JP5802081B2 - Anisotropic conductive paste - Google Patents

Description

  The present invention relates to an anisotropic conductive paste used for connecting an electronic component and a wiring board.

  In recent years, connection methods using anisotropic conductive materials (anisotropic conductive films and anisotropic conductive pastes) have been used for connecting electronic components and wiring boards. For example, when an electronic component and a wiring board are connected, an anisotropic conductive material is disposed between the electronic component on which the electrode is formed and the wiring board on which the electrode pattern is formed, and the electronic component and the wiring are connected. The electrical connection is ensured by thermocompression bonding with the substrate.

  As an anisotropic conductive material, for example, a material in which a conductive filler such as a metal fine particle or a resin ball having a conductive film formed on a surface is dispersed in a binder resin as a base material has been proposed (for example, Patent Documents). 1). When the electronic component and the wiring board are thermocompression bonded, the conductive filler is arranged in a plane because there is a certain probability between the electronic component to be connected and the electrodes of the wiring board. It becomes a state. In this way, when the electrodes of the electronic component to be connected and the wiring board are brought into contact with each other via the conductive filler, conductivity between these electrodes is ensured. On the other hand, in the gap between the electrodes of the electronic component and the gap between the electrodes of the wiring board, the conductive filler is embedded in the binder resin, and insulation in the surface direction is ensured.

JP 2003-165825 A

  However, when the anisotropic conductive material described in the above-mentioned patent document is used, the adhesive strength at the connection portion cannot be sufficiently ensured. In addition, when the anisotropic conductive material described in the above-mentioned patent document is used, in order to ensure the connection reliability of the connection portion, the electronic component to be connected and the electrode of the wiring board are subjected to a gold plating process. There was a problem in connection reliability, such as necessity.

  Accordingly, an object of the present invention is to provide an anisotropic conductive paste that can sufficiently secure the bonding strength of the connection portion and has high connection reliability.

In order to solve the above problems, the present invention provides the following anisotropic conductive paste.
That is, the anisotropic conductive paste of the present invention is a thermosetting resin composition containing a lead-free solder powder having a melting point of 240 ° C. or less and 10% by mass to 50% by mass, and a thermosetting resin and a curing agent. 50% by mass or more and 90% by mass or less, and the curing agent is a carboxylic acid curing agent, 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine And an amine adduct curing agent .

In the anisotropic conductive paste of the present invention, the content of the carboxylic acid curing agent is preferably 2% by mass or more and 10% by mass or less with respect to 100% by mass of the thermosetting resin composition.
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, bismuth, antimony, indium and zinc.

In the present invention, the anisotropic conductive paste is conductive in the thermocompression bonding direction (thickness direction) at a place where heat of a predetermined value or more and pressure of a predetermined value or more are applied. This means a paste that can form an anisotropic conductive material having insulation in the surface direction.
Further, the reason why the anisotropic conductive paste of the present invention can sufficiently secure the adhesive strength of the connection portion and has high connection reliability is not necessarily clear, but the present inventors are as follows. I guess.

That is, unlike the conventional anisotropic conductive material, the anisotropic conductive paste of the present invention contains lead-free solder powder. When this 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 melt and come close to each other. It becomes larger by joining together. On the other hand, since the distance between the electrodes of the electronic component and the wiring board is shortened by thermocompression bonding, the electrodes can be soldered to each other by the lead-free solder that has been enlarged as described above. As described above, in the present invention, since the electrodes of the electronic component and the wiring board are soldered to each other, the electrodes and the conductive filler are connected by contact with each other like a conventional anisotropic conductive material. The present inventors infer that the connection reliability is extremely high as compared with the case where it is present.
On the other hand, solder bonding is performed as described above in the places where the thermocompression bonding is not performed with the heat above the predetermined value and the pressure above the predetermined value (such as the gap between the electrodes of the electronic component and the gap between the electrodes of the wiring board). The lead-free solder powder is embedded in the thermosetting resin composition. Therefore, insulation is ensured for portions that are not thermocompression-bonded with heat of a predetermined value or higher and pressure of a predetermined value or higher.

  When the electronic component and the wiring board are connected with the anisotropic conductive paste of the present invention, as described above, the electrodes of the electronic component and the wiring board are soldered together, and the soldered portion is a thermosetting resin. It is inferred that the composition is covered. As described above, in the present invention, since the electronic component and the wiring board are connected by two kinds of methods, that is, solder bonding and thermosetting resin, the bonding strength of the connection portion is increased. In the present invention, the solder joint portion is covered with the thermosetting resin composition, and the solder joint portion can be reinforced by being cured by heat. And since the hardening | curing agent in this thermosetting resin composition contains three types of hardening | curing agents called a carboxylic acid type hardening | curing agent, an imidazole type hardening | curing agent, and an amine hardening | curing agent, The part can be sufficiently reinforced. In this way, when the electronic component and the wiring board are connected with the anisotropic conductive paste of the present invention, it is possible to sufficiently secure the adhesive strength of the connection portion.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive strength of a connection part can fully be ensured and the anisotropic conductive paste which has high connection reliability can be provided.

The anisotropic conductive paste of the present invention is an anisotropic conductive paste used for connecting an electronic component and a wiring board. And this anisotropic conductive paste contains 10 mass% or more and 50 mass% or less of the lead-free solder powder described below, and contains 50 mass% or more and 90 mass% or less of the thermosetting resin composition described below. It is.
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), the obtained anisotropic conductive paste is subjected to thermocompression bonding. When a sufficient solder joint cannot be formed between the electronic component and the wiring board, the conductivity between the electronic component and the wiring board becomes insufficient, and on the other hand, the content of the lead-free solder powder exceeds 50% by mass ( In the case where the content of the thermosetting resin composition is less than 50% by mass), the insulating property of the obtained anisotropic conductive paste, particularly the insulating property in the moisture when left in a humidified state, is insufficient. As a result, the solder bridges do not exhibit anisotropy. Further, in the obtained anisotropic conductive paste, the content of the lead-free solder powder is 20% by mass or more and 45% by mass or less from the viewpoint of balancing the insulation and the conductivity when thermocompression bonded. It is preferable that it is 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 lead-free solder powder having a melting point exceeding 240 ° C. is used, the lead-free solder powder cannot be melted at a normal 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 less, and more preferably 150 ° C. or less.
Here, the lead-free solder powder refers to a solder metal or alloy powder to which lead is not added. However, it is allowed that lead is present as an inevitable impurity in the lead-free solder powder, but in this case, the amount of lead is preferably 100 mass ppm or less.

The lead-free solder powder is at least one selected from the group consisting of tin (Sn), copper (Cu), silver (Ag), bismuth (Bi), antimony (Sb), indium (In), and zinc (Zn). It is preferred to include a seed metal.
Moreover, as a specific solder composition (mass ratio) in the said lead-free solder powder, the following can be illustrated.
As binary alloys, for example, Ag-Bi type such as 95.3Ag / 4.7Bi, Ag-Li type such as 66Ag / 34Li, Ag-In type such as 3Ag / 97In, Ag-type such as 67Ag / 33Te, etc. Te, Ag-Tl such as 97.2Ag / 2.8Tl, Ag-Zn such as 45.6Ag / 54.4Zn, Au-Sn such as 80Au / 20Sn, 52.7Bi / 47.3In, etc. Bi-In series, 35In / 65Sn, 51In / 49Sn, In-Sn series such as 52In / 48Sn, Bi-Zn series such as 8.1Bi / 91.9Zn, Sn-Bi series such as 43Sn / 57Bi, 42Sn / 58Bi , 98Sn / 2Ag, 96.5Sn / 3.5Ag, 96Sn / 4Ag, Sn-Ag series such as 95Sn / 5Ag, 91Sn / 9Zn, 30Sn / 7 Sn-Zn-based, such as Zn, Sn-Cu system, such 99.3Sn / 0.7Cu, include Sn-Sb system, such as 95Sn / 5Sb.
Examples of ternary alloys include Sn—Ag—In such as 95.5Sn / 3.5Ag / 1In, Sn—Zn—In such as 86Sn / 9Zn / 5In, 81Sn / 9Zn / 10In, and 95.5Sn. Sn-Ag-Cu system such as /0.5Ag/4Cu, 96.5Sn / 3.0Ag / 0.5Cu, Sn- such as 90.5Sn / 7.5Bi / 2Ag, 41.0Sn / 58Bi / 1, 0Ag Examples thereof include Sn—Zn—Bi systems such as Bi—Ag system and 89.0Sn / 8.0Zn / 3.0Bi.
Examples of other alloys include Sn / Ag / Cu / Bi system.

  The average particle size 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. If the average particle size of the lead-free solder powder is less than the lower limit, the conductivity between the electronic component and the wiring board tends to decrease. On the other hand, if the upper limit is exceeded, the insulating property in the anisotropic conductive paste decreases. There is a tendency.

  The thermosetting resin composition used in the present invention contains a thermosetting resin and a curing agent. And it is preferable that the acid value of this thermosetting resin composition is 20 mgKOH / g or more and 50 mgKOH / g. When the acid value is less than 20 mgKOH / g, when the obtained anisotropic conductive paste is thermocompression bonded, the solder cannot be sufficiently activated, and the conductivity between the electronic component and the wiring board is low. On the other hand, when it exceeds 50 mgKOH / g, the insulating property of the obtained anisotropic conductive paste, particularly in the humidity when left in a humidified state, tends to be insufficient. Further, in the obtained anisotropic conductive paste, the acid value of the thermosetting resin composition is 30 mgKOH / g or more and 45 mgKOH / g from the viewpoint of balancing the insulation and the conductivity when thermocompression bonded. It is preferable that

As the thermosetting resin used in the present invention, a known thermosetting resin can be used as appropriate, but it is particularly preferable to use an epoxy resin from the viewpoint of having a flux action.
In the present invention, having a flux action means that the coating film covers the metal surface of the object to be soldered and shields the atmosphere, like metal rosin flux, and the metal surface of the metal surface is oxidized during soldering. The material is reduced, and the coating film is pushed away by the molten solder to allow contact between the molten solder and the metal surface, and the residue has a function of insulating between the circuits.

As such an epoxy resin, a known epoxy resin can be appropriately used. Examples of such epoxy resins include bisphenol A type, bisphenol F type, biphenyl type, naphthalene type, cresol novolak type, phenol novolak type and the like. These epoxy resins may be used individually by 1 type, and may mix and use 2 or more types. Further, these epoxy resins preferably contain a liquid at normal temperature, and when a solid at normal temperature is used, it is preferably used in combination with a liquid at normal temperature. In addition, among these epoxy resin molds, the dispersibility of the metal particles and the paste viscosity can be adjusted, and further, the resistance to the drop impact of the cured product can be improved, and the wettability of the solder can be improved. Liquid bisphenol A type, liquid bisphenol F type, and liquid hydrogenated bisphenol A type are preferred.
As content of the said epoxy resin, it is preferable that it is 65 to 92 mass% with respect to 100 mass% of thermosetting resin compositions, and it is more preferable that it is 70 to 85 mass%. . If the content of the epoxy resin is less than the lower limit, sufficient strength for fixing the electronic component cannot be obtained, and thus the resistance to drop impact tends to decrease. On the other hand, if the content exceeds the upper limit, the thermosetting resin The content of the curing agent in the composition is decreased, and the rate at which the epoxy resin is cured tends to be delayed.

  The curing agent used in the present invention contains a carboxylic acid curing agent, an imidazole curing agent, and an amine curing agent. In the present invention, it is necessary to use these three kinds of curing agents in combination, and when any of these three kinds of curing agents is not contained, the effects of the present invention cannot be achieved. In addition to these three kinds of curing agents, other curing agents may be used in combination.

As the carboxylic acid curing agent used in the present invention, a known organic acid can be appropriately used. Among these organic acids, it is preferable to use a dibasic acid having an alkylene group from the viewpoint of excellent solubility with an epoxy resin and from the viewpoint that crystals are hardly precipitated during storage. Examples of such a dibasic acid having an alkylene group include adipic acid, 2,5-diethyladipic acid, glutaric acid, 2,4-diethylglutaric acid, 2,2-diethylglutaric acid, and 3-methylglutaric acid. 2-ethyl-3-propylglutaric acid, sebacic acid, succinic acid, malonic acid, diglycolic acid and the like. Among these, adipic acid is preferable.
The content of the carboxylic acid curing agent is preferably 2% by mass to 10% by mass, and preferably 3% by mass to 8% by mass with respect to 100% by mass of the thermosetting resin composition. Is more preferable. When the content of the carboxylic acid-based curing agent is less than the lower limit, the curing rate of the thermosetting resin such as epoxy resin tends to be delayed, resulting in poor curing. There is a tendency for the insulation in the isotropic conductive paste to decrease.

As the imidazole-based curing agent used in the present invention, a curing agent having an imidazole skeleton and not having a carboxyl group or an amino group can be appropriately used. Such an imidazole curing accelerator is preferably solid at room temperature. Moreover, the thing which has a hydroxyl group from a viewpoint that generation | occurrence | production of stress can be prevented, without the hardening reaction of a thermosetting resin advancing rapidly, is especially preferable. Examples of such imidazole curing accelerators include 2P4MHZ, 2MZA, 2PZ, C11Z, C17Z, 2E4MZ, 2P4MZ, C11Z-CNS, and 2PZ-CNZ (trade names, manufactured by Shikoku Kasei Kogyo Co., Ltd.).
As content of the said imidazole type hardening | curing agent, it is preferable that it is 3 mass% or more and 20 mass% or less with respect to 100 mass% of thermosetting resin compositions, and it is 6 mass% or more and 12 mass% or less. More preferred. If the content of the imidazole-based curing agent is less than the lower limit, the adhesive strength of the connection part between the electronic component and the wiring board tends to decrease. On the other hand, if the content exceeds the upper limit, the strength is sufficient to fix the electronic component. Cannot be obtained, the resistance to drop impact tends to decrease.

As the amine curing agent used in the present invention, a curing agent having an amino group such as melamine, dicyandiamide, and derivatives thereof can be used in addition to a polyamine curing agent and an amine adduct curing agent. As such an amine hardening accelerator, a solid thing at normal temperature is preferable.
Examples of the polyamine-based curing agent include Fujicure FXR-1020, FXR-1030, FXR-1050, and FXR-1080 (trade name, manufactured by Fuji Kasei Kogyo Co., Ltd.).
Examples of the 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., trade names), EH-3615S, and EH. -3293S, EH-3366S, EH-3842, EH-3670S, EH-3636AS, EH-4346S (trade name, manufactured by Asahi Denka Kogyo Co., Ltd.).
The content of the amine-based curing agent is preferably 3% by mass or more and 15% by mass or less, and preferably 6% by mass or more and 10% by mass or less with respect to 100% by mass of the thermosetting resin composition. More preferred. If the content of the amine curing agent is less than the lower limit, the adhesive strength of the connection portion between the electronic component and the wiring board tends to decrease. On the other hand, if the upper limit is exceeded, the strength is sufficient to fix the electronic component. Cannot be obtained, the resistance to drop impact tends to decrease.

In the present invention, the following can be used as other curing agents.
Examples of the acid anhydride curing agent include NOVACURE HX-3721 (manufactured by Asahi Kasei E-Materials Co., Ltd., trade name).
Examples of the latent curing agent include NOVACURE HX-3722, HX-3748, HX-3088, HX-3613, HX-392HP, and HX-3941HP (trade name, manufactured by Asahi Kasei E-Materials Co., Ltd.).

  The total content of the curing agent is preferably 7% by mass to 35% by mass and more preferably 14% by mass to 30% by mass with respect to 100% by mass of the thermosetting resin composition. More preferred. If the total content of the curing agent is less than the lower limit, the rate at which the thermosetting resin is cured tends to be delayed. On the other hand, if the upper limit is exceeded, the reactivity tends to be faster and the paste usage time tends to be shorter. It is in.

The thermosetting resin composition used in the present invention preferably uses a thixotropic agent in addition to the thermosetting resin and the curing agent.
As the thixotropic agent used in the present invention, a known thixotropic agent can be appropriately used. Examples of such thixotropic agents include sorbitol derivatives, fatty acid amides, and hydrogenated castor oil. Among these, a sorbitol derivative and a fatty acid amide are preferable.
The thixotropic agent content is preferably 0.5% by mass or more and 10% by mass or less, and preferably 1% by mass or more and 5% by mass or less with respect to 100% by mass of the thermosetting resin composition. More preferred. If the content of the thixotropic agent is less than the above lower limit, thixotropy cannot be obtained, the sagging is likely to occur on the electrode of the wiring board, and the adhesive force when electronic components are mounted on the electrode of the wiring board tends to decrease. On the other hand, if the upper limit is exceeded, the thixotropy is too high and the syringe needles tend to become defective due to clogging.

  The thermosetting resin composition used in the present invention, if necessary, in addition to the epoxy resin, the curing agent and the thixotropic agent, a surfactant, a coupling agent, an antifoaming agent, a powder surface treatment agent, a reaction inhibitor An additive such as an agent and an anti-settling agent may be contained. The content of these additives is preferably 0.01% by mass or more and 10% by mass or less, and 0.05% by mass or more and 5% by mass or less with respect to 100% by mass of the thermosetting resin composition. More preferably. If the content of the additive is less than the lower limit, the effect of each additive tends to be difficult to achieve. On the other hand, if the content exceeds the upper limit, the bonding strength due to the thermosetting resin composition tends to decrease.

Next, a method for connecting electronic components using the anisotropic conductive paste of the present invention will be described.
The anisotropic conductive paste of the present invention can be used to connect an electronic component and a wiring board. Here, as an electronic component, a wiring board may be used in addition to a chip, a package component, and the like. As the wiring substrate, either a flexible substrate having flexibility or a rigid substrate having no flexibility can be used. Further, when a flexible substrate is used as an electronic component, the rigid substrates can be electrically connected to each other via the flexible substrate by connecting to two wiring substrates (rigid substrates). Further, the flexible boards may be electrically connected through the flexible boards.
Such an electronic component connection method includes an application step of applying the anisotropic conductive paste on the wiring board, and arranging the electronic component on the anisotropic conductive paste, and the lead-free solder powder. And a thermocompression bonding step of thermocompression bonding the electronic component to the wiring board at a temperature higher than the melting point (preferably a temperature higher by 20 ° C. or more).

In the applying step, the anisotropic conductive paste is applied on the wiring board.
Examples of the coating device used here include a dispenser, a screen printer, and a jet dispense metal mask printer.
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. If the thickness is less than the lower limit, the adhesive force when electronic components are mounted on the electrodes of the wiring board tends to decrease. On the other hand, if the thickness exceeds the upper limit, the paste tends to protrude beyond the connection portion. .

In the thermocompression bonding step, the electronic component is disposed on the anisotropic conductive paste, and the electronic component is placed at a temperature higher than the melting point of the lead-free solder powder (preferably a temperature higher by 20 ° C. or more). Thermocompression bonding to the wiring board.
If the temperature at the time of thermocompression bonding does not satisfy the condition that it is higher than the melting point of the lead-free solder powder, the lead-free solder cannot be sufficiently melted, and sufficient solder is provided between the electronic component and the wiring board. Bonding cannot be formed, and the electrical conductivity between the electronic component and the wiring board tends to be insufficient.
Although the pressure at the time of thermocompression bonding is not particularly limited, it is preferably 0.1 MPa or more and 2 MPa or less, and more preferably 0.2 MPa or more and 1.0 MPa or less. If the pressure is less than the upper limit, sufficient solder joints cannot be formed between the electronic component and the wiring board, and the electrical conductivity between the electronic component and the wiring board tends to decrease. It tends to be stressed and the dead space has to be widened.
In the present invention, as described above, the pressure at the time of thermocompression bonding can be set to a lower pressure range than in the case of the conventional method. Therefore, cost reduction of the apparatus used for a thermocompression bonding process can also be achieved.
The time for thermocompression bonding is not particularly limited, but is usually 5 seconds to 60 seconds and preferably 7 seconds to 20 seconds.

EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these examples. In addition, the material used in the Example and the comparative example is shown below.
Thermosetting resin: bisphenol A type epoxy resin, trade name “EPICLON 860”, DIC Corporation thixotropic agent: trade name “Gelall D”, Shin Nippon Rika Co., Ltd. carboxylic acid curing agent: adipic acid, manufactured by Kanto Denka Kogyo Co., Ltd. Imidazole-based curing agent: Trade name “Cureazole 2MZA-PW”, amine-based curing agent manufactured by Shikoku Kasei Kogyo Co., Ltd .: product name “PN-F”, acid anhydride-based curing agent manufactured by Ajinomoto Fine Techno Co., Ltd .: trade name “Novacure HX- 3721 ", surfactants manufactured by Asahi Kasei E-materials: trade name" BYK361N ", defoaming agent manufactured by Big Chemie Japan: trade name" KS-66 ", lead-free solder powder A manufactured by Shin-Etsu Silicone Co., Ltd. 5 μm, melting point of solder is 139 ° C., solder composition is 42 Sn / 58 Bi
Lead-free solder powder B: average particle size is 5 μm, solder melting point is 217 ° C., solder composition is 96.5Sn / 3Ag / 0.5Cu
[Example 1]
76% by mass of thermosetting resin, 2% by mass of thixotropic agent, 3% by mass of carboxylic acid type curing agent, 12% by mass of imidazole type curing agent, 6% by mass of amine type curing agent, 0.5% by mass of surfactant and defoaming 0.5 mass% of the agent was put into a container and mixed using a rough machine to obtain a thermosetting resin composition.
Thereafter, 62.5% by mass of the obtained thermosetting resin composition and 37.5% by mass of lead-free solder powder A are charged into a container and mixed for 2 hours in a kneader to obtain an anisotropic conductive paste. Prepared.
Next, the obtained anisotropic conductive paste was applied on a wiring board (electrode: copper electrode with gold plating (Cu / Ni / Au)) (thickness: 0.2 mm). Then, on the anisotropic conductive paste after application, an electronic component (electrode: copper electrode with gold plating (Cu / Ni / Au)) is arranged, and a thermocompression bonding apparatus (manufactured by Advancel) is used, The electronic component was thermocompression bonded to the wiring board under the conditions (i) and (ii).
(I) Temperature 240 ° C., pressure 1 MPa, pressure bonding time 5 seconds (ii) Temperature 150 ° C., pressure 1 MPa, pressure bonding time 15 seconds

[Examples 2 to 5]
A thermosetting resin composition and an anisotropic conductive paste were obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.
In the same manner as in Example 1 except that the anisotropic conductive paste obtained as described above was used instead of the anisotropic conductive paste used in Example 1, the electronic component was thermocompression bonded to the wiring board. did.

[Comparative Examples 1-4]
A thermosetting resin composition and an anisotropic conductive paste were obtained in the same manner as in Example 1 except that each material was blended according to the composition shown in Table 1.
In the same manner as in Example 1 except that the anisotropic conductive paste obtained as described above was used instead of the anisotropic conductive paste used in Example 1, the electronic component was thermocompression bonded to the wiring board. did.

<Evaluation of electronic component connection status>
Evaluation of the connection state of electronic components (initial resistance value, peel strength, insulation resistance value) was evaluated or measured by the following method. The obtained results are shown in Tables 1 and 2.
(1) Initial resistance value A wiring board having a 0.2 mm pitch land (line / space = 100 μm / 100 μm) as a circuit pattern was prepared. Then, electronic components having a 0.2 mm pitch land (line / space = 100 μm / 100 μm) were thermocompression-bonded on the lands of the wiring board by the methods described in the above-described examples and comparative examples, respectively. And the resistance value between the terminals of the connected land was measured using the digital multimeter (The product made by Agilent, brand name "34401A"). In addition, when the resistance value was too high (100 MΩ or more) and conduction was not possible, it was determined that “conduction was not possible”.
(2) Peel strength (adhesive strength)
Evaluation is performed using the substrate whose initial resistance value is measured in (1). The wiring substrate and the electronic component were each fixed to a jig, and the electronic component was pulled at a pulling speed of 50 mm / min in a direction forming an angle of 90 ° with the substrate surface of the wiring substrate, and the peel strength at that time was measured. In addition, when the electronic component was destroyed without peeling at the connection portion between the wiring board and the electronic component, it was determined as “destructed”. The determination of “destruction” indicates that the bonding strength of the connection portion between the wiring board and the electronic component is sufficient.
(3) Insulation resistance value A wiring board having a 0.2 mm pitch land (line / space = 100 μm / 100 μm) as a circuit pattern was prepared. Then, an electronic component having a 0.2 mm pitch land (line / space = 100 μm / 100 μm) is thermocompression-bonded on the land of this wiring board by the methods described in the above-mentioned examples and comparative examples. Obtained. A voltage of 15 V was applied to the test piece in 85 ° C. and 85% RH (relative humidity), and an insulation resistance value after 168 hours was measured.

As is apparent from the results shown in Table 1 and Table 2, when the wiring board and the electronic component are connected using the anisotropic conductive paste of the present invention (Examples 1 to 5), the connection portion It was confirmed that high adhesive strength and high connection reliability can be secured.
On the other hand, when an anisotropic conductive paste not containing a carboxylic acid curing agent is used (Comparative Example 1), electrical connection between the wiring board and the electronic component cannot be achieved, and the thermocompression bonding temperature The adhesive strength could not be secured when the value was low.
Further, when an anisotropic conductive paste not containing an imidazole curing agent is used (Comparative Examples 2 and 4), and when an anisotropic conductive paste not containing an amine curing agent is used (Comparative Example 3). ), Particularly when the thermocompression bonding temperature was low, the adhesive strength could not be secured.
Furthermore, in the anisotropic conductive paste of the present invention, when the content of the carboxylic acid curing agent is 2% by mass or more and 10% by mass or less with respect to 100% by mass of the thermosetting resin composition (implementation) In Examples 1 to 4), it was confirmed that the insulation resistance value could be higher and a higher degree of insulation could be secured.

  The anisotropic conductive paste of the present invention can be suitably used as a technique for connecting an electronic component and a wiring board.

Claims (3)

A lead-free solder powder having a melting point of 240 ° C. or lower, 10% by weight to 50% by weight, and a thermosetting resin composition containing a thermosetting resin and a curing agent, 50% by weight to 90% by weight,
The curing agent contains a carboxylic acid curing agent, 2,4-diamino-6- [2′-methylimidazolyl- (1 ′)]-ethyl-s-triazine , and an amine adduct curing agent. An anisotropic conductive paste characterized. The anisotropic conductive paste according to claim 1,
An anisotropic conductive paste, wherein the content of the carboxylic acid curing agent is 2% by mass or more and 10% by mass or less with respect to 100% by mass of the thermosetting resin composition. In the anisotropic conductive paste according to claim 1 or 2,
The anisotropic conductive paste, wherein the lead-free solder powder contains at least one metal selected from the group consisting of tin, copper, silver, bismuth, antimony, indium and zinc.