HK1226862A1 - Connection body - Google Patents

Description

Connecting body

Technical Field

The present invention relates to a connector for connecting an electronic component and a circuit board, and more particularly to a connector for connecting an electronic component to a circuit board via an adhesive containing conductive particles. The present application claims priority based on japanese patent application No. 2014-018532 applied on 3/2/2014 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 televisions, PC monitors, mobile phones, smartphones, portable game machines, tablet terminals, wearable terminals, and in-vehicle monitors. In recent years, in such a display device, a so-called COG (chip on glass) in which a driving IC is directly mounted on a glass substrate of a display panel has been used from the viewpoint of fine pitch, thinning, and the like.

For example, in a liquid crystal display panel adopting a COG mounting method, as shown in fig. 7 (a) and (B), a plurality of transparent electrodes 102 made of ITO (indium tin oxide) or the like are formed on a transparent substrate 101 made of a glass substrate or the like, and electronic components such as a liquid crystal driving IC103 or the like are connected to these transparent electrodes 102. The liquid crystal driving IC103 has a plurality of electrode terminals 104 formed on its mounting surface corresponding to the transparent electrodes 102, and is thermally bonded to the transparent substrate 101 via an anisotropic conductive film 105 to connect the electrode terminals 104 and the transparent electrodes 102.

The anisotropic conductive film 105 is formed in a film shape by mixing conductive particles into a binder resin, and electrically conducts between the conductors by the conductive particles by heating and pressure bonding between the two conductors, and maintains mechanical connection between the conductors by the binder resin. As the adhesive constituting the anisotropic conductive film 105, a highly reliable thermosetting adhesive resin is generally used, but a photocurable adhesive resin or a photothermal adhesive resin may be used.

When the liquid crystal driving IC103 is connected to the transparent electrode 102 via the anisotropic conductive film 105, first, the anisotropic conductive film 105 is temporarily attached to the transparent electrode 102 of the transparent substrate 101 by a temporary pressure bonding means not shown. Next, after the liquid crystal driving IC103 is mounted on the transparent substrate 101 via the anisotropic conductive film 105 to form a temporary connection body, the liquid crystal driving IC103 is heated and pressed together with the anisotropic conductive film 105 toward the transparent electrode 102 by a thermal compression unit such as a thermal compression joint 106. The anisotropic conductive film 105 is thermally cured by heating with the thermal pressure-bonding head 106, and the liquid crystal driving IC103 is bonded to the transparent electrode 102.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 4789738

Patent document 2: japanese patent laid-open publication No. 2004-214374

Patent document 3: japanese patent laid-open No. 2005-203758.

Disclosure of Invention

Problems to be solved by the invention

With the recent miniaturization and high precision of liquid crystal display devices and other electronic devices, the wiring pitch of circuit boards and the fine pitch of electrode terminals of electronic components have been made, and when electronic components COG such as IC chips are connected to circuit boards with fine pitches by anisotropic conductive films, anisotropic conductive films filled with small-diameter conductive particles at high density are used in order to reliably capture conductive particles between the electrode terminals and the substrate electrodes and to prevent short-circuiting between the terminals due to the connection of the conductive particles between the electrode terminals with small sizes.

In addition, a protective film is formed on the substrate surface of the circuit substrate to prevent physical damage, short circuit, and the like. The substrate electrode formed on the substrate surface has a stepped portion formed by the formation of the protective film on the side edge portion. In an electronic component such as an IC chip, a step portion is formed at a side edge portion of a metal electrode terminal. Thus, the substrate electrode and the electrode terminal have a shape in which the step portion is raised around the flat main surface portion.

When an electronic component is connected to a circuit board, the step portions of the board electrodes and the step portions of the electrode terminals are butted and connected. In this case, if the conductive particles are present between the stepped portion of the substrate electrode and the stepped portion of the electrode terminal, the conductive particles are caught between the stepped portions, and therefore the conductive particles cannot be sufficiently crushed between the main surface portions of the substrate electrode and the electrode terminal, which may impair conductivity. Further, since the step portion of the substrate electrode is formed by the protective film, the conductivity is low, and the conductivity cannot be secured by the conductive particles which are caught between both step portions. Further, when the diameter of the conductive particles is reduced, the insufficient press-fitting of the conductive particles due to the biting of the conductive particles between the stepped portions of the substrate electrode and the electrode terminal becomes more remarkable.

Further, there has been proposed an anisotropic conductive film in which conductive particles are regularly arranged in accordance with the pitch of metal wires of a circuit board or the fine pitch of electrode terminals of an electronic component, but, although the conductive particles can be reliably captured in the main surface portions of a substrate electrode and an electrode terminal by regularly arranging the conductive particles, the conductive particles are likely to bite into the stepped portions.

Accordingly, an object of the present invention is to provide a circuit board and an electronic component connected body in which conductivity is ensured by sufficiently pressing conductive particles held between main surface portions of a substrate electrode and an electrode terminal even when the conductive particles are caught between a step portion of the substrate electrode and a step portion of the electrode terminal.

Means for solving the problems

In order to solve the above problem, a connector according to the present invention includes: a circuit substrate; and an electronic component connected to the circuit board via an anisotropic conductive adhesive, wherein stepped portions are formed at respective side edge portions of a board electrode formed on the circuit board and an electrode terminal formed on the electronic component, the board electrode and the electrode terminal sandwich conductive particles contained in the anisotropic conductive adhesive between respective main surface portions and between the stepped portions formed at the respective side edge portions, and the conductive particles, the board electrode, and the respective stepped portions of the electrode terminal satisfy the following formula (1).

a＋b＋c≤0.8D　（1）

[ a: height of step portion of electrode terminal, b: step height of substrate electrode, c: gap between step portions, D: diameter of conductive particle

Effects of the invention

According to the present invention, the conductive particles held between the main surface portions of the substrate electrode and the electrode terminal can be compressed to at least 80% of the particle diameter, and sufficient conductivity can be ensured.

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

Fig. 3 is a plan view showing electrode terminals (bumps) and spaces between the terminals of the liquid crystal driving IC.

Fig. 4 is a sectional view showing an anisotropic conductive film.

Fig. 5 is a plan view showing an anisotropic conductive film in which conductive particles are regularly arranged in a lattice shape.

Fig. 6 is a sectional view showing the substrate electrode and the electrode terminal sandwiching the conductive particles.

Fig. 7 is a sectional view showing a process of connecting an IC chip to a transparent substrate of a liquid crystal display panel, where (a) shows a process before connection, and (B) shows a connection process.

Detailed Description

Hereinafter, a connecting body to which the present invention is applied will be described in detail with reference to the accompanying 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 present invention. The drawings are schematic, and the scale of each dimension and the like may be different from those in reality. Specific dimensions and the like should be determined with reference to the following description. Further, it should be understood that the drawings also include portions having different dimensional relationships or proportions 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 with 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 are formed on both inner surfaces facing each other so that a pair of stripe-shaped transparent electrodes 16 and 17 made of ITO (indium tin oxide) or the like intersect each other. The two transparent electrodes 16 and 17 form a pixel which is a minimum unit of liquid crystal display by the intersection of the two transparent electrodes 16 and 17.

One transparent substrate 12 of the two transparent substrates 11 and 12 is formed to have a larger plane size than the other transparent substrate 11, and a COG mounting portion 20 for mounting a liquid crystal driving IC18 as an electronic component is provided at an edge portion 12a of the transparent substrate 12 formed to be larger. In the COG mounting portion 20, terminal portions 17a of the transparent electrodes 17 and substrate-side alignment marks 21 overlapping with IC-side alignment marks 22 provided in the liquid crystal driving IC18 are formed.

[ terminal part ]

As shown in fig. 2, the transparent substrate 12 has an insulating protective film 23 formed on the surface thereof, which is an inorganic film such as a nitride film or a silicon oxide film, an organic film, or the like, in order to prevent physical damage, short circuit, or the like. The protective film 23 is formed in a region other than the terminal portions 17a and the substrate side alignment marks 21 by a known film formation method. Thus, a step portion 28 is formed by the protective film 23 at the side edge portion of the terminal portion 17a adjacent to the protective film 23. Thus, in the sectional view, the step portion 28 of the terminal portion 17a is raised in both side edge portions, and the main surface portion is flattened.

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. 2, the liquid crystal driving IC18 has a plurality of electrode terminals 19 (bumps) formed on the mounting surface 18a of the transparent substrate 12 and electrically connected to the terminal portions 17a of the transparent electrodes 17. For example, a copper bump, a gold bump, or a material obtained by plating gold on a copper bump is suitably used for the electrode terminal 19.

[ electrode terminals ]

As shown in fig. 3, for example, the liquid crystal driving IC18 has the electrode terminals 19 (input bumps) aligned in a row along one side edge of the mounting surface 18a, and the electrode terminals 19 (output bumps) aligned in a plurality of rows in a staggered manner along the other side edge opposite to the one side edge. The electrode terminals 19 and the terminal portions 17a provided on the COG mounting portion 20 of the transparent substrate 12 are formed at the same number and the same pitch, and are connected by aligning and connecting the transparent substrate 12 and the liquid crystal driving IC 18.

In addition, with the recent miniaturization and higher 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 electrode terminal 19 is also reduced (for example, 6 to 15 μm).

As shown in fig. 2, the electrode terminal 19 has stepped portions 27 formed on both side edges. Since the step portion 27 is formed when the metal electrode terminal 19 is manufactured, both side edge portions of the electrode terminal 19 are raised in a cross-sectional view, and the main surface portion is flattened.

The liquid crystal driving IC18 is anisotropically conductively connected to the COG mounting portion 20 so that the step portions 28 formed on both side edge portions of the electrode terminal 19 abut against the step portions 27 formed on both side edge portions of the terminal portion 17 a. At this time, the terminal portion 17a and the electrode terminal 19 bite into the conductive particles 4 between the step portions 27 and 28, and face each other with a predetermined gap therebetween. The conductive particles 4 biting into the gap between the stepped portions 27 and 28 are pressed by the liquid crystal driving IC18 by the thermocompression bonding head 33, and are significantly crushed or broken between the stepped portions 27 and 28.

Thus, the terminal portion 17a and the main surface portion of the electrode terminal 19 face each other with a distance obtained by adding the diameter of the conductive particle 4 sandwiched between the step portions 27 and 28 when pressed (or broken) to the height of the step portions 27 and 28. Further, the height of the stepped portion 27 refers to a distance between the main surface portion of the terminal portion 17a in the normal direction and the top of the stepped portion 27, and the height of the stepped portion 28 refers to a distance between the main surface portion of the electrode terminal 19 in the normal direction and the top of the stepped portion 28.

In the liquid crystal drive IC18, an IC side alignment mark 22 that performs alignment with the transparent substrate 12 by being overlapped with the substrate side alignment mark 21 is formed on the mounting surface 18 a. Further, the wiring pitch of the transparent electrodes 17 of the transparent substrate 12 and the fine pitch of the electrode terminals 19 of the liquid crystal driving IC18 are made, and therefore, high-precision alignment adjustment of the liquid crystal driving IC18 and the transparent substrate 12 is required.

The substrate side alignment marks 21 and the IC side alignment marks 22 can be various marks that can be combined to achieve alignment between the transparent substrate 12 and the liquid crystal driving IC 18.

The liquid crystal driving IC18 is connected to the terminal portion 17a of the transparent electrode 17 formed on the COG mounting portion 20 by using the anisotropic conductive film 1 as an adhesive for circuit connection. The anisotropic conductive film 1 contains conductive particles 4, and electrically connects the electrode terminals 19 of the liquid crystal driving IC18 and the terminal portions 17a of the transparent electrodes 17 formed on the edge portion 12a 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, and the adhesive resin flows, so that the conductive particles 4 are crushed between the terminal portion 17a and the electrode terminal 19 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, an alignment film 24 subjected to a predetermined rubbing treatment is formed on both the transparent electrodes 16 and 17, and the initial alignment of the liquid crystal molecules is defined by the alignment film 24. A pair of polarizers 25, 26 are disposed outside the transparent substrates 11, 12, and the polarizers 25, 26 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. 4, 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 heat-curable adhesive such as a heat-curable adhesive or an ultraviolet-curable adhesive, is adhered to the transparent electrode 17 formed on the transparent substrate 12 of the liquid crystal display panel 10, is mounted with the liquid crystal driving IC18, and is fluidized by heat pressing with the heat pressure tab 33, whereby the conductive particles 4 are crushed between the terminal portion 17a of the transparent electrode 17 and the electrode terminal 19 of the liquid crystal driving IC18 which are opposed to each other, and are cured in a state where the conductive particles 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.

The anisotropic conductive film 1 has 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, and conductive particles 4. As shown in fig. 4, the anisotropic conductive film 1 preferably has conductive particles 4 regularly arranged in a predetermined pattern in the adhesive resin layer 3.

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 curing agent is usually not 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, and starting a curing reaction; a method of melting out a molecular sieve-encapsulated curing agent at a high temperature and starting a curing reaction; a melting/curing method using microcapsules, and the like. The thermally active latent curing agent may be an imidazole, a hydrazide, a boron trifluoride-amine complex, a sulfonium salt, an aminimide, a polyamine salt, a dicyandiamide, or a modified product 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 ]

As the conductive particles 4, any known conductive particles used in the anisotropic conductive film 1 can be cited. Examples of the conductive particles 4 include particles of various metals or metal alloys such as nickel, iron, copper, aluminum, tin, lead, chromium, cobalt, silver, and gold; plating particles of metal on the surface of particles of metal oxide, carbon, graphite, glass, ceramic, plastic, or the like; alternatively, the surface of these particles is further plated with particles of an insulating film, or the like. In the case of plating the surface of the resin particles with metal, examples of the resin particles include particles of epoxy resin, phenol resin, acrylic resin, Acrylonitrile Styrene (AS) resin, benzoguanamine resin, divinylbenzene-based resin, styrene-based resin, and the like.

[ regular arrangement of conductive particles ]

In the anisotropic conductive film 1, the conductive particles 4 are preferably regularly arranged in a predetermined arrangement pattern in a plan view, and are preferably arranged in a lattice shape and uniformly as shown in fig. 5, for example. Since the conductive particles 4 are regularly arranged in a plan view, the anisotropic conductive film 1 can prevent a short circuit between the electrode terminals 19 due to aggregates of the conductive particles 4 in the connection step of the liquid crystal driving IC18, even if the fine pitch between the adjacent electrode terminals 19 of the liquid crystal driving IC18 is made, the area between the terminals is narrowed, and the conductive particles 4 are filled at a high density, as compared with the case where the conductive particles 4 are randomly dispersed.

In addition, in the anisotropic conductive film 1, since the conductive particles 4 are regularly arranged, when the adhesive resin layer 3 is filled at a high density, the occurrence of density due to aggregation of the conductive particles 4 is also prevented. Therefore, according to the anisotropic conductive film 1, the conductive particles 4 can be captured also in the terminal portions 17a and the electrode terminals 19 having a fine pitch. The uniform arrangement pattern of the conductive particles 4 can be set arbitrarily, for example, a lattice shape in a plan view. The connection process of the liquid crystal driving IC18 will be described in detail later.

Such an anisotropic conductive film 1 can be formed by, for example, a method of coating an adhesive on an extensible sheet, arranging conductive particles 4 in a monolayer thereon, and then stretching the sheet at a desired stretching ratio; a method of aligning conductive particles 4 in a predetermined alignment pattern on a substrate and then transferring the conductive particles 4 to a pressure-sensitive adhesive resin layer 3 supported by a release film 2; or a method in which the conductive particles 4 are supplied onto the pressure-sensitive adhesive resin layer 3 supported by the release film 2 through an array plate having openings corresponding to the array pattern.

The shape of the anisotropic conductive film 1 is not particularly limited, but for example, as shown in fig. 4, it may be formed in a long tape shape that can be wound around a reel 6 and cut into a predetermined length.

In the above embodiment, the anisotropic conductive film 1 has been described as an example of an adhesive film formed by molding a thermosetting resin composition in which the conductive particles 4 are regularly arranged in the adhesive resin layer 3 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 adhesive resin 3 and a conductive particle-containing layer composed of the adhesive resin 3 in which the conductive particles 4 are regularly arranged are stacked. In the anisotropic conductive film 1, as long as the conductive particles 4 are regularly arranged in a plan view, the conductive particles 4 may be arranged in a single layer as shown in fig. 4, or may be arranged in a plurality of adhesive resin layers 3 and regularly arranged in a plan view. The anisotropic conductive films 1 may be dispersed uniformly at a predetermined distance in at least one layer of the multilayer structure.

[ relationship between the conductive particles and the height of each step of the substrate electrode and electrode terminal ]

Here, when the anisotropic conductive film 1 in which the conductive particles 4 are regularly arranged is used, the conductive particles 4 may be caught between the step portions 27 and 28 of the electrode terminal 19 and the terminal portion 17a as shown in fig. 6. At this time, the conductive particles 4 and the respective stepped portions 27 and 28 of the electrode terminal 19 and the terminal portion 17a sandwiching the conductive particles 4 satisfy the following formula (1).

a＋b＋c≤0.8D　（1）

[ a: height of step portion of electrode terminal 19, b: step height of terminal portion 17a, c: gap between step portions, D: diameter of conductive particle 4

By satisfying the formula (1), the liquid crystal display panel 10 can compress the conductive particles 4 held between the terminal portion 17a and the main surface portion of the electrode terminal 19 to at least 80% of the uncompressed particle diameter, and can secure sufficient conductivity.

That is, when the liquid crystal display panel 10 is connected to the liquid crystal driving IC18 via the anisotropic conductive film 1, the conductive particles 4 are inserted between the step portion 27 of the electrode terminal 19 and the step portion 28 of the terminal portion 17 a. At this time, the distance between the terminal portion 17a and the main surface portions of the electrode terminal 19 is a distance (a + b + c) obtained by adding the height a of the stepped portion of the electrode terminal 19, the height b of the stepped portion of the terminal portion 17a, and the gap c between the stepped portions 27 and 28 separated by the conductive particles 4 being embedded. Therefore, the distance (a + b + c) between the terminal portion 17a and the main surface portion of the electrode terminal 19 is 80% or less of the diameter D of the conductive particles 4, and the conductive particles 4 can be pressed into the terminal portion so as to be compressed to at least 80% or less of the particle diameter.

On the other hand, if expression (1) is not satisfied, the conductive particles 4 bite into the space between the stepped portion 27 of the electrode terminal 19 and the stepped portion 28 of the terminal portion 17a, and the distance between the terminal portion 17a and the main surface portion of the electrode terminal 19 is at least greater than 80% of the particle diameter of the conductive particles 4, and the compressibility of the conductive particles 4 is less than 20%, and press-fitting becomes insufficient. Therefore, the conductivity between the terminal portion 17a and the electrode terminal 19 may be deteriorated.

In the present invention, the following formula (2) may be satisfied.

c≤1μm　（2）

As shown in the formula (2), the conductive particles 4 which are inserted between the step portion 27 of the terminal portion 17a and the step portion 28 of the electrode terminal 19 are compressed to a particle diameter of approximately 1 μm or less by applying a pressure larger than that which is applied between the main surface portions. In addition, when the conductive particles 4 are broken by compression, the size thereof is approximately 1 μm or less. That is, the gap c between the step portions 27 and 28 is 1 μm or less.

On the other hand, when expression (2) is not satisfied, since the gap between the step portions 27 and 28 exceeds 1 μm, the distance between the terminal portion 17a and each main surface portion of the electrode terminal 19 is increased, and the compression of the conductive particles 4 held between the main surface portions is less than 20%, so that the press-in becomes insufficient. Therefore, the conductivity between the terminal portion 17a and the electrode terminal 19 may be deteriorated.

[ joining Process ]

Next, a connection step 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 COG mounting portion 20 of the transparent substrate 12 on which the terminal portion 17a is 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 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 COG mounting portion 20 of the transparent substrate 12, and the conductive particles 4 in the adhesive resin layer 3 are sandwiched and crushed between the electrode terminals 19 of the liquid crystal driving IC18 and the terminal portions 17a of the transparent substrate 12.

At this time, as described above, the conductive particles 4 and the respective step portions 27 and 28 of the electrode terminal 19 and the terminal portion 17a sandwiching the conductive particles 4 satisfy the following formula (1).

a＋b＋c≤0.8D　（1）

[ a: height of step portion of electrode terminal 19, b: step height of terminal portion 17a, c: gap between step portions, D: diameter of conductive particle 4

Therefore, the liquid crystal display panel 10 can compress the conductive particles 4 held between the terminal portion 17a and the main surface portion of the electrode terminal 19 to at least 80% of the particle diameter, and can secure sufficient conductivity.

In particular, in the case of the liquid crystal display panel 10 using the anisotropic conductive film 1 in which conductive particles are regularly arranged and densely filled in accordance with the fine pitch of the terminal portion 17a and the electrode terminal 19, the conductive particles 4 are likely to be caught not only in the main surface portions of the terminal portion 17a and the electrode terminal 19 but also between the step portions 27 and 28. In this case, by satisfying the above expression (1), the conductive particles 4 held between the main surface portions of the terminal portion 17a and the electrode terminal 19 can be compressed by 20% or more, and good conduction reliability can be ensured.

As a result, the conductive particles 4 are sandwiched between the electrode terminals 19 and the terminal portions 17a to be electrically connected, and the binder resin heated by the thermocompression bonding head 33 is cured in this state. This makes it possible to manufacture the liquid crystal display panel 10 in which the electrical continuity is ensured between the electrode terminals 19 of the liquid crystal driving IC18 and the terminal portions 17a formed on the transparent substrate 12.

The conductive particles 4 not present between the electrode terminals 19 and the terminal portions 17a are dispersed in the binder resin in the inter-terminal space between the adjacent electrode terminals 19, and are maintained in an electrically insulated state. This allows electrical conduction to be established only between the electrode terminals 19 of the liquid crystal driving IC18 and the terminal portions 17a of the transparent substrate 12. Further, as the binder resin, a radical polymerization type fast curing type binder resin is used, and the binder resin can be fast cured even in a short heating time. The anisotropic conductive film 1 is not limited to a thermosetting type, and a photocurable or photothermal adhesive may be used as long as it can be connected by pressure.

Examples

Next, examples of the present invention will be explained. In the present example, a sample of a connection body for connecting an evaluation IC to an evaluation glass substrate was prepared using an anisotropic conductive film in which conductive particles are regularly arranged, and the compressibility of the conductive particles captured between a substrate electrode formed on the evaluation glass substrate and an IC bump formed on the evaluation IC and the on-resistance after a reliability test (examples 1 to 6, comparative examples 1 and 2) or the occurrence rate of short circuit between adjacent IC bumps (example 7 and comparative example 3) were measured.

[ Anisotropic conductive film ]

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

Then, an adhesive is applied to an extensible sheet, conductive particles are uniformly arranged in a single layer in a lattice shape on the sheet, and then an adhesive resin layer is laminated in a state where the sheet is extended at a desired extension ratio to obtain an anisotropic conductive film.

The arrangement of the conductive particles in the present invention is not limited to the case described in the present embodiment.

[ IC for evaluation ]

As evaluation elements for measuring on-resistance, the following external shapes were used: 1.8mm multiplied by 20mm, thickness 0.5 mm; bump (Au-plated): width 30 μm × length 85 μm, height 15 μm; inter-bump space width: IC for evaluation of 50 μm.

[ glass substrate for evaluation ]

As the glass substrate for evaluation to which the IC for evaluation for on-resistance measurement was connected, ITO pattern glass having an outer shape of 30mm × 50mm, a thickness of 0.5mm, a comb-shaped electrode pattern formed with the same size and pitch as the bumps of the IC for evaluation for on-resistance measurement, and a protective film formed in a region other than the electrode pattern was used.

[ IC for evaluation ]

As evaluation elements for measuring the occurrence rate of short circuit between adjacent IC bumps, the following outer shapes were used: 1.5mm multiplied by 13mm, thickness 0.5 mm; bump (Au-plated): width 25 μm × length 140 μm, height 15 μm; inter-bump space width: IC for evaluation of 7.5 μm.

[ glass substrate for evaluation ]

As a glass substrate for evaluation to be connected to an IC for evaluation for measuring the occurrence rate of short circuit between adjacent IC bumps, ITO pattern glass was used, which had an outer shape of 30mm × 50mm and a thickness of 0.5mm, and which had comb-shaped electrode patterns formed with the same size and pitch as the bumps of the IC for evaluation for measuring the occurrence rate of short circuit between adjacent IC bumps, and which had a protective film formed in a region other than the electrode patterns.

After the anisotropic conductive film is temporarily attached to these evaluation glass substrates, the evaluation glass substrates are mounted with the evaluation IC while aligning the IC bumps with the substrate electrodes, and are pressure-bonded by thermocompression bonding. In examples 1 to 7, comparative examples 1 and 3, samples of the interconnectors were prepared by thermocompression bonding at 180 ℃ for 5sec at 80 MPa. In comparative example 2, a sample of a connected body was prepared by thermocompression bonding at 180 ℃ for 5sec under 40 MPa. For each sample of the connected body, the compressibility of the conductive particles held between the IC bumps and the substrate electrodes and the occurrence rate of short circuit between the adjacent IC bumps or on-resistance after the reliability test were measured. The reliability test conditions were 85 deg.C, 85% RH, 500 hr.

[ example 1]

In example 1, conductive particles having a particle size of 4 μm were used as the anisotropic conductive film. The number density of particles before connection was 28000 particles/mm². The height a of the step formed at the side edge of the IC bump was 0.8 μm, and the height b of the step formed at the side edge of the substrate electrode formed on the glass substrate was 0.8 μm.

In the connector sample according to example 1, the gap c between the step portions due to the conductive particles being caught between the IC bump and the both step portions of the substrate electrode was 0.8 μm, the compressibility of the conductive particles held between the both main surface portions of the IC bump and the substrate electrode was 40%, and the on-resistance after the reliability test was 3 Ω.

[ example 2]

In example 2, an anisotropic conductive film using conductive particles having a particle diameter of 3.5 μm was used. The number density of particles before connection was 28000 particles/mm². The heights a and b of the respective step portions of the IC bump and the substrate electrode were the same as those in example 1.

In the connector sample according to example 2, the gap c between the step portions due to the conductive particles being caught between the IC bump and the both step portions of the substrate electrode was 1.0 μm, the compressibility of the conductive particles held between the both main surface portions of the IC bump and the substrate electrode was 26%, and the on-resistance after the reliability test was 4 Ω.

[ example 3]

In example 3, an anisotropic conductive film using conductive particles having a particle diameter of 3.0 μm was used. The number density of particles before connection was 28000 particles/mm². The heights a and b of the respective step portions of the IC bump and the substrate electrode were the same as those in example 1.

In the connector sample according to example 3, the gap c between the step portions due to the conductive particles being caught between the IC bump and the both step portions of the substrate electrode was 0.8 μm, the compressibility of the conductive particles held between the both main surface portions of the IC bump and the substrate electrode was 20%, and the on-resistance after the reliability test was 5 Ω.

[ example 4]

In example 4, an anisotropic conductive film using conductive particles having a particle diameter of 3.5 μm was used. The number density of particles before connection was 28000/mm². The height a of the step formed at the side edge of the IC bump was 0.8 μm, and the height b of the step formed at the side edge of the substrate electrode formed on the glass substrate was 1.2 μm.

In the connector sample according to example 4, the gap c between the step portions due to the conductive particles being caught between the IC bump and the both step portions of the substrate electrode was 0.8 μm, the compressibility of the conductive particles held between the both main surface portions of the IC bump and the substrate electrode was 20%, and the on-resistance after the reliability test was 5 Ω.

[ example 5]

In example 5, an anisotropic conductive film using conductive particles having a particle diameter of 3.0 μm was used. The number density of particles before connection was 28000 particles/mm². The heights a and b of the respective step portions of the IC bump and the substrate electrode were the same as those in example 1.

In the connector sample according to example 5, the conductive particles were not caught between the two step portions of the IC bump and the substrate electrode, the gap c between the step portions was 0 μm, the compressibility of the conductive particles held between the two main surface portions of the IC bump and the substrate electrode was 47%, and the on resistance after the reliability test was 3 Ω.

[ example 6]

In example 6, an anisotropic conductive film using conductive particles having a particle diameter of 3.0 μm was used. The number density of particles before connection was 28000 particles/mm². The heights a and b of the respective step portions of the IC bump and the substrate electrode were the same as those in example 1.

In the connector sample according to example 6, the opposed side edge portions of the IC bump and the side edge portions of the substrate electrode were shifted, so that the gap c between the step portions was-0.2 μm, the compressibility of the conductive particles held between the both main surface portions of the IC bump and the substrate electrode was 53%, and the on-resistance after the reliability test was 3 Ω.

[ example 7]

In example 7, an anisotropic conductive film using conductive particles having a particle size of 4.0 μm was used. The number density of particles before connection was 28000 particles/mm². The height a of the step formed at the side edge of the IC bump was 0.8 μm, and the height b of the step formed at the side edge of the substrate electrode formed on the glass substrate was 1.4 μm.

In the connector sample according to example 7, the gap c between the step portions due to the conductive particles being caught between the IC bump and the two step portions of the substrate electrode was 1.0 μm, the compression ratio of the conductive particles held between the two main surface portions of the IC bump and the substrate electrode was 20%, and the occurrence rate of the termination short circuit between the adjacent IC bumps was 20 ppm.

Comparative example 1

In comparative example 1, an anisotropic conductive film using conductive particles having a particle diameter of 3.0 μm was used. The number density of particles before connection was 28000 particles/mm². The height a of the step formed at the side edge of the IC bump was 0.8 μm, and the height b of the step formed at the side edge of the substrate electrode formed on the glass substrate was 1.4 μm.

In the connector sample according to comparative example 1, the gap c between the step portions due to the conductive particles being caught between the IC bump and the both step portions of the substrate electrode was 0.35 μm, the compressibility of the conductive particles held between the both main surface portions of the IC bump and the substrate electrode was 15%, and the on-resistance after the reliability test was 30 Ω.

Comparative example 2

In comparative example 2, an anisotropic conductive film using conductive particles having a particle size of 4.0 μm was used. The number density of particles before connection was 28000 particles/mm². The height a of the step formed at the side edge of the IC bump was 0.8 μm, and the height b of the step formed at the side edge of the substrate electrode formed on the glass substrate was 0.8 μm.

In the connected body sample according to comparative example 2, the pressing force of the thermocompression bonding was reduced to 40MPa, so that the gap c between the step portions due to the conductive particles being caught between the IC bump and the both step portions of the substrate electrode was 2.0 μm, the compression ratio of the conductive particles between the both main surface portions sandwiching the IC bump and the substrate electrode was 10%, and the on-resistance after the reliability test was 40 Ω.

Comparative example 3

In comparative example 3, an anisotropic conductive film using conductive particles having a particle size of 4.0 μm was used. The number density of the particles before connection is 40000 particles/mm². The height a of the step formed at the side edge of the IC bump was 0.8 μm, and the height b of the step formed at the side edge of the substrate electrode formed on the glass substrate was 1.4 μm.

In the connector sample according to comparative example 3, the gap c between the step portions due to the conductive particles being caught between the IC bump and the both step portions of the substrate electrode was 1.1 μm, the compressibility of the conductive particles held between the both main surface portions of the IC bump and the substrate electrode was 17.5%, and the occurrence rate of the termination short circuit between the IC bumps over the adjacent object was 1000 ppm.

As shown in table 1, in examples 1 to 6, the distance between the IC bump and the main surface portion of the substrate electrode, which is obtained by adding the height a of the stepped portion formed on the side edge portion of the IC bump, the height b of the stepped portion formed on the edge portion of the substrate electrode formed on the glass substrate, and the gap c between the IC bump and the stepped portion of the substrate electrode, is 80% or less of the diameter of the conductive particle. Therefore, in examples 1 to 6, the conductive particles held between the IC bump and the two main surface portions of the substrate electrode were compressed by 20% or more, and good conductivity was maintained even after the reliability test.

On the other hand, in comparative example 1, the distance between the IC bump and the two main surface portions of the substrate electrode was as wide as 85% of the diameter of the conductive particles, and the conductive particles were compressed by only 15%. In comparative example 2, the distance between the IC bump and the two main surface portions of the substrate electrode was as wide as 90% of the diameter of the conductive particles, and the conductive particles were compressed by only 10%. Therefore, in comparative example 1 and comparative example 2, the conductive particles were insufficiently pressed, and the on-resistance reached 30 Ω or more after the reliability test, and the conductivity was significantly deteriorated.

As shown in Table 2, the number density of particles in example 7 was 28000 particles/mm²And the number density of the particles of comparative example 3 was 40000 particles/mm²And is filled with high density. Therefore, in the connector sample according to example 7, the inter-particle distance in the space between the IC bumps was 2 μm on average (0.5 times the particle diameter), while in the connector sample according to comparative example 3, the inter-particle distance in the space between the IC bumps was 1 μm on average (0.25 times the particle diameter). Further, the conductive particles between the IC bumps and the stepped portions of the substrate electrode were also connected, and the occurrence rate of short circuit between the IC bumps was significantly higher in comparative example 3 than in example 7.

Description of the reference symbols

1 an anisotropic conductive film; 2 stripping the film; 3 a binder resin layer; 4 conductive particles; 6, coiling a disc; 10 a liquid crystal display panel; 11. 12a transparent substrate; 12a edge portion; 13 sealing material; 14 liquid crystal; 15 a panel display section; 16. 17a transparent electrode; 17a terminal portion; 18a liquid crystal driving IC; 18a mounting surface; 19 electrode terminals; 20 COG mounting portions; 21 a substrate side alignment mark; 22 IC side alignment marks; 23 protecting the film; 27. 28 step part; 33 thermal compression bonding.

Claims (3)

1. A connector is provided with:

a circuit substrate; and

an electronic component connected to the circuit substrate via an anisotropic conductive adhesive,

a step portion is formed on each side edge portion of the substrate electrode formed on the circuit substrate and the electrode terminal formed on the electronic component,

the substrate electrode and the electrode terminal sandwich conductive particles contained in the anisotropic conductive adhesive between the main surface portions and step portions formed on the side edge portions,

the conductive particles and the step portions of the substrate electrode and the electrode terminal satisfy the following formula (1):

a＋b＋c≤0.8D　（1）

wherein, a: height of step portion of electrode terminal, b: step height of substrate electrode, c: gap between step portions, D: diameter of the conductive particles.

2. The connected body according to claim 1, wherein the conductive particles and the step portions of the substrate electrode and the electrode terminal further satisfy the following formula (2):

c≤1μm　（2）。

3. the connected body according to claim 1 or 2, wherein the anisotropic conductive adhesive is formed in a film shape, and the conductive particles are regularly arranged.