TWI521027B - Anisotropic conductive paste and the connection method using the electronic parts thereof - Google Patents

Description

Anisotropic conductive paste and connection method of electronic parts using the same

The present invention relates to an anisotropic conductive paste in which an electronic component is connected to a wiring substrate, and a method of connecting the electronic component using the same.

In recent years, when an electronic component is connected to a wiring board, a connection method using an anisotropic conductive material (an anisotropic conductive film or an anisotropic conductive paste) is used. For example, when an electronic component is connected to a wiring board, an anisotropic conductive material is disposed between the electronic component in which the electrode is formed and the wiring substrate on which the electrode is formed, and the electronic component and the wiring substrate are thermocompression bonded and secured. Electrical connection.

As the anisotropic conductive material, for example, a material in which a conductive filler such as a resin ball or a resin ball having a conductive film formed on a surface thereof is dispersed in a binder resin to be a substrate is disclosed (for example, Document 1: Japanese Patent) Japanese Patent Publication No. 2003-165825). When the electronic component and the wiring board are thermocompression-bonded, the conductive filler is present in a certain probability between the electronic component to be connected and the electrode of the wiring substrate. Therefore, the conductive filler is placed in a planar shape. In this manner, the electronic component to be connected and the electrodes of the wiring substrate are in contact with each other via the conductive filler, thereby ensuring electrical conductivity between the electrodes. On the other hand, in the gap between the electrodes of the electronic component or the gap between the electrodes of the wiring board, the conductive filler is embedded in the adhesive resin, and the insulation in the intersecting direction is ensured.

However, in the mounting method as described above, the mounting state of the electronic component after the thermocompression is caused by a positional deviation caused by, for example, poor conduction or pressurization. When an abnormality such as a shift occurs, the electronic component or the anisotropic conductive film is mechanically peeled off, and the residue remaining on the wiring board is wiped and cleaned with a solvent or the like, and then the wiring board is used. Here, the anisotropic conductive material after thermocompression bonding requires not only sufficient mechanical strength but also sufficient repairability due to hardening of the thermosetting resin (it is possible to peel off the anisotropic conductive material from the wiring substrate without residue or less residue) The nature of the connection between the wiring substrate and the electronic component can be achieved by using the anisotropic conductive material again.

However, the anisotropic conductive material described in the above-mentioned Document 1 is troublesome in that the residue of the resin or the conductive filler on the wiring board is sufficiently removed, and on the other hand, a certain residue remains on the wiring substrate. In the case of the degree of residue, when the connection to the electronic component is again performed using the anisotropic conductive material, there is a problem that the conductivity cannot be ensured. As described above, the anisotropic conductive material described in the above Document 1 has a certain degree of repairability, but is not a sufficient level. In the case of using the anisotropic conductive material described in the above document 1, in order to secure the connection reliability of the connection portion, it is necessary to perform gold plating treatment on the electrode of the electronic component and the wiring substrate to be connected, which is equivalent to reliable connection. There is a problem with sex.

Here, an object of the present invention is to provide an anisotropic conductive paste which has sufficient repairability and has high connection reliability, and a connection method of an electronic component using the same.

The anisotropic conductive paste of the present invention is characterized in that the electronic component and the wiring board are connected, and the anisotropic conductive paste contains 10% by mass or more and 50% by mass of the lead-free solder powder having a melting point of 240 ° C or lower. Below, and The thermosetting resin composition containing a thermosetting resin and an organic acid is 50% by mass or more and 90% by mass or less, and the acid value of the thermosetting resin composition is 15 mgKOH/g or more and 55 mgKOH/g or less.

In the anisotropic electrically conductive paste of the present invention, it is preferred that the thermosetting resin is an epoxy resin, and the organic acid has a dibasic acid having an alkyl group.

In the anisotropic conductive paste of the present invention, it is preferable that the thermosetting resin composition further contains a thixotropic agent, and the content of the inorganic thixotropic agent in the thixotropic agent is preferably 0.5% by mass or more and 22% by mass or less. .

In the anisotropic conductive paste of the present invention, it is preferable that the lead-free solder powder has an average particle diameter of 1 μm or more and 34 μm or less.

In the anisotropic conductive paste of the present invention, it is preferable that the lead-free solder powder contains at least one metal selected from the group consisting of tin, copper, silver, lanthanum, cerium, indium, and zinc.

In the anisotropic conductive paste of the present invention, it is preferable that at least one of the electrode of the electronic component or the electrode of the wiring substrate is not subjected to gold plating.

The method of connecting an electronic component according to the present invention is characterized in that the anisotropic conductive paste is used, and includes a coating step of applying the anisotropic conductive paste on the wiring substrate; and heat In the pressure bonding step, the electronic component is placed on the anisotropic conductive paste, and the electronic component is thermocompression bonded to the wiring substrate at a temperature higher than a melting point of the lead-free solder powder by 5° C. or more.

In the method of connecting an electronic component according to the present invention, it is preferable to further include: a peeling step of increasing the melting point of the lead-free solder powder by more than 5 ° C a temperature at which the electronic component is peeled off from the wiring substrate, and a coating step of applying the anisotropic conductive paste to the wiring substrate after the peeling step; and a reheat bonding step of recoating The electronic component is placed on the anisotropic conductive paste after the step of coating, and the electronic component is thermocompression bonded to the wiring substrate at a temperature higher than a melting point of the lead-free solder powder by 5 ° C or higher.

In the present invention, the anisotropic conductive paste refers to a paste which can form an anisotropic conductive material which is applied to a portion of a heat of a specific value or more and a pressure of a specific value or more. It has electrical conductivity in the thermocompression bonding direction (thickness direction), but has insulating properties in the cross direction in other portions.

Further, the reason why the anisotropic conductive paste of the present invention has sufficient repairability and mechanical strength and has high connection reliability is not necessarily clear, but the inventors of the present invention presume the following.

That is, the anisotropic conductive paste of the present invention contains a lead-free solder powder unlike the prior anisotropic conductive material. Further, when the anisotropic conductive paste is thermocompression bonded at a temperature equal to or higher than the melting point of the lead-free solder powder, the lead-free solder powders are melted and brought close to each other, and the lead-free solders around them are joined to each other and increased. On the other hand, by thermocompression bonding, the distance between the electrodes of the electronic component and the wiring substrate is also shortened, so that the electrodes can be solder-bonded to each other by the lead-free solder which is increased in the above manner. As described above, in the present invention, the electrode of the electronic component and the wiring board are solder-bonded to each other. Therefore, the inventors of the present invention presumed that the electrode of the anisotropic conductive material and the conductive filler are in contact with each other as in the prior art. When compared, it is extremely high Connection reliability.

On the other hand, it is not necessary to perform the solder as described above for the portion where the heat is not more than the specific value and the pressure of the specific value or more (the gap between the electrodes of the electronic component or the gap between the electrodes of the wiring substrate). Bonding is a state in which a lead-free solder powder is embedded in the thermosetting resin composition. Therefore, insulation can be ensured in a portion that is not thermocompression bonded to a heat of a specific value or more and a pressure of a specific value or more.

When the electronic component and the wiring board are connected by the anisotropic conductive paste of the present invention, it is presumed that the electrodes of the electronic component and the wiring substrate are solder-bonded to each other, and the solder joint portion is covered with the thermosetting resin composition. on. Further, after the thermocompression bonding, when heat of a temperature equal to or higher than the melting point of the lead-free solder powder is applied, the solder can be melted, and the thermosetting resin composition can be softened, so that the electronic component can be easily peeled off from the wiring substrate. Further, in the present invention, when the wiring board and the electronic component are connected by using the anisotropic conductive paste again after peeling, even if a certain amount of residue (solder or the like) remains on the electrode or the like, These residues are collectively solder bonded to ensure electrical conductivity. In the case where the anisotropic conductive material is used again to connect to the electronic component, the anisotropic conductive material is used again in a state in which a certain amount of residue (conductive filler or the like) remains on the wiring board. It is impossible to ensure conductivity. Therefore, it is necessary to sufficiently remove the residue such as the resin or the conductive filler on the wiring board, which is a problem that is troublesome in performing the work. As described above, the anisotropic conductive paste of the present invention is superior in repairability to the conventional anisotropic conductive material.

Furthermore, in the present invention, the solder joint is partially covered with the thermosetting resin. On the composition, the thermosetting resin composition is hardened by heat, so that the portion of the solder joint can be reinforced. Therefore, when the electronic component and the wiring board are connected by the anisotropic conductive paste of the present invention, sufficient mechanical strength can be secured.

According to the present invention, it is possible to provide an anisotropic conductive paste which has sufficient repairability and has high connection reliability, and a connection method of an electronic component using the same.

First, the anisotropic conductive paste of the present invention will be described.

The anisotropic conductive paste of the present invention is an anisotropic conductive paste in which an electronic component and a wiring board are connected. In addition, the anisotropic conductive paste contains 10% by mass or more and 50% by mass or less of the lead-free solder powder described below, and 50% by mass or more and 90% by mass or less of the thermosetting resin composition described below.

When the content of the lead-free solder powder is less than 10% by mass (when the content of the thermosetting resin composition exceeds 90% by mass), when the obtained anisotropic conductive paste is thermocompression bonded, In the case where the content of the lead-free solder powder exceeds 50% by mass, the thermal conductivity between the electronic component and the wiring substrate is insufficient, and sufficient solder bonding is not formed between the electronic component and the wiring substrate. When the content of the resin composition is less than 50% by mass, the insulating property in the obtained anisotropic conductive paste, particularly in the case of being placed in a humidified state, becomes insufficient. As a result, the anisotropy is no longer exhibited by solder bridging. Moreover, the lead-free solder powder is obtained from the viewpoint of obtaining a balance between the insulating property and the conductivity in the case of performing thermocompression bonding on the obtained anisotropic conductive paste. The content is preferably 20% by mass or more and 45% by mass or less, more preferably 30% by mass or more and 40% by mass or less.

The lead-free solder powder used in the present invention has a melting point of 240 ° C or lower. When the melting point of the lead-free solder powder is more than 240 ° C, the lead-free solder powder cannot be melted by the usual thermocompression bonding temperature in the anisotropic conductive paste. Further, from the viewpoint of lowering the thermocompression bonding temperature in the anisotropic conductive paste, the melting point of the lead-free solder powder is preferably 220 ° C or lower, more preferably 150 ° C or lower.

Here, the lead-free solder powder refers to a powder of a solder metal or alloy to which no lead is added. Among them, in the lead-free solder powder, lead which is an unavoidable impurity is allowed to exist, but in this case, the amount of lead is preferably 100 ppm by mass or less.

Preferably, the lead-free solder powder comprises a group selected from the group consisting of tin (Sn), copper (Cu), silver (Ag), bismuth (Bi), antimony (Sb), indium (In), and zinc (Zn). At least one metal.

Moreover, as a specific solder composition (mass ratio) in the above-mentioned lead-free solder powder, the following may be exemplified.

Examples of the binary alloy include Ag-Bi based on 95.3Ag/4.7Bi, Ag-Li based on 66Ag/34Li, Ag-In based on 3Ag/97In, and Ag-Te based on 67Ag/33Te, 97.2. Ag-T1 system such as Ag/2.8T1, Ag-Zn system such as 45.6Ag/54.4Zn, Au-Sn system such as 80Au/20Sn, Bi-In system such as 52.7Bi/47.3In, 35In/65Sn, 51In/49Sn, 52In In-Sn system such as /48Sn, Bi-Zn system such as 8.1Bi/91.9Zn, Sn-Bi system such as 43Sn/57Bi or 42Sn/58Bi, 98Sn/2Ag, 96.5Sn/3.5Ag, 96Sn/4Ag, 95Sn/5Ag, etc. Sn-Ag system, 91Sn/9Zn, Sn-Zn system such as 30Sn/70Zn, Sn-Cu system such as 99.3Sn/0.7Cu, and Sn-Sb system such as 95Sn/5Sb.

Examples of the ternary alloy include Sn-Ag-In based on 95.5Sn/3.5Ag/1In, Sn-Zn-In based on 86Sn/9Zn/5In, 81Sn/9Zn/10In, and 95.5Sn/0.5Ag. /4Cu, 96.5Sn/3.0Ag/0.5Cu, etc. Sn-Ag-Cu system, 90.5Sn/7.5Bi/2Ag, 41.0Sn/58Bi/1, 0Ag, etc. Sn-Bi-Ag system, 89.0Sn/8.0Zn/3.0 Bi and other Sn-Zn-Bi systems.

Examples of other alloys include Sn/Ag/Cu/Bi and the like.

Further, the average particle diameter of the lead-free solder powder is preferably 1 μm or more and 34 μm or less, and more preferably 3 μm or more and 20 μm or less. When the average particle diameter of the lead-free solder powder is less than the above lower limit, the electrical conductivity between the electronic component and the wiring substrate tends to decrease. On the other hand, when the average thickness exceeds the above upper limit, the insulating property in the anisotropic conductive paste is lowered. The tendency. Further, the average particle diameter can be measured by a dynamic light scattering type particle size measuring device.

The thermosetting resin composition used in the present invention contains a thermosetting resin and an organic acid. Further, the acid value of the thermosetting resin composition must be 15 mgKOH/g or more and 55 mgKOH/g or less. When the acid value is less than 15 mgKOH/g, when the obtained anisotropic conductive paste is thermocompression bonded, the solder cannot be sufficiently activated to conduct electrical conduction between the electronic component and the wiring substrate. On the other hand, if it exceeds 55 mgKOH/g, the insulating property in the obtained anisotropic conductive paste, especially in the case of being placed in a humidified state, becomes not high. full. Further, regarding the obtained anisotropic conductive paste, the thermosetting tree is obtained from the viewpoint of obtaining the balance between the insulating property and the conductivity in the case of thermocompression bonding. The acid value of the fat composition is preferably 20 mgKOH/g or more and 50 mgKOH/g or less, more preferably 30 mgKOH/g or more and 45 mgKOH/g or less.

As the thermosetting resin used in the present invention, a known thermosetting resin can be suitably used. However, from the viewpoint of having a flux action, it is particularly preferable to use an epoxy resin.

Further, in the present invention, the term "having a flux" means that the coating film covers the metal surface of the object to be welded to block the atmosphere as in the case of a usual rosin-based flux, and the metal oxide of the metal surface is reduced during welding. The coating film is pushed away by the molten solder to bring the molten solder into contact with the metal surface, and the residue has a function of insulating the circuits.

As such an epoxy resin, a well-known epoxy resin can be used suitably. Examples of such an epoxy resin include epoxy resins such as bisphenol A type, bisphenol F type, biphenyl type, naphthalene type, cresol novolac type, phenol novolac type, and dicyclopentadiene type. These epoxy resins may be used alone or in combination of two or more. Moreover, it is preferable that these epoxy resins are liquids at normal temperature, and when they are solid at normal temperature, they are preferably used in combination with liquid at normal temperature. Further, among these epoxy resin types, the dispersibility of the metal particles and the paste viscosity can be adjusted, and the viewpoint of the resistance to the drop impact of the cured product or the wet diffusion property of the solder can be improved. Preferred are liquid bisphenol A type, liquid bisphenol F type, liquid hydrogenated type bisphenol A type, naphthalene type, and dicyclopentadiene type. Further, from the viewpoint of storage stability of the obtained anisotropic conductive paste, it is preferred to use a liquid bisphenol A type and a liquid bisphenol F type in combination.

As the content of the above epoxy resin, relative to the thermosetting resin composition 100 The mass% is preferably 70% by mass or more and 92% by mass or less, more preferably 75% by mass or more and 85% by mass or less. When the content of the epoxy resin is less than the above lower limit, the sufficient strength is not obtained to fix the electronic component, so that the resistance to the drop impact tends to be lowered. On the other hand, if the upper limit is exceeded, the thermosetting resin is used. The content of the organic acid or hardener in the composition is reduced, and the rate at which the epoxy resin is hardened is liable to be delayed.

As the organic acid used in the present invention, a known organic acid can be suitably used. Among such organic acids, a dibasic acid having an alkylene group is preferably used from the viewpoint of excellent solubility in an epoxy resin and from the viewpoint that precipitation of crystals is less likely to occur during storage. As such a dibasic acid having an alkylene group, for example, adipic acid, 2,5-diethyladipate, glutaric acid, 2,4-diethylglutaric acid, 2, 2 may be mentioned. 2-diethylglutaric acid, 3-methylglutaric acid, 2-ethyl-3-propylglutaric acid, sebacic acid, succinic acid, malonic acid, diglycolic acid. Among these, adipic acid, glutaric acid, and succinic acid are preferred, and adipic acid is particularly preferred.

The content of the organic acid is preferably 1% by mass or more and 8% by mass or less, and more preferably 2% by mass or more and 7% by mass or less based on 100% by mass of the thermosetting resin composition. When the content of the organic acid is less than the lower limit, the rate of curing of the thermosetting resin such as an epoxy resin is delayed, and the curing tends to be poor. On the other hand, if the content exceeds the above upper limit, the anisotropic conductivity obtained is obtained. The tendency of the insulation in the paste to decrease.

Moreover, it is preferable that the thermosetting resin composition used in the present invention uses a thixotropic agent and a curing agent in addition to the above-mentioned thermosetting resin and the above organic acid.

As the thixotropic agent used in the present invention, a known thixotropic change can be suitably used. Agent. Examples of such a thixotropic agent include organic thixotropic agents (fatty guanamine, hydrogenated castor oil, olefin-based wax, and the like) and inorganic thixotropic agents (colloidal cerium oxide, chlorinated polyether, and the like). Among these, fatty amide, colloidal cerium oxide, and chlorinated polyether are preferred. Further, from the viewpoint that the obtained anisotropic conductive paste is less likely to bleed out, it is preferred to use an organic thixotropic agent and an inorganic thixotropic agent in combination. Specifically, a fatty guanamine and a colloidal cerium oxide are combined, and a fatty guanamine and a chlorinated polyether are combined.

The content of the above-mentioned thixotropic agent is preferably 0.5% by mass or more and 25% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and particularly preferably 1% by mass or more, based on 100% by mass of the thermosetting resin composition. Below mass%. When the content of the thixotropic agent is less than the above lower limit, thixotropy is not obtained, and the electrode is liable to fall on the electrode of the wiring board, and the adhesion of the electronic component when mounted on the electrode of the wiring substrate tends to decrease. On the other hand, when the above upper limit is exceeded, the thixotropy is too high and the injection needle is clogged, which tends to cause coating failure.

In the case where the organic thixotropic agent and the inorganic thixotropic agent are used in combination as the thixotropic agent to be used in the present invention, the content of the inorganic thixotropic agent is 100% by mass based on the thermosetting resin composition. It is preferably 0.5% by mass or more and 22% by mass or less, more preferably 1% by mass or more and 20% by mass or less.

As the curing agent used in the present invention, a known curing agent can be suitably used. For example, as the thermosetting resin, in the case of using an epoxy resin, the following may be used.

Examples of the latent curing agent include Novacure HX-3722, HX-3721, HX-3748, HX-3088, HX-3613, HX-3921HP, HX-3941HP (manufactured by Asahi Kasei Epoxy Co., Ltd., trade name).

Examples of the aliphatic polyamine-based curing agent include Fujicure FXR-1020, FXR-1030, FXR-1050, and FXR-1080 (trade name, manufactured by Fuji Chemical Industry Co., Ltd.).

Examples of the epoxy resin amine adduct-based curing agent include Amicure PN-23, PN-F, MY-24, VDH, UDH, PN-31, and PN-40 (manufactured by Ajinomoto Fine-Techno Co., Ltd.). Name), EH-3615S, EH-3293S, EH-3366S, EH-3842, EH-3670S, EH-3636AS, EH-4346S (manufactured by Asahi Kasei Kogyo Co., Ltd., trade name).

Examples of the imidazole-based hardening accelerator include 2P4MHZ, 2MZA, 2PZ, C11Z, C17Z, 2E4MZ, 2P4MZ, C11Z-CNS, and 2PZ-CNZ (the above are trade names).

From the viewpoint of the insulating property of the obtained anisotropic conductive paste, it is preferred to use a latent curing agent, an epoxy resin amine adduct-based curing agent, and an imidazole-based hardening accelerator in combination.

The content of the curing agent is preferably 5% by mass or more and 20% by mass or less, and more preferably 10% by mass or more and 18% by mass or less based on 100% by mass of the thermosetting resin composition. When the content of the curing agent is less than the above lower limit, the rate at which the thermosetting resin is cured tends to be delayed. On the other hand, when the content exceeds the above upper limit, the reactivity is accelerated, and the use time of the paste tends to be shortened.

The thermosetting resin composition used in the present invention may contain, in addition to the epoxy resin, the organic acid, the thixotropic agent, and the curing agent, as needed. It may also contain additives such as a surfactant, a coupling agent, an antifoaming agent, a powder surface treatment agent, a reaction inhibitor, and a precipitation inhibitor. The content of the additives is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 5% by mass or less based on 100% by mass of the thermosetting resin composition. When the content of the additive is less than the above lower limit, the effect of each additive tends to be less likely to occur. On the other hand, when the content exceeds the above upper limit, the bonding strength of the thermosetting resin composition tends to decrease.

Next, a method of connecting the electronic component of the present invention will be described.

The method of connecting an electronic component according to the present invention is characterized in that the above-described anisotropic conductive paste of the present invention is used, and includes a coating step of applying the anisotropic conductive paste on the wiring substrate. And a thermocompression bonding step of disposing the electronic component on the anisotropic conductive paste, and the electron is higher than a melting point of the lead-free solder powder by 5 ° C or higher (preferably 20 ° C or higher) The parts are thermocompression bonded to the wiring board described above.

Here, as the electronic component, a wiring board can be used in addition to a wafer, a package component, or the like. As the wiring board, any of a flexible flexible substrate and a flexible substrate that does not have flexibility can be used. Further, when a flexible substrate is used as the electronic component, the rigid substrates can be electrically connected to each other via the flexible substrate by being connected to each of the two wiring substrates (hard substrates). Further, the flexible substrates may be electrically connected to each other via the flexible substrate.

In the coating step, the anisotropic conductive paste is applied onto the wiring board.

As a coating apparatus used here, for example, a dispenser, The stencil printing machine and the jet dispensing metal mask printing machine.

Further, the thickness of the coating film is not particularly limited, but is preferably 50 μm or more and 500 μm or less, and more preferably 100 μm or more and 300 μm or less. When the thickness is less than the above lower limit, the adhesion force when the electronic component is mounted on the electrode of the wiring board tends to be lowered. On the other hand, if the thickness exceeds the above upper limit, the paste tends to overflow beyond the connection portion.

In the thermocompression bonding step, the electronic component is placed on the anisotropic conductive paste, and the electronic component is thermocompression bonded to the wiring substrate at a temperature higher than a melting point of the lead-free solder powder by 5 ° C or higher.

When the temperature at the time of thermocompression bonding does not satisfy the condition that the melting point of the lead-free solder powder is higher than 5 ° C, the lead-free solder cannot be sufficiently melted, and sufficient solder bonding cannot be formed between the electronic component and the wiring substrate. Therefore, the electrical conductivity between the electronic component and the wiring substrate becomes insufficient.

The pressure at the time of thermocompression bonding is not particularly limited, but is preferably 0.2 MPa or more and 2 MPa or less, and more preferably 0.5 MPa or more and 1.5 MPa or less. When the pressure is less than the lower limit, sufficient solder bonding cannot be formed between the electronic component and the wiring substrate, and the electrical conductivity between the electronic component and the wiring substrate tends to decrease. On the other hand, if the upper limit is exceeded, the pair may be The wiring substrate is subjected to pressure, and it is necessary to expand the ineffective space.

Further, in the present invention, as described above, the pressure at the time of thermocompression bonding can be set to a lower pressure range as compared with the case of using the prior method. Therefore, the cost of the apparatus used in the thermocompression bonding step can also be reduced.

The time during thermocompression bonding is not particularly limited, but is usually preferably 5 seconds or more and 60 seconds. Less than seconds, 7 seconds or more and 20 seconds or less.

Moreover, in the method of connecting electronic components of the present invention, it is preferable to further include a peeling step, a recoating step, and a reheat pressing step described below.

In the peeling step, the electronic component is peeled off from the wiring board at a temperature higher than a melting point of the lead-free solder powder by 5 ° C or higher.

Here, the method of peeling an electronic component from a wiring board is not specifically limited. As such a method, for example, a method of peeling an electronic component from a wiring substrate while heating a connecting portion using a welding torch or the like can be employed. Further, in such a case, a known peeling device used in the repair can also be used.

Moreover, after the electronic component is peeled off from the wiring substrate, the wiring substrate may be cleaned by a solvent or the like as necessary.

In the recoating step, the anisotropic conductive paste is applied onto the wiring substrate after the peeling step. Here, the thickness of the coating device or the coating film may be the same as or the same as the above coating step.

In the reheating bonding step, the electronic component is placed on the anisotropic conductive paste after the recoating step, and the electronic component and the wiring are formed at a temperature higher than a melting point of the lead-free solder powder by 5° C. or higher. The substrate is thermocompression bonded. Here, the temperature, pressure, and time at the time of thermocompression bonding may be the same as those of the above coating step.

According to the connection method of the electronic component of the present invention described above, since the electrodes of the electronic component and the wiring substrate are solder-bonded to each other, contact with the electrode and the conductive filler of the anisotropic conductive material as before can be achieved. In the case of connection, the connection reliability is extremely high. Moreover, after thermocompression bonding, if the temperature above the melting point of the lead-free solder powder is applied When it is heated, the solder can be melted, and the thermosetting resin composition can be softened, so that the electronic component can be easily peeled off from the wiring substrate. Further, in the present invention, when the wiring board and the electronic component are connected by using the anisotropic conductive paste again after peeling, even if a certain amount of residue (solder or the like) remains on the electrode or the like, it may be These residues are collectively solder bonded to ensure electrical conductivity. Therefore, the method of joining electronic parts of the present invention is superior in repairability as compared with the method of using the prior anisotropic conductive material.

[Examples]

Hereinafter, the present invention will be described in detail by way of examples and comparative examples, but the invention is not limited by the examples.

[Example 1]

Thermosetting resin A (bisphenol A type epoxy resin, DIC (Daily Ink Chemical Co., Ltd.), trade name "EPICLON 860") 82.9 mass%, thixotropic agent A (fatty decylamine, manufactured by Nippon Kasei Co., Ltd., product "thylenebis H") 2% by mass, organic acid A (adipate, manufactured by Kanto Electrochemical Co., Ltd.), 2.6% by mass, and hardener A (manufactured by Shikoku Chemical Co., Ltd., trade name "Curezol 2P4MHZ"), 11.5% by mass, interface 0.5% by mass of an active agent (manufactured by BYK-Chemie Japan Co., Ltd., trade name "BYK361N") and an antifoaming agent (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Floren AC-326F") 0.5% by mass in a container, using a stone mill The machine was mixed to obtain a thermosetting resin composition.

Thereafter, 62.5% by mass of the obtained thermosetting resin composition and 37.5 mass% of lead-free solder powder A (average particle diameter: 5 μm, melting point of solder: 139 ° C, composition of solder: 42 Sn/58 Bi) were put into a container. The mixture was mixed by a kneader for 2 hours to prepare an anisotropic conductive paste.

Then, the obtained anisotropic conductive paste (thickness: 0.2 mm) was applied onto a wiring board (electrode: gold plating treatment (Cu/Ni/Au) on the copper electrode). Further, an electronic component (electrode: gold plating treatment (Cu/Ni/Au) on the copper electrode) was placed on the anisotropic conductive paste after application, and a thermocompression bonding apparatus (manufactured by ADVANSEL Co., Ltd.) was used at a temperature of 200 The electronic component and the wiring substrate are thermocompression bonded under the conditions of °C, pressure of 1 MPa, and crimping time of 8 to 10 seconds.

[Embodiment 2]

In the same manner as in the first embodiment, the electronic component and the wiring substrate are used in the same manner as in the first embodiment, except that the electrode is subjected to a water-soluble pre-flux treatment (manufactured by Tamura Seisakusho Co., Ltd., trade name "WPF-8"). Perform thermocompression bonding.

[Example 3]

The electronic component and the wiring board were thermocompression bonded in the same manner as in the second embodiment except that the electrode was made of tin (Sn) as the electronic component.

[Example 4]

A thermosetting resin composition and an anisotropic conductive paste were obtained in the same manner as in Example 1 except that each of the materials was blended according to the composition shown in Table 1.

An electronic component and a wiring substrate were produced in the same manner as in Example 2 except that the anisotropic conductive paste obtained in the above manner was used instead of the anisotropic conductive paste used in Example 2. Hot crimping.

[Example 5]

A thermosetting resin composition and an anisotropic conductive paste were obtained in the same manner as in Example 1 except that each of the materials was blended according to the composition shown in Table 1.

Further, in Example 5, lead-free solder powder B (average particle diameter: 5 μm, melting point of solder: 217 ° C, composition of solder: 96.5 Sn / 3 Ag / 0.5 Cu) was used.

In addition, the anisotropic conductive paste obtained as described above was used instead of the anisotropic conductive paste used in Example 2, and the temperature at the time of thermocompression bonding was 240° C. In the same manner as in Example 2, the electronic component and the wiring substrate were thermocompression bonded.

[Comparative Examples 1 to 4]

A thermosetting resin composition and an anisotropic conductive paste were obtained in the same manner as in Example 1 except that each of the materials was blended according to the composition shown in Table 1.

The electronic component and the wiring substrate were heated in the same manner as in Example 2 except that the anisotropic conductive paste obtained in the above manner was used instead of the anisotropic conductive paste used in Example 2. Crimp.

[Comparative Example 5]

A thermosetting resin composition and an anisotropic conductive paste were obtained in the same manner as in Example 1 except that each of the materials was blended according to the composition shown in Table 1.

Further, in Comparative Example 5, a resin powder (Au/Ni plating resin powder, manufactured by Sekisui Chemical Co., Ltd., trade name "Micropearl Au-205") subjected to gold plating treatment was used.

The electronic component and the wiring substrate were heated in the same manner as in Example 1 except that the anisotropic conductive paste obtained in the above manner was used instead of the anisotropic conductive paste used in Example 1. Crimp.

[Comparative Example 6]

In the copper electrode, the electrode is subjected to a water-soluble pre-flux treatment (manufactured by Tamura Seisakusho Co., Ltd., trade name "WPF-8") as a wiring substrate. Otherwise, the electronic component and the wiring board were thermocompression bonded in the same manner as in Comparative Example 5.

[Comparative Example 7]

The electronic component and the wiring board were thermocompression bonded in the same manner as in Comparative Example 5 except that the electrode was made of tin (Sn) as the electronic component.

<Evaluation of connection method of anisotropic conductive paste and electronic parts>

Evaluation of the properties of the anisotropic conductive paste (the acid value of the resin composition, the insulation resistance value after pressure bonding), and the connection method of the electronic component (initial resistance value after crimping, repairability (with or without a substrate at the time of repair) The resistance value after destruction and repair)) was evaluated or measured in the following manner. The results obtained are shown in Tables 1 and 2. Further, in Comparative Examples 6 to 7, since the initial resistance value after the pressure bonding could not be conducted, the measurement could not be performed, and therefore the repairability was not evaluated.

(1) Acid value of resin composition

The resin composition was weighed and dissolved in a solvent. And the phenolphthalein solution is used as an indicator at 0.5 mol/L. KOH was titrated.

(2) Initial resistance value after crimping

A wiring substrate having a 0.2 mm pitch pad (line/space = 100 μm/100 μm) as a circuit pattern is prepared. Further, on the pads of the wiring board, the electronic components having the 0.2 mm pitch pads (line/space = 100 μm/100 μm) are thermocompression bonded by the methods described in the above embodiments and comparative examples. . Further, a digital multimeter (manufactured by Agilent, trade name "34401A") was used, and the resistance values between the terminals of the connected pads were measured. In addition, when the resistance value is too high (100 MΩ or more) and cannot be turned on, it is judged as "unable to turn on".

(3) Whether there is substrate damage during repair

The substrate having the initial resistance value measured in the above (2) was used for evaluation. The electronic component is peeled off from the substrate while the connection portion of the substrate to the electronic component is heated at the same temperature as the thermocompression bonding temperature, and then the surface is cleaned with ethyl acetate. Further, the state of the substrate after peeling was visually observed to check whether or not the substrate was broken.

(4) Resistance value after repair

The substrate was evaluated for the presence or absence of substrate damage in the above (3). The electronic components were again thermocompression bonded to the pads of the substrate by the methods described in the above Examples and Comparative Examples. Further, a digital multimeter (manufactured by Agilent, trade name "34401A") was used, and the resistance values between the terminals of the connected pads were measured. In addition, when the resistance value is too high (100 MΩ or more) and cannot be turned on, it is judged as "unable to turn on".

(5) Insulation resistance value after crimping

The anisotropic conductivity obtained in the examples and comparative examples on the copper foil pads of a comb-shaped electrode substrate (glass epoxy substrate) of 0.2 mm pitch (line/space = 100 μm/100 μm) After the paste was printed at a thickness of 0.1 mm, it was heated at a temperature of 240 ° C by a reflow furnace (manufactured by Tamura Seisakusho Co., Ltd., trade name "TNP") to obtain a test piece. The test piece was applied with a voltage of 15 V at 85 ° C and 85% RH (relative humidity), and the insulation resistance value after 168 hours was measured.

According to the results shown in Tables 1 and 2, it is clear that when the wiring board and the electronic component are connected by using the anisotropic conductive paste of the present invention (Examples 1 to 5), it is confirmed that sufficient repairability can be ensured. And higher connection reliability.

On the other hand, when the amount of the lead-free solder powder in the anisotropic conductive paste is 5% by mass (Comparative Example 1), and the acid value of the resin composition in the anisotropic conductive paste is 5 mgKOH/ In the case of g (Comparative Example 3), it was confirmed that the initial resistance value after the crimping was increased, and the conductivity of the wiring board and the electronic component could not be ensured.

In addition, when the amount of the lead-free solder powder in the anisotropic conductive paste is 60% by mass (Comparative Example 2), and the acid value of the resin composition in the anisotropic conductive paste is 70 mgKOH/g In the case of Comparative Example 4, it was confirmed that the insulation resistance value after the pressure bonding was lowered, and the insulation of the portion which was not thermocompression bonded could not be ensured.

Further, in the case of using an anisotropic conductive paste containing no solder powder (Comparative Examples 5 to 7), the wiring substrate and the wiring substrate cannot be realized unless both the electrode of the wiring substrate and the electrode of the electronic component are not subjected to gold plating treatment. Conduction of electronic components. In addition, even when the gold plating treatment is not performed on both the electrode of the wiring board and the electrode of the electronic component (Comparative Example 5), it is confirmed that the conduction cannot be achieved after the repair, and the repairability is inferior.

[Examples 6 to 17]

A thermosetting resin composition and an anisotropic conductive paste were obtained in the same manner as in Example 1 except that the materials were blended according to the compositions shown in Tables 3 and 4.

Instead of performing the use of the anisotropic conductive paste obtained as described above In the same manner as in Example 1, except that the anisotropic conductive paste used in Example 1 was used, the electronic component and the wiring board were thermocompression bonded.

Further, the materials used in Examples 6 to 17 are shown below.

Thermosetting Resin A: Bisphenol A type epoxy resin, trade name "EPICLON 860", manufactured by DIC

Thermosetting Resin B: Bisphenol F-type epoxy resin, trade name "EPICLON 830CRP", manufactured by DIC

Thermosetting resin C: Mixed epoxy resin of bisphenol A type and bisphenol F type, trade name "EPICLON EXA-830LVP", manufactured by DIC

Thermosetting resin D: Dicyclopentadiene type epoxy resin, trade name "EPICLON HP-7200H", manufactured by DIC

Thermosetting resin E: naphthalene type epoxy resin, trade name "EPICLON HP-4032D", manufactured by DIC

Thixotropic agent A: Fatty amide, manufactured by Nippon Kasei Co., Ltd. under the trade name "thylenebis H"

Thixotropic agent B: colloidal cerium oxide, trade name "AEROSIL R974", manufactured by Japan Aerosil Co., Ltd.

Thixotropic agent C: chlorinated polyether, manufactured by WILBUR-ELLIS

Organic acid A: adipic acid, manufactured by Kanto Electrochemical Industry Co., Ltd.

Organic acid B: glutaric acid, manufactured by Tokyo Chemical Industry Co., Ltd.

Organic acid C: succinic acid, manufactured by Mitsubishi Chemical Corporation

Hardener A: Imidazole hardening accelerator, trade name "Curezol 2P4MHZ", manufactured by Shikoku Chemicals Co., Ltd.

Hardener B: an imidazole-based hardening accelerator, trade name "Curezol 2MZA-PW", Made by Shikoku Chemicals Co., Ltd.

Hardener C: Epoxy resin amine adduct hardener, "Amicure PN-F", manufactured by Ajinomoto Fine-Techno

Hardener D: latent hardener, trade name "Novacure HX-3721", manufactured by Asahi Kasei Epoxy Co., Ltd.

Surfactant: trade name "BYK361N", manufactured by BYK-Chemie Japan

Defoamer: trade name "Flowlen AC-326F", manufactured by Kyoeisha Chemical Co., Ltd.

Lead-free solder powder A: average particle size 5 μm, solder melting point 139 ° C, solder composition 42Sn/58Bi

Lead-free solder powder B: average particle size is 5 μm, solder has a melting point of 217 ° C, and solder composition is 96.5Sn/3Ag/0.5Cu

<Evaluation of connection method of anisotropic conductive paste and electronic parts>

With respect to Example 1 and Examples 6 to 17, the performance of the anisotropic conductive paste (the acid value of the resin composition, the insulation resistance value after pressure bonding, the storage stability), and the evaluation method of the connection method of the electronic component were evaluated ( The initial resistance value after the pressure bonding, the repairability (whether or not the substrate was damaged during repair, and the resistance value after repair) were evaluated or measured by the above method and the following method by X-ray bridge observation. The results obtained are shown in Tables 3 and 4.

(6) Using X-ray bridge observation

The substrate after the pressure bonding was subjected to X-ray observation using a microfocus X-ray fluoroscopy apparatus (manufactured by SHIMADZU Co., Ltd.: SMX-160E), and the presence or absence of bridging or anisotropic conductive paste exudation was determined according to the following criteria. Furthermore, the terminals adjacent to the bridge are not expected to be shorted to each other.

A: There is no bridging, and there is no exudation of the anisotropic conductive paste.

B: No bridging, but a slight anisotropic conductive paste exudation.

C: There is a bridge.

(7) preservation stability

The viscosity of the anisotropic conductive paste after storage at 10 ° C was measured, and the time rate of change from the initial value was not more than ± 20%. The viscosity was measured in a thermostat tank and the resin in a polyethylene container adjusted to 25 ° C was measured using a viscometer (manufactured by Malcom: PCU-205).

Based on the results shown in Tables 3 and 4, the following aspects can be confirmed.

According to the results of Example 1 and Example 6, when an organic thixotropic agent and an inorganic thixotropic agent were used in combination as a thixotropic agent, it was confirmed that the anisotropic conductive paste was less likely to bleed out.

According to the results of Example 6 and Example 7, when a latent curing agent, an epoxy resin amine adduct-based curing agent, and an imidazole-based hardening accelerator were used in combination as a curing agent, the insulation resistance value after crimping was confirmed. improve.

According to the results of Examples 7, 8, and 12 to 14, when the epoxy resin was used in combination with the liquid bisphenol A type and the liquid bisphenol F type, it was confirmed that the storage stability of the anisotropic conductive paste was improved. .

From the results of Examples 8, 15, and 16, it was confirmed that a dibasic acid having an alkylene group was preferably used as the organic acid. Further, in particular, when adipic acid was used as the organic acid (Example 8), it was confirmed that the initial resistance value after pressure bonding or the resistance value after repair was lowered.

Claims (9)

An anisotropic conductive paste characterized in that the electronic component and the wiring board are connected, and the anisotropic conductive paste contains 10% by mass or more and 50% by mass or less of the lead-free solder powder having a melting point of 240 ° C or lower. And the thermosetting resin composition is 50% by mass or more and 90% by mass or less, and the thermosetting resin composition contains an epoxy resin, an organic acid, and a curing agent, and the curing agent contains a latent curing agent and an epoxy resin amine adduct-based curing agent. And an imidazole-based hardening accelerator, wherein the thermosetting resin composition has an acid value of 15 mgKOH/g or more and 55 mgKOH/g or less. The anisotropic conductive paste of claim 1, wherein the organic acid has a dibasic acid having an alkyl group. The anisotropic conductive paste according to claim 1, wherein the thermosetting resin composition further contains a thixotropic agent, and the thixotropic agent contains an organic thixotropic agent and an inorganic thixotropic agent. The anisotropic conductive paste according to claim 1, wherein the thermosetting resin composition further contains a thixotropic agent, and the content of the inorganic thixotropic agent in the thixotropic agent is 0.5% by mass or more and 22% by mass or less. The anisotropic conductive paste according to claim 1, wherein the lead-free solder powder has an average particle diameter of from 1 μm to 34 μm. The anisotropic conductive paste of claim 1, wherein the lead-free solder powder is selected from the group consisting of tin, copper, silver, rhodium, iridium, a metal of at least one of the group consisting of indium and zinc. The anisotropic conductive paste of claim 1, wherein at least one of the electrode of the electronic component or the electrode of the wiring substrate is not subjected to gold plating. A method of connecting an electronic component, comprising: using an anisotropic conductive paste according to any one of claims 1 to 7, and comprising: a coating step of coating the wiring substrate An anisotropic conductive paste; and a thermocompression bonding step of disposing the electronic component on the anisotropic conductive paste, and heating the electronic component at a temperature higher than a melting point of the lead-free solder powder by 5 ° C or higher The voltage is bonded to the wiring board. The method of connecting electronic components according to claim 8, further comprising: a peeling step of peeling off the electronic component from the wiring substrate at a temperature higher than a melting point of the lead-free solder powder by 5 ° C or more; and then applying a coating step And applying the anisotropic conductive paste to the wiring substrate after the peeling step; and a reheat bonding step of disposing the electronic component on the anisotropic conductive paste after the recoating step The electronic component is thermocompression bonded to the wiring board at a temperature higher than a melting point of the lead-free solder powder by 5 ° C or higher.