preparation step of preparing a mixture by mixing at least the uncured binder resin and the inorganic filler powder;
A pair of mold members arranged to face each other with a gap, a seal portion that seals a peripheral portion of the mold member and defines a molding cavity together with the mold member, and an injection port that communicates with the molding cavity An exhaust process for exhausting the molding cavity of the mold;
An injection step of injecting the mixture into the molding cavity from the injection port;
A curing step of curing the mixture injected into the molding cavity;
A method for producing a thermally conductive resin molded product, characterized in that a molded product is obtained through the process.
Furthermore, before the exhausting step, including the step of storing the mold and the resin reservoir pan containing the mixture in an injection chamber,
The exhausting step is a step of exhausting the molding cavity by exhausting the injection chamber,
2. The heat according to claim 1, wherein the injection step is a step of injecting the mixture into the molding cavity by increasing the pressure in the injection chamber after the injection port is immersed in the mixture in the resin reservoir. A method for producing a conductive resin molding.
Furthermore, the manufacturing method of the heat conductive resin molded object of Claim 1 including the process of removing the said molded object from the said shaping | molding die after the said hardening process.
4. The method for producing a thermally conductive resin molded body according to claim 3, wherein at least the seal portion is removed and the molded body is removed from the mold while being in close contact with at least one of the pair of mold members.
The method for producing a thermally conductive resin molded body according to claim 1, wherein the inorganic filler powder contains hexagonal boron nitride.
The method for producing a thermally conductive resin molded body according to claim 1, wherein the molded body is a sheet-like thermally conductive resin sheet.
The thermally conductive resin according to any one of claims 1 to 6, wherein the mixture includes a diluting solvent, and the curing step is a step of curing the mixture while pressing the mold member from the outside of the mold. Manufacturing method of a molded object.
A method for producing a thermally conductive resin molded body, wherein the exhaust step and the injection step in the method for producing a thermally conductive resin molded body according to claim 1 are performed simultaneously.