JP2010283188A - Connection method, connection structure, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection method for inexpensively achieving 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. Surfaces of the respective electrodes 22, 26 are covered with an organic film 25, namely an oxidation inhibition film formed by OSP treatment. Connection by an adhesive 30 is performed to form the adhesive connection structure C, and then solder reflow processing is performed to form solder connection structure D. In this case, the connection is performed so that an increase in the connection resistance between an electrode 12 and the electrode 22 before and after the solder reflow processing is within a prescribed range. An increase in the connection resistance after the solder reflow processing can be suppressed while continuity is ensured in the respective electrodes 22, 26, thus smoothly forming the solder connection structure and the 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 covering the adhesive connecting electrode with the antioxidant film, the adhesive connecting electrode and the conductor to be connected are electrically bonded to each other through an adhesive mainly composed of a thermosetting resin. Connecting. Thereafter, the solder connection electrode is joined to the solder connection conductor by performing a solder reflow process. At this time, the connection is performed so that the increase in the connection resistance between the adhesive connecting electrode and the connected conductor before and after the solder reflow process is within a predetermined range.
As will be described later, the adhesive includes so-called anisotropic conductive adhesive (ACF) and insulating adhesive (NCF), and any adhesive may be used.
Examples of the antioxidant film include a noble metal plating layer such as gold plating and an organic film.
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.
It is known that the connection resistance increases when the solder reflow process is performed after the connection with the adhesive is performed first. The reason is that the solder reflow treatment causes a relaxation phenomenon of the adhesive and reduces the adhesive clamping force.
In the present invention, since the change in the connection resistance before and after the solder reflow process is within a predetermined range, the occurrence of poor conduction between the electrode for connecting the adhesive on the base material and the connected conductor on the connected member Can be suppressed.

In particular, before the solder reflow, the adhesive connection electrode - a connection resistance between the connected conductors and R _1, the adhesive strength of the adhesive and F _1, after solder reflow, the adhesive connecting electrode - the connection between conductors When the connection resistance is R ₂ and the adhesive strength of the adhesive is F ₂ ,
The following relational expressions (1), (2)
R ₂ <1.2 × R ₁ (1)
F ₂ > 0.8 × F ₁ (2)
It was found that the connection reliability is improved by connecting so that

For this purpose, the present inventors have confirmed that it is effective to use a resin material having a glass transition temperature after curing of 100 ° C. or higher as the resin composition of the adhesive.
The glass transition temperature is a temperature at which the rigidity and viscosity of the resin composition change abruptly. The higher the temperature, the lower the strength (clamping force) of the adhesive at a high temperature. Therefore, it is considered that by using a resin material having a glass transition temperature of 100 ° C. or higher, it is easy to make a connection that satisfies the above formulas (1) and (2).

By forming an organic film as the antioxidant film, manufacturing cost can be reduced. The treatment for forming the organic film is generally called preflux treatment (OSP treatment: Organic Solderability Preservation).
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, connection using an adhesive can be performed at low cost.

  The adhesive used is preferably an anisotropic conductive adhesive containing conductive particles. The conductive particles can easily penetrate the organic film and contact the adhesive connecting electrode.

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, since the repulsive force of electroconductive particle becomes small, the fall of adhesive strength and the raise of connection resistance can be suppressed.

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 bond 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)-(c) 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 (a silver plating layer, a platinum plating layer, a 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.
However, a noble metal plating layer such as a gold plating layer may be provided in place of the organic film 15.

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.

  However, in the present invention, as will be described later, since the connection with the adhesive is performed first and then the connection with the solder is performed, the organic film 15 is covered with the adhesive during the connection with the solder. Therefore, even if the organic film 15 is thermally decomposed in the solder reflow process, the thermally decomposed substance remains between the adhesive and the electrode. Therefore, although the connection resistance does not rapidly deteriorate, it is preferable that the thermal decomposition temperature of the organic film 15 is higher than the solder reflow temperature in consideration of long-term reliability.

  Examples of organic compounds that meet the above conditions include 2-phenyl-4-methyl-5-benzylimidazole, 2,4-diphenylimidazole, 2,4-diphenyl-5-methylimidazole and the like among the above azole compounds. Examples include 2-phenylimidazoles, and benzimidazoles such as 5-methylbenzimidazole, 2-alkylbenzimidazole, 2-arylbenzimidazole, and 2-phenylbenzimidazole.

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.

  In the present invention, as described later, since the connection with the adhesive 30 is performed first, and then the connection with the solder layer 50 is performed, the organic films 15 and 25 are bonded to the adhesive 30 when the connection with the solder layer 50 is performed. Covered by. Therefore, even if the organic films 15 and 25 are thermally decomposed in the solder reflow process, the thermally decomposed substance remains between the adhesive 30 and the electrodes 12 and 22. Therefore, although the connection resistance does not deteriorate rapidly, it is preferable that the thermal decomposition temperature of the organic films 15 and 25 is higher than the solder reflow temperature in consideration of long-term reliability.

When performing the solder reflow process without thermally decomposing the organic film before the connection with the adhesive, the management of the film thickness of the organic film 15 is important. This is because, as will be described later, it is necessary that part of the electrodes, conductive particles, and the like break through the organic film 15 to realize reliable conduction between the conductors. Specifically, the average film thickness of the organic film 15 is within an appropriate range (for example, 0.05 μm or more and 0.5 μm or less), or the area ratio of a region with a small film thickness is increased (for example, a region that is 0.1 μm or less). The area of the organic film 15 is 30% or more of the total area of the organic film 15).
On the other hand, in the present embodiment, as will be described later, since the connection with the adhesive is performed first, no problem occurs even if the film thickness of the organic film 15 during the OSP process is 0.5 μm or more, for example.

  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.

  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, naphthalene type epoxy resin, novolac type epoxy resin, biphenyl type epoxy resin, dicyclo A pentadiene type epoxy resin or the like can be used. A phenoxy resin that is a high molecular weight epoxy resin can also be used.

  In the present embodiment, among the various thermosetting resins, those having a glass transition temperature of 100 ° C. or higher are used. Examples of such a thermosetting resin include an epoxy resin, a phenol resin, and a polyimide resin.

Here, before forming the adhesive connection structure C and the solder connection structure D, the electrodes 12, 22, 26, and 42 are covered with the organic films 15 and 25, respectively. Then, the electrodes 12 and 22 are connected by an adhesive 30 to form an adhesive connection structure C, and then the electrodes 26 and 42 are connected by a solder layer 50 to form a solder connection structure D.
However, another antioxidant film such as a gold plating layer may be formed on each electrode 12, 22, 26, 42 instead of the organic films 15, 25.

At the time of connection by the adhesive 30, the adhesive 30 is heated and melted while being pressed at a predetermined pressure in the direction of the mother board 20 through the FPC 10 (hereinafter referred to as “heating and pressurizing process”). . 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.
At the time of connection by the solder layer 50, the mother board 20 and the electronic component 40 are put in a solder reflow furnace having a peak temperature of about 260 ° C. to reflow the solder. At this time, the organic film on the solder connection electrode 26 and the chip side electrode 42 (solder connection conductor) is dissolved in the solder layer 50.

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.

In the present embodiment, the increase in the connection resistance between the adhesive connecting electrodes 12 and 22 before and after the solder reflow process is performed within a predetermined range. Specifically, the connection resistance between the electrodes 12 and 22 before the solder reflow process is R ₁ , the adhesive strength of the adhesive 30 is F _1, and the connection resistance between the electrodes 12 and 22 after the solder reflow process is R _2. when the adhesive strength of the adhesive 30 was _{F 2,} the following equation (1), (2)
R ₂ <1.2 × R ₁ (1)
F ₂ > 0.8 × F ₁ (2)
Is established.
Specifically, the conditions for satisfying the relational expressions (1) and (2) are found by selecting the type of the thermosetting resin, setting the temperature of the solder reflow process, and the like.

According to this example 1, in addition to the effect of the electrode structure, the following effects can be exhibited.
Generally, when the adhesive connection structure C and the solder connection structure D exist on a common base material, a procedure for forming the solder connection structure D by first performing the solder reflow process is adopted. This is because if the adhesive connection structure C is formed first, the connection resistance may increase.

On the other hand, in the present embodiment, for example, the relational expression (1) is established so that the increase in connection resistance between the electrodes 12 and 22 before and after the solder reflow process is within a predetermined range. Connecting. Therefore, even if the adhesive connection structure C is formed before the solder connection structure D is formed, an increase in connection resistance between the adhesive connection electrode 12 (connected conductor) and the adhesive connection electrode 22 is suppressed. can do.
Further, the connection is performed so that, for example, the relational expression (2) is established so that the loosening of the tightening force of the adhesive 30 falls within a predetermined range. Therefore, increase in connection resistance (deterioration of connection reliability) during long-term use can be suppressed.

  Further, the adhesive connection electrodes 12 and 22 have been conventionally subjected to gold plating for preventing oxidation. 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, connection using an adhesive can be performed at low cost.

-Example of adhesive connection structure 2-
FIG. 5 is a cross-sectional view showing Example 2 of the adhesive connection structure C and the solder connection structure D. In FIG. 5, the same members as those in FIG. 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, an adhesive connection electrode 22 and a solder connection electrode 26 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 chip side electrode 42 (solder connection conductor) is dissolved in the solder layer 50.

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.

  As the anisotropic conductive adhesive used in Example 2, the conductive particles 36 are used in a widely used material, that is, 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” referred to here means a polystyrene-reduced weight average molecular weight determined 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 the second example, the same effect as in the first example can be exhibited by forming the adhesive connection structure C first and then forming the solder connection structure D under the same conditions as in the first example.

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, the conductive particles 36 having such a shape exist in an elastically deformed state by the fastening force of the adhesive 30. Therefore, even if the tightening force of the adhesive 30 is loosened by the solder reflow process, the contact with the electrodes 12 and 22 can be more reliably maintained by the restoring force from the elastically deformed state of the conductive particles 36. However, since the repulsive force of the conductive particles 36 is small, the force that weakens the tightening force of the adhesive 30 is small.

  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 includes 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 7C 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.

  Next, in the step shown in FIG. 7B, the adhesive connecting electrode 22 and the adhesive connecting electrode 12 of the FPC 10 are electrically connected by bonding with the 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.

Next, in the step shown in FIG. 7C, 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.

  When the thermal decomposition temperature of the organic films 15 and 25 is lower than the temperature of the solder reflow process, the adhesive reflow process is performed at a temperature equal to or higher than the thermal decomposition temperature. The organic films 15 and 25 on the connection electrodes 12 and 22 are thermally decomposed. The thermally decomposed organic films 15 and 25 remain as liquid or carbonized powder inside the adhesive 30. Or depending on the material of the organic films 15 and 25, it may become gas. In any case, since the adhesive connection structure C is formed, there is almost no risk of increasing the connection resistance.

  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 7C 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 solder connection and adhesive connection are performed on the same substrate, the organic film 25 is formed on the adhesive connection electrode 22, and then the solder connection is performed first, and then the connection using the adhesive is performed. It will be. This is because, when the adhesive is connected first, the adhesive tightening is loosened at the time of the solder reflow process, and the probability of causing a connection failure increases.
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.
In the connection method of the present embodiment, the adhesive connection structure C is first formed in the step shown in FIG. Therefore, in the step shown in FIG. 7B, the conductive particles 36 easily penetrate the organic films 15 and 25 and contact the electrodes 12 and 22, thereby ensuring conduction between the electrodes 12 and 22.
On the other hand, before and after the step shown in FIG. 7C, for example, the relational expressions (1) and (2) are established so that the increase in the connection resistance between the electrodes 12 and 22 is within a predetermined range. So that the connection is done. Therefore, even if the adhesive connection structure C is formed before the solder connection structure D is formed, an increase in connection resistance and a deterioration in reliability between the adhesive connection electrodes 12 and 22 can be suppressed.

  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.

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.

Moreover, in order to keep the increase in connection resistance between the electrodes 12 and 22 within a predetermined range, for example, connection by adhesion and connection by solder are performed so that the above relational expressions (1) and (2) are satisfied. ing. Therefore, even if the adhesive connection structure C is formed before the semi-connection structure D is formed, an increase in connection resistance between the adhesive connection electrode 12 and the adhesive connection electrode 22 (connected conductor) is suppressed. can do.
In addition, since the connection with the adhesive 30 is performed before the solder reflow process, 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 the adhesive connecting electrodes 22 and the adhesive connecting electrodes 12 at once and independently. 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 the adhesive connecting electrodes 22 and the adhesive connecting electrodes 12 at once and independently. 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, so that the connection between the mother board 20 and the FPC 10 is possible. 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.
Alternatively, all the electrodes 12, 22, 26, 42 may be provided with a gold plating layer without providing an organic film by OSP treatment.

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
(Create 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 & 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 in 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 with a magnetic flux density of 100 mT at 60 ° C. for 30 minutes. An anisotropic conductive adhesive having a film-like anisotropic conductivity having a thickness of 25 μm oriented in the magnetic field direction was produced. The glass transition temperature after curing of the anisotropic conductive adhesive was 115 ° C.

(Create 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 2-phenyl-4-methyl-5-benzylimidazole was formed on the adhesive connecting electrode. The thermal decomposition temperature was 310 ° 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%.

(Preparation of joined body)
The flexible printed wiring boards are arranged facing each other so as to form a daisy chain capable of measuring connection resistance at 30 consecutive locations, and the adhesive created between these flexible printed wiring boards is sandwiched and heated to 190 ° C. However, it was made to press and adhere for 15 seconds at a pressure of 5 MPa to obtain a joined body of flexible printed wiring boards.
(Measurement of connection resistance and adhesive strength)
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. The connection resistance per connected place was determined. The case where the connection resistance was 50 mΩ or less was judged as ensuring conductivity. Moreover, the adhesive strength when the obtained joined body was peeled by 90 ° in the electrode direction at a speed of 50 mm / min was measured. When the adhesive strength was 300 N / m or more, it was judged that good adhesive strength was obtained.
(Measurement of connection resistance and adhesive strength after solder reflow treatment)
Next, in a solder reflow bath, after performing solder reflow treatment with a peak temperature of 260 ° C., connection resistance and adhesive strength were measured in the same manner as described above.
(Connection reliability evaluation)
The connection body prepared as described above was allowed to stand for 500 hours in an 85 ° C., 85% RH high-temperature and high-humidity tank, and then 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)
Flexible printed wiring as in Example 1, except that the weight ratio of the adhesive was (1) 35 / (2) 20 / (3) 0 / (4) 20 / (5) 5 A joined body between the plates was obtained. The glass transition temperature after curing of the adhesive was 80 ° C.

(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.
(Measurement of glass transition temperature of adhesive)
The glass transition temperature of the adhesive was measured using a dynamic viscoelasticity measuring apparatus after the adhesive was completely cured. The temperature at which tan δ takes the maximum value when measured at a frequency of 1 Hz at a temperature increase rate of 10 ° C./min is defined as the glass transition temperature.

Table 1 above shows the evaluation results of connection resistance, adhesive strength, and connection reliability 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.
In Example 1, the connection resistance R ₁ before solder reflow processing is R ₁ = 42 (mΩ), the adhesive strength F ₁ = 620 (N / m), and the connection resistance R ₂ after solder reflow processing = 43 (mΩ), adhesive strength F ₂ = 600 (N / m) of the adhesive, the above relational expressions (1) and (2)
R ₂ = 43 <1.2 × R ₁ = 1.2 × 42 = 50.4 (1)
F ₂ = 600> 0.8 × F ₁ = 0.8 × 620 = 496 (2)
Is satisfied.
Similarly, in Example 2, the connection resistance R ₁ before solder reflow processing is 43 (mΩ), the adhesive strength F ₁ = 680 (N / m), and the connection resistance R ₂ after solder reflow processing. = 45 (milliohms), the adhesive strength of the adhesive _F 2 = 650 because the (N / m), the above equation (1), (2)
R ₂ = 45 <1.2 × R ₁ = 1.2 × 43 = 51.6 (1)
F ₂ = 650> 0.8 × F ₁ = 0.8 × 680 = 544 (2)
Is satisfied.
That is, in the first and second embodiments, the connection resistance is increased so as to be within a predetermined range.

On the other hand, in the comparative example 1, although the initial connection resistance is high, the conductivity is somehow secured. However, after the solder reflow process, the connection resistance exceeds 50 (mΩ), and the resistance increase rate is ∞ (infinite).
In Comparative Example 1, the connection resistance R ₁ before solder reflow processing is R ₁ = 49 (mΩ), the adhesive strength F ₁ = 320 (N / m), and the connection resistance R ₂ after solder reflow processing = 0.99 (milliohms), since an adhesive strength of the adhesive _{F 2 = 120 (N / m} ),
R ₂ = 150> 1.2 × R ₁ = 1.2 × 49 = 58.8
F ₂ = 120 <0.8 × F ₁ = 0.8 × 320 = 256
Thus, the above relational expressions (1) and (2) are not satisfied. That is, in the case of Comparative Example 1, the connection resistance is not increased so as to be within a predetermined range.
This is because the adhesive strength of the adhesive decreased from 320 (N / m) to 120 (N / m) during the solder reflow process, that is, the adhesive tightening force was loosened. This is thought to be due to the deterioration of continuity due to. That is, it can be seen that the connection reliability is deteriorated because the composition of the adhesive cannot satisfy the relational expressions (1) and (2).
Furthermore, when Examples 1 and 2 are compared, both the connection resistance and the rate of increase in resistance are substantially equal. Therefore, as in Example 2, even if the average film thickness is 0.5 μm or more and the area ratio of the region where the film thickness is 0.1 μm or less is reduced, the above relational expressions (1) and (2) are satisfied. It turns out that connection reliability becomes high by setting it as the mixing | blending of the adhesive agent which is materialized.

  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 this invention can be used for connection of various wiring boards, such as a rigid printed wiring board (PCB) other than FPC, and various electronic components.

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 (12)

Preparing a substrate provided with an adhesive connecting electrode and a solder connecting electrode (a);
Coating the adhesive connection electrode and the solder connection electrode on the substrate with an antioxidant film (b);
After the step (b), a step (c) of electrically connecting the adhesive connecting electrode and the conductor to be connected to each other via an adhesive mainly composed of a thermosetting resin;
After the step (c), a step (d) of joining the solder connection conductor to the solder connection conductor by performing a solder reflow process in a non-oxidizing atmosphere;
Including
A connection method, wherein an increase in connection resistance between the adhesive connecting electrode and the connected conductor is performed within a predetermined range before and after the step (d). The connection method according to claim 1,
The connection resistance between the adhesive connecting electrode and the connected conductor after the step (c) and before the step (d) is R _1, and the adhesive strength of the adhesive is F ₁ ,
Definitive after the step (d), the adhesive connection electrode - when the connection resistance between the connected conductors and R _2, the adhesive strength of the adhesive was F _2,
The following relational expressions (1), (2)
_{R 2 <1.2 × R 1 (} 1)
F ₂ > 0.8 × F ₁ (2)
The connection method is performed so that is established. The connection method according to claim 1 or 2,
The connection method using the resin material whose glass transition temperature after hardening is 100 degreeC or more as a resin composition of the said adhesive agent. In the connection method according to any one of claims 1 to 3,
In the step (c), an organic film is formed as the antioxidant film. In the connection method as described in any one of Claims 1-4,
In the step (c), a connection method using an anisotropic conductive adhesive containing conductive particles as the adhesive. The connection method according to claim 5, wherein
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 6, wherein
The connection method, wherein the conductive particles have an aspect ratio of 5 or more. In the connection method according to any one of claims 5 to 7,
A connection method using an adhesive having a film shape. The connection method according to claim 8, wherein
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 9,
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 1-10.   The electronic device assembled using the connection method as described in any one of Claims 1-10.

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