JP7356217B2 - Conductive material, connected structure, and method for manufacturing connected structure - Google Patents

Description

The present invention relates to conductive materials containing solder particles. The present invention also relates to a connected structure using the above-mentioned conductive material and a method for manufacturing the connected structure.

Anisotropic conductive materials such as anisotropic conductive pastes and anisotropic conductive films are widely known. In the above anisotropic conductive material, conductive particles are dispersed in a binder resin.

The above-mentioned anisotropic conductive material is used to obtain various connected structures. Examples of connections using the anisotropic conductive material include connections between flexible printed circuit boards and glass substrates (FOG (Film on Glass)), connections between semiconductor chips and flexible printed circuit boards (COF (Chip on Film)), and semiconductor Examples include connection between a chip and a glass substrate (COG (Chip on Glass)), connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)), and the like.

For example, when electrically connecting the electrodes of a flexible printed circuit board and the electrodes of a glass epoxy board using the anisotropic conductive material, the anisotropic conductive material containing conductive particles is placed on the glass epoxy board. do. Next, flexible printed circuit boards are laminated and heated and pressurized. Thereby, the anisotropic conductive material is cured, the electrodes are electrically connected via the conductive particles, and a connected structure is obtained.

Patent Document 1 listed below discloses a conductive material that includes a plurality of conductive particles having solder and a thermosetting component on the outer surface of a conductive part. In the above conductive material, the minimum value of the viscosity of the conductive material at 25° C. or higher and below the melting point of the solder in the conductive particles is 25 Pa·s or more and 255 Pa·s or less. The average particle diameter of the conductive particles is 3 μm or more and 15 μm or less. In the conductive material, where A is the average particle diameter (μm) of the conductive particles, and B is the viscosity (Pa・s) of the conductive material at the melting point of the solder in the conductive particles, the B is , (-5A+100) or more and (-15A+300) or less.

WO2017/033931A1

In recent years, with regard to conductive materials containing solder particles or conductive particles having solder on their surfaces, the finer pitch of wiring in printed wiring boards, etc. has led to miniaturization and smaller particle diameters of solder particles or conductive particles having solder on their surfaces. is in progress.

If solder particles or the like are simply reduced in particle size, there is a problem that the solder particles or the like cannot be efficiently arranged between the upper and lower electrodes to be connected during conductive connection using a conductive material. In particular, when heating and curing the conductive material, the viscosity of the conductive material increases before the solder particles and the like sufficiently move onto the electrodes, and the solder particles and the like may remain in areas where there are no electrodes. As a result, it may not be possible to sufficiently improve the continuity reliability between electrodes that should be connected and the insulation reliability between adjacent electrodes that should not be connected.

Furthermore, as the particle size of solder particles, etc. becomes smaller, the surface area of the solder particles, etc. increases, so the total amount of oxides due to the oxide film on the surface of the solder particles, etc. also increases. If an oxide film exists on the surface of solder particles, etc., the solder particles, etc. cannot be efficiently agglomerated on the electrode, so with conventional conductive materials, countermeasures such as increasing the flux content in the conductive material are taken. It becomes necessary. However, when the content of flux in the conductive material is increased, voids may be generated in the cured product of the conductive material or curing failure of the conductive material may occur. It is difficult to solve the above problems with conventional conductive materials.

It is an object of the present invention to efficiently arrange solder on electrodes, to effectively improve insulation reliability between adjacent electrodes, and to provide continuity reliability between upper and lower electrodes to be connected. An object of the present invention is to provide a conductive material that can effectively improve the properties. Another object of the present invention is to provide a connected structure using the above conductive material and a method for manufacturing the connected structure.

According to a broad aspect of the present invention, the conductive material includes a thermosetting compound, a curing accelerator, and solder particles, and the solder particles in the conductive material have a particle size of 30 μm or less. When the melt viscosity of the composition is measured, and the temperature at which the minimum value of the melt viscosity occurs is defined as X°C, the melt viscosity at X-10°C and the melt viscosity at X+10°C are each 10 Pa s or less, A conductive material is provided.

In a particular aspect of the conductive material according to the present invention, the temperature at which the melt viscosity exhibits a minimum value is 100°C or more and 110°C or less.

In a particular aspect of the conductive material according to the present invention, the content of the curing accelerator is 0.1 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the thermosetting compound.

In a particular aspect of the conductive material according to the present invention, the content of the solder particles in 100% by weight of the conductive material is 55% by weight or more and 75% by weight or less.

In a particular aspect of the conductive material according to the present invention, the conductive material is a conductive paste.

According to a broad aspect of the present invention, 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 the first connection target member, a connecting portion connecting the second connection target member, the material of the connecting portion is the above-mentioned conductive material, and the first electrode and the second electrode are connected to the connecting portion. A connection structure is provided that is electrically connected by a solder portion therein.

In a particular aspect of the connection structure according to the present invention, the first electrode and the second electrode may face each other in a stacking direction of the first electrode, the connection portion, and the second electrode. When looking at the portion, the solder portion in the connection portion is disposed on 50% or more of the 100% area of the portion where the first electrode and the second electrode face each other.

According to a broad aspect of the present invention, the above-described conductive material is disposed on the surface of a first connection target member having a first electrode on its surface; A second connection target member having a second electrode on its surface is arranged on a surface opposite to the first connection target member side so that the first electrode and the second electrode face each other. forming a connection portion connecting the first connection target member and the second connection target member with the conductive material by heating the conductive material to a temperature equal to or higher than the melting point of the solder particles; There is provided a method for manufacturing a connected structure, comprising the steps of: electrically connecting the first electrode and the second electrode with a solder portion in the connecting portion.

In a particular aspect of the method for manufacturing a connected structure according to the present invention, the first electrode and the second electrode are stacked in the stacking direction of the first electrode, the connecting portion, and the second electrode. A connection in which the solder part in the connecting part is arranged in 50% or more of the 100% area of the facing part of the first electrode and the second electrode when looking at the facing parts. Get the struct.

The conductive material according to the present invention is a conductive material containing a thermosetting compound, a curing accelerator, and solder particles. In the conductive material according to the present invention, the particle size of the solder particles is 30 μm or less. In the conductive material according to the present invention, the melt viscosity of the composition excluding the solder particles in the conductive material is measured, and the melt viscosity at Each has a melt viscosity of 10 Pa·s or less at X+10°C. Since the conductive material according to the present invention has the above configuration, it is possible to efficiently arrange the solder on the electrodes, effectively increasing the insulation reliability between adjacent electrodes, and further, The reliability of conduction between the upper and lower electrodes to be connected can be effectively increased.

FIG. 1 is a cross-sectional view schematically showing a connected structure obtained using a conductive material according to an embodiment of the present invention. FIGS. 2(a) to 2(c) are cross-sectional views for explaining each step of an example of a method for manufacturing a connected structure using a conductive material according to an embodiment of the present invention. FIG. 3 is a sectional view showing a modification of the connected structure.

The details of the present invention will be explained below.

(conductive material)
The conductive material according to the present invention is a conductive material containing a thermosetting compound, a curing accelerator, and solder particles. In the conductive material according to the present invention, the particle size of the solder particles is 30 μm or less. The particle size of the solder particles is relatively small. In the conductive material according to the present invention, the melt viscosity of the composition excluding the solder particles in the conductive material is measured, and the melt viscosity at Each has a melt viscosity of 10 Pa·s or less at X+10°C. The composition of the conductive material excluding the solder particles is the conductive material excluding the solder particles, and contains all components contained in the conductive material other than the solder particles in the proportions in the conductive material. The composition of the conductive material excluding the solder particles is obtained by blending all the components contained in the conductive material other than the solder particles at the same mixing ratio as in the conductive material, or by removing only the solder particles from the conductive material. It can be made.

Since the conductive material according to the present invention has the above configuration, it is possible to efficiently arrange the solder on the electrodes, effectively increasing the insulation reliability between adjacent electrodes, and further, The reliability of conduction between the upper and lower electrodes to be connected can be effectively increased.

In a conductive material in which solder particles are simply reduced in particle size, the viscosity of the conductive material tends to increase before the solder particles sufficiently move onto the electrode when the conductive material is heated and hardened. For this reason, solder particles may remain in areas where there are no electrodes, making it impossible to efficiently arrange the solder particles between the upper and lower electrodes to be connected. Furthermore, it may not be possible to sufficiently improve the continuity reliability between electrodes that should be connected and the insulation reliability between adjacent electrodes that should not be connected.

By using solder particles with a specific particle size and controlling the melt viscosity of the conductive material under specific conditions, the present inventors succeeded in reducing heat generated by the temperature difference between the conductive material and the electrodes during conductive connection between the electrodes. It has been found that convection is generated and the solder particles can be efficiently moved, and the solder can be efficiently placed on the electrode. In the present invention, although the solder particles are made to have a small particle size, the solder particles can sufficiently move onto the electrodes, and the solder can be efficiently placed between the electrodes to be connected. It is possible to improve conduction reliability and insulation reliability.

Furthermore, when the electrode width or the inter-electrode width is narrow, it tends to be difficult to gather the solder on the electrode, but in the present invention, even if the electrode width or the inter-electrode width is narrow, the solder can be gathered sufficiently on the electrode. can be collected. Since the present invention has the above configuration, when the electrodes are electrically connected, the solder particles easily gather between the upper and lower opposing electrodes, and the solder particles are efficiently transferred onto the electrodes (lines). can be placed in Further, in the present invention, when the electrode width is wide, the solder particles are more efficiently arranged on the electrode.

Furthermore, in the present invention, by using solder particles having a specific particle size and controlling the melt viscosity of the conductive material under specific conditions, the solder particles can be efficiently aggregated on the electrode. , there is no need to excessively increase the content of flux in the conductive material. As a result, the generation of voids in the cured material of the conductive material can be effectively suppressed, and the occurrence of curing defects of the conductive material can be effectively suppressed.

In the present invention, in order to obtain the above effects, using solder particles having a specific particle size and controlling the melt viscosity of the conductive material under specific conditions greatly contributes.

Furthermore, since the present invention has the above-mentioned configuration, when the electrodes are electrically connected, a plurality of solder particles tend to gather between the upper and lower opposing electrodes, and the plurality of solder particles are connected to the electrodes ( line). Furthermore, some of the plurality of solder particles are less likely to be placed in areas (spaces) where electrodes are not formed, and the amount of solder particles placed in areas where electrodes are not formed can be considerably reduced. Therefore, the reliability of conduction between the electrodes can be improved. Moreover, electrical connection between horizontally adjacent electrodes that should not be connected can be prevented, and insulation reliability can be improved.

Furthermore, in the present invention, positional displacement between the electrodes can be prevented. In the present invention, when the second connection target member is superimposed on the first connection target member having a conductive material disposed on the upper surface, the electrodes of the first connection target member and the second connection target member are connected to each other. Even in a state where the alignment is misaligned, the misalignment can be corrected and the electrodes can be connected to each other (self-alignment effect).

From the viewpoint of arranging the solder more uniformly on the electrode, the conductive material is preferably liquid at 25° C., and is preferably a conductive paste.

From the viewpoint of disposing the solder more uniformly on the electrode, the viscosity (η25) at 25°C of the conductive material is preferably 50 Pa·s or more, more preferably 100 Pa·s or more, and preferably 400 Pa·s. s or less, more preferably 200 Pa·s or less. The above viscosity (η25) can be adjusted as appropriate depending on the types and amounts of the ingredients.

The viscosity (η25) can be measured, for example, using an E-type viscometer (“TVE22L” manufactured by Toki Sangyo Co., Ltd.) at 25° C. and 5 rpm.

The melt viscosity of the composition of the conductive material excluding the solder particles is measured, and the temperature at which the melt viscosity shows the minimum value is defined as X°C. The melt viscosity at X-10°C (ηX-10) and the melt viscosity at X+10°C (ηX+10) are each 10 Pa·s or less. The melt viscosity (ηX-10) and the melt viscosity (ηX+10) are preferably 8 Pa·s or less, more preferably 6 Pa·s or less. The lower limits of the melt viscosity (ηX-10) and the melt viscosity (ηX+10) are not particularly limited. The melt viscosity (ηX−10) and the melt viscosity (ηX+10) may each be 1 Pa·s or more. When the melt viscosity (ηX-10) and the melt viscosity (ηX+10) are at least the lower limit and at most the upper limit, the solder can be placed on the electrode even more efficiently, and the insulation reliability can be further improved. Furthermore, the conduction reliability can be improved even more effectively.

The above melt viscosity (ηX-10) and the above melt viscosity (ηX+10) are determined using, for example, a rheometer "HAAKE MARS III" manufactured by Thermo Fisher Scientific, at a frequency of 2 Hz, a heating rate of 0.11 °C/sec, and a measurement temperature. Measurement is possible under conditions ranging from 40°C to 200°C. In this measurement, the temperature showing the minimum value of melt viscosity is defined as X°C.

The temperature (X°C) at which the above-mentioned minimum value of melt viscosity is shown is preferably 95°C or higher, more preferably 100°C or higher, even more preferably 103°C or higher, preferably 120°C or lower, more preferably 118°C or lower, The temperature is more preferably 115°C or lower, particularly preferably 110°C or lower. When the temperature (X°C) indicating the minimum value of the melt viscosity is above the above lower limit and below the above upper limit, the solder can be placed on the electrode even more efficiently, and the insulation reliability can be further improved. It is possible to improve the conduction reliability even more effectively.

The above-mentioned conductive material can be used as a conductive paste, a conductive film, and the like. The conductive paste is preferably an anisotropic conductive paste, and the conductive film is preferably an anisotropic conductive film. From the viewpoint of arranging the solder more uniformly on the electrode, the conductive material is preferably a conductive paste. The above-mentioned conductive material is suitably used for electrical connection of electrodes. Preferably, the conductive material is a circuit connection material.

Each component contained in the conductive material will be explained below. In addition, in this specification, "(meth)acrylic" means one or both of "acrylic" and "methacrylic."

(solder particles)
Both the center portion and the outer surface of the solder particles are made of solder. The solder particles described above are particles in which both the center portion and the outer surface are solder. When conductive particles comprising base particles made of a material other than solder and a solder portion disposed on the surface of the base particles are used instead of the solder particles described above, conductive particles can be placed on the electrodes. Particles become difficult to collect. In addition, since the conductive particles described above have low solder bondability between conductive particles, the conductive particles that have moved onto the electrode tend to move out of the electrode, and the effect of suppressing misalignment between the electrodes is also low. tends to be lower.

The solder is preferably a metal having a melting point of 450° C. or lower (low melting point metal). The solder particles are preferably metal particles having a melting point of 450° C. or lower (low-melting point metal particles). 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. The melting point of the low melting point metal is preferably 300°C or lower, more preferably 160°C or lower. The solder particles are preferably a low melting point solder having a melting point of less than 150°C.

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

Further, it is preferable that the solder particles contain tin. 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 in 100% by weight of the metal contained in the solder particles. . When the content of tin in the solder particles is equal to or higher than the lower limit, the reliability of connection between the solder portion and the electrode becomes even higher.

The above tin content was measured using a high frequency inductively coupled plasma emission spectrometer ("ICP-AES" manufactured by Horiba Ltd.) or a fluorescent X-ray analyzer ("EDX-800HS" manufactured by Shimadzu Corporation), etc. can be measured.

By using the above-mentioned solder particles, the solder melts and joins to the electrodes, and the solder portion establishes conduction between the electrodes. For example, since the solder portion and the electrode tend to make surface contact rather than point contact, the connection resistance becomes low. Furthermore, the use of the solder particles increases the bonding strength between the solder part and the electrode, making it even more difficult for the solder part to separate from the electrode, resulting in even higher conduction reliability and connection reliability.

The metal constituting the solder particles is not particularly limited. Preferably, the metal is 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, tin-indium alloy, and the like. The low melting point metal is preferably tin, tin-silver alloy, tin-silver-copper alloy, tin-bismuth alloy, or tin-indium alloy, since they have excellent wettability to the electrode. More preferred are tin-bismuth alloys and tin-indium alloys.

The solder particles are preferably filler metals whose liquidus line is 450° C. or less based on JIS Z3001: Welding terminology. Examples of the composition of the solder particles include metal compositions containing zinc, gold, silver, lead, copper, tin, bismuth, indium, and the like. Preferred are tin-indium (117° C. eutectic) or tin-bismuth (139° C. eutectic) which have a low melting point and are lead-free. That is, the solder particles preferably do not contain lead, and preferably contain tin and indium, or tin and bismuth.

In order to further increase the bonding strength between the solder part and the electrode, the solder particles include nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium, cobalt, bismuth, manganese, chromium, It may also contain metals such as molybdenum and palladium. Moreover, from the viewpoint of further increasing the bonding strength between the solder part 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 part and the electrode, the content of these metals for increasing the bonding strength is preferably 0.0001% by weight or more, preferably 1% by weight based on 100% by weight of the solder particles. % or less.

The particle size of the solder particles is 30 μm or less. The particle diameter of the solder particles is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 3 μm or more, and preferably 25 μm or less, more preferably 20 μm or less, and still more preferably 10 μm or less. When the particle diameter of the solder particles is not less than the above lower limit and not more than the above upper limit, the solder can be more efficiently disposed on the electrode. It is particularly preferable that the particle diameter of the solder particles is 3 μm or more and 10 μm or less. When the particle size of the solder particles satisfies the above preferred embodiments, the solder can be more efficiently disposed on the electrodes, and the insulation reliability can be improved even more effectively.

The particle size of the solder particles is preferably an average particle size, and preferably a number average particle size. The particle size of the solder particles can be determined, for example, by observing 50 arbitrary solder particles with an electron microscope or optical microscope and calculating the average value of the particle size of each solder particle, or by performing laser diffraction particle size distribution measurement. It is determined by In observation using an electron microscope or an optical microscope, the particle diameter of each solder particle is determined as the particle diameter in equivalent circle diameter. In observation using an electron microscope or an optical microscope, the average particle diameter of any 50 solder particles in equivalent circle diameter is approximately equal to the average particle diameter in equivalent sphere diameter. In the laser diffraction particle size distribution measurement, the particle diameter of each solder particle is determined as the particle diameter in equivalent sphere diameter. The average particle diameter of the solder particles is preferably calculated by laser diffraction particle size distribution measurement.

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

The above coefficient of variation (CV value) can be measured as follows.

CV value (%) = (ρ/Dn) x 100
ρ: Standard deviation of particle diameter of solder particles Dn: Average value of particle diameter of solder particles

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

The content of the solder particles in 100% by weight of the conductive material is preferably 55% by weight or more, more preferably 62% by weight or more, and preferably 75% by weight or less, more preferably 70% by weight or less. When the content of the solder particles is not less than the lower limit and not more than the upper limit, it is easier to arrange the solder on the electrode more efficiently, and the conduction reliability is further effectively increased. From the viewpoint of further effectively increasing conduction reliability, it is preferable that the content of the solder particles be large.

The electrically conductive material includes a thermosetting compound and a curing accelerator as thermosetting components. In order to increase the degree of curing of the conductive material, the conductive material preferably contains a thermosetting agent as a thermosetting component.

Each component contained in the conductive material will be explained below.

(thermosetting compound)
The above thermosetting compound is not particularly limited. Examples of the 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. From the viewpoint of further improving the curability and viscosity of the conductive material, from the viewpoint of further effectively increasing conduction reliability, and from the viewpoint of further effectively increasing insulation reliability, epoxy compounds or episulfide compounds are preferable. Epoxy compounds are more preferred. The thermosetting compound preferably includes an epoxy compound. The above thermosetting compounds may be used alone or in combination of two or more.

The above epoxy compound is a compound having at least one epoxy group. The above-mentioned epoxy compounds include bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, phenol novolak type epoxy compounds, biphenyl type epoxy compounds, biphenyl novolac type epoxy compounds, biphenol type epoxy compounds, and naphthalene type epoxy compounds. , 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 Examples include epoxy compounds and epoxy compounds having a triazine nucleus in their skeleton. Only one kind of the above-mentioned epoxy compound may be used, or two or more kinds thereof may be used in combination.

The epoxy compound is liquid or solid at room temperature (23° C.), and when the epoxy compound is solid at room temperature, the melting temperature of the epoxy compound is preferably equal to or lower than the melting point of the solder particles.

From the viewpoint of further effectively increasing the insulation reliability and the viewpoint of further effectively increasing the conduction reliability, the thermosetting compound preferably contains an epoxy compound.

From the viewpoint of further effectively increasing the heat resistance of the cured product, the thermosetting compound preferably contains a thermosetting compound having an isocyanuric skeleton.

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

The content of the thermosetting compound in 100% by weight of the conductive material is preferably 20% by weight or more, more preferably 40% by weight or more, even more preferably 50% by weight or more, and preferably 99% by weight or less, more preferably It is preferably 98% by weight or less, more preferably 90% by weight or less, particularly preferably 80% by weight or less. When the content of the thermosetting compound is not less than the lower limit and not more than the upper limit, the solder can be more efficiently placed on the electrodes, and the insulation reliability between the electrodes can be further effectively increased. The reliability of conduction between the electrodes can be further effectively improved. From the viewpoint of increasing impact resistance even more effectively, it is preferable that the content of the thermosetting compound is as large as possible.

The content of the epoxy compound in 100% by weight of the conductive material is preferably 20% by weight or more, more preferably 40% by weight or more, even more preferably 50% by weight or more, and preferably 99% by weight or less, more preferably It is 98% by weight or less, more preferably 90% by weight or less, particularly preferably 80% by weight or less. When the content of the epoxy compound is at least the above lower limit and below the above upper limit, the solder can be more efficiently placed on the electrodes, the insulation reliability between the electrodes can be further effectively increased, and the The conduction reliability can be further effectively improved. From the viewpoint of further improving impact resistance, it is preferable that the content of the epoxy compound is as large as possible.

(Thermosetting agent)
Preferably, the conductive material includes a thermosetting agent. The above thermosetting agent is not particularly limited. The thermosetting agent thermosets the thermosetting compound. Examples of the above-mentioned thermosetting agents include thiol curing agents such as imidazole curing agents, amine curing agents, phenol curing agents, and polythiol curing agents, acid anhydride curing agents, thermal cationic initiators (thermal cationic curing agents), thermal radical generators, etc. can be mentioned. The above thermosetting agents may be used alone or in combination of two or more.

From the viewpoint of enabling the conductive material to be cured more rapidly at low temperatures, the thermosetting agent is preferably an imidazole curing agent, a thiol curing agent, or an amine curing agent. Further, from the viewpoint of improving the storage stability when the thermosetting compound and the thermosetting agent are mixed, the thermosetting agent is preferably a latent curing agent. Preferably, the latent curing agent is a latent imidazole curing agent, a latent thiol curing agent or a latent amine curing agent. Note that the thermosetting agent may be coated with a polymeric substance such as polyurethane resin or polyester resin.

The above imidazole curing agent is not particularly limited. Examples of the 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-paratolyl-4-methyl-5 -5-position of 1H-imidazole in hydroxymethylimidazole, 2-metatolyl-4-methyl-5-hydroxymethylimidazole, 2-metatolyl-4,5-dihydroxymethylimidazole, 2-paratolyl-4,5-dihydroxymethylimidazole, etc. Examples include imidazole compounds in which hydrogen at the 2-position is substituted with a hydroxymethyl group and hydrogen at the 2-position is substituted with a phenyl group or a tolyl group.

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

The above amine curing agent is not particularly limited. Examples of the amine curing agent include hexamethylene diamine, octamethylene diamine, decamethylene diamine, 3,9-bis(3-aminopropyl)-2,4,8,10-tetraspiro[5.5]undecane, bis(4 -aminocyclohexyl)methane, metaphenylenediamine, and diaminodiphenylsulfone.

The acid anhydride curing agent is not particularly limited, and any acid anhydride that can be used as a curing agent for thermosetting compounds such as epoxy compounds can be used. The 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, methyl nadic anhydride, glutaric anhydride, succinic anhydride, glycerin bis-trimellitic anhydride monoacetate, and difunctional compounds such as ethylene glycol bis-trimellitic anhydride. trifunctional acid anhydride curing agents such as trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, methylcyclohexenetetracarboxylic anhydride, polyazelaic anhydride, etc. Examples include acid anhydride curing agents having four or more functional groups.

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

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

The reaction initiation temperature of the thermosetting agent is preferably 50°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, preferably 250°C or lower, more preferably 200°C or lower, and even more preferably 150°C. The temperature below is particularly preferably 140°C or below. When the reaction initiation temperature of the thermosetting agent is at least the above lower limit and below the above upper limit, the solder can be more efficiently disposed on the electrode. It is particularly preferable that the reaction initiation temperature of the thermosetting agent is 80°C or more and 140°C or less.

From the viewpoint of disposing the solder on the electrode more efficiently, the reaction initiation temperature of the thermosetting agent is preferably higher than the melting point of the solder in the solder particles, more preferably 5° C. or more, and 10° C. or higher. It is more preferable that the temperature is higher than ℃.

The reaction start temperature of the thermosetting agent means the temperature at which the exothermic peak starts rising in DSC.

The content of the thermosetting agent is not particularly limited. With respect to 100 parts by weight of the thermosetting compound, the content of the thermosetting agent is preferably 0.01 parts by weight or more, more preferably 1 part by weight or more, and preferably 200 parts by weight or less, more preferably The amount is 100 parts by weight or less, more preferably 75 parts by weight or less. When the content of the thermosetting agent is at least the above lower limit, it is easy to sufficiently cure the conductive material. When the content of the thermosetting agent is below the above upper limit, it becomes difficult for surplus thermosetting agent that did not take part in curing to remain after curing, and the heat resistance of the cured product becomes even higher.

(hardening accelerator)
The above-mentioned curing accelerator is not particularly limited. The curing accelerator acts as a curing catalyst in the reaction with the thermosetting compound. As for the said hardening accelerator, only 1 type may be used, and 2 or more types may be used together.

Examples of the curing accelerator include phosphonium salts, tertiary amines, tertiary amine salts, quaternary onium salts, tertiary phosphines, crown ether complexes, and phosphonium ylides. Specifically, the curing accelerators include imidazole compounds, isocyanurates of imidazole compounds, dicyandiamide, derivatives of dicyandiamide, melamine compounds, derivatives of melamine compounds, diaminomaleonitrile, diethylenetriamine, triethylenetetramine, and 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) Examples include -2,4,8,10-tetraoxaspiro[5,5]undecane, and organic phosphorus compounds such as triphenylphosphine, tricyclohexylphosphine, tributylphosphine, and methyldiphenylphosphine.

The above phosphonium salt is not particularly limited. The above phosphonium salts include tetra-n-butylphosphonium bromide, tetra-n-butylphosphonium O-O diethyldithiophosphate, methyltributylphosphonium dimethyl phosphate, tetra-n-butylphosphonium benzotriazole, tetra-n-butylphosphonium tetrafluoroborate, and tetra-n-butyl phosphonium. Examples include phosphonium tetraphenylborate.

The content of the curing accelerator is appropriately selected so that the thermosetting compound is well cured. The content of the curing accelerator relative to 100 parts by weight of the thermosetting compound is preferably 0.001 parts by weight or more, more preferably 0.1 parts by weight or more, even more preferably 0.5 parts by weight or more, and even more preferably is 4 parts by weight or more, particularly preferably 6 parts by weight or more. The content of the curing accelerator relative to 100 parts by weight of the thermosetting compound is 30 parts by weight or less, more preferably 20 parts by weight or less, still more preferably 16 parts by weight or less, particularly preferably 12 parts by weight or less. When the content of the curing accelerator is at least the above lower limit and at most the above upper limit, the thermosetting compound can be cured well. When the content of the curing accelerator is not less than the lower limit and not more than the upper limit, the solder can be more efficiently disposed on the electrodes, and the insulation reliability between the electrodes can be further effectively improved. In particular, when the content of the curing accelerator is below the upper limit, the minimum value of the melt viscosity can be further lowered, and the values of the melt viscosity (ηX-10) and the melt viscosity (ηX+10) can be further lowered. can be made even lower.

(flux)
The conductive material may contain flux. By using flux, solder can be placed on the electrodes more efficiently. The above flux is not particularly limited. As the above-mentioned flux, a flux commonly used for soldering and the like can be used.

The above fluxes 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 Examples include pine resin. The above fluxes may be used alone or in combination of two or more.

Examples of the molten salt include ammonium chloride. Examples of the organic acids include lactic acid, citric acid, stearic acid, glutamic acid, and glutaric acid. Examples of the pine resin include activated pine resin and non-activated pine resin. The flux is preferably an organic acid having two or more carboxyl groups or pine resin. The above-mentioned flux may be an organic acid having two or more carboxyl groups, or may be pine resin. By using an organic acid or pine resin having two or more carboxyl groups, the reliability of conduction between the electrodes is further increased.

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

Examples of the amine compounds include cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, imidazole, benzimidazole, phenylimidazole, carboxybenzimidazole, benzotriazole, and carboxybenzotriazole.

The above-mentioned pine resin is a rosin whose main component is abietic acid. Examples of the rosins include abietic acid and acrylic modified rosin. The flux is preferably a rosin, more preferably abietic acid. By using this preferable flux, the reliability of conduction between the electrodes is further increased.

The activation temperature (melting point) of the above flux is preferably 50°C or higher, more preferably 70°C or higher, even more preferably 80°C or higher, preferably 200°C or lower, more preferably 190°C or lower, even more preferably 160°C or lower. The temperature is preferably 150°C or lower, even more preferably 140°C or lower. When the activation temperature of the flux is equal to or higher than the lower limit and lower than the upper limit, the flux effect is even more effectively exhibited, and the solder is disposed on the electrode more efficiently. The activation temperature (melting point) of the flux is preferably 80°C or more and 190°C or less. It is particularly preferable that the activation temperature (melting point) of the above-mentioned flux is 80°C or more and 140°C or less.

Examples of the above-mentioned fluxes having an active temperature (melting point) of 80°C or higher and 190°C or lower include succinic acid (melting point 186°C), glutaric acid (melting point 96°C), adipic acid (melting point 152°C), and pimelic acid (melting point 104°C). C), dicarboxylic acids such as suberic acid (melting point 142°C), benzoic acid (melting point 122°C), malic acid (melting point 130°C), and the like.

Moreover, it is preferable that the boiling point of the above-mentioned flux is 200° C. or lower.

From the viewpoint of disposing the solder on the electrodes more efficiently, the melting point of the flux is preferably higher than the melting point of the solder particles, more preferably 5°C or more higher, and still more preferably 10°C or more higher. preferable.

From the viewpoint of disposing the solder on the electrode more efficiently, the melting point of the flux is preferably higher than the reaction initiation temperature of the thermosetting agent, more preferably 5°C or more higher, and 10°C or more higher. It is even more preferable.

The flux may be dispersed in the conductive material or may be attached to the surface of the solder particles.

Since the melting point of the flux is higher than the melting point of the solder particles, the solder particles can be efficiently aggregated on the electrode portion. This means that when heat is applied during bonding, when comparing the electrode formed on the member to be connected and the part of the member to be connected around the electrode, the thermal conductivity of the electrode part is lower than that of the part of the member to be connected around the electrode. This is due to the fact that the temperature of the electrode portion rises quickly due to its higher thermal conductivity. When the melting point of the solder particle is exceeded, the inside of the solder particle melts, but the oxide film formed on the surface is not removed because it has not reached the melting point (activation temperature) of the flux. In this state, the temperature of the electrode reaches the melting point (activation temperature) of the flux first, so the oxide film on the surface of the solder particles that have moved onto the electrode is removed preferentially, and the solder particles are transferred onto the surface of the electrode. Can get wet and spread. Thereby, solder particles can be efficiently aggregated on the electrodes.

The above-mentioned flux is preferably a flux that releases cations when heated. The use of a flux that releases cations upon heating allows the solder to be placed on the electrodes more efficiently.

Examples of the flux that releases cations upon heating include the thermal cation initiator (thermal cation curing agent).

From the viewpoint of arranging the solder more efficiently on the electrode, from the viewpoint of further effectively increasing the insulation reliability, and from the viewpoint of further effectively increasing the continuity reliability, the above-mentioned flux is composed of an acid compound and a basic compound. It is preferable that it is a salt with.

The acid compound is preferably an organic compound having a carboxyl group. The above acid compounds include aliphatic carboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, citric acid, malic acid, and cycloaliphatic carboxylic acids. Examples include cyclohexylcarboxylic acid, 1,4-cyclohexyldicarboxylic acid, aromatic carboxylic acids such as isophthalic acid, terephthalic acid, trimellitic acid, and ethylenediaminetetraacetic acid. From the viewpoint of arranging the solder more efficiently on the electrode, from the viewpoint of further effectively increasing the insulation reliability, and from the viewpoint of further effectively increasing the conduction reliability, the above acid compounds include glutaric acid, cyclohexyl Preferably, it is carboxylic acid or adipic acid.

The basic compound is preferably an organic compound having an amino group. The above basic compounds 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 viewpoint of arranging the solder on the electrode more efficiently, from the viewpoint of further effectively increasing insulation reliability, and from the viewpoint of further effectively increasing continuity reliability, the above basic compound is benzylamine. It is preferable.

The content of the flux in 100% by weight of the conductive material is preferably 0.5% by weight or more, preferably 30% by weight or less, and more preferably 25% by weight or less. The above-mentioned conductive material does not need to contain flux. When the content of the flux is more than the above lower limit and less than the above upper limit, it becomes even more difficult to form an oxide film on the surfaces of the solder and electrodes, and furthermore, it becomes even more difficult to form an oxide film on the surfaces of the solder and electrodes. Can be removed effectively.

(filler)
The conductive material according to the present invention may contain a filler. The filler may be an organic filler or an inorganic filler. By containing the filler in the conductive material, solder particles can be uniformly aggregated over all the electrodes of the substrate.

It is preferable that the conductive material does not contain the filler or contains 5% by weight or less of the filler. When using the above-mentioned thermosetting compound, the smaller the filler content, the easier the solder particles will move onto the electrode.

The content of the filler in 100% by weight of the conductive material is preferably 0% by weight or more (not contained), preferably 5% by weight or less, more preferably 2% by weight or less, and even more preferably 1% by weight or less. be. When the content of the filler is not less than the lower limit and not more than the upper limit, the solder is more uniformly disposed on the electrode.

(other ingredients)
The above-mentioned conductive material may contain, if necessary, a filler, an extender, a softener, a plasticizer, a thixotropic agent, a leveling agent, a polymerization catalyst, a curing catalyst, a coloring agent, an antioxidant, a heat stabilizer, and a light stabilizer. , an ultraviolet absorber, a lubricant, an antistatic agent, a flame retardant, and other various additives.

(Connected structure and method for manufacturing the connected 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, and the first connection target member, and a connecting portion connecting the second connection target member. In the connected structure according to the present invention, the material of the connecting portion is the conductive material described above. In the connected structure according to the present invention, the first electrode and the second electrode are electrically connected by a solder part in the connecting part.

A method for manufacturing a connected structure according to the present invention includes a step of using the above-mentioned conductive material and arranging the above-described conductive material on the surface of a first connection target member having a first electrode on the surface. The method for manufacturing a connected structure according to the present invention includes a method for manufacturing a connected structure, in which a second connection target member having a second electrode on the surface is placed on a surface of the conductive material opposite to the first connection target member side. The method includes a step of arranging the first electrode and the second electrode so as to face each other. The method for manufacturing a connected structure according to the present invention provides a connection between the first connection target member and the second connection target member by heating the conductive material above the melting point of the solder particles. forming the part from the conductive material, and electrically connecting the first electrode and the second electrode by a solder part in the connecting part.

In the bonded structure and the method for manufacturing the bonded structure according to the present invention, since a specific conductive material is used, solder particles tend to collect between the first electrode and the second electrode. line). Furthermore, some of the solder particles are less likely to be placed in areas (spaces) where no electrodes are formed, and the amount of solder particles placed in areas where no electrodes are formed can be considerably reduced. Therefore, the reliability of conduction between the first electrode and the second electrode can be improved. Moreover, electrical connection between horizontally adjacent electrodes that should not be connected can be prevented, and insulation reliability can be improved.

In addition, in order to efficiently arrange the solder on the electrodes and to significantly reduce the amount of solder placed in areas where no electrodes are formed, the above-mentioned conductive material should be a conductive paste instead of a conductive film. It is preferable.

The thickness of the solder portion between the electrodes is preferably 10 μm or more, more preferably 20 μm or more, and preferably 100 μm or less, more preferably 80 μm or less. The solder wetted area on the surface of the electrode (the area in contact with the solder out of 100% of the exposed area of the electrode) is preferably 50% or more, more preferably 70% or more, and preferably 100% or less.

In the method for manufacturing a connected structure according to the present invention, in the step of arranging the second connection target member and the step of forming the connection part, no pressure is applied to the conductive material, and the second connection target member is not pressurized. Preferably, the weight of the target member is added. In the method for manufacturing a connected structure according to the present invention, in the step of arranging the second member to be connected and the step of forming the connecting portion, the conductive material is subjected to the force of the weight of the second member to be connected. It is preferable not to apply pressure exceeding . In these cases, the uniformity of the amount of solder can be further improved in the plurality of solder parts. Furthermore, the thickness of the solder part can be increased even more effectively, making it easier for multiple solder particles to gather between the electrodes, making it possible to more efficiently arrange multiple solder particles on the electrodes (lines). can. In addition, it is difficult for some of the plurality of solder particles to be placed in areas (spaces) where electrodes are not formed, and it is possible to further reduce the amount of solder in solder particles placed in areas where electrodes are not formed. can. Therefore, the reliability of conduction between the electrodes can be further improved. Moreover, electrical connections between horizontally adjacent electrodes that should not be connected can be further prevented, and insulation reliability can be further improved.

Further, 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 by adjusting the amount of conductive paste applied. On the other hand, with conductive films, there is a problem in that in order to change or adjust the thickness of the connection part, it is necessary to prepare conductive films of different thicknesses or to prepare conductive films of a predetermined thickness. There is. Moreover, in a conductive film, compared to a conductive paste, the melt viscosity of the conductive film cannot be sufficiently lowered at the melting temperature of the solder, and aggregation of solder particles tends to be inhibited.

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

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

The connection structure 1 shown in FIG. 1 includes a first connection target member 2, a second connection target member 3, and a connection connecting the first connection target member 2 and the second connection target member 3. 4. The connecting portion 4 is made of the above-mentioned conductive material. In this embodiment, the conductive material includes a thermosetting compound, a curing accelerator, and solder particles. In this embodiment, a conductive paste is used as the conductive material.

The connecting portion 4 includes a solder portion 4A in which a plurality of solder particles are gathered and bonded to each other, and a cured material portion 4B in which a thermosetting compound is thermoset.

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 the front surface (lower surface). The first electrode 2a and the second electrode 3a are electrically connected by a 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. Note that, in the connecting portion 4, no solder particles exist in a region different from the solder portion 4A gathered between the first electrode 2a and the second electrode 3a (cured material portion 4B portion). In a region different from the solder portion 4A (cured material portion 4B portion), there are no solder particles separate from the solder portion 4A. Note that solder particles may be present in a region different from the solder portion 4A gathered between the first electrode 2a and the second electrode 3a (cured material portion 4B portion) as long as the amount is small.

As shown in FIG. 1, in the connection structure 1, a plurality of solder particles gather between a first electrode 2a and a second electrode 3a, and after the plurality of solder particles are melted, a melted solder particle is formed. The solder portion 4A is formed by wetting and spreading the surface of the electrode and solidifying the solder portion 4A. Therefore, the connection area between the solder portion 4A and the first electrode 2a and between the solder portion 4A and the second electrode 3a becomes large. That is, by using solder particles, the solder part 4A, the first electrode 2a, and the solder part The contact area between 4A and the second electrode 3a becomes larger. This also increases the conduction reliability and connection reliability in the connection structure 1. Note that when the conductive material contains flux, the flux is generally gradually deactivated by heating.

In addition, in the connection structure 1 shown in FIG. 1, all of the solder parts 4A are located in the opposing region between the first and second electrodes 2a and 3a. The modified connected structure 1X shown in FIG. 3 differs from the connected structure 1 shown in FIG. 1 only in the connecting portion 4X. The connecting portion 4X has a solder portion 4XA and a cured material portion 4XB. Like the connection structure 1X, most of the solder portion 4XA is located in the area where the first and second electrodes 2a and 3a are facing each other, and a part of the solder portion 4XA is located in the area where the first and second electrodes 2a and 3a face each other. It may protrude laterally from the opposing regions of the electrodes 2a and 3a. The solder portion 4XA that protrudes laterally from the opposing region of the first and second electrodes 2a and 3a is a part of the solder portion 4XA, and is not a solder particle separated from the solder portion 4XA. In addition, in this embodiment, the amount of solder particles separated from the solder part can be reduced, but the solder particles separated from the solder part may exist in the cured material part.

By reducing the amount of solder particles used, it becomes easier to obtain the connected structure 1. If the amount of solder particles used is increased, it becomes easier to obtain the connected structure 1X.

In the connection structures 1 and 1X, when looking at the opposing portions of the first electrode 2a and the second electrode 3a in the stacking direction of the first electrode 2a, the connection parts 4 and 4X, and the second electrode 3a Preferably, the solder portions 4A and 4XA in the connecting portions 4 and 4X are arranged in 50% or more of the 100% area of the opposing portions of the first electrode 2a and the second electrode 3a. . When the solder portions 4A and 4XA in the connection portions 4 and 4X satisfy the above-mentioned preferred embodiments, the continuity reliability can be further improved.

When looking at the opposing portions of the first electrode and the second electrode in the stacking direction of the first electrode, the connecting portion, and the second electrode, the first electrode and the second electrode It is preferable that the solder portion in the connection portion is disposed on 50% or more of the 100% area of the portion facing the second electrode. When looking at the opposing portions of the first electrode and the second electrode in the stacking direction of the first electrode, the connecting portion, and the second electrode, the first electrode and the second electrode It is more preferable that the solder portion in the connection portion is disposed on 60% or more of the 100% area of the portion facing the second electrode. When looking at the opposing portions of the first electrode and the second electrode in the stacking direction of the first electrode, the connecting portion, and the second electrode, the first electrode and the second electrode It is more preferable that the solder part in the connection part is disposed on 70% or more of the 100% area of the part facing the second electrode. When looking at the opposing portions of the first electrode and the second electrode in the stacking direction of the first electrode, the connecting portion, and the second electrode, the first electrode and the second electrode It is particularly preferable that the solder portion in the connection portion is disposed on 80% or more of the 100% area of the portion facing the second electrode. When looking at the opposing portions of the first electrode and the second electrode in the stacking direction of the first electrode, the connecting portion, and the second electrode, the first electrode and the second electrode It is most preferable that the solder part in the connection part is disposed on 90% or more of the 100% area of the part facing the second electrode. When the solder portion in the connection portion satisfies the preferred embodiments described above, conduction reliability can be further improved.

When the opposing portions of the first electrode and the second electrode are viewed in a direction perpendicular to the stacking direction of the first electrode, the connection portion, and the second electrode, the first It is preferable that 60% or more of the solder portion in the connection portion is disposed at the portion where the electrode and the second electrode face each other. When the opposing portions of the first electrode and the second electrode are viewed in a direction perpendicular to the stacking direction of the first electrode, the connection portion, and the second electrode, the first More preferably, 70% or more of the solder portion in the connection portion is disposed in a portion where the electrode and the second electrode face each other. When the opposing portions of the first electrode and the second electrode are viewed in a direction perpendicular to the stacking direction of the first electrode, the connection portion, and the second electrode, the first It is further preferable that 90% or more of the solder portion in the connection portion be disposed at a portion where the electrode and the second electrode face each other. When the opposing portions of the first electrode and the second electrode are viewed in a direction perpendicular to the stacking direction of the first electrode, the connection portion, and the second electrode, the first It is particularly preferable that 95% or more of the solder portion in the connection portion is disposed at the portion where the electrode and the second electrode face each other. When the opposing portions of the first electrode and the second electrode are viewed in a direction perpendicular to the stacking direction of the first electrode, the connection portion, and the second electrode, the first It is most preferable that 99% or more of the solder portion in the connecting portion is disposed at the portion where the electrode and the second electrode face each other. When the solder portion in the connection portion satisfies the preferred embodiments described above, conduction reliability can be further improved.

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

First, a first connection target member 2 having a first electrode 2a on its surface (upper surface) is prepared. Next, as shown in FIG. 2(a), a conductive material 11 containing a thermosetting component 11B and a plurality of solder particles 11A is placed on the surface of the first connection target member 2 (first process). The conductive material 11 used includes a thermosetting compound and a curing accelerator as the thermosetting component 11B.

A conductive material 11 is placed on the surface of the first connection target member 2 on which the first electrode 2a is provided. After the conductive material 11 is placed, the solder particles 11A are placed both on the first electrode 2a (line) and on the area (space) where the first electrode 2a is not formed.

Methods for disposing the conductive material 11 include, but are not particularly limited to, application using a dispenser, screen printing, and ejection using an inkjet device.

Further, a second connection target member 3 having a second electrode 3a on its surface (lower surface) is prepared. Next, as shown in FIG. 2(b), in the conductive material 11 on the surface of the first connection target member 2, on the surface of the conductive material 11 opposite to the first connection target member 2 side, Arranging the second connection target member 3 (second step). The second connection target member 3 is placed on the surface of the conductive material 11 from the second electrode 3a side. At this time, the first electrode 2a and the second electrode 3a are made to face each other.

Next, the conductive material 11 is heated to a temperature higher than the melting point of the solder particles 11A (third step). Preferably, the conductive material 11 is heated to a temperature higher than the curing temperature of the thermosetting component 11B (thermosetting compound). During this heating, the solder particles 11A existing in the region where no electrode is formed gather between the first electrode 2a and the second electrode 3a (self-agglomeration 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. Further, the solder particles 11A are melted and bonded to each other. Further, the thermosetting component 11B is thermoset. As a result, as shown in FIG. 2(c), the connection portion 4 connecting the first connection target member 2 and the second connection target member 3 is formed of the conductive material 11. A connecting portion 4 is formed by the conductive material 11, a solder portion 4A is formed by joining a plurality of solder particles 11A, and a cured material portion 4B is formed by thermosetting the thermosetting component 11B. If the solder particles 11A move sufficiently, the solder particles 11A that are not located between the first electrode 2a and the second electrode 3a start moving, and then the first electrode 2a and the second electrode 11A start moving. It is not necessary to keep the temperature constant until the movement of the solder particles 11A between the solder particles 3a and the solder particles 11A is completed.

In this embodiment, it is preferable not to apply pressure in the second step and the third step. 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 second step and the third step, the solder particles 11A tend to gather between the first electrode 2a and the second electrode 3a. is more likely to be inhibited.

Furthermore, in this embodiment, since no pressure is applied, the first connection target member 2 and the second connection target member 3 Even when these electrodes are overlapped, it is possible to correct the deviation and connect the first electrode 2a and the second electrode 3a (self-alignment effect). This is because the molten solder that has self-agglomerated between the first electrode 2a and the second electrode 3a is mixed with the solder between the first electrode 2a and the second electrode 3a and other parts of the conductive material. This is because energy is more stable when the area in contact with the component is minimized, and a force acts to create an aligned connection structure that has 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.

The viscosity of the conductive material at the melting point of the solder particles is preferably 50 Pa·s or less, more preferably 10 Pa·s or less, even more preferably 1 Pa·s or less, preferably 0.1 Pa·s or more, more preferably 0. .2 Pa·s or more. If the above-mentioned viscosity is below the above-mentioned upper limit, solder particles can be efficiently aggregated. If the above-mentioned viscosity is more than the above-mentioned lower limit, it is possible to suppress voids in the connection portion and to suppress the conductive material from protruding outside the connection portion.

The viscosity of the conductive material at the melting point of the solder particles mentioned above was measured using STRESSTECH (manufactured by REOLOGICA), etc., with strain control of 1 rad, frequency of 1 Hz, temperature increase rate of 20 °C/min, and measurement temperature range of 25 to 200 °C (however, solder If the melting point of the particles exceeds 200° C., the temperature can be measured under the following conditions: the upper temperature limit is the melting point of the solder particles. From the measurement results, the viscosity at the melting point (°C) of the solder particles is evaluated.

In this way, the connected structure 1 shown in FIG. 1 is obtained. In addition, the said 2nd process and the said 3rd process may be performed continuously. Further, after performing the second step, the obtained laminate of the first connection target member 2, the conductive material 11, and the second connection target member 3 is moved to a heating section, and the third You may perform the process. In order to perform the heating, the laminate may be placed on a heating member, or the laminate may be placed in a heated space.

The heating temperature in the third step is preferably 140°C or higher, more preferably 160°C or higher, preferably 450°C or lower, more preferably 250°C or lower, even more preferably 200°C or lower.

The heating method in the third step includes a method of heating the entire connected structure using a reflow oven or an oven to a temperature higher than the melting point of the solder particles and the curing temperature of the thermosetting component; One example is a method of locally heating only the connecting parts of the body.

Examples of devices used in the local heating method include a hot plate, a heat gun that applies hot air, a soldering iron, and an infrared heater.

In addition, when heating locally with a hot plate, use a highly thermally conductive metal directly below the connection, and use a low thermally conductive material such as fluororesin for other areas where it is not desirable to heat. , preferably forming the top surface of the hot plate.

The first and second connection target members are not particularly limited. Specifically, the first and second connection target members include semiconductor chips, semiconductor packages, LED chips, LED packages, electronic components such as capacitors and diodes, resin films, printed circuit boards, flexible printed circuit boards, and flexible Examples include electronic components such as flat cables, rigid-flexible boards, circuit boards such as glass epoxy boards, and glass boards. It is preferable that the first and second connection target members are electronic components.

It is preferable that at least one of the first connection target member and the second connection target member is a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board. It is preferable that the second connection target member is a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board. Resin films, flexible printed circuit boards, flexible flat cables, and rigid-flexible circuit boards have the properties of being highly flexible and relatively lightweight. When a conductive film is used to connect such connection target members, solder particles tend to be difficult to collect on the electrodes. On the other hand, by using a conductive paste, even if a resin film, flexible printed circuit board, flexible flat cable, or rigid-flex board is used, the solder particles can be efficiently collected on the electrodes, ensuring continuity between the electrodes. You can fully enhance your sexuality. When using resin films, flexible printed circuit boards, flexible flat cables, or rigid-flex circuit boards, the reliability of conduction between electrodes can be improved by not applying pressure, compared to when using other connection objects such as semiconductor chips. The improvement effect can be obtained even more effectively.

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 member to be connected 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 member to be connected is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, a silver electrode, or a tungsten electrode. In addition, when the said electrode is an aluminum electrode, it may be an electrode formed only with aluminum, and the electrode may be an electrode in which an aluminum layer is laminated|stacked on the surface of a metal oxide layer. Examples of the material for 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 elements include Sn, Al, and Ga.

In the connected structure according to the present invention, it is preferable that the first electrode and the second electrode are arranged in an area array or a peripheral. The effects of the present invention are even more effectively exhibited when the first electrode and the second electrode are arranged in an area array or peripherally. The above-mentioned area array is a structure in which electrodes are arranged in a grid pattern on the surface of the connection target member on which the electrodes are arranged. The above-mentioned peripheral refers to a structure in which electrodes are arranged on the outer periphery of a member to be connected. In the case of a structure in which the electrodes are arranged in a comb shape, the solder particles only need to aggregate along the direction perpendicular to the comb, whereas in the above area array or peripheral structure, the solder particles aggregate on the entire surface on the surface where the electrodes are arranged. It is necessary for the solder particles to coagulate uniformly. Therefore, in the conventional method, the amount of solder tends to be non-uniform, whereas in the method of the present invention, the effects of the present invention are more effectively exhibited.

Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples. The invention is not limited only to the following examples.

Thermosetting compound:
Thermosetting compound 1: Phenol novolac type epoxy compound, “DEN431” manufactured by DOW
Thermosetting compound 2: Bisphenol F type epoxy compound, "YDF-8170C" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.
Thermosetting compound 3: Bisphenol A type epoxy compound, "YD-8125" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.
Thermosetting compound 4: Aliphatic epoxy compound, "Epolite 1600" manufactured by Kyoeisha Chemical Co., Ltd.
Thermosetting compound 5: Isocyanuric skeleton-containing epoxy compound, “TEPIC-SP” manufactured by Nissan Chemical Co., Ltd.

Thermosetting agent:
Thermosetting agent 1: Acid anhydride curing agent, "Rikacid MH" manufactured by Shin Nippon Rika Co., Ltd.
Thermosetting agent 2: Acid anhydride curing agent, "Rikacid TH" manufactured by Shin Nippon Rika Co., Ltd.

Curing accelerator:
Curing accelerator 1: Organic phosphonium salt, “PX-4MP” manufactured by Nihon Kagaku Kogyo Co., Ltd., liquid at 25°C

Solder particles:
Solder particle 1: SnBi solder particles, melting point 138°C, solder particles selected from "Sn42Bi58" manufactured by Mitsui Kinzoku Co., Ltd., average particle size: 20 μm
Solder particle 2: SnBi solder particles, melting point 138°C, solder particles selected from "Sn42Bi58" manufactured by Mitsui Kinzoku Co., Ltd., average particle size: 10 μm
Solder particle 3: SnBi solder particles, melting point 138°C, solder particles selected from "Sn42Bi58" manufactured by Mitsui Kinzoku Co., Ltd., average particle size: 5 μm
Solder particle 4: SnBi solder particles, melting point 138°C, solder particles selected from "Sn42Bi58" manufactured by Mitsui Kinzoku Co., Ltd., average particle size: 2 μm

flux:
Flux 1: “Glutaric acid benzylamine salt”, melting point 108°C

How to make Flux 1:
24 g of water as a reaction solvent and 13.212 g of glutaric acid (manufactured by Wako Pure Chemical Industries, Ltd.) were placed in a glass bottle and dissolved until uniform at room temperature. 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 resulting mixture was placed in a refrigerator at 5 to 10°C and left overnight. The precipitated crystals were collected by filtration, washed with water, and vacuum dried to obtain Flux 1.

(Particle size of solder particles)
The particle diameter of the solder particles was measured as follows.

How to measure the particle size of solder particles:
The particle diameter of the solder particles was measured using a laser diffraction particle size distribution analyzer (“LA-920” manufactured by Horiba, Ltd.).

(Examples 1 to 17 and Comparative Examples 1 and 2)
(1) Preparation of conductive material (anisotropic conductive paste) A conductive material (anisotropic conductive paste) was obtained by blending the ingredients shown in Tables 1 and 2 below in the amounts shown in Tables 1 and 2 below. Ta.

(2) Preparation of connection structure As the second connection target member, 250 μm copper electrodes are arranged in an area array at a 400 μm pitch on the surface of the semiconductor chip body (size 5 × 5 mm, thickness 0.4 mm). A semiconductor chip was prepared in which a passivation film (made of polyimide, thickness 5 μm, opening diameter of electrode portion 200 μm) was formed on the outermost surface. The number of copper electrodes is 10×10, 100 in total, per semiconductor chip.

As the first connection target member, the surface of the glass epoxy board body (size 20 x 20 mm, thickness 1.2 mm, material FR-4) is coated with the same pattern as the electrode of the second connection target member. A glass epoxy substrate was prepared in which copper electrodes were arranged and a solder resist film was formed in areas where the copper electrodes were not arranged. The level difference between the surface of the copper electrode and the surface of the solder resist film is 15 μm, and the solder resist film protrudes from the copper electrode.

A conductive material (anisotropic conductive paste) immediately after preparation was applied to a thickness of 100 μm on the upper surface of the glass epoxy substrate to form a conductive material (anisotropic conductive paste) layer. Next, semiconductor chips were stacked on the upper surface of the conductive material (anisotropic conductive paste) layer so that the electrodes faced each other. The weight of the semiconductor chip is added to the conductive material (anisotropic conductive paste) layer. From this state, the temperature of the conductive material (anisotropic conductive paste) layer was heated to the melting point of the solder 5 seconds after the start of temperature rise. Furthermore, 15 seconds after the start of temperature rise, the conductive material (anisotropic conductive paste) layer is heated to a temperature of 160°C to harden the conductive material (anisotropic conductive paste) layer, and the connected structure is formed. Obtained. No pressure was applied during heating.

(evaluation)
(1) Melt viscosity of conductive material composition excluding solder particles (conductive material excluding solder particles) Among the components shown in Tables 1 and 2 below, the components excluding solder particles are blended as shown in Tables 1 and 2 below. A sample for melt viscosity measurement was obtained by blending in a certain amount. The obtained sample was measured using a rheometer "HAAKE MARS III" manufactured by Thermo Fisher Scientific under conditions of a frequency of 2 Hz, a heating rate of 0.11° C./sec, and a measurement temperature range of 40° C. to 200° C. From the obtained measurement results, the minimum value of the melt viscosity and the temperature (X° C.) indicating the minimum value of the melt viscosity were determined. Further, from the obtained measurement results, the melt viscosity at X-10°C (ηX-10) and the melt viscosity at X+10°C (ηX+10) were determined.

(2) Solder Remains In the obtained connection structure, the first connection target member and the second connection target member face each other in the stacking direction of the first connection target member, the connecting portion, and the second connection target member. When looking at the mating portion, the solder particles in the connection portion are arranged within 100% of the area of the facing portion of the first connection target member and the second connection target member between adjacent electrodes. The area ratio X was evaluated. Solder residue was judged based on the following criteria.

[Criteria for determining solder residue]
○○: Proportion X is less than 5% ○: Proportion X is 5% or more and less than 10% △: Proportion X is 10% or more and less than 30% ×: Proportion

(3) Void In the obtained bonded structure, the bonded portion was observed using a scanning electron microscope to confirm whether or not voids were generated in the bonded portion. Void was determined based on the following criteria.

[Void judgment criteria]
○: No voids have occurred ×: Voids have occurred

(4) Accuracy of placement of solder on electrodes In the obtained connection structure, the portions where the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connecting portion, and the second electrode The ratio Y of the area where the solder part in the connection part is arranged to 100% of the area of the opposing part of the first electrode and the second electrode was evaluated. The placement accuracy of the solder on the electrode was judged based on the following criteria.

[Criteria for determining accuracy of solder placement on electrodes]
○○: Proportion Y is 70% or more ○: Proportion Y is 60% or more but less than 70% △: Proportion Y is 50% or more but less than 60% ×: Proportion Y is less than 50%

(5) Continuity reliability between upper and lower electrodes In the obtained connected structures (n=15 pieces), the connection resistance per connection point between the upper and lower electrodes was measured using a four-terminal method. The average value of connection resistance was calculated. Note that from the relationship of voltage=current×resistance, the connection resistance can be determined by measuring the voltage when a constant current is passed. Continuity reliability was judged based on the following criteria.

[Criteria for determining continuity reliability]
○○: The average value of connection resistance is 50mΩ or less ○: The average value of connection resistance is more than 50mΩ and 70mΩ or less △: The average value of connection resistance is more than 70mΩ and 100mΩ or less ×: The average value of connection resistance is more than 100mΩ , or there is a poor connection.

(6) Insulation reliability between adjacent electrodes After leaving the obtained connected structures (n = 15 pieces) in an atmosphere of 85°C and 85% humidity for 100 hours, 5V was applied between adjacent electrodes. , resistance values were measured at 25 locations. Insulation reliability was judged based on the following criteria.

[Judgment criteria for insulation reliability]
○○: Average value of connection resistance is 10 ⁷ Ω or more ○: Average value of connection resistance is 10 ⁶ Ω or more, less than 10 ⁷ Ω △: Average value of connection resistance is 10 ⁵ Ω or more, less than 10 ⁶ Ω ×: Connection Average resistance value is less than 10 ⁵ Ω

The results are shown in Tables 1 and 2 below.

Similar trends were observed even when flexible printed circuit boards, resin films, flexible flat cables, and rigid-flex circuit boards were used.

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 ...Cured product part 11...Conductive material 11A...Solder particles 11B...Thermosetting component

Claims (9)

A conductive material containing a thermosetting compound, a curing accelerator, and solder particles,
The particle size of the solder particles is 30 μm or less,
The melt viscosity of the composition excluding the solder particles in the conductive material is measured, and when the temperature at which the melt viscosity shows the minimum value is X ° C., the melt viscosity at X-10 ° C. and the melt viscosity at X + 10 ° C. are respectively, 1 Pa・s or more and 10 Pa・s or less ,
The temperature X° C. showing the minimum value of the melt viscosity is 100° C. or more and 115° C. or less,
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)) )) or for connecting flexible printed circuit boards and glass epoxy boards (FOB (Film on Board)) . The conductive material according to claim 1, wherein the temperature at which the melt viscosity shows a minimum value is 100°C or more and 110°C or less. The conductive material according to claim 1 or 2, wherein the content of the curing accelerator with respect to 100 parts by weight of the thermosetting compound is 0.1 parts by weight or more and 20 parts by weight or less. The conductive material according to any one of claims 1 to 3, wherein the content of the solder particles in 100% by weight of the conductive material is 55% by weight or more and 75% by weight or less. The conductive material according to any one of claims 1 to 4, which is a conductive paste. a first connection target member having a first electrode on its surface;
a second connection target member having a second electrode on its surface;
comprising a connection part connecting the first connection target member and the second connection target member,
The material of the connecting portion is the conductive material according to any one of claims 1 to 5,
A connection structure in which the first electrode and the second electrode are electrically connected by a solder part in the connection part. When looking at the opposing portions of the first electrode and the second electrode in the stacking direction of the first electrode, the connecting portion, and the second electrode, the first electrode and the second electrode are 7. The connection structure according to claim 6, wherein the solder part in the connection part is disposed in 50% or more of 100% of the area of the part facing the second electrode. using the conductive material according to any one of claims 1 to 5, disposing the conductive material on the surface of the first connection target member having the first electrode on the surface;
A second connection target member having a second electrode on its surface is placed on a surface of the conductive material opposite to the first connection target member side, and the first electrode and the second electrode are opposite to each other. a step of arranging the
A connecting portion connecting the first connection target member and the second connection target member is formed from the conductive material by heating the conductive material to a temperature higher than the melting point of the solder particles, and A method for manufacturing a connected structure, comprising the step of electrically connecting the first electrode and the second electrode with a solder part in the connecting part. When looking at the opposing portions of the first electrode and the second electrode in the stacking direction of the first electrode, the connecting portion, and the second electrode, the first electrode and the second electrode are 9. The method for manufacturing a connected structure according to claim 8, wherein the solder part in the connecting part is disposed in 50% or more of 100% of the area of the part facing the second electrode. .

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