JP7031275B2 - Thermocompression bonding sheet - Google Patents

Description

The present invention relates to a thermocompression bonding sheet.

In recent years, composite laminates and sheet-shaped members (composite laminated sheets) made of composite materials having functionality such as thermal conductivity have been used for various purposes.

A thermocompression bonding method is known as a method of joining and adhering materials of the same type or different types to each other. In the thermocompression bonding method, for example, the materials can be heat-welded to each other by applying heat and pressure at a temperature equal to or lower than the melting point of the material to be bonded / bonded. It is also possible to apply a low melting point adhesive between the materials to be joined and bonded, and apply heat and pressure at a temperature below the melting point of the material to heat-weld the materials together with high adhesion. .. Then, in the thermocompression bonding method, usually, the materials via an adhesive are laminated and arranged between the heating device and the fixture, and heating and pressurization are performed from the heating device side facing one of the materials. While doing so, the adhesive is melted while heat is transferred to the fixture side where the other material is fixed, and the materials are heat-welded to each other with high adhesion.

At the time of thermocompression bonding, a composite laminated sheet as a thermocompression bonding sheet may be interposed between the heating device and the fixture or between the material and the fixture for the purpose of protecting the material. Conventionally, as a sheet for thermal pressure bonding, a component (A) made of organopolysiloxane and a heat conductive filler (B) made of crushed metallic silicon powder, crushed crystalline silicon dioxide powder or crushed aluminum oxide powder are used. , A silicone rubber sheet containing a component (C) made of carbon black powder for imparting heat resistance and antistatic property has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2010-100692

The pressurization during thermocompression bonding presses the thermocompression bonding sheet arranged at a predetermined position against the material. For this reason, the sheet placed for the purpose of protecting the material may actually damage the material. In addition, due to the synergistic effect of heating and pressurization during thermocompression bonding, the components of the thermocompression bonding sheet may be transferred to the material. Furthermore, if the thermal conductivity of the thermocompression bonding sheet is insufficient, whitening may occur due to deterioration of the material on the surface of the material. However, the conventional thermocompression bonding sheet as described in Patent Document 1 cannot sufficiently protect the material, and the constituent components of the thermocompression bonding sheet may be transferred to the material. There was a risk of whitening due to insufficient heat conduction.

Therefore, an object of the present invention is to provide a thermocompression bonding sheet capable of parallelizing material protection performance, transfer resistance, and whitening prevention performance at a high level.

The present inventors have made diligent studies to achieve the above object. The present inventor has a laminated structure including a heat conductive sheet and a protective sheet having a 10% compressive stress within a predetermined range, and the thermal resistance value at the time of pressurizing 0.30 MPa is within a predetermined range. We have newly found that the thermocompression bonding sheet inside can stand side by side at a high level of material protection performance, transfer resistance, and whitening prevention performance, and completed the present invention.

That is, the present invention aims to advantageously solve the above problems, and the thermocompression bonding sheet of the present invention has a heat conductive sheet and a 10% compressive stress of 2.0 N / cm ² or more. It has a laminated structure including a protective sheet of 0 N / cm ² or less, and the thermal resistance value of the thermocompression bonding sheet at 0.30 MPa pressurization is 5.0 ° C / W or more and 12.0 ° C / W or less. It is characterized by being.
When used for thermocompression bonding, the thermocompression bonding sheet having such characteristics can have high levels of material protection performance, transfer resistance, and anti-whitening performance.
The "10% compressive stress" of the protective sheet can be measured according to JIS K 6767.
Further, the "thermal resistance value at the time of pressurizing 0.30 MPa" of the thermocompression bonding sheet can be measured according to the method described in the examples of the present specification.

Further, the thermocompression bonding sheet of the present invention preferably has a stress relaxation rate of 15% or more and 50% or less. A thermocompression bonding sheet having a stress relaxation rate of 15% or more and 50% or less is further excellent in material protection performance.
The "stress relaxation rate" of the thermocompression bonding sheet can be measured according to the method described in the examples of the present specification.

Further, in the thermocompression bonding sheet of the present invention, it is preferable that the protective sheet is a foam sheet. A thermocompression bonding sheet provided with a foam sheet as a protective sheet is further excellent in transfer resistance and material protection properties.

Furthermore, in the thermocompression bonding sheet of the present invention, the apparent density of the protective sheet is preferably 0.070 g / cm ³ or less. A thermocompression bonding sheet provided with a protective sheet having an apparent density of 0.070 g / cm ³ or less is further excellent in anti-whitening performance and material protection performance.
The "apparent density" of the protective sheet can be measured according to JIS K 6767.

The thermocompression bonding sheet of the present invention preferably has a thermal conductivity of 4 W / (m · K) or more and 20 W / (m · K) or less in the thickness direction of the heat conductive sheet. A thermocompression bonding sheet containing a heat conductive sheet having a thermal conductivity of 4 W / (m · K) or more and 20 W / (m · K) or less in the thickness direction is further excellent in anti-whitening performance.
The "thermal conductivity in the thickness direction" of the heat conductive sheet can be measured by the method described in the examples of the present specification.

According to the present invention, it is possible to provide a thermocompression bonding sheet that can stand side by side at a high level of material protection performance, transfer resistance, and whitening prevention performance.

It is a figure explaining one step at the time of manufacturing the thermocompression bonding sheet according to this invention.

Hereinafter, embodiments of the present invention will be described in detail.
The thermocompression bonding sheet of the present invention is suitably used as a thermocompression bonding sheet interposed between a material and a heating device in, for example, a thermocompression bonding method for joining and adhering materials to each other using a heating device and a fixture. be able to. For example, if the heating device is an ultrasonic welder, the ultrasonic welder may include an ultrasonic oscillator and a pedestal, which is a fixture for placing and fixing the material. Then, at the time of thermocompression bonding using such an ultrasonic welding machine, the thermocompression bonding sheet of the present invention can be arranged between the material and the pedestal. That is, in an example of thermocompression bonding using the thermocompression bonding sheet of the present invention, the thermal energy generated by the ultrasonic oscillator first passes through the material and then is transmitted to the thermocompression bonding sheet in the thickness direction, and then the pedestal side. Exit to. At this time, it is important that the thermal energy that has passed through the material in the thickness direction escapes to the pedestal side without staying at the interface with the thermocompression bonding sheet or the like.

(Thermocompression bonding sheet)
The thermocompression bonding sheet of the present invention has a laminated structure including a heat conductive sheet and a protective sheet having a 10% compressive stress of 2.0 N / cm ² or more and 10.0 N / cm ² or less. Here, the thermocompression bonding sheet of the present invention is characterized in that the thermal resistance value at the time of pressurizing 0.30 MPa is 5.0 ° C./W or more and 12.0 ° C./W or less. Since the thermocompression bonding sheet of the present invention has the above-mentioned specific laminated structure and the thermal resistance value under predetermined conditions is within the above-mentioned range, the material protection performance, transfer resistance, and whitening prevention performance are at a high level. Can stand side by side.

<Protective sheet>
The protective sheet contained in the thermocompression bonding sheet of the present invention transfers heat in the thickness direction and suppresses the transfer of components of the thermocompression bonding sheet (particularly, components of the thermocompression bonding sheet) to the material. Furthermore, it functions to improve the durability of the thermocompression bonding sheet. When the thermocompression bonding sheet of the present invention is used for thermocompression bonding, it is preferable to arrange the protective sheet so as to be in contact with the material.

[10% compressive stress of protective sheet]
The protective sheet contained in the thermocompression bonding sheet of the present invention requires a 10% compressive stress of 2.0 N / cm ² or more and 10.0 N / cm ² or less, preferably 8.0 N / cm ² or less. Is. When the 10% compressive stress of the protective sheet is at least the above lower limit value, the thermocompression bonding sheet can exhibit excellent material protection performance. The reason is not clear, but when the 10% compressive stress is low, the strength and / or flexibility of the protective sheet is insufficient, so for example, the heating device used for thermocompression bonding is an ultrasonic welder. In some cases, it is presumed that this is because the vibration cannot be sufficiently absorbed.
Further, when the 10% compressive stress of the protective sheet is not more than the above upper limit value, the thermocompression bonding sheet can exhibit excellent anti-whitening performance. If the 10% compressive stress is higher than the above upper limit, the adhesion between the material and the thermocompression bonding sheet on the contact surface becomes insufficient, the transfer of thermal energy on the contact surface is delayed, and the thermal energy comes into contact. There is a risk that it will stay on the surface and temporarily generate excessive heat. As a result, it can be assumed that the surface of the material in contact with the thermocompression bonding sheet is once melted and then recrystallized, resulting in whitening.

[Structure of protective sheet]
The protective sheet is preferably a foamed sheet. If the protective sheet is a foam sheet, the cushioning effect of the protective sheet is enhanced, so that the material protection performance of the thermocompression bonding sheet can be further enhanced, and the contact area with the material is reduced to withstand the thermocompression bonding sheet. The transferability can be further enhanced. The foamed sheet includes a closed bubble sheet and an open bubble sheet, and a closed bubble sheet having a water absorption rate of 0.01 or less measured according to JIS K 6767 is preferable.
Further, the foaming ratio of the "foamed sheet" used as the protective sheet is preferably 5 times or more, more preferably 15 times or more, preferably 50 times or less, and preferably 30 times or less. More preferred. When the foaming ratio of the foamed sheet used is 5 times or more, the cushioning effect that can be exerted by the protective sheet can be further enhanced. Further, when the foaming ratio of the foamed sheet used is 50 times or less, the impact resistance performance that can be achieved by the protective sheet can be enhanced. The "foaming ratio" is a value that can be calculated by dividing the specific gravity of the foamed sheet by the specific gravity of the sheet before foaming, and is generally disclosed as an attribute value of a product marketed as a "foamed sheet". It is a possible value. Therefore, in forming the thermocompression bonding sheet of the present invention, it is possible to select a sheet suitable as a protective sheet by using the foaming ratio as an index.

[Apparent density of protective sheet]
The protective sheet preferably has an apparent density of 0.070 g / cm ³ or less, and more preferably 0.060 g / cm ³ or less. The apparent density of the protective sheet is usually 0.001 g / cm ³ or more. When the apparent density is not more than the above upper limit, heat energy can be smoothly conducted in the thickness direction in the protective sheet which may be interposed between the material and the heat conductive sheet when the heat pressure bonding sheet is used, and the material. Since it is possible to suppress the retention of heat energy on the contact surface between the heat crimping sheet and the heat crimping sheet, it is presumed that the whitening prevention performance of the heat crimping sheet can be further improved. Further, when the apparent density is not more than the above upper limit value, the elasticity of the protective sheet is increased, so that the material protection performance of the thermocompression bonding sheet can be further improved.

[Composition of protective sheet]
The composition of the protective sheet is not particularly limited as long as it satisfies the above-mentioned suitable attributes. For example, the resin material that can form the protective sheet is not particularly limited, and is not particularly limited, and is a polyolefin resin such as polyurethane resin, polystyrene resin, polyethylene resin and polypropylene resin, phenol resin, polyvinyl chloride resin, urea resin, silicone resin, and the like. Examples thereof include polyimide resin and melamine resin. The protective sheet may contain one or more of these resins without particular limitation.

<Heat conduction sheet>
The heat conductive sheet contained in the heat pressure bonding sheet of the present invention exhibits heat conductivity, and the heat resistance value of the obtained heat pressure bonding sheet at 0.30 MPa pressurization is 5.0 ° C./W or more 12. Any sheet having thermal conductivity is not particularly limited as long as it can be in the range of 0 ° C./W or less. For example, the heat conductive sheet is a heat conductive sheet containing a liquid resin under normal temperature and pressure, a solid resin under normal temperature and pressure, and a particulate carbon material, and optionally further containing a fibrous carbon material and an additive. possible. Since such a heat conductive sheet is excellent in heat conductivity, elasticity, etc., when it is provided in a thermocompression bonding sheet, the heat conductivity of the thermocompression bonding sheet is increased to provide high whitening prevention performance to the thermocompression bonding sheet. Can be granted. Hereinafter, various components that may be contained in the heat conductive sheet will be described in detail.

[Liquid resin under normal temperature and pressure]
The liquid resin under normal temperature and pressure that can be contained in the heat conductive sheet constitutes a matrix resin of the heat conductive sheet together with the solid resin under normal temperature and pressure described later, and binds a particulate carbon material or the like in the heat conductive sheet. It also functions as a binder. Since the heat conductive sheet contains a liquid resin under normal temperature and pressure, the adhesion between the heat conductive sheet and the protective sheet can be improved when the thermocompression bonding sheet of the present invention is used, and is used for thermocompression bonding. The heat conductivity of the sheet is further enhanced, and the whitening prevention performance can be exhibited more effectively. In the present specification, "normal temperature" means 23 ° C., and "normal pressure" means 1 atm (absolute pressure).
Here, examples of the resin that is liquid under normal temperature and pressure include a thermoplastic resin that is liquid under normal temperature and pressure and a thermosetting resin that is liquid under normal temperature and pressure. Above all, from the viewpoint of improving the adhesion between the heat conductive sheet and the protective sheet when using the heat pressure bonding sheet and further improving the heat conductivity of the entire heat pressure bonding sheet, it is a liquid resin under normal temperature and pressure. It is preferable to use a liquid thermoplastic resin under normal temperature and pressure.

Examples of the thermoplastic resin that is liquid under normal temperature and pressure include acrylic resin, epoxy resin, silicon resin, and fluororesin.
Examples of the thermosetting resin that is liquid under normal temperature and pressure include natural rubber; butadiene rubber; isoprene rubber; nitrile rubber; hydride nitrile rubber; chloroprene rubber; ethylene propylene rubber; chlorinated polyethylene; chlorosulfonated polyethylene; Butyl rubber; halogenated butyl rubber; polyisobutylene rubber; epoxy resin; polyimide resin; bismaleimide resin; benzocyclobutene resin; phenol resin; unsaturated polyester; diallyl phthalate resin; polyimide silicone resin; polyurethane; thermosetting polyphenylene ether; thermosetting Type-modified polyphenylene ether; and the like.

The content ratio of the liquid resin under normal temperature and pressure may be 40% by mass or more and 90% by mass or less of the total content of the liquid resin under normal temperature and pressure and the solid resin under normal temperature and pressure described later. When the content ratio of the liquid resin under normal temperature and pressure is equal to or higher than the above lower limit, the flexibility of the heat conductive sheet is further increased, the adhesion between the heat conductive sheet and the protective sheet is improved, and the entire thermocompression bonding sheet is obtained. It is possible to increase the thermal conductivity as a. By increasing the flexibility of the heat conductive sheet, it is possible to prevent the stress relaxation rate of the thermocompression bonding sheet provided with the heat conductive sheet from being excessively lowered. Further, when the content ratio of the liquid resin is within the above range under normal temperature and pressure, the elasticity of the heat conductive sheet can be appropriately increased, and the durability of the thermocompression bonding sheet can be improved.

[Solid resin under normal temperature and pressure]
Examples of the resin that is solid under normal temperature and pressure include a solid thermoplastic resin under normal temperature and pressure and a solid thermosetting resin under normal temperature and pressure. If the heat conductive sheet contains a solid resin under normal temperature and pressure, the durability of the thermocompression bonding sheet provided with the heat conductive sheet can be enhanced. Above all, from the viewpoint of improving the adhesion between the heat conductive sheet and the protective sheet when using the heat pressure bonding sheet and improving the heat conductivity of the heat pressure bonding sheet as a whole, as a solid resin under normal temperature and pressure. , It is preferable to contain a solid thermoplastic resin under normal temperature and pressure.

Examples of the solid thermoplastic resin under normal temperature and pressure include poly (2-ethylhexyl acrylate), a copolymer of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or an ester thereof, polyacrylic acid or Acrylic resin such as the ester; Silicon resin; Fluorine resin; Polyethylene; Polypropylene; Ethylene-propylene copolymer; Polymethylpentene; Polyvinyl chloride; Polyvinyl chloride; Polyacetic acid vinyl; Ethylene-vinyl acetate copolymer; Polyvinyl alcohol Polyacetal; polyethylene terephthalate; polybutylene terephthalate; polyethylene naphthalate; polystyrene; polyacrylonitrile; styrene-acrylonitrile copolymer; acrylonitrile-butadiene-styrene copolymer (ABS resin); styrene-butadiene block copolymer or hydrogenation thereof Material; styrene-isoprene block copolymer or hydrogenated product thereof; polyphenylene ether; modified polyphenylene ether; aliphatic polyamides; aromatic polyamides; polyamideimide; polycarbonate; polyphenylene sulfide; polysulfone; polyether sulfone; polyether nitrile ; Polyether ketone; Polyketone; Polyurethane; Liquid polymer; Ionomer;
Examples of the thermosetting resin that is solid under normal temperature and pressure include natural rubber; butadiene rubber; isoprene rubber; nitrile rubber; hydride nitrile rubber; chloroprene rubber; ethylene propylene rubber; chlorinated polyethylene; chlorosulfonated polyethylene; Butyl rubber; halogenated butyl rubber; polyisobutylene rubber; epoxy resin; polyimide resin; bismaleimide resin; benzocyclobutene resin; phenol resin; unsaturated polyester; diallyl phthalate resin; polyimide silicone resin; polyurethane; thermosetting polyphenylene ether; thermosetting Type-modified polyphenylene ether; and the like.

The above-mentioned resins may be used alone or in combination of two or more.

[Particulate carbon material]
The particulate carbon material that can be contained in the heat conductive sheet is not particularly limited, and is, for example, artificial graphite, scaly graphite, flaky graphite, natural graphite, acid-treated graphite, expansive graphite, expanded graphite, and the like. Graphite; carbon black; or the like can be used. These may be used alone or in combination of two or more.
Above all, it is preferable to use expanded graphite as the particulate carbon material. This is because if expanded graphite is used, the thermal conductivity of the heat conductive sheet can be increased, and thus the heat conductivity of the thermocompression bonding sheet as a whole can be further improved.

The average particle size of the particulate carbon material may be 1 μm or more and 500 μm or less in terms of volume average particle size. The "volume average particle size" is, for example, a particle size distribution measured by a laser diffraction method using a laser diffraction / scattering type particle size distribution measuring device (manufactured by Horiba Seisakusho, model "LA-960"). In, it may be the particle diameter (D50) when the cumulative volume calculated from the small diameter side is 50%.

The content ratio of the particulate carbon material in the heat conductive sheet may be 25% by volume or more and 40% by volume or less. When the content ratio of the particulate carbon material is at least the above lower limit, the heat transfer path of the particulate carbon material can be satisfactorily formed in the heat conductive sheet. Further, when the content ratio of the particulate carbon material is not more than the above upper limit, the flexibility of the heat conductive sheet is enhanced to prevent the stress relaxation rate of the thermocompression bonding sheet provided with the heat conductive sheet from being excessively increased. Can be done.

[Other ingredients]
In addition to the various components described above, the heat conductive sheet may optionally further contain other components such as fibrous carbon materials and additives.

-Fibrous carbon material The fibrous carbon material that can be optionally contained in the heat conductive sheet is not particularly limited, and is, for example, carbon nanotubes, vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and carbon fibers. Those cut pieces and the like can be used. These may be used alone or in combination of two or more. Above all, it is preferable that the heat conductive sheet contains carbon nanotubes as the fibrous carbon material.

-Additives The additives that can be optionally contained in the heat conductive sheet are not particularly limited, and are, for example, flame retardants such as red phosphorus flame retardants; plasticizers such as phosphoric acid ester plasticizers; calcium oxide, Moisture absorbents such as magnesium oxide; adhesive strength improvers such as silane coupling agents, titanium coupling agents and acid anhydrides; wettability improvers such as nonionic surfactants and fluorine-based surfactants; inorganic ion exchangers, etc. Ion trapping agent; particulate carbon material; etc.

[Method of forming a heat conductive sheet]
The heat conductive sheet is not particularly limited, and can be formed through, for example, a preheat conductive sheet forming step, a laminate forming step, a slicing step, and the like according to the method described in International Publication No. 2016/185688.

-Preheat conductive sheet molding process In the preheat conductive sheet molding process, a liquid resin under normal temperature and pressure, a solid resin under normal temperature and pressure, and a particulate carbon material are included, and fibrous carbon materials and additives are used. A composition further containing an optional component is pressurized and molded into a sheet to obtain a preheat conductive sheet.

Here, the composition is a mixture of a liquid resin under normal temperature and pressure, a solid resin under normal temperature and pressure, a particulate carbon material, and the above-mentioned optional components (fibrous carbon material, additives, etc.). Can be prepared. The above-mentioned various components can be used as the liquid resin under normal temperature and pressure, the solid resin under normal temperature and pressure, the particulate carbon material, and any fibrous carbon material and additives.

Further, the mixing of the above-mentioned components is not particularly limited, and can be performed using a known mixing device such as a kneader, a roll, or a mixer. Further, the mixing may be carried out in the presence of a solvent such as an organic solvent. The mixing time can be, for example, 5 minutes or more and 60 minutes or less. Further, the mixing temperature can be, for example, 5 ° C. or higher and 150 ° C. or lower.

Then, the composition prepared as described above can be optionally defoamed and crushed, and then pressurized (primary pressurized) to be formed into a sheet. In the preheat conductive sheet formed by pressurizing the composition into a sheet, the particulate carbon material and any fibrous carbon material are arranged mainly in the in-plane direction, and the thermal conductivity in the in-plane direction is particularly high. It is presumed that it will improve. The thickness of the preheat conductive sheet is not particularly limited and may be, for example, 0.05 mm or more and 2 mm or less.

-Laminated body forming step In the laminated body forming step, a plurality of preheated conductive sheets obtained in the preheated conductive sheet forming step are laminated in the thickness direction, or the preheated conductive sheet is folded or rolled to be laminated. Get the body. Here, from the viewpoint of efficiently suppressing delamination, it is preferable to further heat press (secondary pressurize) the laminated body in which the preheat conductive sheets are laminated in the laminating direction. The conditions for the secondary pressurization are not particularly limited, and may be 10 seconds to 30 minutes at a pressure of 0.05 MPa or more and 0.5 MPa or less in the stacking direction and a temperature of 80 ° C. or more and 170 ° C. or less. Then, in the laminate obtained by laminating, folding or winding the preheat conductive sheet, it is presumed that the particulate carbon material and arbitrary fibrous carbon fibers are arranged in a direction substantially orthogonal to the laminating direction.

-Slicing step In the slicing step, the laminate obtained in the laminate forming step is sliced at an angle of 45 ° or less with respect to the lamination direction to obtain a heat conductive sheet made of sliced pieces of the laminate. Here, the method for slicing the laminate is not particularly limited, and examples thereof include a multi-blade method, a laser processing method, a water jet method, and a knife processing method. The cutting tool for slicing the laminated body is not particularly limited, and includes, for example, a fixing tool such as a metal plate for pressing and fixing the laminated body in the stacking direction, and a double-edged cutting tool. A slicer can be used which comprises a slice member and slices the laminated body by moving the cutting blade in the laminated direction while pressing the laminated body with a fixture.

From the viewpoint of enhancing the thermal conductivity of the heat conductive sheet, the angle at which the laminated body is sliced is preferably approximately 0 ° with respect to the laminating direction (that is, the direction along the laminating direction). The heat conductive sheet obtained through each of the above steps has a structure in which strips containing a resin, a particulate carbon material, and the like are joined in parallel. In such a heat conductive sheet, the particulate carbon material or the like is oriented in the thickness direction of the heat conductive sheet in each strip, so that the heat conductive sheet is excellent.

[Characteristics of heat conductive sheet]
-Thermal conductivity The thermal conductivity of the heat conductive sheet is preferably 4 W / (m · K) or more, more preferably 10 W / (m · K), and preferably 20 W / (preferably 20 W / K) in the thickness direction. m · K) or less. When the thermal conductivity in the thickness direction of the heat conductive sheet is at least the above lower limit value, the whitening prevention performance of the thermocompression bonding sheet can be further improved. Further, when the thermal conductivity in the thickness direction of the heat conductive sheet is not more than the above upper limit value, deterioration of the protective sheet due to heat can be suppressed, and the durability of the thermocompression bonding sheet can be enhanced.
The thermal conductivity of the heat conductive sheet can be controlled, for example, by appropriately adjusting the content of the liquid resin under normal temperature and pressure, the content of the solid resin under normal temperature and pressure, the content of the particulate carbon material, and the like. can.

-Thickness The heat conductive sheet preferably has a thickness of 100 μm or more, more preferably 200 μm or more, preferably 1.5 mm or less, and more preferably 1.2 mm or less. When the thickness of the heat conductive sheet is at least the above lower limit value, the durability of the thermocompression bonding sheet of the present invention can be enhanced. Further, when the thickness of the heat conductive sheet is not more than the above upper limit value, it is possible to prevent the thermal resistance of the thermocompression bonding sheet of the present invention from becoming excessively high, and it is possible to further improve the whitening prevention performance.

<Thermal resistance value of the thermocompression bonding sheet when pressurized at 0.30 MPa>
The thermal resistance value of the thermocompression bonding sheet including the above-mentioned laminated structure of the protective sheet and the heat conductive sheet at the time of pressurizing 0.30 MPa needs to be 5.0 ° C./W or more and 12.0 ° C./W or less. When the thermal resistance value of the thermocompression bonding sheet at the time of pressurizing 0.30 MPa is within the above range, both the durability of the thermocompression bonding sheet and the whitening prevention performance can be improved.
The thermal resistance value of the thermocompression bonding sheet at the time of pressurizing 0.30 MPa can be adjusted based on appropriately changing the composition of the heat conductive sheet, appropriately changing the apparent density of the protective sheet, and the like. ..

<Stress relaxation rate of thermocompression bonding sheet>
The stress relaxation rate of the thermocompression bonding sheet of the present invention is preferably 7% or more, more preferably 15% or more, preferably 50% or less, and more preferably 45% or less. When the stress relaxation rate of the thermocompression bonding sheet is at least the above lower limit value, the material protection performance is further excellent. Further, when the stress relaxation rate of the thermocompression bonding sheet is not more than the above upper limit value, the durability of the thermocompression bonding sheet can be enhanced.
The stress relaxation rate of the thermocompression bonding sheet can be determined by, for example, appropriately changing the composition of the matrix resin of the heat conductive sheet, or selecting a sheet having an appropriate value of 10% compressive stress as the protective sheet. , Can be adjusted.

<Method of manufacturing thermocompression bonding sheet>
The thermocompression bonding sheet having a laminated structure of the protective sheet and the heat conductive sheet as described above is not particularly limited, and is manufactured by arranging the protective sheet on one surface of the heat conductive sheet. can do.
Prior to arranging the protective sheet on one surface of the heat conductive sheet, an adhesive layer is arranged on at least a part of one surface of the heat conductive sheet, and the heat conductive sheet and protection are provided through the adhesive layer. The sheets can be glued together. The adhesive layer is not particularly limited as long as it does not significantly impair the thermal conductivity of the thermocompression bonding sheet, and can be formed by a known adhesive, double-sided tape, or the like. Further, the position where the adhesive layer is formed is not particularly limited, and may be, for example, the peripheral portion of the sheet. More specifically, when the shape of the thermocompression bonding sheet is rectangular or substantially rectangular, adhesive layers may be formed at the four corners thereof. Further, after laminating the heat conductive sheet and the protective sheet, the laminated body may be optionally pressed in the thickness direction. Even if such pressing is not performed, when the thermocompression bonding sheet is used, the thermocompression bonding sheet is pressed through the material and heat energy is applied to form a recess along the shape of the material. As long as it continues to be used for thermocompression bonding of materials of the same shape, such a shape can be maintained, and the protective sheet and the heat conductive sheet can be maintained in close contact with each other.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the following description, "%" and "part" representing quantities are based on mass unless otherwise specified.
In the examples and comparative examples, the thermal conductivity in the thickness direction of the heat conductive sheet, the thermal resistance value of the heat pressure bonding sheet at 0.30 MPa pressurization, and the stress relaxation rate of the heat pressure bonding sheet are as follows. Measured according to the method. Further, in Examples and Comparative Examples, the transfer resistance, material protection performance, whitening prevention performance, and sheet durability of the thermocompression bonding sheet were evaluated according to the following methods, respectively.

<Thermal conductivity in the thickness direction of the heat conductive sheet>
For the heat conductive sheets obtained in Examples and Comparative Examples, the thermal diffusivity α (m ² / s) in the thickness direction, the constant pressure specific heat Cp (J / g · K) and the specific gravity ρ (g / m ³ ) were obtained by the following methods. Measured at.
[Thermal diffusivity]
The thermal diffusivity at a temperature of 25 ° C. was measured using a thermophysical property measuring device (manufactured by Bethel Co., Ltd., product name "Thermowave Analyzer TA35").
[Constant pressure specific heat]
Using a differential scanning calorimeter (manufactured by Rigaku, product name "DSC8230"), the specific heat at a temperature of 25 ° C. was measured under a heating condition of 10 ° C./min.
[specific gravity]
The measurement was performed using an automatic hydrometer (manufactured by Toyo Seiki Co., Ltd., trade name "DENSIMTER-H").
Then, using the obtained measured values, the following formula (I):
λ = α × Cp × ρ ・ ・ ・ (I)
Further, the thermal conductivity λ (W / (m · K)) in the thickness direction of the heat conductive sheet at a temperature of 25 ° C. was determined.

<Thermal resistance value of the thermocompression bonding sheet when pressurized at 0.30 MPa>
The thermal resistance value of the thermocompression bonding sheet was measured using a resin material thermal resistance tester (manufactured by Hitachi Technology and Service Co., Ltd.). The thermocompression bonding sheets prepared in Examples and Comparative Examples were cut into substantially squares of 1 cm square and used as samples. Then, the thermal resistance value (° C./W) was measured when the sample temperature was 50 ° C. and 0.30 MPa, which was a relatively low pressure, was applied. The smaller the thermal resistance value, the better the thermal conductivity of the thermocompression bonding sheet.
<Stress relaxation rate of thermocompression bonding sheet>
The stress relaxation rate of the thermocompression bonding sheet was measured using a probe tack tester (“TAC1000” manufactured by Resca). A flat probe tip with a diameter of 10 mm is pressed against the surface of the thermocompression bonding sheet produced in Examples and Comparative Examples, and the load is gradually increased. When the load reaches 4.0 N (400 gf), the load is applied. The increase was stopped and held for 10 seconds. When the maximum load at the time of pressing was A and the load after holding for 10 seconds was B, the relaxation rate was calculated by the following formula (I).
Stress relaxation rate [%] = (AB) / A × 100 ・ ・ ・ (I)

<Transfer resistance>
Using the thermocompression bonding sheets produced in Examples and Comparative Examples, the transfer resistance when the synthetic resin materials A and B were thermocompression bonded was evaluated. Both the synthetic resin materials A and B were made of polypropylene, and each was molded into a star shape (a size that fits in a circle having a diameter of 6 cm). Next, 0.20 g of an adhesive made of acrylonitrile-butadiene-styrene copolymer synthetic resin (ABS resin) is applied between the synthetic resin materials A and B, and the synthetic resin material A and the synthetic resin material B are adhered to each other. It was laminated via an agent. At this time, the adhesive was in a solid state at room temperature, and the synthetic resin materials A and B were not adhered by the adhesive.
Subsequently, the obtained laminate of the synthetic resin material A / adhesive / synthetic resin material B is fixed to an ultrasonic welding machine (manufactured by Herman Ultrasonic, product name "HiQ VARIO") via a thermocompression bonding sheet. did. The ultrasonic welding machine was equipped with an ultrasonic oscillator and a fixture. Specifically, on the lower side of the ultrasonic welder, there is a pedestal having a metal jig as a fixture, and on the upper side of the ultrasonic welder, a horn that generates ultrasonic waves is attached. The laminate was fixed between the pedestal and the horn so that the synthetic resin material A was on the upper side (the side facing the horn) and the synthetic resin material B was on the lower side (the side fixed to the pedestal). Further, at the time of fixing, the thermocompression bonding sheet obtained in Examples and Comparative Examples is interposed between the synthetic resin material B side and the pedestal of the laminate so that the protective sheet side is in contact with the synthetic resin material B. rice field. That is, from the upper side, a pedestal having a horn (ultrasonic oscillator) / synthetic resin material A / adhesive / synthetic resin material B / thermocompression bonding sheet (protective sheet / heat conductive sheet) / metal jig as a fixture. The laminate was fixed to the ultrasonic welder in this order.
Subsequently, ultrasonic waves are radiated from the upper horn to the synthetic resin material A side, and the heat generated from the vibration energy of the ultrasonic waves is transmitted to melt the adhesive, whereby the synthetic resin materials A and B are thermocompression bonded. rice field. Here, the synthetic resin material A and the horn were in contact with each other while being irradiated with ultrasonic waves. The conditions for thermocompression bonding by ultrasonic irradiation were press pressure: 180 N / mm ² , ultrasonic frequency: 30 kHz, ultrasonic processing time: about 5 seconds, and output: 1800 W.
Then, after the synthetic resin materials A and B are heat-welded as described above, the laminate is removed from the ultrasonic welding machine, and the surface of the laminate on the synthetic resin material B side, that is, the protection contained in the thermocompression bonding sheet. The state of the surface in contact with the sheet (hereinafter, also referred to as “surface X”) was visually observed, and the presence or absence and degree of contamination on the surface of the synthetic resin material were evaluated according to the following criteria. The less the surface of the synthetic resin material is soiled, the better the thermocompression bonding sheet is.
Here, in this evaluation standard, the "dirt" is a component of the film or resin adhered to the surface of the synthetic resin material B on the side fixed to the pedestal via the thermocompression bonding sheet. Then, the "dirt size" is defined as the diameter when an circumscribed circle is set for the contour of the adhered portion. The "dirt" includes those having a size that is difficult to visually confirm, and the "dirt" of such a size can be easily observed by using a microscope such as an electron microscope. Further, the "dirt" referred to here is physically in close contact with the synthetic resin and is different from dust that can be easily removed by air spray or the like. On the other hand, it can be removed by wiping with a cloth or the like.
A: Dirt cannot be confirmed even with a microscope.
B: The size of dirt is 20 μm or more and 500 μm or less.
C: There is dirt exceeding 500 μm.

<Material protection performance>
In the evaluation of transfer resistance, it was evaluated whether or not there were scratches on the same surface (surface X) as the target surface.
The presence or absence of scratches was confirmed using a laser microscope (“VX-200” manufactured by KEYENCE CORPORATION). The magnification was measured at 200 times, and scratches were confirmed according to the following evaluation criteria.
The scratches referred to here are linear scratches, and refer to scratches having a depth of 1 μm or more and a length of 30 μm or more.
A: The scratch cannot be confirmed even with a microscope.
B: There are 1 to 5 scratches.
C: There are 5 or more scratches.

<Whitening evaluation>
With respect to the same surface (surface X) whose transfer resistance and material protection performance were evaluated, a visual evaluation was performed to see if there was a whitened region on the surface.
Thermal energy is generated by ultrasonic irradiation, but if the thermal energy transmitted from the horn side in this order to the material and the thermal crimping sheet is smoothly released to the pedestal side, discoloration does not occur, but it is combined with the thermal crimping sheet. When thermal energy stays between the resin material B, excessive heat generation is temporarily generated at the interface between the heat pressure bonding sheet and the synthetic resin material B, and as a result, whitening occurs on the surface of the synthetic resin B.
A: There is no whitened area on the surface.
B: The occupancy rate of the area of the whitened area is less than 10% of the area of the entire surface.
C: The occupancy rate of the area of the whitened area is 10% or more of the area of the entire surface.

<Repeat durability>
The operation of thermocompression bonding the synthetic resin materials A and B was repeated 1000 times under the same conditions as when the transfer resistance was evaluated. With respect to the thermocompression bonding sheet after being used 1000 times, the state of the sheet surface was visually observed, and the durability was evaluated according to the following criteria.
In this evaluation standard, "crack" refers to a crevice having a length of 3 mm or more in the plane direction of at least one of the surfaces of the thermocompression bonding sheet. Further, in this evaluation standard, "tear" refers to a state in which cracks further progress in the thickness direction of the thermocompression bonding sheet and penetrate from one surface to the other surface of the thermocompression bonding sheet. Further, the “crack” refers to a crevice that can be visually confirmed, and does not correspond to a crevice at a minute level that cannot be discriminated without using a microscope such as an electron microscope, for example.
A: There are no cracks or tears on the surface of the thermocompression bonding sheet.
B: There are cracks on the surface of the thermocompression bonding sheet, but there is no tear.
C: There is a tear on the surface of the thermocompression bonding sheet.

(Example 1)
<Preparation of easily dispersible aggregates of fibrous carbon nanostructures>
400 mg of a fibrous carbon nanostructure (SGCNT, manufactured by Nippon Zeon Corporation, specific surface area: 600 m ² / g) was weighed, mixed in 2 L of methyl ethyl ketone as a solvent, and stirred with a homogenizer for 2 minutes to obtain a crude dispersion. .. Next, using a wet jet mill (manufactured by Tsunemitsu Co., Ltd., product name "JN-20"), the obtained crude dispersion liquid was passed through a 0.5 mm flow path of the wet jet mill for 2 cycles at a pressure of 100 MPa. The fibrous carbon nanostructures were dispersed in methyl ethyl ketone. Then, a dispersion liquid having a solid content concentration of 0.20% by mass was obtained.
Then, the dispersion obtained above was filtered under reduced pressure using Kiriyama filter paper (No. 5A) to obtain an easily dispersible aggregate of sheet-like fibrous carbon nanostructures as a fibrous carbon material. ..

<Preparation of composition>
70 parts of liquid thermoplastic fluororesin (manufactured by Daikin Industries, Ltd., trade name "Daiel G-101") under normal temperature and pressure, and solid thermoplastic fluororesin (manufactured by 3M Japan Co., Ltd., trade name) under normal temperature and pressure. 30 parts of "Dynion FC2211", Mooney viscosity: 27ML _{1 + 4} , 100 ° C., and expanded fluoropolymer as a particulate carbon material (manufactured by Ito Graphite Industry Co., Ltd., trade name "EC50", volume average particle diameter: 250 μm) ) And 0.5 parts of the easily dispersible aggregate of the fibrous carbon nanostructure obtained above as the fibrous carbon material, using a pressurized kneader (manufactured by Nippon Spindle). The mixture was stirred and mixed at a temperature of 150 ° C. for 20 minutes. Next, the obtained mixture was put into a crusher and crushed for 10 seconds to obtain a composition.

<Formation of preheat conduction sheet>
Next, 50 g of the obtained composition was sandwiched between a PET film (protective film) having a thickness of 50 μm subjected to sandblasting, and the conditions were that the roll gap was 550 μm, the roll temperature was 50 ° C., the roll linear pressure was 50 kg / cm, and the roll speed was 1 m / min. A preheat conductive sheet having a thickness of 0.5 mm was obtained by rolling and molding (primary pressurization).

<Formation of laminated body>
Subsequently, the obtained preheat conductive sheet was cut into a length of 150 mm × width of 150 mm × thickness of 0.5 mm, 120 sheets were laminated in the thickness direction of the preheat conductive sheet, and further, at a temperature of 120 ° C. and a pressure of 0.1 MPa, 3 By pressing (secondary pressurization) in the stacking direction for a minute, a laminated body having a height of about 60 mm was obtained.

<Formation of heat conductive sheet>
Then, the entire upper surface of the obtained laminate was pressed with a metal plate, leaving the required length for slicing, and a pressure of 0.1 MPa was applied from above to fix the laminate. The sides and back of the laminate were not fixed.
Next, the cutting blade 10 (double-edged, blade angle 2θ: 20 °, maximum thickness of the blade: 3.5 mm, material: super) having the shape shown in FIG. Steel, Rockwell hardness: 91.5, blade surface silicon processing: none, total length: 200 mm), and the stacking direction (in other words, stacking) of the laminate under the conditions of slice speed 200 mm / sec and slice width 1.0 mm. The heat conductive sheet 30 having a length of 150 mm, a width of 60 mm, and a thickness of 1.0 mm was obtained by slicing in the direction corresponding to the normal of the main surface of the pre-heat conductive sheet. The posture of the cutting blade at the time of slicing was such that the angle α shown in FIG. 1 was 10 ° and the extending direction of the blade surface 11 was parallel to the slice surface 21 of the laminated body 20.
The obtained thermal conductivity sheet was evaluated for thermal conductivity in the thickness direction according to the above. The results are shown in Table 1. The content ratio of the particulate carbon material in the heat conductive sheet was 28% by volume.

<Making a thermocompression bonding sheet>
A 5 mm × 5 mm double-sided tape is placed at the four corners of the heat conductive sheet obtained according to the above, and a protective sheet cut out to the same size as the heat conductive sheet is placed on the double-sided tape to obtain a thermocompression bonding sheet. rice field. As a protective sheet, foamed polyethylene sheet (manufactured by Inoac Corporation, "PE Light White A-155", closed cell, thickness = 1 mm, 10% compressive stress = 2.6 N / cm ² , apparent density = 0.007 g / cm ³ ) was used.
The obtained thermocompression bonding sheet was subjected to various measurements and evaluations according to the above. The results are shown in Table 1.

(Examples 2 to 3)
Various measurements and evaluations were carried out in the same manner as in Example 1 except that the protective sheets having various attributes shown in Table 1 were used. The results are shown in Table 1.
In Example 2, "PE Light Gray B-4" manufactured by Inoac Corporation was used as a protective sheet, and in Example 3, "PE Light Blue A-8" manufactured by Inoac Corporation was used as a protective sheet. Each was used.

(Examples 4 to 6)
Example 4 is the same as that of Example 1 except that the thickness of the heat conductive sheet is 0.15 mm, and Example 5 is the same as that of Example 2 except that the thickness of the heat conductive sheet is 0.15 mm. In Example 6, various measurements and evaluations were carried out in the same manner as in Example 3 except that the thickness of the heat conductive sheet was 0.15 mm. The results are shown in Table 1. When changing the thickness of the heat conductive sheet, the thickness to be sliced was changed to 0.15 mm in the <formation of heat conductive sheet> step.

(Comparative Example 1)
Instead of the foamed polyethylene sheet as the protective sheet in Example 1, a film made of a non-foaming sheet PFA resin (tetrafluoroethylene-perfluoro (alkyl vinyl ether) resin) (manufactured by Daikin Industries, Ltd., "neoflon PFA film", thickness) Various measurements and evaluations were carried out in the same manner as in Example 1 except that (s: 15 μm, Tg: 100 ° C.) was used. The results are shown in Table 1. The protective sheet used in this example did not exhibit 10% compressive stress, and the value could not be measured. Moreover, since the protective sheet used in this example is a non-foaming sheet, the "apparent density" could not be measured.

(Comparative Example 2)
Instead of the foamed polyethylene sheet as the protective sheet in Example 4, a film made of PFA resin (manufactured by Daikin Industries, Ltd., "Neoflon PFA film", thickness: 15 μm, Tg: 100 ° C.) was used. Performed various measurements and evaluations in the same manner as in Example 4. The results are shown in Table 1. As in Comparative Example 1, the protective sheet used in this example could not measure the values of 10% compressive stress and apparent density.

(Comparative Example 3)
The heat conductive sheet itself obtained in the same manner as in Example 1 without providing a protective sheet was used as it was as a thermocompression bonding sheet. Except for these points, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 4)
As the heat conductive sheet, the pre-heat conductive sheet obtained in the <formation of pre-heat conductive sheet> step in Example 1 was used. Except for these points, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 5)
The same protective sheet itself as that used in Example 1 was used as it was as a thermocompression bonding sheet without providing a heat conductive sheet. Except for these points, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

From Table 1, it has a laminated structure including a protective sheet with a 10% compressive stress of 2.0 N / cm ² or more and 10.0 N / cm ² or less, and a heat conductive sheet, and 0.30 MPa of the entire thermocompression bonding sheet. The thermocompression bonding sheets of Examples 1 to 6 having a thermal resistance value of 5 ° C./W or more and 12 ° C./W or less at the time of pressurization are excellent in all of transfer resistance, material protection performance, and whitening prevention performance. I understand.
On the other hand, Comparative Examples 1 and 2 in which the protective sheet did not exhibit 10% compressive stress and the thermal resistance value of the entire thermocompression bonding sheet at the time of pressurizing 0.30 MPa was less than 5 ° C./W, and the protective sheet. In Comparative Example 3 which is not provided, Comparative Example 4 in which the thermal resistance value of the entire thermocompression bonding sheet at the time of pressurizing 0.30 MPa is more than 12 ° C./W, and Comparative Example 5 which is not provided with the heat conductive sheet, the transfer resistance is improved. It can be seen that all of the material protection performance and the whitening prevention performance could not be arranged at a high level.

According to the present invention, it is possible to provide a thermocompression bonding sheet that can stand side by side at a high level of material protection performance, transfer resistance, and whitening prevention performance.

10 Cutting blade 11 Blade surface 20 Laminated body 21 Sliced surface 30 Heat conductive sheet

Claims (5)

It is a thermocompression bonding sheet
It has a laminated structure including a heat conductive sheet and a protective sheet having a 10% compressive stress of 2.0 N / cm ² or more and 10.0 N / cm ² or less.
The thermal resistance value of the thermocompression bonding sheet when pressurized at 0.30 MPa is 5.0 ° C / W or more and 12.0 ° C / W or less, and further.
The heat conductive sheet has a structure in which strips containing a liquid resin under normal temperature and pressure, a solid resin under normal temperature and pressure, and a particulate carbon material are joined in parallel, and has a thermal conductivity of 4 W in the thickness direction. / (M ・ K) or more and 20W / (m ・ K) or less ,
Thermocompression bonding sheet. The thermocompression bonding sheet according to claim 1, wherein the stress relaxation rate is 7% or more and 50% or less. The thermocompression bonding sheet according to claim 1 or 2, wherein the protective sheet is a foam sheet. The thermocompression bonding sheet according to any one of claims 1 to 3, wherein the protective sheet has an apparent density of 0.070 g / cm ³ or less. The thermocompression bonding sheet according to any one of claims 1 to 4, further comprising a fibrous carbon material.

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