JP5324322B2 - Connection method, connection structure, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection method for inexpensively achieving an adhesive connection structure while simplifying manufacturing processes, and to provide an electronic apparatus. <P>SOLUTION: A motherboard 20 includes a rigid substrate 21, and an electrode 22 for adhesive connection and an electrode 26 for solder connection that are provided on the rigid substrate 21. Each of surfaces of the respective electrodes 22, 26 is covered with an organic film 25, namely an oxidation inhibition film formed by OSP treatment. When forming solder connection structure D by a solder layer 50, the organic film 25 is thermally decomposed. Then, an electrode 12 and the electrode 22 are connected by an adhesive 30 to form adhesive connection structure C. In this case, the organic film 25 has already been thermally decomposed, so that the respective electrodes 22, 26 easily conduct electricity, thus smoothly forming the solder connection structure and adhesive connection structure. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a connection method in which electrical connection is performed using an adhesive, a connection structure formed by the connection method, and an electronic apparatus.

  In recent years, electronic devices have been miniaturized and functionalized, and connection terminals in component parts (for example, electronic parts in liquid crystal products) have been miniaturized. For this reason, in the field of electronics mounting, film adhesives are widely used as various anisotropic conductive adhesives that can easily connect such terminals. For example, a glass having a printed wiring board such as a flexible printed wiring board (FPC) or a rigid printed wiring board (PWB or PCB) provided with an adhesive connecting electrode such as a copper electrode, and a wiring electrode such as a copper electrode. It is used for bonding to a wiring board such as a substrate, and bonding between a printed wiring board and an electronic component such as an IC chip.

  This anisotropic conductive adhesive is an adhesive in which conductive particles are dispersed in an insulating resin composition. The anisotropic conductive adhesive is sandwiched between connected members and heated and pressurized to connect the connected members to each other. Glue. That is, when the resin in the adhesive flows by heating and pressurizing, for example, the gap between the adhesive connecting electrode formed on the surface of the printed wiring board and the wiring electrode formed on the surface of the wiring board is sealed. At the same time, a part of the conductive particles is caught between the facing wiring electrode and the adhesive connecting electrode to achieve electrical connection. Here, in general, each of the adhesive connection electrode of the printed wiring board and the wiring electrode of the wiring board is plated with gold for the purpose of preventing oxidation and ensuring conductivity (for example, Patent Document 1). reference).

JP-A-10-79568

  However, since this gold plating forms a gold plating layer after forming a nickel plating layer on the surfaces of the adhesive connecting electrode and the wiring electrode, the manufacturing process becomes complicated. As a result, there is a problem that the manufacturing cost when connecting the flexible printed wiring board and the wiring board to each other becomes high.

  An object of the present invention is to provide a connection method for realizing an adhesive connection structure at a low cost while simplifying the manufacturing process.

The connection method of the present invention is performed using a base material provided with an adhesive connection electrode and a solder connection electrode. Then, after the adhesive connection electrode and the solder connection electrode are coated with an organic film for preventing oxidation, solder reflow treatment is performed at a temperature at which the organic film is thermally decomposed in a non-oxidizing atmosphere. Bond the electrode to the soldered connection conductor. Thereafter, a connecting step is performed in which the adhesive connecting electrode and the conductor to be connected are electrically bonded to each other via an adhesive mainly composed of a thermosetting resin.
As the adhesive, using the so-called anisotropic conductive adhesive (ACF).
The treatment for forming the organic film is generally called preflux treatment (OSP treatment: Organic Solderability Preservation).
Examples of the substrate include a substrate film of a printed wiring board and a base member for an electrode of an electronic component. Examples of the conductor to be connected and the solder conductor to be connected include an electrode of another printed wiring board, an electrode of an electronic component, and an electrode of a connector. Moreover, the to-be-connected conductor and the to-be-soldered connecting conductor may be provided on a common member, or may be provided on different members.

The following effects can be obtained by the present invention.
Conventionally, gold plating for preventing oxidation has been applied to the adhesive connecting electrode. On the other hand, the process of forming the organic film by the OSP process simplifies the manufacturing process as compared with the process of forming the gold plating layer. Moreover, since expensive gold is not used, the material cost is also reduced. Therefore, according to the present invention, an electrode structure for performing a connection using an adhesive can be manufactured at low cost.
On the other hand, the organic film formed by the OSP process has a range of hardness depending on the type of constituent material and the subsequent environment. For example, when the number of cross-linked portions increases due to high-temperature treatment such as solder reflow or exposure to ultraviolet rays, the hardness may be extremely high. In that case, when an insulating adhesive is used, it becomes difficult for each part to break through the organic film and come into phase contact between the adhesive connecting electrode and the conductor to be connected in the connecting step. In addition, when an anisotropic conductive adhesive containing conductive particles is used, it becomes difficult for the conductive particles to break through the organic film and come into contact with the electrode or the like in the connection step. As a result, in the connecting step, there is a possibility that poor conduction occurs between the adhesive connecting electrode and the connected conductor.
On the other hand, in the present invention, the organic film is thermally decomposed during the solder reflow process. Thereafter, since the connection by the adhesive process, electrodeposition and poles and the connection conductor, mutually connected to each other via the conductive particles. Therefore, generation | occurrence | production of the conduction defect between the electrode for adhesive agent connection on a base material and the to-be-connected conductor on a to-be-connected member can be suppressed.
In addition, since the organic film is finally thermally decomposed, it is possible to ensure conduction between the adhesive connecting electrode and the connected conductor regardless of the thickness of the organic film during the OSP process.
Even if the organic film is pyrolyzed, the oxidation of the electrode and the conductor to be connected can be suppressed just before the connection with the adhesive.
Further, by performing the reflow treatment in a non-oxidizing atmosphere, even if the electrode for connecting the adhesive is exposed, the progress of oxidation of the electrode and the conductor surface is suppressed, so that occurrence of poor conduction can be suppressed.

Further, since the anisotropic conductive adhesive containing conductive particles is used as the adhesive, the conductive particles can easily break through the organic film and contact the adhesive connecting electrode.

Prior to the solder reflow process, a protective film covering the organic film on the adhesive connection electrode may be formed, and the protective film may be removed before connection with the adhesive. Thereby, after the organic film is thermally decomposed, contact with oxygen can be suppressed, and oxidation of the adhesive connecting electrode can be suppressed.

It is preferable to use an adhesive containing conductive particles made of a metal powder having a shape in which a plurality of metal particles are connected in a chain or a needle shape. Thereby, the function in which electroconductive particle pierces an organic film becomes high in a manufacture process, and an adhesive agent connection structure can be formed smoothly.
In that case, when the aspect ratio of the conductive particles is 5 or more, the contact probability between the conductive particles increases. As a result, the adhesive connection structure can be smoothly formed without increasing the blending amount of the conductive particles.

Moreover, when using an anisotropic conductive adhesive, it is preferable to use what has a film shape. This facilitates the handling of the anisotropic conductive adhesive. Moreover, the workability | operativity at the time of forming an adhesive bond structure by heat-pressing processing improves.
In that case, it is more preferable to orient the major axis direction of the conductive particles in the thickness direction of the adhesive having a film shape. Thereby, in the surface direction of an adhesive agent, a short circuit can be prevented by maintaining insulation between adjacent electrodes or conductors. On the other hand, in the thickness direction of the adhesive, it is possible to obtain a low resistance by conducting a conductive connection between a large number of electrodes and conductors at once and independently.

There are various wiring members and substrates as the base material of the present invention.
The wiring member includes various wirings having electrodes such as wiring boards such as flexible printed wiring boards and rigid printed wiring boards, and cable wirings such as coaxial cable wiring and flat cable wiring.
In particular, flexible printed wiring boards are built into many electronic devices such as mobile phones, digital cameras, camcorders such as video cameras, portable audio players, portable DVD players, portable notebook computers, etc. A special effect is obtained.

The connection structure of the present invention is formed using the above connection method, and the electronic device of the present invention is assembled using the above connection method.
With the connection structure and electronic device of the present invention, it is possible to realize a reduction in manufacturing cost through simplification of the manufacturing process and reduction of the amount of gold plating used.

  According to the connection method, connection structure, or electronic device of the present invention, it is possible to reduce the manufacturing cost while simplifying the manufacturing process.

It is a perspective view which shows roughly the structure of the portable terminal which is an electronic device which concerns on embodiment of this invention. It is a cross section which shows the structural example of the connection part of the portable terminal which concerns on embodiment. It is a perspective view which shows the edge part of the wiring body before forming the adhesive agent connection structure which concerns on embodiment. It is sectional drawing which shows Example 1 of the adhesive agent connection structure and solder connection structure formed between a flexible printed wiring board and an electronic component, and a motherboard. It is sectional drawing which shows Example 2 of an adhesive agent connection structure and a solder connection structure. It is a figure explaining the ratio of the minor axis of a conductive particle and a major axis. (A)-(d) is sectional drawing which shows the procedure of the assembly method of the electronic component which has an adhesive agent connection structure and a solder connection structure.

-Electronic equipment-
FIG. 1 is a perspective view schematically showing a structure of a portable terminal 100 which is an electronic apparatus according to an embodiment of the present invention.
The portable terminal 100 includes a display unit 103 for displaying various types of information, an input unit 104, and a hinge unit 105. The display unit 103 is provided with a display device 106 using a liquid crystal display panel, a speaker, and the like. The input unit 104 is provided with input keys and a microphone. The hinge unit 105 connects the input unit 104 and the display unit 103 in a rotatable manner.

FIG. 2 is a cross-sectional view illustrating a configuration of a connection portion via the hinge portion 105 of the mobile terminal 100 according to the embodiment.
The display unit 103 is provided with a display unit casing 131 and a display unit substrate 135 as main members. The display unit substrate 135 includes a circuit for sending a display signal to the display device 106. The display unit casing 131 includes a first casing 131a and a second casing 131b that are connected to each other. A through hole 133 is provided between the first housing 131a and the second housing 131b.

  The input unit 104 is provided with an input unit casing 141 and an input unit substrate 145 as main members. The input key board 145 includes a circuit for controlling a signal sent from the input key. The input unit housing 141 includes a first housing 141a and a second housing 141b that are connected to each other. A through hole 143 is provided between the first housing 141a and the second housing 141b.

Further, a wiring body A that connects the input key substrate 145 and the display unit substrate 135 through the hinge unit 105 is provided. The wiring body A includes an FPC 10 and an adhesive connection structure C provided at both ends of the FPC 10 with an anisotropic conductive adhesive 30 interposed therebetween.
Further, the input key board 145 is provided with a solder joint D in which electronic components are joined by solder. Although not shown, similarly, the display unit substrate 135 is also provided with a solder joint D in which electronic components are joined by solder.

-Electrode structure and wiring body-
FIG. 3 is a perspective view showing an end portion of the wiring body A before forming the adhesive connection structure C of the present embodiment. The wiring body A has FPC10 (base material) and the electrode structure B provided in the edge part.

  The FPC 10 generally has a structure including a base film 11 on which a circuit layer (see a broken line) is formed and a cover lay 13 that covers the base film 11. The end portion of the circuit layer is an adhesive connecting electrode 12 for electrical connection with a connected conductor.

  Examples of the material of the base film 11 of the FPC 10 include polyimide resin, polyester resin, and glass epoxy resin. As the material of the coverlay 13, generally, the same material as the base film is used. In addition, an epoxy resin, an acrylic resin, a polyimide resin, a polyurethane resin, or the like is used.

The circuit layer of the FPC 10 is formed by laminating a metal foil such as a copper foil on the base film 11, and exposing and etching the metal foil by a conventional method. The circuit layer is generally made of copper or a copper alloy. Among the circuit layers, the adhesive connecting electrode 12 is exposed, and generally, a gold plating layer that functions as an antioxidant film of the adhesive connecting electrode 12 is provided.
On the other hand, in the electrode structure B of the present embodiment, the adhesive connecting electrode 12 is provided with a gold plating layer and other noble metal plating layers (silver plating layer, platinum plating layer, palladium plating layer, etc.). Absent. The adhesive connecting electrode 12 is covered with an organic film 15 as an antioxidant film instead of the noble metal plating layer.

The organic film 15 is formed by a water-soluble preflux process (OSP process: Organic Solderability Preservation).
As a method for performing the OSP treatment, for example, a spray method, a shower method, a dipping method, or the like is used, and then it may be washed with water and dried. The temperature of the water-soluble preflux at that time is preferably 25 to 40 ° C., and the contact time between the water-soluble preflux and the adhesive connecting electrode 12 is preferably 30 to 60 seconds.

  In general, the water-soluble preflux is an acidic aqueous solution containing an azole compound. Examples of the azole compound include imidazole, 2-undecylimidazole, 2-phenylimidazole, 2,4-diphenylimidazole, triazole, aminotriazole, pyrazole, benzothiazole, 2-mercaptobenzothiazole, benzimidazole, and 2-butyl. Benzimidazole, 2-phenylethylbenzimidazole, 2-naphthylbenzimidazole, 5-nitro-2-nonylbenzimidazole, 5-chloro-2-nonylbenzimidazole, 2-aminobenzimidazole, benzotriazole, hydroxybenzotriazole, carboxy Examples thereof include azole compounds such as benzotriazole.

  In the present embodiment, the organic film 15 has a decomposition temperature lower than the solder reflow temperature when the solder connection structure D is formed. Generally, the reflow temperature of lead-free solder is around 260 ° C. Therefore, as the organic film 15, a resin having a thermal decomposition temperature of 260 ° C. or lower, more preferably 240 ° C. or lower is used.

  Among the above azole compounds, the organic compounds that meet the above conditions include alkyl imidazoles such as imidazole, 2-methylimidazole, 2-ethylimidazole, 1,2-dimethylimidazole, pyrazole, 1-methylpyrazole, etc. And alkylpyrazoles.

According to the electrode structure B and the wiring body A of the present embodiment, the following effects can be exhibited.
Conventionally, a noble metal plating layer such as a gold plating layer is formed as an anti-oxidation film on an electrode for connecting an adhesive that is connected using an anisotropic conductive adhesive (ACF) or an insulating adhesive (NCF). Has been.

  On the other hand, in this embodiment, the adhesive connecting electrode 12 is covered with an organic film 15 which is an OSP film instead of the noble metal plating layer. The organic film 15 is formed by a spray method, a shower method, a dipping method, or the like, and then formed only by washing with water and drying. Therefore, the process of forming the antioxidant film is simplified as compared with the case where a noble metal plating layer such as a gold plating layer is formed. In addition, the material cost is reduced as compared with the case of using a noble metal such as gold. Moreover, compared with the case where a gold plating layer is formed, the connection strength (shear strength) between the adhesive connecting electrode 12 and the electrode to be connected can be improved.

  The base material on which the electrode structure B is provided is not limited to a flexible printed wiring board (FPC), but other types of wiring boards such as a hard printed wiring board (PWB), cable wiring, electronic components, connectors, and the like. Also good.

-Example 1 of adhesive connection structure
FIG. 4 is a cross-sectional view showing an example 1 of the adhesive connection structure C and the solder connection structure D formed between the FPC 10 (flexible printed wiring board) and the electronic component 40 and the mother board 20. The adhesive connection structure C is formed using an insulating adhesive (NCF).

  The mother board 20 includes a rigid board 21, an adhesive connection electrode 22 and a solder connection electrode 26 provided on the rigid board 21. The mother board 20 is a PWB (rigid printed wiring board) corresponding to the display unit board 135 and the input key board 145 shown in FIG. The FPC 10 is mounted on the mother board 20 with the adhesive connecting electrode 12 (connected conductor) facing the lower side of the base film 11. The electronic component 40 has a chip-side electrode 42 (soldered connection conductor) in a part of the chip 41, and the chip-side electrode 42 is arranged facing the lower side of the chip 41.

The adhesive connecting electrode 22 and the solder connecting electrode 26 of the mother board 20 are formed by laminating a metal foil such as a copper foil on the rigid board 21, and exposing and etching the metal foil in a usual manner. Yes.
In the adhesive connection structure C, the electrodes 12 and 22 are in strong contact with each other and are electrically connected by the tightening force of the adhesive 30 which is NCF. In the solder connection structure D, the electrodes 26 and 42 are electrically connected to each other due to the alloying of the solder layer 50 and the electrodes 26 and 42.

  The adhesive 30 has a thermosetting resin as a main component, and is added with a curing agent and various fillers. Examples of the thermosetting resin include an epoxy resin, a phenol resin, a polyurethane resin, an unsaturated polyester resin, a urea resin, and a polyimide resin. Among these, in particular, by using an epoxy resin as the thermosetting resin, it is possible to improve film formability, heat resistance, and adhesive strength. Moreover, the adhesive 30 should just have at least 1 sort (s) as a main component among the above-mentioned thermosetting resins.

  The epoxy resin to be used is not particularly limited. For example, bisphenol A type, F type, S type, AD type, or a copolymer type epoxy resin of bisphenol A type and bisphenol F type, or naphthalene type epoxy is used. Resin, novolac type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin and the like can be used. A phenoxy resin that is a high molecular weight epoxy resin can also be used.

  Here, before forming the adhesive connection structure C and the solder connection structure D, each of the electrodes 12, 22, 26, and 42 is covered with an organic film similar to the organic film 15 shown in FIG. In the solder reflow process, the organic film on the solder connection electrode 26 and the solder connection electrode 42 is dissolved in the solder layer 50. On the other hand, the organic film on the adhesive connecting electrode 12 and the adhesive connecting electrode 22 is thermally decomposed in a solder reflow process and then removed (see FIGS. 7A to 7D described later). The solder reflow process is performed in a non-oxidizing atmosphere having an oxygen concentration of 1% by volume or less.

However, the organic film 15 may remain on the surface of the adhesive connecting electrode 12 (see the broken line in FIG. 4). For example, when the FPC 10 does not undergo solder reflow processing, the organic film 15 is not thermally decomposed.
In addition, if it is before the grace time of about 3 days has passed since the organic film is thermally decomposed, adhesion is not caused on the surfaces of the electrodes 12 and 22 without generating an oxide film that greatly increases the connection resistance. A connecting step using the agent 30 can be performed. Even when stored in a low temperature, low humidity, or non-oxidizing atmosphere, the grace time becomes longer.

  At the time of connection by the adhesive 30, after removing the thermally decomposed organic film, the adhesive 30 is heated and melted while pressing the adhesive 30 toward the mother board 20 with a predetermined pressure via the FPC 10 (hereinafter, referred to as “adhesive 30”). This is referred to as “heat and pressure treatment”). As a result, the thermosetting resin in the adhesive 30 is cured, and the FPC 10 and the electrodes 12 and 22 of the mother board 20 are brought into strong contact with each other by the tightening force accompanying the contraction, and are brought into conduction. At this time, a part (conductive portion) of the adhesive connecting electrode 12 is electrically connected to each other without being covered with the organic film 15.

In the present embodiment, the adhesive connecting electrode 12 of the FPC 10 is processed so that the surface becomes rough by etching. However, not only etching but machining such as embossing may be used.
When the electrodes 12 and 22 are covered with the organic films 15 and 25, if there is a protrusion on the surface of at least one of the electrodes, the protrusion breaks through the organic films 15 and 25. Can come into contact. A bump may be disposed between the electrodes 12 and 22.

According to this example 1, in addition to the effect of the electrode structure, the following effects can be exhibited.
For example, when at least one of the FPC 10 and the mother board 20 undergoes a solder reflow process, the organic film is hardened. In that case, conduction between the electrodes 12 and 22 is hindered by the organic film, which may increase the connection resistance for electrical connection. In particular, when heated in a solder reflow furnace, the organic film tends to harden.
As a result, the protrusion of the adhesive connecting electrode 12 is less likely to break through the hardened organic film, resulting in an increase in connection resistance.

  On the other hand, in this embodiment, since the organic film on each of the electrodes 12 and 22 is thermally decomposed and then the connection process is performed, the protruding portion of the adhesive connecting electrode 12 and the adhesive connecting electrode 22 are easy. To touch. Moreover, since it processes in non-oxidizing atmosphere, generation | occurrence | production of the conduction defect by the oxidation of each electrode 12 and 22 surface can be suppressed.

When the organic film on the adhesive connecting electrode 12 does not go through the solder reflow process, the organic film 15 (see the broken line) remains. However, since the organic film 15 is not hardened, it is easy for the protrusions of the adhesive connecting electrode 12 to break through the organic film.
Therefore, it is possible to suppress the occurrence of poor conduction (such as an increase in connection resistance) between the adhesive connecting electrode 12 and the adhesive connecting electrode 22 (connected conductor).

In addition, when the organic film that has undergone the solder reflow process remains, the average film thickness of the organic film may fall within an appropriate range (for example, 0.05 μm or more and 0.5 μm or less) in order to achieve reliable conduction between conductors. In addition, it is necessary to increase the area ratio of the region having a small film thickness (for example, the area of the region having a thickness of 0.1 μm or less is set to 30% or more of the total area of the organic film).
On the other hand, in this embodiment, since the organic film is thermally decomposed, no problem occurs even if the film thickness of the organic film during the OSP process is 0.5 μm or more, for example.

-Example of adhesive connection structure 2-
FIG. 5 is a cross-sectional view showing an example 2 of the adhesive connection structure C. In the adhesive connection structure C, an adhesive 30 that is an anisotropic conductive adhesive (ACF) is used. That is, the adhesive 30 of this example is one in which conductive particles 36 are included in a resin composition 31 containing a thermosetting resin as a main component.
Also in this example, the mother board 20 includes a rigid board 21 and an adhesive connecting electrode 22 provided on the rigid board 21. Also in this example, the surfaces of the adhesive connecting electrode 12 and the adhesive connecting electrode 22 are both covered with the organic films 15 and 25 except for the conductive portion.
The electrodes 12 and 22 are electrically connected to each other through the conductive particles 36. The conductive particles 36 are made of a metal powder having a shape in which a large number of fine metal particles are connected in a straight chain or a needle shape.
Also in this example, there may be a portion where the electrodes 12 and 22 are in direct contact with each other as in Example 1.

Also in this example, before forming the adhesive connection structure C and the solder connection structure D, each electrode 12, 22, 26, 42 is covered with an organic film similar to the organic film 15 shown in FIG. In the solder reflow process, the organic film on the solder connection electrode 26 and the solder connection electrode 42 is dissolved in the solder layer 50. On the other hand, the organic film on the adhesive connecting electrode 22 and the adhesive connecting electrode 12 is thermally decomposed in a solder reflow process and then removed. Also in this example, the solder reflow process is performed in a non-oxidizing atmosphere having an oxygen concentration of 1% by volume or less.
However, when the FPC 10 does not go through the solder reflow process, the organic film 15 indicated by a broken line in the drawing remains.

At the time of connection, the thermosetting resin in the adhesive 30 is cured by the above-described heat and pressure treatment, and the electrodes 12 and 22 are connected to each other via the conductive particles 36 by the tightening force accompanying the shrinkage. .
In this example, conductive particles 36 having a shape in which a large number of fine metal particles are connected in a linear shape or a needle shape are included in the resin composition 31 from the beginning.
However, a resin composition 31 in which conductive particles made of fine metal particles are randomly dispersed may be used. Even in that case, by performing the heating and pressurizing treatment, the electrodes 12 and 22 have a shape in which a large number of fine metal particles are connected.

  As the anisotropic conductive adhesive used in Example 2, the conductive particles 36 are used in a widely used material, that is, in a resin composition mainly composed of an insulating thermosetting resin such as an epoxy resin. Distributed ones can be used. For example, an epoxy resin in which powder of conductive particles such as nickel, copper, silver, gold, or graphite is dispersed can be used. Here, examples of the thermosetting resin include an epoxy resin, a phenol resin, a polyurethane resin, an unsaturated polyester resin, a urea resin, and a polyimide resin. Among these, in particular, by using an epoxy resin as the thermosetting resin, it becomes possible to improve the film formability, heat resistance, and adhesive strength of the anisotropic conductive adhesive. Moreover, the anisotropic conductive adhesive should just have at least 1 sort (s) as a main component among the above-mentioned thermosetting resins.

  The epoxy resin to be used is not particularly limited. For example, bisphenol A type, F type, S type, AD type, or a copolymer type epoxy resin of bisphenol A type and bisphenol F type, or naphthalene type epoxy is used. Resin, novolac type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin and the like can be used. A phenoxy resin that is a high molecular weight epoxy resin can also be used.

  The molecular weight of the epoxy resin can be appropriately selected in consideration of the performance required for the anisotropic conductive adhesive. When a high molecular weight epoxy resin is used, the film-forming property is high, the melt viscosity of the resin at the connection temperature can be increased, and there is an effect that the connection can be made without disturbing the orientation of conductive particles described later. On the other hand, when a low molecular weight epoxy resin is used, the effect of increasing the crosslink density and improving the heat resistance is obtained. Moreover, the effect of reacting with the above-mentioned hardening | curing agent rapidly at the time of a heating, and improving adhesive performance is acquired. Therefore, it is preferable to use a combination of a high molecular weight epoxy resin having a molecular weight of 15000 or more and a low molecular weight epoxy resin having a molecular weight of 2000 or less in order to balance performance. In addition, the compounding quantity of a high molecular weight epoxy resin and a low molecular weight epoxy resin can be selected suitably. In addition, the “average molecular weight” here refers to a polystyrene-reduced weight average molecular weight obtained from gel permeation chromatography (GPC) developed with THF.

  Further, as the adhesive 30 used in this example and Example 1, an adhesive containing a latent curing agent can be used. This latent curing agent is a curing agent that is excellent in storage stability at low temperatures and hardly undergoes a curing reaction at room temperature, but rapidly undergoes a curing reaction by heat, light, or the like. As this latent curing agent, imidazole series, hydrazide series, boron trifluoride-amine complex, amine imide, polyamine series, tertiary amine, alkyl urea series and other amine series, dicyandiamide series, acid anhydride series, phenol series These modified products are exemplified, and these can be used alone or as a mixture of two or more.

  Among these latent curing agents, an imidazole-based latent curing agent is preferably used from the viewpoint that it is excellent in storage stability at a low temperature and fast curability. As the imidazole-based latent curing agent, a known imidazole-based latent curing agent can be used. More specifically, an adduct of an imidazole compound with an epoxy resin is exemplified. Examples of imidazole compounds include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-dodecylimidazole, 2-finylimidazole, 2-finyl-4-methylimidazole, and 4-methylimidazole. .

  In particular, these latent curing agents coated with a polymer material such as polyurethane and polyester, a metal thin film such as nickel and copper, and an inorganic material such as calcium silicate, This is preferable because it is possible to achieve both contradictory properties of storage stability and fast curability. Therefore, a microcapsule type imidazole-based latent curing agent is particularly preferable.

  According to Example 2, the same effect as Example 1 can be exhibited by thermally decomposing the organic film in the solder reflow process. However, in this example, the electrodes 12 and 22 are electrically connected to each other via the conductive particles 36.

Moreover, when using what has a shape shown in FIG. 5 as an anisotropic conductive adhesive, the following structures can be taken especially.
Specifically, as the anisotropic conductive adhesive, for example, an insulating thermosetting resin such as the above-described epoxy resin is a main component, and fine metal particles (for example, spherical metal fine particles or Conductive particles 36 formed of metal powder having a shape in which a large number of metal fine particles made of spherical resin particles plated with metal) are connected in a linear shape or a needle shape, that is, a shape having a large aspect ratio is dispersed. Can be used. The aspect ratio referred to here is the ratio of the short diameter (cross-sectional length of the conductive particles 36) R and the long diameter (length of the conductive particles 36) L of the conductive particles 36 shown in FIG. Say.

  By using such conductive particles 36, as the anisotropic conductive adhesive, the surface direction of the anisotropic conductive adhesive (the direction perpendicular to the thickness direction X and the direction of the arrow Y in FIG. 5). In the thickness direction X, while maintaining insulation between adjacent electrodes to prevent short circuit, a large number of the adhesive connecting electrodes 22 and the adhesive connecting electrodes 12 are separated from each other at once. And low resistance can be obtained.

  Further, in this anisotropic conductive adhesive, a magnetic field applied in the direction of the long diameter L of the conductive particles 36 in the thickness direction X of the anisotropic conductive adhesive at the time of forming the film-like anisotropic conductive adhesive. It is preferable to use it in the thickness direction X by passing through the inside. By having such an orientation, while maintaining the insulation between the adjacent electrodes described above to prevent short circuits, a large number of adhesive connecting electrodes 22 and the adhesive connecting electrodes 12 are formed at once and each. The effect that the conductive connection can be made independently is further improved.

  In addition, the metal powder used in the present invention preferably contains a ferromagnetic material in part, such as a single metal having ferromagnetism, two or more kinds of alloys having ferromagnetism, a metal having ferromagnetism and others. It is preferably any one of an alloy with the above metal and a composite containing a metal having ferromagnetism. This is because by using a metal having ferromagnetism, the magnetic properties of the metal itself enable the metal particles to be oriented using a magnetic field. For example, nickel, iron, cobalt, and two or more kinds of alloys containing these can be used.

  The aspect ratio of the conductive particles 36 is preferably 5 or more. By using such conductive particles 36, when an anisotropic conductive adhesive is used as the adhesive 30, the contact probability between the conductive particles 36 and the electrodes 12 and 22 is increased. Therefore, the electrodes 12 and 22 can be electrically connected to each other without increasing the blending amount of the conductive particles 36.

  The aspect ratio of the conductive particles 36 is directly measured by a method such as observation with a CCD microscope. In the case of the conductive particles 36 whose cross section is not a circle, the aspect ratio is obtained by setting the maximum length of the cross section as the short diameter. The conductive particles 36 do not necessarily have a straight shape, and can be used without any problems even if they are slightly bent or branched. In this case, the aspect ratio is obtained with the maximum length of the conductive particles 36 as the major axis.

-Connection method-
7A to 7D are cross-sectional views showing a procedure of a connection method for realizing the adhesive connection structure C and the solder connection structure D. FIG.
First, in the process shown in FIG. 7A, a mother board 20 (common base material) having an adhesive connection region Rc and a solder connection region Rd is prepared. In the mother board 20, an adhesive connection electrode 22 for connecting an adhesive is provided in the adhesive connection region Rc, and a solder connection electrode 26 for solder connection is provided in the solder connection region Rd.
Next, an organic film 25 that covers the adhesive connecting electrodes 22 and 26 is formed. In the present embodiment, the thermal decomposition temperature of the organic film 25 is lower than the solder reflow temperature.

  At this time, the protective film 28 that covers the organic film 25 is formed only in the adhesive connection region Rc. Specifically, the organic film 25 is covered with an adhesive tape or the like. A protective film 28 other than the adhesive tape can also be used.

Next, in the step shown in FIG. 7B, the electronic component 40 having the chip-side electrode 42 on a part of the chip 41 is mounted in the solder connection region Rd. At this time, the chip-side electrode 42 is aligned with the position of the solder connection electrode 26, and lead-free solder is interposed between the electrodes 26 and 42. Then, the mother board 20 and the electronic component 40 are put into a solder reflow furnace having a peak temperature of about 260 ° C. to reflow the solder. Thus, the electrodes 26 and 42 are joined to each other via the solder layer 50, whereby the electrodes 26 and 42 are electrically connected to each other.
Thereby, the solder connection structure D is formed in the solder connection region Rd.
Note that the organic film 25 covering the solder connection electrode 26 reacts with the flux contained in the lead-free solder and is dissolved in the solder layer 50.

  On the other hand, in the adhesive connecting region Rc, the solder reflow process is performed at a temperature equal to or higher than the thermal decomposition temperature of the organic film 25, whereby the organic film 25 on the adhesive connecting electrode 22 is thermally decomposed. The thermally decomposed organic film 25 remains as a liquid or carbonized powder inside the protective film 28. Or depending on the material of the organic film 25, it may become a gas.

  Next, in the step shown in FIG. 7C, the protective film 28 is removed, and the organic film 25 that has become liquid or powder is removed.

  Next, after the process shown in FIG. 7C, the adhesive connecting electrode 22 and the adhesive connecting electrode 12 of the FPC 10 are used in the process shown in FIG. Are electrically connected by bonding with an adhesive 30. Thereby, the adhesive connection structure C is formed in the adhesive connection region Rc. The procedure for forming the adhesive connection structure C is the same as described in Example 2 (see FIG. 5) of the adhesive connection structure.

  In the present embodiment, the organic film on the adhesive connecting electrode 12 of the FPC 10 is also thermally decomposed when the FPC 10 undergoes a solder reflow process. However, when the FPC 10 does not go through the solder reflow process, the organic film 15 remains without being thermally decomposed.

  As described above, the adhesive 30 (anisotropic conductive adhesive) containing the conductive particles 36 is mainly composed of a thermosetting resin. Therefore, the anisotropic conductive adhesive is once softened when heated, but is cured by continuing the heating. And when the preset curing time of the anisotropic conductive adhesive has elapsed, the maintenance state of the curing temperature of the anisotropic conductive adhesive and the pressure state are released, and cooling is started. Thus, the electrodes 12 and 22 are connected to each other through the conductive particles 36 in the adhesive 30, and the FPC 10 is mounted on the mother board 20.

7A to 7D show an example in which the adhesive connection structure C and the solder connection structure D are formed on the mother board 20 which is a PWB.
However, the adhesive connection structure C and the solder connection structure D may be formed on the FPC 10 using the FPC 10 as a common base material. In that case, the mother substrate 20 shown in FIG. 7 is replaced with the FPC 10, and the organic film 15 is formed on the adhesive connecting electrode 12. The processing procedure is as described above.
The FPC has not only a single-sided circuit type structure but also a double-sided circuit type structure. In the case of a double-sided circuit type structure, it is put in the solder reflow furnace twice.

According to the connection method of this embodiment, the following effects can be exhibited.
Usually, when the solder connection and the adhesive connection are performed on the same substrate, the organic film 25 is formed on both the solder connection electrode 26 and the adhesive connection electrode 22, and then the solder connection is performed. Connection by adhesive will be performed. This is because, when the adhesive is connected first, the adhesive is loosened during the solder reflow process, and the probability of connection failure increases.
In the connection method of the present embodiment, the organic film 25 formed on the adhesive connecting electrode 22 has a thermal decomposition temperature lower than the solder reflow temperature in the step shown in FIG. Therefore, in the step shown in FIG. 7B, the solder reflow process is performed at a temperature at which the organic film 25 is thermally decomposed.
In addition, since the treatment is performed in a non-oxidizing atmosphere, the progress of oxidation is suppressed even when the adhesive connecting electrode 22 is exposed due to the decomposition of the organic film 25, so that the occurrence of poor conduction can be suppressed.
As a result, in the step shown in FIG. 7D, the conductive particles 36 in the adhesive 30 easily come into contact with the adhesive connecting electrodes 12 and 22, and the adhesive connecting electrodes 12 and 22 are securely connected. Can be conducted.
Since the organic film 25 is thermally decomposed, it is not necessary to strictly manage the film thickness of the organic film 25 during the OSP process.

  Further, by forming the organic film 25 as an antioxidant film on the solder connection electrode 26, the connection strength (shear strength) between the electrodes 26 and 42 can be improved.

On the other hand, when the adhesive connection structure C is formed after the solder reflow process, the connection resistance for electrical connection between the electrodes 12 and 22 is increased as compared with the case where the adhesive connection structure C is not passed. There is a fear. This is presumably because the conductive particles 36 are less likely to break through the organic film 25 due to deterioration such as the organic film 25 becoming hard by being heated in a solder reflow furnace.
Therefore, by setting the average thickness Tm of the organic film 25 to 0.05 μm or more and 0.5 μm or less, the conductive particles 36 can easily break through the organic film 25 while suppressing the oxidation of the electrodes 12 and 22. . Therefore, even if the adhesive connection structure C is formed after the organic films 15 and 25 have passed through the solder reflow furnace, the electrical connection resistance between the electrodes 12 and 22 can be more reliably suppressed.

  In addition, by setting the area of the region where the thickness of the organic films 15 and 25 is 0.1 μm or less to 30% or more of the total area of the organic films 15 and 25, the conductive particles 36 can reliably break through the organic film 25. Area is secured. Therefore, even if the adhesive connection structure C is formed after the organic films 15 and 25 have passed through the solder reflow furnace, the electrical connection resistance between the electrodes 12 and 22 can be more reliably suppressed.

In summary, the following effects can be obtained in the present embodiment.
(1) In the adhesive connection structure C of the present embodiment, the surfaces of the adhesive connection electrode 22 of the mother board 20 and the adhesive connection electrode 12 of the FPC 10 are subjected to OSP treatment to form an antioxidant film. The organic films 15 and 25 are formed respectively. According to this structure, the process of forming an antioxidant film is simplified compared with the case where each electrode 12 and 22 is coat | covered with a gold plating layer. In addition, the material cost is reduced as compared with the case of using a noble metal such as gold. As a result, it is possible to reduce the manufacturing cost when connecting the electrodes 12 and 22 to each other.

In addition, since the organic films 15 and 25 are thermally decomposed in the solder reflow process before the connection with the adhesive 30, the conductive particles 36 easily come into contact with the adhesive connection electrodes 15 and 25. Therefore, it is possible to suppress deterioration in conductivity between the electrodes 12 and 22 caused by the conductive particles 36 not being able to penetrate the organic films 15 and 25.
Further, it is not necessary to strictly manage the average film thickness of the organic films 15 and 25 and the area ratio of the area where the film thickness is small during the OSP process.

  (2) In this embodiment, the conductive particles 36 in the adhesive 30 that is the anisotropic conductive adhesive to be used are a metal powder having a shape in which a number of fine metal particles are connected in a straight chain, or a needle shape. It is comprised by. According to this configuration, in the Y direction which is the surface direction of the adhesive 30, adhesion is maintained while maintaining insulation between adjacent adhesive connection electrodes 22 or between the adhesive connection electrodes 12 to prevent a short circuit. In the X direction, which is the thickness direction of the agent 30, it is possible to obtain a low resistance by electrically connecting a large number of the adhesive connecting electrodes 22 and the adhesive connecting electrodes 12 at a time and independently of each other. It becomes.

  (3) In the present embodiment, the aspect ratio of the conductive particles 36 is 5 or more. According to this configuration, when an anisotropic conductive adhesive is used, the contact probability between the conductive particles 36 is increased. As a result, it becomes easy to electrically connect the electrodes 12 and 22 to each other without increasing the blending amount of the conductive particles 36.

  (4) In this embodiment, what has a film shape is used as the adhesive 30 (anisotropic conductive adhesive) before forming the adhesive connection structure C. According to this configuration, the anisotropic conductive adhesive can be easily handled. Moreover, the workability | operativity at the time of forming the adhesive bond structure C by heat-pressing processing improves.

  (5) In the present embodiment, the conductive particles 36 are aligned in the major axis direction in the X direction which is the thickness direction of the adhesive 30 (anisotropic conductive adhesive) having a film shape. According to this configuration, in the Y direction which is the surface direction of the adhesive 30, adhesion is maintained while maintaining insulation between adjacent adhesive connection electrodes 22 or between the adhesive connection electrodes 12 to prevent a short circuit. In the X direction, which is the thickness direction of the agent 30, it is possible to obtain a low resistance by electrically connecting a large number of the adhesive connecting electrodes 22 and the adhesive connecting electrodes 12 at a time and independently of each other. It becomes.

  (6) In this embodiment, the flexible printed wiring board (FPC 10) is connected to the hard printed circuit board (PWB) which is the mother board 20. According to this configuration, it is possible to provide a multilayer conductive pattern structure at a lower cost than when the mother board 20 is an FPC. In addition, by connecting the FPC 10 on the mother board 20, as shown in FIG. 2, when connecting the FPC 10 to a connector on another board, as compared with the case where a hard printed wiring board is connected instead of the FPC 10, The degree of freedom of arrangement of other substrates can be improved. In addition, since the adhesive connection wiring electrodes 12 and 22 are covered with the organic films 15 and 25, the electrodes 12 and 22 can be made cheaper than the gold plating. The body can be provided at low cost.

In addition, you may change the said embodiment as follows.
In the above embodiment, a hard printed circuit board (PWB) is used as the mother board 20, but other configurations may be used. For example, a flexible printed wiring board (FPC) may be used as the mother board 20.

  In the above embodiment, the adhesive connection structure C is used to connect the electrodes of the FPC 10 and the mother board 20 that is a PWB, but the adhesive connection structure of the present invention is not limited to this. For example, an adhesive connection structure C may be used between a protruding electrode (or bump) of an electronic component such as an IC chip as a conductor and an electrode on a PWB or FPC.

  In place of the FPC 10 in the above embodiment, PWB may be mounted on the mother board 20. Further, electronic components may be mounted instead of the FPC 10.

  In the above embodiment, the water-soluble preflux treatment is applied to the adhesive connecting electrodes 12 and 22 as the OSP treatment. However, the OSP treatment may be a heat-resistant preflux treatment, for example. Moreover, although it was set as the acidic aqueous solution containing an azole compound as a water-soluble preflux process, another aqueous solution may be sufficient.

  In the above-described embodiment, both the adhesive connection electrodes 12 and 22 are subjected to OSP treatment. However, for example, only one adhesive connection electrode 12 or 22 may be subjected to OSP treatment. In this case, a noble metal plating layer such as a gold plating layer is formed on the other adhesive connecting electrode 22 or 12, but the effect (1) of the above embodiment can also be obtained by this.

Below, this invention is demonstrated based on an Example and a comparative example. In addition, this invention is not limited to these Examples, These Examples can be changed and changed based on the meaning of this invention, and they are excluded from the scope of the present invention. is not.
Example 1
(Production of adhesive)
As the conductive particles, linear nickel fine particles having a long diameter L distribution of 1 μm to 10 μm and a short diameter R distribution of 0.1 μm to 0.4 μm were used. Insulating thermosetting resins include two types of bisphenol A-type solid epoxy resins (trade name Epicoat 1256 and (2) Epicoat 1004 manufactured by Japan Epoxy Resin Co., Ltd.), naphthalene type epoxy. Resin [(3) manufactured by Dainippon Ink and Chemicals, trade name: Epicron 4032D] was used. In addition, a polyvinyl butyral resin [(4) manufactured by Sekisui Chemical Co., Ltd., trade name ESREC BM-1], which is thermoplastic, is used as a microcapsule type latent curing agent. Using a curing agent [trade name NOVACURE HX3941 manufactured by Asahi Kasei Epoxy Co., Ltd.], these (1) to (5) are (1) 35 / (2) 20 / (3) 25 / (4) 10 by weight ratio. / (5) Blended at a ratio of 30.

  These epoxy resin, thermoplastic resin, and latent curing agent were dissolved and dispersed in cellosolve acetate, and then kneaded with three rolls to prepare a solution having a solid content of 50% by weight. The Ni powder was added to this solution so that the metal filling rate represented by the ratio of the total solid content (Ni powder + resin) was 0.05% by volume, and then stirred using a centrifugal mixer. As a result, Ni powder was uniformly dispersed to produce a composite material for an adhesive. Next, this composite material was applied onto a PET film subjected to a release treatment using a doctor knife, and then dried and solidified in a magnetic field having a magnetic flux density of 100 mT at 60 ° C. for 30 minutes, whereby the linear particles in the film were formed. An anisotropic conductive adhesive having a film-like anisotropic conductivity having a thickness of 25 μm oriented in the magnetic field direction was produced.

(Preparation of printed wiring board)
A flexible printed wiring board was prepared in which 30 adhesive connection electrodes, which are copper electrodes having a width of 150 μm, a length of 4 mm, and a height of 18 μm, were arranged at intervals of 150 μm. By the OSP treatment, an antioxidant film containing 1,2-dimethylimidazole was formed on the adhesive connecting electrode. The thermal decomposition temperature was 210 ° C., the average film thickness was 0.10 μm, and the area ratio of the region having a thickness of 0.1 μm or less was 60%.

(Connection resistance evaluation)
The flexible printed wiring board was subjected to a solder reflow treatment with a peak temperature of 260 ° C. in a reflow bath in which the oxygen concentration was 1% or less by flowing nitrogen. Thereafter, the flexible printed wiring boards are arranged to face each other so as to form a daisy chain capable of measuring connection resistances at 30 consecutive locations, and the prepared adhesive is sandwiched between the flexible printed wiring boards at 190 ° C. While heating, pressure was applied at a pressure of 5 MPa for 15 seconds to bond them, and a joined body of flexible printed wiring boards was obtained. Next, in this joined body, the resistance value at 30 consecutive points connected via the adhesive connecting electrode, the adhesive, and the adhesive connecting electrode is obtained by the four-terminal method, and the obtained value is divided by 30. Thus, the connection resistance per connected place was obtained. And this evaluation was repeated 10 times and the average value of connection resistance was calculated | required. And the case where connection resistance was 50 m (ohm) or less was judged as what ensured electroconductivity.

(Connection reliability evaluation)
After the connection body produced as described above was allowed to stand for 500 hours in an 85 ° C., 85% RH high-temperature and high-humidity tank, the connection resistance was measured in the same manner as described above. And when the rate of increase in connection resistance was 50% or less, it was judged that the connection reliability was good.

(Example 2)
A joined body of flexible printed wiring boards is formed in the same manner as in Example 1 except that the average film thickness of the antioxidant film is 0.60 μm and the area ratio of the region where the thickness is 0.1 μm or less is 2%. Obtained. Thereafter, connection resistance evaluation and connection reliability evaluation were performed under the same conditions as in Example 1.

(Comparative Example 1)
A joined body of flexible printed wiring boards was obtained in the same manner as in Example 2 except that an antioxidant film containing 2-phenyl-4-methyl-5-benzylimidazole was formed on the adhesive connecting electrode. The thermal decomposition temperature of the antioxidant film was 310 ° C., the average film thickness was 0.60 μm, and the area ratio of the region having a thickness of 0.1 μm or less was 2%. Then, connection resistance evaluation and connection reliability evaluation were performed on the same conditions as the above-mentioned Example 1.

(Measurement of thermal decomposition temperature)
The thermal decomposition temperature was measured using differential scanning calorimetry (DSC). The heat generation start temperature when the temperature is raised at a rate of 10 ° C./min is defined as a thermal decomposition temperature.
(Film thickness measurement)
The cross section of the adhesive connecting electrode on which the antioxidant film is formed is observed. The film thickness is measured at intervals of 0.2 μm, and the area ratio of the region having an average film thickness of 0.1 μm or less is calculated.

Table 1 above shows the results of connection resistance evaluation and connection reliability evaluation of Examples 1 and 2 and the comparative example.
As shown in Table 1, in both cases of Examples 1 and 2, the initial connection resistance is 50 mΩ or less, and the connection resistance is sufficiently small and good. Further, in Examples 1 and 2, since the resistance increase rate is 50% or less, it can be seen that the connection reliability is also good.
On the other hand, in Comparative Example 1, the initial connection resistance was as high as 50 mΩ or more. Moreover, the rate of increase in resistance after standing in a high-temperature and high-humidity tank for 500 hours is also high. This is because the anti-oxidation film of Comparative Example 1 was hardened without being thermally decomposed during the solder reflow treatment, and the conductive particles could not surely break through the anti-oxidation film. This is considered to be because the contact between the electrode and the adhesive connecting electrode became unstable.
Further, when Examples 1 and 2 are compared, both the initial connection resistance and the rate of increase in resistance are substantially equal. Therefore, as in Example 2, even when the area ratio of the region where the average film thickness is 0.5 μm or more and the film thickness is 0.1 μm or less is reduced, the solder reflow process is performed in a non-oxidizing atmosphere. In addition, it can be seen that the antioxidant film is thermally decomposed, so that the initial connection resistance can be lowered and the connection reliability can be maintained high.

  The structure of the embodiment of the present invention disclosed above is merely an example, and the scope of the present invention is not limited to the scope of these descriptions. The scope of the present invention is indicated by the description of the scope of claims, and further includes meanings equivalent to the description of the scope of claims and all modifications within the scope.

  The electrode structure, wiring body, and adhesive connection structure of the present invention are members disposed in electronic devices such as mobile phones, cameras such as digital cameras and video cameras, portable audio players, portable DVD players, and portable laptop computers. It can be used for the electrode structure and the connection structure. Moreover, the release sheet body of the present invention can be used for connection of various wiring boards such as a rigid printed wiring board (PCB) and various electronic components in addition to the FPC.

10 FPC
11 Base film 12 Adhesive connecting electrode (connected conductor)
DESCRIPTION OF SYMBOLS 13 Coverlay 15 Organic film 20 Mother board 21 Rigid board 22 Adhesive connection electrode 25 Organic film 26 Solder connection electrode 30 Adhesive 31 Resin composition 36 Conductive particle 40 Electronic component 41 Chip 42 Chip side electrode (soldered connection) conductor)
50 Solder layer

Claims (9)

Preparing a substrate provided with an adhesive connecting electrode and a solder connecting electrode (a);
Coating the adhesive connecting electrode and the solder connecting electrode on the substrate with an organic film for preventing oxidation (b);
(C) joining the solder connection electrode to the solder connection conductor by performing a solder reflow process at a temperature at which the organic film is thermally decomposed in a non-oxidizing atmosphere;
After the step (c), a step (d) of electrically connecting the adhesive connecting electrode and the conductor to be connected to each other through an adhesive mainly composed of a thermosetting resin;
Only including,
In the step (d), a connection method using an anisotropic conductive adhesive containing conductive particles as the adhesive . The connection method according to claim 1,
Before the step (c), forming a protective film covering the organic film on the adhesive connecting electrode,
The connection method of removing the protective film after the step (c) and before the step (d). The connection method according to claim 1 or 2,
A connection method using a conductive particle made of metal powder having a shape in which a plurality of metal particles are connected in a chain or a needle shape as the adhesive. The connection method according to claim 3,
The connection method, wherein the conductive particles have an aspect ratio of 5 or more . In the connection method as described in any one of Claims 1-4 ,
A connection method using an adhesive having a film shape . In connection method according to claim 5 Symbol mounting,
The connection method using the thing which orientated the major axis direction of the said electroconductive particle as the said adhesive agent in the thickness direction of the adhesive agent which has the said film shape . In the connection method according to any one of claims 1 to 6 ,
In the step (a), a flexible printed wiring board is prepared as the base material . The connection structure formed using the connection method as described in any one of Claims 1-7. The electronic device assembled using the connection method as described in any one of Claims 1-8.

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