CN107079589B

CN107079589B - Method for manufacturing connected body, method for connecting electronic component, and connected body

Info

Publication number: CN107079589B
Application number: CN201580052796.8A
Authority: CN
Inventors: 浅羽康佑; 林慎一; 田中雄介
Original assignee: Dexerials Corp
Current assignee: Dexerials Corp
Priority date: 2014-10-16
Filing date: 2015-10-13
Publication date: 2020-06-09
Anticipated expiration: 2035-10-13
Also published as: JP6609406B2; KR20170069962A; TWI688176B; KR102476432B1; CN107079589A; WO2016060098A1; JP2016082070A; TW201633638A

Abstract

The invention ensures the bonding strength of the electronic component caused by the formation of the adhesive bead, and prevents the fouling of the support table, the bonding of the substrate and the increase of the connection resistance of the electronic component caused by the adhesive resin. The method comprises an adhesive disposing step of disposing a circuit connecting adhesive (6) containing a photopolymerization initiator on a circuit board (2) having light permeability, and a pressure bonding step of disposing an electronic component (5) on the circuit board (2) with the circuit connecting adhesive (6) therebetween, heating and pressing the electronic component (5) against the circuit board (2), and curing the circuit connecting adhesive (6), wherein the melt viscosity of the circuit connecting adhesive (6) at the heating temperature in the pressure bonding step is 4000Pa · s or less.

Description

Method for manufacturing connected body, method for connecting electronic component, and connected body

Technical Field

The present invention relates to a method for manufacturing a connected body in which an electronic component is connected to a transparent substrate via a circuit-connecting adhesive containing a photopolymerization initiator, a method for connecting an electronic component to a transparent substrate via a circuit-connecting adhesive containing a photopolymerization initiator, and a connected body manufactured by the manufacturing method.

This application claims priority based on japanese patent application No. 2014-212108, filed on 16/10/2014 in japan, which is incorporated herein by reference.

Background

Conventionally, when a rigid substrate such as a glass substrate or a glass epoxy substrate is connected to an electronic component such as a flexible substrate or an IC chip, an anisotropic conductive film in which a binder resin in which conductive particles are dispersed is formed into a film shape has been used. In the case of connecting the connection terminals of the flexible substrate and the connection terminals of the rigid substrate, as shown in fig. 6 (a), an anisotropic conductive film 53 is disposed between the flexible substrate 51 and the rigid substrate 54 in the region where the

connection terminals

52 and 55 are formed, the buffer material 50 is appropriately disposed, and heat pressing is performed from the flexible substrate 51 by a heat press tool 56. Then, as shown in fig. 6 (B), the adhesive resin exhibits fluidity and flows out from between the connection terminal 52 of the flexible substrate 51 and the connection terminal 55 of the rigid substrate 54, and the conductive particles in the anisotropic conductive film 53 are pinched between both the connection terminals and crushed.

As a result, the connection terminal 52 of the flexible substrate 51 and the connection terminal 55 of the rigid substrate 54 are electrically connected by the conductive particles, and the binder resin is cured in this state. The conductive particles not present between the

connection terminals

52 and 55 are dispersed in the binder resin, and maintain an electrically insulated state. Thereby, electrical conduction is achieved only between the connection terminal 52 of the flexible substrate 51 and the connection terminal 55 of the rigid substrate 54.

Further, on the side surface of the rigid substrate 54, the binder resin is squeezed out from between the flexible substrate 51, and a burr (fillet) is formed between the connection surface with the flexible substrate 51, thereby improving the bonding strength.

However, in recent years, for example, in connection between a glass substrate and a flexible substrate of a liquid crystal panel, thinning of the glass substrate has progressed, and a so-called picture frame portion, which is an outer edge portion of a screen, has also progressed to be narrowed with an increase in size of a liquid crystal screen with respect to a housing of an electronic apparatus. Therefore, in the connection method using the thermosetting anisotropic conductive film, the heat pressing temperature is high, and the thermal shock to the glass substrate or the flexible substrate becomes large. When the temperature is lowered to room temperature after the anisotropic conductive film is connected, the adhesive shrinks due to the temperature difference, and the thinned glass substrate may warp. Therefore, there is a possibility that display unevenness and poor connection of the flexible substrate may occur.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2005-26577

Disclosure of Invention

Problems to be solved by the invention

Therefore, a connection method of an anisotropic conductive film using an ultraviolet curing adhesive instead of such a thermosetting adhesive has been proposed. In a connection method using an ultraviolet-curable adhesive, the adhesive is softened and fluidized by heat, heated to a temperature sufficient for trapping conductive particles between electrodes of a glass substrate and a flexible substrate, and cured by ultraviolet irradiation.

In the connection method using such an ultraviolet-curable adhesive, it is not necessary to apply high heat for curing the binder resin, and it is possible to prevent troubles such as distortion due to thermal shock to the glass substrate or the flexible substrate.

In recent years, as displays in portable electronic devices and the like have been increased in size, plastic substrates having light weight and flexibility have been used. Plastic substrates also have lower resistance to thermal shock than glass substrates and the like, and in a connection process using an ultraviolet-curable adhesive, connection under further low-temperature and low-pressure conditions is required.

Here, since the low-temperature connection is performed using the ultraviolet curing adhesive, thermal shock due to low temperature can be prevented, but on the other hand, the flow of the adhesive in the adhesive is insufficient, and insufficient pushing of the conductive particles into the terminal portion may occur, resulting in poor conduction reliability. Therefore, the ultraviolet-curable adhesive needs to reduce the viscosity of the adhesive resin itself.

However, if the viscosity of the binder resin is reduced, there is a possibility that: when an electronic component such as a flexible substrate is mounted and pressed by a thermocompression bonding tool, the melted adhesive resin is pushed out from the side surface of the substrate and spreads to the back surface side of the substrate. Further, since the adhesive resin flows into the back surface of the substrate, there is a possibility that a supporting base for supporting the substrate is contaminated, and there is a possibility that the substrate is damaged when the substrate attached to the supporting base is peeled off.

If the melt viscosity of the binder resin is increased in order to prevent such extrusion of the binder resin, formation of burrs is inhibited, and the adhesive strength is insufficient. In addition, under low temperature and low pressure conditions, the press-fitting of electronic components such as flexible substrates is insufficient, resulting in an increase in on-resistance.

Further, such a problem may occur not only in the case of using a photo-curable anisotropic conductive adhesive but also in the case of using a thermosetting type and photo-thermosetting type anisotropic conductive adhesives.

The present invention solves the above problems, and an object thereof is to provide: a method for manufacturing a connection body which secures the bonding strength of an electronic component by forming a fillet and prevents the contamination of a support base, the bonding of a substrate, and the increase of the connection resistance of the electronic component by a binder resin; a method for connecting electronic components and a connected body manufactured by the manufacturing method.

Means for solving the problems

In order to solve the above problems, a method for manufacturing a connected body according to the present invention includes an adhesive disposing step of disposing an adhesive for circuit connection containing a photopolymerization initiator on a circuit board having light permeability, and a pressure bonding step of disposing an electronic component on the circuit board via the adhesive for circuit connection, heating and pressing the electronic component to the circuit board, and curing the adhesive for circuit connection, wherein a melt viscosity of the adhesive for circuit connection at a heating temperature in the pressure bonding step is 4000Pa · s or less.

The method for connecting an electronic component according to the present invention includes an adhesive placing step of placing an adhesive for circuit connection containing a photopolymerization initiator on a circuit board having optical transparency, and a pressure bonding step of placing an electronic component on the circuit board with the adhesive for circuit connection interposed therebetween, heating and pressing the electronic component to the circuit board, and curing the adhesive for circuit connection, wherein the melt viscosity of the adhesive for circuit connection at the heating temperature in the pressure bonding step is 4000Pa · s or less.

The present invention also relates to a connected body produced by the above-described production method.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, since the melt viscosity at the heating temperature in the main pressure bonding step is 4000Pa · s or less, it is possible to obtain good conduction reliability by sufficiently pressing in the conductive particles by excluding the binder resin. Further, according to the present invention, the extrusion width W of the fillet formed between the circuit board and the electronic component is also made appropriate, and the connection strength between the circuit board and the electronic component can be improved and the contamination of the support table can be prevented.

Drawings

Fig. 1 is a sectional view showing an example of a method for producing a connected body to which the present invention is applied.

Fig. 2 is a perspective view showing an example of a method for producing a connected body to which the present invention is applied.

Fig. 3 is a side view showing one embodiment of an anisotropic conductive film.

Fig. 4 is a sectional view schematically showing a main pressure bonding step.

Fig. 5 is a plan view schematically showing the areal density distribution of the conductive particles of the connector.

Fig. 6 is a sectional view showing a conventional method for producing a connected body, fig. 6 (a) is an exploded sectional view, and fig. 6 (B) is a sectional view at the time of main pressure bonding.

Detailed Description

Hereinafter, a method for manufacturing a connected body, a method for connecting an electronic component, and a connected body to which the present invention is applied will be described in detail with reference to the drawings. It is to be understood that the present invention is not limited to the following embodiments, and various changes and modifications may be made without departing from the scope of the present invention. The drawings are schematic, and the ratio of the dimensions and the like may be different from the actual ratio. Specific dimensions and the like should be determined with reference to the following description. It is to be noted that, of course, the portions having different dimensional relationships and ratios from each other in the drawings are also included.

The connector to which the present invention is applied is a connector in which an electronic component such as a flexible substrate is connected to a circuit substrate having light transmissivity through an anisotropic conductive adhesive, and can be used for a display device such as a television, a PC, a smart phone, a mobile phone, a game machine, an audio device, a tablet terminal, a wearable terminal, and a display panel for a vehicle, a touch panel, and a substrate in which all other electronic devices are built. In such a substrate, from the viewpoint of making a pitch fine, making a weight light, and making a thickness thin, so-called COF (chip on film), COG (chip on glass), FOF (film on film), and FOG (film on glass) are used in which an IC chip or a flexible substrate on which various circuits are formed is directly mounted on a circuit board having light transmissivity. In addition, as a bonding film used for bonding various substrates to an IC chip, a flexible substrate, or the like, an Anisotropic Conductive Film (ACF) in which conductive particles are dispersed in a binder resin layer is often used.

Hereinafter, a touch sensor 1 incorporated as an input device in various display panels will be described as an example of a connected body to which the present invention is applied. As the touch sensor 1, a touch sensor in which two substrates such as a film and a plastic substrate formed with an electrode pattern are combined and a touch sensor in which electrode patterns are formed on both surfaces of one substrate are widely used.

The transparent film 2 as a base is formed with electrode patterns as sensor portions in a matrix, and each electrode pattern is connected to a connection terminal 3 formed at the outer edge portion of the transparent film 2 via a wiring pattern. As shown in fig. 1 and 2, the touch sensor 1 has a flexible substrate 5 connected to a position detection controller connected to a mounting portion 4 in which a plurality of connection terminals 3 are arranged.

As the transparent film 2 serving as the base of the touch sensor 1, for example, a film material made of a transparent synthetic resin such as PET (polyethylene terephthalate), polycarbonate, a material reinforced by attaching a polyimide film to a PET film, or a film of a cycloolefin resin composition film in which an elastomer or the like is dispersed in a cycloolefin resin can be used. As the electrode pattern constituting the sensor portion, a transparent conductive material containing an organic conductive polymer as a main component can be used. For example, a composition containing at least a polythiophene derivative polymer, a water-soluble organic compound, and a dopant is given. By using a paste made of such an organic conductive polymer as a printing ink, for example, direct patterning by screen printing can form an electrode pattern having a predetermined shape on the surface of the transparent film 2. Alternatively, after applying the organic conductive polymer to both surfaces of the transparent film 2, the layer portion of the organic conductive polymer may be degraded by a transparent printing ink containing an acid or an alkali agent, thereby forming an electrode pattern. In addition, various methods such as gravure printing and inkjet printing can be used for patterning the electrode pattern. Further, photolithography or the like in which a surface of a substrate coated with a photosensitive substance is pattern-wise exposed to form a predetermined pattern may be used. That is, as the electrode pattern, a method other than the above-described method may be used as long as a transparent conductive material containing an organic conductive polymer as a main agent can be formed.

The plurality of connection terminals 3 connected with each other through the electrode patterns and the wiring patterns may be formed by forming an ITO transparent conductive film by a known method such as sputtering or vacuum deposition, directly patterning the ITO transparent conductive film by screen printing of a silver paste, or etching a copper foil. The plurality of connection terminals 3 are formed in a substantially rectangular shape, for example, and as shown in fig. 2, a plurality of connection terminals are formed in an outer edge portion of the transparent film 2 so as to be aligned in a direction orthogonal to the longitudinal direction, thereby constituting a mounting portion 4 to which the flexible substrate 5 is connected.

As a conductive adhesive, an Anisotropic Conductive Film (ACF) 6 can be used for connecting the mounting portion 4 and the flexible substrate 5. As will be described later, the anisotropic conductive film 6 contains conductive particles in a binder resin, and electrically connects the connection terminal 7 of the flexible substrate 5 and the connection terminal 3 formed on the transparent film 2 via the conductive particles.

[ Flexible substrate ]

The flexible substrate 5 connected to the mounting portion 4 of the transparent film 2 is connected to a not-shown controller for position detection, and serves as a connector for connecting the connection terminals 3 provided for each electrode pattern constituting the sensor portion to the controller. As shown in fig. 2, in the flexible substrate 5, a plurality of connection terminals 7 connected to the connection terminals 3 of the transparent film 2 are formed in a line on one surface 9a of a flexible substrate 9 made of polyimide or the like. The connection terminal 7 is formed by patterning a copper foil or the like, and appropriately performing plating coating such as nickel-gold plating on the surface, and is formed, for example, substantially rectangular like the connection terminal 3, and a plurality of the connection terminals are arranged in a direction orthogonal to the longitudinal direction. The width of the connection terminal 7 and the width of the connection terminal 3, and the interval between the adjacent connection terminals 7 and the interval between the adjacent connection terminals 3 are arranged in substantially the same pattern, and the connection terminal 7 and the connection terminal 3 are overlapped with each other with the anisotropic conductive film 6 interposed therebetween.

[ covering layer ]

In addition, the flexible substrate 5 is provided with a cover layer 8 in the vicinity of the connection terminal 7. The cover layer 8 protects the other wiring pattern formed on the one surface 9a of the substrate 9 connected to the transparent film 2, and an adhesive layer is provided on the one surface of the insulating base film, and is adhered to the one surface 9a of the substrate 9 via the adhesive layer.

In the touch sensor 1, the mounting portion 4 of the transparent film 2 on which the connection terminal 3 is provided and the outer edge portion of the flexible substrate 5 on which the connection terminal 7 is provided are narrowed, and therefore, as shown in fig. 2, the mounting portion and the outer edge portion include a part of the cover layer 8 covering the vicinity of the outer edge of the flexible substrate 5 and are connected to each other through the anisotropic conductive film 6. Thus, the touch sensor 1 ensures electrical connection reliability and mechanical connection reliability between the transparent film 2 and the flexible substrate 5.

[ Anisotropic conductive film ]

The anisotropic conductive film 6 is a photocurable adhesive, and is fluidized by being thermally pressed by a thermal compression bonding tool 20 described later, so that the conductive particles 16 are crushed between the transparent film 2 and the

connection terminals

3 and 7 of the flexible substrate 5, and the conductive particles 16 are cured in a crushed state by light irradiation. Thereby, the anisotropic conductive film 6 electrically and mechanically connects the transparent film 2 and the flexible substrate 5.

As shown in fig. 3, for example, the anisotropic conductive film 6 is formed into a film shape by dispersing conductive particles 16 in a binder resin 15 (adhesive) and applying the thermosetting adhesive composition to a base film 17.

The base film 17 is formed by coating a release agent such as silicone on PET (polyethylene terephthalate), OPP (oriented polypropylene), PMP (poly-4-methylpentene-1), PTFE (polytetrafluoroethylene), or the like, for example.

The binder resin 15 is not particularly limited if it is photocurable, and may be of a radical polymerization type, a cationic polymerization type, or the like. The radical polymerizable binder resin will be described below.

The radical polymerizable adhesive resin contains a film-forming resin, a radical polymerizable compound, and a radical polymerization initiator. As the film-forming resin, a phenoxy resin, an epoxy resin, a polyester resin, a polyurethane resin, a polyamide, a thermoplastic elastomer such as EVA, or the like can be used. Among them, bisphenol a type phenoxy resins synthesized from bisphenol a and epichlorohydrin are preferably used for heat resistance and adhesiveness.

The radical polymerizable compound may be appropriately selected from (meth) acrylates used in the field of adhesives and the like. In the present specification, the term (meth) acrylate is used to include acrylate (acrylate) and methacrylate (methacrylate).

Specific examples of the radical polymerizable compound include epoxy acrylate, EO-modified isocyanurate diacrylate, tricyclodecane dimethanol diacrylate, dimethylol-tricyclodecane diacrylate, polyethylene glycol diacrylate, urethane acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, isobutyl acrylate, t-butyl acrylate, isooctyl acrylate, bisphenoxyethanol fluorene diacrylate, 2-acryloyloxyethyl succinic acid, lauryl acrylate, stearyl acrylate, isobornyl acrylate, cyclohexyl acrylate, tris (2-hydroxyethyl) isocyanurate triacrylate, tetrahydrofurfuryl acrylate, diglycidyl phthalate acrylate, ethoxylated bisphenol A dimethacrylate, ethylene glycol diacrylate, propylene glycol diacrylate, bisphenol A type epoxy acrylate, and their corresponding (meth) acrylate, etc., and can use their 1 or more than 2. Among them, acrylates, urethane acrylates and the like are preferably used. Specific examples of commercially available products include trade names "M-315" and "M1600" manufactured by Toyo Seiko Kabushiki Kaisha.

The photo radical polymerization initiator can be suitably selected from known radical polymerization initiators and used.

Examples of the photopolymerization type radical polymerization initiator include thioxanthones such as ethanone, 1- [ 9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl ] -,1- (O-acetyloxime), benzophenone, 4-bis (diethylamino) benzophenone, and 2,4, 6-trimethylbenzophenone; acetophenones such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one and benzil dimethyl ketal; benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether; acylphosphine oxides such as 2,4, 6-trimethylbenzoyldiphenylphosphine oxide, bis (2, 6-dimethoxybenzoyl) -2,4, 4-trimethylpentylphosphine oxide, bis (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide and the like.

These radical polymerization initiators may be used alone in 1 kind, or 2 or more kinds may be used in combination. Among them, 1-bis (t-butylperoxy) cyclohexane, bis (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide, and the like are preferably used. Specific examples of commercially available products include "IRGACURE OXE 02" available under the trade name BASF Japan (strain).

Further, as other additives to be added to the circuit connecting material, a silane coupling agent, an inorganic filler, an acrylic rubber, a diluting monomer such as various acrylic monomers, a filler, a softening agent, a colorant, a flame retardant, a thixotropic agent, and the like may be contained as necessary.

The silane coupling agent is not particularly limited, and examples thereof include epoxy-based, amino-based, mercapto-sulfide-based, and urea-based. By adding the silane coupling agent, the adhesiveness at the interface between the organic material and the inorganic material can be improved.

The inorganic filler is not particularly limited, and silica, talc, titanium oxide, calcium carbonate, magnesium oxide, or the like can be used. By adding the inorganic filler, the fluidity of the binder resin 15 can be controlled, and the particle collection rate can be improved.

As the conductive particles 16, any known conductive particles used in the anisotropic conductive film 6 can be cited. Examples of the conductive particles 16 include particles of various metals and metal alloys such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, and gold; particles in which metal is coated on the surface of particles of metal oxide, carbon, graphite, glass, ceramic, plastic, or the like; or particles in which the surfaces of these particles are further coated with an insulating film. When the surface of the resin particle is coated with a metal particle, examples of the resin particle include particles of an epoxy resin, a phenol resin, an acrylic resin, an acrylonitrile-styrene (AS) resin, a benzoguanamine resin, a divinylbenzene resin, a styrene resin, and the like.

In addition, the anisotropic conductive film 6 may be configured such that a cover film is provided on one surface opposite to the surface on which the base film 17 is laminated, from the viewpoints of ease of handling, storage stability, and the like. The shape of the anisotropic conductive film 6 is not particularly limited, and for example, a long tape shape that can be wound around a winding reel 18 and cut to a predetermined length may be used.

The anisotropic conductive film 6 according to the present invention may be a multilayer anisotropic conductive film in which a pressure-sensitive adhesive resin layer containing conductive particles 16 and an insulating adhesive layer formed of an insulating adhesive composition containing no conductive particles are laminated. The anisotropic conductive adhesive used for connecting the flexible substrate 5 may be a paste-like anisotropic conductive paste, in addition to the anisotropic conductive film 6 formed into a film shape.

[ melt viscosity ]

Here, the anisotropic conductive film 6 according to the present technology has a melt viscosity of 4000Pa · s or less at a heating temperature by the thermocompression bonding tool 20 in a main bonding step of the flexible substrate 5 described later. By setting the melt viscosity of the anisotropic conductive film 6 at the heating temperature in the primary pressure bonding step to be in this range, the adhesive resin 15 exhibits appropriate fluidity even in the primary pressure bonding step under low-temperature and low-pressure conditions in which the photocurable anisotropic conductive film 6 is used, and the conductive particles 16 are sufficiently pressed into the

connection terminals

3 and 7, whereby conduction reliability can be secured.

The binder resin 15 exhibits appropriate fluidity, and the binder resin is appropriately pushed out from the side surface 2a of the transparent film 2 protruding from the flexible substrate 5, and the burrs 21 are formed by irradiation with ultraviolet light. This increases the contact area of the adhesive resin 15 between the transparent film 2 and the flexible substrate 5, and the adhesive resin 15 is fused to the base material of the transparent film 2 or the flexible substrate 5 and cured to exhibit the so-called anchor effect, thereby improving the adhesive strength.

In addition, the anisotropic conductive film 6 according to the present technology preferably has a melt viscosity of 1000Pa · s or more at a heating temperature by the thermocompression bonding tool 20 in the main bonding step of the flexible substrate 5. By setting the melt viscosity of the anisotropic conductive film 6 at the heating temperature in the main pressure bonding step to the above range, the adhesive resin 15 is extruded on the side surface 2a of the transparent film 2 from which the flexible substrate 5 protrudes, and the extrusion width W of the formed nodules 21 is set to an appropriate length, whereby the adhesive strength can be improved by increasing the connection area with the adhesive resin 15, and the adhesive resin 15 can be prevented from spreading from the side surface 2a of the transparent film 2 to the back surface to contaminate the support table.

In particular, in the anisotropic conductive film 6 according to the present technology, in the low-temperature bonding step in which the heating temperature by the thermocompression bonding tool 20 in the main bonding step is set to 100 ℃ or lower, the melt viscosity at the heating temperature is set to 1000Pa · s or more and 4000Pa · s or less, whereby the conduction reliability can be ensured and the adhesive strength with the flexible substrate 5 can be improved, and the thermal shock to the transparent film 2 and the flexible substrate 5 can be suppressed, and the trouble such as the distortion can be prevented.

[ production Process ]

Next, a manufacturing process of the touch sensor 1 will be described. The manufacturing process of the touch sensor 1 includes the following steps: an adhesive disposing step of disposing the anisotropic conductive film 6 on the mounting portion 4 of the transparent film 2; and a main pressure bonding step of disposing the flexible substrate 5 on the transparent film 2 with the anisotropic conductive film 6 interposed therebetween, heating and pressing the flexible substrate 5 against the transparent film 2, and irradiating ultraviolet light to cure the anisotropic conductive film 6.

[ temporary sticking step ]

First, the anisotropic conductive film 6 is temporarily attached to the transparent film 2 (adhesive disposing step). The anisotropic conductive film 6 is temporarily attached by disposing the anisotropic conductive film 6 on the connection terminal 3 of the transparent film 2 so that the adhesive resin 15 is on the connection terminal 3 side. After the adhesive resin 15 is disposed on the connection terminals 3, the adhesive resin 15 is transferred to the transparent film 2 by heating and pressing from the base film 17 side with a thermocompression bonding tool, and the base film 17 is peeled from the adhesive resin 15.

[ Aligning Process/temporary crimping Process ]

Next, the flexible substrate 5 is placed on the transparent film 2 while aligning the flexible substrate 5 so that the transparent electrode 6 and the connection terminal 7 of the flexible substrate 5 face each other with the adhesive resin 15 interposed therebetween, and the flexible substrate 5 is temporarily pressure-bonded under low-temperature and low-pressure conditions to the extent that the adhesive resin 15 exhibits fluidity. This minimizes warpage of the transparent film 2 and prevents thermal damage to the flexible substrate 5.

[ formal crimping step ]

Next, as shown in fig. 4, the flexible substrate 5 is heated and pressed against the transparent film 2, and ultraviolet light is irradiated thereon, whereby electrical connection and mechanical connection are performed (main pressure bonding step). In the main pressure bonding step, the pressure bonding tool 20 heats the adhesive resin 15 at a low temperature, and applies pressure at a predetermined pressure so that the conductive particles 4 are sandwiched between the connection terminal 7 of the flexible substrate 5 and the connection terminal 3 of the transparent film 2. Further, a cushion material 22 made of a sheet-like elastic material such as silicone rubber is interposed between the hot pressing surfaces of the thermocompression bonding tool 20.

In the main pressure bonding step, ultraviolet light is irradiated from the back side of the transparent film 2 by the ultraviolet irradiator 23. Ultraviolet rays emitted from the ultraviolet irradiator 23 are transmitted through a transparent support base 24 such as glass supporting the transparent film 2 and irradiated on the binder resin 15.

As the ultraviolet irradiator 23, an LED lamp, a mercury lamp, a metal halide lamp, or the like can be used. The ultraviolet irradiator 23 is disposed on the back side of the support table 24, and starts irradiation of ultraviolet rays simultaneously with the start of heating and pressing of the flexible substrate 5 by the thermocompression bonding tool 20 or after a delay of a predetermined time from the start of heating and pressing. Accordingly, the viscosity is reduced by being heated and pressed by the thermocompression bonding tool 20, the conductive particles 16 are sandwiched between the connection terminal 3 of the transparent film 2 and the connection terminal 7 of the flexible substrate 5, and the adhesive resin 15 is pushed out on the side surface of the transparent film 2, and at such timing, the ultraviolet irradiator 23 irradiates ultraviolet rays to cure the adhesive resin 15.

Thereby, the flexible substrate 5 is electrically and mechanically connected to the transparent film 2, and the burrs 21 are provided, thereby forming the touch sensor 1 having improved adhesive strength.

Here, as described above, the melt viscosity of the anisotropic conductive film 6 at the heating temperature by the thermocompression bonding tool 20 is 4000Pa · s or less. Therefore, according to the present technology, even in the main pressure bonding step under a low pressure condition of less than 10MPa, for example, 3 to 5MPa, the binder resin 15 can exhibit appropriate fluidity and sufficiently press-fit the conductive particles 16 through the

connection terminals

3 and 7.

On the other hand, if the melt viscosity of the anisotropic conductive film 6 at the heating temperature by the thermocompression bonding tool 20 is higher than 4000Pa · s, the fluidity of the adhesive resin 15 is low, and the elimination of the adhesive resin between the

connection terminals

3 and 7 is insufficient, so that the press-fitting of the conductive particles 16 is insufficient, and the conduction reliability is impaired.

Further, by setting the melt viscosity of the anisotropic conductive film 6 at the heating temperature by the thermocompression bonding tool 20 to 1000Pa · s or more, the extrusion width W of the adhesive resin 15 extruded on the side surface of the transparent film 2 protruding from the flexible substrate 5 becomes an appropriate length, and the build-up 21 having an appropriate size can be formed by irradiation with ultraviolet light, and the bonding strength can be improved.

On the other hand, if the melt viscosity of the anisotropic conductive film 6 at the heating temperature by the thermocompression bonding tool 20 is less than 1000Pa · s, the adhesive resin 15 spreads to the back surface of the transparent film 2, and there is a possibility that the transparent support 24 is stained and the transparent film 2 is broken when the transparent film 2 bonded to the support 24 is peeled off.

Further, according to the present technology, when the hot press bonding tool 20 is used to perform the low temperature press bonding at a heating temperature of 100 ℃ or lower, for example, 80 ℃, as the main press bonding step, the melt viscosity at the heating temperature is set to 1000Pa · s or higher and 4000Pa · s or lower, whereby it is possible to secure conduction reliability and improve the bonding strength with the flexible substrate 5, and it is possible to suppress thermal shock to the transparent film 2 and the flexible substrate 5 and prevent troubles such as distortion.

[ surface Density distribution of conductive particles ]

Here, in the touch sensor 1 manufactured in the present manufacturing process, the conductive particles 16 bonded by the thermocompression bonding tool 20 exhibit a predetermined surface density distribution, thereby improving the bonding strength and the conduction reliability. Specifically, as shown in fig. 5, in the touch sensor 1, the surface density distribution of the conductive particles 16 after the transparent film 2 and the flexible substrate 5 are connected is: when the particle density from the mounting portion 4 where the thermal compression bonding tool 20 presses the flexible substrate 5 and the anisotropic conductive film 6 to the outer edge portion 12 of the outer edge of the transparent film 2 where the burrs 21 are formed is (a) and the particle density on both the

connection terminals

3 and 7 in the mounting portion 4 pressed by the thermal compression bonding tool 20 is (b), a > b.

Here, the area density distribution refers to a distribution of densities a and b of the conductive particles 16 on the same plane as the outer edge portion 12 and the mounting portion 4, and is obtained by comparing a particle density a of the outer edge portion 12 on the same plane as a plane where the conductive particles 16 are sandwiched between the two

connection terminals

3 and 7 in the mounting portion 4 with a particle density b of the two

connection terminals

3 and 7 in the mounting portion 4.

The main purposes of the invention are as follows: by the heat and pressure of the thermocompression bonding tool 20, the adhesive resin 15 of the anisotropic conductive film 6 flows, and the burrs 21 are formed on the side surfaces of the transparent film 2, thereby achieving both conduction reliability and bonding strength. Further, if the flashes 21 are appropriately cured by the ultraviolet irradiation, the flow in the outer edge portion 12 is blocked, and therefore the conductive particles 16 have different flowability on the same plane, and are accumulated at the maximum amount in the outer edge portion 12 to have a high density. In the mounting portion 4 in which the conductive particles 16 are sandwiched between the both

connection terminals

3 and 7, the binder resin 15 is extruded by the heat pressure of the thermocompression bonding tool 20, and thus the particle density becomes relatively small.

By providing such a density distribution of the conductive particles 16, the anisotropic conductive film 6 can be formed with the nodules 21 between the transparent film 2 and the flexible substrate 5 by the binder resin 15, and the adhesive strength can be improved. That is, according to the anisotropic conductive film 6, the density (a) of the conductive particles 16 in the outer edge portion 12 is higher than the density (b) of the conductive particles in the mounting portion 4, and therefore, it is known that more of the binder resin 15 flows and is cured in the outer edge portion 12. As shown in fig. 4, the adhesive resin 15 flowing through the outer edge portion 12 forms a bead 21 between the transparent film 2 and the flexible substrate 5. This enables the anisotropic conductive film 6 to firmly bond the transparent film 2 and the flexible substrate 5.

Further, since the anisotropic conductive film 6 has such a density distribution of the conductive particles 16, the adhesive resin 15 appropriately flows out from between the both

connection terminals

3 and 7, and thus the conductive particles 16 can be reliably held by press-fitting with the thermocompression bonding tool 20, and conduction reliability can be improved.

That is, by confirming the surface density distribution of the conductive particles 16 in the mounting portion 4 and the outer edge portion 12, it can be easily checked that both the adhesiveness and the functionality are achieved. That is, it is known that the particle surface density is measured without performing a breakdown test such as a peel strength test, and the conductive particles 16 are biased so that the end portion as a peeling start point is reinforced by an increase in the local strength of the bead portion and the conductive particles 16 are appropriately sandwiched between the both

connection terminals

3 and 7 in the mounting portion 4 pressed by the thermocompression bonding tool 20 so that the anisotropic conductivity is favorably maintained, and the adhesion strength and the conduction reliability of the transparent film 2 and the flexible substrate 5 can be easily tested without breaking.

[ others ]

Among the above, the case where the flexible substrate 5 is used as the electronic component is described as an example, but the present invention may be applied to an IC chip, a flexible flat cable, a rigid substrate, a Tape Carrier Package (TCP), and the like, in addition to the flexible substrate 5.

Examples

Next, examples of the present invention will be described. In this example, a sample of a connected body in which a flexible substrate for evaluation was connected to a plastic film substrate for evaluation was formed using an anisotropic conductive film containing a photo-curing or heat-curing agent. For each of the connected body samples, conduction reliability evaluation, measurement of an extrusion width (mm) of the bead, measurement of a particle area density (pcs/200 × 200 μm), and distortion evaluation of the plastic film substrate after the pressure bonding step were performed.

[ Anisotropic conductive film ]

The anisotropic conductive films used for the production of the connected body samples according to the examples and comparative examples were prepared in 4 kinds, a to D, according to the formulation (unit: part by mass) shown in table 1. The anisotropic conductive films according to formulas a to C are photocurable adhesives, and the anisotropic conductive film according to formula D is a thermosetting adhesive.

[ Table 1]

The mixed solutions according to the respective formulations A to D were applied to a PET film and dried in an oven to form a film having a thickness of 16 μm, a width of 20cm and a length of 30 cm. The density of the conductive particles of the anisotropic conductive films according to the respective formulations A to D before pressure bonding was 20 pcs/200X 200. mu.m.

[ Flexible substrate for evaluation ]

The flexible substrate for evaluation used a substrate having a copper wiring pattern of 12 μm thickness formed by Au plating on one surface of a polyimide substrate of 25 μm thickness. The pitch of the wiring was 400 μm, and L/S was 1/1.

[ Plastic film substrate for evaluation ]

As a circuit board for evaluation used for the anisotropic conductive film, a transparent plastic film was used in which an ITO electrode was provided on a PET film having a thickness of 50 μm and a Cu electrode was laminated on the ITO electrode (the thickness of each electrode was 0.1 μm). The pitch of the wiring was 400 μm, and L/S was 1/1.

The anisotropic conductive film was temporarily bonded to the plastic film substrate and the flexible substrate for evaluation was temporarily pressure-bonded, and then a main pressure-bonding was performed while using heat pressure by a heat pressure-bonding tool and ultraviolet irradiation by an ultraviolet irradiation device (ZUV-C30H: available from ohilon corporation), thereby forming a connected body sample.

The main pressure bonding temperature of the thermal compression bonding tool was 80 ℃ in examples 1 and 2, comparative examples 1 and 3, and 130 ℃ in comparative examples 2 and 4. In each of examples and comparative examples, the final pressure bonding pressure and time of the thermocompression bonding tool were 4MPa and 5 seconds, and a cushioning material of silicone rubber having a thickness of 450 μm was interposed between the thermocompression surfaces of the thermocompression bonding tool. In addition, the ultraviolet irradiator was disposed on the back side of the transparent support table supporting the transparent plastic film substrate, and irradiation with ultraviolet light was started for 1 second from 4 seconds after the start of heating and pressing of the flexible substrate by the thermocompression bonding tool, in addition to comparative example 3. The end of irradiation and the end of thermal pressing by the thermal compression bonding tool are set to be the same. Further, the illuminance of ultraviolet ray was 180mW/cm²(peak wavelength: 365 nm).

Then, the initial on-resistance value (Ω) and the on-resistance value (Ω) after the reliability test were measured for the samples of the interconnectors according to the examples and comparative examples. The conditions for the reliability test were 60 ℃ 95% RH100 hr. The on-resistance value was measured by connecting a digital multimeter to an ITO electrode or a Cu electrode of a transparent plastic film substrate connected to a connection terminal of the flexible substrate for evaluation, measuring the resistance value when a current of 2mA was applied by a so-called 4-terminal method, measuring 30 times, and taking the average value thereof as the on-resistance value. For the on-reliability evaluation, 5 Ω or less was OK, and a case of more than 5 Ω was NG.

The extrusion width W of the bead of the connected body sample was measured by measuring the width W of the bead formed in the planar direction on the side surface of the plastic film substrate extending from the flexible substrate (see fig. 4). After the connection, the connected body sample is lifted from the transparent support table, and the extruded adhesive is OK if it is not attached and NG if it is attached to either the transparent plastic film substrate side (the side opposite to the surface in contact with the heat pressing surface of the heat press tool) or the transparent support table itself of the connected body sample.

Regarding the surface density distribution of the conductive particles of the connected body sample, the particle density in the outer edge region extending from the pressing region of the thermocompression bonding tool to the outer edge of the transparent plastic film substrate on which the burrs are formed was set to (a), and the particle density in the pressing region by the thermocompression bonding tool was set to (b), and the particle density on the same plane in each region was measured at 200 × 200 μm.

Distortion of the transparent plastic film after pressure bonding was visually observed, and a case where the pressing region by the thermal compression bonding tool had a wavy appearance was x, and a case where the wavy appearance was not confirmed and the same appearance as that outside the pressing region was exhibited was ○.

[ example 1]

In example 1, the photocurable anisotropic conductive film according to formulation a was used. The melt viscosity of the anisotropic conductive film according to the formula A at a heating temperature (80 ℃) in the main pressure bonding step was 1000 pas. The sample of the interconnector of example 1 was evaluated for conduction reliability of 5 Ω or less (OK) and for extrusion width W of the glioma of 550 μm (OK). Further, the particle density (a) in the outer peripheral region was 12.1 pcs/200X 200. mu.m, and the particle density (b) in the nip region was 4.2 pcs/200X 200. mu.m. Further, no distortion of the transparent plastic film of the sample web was confirmed.

[ example 2]

In example 2, the photocurable anisotropic conductive film according to formulation B was used. The melt viscosity of the anisotropic conductive film according to the formula B at a heating temperature (80 ℃) in the main pressure bonding step is 4000 pas. The sample of the interconnector of example 2 was evaluated for conduction reliability of 5 Ω or less (OK) and for extrusion width W of the glioma of 400 μm (OK). Further, the particle density (a) in the outer peripheral region was 11.1 pcs/200X 200. mu.m, and the particle density (b) in the nip region was 4.5 pcs/200X 200. mu.m. Further, no distortion of the transparent plastic film of the sample web was confirmed.

Comparative example 1

In comparative example 1, the photocurable anisotropic conductive film according to formulation C was used. The melt viscosity of the anisotropic conductive film according to formulation C at the heating temperature (80 ℃) in the main pressure bonding step was 10000 pas. The connection reliability of the sample of the connection body according to comparative example 1 was evaluated as 20 Ω or more (NG), and the extrusion width W of the nodules was 200 μm (OK). Further, the particle density (a) in the outer peripheral region was 8.4 pcs/200X 200. mu.m, and the particle density (b) in the nip region was 4.2 pcs/200X 200. mu.m. In addition, no distortion of the transparent plastic film of the sample web was confirmed.

Comparative example 2

In comparative example 2, the photocurable anisotropic conductive film according to formulation C was used. In comparative example 2, the heating temperature in the main pressure bonding step was set to 130 ℃. The sample of the interconnect according to comparative example 2 was evaluated for conduction reliability of 5 Ω or less (OK) and for extrusion width W of the bead of 350 μm (OK). Further, the particle density (a) in the outer peripheral region was 11.5 pcs/200X 200. mu.m, and the particle density (b) in the nip region was 4.6 pcs/200X 200. mu.m. In addition, distortion of the transparent plastic film of the sample web was confirmed.

Comparative example 3

In comparative example 3, a heat-curable anisotropic conductive film according to formulation D was used. The melt viscosity of the anisotropic conductive film according to formulation D at the heating temperature (80 ℃) in the main pressure bonding step was 1000 pas. The connection reliability of the sample of the connection body according to comparative example 3 was evaluated as 20 Ω or more (NG), and the extrusion width W of the nodules was 550 μm (OK). Further, the particle density (a) in the outer peripheral region was 13.5 pcs/200X 200. mu.m, and the particle density (b) in the nip region was 5.1 pcs/200X 200. mu.m. In addition, no distortion of the transparent plastic film of the sample web was confirmed.

Comparative example 4

In comparative example 4, the photocurable anisotropic conductive film according to formulation a was used. In comparative example 4, the heating temperature in the main pressure bonding step was set to 130 ℃. The connection reliability of the connection body sample of comparative example 4 was evaluated as 5 Ω or less (OK), and the width W of the extrusion of the burrs was 900 μm (ng). Further, the particle density (a) in the outer peripheral region was 12.9 pcs/200X 200. mu.m, and the particle density (b) in the nip region was 4.7 pcs/200X 200. mu.m. In addition, distortion of the transparent plastic film of the sample web was confirmed.

[ Table 2]

As shown in table 2, in the samples of the interconnectors according to examples 1 and 2, since the melt viscosity at the heating temperature in the main pressure bonding step is 1000 to 4000Pa · s, the conductive particles can be sufficiently pressed by excluding the binder resin, and good conduction reliability is obtained. In addition, in the connected body samples according to example 1 and example 2, the extrusion width W of the bead was also set to an appropriate width, and the connection strength between the plastic film substrate and the flexible substrate was improved. This can also be confirmed by the particle density distribution of the linker samples according to examples 1 and 2. Further, in the connected body samples according to example 1 and example 2, no distortion of the plastic film substrate was observed.

On the other hand, in the connected body sample according to comparative example 1, the melt viscosity at the heating temperature in the main crimping step was as high as 10000Pa · s, and the evaluation of conduction reliability was lowered due to insufficient penetration of the conductive particles, and the extrusion width W of the binder resin was also small, and the connection strength was also lowered.

In addition, in the connected body sample according to comparative example 2, the fluidity of the binder resin was improved by increasing the pressure bonding temperature in the main pressure bonding step as compared with comparative example 1, and therefore, improvement was observed in the conduction reliability and the extrusion width W of the burrs, but the plastic film substrate after pressure bonding exhibited distortion.

In the connected body sample of comparative example 3 using the thermosetting anisotropic conductive film, the curing reaction was insufficient due to the low-temperature heating at 80 ℃.

In the connected body sample according to comparative example 4, since the anisotropic conductive film of formulation a having a low melt viscosity at 80 ℃ and a melt viscosity of 1000Pa · s was used and the pressure bonding temperature in the main pressure bonding step was increased to 130 ℃, the fluidity of the adhesive resin became excessive, the extrusion width W of the bead became large, the adhesive resin spread to the back surface of the plastic film substrate, and the plastic film substrate after pressure bonding showed distortion.

Description of the symbols

1: a touch sensor; 2: a transparent film; 3: a connection terminal; 4: an installation part; 5: a flexible substrate; 6: an anisotropic conductive film; 7: a connection terminal; 8: a cover layer; 9: a substrate; 12: an outer edge portion; 20: a thermocompression bonding tool; 21: colloid tumors; 22: a cushioning material; 23: an ultraviolet irradiator; 24: a support table.

Claims

1. A method for manufacturing a connected body, comprising the steps of:

an adhesive preparation step of providing a circuit connection adhesive containing a photopolymerization initiator on a circuit board having light transmissivity; and

a pressure bonding step of disposing an electronic component on the circuit board with the circuit connecting adhesive interposed therebetween, heating and pressing the electronic component against the circuit board, and curing the circuit connecting adhesive,

the melt viscosity of the circuit connecting adhesive at the heating temperature in the pressure bonding step is 1000Pa s to 4000Pa s,

in the pressure bonding step, the electronic component is heated at a temperature of 100 ℃ or lower,

in the press-bonding step, the circuit-connecting adhesive is extruded on a side surface of the circuit board from which the electronic component protrudes to form a bead,

the burr region is higher than a pressing region of the electronic component with respect to a particle density of conductive particles contained in the adhesive for circuit connection after the pressure bonding step.

2. The method for manufacturing a connected body according to claim 1, wherein the circuit substrate is a plastic film substrate.

3. The method for manufacturing a connected body according to claim 1, wherein the circuit substrate is a sensor film of a touch panel.

4. The method for manufacturing a connected body according to claim 1, wherein the electronic component is a flexible substrate.

5. A method for connecting electronic components, comprising the steps of:

6. A connector produced by the method of any one of claims 1 to 4.