JP2010024416A - Adhesive for connecting electrodes - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive for connecting electrodes, which is hardened at low temperature and within a short period of time, with which connection reliability between the electrodes is improved, and which is excellent in stability during storage and heat resistance, in connecting between electrodes via the adhesive for connecting electrodes. <P>SOLUTION: The metal electrode 5 of a flexible printed circuit board 3 and the metal electrode 4 of a wiring substrate 1 are connected with each other via the adhesive 2 for connecting the electrodes, the adhesive 2 containing an epoxy resin as a main component, electroconductive particles and a hardening agent, wherein the adhesive 2 for connecting the electrodes contains a phenoxy resin having a molecular weight of 10,000 or more and a glass transition temperature of 80°C or more and a crystalline epoxy resin as the epoxy resin, and contains a pulverized urea-based hardening agent and a microcapsule type hardening agent as the hardening agents. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrode connecting adhesive that is provided between a plurality of members to be joined and connects electrodes formed on each of the plurality of members to be joined by performing a heat and pressure treatment.

  In recent years, electronic devices have been miniaturized and functionalized, and connection terminals in component parts (for example, electronic parts in liquid crystal products) have been miniaturized. For this reason, in the field of electronics mounting, film adhesives are widely used as various electrode connecting adhesives that can easily connect such terminals. For example, a flexible printed wiring board (FPC) on which a metal electrode made of gold-plated copper electrode is formed and a wiring board such as a glass substrate on which a wiring electrode made of ITO is formed, or an electronic component such as an IC chip And a rigid substrate (PCB).

  This electrode connecting adhesive is, for example, an adhesive in which conductive particles are dispersed in an insulating thermosetting resin such as an epoxy resin and a curing agent for promoting the curing of the thermosetting resin. It is sandwiched between and heated and pressurized to bond the connection object. That is, the resin in the adhesive flows by heating and pressurizing, for example, simultaneously sealing the gap between the copper electrode formed on the surface of the flexible printed wiring board and the ITO electrode formed on the surface of the wiring board, Electrical connection is achieved by interposing a portion of the conductive particles between the copper electrode and the ITO electrode facing each other. In the electrode connecting adhesive, the conductive performance of reducing the resistance (connection resistance or conduction resistance) between the connected electrodes, which is relatively in the thickness direction of the electrode connecting adhesive, and for electrode connection Insulation performance is required to increase the resistance (insulation resistance) between electrodes adjacent in the surface direction of the adhesive.

  In general, the electrode connecting adhesive is required to have low temperature (150 ° C. or lower) curability and high storage stability, and an electrode connecting adhesive for achieving both low temperature curability and storage stability is provided. Proposed. More specifically, an electrode connecting adhesive using an epoxy resin as a main component and a urea curing agent and an amide curing agent in combination as an epoxy resin curing agent is disclosed. And it is described that such a structure can provide an adhesive for electrode connection that is excellent in storage stability and can realize low-temperature curing (see, for example, Patent Document 1).

Also, the main component is an epoxy resin having a polysulfite skeleton, an epoxy resin containing a thermoplastic elastomer component and an epoxy resin containing a crosslinked rubber component, and a solid epoxy resin having a softening point of 50 ° C. or higher. An electrode connecting adhesive using a urea curing agent and a latent curing agent in combination as a component and an epoxy resin curing agent is disclosed. And it is described that such a structure can provide an adhesive for electrode connection that is excellent in storage stability and can realize low-temperature curing (for example, see Patent Document 2).
JP 59-136368 A Japanese Patent No. 3400881

  However, in the electrode connecting adhesive described in Patent Document 1, since the reaction rate of the epoxy resin and the amide curing agent is slow, the electrode connecting adhesive is kept at a low temperature (150 ° C. or lower) for a short time (for example, 10 It was difficult to cure in less than a second). In addition, the electrode connecting adhesive described in Patent Document 2 has a problem that the heat resistance of the adhesive is poor and the environmental resistance required for the electrode connecting adhesive cannot be cleared. In addition, since the reaction rate of the epoxy resin and the epoxy resin curing agent is very slow and it takes a long time to cure the adhesive, the electrode connecting adhesive should be kept at a low temperature (150 ° C. or less) and for a short time (eg, 10 seconds or less) It was difficult to cure with. In addition, sufficient adhesion to flexible printed wiring board substrates (for example, substrates made of polyimide resin) and wiring substrates such as glass epoxy substrates cannot be obtained, and the electrodes are connected via an electrode connecting adhesive. In doing so, there is a problem that the connection reliability between the electrodes is lowered.

  Therefore, the present invention has been made in view of the above-described problems, and can be cured at a low temperature and in a short time when connecting the electrodes via the electrode connecting adhesive, and the connection between the electrodes. An object of the present invention is to provide an electrode connecting adhesive that can improve reliability and is excellent in storage stability and heat resistance.

  In order to achieve the above object, the invention according to claim 1 is an adhesive for electrode connection containing an epoxy resin as a main component and containing conductive particles and a curing agent, and the epoxy resin has a molecular weight of 10,000 or more. In addition, a phenoxy resin having a glass transition temperature of 80 ° C. or higher and a crystalline epoxy resin are included, and the curing agent includes a powdery urea curing agent and a microcapsule curing agent.

  According to this configuration, the epoxy resin contained in the electrode connecting adhesive uses a phenoxy resin having a molecular weight of 10,000 or more and a glass transition temperature of 80 ° C. or more. (For example, the adhesive force with respect to wiring boards, such as a base material consisting of a polyimide resin) and a glass epoxy board | substrate improves. As a result, for example, a metal electrode (for example, a copper electrode plated with gold) on a flexible printed wiring board and a wiring electrode (for example, a copper electrode plated with gold) on a wiring board are interposed via an electrode connecting adhesive. Connection reliability between the electrodes is improved. In addition, since crystalline epoxy resin is used as the epoxy resin contained in the electrode connection adhesive, the heat resistance of the electrode connection adhesive is improved and the environmental resistance required for the electrode connection adhesive is cleared. And the reactivity with the epoxy resin curing agent is increased, and the reaction rate between the epoxy resin and the epoxy resin curing agent is increased, so that the electrode connecting adhesive can be used in a short time (for example, 10 seconds). It can be cured. In addition, since a powdery urea-based curing agent and a microcapsule-type curing agent are used in combination as a curing agent contained in the electrode connection adhesive, the electrode connection adhesive containing a crystalline epoxy resin has a low temperature (150 ° C. And the like, and it is possible to improve the storage stability of the electrode connecting adhesive.

  Invention of Claim 2 is the adhesive agent for electrode connection of Claim 1, Comprising: The compounding quantity of the urea type hardening | curing agent with respect to the whole adhesive agent for electrode connection is 1 mass% or more and 20 mass% or less. In addition, the compounding amount of the urea curing agent with respect to 100 parts by mass of the microcapsule type curing agent is 20 parts by mass or more and 100 parts by mass or less. According to this configuration, the electrode connecting adhesive can be reliably cured at a low temperature, and the storage stability of the electrode connecting adhesive can be reliably improved.

  Invention of Claim 3 is the adhesive agent for electrode connection of Claim 1 or Claim 2, Comprising: The molecular weight of a phenoxy resin is 30000 or more, It is characterized by the above-mentioned. According to this configuration, the adhesion force of the flexible printed wiring board to the wiring board such as the base material or the glass epoxy board is further improved. Therefore, when connecting the metal electrode and the wiring electrode via the electrode connecting adhesive. The connection reliability between the electrodes is further improved.

  Invention of Claim 4 is the adhesive agent for electrode connections of any one of Claim 1 thru | or 3, Comprising: The average particle diameter of a urea type hardening | curing agent is 3 micrometers or more and 15 micrometers or less. Features.

  According to this configuration, the storage stability of the electrode connecting adhesive can be reliably improved, and when the metal electrode and the wiring electrode are connected via the electrode connecting adhesive, the connection reliability between the electrodes is reliable. Can be improved with certainty.

  Invention of Claim 5 is the adhesive agent for electrode connection in any one of Claim 1 thru | or 4, Comprising: Conductive particle | grains are a metal single body which has magnetism, 2 or more types of alloys which have magnetism, magnetic It is one metal selected from the group consisting of an alloy of a metal having a metal and another metal and a composite containing a metal having magnetism, or a composite.

  According to this configuration, the conductive particles include a group consisting of a single metal having magnetism, two or more kinds of alloys having magnetism, an alloy of a metal having magnetism with another metal, and a composite containing a metal having magnetism. By using one selected metal or composite, it becomes possible to orient the conductive particles using a magnetic field due to the magnetism of the metal or composite itself.

  The invention according to claim 6 is the adhesive for electrode connection according to claim 5, wherein the conductive particles are conductive particles having a diameter to length ratio (aspect ratio) of 5 or more, and The electrode connecting adhesive has a film shape, and the conductive particles are oriented in the thickness direction of the film.

  According to this configuration, since the conductive particles are conductive particles having a diameter to length ratio (aspect ratio) of 5 or more, the electrodes to be connected can be electrically connected without increasing the blending amount of the conductive particles. It becomes possible to connect. In addition, since the conductive particles are oriented in the thickness direction of the film, while maintaining insulation between adjacent electrodes to prevent short-circuiting, a plurality of electrodes to be connected can be electrically connected at a time and independently. The effect of being able to connect is further improved.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to harden | cure in low temperature and a short time, the connection reliability between electrodes can be improved, and the adhesive agent for electrode connection which is excellent in storage stability and heat resistance is provided. It becomes possible.

  Hereinafter, a preferred embodiment of the present invention will be described. In this embodiment, the member to be joined by the electrode connecting adhesive is formed on the wiring substrate having the first electrode formed on the rigid base material and the flexible base material. A flexible printed wiring board having the second electrode will be described as an example. FIG. 1 is a cross-sectional view showing a wiring board on which a flexible printed wiring board is mounted with an electrode connecting adhesive according to the present embodiment. As shown in FIG. 1, a wiring substrate 1 (for example, a glass substrate or a glass epoxy substrate) which is a first substrate through an electrode connecting adhesive 2 having a thermosetting resin as a main component and having a film shape. The metal electrode 4 that is the first electrode included in is connected to the metal electrode 5 that is the second electrode of the flexible printed wiring board 3 that is the second substrate. In addition, as a base material of the flexible printed wiring board 3, the film-form base material which consists of a resin material excellent in the softness | flexibility is used. As such a resin film, for example, any resin film having heat resistance for a flexible printed wiring board, such as polyimide and polyamideimide, can be used. Moreover, as a versatile resin film, for example, a polyamide-based resin film, particularly polyethylene terephthalate or polyethylene naphthalate is preferably used.

  As the metal electrodes 4 and 5 of the present invention, for example, a metal foil such as a copper foil is laminated on the surface of the flexible printed wiring board 3, and the metal foil is exposed, etched, and plated by a conventional method. The formed copper electrode with gold plating is used.

  Moreover, the adhesive 2 for electrode connection used for this invention is set as the structure which uses the epoxy resin which is a thermosetting resin, an epoxy resin hardening | curing agent, and electroconductive particle. For example, an epoxy resin as a main component, in which conductive particles are dispersed in the resin, can be used, and conductive resin powder such as nickel, copper, silver, gold or graphite is dispersed in the epoxy resin Is mentioned. In addition, as the adhesive agent 2 for electrode connection, a thing with a thickness of 10 micrometers-40 micrometers can be used.

  And in this embodiment, it is set as the structure which uses the phenoxy resin which is a high molecular weight epoxy resin whose molecular weight is 10,000 or more as an epoxy resin. By using such a phenoxy resin, the hydroxyl group content in the resin increases, so that strong hydrogen bonds can be obtained, and the flexible printed wiring board 3 base material (for example, from polyimide resin) The affinity for the wiring substrate 1 such as a base material) or a glass epoxy substrate is improved. Therefore, since the adhesion of the flexible printed wiring board 3 to the base material or the wiring board 1 is improved, when the metal electrode 5 and the metal electrode 4 are connected via the electrode connecting adhesive 2, the connection reliability between the electrodes is reliable. Improves. From the viewpoint of further improving the adhesion, it is preferable to use a phenoxy resin having a molecular weight of 30000 or more.

  Further, when a high molecular weight epoxy resin is used, the film forming property is enhanced, and the melt viscosity of the resin at the connection temperature can be increased, and the effect that the connection can be made without disturbing the orientation of the conductive particles described later is obtained.

  Moreover, in this embodiment, it is set as the structure which uses the glass transition temperature of 80 degreeC or more as said phenoxy resin. With such a configuration, since the glass transition temperature of the electrode connecting adhesive 2 is improved and the heat resistance is improved, the environmental resistance required for the electrode connecting adhesive 2 can be cleared. The “glass transition temperature” used herein refers to each of the electrode connecting adhesive 2 measured using a dynamic viscoelasticity measuring device (DMA) and each of the phenoxy resins constituting the electrode connecting adhesive 2. A physical property value.

  Moreover, in this embodiment, it is set as the structure which uses a crystalline epoxy resin together with the above-mentioned phenoxy resin as an epoxy resin. The term “crystallinity” as used herein refers to a “phenomenon that has a melting point and suddenly decreases when the melting point is exceeded”. With such a configuration, the viscosity of the crystalline epoxy resin is quickly reduced by heating, so that the reaction rate between the epoxy resin and the epoxy resin curing agent is increased. Therefore, the electrode connecting adhesive 2 can be cured in a short time (for example, 10 seconds or less). The melting point of the crystalline epoxy resin is preferably 50 ° C. or higher and 90 ° C. or lower. Film formation becomes difficult when the melting point is lower than 50 ° C. On the other hand, when the melting point exceeds 90 ° C., the effect of improving the reaction rate becomes low.

  Examples of the crystalline epoxy resin that can be used include bisphenol A-type and F-type distilled products, naphthalene-type epoxy resins, novolac-type epoxy resins, and biphenyl-type epoxy resins.

  Moreover, as a crystalline epoxy resin, it is preferable to use a low molecular weight epoxy resin of 500 or less. This is because, when a low molecular weight epoxy resin is used, the crosslinking density is increased, the heat resistance is improved, and the cohesive force of the resin is increased, so that the effect of increasing the adhesive force is obtained.

  Thus, in this embodiment, the performance of the electrode connecting adhesive 2 is balanced by using a combination of a phenoxy resin that is a high molecular weight epoxy resin and a crystalline epoxy resin that is a low molecular weight epoxy resin. It becomes possible. The blending amount of the phenoxy resin and the crystalline epoxy resin can be appropriately selected in consideration of the balance of the performance of the electrode connecting adhesive 2.

  In addition, in this embodiment, it is set as the structure which makes the compounding quantity of the phenoxy resin with respect to the whole adhesive agent 2 for electrode connection 10 mass% or more and 40 mass% or less. This is because when the blending amount of the phenoxy resin is less than 10% by mass, there is a problem that the film cannot be formed well, and when it is greater than 40% by mass, the fluidity at the time of mounting is deteriorated and the connection resistance is increased. .

  Moreover, in this embodiment, it is set as the structure which makes the compounding quantity of the crystalline epoxy resin with respect to the whole adhesive agent 2 for electrode connection 10 mass% or more and 40 mass% or less. This is because when the compounding amount of the crystalline epoxy is smaller than 10% by mass, the effect of increasing the reaction rate is reduced, and when it is larger than 40% by mass, the resin flows too much at the time of mounting and the connection reliability is impaired. is there.

  In this embodiment, a urea-based curing agent is used as the epoxy resin curing agent. Since this urea-based curing agent is excellent in curability at a low temperature (150 ° C. or less), by using the urea-based curing agent in combination with the above-described electrode-connecting adhesive 2 containing the crystalline epoxy resin, electrode connection is achieved. It is possible to cure the adhesive 2 for use at a low temperature (150 ° C. or less) and in a short time (10 seconds or less).

  Moreover, it is preferable to use what has a powder shape as a urea type hardening | curing agent. By dispersing the powdery curing agent in the adhesive so as not to dissolve, it is possible to realize a situation where the epoxy resin and the curing agent are not sufficiently in contact with each other, so the storage stability of the electrode connecting adhesive 2 can be improved. become.

  In the present embodiment, it is preferable to use a urea curing agent having a powder shape having an average particle size of 3 μm or more and 15 μm or less. This is because when the average particle size is smaller than 3 μm, the contact area between the crystalline epoxy resin and the urea curing agent increases, so that the reaction between the crystalline epoxy resin and the urea curing agent starts at room temperature. Therefore, there may be a disadvantage that the storage stability of the electrode connecting adhesive 2 is lowered. When the average particle size is larger than 15 μm, when the electrode connecting adhesive 2 having a film shape is formed, the surface of the film becomes uneven, and the metal electrode 5 and the electrode electrode 2 are connected via the electrode connecting adhesive 2. This is because when the metal electrodes 4 are connected, the urea-based curing agent remains undissolved, and the connection reliability between the metal electrodes 5 and 4 may be reduced.

  In addition, in this embodiment, it is set as the structure which makes the compounding quantity of the urea type hardening | curing agent with respect to the whole adhesive agent 2 for electrode connection 1 mass% or more and 20 mass% or less. This is because when the blending amount of the urea-based curing agent is smaller than 1% by mass, the low temperature curability may not be sufficiently improved, and when it is larger than 20% by mass, the storage stability may be deteriorated. It is.

  Moreover, in this embodiment, it is set as the structure which uses a latent hardening agent together with the above-mentioned urea type hardening | curing agent as an epoxy resin hardening | curing agent. This latent curing agent is a curing agent that is excellent in storage stability at a low temperature and hardly undergoes a curing reaction at room temperature, but rapidly performs a curing reaction by heat, light, or the like. As this latent curing agent, imidazole series, hydrazide series, boron trifluoride-amine complex, amine imide, polyamine series, tertiary amine, alkyl urea series and other amine series, dicyandiamide series, acid anhydride series, phenol series These modified products are exemplified, and these can be used alone or as a mixture of two or more.

  Among these latent curing agents, an imidazole-based latent curing agent is preferably used from the viewpoint of excellent storage stability at low temperatures and excellent rapid curability. As the imidazole-based latent curing agent, a known imidazole-based latent curing agent can be used. More specifically, an adduct of an imidazole compound with an epoxy resin is exemplified. Examples of the imidazole compound include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-propylimidazole, 2-dodecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 4-methylimidazole.

  In this embodiment, in particular, these latent hardeners are coated with a polymer material such as polyurethane or polyester, a metal thin film such as nickel or copper, and an inorganic material such as calcium silicate, to form a microcapsule. The microcapsule type curing agent is used. By using such a microcapsule type curing agent, the storage stability and heat resistance of the electrode connecting adhesive 2 are improved.

  In the present embodiment, it is preferable to use a microcapsule type curing agent having an average particle size of 5 μm or less. This is because when the average particle size is larger than 5 μm, there may be a disadvantage that it does not dissolve sufficiently during mounting and remains undissolved.

  In addition, in this embodiment, it is set as the structure which makes the compounding quantity of the microcapsule type hardening | curing agent with respect to the whole adhesive agent 2 for electrode connection 20 mass% or more and 50 mass% or less. This is because when the blending amount of the microcapsule type curing agent is less than 20% by mass, there may be a disadvantage that the curing reaction does not proceed completely, and when it is greater than 50% by mass, the excess curing agent is bonded. This is because there may be a disadvantage that it remains in the agent and adversely affects connection reliability.

  Moreover, in this embodiment, it is set as the structure which makes 20 mass parts or more and 100 mass parts or less the compounding quantity of the urea type hardening | curing agent with respect to 100 mass parts of microcapsule type hardening | curing agents. This is because when the blending amount of the urea-based curing agent is less than 20% by mass, the low-temperature curability may not be sufficiently improved, and when it is greater than 100% by mass, the storage stability may be deteriorated. It is.

  Further, as shown in FIG. 2, an anisotropic conductive adhesive containing conductive particles 6 can be used as the electrode connecting adhesive 2. More specifically, as the anisotropic conductive adhesive, for example, a phenoxy resin that is the above-described epoxy resin and a crystalline epoxy resin are the main components, and fine metal particles (for example, spherical particles) are contained in the resin. A large number of metal fine particles or metal fine particles composed of spherical resin particles plated with metal), a conductive shape formed of a metal powder having a shape connected in a straight chain or a needle shape, so-called a large aspect ratio What dispersed the particle | grains 6 can be used. The aspect ratio referred to here is the ratio between the short diameter (the length of the cross section of the conductive particles 6) R of the conductive particles 6 and the long diameter (the length of the conductive particles 6) L shown in FIG. Say.

  By using such conductive particles 6, as the anisotropic conductive adhesive, the surface direction of the electrode connecting adhesive 2 (the direction perpendicular to the thickness direction X and the direction of the arrow Y in FIG. 2). In the thickness direction X, a large number of metal electrodes 4 to 5 are connected independently at a time while maintaining insulation between adjacent electrodes to prevent short circuits, and low resistance Can be obtained.

  The aspect ratio of the conductive particles 6 is preferably 5 or more. By using such conductive particles 6, when an anisotropic conductive adhesive is used as the electrode connecting adhesive 2, the contact probability between the conductive particles 6 is increased. Therefore, the metal electrode 4 and the metal electrode 5 can be electrically connected without increasing the blending amount of the conductive particles 6.

  In this anisotropic conductive adhesive, the magnetic field applied to the thickness direction X of the anisotropic conductive adhesive when the direction of the long diameter L of the conductive particles 6 is formed into a film-like anisotropic conductive adhesive is formed. It is preferable to use it in the thickness direction X by passing through the inside. By adopting such an orientation, the above-described insulation between adjacent electrodes is maintained to prevent a short circuit, and a large number of metal electrodes 4 to metal electrodes 5 are electrically connected at a time and independently. The effect that it becomes possible to improve is further improved.

  In addition, the metal powder used in the present invention preferably contains a ferromagnetic material in part, such as a single metal having ferromagnetism, two or more kinds of alloys having ferromagnetism, a metal having ferromagnetism and others. It is preferably any one of an alloy with the above metal and a composite containing a metal having ferromagnetism. This is because the use of a ferromagnetic metal makes it possible to orient the conductive particles 6 using a magnetic field due to the magnetism of the metal itself. For example, nickel, iron, cobalt, and two or more kinds of alloys containing these can be used.

  The aspect ratio of the conductive particles 6 is directly measured by a method such as observation with a CCD microscope. In the case of the conductive particles 6 whose cross section is not a circle, the aspect ratio is obtained by setting the maximum length of the cross section as the short diameter. The conductive particles 6 do not necessarily have a straight shape, and can be used without any problems even if they are slightly bent or branched. In this case, the aspect ratio is obtained by setting the maximum length of the conductive particles 6 as the major axis.

  As a method for mounting a wiring board such as a flexible printed wiring board using the electrode connecting adhesive of the present embodiment, heat and pressure treatment is performed via the electrode connecting adhesive 2 mainly composed of an epoxy resin. Thus, the epoxy resin is cured, and the metal electrode 5 of the flexible printed wiring board 3 is connected to the metal electrode 4 of the wiring board 1.

  More specifically, a conductive electrode comprising a phenoxy resin and a crystalline epoxy resin as main components and a microcapsule type curing agent, a urea-based curing agent, and conductive particles on a wiring substrate 1 such as a glass substrate. The connecting adhesive 2 is placed, and the electrode connecting adhesive 2 is heated to a predetermined temperature and pressurized in the direction of the wiring substrate 1 with a predetermined pressure, and the electrode connecting adhesive 2 is applied to the wiring substrate 1. Temporarily adhere to the top. Next, with the flexible printed wiring board 3 facing downward, while aligning the metal electrode 4 formed on the surface of the wiring substrate 1 and the metal electrode 5 formed on the surface of the flexible printed wiring board 3, By placing the flexible printed wiring board 3 on the electrode connecting adhesive 2, the electrode connecting adhesive 2 is interposed between the wiring substrate 1 and the flexible printed wiring board 3. Next, by pressing the electrode connecting adhesive 2 with a predetermined pressure in the direction of the wiring board 1 through the flexible printed wiring board 3 in a state where the electrode connecting adhesive 2 is heated to a predetermined temperature, The electrode connecting adhesive 2 is heated and melted. As described above, since the electrode connecting adhesive 2 is mainly composed of an epoxy resin which is a thermosetting resin, the electrode connecting adhesive 2 is once softened when heated at the above temperature. However, it will be cured by continuing the heating. In addition, since the microcapsule type curing agent requires a certain temperature in order to release the capsule-covered state and melt the curing agent inside the capsule, in the above-described heat and pressure treatment, first, urea is used. The curing reaction between the system curing agent and the epoxy resin is started, and then the curing reaction between the microcapsule type curing agent and the epoxy resin is started. When a predetermined curing time of the electrode connecting adhesive 2 elapses, the state of maintaining the curing temperature of the electrode connecting adhesive 2 and the pressurized state are released, and cooling is started. The metal electrode 4 and the metal electrode 5 are connected through the connection adhesive 2, and the flexible printed wiring board 3 is mounted on the wiring board 1.

According to the present embodiment described above, the following effects can be obtained.
(1) In this embodiment, as an epoxy resin contained in the electrode connecting adhesive 2, a phenoxy resin having a molecular weight of 10,000 or more and a glass transition temperature of 80 ° C. or more is used. Therefore, in order to improve the adhesion of the flexible printed wiring board 3 to the wiring substrate 1 such as a base material or a glass epoxy substrate, when connecting the metal electrode 5 and the metal electrode 4 via the electrode connecting adhesive 2, The connection reliability between the electrodes can be improved. In addition, a crystalline epoxy is used as the epoxy resin contained in the electrode connecting adhesive 2. Therefore, since the heat resistance of the electrode connecting adhesive 2 is improved, it is possible to clear the environmental resistance required for the electrode connecting adhesive 2. Furthermore, by using crystalline epoxy, the reactivity with the epoxy resin curing agent is increased, and the reaction rate between the epoxy resin and the epoxy resin curing agent is increased. 10 seconds). Moreover, in this embodiment, it is set as the structure which uses a powdery urea type hardening | curing agent as a hardening | curing agent contained in the adhesive agent 2 for electrode connection. Accordingly, by using a urea curing agent in combination with the electrode connecting adhesive 2 containing a crystalline epoxy resin, the electrode connecting adhesive 2 is cured at a low temperature (150 ° C. or less) and in a short time (for example, 10 seconds). And the storage stability of the electrode connecting adhesive 2 can be improved. Further, a microcapsule type curing agent is used as the curing agent contained in the electrode connecting adhesive 2. Therefore, the storage stability and heat resistance of the electrode connecting adhesive 2 can be improved.

  (2) In the present embodiment, a phenoxy resin having a molecular weight of 30,000 or more is used. Therefore, since the adhesive force with respect to the base material of the flexible printed wiring board 3 or the wiring board 1 such as a glass epoxy board is further improved, when the metal electrode 5 and the metal electrode 4 are connected through the electrode connecting adhesive 2. In addition, the connection reliability between the electrodes is further improved.

  (3) In this embodiment, the amount of the urea-based curing agent with respect to the entire electrode connecting adhesive 2 is set to 1% by mass or more and 20% by mass or less, and the urea-based curing agent with respect to 100 parts by mass of the microcapsule type curing agent. It is set as the structure which sets the compounding quantity of a hardening | curing agent to 20 to 100 mass parts. Accordingly, the electrode connecting adhesive 2 can be reliably cured at a low temperature, and the storage stability of the electrode connecting adhesive 2 can be reliably improved.

  (4) In this embodiment, the average particle diameter of the urea-based curing agent is set to 3 μm or more and 15 μm or less. Accordingly, the storage stability of the electrode connecting adhesive 2 can be reliably improved, and the connection reliability between the electrodes can be increased when the metal electrode 5 and the metal electrode 4 are connected via the electrode connecting adhesive 2. Can be improved with certainty.

In addition, you may change the said embodiment as follows.
In the above embodiment, the metal electrode 5 of the flexible printed wiring board 3 is connected to the metal electrode 4 of the wiring board 1 through the electrode connecting adhesive 2, but the electrode connecting adhesive of the present invention 2 may be used, for example, for connection between the protruding electrodes (or bumps) of an electronic component such as an IC chip and the metal electrodes 4 of the wiring board 1.

  Below, this invention is demonstrated based on an Example and a comparative example. In addition, this invention is not limited to these Examples, These Examples can be changed and changed based on the meaning of this invention, and they are excluded from the scope of the present invention. is not.

Example 1
(Production of adhesive)
As the conductive particles, linear nickel fine particles having a long diameter L distribution of 3 μm to 20 μm and a short diameter R distribution of 0.1 μm to 0.3 μm were used. Examples of the epoxy resin include (1) phenoxy resin [manufactured by InChem, trade name PKHH, molecular weight: 52000, glass transition temperature: 92 ° C.], and (2) crystalline epoxy resin [Dainippon Ink Chemical Co., Ltd. ( Product name, Epicron 4032D, molecular weight: about 280, melting point: about 75 ° C.]. Further, as the curing agent, (3) microcapsule type imidazole type curing agent (manufactured by Asahi Kasei Epoxy Co., Ltd., trade name Novacure HX3932HP, average particle size: 3 μm), and (4) powdery urea type curing agent [ADEKA Manufactured by Co., Ltd., trade name EH-4370S, average particle size: 5 μm], and (1) to (4) are weight ratios of (1) 60 / (2) 40 / (3) 40 / (4 ) 20 proportions. Then, these epoxy resin and curing agent were dissolved and dispersed in 2-ethoxyethyl acetate, and then kneaded with three rolls to prepare a solution having a solid content of 50% by weight. To this solution, the Ni powder was added so that the metal filling ratio represented by the ratio of the total solid content (Ni powder + resin) was 0.2% by volume, and then stirred using a centrifugal mixer. As a result, Ni powder was uniformly dispersed to produce a composite material for an adhesive. Next, after applying this composite material on a PET film subjected to a release treatment using a doctor knife, it is dried and solidified at 60 ° C. for 30 minutes in a magnetic field having a magnetic flux density of 100 mT, whereby linear particles in the film are obtained. An electrode connecting adhesive having anisotropic conductivity in the form of a film having a thickness of 30 μm was prepared.

(Connection reliability evaluation)
First, a flexible printed wiring board (having a base material made of polyimide resin) in which 32 copper electrodes plated with gold of 80 μm width, 3 m length and 18 μm height are arranged at intervals of 120 μm, width 80 μm, length A wiring board (glass cloth epoxy board) in which 32 copper electrodes having a gold plating of 3 mm in height and 18 μm in height were arranged at intervals of 120 μm was prepared. Then, the adhesive prepared between the flexible printed wiring board and the wiring board is sandwiched, and the press head heated to an appropriate temperature (150 ° C.) is flexible so that the adhesive has a predetermined temperature (140 ° C.). Installed above the printed wiring board, moved the press head in the direction of the wiring board, and heated and bonded the electrode connecting adhesive to a predetermined temperature (140 ° C) at a pressure of 4 MPa for 10 seconds for bonding The flexible printed wiring board and the wiring board bonded to each other were obtained through the electrode connecting adhesive. Next, in this joined body, the resistance value of 32 electrodes connected via a copper electrode and an adhesive is obtained by a four-terminal method, and the obtained value is divided by 32 to obtain the resistance per electrode. Connection resistance (hereinafter referred to as “initial connection resistance”) was obtained. And this evaluation was repeated 10 times and the average value of initial connection resistance was calculated | required. The results are shown in Table 1.

(Heat resistance evaluation)
Further, as a heat resistance test, the flexible printed wiring board and wiring board assembly mounted at the above temperature (140 ° C.) was left in a constant temperature and humidity chamber set at a temperature of 80 ° C. for 500 hours, The joined body was taken out from the constant temperature and humidity chamber, and the average value of the connection resistance (hereinafter referred to as “connection resistance after 500 hours”) was obtained again in the same manner as described above. The results are shown in Table 1.

(Storage stability evaluation)
Moreover, after leaving the produced adhesive agent for one month at the temperature of 25 degreeC, it carried out similarly to the above, and obtained the conjugate | zygote of the flexible printed wiring board and the wiring board. Then, the above results of performing connection reliability evaluation and heat resistance evaluation under the same conditions as described above are shown in Table 1.

(Reaction rate evaluation)
As a reaction rate evaluation, in the joined body of the flexible printed wiring board and the wiring board mounted at the above temperature (140 ° C.), a resin cured product existing between the electrodes was collected and analyzed by Fourier transform infrared spectroscopy. The residual rate of the epoxy group in the reaction was measured, and the curing reaction rate was determined from the result. The results are shown in Table 1.

(Measurement of glass transition temperature)
Ten sheets of the prepared adhesives were stacked and heated and pressed at 140 ° C. for 5 minutes to prepare a cured film having a thickness of 200 μm. Next, using a dynamic viscoelasticity measuring apparatus (SII Nanotechnology, EXSTAR6000 DMS), a dynamic viscoelasticity measurement method (DMA method) under the conditions of a temperature rising rate of 10 ° C./min, a frequency of 1 Hz, and a weight of 5 g. ), The glass transition temperature of the cured product of the resin constituting the produced adhesive was measured. More specifically, tan δ corresponding to the ratio between the storage elastic modulus and the loss elastic modulus was measured, and the maximum value was taken as the glass transition temperature. In addition, the sample of width 2mm and length 10mm was used as a sample of hardened | cured material.

(Comparative Example 1)
In producing the adhesive, instead of the microcapsule type imidazole curing agent used in Example 1, dicyandiamide (trade name EH-3636AS, manufactured by Adeka Co., Ltd., average particle diameter: 18 μm), which is an amide curing agent, was used. An adhesive was prepared in the same manner as in Example 1 except that was used, and a joined body of a flexible printed wiring board and a wiring board was obtained. Thereafter, under the same conditions as in Example 1 above, connection reliability evaluation, heat resistance evaluation, storage stability evaluation, reaction rate evaluation, and glass transition temperature measurement were performed. The above results are shown in Table 1.

(Comparative Example 2)
In producing the adhesive, in place of the crystalline epoxy resin used in Example 1, a non-crystalline epoxy resin bisphenol A type epoxy resin [manufactured by Dainippon Ink & Chemicals, Inc., trade name Epicron 850] was used. Except having used, it carried out similarly to the above-mentioned Example 1, and produced the adhesive agent, and obtained the conjugate | zygote of the flexible printed wiring board and the wiring board. Thereafter, under the same conditions as in Example 1 above, connection reliability evaluation, heat resistance evaluation, storage stability evaluation, reaction rate evaluation, and glass transition temperature measurement were performed. The above results are shown in Table 1.

(Comparative Example 3)
In producing the adhesive, in place of the phenoxy resin used in Example 1, bisphenol A / F type phenoxy resin [manufactured by JER, trade name: JER4275, molecular weight: about 60000, glass transition temperature: 68 ° C.] An adhesive was prepared in the same manner as in Example 1 except that was used, and a joined body of a flexible printed wiring board and a wiring board was obtained. Thereafter, under the same conditions as in Example 1 above, connection reliability evaluation, heat resistance evaluation, storage stability evaluation, reaction rate evaluation, and glass transition temperature measurement were performed. The above results are shown in Table 1.

表１に示すように、実施例１においては、初期接触抵抗、および５００時間後の接続抵抗が殆ど変化しておらず、電極間の接続信頼性が高いことが判る。これは、実施例１の電極接続用接着剤においては、エポキシ樹脂として、分子量が１００００以上であるとともに、ガラス転移温度が８０℃以上であるフェノキシ樹脂を使用したため、フレキシブルプリント配線板の基材や配線基板１に対する密着力が向上したためであると考えられる。また、実施例１においては、初期接触抵抗に対して５００時間後の接続抵抗が殆ど変化しておらず、耐熱性に優れていることが判る。これは、実施例１の電極接続用接着剤においては、エポキシ樹脂として、結晶性エポキシを使用するとともに、硬化剤として、マイクロカプセル型硬化剤を使用したためであると考えられる。また、実施例１においては、接着剤を２５℃の温度で１ヶ月間放置した後の初期接触抵抗、および５００時間後の接続抵抗が殆ど変化しておらず、保存安定性に優れていることが判る。これは、実施例１の電極接続用接着剤においては、硬化剤として、粉末状の尿素系硬化剤とマイクロカプセル型硬化剤を使用したためであると考えられる。また、実施例１においては、硬化反応率が高く、エポキシ樹脂とエポキシ樹脂硬化剤の反応速度が速くなり、電極接続用接着剤を低温（１５０℃以下）かつ短時間（例えば、１０秒間）で硬化させることができることが判る。これは、実施例１の電極接続用接着剤においては、結晶性エポキシ樹脂を含有する電極接続用接着剤において尿素系硬化剤を併用したためであると考えられる。なお、実施例１においては、接着剤を構成する樹脂の硬化物のガラス転移温度が比較例１，２に比し高くなっているが、これは、実施例１の電極接続用接着剤においては、エポキシ樹脂として、ガラス転移温度が８０℃以上であるフェノキシ樹脂を使用したためであると考えられる。

As shown in Table 1, in Example 1, the initial contact resistance and the connection resistance after 500 hours hardly change, and it can be seen that the connection reliability between the electrodes is high. This is because, in the adhesive for electrode connection of Example 1, a phenoxy resin having a molecular weight of 10,000 or more and a glass transition temperature of 80 ° C. or more was used as an epoxy resin. This is probably because the adhesion to the wiring board 1 has been improved. Moreover, in Example 1, it turns out that the connection resistance after 500 hours hardly changes with respect to initial stage contact resistance, and is excellent in heat resistance. This is presumably because, in the adhesive for electrode connection of Example 1, a crystalline epoxy was used as the epoxy resin and a microcapsule type curing agent was used as the curing agent. In Example 1, the initial contact resistance after leaving the adhesive at a temperature of 25 ° C. for 1 month and the connection resistance after 500 hours hardly change, and the storage stability is excellent. I understand. This is presumably because the electrode connecting adhesive of Example 1 used a powdery urea curing agent and a microcapsule curing agent as the curing agent. In Example 1, the curing reaction rate is high, the reaction rate between the epoxy resin and the epoxy resin curing agent is increased, and the electrode connecting adhesive is kept at a low temperature (150 ° C. or lower) and in a short time (for example, 10 seconds). It can be seen that it can be cured. This is considered to be because in the electrode connecting adhesive of Example 1, a urea curing agent was used in combination with the electrode connecting adhesive containing a crystalline epoxy resin. In Example 1, although the glass transition temperature of the cured product of the resin constituting the adhesive is higher than that in Comparative Examples 1 and 2, this is the case with the adhesive for electrode connection in Example 1. This is probably because a phenoxy resin having a glass transition temperature of 80 ° C. or higher was used as the epoxy resin.

  On the other hand, in Comparative Example 1, as shown in Table 1, the connection resistance after 500 hours was significantly increased as compared with the initial contact resistance, and the connection reliability between the electrodes could not be maintained. I understand that. As shown in Table 1, since the amide type curing agent is used in Comparative Example 1, the curing reaction rate is lower than in Example 1, and the reaction rate of the epoxy resin and the epoxy resin curing agent is low. This is considered to be because the reaction efficiency was greatly reduced when the epoxy resin and the curing agent were reacted. From the above, it can be seen that in Comparative Example 1, it is difficult to cure the electrode connecting adhesive at a low temperature (150 ° C. or less) and in a short time (for example, 10 seconds).

  In Comparative Example 2, as shown in Table 1, the initial contact resistance and the connection resistance after 500 hours were hardly changed, but compared with Example 1, the initial contact resistance and after 500 hours were changed. It can be seen that all of the connection resistances have large values. In particular, as compared with Example 1, the connection resistance after 500 hours is a large value, and it can be seen that the heat resistance is poor. This is considered to be due to the use of an amorphous epoxy resin in Comparative Example 2. In Comparative Example 2, as shown in Table 1, the initial contact resistance and the connection resistance after 500 hours were hardly changed, but compared with Example 1, the initial contact resistance and after 500 hours were changed. Each of the connection resistances is a large value, and it can be seen that the connection reliability between the electrodes is inferior to that of Example 1. This is because, in Comparative Example 2, since an amorphous epoxy resin is used, the curing reaction rate is lower than that of Example 1, and the reaction rate of the epoxy resin and the epoxy resin curing agent is low. This is considered to be because the reaction efficiency was lowered when the curing agent was reacted.

  As an application example of the present invention, an adhesive for electrode connection that is provided between a plurality of members to be joined and connects electrodes formed on each of the plurality of members to be joined by performing a heat and pressure treatment, and The electrode connection method using this is mentioned.

It is sectional drawing which shows the wiring board which mounted the flexible printed wiring board with the adhesive agent for electrode connection which concerns on this embodiment. As an electrode connecting adhesive according to an embodiment of the present invention, an anisotropic conductive adhesive containing conductive particles is used, and a flexible printed wiring board is mounted on a wiring board via the anisotropic conductive adhesive. It is sectional drawing which shows a state. It is a figure for demonstrating the electroconductive particle used in the adhesive agent for electrode connection which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Wiring board, 2 ... Adhesive for electrode connection, 3 ... Flexible printed wiring board, 4 ... Metal electrode (copper electrode plated with gold), 5 ... Metal electrode (copper electrode plated with gold), 6 ... Conductive particles.

Claims (6)

In an adhesive for electrode connection containing an epoxy resin as a main component, conductive particles, and a curing agent,
The epoxy resin contains a phenoxy resin having a molecular weight of 10,000 or more and a glass transition temperature of 80 ° C. or more, and a crystalline epoxy resin, and the curing agent is a powdery urea curing agent and a microcapsule type An adhesive for electrode connection comprising a curing agent.   The amount of the urea-based curing agent is 1% by mass or more and 20% by mass or less with respect to the whole electrode connecting adhesive, and the amount of the urea-based curing agent is 20% with respect to 100 parts by mass of the microcapsule-type curing agent. The adhesive for electrode connection according to claim 1, wherein the adhesive is in an amount of not less than 100 parts by mass.   The molecular weight of the said phenoxy resin is 30000 or more, The adhesive agent for electrode connections of Claim 1 or Claim 2 characterized by the above-mentioned.   4. The electrode connecting adhesive according to claim 1, wherein an average particle size of the urea-based curing agent present in the adhesive is 3 μm or more and 15 μm or less. 5.   The conductive particles are one metal selected from the group consisting of a single metal having magnetism, two or more kinds of alloys having magnetism, an alloy of a metal having magnetism and another metal, and a composite containing a metal having magnetism. The adhesive for electrode connection according to any one of claims 1 to 4, which is a composite.   The conductive particles are conductive particles having a diameter to length ratio (aspect ratio) of 5 or more, and the shape of the electrode connecting adhesive is a film, and the conductive particles are in the thickness direction of the film. 6. The electrode connecting adhesive according to claim 5, wherein the adhesive is oriented.

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