JP2012251089A - Heat-conductive flexible epoxy resin sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-conductive flexible epoxy resin sheet in close contact with opposed faces of a heating element and a heat radiating element, to conduct heat efficiently from the heating element to the heat radiating element; and heat radiation structure using the same.SOLUTION: The heat-conductive flexible epoxy resin sheet is a sheet obtained by reacting a composition containing any one or more of epoxy compounds selected from the group comprising glycidyloxy fatty acid glycidyl esters, polyalkylene glycol diglycidyl ethers and alkylene glycol diglycidyl ethers, a curing agent, and a heat-conductive filler, and has 94 or less of hardness measured corresponding to JIS K7312 by an Asker rubber hardness meter C2 type. The heat radiation structure is interposed with the sheet 1 between the heating elements 2, 3 and the heat radiating element 4. The heat-conductive flexible epoxy resin sheet 1 having 94 or less of Asker rubber C2 hardness comes into close contacts with the opposed faces of the heating element and the heat radiating element, while deformed following to irregularities thereon, and heat is thereby conducted efficiently from the heating element to the heat radiating element, to be heat-radiated quickly.

Description

  The present invention relates to a thermally conductive soft epoxy resin sheet used by being interposed between a heating element and a radiator, and more specifically, has excellent adhesion to the opposing surface of the heating element and the radiator, and is peeled off. The present invention relates to a heat conductive soft epoxy resin sheet having reworkability that can be reused.

  In recent years, heat generated from LEDs, IC chips, LSI packages, and other heat-generating components (heat-generating elements) has been released to the outside using heat-dissipating elements with high thermal conductivity such as aluminum plates and copper plates, as a heat dissipation measure for electronic devices. I am doing so. At that time, an electrically insulating material having a high thermal conductivity is interposed between the heat generating body and the heat radiating body, so that heat is smoothly transferred from the heat generating body to the heat radiating body.

Epoxy materials are well known as the material interposed between the heat generator and the heat radiator. For example, Patent Document 1 discloses a paste-like epoxy resin composition containing an epoxy resin, a curing agent, and thermally conductive particles, and Patent Document 2 discloses an epoxy resin, a curing agent, and a filler (alumina). ), A surface treatment agent, and a solvent are applied to the surface of a carrier material, and a thermally conductive epoxy resin sheet formed by drying in a semi-cured state is disclosed.
Silicone-based materials are also well known as the above materials and have been developed from hard silicone resin sheets to soft silicone resin sheets.

JP 2008-45123 A JP 2010-229269 A

  However, when the paste-like epoxy resin composition of Patent Document 1 is cured by interposing it between the heat generator and the heat radiator, the heat generator and the heat radiator are bonded and fixed. If you try to peel the heat sink from the heating element when a problem such as this occurs, the heating element (heating component) may be damaged, or the cured product of the epoxy resin composition may remain on the bonding surface of the heating element and the heat dissipation element was there.

  Further, when the heat conductive epoxy resin sheet of Patent Document 2 is also interposed between a heating element and a heat radiator and heated and pressurized, the semi-cured sheet is once melted and cured, and the heating element Since the radiator is bonded and fixed, there is a problem similar to the above.

  On the other hand, when the above-mentioned silicone resin sheet is used with a heating element and a heat dissipation element interposed between them, low-molecular siloxane leaches with time. There was a fear of causing contact failure.

  The present invention has been made under the above circumstances, and the problem to be solved is to conduct heat efficiently from the heating element to the heat radiation element in close contact with the opposed surfaces of the heat generation element and the heat radiation element. Providing a heat conductive soft epoxy resin sheet having reworkability that can be easily peeled off from the heating element and the radiator and reused even if a positioning failure between the heater and the radiator occurs. An object is to provide a heat dissipation structure using a conductive soft epoxy resin sheet.

  In order to solve the above-mentioned problems, the thermally conductive soft epoxy resin sheet according to the present invention is characterized in that the hardness measured with an Asker rubber hardness meter C2 type is 94 or less according to JIS K7312.

  The heat conductive soft epoxy resin sheet of the present invention includes one or more epoxy compounds of glycidyloxy fatty acid glycidyl ester, polyalkylene glycol diglycidyl ether, alkylene glycol diglycidyl ether, a curing agent, and a heat conductive filler. It is preferable that the sheet is obtained by reacting the composition, and the adhesive strength by a peeling test conducted according to JIS Z0237 is preferably 0.1 to 2.0 N / 25 mm.

  The curing agent is preferably an alicyclic amine, and the ratio of the number of epoxy groups in the epoxy compound to the number of active hydrogens in the curing agent (number of epoxy groups / number of active hydrogens) is greater than 1 and 3 It is preferable that it is less than. Furthermore, it is preferable that a coupling agent is contained in the composition.

  In addition, the heat dissipation structure according to the present invention is characterized in that the above-described heat conductive soft epoxy resin sheet is interposed between the heating element and the heat dissipation element.

  Like the thermally conductive soft epoxy resin sheet according to the present invention, a flexible sheet having a hardness measured with an Asker rubber hardness meter C2 type according to JIS K7312 is interposed between the heat generator and the heat radiator. When this is done, the soft epoxy resin sheet follows the irregularities of the opposing surfaces of the heating element and the radiator and deforms closely without any gaps. Therefore, heat is efficiently conducted from the heating element to the radiator and from the radiator. Heat can be released to the outside. When the hardness is 94 or more, the epoxy resin sheet becomes difficult to deform following the unevenness of the opposing surfaces of the heating element and the radiator, and a gap (air layer) is generated, so that the heat conduction efficiency from the heating element to the radiator is increased. Is unfavorable because it decreases.

  Although there is no lower limit of the hardness of the heat conductive soft epoxy resin sheet, as will be described later, when the hardness is 20 or more, the heating element and the heat radiating body are clamped and fixed with a stopper, for example, with the epoxy resin sheet interposed In addition, the tightening force eliminates the risk of the epoxy resin sheet protruding outside from the gap between the heating element and the heat radiating body and interfering with surrounding electronic components. The epoxy resin sheet that has not been removed can be reused by being peeled off from the heating element and the heat dissipation element. Moreover, the concern that the opposite side portion where the epoxy resin sheet is weakly tightened with respect to the opposing surfaces of the heating element and the heat radiating member due to the one-side tightening may be eliminated.

  In particular, a book obtained by reacting a composition containing one or more epoxy compounds of glycidyloxy fatty acid glycidyl ester, polyalkylene glycol diglycidyl ether, alkylene glycol diglycidyl ether, a curing agent, and a heat conductive filler. The heat conductive soft epoxy resin sheet of the invention has an appropriate flexibility because the epoxy compound does not have a benzene ring or a carbon ring that suppresses molecular motion by steric hindrance, and has good heat conductivity due to the heat conductive filler. Is expressed. Therefore, when this heat conductive soft epoxy resin sheet is interposed between the heat generating body and the heat radiating body, excellent heat conductivity can be exhibited in close contact with the opposed surfaces of the heat generating body and the heat radiating body. The thermally conductive soft epoxy resin sheet in which the reaction between the epoxy compound and the curing agent is completed as described above is similar to the pasty epoxy resin composition of Patent Document 1 and the thermally conductive epoxy resin sheet of Patent Document 2. In addition, it is not adhesively fixed to the heating element or radiator by a curing reaction, but is only in close contact with the heating element or radiator in an adhesive or non-adhesive state. Can do. Therefore, even if a problem such as misalignment between the heating element and the radiator occurs, the heating element (heating component) may be damaged, or a sheet piece (residue) may be left on the opposing surface of the heating element or radiator. In addition, the heat conductive soft epoxy resin sheet is peeled off and reused, and the heating element and the heat radiating element can be accurately positioned.

  The heat conductive soft epoxy resin sheet of the present invention preferably has an adhesive strength of 0.1 to 2.0 N / 25 mm according to a peeling test conducted according to JIS Z0237, and has an appropriate adhesive strength in this range. The epoxy resin sheet adheres to the opposing surface of the heating element and the radiator when in contact between the heating element and the radiator, and exhibits excellent thermal conductivity, and Also, peeling is easy.

  And the heat conductive soft epoxy resin sheet of the present invention using an alicyclic amine as a curing agent exhibits good flexibility and moderate adhesiveness, and the number of epoxy groups of the epoxy compound in the composition The heat conductive soft epoxy resin sheet of the present invention having a ratio of the number of active hydrogens to the number of active hydrogens (number of epoxy groups / number of active hydrogens) of greater than 1 and less than 3 is such that the epoxy compound and the curing agent undergo a moderate crosslinking reaction. Since the density is neither too high nor too low, the present invention exhibits moderate flexibility, tackiness and shape retention (shape retention), and further includes a coupling agent in the composition. Since the heat conductive soft epoxy resin sheet has good compatibility between the epoxy compound or the cured epoxy resin and the heat conductive filler and the dispersion state of the heat conductive filler becomes uniform, it can exhibit excellent heat conductivity.

  Moreover, since the heat dissipation structure according to the present invention includes the above-described heat conductive soft epoxy resin sheet of the present invention interposed between the heat generator and the heat radiator, the heat conductive soft epoxy resin sheet is the heat generator. The heat can be efficiently conducted from the heat generating element to the heat dissipating member in close contact with the opposite surface of the heat dissipating member, and the heat can be quickly released from the heat dissipating member to the outside. And even when a positioning failure between the heating element and the radiator occurs, the heat conductive soft epoxy resin sheet can be easily peeled off from the heating element and the radiator and reused for accurate positioning, etc. it can.

It is sectional drawing which shows one Embodiment of the thermal radiation structure which concerns on this invention. It is an enlarged view of the part enclosed with the circle | round | yen of FIG. It is explanatory drawing of other embodiment of the thermal radiation structure which concerns on this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view showing an embodiment of a heat dissipation structure according to the present invention, and FIG. 2 is an enlarged view of a portion surrounded by a circle in FIG.

  The heat dissipation structure shown in FIG. 1 is the heat conduction of the present invention between a phenol resin wiring board 3 on which an LED (light emitting diode) 2 that is a heat generator is mounted and an aluminum heat sink 4 that is a heat radiator. The wiring board 3, the heat conductive soft epoxy resin sheet 1 and the heat sink 4 are integrally fastened and fixed by screws 5 and 5 with the heat conductive soft epoxy resin sheet 1 interposed therebetween. Is a sheet having moderate flexibility, and as shown in FIG. 2, it closely follows the concavity and convexity of the opposing surfaces 3a and 4a of the wiring board 3 and the heat sink 4 while closely contacting the opposing surfaces 3a and 4a without deformation. Yes. Therefore, the heat generated when the LED 2 is turned on is efficiently conducted from the wiring board 3 to the heat sink 4 through the heat conductive soft epoxy resin sheet 1 and quickly radiated from the heat sink 4. The heat sink 4 is provided with a plurality of fins 4b on the lower surface to increase the heat radiation area in order to improve the heat radiation efficiency, but a plate-like heat sink without fins may of course be used.

  The heat conductive soft epoxy resin sheet 1 of the present invention (hereinafter referred to as the heat conductive sheet 1) used in the heat dissipation structure described above is for increasing the close contact with the facing surfaces 3a and 4a of the wiring board 3 and the heat sink 4. It is a sheet provided with flexibility so that the hardness (hereinafter referred to as Asker rubber C2 hardness) measured with an Asker rubber hardness meter C2 type according to JIS K7312 is 94 or less. The heat conductive sheet 1 having an Asker rubber C2 hardness of more than 94 is inferior in flexibility and hardly deforms following the concavities and convexities of the opposed surfaces 3a and 4a, so that the portion between the opposed surfaces 3a and 4a and the thermally conductive sheet 1 A gap (gap) is generated, and the heat conduction from the wiring board 3 to the heat sink 4 is hindered by this gap and sufficient heat dissipation is not exhibited. Therefore, the object of the present invention cannot be achieved.

Although there is no particular lower limit of the Asker rubber C2 hardness of the heat conductive sheet 1, it is preferably 20 or more. Since the heat conductive sheet 1 having an Asker rubber C2 hardness of less than 20 is too flexible, the heat conductive sheet 1 is sandwiched between the wiring board 3 and the heat sink 4 and fixed with screws 5 and 5 by the tightening force. It becomes easy to protrude outside between the wiring board 3 and the heat sink 4. If the thermal conductive sheet 1 protrudes in this way, there is a risk of interference with surrounding electronic components and the like. Therefore, it is necessary to cut off the protruding portion. It is uneconomical because it cannot be reused by peeling from the substrate 3 and the heat sink 4. Further, if the thermal conductive sheet 1 is too flexible, it is likely to be in a single-clamped state (a state in which one screw 5 is strongly tightened and the other screw 5 is loosely tightened). There is also a possibility that the side portion is in close contact with the facing surfaces 3 a and 4 a of the wiring board 3 and the heat sink 4.
On the other hand, since the heat conductive sheet 1 having an Asker rubber C2 hardness of 20 or more is not too flexible, all the above disadvantages can be eliminated. The more desirable lower limit value of the Asker rubber C2 hardness of the heat conductive sheet 1 is 50, and the more desirable lower limit value is 60.

  The thermal conductive sheet 1 is a liquid which is prepared by appropriately blending a coupling agent and a curing accelerator, which contains an epoxy compound, a curing agent, and a thermal conductive filler as essential components on a release-treated base film. A soft epoxy resin sheet obtained by applying the composition, reacting and curing the composition by heating, and then peeling it from the base film. The curing reaction may be performed by adopting general reaction conditions of an epoxy compound. For example, the curing reaction may be performed at a temperature of about 130 ° C. for about 1 hour.

  In order to obtain the flexible heat conductive sheet 1, any one or more of glycidyloxy fatty acid glycidyl ester, polyalkylene glycol diglycidyl ether, and alkylene glycol diglycidyl ether is used as the main component epoxy compound of the composition. It is preferable. These epoxy compounds do not have a structure that suppresses molecular movement by steric hindrance in the compounds (for example, benzene rings in aromatic epoxy compounds and carbocycles in alicyclic epoxy compounds). Can be formed. These epoxy compounds are preferably used in liquid form at normal temperature because they contain a heat conductive filler, but those that are solid at normal temperature can also be used in combination with other liquid epoxy compounds.

  Preferred examples of the glycidyloxy fatty acid glycidyl ester include 12- (glycidyloxy) -9-octadecenoic acid glycidyl ester represented by the following [Chemical Formula 1] and 12- (glycidyloxy) -octadecanoic acid glycidyl represented by the following [Chemical Formula 2]. Examples include esters. The former 12- (glycidyloxy) -9-octadecenoic acid glycidyl ester is an epoxy compound obtained by reacting 12-hydroxy-9-octadecenoic acid (ricinoleic acid) with epichlorohydrin, and the latter 12- ( Glycidyloxy) -octadecanoic acid glycidyl ester is an epoxy compound obtained by hydrogenating 12-hydroxy-9-octadecenoic acid (ricinoleic acid) and reacting with epichlorohydrin.

  In addition, preferable examples of the polyalkylene glycol diglycidyl ether include polyethylene glycol diglycidyl ether represented by the following [Chemical Formula 3] and polypropylene glycol diglycidyl ether represented by the following [Chemical Formula 4]. Preferable examples of glycidyl ether include 1,6-hexanediol diglycidyl ether shown in the following [Chemical Formula 5].

  In the said composition, 1 or more types of the epoxy compound illustrated below other than the said epoxy compound of a main component can also be mix | blended. That is, bisphenol A type epoxy compound, bisphenol F type epoxy compound, bisphenol S type epoxy compound, phenol novolac type epoxy compound, alkylphenol novolac type epoxy compound, aralkyl type epoxy compound, biphenol type epoxy compound, naphthalene type epoxy compound, dicyclopentadiene Type epoxy compounds, epoxy compounds of condensates of phenols and aromatic aldehydes having a phenolic hydroxyl group, triglycidyl isocyanurate, alicyclic epoxy compounds, and the like can also be blended. Since these epoxy compounds have a benzene ring or a carbon ring that suppresses molecular motion and tend to reduce the flexibility of the resulting heat conductive sheet 1, they cannot be used as the main component epoxy compound.

  In order to obtain the flexible thermal conductive sheet 1, the main component epoxy compound is such that the main component epoxy compound occupies 61 parts by mass or more with respect to 100 parts by mass of the total amount of the epoxy compound in the composition. Is preferably blended. When the amount of the main component epoxy compound is less than 61 parts by mass, the resulting heat conductive sheet 1 has an Asker rubber C2 hardness of more than 94, making it difficult to achieve the object of the present invention.

  Examples of the curing agent to be blended in the composition include amines, acid anhydrides, polyphenols and polymercaptans, and these may be used alone or in combination of two or more. Among these curing agents, amines such as alicyclic amines and aliphatic amines are suitable. Examples of alicyclic amines include 1,3-bisaminomethylcyclohexane, and examples of aliphatic amines include Ethyltris {aminopropyloxy (n = 1 to 3) methyl} methane and the like are preferably used. In particular, the former alicyclic amine is extremely preferable because the heat conductive sheet 1 having both good flexibility and appropriate adhesiveness can be obtained.

  In order to impart moderate flexibility to the heat conductive sheet 1, the ratio of the number of epoxy groups of the epoxy compound to the number of active hydrogens of the curing agent (number of epoxy groups / number of active hydrogens) in the composition is greater than 1 3 It is preferable to adjust the blending ratio of the epoxy compound and the curing agent so as to be less than When the number of epoxy groups / active hydrogen is 1 or less, most of the epoxy compound and the curing agent undergo a cross-linking reaction and the cross-linking density increases, so that a flexible heat conductive sheet 1 cannot be obtained. When the number of hydrogen is 3 or more, since most epoxy compounds do not undergo a curing reaction, it is difficult to obtain a heat conductive sheet 1 having shape retention (shape retention). However, if the number of epoxy groups / active hydrogen is adjusted within the range of more than 1 and less than 3 as described above, the epoxy compound and the curing agent undergo a moderate crosslinking reaction, and flexibility, tackiness and shape retention It becomes possible to obtain the heat conductive sheet 1 which has (shape retainability). Preferably, the number of epoxy groups / the number of active hydrogens is 1.1 or more and 2.8 or less, and more preferably 1.3 or more and 2.6 or less.

  The heat conductive sheet 1 has an adhesive strength of 0.1 to 2.0 N by a peeling test according to JIS Z0237 by using the alicyclic amine as a curing agent or controlling the number of epoxy groups / active hydrogen. / 25 mm is preferably adjusted. When the heat conductive sheet 1 having an appropriate adhesive strength in this range is interposed between the wiring board 3 that holds the LED 2 that is a heat generator and the heat sink 4 that is a heat radiator, Since it adheres to the opposing surfaces 3a and 4a of the heat sink 4 and is in close contact with no gap, it exhibits excellent thermal conductivity and is easy to peel off. In addition, the positioning operation of the heat conductive sheet 1 is facilitated. When the adhesive strength is stronger than 2.0 N / 25 mm, the heat conductive sheet 1 is likely to stick to another member or a sticking jig, so that handling properties (handleability) are deteriorated.

  As described in the examples below, the adhesive force is a sample of a heat conductive sheet 100 mm long x 25 mm wide x 200 μm thick, and the sample is roll-bonded to an aluminum plate according to JIS Z0237 at room temperature. 30 minutes later, the peel strength measured in a peeling test conducted under conditions of a peel angle of 180 ° and a peel speed of 300 mm / sec.

  In addition, you may mix | blend a suitable quantity with a hardening accelerator in the said composition with a hardening | curing agent. Examples of the curing accelerator include tertiary amines, imidazoles, Lewis acids, Lewis bases, organic metal compounds, organic acid metal salts, and the like. These may be used alone or in combination of two or more. May be. Among these curing accelerators, tertiary amines are optimal, and for example, 2,4,6-tris (dimethylaminomethyl) phenol is preferably used.

Examples of the heat conductive filler blended in the composition include (1) metal oxide powder such as alumina, magnesium oxide, beryllium oxide, titanium oxide, and zinc oxide, (2) boron nitride, silicon nitride, aluminum nitride, Inorganic powder such as silicon carbide, (3) Metal powder such as copper, silver, iron, aluminum and nickel, (4) Metal alloy powder such as titanium, (5) Carbon powder such as diamond, carbon black and carbon fiber Or a fiber, (6) Silica powder, such as quartz and coal glass, etc. are mentioned, These may be used independently and may be used together 2 or more types.
Since the heat conductive sheet 1 sandwiched between the wiring board 3 and the heat sink 4 is required to be electrically insulating, among the above heat conductive fillers, the electrically insulating aluminum nitride, boron nitride, magnesium oxide, alumina, diamond Etc. are particularly preferably used. In addition, these heat conductive fillers may have a uniform particle size, or may be a mixture of materials having different particle sizes.

  The blending amount of the heat conductive filler can be up to 90% by mass of the total amount of the composition (in other words, 90% by mass of the entire heat conductive sheet 1) corresponding to the heat conductivity required for the heat conductive sheet 1. It is. If it exceeds 90% by mass, the fluidity of the composition will decrease, making it difficult to apply and form a film on the base film, and the Asker rubber C2 hardness of the thermally conductive sheet 1 obtained by curing will be 94. Since it becomes a sheet | seat lacking in flexibility exceeding it, it will become difficult to achieve the objective of this invention. There is no particular lower limit on the amount of the heat conductive filler, but if it is too small, the heat conductivity of the heat conductive sheet 1 is lowered and the heat dissipation performance is deteriorated, so the lower limit is 50% by mass, preferably 70% by mass. It is good to do. A very preferable blending amount of the heat conductive filler is in the range of 80 to 87% by mass.

  A coupling agent such as epoxy silane, aluminum or titanate may be appropriately blended with the composition. These coupling agents may be blended directly in the composition, or may be blended by surface-coating the heat conductive filler. Among these coupling agents, aluminum-based or titanate-based coupling agents that do not contain silicon are preferably used, and specifically, acetoalkoxyaluminum diisopropylate and the like are extremely preferably used. When such a coupling agent is blended, the compatibility between the epoxy compound or the cured epoxy resin and the heat conductive filler is improved, and the dispersion state of the heat conductive filler becomes uniform. The heat conductive sheet 1 which has can be obtained.

  Although the compounding quantity of a coupling agent is not specifically limited, When surface-coating to a heat conductive filler and mix | blending, a coupling agent may be added within the range of 0.01-1 mass% with respect to the heat conductive filler amount. preferable. A more preferable blending amount of the coupling agent is 0.01 to 0.5% by mass.

  The thickness of the heat conductive sheet 1 is not limited and may be appropriately determined in consideration of the distance between the heat generator and the heat radiating body. However, as in the heat radiating structure shown in FIG. When the heat conductive sheet 1 is interposed between the two, it is preferable to set the thickness of the heat conductive sheet 1 to about 50 μm to 2 mm.

  1 and 2, the heat conductive sheet 1 is interposed between the wiring board 3 on which the LED 2 is mounted and the heat sink 4 and tightened with screws 5 and 5 to wire the heat conductive sheet 1. Since the substrate 3 and the heat sink 4 are in close contact with the uneven surfaces 3a and 4a, the heat generated when the LED 2 is turned on is efficiently conducted from the wiring board 3 to the heat sink 4 through the heat conductive sheet 1, and the heat sink. Heat can be quickly radiated from 4 to the outside. And when the malfunction of positioning of the wiring board 3 and the heat sink 4 or the malfunction of positioning of the heat conductive sheet 1 occurs, the screws 5 and 5 are removed and the heat conductive sheet 1 is removed from the wiring board 3 and the heat sink 4. Can be easily peeled off and reused for accurate positioning, etc., so that reworkability is also excellent.

  FIG. 3 is an explanatory view of another embodiment of the heat dissipation structure according to the present invention.

  In this heat dissipation structure, aluminum heat is dissipated by interposing the above-described heat conductive sheet 1 of the present invention on an electronic component 20 (heating element) such as an IC chip or LSI package mounted on a wiring board 30 made of phenol resin. A plate 40 (heat radiating body) is placed, and these are integrally tightened and fixed with screws 5 and 5, and the flexible heat conductive sheet 1 is uneven on the opposing surfaces of the electronic component 20 and the aluminum heat radiating plate 40. While following the deformation (not shown), it is in close contact with the opposing surface without any gap, and the heat generated when driving the electronic component 20 is efficiently conducted to the aluminum heat sink 40 through the heat conductive sheet 1, and the aluminum heat sink Heat is quickly released from 40.

  This heat dissipation structure also has the same excellent effect as the heat dissipation structure of the embodiment shown in FIGS. 1 and 2 because the above-described heat conductive sheet 1 of the present invention is interposed between the heat generating element and the heat dissipation element. Needless to say, the effect (the operational effect resulting from the above-described heat conductive sheet 1) is obtained.

  Next, more specific examples of the heat conductive sheet according to the present invention will be described.

[Examples 1 to 10]
The epoxy compounds, curing agents, curing accelerators, and coupling agents described in Tables 1 and 2 below are mixed in the addition amounts (blending amounts) described in Examples 1 to 10 in Tables 1 and 2. As a result, 10 types of mixed liquids having different compositions were obtained. And to these liquid mixture, the heat conductive filler described in Table 1 and Table 2 is added in the addition amount described in Examples 1 to 10 in Table 1 and Table 2, and the mixture is stirred and degassed. The coating liquid compositions of Examples 1 to 10 having different values were prepared.

By applying these liquid coating compositions to the surface of a release-treated polyethylene terephthalate film (PET film) with a comma coater, heating and curing at 130 ° C. for 1 hour, and then peeling off from the PET film Samples of thermally conductive sheets of Examples 1 to 10 were produced.
As will be described later, the thickness of the sample is 1 mm in the case of the thermal conductivity measurement sample, 200 μm in the case of the peeling test sample, and a plurality of sheets in the case of the Asker rubber C2 hardness measurement sample. Samples were stacked to 8 mm.

About the produced sample of the heat conductive sheet of Examples 1-10, thermal conductivity, adhesive force (peeling strength), and Asker rubber C2 hardness were measured by the following methods.
1) Measurement of thermal conductivity A laser flash measuring machine (manufactured by ULVAC-RIKO, Inc., TC-7000) was used, and the thermal conductivity of a sample having a thickness of 1 mm was measured in accordance with JIS R1611-11991.
2) Measurement of adhesive strength At room temperature, according to JIS Z0237, a sample of length 100 mm x width 25 mm x thickness 200 μm was roll-bonded to an aluminum plate (150 mm x 150 mm x 0.5 mm), and after 30 minutes, the peel angle A peeling test was conducted at 180 ° and a peeling speed of 300 mm / sec, and the adhesive strength (peel strength) of the sample was measured.
3) Measurement of Asker rubber C2 hardness A plurality of samples were stacked to prepare a sample having a thickness of 8 mm, and the hardness of the sample was measured with an Asker rubber hardness meter C2 type (manufactured by Kobunshi Keiki Co., Ltd.) according to JIS K7312. .
The measurement results are shown in Tables 1 and 2.

[Comparative Examples 1-4]
For comparison, the epoxy compound, the curing agent, the curing accelerator, and the coupling agent described in Table 2 below are mixed in the addition amount (blending amount) described in Comparative Examples 1 to 4 in Table 2, Comparative Examples 1 to 2 having different compositions by adding the heat conductive fillers described in Table 2 to these mixed solutions in the addition amounts described in Comparative Examples 1 to 4 in Table 2 and stirring and degassing. A coating liquid composition No. 4 was prepared. And the sample of the heat conductive sheet of Comparative Examples 1-4 was produced similarly to the said Examples 1-10 using these coating liquid compositions.
For these comparative samples, the thermal conductivity, adhesive strength (peel strength), and Asker rubber C2 hardness were measured in the same manner as in Examples 1 to 10, and the results are also shown in Table 2 below.

The epoxy compounds (1) described in Tables 1 and 2 above are commercially available as SR-CF2 (epoxy equivalent 260) manufactured by Sakamoto Pharmaceutical Co., Ltd.
The epoxy compound (2) is commercially available as JER811 (epoxy equivalent 186) manufactured by Mitsubishi Chemical Corporation.
The epoxy compound (3) is commercially available as SR-8EG (epoxy equivalent 285) manufactured by Sakamoto Pharmaceutical Co., Ltd.
The epoxy compound (4) is commercially available as SR-4PG (epoxy equivalent 305) manufactured by Sakamoto Pharmaceutical Co., Ltd.
The epoxy compound (5) is commercially available as EP-4088S (epoxy equivalent 170) manufactured by Adeka Corporation.
The epoxy compound (6) is commercially available as YED216M (epoxy equivalent 150) manufactured by Mitsubishi Chemical Corporation.
The curing agent (1) is commercially available as J-882 (active hydrogen equivalent 80) manufactured by Daito Sangyo Co., Ltd.
The curing agent (2) is commercially available as B-2413 (active hydrogen equivalent 47) manufactured by Daito Sangyo Co., Ltd.
The curing accelerator is commercially available as HD-Acc43 manufactured by Daito Sangyo Co., Ltd.
The coupling agent is commercially available as Plenact AL-M manufactured by Ajinomoto Fine Techno Co., Ltd.
The epoxy compounds (1) to (6), the curing agents (1) and (2), and the coupling agent are liquid materials.

From Tables 1 and 2 above, the samples of the heat conductive sheets of Examples 1 to 5, 9, and 10 having glycidyloxy fatty acid glycidyl ester as the main component, and examples having polyalkylene glycol diglycidyl ether as the main component. Samples of the heat conductive sheets 6 and 7 and the sample of the heat conductive sheet of Example 8 mainly composed of alkylene glycol diglycidyl ether have benzene rings in which the main component epoxy compound suppresses molecular motion. Since it does not have a carbon ring, it is flexible and the Asker rubber C2 hardness is 94 or less.
On the other hand, the sample of the comparative example 3 which has the aromatic epoxy compound (bisphenol A diglycidyl ether and bisphenol F diglycidyl ether) provided with a pair of benzene ring which suppresses a molecular motion as a main component, and the carbon ring were provided. All of the samples of Comparative Example 4 containing an alicyclic epoxy compound as a main component are inferior in flexibility, and the Asker rubber C2 hardness is 97 or more.
From this, it can be seen that glycidyloxy fatty acid glycidyl ester, polyalkylene glycol diglycidyl ether, and alkylene glycol diglycidyl ether are effective epoxy compounds for obtaining a flexible thermal conductive sheet.

  Moreover, even if the glycidyloxy fatty acid glycidyl ester that is effective for imparting flexibility is the main component as in the sample of Comparative Example 2, the blending amount of the main component glycidyloxy fatty acid glycidyl ester is When the total amount is less than 61 parts by mass with respect to 100 parts by mass, the flexibility decreases and the Asker rubber C2 hardness exceeds 94. From this, in order to obtain a thermal conductive sheet having an Asker rubber C2 hardness of 94 or less, 61 parts by mass or more is blended with 100 parts by mass as a main component of the epoxy compound, which is effective for imparting flexibility. It turns out that is important.

The samples of Examples 9 and 10 and the sample of Comparative Example 1 all contain 80 parts by mass of a glycidyloxy fatty acid glycidyl ester that is effective for imparting flexibility, but these samples contain a curing agent. Since the amount is 8.3 parts by weight for the sample of Example 9, 11.0 parts by weight for the sample of Example 10, and 17.3 parts by weight for the sample of Comparative Example 1, the number of epoxy groups / curing agent activity The ratio of the hydrogen numbers is 2.2 for the sample of Example 9, 1.6 for the sample of Example 10, and 1.0 for the sample of Comparative Example 1. The samples of Examples 9 and 10 in which the ratio of the number of epoxy groups / the number of active hydrogens in the curing agent is in the range of more than 1 and less than 3 are both flexible with an Asker rubber C2 hardness of 94 or less. / The sample of Example 9 having a larger ratio of the number of active hydrogens in the curing agent has a smaller Asker rubber C2 hardness and more flexibility than the sample of Example 10 having a smaller ratio. In contrast, the sample of Comparative Example 1 in which the ratio of the number of epoxy groups / the number of active hydrogens in the curing agent is 1, the Asker rubber C2 hardness is 97 and lacks flexibility, and it is difficult to achieve the object of the present invention. Is.
From this, the flexibility of the heat conductive sheet increases as the ratio of the number of epoxy groups / the number of active hydrogens in the curing agent increases, and in order to obtain a soft heat conductive sheet having an Asker rubber C2 hardness of 94 or less, the number of epoxy groups It turns out that the compounding quantity of an epoxy compound and a hardening | curing agent needs to be determined so that the ratio of the number of active hydrogens of / hardening agent may be larger than 1 and 3 or less.

The sample of Example 1 containing an aliphatic amine as a curing agent has a weak adhesive strength of 0.1 N / 25 mm as measured by a peeling test, whereas the sample of Example 2 contains an alicyclic amine as a curing agent. The adhesive strength increased to 0.3 N / 25 mm, and the sample of Example 9 in which a coupling agent was further added had an adhesive strength as large as 0.5 N / 25 mm.
From this, in order to obtain a heat conductive sheet having adhesive strength, it is more effective to use an alicyclic amine than an aliphatic amine as a curing agent, and it is more effective when used in combination with a coupling agent. I understand.

  Moreover, as for the sample of Examples 1-10 and the samples of Comparative Examples 1-4, all are spherical alumina (what mixed two types of average particle diameters 35 micrometers and 3 micrometers, φ35: φ3 = 7: 3, Alternatively, by including 83% by mass of φ35: φ3 = 6: 4), a good thermal conductivity of 2.0 W / m · K is imparted. This is because spherical alumina with an average particle diameter of 3 μm is filled in the gaps between spherical aluminas with an average particle diameter of 35 μm, and a highly conductive filler (80% or more) can be filled, and large and small spherical aluminas are in contact with each other. In order to conduct heat efficiently.

1 Thermally conductive soft epoxy resin sheet 2 LED (heating element)
20 Electronic components (heating elements)
3,30 Wiring board 4 Heat sink
40 Aluminum heat sink (heat sink)
5 Screw

Claims (7)

  A heat conductive soft epoxy resin sheet having a hardness measured by an Asker rubber hardness tester C2 type according to JIS K7312 of 94 or less.   It is a sheet obtained by reacting a composition containing at least one epoxy compound of glycidyloxy fatty acid glycidyl ester, polyalkylene glycol diglycidyl ether, alkylene glycol diglycidyl ether, a curing agent, and a heat conductive filler. The thermally conductive soft epoxy resin sheet according to claim 1, wherein   The heat conductive soft epoxy resin sheet according to claim 1 or 2, wherein an adhesive strength according to a peeling test conducted in accordance with JIS Z0237 is 0.1 to 2.0 N / 25 mm.   The thermally conductive soft epoxy resin sheet according to claim 2 or 3, wherein the curing agent is an alicyclic amine.   5. The ratio of the number of epoxy groups of the epoxy compound in the composition to the number of active hydrogens of the curing agent (number of epoxy groups / number of active hydrogens) is greater than 1 and less than 3, 5. A heat conductive soft epoxy resin sheet according to claim 1.   6. The thermally conductive soft epoxy resin sheet according to claim 2, further comprising a coupling agent in the composition.   A heat dissipation structure, wherein the heat conductive soft epoxy resin sheet according to any one of claims 1 to 6 is interposed between a heat generator and a heat radiator.

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