JP2005203735A - Thermally conductive composite sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermally conductive composite sheet whereby a radiator or a thermal block can be easily detached from a heat generating electronic component after the heat generating electronic component and the radiator or the thermal block are mounted, and heat generated from the heat generating electronic component can be efficiently transmitted to the radiator or the thermal block. <P>SOLUTION: In the thermally conductive composite sheet, a metal foil 2 is bonded and fixed on an adhesive surface of a resin film 1 having an adhesive, and a thermally conductive compound 3 in which a thermally conductive filler is added to a base polymer is formed like a thin film on the surface of the metal foil 2. The thermally conductive compound is formed after the thin metal foil having a low mechanical strength is bonded and fixed on the resin film having the adhesive, thereby obtaining a heat dissipating sheet which can be removed with ease. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat conductive composite sheet suitable for heat dissipation of a heat-generating electronic component.

  In recent years, removing heat from a heating element has become a problem in various fields. In particular, in electronic devices such as electronic devices and personal computers, it is an important issue to remove heat from heat-generating electronic components. These heat-generating electronic components generate heat during operation and the temperature rises remarkably. As the temperature rises, the heat generated from the heat-generating electronic component causes a malfunction, and the characteristics of the heat-generating electronic component deteriorates, causing a failure of the device.

Conventionally, for the heat dissipation of these heat-generating electronic components, a method of attaching a heat radiator or a thermal block to the heat-generating electronic components and transferring and releasing the heat is often used. Since the contact surface between the heat-generating electronic component and the radiator or thermal block is contact between metals or between plastic and metal, between the heat-generating electronic component and the radiator or thermal block for the purpose of supplementing the adhesion between the contact surfaces. Are used in various fields, such as a heat-dissipating sheet, a heat-dissipating grease, and a phase change-type sheet in which a heat conductive filler is blended with silicone rubber or silicone oil (for example, Patent Document 1 below).
JP 2002-329989 A

  The amount of heat generated by heat-generating electronic components has been increasing in recent years. Conventional heat-dissipating sheets, heat-dissipating greases and phase-change-type sheets containing silicone rubber or silicone oil and heat-conducting fillers have higher heat conductivity. Things are sought. Furthermore, after mounting a heat-dissipating sheet, heat-dissipating grease, phase change-type sheet, etc., between the heat-generating electronic component and the heat-dissipator or thermal block, the heat generated by energization causes the two parts to adhere firmly to each other. When removing a heatsink or a thermal block from a component, it is necessary to remove it with a large force, and there is often a problem that the heat-generating electronic component is detached from the substrate, deformed, or damaged.

  In order to solve the above-described conventional problems, the present invention can easily remove the heat radiator and the thermal block from the heat generating electronic component after mounting the heat generating electronic component and the heat radiator and the thermal block, and can efficiently remove the heat generating electronic component. Provided is a thermally conductive composite sheet capable of transferring heat generated from a component to a radiator or a thermal block.

  The present invention relates to a thermally conductive composite in which a metal foil is adhesively fixed to an adhesive surface of a resin film with an adhesive, and a heat conductive compound in which a heat conductive filler is added to a base polymer is formed into a thin film on the surface. It is a sheet.

  Since the heat conductive composite sheet of the present invention contains a heat conductive filler, the heat resistance value is low, and furthermore, the interface breaks at the metal foil portion. The block can be easily removed.

  It is preferable that the adhesive strength of the adhesive resin film to be adhesively fixed used when the heat conductive compound is formed into a film on a metal foil is 6 gf / 25 mm or less. If the adhesive strength of the adhesive resin film is too strong, when the heat conductive composite sheet is peeled off from the adhesive resin film, the metal foil is wrinkled or blurred, and cannot be removed cleanly. Also, if the adhesive strength of the adhesive resin film is too weak, the thermal conductive composite sheet and the adhesive resin film are in a discrete single product state after the product is cut, so management of the adhesive strength is important.

  There are polypropylene, polyester, and the like as the material of the resin film used as the base material of the adhesive resin film, and commercially available materials can be used. However, in consideration of heat resistance, polyester such as polyethylene terephthalate is preferable.

  Any commercially available acrylic or silicone adhesive may be used to apply and fix the metal foil to the surface of the resin film. More preferably, it is a silicone type.

  The thickness of the metal foil is preferably 8 μm or more and 80 μm or less, more preferably 10 to 40 μm. The material of the metal foil is preferably a relatively soft metal such as copper or aluminum. When the thickness of the metal foil is less than 8 μm, the handleability is poor because the metal foil may be blurred or have large wrinkles on the surface due to the force when the thermally conductive compound flows on the metal foil during rolling. On the other hand, if the metal foil is too thick, the contact between the heat generating electronic component and the heat sink or thermal block deteriorates due to lack of flexibility and followability to the unevenness of the surface of the heat generating electronic component, heat sink or thermal block. Conductive performance is reduced.

  When sticking a metal foil to a resin film with adhesive, it is necessary to stick together carefully so that air bubbles and wrinkles do not enter between the layers of the resin film and the metal foil. Bonding is preferred.

  There are various methods for placing a heat conductive compound on one side of a metal foil adhesively fixed to an adhesive resin film, such as a rolling method using a calender roll, a coating method, a laminating method, and a pressing method. In consideration of mass productivity, it is preferable to form a heat conductive compound on a metal foil on a thin film by a coating method or a laminating method.

  The heat conductive compound is preferably a polymer base material such as resin, rubber, oil or the like to which a heat conductive filler is added. When 100 parts by mass of the thermally conductive filler is added to 100 parts by mass of the polymer base material, the thermal conductivity becomes about 0.5 W / m · K. The upper limit with preferable heat conductive filler is 3000 mass parts.

  The thermally conductive compound is preferably an unvulcanized putty-like compound. The unvulcanized state includes those in which vulcanization is intentionally stopped during the process. The thickness of the heat conductive compound on the metal foil is preferably 0.05 mm or more and 3.0 mm or less.

  The polymer base material is ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methacrylate copolymer, synthetic resin such as epoxy, rubber is silicone rubber, butyl rubber, styrene-isoprene copolymer, styrene -Butadiene copolymer, oil includes silicone oil.

  However, from the viewpoint of heat resistance, it is preferable to use a silicone compound as a polymer base material.

  Thermally conductive fillers added to the thermally conductive compound include metal oxides, nitrides, carbides, ferrites and the like, and one kind or a mixture of two or more kinds thereof can be used. Further, the surface of the heat conductive filler may be surface-treated by a known technique.

Known antioxidants and flame retardants to be added to the heat conductive compound can also be used.
As the tackifier for the heat conductive compound, a known one can be used.

  The surface of the metal foil may be subjected to a primer treatment for the purpose of enhancing the adhesion between the heat conductive compound and the metal foil. Depending on the heat conductive compound to be placed on the metal foil, primer treatment can be appropriately selected and used.

  Next, it demonstrates using drawing. FIG. 1 is a cross-sectional view illustrating a method for producing a thermally conductive compound sheet with a metal foil according to an embodiment of the present invention. A metal foil 2 is pasted on an adhesive resin film 1, and a thermally conductive compound compound 3 'in which a thermally conductive filler is mixed with a base resin such as silicone oil is placed thereon and coated with a knife 4 (see FIG. 1A-B). The composite sheet 10 obtained in this way is shown in FIG. 1C. That is, the metal foil 2 is affixed on the adhesive resin film 1, and the heat conductive compound sheet 3 is laminated thereon.

  FIG. 2 is a cross-sectional view showing a use state. The metal foil 2 and the heat conductive compound sheet 3 are attached to the surface of the die portion 5 of the CPU via the heat conductive adhesive 6, and the radiator 7 is integrated thereon. When removing the radiator 7, if it is pulled in the direction of the arrow 8, the interface can be easily broken and removed at the portion of the metal foil 2.

Hereinafter, the present invention will be described more specifically with reference to examples. The measurement methods in the following examples are as follows.
(1) Thermal resistance value: Measured with a load of 5 Psi (34.5 kPa) according to ASTM D5470.
(2) Removal test after mounting: A CPU having a surface size of 31 mm × 31 mm was inserted into a socket, and after energization, the heat sink was pulled up to measure the separation from the CPU.

The material used for the heat conductive sheet used in the following examples is as follows.
(1) Adhesive resin film The adhesive resin film was produced as follows. 0.9 parts by mass of SRX212 (Toray Dow Corning Silicone) and 100 parts by mass of xylene were added to 100 parts by mass of SD4560 (Toray Dow Corning Silicone) to obtain an adhesive solution.
(2) Adhesive Next, the adhesive solution was uniformly applied to a 100 μm thick polyester film by a knife coating method and heat cured at 120 ° C. for 15 minutes in a heating furnace, and the adhesive layer had an adhesive layer thickness of 3 μm. A film was obtained.

The adhesive strength of the adhesive resin film with the thickness of the adhesive layer of 3 μm was measured according to JIS-Z-0238 and found to be 3 gf / 25 mm to the surface of the stainless steel SUS304 plate.
(3) Metal foil The metal foil is an aluminum foil 30 μm thick hard material (manufactured by Sumitomo Light Metal Industry Co., Ltd.), and the copper foil is a 35 μm thick hard material (manufactured by Nihon Foil Co., Ltd.). In order to make it easy to form a uniform composition into a thin film, a product degreased and washed with isopropanol was used.
(4) Lamination of metal foil and adhesive resin film The method of laminating metal foil and adhesive resin film to each other was performed by a laminating method.
(5) Surface treatment of heat conductive compound Next, a heat conductive compound was prepared as follows. The aluminum oxide used in the examples was surface-treated by adding 1% by mass of hexamethyldisilazane (TSL8802 GE, Toshiba Silicone).
(6) Thermally conductive compound A
100 parts by mass of silicone oil (SH200CV 300cs, manufactured by Toray Dow Corning Silicone), aluminum oxide, 900 parts by mass (AS30, manufactured by Showa Denko), iron black, and 4 parts by mass are uniformly kneaded and thermally conductive compound A did.

(Example 1)
After sticking and fixing 30 μm thick aluminum foil on the adhesive surface of the resin film with adhesive, heat conductive compound A is formed on the aluminum foil surface into a 170 μm thick sheet by rolling, and the aluminum foil and the heat conductive compound are formed. A heat conductive composite sheet having a total thickness of A of 0.2 mm was obtained.

(Example 2)
After sticking and fixing a 35 μm thick copper foil to the adhesive surface of the adhesive resin film, a heat conductive compound A is placed on the copper foil surface by a rolling method to a thickness of 165 μm, and the total thickness of the copper foil and the heat conductive compound A A 0.2 mm heat conductive composite sheet was obtained.

(Comparative Example 1)
The heat conductive compound A was directly placed on one surface of the aluminum foil by a rolling method on an aluminum foil having a thickness of 30 μm to obtain a heat conductive composite sheet having a total thickness of the aluminum foil and the heat conductive compound A of 0.2 mm. . In this case, an adhesive resin film was not used.

(Comparative Example 2)
The heat conductive compound A was placed directly on one surface of the copper foil by a rolling method on a copper foil having a thickness of 35 μm to obtain a heat conductive composite sheet having a total thickness of the copper foil and the heat conductive compound A of 0.2 mm. . In this case, an adhesive resin film was not used.

  Each heat conductive composite sheet prepared in Example 1 to Example 2 and Comparative Example 1 to Comparative Example 2 was cut into 30 × 30 mm, and the thermal resistance value was measured. The results are shown in Table 1.

  In Examples 1 and 2 of the present invention, aluminum and copper foils were each adhesively fixed to an adhesive resin film, and then a thermally conductive compound was formed into a thin film on a metal foil using a rolling method or a knife coating method. By doing so, the heat conductive compound sheet was uniformly put on the surface of the metal foil, and a heat conductive composite sheet could be obtained without wrinkles or blurring.

  On the other hand, in Comparative Examples 1 and 2, the aluminum foil and the copper foil were not adhered and fixed to the adhesive resin film, respectively, and the heat conductive compound was formed into a thin film on the metal foil using a rolling method or a knife coating method. In the case of forming into a metal foil, wrinkles or jabbles entered into the metal foil, and the desired heat conductive composite sheet could not be obtained.

  Next, a heat conductive composite sheet formed by forming a thin film of a heat conductive compound on both sides of a metal foil was examined. The present invention will be described more specifically with reference to Examples 3 to 4.

  The resin film with adhesive was produced as follows. 0.9 parts by mass of SRX212 (Toray Dow Corning Silicone) and 100 parts by mass of xylene were added to 100 parts by mass of SD4560 (Toray Dow Corning Silicone) to obtain an adhesive solution.

  Next, the pressure-sensitive adhesive solution was uniformly applied to a polyester film having a thickness of 100 μm by a knife coating method, and was heat-cured at 120 ° C. for 15 minutes in a heating furnace to obtain a pressure-sensitive adhesive resin film having a pressure-sensitive adhesive layer thickness of 3 μm.

  The adhesive strength of the adhesive resin film having a thickness of the adhesive layer of 3 μm was measured according to JIS-Z-0238 and found to be 3 gf / 25 mm to the surface of the SUS304 plate.

  The metal foil is an aluminum foil 30 μm thick hard material (manufactured by Sumitomo Light Metal Industry Co., Ltd.), and the copper foil is a 35 μm thick hard material (manufactured by Nihon Foil Co., Ltd.). In order to make it easier to form a thin film, it was degreased and washed with isopropanol.

  The method of laminating the metal foil and the adhesive resin film to each other was performed by a laminating method.

  Next, the heat conductive compound was prepared as follows. The aluminum oxide used in the examples was surface-treated by adding 1% by mass of hexamethyldisilazane (TSL8802 GE, Toshiba Silicone).

(Thermal conductive compound A)
To 100 parts by mass of silicone oil (SH200CV 300cs, Toray Dow Corning Silicone), 900 parts by mass of aluminum oxide (AS30 Showa Denko) and 4 parts by mass of iron black were uniformly kneaded to obtain a heat conductive compound A.

(Thermal conductive compound C)
Addition of 450 parts by mass of aluminum oxide (AL43L Showa Denko) to 100 parts by mass of silicone rubber (TSE3033 GE / Toshiba Silicone Co., Ltd.) did.

(Example 3)
A sheet with a total thickness of 0.2 mm of the aluminum foil and the heat conductive compound A is placed on the surface of the aluminum foil with a 30 μm thick aluminum film adhered to the adhesive surface of the adhesive resin film by rolling. Got.

  Next, after temporarily fixing the surface which formed the heat conductive compound A in the thin film shape on the embossed film, the resin film with adhesion was peeled off and the aluminum foil surface was exposed.

  Next, a dispersion of the heat conductive compound C was placed on the exposed aluminum foil surface by a knife coat method, then dried and vulcanized, and a heat conductive compound C having a thickness of 10 μm was placed on one surface of the aluminum foil. A 21 mm heat conductive composite sheet was obtained.

  A heat conductive composite sheet on which one surface was placed with the heat conductive compound A and the other surface was vulcanized heat conductive composition C was obtained with an aluminum foil interposed therebetween.

Example 4
A heat conductive compound A is placed on the copper foil surface of the adhesive film of the adhesive resin film with a 35 μm copper foil adhered and fixed by rolling, and a sheet of copper foil and the heat conductive compound A having a total thickness of 0.2 mm is formed. Obtained.

  Next, after temporarily fixing the surface which formed the heat conductive compound A in the shape of a thin film on the embossed film, the adhesive-attached resin film was peeled off to expose the copper foil surface.

  Next, the dispersion of the heat conductive compound C was placed on the exposed copper foil surface by a knife coat method, then dried and vulcanized, and the heat conductive compound C having a thickness of 10 μm was placed on one side of the copper foil. A 0.21 mm heat conductive composite sheet was obtained. A heat conductive composite sheet with a heat conductive compound A on one side and a vulcanized heat conductive compound C on the other side was obtained with a copper foil in between.

(Comparative Example 3)
The heat conductive compound A is directly placed on the surface of one side of the aluminum foil by a rolling method on the adhesive surface of the adhesive resin film with 30 μm aluminum foil, and the total thickness of the aluminum foil and the heat conductive compound A is 0. A 2 mm heat conductive composite sheet was obtained.

(Comparative Example 4)
The heat conductive compound A is directly placed on one surface of the copper foil by a rolling method on the adhesive surface of the adhesive resin film having a 35 μm copper foil adhered and fixed, and the total thickness of the copper foil and the heat conductive compound A is 0. A 2 mm heat conductive composite sheet was obtained.

(Comparative Example 5)
The heat conductive compound A was sandwiched between two upper and lower polypropylene films and rolled by a rolling method to obtain a sheet of the heat conductive compound A having a thickness of 0.2 mm.

  Table 2 shows the examination results obtained by measuring the thermal resistance values of all the thermally conductive composite sheets prepared in Examples 3 to 4 and Comparative Examples 3 to 5 cut to 30 × 30 mm.

  As can be seen from the above results, in the examples of the present invention, the thermally conductive composite sheet integrated with the metal foil could be easily removed after mounting. Furthermore, the heat conductive composite sheet in which the heat conductive compound C is placed on the opposite surface of the metal foil on which the heat conductive compound A is placed improves the contact state between the heat-generating electronic component and the radiator or the thermal block. The resistance value could be further reduced.

  On the other hand, the sheets of Comparative Examples 3 to 4 were not preferable because the thermal conductive compound C having a thickness of 10 μm was not present and the metal foil surface was exposed, and the contact thermal resistance of the contact surface was high. In Examples 3 and 4, the presence of the layer of the thermally conductive compound C on the 10 μm metal foil surface reduces the contact thermal resistance of the contact surface. Therefore, the thermal resistance of the entire heat dissipation sheet can be lowered.

  In addition, the sheet of Comparative Example 5 had high adhesion between the heat-generating electronic component and the radiator or thermal block, and it was not easy to remove the radiator or thermal block from the heat-generating electronic component after mounting.

  As described above, the heat conductive composite sheets obtained in Examples 1 to 4 of the present invention are thermally conductive without causing wrinkles, blurring or unevenness by bonding and fixing a metal foil to a resin film with an adhesive. The composition was thin and evenly formed on the metal foil. The heat conductive composite sheet thus obtained has a low thermal resistance value, and furthermore, the heat conductive composite sheet is very easy to remove from the heat-generating electronic component after mounting the heat radiator and the thermal block. The goal was achieved. In addition, the heat conductive composite sheets obtained in Examples 3 to 4 have lower contact thermal resistance between the heat generating electronic component and the radiator or thermal block than those of Examples 1 and 2, and the above heat conductive composite sheet. The seat was very easy to remove the heatsink and thermal block, and the target was fully achieved.

[Industrial applicability]
Conventionally, grease and putty are often used as a heat dissipation material as a cooling measure for heat-generating electronic components (such as CPUs). Remove heatsinks and thermal blocks from heat-generating electronic components due to adhesion and vacuum effect through the heat dissipation material. However, in the present invention, a thin metal foil having a low mechanical strength is adhered and fixed to an adhesive resin film, and then uniformly removed from the heat conductive compound without unevenness. It can be set as an easy heat dissipation sheet.

It is sectional drawing which shows the manufacturing method of the heat conductive compound sheet with a metal foil of one Example of this invention. It is sectional drawing which shows a use condition same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Adhesive resin film 2 Metal foil 3 Thermal conductive compound sheet 3 'Thermal conductive compound compound 4 Coating knife 5 CPU die part 6 Thermal conductive adhesive 7 Radiator 10 Thermal conductive composite sheet

Claims (6)

  A thermally conductive composite sheet in which a metal foil is adhered and fixed to an adhesive surface of a resin film with an adhesive, and a thermally conductive compound in which a thermally conductive filler is added to a base polymer is formed into a thin film on the surface.   The heat conductive composite sheet according to claim 1, wherein the heat conductivity of the heat conductive compound is 0.5 W / m · K or more.   The heat conductive composite sheet according to claim 1, wherein the heat conductive compound is compounded in a range of 100 parts by mass or more and 3000 parts by mass or less with respect to 100 parts by mass of the base polymer.   The heat conductive composite sheet according to claim 1, wherein a thickness of the thin film of the heat conductive compound is 0.05 mm or more and 3.0 mm or less.   The thermally conductive composite sheet according to claim 1, wherein the metal foil has a thickness of 8 μm or more and 80 μm or less.   The heat conductive composite sheet according to claim 1, wherein the heat conductive composite sheet is for heat dissipation of a heat-generating electronic component.

Images