TWI550650B - Conductive sheet and electonic parts - Google Patents

Description

Conductive sheet and electronic parts

The present invention relates to a conductive sheet which can be used, for example, to be adhered to an adherend such as a printed wiring board, and a method for producing the same. Moreover, the present invention relates to an electronic component including the above conductive sheet.

In recent years, in addition to the miniaturization of printed wiring boards, flexible printed wiring boards have been used in addition to the reduction in size and thickness of electronic equipment. In these wiring boards, various conductive sheets are used in order to achieve high functionality.

For example, Patent Document 1 discloses a thermosetting conductive adhesive sheet having a three-layer structure in which a conductive layer is sandwiched by an adhesive layer containing a thermosetting adhesive. The conductive layer constituting the adhesive sheet has a projection that is raised in the surface direction. The protruding portion of the conductive layer is electrically connected to the adherend by directly pressing and bonding the adhesive layer to the adherend to penetrate the adhesive layer. Thereby, it functions as a conductive adhesive sheet.

Further, Patent Document 2 discloses a conductive adhesive film containing a thermoplastic resin having a glass transition temperature of -10 ° C or more and 50 ° C or less and silver powder. The silver powder is generally used in combination of at least two kinds of atomized silver powder, spherical, fine spherical, and flake.

Patent Document 3 discloses an electromagnetic wave shielding adhesive film containing a polyurethane polyurea resin, an epoxy resin having two or more epoxy groups, and a conductive filler.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2002-97424

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2004-288560

[Patent Document 3] WO2006/088127

However, the conductive adhesive sheet disclosed in Patent Document 1 has a structure in which a conductive layer containing a metal foil of copper, iron, aluminum or the like is sandwiched by an adhesive layer, and thus it is not suitable for a printed wiring board. The problem of the case where the thickness is thin. Further, since the metal foil is inferior in flexibility, it is difficult to use it for a flexible printed wiring board in which the conductive adhesive sheet is repeatedly bent.

Further, the conductive adhesive film disclosed in Patent Document 2 is not suitable for use in a high-temperature environment because the thermoplastic resin has low heat resistance.

Further, when the conductive sheet is attached to a printed wiring board or the like, if the conductive layer bleeds out, the electrical characteristics of the electronic device are greatly affected. Therefore, there is a strict demand for bleed out of the conductive sheet on the market, and further improvement of the bleed out of the conductive layer is required for the previously conductive sheet of Patent Document 2 or Patent Document 3.

The present invention has been made in view of the above-described background, and an object of the invention is to provide a method of heating and pressing a conductive sheet such as a printed wiring board, which can reduce the bleeding of the conductive layer to a minimum. A conductive sheet, a method for producing the same, and an electronic component.

The conductive sheet of the present invention includes a conductive layer containing at least a thermosetting resin (A) and dendritic conductive fine particles (B), and the thickness of the conductive layer satisfies the following (i) and ( At least one of ii): (i) a thickness after heating and pressing under conditions of 150 ° C, 2 MPa, and 30 minutes, and a range of 30 or more and 95 or less when the thickness of the conductive layer before heat pressing is 100; (ii) The average particle diameter D ₉₀ of the dendritic conductive fine particles (B) is in a range of 0.5 times or more and 3 times or less with respect to the thickness of the conductive layer; and the average particle of the dendritic conductive fine particles (B) The diameter D ₅₀ is 3 μm or more and 50 μm or less, and the dendritic conductive fine particles (B) are contained in the conductive layer in a range of 50% by weight or more and 90% by weight or less.

The electronic component of the present invention is adhered to the conductive sheet of the above aspect.

The method for producing a conductive sheet of the present invention includes the step of: conducting a conductive resin containing dendritic conductive fine particles (B) having an average particle diameter D ₅₀ of 3 μm or more and 50 μm or less and a thermosetting resin (A). The composition is applied to the release sheet, and a conductive layer containing the dendritic conductive fine particles (B) in a range of 50% by weight or more and 90% by weight or less is formed, and 2.5 MPa or more and 50 MPa or less are applied to the conductive layer. pressure.

According to the present invention, by using the dendritic conductive fine particles, a conductive layer containing a large number of voids is formed before the heat pressing, and thus, for example, the heat which flows when the conductive sheet is heated and pressed onto the printed wiring board can be absorbed by the void. Curable resin, etc. Thereby, the bleeding of the conductive layer can be prevented, and the workability can be improved. As a result, in the electronic component such as a printed wiring board using the conductive sheet, the defective product due to bleeding is greatly reduced, and the yield is good. Further, it is possible to greatly reduce short circuits or ionic migration of circuits of electronic components such as printed wiring boards.

According to the present invention, there is an effect that conductivity can be provided The sheet is attached to a conductive pressing step of a adherend such as a printed wiring board, and the conductive sheet can be reduced to a minimum of excellent workability, a conductive sheet, a method for producing the same, and an electronic component.

Hereinafter, embodiments of the present invention will be described in detail. Further, other embodiments may fall within the scope of the present invention as long as they conform to the gist of the present invention. Further, the following embodiments can be combined as appropriate with each other. In the present specification, the description of the "arbitrary number A to the arbitrary number B" indicates a range in which the number A and the ratio A are large, and the number B and the number B are smaller.

The conductive sheet of the present invention has at least a conductive layer. The conductive sheet may include a conductive layer of one layer, or a plurality of conductive layers may be laminated, and a layer other than the conductive layer (for example, a support layer, an insulating layer, a protective layer, an adhesive layer) may be laminated. Further, the conductive sheet referred to in the present specification does not necessarily have to have conductive characteristics as a whole, and at least the conductive layer may have conductive characteristics. The conductive property of the conductive layer can be appropriately set depending on the use or demand, and is not particularly limited.

[First Embodiment]

In the first embodiment, an example of a conductive layer including one layer as an embodiment of the conductive sheet will be described. The conductive layer of the conductive sheet of the first embodiment contains the thermosetting resin (A) and the dendritic conductive fine particles (B) as essential structures. The thickness of the conductive layer is as follows: under the conditions of 150 ° C, 2 MPa, 30 minutes, and in the case where the pressing with the adherend is performed, the thickness of the conductive layer before the heat pressing is set to 100, and the heating is pressed. The thickness after the thickness is in the range of 30 or more and 95 or less. In addition, The "conductive layer before heating and pressing" refers to a conductive layer that is to be attached to a surface of a member such as a printed wiring board. In addition, the adherend means the entire object to which the conductive sheet is attached, and examples thereof include a printed wiring board and a flexible board.

The thickness of the conductive layer after heat pressing under the above-described conditions of the conductive layer of the conductive sheet is more preferably 40 or more, still more preferably 45 or more. Further, the thickness of the conductive layer after the heat pressing is more preferably 90 or less, further preferably 85 or less. Especially good for the range of 60~80. In the case where the thickness after the heat pressing is more than 95, it is conceivable that the number of voids in the conductive layer before the heat pressing is small, so that the thickness variation is small before and after the heating pressing, and the thermosetting resin (A) which is horizontally oriented during the heating pressing is used. The oozing is increased. On the other hand, in the case where the thickness after the heat pressing is less than 30, it is assumed that there are too many voids in the conductive layer, and therefore there is a tendency that the thickness variation before and after the heating press is large, and voids remain by heating and pressing, and it is difficult to achieve desired conductivity. Sex. In addition, "exudation" as referred to in the specification includes exudation of a low molecular weight component and exposure of a flow of a conductive layer.

The conductive sheet of the first embodiment is heated and pressed under the conditions of a temperature of 150 ° C, a time of 30 minutes, and a pressure of 2 MPa, whereby the voids formed by the dendritic conductive fine particles (B) can be filled in the conductive layer. In addition, the conditions when the conductive sheet of the first embodiment is attached to a adherend such as a printed wiring board are described below under the above-described heating and pressing conditions, but different heating and pressing steps may be employed to conduct the conductive material. The sheet is attached to a adherend such as a printed wiring board. For example, heating conditions, pressing conditions, and the like can be adjusted depending on the type of the thermosetting resin to be used.

The conductive sheet according to the first embodiment is the conductivity of the first embodiment. The conductive layer side of the sheet is laminated so as to be in contact with the adherend such as a printed wiring board, and is subjected to the above-described heat pressing step, whereby the conductive sheet can be attached to the adherend. According to the conductive sheet of the first embodiment, since the thermosetting resin is contained, the adhesion to the adherend can be favorably maintained. Further, an example in which a conductive layer is bonded to an adherend has been described, and depending on the use or demand, an additional adhesive layer different from the conductive layer may be provided on the conductive sheet, and the adhesive layer may be The state of adhesion of the body.

The thermosetting resin (A) used in the first embodiment is not particularly limited as long as it does not deviate from the gist of the present invention, but is preferably an acrylic, phenol, epoxy or urethane system. A resin such as urethane, melamine or alkyd. Further, when it is used by being bonded and adhered by a heating and pressing step as in a flexible printed wiring board, it is more preferably an acrylic resin or a urethane resin having heat resistance and flexibility. . In addition, one type of the thermosetting resin (A) may be used, or two or more types may be used in combination.

Among the conductive layers, it is preferred to use a curing agent in combination with the thermosetting resin (A). As the hardener, a known compound corresponding to the functional group of the resin to be used can be used. For example, when the resin contains a carboxyl group, an epoxy hardener, an aziridine hardener or the like is preferable. Further, when the resin contains a hydroxyl group, an isocyanate curing agent or an acid anhydride group-containing compound or the like is preferable.

FIG. 1A shows a scanning electron microscope (SEM) image of an example of the dendritic conductive fine particles (B) suitable for the conductive layer of the first embodiment. Dendritic Words refer to dendrites, such as the shape of branches of trees. The material of the dendritic conductive fine particles (B) may, for example, be a conductive metal such as gold, silver, copper, nickel, zinc or iron or an alloy thereof, polyaniline, polythiophene or polyacetylene. A conductive organic compound or the like, or a conductive compound obtained by combining these. Alternatively, conductive fine particles having a metal or an organic compound or an inorganic compound as a core and having a surface coated with a conductive material may be cited as a preferred example.

Among the conductive fine particles of the conductive coating layer, particles having a coating layer formed on the surface of the core of the core are exemplified as preferred examples. The core may be a metal such as copper, nickel or cadmium or an alloy thereof, a conductive organic compound such as polyaniline, polythiophene or polyacetylene, or a general non-conductive organic compound. Further, examples of the coating layer include metals having excellent conductivity such as gold, silver, and copper. Further, conductive fine particles having copper as a core and a coating layer formed of silver are exemplified as a more preferable example. Further, the dendritic conductive fine particles (B) may be used singly or in combination of a plurality of types.

The proportion of the coating layer in the conductive fine particles of the conductive coating layer is preferably from 1% by weight to 40% by weight, and more preferably 5% by weight, based on 100% by weight of the dendritic conductive fine particles (B). 20% by weight. By using the conductive fine particles to be coated, it is possible to reduce the cost due to the reduction in the amount of expensive silver used, or to suppress the decrease in conductivity due to oxidation of copper in the case where conductive fine particles of copper are used.

The thickness of the conductive sheet changes before and after the heating and pressing, and it is presumed that the void is easily formed in the conductive layer due to the presence of the bulky dendritic conductive fine particles (B), and the thermosetting resin (A) flows by heat pressing. Thereby causing the void to be filled. The voids of the dendritic conductive fine particles (B) are more susceptible to the relationship between the average particle diameter D ₅₀ and the average particle diameter D ₉₀ of the dendritic conductive fine particles (B) to be used. Moreover, the more the voids in the conductive layer before the heat pressing, the greater the thickness variation. That is, it is considered that when the thickness before the heat pressing is set to 100, the smaller the value of the thickness after the heat pressing, the larger the number of voids in the conductive layer.

The average particle diameter D _{50 of the} dendritic conductive fine particles (B) is preferably from 3 μm to 50 μm, and the average particle diameter D _{90 is} preferably from 1.5 to 5 times the average particle diameter D ₅₀ . Further, the average particle diameter D _{50 is more} preferably from 3 μm to 40 μm, still more preferably from 5 μm to 25 μm. The average particle diameter D ₅₀ is 3 μm or more, whereby voids are easily generated in the conductive layer, and bleeding can be reduced. On the other hand, the average particle diameter D ₅₀ is 50 μm or less, whereby it is easy to form a conductive layer having an appropriate thickness.

The average particle diameter D _{90 of the} dendritic conductive fine particles (B) is preferably 1.5 to 5 times, more preferably 2 to 3.5 times the average particle diameter D ₅₀ . The value of the average particle diameter D ₉₀ tends to depend on the average particle diameter of the average particle diameter D ₅₀ , and is preferably from 4.5 μm to 250 μm. Since the average particle diameter D ₉₀ is 1.5 times or more of the average particle diameter D ₅₀ , the range of the particle diameter distribution is broadened, and thus the conductive layer tends to be likely to generate voids. On the other hand, the average particle diameter D ₉₀ is not _more than 5 times the average particle diameter D ₅₀ , whereby the range of the particle diameter distribution is not excessively wide, and the filling of the dendritic conductive fine particles (B) in the conductive layer is provided. The tendency to become appropriate. Further, due to the presence of the large dendritic particles, the phenomenon that the large dendritic particles protrude from the conductive layer after the heat pressing is less likely to occur.

The dendritic conductive fine particles (B) preferably have a tap density (hereinafter referred to as "TD") of 0.8 g/cm ³ to 2.5 g/cm ³ . By the TD being 0.8 g/cm ³ or more, the filling of the conductive fine particles in the conductive layer can be made closer. On the other hand, when TD is 2.5 g/cm ³ or less, there is a tendency that the filling of the conductive fine particles in the conductive layer is less likely to be excessively dense, and the film thickness change before and after the heating press can be maintained large, and thus further Reduce oozing.

Further, the dendritic conductive fine particles (B) preferably have an apparent density (hereinafter referred to as "AD") of 0.4 g/cm ³ to 1.5 g/cm ³ . When AD is 0.4 g/cm ³ or more, the filling of the conductive fine particles in the conductive layer can be made closer. On the other hand, when TD is 1.5 g/cm ³ or less, the filling of the conductive fine particles in the conductive layer is less likely to become too dense, and the change in film thickness before and after the heating press can be maintained, so that the film thickness can be further reduced. Exudation.

By setting the values of the apparent density AD and the knock tightness TD of the dendritic conductive fine particles (B) to appropriate values, it is possible to form voids more appropriately in the conductive layer. That is, the ratio of AD to TD (AD/TD) of the dendritic conductive fine particles (B) is more preferably from 0.3 to 0.9. By setting AD/TD to 0.3 or more, the values of AD and TD are more appropriate, and the film thickness change after heat pressing does not tend to become excessive. On the other hand, by setting AD/TD to 0.9 or less, the values of AD and TD are more appropriate, and the film thickness change after heat pressing tends not to be too small.

The ratio of dendritic conductive fine particles (B) used in the conductive layer is The conductive layer is preferably 50% by weight to 90% by weight, more preferably 60% by weight to 80% by weight, based on 100% by weight of the conductive layer. The use amount is preferably 50% by weight or more, and tends to easily obtain desired conductivity. On the other hand, since the amount used is 90% by weight or less, there is a tendency to easily secure the amount of resin used for sheeting.

When the dendritic conductive fine particles (B) are compared with the spherical conductive fine particles or the flake conductive fine particles (see FIG. 1B), since a shape like a branch is formed, it is easy to form a gap between the respective particles. . Therefore, when the conductive layer is formed using the dendritic conductive fine particles (B), voids are likely to occur. By using the dendritic conductive fine particles (B), it is possible to further reduce the amount of the conductive sheet using the spherical conductive particles or the sheet-like conductive fine particles as a main component under the same conditions. Exudation in the transverse direction.

In addition to the thermosetting resin (A) and the dendritic conductive fine particles (B) in the conductive layer, other additives may be added without departing from the gist of the invention. For example, a decane coupling agent, an antioxidant, a pigment, a dye, a tackifying resin, a plasticizer, a UV absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, and the like may be contained.

Next, a method of producing the conductive sheet of the first embodiment will be described. First, the conductive resin composition (C) is blended by mixing at least the thermosetting resin (A) and the dendritic conductive fine particles (B). The mixing method is not particularly limited, and a preferred example thereof includes a mixer, a dissolver, a hoover muller, a 3-roll mill, a sand mill, and the like. Methods.

The conductive resin composition (C) is applied, for example, to a release sheet to form a coating film of a conductive layer. The coating method is not particularly limited, and a conventionally known method can be used without limitation. For example, it may be a gravure coating method, a kiss coating method, a die coating method, a lip coating method, a comma coating method, or the like. Blade coating method, roll coating method, knife coating method, spray coating method, bar coating method, spin coating method, dip coating ( A coating film is formed by a dip coating method or the like.

The thickness of the conductive layer before the heat pressing can be appropriately set depending on the application, but is preferably 5 μm to 100 μm. Further, the thickness is a value measured in accordance with JIS B7503 (dial gauge).

The film thickness after the heat pressing of the conductive sheet of the first embodiment is preferably 0.25 to 10 times, more preferably 0.5 to 5 times the average particle diameter D ₅₀ of the dendritic conductive fine particles (B).

The use of the conductive sheet of the first embodiment is not particularly limited, and can be used in all applications in which a conductive sheet is to be attached. For example, it is used for the purpose of shielding electromagnetic waves from being attached to a printed wiring board, or used to obtain grounding of a circuit formed on a printed wiring board. In addition, it can be attached to various electronic devices such as home appliances such as microwave ovens.

According to the conductive sheet of the first embodiment, as long as the three-layer structure is not provided and only one layer is provided, the adhesion to the adherend can be exhibited by using the thermosetting resin. As a result, it can also be used for thin Excellent advantages of membrane use. In addition, since a metal foil such as Patent Document 1 is not used, and a conductive layer containing a thermosetting resin and dendritic conductive fine particles as essential constituent components is used, flexibility is excellent. Therefore, it can be suitably applied to a flexible printed wiring board or the like. In addition, dendritic conductive fine particles are used as the conductive fine particles, whereby voids or the like can be formed in the conductive layer, and voids can be absorbed by the voids during heat pressing. As a result, the bleed out of the conductive layer can be minimized. Further, even in a resin having low heat resistance which is difficult to use in a high-temperature environment, by using dendritic conductive fine particles, bleeding of the conductive layer can be effectively suppressed. The conductive sheet according to the present invention can be preferably used as a use under severe conditions such as high temperature and high humidity.

[Second Embodiment]

Next, an example of a conductive sheet different from the above-described first embodiment will be described. The conductive sheet of the second embodiment is an electrically conductive sheet having an insulating layer and an insulating layer in which the insulating layer of the first embodiment is laminated.

The insulating layer used in the conductive sheet of the second embodiment is not particularly limited as long as it does not deviate from the gist of the invention. The material of the insulating layer is not particularly limited, and for example, an insulating resin such as a thermosetting resin (A) which can be used in the conductive layer is preferably used. Further, a plastic film such as polyester, polycarbonate, polyimide or polyphenylene sulfide can also be used.

Further, the insulating layer may optionally contain a decane coupling agent, an antioxidant, a pigment, a dye, a tackifying resin, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling adjuster, a filler, a flame retardant, and the like.

The use of the conductive sheet of the second embodiment is not particularly limited, and for example, The conductive layer side can be attached to the outer main surface of the printed wiring board to serve as an electromagnetic wave shielding film.

The method for forming the insulating layer of the conductive sheet of the second embodiment and the method for laminating the conductive layer and the insulating layer can be carried out without any limitation. For example, a conductive layer may be formed on a previously formed insulating layer, or may be formed on the insulating layer by the same manufacturing method as the conductive layer described in the first embodiment. The thickness of the insulating layer may vary depending on the application, and is, for example, preferably 5 μm to 50 μm.

According to the second embodiment, since the conductive layer is the same as that of the first embodiment, the same effects as those of the first embodiment can be obtained. Further, by forming a laminate with the insulating layer, the mechanical strength of the conductive sheet can be improved, or the surface can be provided with insulating properties.

In the second embodiment, an example of a conductive sheet in which an insulating layer and a conductive layer are laminated is described. However, the layer to be laminated with the conductive layer is not particularly limited, and a layer having various functions can be laminated depending on the purpose. . For example, it may be a conductive sheet in which an optical film such as a support layer, a semiconductor layer, a protective film, or an antireflection film is laminated.

[Third embodiment]

Next, an example of a conductive sheet produced by a manufacturing method different from the above-described first embodiment will be described. The method for producing a conductive sheet according to the third embodiment differs from the method for producing a conductive sheet according to the first embodiment in that the pressurization step is included before the hot press described in the first embodiment. Regarding the other points, the configuration of the conductive layer used is the same as in the steps described in the first embodiment.

After the conductive sheet of the third embodiment is applied to form a conductive layer, it is subjected to a pressurization step (hereinafter, in order to heat the adherend and the conductive sheet before heating and pressing when adhering to the adherend). The step of pressing is divided and referred to as "pre-pressurization step"). The pre-pressurization step can be appropriately changed depending on the use, and it is preferred to apply a pressure of 2.5 MPa to 50 MPa ( ²⁵ k g/cm ² to 510 k g/cm ² ). In the pre-pressurization step, heating is not excluded, but the purpose of promoting the flow of the thermosetting resin is not caused by deformation or breakage of the dendritic conductive fine particles (B), so heating is not performed, or It is preferable to set it as heating below the temperature which accelerates the flow of a thermosetting resin.

Before the adherend and the conductive sheet are joined, pressure is applied to the conductive sheet to deform the dendritic conductive fine particles (B), or the dendritic particles are broken, whereby the dendritic conductive fine particles (B) The contact with each other becomes tight, so that the conductive characteristics of the conductive layer can be further improved.

As a method of applying pressure to the conductive sheet, there is a method using a flat press, a roll press, or the like. Among these, a (pressurizing line pressure) roll press which is easy to increase the pressure is preferable. As the roll to be used, a roll having a different surface hardness such as a metal roll or a resin roll can be used. By using the pressed conductive sheet and bonding it to a adherend such as a printed wiring board, it is possible to more effectively suppress the bleeding of the conductive layer.

The conductive layer of the third embodiment is a conductive layer that is subjected to a pre-pressurization step. However, when the adherend is bonded to the conductive sheet, it is heated at 150 ° C, 2 MPa, and 30 minutes as described in the first embodiment. The thickness after pressing must be 30 when the thickness of the conductive layer before heat pressing is set to 100. Above and below 95. That is, in the case where the thickness of the conductive layer before bonding with the adherend after the pre-pressurization step is heated and pressed under the above conditions (heat-pressed under conditions of 150 ° C, 2 MPa, and 30 minutes) The thickness change must be included in the above range (the thickness of the conductive layer is set to 100, and is in the range of 30 or more and 95 or less). Further, as long as the above conditions are satisfied, the film thickness may be changed in the pre-pressurization step. This is because, even if the film thickness changes in the pre-pressurization step, there is a gap for moving the thermosetting resin composition or the leaked low-molecular weight component, even if the adherend is bonded to the conductive sheet. When the heating is performed, the bleeding of the conductive layer can be effectively suppressed.

According to the third embodiment, since the conductive sheet having the same conductive layer as that of the first embodiment is used, the same effects as those of the first embodiment can be obtained. Further, the printed wiring board or the like is pressed against the conductive layer before the conductive sheet is heated and pressed, and the dendritic conductive fine particles (B) are crushed, so that the conductive property can be efficiently extracted.

Further, in the third embodiment, an example of a conductive sheet having one conductive layer has been described. However, in the conductive sheet having an insulating layer or a conductive sheet in which another layer is laminated as in the second embodiment, The pre-pressurization step of the third embodiment may be added as appropriate. In the case where the conductive sheet is a conductive sheet with an insulating layer, the period in which the pre-pressurization step is performed is not limited, and it is more preferable to perform a pre-pressurization step before laminating the insulating layer. When the conductive layer is pre-pressurized, the surface of the conductive layer becomes smoother. Therefore, in the case of the laminated insulating layer, the thickness precision of the insulating layer is improved, so that the thickness of the insulating layer can be easily obtained even if the thickness of the insulating layer is reduced. Desired insulation properties.

[Fourth embodiment]

Next, an example of a conductive sheet different from the above-described first embodiment will be described. The conductive sheet of the fourth embodiment includes one conductive layer. The conductive layer of the conductive sheet of the fourth embodiment contains the thermosetting resin (A) and the dendritic conductive fine particles (B) as essential structures, and the dendritic conductive fine particles (B) in the conductive layer The average particle diameter D ₉₀ is in the range of 0.5 to 3 times the film thickness of the conductive layer.

Further, the thickness of the specific conductive layer in the first embodiment is not necessarily the following: the thickness after heat pressing under the conditions of 150 ° C, 2 MPa, and 30 minutes, and the thickness of the conductive layer before the heat pressing is set to 100. It is a range of 30 or more and 95 or less. This is because the average particle diameter D _{90 of the} dendritic conductive fine particles (B) is set to be 3 times or less with respect to the thickness of the conductive layer, and the front end having the fine particles is less likely to protrude from the conductive layer when subjected to heat pressing. Propensity. Further, this is because, by setting the average particle diameter D ₉₀ to 0.5 or more, it is not easy to excessively generate voids in the conductive layer. Among them, from the viewpoint of more effectively preventing the bleeding of the conductive layer, it is more preferable to satisfy the following conditions: the thickness after heating and pressing under the conditions of 150 ° C, 2 MPa, and 30 minutes, the conductive layer before the heat pressing When the thickness is 100, it is in the range of 30 or more and 95 or less.

The conductive sheet of the fourth embodiment is laminated on the conductive layer side of the conductive sheet of the fourth embodiment so as to be in contact with the adherend such as a printed wiring board, and is subjected to the heating and pressing step described in the first embodiment. This attaches the conductive sheet to the adherend. According to the conductive sheet of the fourth embodiment, since the conductive layer contains a thermosetting resin, adhesion to the adherend can be obtained. Keep it good. Further, the conditions of the heat pressing may be arbitrarily set depending on the use or demand of the conductive layer (for example, based on the obtained conductive characteristics or the ratio of the voids, etc.).

In the conductive sheet of the fourth embodiment, the voids of the dendritic conductive fine particles (B) are preferably filled in the conductive layer by heat pressing, but they may be used as voids without being filled. For example, the heat-pressing step may not be performed, and the adherend may be bonded to the conductive sheet via the adhesive layer, for example. The method of passing the adhesive layer is not particularly limited, and for example, an adhesive layer different from the conductive layer may be provided on the conductive sheet, or the adhesive layer may be provided on the adherend side via the adhesive layer. The method of joining the adherends.

The thermosetting resin (A) constituting the conductive layer is preferably as described in the first embodiment. Further, it is preferable to use a curing agent in combination with the thermosetting resin (A) in the conductive layer. Examples of the curing agent are also as described in the first embodiment.

In the preferred embodiment and material of the dendritic conductive fine particles (B), the aspect and material described in the first embodiment can be preferably used.

The dendritic conductive fine particles (B) preferably have an average particle diameter D _{50 of} from 3 μm to 50 μm, and an average particle diameter D ₉₀ of from 1.5 to 5 times the average particle diameter D ₅₀ . Further, the average particle diameter D _{50 is more} preferably from 3 μm to 40 μm, still more preferably from 5 μm to 25 μm. When the average particle diameter D ₅₀ is 3 μm or more, voids are easily generated in the conductive layer, and bleeding can be reduced. On the other hand, when the average particle diameter D ₅₀ is 50 μm or less, it is easy to form a conductive layer having an appropriate thickness.

The average particle diameter D _{90 of the} dendritic conductive fine particles (B) is preferably 1.5 to 5 times, more preferably 2 to 3.5 times the average particle diameter D ₅₀ . The value of the average particle diameter D ₉₀ tends to depend on the average particle diameter of the average particle diameter D ₅₀ , but is preferably 4.5 μm to 250 μm. The reason is as described in the first embodiment.

The knocking degree of the dendritic conductive fine particles (B) (hereinafter also referred to as "TD") is preferably 0.8 g/cm ³ to 2.5 g/cm ³ . Further, the apparent density (hereinafter referred to as "AD") of the dendritic conductive fine particles (B) is preferably 0.4 g/cm ³ to 1.5 g/cm ³ . Further, the ratio of AD to TD (AD/TD) of the dendritic conductive fine particles (B) is more preferably from 0.3 to 0.9. The reason for these is as described in the first embodiment.

The thickness of the conductive sheet of the fourth embodiment is not particularly limited, but is preferably 5 μm to 100 μm, and more preferably 10 μm to 50 μm. Further, the thickness is a value measured in accordance with JIS B7503 (needle gauge). When the thickness of the conductive layer is 5 μm or more, conductivity is easily obtained. Further, when it is 100 μm or less, it is easy to obtain a balance of bendability.

The proportion of the dendritic conductive fine particles (B) used in the conductive layer is preferably from 50% by weight to 90% by weight, more preferably from 60% by weight to 80% by weight, based on 100% by weight of the conductive layer. The reason is as described in the first embodiment. Further, in the conductive layer of the fourth embodiment, an additive may be added as needed, and as an example thereof, the additive described in the first embodiment may be mentioned. Further, the method for producing a conductive sheet is as described in the first embodiment.

According to the fourth embodiment, the same effects as those of the first embodiment described above can be obtained. Moreover, there is an advantage that a highly reliable conductive sheet can be provided by using a conductive layer as follows, and by designing a film thickness and an average particle diameter D _{90 of the} conductive layer, The bleed out of the conductive layer can be minimized. The thickness of the conductive layer in the conductive layer is such that the average particle diameter D ₉₀ of the dendritic conductive fine particles (B) in the conductive layer is in the range of 0.5 to 3 times the film thickness of the conductive layer.

[Fifth Embodiment]

Next, an example of an electromagnetic wave shielding film which is applied to the conductive sheet of the fifth embodiment will be described. The conductive laminated layer of the fifth embodiment has an insulating layer and a conductive layer of the fourth embodiment. As the application, for example, it can be used as an electromagnetic wave shielding film attached to an electronic component such as a printed wiring board. Further, the electromagnetic wave shielding film may be laminated with an insulating layer and other layers (for example, a protective layer or an adhesive layer) other than the conductive layer.

The material used in the insulating layer is not particularly limited, and a preferred embodiment is a material described in the second embodiment. Further, the insulating layer may optionally contain a decane coupling agent, an antioxidant, a pigment, a dye, a tackifying resin, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling adjuster, a filler, a flame retardant, and the like. The method of forming the insulating layer is as described in the second embodiment.

Further, when the thickness of the insulating layer is set to 100, the thickness of the insulating layer is preferably a ratio of 50 to 200. By setting the thickness within the above range, the physical property balance of the electromagnetic wave shielding film can be easily obtained. Further, the conductive layer of the conductive sheet of the fifth embodiment does not have to be subjected to a heating process, and the film thickness of the conductive layer shows the film thickness at the time of actual use, and may be a film thickness before the heating process or a film after the heating process. thick.

The adherend to which the electromagnetic wave shielding film can be attached is not particularly limited, and for example, a flexible printed wiring board subjected to repeated bending is exemplified. Of course, it can be applied to various substrates including rigid printed wiring boards. Home appliances such as microwave ovens that require electromagnetic wave shielding, all electronic devices, and all components that are intended to shield electromagnetic waves.

According to the electromagnetic wave shielding film of the fifth embodiment, the same effects as those of the above embodiment are obtained.

[Example]

Hereinafter, the present invention will be specifically described by way of examples and comparative examples, but the present invention is not limited to the following examples. In addition, the following "parts" and "%" are values based on "parts by weight" and "% by weight", respectively.

The average measured particle diameter and the average particle diameter D ₅₀ D ₉₀ using Microtrac MT3300 manufactured by Nikkiso. The apparent density was determined by the apparent density test method of the metal powder specified by JIS Z 2504:2000. The knocking degree was determined by JIS Z 2512: Metal powder-knocking tightness measuring method.

<Example 1 to Example 5>

As the dendritic conductive fine particles, a conductive sheet was produced using a urethane resin (manufactured by Toyo-Chem Co., Ltd.) as a thermosetting resin. The ratio of the dendritic conductive fine particles (B) to the thermosetting resin (A) was 250 parts by weight with respect to 100 parts by weight of the resin solid content, and the dendritic conductive fine particles (B). Further, the polyethylene terephthalate film having a thickness of 100 μm after being subjected to a release treatment on the surface was applied by a bar coater at a dry film thickness of 10 μm, and dried at 100 ° C for 3 minutes. Thereby, a conductive sheet was obtained.

<Example 6 to Example 10>

A urethane resin (manufactured by Toyo-Chem Co., Ltd.) as an insulating layer was used on one surface of the conductive sheet obtained in Examples 1 to 5 to dry The dried film was coated and dried so as to have a thickness of 10 μm, thereby obtaining a conductive sheet with an insulating layer having a total thickness of 20 μm.

<Example 11>

Pre-pressurization was carried out by applying a pressure of 3 MPa to the surface of the electroconductive sheet obtained in Example 2 using a roll press. Then, a urethane resin (manufactured by Toyo-Chem Co., Ltd.) as an insulating layer was applied and dried on the surface of the pre-pressurized conductive sheet so as to have a dry film thickness of 10 μm. A conductive sheet with an insulating layer and a total thickness of 20 μm.

<Example 12, Example 13>

A conductive sheet with an insulating layer was obtained in the same manner as in Example 11 except that the pressure of the pre-pressurization was changed to 10 MPa and 40 MPa, respectively.

<Comparative Example 1 to Comparative Example 2>

Using the conductive fine particles shown in Table 1B, a conductive sheet was obtained by the same method as in Examples 1 to 5.

<Comparative Example 3 to Comparative Example 4>

Using the conductive fine particles shown in Table 1B, a conductive sheet with an insulating layer was obtained by the same method as in Examples 6 to 10.

<Exudency assessment>

The conductive sheets of the respective examples and the comparative examples were attached to one surface of a polyimine film ("kapton 200EN" manufactured by Du Pont-Toray Co., Ltd.) having a thickness of 50 μm by lamination, and the diameter was made through a perforator. 5mm hole.

Further, a polyimide film having a thickness of 50 μm ("kapton 200EN" manufactured by Du Pont-Toray Co., Ltd.) was prepared, and the above-mentioned conductive sheet was at 150 ° C, A heat pressing treatment was carried out under the conditions of 30 minutes and 2.0 MPa, whereby a sample of the conductive sheet held by the polyimide film was obtained. After the heat pressing treatment, the pore portion of the conductive sheet was observed with a magnifying glass to measure the amount of bleeding. The evaluation criteria are as follows.

○: The amount of exudation of the conductive sheet is less than 0.01 mm

△: The amount of exudation of the conductive sheet is 0.01 mm or more and less than 0.05 mm.

×: The amount of exudation of the conductive sheet is 0.05 mm or more

<Measurement of connection resistance value A>

For the conductive sheets of Examples 1 to 5 and Comparative Examples 1 and 2, samples having a width of 20 mm and a length of 50 mm were prepared, and the connection resistance value A was measured using a separately manufactured flexible printed wiring board. Specifically, as shown in FIG. 2A to FIG. 2F, a flexible printed wiring board having a copper foil having a thickness of 18 μm and a non-electrical connection was formed on the polyimide film 1 having a thickness of 12.5 μm. In the circuit 2, on the circuit 2, a cover film 3 having a through hole 4 having a thickness of 37.5 μm and a diameter of 0.8 mm with an adhesive is laminated. Then, the conductive sheet 5 was placed on the cover film 3, and a stainless steel plate 6 having a thickness of 200 μm which had been treated with nickel having a thickness of 0.1 μm was placed on the conductive sheet 5, and the conditions were 150 ° C, 30 minutes, and 2.0 MPa. The heat is pressed under. Thereafter, the resistance value in the longitudinal direction between the circuit 2 and the stainless steel plate 6 was measured using a four-point probe of "Losta GP" manufactured by Mitsubishi Chemical Corporation. The evaluation criteria are as follows.

○: less than 200mΩ

△: 200mΩ or more and less than 500mΩ

×: 500mΩ or more

<Measurement of connection resistance value B>

For the conductive sheets with insulating layers of Examples 6 to 13 and Comparative Examples 3 and 4, samples having a width of 20 mm and a length of 50 mm were prepared, and the connection electrical limit B was measured using a separately produced flexible printed wiring board. Specifically, as shown in FIG. 3A to FIG. 3F, a flexible printed wiring board having a copper foil having a thickness of 18 μm and a non-electrical connection was formed on the polyimide film 1 having a thickness of 12.5 μm. In the circuit 2A and the circuit 2B, a cover film 3 having a via hole 4 having a thickness of 37.5 μm and a diameter of 0.8 mm with an adhesive is laminated on the circuit 2A. Then, the conductive sheet 5 is placed on the cover film 3, and an insulating layer 7 having a thickness of 200 μm which has been treated with nickel having a thickness of 0.1 μm is placed on the conductive sheet 5 at 150 ° C, 30 minutes, and 2.0 MPa. The heating was pressed under the conditions, and the resistance between the circuit 2A and the circuit 2B was measured using a four-point probe manufactured by Mitsubishi Chemical Corporation "loresta GP". The evaluation criteria are as follows.

○: less than 300mΩ

△: 300 mΩ or more and less than 500 mΩ

×: 500mΩ or more

<bending>

The conductive sheet having a width of 6 mm and a length of 120 mm and a comparative example were pressure-bonded to a separately prepared flexible printed wiring board under conditions of 150 ° C, 30 minutes, and 2.0 MPa (polyimine at a thickness of 25 μm) On the film, a circuit pattern including a copper foil having a thickness of 12 μm was formed, and a cover film surface on which a cover film having a thickness of 40 μm with an adhesive was laminated on the circuit pattern was formed. Then, at a radius of curvature of 0.38 mm, the load The bending resistance was evaluated on the MIT bending tester under conditions of 500 g and a speed of 180 times/min, and the number of times the circuit pattern was broken. The evaluation criteria are as follows.

○: 3,000 times or more

△: 2500 times or more and less than 3000 times

×: less than 2500 times

As is clear from the results of Tables 1A and 1B, by using the dendritic conductive fine particles, the amount of bleeding in the lateral direction after the heat pressing is smaller than that of the conductive fine particles having the previous shape. Further, it is understood that the connection resistance A in the longitudinal direction is superior in characteristics to the conductive fine particles of the prior shape by using the dendritic conductive fine particles. Further, it was confirmed that the conductive sheet using the dendritic conductive fine particles is excellent in flexibility.

<Example 14>

A conductive layer was produced by using silver having an average particle diameter D ₉₀ of 25 μm and an average particle diameter D ₅₀ of 13 μm as dendritic conductive fine particles. A urethane resin (manufactured by Toyo-Chem Co., Ltd.) is used as the thermosetting resin, and the ratio of the dendritic conductive fine particles (B) to the thermosetting resin is dendritic conductivity with respect to 100 parts by weight of the resin. The microparticles were used in an amount of 250 parts by weight, and were coated on a polyethylene terephthalate film having a thickness of 100 μm on a surface having a thickness of 100 μm by a bar coater at 100 ° C. Drying was carried out for 3 minutes to obtain a conductive layer. A urethane resin (manufactured by Toyo-Chem Co., Ltd.) as an insulating layer was used for one surface of the above-mentioned conductive layer, and dried and coated to have a dry film thickness of 15 μm to obtain an insulating layer having a total thickness of 25 μm. Electromagnetic wave shielding film.

<Example 15~Example 17>

In Examples 15 to 17, except that the conductive fine particles, the portion having the average particle diameter D ₉₀ and the average particle diameter D ₅₀ were replaced with the raw materials shown in Table 2A, the same procedure as in Example 1 was carried out to obtain an electromagnetic wave shielding film. .

<Example 18>

As the dendritic conductive fine particles (B), a material of Table 2A was used, and as the thermosetting resin (A), a conductive layer was produced using a urethane resin (manufactured by Toyo-Chem Co., Ltd.). The ratio of the dendritic conductive fine particles (B) to the thermosetting resin (A) is 250 parts by weight of the dendritic conductive fine particles with respect to 100 parts by weight of the resin, and the dry film thickness is 10 μm. The surface having a thickness of 100 μm was subjected to a release-treated polyethylene terephthalate film, coated with a bar coater, and dried at 100 ° C for 3 minutes to obtain a conductive sheet. On the one surface of the above-mentioned conductive sheet, a urethane resin (manufactured by Toyo-Chem Co., Ltd.) as an insulating layer was used, and dried and coated to have a dry film thickness of 8 μm to obtain an insulating layer having a total thickness of 18 μm. Electromagnetic wave shielding film.

<Example 19>

A conductive sheet was produced using the material of Table 2A as dendritic conductive fine particles. Using a urethane resin (manufactured by Toyo-Chem Co., Ltd.) The thermosetting resin, and the ratio of the dendritic conductive fine particles (B) to the thermosetting resin is 250 parts by weight with respect to 100 parts by weight of the resin, and the dried film thickness is 10 μm. In the manner of coating on a polyethylene terephthalate film having a surface of 100 μm in thickness, which was subjected to a release treatment using a bar coater, it was dried at 100 ° C for 3 minutes to obtain a conductive sheet. A urethane resin (manufactured by Toyo-Chem Co., Ltd.) as an insulating layer was used as one surface of the above-mentioned conductive sheet, and a dry film thickness of 25 μm was used to obtain an electromagnetic wave shielding film having an insulating layer having a total thickness of 35 μm. .

<Example 20>

Pre-pressurization was carried out by applying a pressure of 3 MPa to the surface of the electroconductive sheet obtained in Example 18 using a roll press. Then, on the surface of the pre-pressurized conductive sheet, a urethane resin (manufactured by Toyo-Chem Co., Ltd.) as an insulating layer was applied and dried to have a dry film thickness of 8 μm, thereby obtaining An electromagnetic wave shielding film having an insulating layer with a total thickness of 20 μm.

<Example 21, Example 22>

An electromagnetic wave shielding film having an insulating layer was obtained in the same manner as in Example 20 except that the pressure of the pre-pressing was changed to 10 MPa and 40 MPa, respectively.

<Comparative Example 11 to Comparative Example 15>

Using the conductive fine particles shown in Table 2B, an electromagnetic wave shielding film having a conductive layer and an insulating layer was obtained by the same method as in Example 14 to Example 18.

Regarding the dendritic silver, dendritic copper powder, flaky silver of Table 2A and Table 2B, The spherical silver is dendritic silver, dendritic copper powder, flaky silver, and spherical silver manufactured by Fukuda Metal Foil Powder Industrial Co., Ltd.

The dendritic silver-coated copper powder of Table 2A and Table 2B is a dendritic copper powder manufactured by Fukuda Metal Foil Powder Co., Ltd., and subjected to silver coating treatment under the following conditions, thereby obtaining 90% by weight of silver core and silver. The coating layer was 10% by weight of dendritic silver-coated copper powder.

<Exudency assessment>

In each of the examples and the comparative examples, the electromagnetic wave shielding film was measured for the amount of bleeding by the same methods as those of Examples 1 to 13 and Comparative Examples 1 to 4. The evaluation criteria are the same as the above benchmarks.

<bending>

The electromagnetic wave shielding film having a width of 6 mm and a length of 120 mm and a comparative example were evaluated by the same method as the refractive index evaluations described in Examples 1 to 13 and Comparative Examples 1 to 4. The evaluation criteria are the same as the above benchmarks. And it is shown below.

<Insulation reliability>

The electromagnetic wave shielding films of Examples 14 to 22 and Comparative Examples 11 to 15 having a width of 100 mm and a length of 100 mm were prepared and subjected to heat pressing treatment under conditions of 150 ° C, 30 minutes, and 2.0 MPa. The insulation reliability of the TYPE URS using a surface resistance tester of Hiresta-UP (MCP-HT450) manufactured by Mitsubishi Chemical Corporation under the condition of a voltage of 100 V for 1 minute after contact with the insulating layer was evaluated. The evaluation criteria are as follows.

◎: 1 × 10 ⁷ Ω / □ or more

○: less than 1 × 10 ⁷ Ω / □ and 1 × 10 ⁴ Ω / □ or more

×: less than 1 × 10 ⁴ Ω / □

According to the results of Table 2A and Table 2B, it is understood that the average particle diameter D ₉₀ of the dendritic conductive fine particles is specified to be in the range of 0.5 times to 3 times with respect to the film thickness of the conductive layer, and is more conductive than the previous shape. The fine particles have less bleed out of the conductive layer in the transverse direction after the heat pressing. Moreover, it was confirmed that excellent bending property was exhibited and high insulation reliability was also achieved.

The following supplementary notes are further disclosed in the embodiment including the above examples.

(Note 1)

A conductive sheet comprising a conductive layer containing at least a thermosetting resin (A) and dendritic conductive fine particles (B), characterized by heating and pressing at 150 ° C, 2 MPa, 30 minutes The thickness of the conductive sheet is 30 to 95 when the thickness before the heat pressing is 100.

(Note 2)

An electromagnetic wave shielding film comprising at least an insulating layer and a conductive layer, wherein the conductive layer contains at least a thermosetting resin (A) and dendritic conductive fine particles (B), and dendritic conductive fine particles (B) The average particle size The film thickness of D90 with respect to the conductive layer is in the range of 0.5 to 3 times.

(Note 3)

The electromagnetic wave shielding film according to the second aspect, wherein the dendritic conductive fine particles (B) have an average particle diameter D50 of from 3 μm to 50 μm.

(Note 4)

The electromagnetic wave shielding film according to the above 2 or 3, wherein the dendritic conductive fine particles (B) comprise a core containing copper and a silver coating layer; and the silver coating layer is 100% by weight of the dendritic conductive fine particles (B) The ratio is from 1% by weight to 40% by weight.

(Note 5)

The electromagnetic wave shielding film according to any one of the items 2 to 4, wherein, when the thickness of the conductive layer is set to 100, the thickness of the insulating layer is 50 to 200.

The priority of the Japanese Patent Application No. 2011-121188 filed on May 31, 2011, and the Japanese Patent Application No. 2011-233528, filed on Oct. 25, 2011, the entire disclosure of which is incorporated by reference. herein.

[Industrial availability]

The conductive sheet of the present invention can minimize the bleeding of the conductive layer in a process such as a heating process, and thus can be preferably applied to a substrate such as a printed wiring board or a flexible printed board. The use of the entire body for use. In particular, it is particularly effective in attaching an electronic component to which the bleeding of the conductive sheet is a problem. The conductive sheet of the present invention may be used by laminating an insulating layer, a support layer, an adhesive layer, or a film having other functions.

1‧‧‧ Polyimine film

2‧‧‧copper circuit

2A, 2B‧‧‧ circuits

3‧‧‧ Cover film

4‧‧‧through hole

5‧‧‧Electrical film

6‧‧‧Stainless steel

7‧‧‧Insulation

Fig. 1A is an SEM image showing an example of dendritic conductive fine particles.

FIG. 1B is an SEM image showing an example of the sheet-like conductive fine particles.

2A is an explanatory view of a circuit for measuring a connection resistance value A, and is a schematic plan view of a flexible printed wiring board in which a cover film is laminated.

Fig. 2B is a cross-sectional view of the cut portion of IIB-IIB of Fig. 2A.

Fig. 2C is a cross-sectional view of the IIC-IIC cutting portion of Fig. 2A.

2D is an explanatory view of a circuit for measuring the connection resistance value A, and is a schematic plan view of a flexible printed wiring board in which a conductive sheet is superposed on a stainless steel plate and heated and pressed.

Fig. 2E is a cross-sectional view of the cut portion of the IIE-IIE of Fig. 2D.

Fig. 2F is a cross-sectional view of the IIF-IIF cut portion of Fig. 2D.

3A is an explanatory view of a circuit for measuring a connection resistance value B, and is a schematic plan view of a flexible printed wiring board in which a cover film is laminated.

Fig. 3B is a cross-sectional view of the cut portion of IIIB-IIIB of Fig. 3A.

Fig. 3C is a cross-sectional view of the cut portion of IIIC-IIIC of Fig. 3A.

3D is an explanatory view of a circuit for measuring the connection resistance value B, and is a schematic plan view in which a conductive sheet is superposed on a stainless steel plate and heated and pressed.

Fig. 3E is a cross-sectional view of the cut portion of IIIE-IIIE of Fig. 3D.

Fig. 3F is a cross-sectional view of the IIIF-IIIF cut portion of Fig. 3D.

1‧‧‧ Polyimine film

2‧‧‧copper circuit

3‧‧‧ Cover film

4‧‧‧through hole

Claims (12)

A conductive sheet for heating and pressing a conductive sheet, comprising a conductive layer having a void, the conductive layer comprising at least: a thermosetting resin (A); and dendritic conductive fine particles (B); The thickness of the conductive layer satisfies at least one of the following (i) and (ii): (i) the conductive layer before being heated and pressed under the condition of 150 ° C, 2 MPa, and 30 minutes under heating with the adherend When the thickness is 100, the range is 30 or more and 95 or less; and (ii) the average particle diameter D ₉₀ of the dendritic conductive fine particles (B) is 0.5 times or more the thickness of the conductive layer before the heating and pressing. In the range of 3 times or less, the dendritic conductive fine particles (B) have an average particle diameter D ₅₀ of 3 μm or more and 50 μm or less, and the conductive layer contains 50% by weight or more and 90% by weight or less of the conductive layer. The dendritic conductive fine particles (B). The conductive sheet according to claim 1, wherein the dendritic conductive fine particles (B) have an average particle diameter D ₉₀ of 1.5 times or more and 5 times or less of the average particle diameter D ₅₀ . The scope of the patent application to item 1 or 2 of the conductive sheet, wherein said dendritic conductive fine particles (B) is ³ or more knock tightness of 0.8g / cm, 2.5g / cm ³ or less. The conductive sheet according to the first or second aspect of the invention, wherein the dendritic conductive fine particles (B) have an apparent density of 0.4 g/cm ³ or more and 1.5 g/cm ³ or less. The conductive sheet according to Item 1 or 2, wherein the ratio of the apparent density AD to the knock-tightness TD of the dendritic conductive fine particles (B) is AD/TD = 0.3 to 0.9. The conductive sheet according to claim 1 or 2, wherein the core of the dendritic conductive fine particles (B) is copper, and the surface thereof has a silver coating layer; and the silver coating layer is dendritic conductive The proportion of 100% by weight of the fine particles (B) is 1% by weight or more and 40% by weight or less. The conductive sheet according to claim 1 or 2, wherein an insulating layer is laminated on the conductive layer. The conductive sheet according to claim 7, wherein the insulating layer has a thickness of 50 to 200 when the thickness of the conductive layer is 100. The conductive sheet according to the first or second aspect of the invention, wherein the film thickness after the heat pressing is 0.25 to 10 times the average particle diameter D ₅₀ of the dendritic conductive fine particles (B). The conductive sheet according to claim 1 or 2, wherein the conductive layer is attached to a polyimide film having a thickness of 50 μm by lamination, and the diameter is made through a hole puncher. After a 5 mm hole, another 50 μm thick polyimide film was prepared and placed in a manner of sandwiching the above conductive layer using two sheets of the above polyimide film at 150 ° C, 30 minutes, and 2.0 MPa. When the heat pressing treatment is performed under the conditions, the amount of bleeding of the above conductive layer is less than 0.05 mm. An electronic component having an adherend and a conductive sheet according to any one of claims 1 to 10, wherein the conductive sheet is attached to the adherend by heat pressing. The electronic component according to claim 11, wherein the adherend is a printed wiring board, and the conductive sheet is used as an electromagnetic wave shielding film.