JP5356111B2 - Connection method, connection structure, and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of connection for achieving an adhesive connection structure inexpensively while simplifying a manufacturing process, and to provide an electronic apparatus. <P>SOLUTION: A mother board 20 includes: a rigid board 21; and an adhesive connecting electrode 22 and a solder connecting electrode 26 formed on the rigid board 21. The surface of each of electrodes 22 and 26 is covered with an organic film 25. After forming a solder connection structure D with a solder layer 50, the organic film 25 is softened by immersing the organic film 25 in an organic solvent 61 in a bath 60 of the organic solvent. Then, electrodes 12 and 22 are connected by using an adhesive 30 to form an adhesive connection structure C. Organic films 15 and 25 are an antioxidation film formed by an OSP treatment, and the organic film 25 is subjected to softening treatment after solder reflow etc. Accordingly, the solder connection structure and the adhesive connection structure can be formed smoothly. <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 on which an adhesive connecting electrode is provided. Then, after covering the adhesive connecting electrode with an organic film for preventing oxidation, the organic film is softened. 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 will be described later, the adhesive includes so-called anisotropic conductive adhesive (ACF) and insulating adhesive (NCF), and any adhesive may be used.
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 include electrodes of other printed wiring boards, electrodes of electronic components, and electrodes of connectors.
Examples of the softening treatment of the organic film include a treatment of swelling a resin component and a treatment of cutting a cross-link between polymers in the resin with an electron beam or the like.

For example, it can be carried out by bringing the organic film into contact with a liquid or vapor of an organic solvent containing at least one functional group selected from a hydroxyl group, a ketone group, an ester group and an ether group.
The compound containing a hydroxyl group (also referred to as a hydroxy group) is a compound represented by R—OH (R is an organic group such as an alkyl group or an aryl group). Examples of the compound containing a hydroxyl group include alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, and phenols.
The compound containing a ketone group is a compound represented by R, R′—C═O (R and R ′ are organic groups such as an alkyl group and an aryl group). Examples of the compound containing a ketone group include acetone, MEK (methyl ethyl ketone), and cyclohexane.
The compound containing an ester group is a compound represented by R—COO—R ′ (R and R ′ are organic groups such as an alkyl group and an aryl group). Examples of the compound containing an ester group include ethyl acetate and butyl acetate.
The compound containing an ether group is a compound represented by R—O—R ′. Examples of the compound containing an ether group include methyl ethyl ether and diethyl ether.
Further, it may be a compound having a plurality of functional groups as described above. For example, there are ethylene glycol monoethyl ether having a hydroxyl group and an ether group, and ethylene glycol monoethyl ether acetate having an ester group and an ether group.
As a method of bringing the organic film into contact with the liquid or vapor of these organic solvents, the organic film is immersed in a solution containing these compounds, or a liquid or vapor containing these compounds is sprayed onto the organic film. There is a method of wiping the organic film with a cloth containing a solution containing a compound. It has been confirmed that the organic film is softened by these methods.

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, since the connection process is performed after the organic film is softened, in any case, it becomes easy for the electrodes and conductive particles to break through the organic film, and the adhesive connection on the substrate Occurrence of poor conduction between the electrode for connection and the connected conductor on the connected member can be suppressed.
Moreover, by softening the organic film, the range of the film thickness of the organic film that can suppress the occurrence of poor conduction with the connected conductor on the connected member is expanded. In practice, it is possible to form an organic film with little concern about the film thickness.

  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, 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.

In general, a solder connection electrode is also provided on a base material on which an adhesive connection electrode is provided. In that case, usually, after forming an organic film on both the solder connection electrode and the adhesive connection electrode, the solder reflow process is performed, and then the connection with the adhesive is performed. This is because, if the adhesive is connected first, then the adhesive tightening is loosened during solder reflow, and the probability of connection failure increases. On the other hand, the organic film may be thermally decomposed during solder reflow.
Therefore, since the adhesive connecting electrode has a thermal decomposition temperature higher than the solder reflow temperature, the organic film reliably remains after the solder reflow. Thereafter, by performing the softening treatment of the organic film, connection by solder and connection by an adhesive can be smoothly performed.

In addition, since the temperature of solder reflow is about 260 degreeC, it is more preferable that the organic film has a thermal decomposition temperature of 300 degreeC or more.
Examples of the organic film having a high thermal decomposition temperature include the following. When the organic film contains an organic compound having a coordination atom capable of coordinating and bonding to the metal constituting the adhesive connection electrode, it forms a complex with the metal constituting the adhesive connection electrode, and is thermally decomposed. The temperature can be increased. In particular, an organic compound having a plurality of coordination atoms in one molecule is preferable because a thermal decomposition temperature can be increased by forming a crosslinked complex.
Specifically, as an organic film, 2-phenylimidazoles such as 2-phenyl-4-methyl-5-benzylimidazole, 2,4-diphenylimidazole, 2,4-diphenyl-5-methylimidazole, It is preferable to use one containing at least one organic compound selected from benzimidazoles such as methylbenzimidazole, 2-alkylbenzimidazole, 2-arylbenzimidazole, and 2-phenylbenzimidazole.

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 in many electronic devices such as mobile phones, digital cameras, camcorders such as video cameras, portable audio players, portable DVD players, portable laptop 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 realize a reduction in 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 formed between a flexible printed wiring board and a motherboard. It is sectional drawing which shows Example 2 of adhesive bond 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 103 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, epoxy resin, acrylic resin, polyimide resin, polyurethane resin, etc. are 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 or other noble metal plating layer (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.
Further, the organic film 15 may be subjected to a softening process described later.

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 higher 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 higher, more preferably 300 ° C. or higher is used.

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. There are 2-phenylimidazoles and benzimidazoles such as 5-methylbenzimidazole, 2-alkylbenzimidazole, 2-arylbenzimidazole, and 2-phenylbenzimidazole.
However, when the solder reflow process is not performed before the connection process using the adhesive, the organic film 15 does not need to have a thermal decomposition temperature higher than the solder reflow temperature. Therefore, it is not limited to the above compounds.

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.

Generally, a member to be mounted with solder is often mounted on a wiring body such as the FPC 10. In that case, if the organic film 15 is formed and then passed through a solder reflow furnace, the organic film 15 may be thermally decomposed.
Here, in the present embodiment, the organic film 15 formed on the adhesive connecting electrode 12 has a thermal decomposition temperature higher than the solder reflow temperature. Therefore, even when the substrate on which the adhesive connecting electrode 12 is formed is passed through a solder reflow furnace, the organic film 15 remains reliably without being thermally decomposed.

  The substrate on which the electrode structure B is provided is not limited to a flexible printed wiring board (FPC), but may be 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 formed between the FPC 10 (flexible printed wiring board) 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 and an adhesive connection electrode 22 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 facing the lower side of the base film 11. In the present embodiment, 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 adhesive connecting electrode 22 of the mother board 20 is formed by laminating a metal foil such as a copper foil on the rigid board 21, and exposing and etching the metal foil by a conventional method.
The two electrodes 12 and 22 are in strong contact with each other and are electrically connected by the tightening force of the adhesive 30 that is NCF.

  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.

In addition, the organic films 15 and 25 are subjected to a softening process before being subjected to the heating and pressurizing process. However, only the organic film 15 or 25 that has undergone the solder reflow process may be softened.
The softening treatment can be performed, for example, by bringing the organic film into contact with a liquid or vapor of an organic solvent containing at least one functional group selected from a hydroxyl group, a ketone group, an ester group, and an ether group.
The compound containing a hydroxyl group (also referred to as a hydroxy group) is a compound represented by R—OH (R is an organic group such as an alkyl group or an aryl group). Examples of the compound containing a hydroxyl group include alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, and phenols.
The compound containing a ketone group is a compound represented by R, R′—C═O (R and R ′ are organic groups such as an alkyl group and an aryl group). Examples of the compound containing a ketone group include acetone, MEK (methyl ethyl ketone), and cyclohexanone.
The compound containing an ester group is a compound represented by R—COO—R ′ (R and R ′ are organic groups such as an alkyl group and an aryl group). Examples of the compound containing an ester group include ethyl acetate and butyl acetate.
The compound containing an ether group is a compound represented by R—O—R ′. Examples of the compound containing an ether group include methyl ethyl ether and diethyl ether.
Further, it may be a compound having a plurality of functional groups as described above. For example, there are ethylene glycol monoethyl ether having a hydroxyl group and an ether group, and ethylene glycol monoethyl ether acetate having an ester group and an ether group.
As a method of bringing the organic films 15 and 25 into contact with the liquid or vapor of these organic solvents, the organic films 15 and 25 are immersed in a solution containing these compounds, or vapor containing these compounds is used as the organic films 15 and 25. 25, or a method of wiping the organic film with a cloth containing a solution containing these compounds. It has been confirmed that the organic films 15 and 25 are softened by these treatments.

  At the time of connection, the adhesive 30 is heated and melted through the FPC 10 while pressing the adhesive 30 in the direction of the mother board 20 with a predetermined pressure (hereinafter referred to as “heat-pressing 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 and are brought into conduction by the tightening force accompanying the shrinkage. At this time, each part (conductive portion) of the adhesive connecting electrode 12 and the adhesive connecting electrode 22 (connected conductor) is electrically connected to each other without being covered with the organic films 15 and 25.

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 or is left for a long time and exposed to ultraviolet rays, the organic films 15 and 25 may be hardened. In that case, conduction between the electrodes 12 and 22 is hindered by the organic films 15 and 25, and there is a possibility that the connection resistance for electrical connection increases. In particular, when heated in a solder reflow furnace, the organic films 15 and 25 tend to harden.
In addition, the organic films 15 and 25 formed by the OSP process have a range of hardness depending on the type of the constituent material, and in some cases, it may be necessary to use a considerably hard material.
As a result, the protruding portions of the adhesive connecting electrode 12 in the organic films 15 and 25 are less likely to break through the hardened organic films 15 and 25, leading to an increase in connection resistance.

  On the other hand, in this embodiment, since the organic film 15, 25 is softened before the connection process is performed, the protrusion of the adhesive connecting electrode 12 can easily break through the organic film 15, 25. It is possible to suppress the occurrence of poor conduction (such as an increase in connection resistance) between the agent connecting electrode 12 and the adhesive connecting electrode 22 (connected conductor).

In addition, when the softening treatment is not performed on the organic films 15 and 25 that have undergone the solder reflow process, the average film thickness is in an appropriate range (for example, 0.05 μm or more and 0.5 μm or less) in order to realize reliable conduction between conductors. Or the area ratio of the region having a small film thickness is increased (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 the present embodiment, by softening the organic films 15 and 25, the appropriate range of the average film thickness of the organic film is expanded, and there is almost no need to increase the area ratio of the small film thickness region. In practice, the organic films 15 and 25 can be formed with little concern about the film thickness.

-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 place where the electrodes 12 and 22 are in direct contact with each other as in Example 1.

  Also in this example, the organic films 15 and 25 are subjected to the same softening process as in Example 1 before the heating and pressurizing process. However, only the organic film 15 or 25 that has undergone the solder reflow process may be softened. The specific method of the softening process is as described in Example 1.

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 such a case, by performing the heating and pressurizing treatment, a shape in which a large number of fine metal particles are connected is formed between the electrodes 12 and 22.

  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 a low temperature and hardly undergoes a curing reaction at room temperature, but rapidly undergoes a curing reaction by heat or light. 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 organic films 15 and 25 are provided, and the organic films 15 and 25 are further subjected to the softening process, so that the same effect as in the first example can be exhibited. However, in this example, the conductive particles 36 break through the organic films 15 and 25 and are in contact with the electrodes 12 and 22.

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. Accordingly, 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 higher than the solder reflow temperature.

  Although not shown in FIG. 7A, a protective film that covers the organic film 25 may be formed only at the adhesive connection region Rc at this time. Specifically, the organic film 25 is covered with an adhesive tape or the like. A protective film 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, so that 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.

Next, in the process shown in FIG. 7C, the above-described organic film 25 is softened. In this example, the mother board 20 and the entire electronic component 40 are immersed in an organic solvent 61 (for example, isopropanol (IPA)) stored in the organic solvent tank 60. The temperature of the organic solvent 61 is about 50 ° C., and the immersion time is about 1 minute.
Thereby, the organic film 25 is softened by swelling or the like. Note that vapor of an organic solvent such as IPA may be sprayed onto the organic film 25. In that case, since it is not necessary to immerse the entire mother board 20 and the electronic component 40 in the organic solvent, the type of the organic solvent can be selected without much considering the influence on other members.

Next, in the step shown in FIG. 7D, the adhesive connecting electrode 22 and the adhesive connecting electrode 12 of the FPC 10 are electrically connected by bonding with the adhesive 30. 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.
Before the step shown in FIG. 7D, the adhesive connecting electrode 12 on the FPC 10 is covered with an organic film 15. At this time, the softening process of the organic film 15 may be performed, but if the organic film 15 is not subjected to the solder reflow process, the softening process is not necessary if unnecessary.
However, the softening treatment of the organic film 15 also has an advantage that it is not necessary to manage the average film thickness of the organic film 15 and the area ratio of a region having a small film thickness.
7A, when a protective film (such as an adhesive material) that covers the organic film 25 is formed, the protective film is removed before bonding with the adhesive 30.
Thereby, the adhesive connection structure C is formed in the adhesive connection region Rc.

  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 the present embodiment, in addition to the effects of the electrode structure B and the adhesive connection structure C, 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. On the other hand, the organic film may be thermally decomposed during the solder reflow process.
In the connection method of the present embodiment, in the step shown in FIG. 7A, the organic film 25 formed on the adhesive connection electrode 22 has a thermal decomposition temperature higher than the solder reflow temperature. Therefore, even in the step shown in FIG. 7B, the organic film 25 remains reliably without being thermally decomposed.
If a protective film is formed on the organic film 25, the organic film 25 can be left more reliably. Therefore, the solder connection structure D and the adhesive connection structure C can be more reliably formed.
The organic film 25 covering the solder connection electrode 26 reacts with the flux contained in the lead-free solder and melts into the solder layer 50 even if the thermal decomposition temperature is higher than the solder reflow temperature. Accordingly, there is no problem in forming the solder connection structure D.

Although it is not always necessary to perform gold plating on the solder connection electrode 26, gold plating is generally performed for the purpose of avoiding discoloration.
In the present embodiment, it is not necessary to apply gold plating to any electrode of the mother board 20. As described above, since the organic film 25 reacts with the flux and dissolves in the solder layer 50, the organic film 25 by OSP treatment can be selected on the solder connection electrode 26 instead of gold plating. Therefore, the effect of reducing the manufacturing cost can be remarkably exhibited.

  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 to 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, the organic film 25 cured by the solder reflow process can be softened by performing the softening process on the organic film 25 before the connecting step using the adhesive. 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.
Further, it is not necessary to strictly manage the average film thickness of the organic film 25 and the area ratio of the region having a small film thickness.

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 respectively formed. 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, the manufacturing cost for connecting the electrodes 12 and 22 to each other can be reduced.

Moreover, even if the organic films 15 and 25 are hardened by solder reflow treatment or exposure to ultraviolet rays, the organic films 15 and 25 are softened before connection with the adhesive 30, so that the conductive particles 36 are formed. It becomes easy to break through the organic films 15 and 25. Therefore, it is possible to suppress deterioration in conductivity between the electrodes 12 and 22 due to 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.

  (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 connecting 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, but 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 embodiment, both the adhesive connection electrodes 12 and 22 are subjected to the OSP treatment. However, for example, only one adhesive connection electrode 12 or 22 may be subjected to the 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
(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 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.

(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%.

(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. Then, after dipping the adhesive connection electrode in an isopropanol bath heated to 50 ° C. for 1 minute, the flexible printed wiring boards face each other so as to form a daisy chain capable of measuring 30 consecutive connection resistances. The adhesive prepared between these flexible printed wiring boards was sandwiched between the flexible printed wiring boards, and heated and heated to 190 ° C. for 15 seconds under a pressure of 5 MPa to be bonded to obtain a joined body of flexible printed wiring boards. 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)
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 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 area ratio of the region where the average thickness of the antioxidant film is 0.60 μm and 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)
Bonding of flexible printed wiring boards in the same manner as in Example 2 except that an antioxidant film made of the same material as in Example 2 was used and the softening process by immersion in an isopropanol bath was not performed after the solder reflow process. Got the body.
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 rate of increase in resistance is 50% or less, it can be seen that the connection reliability is substantially good.
On the other hand, in Comparative Example 1, the initial connection resistance was as high as 50 mΩ or more. Moreover, after leaving it to stand in a high-temperature and high-humidity tank for 500 hours, the connection was opened, and the resistance increase rate was ∞ (infinite). The reason for this is that, although the antioxidant film of Comparative Example 1 was hardened during the solder reflow treatment, the softening treatment was not performed, so that the conductive particles could not reliably break through the antioxidant film. Therefore, it is considered that the contact between the conductive particles and the adhesive connecting electrode becomes unstable.
Further, when Examples 1 and 2 are compared, Example 1 has a smaller initial connection resistance and higher connection reliability. Therefore, it can be seen that the softening effect becomes more remarkable as the area ratio of the region where the average film thickness is smaller and the film thickness is 0.1 μm or less is higher.

  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 a camera such as a digital camera and a video camera, a portable audio player, a portable DVD player, and a portable laptop computer in addition to a mobile phone. 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
DESCRIPTION OF SYMBOLS 11 Base film 12 Adhesive connection electrode 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 (connected conductor)
50 Solder layer 60 Organic solvent tank 61 Organic solvent

Claims (10)

Preparing a substrate provided with an adhesive connecting electrode (a);
Covering the adhesive connecting electrode on the substrate with an organic film for preventing oxidation (b);
(C) performing a softening treatment on the organic film by bringing the organic film into contact with a liquid or vapor of an organic solvent containing at least one functional group selected from a hydroxyl group, a ketone group, an ester group and an ether group ;
After the step (c), a step (d) of electrically connecting the adhesive connecting electrode and the body to be connected to each other through an adhesive mainly composed of a thermosetting resin;
Including connection method. The connection method according to claim 1,
In the step (d), a connection method using an anisotropic conductive adhesive containing conductive particles as the adhesive . The connection method according to claim 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 2-4 ,
A connection method using an adhesive having a film shape . The connection method according to claim 5 , 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 6 ,
In the step (a), as the base material, a base material provided with solder connection electrodes is prepared,
After the step (b) and before the step (c), the method further includes a step (e) of joining the solder connection electrode to the solder connection conductor by performing a solder reflow process in a non-oxidizing atmosphere. Connection method. In the connection method as described in any one of Claims 1-7,
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 1-8 . The electronic device assembled using the connection method as described in any one of Claims 1-8 .

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