JP2009001661A - Adhesive and bonded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive which is heat curable at low temperature while having high connecting reliability. <P>SOLUTION: The adhesive comprises a dicyclopentadiene type epoxy resin, a phenoxy resin, a curing agent, and conductive particles. The adhesive can be made to be an anisotropic conductive adhesive by including the conductive particles in an amount ranging from 0.1 vol% to less than 30 vol%, and can be made to a conductive adhesive by including the conductive particles in an amount ranging from 30 vol% to 80 vol%. The conductive particles preferably have an average particle size of 1 to 20 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

Conventionally, anisotropic conductive adhesives and conductive adhesives are well known as adhesives containing conductive particles. Among these, anisotropic conductive adhesives are adhesives that connect the electrodes (connection electrodes and connected electrodes) by deforming the conductive particles to some extent by heating and pressurizing the intended connection electrodes and connected electrodes. A bonded body can be obtained by curing.
As an adhesive used for the anisotropic conductive adhesive, an adhesive using an epoxy resin, a phenoxy resin, or a latent curing agent is known (for example, Patent Documents 1 and 2).

  A method for connecting the connection electrode and the electrode to be connected in the case where the anisotropic conductive adhesive is used will be described. First, an anisotropic conductive adhesive is placed on a substrate having a connection electrode, for example, a glass panel, and a base material having an electrode to be connected, for example, an IC chip or a polyimide FPC (flexible printed circuit board) is placed. To do. Next, the heating head is pressed against the structure and heated and pressed to cure the adhesive in the anisotropic conductive adhesive, so that the adjacent electrodes are connected while the electrodes of the different substrates are connected by the conductive particles. The insulation can be kept between.

  However, when an epoxy-based thermosetting resin is contained in the adhesive, sufficient characteristics can be obtained if heating at the time of connection is not performed at a high temperature exceeding 150 ° C. and a high pressure of 3 MPa or more. There wasn't. Therefore, there is a problem that it cannot be applied to a specific flexible base material such as a film base material having high transparency but no heat resistance, such as a polyethylene terephthalate (PET) film or polycarbonate (PC).

  In the case of a thermoplastic resin other than an epoxy resin, the adhesive can be bonded at a low temperature (for example, Patent Document 3). However, even in the temperature lowering operation after the adhesive is cured, there is a problem that the connection cannot be maintained unless the heating head is kept in pressure contact. Further, if the heating head is kept in pressure contact, there is a problem that a long working time is required. In the case of an adhesive using a thermoplastic resin, there is a problem that the heat resistance temperature of the bonded body is poor, the resin softens in a heat resistance test at around 80 ° C., and the reliability of the bonded body is not sufficient. .

JP-A-8-315885 JP-A-5-320610 JP 2003-268346 A

  An object of the present invention is to provide an adhesive that can overcome the above-described problems and can be cured by heating at a low temperature of 150 ° C. or less and has high connection reliability.

As a result of intensive studies to solve the above problems, the present inventor has come to the following invention.
That is, the present invention is as follows.
(1) An adhesive comprising a dicyclopentadiene type epoxy resin, a phenoxy resin, a curing agent, and conductive particles.
(2) The adhesive according to (1), wherein the conductive particles are conductive particles having an average particle diameter of 1 to 20 μm.
(3) The adhesive according to (1) or (2), wherein the curing agent is a latent curing agent.
(4) The adhesive according to any one of (1) to (3), wherein the adhesive contains 0.1% by volume or more and less than 30% by volume and can exhibit anisotropy.
(5) The adhesive according to any one of (1) to (3), wherein the conductive particles are contained in an amount of 30% by volume to 80% by volume.
(6) A method for producing a joined body, wherein the adhesive according to (4) or (5) is disposed on a substrate having a conductive electrode or a conductive electrode, and an electronic component is subjected to thermocompression bonding.
(7) A joined body produced by the production method according to (6).

The adhesive of the present invention is characterized by containing a dicyclopentadiene type epoxy resin and a phenoxy resin. By containing dicyclopentadiene type epoxy resin, heat curing at a low temperature of 150 ° C or lower is possible compared to conventional adhesives using epoxy resin such as bisphenol A type phenoxy resin, naphthalene type, and novolac type. Thus, an epoch-making adhesive having high connection reliability can be provided.
For this reason, by using the adhesive of the present invention, a film substrate having high transparency but not heat resistance, such as PET film and polycarbonate, which has not been possible in the past, and an electronic component or conductive electrode represented by an IC chip are used. Conductive connection with the material is now possible.

The adhesive of the present invention contains at least a dicyclopentadiene type epoxy resin, a phenoxy resin, and a curing agent.
As a dicyclopentadiene type epoxy resin, Dainippon Ink Co., Ltd. Epicron HP7200 is mentioned, for example.
The amount of dicyclopentadiene type epoxy resin used is preferably 1 to 40% by volume in the adhesive.

  The adhesive of the present invention may contain a conventional epoxy resin in addition to the dicyclopentadiene type epoxy resin. The epoxy resin is a compound having two or more epoxy groups in one molecule, and specific epoxy resins include bisphenol A type, bisphenol F type, naphthalene type, bisphenol S type, phenol novolak type, cresol novolak. Type, alicyclic type other than dicyclopentadiene type, biphenyl type, glycidylamine type, glycidyl ester type, and biphenyl type. The number of functional groups of the epoxy functional group at this time is preferably 2 to 4. Moreover, these epoxy resins may consist of a plurality of resins.

The adhesive of the present invention contains a phenoxy resin. The phenoxy resin preferably has a molecular weight of 10,000 or more and 200,000 or less from the viewpoint of solubility as an adhesive and handleability. Specifically, bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, caprolactam modified phenoxy resin, polyol modified phenoxy resin and the like can be mentioned. In addition, an acrylic resin and a high molecular weight epoxy resin can be mixed and used.
The blending amount of the phenoxy resin is preferably 5% by volume or more and preferably 70% by volume or less in the adhesive component.

  In the adhesive of the present invention, by using a dicyclopentadiene type epoxy resin and a phenoxy resin at the same time, it can be cured with a latent curing agent at a low temperature, thereby reducing the connection reliability under high humidity. Can be prevented. Further, when used as an anisotropic conductive adhesive or conductive adhesive, it is possible to suppress deterioration of conductive particles due to moisture absorption.

The curing agent used in the adhesive of the present invention may be any one that can cure the dicyclopentadiene type epoxy resin. When the adhesive of the present invention is used by heating, a certain degree of storage is required after mixing and before the start of use. For this reason, it is preferable that a hardening agent is a latent hardening agent, for example, an acid anhydride, a polyamine, an amine compound, phenols, imidazoles etc. can be used. In order to ensure storage stability at room temperature, it is more preferable to encapsulate the latent curing agent. In particular, a latent curing agent obtained by microencapsulating an imidazole curing agent is preferable.
As for the usage-amount of a latent hardener, 5-300 volume% is preferable with respect to the epoxy resin containing a dicyclopentadiene type epoxy resin.

The adhesive of the present invention can contain conductive particles. The conductive particles are preferably those having an average particle diameter of 1 to 20 μm. If it is less than 1 μm, sufficient electrical connection cannot be obtained because it is included in the range of height variation between the connection electrodes at the time of heating connection. On the other hand, when the thickness exceeds 20 μm, when the adhesive is made into a film, the thickness of the film becomes too thick and it becomes difficult to handle. The average particle diameter of the conductive particles is more preferably 2 to 10 μm.
As the average particle diameter of the conductive particles, a value at an integrated value of 50% of the volume integrated particle size distribution measured by laser diffraction of an airflow particle size distribution analyzer (RODOS SR) is used.

  Known conductive particles can be used as the conductive particles. Examples of the conductive particles include particles obtained by plating nickel, gold, copper, and silver on plastic particles, copper, silver, nickel, gold, tin, solder, non-lead solder powder, and particles plated on these particles. Can be used. Among these, metal particles, particularly copper, silver, copper, or silver alloys are preferable because they are soft and nondestructive. Therefore, connection at a low pressure of 0.5 MPa or less is possible, and there is an advantage that the electrode on the flexible substrate is not destroyed.

The adhesive of the present invention is a conductive adhesive that can exhibit anisotropy by containing conductive particles in an amount of 0.1% by volume or more and less than 30% by volume (hereinafter referred to as “anisotropic conductive adhesive”). Can be used as The volume% of the conductive particles is calculated from the specific gravity by measuring the mass. The anisotropic conductive adhesive may be used in either a paste form or a film form.
When used in the form of a film, the thickness of the film is preferably 10 μm or more and 40 μm or less, and more preferably 12 μm or more and 35 μm or less.
When used in the form of a paste, it is preferably used after adjusting to an appropriate viscosity using an appropriate solvent or reactive diluent. The diluent is preferably adjusted using a bisphenol A type epoxy liquid.

  A base material having a first conductive electrode, such as an FPC (flexible printed circuit board), or an electronic component such as an electronic component represented by an IC chip, an anisotropic conductive adhesive on a base material having a second conductive electrode In the case of using and connecting, an appropriate amount of anisotropic conductive adhesive is applied on the base material having the second conductive electrode using a dispenser or syringe, and the base material or electronic component having the first conductive electrode; A method is preferred in which the counter electrode of the base material having the second conductive electrode is aligned and then heated and cured from the base material or electronic component side having the first conductive electrode.

Similarly, when the anisotropic conductive adhesive is used in the form of a film, the film is pasted on the substrate having the second conductive electrode, heated at 110 to 150 ° C., and pressurized at 0.2 to 3 Mpa. The curing method is preferred.
The electrode provided on the base material having the first conductive electrode, the electronic component, and the base material having the second conductive electrode are ITO, copper, gold, silver, aluminum, tantalum, tin, solder, titanium, nickel, An electrode containing one or more selected from IZO is preferable.

Furthermore, the anisotropic conductive adhesive of the present invention can be used even on a flexible substrate in which at least one of the substrate having the first conductive electrode and the substrate having the second conductive electrode has poor heat resistance. A flexible base material with poor heat resistance is a base material that cannot withstand heating at 160 ° C. or higher, and is, for example, a PET film or a PC film.
Moreover, the adhesive agent of this invention can be made to contain 30-80 volume% of electroconductive particles in an adhesive agent, and can be used as a conductive adhesive agent. The content of the conductive particles is more preferably 40 to 60% by volume.

When a base material having a first conductive electrode, such as an FPC, or an electronic component such as an electronic component represented by an IC chip is connected to a base material having a second conductive electrode using a conductive adhesive It is possible to use a method in which a base material having a first conductive electrode, or an electronic component, or a base material having a second conductive electrode is applied on the electrode by coating or printing and is heated and cured at 110 to 150 ° C. it can. At this time, pressurization can be performed at 0.2 to 3 MPa as necessary.
For example, the ITO electrode connection on a flexible substrate using a film with poor heat resistance can be connected at a low temperature of 150 ° C. or lower, and cannot be performed with the conventional adhesive that required a heating temperature of 150 ° C. or higher. It became possible to join at low temperature.

  The adhesive of the present invention is a substrate on which a connection electrode or a connection electrode is formed, such as polyethylene terephthalate (PET), polyimide, polycarbonate (PC), polyethylene naphthalate (PEN), polyethersulfone, glass epoxy, build It is possible to provide a bonded body based on the above-mentioned conditions of a base material selected from an up substrate and glass and an adhesive, and an epoch-making adhesive that can connect electrodes to a flexible base material that does not have heat resistance. It is an agent.

The present invention will be described below based on examples.
The raw material components of the adhesive used in the examples and comparative examples are as follows.
Bisphenol A type epoxy resin (AER-260, manufactured by Asahi Kasei Chemicals Corporation),
Bisphenol F type epoxy resin (Nippon Kayaku Co., Ltd., RE-303S)
Naphthalene type epoxy (Dainippon Ink Co., Ltd., HP-4032D)
Dicyclopentadiene type epoxy resin (Dainippon Ink Co., Ltd., Epicron HP7200)
Bisphenol A-type phenoxy resin (manufactured by Inchem Co., PKHC)
Latent curing agent (Asahi Kasei Chemicals Corporation, solid amount of microcapsule type imidazole (latent curing agent) contained in HX-3941HP)
Epoxy silane coupling agent (Shin-Etsu Chemical Co., Ltd., KBM-403)
In addition, although the mixture ratio of the structural component of an adhesive agent was shown by the volume%, the epoxy-type silane coupling agent was shown by the outer split.

<Examples 1-3>
Compositions 1 and 2 were prepared in the proportions shown in Table 1, applied onto a 50 μm thick PET film separator using a bar coater, dried at 60 ° C. for 10 minutes, and a 16 μm thick film-like anisotropic conductivity. An adhesive was obtained.
Moreover, the following base material was used as a test connection base material.
(Base material having first conductive electrode)
Polyimide flexible board with copper foil (200 micron pitch with nickel gold plating on the surface of copper foil)
(Base material having second conductive electrode)
Base material (300Ω sheet resistance) on which an ITO electrode is provided on a PET film / Example 1
Substrate (300Ω sheet resistance) with ITO electrode provided on PEN film / Example 2
Base material with ITO electrode on PC film (300Ω sheet resistance) / Example 3

The base material having the first conductive electrode and the base material having the second conductive electrode were joined using the film-like anisotropic conductive adhesive obtained as described above.
The bonding is performed by attaching a film-like anisotropic conductive adhesive to the base material having the second conductive electrode, and 130 ° C. for 30 seconds from the flexible base material side which is the base material having the first conductive electrode. This was carried out by applying pressure and heating with a 1.5 mm head at 0.5 MPa.
The bonded body thus obtained was evaluated for an initial connection resistance value and a resistance value after a connection reliability test (after leaving at 85 ° C. and a humidity of 85% for 200 hours).
The connection resistance was measured by a 4-terminal method using a Hioki 9455 type multimeter. In the measurement, four pairs of resistances of a pair of copper foils on the polyimide side were measured to obtain an average value. The results are shown in Table 2.
As for the initial connection resistance value, a case where it is 50Ω or less is regarded as “good”, and a case where it exceeds 50Ω is regarded as “defective”.
As for the resistance value after the connection reliability test, the connection reliability is “bad” when the connection resistance value exceeds 100Ω, and the connection reliability is “good” when the connection resistance value is 100Ω or less.

<Comparative Examples 1 and 2>
Compositions 3 and 4 were prepared at the ratios shown in Table 1, applied onto a 50 μm thick PET film separator using a bar coater, dried at 60 ° C. for 10 minutes, and a 16 μm thick film-like anisotropic conductivity. An adhesive was obtained.
The following base materials were used as test connection base materials.
(Base material having first conductive electrode)
Polyimide flexible substrate with copper foil (etched with 200 micron pitch and plated with gold on the surface)
(Base material having second conductive electrode)
Base material (300Ω sheet resistance) on which an ITO electrode is provided on a PET film / Comparative Example 1
Base material (300Ω sheet resistance) with ITO electrode provided on PEN film / Comparative Example 2
In the same manner as in Example 1, the base material having the first conductive electrode and the base material having the second conductive electrode were joined. After the initial connection resistance value and the connection reliability test were performed on the obtained joined body. The resistance value of was evaluated. The results are shown in Table 2.

<Examples 4 and 5>
Compositions 5 and 6 were prepared at the ratio shown in Table 3 to obtain a conductive adhesive.
The following base materials were used as test connection base materials.
(Base material having first conductive electrode)
Chip Capacitor / Example 4
IC (Gold Stud Bump) / Example 5
(Base material having second conductive electrode)
Base material (300Ω sheet resistance) with ITO electrode provided on PET film / Example 4
Base material (300Ω sheet resistance) with ITO electrode provided on PEN film / Example 5
In the bonding, a conductive adhesive is applied to a base material having a second conductive electrode, and the flexible base side that is the base material having the first conductive electrode is 1.degree. This was carried out by heating under pressure with a 5 mm head.

The bonded body thus obtained was evaluated in the same manner as in Example 1 for the initial connection resistance value and the resistance value after the connection reliability test. The results are shown in Table 4.
As the conductive adhesive evaluation criteria, the expected connection resistance value was determined as “good” when the resistance was 1Ω or less, and as “bad” when it exceeded 1Ω. Regarding the resistance value after connection reliability test (after leaving for 200 hours at 85 ° C and 85% humidity), if the connection resistance value exceeds 10Ω, the connection reliability is “bad” and the connection resistance value is 10Ω or less The connection reliability was “good”.

  The adhesive of the present invention can be used for electronic paper, wearable displays, organic EL and liquid crystal flexible displays, and mounting of electronic components on flexible substrates.

Claims (7)

  An adhesive comprising a dicyclopentadiene type epoxy resin, a phenoxy resin, a curing agent, and conductive particles.   The adhesive according to claim 1, wherein the conductive particles are conductive particles having an average particle diameter of 1 to 20 μm.   The adhesive according to claim 1 or 2, wherein the curing agent is a latent curing agent.   The adhesive according to claim 1, wherein the adhesive contains 0.1% by volume or more and less than 30% by volume and can exhibit anisotropy.   The adhesive according to any one of claims 1 to 3, wherein the adhesive contains 30% by volume or more and 80% by volume or less of conductive particles.   A method for producing a joined body, comprising: placing the adhesive according to claim 4 or 5 on a substrate having a conductive electrode or a conductive electrode, and thermocompression bonding the electronic component.   A joined body produced by the production method according to claim 6.