WO2010140469A1 - 接続方法,接続構造および電子機器 - Google Patents
接続方法,接続構造および電子機器 Download PDFInfo
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- WO2010140469A1 WO2010140469A1 PCT/JP2010/058356 JP2010058356W WO2010140469A1 WO 2010140469 A1 WO2010140469 A1 WO 2010140469A1 JP 2010058356 W JP2010058356 W JP 2010058356W WO 2010140469 A1 WO2010140469 A1 WO 2010140469A1
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- adhesive
- connection
- solder
- electrode
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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
- H05K3/36—Assembling printed circuits with other printed circuits
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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
- H05K3/36—Assembling printed circuits with other printed circuits
- H05K3/361—Assembling flexible printed circuits with other printed circuits
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
- C23F11/00—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent
- C23F11/08—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids
- C23F11/10—Inhibiting corrosion of metallic material by applying inhibitors to the surface in danger of corrosion or adding them to the corrosive agent in other liquids using organic inhibitors
- C23F11/14—Nitrogen-containing compounds
- C23F11/149—Heterocyclic compounds containing nitrogen as hetero atom
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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
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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
- H05K3/30—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
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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
- H05K3/30—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
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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
- H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
- H05K3/4007—Surface contacts, e.g. bumps
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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
- 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
- H05K2201/09—Shape and layout
- H05K2201/09209—Shape and layout details of conductors
- H05K2201/09372—Pads and lands
- H05K2201/094—Array of pads or lands differing from one another, e.g. in size, pitch, thickness; Using different connections on the pads
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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
- H05K2201/10—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
- 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
- H05K2201/10992—Using different connection materials, e.g. different solders, for the same connection
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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
- H05K2203/30—Details of processes not otherwise provided for in H05K2203/01 - H05K2203/17
- H05K2203/308—Sacrificial means, e.g. for temporarily filling a space for making a via or a cavity or for making rigid-flexible PCBs
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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
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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
- H05K3/30—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
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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
- H05K3/30—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
- H05K3/341—Surface mounted components
- H05K3/3431—Leadless components
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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
- Y10T156/00—Adhesive bonding and miscellaneous chemical manufacture
- Y10T156/10—Methods of surface bonding and/or assembly therefor
Definitions
- 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 device.
- a printed wiring board such as a flexible printed wiring board (FPC) or a hard printed wiring board (PWB or PCB) provided with an adhesive connecting electrode such as a copper electrode, and a connecting electrode such as a copper electrode were formed. It is used for bonding with a wiring substrate such as a glass substrate, and bonding between a printed wiring board and an electronic component such as an IC chip.
- FPC flexible printed wiring board
- PWB or PCB hard 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, the resin in the adhesive flows due to heating and pressurization, for example, sealing the gap between the adhesive connection electrode formed on the surface of the printed wiring board and the connection electrode formed on the surface of the wiring board. At the same time, a part of the conductive particles is engaged between the connecting electrode and the adhesive connecting electrode, and electrical connection is achieved.
- each of the adhesive connection electrode of the printed wiring board and the connection electrode of the wiring board is plated with gold for the purpose of preventing oxidation and ensuring conductivity (for example, Patent Documents). 1).
- 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.
- connection method of the invention described in claims 1 to 3 is performed using a base material provided with an adhesive connecting electrode. Then, after covering the adhesive connecting electrode with an organic film for preventing oxidation (b1), the organic film is removed or thinned (c1). Thereafter, a connection step (d1) is performed in which the adhesive connecting electrode and the conductor to be connected are electrically bonded to each other through an adhesive mainly composed of a thermosetting resin.
- the adhesive includes so-called anisotropic conductive adhesive (ACF) and insulating adhesive (NCF), and any adhesive may be used.
- ACF anisotropic conductive adhesive
- NCF insulating adhesive
- the process for forming the organic film is generally called a preflux process (OSP process: Organic Solderability Preservation).
- Examples of the base material include a base film for 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.
- the invention described in claims 1 to 3 provides the following operational effects.
- gold plating for preventing oxidation has been applied to the adhesive connecting electrode.
- the manufacturing process is simplified in the step (b1) of forming the organic film by the OSP process as compared with the step 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.
- the organic film formed by the OSP process has a range of hardness depending on the type of constituent material and the subsequent environment.
- the hardness may be extremely high.
- an insulating adhesive 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.
- an anisotropic conductive adhesive containing conductive particles 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.
- the connecting step there is a possibility that poor conduction occurs between the adhesive connecting electrode and the connected conductor.
- the process (d1) is performed after the treatment (c1) for removing or thinning the organic film, so that in any case, the electrode and the conductor to be connected are reliably directly or electrically conductive. They are electrically connected to each other through the conductive particles. Therefore, generation
- the organic film is finally removed or thinned, conduction between the adhesive connecting electrode and the connected conductor can be ensured regardless of the film thickness of the organic film during the OSP process. Even if the organic film is removed, the oxidation of the electrode and the connected conductor can be suppressed if the time until the connection with the adhesive is not so long.
- the treatment (c1) for removing or thinning the organic film can be performed, for example, by bringing the organic film into contact with a liquid or vapor containing an inorganic acid such as hydrochloric acid or an organic acid such as carboxylic acid or sulfonic acid. .
- a liquid or vapor containing an inorganic acid such as hydrochloric acid or an organic acid such as carboxylic acid or sulfonic acid.
- the organic film is immersed in a solution containing these acids, or a liquid or vapor containing these acids is sprayed onto the organic film, or these acids are contained. It has been confirmed that the organic film is removed or thinned by wiping the organic film with a cloth soaked with liquid.
- 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.
- an adhesive containing conductive particles made of metal powder having a shape in which a plurality of metal particles are connected in a chain or a needle shape.
- 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
- a solder connection electrode is also provided on a base material on which an adhesive connection electrode is provided.
- 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. Therefore, since the organic film has a thermal decomposition temperature higher than the solder reflow temperature, the organic film reliably remains even after the solder reflow. Thereafter, by performing a process of removing or thinning the organic film, the solder connection and the adhesive connection can be smoothly performed.
- the organic film has a thermal decomposition temperature of 300 degreeC or more.
- the organic film having a high thermal decomposition temperature include the following.
- 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.
- 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-phenylimidazoles such as 2-phenyl-4-methyl-5-benzylimidazole, 2,4-diphenylimidazole, 2,4-diphenyl-5-methylimidazole
- one containing at least one organic compound selected from benzimidazoles such as methylbenzimidazole, 2-alkylbenzimidazole, 2-arylbenzimidazole, and 2-phenylbenzimidazole.
- 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 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.
- connection method of the invention described in claims 4 to 7 is performed using a base material provided with an adhesive connecting electrode and a solder connecting electrode. Then, only the solder connection electrode is covered with an organic film or a noble metal plating layer by OSP treatment (b2), and then solder reflow processing is performed in a non-oxidizing atmosphere, so that the solder connection electrode is connected to the solder connection conductor. (C2). After that, the adhesive connection electrode and the conductor to be connected are electrically connected to each other through an adhesive mainly composed of a thermosetting resin to be electrically connected (d2). As will be described later, the adhesive includes so-called anisotropic conductive adhesive (ACF) and insulating adhesive (NCF), and any adhesive may be used.
- ACF anisotropic conductive adhesive
- NCF insulating adhesive
- the adhesive connection electrode is not formed with the organic film or noble metal plating layer by OSP treatment, but only the solder connection electrode is covered with the organic film or noble metal plating layer by OSP treatment (b2), Bonding by solder (solder reflow process) is performed (c2). And since the connection process (d2) by an adhesive agent is performed after that, an electrode and a to-be-connected conductor mutually conduct
- solder connection electrode When the solder connection electrode is covered with an organic film formed by OSP treatment, as described above, gold plating is not necessary, and the manufacturing cost is reduced. Even when the solder connection electrode is covered with a noble metal plating layer, no noble metal plating is required on the adhesive connection electrode, and no OSP treatment is performed, so that the manufacturing cost is reduced.
- a removable protective film is formed on the adhesive connection electrode, and the protective film can be removed before the connection with the adhesive. Also by this, the electrode and the conductor to be connected are electrically connected to each other directly or via the conductive particles. In addition, formation of an oxide film on the adhesive connecting electrode can be suppressed, and poor conduction between the adhesive connecting electrode and the connected conductor can be reliably suppressed.
- the oxide film on the adhesive connecting electrode may be removed before connecting with the adhesive. Thereby, the conduction
- Bonding with solder is preferably performed in a non-oxidizing atmosphere with an oxygen concentration of 1% or less. Thereby, even if the surface of the adhesive connecting electrode is exposed, formation of an oxide film on the surface can be suppressed.
- connection method of the invention described in claims 8 to 12 is performed using a base material provided with an adhesive connecting electrode and a solder connecting electrode. Then, after the adhesive connecting electrode is coated with the antioxidant film (b3), the adhesive connecting electrode and the conductor to be connected are bonded to each other through an adhesive mainly composed of a thermosetting resin. Electrical connection is made (c3). Thereafter, solder reflow processing is performed to join the solder connection electrode to the solder connection conductor (d3). At this time, the connection is performed so that the increase in the connection resistance between the adhesive connecting electrode and the connected conductor before and after the solder reflow process is within a predetermined range.
- the adhesive includes so-called anisotropic conductive adhesive (ACF) and insulating adhesive (NCF), and any adhesive may be used.
- ACF anisotropic conductive adhesive
- NCF insulating adhesive
- the antioxidant film include a noble metal plating layer such as gold plating and an organic film.
- the base material include a base film for a printed wiring board and a base member for an electrode of an electronic component.
- the conductor to be connected and the solder conductor to be connected include electrodes of other printed wiring boards, electrodes of electronic parts, electrodes of connectors, and the like.
- the to-be-connected conductor and the to-be-soldered connecting conductor may be provided on a common member, or may be provided on different members.
- connection resistance increases when the solder reflow process is performed after the connection with the adhesive is performed first.
- the solder reflow treatment causes a relaxation phenomenon of the adhesive and reduces the adhesive clamping force.
- the adhesive connecting electrode on the substrate and the cover on the member to be connected Occurrence of poor continuity with the connection conductor can be suppressed.
- connection resistance between the adhesive connecting electrode and the connected conductor before solder reflow is R 1
- the adhesive strength of the adhesive is F 1
- F 2 after the solder reflow, between the adhesive connecting electrode and the connected conductor
- the present inventors have confirmed that it is effective to use a resin material having a glass transition temperature of 100 ° C. or higher after curing as the resin composition of the adhesive.
- the glass transition temperature is a temperature at which the rigidity and viscosity of the resin composition change abruptly. The higher the temperature, the lower the strength (clamping force) of the adhesive at a high temperature. Therefore, it is considered that the connection satisfying the relational expressions (1) and (2) is facilitated by using a resin material having a glass transition temperature of 100 ° C. or higher.
- Manufacturing cost can be reduced by forming an organic film as an antioxidant film.
- gold plating for preventing oxidation has been applied to the adhesive connecting electrode.
- OSP process Organic Solderability Preservation
- the process of forming the organic film by the preflux process is simplified in comparison with the step of forming the gold plating layer.
- expensive gold is not used, the material cost is also reduced. Therefore, connection using an adhesive can be performed at low cost.
- connection structure of the present invention is formed using the connection method, and the electronic device of the present invention is assembled using the connection method.
- the following structure can be adopted as a connection structure between the first conductor on the first member and the second conductor on the second member. That is, the surface of at least one of the first conductor and the second conductor is covered with an antioxidant film having a thickness of 0.05 ⁇ m or less except for a conductive portion, or without being covered with an antioxidant film. Expose to adhesive.
- connection method, connection structure, or electronic device of the present invention the manufacturing cost can be reduced while simplifying the manufacturing process.
- (A)-(d) is sectional drawing which shows the procedure of the assembly method of the electronic component which has the adhesive agent connection structure and solder connection structure which concern on 1st Embodiment. It is sectional drawing which shows Example 1 which concerns on 2nd Embodiment of the adhesive agent connection structure and solder connection structure which are formed between a flexible printed wiring board and an electronic component, and a motherboard. It is sectional drawing which shows Example 2 which concerns on 2nd Embodiment of an adhesive agent connection structure and a solder connection structure. (A)-(d) is sectional drawing which shows the procedure of the example 1 of the assembly method which concerns on 2nd Embodiment of the electronic component which has an adhesive agent connection structure and a solder connection structure.
- (A)-(d) is sectional drawing which shows the procedure of the example 2 of the assembly method which concerns on 2nd Embodiment of the electronic component which has an adhesive agent connection structure and a solder connection structure. It is sectional drawing which shows the example 1 which concerns on 3rd Embodiment of the adhesive agent connection structure and solder connection structure which are formed between a flexible printed wiring board and an electronic component, and a motherboard. It is sectional drawing which shows Example 2 which concerns on 3rd Embodiment of an adhesive agent connection structure and a solder connection structure.
- (A)-(c) is sectional drawing which shows the procedure of the assembly method which concerns on 3rd Embodiment of the electronic component which has an adhesive agent connection structure and a 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 105 of the mobile terminal 100 according to the embodiment.
- the display unit 103 is provided with a display unit casing 131 and a display unit substrate 135 as main members.
- the display unit substrate 135 includes a circuit for sending a display signal to the display device 106.
- the display unit casing 131 includes a first casing 131a and a second casing 131b that are connected to each other.
- a through hole 133 is provided between the first housing 131a and the second housing 131b.
- the input unit 104 is provided with an input unit casing 141 and an input key board 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.
- the 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.
- the input key board 145 is provided with a solder connection structure D in which electronic components are joined by solder.
- the display unit substrate 135 is also provided with a solder connection structure 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.
- 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.
- 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 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.
- 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 azole compounds.
- Examples include 2-phenylimidazoles, and benzimidazoles such as 5-methylbenzimidazole, 2-alkylbenzimidazole, 2-arylbenzimidazole, and 2-phenylbenzimidazole.
- the organic film 15 does not need to have a thermal decomposition temperature higher than the solder reflow temperature. Therefore, it is not restricted to the said compound.
- the following effects can be exhibited.
- 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).
- ACF anisotropic conductive adhesive
- NCF 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 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.
- 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 illustrating Example 1 according to the first embodiment 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 hard printed wiring board 21 and an adhesive connecting electrode 22 provided on the hard printed wiring 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 adhesive connecting electrode 22 of the mother board 20 is formed by laminating a metal foil such as a copper foil on the hard printed wiring board 21, and exposing and etching the metal foil by a conventional method.
- the adhesive connecting electrodes 12 and 22 are in strong contact with each other and are electrically connected by the fastening force of the adhesive 30 which 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.
- each of the adhesive connection electrodes 12 and 22 was covered with an organic film for preventing oxidation, but was removed after a solder reflow process.
- the organic film 15 may be left on the surface of any one of the electrodes (for example, the adhesive connecting electrode 12) (see the broken line in FIG. 4).
- the organic film 15 may be thinned to about 0.05 ⁇ m or less, for example. In order to remove or thin these organic films, the organic film is brought into contact with the acidic liquid or its vapor.
- the organic film is immersed in these solutions, or the acidic liquid or vapor is sprayed onto the organic film.
- There are methods such as wiping the organic film with a cloth containing a liquid containing these acids. It has been confirmed that the organic film is removed or thinned by these treatments. And if it is before the grace time of about 3 days passes after removing an organic film, the connection by the adhesive agent 30 will hardly produce an oxide film on the surface of each adhesive agent connection electrode 12 and 22. A process can be performed. If the organic film is not completely removed but left a little, the grace time is further increased. Even when stored in a low temperature, low humidity, or non-oxidizing atmosphere, the grace time becomes longer.
- 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 adhesive connecting electrodes 12 and 22 of the mother board 20 are brought into strong contact with each other and are made conductive by the tightening force accompanying the shrinkage.
- a part (conductive portion) of the adhesive connecting electrode 12 is electrically connected to each other without being covered with the organic film 15.
- 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.
- machining such as embossing may be used.
- the organic film 15 may be hardened 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 electrical connection between the adhesive connecting electrodes 12 and 22 is hindered by the organic film, and the connection resistance for electrical connection may increase.
- the organic film tends to harden.
- the organic film formed by the OSP process has a range of hardness depending on the type of the constituent material, and sometimes it may be necessary to use a considerably hard material.
- the protrusion of the adhesive connecting electrode 12 is less likely to break through the hardened organic film, resulting in an increase in connection resistance.
- the connecting step is performed, so that the protrusion of the adhesive connecting electrode 12 and the adhesive connecting electrode are used.
- the electrode 22 easily comes into contact. If the organic film on one electrode does not go through the solder reflow process, it is easy for the protrusions of the adhesive connecting electrode 12 to break through the organic film, so it is necessary to remove or thin the organic film. Absent. Accordingly, it is possible to suppress the occurrence of poor conduction (such as an increase in connection resistance) between the adhesive connecting electrode 12 and the adhesive connecting electrode 22 (connected conductor).
- the average film thickness of the organic film is within an appropriate range (for example, 0.05 ⁇ m or more and 0.5 ⁇ m or less) in order to achieve reliable conduction between conductors. It is necessary to manage such as storing or increasing the area ratio of the region having a small film thickness (for example, the area of the region having a thickness of 0.1 ⁇ m or less is set to 30% or more of the entire organic film). On the other hand, in this embodiment, since the organic film is removed or thinned, no problem occurs even if the thickness of the organic film during the OSP process is 0.5 ⁇ m or more, for example.
- FIG. 5 is a cross-sectional view showing an example 2 of the adhesive connection structure C according to the first embodiment.
- 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.
- ACF anisotropic conductive adhesive
- the mother board 20 has a hard printed wiring board 21 and an adhesive connecting electrode 22 provided on the hard printed wiring 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 film 15 except for the conductive portion.
- the adhesive connecting 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 adhesive connecting electrodes 12 and 22 are in direct contact with each other as in Example 1 according to the first embodiment.
- the adhesive connecting electrodes 12 and 22 were covered with the organic film before the adhesive connecting structure C was formed, but are removed or thinned after the solder reflow process.
- the FPC 10 does not go through the solder reflow process, it is not necessary to remove or thin the organic film 15 indicated by a broken line in the drawing.
- the specific method of removing or thinning the organic film is as described in Example 1.
- thermosetting resin in the adhesive 30 is cured by the above-described heat and pressure treatment, and the adhesive connecting electrodes 12 and 22 are connected to each other via 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.
- a resin composition 31 in which conductive particles made of fine metal particles are randomly dispersed may be used. Even in that case, by performing the heating and pressurizing treatment, the adhesive connecting electrodes 12 and 22 have a shape in which a large number of fine metal particles are connected.
- thermosetting resin examples 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.
- 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.
- This latent curing agent includes 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 temperatures 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. .
- Example 2 the same effect as Example 1 according to the first embodiment can be exhibited by removing or thinning the organic film that has undergone the solder reflow process.
- the adhesive connecting electrodes 12 and 22 are electrically connected to each other through the conductive particles 36.
- 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.
- 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.
- FIGS. 7A to 7D are cross-sectional views showing the procedure of the connection method according to the first embodiment for realizing 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.
- the organic film 15 that covers the adhesive connecting electrodes 22 and 26 is formed.
- the thermal decomposition temperature of the organic film 15 is higher than the solder reflow temperature.
- a protective film covering the organic film 15 may be formed only in the adhesive connection region Rc.
- the organic film 15 is covered with an adhesive tape or the like.
- a protective film other than the adhesive tape can also be used.
- 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, so that the electrodes 26 and 42 are electrically connected to each other.
- the solder connection structure D is formed in the solder connection region Rd.
- the above-described organic film 15 is removed.
- the organic film 15 is brought into contact with the acidic liquid or its vapor.
- the mother board 20 and the electronic component 40 are immersed in an acidic liquid at a temperature of 30 ° C. for about 1 minute, or the acidic liquid or its vapor is sprayed onto the organic film 15.
- the influence on other members can be suppressed.
- the adhesive connecting electrode 22 and the adhesive connecting electrode 12 of the FPC 10 are used in the process shown in FIG. Are electrically connected by bonding with an adhesive 30.
- the procedure for forming the adhesive connection structure C is as described in Example 2 (see FIG. 5) of the adhesive connection structure.
- the organic film 15 covering the adhesive connecting electrode 12 on the FPC 10 is also removed or thinned. However, when the FPC 10 does not go through the solder reflow process, it is not necessary to remove or thin the organic film 15.
- 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.
- the adhesive connecting 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 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.
- 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.
- 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.
- the organic film 15 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.
- the connection method of the present embodiment in the step shown in FIG.
- the organic film 15 formed on the adhesive connecting 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 15 remains reliably without being thermally decomposed. In addition, if a protective film is formed on the organic film 15, the organic film 15 can remain more reliably. Therefore, the solder connection structure D and the adhesive connection structure C can be more reliably formed.
- the organic film 15 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. 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 15 reacts with the flux and dissolves in the solder layer 50, the organic film 15 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 for electrically connecting the adhesive connection electrodes 12 and 22 is compared with the case where the adhesive connection structure C is not passed. Resistance may increase. It is considered that this is because the conductive particles 36 are difficult to break through the organic film 15 due to deterioration such as the organic film 15 is hardened by being heated in the solder reflow furnace.
- the conductive particles can easily break through the organic film 15 cured by the solder reflow process. Therefore, even if the adhesive connection structure C is formed after the organic film 15 passes 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 15 during the OSP process or the area ratio of the region having a small film thickness.
- 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.
- Each of the organic films 15 is formed.
- the process of forming the antioxidant film is simplified as compared with the case where the adhesive connecting electrodes 12 and 22 are covered with the gold plating layer.
- 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 adhesive connecting electrodes 12 and 22 to each other.
- the conductive particles 36 are removed because the organic film 15 is removed or thinned before connection by the adhesive 30. It becomes easy to break through the organic film 15. Therefore, it is possible to suppress the deterioration of the conductivity between the adhesive connecting electrodes 12 and 22 caused by the conductive particles 36 not breaking through the organic film 15. Further, it is not necessary to strictly manage the average film thickness of the organic film 15 and the area ratio of the region where the film thickness is small during the OSP process.
- 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 conductive particles 36 have an aspect ratio of 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 adhesive connecting electrodes 12 and 22 to each other without increasing the blending amount of the conductive particles 36.
- the adhesive 30 anisotropic conductive adhesive
- one having 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
- 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 wiring board (PWB) which is the mother board 20.
- PWB hard printed wiring board
- a hard printed wiring board PWB
- a flexible printed wiring board FPC
- the adhesive connection structure C is used for connecting electrodes of the FPC 10 and the mother board 20 that is 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.
- 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 performed on 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 of the adhesive connection electrodes 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 embodiment can also be obtained by this.
- 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%.
- connection resistance value at 30 consecutive points connected via the adhesive connecting electrode, the adhesive, and the adhesive connecting electrode is obtained by the four-terminal method, and the obtained value is divided by 30.
- the connection resistance per connected place was obtained.
- this evaluation was repeated 10 times and the average value of connection resistance was calculated
- 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 the connection resistance was measured in the same manner as described above. And when the rate of increase in connection resistance was 50% or less, it was judged that the connection reliability was good.
- Example 2 A joined body of flexible printed wiring boards is formed in the same manner as in Example 1 except that the average film thickness of the antioxidant film is 0.60 ⁇ m and the area ratio of the region where the thickness is 0.1 ⁇ m or less is 2%. 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 2 except that the immersion treatment in an aqueous hydrochloric acid solution was not performed after the solder reflow treatment. 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 shows the results of connection resistance evaluation and connection reliability evaluation of Examples 1 and 2 and the comparative example according to the first embodiment.
- the initial connection resistance is 50 m ⁇ or less, and the connection resistance is sufficiently small and good.
- the rate of increase in resistance is 50% or less, it can be seen that the connection reliability is also good.
- Comparative Example 1 the initial connection resistance was as high as 50 m ⁇ or more.
- the connection was opened after standing in a high-temperature and high-humidity tank for 500 hours, and the resistance increase rate was ⁇ (infinite).
- FIG. 8 is a cross-sectional view illustrating Example 1 according to the second embodiment of the adhesive connection structure C and the solder connection structure D formed between the FPC 210 (flexible printed wiring board) and the electronic component 240 and the mother board 220.
- the adhesive connection structure C is formed using an insulating adhesive (NCF).
- the mother board 220 includes a hard printed wiring board 221, an adhesive connecting electrode 222 and a solder connecting electrode 226 provided on the hard printed wiring board 221.
- the mother board 220 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 210 is mounted on the mother board 220 with the adhesive connecting electrode 212 (connected conductor) facing the lower side of the base film 211.
- the electronic component 240 includes a chip-side electrode 242 (soldered connection conductor) in a part of the chip 241, and the chip-side electrode 242 is arranged facing the lower side of the chip 241.
- the adhesive connecting electrode 222 and the solder connecting electrode 226 of the mother board 220 are formed by laminating a metal foil such as a copper foil on the hard printed wiring board 221, and exposing and etching the metal foil in a usual manner. Has been.
- the electrodes 212 and 222 are in strong contact with each other and are electrically connected by the tightening force of the adhesive 230 that is NCF.
- the electrodes 226 and 242 are electrically connected to each other due to the alloying of the solder layer 250 and the electrodes 226 and 242.
- the adhesive 230 has a thermosetting resin as a main component and is added with a curing agent and various fillers. Since components and the like are the same as those of the adhesive 30 according to the first embodiment, description thereof is omitted.
- the solder connection electrodes 226 and 242 are covered with an organic film formed by an OSP process described later.
- the organic film on the solder connection electrode 226 and the solder connection electrode 242 is dissolved in the solder layer 250.
- the protective film similar to the organic film 15 shown in FIG. 3 was attached to the adhesive connecting electrode 222 and the adhesive connecting electrode 212, but was removed after the solder reflow process was completed ( (See FIGS. 10B and 10C described later).
- an organic film 215 by OSP treatment may be formed on the surface of the adhesive connecting electrode 212 (see the broken line in FIG. 8).
- the thermally decomposed organic film is removed, and then the adhesive 230 is heated and melted while being pressed at a predetermined pressure in the direction of the mother substrate 220 through the FPC 210 (heating applied). Pressure treatment).
- the thermosetting resin in the adhesive 230 is cured, and the FPC 210 and the electrodes 212 and 222 of the mother board 220 are brought into strong contact with each other and are made conductive by the tightening force accompanying the shrinkage.
- a part (conductive portion) of the adhesive connecting electrode 212 is electrically connected to each other without being covered with the organic film 215.
- the adhesive connecting electrode 212 of the FPC 210 is processed so that the surface becomes rough by etching.
- etching not only etching but machining such as embossing may be used.
- the electrode 212 is covered with the organic film 215, if there is a protrusion on the surface of at least one of the electrodes, the protrusion breaks through the organic film 215, so that both the electrodes 212 and 222 can be in contact with each other.
- the surface of the adhesive electrode 212 does not necessarily have to be processed rough, but it is easier to ensure contact if the surface is processed rough.
- a bump may be disposed between the electrodes 212 and 222.
- Example 1 the following effects can be exhibited in addition to the effects of the electrode structure.
- the adhesive connecting electrode 222 is covered with an organic film obtained by OSP processing to be described later, the organic film is hardened by the solder substrate reflow process.
- the connection resistance for electrically connecting the electrodes 212 and 222 is increased.
- the organic film tends to harden.
- the protruding portion of the adhesive connecting electrode 212 is difficult to break through the hardened organic film, resulting in an increase in connection resistance.
- connection step is performed without forming an organic film on each of the electrodes 212 and 222, so that the protrusion of the adhesive connecting electrode 12 and the adhesive connecting electrode 222 are easy. To touch.
- FIG. 9 is a cross-sectional view illustrating Example 2 according to the second embodiment of the adhesive connection structure C and the solder connection structure D.
- an adhesive 230 that is an anisotropic conductive adhesive (ACF) is used. That is, the adhesive 230 of this example is one in which conductive particles 236 are included in a resin composition 231 mainly composed of a thermosetting resin.
- the mother board 220 has a hard printed wiring board 221, an adhesive connecting electrode 222 and a solder connecting electrode 226 provided on the hard printed wiring board 221. Also in this example, neither the gold plating layer nor the organic film by OSP treatment is formed on the surfaces of the adhesive connecting electrode 212 and the adhesive connecting electrode 222.
- the electrodes 212 and 222 are electrically connected to each other through the conductive particles 236.
- the conductive particles 236 are made of a metal powder having a shape in which a 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 212 and 222 are in direct contact with each other as in Example 1 according to the second embodiment.
- the electrodes 226 and 242 are covered with an organic film similar to the organic film 15 shown in FIG.
- the organic film on the solder connection electrode 226 and the solder connection electrode 242 is dissolved in the solder layer 250.
- a removable protective film was provided on the adhesive connecting electrode 222 and the adhesive connecting electrode 212, but it was removed after the solder reflow process.
- an organic film 215 indicated by a broken line in the drawing may be provided on the adhesive connecting electrode 222 of the FPC 10.
- the thermosetting resin in the adhesive 230 is cured by the above-described heat and pressure treatment, and the electrodes 212 and 222 are connected to each other via the conductive particles 236 by the tightening force accompanying the shrinkage.
- the resin composition 231 includes conductive particles 236 having a shape in which a large number of fine metal particles are linearly connected or a needle shape.
- a resin composition 231 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, the electrodes 212 and 222 have a shape in which a large number of fine metal particles are connected.
- Example 2 according to the second embodiment As in Example 2 according to the second embodiment, as in Example 2 according to the first embodiment, it is widely used, that is, an insulating material such as an epoxy resin.
- a resin composition in which conductive particles 36 are dispersed in a resin composition containing a thermosetting resin as a main component can be used. Since the components and the like are the same as in Example 2 according to the first embodiment, the description thereof is omitted.
- the adhesive connection electrodes 212 and 222 are provided with neither an organic film by OSP treatment nor a noble metal plating layer such as a gold plating layer, and thus the example according to the second embodiment. 1 can be exhibited. However, in this example, the electrodes 212 and 222 are electrically connected to each other through the conductive particles 236.
- an anisotropic conductive adhesive having the shape shown in FIG. 6 according to the first embodiment can be used.
- FIGS. 10A to 10D are cross-sectional views showing the procedure in Example 1 according to the second embodiment of the connection method for realizing the adhesive connection structure C and the solder connection structure D.
- FIG. 10A a mother board 220 (common base material) having an adhesive connection region Rc and a solder connection region Rd is prepared.
- an adhesive connection electrode 222 for adhesive connection is provided in the adhesive connection region Rc
- a solder connection electrode 226 for solder connection is provided in the solder connection region Rd.
- an organic film 225 that covers only the solder connection electrode 226 is formed.
- a removable protective film 228 covering the adhesive connecting electrode 222 is formed.
- the adhesive connecting electrode 222 is covered with an adhesive tape or the like.
- a protective film 228 other than the adhesive tape may be used, but it must withstand the temperature of the solder reflow process and be removable.
- the organic film 225 is formed by a water-soluble preflux process (OSP process: Organic Solderability Preservation), as in the first embodiment.
- OSP process Organic Solderability Preservation
- the electronic component 240 having the chip-side electrode 242 on a part of the chip 241 is mounted in the solder connection region Rd.
- lead-free solder is interposed between the electrodes 226 and 242 with the chip-side electrode 242 aligned with the position of the solder connection electrode 226.
- the mother board 220 and the electronic component 240 are put in a solder reflow furnace having a peak temperature of about 260 ° C. to reflow the solder.
- the electrodes 226 and 242 are joined to each other via the solder layer 250, so that the electrodes 226 and 242 are electrically connected to each other.
- the solder connection structure D is formed in the solder connection region Rd.
- the organic film 225 covering the solder connection electrode 226 reacts with the flux contained in the lead-free solder and is dissolved in the solder layer 250.
- the protective film 228 on the adhesive connecting electrode 222 is removed. As a result, the adhesive connecting electrode 222 is exposed.
- the adhesive connection electrode 222 and the FPC 210 are connected in the process shown in FIG.
- the electrode 212 is electrically connected by bonding with an adhesive 230.
- the adhesive connection structure C is formed in the adhesive connection region Rc.
- the procedure for forming the adhesive connection structure C is as described in Example 2 (see FIG. 9) according to the second embodiment of the adhesive connection structure.
- the protective film is also provided on the adhesive connection electrode 212 of the FPC 210, but it is removed immediately before connection with the adhesive 230.
- the adhesive 230 (anisotropic conductive adhesive) containing the conductive particles 236 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.
- the electrodes 212 and 222 are connected to each other via the conductive particles 236 in the adhesive 230, and the FPC 210 is mounted on the mother board 220.
- FIGS. 10A to 10D show an example in which an adhesive connection structure C and a solder connection structure D are formed on a mother board 220 that is a PWB.
- the adhesive connection structure C and the solder connection structure D may be formed on the FPC 210 using the FPC 210 as a common base material.
- the mother substrate 220 shown in FIG. 10 is replaced with the FPC 210, and the organic film 215 is formed on the adhesive connecting electrode 212.
- 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.
- connection method According to the connection method according to the second embodiment, the following effects can be exhibited.
- the organic film 225 is formed on both the solder connection electrode 226 and the adhesive connection electrode 222, 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 adhesive connection structure C is formed after the solder reflow process, the connection resistance for electrical connection between the electrodes 212 and 222 is increased as compared with the case where the adhesive connection structure C is not passed. There is a fear.
- a removable protective film 228 is formed on the adhesive connecting electrode 222 without forming an organic film.
- the surface of the adhesive connecting electrode 222 is covered with the protective film 228, and the solder reflow process is performed while suppressing the formation of the oxide film.
- the protective film 228 is removed. As a result, in the step shown in FIG.
- the conductive particles 236 in the adhesive 230 easily come into contact with the adhesive connecting electrodes 212 and 222 without going through the organic film, and the adhesive connecting electrode The electrodes 212 and 222 can be reliably conducted. Therefore, even if the adhesive connection structure C is formed after the organic films 215 and 225 have passed through the solder reflow furnace, the electrical connection resistance between the electrodes 212 and 222 can be more reliably suppressed.
- a noble metal plating layer such as a gold plating layer may be provided as an antioxidant film on the solder connection electrode 226, but by providing an organic film 225 by OSP treatment, The following effects are obtained. Even when a noble metal plating layer such as a gold plating layer is provided as an anti-oxidation film on the solder connection electrode 226, it is not necessary to perform the OSP process to cover the adhesive connection electrode 222, thereby reducing the manufacturing cost. The reduction effect can be obtained.
- FIGS. 11A to 11D are cross-sectional views showing the procedure in Example 2 according to the second embodiment of the connection method for realizing the adhesive connection structure C and the solder connection structure D.
- FIG. 11 the same members as those shown in FIG. In FIGS. 11A to 11D, processing is basically performed in the same procedure as in FIGS. 10A to 10D in Example 1 according to the second embodiment. Therefore, the description of the same processing as Example 1 according to the second embodiment is omitted, and only different processing is described.
- no protective film is provided on the adhesive connecting electrode 222. Therefore, a thin oxide film 222a is formed on the adhesive connecting electrode 222 in the solder reflow process shown in FIG.
- the atmosphere in the solder reflow furnace is maintained in a non-oxidizing atmosphere having a very low oxygen concentration (for example, 1% or less), the thickness of the oxide film can be made negligibly thin.
- the oxide film 222a is removed in the step shown in FIG.
- a method for removing the oxide film 222a there are methods such as cleaning with an acidic solution and cleaning with plasma.
- the conductive particles 236 in the adhesive 230 can be easily connected to the adhesive without passing through the organic film in the process shown in FIG.
- the electrodes 212 and 22 can be brought into contact with each other, and the adhesive connecting electrodes 212 and 222 can be reliably conducted.
- Example 2 according to the second embodiment can provide basically the same effect as the method of Example 1 according to the second embodiment.
- the following effects can be obtained.
- the surfaces of the adhesive connection electrode 222 of the mother board 220 and the adhesive connection electrode 212 of the FPC 210 are not subjected to OSP treatment, and noble metals such as gold plating are used. Since no plating layer is formed, the manufacturing cost can be reduced by simplifying the process and reducing the material cost.
- connection with the adhesive 230 when the connection with the adhesive 230 is performed, there is no organic film formed by the OSP process on the adhesive connection electrodes 212 and 222, so that the conductive particles 236 can easily come into contact with the adhesive connection electrodes 212 and 222. To do. Therefore, it is possible to suppress deterioration in conductivity between the electrodes 212 and 222 caused by the conductive particles 236 not breaking through the organic film.
- the conductive particles 236 in the adhesive 230 which is an 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 230
- adhesion is maintained while maintaining insulation between adjacent adhesive connection electrodes 222 or between the adhesive connection electrodes 212 to prevent a short circuit.
- the X direction which is the thickness direction of the agent 230, it is possible to obtain a low resistance by electrically connecting a large number of the adhesive connecting electrodes 222 and the adhesive connecting electrodes 212 at a time and independently of each other. It becomes.
- the aspect ratio of the conductive particles 236 is 5 or more. According to this configuration, when an anisotropic conductive adhesive is used, the contact probability between the conductive particles 236 is increased. As a result, it becomes easy to electrically connect the electrodes 212 and 222 to each other without increasing the blending amount of the conductive particles 236.
- the adhesive 230 anisotropic conductive adhesive
- an adhesive having a film shape is used as the adhesive 230 (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
- the conductive particles 236 having the major axis direction oriented in the X direction which is the thickness direction of the adhesive 230 having a film shape (anisotropic conductive adhesive) is used.
- the Y direction which is the surface direction of the adhesive 230
- adhesion is maintained while maintaining insulation between adjacent adhesive connection electrodes 222 or between the adhesive connection electrodes 212 to prevent a short circuit.
- the X direction which is the thickness direction of the agent 230, it is possible to obtain a low resistance by electrically connecting a large number of the adhesive connecting electrodes 222 and the adhesive connecting electrodes 212 at a time and independently of each other. It becomes.
- the flexible printed wiring board (FPC 210) is connected to the hard printed wiring board (PWB) which is the mother board 220.
- PWB hard printed wiring board
- this configuration it is possible to provide a multilayer conductive pattern structure at a lower cost than when the mother board 220 is an FPC.
- FPC 210 on the mother board 220, 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 210, The degree of freedom of arrangement of other substrates can be improved.
- a protective film (adhesive tape) is applied to the adhesive connecting electrodes 212 and 222, or the oxide film is simply removed by acid treatment or the like, so that the electrodes 212 and 222 are covered with gold plating or OSP. Since it can be made cheaper than processing, the connection body of the mother board 220 and the FPC 210 can be provided at low cost.
- a hard printed wiring board PWB
- FPC flexible printed wiring board
- the adhesive connection structure C is used to connect the electrodes of the FPC 210 and the mother board 220, which 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 220.
- an electronic component may be mounted instead of the FPC 210.
- the water-soluble preflux process is performed on the solder connection electrodes 226 and 242 as the OSP process, but the OSP process may be a heat-resistant preflux process, for example.
- the acidic aqueous solution containing an azole compound as a water-soluble preflux process
- another aqueous solution may be sufficient.
- neither the organic film or the noble metal plating layer by the OSP process is provided on both the adhesive connection electrodes 212 and 222, but the organic film by the OSP process is provided only on one adhesive connection electrode 212. Or a noble metal plating layer may be provided. Also by this, the effect (1) of the embodiment can be obtained.
- 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.
- the adhesive connecting electrode is not covered with an organic film by OSP treatment or a noble metal plating layer.
- 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 value at 30 consecutive points connected via the adhesive connecting electrode, the adhesive, and the adhesive connecting electrode is obtained by the four-terminal method, and the obtained value is divided by 30.
- the connection resistance per connected place was obtained.
- this evaluation was repeated 10 times and the average value of connection resistance was calculated
- Example 2 (Example 2 according to the second embodiment) The second embodiment, except that after the solder reflow process is performed and before the bonded body using the anisotropic conductive adhesive is manufactured, the adhesive connecting electrode is washed with an acetic acid solution to remove the oxide film. In the same manner as in Example 1, a joined body of flexible printed wiring boards was 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-phenyl-4-methyl-5-benzylimidazole was formed on the adhesive connecting electrode.
- the thermal decomposition temperature of the antioxidant film was 310 ° C.
- the average film thickness was 0.60 ⁇ m
- the area ratio of the region having a thickness of 0.1 ⁇ m or less was 4%.
- connection resistance evaluation and connection reliability evaluation were performed on the same conditions as Example 1 which concerns on the above-mentioned 2nd Embodiment.
- Comparative Example 2 A joined body of flexible printed wiring boards was obtained in the same manner as in Example 1 except that the atmosphere in the reflow bath was changed to an air atmosphere. Thereafter, connection resistance evaluation and connection reliability evaluation were performed under the same conditions as in Example 1.
- Table 2 shows the results of connection resistance evaluation and connection reliability evaluation of Example 1 according to the second embodiment, Example 2 according to the second embodiment, and Comparative Examples 1 and 2.
- 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, so that it can be seen that the connection reliability is also good.
- the initial connection resistance was as high as 50 m ⁇ or more, and the resistance increase rate was ⁇ (infinity).
- the adhesive connecting electrode is covered with the antioxidant film during the solder reflow process, and therefore no oxide film is formed on the adhesive connecting electrode.
- Example 2 according to the second embodiment is superior to Example 1 according to the second embodiment, although both the initial connection resistance and the resistance increase rate are slight. Therefore, it can be seen that by performing the step of removing the oxide film as in Example 2 according to the second embodiment, the initial connection resistance can be kept lower and the connection reliability can be kept higher.
- FIG. 12 is a cross-sectional view illustrating Example 1 according to the third embodiment of the adhesive connection structure C and the solder connection structure D formed between the FPC 310 (flexible printed wiring board) and the electronic component 340 and the mother board 320.
- the adhesive connection structure C is formed using an insulating adhesive (NCF).
- the mother board 320 includes a hard printed wiring board 321, an adhesive connecting electrode 322 and a solder connecting electrode 326 provided on the hard printed wiring board 321.
- the mother board 320 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 310 is mounted on the mother board 320 with the adhesive connecting electrode 312 (connected conductor) facing the lower side of 311.
- the electronic component 340 includes a chip-side electrode 342 (soldered connection conductor) in a part of the chip 341, and the chip-side electrode 342 is arranged with the chip 341 below.
- the adhesive connection electrode 322 and the solder connection electrode 326 of the mother board 320 are formed by laminating a metal foil such as a copper foil on the hard printed wiring board 321, and exposing and etching the metal foil in a usual manner. Has been.
- the electrodes 312 and 322 are in strong contact with each other and are electrically connected by the tightening force of the adhesive 330 that is NCF.
- the electrodes 326 and 342 are electrically connected to each other due to the alloying of the solder layer 350 and the electrodes 326 and 342.
- the adhesive 330 has a thermosetting resin as a main component, and is added with a curing agent and various fillers. Since components and the like are the same as those of the adhesive 30 according to the first embodiment, description thereof is omitted.
- thermosetting resins those having a glass transition temperature of 100 ° C. or higher are used.
- thermosetting resin include an epoxy resin, a phenol resin, and a polyimide resin.
- the electrodes 312, 322, 326 and 342 are covered with organic films 315 and 325, respectively. Then, the electrodes 312 and 322 are connected by an adhesive 330 to form an adhesive connection structure C, and then the electrodes 326 and 342 are connected by a solder layer 350 to form a solder connection structure D.
- another oxidation film such as a gold plating layer may be formed on each electrode 312, 322, 326, 342 instead of the organic films 315, 325.
- the adhesive 330 is heated and melted while being pressed at a predetermined pressure in the direction of the mother board 320 via the FPC 310 (heating and pressing process).
- the thermosetting resin in the adhesive 330 is cured, and the FPC 310 and the electrodes 312 and 322 of the mother board 320 are brought into strong contact with each other and are made conductive by the tightening force accompanying the shrinkage.
- a part (conductive portion) of the adhesive connecting electrode 312 is electrically connected to each other without being covered with the organic film 315.
- the mother board 320 and the electronic component 340 are placed in a solder reflow furnace having a peak temperature of about 260 ° C. to reflow the solder.
- the organic film on the solder connection electrode 326 and the chip-side electrode 342 is dissolved in the solder layer 350.
- the adhesive connecting electrode 312 of the FPC 310 is processed so that the surface becomes rough by etching.
- etching not only etching but machining such as embossing may be used.
- the electrodes 312 and 322 are covered with the organic films 315 and 325, if there is a protrusion on the surface of at least one of the electrodes, the protrusion breaks through the organic films 315 and 325. Can come into contact.
- a bump may be disposed between the electrodes 312 and 322.
- the increase in the connection resistance between the adhesive connecting electrodes 312 and 322 before and after the solder reflow process is performed within a predetermined range.
- the connection resistance between the electrodes 312 and 322 before the solder reflow process is R 1
- the adhesive strength of the adhesive 330 is F 1
- the connection resistance between the electrodes 312 and 322 after the solder reflow process is R 2.
- the adhesive strength of the adhesive 330 was F 2
- F 2 > 0.8 ⁇ F 1 (2) Is established.
- the conditions for satisfying the relational expressions (1) and (2) are found by selecting the type of the thermosetting resin, setting the temperature of the solder reflow process, and the like.
- the following effects can be exhibited.
- a procedure for forming the solder connection structure D by performing solder reflow processing first is employed. This is because if the adhesive connection structure C is formed first, the connection resistance may increase.
- the relational expression (1) is established so that the increase in connection resistance between the electrodes 312 and 322 before and after the solder reflow process is within a predetermined range. Connecting. Therefore, even if the adhesive connection structure C is formed before the solder connection structure D is formed, an increase in connection resistance between the adhesive connection electrode 312 and the adhesive connection electrode 322 (connected conductor) is suppressed. can do. Further, the connection is performed so that, for example, the relational expression (2) is established so that the loosening of the tightening force of the adhesive 330 falls within a predetermined range. Therefore, increase in connection resistance (deterioration of connection reliability) during long-term use can be suppressed.
- connection electrodes 312 and 322 have been conventionally subjected to gold plating for oxidation prevention.
- 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.
- expensive gold is not used, the material cost is also reduced. Therefore, connection using an adhesive can be performed at low cost.
- FIG. 13 is a cross-sectional view showing Example 2 of the adhesive connection structure C and the solder connection structure D according to the third embodiment.
- an adhesive 330 that is an anisotropic conductive adhesive (ACF) is used in the adhesive connection structure C. That is, the adhesive 330 of this example is one in which conductive particles 336 are included in a resin composition 331 mainly composed of a thermosetting resin.
- the mother board 320 has a hard printed wiring board 321, an adhesive connecting electrode 322 and a solder connecting electrode 326 provided on the hard printed wiring board 321. Also in this example, the surfaces of the adhesive connecting electrode 312 and the adhesive connecting electrode 322 are covered with the organic films 315 and 325 except for the conductive portion.
- the electrodes 312 and 322 are electrically connected to each other through the conductive particles 336.
- the conductive particles 336 are made of a metal powder having a shape in which a 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 312 and 322 are in direct contact with each other as in Example 1 according to the third embodiment.
- the electrodes 312, 322, 326, and 342 are covered with the same organic film as the organic film 15 shown in FIG. In the solder reflow process, the organic film on the solder connection electrode 326 and the chip-side electrode 342 is dissolved in the solder layer 350.
- the thermosetting resin in the adhesive 330 is cured by the heat and pressure treatment described above, and the electrodes 312 and 322 are connected to each other via the conductive particles 336 by the tightening force accompanying the shrinkage.
- the resin composition 331 includes conductive particles 336 having a shape in which a large number of fine metal particles are linearly connected or a needle shape.
- Example 2 As the anisotropic conductive adhesive used in Example 2 according to the third embodiment, the same one as in the above-described embodiment can be used.
- Example 2 the adhesive connection structure C is first formed under the same conditions as Example 1 according to the third embodiment, and then the solder connection structure D is formed.
- the effect similar to Example 1 which concerns on 3 embodiment can be exhibited.
- an anisotropic conductive adhesive having the shape shown in FIG. 6 can be used.
- the metal powder used for this invention can use the thing similar to embodiment mentioned above.
- FIGS. 14A to 14C are cross-sectional views showing the procedure of the connection method for realizing the adhesive connection structure C and the solder connection structure D.
- FIG. 14A a mother board 320 (common base material) having an adhesive connection region Rc and a solder connection region Rd is prepared.
- an adhesive connection electrode 322 for adhesive connection is provided in the adhesive connection region Rc
- a solder connection electrode 326 for solder connection is provided in the solder connection region Rd.
- an organic film 325 that covers the adhesive connecting electrodes 322 and 326 is formed.
- the adhesive connecting electrode 322 and the adhesive connecting electrode 312 of the FPC 310 are electrically connected by bonding with the adhesive 330.
- the adhesive connection structure C is formed in the adhesive connection region Rc.
- the procedure for forming the adhesive connection structure C is as described in Example 2 (see FIG. 13) according to the third embodiment of the adhesive connection structure.
- the electronic component 340 having the chip-side electrode 342 in a part of the chip 341 is mounted in the solder connection region Rd.
- lead-free solder is interposed between the electrodes 326 and 342 with the chip side electrode 342 aligned with the position of the solder connection electrode 326.
- the mother board 320 and the electronic component 340 are put into a solder reflow furnace having a peak temperature of about 260 ° C. to reflow the solder.
- the electrodes 326 and 342 are joined to each other via the solder layer 350, whereby the electrodes 326 and 342 are electrically connected to each other.
- the solder connection structure D is formed in the solder connection region Rd.
- the organic film 325 covering the solder connection electrode 326 is dissolved in the solder layer 350 by reacting with the flux contained in the lead-free solder.
- the adhesive reflow process is performed at a temperature equal to or higher than the thermal decomposition temperature, so that the adhesive in the adhesive connection structure C
- the organic films 315 and 325 on the connection electrodes 312 and 322 are thermally decomposed.
- the thermally decomposed organic films 315 and 325 remain as liquid or carbonized powder inside the adhesive 330.
- a gas may be formed depending on the material of the organic films 315 and 325. In any case, since the adhesive connection structure C is formed, there is almost no risk of increasing the connection resistance.
- the adhesive 330 (anisotropic conductive adhesive) including the conductive particles 336 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 312 and 322 are connected to each other via the conductive particles 336 in the adhesive 330, and the FPC 310 is mounted on the mother board 320.
- FIGS. 14A to 14C show an example in which the adhesive connection structure C and the solder connection structure D are formed on the mother board 320 which is a PWB.
- the adhesive connection structure C and the solder connection structure D may be formed on the FPC 310 using the FPC 310 as a common base material.
- the mother substrate 320 shown in FIG. 14 is replaced with the FPC 310, and the organic film 315 is formed on the adhesive connecting electrode 312.
- 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.
- connection method According to the connection method according to the third embodiment, the following effects can be exhibited. Normally, when solder connection and adhesive connection are performed on the same substrate, the organic film 325 is formed on the adhesive connection electrode 322, the solder connection is performed first, and then the connection using the adhesive is performed. It will be. This is because, when the adhesive is connected first, the adhesive is loosened during the solder reflow process, and the probability of connection failure increases. On the other hand, when the adhesive connection structure C is formed after the solder reflow process, the connection resistance for electrical connection between the electrodes 312 and 322 is larger than when the solder reflow furnace is not passed. There is a fear.
- the adhesive connection structure C is first formed in the step shown in FIG.
- the conductive particles 336 easily penetrate the organic films 315 and 325 and come into contact with the electrodes 312 and 322, so that conduction between the electrodes 312 and 322 is ensured.
- the relational expressions (1) and (2) are established so that the increase in connection resistance between the electrodes 312 and 322 falls within a predetermined range. So that the connection is done. Therefore, even if the adhesive connection structure C is formed before the solder connection structure D is formed, an increase in connection resistance and a deterioration in reliability between the adhesive connection electrodes 312 and 322 can be suppressed.
- connection strength (shear strength) between the electrodes 326 and 342 can be improved.
- the following effects can be obtained.
- the surfaces of the adhesive connection electrode 322 of the mother board 320 and the adhesive connection electrode 312 of the FPC 310 are subjected to OSP treatment to form an antioxidant film.
- Organic films 315 and 325 are respectively formed.
- the process of forming the antioxidant film is simplified compared to the case where the electrodes 312 and 322 are covered with the gold plating layer.
- 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 312 and 322 to each other can be reduced.
- connection by bonding and the connection by solder are performed so that the relational expressions (1) and (2) are satisfied, for example, so that the increase in the connection resistance between the electrodes 312 and 322 falls within a predetermined range. ing. Therefore, even if the adhesive connection structure C is formed before the solder connection structure D is formed, an increase in connection resistance between the adhesive connection electrode 312 and the adhesive connection electrode 322 (connected conductor) is suppressed. can do. In addition, since the connection with the adhesive 330 is performed before the solder reflow process, it is not necessary to strictly manage the average film thickness of the organic films 315 and 325 and the area ratio of the area where the film thickness is small during the OSP process.
- the conductive particles 336 in the adhesive 330 that is an 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 330
- adhesion is maintained while maintaining insulation between adjacent adhesive connection electrodes 322 or between the adhesive connection electrodes 312 to prevent a short circuit.
- the X direction which is the thickness direction of the agent 330, it is possible to obtain a low resistance by electrically connecting a large number of the adhesive connecting electrodes 322 and the adhesive connecting electrodes 312 at a time and independently of each other. It becomes.
- the conductive particles 336 have an aspect ratio of 5 or more. According to this configuration, when an anisotropic conductive adhesive is used, the contact probability between the conductive particles 336 increases. As a result, it becomes easy to electrically connect the electrodes 312 and 322 to each other without increasing the blending amount of the conductive particles 336.
- the adhesive 330 anisotropic conductive adhesive
- one having a film shape is used as the adhesive 330 (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
- the conductive particles 336 having the major axis direction oriented in the X direction which is the thickness direction of the adhesive 330 having a film shape (anisotropic conductive adhesive)
- the Y direction which is the surface direction of the adhesive 330
- adhesion is maintained while maintaining insulation between adjacent adhesive connection electrodes 322 or between the adhesive connection electrodes 312 to prevent a short circuit.
- the X direction which is the thickness direction of the agent 330
- the flexible printed wiring board (FPC 310) is connected to the hard printed wiring board (PWB) which is the mother board 320.
- PWB hard printed wiring board
- a multi-layered conductive pattern structure can be provided at a lower cost than when the mother board 320 is an FPC.
- FPC 310 on the mother board 320, as shown in FIG. 2, when connecting the FPC 10 to the connector of another board, as compared with the case where a hard printed wiring board is connected instead of the FPC 310, The degree of freedom of arrangement of other substrates can be improved.
- the adhesive connection electrodes 312 and 322 are covered with the organic films 315 and 325, the electrodes 312 and 322 can be made cheaper than the gold plating, so that the connection body of the mother board 320 and the FPC 310 is obtained. Can be provided at low cost.
- a hard printed wiring board PWB
- a flexible printed wiring board FPC
- the adhesive connection structure C is used to connect the electrodes of the FPC 310 and the mother board 320, which 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 320.
- electronic components may be mounted instead of the FPC 310.
- the water-soluble preflux treatment is performed on the adhesive connecting electrodes 312 and 322 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 312 and 322 are subjected to the OSP process.
- only one adhesive connection electrode 312 or 322 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 322 or 312, and the effect (1) of the embodiment can also be obtained by this.
- all the electrodes 312, 322, 326, and 342 may be provided with a gold plating layer without providing an organic film by OSP treatment.
- Example 1 (Example 1 according to the third embodiment) (Create adhesive) Since the creation of the adhesive is the same as that in Example 1 according to the first embodiment described above, description thereof is omitted. In addition, the glass transition temperature after hardening of this anisotropic conductive adhesive was 115 degreeC.
- 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%.
- connection resistance and adhesive strength In this joined body, the resistance value at 30 consecutive points connected via the adhesive connecting electrode, the adhesive, and the adhesive connecting electrode is obtained by the four-terminal method, and the obtained value is divided by 30. The connection resistance per connected place was determined. The case where the connection resistance was 50 m ⁇ or less was judged as ensuring conductivity.
- connection strength when the obtained joined body was peeled by 90 ° in the electrode direction at a speed of 50 mm / min was measured. When the adhesive strength was 300 N / m or more, it was judged that good adhesive strength was obtained.
- connection resistance and adhesive strength after solder reflow treatment Next, in a solder reflow bath, after performing solder reflow treatment with a peak temperature of 260 ° C., connection resistance and adhesive strength were measured in the same manner as described above. (Connection reliability evaluation) The connection body prepared as described above was allowed to stand for 500 hours in an 85 ° C., 85% RH high-temperature and high-humidity tank, and the connection resistance was measured in the same manner as described above. And when the rate of increase in connection resistance was 50% or less, it was judged that the connection reliability was good.
- Example 2 A joined body of flexible printed wiring boards is formed in the same manner as in Example 1 except that the average film thickness of the antioxidant film is 0.60 ⁇ m and the area ratio of the region where the thickness is 0.1 ⁇ m or less is 2%. Obtained. Thereafter, connection resistance evaluation and connection reliability evaluation were performed under the same conditions as in Example 1.
- Example 1 according to the third embodiment except that the composition of the adhesive was (1) 35 / (2) 20 / (3) 0 / (4) 20 / (5) 5 by weight ratio Similarly, the joined body of flexible printed wiring boards was obtained. The glass transition temperature after curing of the adhesive was 80 ° C.
- 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 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.
- the glass transition temperature of the adhesive was measured using a dynamic viscoelasticity measuring apparatus after the adhesive was completely cured.
- the temperature at which tan ⁇ takes the maximum value when measured at a frequency of 1 Hz at a temperature increase rate of 10 ° C./min is defined as the glass transition temperature.
- Table 3 shows the evaluation results of connection resistance, adhesive strength, and connection reliability of Examples 1 and 2 and Comparative Example according to the third embodiment.
- the initial connection resistance is 50 m ⁇ or less, and the connection resistance is sufficiently small and good.
- the rate of increase in resistance is 50% or less, it can be seen that the connection reliability is also good.
- the connection resistance R 1 before the solder reflow process is 42 (m ⁇ )
- the adhesive strength F 1 of the adhesive is 620 (N / m)
- the solder reflow process is performed.
- connection resistance R 1 43 (m ⁇ )
- adhesive strength F 1 680 (N / m)
- solder reflow is performed.
- connection resistance R 1 before solder reflow processing is 49 (m ⁇ )
- the adhesive strength F 1 320 (N / m)
- connection resistance is not increased so as to be within a predetermined range. This is because the adhesive strength of the adhesive decreased from 320 (N / m) to 120 (N / m) during the solder reflow process, that is, the tightening force of the adhesive was loosened. This is thought to be due to the deterioration of conductivity. That is, it can be understood that the connection reliability is deteriorated because the composition of the adhesive cannot satisfy the relational expressions (1) and (2). Furthermore, when Examples 1 and 2 according to the third embodiment are compared, both the connection resistance and the rate of increase in resistance are substantially equal.
- Example 2 even if the average film thickness is 0.5 ⁇ m or more and the area ratio of the region where the film thickness is 0.1 ⁇ m or less is reduced, the relational expressions (1) and (2) are It turns out that connection reliability becomes high by setting it as the mixing
- 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.
- the release sheet body of this invention can be used for connection of various wiring boards, such as a hard printed wiring board (PCB) other than FPC, and various electronic components.
- PCB hard printed wiring board
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- Combinations Of Printed Boards (AREA)
- Electric Connection Of Electric Components To Printed Circuits (AREA)
Abstract
Description
そこで、有機膜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ことにより、半田リフロー後にも,確実に有機膜が残存する。その後、有機膜を除去または薄くする処理を行うことにより、半田接続と接着剤接続とを円滑に行うことができる。
下記関係式(1),(2)
R2<1.2×R1 (1)
F2>0.8×F1 (2)
が成立するように、接続を行うことで、接続信頼性がより高くなることがわかった。
ガラス転移温度は、樹脂組成物の剛性と粘性が急激に変化する温度であり、この温度が高いほど高温での接着剤の強度(締め付け力)が低下する。そこで、ガラス転移温度が100℃以上の樹脂材料を用いることにより、前記関係式(1),(2)が成立する接続を行うことが容易となると考えられる。
特に、請求項19に記載された発明のように、第1部材上の第1導体と第2部材上の第2導体との間の接続構造として、以下の構造を採ることができる。すなわち、第1導体及び第2導体のうち少なくとも一方の導体の表面を、導通部分を除き、0.05μm以下の厚みを有する酸化防止膜で覆っておくか、あるいは、酸化防止膜で覆わずに接着剤に露出させる。
本発明の接続構造や電子機器により、製造工程の簡素化と金めっきの使用量の低減とを通じて、製造コストの削減を実現することができる。
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続構造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続構造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。
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。
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の第1の実施形態に係る例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、硬質プリント配線板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、両接着剤接続用電極12,22が互いに強く接触しあって導通している。
ただし、いずれか一方の電極(たとえば接着剤接続用電極12)の表面に有機膜15を残しておいてもよい(図4の破線参照)。たとえば、FPC10が半田リフロー処理を経ないなど、有機膜15が硬質化していない場合には、除去する必要がないからである。
なお、有機膜を除去する代わりに、有機膜を、たとえば0.05μm程度またはそれ以下に薄くしてもよい。
これらの有機膜を除去または薄くするために、酸性液またはその蒸気に、有機膜を接触させる方法としては、これらの溶液に有機膜を浸漬したり、酸性液または蒸気を有機膜に吹き付けたり、これらの酸を含む液を含ませた布で有機膜を拭いたりする、などの方法がある。これらの処理により、有機膜が除去または薄くされることが確認されている。
そして、有機膜を除去してから3日程度の猶予時間が経過する前であれば、各接着剤接続用電極12,22の表面に、ほとんど酸化膜を生じさせることなく、接着剤30による接続工程を行うことができる。有機膜を完全に除去せずに,少し残存させた場合には、前記猶予時間はさらに長くなる。低温、或いは低湿、或いは非酸化性雰囲気で保管した場合にも、猶予時間は長くなる。
各接着剤接続用電極12,22が有機膜15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を突き破るので、両接着剤接続用電極12,22が確実に接触しうる。なお、両接着剤接続用電極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り、長期間放置されて紫外線を浴びることで、有機膜15が硬質化する場合がある。その場合、各接着剤接続用電極12,22間の導通が有機膜によって妨げられ、電気的に接続する接続抵抗が大きくなるおそれがある。特に、半田リフロー炉において加熱されると、有機膜が硬質化しやすい。
また、OSP処理により形成された有機膜は、構成材料の種類によっても硬さの幅があり、ときには、相当に硬いものを使用せざるを得ない場合もあり得る。
その結果、接着剤接続用電極12の突起部が、硬質化した有機膜を突き破りにくくなり、接続抵抗の増大を招くことになる。
それに対し、本実施の形態では、各接着剤接続用電極12,22上の有機膜を除去または薄くしてから、接続工程を行うので、接着剤接続用電極12の突起部と接着剤接続用電極22とが容易に接触する。なお、一方の電極上の有機膜が半田リフロー工程を経ない場合には、接着剤接続用電極12の突起部が有機膜を突き破ることは容易であるので、有機膜を除去または薄くする必要はない。
よって、接着剤接続用電極12と,接着剤接続用電極22(被接続導体)との間における導通不良の発生(接続抵抗の増大など)を抑制することができる。
それに対し、本実施の形態では、有機膜が除去または薄くされるので、OSP処理時における有機膜の膜厚をたとえば0.5μm以上にしても不具合は生じない。
図5は、接着剤接続構造Cの第1の実施形態に係る例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(ACF)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、各接着剤接続用電極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、第1の実施形態に係る例1のように接着剤接続用電極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。
FPC10が半田リフロー工程を経ない場合には、図中破線で示す有機膜15は除去または薄くする必要はない。
有機膜を除去または薄くする処理の具体的方法については、例1で説明した通りである。
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。その場合でも、加熱加圧処理を行うことにより、各接着剤接続用電極12,22間では、微細な金属粒子が多数繋がった形状になるからである。
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7(a)~(d)は、接着剤接続構造Cおよび半田接続構造Dを実現するための第1の実施形態に係る接続方法の手順を示す断面図である。
まず、図7(a)に示す工程で、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15を形成する。本実施の形態では、有機膜15の熱分解温度は、半田リフロー温度よりも高い。
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。
また、図7(d)に示す工程の前に、FPC10上の接着剤接続用電極12を覆っていた有機膜15も除去または薄くする処理を行っておく。
ただし、FPC10が半田リフロー工程を経ない場合には、有機膜15を除去または薄くする処理を行う必要がない。
有機膜15を除去または薄くする処理も行うことで、OSP処理時における有機膜15の平均膜厚や、膜厚の小さい領域の面積率の管理をほとんど行う必要がなくなる利点もある。
なお、図7(a)に示す工程の際、有機膜15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。
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15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。
本実施の形態の接続方法では、図7(a)に示す工程で、接着剤接続用電極22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、図7(b)に示す工程でも、有機膜15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15の上に保護膜を形成すれば、より確実に、有機膜15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15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15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15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。
一方、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、各接着剤接続用電極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、接着剤による接続工程の前に、有機膜15を除去または薄くする処理を施すことで、半田リフロー処理によって硬化した有機膜15を導電性粒子が突き破ることが容易となる。よって、有機膜15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。
また、OSP処理時における有機膜15の平均膜厚や、膜厚が小さい領域の面積率を厳しく管理する必要がない。
(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それぞれ形成する構成としている。この構成によれば、各接着剤接続用電極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、各接着剤接続用電極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。
また、有機膜15の平均膜厚や、OSP処理時における膜厚が小さい領域の面積率を厳しく管理する必要がない。
・前記実施形態においては、母基板20として硬質プリント配線板(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。
(第1の実施形態に係る実施例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。
前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、接着剤接続用電極を塩酸水溶液(30℃、pH=4)に1分間浸漬することで、酸化防止膜を除去した後、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。
前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、前記と同様に、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0.60μm、厚さ0.1μm以下となる領域の面積率を2%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。
半田リフロー処理後に塩酸水溶液中への浸漬処理を行わなかったこと以外は実施例2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、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、第1の実施形態に係る実施例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、第1の実施形態に係る実施例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50mΩ以上と高かった。また、高温高湿槽中に500hr静置した後は接続オープンとなり、抵抗上昇率は∞(無限大)となった。この原因は、半田リフロー処理の際に比較例1の酸化防止膜が硬質化したにも拘わらず酸化防止膜を除去または薄くする処理を施さなかったことで、導電性粒子が酸化防止膜を確実に突き破ることができず、そのために導電性粒子と接着剤接続用電極との接触が不安定になったことによると考えられる。
さらに、第1の実施形態に係る実施例1、2を比較すると、初期接続抵抗,抵抗上昇率共に、ほぼ同等である。よって、実施例2のごとく、平均膜厚を0.5μm以上に、かつ、膜厚が0.1μm以下となる領域の面積率を小さくしても、酸化防止膜を除去または薄くする処理を施すことで、初期接続抵抗を低く、かつ、接続信頼性を高く維持しうることがわかる。
図8は、FPC210(フレキシブルプリント配線板)および電子部品240と、母基板220との間に形成される接着剤接続構造Cおよび半田接続構造Dの第2の実施形態に係る例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220の接着剤接続用電極222および半田接続用電極226は、硬質プリント配線板221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、接着剤接続構造Cにおいては、NCFである接着剤230の締め付け力によって、両電極212,222が互いに強く接触しあって導通している。半田接続構造Dにおいては、半田層250と各電極226,242との合金化により、両電極226,242が互いに導通している。
ただし、接着剤接続用電極212の表面にOSP処理による有機膜215を形成しておいてもよい(図8の破線参照)。FPC210が半田リフロー処理を経ない場合には、有機膜215の熱分解温度は半田リフロー処理の温度よりも高い必要はない。
電極212が有機膜215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215を突き破るので、両電極212,222が確実に接触しうる。なお、有機膜215が形成されていない場合には、必ずしも接着剤用電極212の表面が粗く加工されている必要はないが、粗く加工されている方が、接触を確保することが容易である。なお、両電極212,222間にバンプが配置されていてもよい。
たとえば、接着剤接続用電極222が、後述するOSP処理による有機膜で覆われている場合、母基板220が半田リフロー工程を経ることで、有機膜が硬質化する。その場合、各電極212,222間を電気的に接続する接続抵抗が大きくなるおそれがある。特に、半田リフロー炉において加熱されると、有機膜が硬質化しやすい。
その結果、接着剤接続用電極212の突起部が、硬質化した有機膜を突き破りにくくなり、接続抵抗の増大を招くことになる。
よって、接着剤接続用電極212と,接着剤接続用電極222(被接続導体)との間における導通不良の発生(接続抵抗の増大など)を抑制することができる。
図9は、接着剤接続構造Cおよび半田接続構造Dの第2の実施形態に係る例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(ACF)である接着剤230を用いている。すなわち、本例の接着剤230は、熱硬化性樹脂を主成分とする樹脂組成物231中に、導電性粒子236を含ませたものである。
そして、各電極212,222は、導電性粒子236を介して互いに導通している。導電性粒子236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、第2の実施形態に係る例1のように電極212,222同士が直接接触している箇所が存在していてもよい。
ただし、FPC10の接着剤接続用電極222の上に、図中破線で示す有機膜215が設けられていてもよい。
この例では、当初から、樹脂組成物231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236を含ませている。
ただし、樹脂組成物231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。その場合でも、加熱加圧処理を行うことにより、各電極212,222間では、微細な金属粒子が多数繋がった形状になるからである。
図10(a)~(d)は、接着剤接続構造Cおよび半田接続構造Dを実現するための接続方法の第2の実施形態に係る例1における手順を示す断面図である。
まず、図10(a)に示す工程で、接着剤接続領域Rcと、半田接続領域Rdとを有する母基板220(共通の基材)を準備する。母基板220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222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226が設けられている。
次に、半田接続用電極226のみを覆う有機膜225を形成する。そして、接着剤接続用電極222の上には、金めっき層も有機膜も形成しない。代わりに、接着剤接続用電極222を覆う,着脱自在な保護膜228を形成しておく。具体的には、粘着剤テープなどによって接着剤接続用電極222を覆っておく。粘着テープ以外の保護膜228を用いてもよいが、半田リフロー処理の温度に耐え、着脱自在であることが必要である。
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、半田接続用電極226上を覆っていた有機膜225は、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250に溶け込んでいる。
なお、接着剤接続用電極222が半田リフロー工程で酸化されても、図10(d)に示す工程の前に、酸化膜を除去する工程を実施すれば、図10(c)の工程の後、3日以上の長時間が経過しても不具合はない。
本実施の形態では、FPC210の接着剤接続用電極212上にも保護膜が設けられていたが、接着剤230による接続を行う直前に除去されている。
ただし、FPC210を共通の基材として、FPC210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10に示す母基板220をFPC210と置き換え、接着剤接続用電極212上に有機膜215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226と接着剤接続用電極222の双方の上に有機膜225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。
一方、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212,222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225が硬質化する等、変質することで、導電性粒子236が、有機膜を突き破りにくくなっていることによると考えられる。
本実施の形態の接続方法では、接着剤接続用電極222上には、有機膜を形成せずに、着脱自在な保護膜228を形成している。そして、図10(b)に示す工程では、接着剤接続用電極222の表面を保護膜228によって覆って、酸化膜の形成を抑制しつつ半田リフロー工程を行い、半田リフロー処理の後、図10(c)に示す工程で、保護膜228を除去している。
その結果、図10(d)に示す工程の際に、接着剤230中の導電性粒子236が、有機膜を介することなく容易に接着剤接続用電極212,222に接触し、接着剤接続用電極212,222間を確実に導通させることができる。
よって、有機膜215,225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212,222間の電気的な接続抵抗を小さく抑えることができる。
なお、半田接続用電極226の上に、酸化防止膜として金めっき層などの貴金属めっき層を設けた場合にも、接着剤接続用電極222を覆うOSP処理を行う必要がないことで、製造コストの削減効果が得られる。
図11(a)~(d)では、基本的には第2の実施形態に係る例1における図10(a)~(d)と同じ手順で処理を進める。そこで、第2の実施形態に係る例1と同じ処理については説明を省略し、異なる処理のみを説明する。
図11(a)に示す工程では、接着剤接続用電極222の上には、保護膜も設けない。従って、図11(b)に示す半田リフロー工程で、接着剤接続用電極222の上に、薄い酸化膜222aが形成されてしまう。
ただし、半田リフロー炉内の雰囲気をきわめて酸素濃度が低い(たとえば1%以下)非酸化性雰囲気に維持した場合には、酸化膜の厚みは無視しうる程度に薄くすることも可能である。
このように、酸化膜222aを除去する工程を実施すれば、前記例1のように半田リフロー処理後の保存期間を気にする必要はなくなる。
その結果、第2の実施形態に係る例1と同様に、図11(d)に示す工程の際に、接着剤230中の導電性粒子236が、有機膜を介することなく容易に接着剤接続用電極212,22に接触し、接着剤接続用電極212,222間を確実に導通させることができる。
(1)本実施形態の接着剤接続構造Cにおいては、母基板220の接着剤接続用電極222およびFPC210の接着剤接続用電極212のそれぞれの表面にOSP処理を施さず、金めっき等の貴金属めっき層も形成しないので、工程の簡素化、材料コストの低減により、製造コストの削減を図ることができる。
・前記実施形態においては、母基板220として硬質プリント配線板(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220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。
(第2の実施形態に係る実施例1)
(接着剤の作成)
接着剤の作成は、上述した第1の実施形態に係る実施例1と同じであるので、説明は省略する。
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。接着剤接続用電極は、OSP処理による有機膜、または貴金属めっき層で被覆していない。
前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。
基準は上述した第1の実施形態に係る実施例1と同様であるので、説明は省略する。
半田リフロー処理を施した後、異方導電性接着剤を用いた接合体を作製する前に、接着剤接続用電極を酢酸溶液で洗浄して酸化膜を除去したこと以外は第2の実施形態に係る実施例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-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、310℃、平均膜厚は0.60μm、厚さ0.1μm以下となる領域の面積率は4%であった。その後、上述の第2の実施形態に係る実施例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。
(比較例2)
リフロー槽内を大気雰囲気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。
手順等は、第1の実施形態に係る実施例2と同じであるので、説明は省略する。
(膜厚測定)
手順等は、第1の実施形態に係る実施例2と同じであるので、説明は省略する。
表2に示すように、第2の実施形態に係る実施例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、第2の実施形態に係る実施例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50mΩ以上と高く、抵抗上昇率は∞(無限大)であった。比較例1では、半田リフロー処理の際には、接着剤接続用電極を酸化防止膜で覆っているので、接着剤接続用電極には酸化膜は形成されていない。しかし、半田リフロー処理の際に、酸化防止膜が硬質化していることで、導電性粒子が酸化防止膜を確実に突き破ることができず、そのために導電性粒子と接着剤接続用電極との接触が不安定になったと考えられる。
また、比較例2では、初期接続抵抗が比較例1よりもさらに高く、抵抗上昇率は∞(無限大)であった。比較例2では、半田リフロー処理の際に接着剤接続用電極を酸化防止膜で覆っておらず、かつ、酸化性雰囲気で半田リフロー処理を行なったことにより、接着剤接続用電極に酸化膜が形成されている。その結果、電極-導電性粒子間の接触抵抗が高くなったと考えられる。
さらに、第2の実施形態に係る実施例1、2を比較すると、初期接続抵抗,抵抗上昇率共に、ほぼ同等である。したがって、実施例1のごとく接着剤接続用電極に酸化膜が形成されないように非酸化性雰囲気で半田リフロー処理するだけでも、初期接続抵抗を低く、かつ、接続信頼性を高く維持しうることがわかる。
ただし、第2の実施形態に係る実施例1よりも第2の実施形態に係る実施例2の方が、初期接続抵抗,抵抗上昇率共に、わずかであるが優れている。よって、第2の実施形態に係る実施例2のごとく酸化膜を除去する工程を実施することにより、初期接続抵抗をより低く、かつ、接続信頼性をより高く維持しうることがわかる。
図12は、FPC310(フレキシブルプリント配線板)および電子部品340と、母基板320との間に形成される接着剤接続構造Cおよび半田接続構造Dの第3の実施形態に係る例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320の接着剤接続用電極322および半田接続用電極326は、硬質プリント配線板321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、接着剤接続構造Cにおいては、NCFである接着剤330の締め付け力によって、両電極312,322が互いに強く接触しあって導通している。半田接続構造Dにおいては、半田層350と各電極326,342との合金化により、両電極326,342が互いに導通している。
ただし、各電極312,322,326,342上に、有機膜315,325に代えて、金めっき層等の他の酸化防止膜を形成しておいてもよい。
半田層350による接続時には、母基板320と電子部品340とを、ピーク温度が約260℃の半田リフロー炉に入れて,半田をリフローさせる。このとき、半田接続用電極326およびチップ側電極342上の有機膜は半田層350に溶け込む。
各電極312,322が有機膜315,325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315,325を突き破るので、両電極312,322が確実に接触しうる。なお、両電極312,322間にバンプが配置されていてもよい。
R2<1.2×R1 (1)
F2>0.8×F1 (2)
が成立している。
具体的には、熱硬化性樹脂の種類の選択や、半田リフロー処理の温度の設定などによって、関係式(1),(2)が成立する条件を見出している。
一般的に、接着剤接続構造Cと半田接続構造Dとが、共通の基材上に存在する場合、先に半田リフロー処理を行なって半田接続構造Dを形成する手順が採用される。先に接着剤接続構造Cを形成すると、接続抵抗が増大するおそれがあるからである。
また、接着剤330の締め付け力の緩みが所定範囲内に収まるように、たとえば、前記関係式(2)が成立するように、接続を行っている。よって、長期間使用時における接続抵抗の増大(接続の信頼性の悪化)を抑制することができる。
図13は、接着剤接続構造Cおよび半田接続構造Dの第3の実施形態に係る例2を示す断面図である。図13において、図12と同じ部材は、同じ符号を付して説明を省略する。接着剤接続構造Cにおいては、異方導電性接着剤(ACF)である接着剤330を用いている。すなわち、本例の接着剤330は、熱硬化性樹脂を主成分とする樹脂組成物331中に、導電性粒子336を含ませたものである。
そして、各電極312,322は、導電性粒子336を介して互いに導通している。導電性粒子336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、第3の実施形態に係る例1のように電極312,322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331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336を含ませている。
図14(a)~(c)は、接着剤接続構造Cおよび半田接続構造Dを実現するための接続方法の手順を示す断面図である。
まず、図14(a)に示す工程で、接着剤接続領域Rcと、半田接続領域Rdとを有する母基板320(共通の基材)を準備する。母基板320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322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326が設けられている。
次に、各接着剤接続用電極322,326を覆う有機膜325を形成する。
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、半田接続用電極326上を覆っていた有機膜325は、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350に溶け込んでいる。
ただし、FPC310を共通の基材として、FPC310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14に示す母基板320をFPC310と置き換え、接着剤接続用電極312上に有機膜315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、接着剤接続用電極322の上に有機膜325を形成してから、先に半田接続を行い、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。
一方、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312,322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325が硬質化する等、変質することで、導電性粒子336が、有機膜325を突き破りにくくなっていることによると考えられる。
本実施の形態の接続方法では、図14(b)に示す工程で、先に接着剤接続構造Cを形成している。そのため、図14(b)に示す工程では、導電性粒子336が容易に有機膜315,325を突き破って、各電極312,322に接触し、各電極312,322間の導通が確保される。
一方、図14(c)に示す工程の前後においては、各電極312,322間の接続抵抗の増大が所定範囲内に収まるように、たとえば、前記関係式(1),(2)が成立するように、接続を行っている。よって、半田接続構造Dの形成前に、接着剤接続構造Cを形成しても、各接着剤接続用電極312,322間における接続抵抗の増大や信頼性の悪化を抑制することができる。
(1)本実施形態の接着剤接続構造Cにおいては、母基板320の接着剤接続用電極322およびFPC310の接着剤接続用電極312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315,325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312,322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312,322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。
また、半田リフロー処理の前に、接着剤330による接続を行うので、有機膜315,325の平均膜厚や、OSP処理時における膜厚が小さい領域の面積率を厳しく管理する必要がない。
・前記実施形態においては、母基板320として硬質プリント配線板(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320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。
あるいは、全ての電極312,322,326,342にOSP処理による有機膜は設けず、金めっき層を設けてもよい。
(接着剤の作成)
接着剤の作成は、上述した第1の実施形態に係る実施例1と同じであるので、説明は省略する。なお、この異方導電性接着剤の硬化後のガラス転移温度は115℃であった。
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。
前記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成した接着剤を挟み、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。
(接続抵抗、接着強度の測定)
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。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。また、得られた接合体を電極方向に50mm/minの速度で90°剥離した際の接着強度を測定した。接着強度が300N/m以上の場合、良好な接着強度が得られたと判断した。
(半田リフロー処理後の接続抵抗、接着強度の測定)
次に、半田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後、前記と同様に接続抵抗、接着強度を測定した。
(接続信頼性評価)
前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、前記と同様に、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0.60μm、厚さ0.1μm以下となる領域の面積率を2%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。
接着剤の配合を重量比で(1)35/(2)20/(3)0/(4)20/(5)5の割合としたこと以外は第3の実施形態に係る実施例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。接着剤の硬化後のガラス転移温度は80℃であった。
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。
(接着剤のガラス転移温度測定)
接着剤のガラス転移温度は、接着剤を完全に硬化させた後、動的粘弾性測定装置を用いて測定した。10℃/minの昇温速度で1Hzの周波数で測定した際にtanδが最大値をとる温度をガラス転移温度とする。
表3に示すように、第3の実施形態に係る実施例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、第3の実施形態に係る実施例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。
また、第3の実施形態に係る実施例1では、半田リフロー処理前の接続抵抗R1=42(mΩ)で、接着剤の接着強度F1=620(N/m)であり、半田リフロー処理後の接続抵抗R2=43(mΩ)、接着剤の接着強度F2=600(N/m)であるから、上述の関係式(1),(2)
R2=43<1.2×R1=1.2×42=50.4 (1)
F2=600>0.8×F1=0.8×620=496 (2)
を満足している。
同様に、第3の実施形態に係る実施例2では、半田リフロー処理前の接続抵抗R1=43(mΩ)で、接着剤の接着強度F1=680(N/m)であり、半田リフロー処理後の接続抵抗R2=45(mΩ)、接着剤の接着強度F2=650(N/m)であるから、上述の関係式(1),(2)
R2=45<1.2×R1=1.2×43=51.6 (1)
F2=650>0.8×F1=0.8×680=544 (2)
を満足している。
つまり、第3の実施形態に係る実施例1,2の場合、接続抵抗の増大が所定範囲内に収まるように行われている。
また、比較例1では、半田リフロー処理前の接続抵抗R1=49(mΩ)で、接着剤の接着強度F1=320(N/m)であり、半田リフロー処理後の接続抵抗R2=150(mΩ)、接着剤の接着強度F2=120(N/m)であるから、
R2=150>1.2×R1=1.2×49=58.8
F2=120<0.8×F1=0.8×320=256
となって、上述の関係式(1),(2)を満足していない。つまり、比較例1の場合、接続抵抗の増大が所定範囲内に収まるように行われていない。
この原因は、半田リフロー処理の際に、接着剤の接着強度が320(N/m)から120(N/m)に低下した、つまり接着剤の締め付け力が緩んだことで、導電性粒子による導通性が悪化したことによると考えられる。つまり、前記関係式(1),(2)を満足することができないような接着剤の配合となっていることで、接続信頼性の悪化を招いていることがわかる。
さらに、第3の実施形態に係る実施例1、2を比較すると、接続抵抗,抵抗上昇率共に、ほぼ同等である。したがって、実施例2のごとく、平均膜厚を0.5μm以上とし、かつ、膜厚が0.1μm以下となる領域の面積率を小さくしても、前記関係式(1),(2)が成り立つような接着剤の配合とすることにより、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(被接続導体)
13 カバーレイ
15 有機膜
20 母基板
21 硬質プリント配線板
22 接着剤接続用電極
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(被半田接続導体)
50 半田層
Claims (20)
- 接着剤接続用電極が設けられた基材を準備する工程(a1)と、
前記基材上の接着剤接続用電極を、酸化防止のための有機膜で被覆する工程(b1)と、
前記有機膜を除去または薄くする工程(c1)と、
前記工程(c1)の後、熱硬化性樹脂を主成分とする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ことにより電気的に接続する工程(d1)と、
を含む接続方法。 - 請求項1記載の接続方法において、
前記工程(c1)では、酸性液またはその蒸気に、前記有機膜を接触させることにより行われる、接続方法。 - 請求項1又は2のいずれかに記載の接続方法において、
前記工程(a1)では、前記基材として、半田接続用導体が設けられた基材を準備し、
前記工程(b1)の後,前記工程(c1)の前に、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半田接続導体に接合する工程(e1)をさらに含む接続方法。 - 接着剤接続用電極および半田接続用電極が設けられた基材を準備する工程(a2)と、
前記基材上の半田接続用電極のみを、OSP処理による有機膜、または貴金属めっき膜で被覆する工程(b2)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、前記半田接続用電極を被半田接続導体に接合する工程(c2)と、
前記工程(c2)の後、熱硬化性樹脂を主成分とする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ことにより電気的に接続する工程(d2)と、
を含む接続方法。 - 請求項4に記載の接続方法において、
前記工程(b2)の後、前記工程(c2)の前に、前記接着剤接続用電極を覆う、着脱自在な保護膜を形成し、
前記工程(c2)は、前記保護膜が残存する温度で行い、
前記工程(d2)の前に、前記保護膜を除去する、接続方法。 - 請求項4又は5のいずれかに記載の接続方法において、
前記工程(c2)の後、前記工程(d2)の前に、前記接着剤接続用電極の表面の酸化膜を除去する、接続方法。 - 請求項4~6のうちいずれか1つに記載の接続方法において、
前記工程(c2)は、酸素濃度が1%以下の非酸化性雰囲気で行われる、接続方法。 - 接着剤接続用電極および半田接続用電極が設けられた基材を準備する工程(a3)と、
前記基材上の接着剤接続用電極および半田接続用電極を、酸化防止膜で被覆する工程(b3)と、
前記工程(b3)の後、熱硬化性樹脂を主成分とする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ことにより電気的に接続する工程(c3)と、
前記工程(c3)の後、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半田接続導体に接合する工程(d3)と、
を含み、
前記工程(d3)の前後における、前記接着剤接続用電極-被接続導体間の接続抵抗の増大が所定範囲内に収まるように行われる、接続方法。 - 請求項8記載の接続方法において、
前記工程(c3)の後で前記工程(d3)の前における、前記接着剤接続用電極-被接続導体間の接続抵抗をR1とし、前記接着剤の接着強度をF1とし、
前記工程(d3)の後における、前記接着剤接続用電極-被接続導体間の接続抵抗をR2とし、前記接着剤の接着強度をF2としたとき、
下記関係式(1),(2)
R2<1.2×R1 (1)
F2>0.8×F1 (2)
が成立するように、行われる、接続方法。 - 請求項8または9のいずれかに記載の接続方法において、
前記接着剤の樹脂組成物として、硬化後におけるガラス転移温度が100℃以上の樹脂材料を用いる、接続方法。 - 請求項8~10のうちいずれか1つに記載の接続方法において、
前記工程(c3)では、前記酸化防止膜として有機膜を形成する、接続方法。 - 請求項1~11のうちいずれか1つに記載の接続方法において、
前記接着剤として、導電性粒子を含有した異方導電性接着剤を用いる、接続方法。 - 請求項12に記載の接続方法において、
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、接続方法。 - 請求項13に記載の接続方法において、
前記導電性粒子のアスペクト比が5以上である、接続方法。 - 請求項1~14のうちいずれか1つに記載の接続方法において、
前記接着剤として、フィルム形状を有するものを用いる、接続方法。 - 請求項15に記載の接続方法において、
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る、接続方法。 - 請求項1~16のうちいずれか1つに記載の接続方法において、
前記基材として、フレキシブルプリント配線板を準備する、接続方法。 - 請求項1~17のうちいずれか1つに記載の接続方法を用いて形成された接続構造。
- 熱硬化性樹脂を主成分とする接着剤を介して互いに接着させることにより電気的に接続される第1部材上の第1導体と第2部材上の第2導体との間の接続構造であって、
前記第1導体の一部と第2導体の一部とは互いに導通しており、
前記第1導体および第2導体のうち少なくとも一方の導体の表面は、前記一部を除いて、0.05μm以下の厚みを有する酸化防止のための有機膜に覆われている、あるいは、有機膜に覆われることなく前記接着剤に露出している、接続構造。 - 請求項1~18のうちいずれか1つに記載の接続方法を用いて組み立てられた電子機器。
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KR20120029406A (ko) | 2012-03-26 |
US20120067619A1 (en) | 2012-03-22 |
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EP2445322A1 (en) | 2012-04-25 |
EP2440024A1 (en) | 2012-04-11 |
EP2453726A1 (en) | 2012-05-16 |
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