JP2009099707A - Molding having anisotropy in thermal conductivity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of conveying heat efficiently to other places with less thermal resistance in the desired direction, especially the method of surely conveying heat with less number of components with no thermal effect on each other in the case where a plurality of heating bodies and heat radiating bodies are present in the same circuit, since the heating amount from IC in a product increases as electronic devices, such as a mobile phone, notebook computer, and portable game machine, provide higher performance, requiring higher heat radiation effect, and since it has become difficult to set a heat radiating body near the heating body as a product is miniaturized for less clearance within the product. <P>SOLUTION: A molding 1 having anisotropy in thermal conductivity is used which is provided by injection molding a mixture containing scaly thermal conductive filler 4 and resin binder, using an injection molding die equipped with a plurality of gates, at least two. Since the transmission direction of heat can be changed, heat is conveyed in a different direction without lowering thermal conductive efficiency. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heat conduction material used for electronic parts such as a mobile phone, a personal computer, a game machine, and a portable terminal.

  Conventionally, heat conduction parts used in mobile phones, personal computers, game consoles, portable terminals, etc., use heat conductive metals (such as aluminum), and heat conduction fillers are dispersed in gels and liquids. Sheets or plates that are processed by dispersing in resin or processed are commercially available.

  However, although the sheet-like material can dissipate heat by changing the heat transfer direction relatively flexibly, it cannot transfer heat without leaking heat in a narrow space.

In addition, liquid and gel-like materials have been proposed to prevent gas generation because contact failure due to low-molecular siloxane or the like is regarded as a problem. (Patent Document 1)
As products that require heat conduction components, there are many electronic devices that use small, high-performance ICs, such as mobile phones, notebook personal computers, and portable game machines, and heat transfer is a very important technology factor. It has become. In addition, since these electronic devices are small in size, the clearance inside the product is often small, and the heat radiating portion cannot always be arranged near the heating element.

  Therefore, in order to transfer heat to the heat dissipating part away from the heating element, a method of transferring heat using a member with high thermal conductivity is used, but all conventional heat conducting members transfer heat in all directions. In many cases, it does not have directionality.

For this reason, a method has also been reported in which heat is transmitted in a block shape and the heat transfer direction can be set. (Patent Document 2) This is a combination of two or more heat conducting materials to change the direction of heat transfer.
JP 2004-35721 A JP 2002-93967 A

  The method described in Patent Document 2 is a combination of two or more heat conductive materials in order to change the direction of heat transfer. However, in this method, the joint surface of the heat conductor becomes a thermal resistance, and heat transfer is performed. Efficiency can be significantly reduced.

  Accordingly, there is a demand for a heat conductive component that is an integral product in which the heat transfer efficiency is unlikely to decrease, and that can change heat transfer in a desired direction by imparting thermal conductivity anisotropy to itself.

  In addition, heat retention may adversely affect other parts because it is small and the clearance between parts is small, and heat transfer parts also radiate heat from themselves during heat transfer. Therefore, in order to avoid the influence of heat on other parts, a method of transferring heat in a desired direction is desired.

  Also, there are many cases where there are a plurality of heat generators and heat radiators in the same circuit, and there is a demand for a method of reliably transferring heat with as few parts as possible so as not to affect the heat of each other.

  The present invention has improved the above-described problems.

  That is, the present invention can be obtained by injection molding a mixture containing at least a scale-like thermally conductive filler and a resin binder by using an injection mold having at least two gates (injection ports). It is a molded article having thermal conductivity anisotropy.

  This invention is also a molded object which has the heat conductivity anisotropy whose content rate of the heat conductive filler which occupies for a resin binder is 3-70 volume%.

  The present invention further provides a molded article having thermal conductivity anisotropy obtained by cutting the molded article from the above-described injection-molded molded article.

  The present invention is an integral resin molded body having high thermal conductivity and thermal conductivity anisotropy, and the direction in which heat is transferred can be changed thereby, without reducing the thermal conductivity efficiency. Heat transfer can be performed in different directions.

  In addition, it can be made difficult to dissipate heat except in the direction of heat transfer, and in products with a small clearance, the effect of heat on other parts can be suppressed, and the degree of freedom in the arrangement of heating elements and radiators can be improved. Can do. Furthermore, heat can be transferred from the plurality of heat generating elements to the plurality of heat dissipating elements by using one heat conductive resin molding.

  Generally, when a scaly heat conductive filler is mixed with a resin and molded, the filler is oriented in a layered manner in the molding direction, and the heat conduction also shows a high value in the molding direction. On the other hand, it has been found that the thermal conductivity is relatively low in the direction perpendicular to the layer direction. As a result of diligent research on the anisotropy of heat conduction due to the orientation of the filler, the present inventor found that the orientation direction of the filler partially changes particularly in the injection molding, and further, for injection molding having two or more gates By using this mold, the alignment of the scale-like heat conductive filler at the joint between the resin and the resin (so-called weld line) becomes almost parallel to each other, and the scale-like thermal conductivity oriented in parallel Since a large amount of resin is present between the fillers, it has been found that heat transfer in the direction crossing the weld line (perpendicular to the weld line) is deteriorated. And in injection molding, paying attention to the fact that the orientation direction of the scaly heat conductive filler partially changes as described above, the heat conduction anisotropy is imparted to the compact by using the scaly heat conductive filler. I found what I can do. Particularly in an injection mold having a plurality of gates, the orientation direction of the filler partially changes at the time of injection molding, and the heat transfer performance in the direction crossing the weld line (perpendicular to the weld line) deteriorates. In addition, it has been found that the heat transfer direction can be changed in the same molded body by utilizing the heat conduction anisotropy resulting from the heat conduction material inherent in good heat conduction. Furthermore, it has been found that the direction of heat transfer in the same molded body can be changed by cutting the molded body alone into an arbitrary shape.

  In this invention, the said subject can be solved by using the resin molding which has the anisotropy of thermal conductivity as a heat transfer member.

  Details will be described below.

  The molded article having thermal conductivity anisotropy of the present invention can be obtained by injection molding using a mold for injection molding, which is mainly composed of a scaly heat conductive filler and a resin binder.

  Examples of the resin binder include vinyl chloride-vinyl acetate copolymer, ethylene-ethyl acrylate resin (EEA), polyamide resin, polystyrene resin, PET (polyethylene terephthalate), PBT (polybutylene terephthalate), PPS (polyphenyl sulfide), Examples thereof include thermoplastic resins such as EVA (ethylene-vinyl acetate copolymer), EVOH (ethylene-vinyl alcohol copolymer), CPE (chlorinated polyethylene), and PVC (polyvinyl chloride). These may be used alone or in combination of two or more. Among these, vinyl chloride-vinyl acetate copolymer is preferable from the viewpoint of cost. However, in the present invention, a heat conductive filler is mixed with a soft material such as ethylene-ethyl acrylate resin (EEA). This is particularly effective when the dispersed pellet is used as a molding material.

  Examples of fillers having good thermal conductivity include graphite (graphite), boron nitride, aluminum nitride, silicon nitride, alumina, magnesia, beryllia, calcium carbonate, aluminum powder, copper powder, iron powder, titanium carbide, diamond, and polymer film. A film pulverized product obtained by baking and graphitizing can be used. In particular, graphite (graphite) is widely used as a thermally conductive filler because of its excellent thermal conductivity, and this material is used because of its shape, cost, availability, and ease of handling. It is most desirable. Of these materials, they may be used alone or in combination of two or more.

  As the heat conductive filler to be used, it is necessary to use a scaly filler having good heat conductivity. Here, the scale shape is, for example, a shape having a ratio of thickness to diameter of approximately 1: 5 to 1: 100 and a ratio of length to width of approximately 1: 1 to 1:50. In the case of a spherical shape, anisotropy of heat conduction cannot be given and an effect cannot be obtained.

  Moreover, the heat conductive filler which has another shape which is not scale-like can be used together with scale-like filler in the range of usually less than 50 weight%, preferably less than 30 weight%. However, when it is 50% by weight or more, the anisotropy of heat conduction tends to be remarkably reduced.

  In addition, the content rate of the heat conductive filler which occupies for a resin binder is 3-70 volume%, Furthermore, 30-60 volume% is more preferable from the effectiveness and the ease of a mixing | blending. When the content of the resin filler is less than 3% by volume, the thermal conductivity tends to be low, and it is difficult to obtain the performance as a thermal conductive resin. If it exceeds 70% by volume, the heat conduction effect is high, but it tends to be difficult to knead the heat conduction filler into the resin binder, and it becomes difficult to form a molded body itself.

  In some cases, the thermally conductive filler and the resin binder are blended with a dispersant, a stabilizer, a lubricant, and the like using a Henschel mixer, and the resin and filler are kneaded and dispersed using a kneader such as a biaxial kneader or a roll mill. Thereafter, the resin kneaded product is pulverized and pelletized by a pulverizer, and injection molding is performed.

  The injection molding conditions may be molding conditions suited to the resin used.

  The mold temperature during molding is preferably 10 to 95 ° C. 30-80 degreeC is more preferable from the ease of injection molding.

  The injection mold may be a very general mold. The cavity may be designed so that the molded product has a desired shape and size, and need not be a special mold.

  However, although one injection mold gate is usually sufficient, at least as shown in FIGS. 2 and 3 in order to meet the purpose of transferring heat from a plurality of heat generating elements to a plurality of heat dissipating elements. Two or more must be provided. Actually, about 2 to 6 locations are preferable. If the number is 7 or more, there are many restrictions on mold production, which tends to be technically difficult, and the mold production cost tends to increase.

  The molded body molded by injection molding can be processed into a desired shape, but when the molded body is processed into a desired size and shape, the weld line portion of the molded body injection-molded as shown in FIG. Must be processed to have a portion including at least one or more. When there are a plurality of heat generating portions and heat dissipating portions and heat transfer needs to be performed at a plurality of locations, it is not always necessary to have one weld line. By adopting a layout in which a weld line is sandwiched between the heat generating portions, heat can be transferred to the heat radiating portions in different directions or in the same direction without interfering with each other's heat. Moreover, heat can be efficiently transferred by determining the shape according to the orientation of the heat conductive filler.

  Further, the effective width M of the portion where the heat of the weld line of the injection-molded resin molded product is difficult to be transferred, with respect to the dimension L of the entire molded product, as shown in FIG. About 0.1 to 30%.

  The design shape can be freely designed, for example, as shown in FIG. 8, such as a T-shape, an L-shape, a plate shape, a block shape, and a bifurcated shape. However, the size of the molded body is determined in accordance with the size to be finally used, but the shape is preferably a square block shape or a cylindrical block shape because of ease of processing.

  As a method of processing the molded body into a desired size and shape, for example, as shown in FIG. 4 (l), the molded body block (1-2) is cut out from the molded body (1-1). At this time, processing is performed so as to sandwich the weld line as shown in FIG.

  Further, for example, when it is necessary to transfer heat to a plurality of heat generating bodies and heat radiating bodies, as shown in FIG. 4 (m), a molded body block ( m-2) may be cut out and processed to include a weld line.

  There is no particular restriction on the cutting from the injection-molded molded body, but it may be machined using an end mill, lathe, milling machine, etc., or when using soft resin, slice it with a cutter. May be used. What is necessary is just to use the processing method matched with the required shape.

  Since heat is transmitted through the molded body, for example, as shown in FIG. 1, it is preferable that the heat is molded in a shape as required depending on the distance from the heat generating body to the heat radiating body. It can also be used vertically or horizontally.

  FIG. 5 shows an example in which a heat conductive resin is used, which is molded and cut using an injection mold having a three-point gate (the gates are installed at diagonal positions). By processing and using the weld lines at the bottom and the center, heat can be transferred from the two heating elements 9 to the two radiators 10. Further, by arranging a weld line between the heating element 9 and the other component 11, the influence of heat on the other component 11 can be reduced.

  FIG. 6 is an example of using a heat conductive resin, which is molded and cut using an injection mold having a three-point gate (the gates are installed at positions diagonal to each other). By processing and using the weld line at the center, heat can be transferred from the heating element 9 to the two radiators 10 separately. The amount of heat generated in the heating element 9 is not easily transmitted to the lower part by the central weld line.

  The heat conductive block made according to the present invention has heat transfer anisotropy as shown in FIG. Heat is easily transferred in the direction 6 but heat transfer is very small in a direction crossing the so-called weld line (perpendicular to the weld line). This makes it possible to suppress heat transfer in a specific direction and provide anisotropy to the heat transfer, increase the degree of freedom of the heat transfer path in the electronic component, perform heat transfer efficiently, and heat to other components. Can suppress the influence of

  As described above, the present invention can provide a heat conductive resin that transfers heat from a heat generating body to a heat radiating body, but the above is an example and does not limit the present invention.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

The thermal conductivity was measured five times by the hot disk method using a TPS 2500 measuring device manufactured by Hot Disk Co., and the average value was obtained.
Example 1
50% by volume of ethylene-ethyl acrylate resin (PES-220 manufactured by Nihon Unicar) as a resin binder (including lubricant, plasticizer and stabilizer), and graphite (CB-150 scale manufactured by Nippon Graphite Industries Co., Ltd.) as a heat conductive filler ) Was 50% by volume, and these were mixed and melt-kneaded in a roll mill. A product obtained by pulverizing the kneaded material into a pellet shape was molded into a shape (φ40 × 20 mm) as shown in FIG.

  The gate used was an injection mold placed on two diagonal lines.

4 (l-1) is cut into a shape (sample shape for measuring thermal conductivity) (10 × 10 × 10 mm) as shown in FIG. 4 (l-2) so as to include the weld line at the center of the molded product. The thermal conductivity was measured. (N = 5)
The results are shown in Table 1.

（実施例２）
樹脂バインダーとしてエチレン−エチルアクリレート樹脂（日本ユニカー製ＰＥＳ−２２０）を５０体積％（滑剤、可塑剤、安定剤を含む）、熱伝導性フィラーとして黒鉛（日本黒鉛工業（株）製ＣＢ−１５０鱗片状）を５０体積％とし、これらを混合しロールミルにて溶融混練した。混練物をペレット状に粉砕した物を射出成形機により図４（ｍ―１）に示すような形状（φ４０×２０ｍｍ）に成形加工した。

(Example 2)
50% by volume of ethylene-ethyl acrylate resin (PES-220 manufactured by Nihon Unicar) as a resin binder (including lubricant, plasticizer and stabilizer), and graphite (CB-150 scale manufactured by Nippon Graphite Industry Co., Ltd.) as a heat conductive filler ) Was 50% by volume, and these were mixed and melt-kneaded in a roll mill. A product obtained by pulverizing the kneaded product into a pellet shape was molded into a shape (φ40 × 20 mm) as shown in FIG.

  Three gates were used, which were injection molds installed at an angle of 180 °, two from 45 ° to the left and right at 45 °.

Cutting into a shape (sample shape for thermal conductivity measurement) as shown in FIG. 4 (m-2) (10 × 10 × 10 mm) so as to include a weld line at the center of the molded product in FIG. 4 (m-1). The thermal conductivity was measured. (N = 5)
The results are shown in Table 1.

(Comparative Example 1)
50% by volume of ethylene-ethyl acrylate resin (PES-220 manufactured by Nihon Unicar) as a resin binder (including lubricant, plasticizer and stabilizer), and graphite (LB-BG spherical by Nippon Graphite Industries Co., Ltd.) as a heat conductive filler ) Was 50% by volume, and these were mixed and melt-kneaded in a roll mill. A product obtained by pulverizing the kneaded material into a pellet shape was molded into a shape (φ40 × 20 mm) as shown in FIG.

  The gate used was an injection mold placed on two diagonal lines.

Fig. 4 (l-1) is cut into a shape (sample shape for thermal conductivity measurement) (10 x 10 x 10 mm) as shown in Fig. 4 (l-2) so as to sandwich the weld line at the center of the molded product. The thermal conductivity was measured. (N = 5)
The results are shown in Table 1.

  Examples 1 and 2 show high thermal conductivity and thermal conductivity anisotropy, but Comparative Example 1 has almost no thermal conductivity anisotropy. The effect of a molded article injection-molded from a mold having two or more gates mixed with a conductive filler clearly appears. In addition, the effect of anisotropy using the poor heat transferability of the weld line clearly appears.

Filler orientation image and heat conduction image of thermally conductive resin molded products and cut molded products Example of gate position and number of gates, filler orientation image and parting line Example of gate position and number of gates, filler orientation image and parting line Thermal conductivity measurement location and direction Thermal conductive resin usage example Thermal conductive resin usage example Weld line heat shut-off range example Thermal resin block processing example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal conductive resin molding 2 Injection gate 3 Cutting molded body 4 Filler (filler orientation layer)
5 Resin 6 Heat Transfer Direction 7 Weld Line 8 Base 9 Heating Element 10 Heat Dissipator (Heat Sink)
11 Other parts a Molded body b by injection molding c Cut-out block c Thermal conductive resin molding example d Thermal conductive resin molding example e Thermal conductive resin molding example f Thermal conductive resin molding example g Thermal conductive resin molding example h Thermal conductive resin molding example i Thermal conductive resin molding example j Thermal conductive resin molding example k Thermal conductive resin molding example 1-1 Thermal conductive resin processing example (two gates)
1-2 Thermal conductivity measurement position and measurement direction m-1 Thermal conductive resin processing example (three gates)
m-2 Heat conduction measurement position and measurement direction n-1 Heat conduction resin processing example (one gate)
n-2 Heat conduction measurement position and measurement direction o Thermal conductive resin processing example p Thermal conductive resin processing example q Thermal conductive resin processing example r Thermal conductive resin processing example s Thermal conductive resin processing example t Thermal conductive resin processing example u Thermal conductive resin Processing example v Heat conduction resin processing example w Heat conduction resin processing example A Heat conduction measurement direction B Heat conduction measurement direction C Heat conduction measurement direction D Heat conduction measurement direction E Heat conduction measurement direction F Heat conduction measurement direction G Heat conduction measurement direction H Heat conduction measurement direction I Heat conduction measurement direction L Molded product width M Non-conductive effective range of weld line heat

Claims (3)

  Anisotropy of heat conduction, characterized by being molded with an injection mold having at least two gates (injection ports) when injection-molding a mixture containing at least scaly heat-conductive filler and a resin binder A molded article having properties.   2. The molded article having thermal conductivity anisotropy according to claim 1, wherein the content of the thermal conductive filler in the resin binder is from 3 to 70% by volume.   The molded body having thermal conductivity anisotropy according to claim 1 or 2, wherein the molded body is cut out from a molded body formed by injection molding.

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