JP2017203165A - Connection film, production method of connection film, connection structure, production method of connection structure and connection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure connection reliability while ensuring sufficient connection strength, even when a frame part to connect a flexible substrate in an anisotropic conductive manner is made narrow.SOLUTION: In a connection film which has an adhesive layer 15 with fillers 16 dispersed therein and which connects connection objects to each other by being pressed, the adhesive layer is provided with difference in flowability in the thickness direction, and the flowability is designed such that volume density distribution of the filler 16 satisfies a condition of c>a>b when filler density in an outer periphery 21c of a pressed region 21 is denoted by (c), filler density in a central portion 21a of the pressed region 21 is denoted by (a), and filler density in an inner periphery 21b of the pressed region 21 is denoted by (b).SELECTED DRAWING: Figure 3

Description

  The present invention includes a connection film in which a plurality of connection terminals are sandwiched between parallel connection objects and connected to each other by crimping, and a connection structure connected using the connection film, and this It relates to a manufacturing method.

  Conventionally, a binder resin in which conductive particles are dispersed as an adhesive when connecting a rigid substrate such as a glass substrate or a glass epoxy substrate and an electronic component such as a flexible substrate or an IC chip, or connecting flexible substrates together. An anisotropic conductive film obtained by forming a film into a film is used. The case where the connection terminal of the flexible substrate and the connection terminal of the rigid substrate are connected will be described as an example. As shown in FIG. 12A, both connection terminals 52 and 55 of the flexible substrate 51 and the rigid substrate 54 are formed. An anisotropic conductive film 53 is disposed between the regions, a buffer material 50 is disposed as appropriate, and heat pressing is performed from above the flexible substrate 51 by the heating and pressing head 56. Then, as shown in FIG. 12B, the binder resin exhibits fluidity and flows out between the connection terminal 52 of the flexible substrate 51 and the connection terminal 55 of the rigid substrate 54, and in the anisotropic conductive film 53. The conductive particles are sandwiched between the connecting terminals and crushed.

  As a result, the connection terminal 52 of the flexible substrate 51 and the connection terminal 55 of the rigid substrate 54 are electrically connected via the conductive particles, and the binder resin is cured in this state. The conductive particles that are not between the connection terminals 52 and 55 are dispersed in the binder resin and maintain an electrically insulated state. As a result, electrical continuity is achieved only between the connection terminal 52 of the flexible substrate 51 and the connection terminal 55 of the rigid substrate 54.

JP 2005-26577 A

  In recent years, for example, in connection between a sensor film of a touch panel and a flexible substrate, with the increase in size of a liquid crystal screen with respect to an outer casing of an electronic device, the so-called frame portion that is the outer edge portion of the screen is narrowed. And when the width of the anisotropic conductive film is the same as before, when the connection area is narrowed, there arises a problem that the temporary adhesion accuracy of the anisotropic conductive film and the alignment accuracy of the connection parts are deteriorated. Therefore, the anisotropic electric film is also becoming narrower according to the narrowing of the frame of the sticking area.

  Here, the anisotropic conductive film is required to stably obtain connection reliability and conduction reliability even in a state where the narrowing has progressed.

  Accordingly, the present invention provides a connection film capable of ensuring connection reliability while securing sufficient connection strength even in a narrowed crimping space, and a connection structure using the connection film and manufacturing of the connection structure The object is to provide a method and a connection method.

  The present inventor obtained the knowledge that the density distribution of the filler after crimping the connecting film contributes to the adhesive strength and the conduction reliability, and the fluidity of the resin occupying the approximate density of the film in the density distribution of the filler. It has been found that the adhesive strength and conduction reliability can be improved by adjusting.

  That is, the connection film according to the present invention has an adhesive layer in which a filler is dispersed, and in the connection film that connects the objects to be connected by being pressed, the adhesive layer is fluid in the thickness direction. A difference is provided, and the volume density distribution of the filler is such that the filler volume density (c) at the outer edge of the pressing area, the filler volume density (a) at the center of the pressing area, and the filler volume density at the inner edge of the pressing area. When (b), the fluidity is designed so that c> a> b.

  Moreover, the manufacturing method of the connection film according to the present invention includes an adhesive layer in which a filler is dispersed, and in the manufacturing method of the connection film that connects the objects to be connected by being pressed, the adhesive layer includes: There is a difference in fluidity in the thickness direction, and the volume density distribution of the filler is such that the filler volume density (c) at the outer edge of the pressing area, the filler volume density (a) at the center of the pressing area, The fluidity is designed so that c> a> b when the filler volume density (b) at the inner edge is set.

  Further, the connection structure according to the present invention sandwiches a connection film having an adhesive layer in which fillers are dispersed between connection objects, and is connected via the connection film by being pressed. In the structure, the volume density distribution of the filler of the connection object after connection is such that the filler volume density (c) at the outer edge of the pressing area, the filler volume density (a) at the center of the pressing area, and the pressing area When the filler volume density (b) at the inner edge portion is set, c> a> b.

  Further, in the method for manufacturing a connection structure according to the present invention, a connection film having an adhesive layer in which a filler is dispersed is sandwiched between connection objects, and the connection object is pressed through the connection film. The filler volume density distribution (c) at the outer edge of the pressing region and the filler volume density (a) at the central portion of the pressing region. When the filler volume density (b) at the inner edge of the pressing region is set, c> a> b.

  Moreover, the connection method according to the present invention includes a step of sandwiching a connection film having an adhesive layer in which fillers are dispersed between connection objects, and pressing and connecting the connection object through the connection film. The volume density distribution of the filler of the connection object after connection is such that the filler volume density (c) at the outer edge of the pressing area, the filler volume density (a) at the center of the pressing area, and the pressing area When the filler volume density (b) at the inner edge portion is set, c> a> b.

  The present invention has a design condition mainly consisting of fluidity that results in a density distribution of a predetermined filler, so that the connection film is appropriately formed with a fillet of an adhesive layer between objects to be connected, thereby improving the adhesive strength. In addition, an appropriate filler distribution state can be obtained between the objects to be connected, and good electrical conductivity can be realized.

FIG. 1 is an exploded perspective view showing a connection structure according to the present invention. FIG. 2 is a cross-sectional view showing an anisotropic conductive film. FIG. 3 is a plan view showing a pressing region by a thermocompression bonding tool. FIG. 4 is a cross-sectional view showing an adhesion state using the anisotropic conductive film according to the present invention. FIG. 5 is a cross-sectional view showing an example of the anisotropic conductive film before heat pressing. FIG. 6 is a cross-sectional view of the anisotropic conductive film at the beginning of heat pressing. FIG. 7 is a graph showing the temperature difference between the minimum melt viscosity and the binder resin. FIG. 8 is a cross-sectional view of an anisotropic conductive film according to Comparative Example 1 at the beginning of heat pressing. FIG. 9 is a cross-sectional view showing an adhesion state using the anisotropic conductive film according to Comparative Example 1. FIG. 10 is a cross-sectional view of an anisotropic conductive film according to Comparative Example 2 at the beginning of heat pressing. FIG. 11 is a cross-sectional view showing an adhesion state using the anisotropic conductive film according to Comparative Example 2. 12A and 12B are cross-sectional views showing a connection process using an anisotropic conductive film, in which FIG. 12A shows a state before heat pressing, and FIG. 12B shows a heat pressing state.

  Hereinafter, a connection film, a method for manufacturing a connection film, a connection structure, a method for manufacturing a connection structure, and a connection method to which the present invention is applied will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention. Further, the drawings are schematic, and the ratio of each dimension may be different from the actual one. Specific dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  The bonding film to which the present invention is applied is a bonding film for bonding an electronic component such as an IC chip or a flexible substrate on a rigid substrate or a flexible substrate, and the connection structure to which the present invention is applied includes the bonding film. Rigid substrate etc. and electronic parts such as IC chips are joined, and are incorporated in all electronic devices such as TVs, PCs, mobile phones, game machines, audio equipment, tablet terminals or in-vehicle monitors. It can be used for a substrate. In such a substrate, from the viewpoints of fine pitch, light weight, and thinning, a so-called COB (chip on board) or COG (chip on glass) in which a flexible substrate on which an IC chip or various circuits are formed is directly mounted on the substrate. ), FOB (film on board), FOG (film on glass), and FOF (film on film) for connecting flexible substrates to each other. In addition, as a bonding film used for bonding various substrates to an IC chip, a flexible substrate, etc., an anisotropic conductive film (ACF) in which conductive particles are dispersed in a binder resin layer is often used. ing.

  A connection structure by FOB will be described as an example. As shown in FIG. 1, the connection structure 1 has a flexible substrate 4 bonded to a substrate 2 via an anisotropic conductive film 3 to which the present invention is applied. To be manufactured.

  The substrate 2 is a rigid substrate such as a glass substrate or a glass epoxy substrate, for example, on which various wiring patterns 10 made of an ITO film or a Cu pattern are formed, and various components such as an IC chip are mounted. And the board | substrate 2 comprises the connection structure 1 by connecting the flexible substrate 4 via the anisotropic conductive film 3. FIG.

  In the substrate 2, a plurality of electrode terminals 6 connected to connection terminals 7 provided on the flexible substrate 4 are formed in the FOB mounting portion 5 to which the flexible substrate 4 is connected. As shown in FIG. 1, the electrode terminals 6 are formed, for example, in a substantially rectangular shape, and are arranged in a plurality over the direction orthogonal to the longitudinal direction. Each electrode terminal 6 is connected to other circuits and electronic components via the wiring pattern 10.

  The FOB mounting portion 5 is connected to the flexible substrate 4 using an anisotropic conductive film 3 as a conductive adhesive. As will be described later, the anisotropic conductive film 3 contains conductive particles in a binder resin, and the connection terminals 7 of the flexible substrate 4 and the electrode terminals 6 formed on the substrate 2 are connected via the conductive particles. Connect them electrically.

[Flexible substrate]
The flexible substrate 4 connected to the FOB mounting portion 5 of the substrate 2 has a connection terminal 7 connected to the electrode terminal 6 on one surface 9a of a flexible substrate 9 such as polyimide as shown in FIG. Multiple arrays are formed. The connection terminal 7 is formed, for example, by patterning a copper foil or the like and appropriately performing a plating coating process such as nickel gold plating on the surface, and is formed in a substantially rectangular shape, for example, like the electrode terminal 6. A plurality are arranged in a direction orthogonal to the longitudinal direction. The connection terminal 7 and the electrode terminal 6, and the region between the connection terminal 7 and the region between the electrode terminals 6 are arranged in substantially the same pattern, have the same width, and are superimposed via the anisotropic conductive film 3. .

  Further, the flexible substrate 5 is provided with a coverlay 8 in the vicinity of the connection terminal 7. The coverlay 8 exposes the connection terminals 7 and protects the wiring pattern formed on the one surface 9a of the substrate 9. An adhesive layer is provided on one surface of the insulating base film, and this adhesive layer Is attached to one surface 9a of the substrate 9.

[Anisotropic conductive film]
The anisotropic conductive film 3 is a thermosetting adhesive and is fluidized by being thermally pressed by a thermocompression bonding tool 20 to be described later, so that the conductive particles 16 are the terminals 6 of the substrate 2 and the flexible substrate 4. 7, and the conductive particles 16 are crushed and hardened by heating. Thereby, the anisotropic conductive film 3 electrically and mechanically connects the substrate 2 and the flexible substrate 4.

  For example, as shown in FIG. 2, the anisotropic conductive film 3 is conductive to a normal binder resin 15 (adhesive) containing a film-forming resin, a thermosetting resin, a latent curing agent, a silane coupling agent, and the like. The particles 16 are dispersed, and this thermosetting adhesive composition is applied onto the base film 17 to be formed into a film shape.

  The base film 17 is formed, for example, by applying a release agent such as silicone to PET (Poly Ethylene Terephthalate), OPP (Oriented Polypropylene), PMP (Poly-4-methylpentene-1), PTFE (Polytetrafluoroethylene), or the like.

  The film forming resin contained in the binder resin 15 is preferably a resin having an average molecular weight of about 10,000 to 80,000. Examples of the film forming resin include various resins such as an epoxy resin, a modified epoxy resin, a urethane resin, and a phenoxy resin. Among these, phenoxy resin is particularly preferable from the viewpoint of film formation state, connection reliability, and the like.

  It does not specifically limit as a thermosetting resin, For example, a commercially available epoxy resin, an acrylic resin, etc. are mentioned.

  The epoxy resin is not particularly limited. For example, naphthalene type epoxy resin, biphenyl type epoxy resin, phenol novolac type epoxy resin, bisphenol type epoxy resin, stilbene type epoxy resin, triphenolmethane type epoxy resin, phenol aralkyl type epoxy resin. Naphthol type epoxy resin, dicyclopentadiene type epoxy resin, triphenylmethane type epoxy resin and the like. These may be used alone or in combination of two or more.

  There is no restriction | limiting in particular as an acrylic resin, According to the objective, an acrylic compound, liquid acrylate, etc. can be selected suitably. For example, methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, epoxy acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate, dimethylol tricyclodecane diacrylate, tetramethylene glycol tetraacrylate, 2-hydroxy- 1,3-diacryloxypropane, 2,2-bis [4- (acryloxymethoxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy) phenyl] propane, dicyclopentenyl acrylate, tricyclo Examples include decanyl acrylate, tris (acryloxyethyl) isocyanurate, urethane acrylate, and epoxy acrylate. In addition, what made acrylate the methacrylate can also be used. These may be used individually by 1 type and may use 2 or more types together.

  Although it does not specifically limit as a latent hardening agent, For example, various heat hardening type hardening agents are mentioned. The latent curing agent does not normally react but is activated by a trigger such as heat or pressure to start the reaction. The activation method of the thermal activation type latent curing agent includes a method of generating active species (cation, anion, radical) by a dissociation reaction by heating, etc., and it is stably dispersed in the epoxy resin near room temperature, and epoxy at high temperature There are a method of initiating a curing reaction by dissolving and dissolving with a resin, a method of initiating a curing reaction by eluting a molecular sieve encapsulated type curing agent at a high temperature, and an elution / curing method using microcapsules. Thermally active latent curing agents include imidazole, hydrazide, boron trifluoride-amine complexes, sulfonium salts, amine imides, polyamine salts, dicyandiamide, etc., and modified products thereof. The above mixture may be sufficient. As the radical polymerization initiator, a known one can be used, and among them, an organic peroxide can be preferably used.

  Although it does not specifically limit as a silane coupling agent, For example, an epoxy type, an amino type, a mercapto sulfide type, a ureido type etc. can be mentioned. By adding the silane coupling agent, the adhesion at the interface between the organic material and the inorganic material is improved.

  Examples of the conductive particles 16 include any known conductive particles used in the anisotropic conductive film 3. Examples of the conductive particles 16 include particles of various metals and metal alloys such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, gold, metal oxide, carbon, graphite, glass, ceramic, Examples thereof include those in which the surface of particles such as plastic is coated with metal, or those in which the surface of these particles is further coated with an insulating thin film. In the case where the surface of the resin particle is coated with metal, examples of the resin particle include an epoxy resin, a phenol resin, an acrylic resin, an acrylonitrile / styrene (AS) resin, a benzoguanamine resin, a divinylbenzene resin, a styrene resin, and the like. Can be mentioned.

[Inorganic filler]
Moreover, in order to control the fluidity | liquidity of the binder resin 15 and to improve a particle capture rate, you may make it contain an inorganic filler in a binder resin composition. The inorganic filler is not particularly limited, and silica, talc, titanium oxide, calcium carbonate, magnesium oxide and the like can be used. Such an inorganic filler can also be appropriately used for the purpose of relaxing the stress of the connection structure connected by the anisotropic conductive film 3.

  In addition, the anisotropic conductive film 3 is good also as a structure which provides a cover film in the surface opposite to the surface where the base film 17 was laminated | stacked from viewpoints of the ease of handling, storage stability, etc. Moreover, the shape of the anisotropic conductive film 3 is not particularly limited. For example, the anisotropic conductive film 3 may be formed into a long tape shape that can be wound around the take-up reel 18 and cut into a predetermined length for use.

[Density distribution of conductive particles]
Here, the anisotropic conductive film 3 according to the present invention is designed so that the conductive particles 16 after being pressed by the thermocompression bonding tool 20 have a predetermined density distribution. Improvements are being made. Specifically, as shown in FIG. 3, the anisotropic conductive film 3 has a density distribution of the conductive particles 16 in the inter-terminal regions 11 after the substrate 2 and the flexible substrate 4 are connected. The particle density at the outer edge portion 21c of the pressing region 21 by the crimping tool 20 is (c), the particle density at the central portion 21a of the pressing region 21 by the thermocompression bonding tool 20 is (a), and the inner edge portion of the pressing region 21 by the thermocompression bonding tool 20 When the particle density in 21b is (b), c>a> b.

  Here, the pressing region 21 of the thermocompression bonding tool 20 refers to a region in which the thermocompression bonding tool 20 presses the flexible substrate 4 and the anisotropic electric film 3 with the heat pressing surface 20a, and is a region surrounded by a dotted line in FIG. . The outer edge portion 21 c of the pressing area 21 refers to an outer area along the edge of the pressing area 21, that is, an area surrounding the pressing area 21 and in contact with the pressing area 21. The inner edge portion 21b of the pressing area refers to an inner area along the edge of the pressing area 21, that is, an area surrounded by the outer edge of the pressing area 21 and in contact with the outer edge.

  The inter-terminal region 11 is a region between the adjacent electrode terminal 6 and the connection terminal 7 when the electrode terminal 6 of the substrate 2 and the connection terminal 7 of the flexible substrate 4 are attached to each other. When the conductive conductive film 3 is hot-pressed, it becomes a flow path for the binder resin 15.

  The main object of the present invention is to have a design in which the conductive particles 16 are optimally arranged in heat flow. Therefore, it has different fluidity within the same film, and the movement of the conductive particles 16 is appropriately performed, thereby improving the bonding performance and eliminating the excessive uneven distribution of the conductive particles 16, thereby improving the bonding performance. ing.

[Fillet]
By providing such a density distribution of the conductive particles 16, the anisotropic conductive film 3 is appropriately formed with a fillet of the binder resin 15 between the substrate 2 and the flexible substrate 4 to improve the adhesive strength. be able to. That is, according to the anisotropic conductive film 3, the density (c) of the conductive particles 16 at the outer edge portion 21 c of the pressing region 21 is higher than the density (b) of the conductive particles at the inner edge portion 21 b of the pressing region 21. From this, it can be seen that a large amount of the binder resin 15 flows and hardens in the outer edge portion 21c of the pressing region 21. Then, as shown in FIG. 4, a fillet 23 is formed between the substrate 2 and the flexible substrate 4 by the binder resin 15 that has flowed to the outer edge portion 21 c of the pressing region 21. Thereby, the anisotropic conductive film 3 can firmly bond the substrate 2 and the flexible substrate 4.

  That is, there is an aspect in which both adhesion and functionality are achieved by controlling the uneven distribution of the conductive particles 16 in the fillet region. That is, uneven distribution is achieved in which the end portion, which is the separation start point, is reinforced by improving the local strength of the fillet region and the anisotropic conductivity is kept good.

  In addition, by providing such a density distribution of the conductive particles 16, the anisotropic conductive film 3 has a binder resin 15 that is appropriately discharged from between the electrode terminal 6 and the connection terminal 7. The conductive particles 16 can be reliably held by being pressed by the crimping tool 20, and the conduction reliability can be improved.

  The anisotropic conductive film 3 has a relatively large diameter fillet 23 formed between the substrate 2 and the flexible substrate 4 at the outer edge 21c of the pressing region. The thickness of the binder resin 15 becomes thicker than the thickness of the binder resin 15 in the inner edge portion 21b and the central portion 21a of the pressing region 21.

[Liquidity]
Thus, the density distribution of the conductive particles 16 after the thermocompression bonding of the anisotropic conductive film 3 results from the fluidity of the binder resin 15. That is, when the anisotropic conductive film 3 is heat-pressed by the thermocompression bonding tool 20, the binder resin 15 exhibits fluidity and flows out between the substrate 2 and the flexible substrate 4. At this time, the binder resin 15 is appropriately discharged from the pressing region 21 to the anisotropic conductive film 3, thereby forming a fillet 23 at the outer edge portion 21 c of the pressing region 21, and by pressing with the thermocompression bonding tool 20. It is necessary that the binder resin 15 has a fluidity that allows the conductive resin 16 to flow out appropriately between the electrode terminal 6 and the connection terminal 7 so that the conductive particles 16 can be sandwiched between the electrode terminal 6 and the connection terminal 7.

  As the anisotropic conductive film 3 exhibiting such fluidity, for example, as shown in FIG. 5, a binder resin is formed from the first surface 3a to the second surface 3b opposite to the first surface 3a. 15 is formed to have a low fluidity. If it expresses typically, if anisotropic conductive film 3 is formed by laminating first binder resin 15a with relatively high fluidity and second binder resin 15b with relatively low fluidity, Good. The anisotropic conductive film 3 is pressed by the thermocompression bonding tool 20 from the first surface 3a side on which the first binder resin 15a having relatively high fluidity of the binder resin 15 is provided. Then, as shown in FIG. 6, in the anisotropic conductive film 3, the first binder resin 15 a on the first surface 3 a side flows, and then the second binder resin 15 b on the second surface 3 b side flows. To do.

  At this time, by appropriately adjusting the difference between the fluidity of the first binder resin 15a on the first surface 3a side and the fluidity of the second binder resin 15b on the second surface 3b side, FIG. As shown, after the first binder resin 15a flows on the second binder resin 15b to the outer edge portion 21c of the pressing region 21, the second binder resin 15b starts to flow, whereby the first and second Both the binder resins 15 a and 15 b are cured at the outer edge portion 21 c of the pressing region 21, and an appropriate fillet 23 covering both surfaces of the substrate 2 and the flexible substrate 4 can be formed.

  The difference in fluidity in the thickness direction of the binder resin 15 is not limited to that provided by the laminated configuration.

  Also, before the first binder resin 15a on the first surface 3a side begins to harden, the second binder resin 15b on the second surface 3b side starts to flow, so that the first binder resin 15a The flow of the second binder resin 15b can be pushed by the thermocompression bonding tool 20 without being suppressed, and electrical conductivity can be ensured. In addition, in FIG. 5, although demonstrated using two binder resin 15a, 15b from which fluidity | liquidity differs, the anisotropic conductive film 3 is equipped with 3 or more binder resin from which fluidity | liquidity differs, and the 1st surface 3a. Alternatively, the fluidity may gradually decrease from the second surface 3b to the second surface 3b.

  Thus, by designing the fluidity of the resin, the uniformly dispersed conductive particles 16 can be arbitrarily distributed. Thereby, it can also contribute to the improvement of adhesiveness.

[Minimum melt viscosity temperature]
As the anisotropic conductive film 3 in which the binder resin 15 exhibits such fluidity, for example, in the anisotropic conductive film 3 shown in FIG. The second binder resin 15b having a relatively low melt viscosity and a relatively low fluidity is formed by using a resin having a relatively low melt viscosity and a relatively low fluidity. Here, as shown in FIG. 7, the ultimate temperature difference between the minimum melt viscosities of the first and second binder resins 15 a and 15 b is preferably 10 to 30 ° C.

  In addition, if the difference in fluidity is obtained on the front and back surfaces in such a way that the temperature difference between the minimum melt viscosities is reached, there is no particular need for the layer configuration as in a laminated film.

  By setting the temperature difference of minimum melt viscosity to 10 to 30 ° C., when the anisotropic conductive film 3 presses the thermocompression bonding tool 20 from the first surface 3 a side, first, the first binder resin 15 a The second binder resin 15b flows to the outer edge portion 21c of the pressing region 21 and then the second binder resin 15b starts to flow. Thereby, in the anisotropic conductive film 3, both the first and second binder resins 15a and 15b are cured at the outer edge portion 21c of the pressing region 21 to form a large fillet 23 over both surfaces of the substrate 2 and the flexible substrate 4. (See FIG. 4).

  By designing the content of the conductive particles 16 in the fillet portion so as to be within a predetermined range and unevenly distributed, the effect of improving the adhesion by the fillet can be expressed more strongly. In addition, if the local balance of the conductive particles 16 is lost, the fillet itself becomes brittle, and it is considered that the adhesiveness is also lowered. That is, the flow of the conductive particles 16 reveals an approximate movement mechanism in the film, whereby the optimum uneven distribution condition of the conductive particles 16 can be obtained and reflected in the design of the film.

  In addition, by increasing the temperature difference of minimum melt viscosity to 10 to 30 ° C., the anisotropic conductive film 3 starts to flow before the binder resin 15a begins to harden. The binder resin 15a can be pushed in by the thermocompression bonding tool 20 without the flow of the binder resin 15b being suppressed. Therefore, the anisotropic conductive film 3 can ensure conduction reliability by sandwiching the conductive particles 16 between the electrode terminals 6 and the connection terminals 7 and curing the binder resin 15 in this state.

  On the other hand, when the temperature difference between the minimum melt viscosities is small and less than 10 ° C., the anisotropic conductive film 3 flows between the first binder resin 15a and the second binder resin 15a as shown in FIG. As shown in FIG. 9, a fillet 23 in which the binder resins 15a and 15b are both biased toward the substrate 2 at the outer edge portion 21c of the pressing region 21 is formed. For this reason, the connection strength between the substrate 2 and the flexible substrate 4 is insufficient. That is, the uneven distribution of the conductive particles 16 does not occur appropriately.

  Further, when the temperature difference of the minimum melt viscosity is higher than 30 ° C., as shown in FIG. 10, the anisotropic conductive film 3 has the second binder resin 15a flowing on the second binder resin 15b, as shown in FIG. Before the binder resin 15b flows. Therefore, the flow of the second binder resin is hindered, and as shown in FIG. 11, the fillet 23 is formed biased toward the substrate 2 side, and the connection strength between the substrate 2 and the flexible substrate 4 is insufficient. Further, since the flow of the second binder resin 15b is hindered, the pressing by the thermocompression bonding tool 20 is insufficient, and the conductive particles 16 cannot be sufficiently sandwiched between the electrode terminals 6 and the connection terminals 7. When the binder resin 15 is cured in the state, the conduction resistance is also increased. That is, the effect of uneven distribution of the conductive particles 16 is lost.

[Strength when pressing the second surface]
The anisotropic conductive film 3 is configured such that the fluidity gradually decreases from the first surface 3a to the second surface 3b. Therefore, if the 2nd surface 3b side is pressed with the thermocompression-bonding tool 20 contrary to the above, the behavior of the binder resin 15 will change and adhesive strength will fall. For example, as the binder resin 15 shown in FIG. 5, a first binder resin 15a having a relatively low minimum melt viscosity reaching temperature and a second binder resin 15b having a relatively low minimum melt viscosity reaching temperature are used. In the anisotropic conductive film 3 formed by laminating, when the thermocompression bonding tool 20 is pressed from the second surface 3b side, the second binder resin 15b is difficult to flow. The fillet 23 is formed to be biased toward the first surface 3a. For this reason, the adhesive strength between the substrate 2 and the flexible substrate 4 is lowered.

  In other words, controlling the overall flow itself is directly attributable to adhesion. The uneven distribution of the conductive particles 16 is controlled by this flow, and it is presumed that the presence of the conductive particles 16 locally affects the bondability of the entire film.

[Others]
The anisotropic conductive film 3 can be formed by laminating a conductive adhesive layer containing the conductive particles 16 and an insulating adhesive layer containing only the binder resin without containing the conductive particles 16. . For example, as shown in FIG. 5, when the first and second binder resins 15a and 15b are laminated, the anisotropic conductive film 3 uses the first binder resin 15a as an insulating adhesive layer, The binder resin 15b can be used as a conductive adhesive layer. The anisotropic conductive film 3 may be formed by laminating a plurality of adhesive layers having different fluidity, and any one or a plurality of layers may be used as a conductive adhesive layer, and the other layers may be used as an insulating adhesive layer. .

  Or the anisotropic conductive film 3 consists of one layer, and the thing adjusted so that fluidity | liquidity may differ on front and back. This adjustment is performed by, for example, the amount of dry air at the time of production. Moreover, you may spray and infiltrate what has dilution property and volatility, such as a solvent. Such a difference in fluidity between the front and back surfaces can be confirmed from the minute compressibility of the surface such as a minute compression test.

  The anisotropic conductive film 3 provided in this way exhibits a specific fluidity by providing a gradient in the temperature at which the lowest melt viscosity is reached in the thickness direction. This is when the film is placed with the first side up on a flat and highly rigid member such as a glass plate, and when the film is placed with the second side up. Thus, when heating is carried out slowly and at a temperature at which curing does not proceed excessively, the difference in fluidity appears remarkably. In other words, the film has a wider area when the gradient of the ultimate temperature of the minimum melt viscosity is larger. Since this is considered to correspond to the fillet after bonding, the gradient is related to the bonding strength.

  The present invention optimizes the functionality of the film by appropriately controlling the adhesiveness depending on the ultimate temperature gradient of the minimum melt viscosity in the thickness direction and the mobility or uneven distribution of the conductive particles 16. Objective.

[Thermo-compression tool]
A thermocompression bonding tool 20 that heat-presses the flexible substrate 4 is provided so as to be movable up and down above the stage on which the substrate 2 and the flexible substrate 4 are placed.

  The thermocompression bonding tool 20 heats and presses the terminal region where the connection terminals 7 of the flexible substrate 4 are arranged in parallel to the FOB mounting portion 5 of the substrate 2 through a cushioning material. The thermocompression bonding tool 20 can apply heat and pressure between the terminals 6 and 7 by heat-pressing the flexible substrate 4 and the substrate 2 to securely sandwich the conductive particles 16, and in this state the binder The resin 15 can be cured.

  The heat pressing surface 20a in contact with the flexible substrate 4 of the thermocompression bonding tool 20 is flattened, and the buffer material appropriately interposed between the heat pressing surface 20a and the flexible substrate 4 is made of a sheet-like elastic material. For example, silicon rubber is used.

[Manufacturing process of connection structure]
Next, the manufacturing process of the connection structure will be described by taking as an example the case where the anisotropic conductive film 3 in which the first binder resin 15a having high fluidity and the second binder resin 15b having low fluidity are laminated is used. . First, the substrate 2 is placed on the stage, and the anisotropic conductive film 3 is temporarily pasted onto the FOB mounting portion 5 by pressing at a low temperature and low pressure. At this time, the anisotropic conductive film 3 is placed with the second surface 3b provided with the second binder resin 15b having low fluidity facing the FOB mounting portion 5 side, and the base film 17 is peeled off. Is done. Next, the flexible substrate 2 is disposed on the first surface 3a on which the first binder resin 15a having high fluidity is provided. At this time, the flexible substrate 4 performs alignment between the connection terminal 7 and the electrode terminal 6 of the substrate 2.

  Next, the thermocompression bonding tool 20 heated to a predetermined temperature for curing the binder resin layer 15 is pressed against the FOB mounting portion 5 with a predetermined pressure. Thereby, the anisotropic conductive film 3 is heat-pressed from the 1st surface 3a side via the flexible substrate 4 with the thermocompression-bonding tool 20. The binder resin 15 exhibits fluidity and flows out from between the connection terminal 7 of the flexible substrate 4 and the electrode terminal 6 of the substrate 2.

  At this time, as shown in FIG. 6, the anisotropic conductive film 3 has a second fluid after the first binder resin 15 a having high fluidity flows on the second binder resin 15 b to the outer edge portion 21 c of the pressing region 21. When the binder resin 15b starts to flow, both the first and second binder resins 15a and 15b are cured at the outer edge portion 21c of the pressing area 21, and as shown in FIG. A large fillet 23 is formed across both sides.

  Also, before the first binder resin 15a on the first surface 3a side begins to harden, the second binder resin 15b on the second surface 3b side starts to flow, so that the first binder resin 15a It can be pushed in by the thermocompression bonding tool 20 without the flow of the binder resin 15b being suppressed. Therefore, the conductive particles 16 can be sandwiched between the electrode terminals 6 and the connection terminals 7, and in this state, the binder resin 15 heated by the thermocompression bonding tool 20 is cured, so that good conductivity can be ensured. The conductive particles 16 that are not between the electrode terminal 6 and the connection terminal 7 are dispersed in the binder resin 15 and maintain an electrically insulated state. Thereby, electrical conduction is achieved only between the connection terminal 7 of the flexible substrate 4 and the electrode terminal 6 of the substrate 2.

  Thereby, the connection structure 1 by which the board | substrate 2 and the flexible substrate 4 were joined via the anisotropic conductive film 3 can be formed.

  Next, examples of the present invention will be described. In this embodiment, as the binder resin, a thickness is obtained by laminating a first binder resin having a relatively low minimum melt viscosity reaching temperature and a second binder resin having a relatively low minimum melt viscosity reaching temperature. A connection structure was formed using anisotropic conductive films having different fluidity in directions, and conduction resistance and bonding strength were measured and evaluated. Samples of the anisotropic conductive film were prepared so that the difference in the reached temperature of the lowest melt viscosity on the front and back surfaces was about 10 ° C.

  The connection structures according to Examples and Comparative Examples are joined bodies in which a flexible substrate is joined to a glass substrate via an anisotropic conductive film. The glass substrate had a thickness of 0.7 mm and was coated with ITO on the entire surface. In the flexible substrate, Cu wiring having a thickness of 8 μm is formed on one surface of a polyimide substrate having a thickness of 38 μm at a pitch of 50 μm (L / S = 50 μm / 50 μm).

[Example 1]
70 parts of phenoxy resin (YP50; manufactured by Tohto Kasei Co., Ltd.), 30 parts of radical polymerizable resin (EB-600; manufactured by Daicel Cytec Co., Ltd.), 5 parts of reaction initiator (Perhexa C; manufactured by Nippon Oil & Fats Co., Ltd.) A first binder resin layer A having a thickness of 10 μm was prepared.

  In a resin composition composed of 70 parts of a phenoxy resin (YP50; manufactured by Toto Kasei Co., Ltd.) and 30 parts of a radical polymerizable resin (EB-600; manufactured by Daicel Cytec Co., Ltd.), a conductive material having an average particle diameter of 5 μm Particles (AUL705; manufactured by Sekisui Chemical Co., Ltd.) were dispersed. In this resin composition, 2 parts of a reaction initiator (Perhexa C; manufactured by Nippon Oil & Fats Co., Ltd.) and 2 parts of a silane coupling agent (KBE-503; manufactured by Shin-Etsu Chemical Co., Ltd.) are added, and the thickness is 10 μm. A second binder resin layer A was created.

  Subsequently, the 1st binder resin layer A and the 2nd binder resin layer A were bonded together, and the anisotropic conductive film which has a 20-micrometer-thick binder resin layer was created.

  Moreover, the reached temperature of the minimum melt viscosity of the 1st binder resin layer A and the 2nd binder resin layer A was measured. Specifically, each binder resin layer was overlaid so as to have a thickness of 500 μm, and using a melt viscometer (HAAKE Rheoless RS-150; manufactured by Thermo Fisher Scientific), the temperature rising temperature was 10 ° C./min, the frequency was 1 Hz, Measurement was performed under conditions of a measurement temperature range of 30 to 180 ° C.

  As a result, the lowest melt viscosity reached temperature of the first binder resin layer A was 91 ° C., and the lowest melt viscosity reached temperature of the second binder resin layer A was 110 ° C. The temperature difference between the minimum melt viscosities of the first binder resin layer A and the second binder resin layer A is 19 ° C. Moreover, the ultimate temperature of the minimum melt viscosity of the whole binder resin layer according to Example 1 was 99 ° C.

[Example 2]
70 parts of phenoxy resin (YP50; manufactured by Tohto Kasei Co., Ltd.), 30 parts of radical polymerizable resin (EB-600; manufactured by Daicel Cytec Co., Ltd.), 4 parts of reaction initiator (Perhexa C; manufactured by Nippon Oil & Fats Co., Ltd.) A first binder resin layer B having a thickness of 10 μm was prepared.

  Subsequently, the 1st binder resin layer B and the 2nd binder resin layer A were bonded together, and the anisotropic conductive film which has a 20-micrometer-thick binder resin layer was created.

  Further, as in Example 1, the temperature at which the lowest melt viscosity of the first binder resin layer B was reached was 99 ° C. The temperature difference between the minimum melt viscosities of the first binder resin layer B and the second binder resin layer A is 11 ° C. Moreover, the ultimate temperature of the minimum melt viscosity of the whole binder resin layer according to Example 2 was 104 ° C.

[Example 3]
70 parts of phenoxy resin (YP50; manufactured by Toto Kasei Co., Ltd.), 30 parts of radical polymerizable resin (EB-600; manufactured by Daicel Cytec Co., Ltd.), 6 parts of reaction initiator (Perhexa C; manufactured by Nippon Oil & Fats Co., Ltd.) A first binder resin layer C having a thickness of 10 μm was prepared.

  Subsequently, the 1st binder resin layer C and the 2nd binder resin layer A were bonded together, and the anisotropic conductive film which has a 20-micrometer-thick binder resin layer was created.

  Further, as in Example 1, the temperature at which the lowest melt viscosity of the first binder resin layer C was measured was 82 ° C. The temperature difference between the minimum melt viscosities of the first binder resin layer C and the second binder resin layer A is 28 ° C. Moreover, the ultimate temperature of the minimum melt viscosity of the whole binder resin layer according to Example 3 was 93 ° C.

[Comparative Example 1]
70 parts of phenoxy resin (YP50; manufactured by Toto Kasei Co., Ltd.), 30 parts of radical polymerizable resin (EB-600; manufactured by Daicel Cytec Co., Ltd.), 2 parts of reaction initiator (Perhexa C; manufactured by Nippon Oil & Fats Co., Ltd.) A first binder resin layer D having a thickness of 10 μm was prepared.

  Subsequently, the 1st binder resin layer D and the 2nd binder resin layer A were bonded together, and the anisotropic conductive film which has a 20-micrometer-thick binder resin layer was created.

  Further, as in Example 1, the temperature at which the lowest melt viscosity of the first binder resin layer D was reached was measured and found to be 108 ° C. The temperature difference between the minimum melt viscosities of the first binder resin layer D and the second binder resin layer A is 2 ° C. Moreover, the ultimate temperature of the minimum melt viscosity of the whole binder resin layer according to Comparative Example 1 was 108 ° C.

[Comparative Example 2]
70 parts of phenoxy resin (YP50; manufactured by Toto Kasei Co., Ltd.), 30 parts of radical polymerizable resin (EB-600; manufactured by Daicel Cytec Co., Ltd.), 8 parts of reaction initiator (Perhexa C; manufactured by Nippon Oil & Fats Co., Ltd.) A first binder resin layer E having a thickness of 10 μm was prepared.

  Subsequently, the 1st binder resin layer E and the 2nd binder resin layer A were bonded together, and the anisotropic conductive film which has a 20-micrometer-thick binder resin layer was created.

  Further, as in Example 1, the temperature at which the lowest melt viscosity of the first binder resin layer E was measured was 72 ° C. The ultimate temperature difference between the minimum melt viscosities of the first binder resin layer E and the second binder resin layer A is 38 ° C. Moreover, the ultimate temperature of the minimum melt viscosity of the whole binder resin layer according to Comparative Example 2 was 89 ° C.

[Reference example]
As a reference example, an anisotropic conductive film composed of a second binder resin layer A single layer having a thickness of 20 μm was prepared.

  The anisotropic conductive films according to Examples 1 to 3, Comparative Examples 1 and 2 and Reference Example were cut to a width of 1.5 mm, placed on the glass substrate described above, and the heat pressing surface having a width of 1.5 mm. Using a temporary pressure bonding tool, temporary pressure bonding was performed under conditions of 70 ° C.-1 MPa-1 sec through 150 μm thick Teflon (registered trademark) as a buffer material. At this time, the anisotropic conductive films according to Examples 1 to 3 and Comparative Examples 1 and 2 are a sample in which the first binder resin layer faces the temporary pressure bonding tool side, and the second binder resin layer is a temporary pressure bonding tool. Two types of samples facing the side were prepared.

  Subsequently, the flexible substrate mentioned above was mounted on each anisotropic conductive film, and was temporarily crimped | bonded on the conditions of 80 degreeC-0.5MPa-0.5sec with the same temporary crimping tool from on the flexible substrate. Finally, a final pressure bonding was performed with a thermocompression bonding tool having a heat pressing surface width of 1.5 mm under the condition of 190 ° C.−2 MPa−10 sec to obtain a connection structure.

  About each obtained connection structure, the conduction resistance and the adhesive strength were measured. As for the conduction resistance, the connection resistance value when a current of 1 mA was passed was measured using a so-called four-terminal method. If it is less than 2.0Ω, there is no practical problem. The adhesive strength was measured by using a tensile tester (manufactured by AND) and measuring the adhesive strength when the flexible substrate was pulled up in the 90 ° direction at a measurement speed of 50 mm / sec. If it is 6.0 N / cm or more, there is no practical problem.

  Moreover, about each connection structure, the thickness of binder resin in the press area | region of the thermocompression-bonding tool and its periphery and the volume number density of electroconductive particle were measured. In addition to the central portion a, the inner edge b, and the outer edge c of the pressing area, the measurement locations are the end d of the binder resin outflow area outside the pressing area, and the longitudinal end of the flexible substrate and the electrode in the pressing area. It was set as the area | region e between (refer FIG. 3). The volume of the conductive particles was calculated by counting the thickness in the area of 200 × 200 μm and the number of conductive particles.

  Moreover, about each connection structure, the fluidity | liquidity of binder resin was calculated | required from the thickness of binder resin in each measurement location. The fluidity of the binder resin was determined in the width direction (a to d direction) of the flexible substrate in the region between the connection terminals and the longitudinal direction (a to e direction) of the flexible substrate in the pressing region. Furthermore, the maximum flow width of the binder resin to the outside of the pressing region of the thermocompression bonding tool was measured for each connection structure.

  As shown in Table 1, in the anisotropic conductive films according to Examples 1 to 3, both are 7.6 N / cm by hot pressing the first binder resin side having high fluidity with a thermocompression bonding tool. The adhesive strength was high as described above, and the conduction resistance value was as low as 1.5Ω or less, which was a favorable result.

  In Examples 1 to 3, in the inter-terminal region in parallel after the glass substrate and the flexible substrate are connected, the central portion a of the pressing region, the inner edge portion b, the outer edge portion c, and the binder outside the pressing region. This is because the density distribution of the conductive particles at the end d of the resin outflow region is c> a> b> d. That is, since the density of the conductive particles is increased in the outer edge portion c of the pressing region, it can be seen that in Examples 1 to 3, more binder resin flows and is cured in the outer edge portion c of the pressing region. And a fillet is formed between a glass substrate and a flexible substrate with the binder resin which flowed to the outer edge part c of a press area | region (refer FIG. 4). Thereby, the anisotropic conductive film which concerns on Examples 1-3 can join a glass substrate and a flexible substrate firmly.

  Further, by providing such a density distribution of conductive particles, the anisotropic conductive films according to Examples 1 to 3 are thermocompression-bonded because the binder resin is appropriately discharged from the terminals of the flexible substrate. The conductive particles can be securely sandwiched between the ITO films by pressing with a tool, and a low conduction resistance can be realized.

  Further, since the anisotropic conductive films according to Examples 1 to 3 have a large-diameter fillet extending between the glass substrate and the flexible substrate at the outer edge c of the pressing area, the outer edge c of the pressing area is formed. The thickness of the binder resin in is larger than the thickness of the binder resin in the inner edge portion b and the central portion a of the pressing area. It can also be seen that there is a bias in the distribution of conductive particles in the fillet peripheral region.

  In Examples 1 to 3, the fluidity of such a binder resin was shown to be within the range where the ultimate temperature difference in minimum melt viscosity between the first binder resin and the second binder resin was 10 ° C to 30 ° C. By doing so, the fluidity on the front and back surfaces is set to the optimum setting. From this, in the thickness direction, optimal fluidity is provided from the first surface to the second surface of the binder resin layer.

  That is, the anisotropic conductive films according to Examples 1 to 3 have a minimum melt viscosity reaching temperature difference of 10 ° C. to 30 ° C., and therefore the thermocompression bonding tool from the first binder resin side having relatively high fluidity. The first binder resin flows on the second binder resin and flows to the outer edge portion c of the pressing region, and then the second binder resin starts to flow (see FIG. 6). Thereby, as for the anisotropic conductive film which concerns on Examples 1-3, both 1st, 2nd binder resin hardens | cures thickly in the outer edge part c of a press area | region (15-16 micrometers), and both surfaces of a glass substrate and a flexible substrate Large fillets could be formed.

  Further, in the anisotropic conductive films according to Examples 1 to 3, the second binder resin starts to flow before the first binder resin starts to cure, so that the second binder resin causes the second binder resin to start to flow. The flow of the binder resin was not suppressed, and it could be pushed in by the thermocompression bonding tool, and the electrical conductivity could be ensured.

  In addition, in the anisotropic conductive films according to Examples 1 to 3, when the heat and pressure are applied from the second binder resin side having low fluidity, the binder resin is biased to flow toward the glass substrate side, and toward the flexible substrate side. No fillet was formed, the adhesive strength decreased, and the difference was a little more than 1.7 to 1.8 times. Since the comparative examples 1 and 2 are about 1.1 times, the difference in adhesive strength is preferably 1.2 times or more, and more preferably 1.7 times or more.

  On the other hand, in Comparative Example 1 in which the temperature difference between the minimum melt viscosities is 2 ° C., the flow of the first binder resin and the second binder resin occurs almost simultaneously, and both the first and second binder resins A fillet biased toward the glass substrate was formed at the outer edge c of the pressing region. For this reason, in the comparative example 1, the thickness of the binder resin in the outer edge part c was also thin (12 micrometers), and the adhesive strength between a glass substrate and a flexible substrate fell. This is almost the same between the case where heat is pressed from the first binder resin side (3.8 N / cm) and the case where heat is pressed from the second binder resin side (4.0 N / cm). As a result. From the above, it is shown that the effect does not appear when there is no difference in fluidity between the front and back surfaces.

  In Comparative Example 1, since the first and second binder resins flow, they can be pushed in by a thermocompression bonding tool, and the conduction resistance is low. The same tendency was seen also in the reference example which consists of a 2nd binder resin single layer.

  Further, in Comparative Example 2 in which the temperature difference in minimum melt viscosity reached 38 ° C., the first binder resin flowed on the second binder resin and cured before the second binder resin flowed. Therefore, in Comparative Example 2, a fillet that is biased toward the glass substrate is formed by preventing the flow of the second binder resin, the thickness of the binder resin at the outer edge c is thin (12 μm), and the glass substrate and the flexible substrate The connection strength between them decreased. This is almost the same between the case where heat is pressed from the first binder resin side (4.3 N / cm) and the case where heat is pressed from the second binder resin side (4.8 N / cm). As a result.

  Further, in Comparative Example 2, since the flow of the second binder resin is hindered, the pressing by the thermocompression bonding tool is insufficient, and the conductive particles are sufficiently sandwiched between the terminal 7 of the flexible substrate and the ITO film. In this state, the binder resin was cured, and the conduction resistance was increased (2.7Ω).

DESCRIPTION OF SYMBOLS 1 Connection structure, 2 board | substrate, 3 anisotropic conductive film, 3a 1st surface, 3b 2nd surface, 4 flexible substrate, 5 FOB mounting part, 6 electrode terminal, 7 connection terminal, 8 coverlay, 9 board | substrate 9a, 10 wiring pattern, 11 terminal area, 15 binder resin, 15a first binder resin, 15b second binder resin, 16 conductive particles, 17 base film, 18 take-up reel, 19 stage, 20 heat Crimping tool, 20a heat pressing surface, 21 pressing area, 21a center, 21b inner edge, 21c outer edge, 23 fillet

Claims (17)

In the connection film that has the adhesive layer in which the filler is dispersed and connects the objects to be connected by being pressed,
The adhesive layer is provided with a difference in fluidity in the thickness direction,
The filler volume density distribution was the filler volume density (c) at the outer edge of the pressing area, the filler volume density (a) at the center of the pressing area, and the filler volume density (b) at the inner edge of the pressing area. sometimes,
c>a> b
A connection film that is designed to have fluidity. When the filler volume density (d) at the end of the binder resin outflow region outside the pressing region,
c>a>b> d
The connection film according to claim 1, wherein the fluidity is designed so that   The connection film according to claim 1, wherein the adhesive layer is provided with a gradient in which fluidity decreases from the first surface to the second surface.   The connection film according to claim 3, wherein the adhesive layer has a minimum melt viscosity reaching temperature from the first surface to the second surface.   The connection film according to claim 4, wherein the difference in the ultimate temperature of the minimum melt viscosity is 10 ° C. to 30 ° C. 6.   When the first surface of the adhesive layer is pressed, the thickness of the adhesive layer at the outer edge portion of the pressing region is thicker than the thickness of the adhesive layer at the inner edge portion and the central portion of the pressing region. The connection film according to any one of 1 to 5.   The connection film according to claim 1, wherein the filler is conductive particles.   The adhesive strength when pressing the first surface of the adhesive layer is higher than the adhesive strength when pressing the second surface opposite to the first surface of the adhesive layer. 8. The connection film according to any one of 7 above.   The adhesive strength when pressing the first surface of the adhesive layer is 1.2 times the adhesive strength when pressing the second surface opposite to the first surface of the adhesive layer. The connection film according to claim 8, which is higher than the above. In the method of manufacturing a connection film having an adhesive layer in which a filler is dispersed and connecting objects to be connected by being pressed,
The adhesive layer is provided with a difference in fluidity in the thickness direction,
The filler volume density distribution was the filler volume density (c) at the outer edge of the pressing area, the filler volume density (a) at the center of the pressing area, and the filler volume density (b) at the inner edge of the pressing area. sometimes,
c>a> b
A method for producing a connecting film whose fluidity is designed to be   The said adhesive bond layer consists of one layer, The manufacturing method of the connection film of Claim 10 adjusted so that fluidity | liquidity may differ on front and back. In the connection structure connected via the connection film, the connection film having the adhesive layer in which the filler is dispersed is sandwiched and pressed between the connection objects.
The volume density distribution of the filler of the connection object after connection is such that the filler volume density (c) at the outer edge of the pressing area, the filler volume density (a) at the center of the pressing area, and the inner edge of the pressing area. When the filler volume density (b) is assumed,
c>a> b
Connection structure that becomes.   The connection structure according to claim 12, wherein the filler volume density (c) is a filler volume density in a fillet formed at an outer edge portion of the pressing region. A connection film having an adhesive layer in which a filler is dispersed is sandwiched between objects to be connected,
Having a step of pressing and connecting the connection object through the connection film;
The volume density distribution of the filler of the connection object after connection is such that the filler volume density (c) at the outer edge of the pressing area, the filler volume density (a) at the center of the pressing area, and the inner edge of the pressing area. When the filler volume density (b) is assumed,
c>a> b
A manufacturing method of a connection structure.   The method for manufacturing a connection structure according to claim 14, wherein the filler volume density (c) is a filler volume density in a fillet formed at an outer edge portion of the pressing region. A connection film having an adhesive layer in which a filler is dispersed is sandwiched between objects to be connected,
Having a step of pressing and connecting the connection object through the connection film;
The volume density distribution of the filler of the connection object after connection is such that the filler volume density (c) at the outer edge of the pressing area, the filler volume density (a) at the center of the pressing area, and the inner edge of the pressing area. When the filler volume density (b) is assumed,
c>a> b
Connection method that becomes.   The connection method according to claim 16, wherein the filler volume density (c) is a filler volume density in a fillet formed at an outer edge portion of the pressing region.