HK1238795A1 - Connector inspection method, connector, conductive particle and anisotropic conductive adhesive - Google Patents

Description

Method for inspecting connected body, conductive particle, and anisotropic conductive adhesive

Technical Field

The present invention relates to a method of inspecting a connected body formed on a transparent electrode of a transparent substrate and connected to a connection terminal of an electronic component for anisotropic conductive connection, and to the connected body, and more particularly, to a method of inspecting a connected body, conductive particles, and an anisotropic conductive adhesive for improving visibility of conductive particles captured between a transparent electrode and a connection terminal.

The present application claims priority based on japanese patent application No. kokai 2014-250384, filed on 10.12.2014 in japan, and is incorporated by reference into the present application.

Background

Conventionally, liquid crystal display devices and organic EL panels have been used as various display units such as television sets, PC monitors, mobile phones, smart phones, portable game machines, tablet personal computer terminals, wearable terminals, and in-vehicle monitors. In recent years, in such display devices, in view of fine pitch, light weight, and thin profile, a method of directly mounting a driving IC on a glass substrate of a display panel using an Anisotropic Conductive Film (ACF) or a method of directly mounting a flexible substrate on which a driving circuit and the like are formed on a glass substrate has been adopted.

A glass substrate on which an IC or a flexible substrate is mounted is provided with a plurality of transparent electrodes made of ITO (indium tin oxide) or the like, and electronic components such as an IC or a flexible substrate are connected to the transparent electrodes. In an electronic component connected to a glass substrate, a plurality of electrode terminals are formed on a mounting surface corresponding to transparent electrodes, and the electrode terminals and the transparent electrodes are connected by thermocompression bonding the electronic component to the glass substrate through an anisotropic conductive film.

The anisotropic conductive film is formed by mixing conductive particles into a binder resin to form a film, and electrically conducts between the conductors by the conductive particles by heating and pressure bonding between the two conductors, and the mechanical connection between the conductors is maintained by the binder resin. As the adhesive constituting the anisotropic conductive film, a highly reliable thermosetting adhesive resin is generally used, but a photocurable adhesive resin or a photothermal adhesive resin may be used.

In the case of connecting an electronic component to a transparent electrode via such an anisotropic conductive film, first, the anisotropic conductive film is temporarily stuck on the transparent electrode of the glass substrate by a temporary pressure bonding means. Next, after the temporary connection body is formed by mounting the electronic component on the glass substrate with the anisotropic conductive film interposed therebetween, the electronic component and the anisotropic conductive film are heated and pressed together toward the transparent electrode side by a thermocompression bonding unit such as a thermocompression bonding head. By heating the thermocompression bonding head, a thermosetting reaction is generated in the anisotropic conductive film, whereby the electronic component is bonded to the transparent electrode.

Documents of the prior art

Patent document

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

Disclosure of Invention

Problems to be solved by the invention

As the conductive particles to be sandwiched between the transparent electrode of the glass substrate and the connection terminal of the electronic component such as the IC chip, particles having a conductive layer formed by plating a conductive material such as nickel or gold on the surface of the resin core are generally used. The conductive particles sandwiched between the transparent electrode and the connection terminal are electrically connected to the transparent electrode and the connection terminal through the conductive layer.

However, the conductive layer may be peeled off from the surface of the resin core due to friction with the transparent electrode or the connection terminal by unexpected vibration generated when pressure bonding is performed during anisotropic connection. Further, the conductive layer may be eluted by an acid or the like generated in the binder resin at the time of anisotropic connection or at the time of treatment before and after the anisotropic connection. In this way, if the conductive particles are sandwiched between the transparent electrode and the connection terminal in a state where the surface of the resin core is exposed, the conductivity may be impaired.

Such a phenomenon occurs not only in the entire conductive particles trapped between the transparent electrode of one group and the connection terminal but also in some of the plurality of conductive particles trapped between the transparent electrode of one group and the connection terminal.

In a connector for anisotropic connection of a glass substrate and an electronic component such as an IC or a flexible substrate, there are various factors that are considered to reduce the conductivity, but since the substrate or the electronic component is thinned and the wiring is finely spaced along with the miniaturization of electronic equipment, it takes a considerable number of man-hours and time to find the connector. In other words, it is examined in advance whether the factors of the conduction failure are caused by the constituent members of the connected body such as the glass substrate and the electronic component, the peeling or elution of the conductive layer of the conductive particles, or the insufficient press-fitting of the conductive particles due to the alignment in the thermocompression bonding step, the setting of the thermocompression bonding tool, the accuracy, and the like, and improvement is strongly desired in order to improve the yield.

Therefore, if the above-described determination as to whether or not the conductive particles have been peeled off or eluted from the conductive layer or whether or not the conductive particles have been sufficiently pressed into the space between the transparent electrode and the connection terminal can be easily performed, the load on the inspection step can be reduced.

However, the resin core of the conductive particles is colorless or translucent, and if the conductive layer peels off or dissolves, it is difficult to grasp the position or collapse of the conductive particles captured on the connection terminal.

Accordingly, an object of the present invention is to provide a method for inspecting a connected body, conductive particles, and an anisotropic conductive adhesive, which can easily and quickly inspect conductive particles after the production of the connected body.

Means for solving the problems

In order to solve the above-described problems, a method for inspecting a connected body in which a transparent electrode formed on a transparent substrate and a connection terminal of an electronic component are connected to each other by an anisotropic conductive adhesive, wherein conductive particles sandwiched between the transparent electrode and the connection terminal are formed by coating a resin core with a conductive layer, the resin core is colored in a color different from that of the connection terminal, and the exposure of the surface of the resin core captured by the transparent electrode is detected by the coloring of the resin core.

In addition, a connector according to the present invention is a connector in which a transparent electrode formed on a transparent substrate and a connection terminal of an electronic component are connected to each other by an anisotropic conductive adhesive, wherein conductive particles sandwiched between the transparent electrode and the connection terminal are formed by coating a resin core with a conductive layer, the resin core is colored in a color different from that of the connection terminal, and the conductive particles captured on the transparent electrode can be visually recognized by coloring the resin core when a surface of the resin core is exposed.

The conductive particles according to the present invention are conductive particles contained in an adhesive for anisotropically and electrically connecting a transparent electrode formed on a transparent substrate and a connection terminal of an electronic component, and the conductive particles comprise: a resin core; and a conductive layer covering a surface of the resin core, wherein the resin core is colored in a color different from that of the connection terminal, and the exposure of the surface of the resin core can be visually recognized by the coloring of the resin core.

An anisotropic conductive adhesive according to the present invention is an anisotropic conductive adhesive which contains conductive particles in a binder resin and connects a transparent electrode formed on a transparent substrate and a connection terminal of an electronic component, wherein the conductive particles include: a resin core; and a conductive layer covering a surface of the resin core, wherein the resin core is colored in a color different from that of the connection terminal, and the exposure of the surface of the resin core can be visually recognized by the coloring of the resin core.

Effects of the invention

According to the present invention, since the conductive particles held between the transparent electrode and the connection terminal are covered with the conductive layer and at least a part of the resin core is colored in a color different from that of the connection terminal, the conductive particles captured by the connection terminal after pressure bonding can be improved in visibility when the colored surface of the resin core is exposed, and the degree of peeling and elution of the conductive layer and the collapse of the conductive particles can be easily grasped.

Drawings

Fig. 1 is a cross-sectional view of a liquid crystal display panel shown as an example of a connector.

Fig. 2 is a plan view showing a mounting portion of the transparent substrate.

Fig. 3 is a sectional view showing a connection process of the liquid crystal driving IC and the transparent substrate.

Fig. 4 is a plan view showing a mounting surface of the liquid crystal driving IC.

Fig. 5 is a sectional view showing an anisotropic conductive film.

Fig. 6 is a sectional view showing conductive particles.

Fig. 7 is a bottom view showing conductive particles captured by bumps from the back surface side of the transparent substrate of the connected body, (a) shows conductive particles in which peeling/elution of the conductive layer has not occurred, (B) shows conductive particles in which peeling/elution of the conductive layer laminated on the colored resin core has occurred, and (C) shows conductive particles in which peeling/elution of the conductive layer laminated on the uncolored resin core has occurred.

Detailed Description

Hereinafter, a method of inspecting a connected body, conductive particles, and an anisotropic conductive adhesive to which the present invention is applied will be described in detail with reference to the drawings. The present invention is not limited to the following embodiments, and it is apparent that various modifications can be made without departing from the scope of the invention. The drawings are schematic, and the scale of each dimension and the like may be different from the actual ones. Specific dimensions and the like should be determined with reference to the following description. It is to be noted that the drawings naturally include portions having different dimensional relationships and ratios from each other.

[ liquid Crystal display Panel ]

Hereinafter, a liquid crystal display panel in which an IC chip for driving a liquid crystal is mounted as an electronic component on a glass substrate will be described as an example of a connector to which the present invention is applied. As shown in fig. 1, the liquid crystal display panel 10 is configured such that two transparent substrates 11 and 12 made of glass substrates or the like are disposed to face each other, and the transparent substrates 11 and 12 are bonded to each other by a frame-shaped sealing material 13. The liquid crystal display panel 10 has a panel display portion 15 formed by sealing a liquid crystal 14 in a space surrounded by transparent substrates 11 and 12.

The transparent substrates 11 and 12 have a pair of stripe-shaped transparent electrodes 16 and 17 made of ITO (indium tin oxide) or the like formed on both inner surfaces facing each other so as to intersect each other. The two transparent electrodes 16 and 17 are arranged so that the pixel, which is the minimum unit of liquid crystal display, is formed by the intersection of the two transparent electrodes 16 and 17.

One transparent substrate 12 of the two transparent substrates 11, 12 is formed to have a larger plane size than the other transparent substrate 11, and a mounting portion 27 for mounting a liquid crystal driving IC18 as an electronic component is provided in an edge portion 12a of the transparent substrate 12 formed to be larger. As shown in fig. 2 and 3, the mounting portion 27 includes: the input terminal row 20 in which the plurality of input terminals 19 of the transparent electrode 17 are arranged, the output terminal row 22 in which the plurality of output terminals 21 are arranged, and the substrate-side alignment mark 31 overlapping with the IC-side alignment mark 32 provided in the liquid crystal driving IC 18.

The mounting portion 27 includes, for example: the 1 st terminal region 27a forming one input terminal row 20; and a 2 nd terminal region 27b in which two output terminal rows 22a, 22b are formed side by side in a width direction orthogonal to the arrangement direction of the output terminals 21. The output terminals 21 and the output terminal row 22 have: a 1 st output terminal row 22a in which the 1 st output terminal 21a is arranged on the inner side, i.e., on the input terminal row 20 side; and a 2 nd output terminal row 22b in which the 2 nd output terminals 21b are arranged on the outer side, i.e., the outer edge side of the mounting portion 27.

The liquid crystal driving IC18 can perform predetermined liquid crystal display by selectively applying a liquid crystal driving voltage to the pixels to locally change the orientation of the liquid crystal. As shown in fig. 3 and 4, the liquid crystal driving IC18 has an input bump array 24 in which a plurality of input bumps 23 electrically connected to the input terminals 19 of the transparent electrodes 17 are arranged, and an output bump array 26 in which a plurality of output bumps 25 electrically connected to the output terminals 21 of the transparent electrodes 17 are arranged, on the mounting surface 18a of the transparent substrate 12.

The liquid crystal driving IC18 includes, for example: the 1 st bump area 18b in which the input bumps 23 are aligned along one side edge of the mounting surface 18 a; and a 2 nd bump region 18c in which two output bump rows 26a, 26b are formed side by side in a width direction orthogonal to the arrangement direction of the output bumps 25. The output bumps 25 and the output bump rows 26 have: a 1 st output bump row 26a in which the 1 st output bumps 25a are arranged on the inner side, i.e., on the input bump row 24 side; and a 2 nd output bump row 26b in which the 2 nd output bumps 25b are arranged on the outer side, i.e., the outer edge side of the mounting surface 18 a.

The 1 st and 2 nd output bumps 25a and 25b are arranged in a plurality of rows in a staggered manner along the other side edge opposite to the one side edge. The input/output bumps 23 and 25 and the input/output terminals 19 and 21 provided on the mounting portion 27 of the transparent substrate 12 are formed in the same number and at the same pitch, respectively, and the transparent substrate 12 and the liquid crystal driving IC18 are aligned and connected to each other.

The arrangement of the input/output bump rows 24 and 26 in the 1 st and 2 nd bump regions 18b and 18c may be any configuration in which one or more input bump rows 24 are arranged on one side edge of the mounting surface 18a and one or more output bump rows 26 are arranged on the other side edge, in addition to the arrangement shown in fig. 4. In the input/output bump rows 24 and 26, a part of the input/output bumps 23 and 25 arranged in a row may be formed in a plurality of rows, or a part of the input/output bumps 23 and 25 arranged in a plurality of rows may be formed in a single row. Further, the input/output bump rows 24 and 26 may be formed in a straight arrangement in which the rows of the input/output bumps 23 and 25 are parallel to each other and the adjacent bumps are aligned side by side, or may be formed in a staggered arrangement in which the rows of the input/output bumps 23 and 25 are parallel to each other and the adjacent bumps are uniformly offset from each other.

The liquid crystal driving IC18 may have the input/output bumps 23 and 25 arranged along the long sides of the IC board and the side bumps formed along the short sides of the IC board. The input/output bumps 23 and 25 may be formed in the same size or in different sizes. The input/output bump rows 24 and 26 may be formed such that the input/output bumps 23 and 25 formed in the same size are arranged symmetrically or asymmetrically, or may be formed such that the input/output bumps 23 and 25 formed in different sizes are arranged asymmetrically.

Further, with the recent miniaturization and high functionality of liquid crystal display devices and other electronic devices, electronic components such as the liquid crystal driving IC18 are also required to be miniaturized and reduced in height, and the height of the input/output bumps 23 and 25 is also reduced (for example, 6 to 15 μm).

In the liquid crystal drive IC18, an IC side alignment mark 32 that performs alignment with respect to the transparent substrate 12 by being overlapped with the substrate side alignment mark 31 is formed on the mounting surface 18 a. Further, since the wiring pitch of the transparent electrodes 17 of the transparent substrate 12 and the fine pitch of the input/output bumps 23 and 25 of the liquid crystal driving IC18 are achieved, it is desirable that the alignment between the liquid crystal driving IC18 and the transparent substrate 12 be adjusted with high accuracy.

As the substrate side alignment marks 31 and the IC side alignment marks 32, various marks can be used which can achieve alignment between the transparent substrate 12 and the liquid crystal driving IC18 by bonding.

The liquid crystal driving IC18 is connected to the input/output terminals 19 and 21 of the transparent electrode 17 formed on the mounting portion 27 by using the anisotropic conductive film 1 as a circuit connecting adhesive. The anisotropic conductive film 1 contains conductive particles 4, and the input/output bumps 23 and 25 of the liquid crystal driving IC18 are electrically connected to the input/output terminals 19 and 21 of the transparent electrode 17 formed on the mounting portion 27 of the transparent substrate 12 via the conductive particles 4. The anisotropic conductive film 1 is thermally pressed by the thermal pressure bonding head 33 to fluidize the adhesive resin and to cause the conductive particles 4 to be crushed between the input/output terminals 19 and 21 and the input/output bumps 23 and 25 of the liquid crystal driving IC18, and the adhesive resin is cured in this state. Thereby, the anisotropic conductive film 1 electrically and mechanically connects the transparent substrate 12 and the liquid crystal driving IC 18.

Further, on both transparent electrodes 16 and 17, an alignment film 28 subjected to a predetermined rubbing treatment is formed so that the initial alignment of the liquid crystal molecules is defined by the alignment film 28. Further, a pair of polarizers 29a and 29b are disposed outside the transparent substrates 11 and 12, and the polarizers 29a and 29b define the vibration direction of the transmitted light from a light source (not shown) such as a backlight.

[ Anisotropic conductive film ]

Next, the anisotropic conductive film 1 will be explained. As shown in fig. 5, an Anisotropic Conductive Film (ACF) 1 is generally formed with a pressure-sensitive adhesive resin layer (adhesive layer) 3 containing conductive particles 4 on a release film 2 serving as a base material. The anisotropic conductive film 1 is a thermosetting adhesive or a light-curable adhesive such as ultraviolet light, is adhered to the mounting portion 27 of the transparent substrate 12 of the liquid crystal display panel 10 on which the input/output terminals 19 and 21 are formed and on which the liquid crystal driving IC18 is mounted, and is fluidized by being heated and pressurized by the heat and pressure bonding head 33, so that the conductive particles 4 are crushed between the input/output terminals 19 and 21 of the transparent electrode 17 and the input/output bumps 23 and 25 of the liquid crystal driving IC18 which are opposed to each other, and is cured in a state in which the conductive particles 4 are crushed by heating or ultraviolet irradiation. Thus, the anisotropic conductive film 1 connects the transparent substrate 12 and the liquid crystal driving IC18, and can be electrically connected.

In the anisotropic conductive film 1, conductive particles 4 are mixed with a general adhesive resin layer 3 containing a film-forming resin, a thermosetting resin, a latent curing agent, a silane coupling agent, and the like.

The release film 2 supporting the adhesive resin layer 3 is formed by coating a release agent such as silicone on PET (PolyEthylene Terephthalate), OPP (Oriented Polypropylene), PMP (Poly 4-methylpentene-1: Poly-4-methylpentene-1), PTFE (Polytetrafluoroethylene), or the like, and not only prevents the anisotropic conductive film 1 from drying but also maintains the shape of the anisotropic conductive film 1.

The film-forming resin contained in the binder resin layer 3 is preferably a resin having an average molecular weight of about 10000 to 80000. Examples of the film-forming resin include various resins such as an epoxy resin, a modified epoxy resin, a urethane resin, and a phenoxy resin. Among them, phenoxy resins are particularly preferable from the viewpoints of film formation state, connection reliability, and the like.

The thermosetting resin is not particularly limited, and examples thereof include commercially available epoxy resins and acrylic resins.

The epoxy resin is not particularly limited, but examples thereof include naphthalene type epoxy resins, biphenyl type epoxy resins, novolak type epoxy resins, bisphenol type epoxy resins, stilbene type epoxy resins, triphenol methane type epoxy resins, phenol aralkyl type epoxy resins, naphthol type epoxy resins, dicyclopentadiene type epoxy resins, triphenylmethane type epoxy resins, and the like. These may be used alone or in combination of 2 or more.

The propylene resin is not particularly limited, and a propylene compound, a liquid acrylate, and the like can be appropriately selected according to the purpose. Examples thereof include methyl acrylate, ethyl acrylate, isopropyl acrylate, isobutyl acrylate, epoxy acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, trimethylolpropane triacrylate, dimethylol tricyclodecane diacrylate, 1, 4-butanediol tetraacrylate, 2-hydroxy-1, 3-diacryloyloxypropane, 2-bis [ 4- (acryloyloxymethyl) phenyl ] propane, 2-bis [ 4- (acryloyloxyethoxy) phenyl ] propane, dicyclopentenyl acrylate, tricyclodecanyl acrylate, dendritic (acryloyloxyethyl) isocyanurate, urethane acrylate, and epoxy acrylate. In addition, a material in which an acrylate is a methacrylate can also be used. These may be used alone in 1 kind, or 2 or more kinds may be used in combination.

The latent curing agent is not particularly limited, but examples thereof include various curing agents such as a heat curing type and a UV curing type. The latent hardener is not generally reacted, and is activated by various initiation conditions selected depending on the application, such as heat, light, and pressure, to start the reaction. The activation method of the heat-active latent curing agent includes: a method of generating active species (cations, anions, radicals) by dissociation reaction by heating or the like; a method of stably dispersing the epoxy resin in the vicinity of room temperature and dissolving/melting the epoxy resin at a high temperature to start a curing reaction; a method of melting out a molecular sieve-encapsulated type hardening agent at a high temperature and starting a hardening reaction; a melting/hardening method using microcapsules, and the like. Examples of the thermally active latent hardener include imidazoles, hydrazides, boron trifluoride-amine complexes, sulfonium salts, aminated imides, polyamine salts, dicyandiamide, and modified forms thereof, and these may be used alone or as a mixture of 2 or more kinds thereof. Among them, microcapsule type imidazole latent curing agents are preferable.

The silane coupling agent is not particularly limited, but examples thereof include epoxy compounds, ammonia compounds, mercapto compounds, sulfide compounds, and urea compounds. By adding the silane coupling agent, the adhesiveness at the interface between the organic material and the inorganic material is improved.

[ conductive particles ]

[ resin core ]

As shown in fig. 6, the conductive particles 4 include resin cores 4a and conductive layers 4b covering the resin cores 4a, and the resin cores 4a are colored in a color different from that of the input bumps 23 and the output bumps 25 of the liquid crystal driving IC 18. The resin core 4a is preferably made of particles made of a plastic material having excellent compression set, and may be formed of, for example, (meth) acrylate resin, polystyrene resin, styrene- (meth) propylene copolymer resin, urethane resin, epoxy resin, phenol resin, Acrylonitrile Styrene (AS) resin, benzoguanamine resin, divinylbenzene resin, styrene resin, polyester resin, or the like.

For example, when the resin core 4a is formed of a (meth) acrylic resin, the (meth) acrylic resin is preferably a copolymer of a (meth) acrylic acid ester, a compound having a reactive double bond copolymerizable with the (meth) acrylic acid ester as required, and a bifunctional or polyfunctional monomer.

When the resin core 4a is formed of a polystyrene-based resin, the polystyrene-based resin is preferably a copolymer of a derivative of styrene, a compound having a reactive double bond copolymerizable with the derivative, and a bifunctional or polyfunctional monomer.

When the conductive particles 4 of the present invention have the resin core 4a made of a (meth) acrylic resin, the (meth) acrylic resin is preferably a (co) polymer of a (meth) acrylic ester, and a copolymer of the (meth) acrylic ester monomer and another monomer can also be used.

Examples of the (meth) acrylate monomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-propyl (meth) acrylate, chloro-2-hydroxyethyl (meth) acrylate, diethylene glycol mono (meth) acrylate, methoxyethyl (meth) acrylate, glycidyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, and isobornyl (meth) acrylate.

In addition, in the case where the resin core 4a forming the conductive particles of the present invention is a polystyrene-based resin, specific examples of the styrene-based monomer include alkylstyrenes such as styrene, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, iodostyrene and chloromethylstyrene; and nitrostyrene, acetyl styrene and methoxystyrene.

The resin core 4a is preferably formed solely of any of the (meth) acrylic resins and styrene resins described above, but may be formed of a composition of these resins. Further, the copolymer may be a copolymer of the above (meth) acrylate monomer and a styrene monomer.

Further, the (meth) acrylic resin or styrene resin may be copolymerized with the (meth) acrylate monomer and/or styrene monomer and further another monomer copolymerizable as necessary.

Examples of the other monomer copolymerizable with the (meth) acrylate monomer or the styrene monomer include ethylene monomers and unsaturated carboxylic acid monomers.

When an example of the resin core 4a made of a propylene resin is given, the resin core 4a is made of a polymer of a propylene monomer, and can be made of a polymer of a monomer containing a urethane compound and an acrylate, for example.

Here, the acrylic monomer refers to both acrylate (acrylate) and methacrylate (methacrylate). In the present invention, the monomer may be polymerized by heating, ultraviolet irradiation, or the like, and may include a polymer of 2 or more monomers, that is, an oligomer.

When the propylene resin constituting the resin core 4a of the present invention is composed of a polymer of a monomer containing a urethane compound and an acrylic ester, the urethane compound is contained preferably in an amount of 5 parts by weight or more, more preferably 25 parts by weight or more, based on 100 parts by weight of the monomer.

As the urethane compound, a polyfunctional urethane acrylate, for example, a 2-functional urethane acrylate, can be used.

[ coloring agent ]

At least a part or the whole of the resin core 4a is colored with a colorant in a color different from that of the input bumps 23 and the output bumps 25 of the liquid crystal driving IC 18. This can improve visibility of the resin core 4a when the conductive layer 4b is peeled off or eluted to expose the surface of the resin core 4 a.

The coloring of the resin core 4a can be performed, for example, by adding a filler to be a colorant and polymerizing a propylene monomer when the resin core 4a is formed of an acrylic resin, or by adding a filler to be a colorant and polymerizing a styrene monomer when the resin core 4a is formed of a polystyrene resin.

The resin core 4a is colored in a complementary color (opposite color) to the colors of the input/output bumps 23 and 25, thereby improving visibility. Complementary color (opposite color) refers to a color on the opposite side of the hue circle. Specifically, when the color of the object is placed at the center of one region into which the tone ring is evenly divided by four, the complementary color (opposite color) refers to a color belonging to a region that is not adjacent to the region to which the color of the object belongs.

When the surfaces of the input/output bumps 23 and 25 are covered with the white conductive layer, the resin core 4a is preferentially colored with a black filler. The resin core 4a may be colored with a white filler when the surfaces of the input/output bumps 23 and 25 are covered with a conductive layer having a yellow metallic luster such as gold.

For example, when the resin core 4a is coated with a material having metallic luster such as gold, silver, or copper as a conductive material constituting the surfaces of the input/output bumps 23 and 25, it is preferably colored with a white filler such as titanium oxide. When the resin core 4a is coated with a white material such as zinc as a conductive material constituting the surfaces of the input/output bumps 23 and 25, it is preferably colored with a black filler such as titanium black, carbon black, or iron oxide.

The colorant for coloring the resin core 4a has an insulating property, and for example, the colorant preferably has an insulation resistance of 1 × 10 measured at 25 ℃ and 70% RH⁸Omega/cm or more. The insulation resistance can be measured by a general insulation resistance meter, for example. By coloring with an insulating colorant, factors in the case of occurrence of migration (migration) and the like can be easily clarified.

The colorant for coloring the resin core 4a may be a conductive material. By coloring with a conductive colorant, the on-resistance values of the input/output bumps 23 and 25 and the input/output terminals 19 and 21 connected via the conductive particles 4 can be easily reduced.

The size of the filler for coloring the resin core 4a is preferably less than 30%, more preferably 20% or less, and still more preferably 10% or less of the particle diameter of the conductive particles 4. This is because, when the size of the filler for coloring the resin core 4a is 30% or more of the particle diameter of the conductive particles 4, the elasticity of the conductive particles 4 is reduced, and the variation in the gap between the input/output bumps 23 and 25 and the input/output terminals 19 and 21 cannot be followed immediately after anisotropic connection or after reliability experiments, and the on-resistance value may be increased.

The filler for coloring the resin core 4a is preferably spherical. This is because, as described later, the connected body can be easily crushed when it is inspected.

Further, the size of the filler for coloring the resin core 4a is preferably uniform. Specifically, the filler is preferably used in such a size that 90% of the total number of the fillers used falls within ± 20% of the average diameter of the fillers. This makes it possible to easily determine the compressed state of the conductive particles in the inspection of the connected body.

The amount of the filler for coloring the resin core 4a is preferably 30 vol% or less. If the amount of the filler is much more than 30 vol%, the elasticity of the conductive particles 4 may be impaired, and the connection reliability may be lowered. The amount of the filler is preferably 2 vol% or more. If the amount of the filler is less than 2 vol%, the visibility of the resin core 4a cannot be improved.

[ conductive layer ]

In the conductive particles 4 of the present invention, the conductive layer 4b formed on the surface of the resin core 4a can be formed using a generally used conductive metal, an alloy containing the metal, a conductive metal oxide, or another conductive material as the conductive layer of the conductive particles. For example, the conductive layer 4b is formed of Ni, Ni alloy, Au, or the like.

The conductive layer 4b can be formed by a physical method such as a vapor deposition method, an ion sputtering method, an electroless plating method, or a thermal spraying method, a chemical method in which a conductive material is scientifically bonded to the surface of a resin core having a functional group, a method in which a conductive material is adsorbed to the surface of a resin core by a surfactant or the like, or the like. The conductive layer 4b does not need to be a single layer, and a plurality of layers may be stacked.

The thickness of the conductive layer 4b is usually 0.01 to 10.0. mu.m, preferably 0.05 to 5 μm, and more preferably 0.2 to 2 μm. An insulating layer made of an insulating resin may be further formed on the surface of the conductive layer 4 b. As a method for forming the insulating layer, for example, a method for forming a discontinuous insulating layer composed of polyvinylidene fluoride by a hybridization system is shown, wherein 2 to 8 parts by weight of polyvinylidene fluoride is used with respect to 400 parts by weight of conductive particles, and the treatment is performed at a temperature of 85 to 115 ℃ for 5 to 10 minutes. The thickness of the insulating layer is usually about 0.1 to 0.5 μm. In addition, the insulating layer may not completely cover the surface of the conductive particles.

In the case where the conductive particles 4 of the present invention are used in an anisotropic conductive adhesive material (anisotropic conductive film) as described later, the conductive particles 4 may have an average particle diameter of usually 1 to 50 μm, preferably 3 to 10 μm.

The shape of the anisotropic conductive film 1 is not particularly limited, and for example, as shown in fig. 5, it is formed in a long tape shape that can be wound around a reel 6, and it can be cut into a predetermined length for use.

In the above embodiment, the anisotropic conductive film 1 has been described by taking as an example an adhesive film formed by molding a binder resin composition in which the binder resin layer 3 is blended with the conductive particles 4 into a film shape, but the adhesive according to the present invention is not limited to this, and may have a structure in which, for example, an insulating adhesive layer composed only of the binder resin 3 and a conductive particle-containing layer composed of the binder resin 3 blended with the conductive particles 4 are laminated. In the present invention, an anisotropic conductive paste made of a binder resin composition in which conductive particles 4 are mixed with a binder resin layer 3 may be used. The anisotropic conductive adhesive according to the present invention includes both the anisotropic conductive film 1 and the anisotropic conductive paste.

[ bump Material ]

The input/output bumps 23 and 25 for trapping the conductive particles 4 are made of a conductive metal, an alloy containing the metal, a conductive ceramic, a conductive metal oxide, or another conductive material.

Examples of the conductive metal include Zn, Al, Sb, U, Cd, Ga, Ca, Au, Ag, Co, Sn, Se, Fe, Cu, Th, Pb, Ni, Pd, Be, and Mg. The metal may be used alone, 2 or more kinds thereof may be used, and other elements, compounds (e.g., solder), and the like may be added. Vo can be given as an example of the conductive ceramic₂、Ru₂O、SiC、ZrO₂、Ta₂N、ZrN、NbN、VN、TiB₂、ZrB、HfB₂、TaB₂、MoB₂、CrB₂、B₄C. MoB, ZrC, VC and TiC. Examples of the conductive material other than the above include carbon particles such as carbon and graphite, ITO, and the like.

Among such conductive materials, it is particularly preferable to contain gold in the input/output bumps 23 and 25. By including gold in the input/output bumps 23 and 25, the electrical resistance value is reduced, and the ductility is improved, so that excellent conductivity can be obtained. Since gold has low hardness, damage is reduced even when the conductive particles 4 are conductively connected to the input/output terminals 19 and 21 by an anisotropic conductive adhesive material (anisotropic conductive film or anisotropic conductive paste) as will be described later.

In particular, as the input/output bumps 23 and 25, for example, bumps (bumps substituted with gold (Au)) in which a gold (Au) layer is formed on the surface of a nickel (Ni) metal layer are preferably used.

[ joining Process ]

Next, a connection process of connecting the liquid crystal driving IC18 to the transparent substrate 12 will be described. First, the anisotropic conductive film 1 is temporarily attached to the mounting portion 27 of the transparent substrate 12 on which the input/output terminals 19 and 21 are formed. Next, the transparent substrate 12 is placed on a stage of a connecting device, and the liquid crystal driving IC18 is disposed on the mounting portion 27 of the transparent substrate 12 via the anisotropic conductive film 1.

Next, the thermocompression bonding head 33 heated to a predetermined temperature for curing the adhesive resin layer 3 starts to heat and press the liquid crystal driving IC18 at a predetermined pressure for a predetermined time. Accordingly, the adhesive resin layer 3 of the anisotropic conductive film 1 exhibits fluidity and flows out from between the mounting surface 18a of the liquid crystal driving IC18 and the mounting portion 27 of the transparent substrate 12, and the conductive particles 4 in the adhesive resin layer 3 are pinched between the input/output bumps 23 and 25 of the liquid crystal driving IC18 and the input/output terminals 19 and 21 of the transparent substrate 12.

As a result, the conductive particles 4 are sandwiched between the input/output bumps 23 and 25 and the input/output terminals 19 and 21, and thereby the adhesive resin heated by the thermocompression bonding head 33 is cured. This makes it possible to manufacture the liquid crystal display panel 10 in which the electrical continuity is ensured between the input/output bumps 23 and 25 of the liquid crystal driving IC18 and the input/output terminals 19 and 21 formed on the transparent substrate 12. As shown in fig. 7, in the liquid crystal display panel 10, the conductive particles 4 sandwiched between the input/output bumps 23 and 25 and the input/output terminals 19 and 21 can be seen from the back surface of the transparent substrate 12 with the input/output bumps 23 and 25 as a background.

The conductive particles 4 not present between the input/output bumps 23 and 25 and the input/output terminals 19 and 21 are dispersed in the binder resin in the space 35 between the adjacent input/output bumps 23 and 25, and are maintained in an electrically insulated state. Therefore, the liquid crystal display panel 10 is electrically connected only between the input/output bumps 23 and 25 of the liquid crystal driving IC18 and the input/output terminals 19 and 21 of the transparent substrate 12. The anisotropic conductive film 1 is not limited to a thermosetting type, and a photo-setting type or photo-thermal type adhesive may be used as long as pressure bonding can be performed.

[ inspection Process ]

As described above, the liquid crystal display panel 10 can visually inspect the conductive particles 4 sandwiched between the input/output bumps 23 and 25 and the input/output terminals 19 and 21 from the back surface of the transparent substrate 12. The conductive particles 4 in which peeling, elution, or the like has not occurred in the conductive layer 4b can be visually recognized with the input/output bumps 23 and 25 as a background as shown in fig. 7 (a), and the number of trapped particles, crushing, or the like can be easily determined.

Here, the conductive particles 4 may be separated from the surface of the resin core 4a by rubbing against the input/output terminals 19 and 21 or the input/output bumps 23 and 25 due to unexpected vibration generated during pressure bonding in anisotropic connection, or the conductive layer 4b may be dissolved by an acid or the like generated in the binder resin during anisotropic connection or during treatment before and after the anisotropic connection, thereby exposing the surface of the resin core 4 a.

Such a phenomenon occurs not only in all the conductive particles 4 trapped between the input/output terminals 19, 21 of one set and the input/output bumps 23, 25, but also in some of the plurality of conductive particles 4 trapped between the input/output terminals 19, 21 of one set and the input/output bumps 23, 25. The conductive layer 4b is peeled off or eluted over the entire surface of the resin core 4a, and the entire surface of the resin core 4a is exposed.

At this time, since the resin core 4a is colored in a color different from that of the input/output bumps 23 and 25 to improve the visibility of the conductive particles 4 in which the peeling or elution of the conductive layer 4B occurs, as shown in fig. 7 (B), the presence or absence, the number, or the crushing of the conductive particles 4 in which the peeling or elution of the conductive layer 4B occurs can be quickly checked even with the input/output bumps 23 and 25 as a background.

That is, as shown in fig. 7 (C), in the case of the resin core 4C which is not colored at all, even if peeling or elution of the conductive layer 4b occurs and the resin core is exposed, since the resin core 4C is generally transparent and translucent, it is difficult to determine the presence or absence or the number of conductive particles which have peeled or eluted the conductive layer 4b with the input/output bumps 23 and 25 as a background. Here, in the conductive particles 4 to which the present invention is applied, since the resin core 4a is colored in a color different from that of the input/output bumps 23 and 25, visibility when peeling or elution of the conductive layer 4B occurs is improved (fig. 7 (B)). Therefore, even in the case of the input/output bumps 23 and 25 as a background, it is possible to quickly perform the inspection of the presence or absence, the number, the crushing, and the like of the conductive particles 4 in which the peeling or elution of the conductive layer 4b occurs.

In this case, from the viewpoint of improving visibility, it is preferable that the resin core 4a is colored with a white filler when the surfaces of the input/output bumps 23 and 25 are covered with a conductive material having a yellow metallic luster such as gold, and is colored with a black filler when the surfaces of the input/output bumps 23 and 25 are covered with a white conductive material.

For example, when the surfaces of the input/output bumps 23 and 25 are covered with a material having metallic luster such as gold, silver, or copper, the resin core 4a is preferably colored with a white filler such as titanium oxide. In addition, when the surfaces of the input/output bumps 23 and 25 are coated with a white material such as zinc, the resin core 4a is preferably colored with a black filler such as titanium black, carbon black, or iron oxide.

Examples

Next, examples of the present invention will be explained. In this example, an anisotropic conductive film using conductive particles in which a conductive layer was formed on a colored resin core and an anisotropic conductive film using conductive particles in which a resin core was not colored were prepared, and a connection body sample of an IC for evaluation was connected to a glass substrate for evaluation through each anisotropic conductive film, and the initial on-resistance of each connection body sample and the on-resistance after a reliability test were measured, and the visibility of conductive particles from which the conductive layer was peeled was evaluated.

[ Anisotropic conductive film ]

An adhesive resin layer of an anisotropic conductive film used for connection of IC for evaluation was formed by adding 60 parts by mass of a phenoxy resin (trade name: YP50, product of shin-iron () chemical corporation), 40 parts by mass of an epoxy resin (trade name: jER828, product of mitsubishi chemical corporation), and 2 parts by mass of a cationic curing agent (trade name: SI-60L, product of shin-shi chemical industries, inc.) to a solvent, applying the adhesive resin composition to a release film, and drying the adhesive resin composition.

The conductive particles contained in the binder resin layer of the anisotropic conductive film have a conductive layer formed on the colored resin core. The resin core was prepared using 60 parts by mass and 40 parts by mass of a-HD-N manufactured by Nippon Korea chemical Co., Ltd, as a propylene monomer, and U-6 LPA manufactured by Nippon Korea chemical Co., Ltd, as a urethane acrylate, respectively. Titanium oxide (TIPAQUE R-820, a filling material: 0.26 μm) was dispersed as a colorant in the propylene monomer and urethane acrylate, and the resulting dispersion was emulsion-polymerized to prepare propylene resin particles.

The acrylic resin particles were coated with nickel by a sputtering method to obtain conductive particles having a particle diameter of 3.2 μm. The thickness of the nickel layer was 0.15. mu.m.

[ IC for evaluation ]

As an evaluation element, an evaluation IC in which a plurality of bumps (Au-plated) having an outer shape of 1.8 mm. times.20 mm, a thickness of 0.5mm, a width of 30 μm. times.85 μm in length, and a height of 15 μm were arranged was prepared. The bump surface of the IC for evaluation had metallic luster.

[ glass substrate for evaluation ]

ITO-plated glass having a thickness of 0.7mm was prepared as a glass substrate for evaluation.

After the anisotropic conductive film was temporarily attached to the evaluation glass substrate, an evaluation IC was mounted thereon, and thermocompression bonding was performed using a thermocompression bonding head under conditions of 170 ℃, 60MPa, and 5sec, thereby producing a sample of a connected body. For each connector sample, the initial on-resistance and the on-resistance after the reliability test were measured. The reliability test was carried out by placing the linker sample in a thermostatic bath at 85 ℃ and 85% RH humidity for 500 hours.

The initial on-resistance is "OK" when less than 10 Ω and "NG" when 10 Ω or more are included. The on-resistance after the reliability test is preferably less than 20 Ω, more preferably less than 10 Ω, and further preferably less than 5 Ω, and 20 Ω or more is not preferable.

In addition, with respect to each of the connected body samples, the conductive particles trapped by the bumps of the evaluation IC were observed from the back surface of the evaluation glass substrate by an optical microscope, and the visibility of the conductive particles from which the conductive layer was peeled was evaluated.

Further, since it is difficult to reproduce a state where the conductive layer of the conductive particles is peeled off and the surface of the resin core is exposed under the connection conditions, conductive particles in which a part of the conductive layer is peeled off and the surface of the resin core is exposed are prepared in advance, and a connected body sample in which the IC for evaluation and the glass substrate for evaluation are connected via an anisotropic conductive film in which the conductive particles are blended is prepared and visibility evaluation is performed. The ligation conditions were the same (170 ℃, 60MPa, 5 sec).

For the evaluation of visibility, the number of conductive particles captured by the bumps of the IC to be evaluated was counted in advance, and a case where the proportion of conductive particles exposed on the surface of the resin core was 90% or more visually recognizable at a magnification of 50 times was regarded as "excellent", a case where the proportion of conductive particles exposed on the surface of the resin core was 50% or more and less than 90% visually recognizable at a magnification of 50 times was regarded as "good", a case where the proportion of conductive particles exposed on the surface of the resin core was 10% or more and less than 50% visually recognizable at a magnification of 50 times was regarded as "Δ (normal)", and a case where the proportion of conductive particles exposed on the surface of the resin core was less than 10% visually recognizable at a magnification of 50 times was regarded as "x (poor)".

[ example 1]

In example 1, 2 vol% of titanium oxide (TIPAQUE R-820, product of stone industries) was dispersed as a colorant in the urethane compound, and emulsion polymerization was carried out to prepare propylene resin particles. The initial on-resistance of the sample of the interconnect according to example 1 was 1.2 Ω, the on-resistance after the reliability test was 2.5 Ω, and the visibility of the conductive particles peeled off from the conductive layer was "Δ (normal)".

[ example 2]

In example 2, 8 vol% of titanium oxide (TIPAQUE R-820, product of stone industries) was dispersed as a colorant in the urethane compound, and emulsion polymerization was carried out to prepare propylene resin particles. The initial on-resistance of the connector sample according to example 2 was 1.7 Ω, the on-resistance after the reliability test was 3.3 Ω, and the visibility of the conductive particles peeled off from the conductive layer was "∘ (good)".

[ example 3]

In example 3, 15 vol% of titanium oxide (TIPAQUE R-820, product of stone industries) was dispersed as a colorant in the urethane compound, and emulsion polymerization was carried out to prepare propylene resin particles. The initial on-resistance of the connector sample according to example 3 was 2.2 Ω, the on-resistance after the reliability test was 4.8 Ω, and the visibility of the conductive particles peeled off from the conductive layer was "∘ (good)".

[ example 4]

In example 4, 23 vol% of titanium oxide (TIPAQUE R-820, product of stone industries) was dispersed as a colorant in the urethane compound, and emulsion polymerization was carried out to prepare propylene resin particles. The initial on-resistance of the connector sample according to example 4 was 3.2 Ω, the on-resistance after the reliability test was 9.3 Ω, and the visibility of the conductive particles peeled off from the conductive layer was "∘ (good)".

[ example 5]

In example 5, 30 vol% of titanium oxide (TIPAQUE R-820, product of stone industries) was dispersed as a colorant in the urethane compound, and emulsion polymerization was carried out to prepare propylene resin particles. The interconnect sample of example 5 had an initial on resistance of 4.3 Ω, an on resistance of 17.5 Ω after the reliability test, and a visibility of conductive particles peeled off from the conductive layer was "∘ (good)".

Comparative example 1

In comparative example 1, no colorant was added to the urethane compound to prepare propylene resin particles. The sample of the interconnect according to comparative example 1 had an initial on resistance of 1.2 Ω, an on resistance of 2.1 Ω after the reliability test, and visibility of conductive particles peeled from the conductive layer was "x (poor)".

Comparative example 2

In comparative example 2, 1 vol% of titanium oxide (TIPAQUE R-820, a product of Shigaku Kogyo Co., Ltd.) was dispersed as a colorant in the urethane compound, and the resultant was emulsion-polymerized to prepare propylene resin particles. The sample of the interconnect according to comparative example 2 had an initial on resistance of 1.1 Ω, an on resistance of 2.2 Ω after the reliability test, and visibility of conductive particles peeled from the conductive layer was "x (poor)".

Comparative example 3

In comparative example 3, 38 vol% of titanium oxide (TIPAQUE R-820, a product of Shigaku Kogyo Co., Ltd.) was dispersed as a colorant in the urethane compound, and the resultant was emulsion-polymerized to prepare propylene resin particles. The interconnect sample of comparative example 3 had an initial on resistance of 6.9 Ω, an on resistance of 21.9 Ω after the reliability test, and a visibility of conductive particles peeled off from the conductive layer was "∘ (good)".

[ Table 1]

As shown in table 1, in examples 1 to 5, the conductive particles were evaluated to have high visibility and to be equal to or greater than "Δ (normal)". This is because the sample connectors according to examples 1 to 5 were formed using a conductive adhesive film containing conductive particles colored by adding an appropriate amount of a colorant, and therefore visibility and connectivity were ensured.

In comparative example 1, the resin core of the conductive particle was not colored, and in comparative example 2, the amount of the colorant added was small, and the visibility of the conductive particle peeled off from the conductive layer was poor with the IC bump as a background, and the inspection process was complicated.

In comparative example 3, since the amount of the colorant added was too large, the resin core became hard, and the followability to the expansion and contraction of the distance between the IC bump and the ITO film became poor, so that the on-resistance was large, and the connection reliability was poor.

Description of the reference symbols

1 an anisotropic conductive film; 2 stripping the film; 3 a binder resin layer; 4 conductive particles; 4a resin core; 4b a conductive layer; 6, coiling a disc; 10 a liquid crystal display panel; 11. 12a transparent substrate; 12a rim portion; 13 sealing material; 14 liquid crystal; 15 a panel display section; 16. 17 a transparent electrode; 18a liquid crystal driving IC; 18a mounting surface; 19 an input terminal; 20 input terminal rows; 21 an output terminal; 22 output terminal rows; 23 inputting a bump; 25 outputting the bump; 24 inputting the bump row; 26 outputting the bump row; 27a mounting part; 33 thermal compression bonding.

Claims (12)

1. A method for inspecting a connected body in which a transparent electrode formed on a transparent substrate and a connection terminal of an electronic component are connected to each other with an anisotropic conductive adhesive,

the conductive particles sandwiched between the transparent electrode and the connection terminal are formed by coating a resin core with a conductive layer, and the resin core is colored in a color different from that of the connection terminal,

the condition that the surface of the resin core is exposed and captured on the transparent electrode is detected by coloring of the resin core.

2. The method of inspecting a connected body according to claim 1, wherein the resin core is colored with a filler of a complementary color (opposite color) to a surface of the connection terminal.

3. The method of inspecting a connected body according to claim 2, wherein the resin core is colored with a filler of a color belonging to a region not adjacent to a region to which the color of the surface of the connection terminal belongs, when the color of the surface of the connection terminal is placed at a center of a region into which the tone ring is evenly divided into four.

4. The method for inspecting a connected body according to any one of claims 1 to 3, wherein the resin core is obtained by polymerizing a propylene monomer.

5. The method for inspecting a connected body according to any one of claims 1 to 3, wherein the size of the filler is less than 30% of the particle diameter of the conductive particles.

6. The method for inspecting a connected body according to any one of claims 1 to 3, wherein the amount of the filler blended is less than 30 vol%.

7. The method of inspecting a connected body according to any one of claims 1 to 3, wherein the filler is spherical.

8. The method of inspecting a connected body according to any one of claims 1 to 3, wherein the filler has a size such that 90% of the total number is within ± 20% of the average diameter of the filler.

9. The method of inspecting a connected body according to any one of claims 1 to 3, wherein the entire surface of the resin core is exposed.

10. A connector in which a transparent electrode formed on a transparent substrate and a connection terminal of an electronic component are connected to each other with an anisotropic conductive adhesive,

the conductive particles sandwiched between the transparent electrode and the connection terminal are formed by coating a resin core with a conductive layer, and the resin core is colored in a color different from that of the connection terminal,

the conductive particles trapped on the transparent electrode can be visually recognized by coloring the resin core so that the surface of the resin core is exposed.

11. A conductive particle contained in an adhesive for anisotropically and electrically connecting a transparent electrode formed on a transparent substrate and a connection terminal of an electronic component, the conductive particle comprising:

a resin core; and

a conductive layer covering the surface of the resin core,

the resin core is colored in a color different from that of the connection terminal, and the surface of the resin core can be visually recognized as being exposed by the coloring of the resin core.

12. An anisotropic conductive adhesive which contains conductive particles in a binder resin and connects a transparent electrode formed on a transparent substrate and a connection terminal of an electronic component,

the conductive particles have:

a resin core; and

a conductive layer covering the surface of the resin core,

the resin core is colored in a color different from that of the connection terminal, and the surface of the resin core can be visually recognized as being exposed by the coloring of the resin core.