WO2010137413A1 - 電極構造、配線体、接着剤接続構造、電子機器およびその組立方法 - Google Patents
電極構造、配線体、接着剤接続構造、電子機器およびその組立方法 Download PDFInfo
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- WO2010137413A1 WO2010137413A1 PCT/JP2010/056554 JP2010056554W WO2010137413A1 WO 2010137413 A1 WO2010137413 A1 WO 2010137413A1 JP 2010056554 W JP2010056554 W JP 2010056554W WO 2010137413 A1 WO2010137413 A1 WO 2010137413A1
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- adhesive
- electrode
- connection structure
- organic film
- film
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/22—Secondary treatment of printed circuits
- H05K3/28—Applying non-metallic protective coatings
- H05K3/282—Applying non-metallic protective coatings for inhibiting the corrosion of the circuit, e.g. for preserving the solderability
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/14—Structural association of two or more printed circuits
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/321—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by conductive adhesives
- H05K3/323—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by conductive adhesives by applying an anisotropic conductive adhesive layer over an array of pads
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/36—Assembling printed circuits with other printed circuits
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/36—Assembling printed circuits with other printed circuits
- H05K3/361—Assembling flexible printed circuits with other printed circuits
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K1/00—Printed circuits
- H05K1/02—Details
- H05K1/14—Structural association of two or more printed circuits
- H05K1/148—Arrangements of two or more hingeably connected rigid printed circuit boards, i.e. connected by flexible means
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/02—Fillers; Particles; Fibers; Reinforcement materials
- H05K2201/0203—Fillers and particles
- H05K2201/0242—Shape of an individual particle
- H05K2201/0248—Needles or elongated particles; Elongated cluster of chemically bonded particles
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/03—Conductive materials
- H05K2201/0332—Structure of the conductor
- H05K2201/0364—Conductor shape
- H05K2201/0373—Conductors having a fine structure, e.g. providing a plurality of contact points with a structured tool
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/08—Magnetic details
- H05K2201/083—Magnetic materials
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
- H05K2201/10—Details of components or other objects attached to or integrated in a printed circuit board
- H05K2201/10613—Details of electrical connections of non-printed components, e.g. special leads
- H05K2201/10954—Other details of electrical connections
- H05K2201/10977—Encapsulated connections
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/10—Using electric, magnetic and electromagnetic fields; Using laser light
- H05K2203/104—Using magnetic force, e.g. to align particles or for a temporary connection during processing
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/303—Surface mounted components, e.g. affixing before soldering, aligning means, spacing means
- H05K3/305—Affixing by adhesive
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/36—Assembling printed circuits with other printed circuits
- H05K3/361—Assembling flexible printed circuits with other printed circuits
- H05K3/363—Assembling flexible printed circuits with other printed circuits by soldering
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49117—Conductor or circuit manufacturing
- Y10T29/49204—Contact or terminal manufacturing
- Y10T29/49208—Contact or terminal manufacturing by assembling plural parts
- Y10T29/4921—Contact or terminal manufacturing by assembling plural parts with bonding
- Y10T29/49211—Contact or terminal manufacturing by assembling plural parts with bonding of fused material
- Y10T29/49213—Metal
Definitions
- the present invention relates to an electrode structure that is electrically connected by an adhesive, a wiring body provided with the electrode structure, an adhesive connection structure, an electronic device, and an assembly method thereof.
- FPC flexible printed wiring board
- PWB or PCB rigid printed wiring board
- 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.
- 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).
- An object of the present invention is to provide an electrode structure capable of realizing an adhesive connection structure at a low cost while simplifying the manufacturing process, a wiring body having the electrode structure, an adhesive connection structure, and the like.
- the electrode structure of the present invention is an electrode structure that is electrically connected to a connected conductor by being bonded through an adhesive mainly composed of a thermosetting resin. And it has the electrode for an adhesive agent provided on the base material, and the organic film as an antioxidant film
- the organic film has a thermal decomposition temperature higher than the maximum temperature of the planned heat treatment.
- the most representative heat treatment to be planned is a solder reflow treatment.
- anisotropic conductive adhesives and insulating adhesives as described later, and this electrode structure is suitable for any adhesive.
- the treatment for forming the organic film is generally called preflux treatment (OSP treatment: Organic Solderability Preservation).
- the substrate include a substrate film of a printed wiring board and a base member for an electrode of an electronic component.
- the conductor to be connected include an electrode of another printed wiring board, an electrode of an electronic component, and an electrode of a connector.
- the present invention can be obtained by the present invention.
- gold plating for preventing oxidation has been applied to the adhesive connecting electrode.
- 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.
- 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.
- 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.
- the organic film may be thermally decomposed during solder reflow.
- the adhesive connecting electrode since the adhesive connecting electrode has a thermal decomposition temperature higher than the solder reflow temperature, the organic film reliably remains even after the solder reflow. Therefore, when this adhesive connecting electrode is provided on various base materials, solder connection and adhesive connection can be performed smoothly.
- the adhesive used for connecting the electrode for connecting an adhesive having this electrode structure and the electrode to be connected is preferably an anisotropic conductive adhesive containing conductive particles.
- the conductive particles can easily penetrate the organic film and contact the adhesive connecting electrode.
- the organic film Since the solder reflow temperature is about 260 ° C., it is more preferable that the organic film has a thermal decomposition temperature of 300 ° C. or higher. Further, the organic film contains an organic compound having a coordination atom capable of coordinating and bonding to the metal constituting the adhesive connecting electrode, thereby forming a complex with the metal constituting the adhesive connecting electrode, The pyrolysis 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.
- 2-phenylimidazole such as 2-phenyl-4-methyl-5-benzylimidazole, 2,4-diphenylimidazole, 2,4-diphenyl-5-methylimidazole
- benzimidazoles such as methylbenzimidazole, 2-alkylbenzimidazole, 2-arylbenzimidazole, and 2-phenylbenzimidazole.
- the average thickness of the organic film is preferably 0.05 ⁇ m or more and 0.5 ⁇ m or less.
- the antioxidant function of the organic film is lowered and the surface of the adhesive connecting electrode may be oxidized.
- the average thickness of the organic film exceeds 0.5 ⁇ m, it becomes difficult to break through the organic film with conductive particles or the like, and there is a possibility that poor connection between the adhesive connecting electrode and the connected electrode may occur.
- the area of the region where the thickness of the organic film is 0.1 ⁇ m or less is preferably 30% or more of the total area of the organic film. Thereby, the area
- the wiring body of the present invention is obtained by providing the above electrode structure on a wiring member. Thereby, it is possible to provide a wiring body that has an electrode structure that exhibits the above-described effects and realizes connection with an adhesive with another wiring board or electronic component.
- 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.
- flexible printed wiring boards are built into many electronic devices such as mobile phones, digital cameras, video cameras and other cameras, portable audio players, portable DVD players, portable notebook computers, and the like. , Special effects can be obtained.
- the adhesive connection structure of the present invention is a connection structure using an adhesive between the adhesive connecting electrode of the wiring body and the connected conductor of the connected component. And each part (electric conduction
- the adhesive is an insulating adhesive
- both or one of the electrodes for connecting the adhesive and the conductors to be connected (projections, etc.) or one of them breaks through the organic film, and the electrodes contact each other to conduct Is done.
- the adhesive is an anisotropic conductive adhesive, the conductive particles break through the organic film, come into contact with both electrodes, and a conductive state is established between the electrodes.
- the adhesive connection structure of the present invention due to the above-described effects, it is possible to realize an inexpensive connection structure while preventing the adhesive connection electrode from being oxidized by the organic film.
- the connected conductor is also preferably an adhesive connecting electrode covered with an organic film as an antioxidant film.
- 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 is preferable to use.
- 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.
- the aspect ratio of the conductive particles is 5 or more, the contact probability between the conductive particles increases.
- the adhesive connection structure can be smoothly formed without increasing the blending amount of the conductive particles.
- an anisotropic conductive adhesive 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
- the electronic device includes a common base material provided with the above-described adhesive connection structure and a solder connection structure in which conductors are electrically connected by being bonded to each other via solder.
- Various printed wiring boards and substrates can be used as the common base material.
- a conductor such as an electrode plated with gold may be present on a part of the electronic device.
- the electronic device assembling method of the present invention is performed in the following procedure. First, the adhesive connecting electrode and the solder connecting conductor of the base material (mother substrate) are covered with an organic film having a decomposition temperature higher than the reflow temperature of the solder. Next, a solder reflow process is performed in a non-oxidizing atmosphere containing an inert gas or hydrogen to join the solder connection conductor to the connection conductor. Thereafter, the electrode for connecting an adhesive and the conductor to be connected are bonded to each other through the above-described adhesive by a heating / pressurizing process. By this method, the organic film remains without being thermally decomposed even after the solder reflow process, so that the adhesive connection structure can be reliably formed.
- the formation of the adhesive connection structure is performed after the formation of the solder connection structure, it is possible to avoid the deterioration of the continuity of the adhesive connection structure that may occur after the solder reflow process. Therefore, the amount of gold plating used can be reduced as much as possible, and electronic equipment can be assembled at low cost.
- the electrode structure, wiring body, adhesive connection structure, electronic device, and assembly method of the present invention it is possible to perform adhesive connection at a low manufacturing cost while simplifying the manufacturing process.
- FIG. 1 is a perspective view schematically showing a structure of a mobile terminal which is an electronic apparatus according to an embodiment of the present invention.
- FIG. 2 is a cross-sectional view illustrating a configuration example of a connection portion of the mobile terminal according to the embodiment.
- FIG. 3 is a perspective view showing an end portion of the wiring body before forming the adhesive connection structure according to the embodiment.
- FIG. 4 is a cross-sectional view showing Example 1 of the adhesive connection structure formed between the flexible printed wiring board and the mother board.
- FIG. 5 is a cross-sectional view showing Example 2 of the adhesive connection structure.
- FIG. 6 is a diagram for explaining the ratio of the minor axis to the major axis of the conductive particles.
- FIG. 7A is a cross-sectional view showing step A of the procedure of the assembling method of the electronic component having the adhesive connection structure and the solder connection structure.
- FIG. 7B is a cross-sectional view illustrating step B of the procedure of the method for assembling the electronic component having the adhesive connection structure and the solder connection structure.
- FIG. 7C is a cross-sectional view illustrating step C of the procedure of the method for assembling the electronic component having the adhesive connection structure and the solder connection structure.
- 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.
- 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 is formed on the FPC 10 and includes an adhesive connection structure C via an anisotropic conductive adhesive 30.
- the input key board 145 is provided with a solder joint D in which electronic components are joined by solder.
- the display unit substrate 135 is also provided with a solder joint D in which electronic components are joined by solder.
- 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.
- the material of the base film 11 of the FPC 10 includes polyimide resin, polyester resin, glass epoxy resin, and the like.
- the material of the coverlay 13 generally, the same material as the base film is used.
- 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.
- 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.
- 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.). Not.
- the adhesive connecting electrode 12 is covered with an organic film 15 as an antioxidant film instead of the noble metal plating layer.
- the organic film 15 is formed by a water-soluble preflux process (OSP process: Organic Solderability Preservation).
- OSP process Organic Solderability Preservation
- 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 is preferably 25 to 40 ° C.
- the contact time between the water-soluble preflux and the adhesive connecting electrode 12 is preferably 30 to 60 seconds.
- the water-soluble preflux is an acidic aqueous solution containing an azole compound.
- 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.
- the organic film 15 has a decomposition temperature higher than the solder reflow temperature when the solder connection structure D is formed.
- 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.
- 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.
- a noble metal plating layer such as a gold plating layer is formed as an anti-oxidation film on an adhesive connecting electrode to be connected using an anisotropic conductive adhesive or an insulating adhesive.
- 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.
- connection strength shear strength
- a member to be mounted with solder is often mounted on a wiring body such as the FPC 10.
- the organic film 15 may be thermally decomposed.
- 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 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.
- FPC flexible printed wiring board
- PWB hard printed wiring board
- cable wiring electronic components, connectors, and the like. Also good.
- 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.
- 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 conductive 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.
- the thermosetting resin include an epoxy resin, a phenol resin, a polyurethane resin, an unsaturated polyester resin, a urea resin, and a polyimide resin.
- an epoxy resin as the thermosetting resin, it is possible to improve film formability, heat resistance, and adhesive strength.
- 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.
- 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 adhesive 30 is heated and melted through the FPC 10 while pressing the adhesive 30 in the direction of the mother board 20 at a predetermined pressure (hereinafter referred to as “heat-pressing process”).
- heat-pressing process a predetermined pressure
- 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.
- 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.
- the adhesive connecting electrode 12 of the FPC 10 is processed so that the surface becomes rough by etching.
- etching not only etching but machining such as embossing may be used.
- 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.
- the following effects can be exhibited.
- the distance between the electrodes 12 and 22 is smaller than when the adhesive connection structure C is not passed.
- the connection resistance for electrical connection will increase. This is because, when heated in a solder reflow furnace, the organic films 15 and 25 are hardened and changed in quality so that the protrusions of the adhesive connecting electrode 12 are less likely to penetrate the organic films 15 and 25.
- the average thickness Tm of the organic films 15 and 25 is 0.05 ⁇ m or more and 0.5 ⁇ m or less, the protrusions of the adhesive connecting electrode 12 are formed on the organic film 15 while suppressing the oxidation of the electrodes 12 and 22. , 25 is easily broken through. 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 reliably reduced.
- the adhesive connecting electrode 12 becomes the organic films 15 and 25 The area that breaks through increases. 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 reliably reduced.
- FIG. 5 is a cross-sectional view showing an example 2 of the adhesive connection structure C.
- an adhesive 30 that is an anisotropic conductive adhesive 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.
- the mother board 20 includes a rigid board 21 and an adhesive connecting electrode 22 provided on the rigid board 21. Also in this example, the surfaces of the adhesive connecting electrode 12 and the adhesive connecting electrode 22 are both covered with the organic films 15 and 25 except for the conductive portion.
- the electrodes 12 and 22 are electrically connected to each other through the conductive particles 36.
- the conductive particles 36 are made of a metal powder having a shape in which a large number of fine metal particles are connected in a straight chain or a needle shape. Also in this example, there may be a portion where the electrodes 12 and 22 are in direct contact with each other as in Example 1.
- 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 through the conductive particles 36 by the tightening force accompanying the shrinkage.
- conductive resin 36 having a shape in which a number of fine metal particles are linearly connected or a needle shape is included in resin composition 31 from the beginning.
- resin composition 31 in which conductive particles made of fine metal particles are randomly dispersed.
- a large number of fine metal particles are connected in a straight chain. It is preferable to use conductive particles 36 having a shape or a needle shape.
- 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.
- an epoxy resin in which powder of conductive particles such as nickel, copper, silver, gold, or graphite is dispersed can be used.
- the thermosetting resin include an epoxy resin, a phenol resin, a polyurethane resin, an unsaturated polyester resin, a urea resin, and a polyimide resin.
- 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.
- 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.
- 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.
- a low molecular weight epoxy resin is used, the effect of increasing the crosslink density and improving the heat resistance is obtained.
- the compounding quantity of a high molecular weight epoxy resin and a low molecular weight epoxy resin can be selected suitably.
- the “average molecular weight” here refers to a polystyrene-reduced weight average molecular weight obtained from gel permeation chromatography (GPC) developed with THF.
- an adhesive containing a latent curing agent can be used as the adhesive 30 used in this example and Example 1.
- 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.
- Examples of the latent curing agent include 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, and phenol series. These modified products are exemplified, and these can be used alone or as a mixture of two or more.
- imidazole-based latent hardeners are preferably used from the viewpoint of excellent storage stability at low temperature and fast curability.
- 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 the imidazole compound include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-dodecylimidazole, 2-finylimidazole, 2-finyl-4-methylimidazole, and 4-methylimidazole. .
- the following effects can be exhibited.
- the distance between the electrodes 12 and 22 is smaller than when the adhesive connection structure C is not passed.
- the connection resistance for electrical connection will increase. It is considered that this is because the conductive particles 36 are difficult to break through the organic films 15 and 25 due to deterioration such as hardening of the organic films 15 and 25 by being heated in the solder reflow furnace. It is done.
- the conductive particles 36 easily break through the organic films 15 and 25 while suppressing the oxidation of the electrodes 12 and 22. Become. 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.
- the conductive particles 36 break through the organic films 15 and 25.
- the area increases. 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.
- an 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.
- 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.
- the anisotropic conductive adhesive 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, a large number of the adhesive connecting electrodes 22 and the adhesive connecting electrodes 12 are separated from each other at a time while maintaining insulation between adjacent electrodes to prevent short circuit. And low resistance can be obtained.
- 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. With such an orientation, the above-described insulation between adjacent electrodes is maintained to prevent a short circuit, and a large number of adhesive connecting electrodes 22 and adhesive connecting electrodes 12 are connected at once and each. The effect that the conductive connection can be made independently is further improved.
- 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.
- 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.
- 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.
- the average thickness Tm of the organic films 15 and 25 is preferably 0.05 ⁇ m or more and 0.5 ⁇ m or less.
- the average thickness Tm of the organic films 15 and 25 on the electrodes 12 and 22 is set to 0.3 ⁇ m.
- the organic films 15 and 25 may not be able to sufficiently protect the surfaces of the electrodes 12 and 22 from being oxidized. As a result, the connection resistance between the electrodes 12 and 22 is increased.
- the average thickness Tm of the organic films 15 and 25 is larger than 0.5 ⁇ m, the surface oxidation of the electrodes 12 and 22 can be surely prevented by the organic films 15 and 25, but the conductivity between the electrodes 12 and 22 can be prevented. May not be secure. That is, when the average thickness Tm of the organic films 15 and 25 is larger than 0.5 ⁇ m, the conductive particles 36 of the anisotropic conductive adhesive may not be able to penetrate the organic films 15 and 25. At that time, the electrodes 12 and 22 cannot be electrically connected to each other by the anisotropic conductive adhesive.
- the area of the region where the thickness of the organic films 15 and 25 is 0.1 ⁇ m or less is preferably 30% or more of the total area of the organic film. Since the area of the region where the thickness of the organic films 15 and 25 is 0.1 ⁇ m or less is 30% or more of the total area of the organic film, the conductive particles 36 reliably penetrate the organic films 15 and 25, A region in contact with the electrodes 12 and 22 can be secured.
- -Electronic component assembly method- 7A to 7C are cross-sectional views showing a procedure of an assembling method of the electronic component having the adhesive connection structure C and the solder connection structure D.
- FIG. 7A a mother board 20 (common base material) having an adhesive connection region Rc and a solder connection region Rd is prepared.
- an adhesive connection electrode 22 for adhesive connection is provided in the adhesive connection region Rc
- a solder connection electrode 26 for solder connection is provided in the solder connection region Rd.
- an organic film 25 that covers the adhesive connecting electrodes 22 and 26 is formed.
- the material and thickness of the organic film 25 are as already described. In particular, it is important that the thermal decomposition temperature of the organic film 25 is higher than the solder reflow temperature.
- a protective film covering the organic film 25 may be formed only at the adhesive connection region Rc at this time.
- Step D 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.
- step B 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.
- 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.
- 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.
- the electrodes 26 and 42 are joined to each other via the solder layer 50 to electrically connect the electrodes 26 and 42 to each other.
- the solder connection structure D is formed in the solder connection region Rd.
- Step C shown in FIG. 7C the adhesive connection electrode 22 and the adhesive connection electrode 12 of the FPC 10 are electrically connected by bonding with the adhesive 30.
- the adhesive connecting electrode 12 on the FPC 10 is covered with an organic film 15.
- 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. 7A, when a protective film (such as an adhesive) that covers the organic film 25 is formed, the protective film is removed before bonding with the adhesive 30. (Process E) Thereby, the adhesive connection structure C is formed in the adhesive connection region Rc.
- 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.
- FIG. 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.
- 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.
- 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.
- the electronic component assembly 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.
- 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.
- the organic film may be thermally decomposed during the solder reflow process.
- the organic film 25 formed on the adhesive connecting electrode 22 has a thermal decomposition temperature higher than the solder reflow temperature. Therefore, even in the process B 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.
- gold plating is generally performed for the purpose of avoiding discoloration or the like. 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.
- the connection strength (shear strength) between the electrodes 26 and 42 can be improved.
- 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.
- the conductive particles 36 are less likely to break through the organic film 25 due to deterioration such as the organic film 25 becoming hard by being heated in a solder reflow furnace. Therefore, by setting the average thickness Tm of the organic film 25 to 0.05 ⁇ m or more and 0.5 ⁇ m or less, the conductive particles 36 can easily break through the organic film 25 while suppressing the oxidation of the electrodes 12 and 22. . Therefore, even if the adhesive connection structure C is formed after the organic films 15 and 25 have passed through the solder reflow furnace, the electrical connection resistance between the electrodes 12 and 22 can be more reliably suppressed.
- the conductive particles 36 can reliably break through the organic film 25. Area is secured. Therefore, even if the adhesive connection structure C is formed after the organic films 15 and 25 have passed through the solder reflow furnace, the electrical connection resistance between the electrodes 12 and 22 can be more reliably suppressed.
- the following effects can be obtained in 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.
- the process of forming an antioxidant film is simplified compared with the case where each electrode 12 and 22 is coat
- 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.
- the average thickness Tm of the organic films 15 and 25 is in the range of 0.05 ⁇ m to 0.5 ⁇ m.
- the average thickness Tm of the organic films 15 and 25 is 0.05 ⁇ m or more, an increase in connection resistance between the electrodes 12 and 22a due to oxidation of the surface of the underlying electrodes 12 and 22 can be suppressed.
- the average thickness Tm of the organic films 15 and 25 is 0.5 ⁇ m or less, the conductive particles 36 easily break through the organic films 15 and 25. Therefore, it is possible to suppress deterioration in conductivity between the electrodes 12 and 22 caused by the conductive particles 36 not being able to penetrate the organic films 15 and 25.
- 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.
- 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.
- 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.
- 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.
- the adhesive 30 (anisotropic conductive adhesive) before forming the adhesive connection structure C is a film having a film shape. According to this configuration, the anisotropic conductive adhesive can be easily handled. Moreover, the workability
- the conductive particles 36 having the major axis direction oriented in the X direction which is the thickness direction of the adhesive 30 (anisotropic conductive adhesive) having a film shape
- the conductive particles 36 having the major axis direction oriented in the X direction which is the thickness direction of the adhesive 30 (anisotropic conductive adhesive) having a film shape
- 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.
- 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.
- the flexible printed wiring board (FPC 10) is connected to the hard printed circuit board (PWB) which is the mother board 20.
- PWB hard printed circuit board
- 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.
- 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.
- 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.
- a hard printed circuit board PWB
- a flexible printed wiring board FPC
- 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.
- 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.
- a PWB may be mounted on the mother board 20.
- electronic components may be mounted instead of the FPC 10.
- 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.
- the acidic aqueous solution containing an azole compound as a water-soluble preflux process, another aqueous solution may be sufficient.
- both the adhesive connection electrodes 12 and 22 are subjected to the OSP process.
- only one adhesive connection electrode 12 or 22 may be subjected to the OSP process.
- 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.
- the average thickness Tm of the organic films 15 and 25 of the adhesive connecting electrodes 12 and 22 is the same value (that is, the average thickness Tm is 0.3 ⁇ m).
- the average thickness Tm may be different from each other.
- the average thickness Tm of the organic film 15 may be 0.3 ⁇ m
- the average thickness Tm of the organic film 25 may be 0.2 ⁇ m.
- Example 1 (Create adhesive)
- the conductive particles linear nickel fine particles having a long diameter L distribution of 1 ⁇ m to 10 ⁇ m and a short diameter R distribution of 0.1 ⁇ m to 0.4 ⁇ m 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
- a thermoplastic polyvinyl butyral resin [(4) manufactured by Sekisui Chemical Co., Ltd., trade name S REC BM-1]
- a microcapsule type latent curing agent (5) a microcapsule type imidazole type is used.
- 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.
- a flexible printed wiring board was prepared in which 30 adhesive connection electrodes, which are copper electrodes having a width of 150 ⁇ m, a length of 4 mm, and a height of 18 ⁇ m, were arranged at intervals of 150 ⁇ m.
- 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 ⁇ m
- the area ratio of the region having a thickness of 0.1 ⁇ m or less was 60%.
- the flexible printed wiring board was subjected to a solder reflow treatment with a peak temperature of 260 ° C. in a reflow bath in which the oxygen concentration was 1% or less by flowing nitrogen. Thereafter, the flexible printed wiring boards are arranged to face each other so as to form a daisy chain capable of measuring connection resistances at 30 consecutive locations, and the prepared adhesive is sandwiched between the flexible printed wiring boards at 190 ° C. While heating, pressure was applied at a pressure of 5 MPa for 15 seconds to bond them, and a joined body of flexible printed wiring boards was obtained.
- connection resistance 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 average thickness of the antioxidant film is 0.20 ⁇ m and the area ratio of the region where the thickness is 0.1 ⁇ m or less is 40%. Obtained. Thereafter, connection resistance evaluation and connection reliability evaluation were performed under the same conditions as in Example 1.
- Example 1 A joined body of flexible printed wiring boards was obtained in the same manner as in Example 1 except that an antioxidant film containing 2-methylimidazole was formed on the adhesive connecting electrode.
- the thermal decomposition temperature of the antioxidant film was 200 ° C.
- the average film thickness was 0.10 ⁇ m
- the area ratio of the region having a thickness of 0.1 ⁇ m or less was 60%. Then, connection resistance evaluation and connection reliability evaluation were performed on the same conditions as the above-mentioned Example 1.
- the thermal decomposition temperature was measured using differential scanning calorimetry (DSC).
- DSC differential scanning calorimetry
- the heat generation start temperature when the temperature is raised at a rate of 10 ° C./min is defined as a thermal decomposition temperature.
- the 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 ⁇ m, and the area ratio of the region having an average film thickness of 0.1 ⁇ m 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.
- the initial connection resistance is 50 m ⁇ or less, and the connection resistance is sufficiently small and good.
- the resistance increase rate is 50% or less, it can be seen that the connection reliability is also good.
- Comparative Example 1 the initial connection resistance was open and measurement was impossible. Therefore, the resistance increase rate cannot be measured. This is considered to be due to the fact that the antioxidant film of Comparative Example 1 was thermally decomposed during the solder reflow process, thereby oxidizing the surface of the adhesive connecting electrode.
- Example 1 has a smaller initial connection resistance and higher connection reliability. Therefore, it can be seen that the connection reliability increases particularly as the area ratio of the region where the average film thickness is small and the film thickness is 0.1 ⁇ m or less is high.
- 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.
- the release sheet body of this invention can be used for connection of various wiring boards, such as a rigid printed wiring board (PBC) other than FPC, and various electronic components.
- PBC rigid printed wiring board
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Abstract
Description
予定される熱処理としてもっとも代表的な熱処理は、半田リフロー処理である。
接着剤としては、後述するように、いわゆる異方導電性接着剤と、絶縁性接着剤とがあるが、この電極構造は、いずれの接着剤にも適合する。
上記有機膜を形成する処理は、一般的には、プリフラックス処理(OSP処理:Organic Solderability Preservation)と呼ばれている。
上記基材としては、プリント配線板の基材フィルム、電子部品の電極の下地部材などがある。被接続導体には、他のプリント配線板の電極、電子部品の電極、コネクタの電極などがある。
接着剤接続用電極には、従来、酸化防止用の金めっきが施されていた。それに対し、OSP処理によって有機膜を形成する工程は、金めっき層を形成する工程と比較して、製造工程が簡素化される。また、高価な金を使用しないので、材料コストも低減される。よって、本発明により、接着剤を用いた接続を行うための電極構造を安価に製造することが可能となる。
また、一般的に、接着剤接続用電極が設けられる基材には、半田接続用電極も設けられている。その場合、通常は、半田接続用電極と接着剤接続用電極の双方の上に有機膜を形成してから、半田リフロー工程を行い、その後、接着剤による接続を行うことになる。先に、接着剤接続を行うと、その後、半田リフローの際に、接着剤の締め付けが緩んで、接続不良をおこす確率が高くなるからである。反面、半田リフローの際に、有機膜が熱分解を生じるおそれもある。
本発明においては、接着剤接続用電極が半田リフロー温度よりも高い熱分解温度を有しているので、半田リフロー後にも、確実に有機膜が残存する。よって、この接着剤接続用電極を種々の基材上に設けると、半田接続と接着剤接続とを円滑に行うことができる。
また、有機膜が、接着剤接続用電極を構成する金属に配位結合可能な配位原子を有する有機化合物を含んでいることにより、接着剤接続用電極を構成する金属と錯体を形成し、熱分解温度を高めることができる。特に、1分子中に複数の配位原子を有する有機化合物は、架橋錯体を形成して熱分解温度を高くすることができるため好ましい。
具体的には、有機膜として、2-フェニル-4-メチル-5-ベンジルイミダゾール、2、4-ジフェニルイミダゾール、2,4-ジフェニル-5-メチルイミダゾール等の2-フェニルイミダゾール類や、5-メチルベンゾイミダゾール、2-アルキルベンゾイミダゾール、2-アリールベンゾイミダゾール、2-フェニルベンゾイミダゾール等のベンゾイミダゾール類から選ばれる少なくとも1つの有機化合物を含んでいるものを用いることが好ましい。
配線部材には、フレキシブルプリント配線板、リジッドプリント配線板などの配線板や、同軸ケーブル配線、フラットケーブル配線などのケーブル配線など、電極を有する多種の配線が含まれる。
特に、フレキシブルプリント配線板は、携帯電話、デジタルカメラ、ビデオカメラ等のカメラ、ポータブルオーディオプレーヤ、ポータブルDVDプレーヤ、ポータブルノートパソコンなど、多くの電子機器に内蔵されており、本発明を適用することで、格別の効果が得られる。
接着剤が絶縁性接着剤である場合には、接着剤接続用電極と被接続導体の各一部(突起など)の双方、または一方が有機膜を突き破って、各電極同士が接触して導通される。接着剤が異方導電性接着剤である場合には、導電性粒子が有機膜を突き破って、両電極に接触して、電極間が導通状態になる。
本発明の接着剤接続構造では、上述の効果により、有機膜によって接着剤接続用電極の酸化を防止しつつ、製造コストの安価な接続構造を実現することができる。
その場合、導電性粒子のアスペクト比が5以上であることにより、導電性粒子同士の接触確率が高くなる。その結果、導電性粒子の配合量を増やすことなく、接着剤接続構造を円滑に形成することができる。
その場合、導電性粒子の長径方向を、フィルム形状を有する接着剤の厚み方向に配向させることがより好ましい。これにより、接着剤の面方向においては、隣り合う電極間や導体間の絶縁を維持して短絡を防止することができる。一方、接着剤の厚み方向においては、多数の電極-導体間を一度に、かつ各々を独立して導電接続して、低抵抗を得ることが可能となる。
これにより、半田接続構造の形成時における半田リフローによっては、接着剤接続構造の有機膜が熱分解されることなく残存しうる。よって、接着剤接続構造と半田接続構造とを有し、安価な電子機器を提供することができる。
この方法により、半田リフロー処理を経ても有機膜が熱分解されずに残るので、接着剤接続構造を確実に形成することができる。また、接着剤接続構造の形成は、半田接続構造の形成後に行われるので、半田リフロー処理を経ると生じうる接着剤接続構造の導通性悪化を回避することができる。よって、金めっきの使用量をできるだけ減らして、安価に電子機器を組み立てることができる。
特に、半田リフロー処理の前に、有機膜の上に保護膜を形成し、半田リフロー後に保護膜を除去することが好ましい。この方法により、半田リフロー処理の後に、有機膜を確実に残すことができる。
-電子機器-
図1は、本発明の実施の形態に係る電子機器である携帯端末100の構造を概略的に示す斜視図である。
携帯端末100は、各種情報を表示するための表示部103と、入力部104と、ヒンジ部105とを備えている。表示部103には、液晶表示パネルを用いた表示装置106やスピーカ等が設けられている。入力部104には、入力キーやマイクが設けられている。ヒンジ部105は、入力部104と表示部103とを回動自在に連結している。
表示部103には、表示部筐体131と、表示部基板135とが主要部材として設けられている。表示部基板135は、表示装置106に表示用信号を送るための回路等を備えている。表示部筐体131は、互いに連結された第1筐体131aと第2筐体131bとを有している。そして、第1筐体131aと第2筐体131bとの間に、貫通穴133が設けられている。
また、入力キー基板145には、電子部品を半田により接合した半田接合部Dが設けられている。図示されていないが、同様に、表示部基板135にも、電子部品を半田により接合した半田接合部Dが設けられている。
図3は、本実施の形態の接着剤接続構造Cを形成する前の配線体Aの端部を示す斜視図である。配線体Aは、FPC10(基材)と、その端部に設けられた電極構造Bとを有している。
FPC10は、回路層(破線参照)が形成されたベースフィルム11と、ベースフィルム11を被覆するカバーレイ13とを備える構造が一般的である。回路層の端部は、被接続導体との電気的接続を行うための接着剤接続用電極12となっている。
それに対し、本実施の形態の電極構造Bにおいては、接着剤接続用電極12には、金めっき層や他の貴金属めっき層(銀めっき層、白金めっき層、パラジウムめっき層等)は、設けられていない。接着剤接続用電極12は、貴金属めっき層に代わる酸化防止膜としての有機膜15により、被覆されている。
OSP処理を施す方法としては、例えば、スプレー法、シャワー法、浸漬法等が用いられ、その後、水洗、乾燥させればよい。その際の水溶性プリフラックスの温度は、25~40℃が好ましく、水溶性プリフラックスと接着剤接続用電極12との接触時間は、30~60秒が好ましい。
従来は、異方導電性接着剤や絶縁性接着剤を用いた接続が行われる接着剤接続用電極上には、酸化防止膜として金めっき層などの貴金属めっき層が形成されている。
それに対し、本実施の形態では、接着剤接続用電極12が貴金属めっき層に代わるOSP膜である有機膜15によって覆われている。有機膜15の形成には、スプレー法、シャワー法、浸漬法等が用いられ、その後、水洗、乾燥させるのみにて形成される。そのため、金めっき層などの貴金属めっき層を形成する場合と比較して、酸化防止膜を形成する工程が簡素化される。また、金などの貴金属を用いる場合と比較して、材料コストも低減される。また、金めっき層を形成した場合と比較して、接着剤接続用電極12と被接続電極との間の接続強度(シェア強度)を向上させることができる。
ここで、本実施の形態では、接着剤接続用電極12上に形成された有機膜15が半田リフロー温度よりも高い熱分解温度を有している。そのため、接着剤接続用電極12が形成された基板が半田リフロー炉に通された場合でも、有機膜15が熱分解することなく、確実に残存する。
図4は、FPC10(フレキシブルプリント配線板)と、母基板20との間に形成される接着剤接続構造Cの例1を示す断面図である。この接着剤接続構造Cは、絶縁性接着剤(NCF)を用いて形成されるものである。
母基板20の接着剤接続用電極22は、リジッド基板21上に銅箔等の金属箔を積層し、金属箔を、常法により、露光、エッチングすることにより形成されている。
そして、NCFである接着剤30の締め付け力によって、両電極12、22が互いに強く接触しあって導通している。
各電極12、22が有機膜15、25で覆われている場合、少なくとも一方の電極の表面に突起部があれば、突起部が有機膜15、25を突き破るので、両電極12、22が確実に接触しうる。なお、両電極12、22間にバンプが配置されていてもよい。
たとえば、FPC10および母基板20の少なくとも一方が、半田リフロー工程を経た後に、接着剤接続構造Cを形成する場合には、半田リフロー炉を通さない場合と比較して、各電極12、22間の電気的に接続する接続抵抗が大きくなるおそれがある。これは、半田リフロー炉において加熱されることによって、有機膜15、25が硬質化する等、変質することで、接着剤接続用電極12の突起部が、有機膜15、25を突き破りにくくなっていることによると考えられる。
そこで、有機膜15、25の平均厚みTmを0.05μm以上0.5μm以下とすることにより、各電極12、22の酸化を抑制しつつ、接着剤接続用電極12の突起部が有機膜15、25を突き破りやすくなる。よって、有機膜15、25が半田リフロー炉を通った後に、接着剤接続構造Cを形成しても、各電極12、22間の電気的な接続抵抗を確実に小さく抑えることができる。
図5は、接着剤接続構造Cの例2を示す断面図である。この接着剤接続構造Cにおいては、異方導電性接着剤である接着剤30を用いている。すなわち、本例の接着剤30は、熱硬化性樹脂を主成分とする樹脂組成物31中に、導電性粒子36を含ませたものである。
そして、各電極12、22は、導電性粒子36を介して互いに導通している。導電性粒子36は、微細な金属粒子が多数直鎖状に繋がった形状、または針形状を有する金属粉末からなる。
なお、本例においても、例1のように電極12、22同士が直接接触している箇所が存在していてもよい。
この例では、当初から、樹脂組成物31中に微細な金属粒子が多数直鎖状に繋がった形状、または針形状を有する導電性粒子36を含ませている。
ただし、樹脂組成物31中に、微細な金属粒子からなる導電性粒子がランダムに分散したものを用いてもよいが、本実施の形態のごとく、微細な金属粒子が多数直鎖状に繋がった形状、または針形状を有する導電性粒子36を用いることが好ましい。
たとえば、FPC10および母基板20の少なくとも一方が、半田リフロー工程を経た後に、接着剤接続構造Cを形成する場合には、半田リフロー炉を通さない場合と比較して、各電極12、22間の電気的に接続する接続抵抗が大きくなるおそれがある。これは、半田リフロー炉において加熱されることによって、有機膜15、25が硬質化する等、変質することで、導電性粒子36が、有機膜15、25を突き破りにくくなっていることによると考えられる。
そこで、有機膜15、25の平均厚みTmを0.05μm以上0.5μm以下とすることにより、各電極12、22の酸化を抑制しつつ、導電性粒子36が有機膜15、25を突き破りやすくなる。よって、有機膜15、25が半田リフロー炉を通った後に、接着剤接続構造Cを形成しても、より確実に各電極12、22間の電気的な接続抵抗を小さく抑えることができる。
具体的には、異方導電性接着剤として、例えば、上述のエポキシ樹脂等の絶縁性の熱硬化性樹脂を主成分とし、当該樹脂中に、微細な金属粒子(例えば、球状の金属微粒子や金属でメッキされた球状の樹脂粒子からなる金属微粒子)が多数直鎖状に繋がった形状、または針形状を有する、所謂アスペクト比が大きい形状を有する金属粉末により形成された導電性粒子36が分散されたものを使用することができる。なお、ここで言うアスペクト比とは、図6に示す、導電性粒子36の短径(導電性粒子36の断面の長さ)Rと長径(導電性粒子36の長さ)Lの比のことをいう。
図7A~Cは、接着剤接続構造Cおよび半田接続構造Dを有する電子部品の組立方法の手順を示す断面図である。
まず、図7Aに示す工程Aで、接着剤接続領域Rcと、半田接続領域Rdとを有する母基板20(共通の基材)を準備する。母基板20において、接着剤接続領域Rcには接着剤接続用の接着剤接続用電極22が設けられており、半田接続領域Rdには半田接続用の半田接続用電極26が設けられている。
次に、各接着剤接続用電極22、26を覆う有機膜25を形成する。有機膜25の材質、厚みについては、すでに説明した通りである。特に、有機膜25の熱分解温度は、半田リフロー温度よりも高い点が重要である。
これにより、半田接続領域Rdにおいて、半田接続構造Dが形成される。
なお、図7Aに示す工程Aの際、有機膜25を覆う保護膜(粘着材など)を形成した場合には、接着剤30で接着する前に、保護膜を除去する。(工程E)
これにより、接着剤接続領域Rcにおいて、接着剤接続構造Cが形成される。
ただし、FPC10を共通の基材として、FPC10に接着剤接続構造Cと、半田接続構造Dとを形成してもよい。その場合には、図7に示す母基板20をFPC10と置き換え、接着剤接続用電極12上に有機膜15を形成することになる。処理の手順は、上述の通りである。
なお、FPCには、片面回路型構造だけでなく両面回路型構造もある。両面回路型構造の場合には、半田リフロー炉に2回入れることになる。
通常、半田接続と接着剤接続とを同じ基板上で行う場合、半田接続用電極26と接着剤接続用電極22の双方の上に有機膜25を形成してから、半田接続を行い、その後、接着剤による接続を行うことになる。先に、接着剤接続を行うと、その後、半田リフロー処理の際に、接着剤の締め付けが緩んで、接続不良をおこす確率が高くなるからである。反面、半田リフロー処理の際に、有機膜が熱分解を生じるおそれもある。
本実施の形態の電子回路の組立方法では、図7Aに示す工程Aで、接着剤接続用電極22上に形成された有機膜25が半田リフロー温度よりも高い熱分解温度を有している。そのため、図7Bに示す工程Bでも、有機膜25が熱分解することなく、確実に残存することになる。
なお、有機膜25の上に保護膜を形成すれば、より確実に、有機膜25を残存させることができる。よって、半田接続構造Dと接着剤接続構造Cとを、より確実に形成することができる。
なお、半田接続用電極26上を覆っていた有機膜25は、熱分解温度が半田リフロー温度よりも高くても、鉛フリー半田に含まれるフラックスなどと反応して、半田層50に溶け込む。したがって、半田接続構造Dの形成に支障が生じることはない。
本実施の形態では、母基板20のどの電極にも金めっきを施す必要がない。上述のように、有機膜25は、フラックスと反応して半田層50に溶け込むので、半田接続用電極26の上にも、金めっきに代えてOSP処理による有機膜25を選択することができる。よって、上述の製造コストの低減効果を顕著に発揮することができる。
そこで、有機膜25の平均厚みTmを0.05μm以上0.5μm以下とすることにより、各電極12、22の酸化を抑制しつつ、導電性粒子36が有機膜25を突き破りやすくすることができる。よって、有機膜15、25が半田リフロー炉を通った後に、接着剤接続構造Cを形成しても、より確実に各電極12、22間の電気的な接続抵抗を小さく抑えることができる。
(1)本実施形態の接着剤接続構造Cにおいては、母基板20の接着剤接続用電極22およびFPC10の接着剤接続用電極12のそれぞれの表面にOSP処理を施して、酸化防止膜である有機膜15、25をそれぞれ形成する構成としている。この構成によれば、各電極12、22が金めっき層で被覆される場合と比較して、酸化防止膜を形成する工程が簡素化される。また、金などの貴金属を用いる場合と比較して、材料コストも低減される。その結果、各電極12、22を互いに接続する際の製造コストを安価にすることが可能となる。
・上記実施形態においては、母基板20として硬質プリント基板(PWB)を使用しているが、他の構成であっても良い。たとえば、母基板20としてフレキシブルプリント配線板(FPC)を使用してもよい。
(実施例1)
(接着剤の作成)
導電性粒子として、長径Lの分布が1μmから10μm、短径Rの分布が0.1μmから0.4μmである直鎖状ニッケル微粒子を用いた。また、絶縁性の熱硬化性樹脂としては、2種類のビスフェノールA型の固形エポキシ樹脂〔(1)ジャパンエポキシレジン(株)製、商品名エピコート1256、および(2)エピコート1004〕、ナフタレン型エポキシ樹脂〔(3)大日本インキ化学工業(株)製、商品名エピクロン4032D〕を使用した。また、熱可塑性であるポリビニルブチラール樹脂〔(4)積水化学工業(株)製、商品名エスレックBM-1〕を使用し、マイクロカプセル型潜在性硬化剤としては、(5)マイクロカプセル型イミダゾール系硬化剤〔旭化成エポキシ(株)製、商品名ノバキュアHX3941〕を使用し、これら(1)~(5)を重量比で(1)35/(2)20/(3)25/(4)10/(5)30の割合で配合した。
幅150μm、長さ4mm、高さ18μmの銅電極である接着剤接続用電極が150μm間隔で30個配列されたフレキシブルプリント配線板を用意した。OSP処理により、接着剤接続用電極に、2-フェニル-4-メチル-5-ベンジルイミダゾールを含む酸化防止膜を形成した。その熱分解温度は、310℃、平均膜厚は、0.10μm、厚さ0.1μm以下となる領域の面積率は、60%であった。
上記フレキシブルプリント配線板に、窒素をフローすることで酸素濃度を1%以下としたリフロー槽内において、ピーク温度を260℃とした半田リフロー処理を施した。その後、フレキシブルプリント配線板同士を、連続する30箇所の接続抵抗が測定可能なデイジーチェーンを形成するように対向させて配置するとともに、これらフレキシブルプリント配線板の間に作製した接着剤を挟み、190℃に加熱しながら、5MPaの圧力で15秒間加圧して接着させ、フレキシブルプリント配線板同士の接合体を得た。次いで、この接合体において、接着剤接続用電極、接着剤、および接着剤接続用電極を介して接続された連続する30箇所の抵抗値を四端子法により求め、求めた値を30で除することにより、接続された1箇所あたりの接続抵抗を求めた。そして、この評価を10回繰り返し、接続抵抗の平均値を求めた。そして、接続抵抗が50mΩ以下の場合を、導電性を確保したものとして判断した。
(接続信頼性評価)
上記のように作成した接続体を、85℃、85%RH高温高湿槽中に500hr静置した後、上記と同様に、接続抵抗を測定した。そして、接続抵抗の上昇率が50%以下の場合を、接続信頼性が良好と判断した。
酸化防止膜の平均膜厚を0.20μm、厚さ0.1μm以下となる領域の面積率を40%としたこと以外は、実施例1と同様にして、フレキシブルプリント配線板同士の接合体を得た。その後、実施例1と同一条件で、接続抵抗評価及び接続信頼性評価を行った。
接着剤接続用電極に2-メチルイミダゾールを含む酸化防止膜を形成したこと以外は実施例1と同様にして、フレキシブルプリント配線板同士の接合体を得た。酸化防止膜の熱分解温度は、200℃、平均膜厚は0.10μm、厚さ0.1μm以下となる領域の面積率は、60%であった。その後、上述の実施例1と同一条件で、接続抵抗評価及び接続信頼性評価を行った。
熱分解温度は、示差走査熱量測定(Differential Scanning Calorimetry、 DSC)を用いて測定した。10℃/minの速度で昇温した際の発熱開始温度を熱分解温度とする。
(膜厚測定)
酸化防止膜が形成された接着剤接続用電極の断面を観察する。0.2μm間隔で膜厚を測定し、平均膜厚0.1μm以下の領域の面積率を算出する。
表1に示すように、実施例1、2のいずれの場合においても、初期接続抵抗が50mΩ以下であり、接続抵抗は、十分小さく良好である。また、実施例1、2では、抵抗上昇率が50%以下であるので、接続信頼性も良好であることがわかる。
一方、比較例1では、初期接続抵抗がオープンとなり、測定不可能であった。よって、抵抗上昇率も測定不可能である。この原因は、半田リフロー処理の際に、比較例1の酸化防止膜が熱分解し、これにより接着剤接続用電極の表面が酸化したことによると考えられる。
さらに、実施例1、2を比較すると、実施例1の方が初期接続抵抗も小さく、接続信頼性も高い。よって、平均膜厚が小さく、かつ、膜厚が0.1μm以下となる領域の面積率が高いほど、特に接続信頼性が高くなることがわかる。
11 ベースフィルム
12 接着剤接続用電極
13 カバーレイ
15 有機膜
20 母基板
21 リジッド基板
22 接着剤接続用電極
25 有機膜
26 半田接続用電極
30 接着剤
31 樹脂組成物
36 導電性粒子
40 電子部品
41 チップ
42 チップ側電極(被接続導体)
50 半田層
Claims (19)
- 熱硬化性樹脂を主成分とする接着剤を介して接着されることにより、被接続導体と電気的に接続される電極の構造であって、
基材上に設けられた接着剤接続用電極と、
前記接着剤接続用電極の表面を覆う酸化防止膜としての有機膜とを有し、
前記有機膜は、予定される熱処理の最高温度よりも高い熱分解温度を有している、電極構造。 - 請求項1記載の電極構造において、
前記熱処理は、半田リフロー処理である、電極構造。 - 請求項1または2記載の電極構造において、
前記接着剤は、導電性粒子を含有した異方導電性接着剤である、電極構造。 - 請求項1~3のうちいずれか1つに記載の電極構造において、
前記有機膜は、300℃以上の熱分解温度を有している、電極構造。 - 請求項1~4のうちいずれか1つに記載の電極構造において、
前記有機膜は、前記接着剤接続用電極を構成する金属に配位結合可能な配位原子を有する有機化合物を含んでいる、電極構造。 - 請求項1~5のうちいずれか1つに記載の電極構造において、
前記有機膜の平均厚みが、0.05μm以上0.5μm以下である、電極構造。 - 請求項1~6のうちいずれか1つに記載の電極構造において、
前記有機膜の厚みが0.1μm以下となる領域の面積は、有機膜全体の面積の30%以上である、電極構造。 - 請求項1~7のうちいずれか1つに記載の電極構造と、
前記電極構造が設けられた配線部材と、
を備えている配線体。 - 請求項8記載の配線体において、
前記配線部材は、フレキシブルプリント配線板である、配線体。 - 請求項1~7のうちいずれか1つに記載の電極構造の接着剤接続用電極と被接続導体との接着剤による接続構造であって、
前記接着剤接続用電極および被接続導体の各一部は、前記有機膜に覆われることなく互いに導通されている、接着剤接続構造。 - 請求項10記載の接着剤接続構造において、
前記被接続導体は、酸化防止膜としての有機膜により被覆された接着剤接続用電極である、接着剤接続構造。 - 請求項10または11記載の接着剤接続構造において、
前記接着剤は、導電性粒子を含有する異方導電性接着剤であり、
前記接着剤接続用電極および被接続導体の各一部は、前記導電性粒子を介して互いに導通されている、接着剤接続構造。 - 請求項12記載の接着剤接続構造において、
前記接着剤として、複数の金属粒子が鎖状に繋がった形状、または針形状を有する金属粉末からなる導電性粒子を含有したものを用いる、接着剤接続構造。 - 請求項13記載の接着剤接続構造において、
前記導電性粒子のアスペクト比が5以上である、接着剤接続構造。 - 請求項12~14のうちいずれか1つに記載の接着剤接続構造において、
前記接着剤として、フィルム形状を有するものを用いる、接着剤接続構造。 - 請求項15記載の接着剤接続構造において、
前記接着剤として、前記導電性粒子の長径方向を、前記フィルム形状を有する接着剤の厚み方向に配向させたものを用いている、接着剤接続構造。 - 請求項10~16のうちいずれか1つに記載の接着剤接続構造と、
導体同士が半田を介して接合されることにより電気的に接続される半田接続構造と、
が設けられた共通の基材を備えている電子機器。 - 請求項17記載の電子機器を組み立てる方法であって、
前記基材上の接着剤接続用電極と半田接続用導体とを、半田のリフロー温度よりも高い分解温度を有する有機膜で被覆する工程Aと、
非酸化性雰囲気中で半田リフロー処理することにより、前記半田接続用導体を被接続導体に接合する工程Bと、
加熱・加圧処理により、前記接着剤を介して前記接着剤接続用電極と被接続導体とを互いに接着させる工程Cと、
を含む電子機器の組立方法。 - 請求項18記載の電子機器の組立方法において、
前記工程Bの前に、前記有機膜の上に保護膜を形成する工程Dと、
前記工程Bの後、かつ工程Cの前に、前記保護膜を除去する工程Eと、
をさらに含む電子機器の組立方法。
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EP10780370.2A EP2437582A4 (en) | 2009-05-25 | 2010-04-13 | ELECTRODE STRUCTURE, CABLING ELEMENT, RESTRICTED STRUCTURE, ELECTRONIC DEVICE AND METHOD FOR THE PRODUCTION THEREOF |
US13/060,845 US8766437B2 (en) | 2009-05-25 | 2010-04-13 | Electrode structure, wiring body, adhesive connection structure, electronic device, and method for fabricating same |
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US20140205851A1 (en) * | 2013-01-23 | 2014-07-24 | Ravindranath V. Mahajan | Magnetic contacts for electronics applications |
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