Conductive material, connection structure, and method for manufacturing connection structure

Abstract

Provided is an electroconductive material with which it is possible to continuously perform an arrangement step during printing and to efficiently arrange solder on an electrode.　The electroconductive material according to the present invention includes a thermosetting component, a plurality of solder particles, and flux, the average particle diameter of the solder particles being less than 10 μm, and the acid value of the solder particles being 0.3-3 mg KOH / g inclusive.

Description

Technical Field

[0001] The present invention relates to a conductive material containing solder particles. The present invention also relates to a connection structure using the above conductive material and a method for manufacturing the connection structure.

Background Art

[0002] Solder pastes containing a relatively large amount of solder are known.

[0003] In addition, anisotropic conductive materials containing a relatively large amount of binder resin are widely known as compared with solder pastes. Examples of the anisotropic conductive materials include anisotropic conductive pastes and anisotropic conductive films. In the above anisotropic conductive materials, conductive particles are dispersed in the binder resin.

[0004] The above anisotropic conductive materials are used to obtain various connection structures. Examples of the connection using the anisotropic conductive materials include connection between a flexible printed circuit board and a glass substrate (FOG (Film on Glass)), connection between a semiconductor chip and a flexible printed circuit board (COF (Chip on Film)), connection between a semiconductor chip and a glass substrate (COG (Chip on Glass)), and connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)).

[0005] When electrically connecting, for example, an electrode of a flexible printed circuit board and an electrode of a glass epoxy substrate with the above anisotropic conductive material, an anisotropic conductive material containing conductive particles is disposed on the glass epoxy substrate. Next, the flexible printed circuit board is laminated and heated and pressurized. Thereby, the anisotropic conductive material is cured, and the electrodes are electrically connected via the conductive particles to obtain a connection structure.

[0006] Patent Documents 1 and 2 below describe materials that can be used for the above anisotropic conductive materials.

[0007] Patent Document 1 below discloses a flux for solder paste containing an adhesive, a solvent, and a thixotropic agent. In this flux for paste, the acid value is 100 mgKOH / g or less, the reduction rate at 300 °C in thermogravimetric measurement is 80 mass% or more, the viscosity is 0.5 Pa·s or more, and the tacking force is 1.0 N or more.

[0008] Patent Document 2 below discloses a solder composition containing solder powder and a flux. In this solder composition, the flux contains a rosin-based resin having a softening point of 110 °C or less and an acid value of 140 mgKOH / g or more, a rosin ester compound having a softening point of 110 °C or less and an acid value of 5 mgKOH / g or less, and a solvent. Further, the acid value of the flux is 5 mgKOH / g or more and 70 mgKOH / g or less.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] When making a conductive connection using a conductive material containing solder particles, a plurality of upper electrodes and a plurality of lower electrodes are electrically connected to make the conductive connection. The solder particles are preferably disposed between the upper and lower electrodes and desirably not disposed between adjacent lateral electrodes. It is desirable that adjacent lateral electrodes are not electrically connected.

[0011] Generally, a conductive material containing solder particles is placed at a specific position on a substrate by printing such as screen printing, and then heated by reflow or the like for use. When the conductive material is heated to a temperature equal to or higher than the melting point of the solder particles, the solder particles melt, and the solder aggregates between the electrodes, thereby electrically connecting the upper and lower electrodes.

[0012] In conventional conductive materials, when printing such as screen printing is repeated, the viscosity of the conductive material during printing may decrease, the screen permeation amount may increase, and bleeding of the conductive material may occur. Also, in conventional conductive materials, when printing such as screen printing is repeated, the viscosity of the conductive material during printing may increase, and the conductive material may clog the mesh, resulting in blurring of the conductive material. Thus, in conventional conductive materials, when continuously performing printing such as screen printing, bleeding, blurring, etc. of the conductive material may occur, making it difficult to continuously perform printing such as screen printing.

[0013] Further, in conventional conductive materials, the moving speed of the solder particles onto the electrodes (lines) may be slow, and it may not be possible to efficiently arrange the solder between the upper and lower electrodes to be connected. If the solder between the upper and lower electrodes to be connected cannot be sufficiently aggregated, solder particles, etc. may remain as side balls, etc., separated from the solder between the upper and lower electrodes, between the lateral electrodes that should not be connected. As a result, there may be cases where the conduction reliability between the electrodes to be connected and the insulation reliability between adjacent electrodes that should not be connected cannot be sufficiently enhanced.

[0014] In recent years, with the miniaturization of electronic devices, the components mounted on the electronic devices have also been miniaturized, and accordingly, it has been required to reduce the average particle diameter of the solder particles contained in the conductive material. However, when the average particle diameter of the solder particles is reduced, the viscosity of the conductive material tends to increase, and it may not be possible to continuously perform placement processes such as printing, or it may not be possible to efficiently arrange the solder on the electrodes.

[0015] An object of the present invention is to provide a conductive material that can continuously perform arrangement steps such as printing, and further can efficiently arrange solder on an electrode. Another object of the present invention is to provide a connection structure using the above conductive material and a method for manufacturing the connection structure.

Means for Solving the Problems

[0016] According to a broad aspect of the present invention, there is provided a conductive material containing a thermosetting component, a plurality of solder particles, and a flux, wherein an average particle diameter of the solder particles is less than 10 μm, and an acid value of the solder particles is 0.3 mgKOH / g or more and 3 mgKOH / g or less.

[0017] In a specific aspect of the conductive material according to the present invention, the frozen conductive material is thawed, and a viscosity of the conductive material at 25°C immediately after reaching 25°C is 100 Pa·s or more and 200 Pa·s or less.

[0018] In a specific aspect of the conductive material according to the present invention, the frozen conductive material is thawed, and a viscosity of the conductive material at 25°C after storing at 25°C and 50% RH for 24 hours is 100 Pa·s or more and 300 Pa·s or less.

[0019] In a specific aspect of the conductive material according to the present invention, the thermosetting component contains an epoxy compound.

[0020] In a specific aspect of the conductive material according to the present invention, the average particle diameter of the solder particles is less than 1 μm.

[0021] In a specific aspect of the conductive material according to the present invention, the conductive material is a conductive paste.

[0022] According to a broad aspect of the present invention, there is provided a connection structure including a first connection target member having a first electrode on its surface, a second connection target member having a second electrode on its surface, and a connection portion connecting the first connection target member and the second connection target member, wherein the material of the connection portion is the above-described conductive material, and the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

[0023] According to a broad aspect of the present invention, there is provided a method for manufacturing a connection structure, including the steps of disposing the above-described conductive material on the surface of a first connection target member having a first electrode on its surface using the above-described conductive material; disposing a second connection target member having a second electrode on its surface on the surface of the conductive material opposite to the first connection target member side of the conductive material so that the first electrode and the second electrode face each other; and heating the conductive material to a temperature equal to or higher than the melting point of the solder particles to form a connection portion connecting the first connection target member and the second connection target member with the conductive material and electrically connecting the first electrode and the second electrode by a solder portion in the connection portion.

Advantages of the Invention

[0024] The conductive material according to the present invention includes a thermosetting component, a plurality of solder particles, and a flux. In the conductive material according to the present invention, the average particle diameter of the solder particles is less than 10 μm, and the acid value of the solder particles is 0.3 mgKOH / g or more and 3 mgKOH / g or less. Since the conductive material according to the present invention has the above-described configuration, placement steps such as printing can be continuously performed, and furthermore, solder can be efficiently placed on the electrodes.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0026] Hereinafter, the details of the present invention will be described.

[0027] (Conductive Material) The conductive material according to the present invention includes a thermosetting component, a plurality of solder particles, and a flux. In the conductive material according to the present invention, the average particle diameter of the solder particles is less than 10 μm, and the acid value of the solder particles is 0.3 mgKOH / g or more and 3 mgKOH / g or less.

[0028] In the conductive material according to the present invention, since the above configuration is provided, placement steps such as printing can be continuously performed, and furthermore, solder can be efficiently placed on the electrode. In the conductive material according to the present invention, even when the average particle diameter of the solder particles is small, placement steps such as printing can be continuously performed, and furthermore, solder can be efficiently placed on the electrode. As a result, the conduction reliability between the upper and lower electrodes to be connected can be effectively enhanced, and the connection reliability between the solder portion and the electrode can be further enhanced. In particular, in the conductive material according to the present invention, printing such as screen printing can be continuously and favorably performed.

[0029] In the above Patent Documents 1 and 2, only the control of the acid value of the flux has been found. Thus, conventionally, it has not been recognized at all that by the acid value of the solder particles being within a specific range, printing can be continuously performed, and furthermore, solder can be efficiently placed on the electrode.

[0030] The inventors have found that by using a conductive material with an acid value of solder particles within a specific range, placement processes such as printing can be continuously performed, and furthermore, solder can be efficiently placed on the electrodes.

[0031] In addition, in the conductive material according to the present invention, since the above configuration is provided, generation of voids during bonding can be suppressed.

[0032] Furthermore, in the present invention, displacement between electrodes can be prevented. In the present invention, when the second connection target member is overlapped with the first connection target member on which the conductive material is disposed on the upper surface, even when the alignment between the electrode of the first connection target member and the electrode of the second connection target member is displaced, the displacement can be corrected to connect the electrodes to each other (self-alignment effect).

[0033] From the viewpoint of more efficiently placing solder on the electrodes, the above conductive material is preferably liquid at 25°C and is preferably a conductive paste. The above conductive material is preferably a conductive paste at 25°C.

[0034] From the viewpoint of more efficiently placing solder on the electrodes, the viscosity (η25) of the above conductive material at 25°C immediately after production is preferably 100 Pa·s or more, more preferably 120 Pa·s or more, still more preferably 140 Pa·s or more, and preferably 200 Pa·s or less, more preferably 180 Pa·s or less. The above viscosity (η25) can be appropriately adjusted according to the types and blending amounts of the blending components.

[0035] Thaw the above-mentioned conductive material stored frozen, and the viscosity (ηA) of the conductive material at 25°C immediately after reaching 25°C is preferably 100 Pa·s or more, more preferably 120 Pa·s or more, preferably 200 Pa·s or less, and more preferably 180 Pa·s or less. When the above viscosity (ηA) is above the above lower limit and below the above upper limit, the solder can be arranged more efficiently on the electrode, and the conduction reliability between the upper and lower electrodes to be connected can be enhanced more effectively. The above viscosity (ηA) can be appropriately adjusted according to the types and blending amounts of the blending components.

[0036] Thaw the above-mentioned conductive material stored frozen, and the viscosity (ηB) of the conductive material at 25°C after storing at 25°C and 50% RH for 24 hours is preferably 100 Pa·s or more, more preferably 120 Pa·s or more, preferably 300 Pa·s or less, and more preferably 200 Pa·s or less. When the above viscosity (ηB) is above the above lower limit and below the above upper limit, the solder can be arranged more efficiently on the electrode, and the conduction reliability between the upper and lower electrodes to be connected can be enhanced more effectively. The above viscosity (ηB) can be appropriately adjusted according to the types and blending amounts of the blending components.

[0037] The ratio of the above viscosity (ηB) to the above viscosity (ηA) (viscosity (ηB) / viscosity (ηA)) is preferably 0.8 or more, more preferably 1.0 or more, preferably 2.0 or less, and more preferably 1.5 or less. When the above ratio (viscosity (ηB) / viscosity (ηA)) is above the above lower limit and below the above upper limit, the solder can be arranged more efficiently on the electrode, and the conduction reliability between the upper and lower electrodes to be connected can be enhanced more effectively.

[0038] The above viscosity (η25), the above viscosity (ηA), and the above viscosity (ηB) can be measured, for example, using an E-type viscometer ("TVE22L" manufactured by Toki Sangyo Co., Ltd.) under the conditions of 25°C and 5 rpm.

[0039] In addition, in this specification, the conditions for cryopreserving the conductive material for measuring viscosity are the conditions of storing it at -40°C for 7 days. On the other hand, the conditions for the above cryopreservation during the actual use of the conductive material are not particularly limited. The temperature for the above cryopreservation during the actual use of the conductive material is not particularly limited as long as it is less than 0°C. The temperature for the above cryopreservation during the actual use of the conductive material may be -10°C or lower, -20°C or lower, or -40°C or lower. The period for the above cryopreservation during the actual use of the conductive material is not particularly limited as long as it is 180 days or less. The period of this cryopreservation may be 30 days or more, 60 days or more, 90 days or more, or 120 days or more.

[0040] Also, in this specification, the thawing conditions for the conductive material for measuring viscosity are the conditions of storing it at 25°C. On the other hand, the method for thawing the above cryopreserved conductive material during the actual use of the conductive material is not particularly limited. Examples of the method for thawing the above cryopreserved conductive material during the actual use of the conductive material include a method of thawing under room temperature conditions, a method of thawing under refrigeration conditions, and a method of thawing under heating conditions. The above room temperature conditions are preferably 20°C or higher and 25°C or lower. The above refrigeration conditions are preferably higher than 0°C and 10°C or lower. The above heating conditions are preferably 30°C or higher and 35°C or lower.

[0041] The above conductive material can be used as a conductive paste, a conductive film, etc. The above conductive paste is preferably an anisotropic conductive paste, and the above conductive film is preferably an anisotropic conductive film. From the viewpoint of more efficiently arranging solder on the electrode, the above conductive material is preferably a conductive paste. The above conductive material is suitably used for the electrical connection of the electrode. The above conductive material is preferably a circuit connection material.

[0042] Hereinafter, each component contained in the above conductive material will be described. In this specification, “(meth)acrylic” means one or both of “acrylic” and “methacrylic”.

[0043] (Solder particles) The above conductive material contains solder particles. Both the central portion and the outer surface of the above solder particles are formed of solder. The above solder particles are particles in which both the central portion and the outer surface are solder. When conductive particles including base material particles formed of a material other than solder and a solder portion disposed on the surface of the base material particles are used instead of the above solder particles, it becomes difficult for the conductive particles to gather on the electrode. Further, in the above conductive particles, since the solder joint property between the conductive particles is low, the conductive particles that have moved onto the electrode tend to easily move outside the electrode, and the effect of suppressing the positional deviation between the electrodes also tends to be low.

[0044] From the viewpoint of continuously performing placement processes such as printing and efficiently placing solder on the electrode and enhancing the conduction reliability between the upper and lower electrodes to be connected, the acid value of the above solder particles is 0.3 mgKOH / g or more and 3 mgKOH / g or less.

[0045] The acid value of the above solder particles is preferably 0.5 mgKOH / g or more, more preferably 0.7 mgKOH / g or more, preferably 2.5 mgKOH / g or less, and more preferably 2.0 mgKOH / g or less. When the acid value of the above solder particles is equal to or higher than the above lower limit and equal to or lower than the above upper limit, the placement process such as printing can be continuously performed even better, the solder can be placed more efficiently on the electrode, and the conduction reliability between the upper and lower electrodes to be connected can be further enhanced.

[0046] The acid value of the above solder particles can be measured as follows.

[0047] Add 1 g of solder particles to 10 g of water and disperse them with ultrasonic waves for 1 minute. Then, using phenolphthalein as an indicator, titrate with a 0.1 mol / L potassium hydroxide ethanol solution.

[0048] Incidentally, it is considered that the acid value of the solder particles varies due to differences in the surface properties of the solder particles. And it is considered that differences in the surface properties of the solder particles cause differences in continuous printability and solder placement accuracy. When the acid value of the solder particles is lower than 0.3 mgKOH / g, it is considered that the solder particles are less likely to aggregate on the electrode and the placement accuracy deteriorates. When the acid value of the solder particles is higher than 3 mgKOH / g, a large number of acidic groups are present on the surface of the solder particles, and a reaction occurs with the resin in the conductive paste, resulting in an increase in viscosity and deterioration of printability and placement accuracy.

[0049] The solder is preferably a metal (low melting point metal) having a melting point of 450°C or lower. The solder particles are preferably metal particles (low melting point metal particles) having a melting point of 450°C or lower. The low melting point metal particles are particles containing a low melting point metal. The low melting point metal refers to a metal having a melting point of 450°C or lower. From the viewpoint of suppressing thermal degradation during the production of the connection structure, the melting point of the low melting point metal is preferably 400°C or lower, more preferably 350°C or lower, and still more preferably 300°C or lower. The solder particles are preferably low melting point solder having a melting point of less than 250°C.

[0050] From the viewpoint of more effectively exerting the effects of the present invention, the melting point of the solder particles is preferably 200°C or higher, more preferably 210°C or higher, and still more preferably 220°C or higher.

[0051] The melting point of the solder particles can be determined by differential scanning calorimetry (DSC). Examples of the differential scanning calorimetry (DSC) apparatus include "EXSTAR DSC7020" manufactured by SII.

[0052] Also, the solder particles preferably contain tin. Among 100% by weight of the metal contained in the solder particles, the content of tin is preferably 30% by weight or more, more preferably 40% by weight or more, still more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the tin content in the solder particles is equal to or higher than the above lower limit, the connection reliability between the solder portion and the electrode becomes even higher.

[0053] Incidentally, the tin content can be measured using a high-frequency inductively coupled plasma optical emission spectrometer ("ICP-AES" manufactured by Horiba, Ltd.) or a fluorescent X-ray analyzer ("EDX-800HS" manufactured by Shimadzu Corporation).

[0054] By using the above solder particles, the solder melts and joins to the electrode, and the solder portion conducts between the electrodes. For example, since the solder portion and the electrode are likely to be in surface contact rather than point contact, the connection resistance is reduced. Further, due to the use of the above solder particles, the bonding strength between the solder portion and the electrode increases, resulting in a further reduction in the likelihood of separation between the solder portion and the electrode, and a further increase in conduction reliability and connection reliability.

[0055] The low-melting-point metal constituting the above solder particles is not particularly limited. The low-melting-point metal is preferably tin or an alloy containing tin. Examples of the alloy include tin-silver alloy, tin-copper alloy, tin-silver-copper alloy, tin-bismuth alloy, tin-zinc alloy, and tin-indium alloy. Since it has excellent wettability with respect to the electrode, the low-melting-point metal is preferably tin, tin-silver alloy, tin-silver-copper alloy, tin-bismuth alloy, or tin-indium alloy. The low-melting-point metal is more preferably tin-bismuth alloy or tin-indium alloy.

[0056] The above solder particles are preferably filler metals having a liquidus temperature of 450°C or lower based on JIS Z3001: Welding Terms. Examples of the composition of the above solder particles include a metal composition containing zinc, gold, silver, lead, copper, tin, bismuth, indium, and the like. A tin-indium-based (117°C eutectic) or tin-bismuth-based (139°C eutectic) that is low-melting and lead-free is preferred. That is, the above solder particles preferably do not contain lead, and preferably contain tin and indium or tin and bismuth.

[0057] From the viewpoint of more effectively exhibiting the effects of the present invention, the above solder particles preferably contain tin and silver or tin and copper, and more preferably contain tin, silver, and copper.

[0058] In order to further increase the bonding strength between the solder portion and the electrode, the solder particles may contain metals such as nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium, cobalt, bismuth, manganese, chromium, molybdenum, and palladium. Further, from the viewpoint of further increasing the bonding strength between the solder portion and the electrode, it is preferable that the solder particles contain nickel, copper, antimony, aluminum or zinc. From the viewpoint of further increasing the bonding strength between the solder portion and the electrode, the content of these metals for increasing the bonding strength is preferably 0.0001% by weight or more and preferably 1% by weight or less based on 100% by weight of the metals contained in the solder particles.

[0059] From the viewpoint of performing the placement process such as printing more continuously and arranging the solder on the electrode more efficiently to enhance the conduction reliability between the upper and lower electrodes to be connected, the average particle diameter of the solder particles is less than 10 μm. In the present invention, even if the average particle diameter of the solder particles is small, the effects of the present invention can be effectively achieved.

[0060] The average particle diameter of the solder particles is preferably 0.1 μm or more, more preferably 2 μm or more, preferably 8 μm or less, and more preferably 5 μm or less. When the average particle diameter of the solder particles is equal to or greater than the lower limit and equal to or less than the upper limit, printing can be performed more continuously, the solder can be arranged on the electrode more efficiently, and the conduction reliability between the upper and lower electrodes to be connected can be enhanced. The average particle diameter of the solder particles may be 2 μm or less, may be 1 μm or less, or may be less than 1 μm. In the present invention, even if the average particle diameter of the solder particles is considerably small, the effects of the present invention can be effectively achieved.

[0061] The average particle diameter of the solder particles is preferably the number average particle diameter. The average particle diameter of the solder particles can be determined, for example, by observing 50 arbitrary solder particles with an electron microscope or an optical microscope and calculating the average value of the particle diameters of each solder particle, or by performing laser diffraction particle size distribution measurement.

[0062] In addition, as a method for adjusting the average particle diameter of the solder particles to the above-preferred range, examples include a method of pulverizing the solder particles with a jet mill or the like, and a sieving method using a sieve or the like.

[0063] The coefficient of variation (CV value) of the particle diameter of the solder particles is preferably 5% or more, more preferably 10% or more, preferably 40% or less, and more preferably 30% or less. When the coefficient of variation of the particle diameter of the solder particles is equal to or greater than the above lower limit and equal to or less than the above upper limit, the solder can be arranged on the electrode more efficiently. However, the CV value of the particle diameter of the solder particles may be less than 5%.

[0064] The coefficient of variation (CV value) can be measured as follows.

[0065] CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of the particle diameter of the solder particles Dn: Average value of the particle diameter of the solder particles

[0066] The shape of the solder particles is not particularly limited. The shape of the solder particles may be spherical, may be a shape other than spherical, or may be a shape such as a flat shape.

[0067] In 100% by weight of the conductive material, the content of the solder particles is preferably 40% by weight or more, more preferably 45% by weight or more, still more preferably 50% by weight or more, and particularly preferably 55% by weight or more, and is preferably 90% by weight or less, more preferably 85% by weight or less, and still more preferably 80% by weight or less. When the content of the solder particles is equal to or greater than the above lower limit and equal to or less than the above upper limit, the solder can be arranged on the electrode more efficiently, it is easy to arrange a large amount of solder between the electrodes, and the conduction reliability can be enhanced more effectively. From the viewpoint of further enhancing the conduction reliability, it is preferable that the content of the solder particles is larger.

[0068] (Thermosetting component) The conductive material according to the present invention contains a thermosetting component. The above conductive material may contain a thermosetting compound and a curing agent as the thermosetting component. In order to cure the conductive material better, it is preferable that the above conductive material contains a thermosetting compound and a curing agent as the thermosetting component. In order to cure the conductive material better, it is preferable that the above conductive material contains a curing accelerator as the thermosetting component.

[0069] (Thermosetting component: Thermosetting compound) The conductive material according to the present invention preferably contains a thermosetting compound. The above thermosetting compound is a compound that can be cured by heating.

[0070] The above thermosetting compound is not particularly limited. Examples of the above thermosetting compound include oxetane compounds, epoxy compounds, episulfide compounds, (meth)acrylic compounds, phenol compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. Only one kind of the above thermosetting compound may be used, or two or more kinds may be used in combination.

[0071] From the viewpoint of further improving the curability and viscosity of the conductive material and further enhancing the conduction reliability, the above thermosetting compound preferably contains an epoxy compound or an episulfide compound, more preferably contains an epoxy compound, even more preferably is an epoxy compound or an episulfide compound, and particularly preferably is an epoxy compound. The above thermosetting component preferably contains an epoxy compound or an episulfide compound, more preferably contains an epoxy compound. The above conductive material preferably contains an epoxy compound or an episulfide compound, more preferably contains an epoxy compound.

[0072] The above epoxy compound is a compound having at least one epoxy group. Examples of the above epoxy compound include bisphenol A type epoxy compound, bisphenol F type epoxy compound, bisphenol S type epoxy compound, phenol novolak type epoxy compound, biphenyl type epoxy compound, biphenyl novolak type epoxy compound, bisphenol type epoxy compound, naphthalene type epoxy compound, fluorene type epoxy compound, phenol aralkyl type epoxy compound, naphthol aralkyl type epoxy compound, dicyclopentadiene type epoxy compound, anthracene type epoxy compound, epoxy compound having an adamantane skeleton, epoxy compound having a tricyclodecane skeleton, naphthylene ether type epoxy compound, and epoxy compound having a triazine nucleus in the skeleton. Only one kind of the above epoxy compound may be used, or two or more kinds may be used in combination.

[0073] The above epoxy compound is liquid or solid at normal temperature (25°C). When the above epoxy compound is solid at normal temperature, the melting temperature of the above epoxy compound is preferably equal to or lower than the melting point of the above solder particles. By using the above preferred epoxy compound, at the stage of bonding the connection target members, the viscosity is high, and when an acceleration is applied due to an impact such as conveyance, the displacement between the first connection target member and the second connection target member can be suppressed. Furthermore, due to the heat during curing, the viscosity of the conductive material can be greatly reduced, and the aggregation of the solder during conductive connection can proceed efficiently.

[0074] From the viewpoint of more effectively arranging the solder on the electrode, the above thermosetting compound preferably contains a thermosetting compound having a polyether skeleton.

[0075] Examples of the above thermosetting compound having a polyether skeleton include a compound having glycidyl ether groups at both ends of an alkyl chain having 3 to 12 carbon atoms, and a polyether type epoxy compound having a polyether skeleton having 2 to 4 carbon atoms and having a structural unit in which 2 to 10 of the polyether skeletons are continuously bonded.

[0076] From the viewpoint of further effectively enhancing the heat resistance of the cured product, it is preferable that the above thermosetting compound contains a thermosetting compound having an isocyanuric skeleton.

[0077] Examples of the thermosetting compound having an isocyanuric skeleton include triisocyanurate type epoxy compounds, such as those of the TEPIC series (TEPIC-G, TEPIC-S, TEPIC-SS, TEPIC-HP, TEPIC-L, TEPIC-PAS, TEPIC-VL, TEPIC-UC) manufactured by Nissan Chemical Industries, Ltd.

[0078] From the viewpoints of more efficiently arranging solder on the electrode, more effectively enhancing the conduction reliability between the upper and lower electrodes to be connected, and more effectively suppressing the discoloration of the thermosetting compound, it is preferable that the above thermosetting compound has high heat resistance, and it is more preferable that it is a novolak type epoxy compound. The novolak type epoxy compound has relatively high heat resistance.

[0079] In 100% by weight of the above conductive material, the content of the above thermosetting compound is preferably 5% by weight or more, more preferably 8% by weight or more, still more preferably 10% by weight or more, preferably 99% by weight or less, more preferably 90% by weight or less, still more preferably 80% by weight or less, and particularly preferably 70% by weight or less. When the content of the above thermosetting compound is equal to or higher than the above lower limit and equal to or lower than the above upper limit, solder can be arranged more efficiently on the electrode, the insulation reliability between the electrodes can be more effectively enhanced, and the conduction reliability between the electrodes can be more effectively enhanced. From the viewpoint of more effectively enhancing the impact resistance, it is preferable that the content of the above thermosetting compound is higher.

[0080] In 100% by weight of the above conductive material, the content of the above epoxy compound is preferably 5% by weight or more, more preferably 8% by weight or more, still more preferably 10% by weight or more, preferably 99% by weight or less, more preferably 90% by weight or less, still more preferably 80% by weight or less, and particularly preferably 70% by weight or less. When the content of the above epoxy compound is not less than the above lower limit and not more than the above upper limit, solder can be arranged more efficiently on the electrode, the insulation reliability between the electrodes can be enhanced more effectively, and the conduction reliability between the electrodes can be enhanced more effectively. From the viewpoint of further enhancing the impact resistance, a larger content of the above epoxy compound is preferable.

[0081] (Thermosetting component: curing agent) The above conductive material may contain a curing agent. The above conductive material may contain a curing agent together with the above thermosetting compound. The above curing agent cures the above thermosetting compound.

[0082] The above curing agent is not particularly limited. Examples of the above curing agent include imidazole curing agents, phenol curing agents, thiol curing agents, amine curing agents, acid anhydride curing agents, thermo cationic curing agents, and thermal radical generators. Only one kind of the above curing agent may be used, or two or more kinds may be used in combination.

[0083] From the viewpoint of enabling the conductive material to be cured more rapidly at a low temperature, the above curing agent is preferably an imidazole curing agent, a thiol curing agent, or an amine curing agent. Further, from the viewpoint of enhancing the storage stability when the above thermosetting compound and the above curing agent are mixed, the above curing agent is preferably a latent curing agent. The latent curing agent is preferably a latent imidazole curing agent, a latent thiol curing agent, or a latent amine curing agent. Incidentally, the above curing agent may be coated with a polymer substance such as a polyurethane resin or a polyester resin.

[0084] The above imidazole curing agent is not particularly limited. Examples of the above imidazole curing agent include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine and 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole, 2-p-tolyl-4-methyl-5-hydroxymethylimidazole, 2-m-tolyl-4-methyl-5-hydroxymethylimidazole, 2-m-tolyl-4,5-dihydroxymethylimidazole, 2-p-tolyl-4,5-dihydroxymethylimidazole and other imidazole compounds in which the hydrogen at the 5-position of 1H-imidazole is replaced by a hydroxymethyl group and the hydrogen at the 2-position is replaced by a phenyl group or a tolyl group.

[0085] The above thiol curing agent is not particularly limited. Examples of the above thiol curing agent include trimethylolpropane tris-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, dipentaerythritol hexa-3-mercaptopropionate and the like.

[0086] The above amine curing agent is not particularly limited. Examples of the above amine curing agent include hexamethylenediamine, octamethylenediamine, decamethylenediamine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraspiro[5.5]undecane, bis(4-aminocyclohexyl)methane, metaphenylenediamine, diaminodiphenyl sulfone and the like.

[0087] The above acid anhydride curing agent is not particularly limited and can be widely used as long as it is an acid anhydride used as a curing agent for thermosetting compounds such as epoxy compounds. Examples of the above acid anhydride curing agents include phthalic anhydride, tetrahydrophthalic anhydride, trialkyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylbutenyltetrahydrophthalic anhydride, anhydrides of phthalic acid derivatives, maleic anhydride, nadic anhydride, methylnadic anhydride, glutaric anhydride, succinic anhydride, glycerin bisanhydrotrimellitic acid monoacetate, and bifunctional acid anhydride curing agents such as ethylene glycol bisanhydrotrimellitic acid, trifunctional acid anhydride curing agents such as trimellitic anhydride, and tetrafunctional or higher acid anhydride curing agents such as pyromellitic anhydride, benzophenone tetracarboxylic anhydride, methylcyclohexene tetracarboxylic anhydride, and polyazelainic anhydride.

[0088] The above thermal cation initiator is not particularly limited. Examples of the above thermal cation initiators include iodonium-based cation curing agents, oxonium-based cation curing agents, and sulfonium-based cation curing agents. Examples of the above iodonium-based cation curing agents include bis(4-tert-butylphenyl)iodonium hexafluorophosphate. Examples of the above oxonium-based cation curing agents include trimethyloxonium tetrafluoroborate. Examples of the above sulfonium-based cation curing agents include tri-p-tolylsulfonium hexafluorophosphate.

[0089] The above thermal radical generator is not particularly limited. Examples of the above thermal radical generators include azo compounds and organic peroxides. Examples of the above azo compounds include azobisisobutyronitrile (AIBN). Examples of the above organic peroxides include di-tert-butyl peroxide and methyl ethyl ketone peroxide.

[0090] The reaction start temperature of the above heat curing agent is preferably 50 °C or higher, more preferably 70 °C or higher, still more preferably 80 °C or higher, and preferably 250 °C or lower, more preferably 200 °C or lower, still more preferably 150 °C or lower, and particularly preferably 140 °C or lower. When the reaction start temperature of the above heat curing agent is equal to or higher than the above lower limit and equal to or lower than the above upper limit, solder is more efficiently arranged on the electrode. From the viewpoint of more efficiently arranging solder on the electrode and more effectively enhancing the conduction reliability between the upper and lower electrodes to be connected, the reaction start temperature of the above heat curing agent is particularly preferably 80 °C or higher and 140 °C or lower.

[0091] The reaction start temperature of the above heat curing agent means the temperature at the start of the rise of the exothermic peak in DSC. Examples of the DSC apparatus include "EXSTAR DSC7020" manufactured by SII Corporation.

[0092] The content of the above heat curing agent is not particularly limited. With respect to 100 parts by weight of the above thermosetting compound, the content of the above heat curing agent is preferably 0.01 part by weight or more, more preferably 1 part by weight or more, and preferably 200 parts by weight or less, more preferably 100 parts by weight or less, still more preferably 75 parts by weight or less. When the content of the above heat curing agent is equal to or higher than the above lower limit, it is easy to sufficiently cure the conductive material. When the content of the above heat curing agent is equal to or lower than the above upper limit, it is difficult for excess heat curing agent that did not participate in the curing to remain after curing, and the heat resistance of the cured product is further increased.

[0093] (Thermosetting component: Curing accelerator) The above conductive material may contain a curing accelerator. The above curing accelerator is not particularly limited. The above curing accelerator preferably acts as a curing catalyst in the reaction between the above thermosetting compound and the above heat curing agent. The above curing accelerator preferably acts as a curing catalyst in the reaction with the above thermosetting compound. Only one kind of the above curing accelerator may be used, or two or more kinds may be used in combination.

[0094] Examples of the above-mentioned curing accelerator include phosphonium salts, tertiary amines, tertiary amine salts, quaternary onium salts, tertiary phosphines, crown ether complexes, amine complex compounds, and phosphonium ylides. Specifically, examples of the above-mentioned curing accelerator include imidazole compounds, isocyanurates of imidazole compounds, dicyandiamide, derivatives of dicyandiamide, melamine compounds, derivatives of melamine compounds, diaminomaleonitrile, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, bis(hexamethylene)triamine, triethanolamine, diaminodiphenylmethane, amine compounds such as organic acid dihydrazide, 1,8-diazabicyclo[5,4,0]undecene-7, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5,5]undecane, boron trifluoride, boron trifluoride-amine complex compounds, and organic phosphorus compounds such as triphenylphosphine, tricyclohexylphosphine, tributylphosphine, and methyldiphenylphosphine.

[0095] The above-mentioned phosphonium salt is not particularly limited. Examples of the above-mentioned phosphonium salt include tetra-n-butylphosphonium bromide, tetra-n-butylphosphonium O,O-diethyldithiophosphate, methyltributylphosphonium dimethylphosphate, tetra-n-butylphosphonium benzotriazole, tetra-n-butylphosphonium tetrafluoroborate, and tetra-n-butylphosphonium tetraphenylborate.

[0096] The content of the above-mentioned curing accelerator is appropriately selected so that the above-mentioned thermosetting compound cures well. The content of the above-mentioned curing accelerator with respect to 100 parts by weight of the above-mentioned thermosetting compound is preferably 0.5 part by weight or more, more preferably 0.8 part by weight or more, preferably 10 parts by weight or less, and more preferably 8 parts by weight or less. When the content of the above-mentioned curing accelerator is equal to or greater than the above-mentioned lower limit and equal to or less than the above-mentioned upper limit, the above-mentioned thermosetting compound can be cured well. Further, when the content of the above-mentioned curing accelerator is equal to or greater than the above-mentioned lower limit and equal to or less than the above-mentioned upper limit, solder can be arranged more efficiently on the electrode, and the conduction reliability between the upper and lower electrodes to be connected can be enhanced more effectively.

[0097] (Flux) The above-mentioned conductive material contains flux. By using flux, solder can be arranged more efficiently on the electrode. The above-mentioned flux is not particularly limited. As the above-mentioned flux, a flux generally used for solder bonding or the like can be used.

[0098] Examples of the above-mentioned flux include zinc chloride, a mixture of zinc chloride and an inorganic halide, a mixture of zinc chloride and an inorganic acid, a molten salt, phosphoric acid, a derivative of phosphoric acid, an organic halide, hydrazine, an amine compound, an organic acid, and rosin. The above-mentioned flux may be used alone or in combination of two or more.

[0099] Examples of the above-mentioned molten salt include ammonium chloride. Examples of the above-mentioned organic acid include lactic acid, citric acid, stearic acid, glutamic acid, and glutaric acid. Examples of the above-mentioned rosin include activated rosin and non-activated rosin. The above-mentioned flux is preferably an organic acid having two or more carboxyl groups or rosin. The above-mentioned flux may be an organic acid having two or more carboxyl groups or rosin. The use of an organic acid having two or more carboxyl groups or rosin further enhances the conduction reliability between the electrodes.

[0100] Examples of the organic acid having two or more carboxyl groups include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid.

[0101] Examples of the amine compound include cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, imidazole, benzimidazole, phenylimidazole, carboxybenzimidazole, benzotriazole, and carboxybenzotriazole.

[0102] The above-mentioned rosin is rosins mainly composed of abietic acid. Examples of the above-mentioned rosins include abietic acid and acrylic modified rosin. The flux is preferably rosins, and more preferably abietic acid. By using this preferred flux, the conduction reliability between electrodes is further enhanced.

[0103] The active temperature (melting point) of the above-mentioned flux is preferably 50°C or higher, more preferably 70°C or higher, still more preferably 80°C or higher, preferably 200°C or lower, more preferably 190°C or lower, even more preferably 160°C or lower, still more preferably 150°C or lower, and particularly preferably 140°C or lower. When the active temperature of the above-mentioned flux is above the above lower limit and below the above upper limit, the flux effect is more effectively exerted, and the solder can be arranged on the electrode more efficiently.

[0104] The melting point of the above-mentioned flux can be determined by differential scanning calorimetry (DSC). Examples of the differential scanning calorimetry (DSC) apparatus include "EXSTAR DSC7020" manufactured by SII.

[0105] Also, the boiling point of the above-mentioned flux is preferably 200°C or lower.

[0106] From the perspective of arranging solder on the electrode more efficiently, the melting point of the flux is preferably higher than the reaction start temperature of the thermosetting agent, more preferably 5°C or higher, and even more preferably 10°C or higher.

[0107] The flux may be dispersed in the conductive material or may adhere to the surface of the solder particles.

[0108] The flux is preferably a flux that releases cations upon heating. By using a flux that releases cations upon heating, solder can be arranged on the electrode more efficiently.

[0109] Examples of the flux that releases cations upon heating include the above-mentioned thermal cation initiator (thermal cation curing agent).

[0110] From the perspective of arranging solder on the electrode more efficiently, enhancing insulation reliability more effectively, and enhancing conduction reliability more effectively, the flux is preferably a salt of an acid compound and a base compound.

[0111] The acid compound is preferably an organic compound having a carboxyl group. Examples of the acid compound include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, citric acid, malic acid, which are aliphatic carboxylic acids, cyclohexylcarboxylic acid, 1,4-cyclohexyl dicarboxylic acid, which are cyclic aliphatic carboxylic acids, isophthalic acid, terephthalic acid, trimellitic acid, and ethylenediaminetetraacetic acid, which are aromatic carboxylic acids. From the perspective of arranging solder on the electrode more efficiently, enhancing insulation reliability more effectively, and enhancing conduction reliability more effectively, the acid compound is preferably glutaric acid, cyclohexylcarboxylic acid, or adipic acid.

[0112] The above base compound is preferably an organic compound having an amino group. Examples of the above base compound include diethanolamine, triethanolamine, methyldiethanolamine, ethyldiethanolamine, cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, 2-methylbenzylamine, 3-methylbenzylamine, 4-tert-butylbenzylamine, N-methylbenzylamine, N-ethylbenzylamine, N-phenylbenzylamine, N-tert-butylbenzylamine, N-isopropylbenzylamine, N,N-dimethylbenzylamine, imidazole compounds, and triazole compounds. From the viewpoints of more efficiently arranging solder on the electrode, more effectively enhancing insulation reliability, and more effectively enhancing conduction reliability, the above base compound is preferably benzylamine.

[0113] In 100% by weight of the above conductive material, the content of the above flux is preferably 0.5% by weight or more, preferably 30% by weight or less, and more preferably 25% by weight or less. When the content of the above flux is within the above lower limit and the above upper limit, it becomes more difficult to form an oxide film on the surfaces of the solder and the electrode, and furthermore, the oxide film formed on the surfaces of the solder and the electrode can be more effectively removed.

[0114] (Filler) The above conductive material may contain a filler. The above filler may be an organic filler or an inorganic filler. By the above conductive material containing a filler, the solder can be more uniformly aggregated on all the electrodes of the substrate. Also, by the above conductive material containing a filler, the above solder particles can be more uniformly dispersed in the above conductive material.

[0115] The above conductive material preferably does not contain the above filler or contains the above filler in an amount of 5% by weight or less. When the above thermosetting compound is used, the smaller the content of the filler, the easier it is for the solder particles to move on the electrode.

[0116] In 100% by weight of the above conductive material, the content of the above filler is preferably 0% by weight (not contained) or more, preferably 5% by weight or less, more preferably 2% by weight or less, and still more preferably 1% by weight or less. When the content of the above filler is within the above lower limit and the above upper limit, the solder is more uniformly arranged on the electrode.

[0117] (Other components) The above conductive material may, if necessary, contain various additives such as fillers, extenders, softeners, plasticizers, thixotropic agents, leveling agents, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, and flame retardants.

[0118] (Connection structure and method for manufacturing connection structure) The connection structure according to the present invention includes a first connection target member having a first electrode on its surface, a second connection target member having a second electrode on its surface, the first connection target member, and a connection portion connecting the first connection target member and the second connection target member. In the connection structure according to the present invention, the material of the connection portion is the above-described conductive material. In the connection structure according to the present invention, the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

[0119] The method for manufacturing a connection structure according to the present invention includes a step of disposing the above-described conductive material on the surface of a first connection target member having a first electrode on its surface using the above-described conductive material. The method for manufacturing a connection structure according to the present invention includes a step of disposing a second connection target member having a second electrode on its surface on the surface of the conductive material opposite to the first connection target member side of the conductive material so that the first electrode and the second electrode face each other. The method for manufacturing a connection structure according to the present invention includes a step of heating the conductive material to a temperature equal to or higher than the melting point of the solder particles to form a connection portion connecting the first connection target member and the second connection target member with the conductive material and electrically connecting the first electrode and the second electrode by a solder portion in the connection portion.

[0120] In the connection structure and the method for manufacturing the connection structure according to the present invention, since a specific conductive material is used, solder particles are likely to gather between the first electrode and the second electrode, and the solder can be efficiently arranged on the electrodes (lines). In addition, it is difficult for a part of the solder to be arranged in a region (space) where no electrode is formed, and the amount of solder arranged in the region where no electrode is formed can be significantly reduced. Therefore, the conduction reliability between the first electrode and the second electrode can be enhanced. Moreover, electrical connection between laterally adjacent electrodes that should not be connected can be prevented, and the insulation reliability can be enhanced.

[0121] In addition, in order to more efficiently arrange the solder on the electrodes and significantly reduce the amount of solder arranged in the region where no electrode is formed, it is preferable to use a conductive paste as the conductive material instead of a conductive film.

[0122] The thickness of the solder part between the electrodes is preferably 10 μm or more, more preferably 20 μm or more, preferably 100 μm or less, and more preferably 80 μm or less. The solder wetting area on the surface of the electrode (the area where the solder is in contact in 100% of the exposed area of the electrode) is preferably 50% or more, more preferably 70% or more, and preferably 100% or less.

[0123] In the method for manufacturing the connection structure according to the present invention, in the step of arranging the second connection target member and the step of forming the connection portion, pressurization is not performed, and it is preferable that the weight of the second connection target member is applied to the conductive material. In the method for manufacturing the connection structure according to the present invention, in the step of arranging the second connection target member and the step of forming the connection portion, it is preferable that a pressurizing pressure exceeding the force of the weight of the second connection target member is not applied to the conductive material. In these cases, in a plurality of solder portions, the uniformity of the solder amount can be further enhanced. Furthermore, the thickness of the solder portion can be made even thicker more effectively, a large number of solder particles are likely to gather between the electrodes, and a plurality of solder particles can be arranged more efficiently on the electrodes (lines). Also, a part of the plurality of solder particles is difficult to be arranged in a region (space) where no electrode is formed, and the amount of solder arranged in the region where no electrode is formed can be made even less. Therefore, the conduction reliability between the electrodes can be further enhanced. Moreover, the electrical connection between adjacent electrodes in the lateral direction that should not be connected can be further prevented, and the insulation reliability can be further enhanced.

[0124] Also, if a conductive paste is used instead of a conductive film, it becomes easy to adjust the thickness of the connection portion and the solder portion according to the coating amount of the conductive paste. On the other hand, in the case of a conductive film, there is a problem that in order to change or adjust the thickness of the connection portion, it is necessary to prepare conductive films of different thicknesses or a conductive film of a predetermined thickness. Also, in a conductive film, compared with a conductive paste, it is difficult to sufficiently lower the melt viscosity of the conductive film at the melting temperature of the solder particles, and there is a tendency that the aggregation of the solder particles is easily inhibited.

[0125] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0126] FIG. 1 is a cross-sectional view schematically showing a connection structure obtained using a conductive material according to an embodiment of the present invention.

[0127] The connection structure 1 shown in Fig. 1 includes a first connection target member 2, a second connection target member 3, and a connection portion 4 that connects the first connection target member 2 and the second connection target member 3. The connection portion 4 is formed of the above-described conductive material. In the present embodiment, the conductive material includes a thermosetting component, a plurality of solder particles, and a flux. The thermosetting component includes a thermosetting compound and a thermosetting agent. In the present embodiment, a conductive paste is used as the conductive material.

[0128] The connection portion 4 has a solder portion 4A in which a plurality of solder particles are gathered and joined to each other, and a cured product portion 4B in which the thermosetting component is thermoset.

[0129] The first connection target member 2 has a plurality of first electrodes 2a on its surface (upper surface). The second connection target member 3 has a plurality of second electrodes 3a on its surface (lower surface). The first electrode 2a and the second electrode 3a are electrically connected by the solder portion 4A. Therefore, the first connection target member 2 and the second connection target member 3 are electrically connected by the solder portion 4A. In the connection portion 4, in a region different from the solder portion 4A where the first electrode 2a and the second electrode 3a gather (the cured product portion 4B portion), there is no solder. In a region different from the solder portion 4A (the cured product portion 4B portion), there is no solder separated from the solder portion 4A. Note that, even if it is a small amount, solder may be present in a region different from the solder portion 4A where the first electrode 2a and the second electrode 3a gather (the cured product portion 4B portion). It is preferable that the solder wets and spreads on the surface of the electrode, and it is not necessarily required that the solder gathers between the upper and lower electrodes.

[0130] As shown in FIG. 1, in the connection structure 1, a plurality of solder particles gather between the first electrode 2a and the second electrode 3a. After the plurality of solder particles are melted, the melt of the solder particles wets and spreads on the surface of the electrodes and then solidifies to form the solder portion 4A. Therefore, the connection areas of the solder portion 4A with the first electrode 2a and the solder portion 4A with the second electrode 3a become larger. That is, by using solder particles, the contact areas of the solder portion 4A with the first electrode 2a and the solder portion 4A with the second electrode 3a are larger than those in the case of using conductive particles whose outer surfaces are metals such as nickel, gold, or copper. This also increases the conduction reliability and connection reliability in the connection structure 1. Note that the flux contained in the conductive material generally gradually deactivates upon heating.

[0131] In the connection structure 1 shown in FIG. 1, all of the solder portion 4A is located in the opposing region between the first and second electrodes 2a and 3a. The connection structure 1X of the modified example shown in FIG. 3 differs from the connection structure 1 shown in FIG. 1 only in the connection portion 4X. The connection portion 4X has a solder portion 4XA and a cured product portion 4XB. In the connection structure 1X, most of the solder portion 4XA is located in the opposing region between the first and second electrodes 2a and 3a, and a part of the solder portion 4XA may protrude laterally from the opposing region between the first and second electrodes 2a and 3a. The solder portion 4XA protruding laterally from the opposing region between the first and second electrodes 2a and 3a is a part of the solder portion 4XA and is not solder separated from the solder portion 4XA. In the present embodiment, the amount of solder separated from the solder portion can be reduced, but the solder separated from the solder portion may be present in the cured product portion.

[0132] If the amount of solder particles used is reduced, it becomes easier to obtain the connection structure 1. If the amount of solder particles used is increased, it becomes easier to obtain the connection structure 1X.

[0133] In the connection structures 1 and 1X, when looking at the portion where the first electrode 2a and the second electrode 3a face each other in the stacking direction of the first electrode 2a, the connection portions 4 and 4X, and the second electrode 3a, it is preferable that the solder portions 4A and 4XA in the connection portions 4 and 4X are arranged in 50% or more of the area of 100% of the portion where the first electrode 2a and the second electrode 3a face each other. By the solder portions 4A and 4XA in the connection portions 4 and 4X satisfying the above preferable mode, the conduction reliability can be further enhanced.

[0134] When looking at the portion where the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connection portion, and the second electrode, it is preferable that the solder portion in the connection portion is arranged in 50% or more of the area of 100% of the portion where the first electrode and the second electrode face each other. When looking at the portion where the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connection portion, and the second electrode, it is more preferable that the solder portion in the connection portion is arranged in 60% or more of the area of 100% of the portion where the first electrode and the second electrode face each other. When looking at the portion where the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connection portion, and the second electrode, it is further preferable that the solder portion in the connection portion is arranged in 70% or more of the area of 100% of the portion where the first electrode and the second electrode face each other. When looking at the portion where the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connection portion, and the second electrode, it is particularly preferable that the solder portion in the connection portion is arranged in 80% or more of the area of 100% of the portion where the first electrode and the second electrode face each other. When looking at the portion where the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connection portion, and the second electrode, it is most preferable that the solder portion in the connection portion is arranged in 90% or more of the area of 100% of the portion where the first electrode and the second electrode face each other. By the solder portion in the connection portion satisfying the above preferable mode, the conduction reliability can be further enhanced.

[0135] When looking at the portion where the first electrode and the second electrode face each other in a direction orthogonal to the lamination direction of the first electrode, the connection portion, and the second electrode, it is preferable that 60% or more of the solder portion in the connection portion is arranged in the portion where the first electrode and the second electrode face each other. When looking at the portion where the first electrode and the second electrode face each other in a direction orthogonal to the lamination direction of the first electrode, the connection portion, and the second electrode, it is more preferable that 70% or more of the solder portion in the connection portion is arranged in the portion where the first electrode and the second electrode face each other. When looking at the portion where the first electrode and the second electrode face each other in a direction orthogonal to the lamination direction of the first electrode, the connection portion, and the second electrode, it is further preferable that 90% or more of the solder portion in the connection portion is arranged in the portion where the first electrode and the second electrode face each other. When looking at the portion where the first electrode and the second electrode face each other in a direction orthogonal to the lamination direction of the first electrode, the connection portion, and the second electrode, it is particularly preferable that 95% or more of the solder portion in the connection portion is arranged in the portion where the first electrode and the second electrode face each other. When looking at the portion where the first electrode and the second electrode face each other in a direction orthogonal to the lamination direction of the first electrode, the connection portion, and the second electrode, it is most preferable that 99% or more of the solder portion in the connection portion is arranged in the portion where the first electrode and the second electrode face each other. By the solder portion in the connection portion satisfying the above preferable modes, the conduction reliability can be further enhanced.

[0136] Next, in FIG. 2, an example of a method for manufacturing the connection structure 1 using the conductive material according to an embodiment of the present invention will be described.

[0137] First, prepare a first connection target member 2 having a first electrode 2a on its surface (upper surface). Next, as shown in FIG. 2(a), on the surface of the first connection target member 2, arrange a conductive material 11 containing a thermosetting component 11B, a plurality of solder particles 11A, and a flux (first step). In the used conductive material 11, as the thermosetting component 11B, it contains a thermosetting compound and a thermosetting agent. In the present embodiment, the conductive material 11 is a conductive paste.

[0138] Arrange the conductive material 11 on the surface of the first connection target member 2 where the first electrode 2a is provided. After the arrangement of the conductive material 11, the solder particles 11A are arranged both on the first electrode 2a (line) and on the region (space) where the first electrode 2a is not formed. Note that the above conductive material may be arranged only on the surface of the first electrode.

[0139] The method of arranging the conductive material 11 is not particularly limited, and examples include coating by a dispenser, screen printing, and ejection by an inkjet device.

[0140] Also, prepare a second connection target member 3 having a second electrode 3a on its surface (lower surface). Next, as shown in FIG. 2(b), on the conductive material 11 on the surface of the first connection target member 2, arrange the second connection target member 3 on the surface of the conductive material 11 opposite to the first connection target member 2 side (second step). Arrange the second connection target member 3 from the side of the second electrode 3a on the surface of the conductive material 11. At this time, the first electrode 2a and the second electrode 3a are opposed to each other.

[0141] Next, the conductive material 11 is heated to a temperature equal to or higher than the melting point of the solder particles 11A (third step). Preferably, the conductive material 11 is heated to a temperature equal to or higher than the curing temperature of the thermosetting component 11B (thermosetting compound). During this heating, the solder particles 11A that were present in the region where no electrode was formed gather between the first electrode 2a and the second electrode 3a (self-aggregation effect). When a conductive paste is used instead of a conductive film, the solder particles 11A gather more effectively between the first electrode 2a and the second electrode 3a. Also, the solder particles 11A melt and join to each other. Further, the thermosetting component 11B cures. As a result, as shown in FIG. 2(c), a connection portion 4 that connects the first connection target member 2 and the second connection target member 3 is formed of the conductive material 11. The connection portion 4 is formed of the conductive material 11, a solder portion 4A is formed by joining a plurality of solder particles 11A, and a cured product portion 4B is formed by curing of the thermosetting component 11B. If the solder particles 11A move sufficiently, the temperature does not have to be kept constant from the start of movement of the solder particles 11A that are not located between the first electrode 2a and the second electrode 3a until the movement of the solder particles 11A between the first electrode 2a and the second electrode 3a is completed.

[0142] In the present embodiment, since a specific conductive material 11 is used, occurrence of bleeding and blurring of the conductive material can be effectively suppressed even if screen printing is repeated. Also, in the present embodiment, since a specific conductive material 11 is used, the shape of the conductive material after printing can be maintained. As a result, the solder particles 11A can be arranged more efficiently between the electrodes to be connected, and the conduction reliability and insulation reliability can be enhanced more effectively. Note that the conductive material according to the present invention can also be used by a method other than printing such as screen printing.

[0143] In the above-described second step and the above-described third step, it is preferable not to apply pressure. In this case, the weight of the second connection target member 3 is applied to the conductive material 11. Therefore, when forming the connection portion 4, the solder particles 11A gather more effectively between the first electrode 2a and the second electrode 3a. Note that if pressure is applied in at least one of the above-described second step and the above-described third step, the tendency for the solder particles 11A to gather between the first electrode 2a and the second electrode 3a is likely to be inhibited.

[0144] Also, in this embodiment, since no pressure is applied, even when the first connection target member 2 and the second connection target member 3 are overlapped in a state where the alignment between the first electrode 2a and the second electrode 3a is slightly deviated, the slight deviation can be corrected to connect the first electrode 2a and the second electrode 3a (self-alignment effect). This is because the molten solder self-aggregated between the first electrode 2a and the second electrode 3a becomes energetically more stable when the area where the solder between the first electrode 2a and the second electrode 3a contacts the other components of the conductive material is minimized. Therefore, a force acts to form a connection structure with alignment, which is the connection structure with the minimum area. At this time, it is desirable that the conductive material is not cured and that the viscosity of the components other than the solder particles of the conductive material is sufficiently low at that temperature and time.

[0145] In this way, the connection structure 1 shown in FIG. 1 is obtained. Note that the above-described second step and the above-described third step may be performed continuously. Also, after performing the above-described second step, the laminate of the obtained first connection target member 2, the conductive material 11, and the second connection target member 3 may be moved to a heating unit to perform the above-described third step. To perform the above heating, the laminate may be disposed on a heating member, or the laminate may be disposed in a heated space.

[0146] The heating temperature in the above-described third step is preferably 230°C or higher, more preferably 250°C or higher, preferably 450°C or lower, more preferably 350°C or lower, and even more preferably 300°C or lower.

[0147] As the heating method in the above-described third step, there are methods of heating the entire connection structure using a reflow furnace or an oven to a temperature equal to or higher than the melting point of the solder and equal to or higher than the curing temperature of the thermosetting component, and methods of locally heating only the connection portion of the connection structure.

[0148] Examples of the instrument used for the method of locally heating include a hot plate, a heat gun for applying hot air, a soldering iron, and an infrared heater.

[0149] Also, when locally heating with a hot plate, it is preferable to form the upper surface of the hot plate with a metal having high thermal conductivity directly below the connection portion, and with a material having low thermal conductivity such as a fluororesin at other locations where heating is not preferable.

[0150] The above-described first and second connection target members are not particularly limited. Specifically, examples of the first and second connection target members include electronic components such as semiconductor chips, semiconductor packages, LED chips, LED packages, capacitors, and diodes, and circuit boards such as resin films, printed circuit boards, flexible printed circuit boards, flexible flat cables, rigid-flexible boards, glass epoxy boards, and glass boards. The first and second connection target members are preferably electronic components.

[0151] It is preferable that at least one of the above-described first connection target member and the above-described second connection target member is a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid-flexible substrate. Resin films, flexible printed circuit boards, flexible flat cables, and rigid-flexible substrates have the properties of high flexibility and relatively low weight. When a conductive film is used for connecting such connection target members, solder particles tend not to gather on the electrodes. On the other hand, by using a conductive paste, even when a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid-flexible substrate is used, the reliability of electrical conduction between the electrodes can be sufficiently enhanced by efficiently gathering solder particles on the electrodes. When using a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid-flexible substrate, the effect of improving the electrical conduction reliability between the electrodes without applying pressure is more effectively obtained compared to the case of using other connection target members such as semiconductor chips.

[0152] Examples of the electrodes provided on the connection target member include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes. When the connection target member is a flexible printed circuit board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, a silver electrode, or a copper electrode. When the connection target member is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, a silver electrode, or a tungsten electrode. When the electrode is an aluminum electrode, it may be an electrode formed only of aluminum or an electrode in which an aluminum layer is laminated on the surface of a metal oxide layer. Examples of the material of the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal element include Sn, Al, and Ga.

[0153] In the connection structure according to the present invention, it is preferable that the first electrode and the second electrode are arranged in an area array or peripherally. When the first electrode and the second electrode are arranged in an area array or peripherally, solder can be more effectively aggregated on the electrodes. The area array refers to a structure in which electrodes are arranged in a grid pattern on the surface where the electrodes of the connection target member are arranged. The periphery refers to a structure in which electrodes are arranged on the outer peripheral portion of the connection target member. In the case of a structure in which the electrodes are arranged in a comb shape, solder may aggregate along the direction perpendicular to the comb, whereas in the area array or peripheral structure, it is necessary for the solder to aggregate uniformly over the entire surface on which the electrodes are arranged. Therefore, in the conventional method, the amount of solder tends to be non-uniform, whereas in the method of the present invention, solder can be aggregated uniformly over the entire surface.

[0154] Hereinafter, the present invention will be specifically described with reference to examples and comparative examples. The present invention is not limited only to the following examples.

[0155] Thermosetting component (thermosetting compound): Thermosetting compound 1: Phenol novolac type epoxy compound, "DEN431" manufactured by DOW Thermosetting compound 2: Bisphenol A type epoxy compound, "DER354" manufactured by DOW Thermosetting compound 3: Bisphenol F type epoxy compound, "YDF-8170C" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.

[0156] Thermosetting component (curing accelerator): Curing accelerator 1: Boron trifluoride - monoethylamine complex, "BF3-MEA" manufactured by Tokyo Chemical Industry Co., Ltd.

[0157] Solder particles: Solder particle 1: Sn96.5Ag3Cu0.5 solder particles (average particle diameter 5 μm, acid value 1.5 mgKOH / g) Solder particle 2: Sn96.5Ag3Cu0.5 solder particles (average particle diameter 2 μm, acid value 1.5 mgKOH / g) Solder particle 3: Sn96.5Ag3Cu0.5 solder particle (average particle diameter 0.1 μm, acid value 1.5 mgKOH / g) Solder particle 4: Sn96.5Ag3Cu0.5 solder particle (average particle diameter 2 μm, acid value 0.1 mgKOH / g) Solder particle 5: Sn96.5Ag3Cu0.5 solder particle (average particle diameter 2 μm, acid value 3.5 mgKOH / g) Solder particle 6: Sn96.5Ag3Cu0.5 solder particle (average particle diameter 10 μm, acid value 1.5 mgKOH / g)

[0158] The average particle diameter and acid value of the solder particles are the values measured by the method described below.

[0159] Flux: Flux 1: "Benzylamine adipate", melting point 171 °C, solid at 23 °C Production method of Flux 1: 45 g of water and 75 g of ethanol, which are reaction solvents, and 13.89 g of adipic acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a glass bottle and dissolved at room temperature until uniform. Then, 10.715 g of benzylamine (manufactured by Wako Pure Chemical Industries, Ltd.) was added and stirred for about 5 minutes to obtain a mixed solution. The obtained mixed solution was placed in a refrigerator at 5 °C to 10 °C and left overnight. The precipitated crystals were separated by filtration, washed with water, and dried in vacuo to obtain Flux 1.

[0160] (Examples 1 to 6 and Comparative Examples 1 to 3) (1) Preparation of conductive material (anisotropic conductive paste) The components shown in Tables 1 and 2 below were blended in the blending amounts shown in Tables 1 and 2 below to obtain a conductive material (anisotropic conductive paste).

[0161] (2) Preparation of connection structure As the first connection target member, a glass epoxy substrate (FR-4 substrate, thickness 0.6 mm) having a copper electrode pattern (L / S: 50 μm / 50 μm, electrode length: 3 mm, electrode thickness: 12 μm) on the upper surface was prepared.

[0162] As the second connection target member, a flexible printed circuit board (formed of polyimide, thickness 0.1 mm) having a copper electrode pattern (L / S: 50 μm / 50 μm, electrode length: 3 mm, electrode thickness: 12 μm) on the lower surface was prepared.

[0163] On the upper surface of the glass epoxy substrate, the conductive material (anisotropic conductive paste) immediately after production was printed by screen printing to a thickness of 100 μm to form a conductive material (anisotropic conductive paste) layer. Next, a flexible printed circuit board was laminated on the upper surface of the conductive material (anisotropic conductive paste) layer so that the electrodes faced each other. The weight of the flexible printed circuit board was applied to the conductive material (anisotropic conductive paste) layer. From that state, the temperature of the conductive material (anisotropic conductive paste) layer was heated so as to reach the melting point of the solder particles 5 seconds after the start of temperature rise. Further, 15 seconds after the start of temperature rise, the temperature of the conductive material (anisotropic conductive paste) layer was heated to 200 °C to cure the conductive material (anisotropic conductive paste) layer, and a connection structure was obtained. During heating, pressure was not applied.

[0164] (Evaluation) (1) Average particle diameter of solder particles The average particle diameter of the solder particles was measured using a laser diffraction particle size distribution measuring device ("LA-920" manufactured by Horiba, Ltd.).

[0165] (2) Acid value of solder particles 1 g of solder particles was added to 10 g of water and dispersed by ultrasonic waves for 1 minute. Thereafter, using phenolphthalein as an indicator, it was titrated with a 0.1 mol / L potassium hydroxide ethanol solution.

[0166] (3) Viscosity (η25) of the conductive material at 25 °C immediately after production The viscosity (η25) at 25 °C and 5 rpm immediately after production of the obtained conductive material (anisotropic conductive paste) was measured using an E-type viscometer ("TVE22L" manufactured by Toki Sangyo Co., Ltd.).

[0167] [Criteria for viscosity (η25)] ○○: 120 Pa·s or more and 180 Pa·s or less ○: 100 Pa·s or more and less than 120 Pa·s, or more than 180 Pa·s and 200 Pa·s or less ×: Less than 100 Pa·s, or more than 200 Pa·s

[0168] (4) Thaw the frozen conductive material, and measure the viscosity (ηA) of the conductive material at 25°C immediately after reaching 25°C The obtained conductive material (anisotropic conductive paste) was stored frozen at -40°C for 7 days. Next, the frozen conductive material was stored at 25°C and thawed. The viscosity (ηA) of the conductive material at 25°C and 5 rpm immediately after thawing the frozen conductive material was measured using an E-type viscometer ("TVE22L" manufactured by Toki Sangyo Co., Ltd.).

[0169] [Judgment criteria for viscosity (ηA)] ○○: 120 Pa·s or more and 180 Pa·s or less ○: 100 Pa·s or more and less than 120 Pa·s, or more than 180 Pa·s and 200 Pa·s or less ×: Less than 100 Pa·s, or more than 200 Pa·s

[0170] (5) Thaw the frozen conductive material, and measure the viscosity (ηB) of the conductive material at 25°C after storing it at 25°C and 50% RH for 24 hours The obtained conductive material (anisotropic conductive paste) was stored frozen at -40°C for 7 days. Next, the frozen conductive material was stored at 25°C and thawed. Then, it was stored at 25°C and 50% RH for 24 hours. The viscosity (ηB) of the conductive material at 25°C and 5 rpm after 24 hours of storage was measured using an E-type viscometer ("TVE22L" manufactured by Toki Sangyo Co., Ltd.).

[0171] Also, from the obtained values of viscosity (ηA) and viscosity (ηB), the ratio (viscosity (ηB) / viscosity (ηA)) was calculated.

[0172] [Judgment criteria for viscosity (ηB)] ○○: Viscosity (ηB) is 120 Pa·s or more and 180 Pa·s or less ○: Viscosity (ηB) is 100 Pa·s or more and less than 120 Pa·s, or exceeds 180 Pa·s and is 300 Pa·s or less ×: Viscosity (ηB) is less than 100 Pa·s or exceeds 300 Pa·s

[0173] [Judgment criteria for ratio (viscosity (ηB) / viscosity (ηA))] ○○: Ratio (viscosity (ηB) / viscosity (ηA)) is 1.0 or more and 1.5 or less ○: Ratio (viscosity (ηB) / viscosity (ηA)) is 0.8 or more and less than 1.0, or exceeds 1.5 and is 2.0 or less ×: Ratio (viscosity (ηB) / viscosity (ηA)) is less than 0.8 or exceeds 2.0

[0174] (6) Solder placement accuracy on the electrode In the obtained connection structure, when looking at the portion where the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connection part, and the second electrode, the ratio X of the area where the solder part in the connection part is arranged in the area of 100% of the facing part of the first electrode and the second electrode was evaluated. The solder placement accuracy on the electrode was judged according to the following criteria.

[0175] [Judgment criteria for solder placement accuracy on the electrode] ○○: Ratio X is 70% or more ○: Ratio X is 50% or more and less than 70% ×: Ratio X is less than 50%

[0176] (7) Continuous printability Regarding the obtained conductive material, screen printing was performed on a slide glass using a metal mask with a size of 130 mm × 175 mm per opening and a thickness of 40 μm. Regarding the printed pattern, the printed surface immediately after printing was observed visually and with a stereomicroscope, and the dimensions were measured to confirm whether bleeding or smearing occurred. Screen printing was continuously performed, and the number of times that printing could be performed without bleeding or smearing was confirmed, and the continuous printability was judged according to the following criteria.

[0177] [Judgment criteria for bleeding or smearing] [Bleeding]: When there are parts that are 20% or more thicker than the plate-making dimensions immediately after printing [Chipping]: When there are parts that are 20% or more missing compared to the plate-making dimensions immediately after printing

[0178] [Criteria for continuous printability] ○○: It is possible to print 25 times or more without bleeding or chipping ○: It is possible to print 11 times or more and 24 times or less without bleeding or chipping ×: It is possible to print 10 times or less without bleeding or chipping

[0179] The details and results are shown in Tables 1 and 2 below. In Tables 1 and 2, the viscosity (η25) is the viscosity of the conductive material at 25°C immediately after preparation. In Tables 1 and 2, the viscosity (ηA) is the viscosity of the conductive material at 25°C immediately after thawing the frozen-stored conductive material and reaching 25°C. In Tables 1 and 2, the viscosity (ηB) is the viscosity of the conductive material at 25°C after thawing the above-mentioned frozen-stored conductive material and storing it at 25°C and 50% RH for 24 hours.

[0180]

Table 1

[0181]

Table 2

[0182] Also, in the obtained connection structure, by observing the connection part with a scanning electron microscope, it was confirmed whether voids were generated in the connection part. As a result, no voids were generated in the connection structures obtained in Examples 1 to 6.

[0183] Similar tendencies were also observed when using a flexible printed circuit board, a resin film, a flexible flat cable, and a rigid-flexible printed circuit board.

Explanation of symbols

[0184] 1, 1X… Connection structure 2…First connection target member 2a…First electrode 3…Second connection target member 3a…Second electrode 4, 4X…Connection part 4A, 4XA…Solder part 4B, 4XB…Hardened part 11…Conductive material 11A…Solder particles 11B…Thermosetting component

Claims

1. A conductive material containing a thermosetting component, a plurality of solder particles, and a flux, wherein an average particle diameter of the solder particles is 5 μm or less, wherein an acid value of the solder particles is 0.3 mgKOH / g or more and 3 mgKOH / g or less, and a viscosity of the conductive material at 25°C immediately after thawing the conductive material stored frozen and reaching 25°C is 100 Pa·s or more and 200 Pa·s or less.

2. The conductive material according to claim 1, wherein a viscosity of the conductive material at 25°C after thawing the conductive material stored frozen and storing it at 25°C and 50% RH for 24 hours is 100 Pa·s or more and 300 Pa·s or less.

3. The conductive material according to claim 1 or 2, wherein the thermosetting component contains an epoxy compound.

4. The conductive material according to any one of claims 1 to 3, wherein the average particle diameter of the solder particles is less than 1 μm.

5. The conductive material according to any one of claims 1 to 4, which is a conductive paste.

6. A first connection target member having a first electrode on its surface, a second connection target member having a second electrode on its surface, and a connection portion connecting the first connection target member and the second connection target member, wherein a material of the connection portion is the conductive material according to any one of claims 1 to 5, and the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

7. A step of disposing the conductive material on a surface of a first connection target member having a first electrode on its surface using the conductive material according to any one of claims 1 to 5, a step of disposing a second connection target member having a second electrode on its surface on a surface of the conductive material opposite to the first connection target member side of the conductive material so that the first electrode and the second electrode face each other, and a step of heating the conductive material to a temperature equal to or higher than the melting point of the solder particles to form a connection portion connecting the first connection target member and the second connection target member with the conductive material and electrically connecting the first electrode and the second electrode by a solder portion in the connection portion.

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