JP2009111070A - Connection method of wiring boards - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a connection method of wiring boards capable of connecting the wiring boards at a low temperature and in a short time when they are connected together using an adhesive. <P>SOLUTION: A curing agent 20 liquid at room temperature is applied onto the surface 6a of a rigid base 6 of a rigid wiring board 1 and onto the surface 4a of a first electrode 4, and an electrically conductive adhesive which is an adhesive 2 whose main component being an epoxy resin which being a thermosetting resin is mounted on the curing agent 20. Next, the alignment of the first electrode 4 and a second electrode 5 is carried out so that the first electrode 4 and the second electrode 5 are connected together while an electrically conductive adhesive is interposed between the rigid wiring board 1 and a flexible wiring board 3. Then, by carrying out heating and pressurizing treatment, the epoxy resin being the main component of the conductive adhesive is heated and melted, and the epoxy resin and the curing agent 20 are made to react together to cure the thermosetting resin and electrically connect the first and the second electrodes 4 and 5 together. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for connecting wiring boards used as components of electronic equipment.

  In recent years, in the electronic equipment field, with the increase in the density of electronic equipment, for example, flexible wiring boards are widely used for applications such as wiring to movable parts of electronic equipment. In addition, along with downsizing and higher functionality of electronic devices, for example, flexible wiring boards and rigid wiring boards, or wiring board assemblies having various shapes formed by connecting a plurality of flexible wiring boards Is used.

  Further, as a method for connecting a plurality of wiring boards, for example, a method for connecting a plurality of flexible wiring boards using a conductive adhesive is known. More specifically, the first electrode provided on the first substrate of the first flexible wiring board and the second flexible by performing a heat and pressure treatment through the conductive adhesive. A method of connecting the first and second flexible wiring boards by electrically connecting the second electrodes provided on the second substrate of the wiring board is disclosed.

  In general, in this conductive adhesive, a curing agent for accelerating the curing of a thermosetting resin such as an epoxy resin which is the main component of the adhesive is used. As this curing agent, Microcapsule type or solid latent curing agents are used.

  Here, it is necessary to lower the curing temperature of the adhesive and shorten the curing time from the viewpoint of suppressing damage to the wiring board and the electronic device and improving the productivity. And in order to reduce the curing temperature and shorten the curing time, it is necessary to quickly cure the thermosetting resin that is the main component of the adhesive, so that the curing with high reactivity with the thermosetting resin is required. It is necessary to use an agent. However, in general, since the curing agent is dispersed in the thermosetting resin (that is, the thermosetting resin and the curing agent coexist), the curing reaction proceeds even during storage, and the long-term operation at a low temperature. There is a problem that the storage stability of the period (for example, storage stability for one month at room temperature) becomes insufficient.

  Therefore, an adhesive having a multilayer structure including an adhesive layer containing a thermosetting resin and an adhesive layer containing a curing agent has been proposed. More specifically, it is formed between the first adhesive layer containing the epoxy resin and the curing agent, the second adhesive layer containing the epoxy resin, and the first and second adhesive layers. And an adhesive having a multi-layer structure comprising a third adhesive layer that does not contain a latent curing agent. And by such a structure, since the 1st adhesive bond layer containing an epoxy resin and a hardening | curing agent and the 2nd adhesive bond layer containing an epoxy resin can be isolate | separated, when a highly reactive epoxy resin is used, Even if it exists, it is described that the adhesive excellent in storage stability can be provided (for example, refer patent document 1).

In addition, as an adhesive for connecting a plurality of wiring boards, a main component layer mainly composed of a thermosetting resin, a latent curing agent and a thermoplastic resin are mixed, and the curing is mainly composed of the latent curing agent. An anisotropic conductive adhesive in which an agent layer is laminated via a separating layer is disclosed. And by using such an anisotropic conductive adhesive, when performing the heating and pressurizing treatment, first, the isolation layer is melted, and then the main agent layer and the curing agent layer are in contact with each other to cause a curing reaction. Since it progresses, it is described that a fast-curing curing agent or resin can be used, and even when the heating temperature is set relatively low, it can be connected in a short time ( For example, see Patent Document 2).
Japanese Patent Laid-Open No. 10-273627 JP 2006-312743 A

  However, since the microcapsule type or solid latent curing agent contained in the conventional adhesive generally requires a high temperature and a long time for curing, it is suitable for an adhesive that needs to be cured at a low temperature in a short time. There was a problem that it was difficult to use. More specifically, for example, when using an adhesive containing a microcapsule-type latent curing agent, first, the curing agent encapsulated in the capsule in the microcapsule-type latent curing agent is eluted by heating, Next, since it is a mechanism for starting the reaction by contacting the eluted curing agent with an epoxy resin, a certain temperature (160 ° C. or higher) is required, and the adhesive needs to be cured at a low temperature (150 ° C. or lower). There was a problem that it was difficult to use. In addition, since the heat energy by heating is consumed as the heat of fusion of the curing agent encapsulated in the capsule, the heat energy by heating cannot be used effectively for the curing reaction, and in a short time (for example, 10 seconds or less). There was a problem that it was difficult to use for adhesives that required curing.

  Then, this invention is made | formed in view of the above-mentioned problem, and when connecting a wiring board using an adhesive agent, it aims at providing the connection method of the wiring board which can be connected in low temperature and a short time. And

  In order to achieve the above-mentioned object, the invention according to claim 1 is the first electrode formed on the surface of the first base member included in the first wiring board, and the second electrode included in the second wiring board. A wiring board connection method for electrically connecting a second electrode formed on the surface of a second base material, the first electrode including the first electrode, and a second electrode A step of applying a liquid curing agent at room temperature to at least one of the surfaces of the second base material including a step of placing a conductive adhesive mainly composed of a thermosetting resin on the curing agent; Alignment of the first electrode and the second electrode with a conductive adhesive interposed between the first and second wiring boards so that the first electrode and the second electrode are connected And heat and pressure treatment to heat and melt the thermosetting resin and to react the thermosetting resin and the curing agent. To cure the thermosetting resin, a step of connecting the first electrode and the second electrode electrically, characterized in that it comprises at least a.

  According to this configuration, unlike the conventional adhesive containing the microcapsule type latent curing agent, the curing agent contained in the capsule is eluted by heating, and the eluted curing agent is brought into contact with the thermosetting resin. It is not necessary to start the reaction. That is, since the heat energy consumed as the heat of fusion of the hardener contained in the capsule becomes unnecessary, it is necessary to heat to a high temperature (160 ° C. or higher) necessary for eluting the hardener contained in the capsule. Disappear. Therefore, the curing reaction can proceed at a low temperature (150 ° C. or lower). Further, it is not necessary to use the heat energy by heating as the heat of fusion of the curing agent contained in the capsule, and it becomes possible to use it effectively for the curing reaction. Accordingly, since it becomes possible to efficiently react the thermosetting resin and the curing agent, the conductive adhesive can be cured in a short time (for example, 10 seconds or less), and the conductive adhesive is cured. The reaction can be accelerated. As a result, when the first and second wiring boards are connected using the conductive adhesive, the connection can be made at a low temperature and in a short time.

  The invention described in claim 2 is the wiring board connection method according to claim 1, wherein the curing agent is an imidazole-based curing agent. According to this configuration, it is possible to react the thermosetting resin, which is the main component of the conductive adhesive, and the curing agent more efficiently by heat treatment, so that the curing reaction of the conductive adhesive can be performed more quickly. Become.

  A third aspect of the present invention is the wiring board connection method according to the first or second aspect, wherein the conductive adhesive contains another curing agent. According to this configuration, since the thermosetting resin that is the main component of the conductive adhesive can be reacted with both the applied curing agent and the other curing agent by heat treatment, The curing reaction can be performed more rapidly.

  The invention according to claim 4 is the wiring board connection method according to any one of claims 1 to 3, wherein the conductive particles are connected in a straight chain with a large number of fine metal particles. It is characterized by being a metal powder having a curved shape or a needle shape.

  According to this configuration, in the surface direction of the electrode connecting adhesive, while maintaining insulation between adjacent electrodes to prevent a short circuit, a number of first electrodes are provided in the thickness direction of the electrode connecting adhesive. It is possible to obtain a low resistance by electrically conducting the second electrodes at once and independently of each other.

  The invention according to claim 5 is the wiring board connection method according to any one of claims 1 to 4, wherein the conductive particles are a single metal having ferromagnetism, 2 having ferromagnetism. It is one of an alloy of at least one kind, an alloy of a metal having ferromagnetism with another metal, and a composite containing a metal having ferromagnetism. According to this configuration, the magnetic property of the metal itself enables the conductive particles to be oriented using a magnetic field.

  A sixth aspect of the present invention is the wiring board connection method according to any one of the first to fifth aspects, wherein the conductive adhesive has a film shape. According to this configuration, the handling of the conductive adhesive is facilitated, and, for example, when the first electrode and the second electrode are connected by performing a heat and pressure treatment via the conductive adhesive. Improved workability.

  The invention according to claim 7 is the wiring board connection method according to claim 6, wherein the major axis direction of the conductive particles is oriented in the thickness direction of the conductive adhesive having a film shape. And

  According to this configuration, it is possible to electrically connect a large number of first electrodes and second electrodes at a time and independently, while maintaining insulation between adjacent electrodes and preventing a short circuit. The effect of becoming further improved.

  According to the present invention, when the first and second wiring boards are connected using the conductive adhesive, the connection can be made at a low temperature and in a short time.

  Hereinafter, a preferred embodiment of the present invention will be described. FIG. 1 is a cross-sectional view for explaining a wiring board assembly in which the wiring board connecting method according to the present invention is used. In the present embodiment, as a plurality of members to be joined, a rigid wiring board having a first electrode formed on the surface of a rigid base material, and a second formed on the surface of a flexible base material. A wiring board assembly using a flexible wiring board having these electrodes will be described as an example.

  As shown in FIG. 1, a wiring board assembly 50 using the wiring board connecting method according to the present invention includes a rigid wiring board 1 as a first wiring board and a flexible wiring board as a second wiring board. 3 between the first electrode 4 formed on the rigid wiring board 1 and the second electrode 5 formed on the flexible wiring board 3 by performing a heat and pressure treatment through the adhesive 2 between It is an electrically connected configuration.

  As shown in FIG. 1, the rigid wiring board 1 includes a plurality of first electrodes 4 (in the present embodiment, on a surface 6 a of a rigid first substrate 6 formed of a glass substrate or the like. 2) provided. In addition, as shown in FIG. 1, the flexible wiring board 3 has a second electrode 5 constituting a conductor circuit layer on a surface 7 a of a flexible second substrate 7 formed of a flexible resin film. This is a so-called single-sided flexible wiring board provided in plural (two in this embodiment). In addition, it is good also as a structure which provides the 2nd electrode 5 on the 2nd base material 7 through an adhesive bond layer (not shown).

  As a resin film which comprises the 2nd base material 7, what consists of a resin material excellent in the softness | flexibility is used. As such a resin film, for example, any resin film that is versatile for flexible wiring boards, such as a polyester film, can be used. In addition, it is particularly preferable that the resin film has high heat resistance in addition to flexibility, and examples of the resin film include polyamide resin films, polyimide resin films such as polyimide and polyamideimide, and polyethylene. Naphthalate is preferably used.

  Moreover, as the 2nd electrode 5 of this invention, metal foil, such as copper foil, is laminated | stacked on the surface 7a of the 2nd base material 7, for example, the said metal foil is exposed, an etching, and plating by a conventional method. A copper electrode with a metal gold plating formed by processing is used. Moreover, as the 1st electrode 4, the copper electrode by which the above-mentioned metal gold plating was given, and the metal ITO electrode formed on the surface 6a of the 1st base material 6 are used, for example.

  In the present embodiment, the first and second electrodes 4 and 5 may be formed on the first and second substrates 6 and 7 by using a metal foil such as the above-described copper foil. However, the first and second electrodes 4 and 5 may be formed by printing a conductive paste. By using such a method, exposure and etching required when using the metal foil are not required, and the manufacturing cost of the rigid wiring board 1 and the flexible wiring board 3 is reduced. Examples of the method for printing the conductive paste include a screen printing method and an intaglio printing method. Alternatively, only one of the first and second electrodes 4 and 5 may be formed of a conductive paste.

  As the conductive paste, for example, a thermosetting conductive paste containing conductive powder, a binder resin, a curing agent, and a solvent as main components can be used. Here, for example, nickel, copper, silver, gold, or graphite can be used as the conductive powder. Moreover, a polyester resin, an epoxy resin, and a polyimide resin can be used for binder resin, for example. As the curing agent, for example, an isocyanate compound can be used when a polyester resin is used as a binder resin, and an amine compound or an imidazole compound can be used when an epoxy resin is used. Furthermore, as the solvent, for example, cellosolve, butyl acetate, cellosolve acetate, or butyl carbitol acetate can be used. Then, by applying the conductive paste to the surfaces of the first and second substrates 6 and 7 by the above-described screen printing method or the like, and applying the heat treatment to cure the binder resin, Two electrodes 4 and 5 are formed.

  In addition, as the adhesive 2 used in the present invention, an epoxy resin, which is an insulating thermosetting resin, which has been conventionally used for connecting the rigid wiring board 1 and the flexible wiring board 3, is mainly used. A conductive adhesive in which conductive particles are dispersed in a resin can be used. For example, an epoxy resin in which powder of conductive particles such as nickel, copper, silver, gold, or graphite is dispersed can be used. By using an epoxy resin as the thermosetting resin, it is possible to improve the film formability, heat resistance, and adhesive strength of the adhesive 2.

  The epoxy resin to be used is not particularly limited. For example, bisphenol A type, F type, S type, AD type, or a copolymer type epoxy resin of bisphenol A type and bisphenol F type, or naphthalene type epoxy is used. Resin, novolac type epoxy resin, biphenyl type epoxy resin, dicyclopentadiene type epoxy resin and the like can be used. A phenoxy resin that is a high molecular weight epoxy resin can also be used.

  The molecular weight of the epoxy resin can be selected as appropriate in consideration of the performance required for the adhesive 2. When a high molecular weight epoxy resin (that is, the above-mentioned phenoxy resin) is used, the film forming property is high, the dissolution viscosity of the resin at the connection temperature can be increased, and the connection effect without disturbing the orientation of the conductive particles described later There is. On the other hand, when a low molecular weight epoxy resin is used, the effect of increasing the crosslink density and improving the heat resistance is obtained. Moreover, the effect of reacting with the above-mentioned hardening | curing agent rapidly at the time of a heating, and improving adhesive performance is acquired. Therefore, it is preferable to use a combination of a high molecular weight epoxy resin having a molecular weight of 15000 or more and a low molecular weight epoxy resin having a molecular weight of 2000 or less in order to balance the performance. In addition, the compounding quantity of a high molecular weight epoxy resin and a low molecular weight epoxy resin can be selected suitably. In addition, the “average molecular weight” here refers to a polystyrene-reduced weight average molecular weight obtained from gel permeation chromatography (GPC) developed with THF.

  As the adhesive 2, an anisotropic conductive adhesive containing conductive particles can also be used. More specifically, as the anisotropic conductive adhesive, for example, the above-described epoxy resin is the main component, and in the resin, fine metal particles (for example, spherical metal fine particles or metal) shown in FIG. Conductive particles 10 made of metal powder having a large number of metal fine particles (plated spherical resin particles) having a linear shape, a needle shape, or a so-called high aspect ratio shape are dispersed. Can be used. The aspect ratio referred to here is the ratio of the short diameter (the length of the cross section of the conductive particles 10) R and the long diameter (the length of the conductive particles 10) L of the conductive particles 10 shown in FIG. Say.

  By using such conductive particles 10, as an anisotropic conductive adhesive, in the surface direction of the adhesive 2 (the direction perpendicular to the thickness direction X and the direction of the arrow Y in FIG. 1), In the thickness direction X, while maintaining insulation between adjacent electrodes and preventing a short circuit, a large number of first electrodes 4 -second electrodes 5 are connected at a time and independently to each other. It becomes possible to obtain resistance.

  The aspect ratio of the conductive particles 10 is preferably 5 or more. By using such conductive particles 10, when an anisotropic conductive adhesive is used as the adhesive 2, the contact probability between the conductive particles 10 is increased. Therefore, the first electrode 4 and the second electrode 5 can be electrically connected without increasing the blending amount of the conductive particles 10.

  In this anisotropic conductive adhesive, a magnetic field applied in the direction of the long diameter L of the conductive particles 10 in the thickness direction X of the anisotropic conductive adhesive at the time of forming the film-like anisotropic conductive adhesive. 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 first electrodes 4 to the second electrodes 5 are formed at once, and each is independent. Thus, the effect of being able to conduct conductive connection 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 by using a metal having ferromagnetism, the conductive particles 10 can be oriented 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 10 is directly measured by a method such as observation with a CCD microscope. In the case of the conductive particles 10 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. Further, the conductive particles 10 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 10 as the major axis.

  Next, a method for manufacturing the wiring board assembly 50 will be described. FIG. 4 is a cross-sectional view for explaining a manufacturing process of the wiring board assembly 50 in which the wiring board connection method according to the embodiment of the present invention is used. First, the rigid wiring board 1 which has the 1st electrode 4 formed on the surface 6a of the rigid base material 6 used as connection object, and the 2nd electrode formed on the surface 7a of the flexible base material 7 A flexible wiring board having 5 is prepared. The rigid wiring board 1 and the flexible wiring board 3 can be manufactured in the same manner as before. That is, for example, when using the above-described conductive paste, by printing the conductive paste on one side of the first substrate 6 formed of a rigid glass substrate by the above-described screen printing method, A rigid wiring board 1 having a plurality of first electrodes 4 is produced. Similarly, a flexible paste having a plurality of second electrodes 5 is obtained by printing a conductive paste on one side of the second substrate 7 formed of a flexible resin film by the above-described screen printing method. The wiring board 3 is produced.

  In addition, as a method of connecting the rigid wiring board 1 and the flexible wiring board 3 using the anisotropic conductive adhesive that is the adhesive 2, heating and pressurizing treatment is performed via the anisotropic conductive adhesive. By performing, a method of curing and connecting the thermosetting resin in the anisotropic conductive adhesive can be adopted.

  Here, in the present embodiment, when the rigid wiring board 1 and the flexible wiring board 3 are connected via the adhesive 2, the surface 6a of the rigid first substrate 6 including the first electrode 4 is connected. Further, it is characterized in that a liquid curing agent is applied to at least one of the surfaces 7a of the flexible second base material 7 including the second electrode 5 at room temperature.

  More specifically, when a liquid curing agent is applied at room temperature on the surface 6a of the rigid first substrate 6 including the first electrode 4, as shown in FIG. The liquid curing agent 20 is applied at room temperature onto the surface 6a of the first base 6 and the surface 4a of the first electrode 4 of the rigid wiring board 1 manufactured by the above method. In addition, "room temperature" here means the temperature (5-40 degreeC) which can change indoors normally, and "liquid at room temperature" means that it is liquid at the temperature of 5-40 degreeC. Say.

  Next, as shown in FIG. 4 (b), the conductive adhesive, which is the adhesive 2 containing the above-mentioned conductive particles 10 as a main component, and the epoxy resin which is an insulating thermosetting resin, is used as the curing agent. 20 is placed. Next, in a state where the conductive adhesive is heated to a predetermined temperature, the conductive adhesive is pressurized with a predetermined pressure toward the rigid wiring board 1 to temporarily bond the conductive adhesive onto the rigid wiring board 1. In this case, a conductive adhesive having a film shape can be suitably used as the conductive adhesive. In addition, although a paste-like conductive adhesive can be used, in the case of a paste-like, the above-described temporary adhesion by applying pressure and temperature is not necessary.

  Next, as shown in FIG. 4B, the rigid wiring board 1 and the flexible wiring board are connected so that the flexible wiring board 3 faces downward and the first electrode 4 and the second electrode 5 are connected. 3, the first electrode 4 of the rigid wiring board 1 and the second electrode 5 of the flexible wiring board 3 are aligned with a conductive adhesive interposed therebetween.

  Next, as shown in FIG. 4C, the flexible wiring board 3 is placed on the conductive adhesive, and the conductive adhesive is interposed between the first and second electrodes 4 and 5. And in the state which heated the conductive adhesive to predetermined temperature (150 degrees C or less), the said conductive adhesive is made into the direction of the rigid wiring board 1 (namely, FIG.4 (c)) via the flexible wiring board 3. FIG. The conductive adhesive is heated and melted by pressurizing at a predetermined pressure in the direction indicated by arrow A).

  Then, the epoxy resin that is the main component of the conductive adhesive is heated and melted, and the epoxy resin and the curing agent come into contact with each other, and the curing reaction proceeds. In this embodiment, as described above, the rigid wiring is used. Since the liquid curing agent 20 is applied at room temperature on the surface 6a of the first substrate 6 and the surface 4a of the first electrode 4 of the plate 1, the conventional microcapsule-type latent curing agent is used. Unlike the adhesive containing, it is not necessary to elute the curing agent included in the capsule in the microcapsule type latent curing agent by heating and to bring the eluted curing agent into contact with the epoxy resin to initiate the reaction. That is, since the heat energy consumed as the heat of fusion of the hardener contained in the capsule becomes unnecessary, it is not necessary to heat to a certain high temperature (160 ° C. or higher). Accordingly, the curing reaction can proceed at a low temperature. Further, it is not necessary to use the heat energy by heating as the heat of fusion of the curing agent contained in the capsule, and it becomes possible to use it effectively for the curing reaction. Accordingly, since the epoxy resin and the curing agent 20 can be reacted efficiently, the adhesive 2 can be cured in a short time (for example, 10 seconds or less), and the curing reaction of the adhesive is accelerated. can do.

  And when the preset curing time of the conductive adhesive elapses, by releasing the maintenance state of the curing temperature of the conductive adhesive and the pressurization state, and starting cooling, via the conductive adhesive, The first electrode 4 and the second electrode 5 are connected, and the flexible wiring board 3 is mounted on the rigid wiring board 1. With the above-described wiring board connection method, the wiring board assembly 50 including the rigid wiring board 1 and the flexible wiring board 3 shown in FIG. 1 can be manufactured.

  The curing agent 20 used in the present invention is not particularly limited as long as it is liquid at room temperature, but is excellent in storage stability at a low temperature and hardly causes a curing reaction at the above room temperature. It is preferable to use a material that rapidly undergoes a curing reaction with light or the like. Examples of the curing agent include imidazole series, hydrazide series, amine imide, polyamine series, tertiary amine, and modified products thereof, and these can be used alone or as a mixture of two or more.

  Among these curing agents, an imidazole-based curing agent is preferably used from the viewpoint that it is excellent in storage stability at low temperatures and excellent in fast curing properties. As the imidazole curing agent, a known imidazole curing agent can be used. More specifically, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1 -Cyanoethyl-2-ethyl-4-methylimidazole is exemplified.

According to the present embodiment described above, the following effects can be obtained.
(1) In the present embodiment, a liquid curing agent 20 is applied at room temperature onto the surface 6 a of the rigid base 6 of the rigid wiring board 1 and the surface 4 a of the first electrode 4, and the curing agent 20 In addition, a conductive adhesive that is an adhesive 2 mainly composed of an epoxy resin that is a thermosetting resin is placed, and then the first electrode 4 and the second electrode 5 are connected, The first electrode 4 and the second electrode 5 are aligned in a state where a conductive adhesive is interposed between the first and second wiring boards 1 and 3. Then, by performing heat and pressure treatment, the epoxy resin that is the main component of the conductive adhesive is heated and melted, the epoxy resin and the curing agent 20 are reacted, the thermosetting resin is cured, and the first resin is cured. The electrode and the second electrodes 4 and 5 are electrically connected. Therefore, unlike the conventional adhesive containing the microcapsule-type latent curing agent, the heat energy consumed as the heat of fusion of the curing agent encapsulated in the capsule becomes unnecessary, and the curing agent encapsulated in the capsule It is not necessary to heat to a high temperature (160 ° C. or higher) necessary to elute Therefore, the curing reaction can proceed at a low temperature (150 ° C. or lower). Moreover, it becomes possible to use the thermal energy by heating effectively for the curing reaction. Accordingly, since the epoxy resin and the curing agent 20 can be reacted efficiently, the adhesive 2 can be cured in a short time (for example, 10 seconds or less), and the curing reaction of the conductive adhesive can be performed. The speed can be increased. As a result, when the rigid wiring board 1 and the flexible wiring board 3 are connected using the conductive adhesive, the connection can be made at a low temperature and in a short time.

  (2) In the present embodiment, as the curing agent 20, an imidazole-based curing agent that is excellent in rapid curing is used. Accordingly, the heat treatment allows the thermosetting resin, which is the main component of the conductive adhesive, to react with the curing agent 20 more efficiently, so that the curing reaction of the conductive adhesive can be performed more rapidly.

  (3) In the present embodiment, as the conductive particles 10, a metal powder having a shape in which a large number of fine metal particles are connected in a straight chain or a needle shape is used. Therefore, in the surface direction Y of the conductive adhesive, insulation between adjacent electrodes is maintained to prevent a short circuit, and in the thickness direction X, a large number of first electrodes 4 to the second electrodes 5 are connected. It is possible to connect each of them independently and obtain a low resistance.

  (4) In the present embodiment, the conductive particles 10 are made of a single metal having ferromagnetism, two or more kinds of alloys having ferromagnetism, an alloy of a metal having ferromagnetism with another metal, and ferromagnetism. It is configured to be formed of any of the composites containing metal. Therefore, the magnetic property of the metal itself makes it possible to orient the conductive particles 10 using a magnetic field.

  (5) In this embodiment, the conductive adhesive has a film shape. Therefore, handling of the conductive adhesive is facilitated, and work for connecting the first electrode 4 and the second electrode 5 by performing, for example, heat and pressure treatment via the conductive adhesive is performed. Improves.

  (6) In this embodiment, it is set as the structure which orientates the direction of the long diameter L of the electroconductive particle 10 in the thickness direction X of the electroconductive adhesive which has a film shape. Accordingly, it is possible to electrically connect the plurality of first electrodes 4 to the second electrodes 5 at a time and independently, while maintaining insulation between adjacent electrodes and preventing a short circuit. This effect is further improved.

In addition, you may change the said embodiment as follows.
In the above embodiment, the liquid curing agent 20 is applied at room temperature onto the surface 6 a of the rigid first base 6 of the rigid wiring board 1 and the surface 4 a of the first electrode 4. However, as shown in FIG. 5, the curing agent 20 may be applied to the surface 7 a of the flexible second base material 7 of the flexible wiring board 3 and the surface 5 a of the second electrode 5. In addition, a curing agent is applied on the surface 6 a of the first substrate 6, the surface 4 a of the first electrode 4, the surface 7 a of the second substrate 7, and the surface 5 a of the second electrode 5. It is good also as a structure. Even in such a configuration, the same effect as in the case of the first embodiment described above can be obtained.

  -Moreover, it is good also as a structure which makes the electrically conductive adhesive used as the adhesive agent 2 contain another hardening | curing agent. With such a configuration, the thermosetting resin that is the main component of the conductive adhesive can be reacted with both the applied curing agent 20 and the other curing agent by heat treatment. It becomes possible to carry out the curing reaction more rapidly. In addition, it does not specifically limit as another hardening | curing agent, Like the above-mentioned hardening | curing agent 20, a liquid thing can be used at room temperature, However A solid thing can also be used at room temperature. In addition, it is preferable to use a material that is excellent in storage stability at a low temperature and hardly undergoes a curing reaction at room temperature, but that rapidly undergoes a curing reaction by heat or light. For example, imidazoles, hydrazides, boron trifluoride-amine complexes, amine imides, polyamines, tertiary amines, alkyl ureas, and other amines, dicyandiamides, acid anhydrides, phenols, and their modifications The thing is illustrated and these can be used individually or in mixture of 2 or more types.

  Among these curing agents, an imidazole-based curing agent is preferably used from the viewpoint that it is excellent in storage stability at low temperatures and excellent in fast curing properties. As the imidazole curing agent, a known imidazole 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 the above embodiment, the wiring board assembly 50 using the rigid wiring board 1 and the flexible wiring board 3 has been described as an example, but instead of the rigid wiring board 1 used in the above embodiment, other wiring board 1 is used. It is good also as a structure which uses a flexible wiring board and uses a some flexible wiring board as a to-be-joined member. Similarly, another rigid wiring board may be used instead of the flexible wiring board 3 used in the above-described embodiment, and a plurality of rigid wiring boards may be used as members to be joined.

  In the above embodiment, the first and second electrodes 4 and 5 are formed of metal foil such as copper foil or conductive paste. However, the first and second electrodes 4 and 5 are Alternatively, it may be formed by an inkjet method. Here, the ink-jet method uses a material obtained by dissolving or dispersing the materials of the first and second electrodes 4 and 5 in a liquid, which is a fluid, as a projectile to produce a predetermined amount of the projectile. A method of forming the first and second electrodes 4 and 5 by injecting them to a predetermined position.

  As an application example of the present invention, there is a method of connecting a wiring board used as a component of an electronic device.

It is sectional drawing for demonstrating the wiring board conjugate | zygote in which the connection method of the wiring board which concerns on this invention was used. It is sectional drawing for demonstrating the wiring board assembly which used the anisotropic conductive adhesive as an adhesive agent, and the wiring board was connected by the connection method of the wiring board which concerns on this invention. It is the schematic for demonstrating the electroconductive fine particles which the anisotropic conductive adhesive used in the connection method of the wiring board which concerns on embodiment of this invention contains. (A)-(c) is sectional drawing for demonstrating the manufacturing process of the wiring board assembly by which the connection method of the wiring board which concerns on this invention was used. It is a figure for demonstrating the modification of the connection method of the wiring board which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Rigid wiring board (1st wiring board), 2 ... Adhesive (conductive adhesive), 3 ... Flexible wiring board (2nd wiring board), 4 ... 1st electrode, 4a ... 1st electrode 5 ... second electrode, 5a ... second electrode surface, 6 ... first substrate, 6a ... first substrate surface, 7 ... second substrate, 7a ... second Surface of base material, 10 ... conductive particles, 20 ... curing agent, 50 ... wiring board assembly, L ... long diameter of conductive particles, R ... short diameter of conductive particles

Claims (7)

A first electrode formed on the surface of the first base material included in the first wiring board, and a second electrode formed on the surface of the second base material included in the second wiring board. A wiring board connection method for electrical connection,
Applying a liquid curing agent at room temperature to at least one of the surface of the first base material including the first electrode and the surface of the second base material including the second electrode;
A step of placing a conductive adhesive in which the thermosetting resin is a main component and the conductive particles are dispersed in the thermosetting resin;
The first electrode and the second electrode with the conductive adhesive interposed between the first and second wiring boards so that the first electrode and the second electrode are connected to each other. The step of aligning the electrodes of
By performing heat and pressure treatment, the thermosetting resin is heated and melted, and the thermosetting resin and the curing agent are reacted to cure the thermosetting resin, and the first electrode and the And a step of electrically connecting the second electrode to the second electrode.   The wiring board connection method according to claim 1, wherein the curing agent is an imidazole-based curing agent.   The wiring board connection method according to claim 1, wherein the conductive adhesive contains another curing agent.   4. The metal powder according to claim 1, wherein the conductive particles are a metal powder having a shape in which a large number of fine metal particles are connected in a straight chain, or a needle shape. 5. Wiring board connection method.   The conductive particles are any of a single metal having ferromagnetism, two or more alloys having ferromagnetism, an alloy of a metal having ferromagnetism and another metal, and a composite containing a metal having ferromagnetism. The wiring board connection method according to claim 1, wherein the wiring board connection method is provided.   The wiring board connection method according to claim 1, wherein the conductive adhesive has a film shape.   The wiring board connection method according to claim 6, wherein a major axis direction of the conductive particles is oriented in a thickness direction of the conductive adhesive having the film shape.

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