JP6408738B1 - Manufacturing method of heat dissipation structure - Google Patents

Abstract

In a heat dissipation structure in an electronic device or the like, a heat conductive adhesive that is excellent in thermal conductivity, electrical insulation, and adhesiveness, can reliably secure a heat dissipation path, and can simplify a forming process. Provided are a sheet, a manufacturing method thereof, a heat dissipation structure using the thermally conductive adhesive sheet, and a manufacturing method thereof. A heat conductive adhesive sheet comprising a predetermined resin and a predetermined inorganic filler, a B stage sheet, wherein the resin is made of a resin composition including a block urethane prepolymer, an epoxy compound and a curing catalyst. Thus, a heat dissipation structure is formed. [Selection figure] None

Description

  The present invention relates to a thermally conductive adhesive sheet that can be suitably used for forming a heat dissipation path in a heat-generating electronic component or the like of an electronic device, a manufacturing method thereof, a heat dissipation structure using the heat conductive adhesive sheet, and its It relates to a manufacturing method.

Electronic components such as LEDs, CPUs, and power semiconductors used in electronic devices are accompanied by a large amount of heat when used. Such heat generation may hinder the normal operation of the electronic device, and may cause failure or breakage. For this reason, heat generated from a heating element such as the electronic component as described above is released to the outside using a heat sink such as a heat sink or a metal frame.
At that time, in order to enhance the heat dissipation effect, a sheet made of an electrically insulating material having high thermal conductivity is sandwiched between the heating element and the radiator, so that the heat conduction from the heating element to the radiator is efficient. To be done. Such a sheet is generally called a heat radiating sheet, a heat conductive sheet or the like (hereinafter, these may be collectively referred to as a heat radiating sheet).

  In recent years, with the miniaturization and high performance of various parts for electronic devices, countermeasures against the heat generation have become even more important. For this reason, the heat dissipation sheet can ensure a heat dissipation path without cracking or shifting even when subjected to external stresses such as impact and vibration as well as thermal conductivity and electrical insulation. It is required to be a thing.

For such problems, various methods have been proposed in which a heat dissipation sheet can be bonded.
For example, Patent Document 1 describes that a heat-dissipating member and a movement-preventing film that prevents movement of the heat-dissipating member are disposed between the heat-dissipating member and the housing.
Patent Document 2 discloses that an adhesive insulating sheet containing an organosilicon compound in an insulating resin is used to cause hydrolysis and dehydration condensation reaction to bond a metal substrate and a heat sink. Is described.
Patent Document 3 describes that an adhesive sheet that includes an inorganic filler, an epoxy resin, and a curing agent thereof, is placed between a metal substrate and a metal foil, and is cured to a C stage state. Has been.

JP 2006-100803 A JP-A-9-224864 JP 2009-49062 A

  However, in the method described in Patent Document 1, the heat dissipation member is applied by applying a heat blocking member for chemically or electronically bonding the heat dissipation member made of a resin material, and then applying the heat dissipation member. In this process, labor and time are increased, and the processing cost is increased.

  On the other hand, in the method described in Patent Document 2, the (adhesive) insulating sheet itself has adhesiveness, but alcohol gas is generated during the dehydration condensation reaction between the organosilicon compound and the insulating resin. If the gas remains at the adhesion interface, the heat conduction is lowered, and the adhesion interface may be peeled off due to swelling. Furthermore, from the viewpoint of the reactivity of the organosilicon compound, it is difficult to suppress thermal expansion or thermal shrinkage of the adhesive insulating sheet by adding an inorganic filler.

  Moreover, since the epoxy resin is a binder component, the adhesive sheet described in Patent Document 3 has a large restriction during storage and use due to the high reactivity of the epoxy group, and is inferior in handleability. Depending on the heating conditions during curing, residues such as unreacted epoxy residues may cause gas accumulation at the adhesion interface due to decomposition or evaporation, and this gas will reduce heat conduction as described above. In addition, the adhesive interface may be peeled off due to swelling.

  Therefore, as a heat dissipation sheet, not only thermal conductivity and electrical insulation, but also sufficient adhesion, it is possible to ensure a heat dissipation path in the heat dissipation structure provided with the heat dissipation sheet, and such a heat dissipation structure It is desired that it can be easily formed.

  The present invention has been made in order to solve the above-described problems, and in a heat dissipation structure in an electronic device or the like, it is excellent in thermal conductivity, electrical insulation, and adhesiveness, and can reliably secure a heat dissipation path. Moreover, it aims at providing the heat conductive adhesive sheet which can simplify a formation process, its manufacturing method, and the thermal radiation structure using the said heat conductive adhesive sheet, and its manufacturing method.

  In the present invention, a B-stage sheet containing a resin comprising a predetermined block urethane prepolymer, a predetermined epoxy compound, and a curing catalyst, and a predetermined inorganic filler is suitable as a thermally conductive adhesive sheet. This is based on the finding.

That is, the present invention provides the following [1] to [9].
[1] A heat conductive adhesive sheet containing a resin and an inorganic filler, wherein the heat conductive adhesive sheet is a B stage sheet, and the resin includes a block urethane prepolymer, an epoxy compound, and a curing catalyst. The block urethane prepolymer comprises a reaction product of an aliphatic diisocyanate compound and a hydrogenated polybutadiene polyol having hydroxyl groups at both ends, the terminal isocyanate group of which is blocked with an aromatic hydroxy compound, and the reaction The structural unit derived from the aliphatic diisocyanate compound in the product is 1.3 to 2.8 moles relative to 1 mole of the structural unit derived from the hydrogenated polybutadiene polyol, and the epoxy compound contains 2 to 6 epoxy groups. And the epoxy group is one hydroxyl group of the aromatic hydroxy compound. The inorganic filler comprises spherical particles (f1) having an average particle size of more than 10 μm and 100 μm or less, and spherical particles (f2) having an average particle size of 0.1 μm or more and 10 μm or less. ), The content of the spherical particles (f1) in the inorganic filler is 58.0 to 80.0% by mass, and the content of the inorganic filler is 80.0 to 94.0% by mass, Thermally conductive adhesive sheet.
[2] The heat according to [1], wherein the inorganic filler contains one or more selected from magnesia, alumina, boron nitride, aluminum nitride, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, and crystalline silica. Conductive adhesive sheet.
[3] The heat conductive adhesive sheet according to the above [1] or [2], wherein the thickness is 100 μm or more and less than 500 μm.
[4] The B stage sheet according to any one of [1] to [3], wherein the tack force value t _B measured under the following measurement conditions is 0.1 to 10.0 N / cm ^2. The heat conductive adhesive sheet of description.
<Measurement conditions>
At 25 ° C., a 15 mm × 15 mm × 15 mm aluminum block is placed on a 30 mm × 30 mm × thickness 0.3 mm sheet sample fixed on the aluminum plate surface, and a mechanical force gauge is used to After pressing from the top in the vertical direction with a load of 50 N for 10 seconds, the force required to peel off the sheet sample and the block is measured by pulling up in the vertical direction, and this measured value is taken as the tack force.
[5] For a C stage sheet obtained by curing the B stage sheet at 220 to 240 ° C., the tack force value t _C measured under the measurement conditions is 0.2 N / cm ² or more, and the t _C and the above the ratio t _C / t _B of t _B is 1.5 or more, heat conductive adhesive sheet according to [4].
[6] The method for producing a thermally conductive adhesive sheet according to any one of [1] to [5] above, the step of preparing a mixture containing the resin composition and the inorganic filler, and the mixture Forming the sheet molded body, and heating and semi-curing the sheet molded body at 120 to 180 ° C. for 5 to 60 minutes to obtain the thermally conductive adhesive sheet, Manufacturing method of heat conductive adhesive sheet.

[7] A cured body of the heat conductive adhesive sheet according to any one of [1] to [5], a member (M1) directly bonded to one surface of the cured body, and the cured body Each of the joint surfaces of the member (M1) and the member (M2) with the cured body includes at least one of a metal and a resin. Heat dissipation structure.
[8] The heat dissipation structure according to [7], in which any one of the member (M1) and the member (M2) is a constituent member of a heat-generating electronic component.
[9] The method for producing a heat dissipation structure according to [7] or [8] above, wherein the heat conductive adhesive sheet is sandwiched between the member (M1) and the member (M2). And curing the thermally conductive adhesive sheet of the structural precursor at 220 to 260 ° C., the cured body of the thermally conductive adhesive sheet, the member (M1) and the member (M2) The manufacturing method of a heat radiating structure which has the process of obtaining the heat radiating structure bonded | bonded.

The heat conductive adhesive sheet of the present invention is excellent in heat conductivity, electrical insulation, and adhesiveness, and by using this, a heat dissipation structure that can reliably secure a heat dissipation path of an electronic device or the like is formed. Moreover, the process of forming such a heat dissipation structure can be simplified.
Therefore, according to this invention, the heat dissipation adhesive body excellent in heat dissipation and its manufacturing method can be provided suitably using the said heat conductive adhesive sheet.

It is a schematic sectional drawing for demonstrating the measuring method of adhesiveness (tack force) in an Example.

  Hereinafter, the heat conductive adhesive sheet of the present invention and the manufacturing method thereof, and the heat dissipation structure using the heat conductive adhesive sheet and the manufacturing method thereof will be described in detail.

[Heat conductive adhesive sheet]
The heat conductive adhesive sheet of the present invention includes a predetermined resin and a predetermined inorganic filler, and is a B stage sheet. The resin comprises a resin composition containing a predetermined block urethane prepolymer, a predetermined epoxy compound, and a predetermined curing catalyst.
Here, the “B stage sheet” means a sheet made of a composition containing a thermosetting resin in a semi-cured (B stage) state. The degree of the semi-cured state is not specified.
Further, the “C stage” referred to in the present specification is a term used for the B stage, and means a state in which the thermosetting resin is almost completely cured.

The thermally conductive adhesive sheet is a resin sheet formed by semi-curing (B-stage) a mixed composition containing the resin composition and the inorganic filler. In such a semi-cured state, the isocyanate group and epoxy group of the block urethane prepolymer and the epoxy compound which are binder components in the resin composition remain, and remain on the surface of the B stage sheet. By these functional groups, an appropriate adhesive force to the adherend can be obtained. For example, when the adherend is a metal such as aluminum or copper, it is presumed that the adhesion is caused by a reaction with a hydroxyl group or sorption water due to oxidation or the like of the metal surface. Further, for example, when the adherend is an exterior resin of a power semiconductor, it is presumed that the adhesion is caused by a reaction with a functional group or sorption water remaining in the exterior resin.
Moreover, the heat conductive adhesive sheet is excellent in flexibility, has an appropriate adhesiveness (tack force) to an adherend, and is excellent in reworkability that can be easily reattached.
Furthermore, the adhesive force is further increased by heating the heat conductive adhesive sheet after being disposed at a predetermined position or by heat generated from a heat-generating electronic component in the vicinity of the position. For this reason, the said heat conductive adhesive sheet can comprise the thermal radiation structure excellent in adhesiveness, and can exhibit the stable thermal conductivity and high electrical insulation with a simple means.

Specifically, the degree of adhesiveness of the thermally conductive adhesive sheet preferably has the following tack force. The B stage sheet preferably has a tack force value t _B measured under the following measurement conditions of 0.1 to 10.0 N / cm ² , more preferably 0.2 to 8.0 N / cm ² . is there.

<Measurement conditions>
At 25 ° C., a 15 mm × 15 mm × 15 mm aluminum block is placed on a 30 mm × 30 mm × thickness 0.3 mm sheet sample fixed on the aluminum plate surface, and a mechanical force gauge is used to After pressing from the top in the vertical direction with a load of 50 N for 10 seconds, the force required to peel off the sheet sample and the block is measured by pulling up in the vertical direction, and this measured value is taken as the tack force.

The contact surface of the block with the sheet sample has a ten-point average roughness Rz _JIS of 5.0 to 10.0 μm. The ten-point average roughness Rz _{JIS referred} to in this specification is a value measured at a reference length of 0.8 mm in accordance with JIS B 0601: 2013, and is an average value of 20 measurements.
Further, during measurement, the entire surface of the sheet sample is pressed against the aluminum plate with a load of 200 N or more from the upper surface of the sheet sample via a release paper so that the sheet sample does not peel from the aluminum plate.
Further, the force required to peel off the sheet sample and the block is the maximum load when the sheet sample is pulled up by a mechanical force gauge.
Specifically, the tack force is measured by the method described in Examples described later.

When the t-force value t _{B of the} B-stage sheet is within the above range, the thermally conductive adhesive sheet (B-stage sheet) has appropriate adhesiveness (tack force) to the adherend. It is easy to re-paste, and it can be said that it is easy to handle.

Further, for a C stage sheet obtained by curing the B stage sheet at 220 to 240 ° C., the tack force value t _C measured under the measurement conditions is 0.2 N / cm ² or more, and the t _C and the t it preferably has a specific t _C / t _B of _B is 1.5 or more. The higher the adhesiveness of the C stage sheet, the more preferable, but in practice, more preferably, t _C is 1.0 to 50.0 N / cm ² , and t _C / t _B is 1.6 to 10.0. .
Since the tack force values t _C and t _C / t _B after the B stage sheet is converted to the C stage are within the above range, the tack force of the C stage sheet is larger than that of the B stage sheet. Thus, it can be said that a heat dissipation structure excellent in adhesiveness can be formed, and that it is more excellent as a heat conductive adhesive sheet.

  The thermally conductive adhesive sheet is mainly composed of the resin and the inorganic filler, and may contain other components such as an additive described later, but sufficient thermal conductivity, electrical insulation and From the viewpoint of obtaining adhesiveness, the total content of the resin and the inorganic filler is preferably 90.0% by mass or more, more preferably 95.0% by mass, among the components of the thermally conductive adhesive sheet. More preferably, it is 98.0-98.8 mass%.

The heat conductive adhesive sheet preferably has a thickness of 100 μm or more and less than 500 μm, more preferably 150 to 450 μm, still more preferably 200 to 400 μm.
When the thickness is 100 μm or more, the thermally conductive adhesive sheet is easy to handle and sufficient electrical insulation is easily obtained. Moreover, if it is less than 500 micrometers, sufficient thermal conductivity is obtained.

(resin)
The resin comprises a resin composition containing a block urethane prepolymer, an epoxy compound, and a curing catalyst.
In the block urethane prepolymer, the terminal isocyanate group of the reaction product of the aliphatic diisocyanate compound and the hydrogenated polybutadiene polyol having hydroxyl groups at both ends is blocked with an aromatic hydroxy compound, The structural unit derived from the aliphatic diisocyanate compound is 1.3 to 2.8 moles with respect to 1 mole of the structural unit derived from the hydrogenated polybutadiene polyol. Moreover, the said epoxy compound has 2-6 epoxy groups, and the said epoxy group is 0.9-2.5 mol with respect to 1 mol of hydroxyl groups of the said aromatic hydroxy compound.

As will be described later, by heating the resin composition to 120 ° C. or higher, a curing reaction proceeds and the resin is obtained. The resin mainly has a gel network structure composed of the following two types of cross-linking polymerization reactions.
In the first cross-linking polymerization reaction, an isocyanate group blocked with the aromatic hydroxy compound at the end of the reaction product of the aliphatic diisocyanate compound and the hydrogenated polybutadiene polyol is deblocked, and uretdione by dimerization is used. Or a multimerization reaction to produce isocyanurate by trimerization. Thereby, characteristics, such as a softness | flexibility, adhesiveness (tack force), and rubber elasticity, are provided to the said resin.
The second crosslinking polymerization reaction is a ring-opening reaction of the epoxy group of the epoxy compound by the hydroxyl group of the aromatic hydroxy compound.
Further, a curing reaction is caused by a reaction between the deblocked isocyanate group and the epoxy group of the epoxy compound.
The gel-like network in the resin formed by these reactions is considered to have an interpenetrating polymer network (IPN) structure. By constructing such an IPN structure, the resin can constitute a thermally conductive adhesive sheet having excellent flexibility, thermal conductivity, adhesiveness, and the like.

The resin composition can be mixed with the inorganic filler and cured at an appropriate viscosity at 100 ° C. or lower without curing, and such a viscosity can be maintained for at least 6 hours. For this reason, in order to disperse | distribute and fill the said inorganic filler uniformly, sufficient kneading time can be ensured with moderate viscosity, and it is excellent in handleability.
In addition, although the said resin composition may contain other components, such as the additive mentioned later, the sum total of the said block urethane prepolymer and the said epoxy compound in the containing component except a solvent among the said resin compositions. The amount is preferably 70.0% by mass or more, more preferably 70.0 to 100% by mass, and even more preferably 75.0 to 100% by mass, from the viewpoint of flexibility and adhesiveness of the resin. is there.

[Block urethane prepolymer]
The block urethane prepolymer contained in the resin composition is a reaction product of an aliphatic diisocyanate compound and a hydrogenated polybutadiene polyol having hydroxyl groups at both ends, and the isocyanate group that the reaction product has at the ends, It has a structure blocked with an aromatic hydroxy compound. The structural unit derived from the aliphatic diisocyanate compound in the reaction product is 1.3 to 2.8 moles with respect to 1 mole of the structural unit derived from the hydrogenated polybutadiene polyol.
In addition, since it is difficult to specify the structure of the reaction product as one kind of compound in the prepolymer as described above, it is difficult to specify the structure of the prepolymer as one kind of compound. This is expressed in terms of what is used for the reaction.

<Aliphatic diisocyanate compound>
The aliphatic diisocyanate compound is a constituent material of the block urethane prepolymer, and is a compound that reacts with the hydrogenated polybutadiene polyol. The term “aliphatic” in the aliphatic diisocyanate compound means not “aromatic”, and the hydrocarbon group of the substituent may be linear, branched or cyclic.
Specific examples of the aliphatic diisocyanate compound include hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), and isophorone diisocyanate (IPDI). These may be used alone or in combination of two or more. Among these, HMDI, IPDI, and the like have a large steric hindrance and hardly cause an isocyanate multimerization reaction. Therefore, HDI having a relatively simple structure is particularly preferable from the viewpoint of easy multimerization.
On the other hand, aromatic diisocyanate compounds such as diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI) have a strong agglomeration force of urethane groups of block urethane prepolymers produced using these, and have a high melting temperature. For this reason, the temperature range in which the prepolymer state can be maintained and mixed with the inorganic filler to be kneaded without causing a curing reaction is narrow, and the handling property when preparing a uniform resin composition is poor. . Furthermore, the urethane group derived from an aromatic diisocyanate compound tends to have a lower decomposition temperature of the urethane group than the urethane group derived from an aliphatic diisocyanate compound, and the resulting resin has poor heat resistance.

The structural unit derived from the aliphatic diisocyanate compound in the reaction product is 1.3 to 2.8 mol, preferably 1.4 to 2.7, based on 1 mol of the structural unit derived from the hydrogenated polybutadiene polyol. Mol, more preferably 1.5 to 2.5 mol.
When the structural unit derived from the aliphatic diisocyanate compound is 1.6 mol or more, an increase in the molecular weight of the block urethane prepolymer is suppressed, and it is easy to handle during mixing to obtain a uniform resin composition. Moreover, if it is 2.8 mol or less, the relative molar amount of the said epoxy compound with respect to the said block urethane prepolymer in the said resin composition is suppressed by the multimerization reaction of the said resin composition, Therefore Generation of gas due to decomposition of residues such as unreacted epoxy residues remaining in the thermally conductive adhesive sheet, which is one of the factors that reduce adhesiveness, is suppressed.

<Hydrogenated polybutadiene polyol>
The hydrogenated polybutadiene polyol is a constituent material of the block urethane prepolymer and a reaction product with the aliphatic diisocyanate compound. The hydrogenated polybutadiene polyol is a polyol compound using butadiene as a raw material and having hydroxyl groups at both ends, and a double bond residue is hydrogenated. Those having a high molecular weight easily impart flexibility to the resulting resin. On the other hand, the thing with a low molecular weight can improve the heat resistance of the resin obtained.
The number average molecular weight of the hydrogenated polybutadiene polyol is preferably 800 to 5000 from the viewpoints of viscosity, heat resistance and availability. In addition, the number average molecular weight in this specification is a value calculated by assuming that the hydrogenated polybutadiene polyol has two hydroxyl groups based on the hydroxyl value measured according to JIS K1557-1: 2007.

Examples of the hydrogenated polybutadiene polyol include GI-3000 (number average molecular weight 3753 (catalog published value 3000)), GI-2000 (number average molecular weight catalog published value 2000), GI-1000 (number average), which are commercially available products. Molecular weight catalog published value 1000) (all manufactured by Nippon Soda Co., Ltd.) and the like can be suitably used. These may be used alone or in combination of two or more. Of these, GI-3000 is particularly preferred.
Polyester polyols, polyether polyols, polycarbonate diols and the like that are generally used as polyurethane raw materials are inferior to hydrogenated polybutadiene polyols in terms of the heat resistance of the resin. For this reason, in the present invention, among the polyol compounds, the hydrogenated polybutadiene polyol is used.

<Aromatic hydroxy compound>
The aromatic hydroxy compound is a compound used as a blocking agent for the terminal isocyanate group of the reaction product, has an aromatic ring, and has an aromatic ring in which one or more hydrogen atoms constituting the aromatic ring are substituted with a hydroxyl group. Group compounds. The aromatic ring is preferably a benzene ring, and more preferably benzenediol in which two hydrogen atoms of the benzene ring are substituted with a hydroxyl group. When the hydroxyl group of the aromatic hydroxy compound reacts with the terminal isocyanate group to form a urethane bond, the terminal isocyanate group of the reaction product is blocked.
In addition, although the isocyanate group blocking agent includes an amine compound, this is not preferable because the reactivity with the epoxy compound is high and the curing of the block urethane prepolymer is accelerated accordingly.

Specific examples of the aromatic hydroxy compound include phenol, 1-cresol, 2-cresol, 3-cresol, 2,3-dimethylphenol, 2,4-dimethylphenol, 2,5-dimethylphenol, 2, 6-dimethylphenol, 2,3,6-trimethylphenol, 2,4,6-trimethylphenol, 2,3,5-trimethylphenol, 3-isopropylphenol, 2-tert-butylphenol, 3-tert-butylphenol, 4 -Tert-butylphenol, 2,4-di-tert-butylphenol, 2,5-di-tert-butylphenol, 2,6-di-tert-butylphenol, 2,4,6-tri-tert-butylphenol, 2-isopropyl -5-methylphenol, 2,6-di-t rt-butyl-4-methylphenol, 2-methoxyphenol, 3-methoxyphenol, 4-methoxyphenol, 2-ethoxyphenol, 3-ethoxyphenol, 4-ethoxyphenol, 2-propoxyphenol, 3-propoxyphenol, 4 -Propoxyphenol, 1,2-benzenediol, 1,3-benzenediol (resorcinol), 1,4-benzenediol, 1,3,5-benzenetriol, 4-tert-butylcatechol, bisphenol A, bisphenol F, etc. Is mentioned. These may be used alone or in combination of two or more.
Among these, in particular, resorcinol and bisphenol F can be deblocked at a relatively low temperature of about 120 ° C. after blocking the isocyanate group, and thus the reaction between the isocyanate group and the epoxy group of the epoxy compound. From the viewpoint of ease of deblocking during heating in obtaining the resin.

[Epoxy compound]
The said epoxy compound has 2-6 epoxy groups, Preferably it is 2-5. In order to obtain a resin having a gel network, it is necessary that the number of epoxy groups is 2 or more, and that the number is 6 or less, thereby obtaining a resin having a suitable gel network having flexibility. It is done.
Further, the epoxy group of the epoxy compound is 0.9 to 2.5 mol, preferably 0.9 to 2.2 mol, more preferably 1.0 to 1 mol of the hydroxyl group of the aromatic hydroxy compound. It is -2.0 mol, More preferably, it is 1.0-1.2 mol. If the epoxy group is 0.9 mol or more, a resin having sufficient heat resistance can be obtained. Moreover, if it is 2.5 mol or less, resin which has sufficient softness | flexibility will be obtained.

In order to obtain a resin having a suitable gel network, the epoxy compound is preferably polyfunctional and has a compact structure. From such a viewpoint, it is preferable that the molecular weight is less than 2000 and the epoxy equivalent is less than 300 g / eq. The molecular weight is more preferably 200 to 2000, and still more preferably 300 to 1500.
As the epoxy resin, from the viewpoint of compatibility with other reactants in the resin composition and heat resistance, for example, a compound having a glycidylamine type epoxy group such as tetraglycidyldiaminodiphenylmethane or triglycidyl isocyanurate, A dicyclopentadiene type epoxy resin is mentioned. These may be used alone or in combination of two or more.

[Curing catalyst]
The curing catalyst performs deblocking of the blocked isocyanate group of the reaction product to accelerate the isocyanate multimerization reaction, and between the epoxy group of the epoxy compound and the phenolic hydroxyl group of the aromatic hydroxy compound. It promotes the reaction.

As the curing catalyst, a quaternary ammonium salt is preferably used, and a tetraalkylammonium salt is more preferably used. Specifically, tetramethylammonium 2-ethylhexanoate, tetraethylammonium 2-ethylhexanoate, ethyltrimethylammonium 2-ethylhexanoate, triethylmethylammonium 2-ethylhexanoate, tetramethylammonium formate, Examples thereof include tetraethylammonium formate, ethyltrimethylammonium formate, triethylmethylammonium formate, tetramethylammonium phenol salt, tetraethylammonium phenol salt, ethyltrimethylammonium phenol salt, and triethylmethylammonium phenol salt. These may be used alone or in combination of two or more. Of these, triethylmethylammonium 2-ethylhexanoate is particularly preferred.
The addition amount of the curing catalyst is preferably 0.1 to 1% by mass, more preferably 0.2 to 0.9% by mass, based on the total amount of the block urethane prepolymer and the epoxy compound. More preferably, it is 0.3-0.6 mass%.

〔Additive〕
In addition to the block urethane prepolymer, the epoxy compound, and the curing catalyst, the resin composition includes additives such as a flame retardant, a plasticizer, and an antioxidant, depending on the characteristics required for the thermally conductive adhesive sheet. May be added. These additives are preferably compatible with other components in the resin composition. Each of these additives is arbitrarily added as necessary, and may be used alone or in combination of two or more.

Examples of the flame retardant include phosphazene compounds and condensed phosphate esters. The amount of the flame retardant added is preferably 1.0 to 40.0 mass%, more preferably 1.0 to 35.0 mass%, based on the total amount of the block urethane prepolymer and the epoxy compound. %, More preferably 3.0 to 30.0% by mass.
Examples of the plasticizer include xylene-based resins, liquid paraffin, ester-based plasticizers, and the like.
Examples of the antioxidant include hindered phenol-based antioxidants.
Each addition amount of the plasticizer and the antioxidant is preferably 0.5 to 10.0% by mass, more preferably 0, based on the total amount of the block urethane prepolymer and the epoxy compound. 0.7 to 8.0 mass%, more preferably 0.8 to 5.0 mass%.

〔solvent〕
The resin composition may optionally contain a solvent so as to be mixed in a uniform state with an appropriate viscosity. The solvent is preferably one that volatilizes when the resin composition is semi-cured (B-staged) from the viewpoint of suppressing a decrease in adhesion due to gas generated from the thermally conductive adhesive sheet.
Examples of the solvent include toluene, tetrahydrofuran (THF), and the like. These may be used alone or in combination of two or more.
The content of the solvent in the resin composition is preferably 30.0 to 70.0% by mass, more preferably 35.0 to 60.0% by mass, and further preferably 40.0 to 60%. 0.0% by mass.

[Method for producing resin composition]
Although the manufacturing method of the resin composition is not particularly limited, for example, it can be obtained by a manufacturing method through the following steps (1-1) to (1-3). Specifically, the reaction (1-1) in which the aliphatic diisocyanate compound and the hydrogenated polybutadiene polyol are reacted in the presence of a urethanization catalyst to obtain the reaction product having an isocyanate group at the terminal, The aromatic hydroxy compound is added to the reaction product, the isocyanate group is blocked to obtain a block urethane prepolymer (1-2), and at least the epoxy compound is added to the block urethane prepolymer. And the curing catalyst, and a step (1-3) for obtaining the resin composition.

<Step (1-1)>
First, in the step (1-1), the aliphatic diisocyanate compound and the hydrogenated polybutadiene polyol are reacted in the presence of a urethanization catalyst to obtain a reaction product having an isocyanate group at the terminal.

The reaction product obtained in the step (1-1) is generated by a urethanation reaction in which the isocyanate group of the aliphatic diisocyanate compound and the hydroxyl groups at both ends of the hydrogenated polybutadiene polyol form urethane bonds. Such a urethanization reaction is preferably performed using a urethanization catalyst in order to accelerate the reaction.
In order to advance the urethanation reaction without using a urethanization catalyst, it is necessary to heat to 100 ° C. or higher, and at such a high temperature, the aliphatic diisocyanate compound tends to volatilize and the reaction system is uneven. This is not preferable.
The urethanization catalyst is not particularly limited. For example, 1,8-diazabicyclo (5.4.0) undecene-7 (DBU), 1,5-diazabicyclo [4.3.0] nonene- 5 (DBN). These may be used alone or in combination of two or more. Of these, DBU is preferably used.
The addition amount of the urethanization catalyst may be an amount that sufficiently promotes the urethanization reaction, and is 0.01% relative to the total amount of the aliphatic diisocyanate compound, the hydrogenated polybutadiene polyol, and the urethanization catalyst. It is preferable that it is -0.5 mass%, More preferably, it is 0.01-0.2 mass%, More preferably, it is 0.02-0.1 mass%.

<Process (1-2)>
In the step (1-2), the aromatic hydroxy compound is added to the reaction product obtained in the step (1-1), and an isocyanate group blocking reaction is performed to obtain the block urethane prepolymer.

  The addition amount of the aromatic hydroxy compound is such that the hydroxyl group of the aromatic hydroxy compound is the isocyanate group 1 of the aliphatic diisocyanate compound from the viewpoint of suppressing the increase in the viscosity of the resin composition and the flexibility of the obtained resin. The amount is preferably 0.8 to 1.1 mol, more preferably 0.8 to 1.0 mol, and still more preferably 0.9 to 1.0 mol with respect to mol.

The blocking reaction with the aromatic hydroxy compound is accompanied by an increase in viscosity. In addition, the aromatic hydroxy compound starts to block after melting above its melting point, but at such high temperatures, a deblocking reaction that is a reversible reaction also occurs, so the blocking reaction must be completed. Is difficult.
For this reason, in order to efficiently complete the blocking reaction, the reaction temperature is lowered to 80 to 60 ° C., preferably about 70 ° C., and the reaction product is appropriately diluted with a solvent, It is preferable to reduce the viscosity of the reaction system.
Examples of the solvent include toluene, THF and the like from the viewpoint of solubility of the reactant. These may be used alone or in combination of two or more. Of these, toluene is preferably used from the viewpoints of volatility and low hygroscopicity.

Moreover, when manufacturing the said heat conductive adhesive sheet using the said resin composition, in order to ensure the dispersibility and the filling property of the inorganic filler mixed, the said block polyurethane prepolymer is, for example, a solvent such as toluene. It is preferable to prepare it as a diluted solution.
The concentration of the block polyurethane prepolymer solution at this time is 20.0 to 60 in terms of ensuring the dispersibility and filling properties of the inorganic filler when manufacturing the thermally conductive adhesive sheet, increasing production efficiency, and the like. It is preferably 0.0% by mass, more preferably 30.0-50.0% by mass, and even more preferably 35.0-45.0% by mass.

<Process (1-3)>
In the step (1-3), at least the epoxy compound and the curing catalyst are blended with the block urethane prepolymer obtained in the step (1-2) to obtain the resin composition. The epoxy compound and the curing catalyst are preferably diluted with the same solvent as used for diluting the block polyurethane prepolymer from the viewpoint of uniformly blending.

The resin composition is preferably one in which the epoxy compound and the curing catalyst are blended with the block urethane prepolymer and then uniformly mixed.
The mixing method is not particularly limited as long as the compounding components can be uniformly dissolved or dispersed in the resin composition. For example, the compounding components may be accommodated in a sealed container and shaken together with the container, or the compounding components accommodated in the container may be mixed by stirring with a stirring blade.
In addition to the block urethane prepolymer, the epoxy compound, and the curing catalyst, the resin composition includes a flame retardant, a plasticizer, an antioxidant, and the like, as described above, depending on characteristics required for the heat conductive adhesive sheet. Various additives may be added.

(Filler)
The filler is mainly composed of an inorganic filler, and the content of the inorganic filler in the heat conductive adhesive sheet is 80.0 to 94.0% by mass, preferably 85.0 to 94. It is 0 mass%, More preferably, it is 90.0-93.0 mass%. The thermal conductive adhesive sheet can exhibit excellent thermal conductivity by including a large amount of inorganic filler in this way, and even if it includes a large amount of inorganic filler, it does not cause cracks or the like. And has sufficient flexibility and adhesiveness.

  Examples of the inorganic filler include magnesia, alumina, boron nitride, aluminum nitride, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, and crystalline silica from the viewpoint of electrical insulation. These may be used alone or in combination of two or more. Of these, magnesia, alumina, boron nitride, and aluminum nitride are preferable from the viewpoint of thermal conductivity. From the viewpoint of flame retardancy, magnesium hydroxide is preferred.

The shape of the inorganic filler is preferably mainly spherical in consideration of the moldability of the heat conductive adhesive sheet. In the range which does not impair the said moldability, the thing of plate shape and a crushed shape may be included. Specifically, in the inorganic filler, the spherical particles are preferably 80.0% by mass or more, more preferably 85.0% by mass or more, and further preferably 90.0% by mass or more.
Considering the balance between performance and cost, for example, it is preferable to use spherical magnesia and spherical alumina in combination, or use spherical spherical magnesia and two types of spherical alumina having different particle diameters. The ratio of various shapes and materials in such combined use takes into consideration the affinity with the resin, the dispersion fluidity and viscosity when mixed with the resin composition, and the combustibility of the heat conductive adhesive sheet. Can be determined as appropriate.
In addition, although the shape said here is not clearly defined, `` spherical '' is rounded regardless of the sphericity, and may have a corner, but on the appearance, What is recognized as almost spherical is sufficient. “Plate” refers to a spherical shape and is generally recognized to be flat or planar.

The particle size of the inorganic filler is preferably such that the dispersibility and filling properties for the resin and the flexibility of the heat conductive adhesive sheet are not impaired. Specifically, the average particle size is preferably 0.1 to 100 μm, more preferably 0.2 to 50 μm, and still more preferably 0.3 to 30 μm.
In the present invention, as the inorganic filler, a mixture containing spherical particles (f1) having an average particle size of more than 10 μm and 100 μm or less and spherical particles (f2) having an average particle size of 0.1 μm or more and 10 μm or less is used. At this time, the content of the spherical particles (f1) in the inorganic filler is 58.0 to 80.0% by mass, preferably 60.0 to 78.0% by mass, more preferably 65.0 to 75%. 0.0% by mass.
In addition, let the average particle diameter of the inorganic filler in this invention be a particle diameter in 50% of the cumulative volume in the particle size distribution calculated | required with the laser diffraction type particle size distribution measuring apparatus.

The inorganic filler is preferably surface-treated with a coupling agent from the viewpoint of increasing the affinity with the resin. Specifically, an aluminum chelate compound is preferably used as the coupling agent. Among these, alkyl acetoacetate aluminum diisopropylate is particularly preferable.
The aluminum chelate compound is preferably added in an amount of 0.1 to 5.0% by mass, more preferably 0.3 to 2.0% by mass, and still more preferably 0.5 to 5.0% by mass with respect to the total amount of the inorganic filler. 1.5% by mass.
The surface treatment can be performed, for example, by dispersing the inorganic filler and the aluminum chelate compound in a solvent such as toluene and then removing the solvent by distillation or drying.

[Method for producing thermally conductive adhesive sheet]
Although the manufacturing method of the heat conductive adhesive sheet is not particularly limited, it can be preferably manufactured by the manufacturing method of the present invention.
The manufacturing method of the heat conductive adhesive sheet of this invention prepares the mixture containing the said resin composition and the said inorganic filler (2-1), and the process of shape | molding the said mixture and producing a sheet molded object ( 2-2) and the step (2-3) of obtaining the heat conductive adhesive sheet by heating and semi-curing the sheet molded body at 150 to 180 ° C. for 5 to 60 minutes.
According to such a manufacturing method, the said sheet molded object can be made into a semi-hardened state, and the said heat conductive adhesive sheet which is a B stage sheet can be obtained easily.

(Process (2-1))
In step (2-1), a mixture containing the resin composition and the inorganic filler is prepared.
In order to make it easy to obtain a uniform mixture, the mixture may contain a solvent similar to that used in the production of the resin composition.

  The compounding ratio of the resin composition and the inorganic filler can be appropriately adjusted according to the thermal conductivity, flexibility, and the like required for the obtained heat conductive adhesive sheet. It is preferable that the compounding quantity of the said inorganic filler is 80.0-94.0 mass parts with respect to a total of 100 mass parts of the said resin composition and this inorganic filler, More preferably, it is 85.0-93%. It is 0 mass part, More preferably, it is 90.0-93.0 mass part.

  The mixing method of the resin composition and the inorganic filler is not particularly limited. When the resin composition is used after being diluted with a solvent, for example, after mixing with the inorganic filler using a stirrer or disperser such as a rotation and revolution mixer, the solvent is removed by distillation or drying. By doing so, the mixture can be obtained. Moreover, when not using a solvent, the said mixture can be obtained by mix | blending the said resin composition and the said inorganic filler using kneading machines, such as a 3 roll mill, in a bulk state.

(Process (2-2))
At a process (2-2), the said mixture obtained at the said process (2-1) is shape | molded, and a sheet molded object is produced.
Specifically, the sheet molded body can be produced, for example, by kneading and rolling the mixture using a press apparatus such as a hot press machine. It is preferable to carry out at 120 ° C. or lower so that the mixture can maintain an uncured state. Moreover, it is preferable to carry out repeatedly, changing the pressure to pressurize so that the said mixture may become a uniform state.
At the time of rolling, from the viewpoint of preventing adhesion of the sheet compact to the pressing apparatus that performs the rolling, for example, a fluororesin film such as polytetrafluoroethylene (PTFE) is used as a release film. It may be.
In addition, in order to obtain a uniform heat conductive adhesive sheet, the sheet molded body is preferably subjected to defoaming treatment before the subsequent step (2-3). The defoaming treatment is preferably performed, for example, by heating to a temperature of less than 150 ° C. and vacuum defoaming in a short time of about 2 to 10 minutes.

(Process (2-3))
At a process (2-3), the said heat conductive adhesive sheet is obtained by heating the said sheet molded object at 150-180 degreeC for 5 to 60 minutes, and making it semi-harden.
In this step, the heat conductive adhesive sheet which is a B stage sheet is obtained by heating and semi-curing. The degree of semi-curing is not particularly limited, and can be appropriately adjusted within the range of the heating temperature and the heating time in consideration of easy handling of the obtained heat conductive adhesive sheet.

  The semi-curing by heating is preferably performed while pressurizing the sheet compact with, for example, a hot press. At this time, from the viewpoint of preventing adhesion of the sheet compact to the hot press or the like, a fluororesin film such as PTFE may be used as a release film as in the case of rolling. The pressurizing pressure is appropriately set according to the thickness and size required for the obtained heat conductive adhesive sheet. Usually, it is about 0.01-5 MPa.

The heating temperature is preferably 150 to 180 ° C., more preferably 155 to 175 ° C., and more preferably 160 to 175 ° C., from the viewpoint of making the sheet compact into a semi-cured state without making it C-stage. It is. From the viewpoint of obtaining a uniform B stage sheet, it is preferable to raise the temperature stepwise.
The heating time can be appropriately set within a range of 5 to 60 minutes depending on the thickness and size required for the obtained heat conductive adhesive sheet.
For example, when a heat conductive adhesive sheet having a thickness of 300 μm is obtained, it is preferable to heat at 160 to 175 ° C. for 10 to 30 minutes with the sheet compact sandwiched between the release films. Furthermore, the said heat conductive adhesive sheet can make it easy to volatilize the gas which arises from the said solvent etc. by setting it as the state which peeled off the said release film from the middle of a heating. Heating in this way is preferable from the viewpoint of obtaining a high-quality thermally conductive adhesive sheet free from generated gas during use.

[Heat dissipation structure]
The heat dissipation structure of the present invention is configured by using the above-described heat conductive adhesive sheet of the present invention, and a member (M1) directly bonded to one surface of the cured body of the heat conductive adhesive sheet and the cured body. ), And a member (M2) that is directly bonded to the other surface of the cured body. And it is preferable that each joining surface with the said hardening body of the said member (M1) and the said member (M2) contains at least any one of a metal and resin.
The heat conductive adhesive sheet, which is a B stage sheet, is further sandwiched between the member (M1) and the member (M2) in a state where the curing reaction further proceeds and the C stage is formed. It is possible to configure the heat dissipation structure that can be firmly bonded and can exhibit excellent thermal conductivity and electrical insulation.
The thermally conductive adhesive sheet does not cause gas accumulation at the adhesion interface between the member (M1) and the member (M2) in the progress of the curing reaction. Since it does not invite, it can use suitably in order to ensure a heat radiation path stably.

As a preferable material of each joint surface with the said hardening body in the said member (M1) and the said member (M2), a metal, resin, carbon, etc. are mentioned. It is preferable that at least a part of the joint surface is made of a material selected from these, and more preferably includes any one selected from metals and resins. In particular, when either one of the member (M1) and the member (M2) is a constituent member of a heat-generating electronic component, the heat-conductive adhesive sheet exhibits excellent thermal conductivity and electrical insulation. be able to.
As said exothermic electronic component, LED, CPU, a power semiconductor etc. are mentioned, for example. Among these, it is preferably applied to an electronic component whose heat generation temperature during use is 175 ° C. or lower.
As a heat dissipation structure in the heat dissipation structure, for example, between a sealing resin such as a power semiconductor and a metal frame such as aluminum or copper, between a heat dissipation plate such as a power semiconductor and a heat dissipation fin, and sealing a power semiconductor or the like Examples include a structure for forming a heat radiation path between the resin and the heat radiation fin, between a metal substrate (including plating) such as a power semiconductor and the heat radiation fin.

[Method of manufacturing heat dissipation structure]
Although the manufacturing method of the said heat radiating structure is not specifically limited, It can manufacture suitably with the manufacturing method of this invention shown below.
The manufacturing method of the present invention includes a step (3-1) of producing a structural precursor in which the thermally conductive adhesive sheet is sandwiched between the member (M1) and the member (M2), and the structural precursor. A step of curing the heat conductive adhesive sheet at 220 to 260 ° C. to obtain a heat dissipation structure in which the cured body of the heat conductive adhesive sheet is joined to the member (M1) and the member (M2) (3 -2).

(Process (3-1))
In the step (3-1), the heat conductive adhesive sheet is sandwiched between the member (M1) and the member (M2) to produce a structural precursor.
Since the said heat conductive adhesive sheet has moderate adhesive force, the said member (M1) and the said member (M2) can be fixed in position. In addition, the heat conductive adhesive sheet is excellent in flexibility, has appropriate adhesiveness, and can be easily reattached. Even if it exists, it can re-paste and can adjust a position. Thus, the heat conductive adhesive sheet is easy to handle, and by using this, the structural precursor can be easily produced.

(Step (3-2))
In the step (3-2), the thermally conductive adhesive sheet of the structural precursor obtained in the step (3-1) is cured at 220 to 260 ° C., and a cured body of the thermally conductive adhesive sheet; A heat dissipation structure in which the member (M1) and the member (M2) are joined is obtained.
By heating the heat conductive adhesive sheet at a high temperature as described above, it can be made into a C stage in about 1 to 10 minutes, the member (M1), a cured body of the heat conductive adhesive sheet, and the member A heat dissipation structure in which (M2) is firmly bonded can be obtained. Also, in this process, since the B stage sheet is converted to the C stage, it can be cured by heating in a shorter time than when applying and curing a heat conductive resin composition, and heat can be released in a stable form. A structure can be manufactured.

The heating temperature is preferably 220 to 260 ° C., more preferably 230 to 260 ° C., from the viewpoint of efficiently making the C stage in a short time as described above, and in consideration of deterioration of the cured body. More preferably, it is 240-260 degreeC.
In addition, when it is not necessary to make the said heat conductive adhesive sheet C-stage for a short time, it is hardened over time by heating at about 80-175 degreeC, and adhesive force is gradually increased with progress of hardening. You may make it raise to.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by this.

[Production of block urethane prepolymer (P)]
The raw materials used in the production examples of the following block urethane prepolymers are shown below.
<Aliphatic diisocyanate compound>
Hexamethylene diisocyanate (HDI); “Desmodur (registered trademark) H”, manufactured by Sumika Covestro Urethane Co., Ltd. <hydrogenated polybutadiene polyol>
"GI-3000", manufactured by Nippon Soda Co., Ltd., molecular weight 3753, hydroxyl value 29.9KOHmg / g
<Aromatic hydroxy compound>
・ Resorcinol; reagent special grade; manufactured by Wako Pure Chemical Industries, Ltd. ・ Bisphenol F; “Resitop BPF-SG”, manufactured by Gunei Chemical Industry Co., Ltd.
-1,8-diazabicyclo [5.4.0] undecene-7 (DBU), manufactured by San Apro Co., Ltd. <solvent>
Toluene; reagent special grade, manufactured by Wako Pure Chemical Industries, Ltd.

(P Production Example 1)
A 300 ml separable flask was charged with 2.56 g of an aliphatic diisocyanate compound (1.6 mol per 1 mol of hydrogenated polybutadiene polyol) and 35.74 g of hydrogenated polybutadiene polyol, a stirring blade, a stirring motor, a Dimroth condenser, And a nitrogen inlet tube was attached. The inside of the flask was purged with nitrogen at a flow rate of 200 ml / min. The flask was immersed in an oil bath at 75 ° C. and stirred at 30 rpm for 5 minutes, and then the number of revolutions was increased to 150 rpm and stirred for 5 minutes. The product was mixed uniformly.
0.02 g of the urethanization catalyst was added and reacted for 3 hours, and the infrared absorption (IR) spectrum of the reaction product was measured to confirm that the 3300 cm ⁻¹ signal derived from the hydroxyl group had disappeared.
After raising the temperature of the oil bath to 125 ° C. and sufficiently heating the flask, 1.68 g of resorcinol was added. After stirring at 400 rpm for 3 minutes, the oil bath was cooled to 110 ° C. and stirred at 50 rpm. When the contents in the flask reach 110 ° C., 22.90 g of dehydrated toluene (dehydrated with molecular sieve 4A) is added, the stirring speed is gradually increased and fixed at 150 rpm, and the oil bath is cooled to 70 ° C. And reacted for 3 hours. With respect to the reaction product, it was confirmed by IR spectrum that the signal of 2270 cm ⁻¹ derived from the isocyanate group had disappeared.
The resulting reaction product was allowed to cool to room temperature (25 ° C.), 37.10 g of toluene was added and mixed with stirring, and a block urethane prepolymer solution (P1) (concentration (calculated value) 40.0% by mass) was obtained. Obtained.

(P Production Example 2)
A 300 ml separable flask was charged with 2.53 g of an aliphatic diisocyanate compound (1.6 mol with respect to 1 mol of hydrogenated polybutadiene polyol) and 35.25 g of hydrogenated polybutadiene polyol, a stirring blade, a stirring motor, a Dimroth condenser, And a nitrogen inlet tube was attached. The inside of the flask was purged with nitrogen at a flow rate of 200 ml / min. The flask was immersed in an oil bath at 75 ° C. and stirred at 30 rpm for 5 minutes, and then the number of revolutions was increased to 150 rpm and stirred for 5 minutes. The product was mixed uniformly.
0.02 g of the urethanization catalyst was added and reacted for 3 hours, and the infrared absorption (IR) spectrum of the reaction product was measured to confirm that the 3300 cm ⁻¹ signal derived from the hydroxyl group had disappeared.
After raising the temperature of the oil bath to 125 ° C. and sufficiently heating the flask, 3.01 g of bisphenol F was added. After stirring at 400 rpm for 3 minutes, the oil bath was cooled to 110 ° C. and stirred at 50 rpm. When the contents in the flask reach 110 ° C., add 22.59 g of dehydrated toluene (dehydrated with molecular sieve 4A), gradually increase the stirring speed and fix at 150 rpm, and lower the temperature of the oil bath to 70 ° C. And reacted for 3 hours. With respect to the reaction product, it was confirmed by IR spectrum that the signal of 2270 cm ⁻¹ derived from the isocyanate group had disappeared.
The resulting reaction product was allowed to cool to room temperature (25 ° C.), 36.60 g of toluene was added and mixed with stirring, and a block urethane prepolymer solution (P2) (concentration (calculated value) 40.8% by mass) was obtained. Obtained.

[Production of Resin Composition (R)]
The raw materials used in the following production examples of the resin composition are shown below.
<Block urethane prepolymer>
(P1) Block urethane prepolymer solution produced in P Production Example 1 (P2) Block urethane prepolymer solution produced in P Production Example 2 <Epoxy compound>
(E1) Tetrafunctional amine type epoxy resin (tetrafunctional polyglycidylamine: tetraglycidyldiaminodiphenylmethane); “Epototo (registered trademark) YH-434L”, manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., epoxy equivalent 118.1 g / eq, concentration 50 Prepared as a 5% by mass toluene solution (E2) dicyclopentadiene type epoxy resin; “EPICLON (registered trademark) HP-7200L”, manufactured by DIC Corporation, epoxy equivalent 247 g / eq, about 6 epoxy groups, concentration 50.5 Prepared as a mass% toluene solution <Curing catalyst>
Triethylmethylammonium 2-ethylhexanoate; “U-CAT (registered trademark) 18X”, manufactured by San Apro Co., Ltd., prepared as a toluene solution with a concentration of 10.0% by mass <additive>
Antioxidant: 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) piropionyloxy] -1,1-dimethylethyl] -2,4,8,10 -Tetraoxaspiro [5.5] undecane; "Sumilyzer (registered trademark) GA-80", manufactured by Sumitomo Chemical Co., Ltd.-Flame retardant: Phosphazene flame retardant; "SPB-100", manufactured by Otsuka Chemical Co., Ltd. <solvent>
・ Toluene: Special grade reagent, Wako Pure Chemical Industries, Ltd.

(R Production Example 1)
In a 250 ml polyethylene jar, 80.07 g of block urethane prepolymer solution (P1), 3.86 g of epoxy compound (solution) (E1) and 3.86 g of epoxy compound (solution) (E2) ((E1) and (E2)) The total epoxy group is 1.0 mol per mol of the hydroxyl group of the aromatic hydroxy compound, epoxy equivalent (calculated value) 159.8 g / eq), curing catalyst (solution) 1.08 g, and as an additive, 0.35 g of antioxidant and 10.78 g of flame retardant were added and mixed by shaking to obtain a resin composition solution (R1) (concentration 47.16% by mass (calculated value)).

(R Production Examples 2 to 4)
In R Production Example 1, resin composition solutions (R2) to (R4) were obtained in the same manner as in R Production Example 1 except that the raw material composition was changed to R Production Examples 2 to 4 shown in Table 1 below. It was.
In Table 1 below, the number of epoxy groups of the epoxy compound is indicated by a calculated value based on the epoxy equivalent.

[Preparation of filler (F)]
The raw materials used in the following filler preparation examples are shown below.
<Inorganic filler>
・ Spherical magnesia; average particle size 20μm
・ Spherical alumina; average particle size 2.8 μm
・ Spherical alumina; average particle size 0.5μm
・ Plate-like magnesium hydroxide; average particle size 1.6μm
<Coupling agent>
・ Alkyl acetoacetate aluminum diisopropylate <colorant>
Carbon black; average particle size 48nm
<Solvent>
・ Toluene; reagent grade, manufactured by Wako Pure Chemical Industries, Ltd.

(F Preparation Example 1)
In a 100 ml polyethylene jar, 52.60 g of spherical magnesia, 18.24 g of spherical alumina (average particle size 2.8 μm), 0.77 g of spherical alumina (average particle size 0.5 μm), and 4.58 g of plate-like magnesium hydroxide , And 0.08 g of a colorant were added and mixed by shaking.
To this, 0.87 g of coupling agent and 22.86 g of solvent were added and mixed by shaking.
Thereafter, the mixture was stirred at 2000 rpm for 2 minutes using a rotation / revolution mixer, then dispersed for 30 minutes by an ultrasonic cleaner, and again stirred at 2000 rpm for 2 minutes by a rotation / revolution mixer. And the obtained mixture was dried with warm air at 60 degreeC, and also vacuum-dried at 70 degreeC for 5 hours, and the filler (F1) was obtained.

(F Preparation Examples 2 and 3)
In F Preparation Example 1, fillers (F2) and (F3) were obtained in the same manner as in F Preparation Example 1 except that the raw material composition was changed to the F preparation examples 2 and 3 shown in Table 2 below.

[Manufacture of heat conductive adhesive sheet]
Example 1
In a 50 ml screw tube, put 18.80 g of filler (F1) and 3.00 g of resin composition solution (R1), and stir at 2000 rpm for 2 minutes using a rotating and rotating mixer. The dispersion treatment was performed for 30 minutes, and the mixture was again stirred and mixed at 2000 rpm for 2 minutes using a rotation and revolution mixer. The obtained mixture was taken out into a stainless steel vat, placed on a hot plate at 90 ° C. and heated for 30 minutes, and then vacuum dried at 90 ° C. for 30 minutes, and the solvent was evaporated and removed.
About 10 g of this mixture was sandwiched between PTFE sheets having a thickness of 200 μm, and kneaded and rolled by repeating pressurization from the outer surfaces of the upper and lower PTFE sheets using a hot flat press at 110 ° C. In the kneading and the rolling, the initial axial force is set to 10 kN, and then the axial force is increased by 5 kN, and the pressure is increased by a total of 10 times while being folded each time, and further the axial force is fixed to 60 kN and pressed. A total of 10 times were performed while folding each time.
The sheet was folded again, and two sheets of 350 μm thick shims were sandwiched between the PTFE sheets to form a disk-shaped sheet molded body having a final thickness of about 350 μm and a diameter of about 110 mm. And the PTFE sheet of the upper surface side of this sheet molded object was peeled off, and vacuum deaeration was performed at 140 degreeC for 3 minute (s).
The defoamed sheet molded product and two 300 μm thick shims were sandwiched between 50 μm thick PTFE sheets, and sized at 175 ° C., 1.2 kN for 30 seconds, 5 kN for 2 minutes, and 10 kN using a small compression molding machine. For 12 minutes and 30 seconds, and further for 15 minutes at 1.2 kN, and a disk-shaped thermally conductive adhesive sheet having a diameter of about 120 mm was produced.

(Examples 2 to 4 and Comparative Examples 1 to 3)
In Example 1, it changed into the raw material mixing | blending composition shown in each of Examples 2-4 of the following Table 3, and Comparative Examples 1-3, and produced the heat conductive adhesive sheet similarly to Example 1 except it. .

[Measurement evaluation]
The following various measurement evaluations were performed on the heat conductive adhesive sheets (sheet samples) obtained in the above Examples and Comparative Examples. These evaluation results are summarized in Table 3 below. In addition, the notation “−” in Table 3 indicates that measurement has not been performed.

(Thickness)
With a digital thickness gauge (“SMD-540S2”, manufactured by Teclock Co., Ltd.), the thickness was measured at any five locations on the sheet sample, and the average value thereof was taken as the thickness.
If thickness is 100-500 micrometers, it can be said that it is excellent in the handleability etc. as a heat conductive adhesive sheet.

(Hardness)
About the sample which laminated | stacked the sheet | seat sample so that thickness might become 20 mm or more (about 20 mm), the hardness of a sheet | seat sample was measured using an Asker C type durometer ("Asker rubber hardness meter C type", manufactured by Kobunshi Keiki Co., Ltd.). It was measured.
The hardness is an index of the flexibility of the heat conductive adhesive sheet. The larger hardness value measured in accordance with JIS K 7312: 1996 hardness test type C indicates that it is harder. If it is 95 or less, it has sufficient flexibility as a heat conductive adhesive sheet. I can say that.

(Thermal conductivity)
Thermal conductivity is represented by the product of density, specific heat, and thermal diffusivity. Therefore, the thermal conductivity was calculated and determined by measuring the density, specific heat and thermal diffusivity of the sheet sample.
If the thermal conductivity is 3.0 W / (m · K) or more, it can be said that sufficient thermal conductivity is obtained.
The density, specific heat, and thermal diffusivity were measured by the following methods.

〔density〕
A sheet sample was punched out using a punch with an engraving blade having a diameter of 9 mm, the weight and thickness were measured in the same manner as described above, and the density was calculated.

〔specific heat〕
Using a differential scanning calorimeter (DSC; “Thermo Plus DSC8230”, manufactured by Rigaku Corporation), α-alumina was measured as a standard substance.

[Thermal diffusivity]
Evaluation was made by temperature wave thermal analysis. The measurement conditions are as follows.
Measuring device: “Eye Phase Mobile 1u”, manufactured by Eye Phase Co., Ltd. Sample size: 10 mm × 10 mm
Measurement mode: Auto measurement Temperature: 23 ° C

(Electrical insulation)
The electrical insulation of the sheet sample was evaluated by measuring the withstand voltage.
A sheet sample is placed on an aluminum plate having a size of 150 mm × 200 mm and a thickness of 2 mm. Using a 10 mm square aluminum bar as a counter electrode, using a withstand voltage measuring device (“TOS9201”, manufactured by Kikusui Electronics Corporation), AC 50 Hz, Sweep was performed at 0 to 5 kV, and the presence or absence of dielectric breakdown at the current threshold upper limit of 1 mA was confirmed.
The evaluation criteria are as follows.
○: No dielectric breakdown ×: Dielectric breakdown

(Adhesiveness)
The tack force value t _B of the sheet sample (B stage) was measured by the method described below.
The tack force of the heat conductive adhesive sheet (B stage sheet) is an indicator of whether or not the heat conductive adhesive sheet has excellent handling properties and reworkability with the adherend. It becomes.

Hereinafter, the procedure of a specific measurement method will be described with reference to the schematic cross-sectional view shown in FIG.
(1) At 25 ° C., an aluminum plate 1 having a surface of 150 mm × 150 mm × thickness 3 mm is horizontally placed on a desk having a flat surface, and on the surface of the aluminum plate 1 (Rz _JIS : 6.40 μm), A sheet sample 2 of 30 mm × 30 mm × thickness 0.3 mm was placed. A PTFE sheet was placed on the sheet sample 2, and the entire surface of the sheet sample 2 was pressed onto the aluminum plate 1 at about 250 N or more from the top of the PTFE sheet, and the sheet sample 2 was stuck on the aluminum plate 1 and fixed.
(2) A through hole having a diameter of 3 mm was provided at the center of a pair of opposing side surfaces of a 15 mm × 15 mm × 15 mm aluminum block 3 (Rz _JIS : 9.27 μm on the bottom surface in contact with the sheet sample 2). Two wires 4 having a diameter of about 0.6 mm and a length of 120 mm were bundled and passed through the through hole, and twisted above the block 3.
(3) The aluminum block 3 is placed on the sheet sample 2, and the upper surface of the aluminum block 3 is 5N per 5 seconds with a mechanical force gauge ("FB-50N", manufactured by Imada Co., Ltd.) (not shown). It was pushed in the vertical direction while increasing the load gradually (downward arrow in the figure), and held for 10 seconds when it reached 50N.
(4) The aluminum plate 1 was fixed by hand, and a hook of a mechanical force gauge was hooked on the wire 4 and pulled up in the vertical direction while increasing the tensile load by about 5 N per 5 seconds (upward arrow in the figure).
(5) The tensile load when the aluminum plate 1 and the aluminum block 3 were peeled was measured, and the maximum value was taken as the tack force. In this evaluation, an average value of five measurements was obtained.

Moreover, after performing (1)-(3) of the said measuring method one by one, it put in the dryer of preset temperature 240 degreeC. After reaching 240 ° C., it was heated for 3 minutes (about 7 minutes after being put in the dryer). After taking out, it stood to cool to room temperature (25 degreeC), and produced the hardening body of the sheet | seat sample.
For the cured body of the sheet sample with an aluminum block, the tack force value t _C of the cured body of the sheet sample (C stage sheet) was measured in the same manner as the measurement methods (4) and (5).
Then, to determine the value of t _C / t _B. If the value of t _C / t _B is 1.5 or more, the tack force is sufficiently increased by converting the B stage sheet to the C stage, and is more excellent as a heat conductive adhesive sheet. I can say that.

As can be seen from the results shown in Table 3, it was confirmed that each of the thermally conductive adhesive sheets of Examples 1 to 4 was excellent in thermal conductivity, electrical insulation, and adhesiveness.
On the other hand, when the inorganic filler has too many spherical particles (f1) having an average particle size of more than 10 μm and not more than 100 μm (Comparative Example 3), it is difficult to perform sheet molding. Moreover, when there is too much content of an inorganic filler (comparative example 1), and when there are too few said spherical particles (f1) (comparative example 2), it is difficult to shape | mold the sheet | seat which was fully extended | stretched and made thin. Yes, cracks occurred at the edge of the sheet, and the hardness exceeded the measurement limit, making it difficult to measure the hardness. Due to the occurrence of cracks, the electrical insulation was insufficient, and thermal conductivity and adhesion were not evaluated.

1 Aluminum plate 2 Sheet sample (thermally conductive adhesive sheet)
3 Aluminum block 4 Wire

Claims (6)

A cured body of a thermally conductive adhesive sheet, a member (M1) directly bonded to one surface of the cured body, and a member (M2) directly bonded to the other surface of the cured body, Each joint surface of the member (M1) and the member (M2) with the cured body is a method for manufacturing a heat dissipation structure including at least one of metal and resin,
The thermally conductive adhesive sheet is a B stage sheet containing a resin and an inorganic filler,
The resin comprises a resin composition containing a block urethane prepolymer, an epoxy compound and a curing catalyst,
In the block urethane prepolymer, the terminal isocyanate group of the reaction product of the aliphatic diisocyanate compound and the hydrogenated polybutadiene polyol having hydroxyl groups at both ends is blocked with an aromatic hydroxy compound, The structural unit derived from the aliphatic diisocyanate compound is 1.3 to 2.8 moles relative to 1 mole of the structural unit derived from the hydrogenated polybutadiene polyol,
The epoxy compound has 2 to 6 epoxy groups, and the epoxy group is 0.9 to 2.5 mol with respect to 1 mol of the hydroxyl group of the aromatic hydroxy compound,
The inorganic filler includes spherical particles (f1) having an average particle size of more than 10 μm and not more than 100 μm, and spherical particles (f2) having an average particle size of 0.1 μm to 10 μm, and the spherical particles (f1) in the inorganic filler ) Content is 58.0-80.0% by mass,
The content of the inorganic filler is Ri from 80.0 to 94.0% by mass,
Producing a structural precursor in which the thermally conductive adhesive sheet is sandwiched between the member (M1) and the member (M2);
A heat dissipation structure in which the thermally conductive adhesive sheet of the structural precursor is cured at 220 to 260 ° C., and the cured body of the thermal conductive adhesive sheet is joined to the member (M1) and the member (M2). The manufacturing method of the thermal radiation structure which has the process of obtaining a body . The manufacturing of the heat dissipation structure according to claim 1, wherein the inorganic filler includes one or more selected from magnesia, alumina, boron nitride, aluminum nitride, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, and crystalline silica. Way . The manufacturing method of the thermal radiation structure of Claim 1 or 2 whose thickness of the said heat conductive adhesive sheet is 100 micrometers or more and less than 500 micrometers. The B-stage sheet, the value t _B tack force measured under the following measuring conditions are 0.1~10.0N / cm ^2, the heat radiating structure according to any one of claims 1 to 3 Manufacturing method .
<Measurement conditions>
At 25 ° C., a 15 mm × 15 mm × 15 mm aluminum block is placed on a 30 mm × 30 mm × thickness 0.3 mm sheet sample fixed on the aluminum plate surface, and a mechanical force gauge is used to After pressing from the top in the vertical direction with a load of 50 N for 10 seconds, the force required to peel off the sheet sample and the block is measured by pulling up in the vertical direction, and this measured value is taken as the tack force. For the C stage sheet obtained by curing the B stage sheet at 220 to 240 ° C., the tack force value t _C measured under the measurement conditions is 0.2 N / cm ² or more, and the t _C and the t _B is the ratio t _C / t _B is 1.5 or more, the manufacturing method of the heat radiating structure according to claim 4. The method for manufacturing a heat dissipation structure according to any one of claims 1 to 5, wherein one of the member (M1) and the member (M2) is a constituent member of a heat-generating electronic component.