TWI676183B - Conductive paste, connection structure, and manufacturing method of connection structure - Google Patents

Abstract

The invention provides a conductive paste, which can efficiently dispose solder particles on electrodes, prevent positional displacement between electrodes, and improve conduction reliability between electrodes.

The conductive paste of the present invention includes a thermosetting compound and a thermosetting agent as a thermosetting component, and a plurality of solder particles. The thermosetting compound includes a crystalline thermosetting compound, and the solder particles are a central portion and conductive. The outer surfaces are all particles of solder.

Description

Conductive paste, connection structure and manufacturing method of connection structure

The present invention relates to a conductive paste containing solder particles. The present invention also relates to a connection structure using the conductive paste and a method for manufacturing the connection structure.

Anisotropic conductive materials such as an anisotropic conductive paste and an anisotropic conductive film are widely known. In the anisotropic conductive material, conductive particles are dispersed in a binder.

In order to obtain various connection structures, the above-mentioned anisotropic conductive material is used, for example, for connection between a flexible printed substrate and a glass substrate (FOG (Film on Glass, coated glass)), connection between a semiconductor wafer and a flexible printed substrate (COF (Chip on Film)), the connection between semiconductor wafers and glass substrates (COG (Chip on Glass)), and the connection between flexible printed substrates and glass epoxy substrates (FOB (Film on Board)) Wait.

When the anisotropic conductive material is used to electrically connect, for example, an electrode of a flexible printed circuit board and an electrode of a glass epoxy substrate, the anisotropic conductive material including conductive particles is disposed on the glass epoxy substrate. Next, the flexible printed circuit board is laminated, and heated and pressurized. Thereby, the anisotropic conductive material is hardened, and the electrodes are electrically connected via the conductive particles to obtain a connection structure.

As an example of the anisotropic conductive material, Patent Document 1 below discloses a tape including a resin layer containing a thermosetting resin, a solder powder, and a hardener, and the solder powder and the hardener are present in In the above resin layer. The tape is film-like and not paste-like.

In addition, Patent Document 1 discloses a bonding method using the above-mentioned tape. Specifically, a first substrate, an adhesive tape, a second substrate, an adhesive tape, and a third substrate are sequentially laminated from the bottom to obtain a laminated body. At this time, the first electrode provided on the surface of the first substrate and the second electrode provided on the surface of the second substrate are opposed to each other. Moreover, the second electrode provided on the surface of the second substrate and the third electrode provided on the surface of the third substrate are opposed to each other. Then, the laminated body is heated at a specific temperature to perform the bonding. Thereby, a connection structure is obtained.

An anisotropic conductive material in which conductive particles are dispersed in an insulating adhesive is disclosed in Patent Document 2 below. The minimum melt viscosity [η ₀ ] of the anisotropic conductive material is 1.0 × 10 ² to 1.0 × 10 ⁶ mPa‧sec. Regarding the anisotropic conductive material, 1 <[η ₁ ] / [η ₀ ] ≦ 3 is satisfied ([η ₀ ] is the lowest melting viscosity of the anisotropic conductive material, and [η ₁ ] is more Melt viscosity at a temperature T ₀ lower than 30 ° C at a temperature T ₁ ).

In addition, Patent Document 3 below discloses an anisotropic conductive material containing a curable compound, a thermal radical initiator, a photo radical initiator, and conductive particles.

The following Patent Document 4 describes an anisotropic conductive material including conductive particles and a resin component that does not end hardening at the melting point of the conductive particles. Specific examples of the conductive particles include tin (Sn), indium (In), bismuth (Bi), silver (Ag), copper (Cu), zinc (Zn), lead (Pb), and cadmium ( Cd), gallium (Ga), silver (Ag) and thallium (Tl) and other metals, or alloys of these metals.

Patent Document 4 describes a resin heating step of heating an anisotropic conductive resin to a temperature higher than the melting point of the conductive particles and the curing of the resin component does not end, and a resin component curing step of curing the resin component. To electrically connect the electrodes. In addition, Patent Document 1 describes mounting with a temperature distribution shown in FIG. 8 of Patent Document 1. In Patent Document 1, the conductive particles are melted in a resin component that does not end hardening at a temperature at which the anisotropic conductive resin is heated.

In addition, Patent Document 5 below discloses a flip-chip mounting method in which a half of a plurality of connection terminals is disposed so as to face a wiring substrate having a plurality of electrode terminals. A conductor wafer, and electrically connecting the electrode terminals of the wiring substrate and the connection terminals of the semiconductor wafer. The flip chip mounting method includes the following steps: (1) a step of supplying a resin containing solder powder and a convective additive to a surface of the wiring substrate having the electrode terminals; (2) abutting the semiconductor wafer on the resin surface (3) a step of heating the wiring board to a temperature at which the solder powder is melted; and (4) a step of hardening the resin after the heating step. In the heating step (3) of the wiring substrate, a connection body for electrically connecting the electrode terminal and the connection terminal is formed, and in the hardening step (4) of the resin, the semiconductor wafer is fixed to the wiring substrate. .

[Prior technical literature] [Patent Literature]

[Patent Document 1] WO2008 / 023452A1

[Patent Document 2] Japanese Patent Laid-Open No. 2009-32657

[Patent Document 3] Japanese Patent Laid-Open No. 2012-186161

[Patent Document 4] Japanese Patent Laid-Open No. 2004-260131

[Patent Document 5] Japanese Patent Laid-Open No. 2006-114865

The tape described in Patent Document 1 is film-like, not paste-like. Therefore, it is difficult to efficiently dispose the solder on the electrodes (wires). For example, in the tape described in Patent Document 1, it is easy to dispose a part of the solder powder in a region (gap) where no electrode is formed. The solder powder arranged in the area where the electrodes are not formed does not help the conduction between the electrodes.

In the conventional solder powder or an anisotropic conductive paste containing conductive particles having a solder layer on the surface, the solder powder or the conductive particles may not be efficiently disposed on the electrode (wire). In the conventional solder powder or conductive particles, the movement speed of the solder powder or conductive particles to the electrode may be slow.

Furthermore, the conventional anisotropic conductive paste may cause a positional shift between electrodes which should be connected up and down.

In addition, in Patent Documents 1 and 2, there is no specific description about the conductive particles used in the anisotropic conductive material. In Examples of Patent Documents 3 and 5, conductive particles are used in which a copper layer is formed on the surface of the resin particles, and a solder layer is formed on the surface of the copper layer. The central portion of the conductive particles is made of resin particles. In addition, even if the anisotropic conductive material described in Patent Documents 1, 2, 3, and 5 is used, conductive particles are not efficiently arranged on the electrodes (wires), or there may be a gap between the electrodes that should be connected up and down. Case of position shift.

In addition, if the anisotropic conductive material described in Patent Document 4 is used and the electrodes are electrically connected by the method described in Patent Document 4, conductive particles including solder are not efficiently disposed on the electrode. (Line) the situation. Further, in the embodiment of Patent Document 4, in order to sufficiently move the solder at a temperature higher than the melting point of the solder and maintain it at a fixed temperature, the manufacturing efficiency of the connection structure is reduced. When mounting is performed with the temperature distribution shown in FIG. 8 of Patent Document 4, the manufacturing efficiency of the connection structure is reduced.

An object of the present invention is to provide a conductive paste that can efficiently dispose solder particles on electrodes, prevent positional displacement between electrodes, and improve conduction reliability between electrodes. The present invention also provides a connection structure using the conductive paste and a method for manufacturing the connection structure.

According to a broad aspect of the present invention, there is provided a conductive paste including a thermosetting compound and a thermosetting agent as a thermosetting component, and a plurality of solder particles, wherein the thermosetting compound includes a crystalline thermosetting compound In addition, the above solder particles are particles in which the central portion and the conductive outer surface are solder.

In a specific aspect of the conductive paste of the present invention, the crystalline thermosetting compound is solid at 25 ° C.

In a specific aspect of the conductive paste of the present invention, the melting point of the crystalline thermosetting compound is 80 ° C or higher and 150 ° C or lower.

In a specific aspect of the conductive paste of the present invention, the molecular weight of the crystalline thermosetting compound is 300 or more and 500 or less.

In a specific aspect of the conductive paste of the present invention, the crystalline thermosetting compound is a benzophenone-type epoxy compound.

In a specific aspect of the conductive paste of the present invention, the average aspect ratio of the crystals of the crystalline thermosetting compound is 5 or less.

In a specific aspect of the conductive paste of the present invention, the average major diameter of the crystals of the crystalline thermosetting compound is less than 1 / 1.5 of the average particle diameter of the solder particles.

In a specific aspect of the conductive paste of the present invention, the average major diameter of the crystals of the crystalline thermosetting compound is 1/10 or more of the average particle diameter of the solder particles.

In a specific aspect of the conductive paste of the present invention, the melting point of the crystalline thermosetting compound is lower than the melting point of the solder.

In a specific aspect of the conductive paste of the present invention, the conductive paste contains a flux, and the melting point of the crystalline thermosetting compound is lower than the activation temperature of the flux.

In a specific aspect of the conductive paste of the present invention, the content of the crystalline thermosetting compound is 10% by weight or more in 100% by weight of the entire thermosetting compound.

In a specific aspect of the conductive paste of the present invention, the above-mentioned conductive paste does not contain a filler, or contains 5 wt% or less of a filler.

In a specific aspect of the conductive paste of the present invention, in the conductive paste, the crystalline thermosetting compound is dispersed in a particulate form.

In a specific aspect of the conductive paste of the present invention, other thermosetting compounds other than the crystalline thermosetting compound are contained.

In a specific aspect of the conductive paste of the present invention, the average particle diameter of the solder particles is 1 μm or more and 60 μm or less.

In a specific aspect of the conductive paste of the present invention, the content of the solder particles is 10% by weight or more and 80% by weight or less.

According to a wider aspect of the present invention, there is provided a connection structure including: a first connection target member having at least one first electrode on a surface; and a second connection target member having at least one first electrode on a surface. 2 electrodes; and a connecting portion that connects the first connection target member and the second connection target member; the connection portion is a hardened material of the conductive paste; and the first electrode and the second electrode system use the connection portion The solder part is electrically connected.

According to a broad aspect of the present invention, a method for manufacturing a connection structure is provided, which includes the steps of using the above conductive paste to arrange the above on the surface of a first connection target member having at least one first electrode on the surface. Conductive paste; a second connection object having at least one second electrode on the surface thereof, which is arranged on the surface of the conductive paste opposite to the side of the first connection object member, so that the first electrode and the second electrode face each other A component; and heating the conductive paste to a temperature above the melting point of the solder particles and a temperature above the curing temperature of the thermosetting component, and forming a connection between the first connection target member and the second connection target member using the conductive paste. The connection portion, and the first electrode and the second electrode are electrically connected by a solder portion of the connection portion.

In a specific aspect of the method for manufacturing a connection structure of the present invention, in the step of disposing the second connection target member and the step of forming the connection portion, the conductive paste is applied with the weight of the second connection target member. Without pressurization, pressurization is performed in at least one of the step of disposing the second connection target member and the step of forming the connecting portion, and the step of disposing the second connection target member and forming the connection portion In both of the steps, the pressure of pressurization did not reach 1 MPa.

In a specific aspect of the manufacturing method of the connection structure of the present invention, in the configuration In the step of the second connection target member and the step of forming the connection portion, the weight of the second connection target member is applied to the conductive paste without pressing.

The second connection target member is preferably a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate.

In the connection structure, it is preferable to observe a portion of the first electrode and the second electrode facing each other in a lamination direction of the first electrode, the connection portion, and the second electrode, in the first The solder portion of the connection portion is disposed in at least 50% of an area of 100% of an electrode and the second electrode facing each other. In the above-mentioned connection structure, it is preferable that when the mutually facing portions of the first electrode and the second electrode are viewed in a direction orthogonal to the lamination direction of the first electrode, the connection portion, and the second electrode, In the part where the first electrode and the second electrode oppose each other, 70% or more of the solder part in the connection part is arranged.

The conductive paste of the present invention contains a thermosetting compound and a thermosetting agent as a thermosetting component, and a plurality of solder particles, and the thermosetting compound includes a crystalline thermosetting compound, and the solder particles are a central portion and The outer surfaces of the conductive material are all solder particles. Therefore, when the electrodes are electrically connected, the solder particles can be efficiently arranged on the electrodes, which can prevent the position shift between the electrodes and improve the electrode-to-electrode position. Continuity reliability.

1‧‧‧ connect structure

1X‧‧‧ Connected Structure

2‧‧‧The first connection target component

2a‧‧‧The first electrode

3‧‧‧ 2nd connection target component

3a‧‧‧Second electrode

4‧‧‧ Connection Department

4A‧‧‧Solder Department

4B‧‧‧Hardened Materials Division

4X‧‧‧Connecting section

4XA‧‧‧Solder Department

4XB‧‧‧Hardened material department

11‧‧‧Conductive paste

11A‧‧‧Solder particles

11B‧‧‧thermosetting ingredients

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

2 (a) to (c) are cross-sectional views for explaining each step of an example of a method of manufacturing a connection structure using a conductive paste according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a modified example of the connection structure.

Hereinafter, details of the present invention will be described.

(Conductive paste)

The conductive paste of the present invention includes a thermosetting compound as a thermosetting component, a thermosetting agent, and a plurality of solder particles. In the conductive paste of the present invention, the thermosetting compound includes a crystalline thermosetting compound. Either the central portion of the solder particles or the conductive outer surface is formed of solder. The solder particles are particles in which the central portion and the outer conductive surface of the solder particles are solder.

Since the conductive paste of the present invention adopts the above-mentioned structure, when the electrodes are electrically connected, a plurality of solder particles easily accumulate between the electrodes facing up and down, and the plurality of solder particles can be efficiently disposed on the electrodes. (on-line. In addition, it is difficult to dispose a part of the plurality of solder particles in a region (gap) where the electrode is not formed, and the amount of solder particles disposed in a region where the electrode is not formed can be considerably reduced. Therefore, the conduction reliability between the electrodes can be improved. In addition, it is possible to prevent electrical connection between electrodes that are adjacent in the lateral direction that should not be connected, and to improve insulation reliability. Furthermore, 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 coated with the conductive paste, the alignment between the electrode of the first connection target member and the electrode of the second connection target member is shifted. Next, even when the first connection target member and the second connection target member overlap, the offset can be corrected, and the electrode of the first connection target member and the electrode of the second connection target member can be connected (self-aligned). effect). In order to obtain such an effect, the conductive material is a conductive paste, the conductive particles used together with the thermosetting compound and the thermosetting agent are solder particles, and the above-mentioned thermosetting compound is a crystalline thermosetting compound that contributes significantly.

Furthermore, when conductive particles including substrate particles not formed of solder and a solder layer disposed on the surface of the substrate particles are used instead of the above-mentioned solder particles, since the conductive particles are unlikely to accumulate on the electrode, Since the conductive particles have low weldability to each other, the conductive particles that have moved to the electrodes easily move outside the electrodes. Therefore, the effect of suppressing the positional shift between the electrodes is also reduced.

The so-called "crystallinity" in a crystalline thermosetting compound refers to a state in which molecular chains are regularly arranged, and the compound has a glass transition temperature and a melting point.

Regarding the conductive paste of the present invention, the average aspect ratio of the crystals of the crystalline thermosetting compound is preferably 5 or less.

Regarding the conventional anisotropic conductive paste, if used after storage, the conductive particles may not be easily arranged on the electrode (wire).

When the average aspect ratio of the crystals of the crystalline thermosetting compound is 5 or less, the storage stability of the conductive paste is excellent. Therefore, in any case before and after the storage of the conductive paste, the solder can be efficiently arranged on the electrodes, and the reliability of conduction between the electrodes can be improved.

By including a crystalline thermosetting compound in the conductive paste, if heat is applied to the conductive paste, the viscosity of the conductive paste is sufficiently reduced. If heat is applied to the conductive paste, the crystallinity of the crystalline thermosetting compound is lost, so the viscosity of the conductive paste is sufficiently reduced, and the migration of solder is promoted. Furthermore, it was found that the conductive paste containing the crystalline thermosetting compound had different migration properties of the solder particles before and after storage of the conductive paste. This is considered to be because the crystalline state of the crystalline thermosetting compound is changed. It has been found that when a crystalline thermosetting compound is used, if the average aspect ratio of the crystals of the crystalline thermosetting compound is 5 or less, it is difficult to change the movement properties of the solder particles before and after the storage of the conductive paste.

Furthermore, in the present invention, it is possible to prevent a positional shift between the electrodes. In the present invention, when the second connection target member is superimposed on the first connection target member having the conductive paste disposed on the upper surface, the alignment between the electrode of the first connection target member and the electrode of the second connection target member is shifted. In the state, even when the first connection target member and the second connection target member overlap, the offset can be corrected to connect the electrode of the first connection target member with the electrode of the second connection target member (self-alignment). Quasi-effect). In order to obtain such an effect, the contribution of using a conductive paste having a specific composition is large.

As a method of making the average aspect ratio of the crystal | crystallization of the said crystalline thermosetting compound into 5 or less, the method of crushing a crystalline thermosetting compound, etc. are mentioned. It is preferable to mix | blend a crystalline thermosetting compound, and mix | blend it into a conductive paste. The crystalline thermosetting compound may be used after screening the crystalline thermosetting compound so that the average aspect ratio becomes 5 or less.

From the viewpoint of further improving the storage stability of the conductive paste, further efficiently disposing the solder on the electrodes, and further suppressing the positional shift between the electrodes, the average aspect ratio of the crystals of the crystalline thermosetting compound is preferably 4 the following. The average aspect ratio is an average of the aspect ratios of a plurality of crystals. The above aspect ratio indicates a major axis / minor axis. The above aspect ratio is the aspect ratio in the conductive paste.

The average aspect ratio of the crystals of the crystalline thermosetting compound is 1 or more. The crystals of the crystalline thermosetting compound are preferably needle-like crystals. From the viewpoint of increasing the initial viscosity of the conductive paste, suppressing excessive wetting and diffusion of the conductive paste, and further efficiently disposing the solder on the electrode, the average aspect ratio of the crystal of the crystalline thermosetting compound is preferably 1.3. The above is more preferably 1.5 or more.

From the viewpoint of further improving the storage stability of the conductive paste, further efficiently disposing the solder on the electrodes, and further suppressing the positional shift between the electrodes, the average long diameter of the crystal of the crystalline thermosetting compound is preferably The average particle diameter of the said solder particle is 1 / 1.5 or less, More preferably, it is 1/2 or less of the average particle diameter of the said solder particle.

From the viewpoint of increasing the initial viscosity of the conductive paste, suppressing excessive wetting and diffusion of the conductive paste, and further efficiently disposing the solder on the electrode, the average long diameter of the crystal of the crystalline thermosetting compound is preferably The average particle diameter of the said solder particle is 1/10 or more, More preferably, it is 1/8 or more of the average particle diameter of the said solder particle.

From the viewpoint of further efficiently disposing the solder on the electrodes and further suppressing the positional shift between the electrodes, the melting point of the crystalline thermosetting compound is preferably lower than the melting point of the solder. The solder is further efficiently disposed on the electrode, further suppressing From the viewpoint of the positional displacement between the electrodes, the absolute value of the difference between the melting point of the crystalline thermosetting compound and the melting point of the solder is preferably 10 ° C or higher, more preferably 20 ° C or higher, and preferably 80 ° C. It is below 70 ° C, more preferably below 70 ° C.

From the viewpoint of further improving the conduction reliability, it is preferable that the conductive paste contains a flux. From the viewpoint of further efficiently disposing the solder on the electrodes and further suppressing the positional shift between the electrodes, the melting point of the crystalline thermosetting compound is preferably lower than the activation temperature of the flux. From the viewpoint of further efficiently disposing the solder on the electrodes and further suppressing the positional shift between the electrodes, the absolute value of the difference between the melting point of the crystalline thermosetting compound and the activity temperature of the flux is preferably 5 Above 10 ° C, more preferably above 10 ° C, more preferably below 60 ° C, even more preferably below 50 ° C.

From the viewpoint that both the improvement effect of the coating property and the improvement effect of the conduction reliability between the electrodes achieved by efficiently moving the conductive particles onto the electrodes can be achieved at a higher level, in the present invention In the conductive paste, the crystalline thermosetting compound is preferably dispersed in a particulate form.

In order to further efficiently dispose the solder particles on the electrode, the viscosity (η25) of the conductive paste at 25 ° C is preferably 10 Pa · s or more, more preferably 50 Pa · s or more, and even more preferably 100 Pa · s or more. It is preferably 800 Pa · s or less, more preferably 600 Pa · s or less, and even more preferably 500 Pa · s or less.

The above-mentioned viscosity (η25) can be appropriately adjusted to the type and amount of the blended components. In addition, by using a filler, the viscosity can be relatively increased.

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

The conductive paste of the present invention can be suitably used in the following connection structure of the present invention and a method for manufacturing the connection structure.

The conductive paste is preferably an anisotropic conductive paste. The conductive paste can be suitably used for electrical connection of electrodes. The conductive paste is preferably a circuit connection material.

Hereinafter, each component contained in the said conductive paste is demonstrated.

(Solder particles)

The solder particles have solder on a surface other than conductive. In the solder particles described above, either the central portion or the conductive outer surface is formed of solder. The solder particles are particles of solder at the central portion and the outer conductive surface.

From the viewpoint of efficiently concentrating the solder particles on the electrode, the zeta potential of the surface of the solder particles is preferably positive. However, in the present invention, the zeta potential of the surface of the solder particles may not be positive.

The zeta potential is measured as follows.

Method for measuring zeta potential:

0.05 g of solder particles were added to 10 g of methanol, and ultrasonic treatment or the like was performed to uniformly disperse them to obtain a dispersion liquid. This dispersion can be used to measure the zeta potential by electrophoresis using "Delsamax PRO" manufactured by Beckman Coulter.

The zeta potential of the solder particles is preferably more than 0 mV, more preferably more than 0 mV, and more preferably 10 mV or less, more preferably 5 mV or less, still more preferably 1 mV or less, still more preferably 0.7 mV or less, particularly preferably 0.5. mV or less. If the zeta potential is equal to or less than the above upper limit, solder particles are less likely to aggregate in the conductive paste before use. When the zeta potential is 0 mV or more, the solder particles are efficiently aggregated on the electrode during mounting.

From the viewpoint of easily making the zeta potential of the surface positive, the solder particles preferably have a solder particle body and an anionic polymer disposed on the surface of the solder particle body. The solder particles are preferably obtained by subjecting the solder particle body to surface treatment with a compound that becomes an anionic polymer or an anionic polymer. It is preferable that the said solder particle is a surface-treated thing formed from the compound which becomes an anionic polymer or an anionic polymer. Only one kind of the anionic polymer and the compound of the anionic polymer may be used, or two or more kinds may be used in combination.

Examples of the method for surface-treating the solder particle body by using an anionic polymer include, for example, a (meth) acrylic polymer obtained by copolymerizing (meth) acrylic acid, and a synthesis of a dicarboxylic acid and a diol. A polyester polymer having carboxyl groups at both ends, a polymer obtained by intermolecular dehydration condensation reaction of a dicarboxylic acid and a carboxyl group at both ends, a polyester polymer synthesized from a dicarboxylic acid and a diamine and carboxyl groups at both ends As an anionic polymer, modified polyvinyl alcohol having a carboxyl group ("GOHSENX T" manufactured by Nippon Synthetic Chemical Co., Ltd.) and the like react the carboxyl group of the anionic polymer with the hydroxyl group on the surface of the solder particle body.

The anionic portion of the anionic polymer include a carboxyl group, in addition, include: toluenesulfonamide acyl _{(pH 3 CC 6 H 4 S} (= O) 2 -), sulfonate ion group (-SO ₃ ^-), phosphate ions and group (-PO ₄ ^-) and the like.

In addition, as another method, there can be mentioned a method of using a compound having a functional group that reacts with a hydroxyl group on the surface of the body of the solder particle body, and further a functional group that can be polymerized by addition or condensation reaction, and applying the compound to the solder. The surface of the particle body is polymerized. Examples of the functional group that reacts with a hydroxyl group on the surface of the solder particle body include a carboxyl group and an isocyanate group. Examples of the functional group that is polymerized by an addition or condensation reaction include a hydroxyl group, a carboxyl group, an amine group, and ( (Meth) acrylfluorenyl.

The weight average molecular weight of the anionic polymer is preferably 2,000 or more, more preferably 3,000 or more, and preferably 10,000 or less, and more preferably 8,000 or less.

If the weight average molecular weight is above the lower limit and below the upper limit, it is easy to dispose the anionic polymer on the surface of the solder particle body, and it is easy to set the zeta potential of the surface of the solder particle to positive, and the solder particle can be further Efficiently placed on the electrode.

The said weight average molecular weight shows the weight average molecular weight in polystyrene conversion measured by gel permeation chromatography (GPC).

Regarding the weight average molecular weight of the polymer obtained by subjecting the solder particle body to surface treatment with a compound that becomes an anionic polymer, the solder in the solder particle can be dissolved, and dilute hydrochloric acid that does not cause decomposition of the polymer can be used. After removing the solder particles, the weight average molecular weight of the remaining polymer was measured and determined.

The solder is preferably a metal (low melting point metal) having a melting point of 450 ° C or lower. The solder particles are preferably metal particles (low melting point metal particles) having a melting point of 450 ° C or lower. The low-melting metal particles are particles containing a low-melting metal. The low melting point metal means 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, and more preferably 160 ° C or lower. The solder particles include tin. The content of tin in 100% by weight of the metal contained in the solder particles is preferably 30% by weight or more, more preferably 40% by weight or more, still more preferably 70% by weight or more, and most preferably 90% by weight or more. When the content of tin in the solder particles is greater than or equal to the above lower limit, the connection reliability between the solder portion and the electrode is further increased.

In addition, the above-mentioned tin content can be measured by a high-frequency inductively coupled plasma emission spectrophotometer ("ICP-AES" manufactured by HORIBA, Ltd.) or a fluorescent X-ray analyzer ("EDX-800HS" manufactured by Shimadzu Corporation) ) And so on.

By using the above-mentioned solder particles, the solder is melted to be bonded to the electrodes, and the solder portion conducts electrical conduction between the electrodes. For example, since the solder portion and the electrode are likely to make surface contact rather than point contact, the connection resistance is reduced. In addition, by using solder particles, the bonding strength between the solder portion and the electrode is increased, and as a result, peeling of the solder portion and the electrode is less likely to occur, and continuity reliability and connection reliability are effectively increased.

The metal (low melting point metal) constituting the solder particles is not particularly limited. The low-melting metal is preferably an alloy containing tin or tin. Examples of the alloy include tin-silver alloy, tin-copper alloy, tin-silver-copper alloy, tin-bismuth alloy, tin-zinc alloy, and tin-indium alloy. Among these, in terms of excellent wettability with respect to the electrode, the above-mentioned low melting point metal is preferably tin, tin-silver alloy, tin-silver-copper alloy, tin-bismuth alloy, and tin-indium alloy. More preferably, it is a tin-bismuth alloy, Tin-indium alloy.

The solder particle is preferably a filler metal based on JIS Z3001: soldering term and having a liquidus of 450 ° C. or lower. Examples of the composition of the solder particles include metal compositions including zinc, gold, silver, lead, copper, tin, bismuth, and indium. Among them, a low melting point and lead-free tin-indium based (117 ° C eutectic) or tin-bismuth based (139 ° C eutectic) is preferred. That is, the above-mentioned solder particles are preferably lead-free, and preferably contain tin and indium, or include tin and bismuth.

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

The average particle diameter of the solder particles is preferably 0.5 μm or more, more preferably 1 μm or more, even more preferably 3 μm or more, particularly preferably 5 μm or more, and more preferably 100 μm or less, more preferably less than 80 μm, and further more It is preferably 75 μm or less, more preferably 60 μm or less, even more preferably 40 μm or less, still more preferably 30 μm or less, still more preferably 20 μm or less, particularly preferably 15 μm or less, and most preferably 10 μm or less. If the average particle diameter of the said solder particle is more than the said lower limit and below the said upper limit, a solder particle can be arrange | positioned on an electrode further efficiently. The average particle diameter of the solder particles is particularly preferably 3 μm or more and 30 μm or less.

The "average particle diameter" of the solder particles indicates a number average particle diameter. The average particle diameter of the solder particles is obtained, for example, by observing 50 arbitrary solder particles with an electron microscope or an optical microscope, calculating the average value, or performing a laser diffraction particle size distribution measurement.

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

The coefficient of variation (CV value) is expressed by the following formula.

CV value (%) = (ρ / Dn) × 100

ρ: standard deviation of the particle diameter of the 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 a shape other than a spherical shape such as a flat shape.

In 100% by weight of the conductive paste, the content of the solder particles is preferably 1% by weight or more, more preferably 2% by weight or more, still more preferably 10% by weight or more, particularly preferably 20% by weight or more, and most preferably 30% by weight or more, and preferably 80% by weight or less, more preferably 60% by weight or less, and even more preferably 50% by weight or less. If the content of the solder particles is above the lower limit and below the upper limit, the solder particles can be further efficiently disposed on the electrodes, a large number of solder particles can be easily disposed between the electrodes, and the conduction reliability can be further increased. From the viewpoint of further improving the conduction reliability, it is preferable that the content of the solder particles is large.

When the line (L) of the portion where the electrode is formed is 50 μm or more and less than 150 μm, from the viewpoint of further improving the conduction reliability, the content of the solder particles is preferably 100% by weight of the conductive paste. 20% by weight or more, more preferably 30% by weight or more, more preferably 55% by weight or less, and even more preferably 45% by weight or less.

When the gap (S) of the portion where the electrode is not formed is 50 μm or more and less than 150 μm, from the viewpoint of further improving the conduction reliability, the content of the solder particles is preferably 100% by weight of the conductive paste. 30% by weight or more, more preferably 40% by weight or more, more preferably 70% by weight or less, and still more preferably 60% by weight or less.

When the line (L) of the portion where the electrode is formed is 150 μm or more and less than 1000 μm, from the viewpoint of further improving the conduction reliability, the content of the solder particles is preferably 100% by weight of the conductive paste. 30% by weight or more, more preferably 40% by weight or more, more preferably 70% by weight or less, and still more preferably 60% by weight or less.

(Thermosetting compound: thermosetting component)

The said thermosetting compound is a compound which can harden | cure by heating. Examples of the thermosetting compound include an oxetane compound, an epoxy compound, an episulfide compound, a (meth) acrylic compound, a phenol compound, an amine compound, an unsaturated polyester compound, and a polyamine group. Formates, polysiloxanes, and polyimide compounds. Among these, an epoxy compound is preferable from the viewpoint of making the conductive paste harder and viscosity better and further improving connection reliability.

From the viewpoint of efficiently disposing the solder particles on the electrodes, effectively suppressing the positional shift between the electrodes, and improving the conduction reliability and insulation reliability between the electrodes, the thermosetting compound includes a crystalline thermosetting compound . These crystalline thermosetting compounds may be used alone or in combination of two or more.

From the viewpoint of further efficiently disposing the solder particles on the electrodes, suppressing the positional shift between the electrodes more effectively, and further improving the conduction reliability and insulation reliability between the electrodes, the above-mentioned crystalline thermosetting properties are preferred. The compound was solid at 25 ° C.

From the viewpoint of further efficiently disposing the solder particles on the electrodes, suppressing the positional shift between the electrodes more effectively, and further improving the conduction reliability and insulation reliability between the electrodes, the melting point of the crystalline thermosetting compound It is preferably 80 ° C or higher, more preferably 85 ° C or higher, and more preferably 150 ° C or lower, and more preferably 140 ° C or lower.

From the viewpoint of further efficiently disposing the solder particles on the electrodes, suppressing the positional displacement between the electrodes more effectively, and further improving the conduction reliability and insulation reliability between the electrodes, the molecular weight of the crystalline thermosetting compound 300 or more is preferable, 350 or more is more preferable, 500 or less is more preferable, and 400 or less is more preferable.

When the molecular weight is a case where the thermosetting compound is not a polymer, and when a structural formula of the thermosetting compound can be specified, it means a molecular weight that can be calculated from the structural formula. When the thermosetting compound is a polymer, it means a weight average molecular weight.

Examples of the crystalline thermosetting compound include epoxy compounds and (meth) acrylic compounds.

Examples of the epoxy compound include an aromatic epoxy compound. Among them, crystalline epoxy compounds such as resorcinol-type epoxy compounds, naphthalene-type epoxy compounds, biphenyl-type epoxy compounds, and benzophenone-type epoxy compounds are preferred. Particularly preferred is 2,4-bis (glycidyloxy) benzophenone, or 4,4'-bis (glycidyloxy) benzophenone. By using the above-mentioned preferred epoxy compound, the viscosity is high at the stage of bonding the connection target member, and when an impact such as conveyance is imparted with acceleration, the position deviation of the first connection target member and the second connection target member can be suppressed, In addition, the viscosity of the conductive paste can be greatly reduced by the heat during hardening, and the agglomeration of the solder particles can be performed efficiently.

The (meth) acrylic compound is a compound having a (meth) acrylfluorenyl group. Examples of the (meth) acrylic compound include epoxy (meth) acrylate compounds. A compound obtained by introducing a (meth) acrylfluorenyl group into an epoxy compound using (meth) acrylic acid or the like is preferred.

From the viewpoint of further efficiently disposing the solder particles on the electrodes, suppressing the positional displacement between the electrodes more effectively, and further improving the conduction reliability and insulation reliability between the electrodes, the crystalline thermosetting compound is particularly preferable. It is a benzophenone-type epoxy compound, and is preferably 2,4-bis (glycidyloxy) benzophenone, or 4,4'-bis (glycidyloxy) benzophenone.

In 100% by weight of the conductive paste, the content of the thermosetting compound is preferably 20% by weight or more, more preferably 40% by weight or more, still more preferably 50% by weight or more, and preferably 99% by weight or less, More preferably, it is 98% by weight or less, and further preferably 90% by weight or more. It is particularly preferably 80% by weight or less. From the viewpoint of further improving the impact resistance, the content of the thermosetting component and the thermosetting compound is preferably large.

The content of the crystalline thermosetting compound is preferably 10% by weight or more, more preferably 30% by weight or more, based on 100% by weight of the entire thermosetting compound (other thermosetting compounds and crystalline thermosetting compounds) It is more preferably 50% by weight or more, particularly preferably 70% by weight or more, and more preferably 100% by weight or less.

(Thermosetting agent: thermosetting component)

The said thermosetting agent thermally hardens the said thermosetting compound. Examples of the thermal hardener include thiol hardeners such as imidazole hardeners, amine hardeners, phenol-based hardeners, and polythiol hardeners, acid anhydrides, thermal cationic initiators (thermal cationic hardeners), and thermal radicals. Generating agent, etc. These thermosetting agents may be used alone or in combination of two or more.

Since the conductive paste can be hardened more quickly at low temperatures, an imidazole hardener, a thiol hardener, or an amine hardener is preferred. In addition, since the storage stability is improved when the thermosetting compound is mixed with the thermosetting agent, a latent curing agent is preferred. The latent curing agent is preferably a latent imidazole curing agent, a latent thiol curing agent, or a latent amine curing agent. The thermosetting agent may be coated with a polymer material such as a polyurethane resin or a polyester resin.

及2,4-二胺基-6-[2'-甲基咪唑基-(1')]-乙基-均三

異三聚氰酸加成物等。 The imidazole curing agent is not particularly limited, and examples thereof include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, and 1-cyanoethyl-2 -Phenylimidazolium trimellitate, 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-mesanthine

And 2,4-diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-mesanthine

Isocyanuric acid adducts and the like.

The thiol curing agent is not particularly limited, and examples thereof include trimethylolpropane tri-3-mercaptopropionate, pentaerythritol tetra-3-mercaptopropionate, and dipentaerythritol hexa-3-mercaptopropionate. .

The amine hardener is not particularly limited, and examples thereof include hexamethylenediamine, octamethylenediamine, decamethylenediamine, and 3,9-bis (3-aminopropyl) -2. , 4,8,10-four spiral [5.5] Undecane, bis (4-aminocyclohexyl) methane, m-phenylenediamine, diaminodiphenylphosphonium, and the like.

Examples of the thermal cationic initiator include a fluorene-based cation hardener, an oxonium-based cation hardener, and a fluorene-based cation hardener. Examples of the fluorene-based cationic hardener include bis (4-thirdbutylphenyl) fluorene hexafluorophosphate and the like. Examples of the oxonium-based cation hardener include trimethyloxonium tetrafluoroborate and the like. Examples of the fluorene-based cation hardener include tri-p-tolyl hexafluorophosphate and the like.

The thermal radical generator is not particularly limited, and examples thereof include an azo compound and an organic peroxide. 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 starting temperature of the above-mentioned thermosetting agent is preferably 50 ° C or higher, more preferably 70 ° C or higher, even more preferably 80 ° C or higher, and more preferably 250 ° C or lower, more preferably 200 ° C or lower, and even more preferably Below 150 ° C, particularly preferably below 140 ° C. When the reaction starting temperature of the thermosetting agent is equal to or higher than the lower limit and lower than the upper limit, the solder is further efficiently disposed on the electrode. The reaction starting temperature of the above-mentioned thermosetting agent is particularly preferably 80 ° C or higher and 140 ° C or lower.

From the viewpoint of further efficiently disposing the solder on the electrode, the reaction starting temperature of the thermal curing agent is preferably higher than the melting point of the solder, more preferably 5 ° C or higher, and further preferably 10 ° C higher. the above.

The above-mentioned reaction initiation temperature of the thermosetting agent refers to a temperature at which a rise of a heating peak in a DSC (Differential Scanning Calorimeter) is started.

The content of the thermosetting agent is not particularly limited. The content of the thermosetting agent is preferably 0.01 part by weight or more, more preferably 1 part by weight or more, and more preferably 200 parts by weight or less, and more preferably 100 parts by weight or less with respect to 100 parts by weight of the thermosetting compound. It is more preferably 75 parts by weight or less. If the content of the thermosetting agent is at least the above lower limit, it is easy to make The conductive paste is sufficiently hardened. If the content of the thermosetting agent is equal to or less than the above-mentioned upper limit, the remaining thermosetting agent that does not participate in hardening after hardening does not easily remain, and the heat resistance of the hardened material is further increased.

The content of the thermosetting agent is preferably 0.01 parts by weight or more, more preferably 1 part by weight or more, and more preferably 200 parts by weight or less, more preferably 100 parts by weight with respect to 100 parts by weight of the crystalline thermosetting compound. Hereinafter, it is more preferably 75 parts by weight or less. In addition, the content of the thermosetting agent is preferably 0.01 part by weight or more, more preferably 1 part by weight or more, and more preferably 200 parts by weight or less, more preferably 100 based on 100 parts by weight of the entire thermosetting compound. Part by weight or less, more preferably 75 parts by weight or less. When the content of the thermosetting agent is at least the above-mentioned lower limit, it is easy to sufficiently harden the conductive paste. If the content of the thermosetting agent is equal to or less than the above-mentioned upper limit, the remaining thermosetting agent that does not participate in hardening after hardening does not easily remain, and the heat resistance of the hardened material is further increased.

(Flux)

The conductive paste preferably contains a flux. By using a flux, the solder can be more efficiently disposed on the electrode. The flux is not particularly limited. As the flux, a flux generally used for soldering or the like can be used. Examples of the flux include zinc chloride, a mixture of zinc chloride and an inorganic halide, a mixture of zinc chloride and an inorganic acid, a molten salt, phosphoric acid, a derivative of phosphoric acid, an organic halide, hydrazine, and an organic acid. And pine resin. These fluxes may be used alone or in combination of two or more.

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

The rosin is a rosin containing rosin acid as a main component. Flux is preferably rosin Class, more preferably abietic acid. By using the better flux, the conduction reliability between the electrodes is further increased.

The activity temperature (melting point) of the above-mentioned flux is preferably 50 ° C or higher, more preferably 70 ° C or higher, further preferably 80 ° C or higher, and more preferably 200 ° C or lower, more preferably 100 ° C or lower, even more preferably The temperature is 160 ° C or lower, more preferably 150 ° C or lower, and even more preferably 140 ° C or lower. When the active temperature of the flux is above the lower limit and below the upper limit, the flux effect is more effectively exhibited, and the solder is further efficiently disposed on the electrode. The activity temperature (melting point) of the flux is preferably 80 ° C or higher and 100 ° C or lower. The activity temperature (melting point) of the above-mentioned flux is particularly preferably 80 ° C or higher and 140 ° C or lower.

Examples of the flux whose activity temperature (melting point) of the flux is 80 ° C or higher and 100 ° C or lower include succinic acid (melting point 186 ° C), glutaric acid (melting point 96 ° C), and adipic acid (melting point 152 ° C). , Dicarboxylic acids such as pimelic acid (melting point: 104 ° C), suberic acid (melting point: 142 ° C), benzoic acid (melting point: 122 ° C), malic acid (melting point: 130 ° C), and the like.

The boiling point of the flux is preferably 200 ° C or lower.

From the viewpoint of further efficiently disposing the solder on the electrode, the melting point of the flux is preferably higher than the melting point of the solder, more preferably 5 ° C or higher, and even more preferably 10 ° C or higher.

From the viewpoint of further efficiently disposing the solder on the electrode, the melting point of the above-mentioned flux is preferably higher than the reaction starting temperature of the above-mentioned thermosetting agent, more preferably 5 ° C or higher, and further preferably 10 ° C or higher. Above ℃.

The above-mentioned flux may be dispersed in the conductive paste or may be adhered to the surface of the solder particles.

The above-mentioned flux is preferably a flux that releases cations by heating. By using a flux that releases cations by heating, the solder can be further efficiently disposed on the electrode.

In 100% by weight of the conductive paste, the content of the flux is preferably 0.5% by weight The above is preferably 30% by weight or less, and more preferably 25% by weight or less. The conductive paste may also be free of flux. If the content of the flux is at least the above lower limit and below the above upper limit, it is more difficult to form an oxide film on the surface of the solder and the electrode, and further, the oxide film formed on the surface of the solder and the electrode can be more effectively removed.

(filler)

A filler may be added to the conductive paste. The filler may be an organic filler, or the filler may be an inorganic filler. By adding a filler, the distance that the solder particles are aggregated can be suppressed, and the solder particles can be uniformly aggregated on all the electrodes of the substrate.

It is preferable that the said conductive paste does not contain the said filler, or contains 5 weight% or less of the said filler. Since a crystalline thermosetting compound is used, the smaller the content of the filler, the easier it is for the solder to move on the electrode.

In 100% by weight of the conductive paste, the content of the filler is preferably 0% by weight (uncontaining), and more preferably 5% by weight or less, more preferably 2% by weight or less, and even more preferably 1% by weight or less. . When the content of the filler is equal to or more than the lower limit and equal to or less than the upper limit, the solder particles are further efficiently disposed on the electrode.

(Other ingredients)

The conductive paste may contain fillers, extenders, softeners, plasticizers, polymerization catalysts, hardening catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, and lubricants, if necessary. Additives, antistatic agents and flame retardants.

(Connection structure and manufacturing method of connection structure)

The connection structure of the present invention includes: a first connection target member having at least one first electrode on the surface; a second connection target member having at least one second electrode on the surface; and a connection portion connected to the first The 1 connection target member and the second connection target member. In the connection structure of the present invention, the connection portion is formed of the conductive paste and is a cured product of the conductive paste. In the connection structure of the present invention, the first electrode and the second electrode are electrically connected by a solder portion of the connection portion.

The manufacturing method of the connection structure of the present invention includes the following steps: using the conductive paste, disposing the conductive paste on a surface of a first connection target member having at least one first electrode on the surface; 1 A second connection target member having at least one second electrode is disposed on a surface opposite to the connection target member side so that the first electrode faces the second electrode, and the conductive paste is heated to The solder particles have a melting point or higher and the thermosetting component has a curing temperature or higher. The conductive paste is used to form a connection portion that connects the first connection target member and the second connection target member, and the solder in the connection portion is used. The part electrically connects the first electrode and the second electrode. The conductive paste is preferably heated to a temperature higher than the curing temperature of the thermosetting compound.

In the connection structure of the present invention and the method of manufacturing the connection structure of the present invention, since a specific conductive paste is used, a plurality of solder particles are easily gathered between the first electrode and the second electrode, and a plurality of solder particles can be used. It is efficiently arranged on the electrode (line). In addition, it is difficult to dispose a part of the plurality of solder particles in a region (gap) where no electrode is formed, and the amount of solder particles disposed in a region where no electrode is formed can be made relatively small. Therefore, the conduction reliability between the first electrode and the second electrode can be improved. In addition, it is possible to prevent electrical connection between electrodes adjacent in a lateral direction that cannot be connected, and to improve insulation reliability.

In addition, in order to efficiently arrange a plurality of solder particles on an electrode and to reduce the amount of solder particles disposed in a region where no electrode is formed, the inventors have found that it is necessary to use a conductive paste instead of a conductive film.

In the present invention, another method of efficiently concentrating a plurality of solder particles between electrodes can also be adopted. Examples of a method for efficiently concentrating a plurality of solder particles between electrodes include a method for conducting heat by applying heat to a conductive paste between a first connection target member and a second connection target member. The viscosity of the paste is reduced, thereby generating convection of the conductive paste between the first connection target member and the second connection target member. Regarding this method, the heat capacity of an electrode connected to the surface of an object member and other surface members can be listed. A method of generating convection by the difference in heat; a method of generating convection by forming the water of the connection target member into water vapor by heat; and a method of generating convection by the temperature difference between the first connection target member and the second connection target member . Thereby, the solder particles in the conductive paste can be efficiently moved to the surface of the electrode.

In the present invention, a method of selectively agglomerating the solder particles on the surface of the electrode can also be adopted. As a method for selectively condensing solder particles on the surface of an electrode, the following methods can be cited: selecting an electrode material having good wettability of the solder particles after melting and other surfaces having poor wettability of the solder particles after melting A method for forming a connection target member made of a material to selectively adhere the solder particles that have reached the surface of the electrode to the electrode, and to melt and adhere other solder particles to the molten solder particles; choose an electrode with good thermal conductivity The method of selectively melting the solder on the electrode when heat is applied to the connection target member formed of other surface materials with poor material and thermal conductivity, by increasing the temperature of the electrode relative to other surface members; A method for selectively agglomerating solder particles on an electrode having a negative charge existing on an electrode formed of a metal treated with a positive charge; and a conductive paste for an electrode having a hydrophilic metal surface Resins other than solder particles in the resin are made hydrophobic, thereby selectively agglomerating the solder particles to electricity The method.

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, and more preferably 80 μm or less. The solder wetting area on the surface of the electrode (the area contacted by the solder in 100% of the exposed area of the electrode) is preferably 50% or more, more preferably 60% or more, still more preferably 70% or more, and more preferably Below 100%.

In the manufacturing method of the connection structure of the present invention, it is preferable that the weight of the second connection target member is not applied to the conductive paste in the step of disposing the second connection target member and the step of forming the connection portion. Pressurization, or at least one of the step of arranging the second connection target member and the step of forming the connection portion, and the step of arranging the second connection target member and the step of forming the connection portion Both In both cases, the pressurized pressure did not reach 1 MPa. By not applying a pressure of 1 MPa or more, the aggregation of solder particles can be greatly promoted. From the viewpoint of suppressing the warpage of the connection target member, in the method of manufacturing the connection structure of the present invention, it is performed in at least one of the step of disposing the second connection target member and the step of forming the connection portion. The pressure may be less than 1 MPa in both the step of disposing the second connection target member and the step of forming the connection portion. In the case of pressurization, pressurization may be performed only in the step of disposing the second connection target member, or pressurization may be performed only in the step of forming the connection portion, or the second connection target member may be disposed. Pressing is performed in both the step of forming the connection portion and the step of forming the connection portion. When the pressurizing pressure does not reach 1 MPa, it includes the case where the pressurizing is not performed. When pressurization is performed, the pressurization pressure is preferably 0.9 MPa or less, and more preferably 0.8 MPa or less. When the pressing pressure is 0.8 MPa or less, the aggregation of solder particles is more significantly promoted than when the pressing pressure exceeds 0.8 MPa.

In the manufacturing method of the connection structure of the present invention, it is preferable that the weight of the second connection target member is not applied to the conductive paste in the step of disposing the second connection target member and the step of forming the connection portion. The pressure is preferably not applied to the conductive paste in the step of arranging the second connection target member and the step of forming the connection portion, the pressing force being greater than the weight of the second connection target member. In these cases, the uniformity of the amount of solder can be further improved in the plurality of solder portions. Furthermore, the thickness of the solder portion can be thickened more effectively, a plurality of solder particles can be easily accumulated in large numbers between the electrodes, and the plurality of solder particles can be further efficiently disposed on the electrodes (wires). In addition, a part of the plurality of solder particles is difficult to arrange in a region (gap) where no electrode is formed, and the amount of solder particles arranged in a region where no electrode is formed can be further reduced. Therefore, it is possible to further improve the conduction reliability between the electrodes. In addition, it is possible to further prevent electrical connection between electrodes that are adjacent in a lateral direction that cannot be connected, and further improve insulation reliability.

Furthermore, the present inventors have also found that if the above-mentioned step of arranging the second connection target member In the step of forming the connection portion, if the weight of the second connection target member is applied to the conductive paste without pressurizing, the solder particles arranged in the area (gap) where the electrode is not formed before the connection portion is formed are more likely to aggregate. Between the first electrode and the second electrode, a plurality of solder particles can be further efficiently disposed on the electrode (wire). In the present invention, in order to obtain the effect of the present invention at a higher level, a combination using a conductive paste instead of a conductive film and a structure in which the weight of the second connection target member is applied to the conductive paste without applying pressure is combined. Adoption is significant.

In addition, in WO2008 / 023452A1, it is described that the solder powder can be pushed to the electrode surface to move efficiently, and it can be pressurized with a specific pressure at the next time. From the viewpoint of forming a solder region, the pressing pressure is, for example, 0 MPa or more, and preferably 1 MPa or more. It is further described that even if the pressure applied to the tape intentionally is 0 MPa, the weight of a member disposed on the tape can be used. Apply specific pressure to the tape. Although WO2008 / 023452A1 states that the pressure applied to the tape intentionally may be 0 MPa, the difference between the effect when a pressure exceeding 0 MPa and the case where it is set to 0 MPa is not described at all. Also, in WO2008 / 023452A1, the importance of using a paste-like conductive paste instead of a film-like conductive paste is not recognized at all.

In addition, if a conductive paste is used instead of a conductive film, it becomes easy to adjust the thickness of the connection portion and the solder portion according to the application amount of the conductive paste. On the other hand, regarding the conductive film, in order to change or adjust the thickness of the connection portion, it is necessary to prepare conductive films of different thicknesses or to prepare conductive films of a specific thickness. In addition, the conductive film has a problem that at the melting temperature of the solder, the melting viscosity of the conductive film cannot be sufficiently reduced, and the aggregation of solder particles is suppressed.

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

FIG. 1 is a cross-sectional view schematically showing a connection structure obtained by using a conductive paste 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 portion 4 that connects the first connection target member 2 and the second connection target member 3. connection The portion 4 is formed of the aforementioned conductive paste. This embodiment includes a thermosetting compound containing a crystalline thermosetting compound, a thermosetting agent, and a plurality of solder particles. The thermosetting compound and the thermosetting agent are thermosetting components.

The connection portion 4 includes a solder portion 4A in which a plurality of solder particles are aggregated and bonded to each other, and a hardened portion 4B in which a thermosetting component is thermally cured.

The first connection target member 2 has a plurality of first electrodes 2a on a surface (upper surface). The second connection target member 3 has a plurality of second electrodes 3a on the surface (lower surface). The first electrode 2a and the second electrode 3a are electrically connected by the solder portion 4A. Therefore, the first connection target member 2 and the second connection target member 3 are electrically connected by the solder portion 4A. Furthermore, solder is not present in the connection portion 4 in a region (a portion of the hardened portion 4B) different from the solder portion 4A collected between the first electrode 2a and the second electrode 3a. There is no solder separated from the solder portion 4A in a region different from the solder portion 4A (the portion of the hardened portion 4B). If the amount is small, solder may be present in a region (a portion of the hardened portion 4B) different from the solder portion 4A collected between the first electrode 2a and the second electrode 3a.

As shown in FIG. 1, in the connection structure 1, a plurality of solder particles are gathered between the first electrode 2a and the second electrode 3a. After the plurality of solder particles are melted, the molten material of the solder particles wets on the surface of the electrode. After the diffusion, curing is performed to form a solder portion 4A. Therefore, the connection area between the solder portion 4A and the first electrode 2a, and the solder portion 4A and the second electrode 3a are increased. That is, by using solder particles, the solder portion 4A and the first electrode 2a, and the solder portion 4A and the second electrode 3a are compared with a case where conductive particles having a conductive outer surface of a metal such as nickel, gold, or copper are used. The contact area increases. Therefore, the connection reliability and connection reliability of the connection structure 1 are increased. Furthermore, the conductive paste may contain a flux. In the case of using a flux, the flux usually becomes gradually inactivated by heating.

Furthermore, in the connection structure 1 shown in FIG. 1, all of the solder portions 4A are located in regions facing each other between the first and second electrodes 2 a and 3 a. The connection structure 1X of the modification shown in FIG. 3 is different from the connection structure 1 shown in FIG. 1 only in the connection portion 4X. The connection part 4X has welding The material portion 4XA and the hardened material portion 4XB. Like the connection structure 1X, most of the solder portion 4XA is located in a region facing the first and second electrodes 2a and 3a, and a portion of the solder portion 4XA is located in a region facing the first and second electrodes 2a and 3a. Extend to the side. The solder portion 4XA protruding laterally from the opposing areas of the first and second electrodes 2a and 3a is a part of the solder portion 4XA, and the solder separated from the non-solder portion 4XA. Furthermore, in this embodiment, the amount of solder separated from the solder portion can be reduced, and the solder separated from the solder portion can also be present in the hardened portion.

When the amount of solder particles is reduced, it becomes easy to obtain the connection structure 1. When the amount of solder particles is increased, it becomes easy to obtain the connection structure 1X.

From the viewpoint of further improving the conduction reliability, it is preferable to observe a portion where the first electrode and the second electrode face each other in a direction in which the first electrode, the connection portion, and the second electrode are laminated, 50% or more of 100% of the area of the first electrode and the second electrode facing each other (preferably 60% or more, more preferably 70% or more, more preferably 80% or more, particularly preferably 90% or more) of the above-mentioned connection portion is provided with a solder portion.

Next, an example of a method for manufacturing the connection structure 1 will be described using a conductive paste according to an embodiment of the present invention.

First, the first connection target member 2 having the first electrode 2a on the surface (upper surface) is prepared. Next, as shown in FIG. 2 (a), a conductive paste 11 including a thermosetting component 11B and a plurality of solder particles 11A is arranged on the surface of the first connection target member 2 (first step). A conductive paste 11 is disposed on a surface of the first connection target member 2 on which the first electrode 2a is provided. After the conductive paste 11 is disposed, the solder particles 11A are disposed on both the first electrode 2a (line) and the area (gap) where the first electrode 2a is not formed.

The arrangement method of the conductive paste 11 is not particularly limited, and examples thereof include coating using a dispenser, screen printing, and discharging using an inkjet device.

Moreover, the second connection target member 3 having the second electrode 3a on the surface (lower surface) is prepared. Next, as shown in FIG. 2 (b), regarding the conductive paste 11 on the surface of the first connection target member 2, a second connection is arranged on the surface of the conductive paste 11 on the side opposite to the first connection target member 2 side. Object component 3 (second step). On the surface of the conductive paste 11, a second connection target member 3 is arranged from the second electrode 3a side. At this time, the first electrode 2a and the second electrode 3a are opposed to each other.

Next, the conductive paste 11 is heated to a temperature higher than the melting point of the solder particles 11A and a temperature higher than the curing temperature of the thermosetting component 11B (third step). That is, the conductive paste 11 is heated to a temperature higher than the lower one of the melting point of the solder particles 11A and the curing temperature of the thermosetting component 11B. During this heating, the solder particles 11A existing in a region where no electrode is formed are collected between the first electrode 2a and the second electrode 3a (self-aggregation effect). In this embodiment, since a conductive paste is used instead of a conductive film, and the conductive paste has a specific composition, the solder particles 11A are effectively gathered between the first electrode 2a and the second electrode 3a. In addition, the solder particles 11A are fused and bonded to each other. 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 using the conductive paste 11. The connecting portion 4 is formed by the conductive paste 11, a plurality of solder particles 11A are joined to form a solder portion 4A, and a thermosetting component 11B is thermally cured to form a hardened portion 4B. If the solder particles 11A move sufficiently, it is also possible to move the solder particles 11A between the first electrode 2a and the second electrode 3a after the movement of the solder particles 11A not located between the first electrode 2a and the second electrode 3a is started. Until the end, the temperature is not kept constant.

In this embodiment, no pressure is applied in the second step and the third step. In this embodiment, the weight of the second connection target member 3 is applied to the conductive paste 11. Therefore, when the connection portion 4 is formed, the solder particles 11A are effectively collected between the first electrode 2a and the second electrode 3a. In addition, in at least one of the second step and the third step, when pressure is applied, the tendency of the solder particles to collect between the first electrode and the second electrode is suppressed. This situation was discovered by the inventors.

However, as long as the distance between the first electrode and the second electrode can be ensured, pressurization may be performed. As a method for ensuring the distance between the electrodes, for example, only the electrode corresponding to the required amount is added. It is only necessary to arrange at least one spacer, preferably three or more spacers between the electrodes. Examples of the spacer include inorganic particles and organic particles. The spacer is preferably an insulating particle.

In this embodiment, since no pressure is applied, when the second connection target member is overlapped with the first connection target member coated with the conductive paste, the electrode of the first connection target member and the second connection target are overlapped. In a state where the alignment of the electrode of the component is shifted, even when the first connection target member overlaps with the second connection target member, the offset can be corrected, and the electrode of the first connection target member and the second connection target member can be corrected. Electrode connection (self-alignment effect) of the connection target member. The reason for this is that the self-agglomerating molten solder between the electrode of the first connection target member and the electrode of the second connection target member is due to the solder between the electrode of the first connection target member and the electrode of the second connection target member. When the contact area of components other than the conductive paste becomes the smallest, it becomes stable in terms of energy. Therefore, the force of the aligned connection structure that becomes the smallest area of the connection structure is exerted. At this time, it is desirable that the conductive paste is not hardened and the viscosity of components other than the solder particles of the conductive paste is sufficiently low at the temperature and time.

The viscosity of the conductive paste at the melting point of the solder is preferably 50 Pa · s or less, more preferably 10 Pa · s or less, still more preferably 1 Pa · s or less, and more preferably 0.1 Pa · s or more, more preferably 0.2 Pa. ‧S or more If it is below a specific viscosity, the solder particles can be efficiently aggregated. If it is above a specific viscosity, the pores in the connection portion can be suppressed, and the conductive paste can be prevented from oozing out of the connection portion.

In this way, the connection structure 1 shown in FIG. 1 is obtained. The second step and the third step may be performed continuously. In addition, after performing the second step described above, the obtained laminated body of the first connection target member 2 and the conductive paste 11 and the second connection target member 3 may be moved to the heating section to perform the third step. In order to perform the above heating, the laminated body may be disposed on the heating member, or the laminated body may be disposed in a heated space.

In addition, after the third step, in order to correct the position or restart the manufacturing, the The first connection target member or the second connection target member is separated from the connection portion. The heating temperature for performing the peeling is preferably equal to or higher than the melting point of the solder particles, and more preferably the melting point (° C) of the solder particles + 10 ° C or higher. The heating temperature for performing the peeling may be the melting point (° C) of the solder particles + 100 ° C or less.

The heating temperature in the third step is not particularly limited as long as it is equal to or higher than the melting point of the solder particles and the curing temperature of the thermosetting component. The heating temperature is preferably 140 ° C or higher, more preferably 160 ° C or higher, and more preferably 450 ° C or lower, more preferably 250 ° C or lower, and even more preferably 200 ° C or lower.

Before the third step, a heating step may be provided in order to uniformize the aggregation of the solder particles before melting. The heating temperature in the above heating step is preferably maintained for 5 seconds or more under a temperature condition of preferably 60 ° C or higher, more preferably 80 ° C or higher, and preferably 130 ° C or lower, more preferably 120 ° C or lower. It is preferably at most 120 seconds. Through this heating step, the thermosetting component is reduced in viscosity by heat, and the solder particles before melting are aggregated to form a network structure. When the solder particles are melted and aggregated in the third step, the remaining amount can be reduced. Solder particles.

In the third step, the melting point of the solder (° C) or higher, more preferably the melting point (° C) of the solder + 5 ° C or higher, and preferably the melting point (° C) of the solder + 20 ° C or lower, more preferably It is preferable that the temperature is maintained at a melting point (° C) of the solder + 10 ° C or lower, preferably for 10 seconds or longer and preferably 120 seconds or lower, and then raised to the hardening temperature of the thermosetting component. Thereby, in a state where the viscosity of the thermosetting component before the thermosetting component is hardened is lowered, the aggregation of the solder particles can be ended, and more uniform aggregation of the solder particles can be performed.

In the temperature increase rate in the third step, the temperature increase from 30 ° C to the melting point of the solder particles is preferably 50 ° C / sec or less, more preferably 20 ° C / sec or less, still more preferably 10 ° C / sec or less, and The temperature is preferably 1 ° C / sec or more, and more preferably 5 ° C / sec or more. When the temperature increase rate is equal to or higher than the above lower limit, the aggregation of solder particles becomes more uniform. If the heating rate is below the above upper limit, excessive viscosity increase caused by curing of the thermosetting component can be suppressed, and It is easy to suppress the aggregation of solder particles.

Examples of the heating method in the third step include a method of heating the entire connection structure to a temperature higher than the melting point of the solder particles and a curing temperature of the thermosetting component using a reflow furnace or an oven; or only the connection structure A method for locally heating the connection portion.

Examples of the device used in the method of locally heating include a hot plate, a hot air gun that imparts hot air, a soldering iron, and an infrared heater.

In addition, when the heating plate is used for local heating, it is preferable that the surface of the heating plate is formed with a metal having high thermal conductivity directly below the connection portion, and other parts that are not suitable for heating are formed with a material having low thermal conductivity such as fluororesin. The surface of the board.

The first and second connection target members are not particularly limited. Specific examples of the first and second connection target members include semiconductor wafers, semiconductor packages, LED (Light Emitting Diode) wafers, electronic components such as LED packages, capacitors, and diodes, and Resin film, printed circuit board, flexible printed circuit board, flexible flat cable, rigid flexible substrate, glass epoxy substrate, and glass substrate and other electronic components. The first and second connection target members are preferably electronic components.

Preferably, 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 substrate. The second connection target member is preferably a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate. Resin films, flexible printed circuit boards, flexible flat cables, and rigid flexible substrates are highly flexible and relatively lightweight. When a conductive film is used for connection of such a connection target member, solder particles tend not to collect on the electrode. On the other hand, even if a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate is used, the solder particles can be efficiently concentrated on the electrodes, and the conduction reliability between the electrodes can be sufficiently improved. When using a resin film, flexible printed circuit board, flexible flat cable, or rigid flexible substrate, and when using other connection target components such as semiconductor wafers Compared with this, the effect of improving the reliability of conduction due to the unpressurized electrodes can be obtained more effectively.

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

The first electrode and the second electrode are preferably arranged in a region array or a peripheral type. When the electrodes are arranged on the surface in a region array and a peripheral type, the effect of the present invention is more effectively exerted. The so-called area array has a structure in which electrodes are arranged in a lattice shape on a surface where electrodes of a connection target member are arranged. The peripheral type has a structure in which electrodes are arranged on the outer periphery of the connection target member. In the case where the electrodes are arranged in a comb shape, the solder particles only need to be aggregated in a direction perpendicular to the comb. In contrast, in the above structure, the solder particles must be uniform on the entire surface on the side where the electrodes are arranged. Condensation, therefore, the amount of solder tends to become non-uniform by the previous method. In contrast, the method of the present invention can more effectively exert the effect of the present invention.

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

Polymer A:

Bisphenol F (contains 4,4'-methylenebisphenol, 2,4'-methylenebisphenol, and 2,2'-methylenebisphenol in a ratio of 2: 3: 1 by weight) 100 130 parts by weight of 1,6-hexanediol diglycidyl ether 5 parts by weight of bisphenol F-type epoxy resin ("EPICLON EXA-830CRP" manufactured by DIC), and 10 parts by weight of resorcinol-type epoxy compound ("EX-201" manufactured by Nagase chemtex) The solution was added to a 3-necked flask and dissolved at 100 ° C under a nitrogen stream. Thereafter, 0.15 parts by weight of triphenylbutylphosphonium bromide as an addition reaction catalyst of a hydroxyl group and an epoxy group was added and subjected to addition polymerization at 140 ° C. for 4 hours under a nitrogen stream, thereby obtaining a reaction. (Polymer A).

The addition polymerization reaction was confirmed by NMR (Nuclear Magnetic Resonance), and it was confirmed that the reactant (Polymer A) had a hydroxyl group derived from bisphenol F and 1,6-hexanediol diglycidyl in the main chain. A structural unit in which the epoxy groups of an ether, a bisphenol F-type epoxy resin, and a resorcinol-type epoxy compound are bonded, and both ends have epoxy groups.

The weight average molecular weight of the reactant (Polymer A) obtained by GPC was 28,000, and the number average molecular weight was 8,000.

Polymer B: epoxy terminal rigid skeleton phenoxy resin at both ends, "YX6900BH45" manufactured by Mitsubishi Chemical Corporation, weight average molecular weight 16000

Thermosetting compound 1: 2,4-bis (glycidyloxy) benzophenone (crystalline thermosetting compound, melting point 94 ° C, molecular weight 362)

Synthesis of 2,4-bis (glycidyloxy) benzophenone:

In a 3-necked flask, 27 g of 2,4-dihydroxybenzophenone, 230 g of epichlorohydrin, 70 g of n-butanol, and 1 g of tetraethylbenzyl ammonium chloride were added, and they were stirred and dissolved at room temperature. Thereafter, under a nitrogen atmosphere, the temperature was raised to 70 ° C. with stirring, and 45 g of an aqueous sodium hydroxide solution (concentration of 48% by weight) was added dropwise under reflux under reduced pressure. The dropwise addition was performed over 4 hours. Thereafter, at 70 ° C, a Dean-Stark tube was used, and the reaction was allowed to proceed for 2 hours while removing water. Thereafter, unreacted epichlorohydrin was removed under reduced pressure.

The obtained reaction product was dissolved in 400 g of a mixed solvent of MEK (Methyl Ethyl Ketone): n-butanol = 3: 1 (weight ratio), and 5 g of an aqueous sodium hydroxide solution (concentration: 10% by weight) was added. And heated at 80 ° C for 2 hours.

After that, it was cooled to room temperature and washed with pure water until the washing liquid became neutral. The organic layer was filtered while being separated, and the residual water and the mixed solvent were removed under reduced pressure to obtain a reaction product.

34 g of the reaction product was purified by recrystallization using n-hexane, and the residual solvent component was removed by vacuum drying.

The obtained epoxy compound: The melting point measured by DSC was 94 ° C, the epoxy equivalent was 176 g / eq., The molecular weight measured by mass spectrometry was 362, and the melt viscosity at 150 ° C was 5 mPa · s.

‧Differential scanning calorimetry (DSC) measurement device and measurement conditions

Device: "X-DSC7000" manufactured by Hitachi High-Tech Science, sample volume: 3mg, temperature condition: 10 ° C / min

‧Melting viscosity at 150 ° C: measured according to ASTM (American Society for Testing Materials) D4287 using an ICI cone and plate viscometer manufactured by MST Engineering

‧Measurement of epoxy equivalent: measured in accordance with JIS K7236: 2001

‧Measurement of molecular weight: measurement using a mass spectrometer GC-MS (Gas Chromatograph Mass Spectrometer) ("JMS K-9" manufactured by Japan Electronics Corporation)

Thermosetting compound 2: 4,4'-bis (glycidyloxy) benzophenone (crystalline thermosetting compound, melting point 132 ° C, molecular weight 362)

Synthesis of 4,4'-bis (glycidyloxy) benzophenone:

In a 3-necked flask, 27 g of 4,4'-dihydroxybenzophenone, 230 g of epichlorohydrin, 70 g of n-butanol, and 1 g of tetraethylbenzyl ammonium chloride were added and stirred at room temperature to dissolve them. . Thereafter, under a nitrogen atmosphere, the temperature was raised to 70 ° C. with stirring, and 45 g of an aqueous sodium hydroxide solution (concentration of 48% by weight) was added dropwise under reflux under reduced pressure. The dropwise addition took place over 4 hours. Thereafter, at 70 ° C, a Dean-Stark tube was used, and the reaction was allowed to proceed for 2 hours while removing water. Thereafter, unreacted epichlorohydrin was removed under reduced pressure.

The obtained reaction product was dissolved in 400 g of a mixed solvent of MEK (methyl ethyl ketone): n-butanol = 3: 1 (weight ratio), and 5 g of an aqueous sodium hydroxide solution (concentration: 10% by weight) was added to the solution at 80%. Heating was performed at 2 ° C for 2 hours.

After that, it was cooled to room temperature and washed with pure water until the washing liquid became neutral. The organic layer was filtered while being separated, and the residual water and the mixed solvent were removed under reduced pressure to obtain a reaction product.

34 g of the reaction product was purified by recrystallization using n-hexane, and the residual solvent component was removed by vacuum drying.

The obtained epoxy compound: the melting point measured by DSC was 135 ° C, the epoxy equivalent was 176 g / eq., The molecular weight measured by mass spectrometry was 362, and the melt viscosity at 150 ° C was 12 mPa · s.

Thermosetting compound 3: 1,6-hexanediol diglycidyl ether ("Epogosey HD" manufactured by Yokkaichi Kasei Co., Ltd., liquid at 25 ° C, molecular weight 230)

Thermosetting compound 4: Bisphenol F-type epoxy compound, "EXA830CRP" manufactured by DIC Corporation

Thermal hardener 1: Pentaerythritol tetra (3-mercaptobutyrate), "Karenz MT PE1" manufactured by Showa Denko Corporation

Latent Epoxy Thermal Hardener 1: "FUJICURE7000" manufactured by T & K TOKA

Flux 1: Adipic acid, manufactured by Wako Pure Chemical Industries, Ltd., melting point (activity temperature) 152 ° C

Production method of solder particles 1 ~ 3:

Solder particles with anionic polymer 1: 200 g of solder particle body, 40 g of adipic acid, and 70 g of acetone are weighed and placed in a 3-necked flask, followed by dehydration condensation of hydroxyl groups on the surface of the solder particle body and carboxyl group of adipic acid Catalyst of 0.3 g of dibutyltin oxide at 60 It was made to react at 4 degreeC for 4 hours. Thereafter, the solder particles are collected by filtration.

The recovered solder particles, 50 g of adipic acid, 200 g of toluene, and 0.3 g of p-toluenesulfonic acid were weighed and placed in a three-necked flask, and evacuated and refluxed while reacting at 120 ° C for 3 hours. At this time, using a Dean-Stark extraction device, the water generated by dehydration condensation is removed and reacted.

After that, the solder particles were recovered by filtration, washed with hexane, and dried. Thereafter, the obtained solder particles were crushed by a ball mill, and then sieved so as to have a specific CV value.

Solder particle 1 (SnBi solder particle, melting point 139 ° C, solder particle body selected from "ST-3" manufactured by Mitsui Metals Co., Ltd. and solder particle having surface treated anionic polymer 1 having an average particle diameter of 4 μm , CV value 7%, zeta potential of the surface: + 0.65mV, polymer molecular weight Mw = 6500)

Solder particle 2 (SnBi solder particle, melting point 139 ° C, solder particle body after screening "DS-10" manufactured by Mitsui Metals Co., Ltd. and solder particle having an anionic polymer 1 having surface treatment, average particle size 13 μm , CV value 20%, zeta potential on the surface: + 0.48mV, polymer molecular weight Mw = 7000)

Solder particles 3 (SnBi solder particles, melting point 139 ° C, solder particles with "10-25" manufactured by Mitsui Metals Co., Ltd. and solder particles having anionic polymer 1 surface-treated, with an average particle size of 25 μm. , CV value 15%, zeta potential on the surface: + 0.4mV, polymer molecular weight Mw = 8000)

Production method of solder particles 4 ~ 6:

Solder particle 4:

Weighed 200 g of SnBi solder particles ("DS-10" manufactured by Mitsui Metals Co., Ltd., with an average particle diameter (median diameter) of 12 µm) and an isocyanate-containing silane coupling agent ("KBE-9007" manufactured by Shin-Etsu Chemical Co., Ltd.) And 70 g of acetone were placed in a 3-necked flask. Stir at room temperature while adding the reaction between hydroxyl groups and isocyanate groups on the surface of the solder particles The catalyst 0.25 g of dibutyltin laurate was heated under stirring in a nitrogen atmosphere at 60 ° C for 30 minutes. Then, 50 g of methanol was added, and it heated at 60 degreeC for 10 minutes in nitrogen atmosphere with stirring.

After that, it was cooled to room temperature, and the solder particles were filtered with a filter paper, and the solvent was removed by vacuum drying at room temperature for 1 hour.

The above solder particles were added to a 3-necked flask, and 70 g of acetone, 30 g of monoethyl adipate, and 0.5 g of monobutyltin oxide as a transesterification reaction catalyst were added, and stirred at 60 ° C. in a nitrogen atmosphere under stirring. Allow to react for 1 hour.

Thereby, a silanol group derived from a silane coupling agent is reacted with an ester group of monoethyl adipate by a transesterification reaction, and covalent bonding is performed.

Then, 10 g of adipic acid was added, and it was made to react at 60 degreeC for 1 hour, and adipic acid was added to the silanol group of the monoethyl adipate, and the unreacted residual ethyl ester group.

After that, it was cooled to room temperature, and the solder particles were filtered with a filter paper, and the solder particles were washed with hexane on the filter paper, thereby removing unreacted and non-covalent bonds attached to the surface of the solder particles. The monoethyl diacid and adipic acid were removed, and then the solvent was removed by vacuum drying at room temperature for 1 hour.

After the obtained solder particles are crushed by a ball mill, a screen is selected so as to have a specific CV value.

The molecular weight of the polymer formed on the solder surface is 0.1N hydrochloric acid. After the solder is dissolved, the polymer is recovered by filtration, and the weight average molecular weight is determined by GPC.

Thereby, solder particles 4 are obtained. Regarding the obtained solder particles 4, the CV value was 20%, the zeta potential of the surface was 0.9 mV, and the molecular weight of the polymer constituting the surface was Mw = 9800.

Solder particle 5:

In addition to using SnBi solder particles (Mitsui Metal Co., Ltd., average particle diameter (median diameter) 30 μm) instead of SnBi solder particles ("DS-10" manufactured by Mitsui Metals Corporation, average particle diameter (median diameter) 12 μm), The solder particles 5 were produced in the same manner as the solder particles 4. turn off In the obtained solder particles 5, the CV value was 15%, the zeta potential of the surface was 1 mV, and the molecular weight of the polymer constituting the surface was Mw = 9900.

Solder particle 6:

In addition to using SnBi solder particles (Mitsui Metal Co., Ltd., average particle diameter (median diameter) 50 μm) instead of SnBi solder particles ("DS-10" manufactured by Mitsui Metals Corporation, average particle diameter (median diameter) 12 μm), In the same manner as the solder particles 4, the solder particles 6 were produced. Regarding the obtained solder particles 6, the CV value was 13%, the zeta potential of the surface was 1.1 mV, and the molecular weight of the polymer constituting the surface was Mw = 10000.

(Zeta potential measurement)

In addition, 0.05 g of the solder particles having the anionic polymer 1 were added to 10 g of methanol to the obtained solder particles, and ultrasonic treatment was performed to uniformly disperse them to obtain a dispersion liquid. Using this dispersion, the zeta potential was measured by electrophoresis using "Delsamax PRO" manufactured by Beckman Coulter.

(Weight average molecular weight of anionic polymer)

The weight-average molecular weight of the anionic polymer 1 on the surface of the solder particles was 0.1N hydrochloric acid. After the solder was dissolved, the polymer was recovered by filtration and determined by GPC.

(CV value of solder particles)

The laser diffraction type particle size distribution measuring device ("LA-920" manufactured by Horiba, Ltd.) was used to measure the CV value.

Conductive particles 1: conductive particles having a copper layer having a thickness of 1 μm on the surface of the resin particles and a solder layer having a thickness of 3 μm (tin: bismuth = 43% by weight: 57% by weight) is formed on the surface of the copper layer

Production method of conductive particles 1:

Electroless nickel plating was performed on divinylbenzene resin particles ("Micropearl SP-210" manufactured by Sekisui Chemical Industry Co., Ltd.) having an average particle diameter of 10 m to form a base nickel plating layer having a thickness of 0.1 m on the surface of the resin particles. Then, the resin particles formed with the underlying nickel plating layer Electrolytic copper plating was performed to form a copper layer having a thickness of 1 μm. Furthermore, an electrolytic plating solution containing tin and bismuth was used for electrolytic plating to form a solder layer having a thickness of 3 μm. In the above manner, conductive particles 1 having a copper layer having a thickness of 1 μm formed on the surface of the resin particles and a solder layer (tin: bismuth = 43% by weight: 57% by weight) formed on the surface of the copper layer were produced. .

Phenoxy resin ("YP-50S" manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd.)

(Examples 1 to 6, 8 and Comparative Example 2)

(1) Production of anisotropic conductive paste

The components shown in the following Table 1 were mixed with the compounding quantity shown in the following Table 1, and the anisotropic conductive paste was obtained. Furthermore, in Comparative Example 2, conductive particles whose center portion is not solder are used.

(2) Fabrication of the first connection structure (L / S = 50μm / 50μm)

A glass epoxy substrate (FR-4 substrate) (first connection target member) having a copper electrode pattern (copper electrode thickness of 12 μm) having an L / S of 50 μm / 50 μm and an electrode length of 3 mm was prepared on the upper surface. A flexible printed circuit board (second connection target member) having a copper electrode pattern (copper electrode thickness of 12 μm) having an L / S of 50 μm / 50 μm and an electrode length of 3 mm was prepared on the lower surface.

The overlapping area of the glass epoxy substrate and the flexible printed substrate was set to 1.5 cm × 3 mm, and the number of connected electrodes was set to 75 pairs.

On the upper surface of the glass epoxy substrate, a thickness of 100 μm is formed on the electrodes of the glass epoxy substrate, and a metal mask is used to apply anisotropic conductive paste immediately after the production by screen printing to form each Anisotropic conductive paste layer. Next, the flexible printed circuit board is laminated on the upper surface of the anisotropic conductive paste layer so that the electrodes face each other. At this time, no pressure was applied. The weight of the flexible printed circuit board is applied to the anisotropic conductive paste layer. Thereafter, while heating the anisotropic conductive paste layer to 190 ° C, the solder was melted, and the anisotropic conductive paste layer was hardened at 190 ° C and 10 seconds to obtain a first connection structure. .

(3) Fabrication of the second connection structure (L / S = 75μm / 75μm)

A glass epoxy substrate (FR-4 substrate) (first connection target member) having a copper electrode pattern (copper electrode thickness of 12 μm) having an L / S of 75 μm / 75 μm and an electrode length of 3 mm was prepared on the upper surface. A flexible printed circuit board (second connection target member) having a copper electrode pattern (copper electrode thickness of 12 μm) having an L / S of 75 μm / 75 μm and an electrode length of 3 mm was prepared on the lower surface.

A second connection structure was obtained in the same manner as in the production of the first connection structure, except that the aforementioned glass epoxy substrate and flexible printed circuit board having different L / S were used.

(4) Fabrication of the third connection structure (L / S = 100μm / 100μm)

A glass epoxy substrate (FR-4 substrate) (first connection target member) having a copper electrode pattern (copper electrode thickness of 12 μm) having an L / S of 100 μm / 100 μm and an electrode length of 3 mm was prepared on the upper surface. A flexible printed circuit board (second connection target member) having a copper electrode pattern (copper electrode thickness of 12 μm) having an L / S of 100 μm / 100 μm and an electrode length of 3 mm was prepared on the lower surface.

A third connection structure was obtained in the same manner as in the production of the first connection structure except that the above-mentioned glass epoxy substrate and flexible printed circuit board having different L / S were used.

(Example 7)

Except that a pressure of 1 MPa was applied during heating of the first conductive paste layer, the first, second, and third connection structures were obtained in the same manner as in Example 1.

(Comparative example 1)

(1) Production of anisotropic conductive paste

The components shown in the following Table 1 were mixed with the compounding quantity shown in the following Table 1, and the anisotropic conductive paste was obtained. The first, second, and third connection structures were obtained in the same manner as in Example 1 except that the obtained anisotropic conductive paste was used while applying a pressure of 1 MPa during heating.

(Comparative example 3)

10 parts by weight of a phenoxy resin ("YP-50S" manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) was dissolved in methyl ethyl ketone (MEK) so that the solid content became 50% by weight, A solution was obtained. The ingredients shown in the following Table 1 other than the phenoxy resin are blended with the blending amount shown in the following Table 1 and the total amount of the dissolving solution, stirred at 2000 rpm for 5 minutes using a planetary mixer, and then applied by a bar coat The cloth machine was coated on a release PET (Polyethylene Terephthalate) film so that the thickness after drying became 30 μm. An anisotropic conductive film was obtained by removing MEK by vacuum drying at room temperature.

The first, second, and third connection structures were obtained in the same manner as in Example 1 except that an anisotropic conductive film was used.

(Examples 9 to 18)

The components shown in the following Tables 3 and 4 were blended with the blending amounts shown in the following Tables 3 and 4 to obtain an anisotropic conductive paste.

First, the thermosetting compounds 1 and 2 were heated to 140 ° C. to make them liquefied. It was cooled to 40 ° C, and a thermosetting agent 1 was added. Then, the thermosetting compound 3 as another thermosetting compound was added, and it stirred with the planetary mixer until it became uniform. Then, it left still at 10 degreeC for 5 hours, and crystallized the thermosetting compound 1,2.

The formulation was kneaded with a 3-roll mill until the crystals of the thermosetting compounds 1 and 2 became specific crystal sizes shown in Tables 2 and 3 below.

Further, other preparations were added and stirred with a planetary mixer.

Using the anisotropic conductive paste before storage, the first, second, and third connection structures were produced in the same manner as in Examples 1 to 6, 8 and Comparative Example 2. The anisotropic conductive paste was stored at 50 ° C for 12 hours. Using the anisotropic conductive paste after storage, the first, second, and third connection structures were produced in the same manner as in Examples 1 to 6, 8 and Comparative Example 2.

(Evaluation)

(0) Average aspect ratio and average major diameter of crystals of crystalline thermosetting compounds

By observing the anisotropic conductive paste before storage with an electron microscope, the average aspect ratio and average length of the crystals of the crystalline thermosetting compound were evaluated.

(1) viscosity

Using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.), the viscosity (η25) of the anisotropic conductive paste before storage at 25 ° C was measured under the conditions of 25 ° C and 5rpm, 25 ° C, and 0.5rpm.

(2) Storage stability

The anisotropic conductive paste was stored at 50 ° C for 24 hours. An E-type viscometer (manufactured by Toki Sangyo Co., Ltd.) was used to measure the viscosity (η25 ') of the anisotropic conductive paste after storage at 25 ° C and 5 rpm at 25 ° C. The storage stability was judged by the following criteria.

[Judgment Criteria for Storage Stability]

○○: viscosity (η25 ') / viscosity (η25) is 1 or more and less than 1.2

○: viscosity (η25 ') / viscosity (η25) is 1.2 or more and less than 1.5

△: viscosity (η25 ') / viscosity (η25) is 1.5 or more and less than 2

×: viscosity (η25 ') / viscosity (η25) is 2 or more

(3) Thickness of solder part

The thickness of the solder portion between the upper and lower electrodes was evaluated by section observation of the first connection structure obtained using the anisotropic conductive paste before storage.

(4) Configuration accuracy of solder on the electrode 1

In the obtained first, second, and third connection structures, when the mutually opposing portions of the first electrode and the second electrode were observed in the laminated direction of the first electrode, the connection portion, and the second electrode, the first The ratio X of the area where the solder portion is disposed in the connection portion among 100% of the area of the first electrode and the second electrode facing each other. The placement accuracy of the solder on the electrodes was judged by the following reference.

[Criteria for determining the placement accuracy of solder on electrodes 1]

○○: Ratio X is 70% or more

○: Ratio X is 60% or more and less than 70%

△: Ratio X is 50% or more and less than 60%

×: Ratio X is less than 50%

(5) Disposition accuracy of solder on the electrode 2

In the obtained first, second, and third connection structures, the mutually opposing directions of the first electrode and the second electrode were observed in a direction orthogonal to the lamination direction of the first electrode, the connection portion, and the second electrode. Partially, the ratio Y of the solder portion in the connection portion of the solder portion of the connection portion, which is disposed in a portion where the first electrode and the second electrode face each other, was evaluated. The accuracy of the solder placement on the electrodes was judged by the following criteria2.

[Criteria for determining the placement accuracy of solder on electrodes 2]

○○: Ratio Y is 99% or more

○: Ratio Y is 90% or more and less than 99%

△: Ratio Y is 70% or more and less than 90%

×: Ratio Y is less than 70%

(6) Reliability between the upper and lower electrodes

In the obtained first, second, and third connection structures (n = 15), the connection resistance at each connection between the upper and lower electrodes was measured by the 4-terminal method, respectively. Calculate the average connection resistance. Furthermore, the connection resistance can be obtained by measuring the voltage when a fixed current is passed based on the relationship of voltage = current × resistance. The following criteria were used to determine the conduction reliability.

[Judgment Criteria for Continuity Reliability]

○○: The average value of the connection resistance is 50mΩ or less

○: The average value of the connection resistance exceeds 50 mΩ and is less than 70 mΩ

△: The average value of the connection resistance exceeds 70 mΩ and is 100 mΩ or less

×: The average value of the connection resistance exceeds 100 mΩ, or a connection failure occurs

(7) Insulation reliability between adjacent electrodes in the transverse direction

In the obtained first, second, and third connection structures (n = 15 pieces), after being left in an atmosphere of 85 ° C. and 85% humidity for 100 hours, 5 V was applied between the adjacent electrodes in the lateral direction, and The resistance value was measured at 25 places. Insulation reliability was judged by the following criteria.

[Judgment Criteria for Insulation Reliability]

○○: The average value of the connection resistance is 10 ⁷ Ω or more

○: The average value of the connection resistance is 10 ⁶ Ω or more and less than 10 ⁷ Ω

△: The average value of the connection resistance is 10 ⁵ Ω or more and less than 10 ⁶ Ω

×: The average value of the connection resistance does not reach 10 ⁵ Ω

(8) Position shift between upper and lower electrodes

In the obtained first, second, and third connection structures, when the mutually opposing portions of the first electrode and the second electrode were observed in the laminated direction of the first electrode, the connection portion, and the second electrode, the first Whether the centerline of the 1 electrode is consistent with the centerline of the 2nd electrode, and the distance of the position deviation. The position deviation between the upper and lower electrodes is determined by the following reference.

[Criteria for judging the position shift between the upper and lower electrodes]

○○: Position deviation is less than 15 μm

○: Position deviation is 15 μm or more and less than 25 μm

△: Position deviation is 25 μm or more and less than 40 μm

×: Position deviation is 40 μm or more

The results are shown in Tables 1 to 3 below.

In addition, the average aspect ratio and average length of the crystals of the crystalline thermosetting compound in the anisotropic conductive paste after storage in Examples 9, 10, and 16 were the same as those of the anisotropic conductive paste before storage. The viscosity of the anisotropic conductive paste in Example 9 after storage at 130 ° C and 5 rpm was 130 mPa · s, and the viscosity of 25 degree C and 0.5 rpm was 450 mPa · s. The anisotropic conductive paste after storage in Example 10 The viscosity at 25 ° C and 5rpm is 160mPa‧s, the viscosity at 25 ° C and 0.5rpm is 500mPa‧s, and the viscosity of the anisotropic conductive paste after storage in Example 16 at 25 ° C and 5rpm is 350mPa‧s. The viscosity at 25 ℃ and 0.5rpm is 1200mPa‧s. The thickness of the solder portion of the first connection structure obtained by using the anisotropic conductive paste after storage was 33 μm in Example 9, 36 μm in Example 10, and 43 μm in Example 16.

The same tendency can be seen when a resin film, a flexible flat cable, and a rigid flexible substrate are used instead of the flexible printed substrate.

Claims (27)

A conductive paste containing a thermosetting compound as a thermosetting component, a thermosetting agent, and a plurality of solder particles, the thermosetting compound including a crystalline thermosetting compound, and a crystalline compound of the crystalline thermosetting compound. The average aspect ratio is 5 or less, and the above-mentioned solder particles are particles in which the central portion and the conductive outer surface are all solder. A conductive paste containing a thermosetting compound as a thermosetting component, a thermosetting agent, and a plurality of solder particles, the thermosetting compound including a crystalline thermosetting compound, and a crystalline compound of the crystalline thermosetting compound. The average major diameter is equal to or less than 1 / 1.5 of the average particle diameter of the solder particles, and the solder particles are particles in which the center portion and the conductive outer surface are all solder. A conductive paste containing a thermosetting compound as a thermosetting component, a thermosetting agent, and a plurality of solder particles, the thermosetting compound including a crystalline thermosetting compound, and a crystalline compound of the crystalline thermosetting compound. The average major diameter is 1/10 or more of the average particle diameter of the solder particles, and the solder particles are particles in which the center portion and the conductive outer surface are all solder. The conductive paste according to claim 1, wherein the crystalline thermosetting compound is solid at 25 ° C. The conductive paste according to claim 2, wherein the crystalline thermosetting compound is solid at 25 ° C. The conductive paste according to claim 3, wherein the crystalline thermosetting compound is solid at 25 ° C. The conductive paste according to any one of claims 1 to 6, wherein the melting point of the crystalline thermosetting compound is 80 ° C or higher and 150 ° C or lower. The conductive paste according to any one of claims 1 to 6, wherein the molecular weight of the crystalline thermosetting compound is 300 or more and 500 or less. The conductive paste according to any one of claims 1 to 6, wherein the crystalline thermosetting compound is a benzophenone-type epoxy compound. The conductive paste according to any one of claims 1 to 6, wherein the melting point of the crystalline thermosetting compound is lower than the melting point of the solder. The conductive paste according to any one of claims 1 to 6, which contains a flux, and the melting point of the crystalline thermosetting compound is lower than the activation temperature of the flux. The conductive paste according to any one of claims 1 to 6, wherein the content of the crystalline thermosetting compound is 10% by weight or more in 100% by weight of the entire thermosetting compound. The conductive paste according to any one of claims 1 to 6, which does not contain a filler or contains a filler of 5% by weight or less. The conductive paste according to any one of claims 1 to 6, wherein in the conductive paste, the crystalline thermosetting compound is dispersed in a particulate form. The conductive paste according to any one of claims 1 to 6, which contains another thermosetting compound different from the crystalline thermosetting compound. The conductive paste according to any one of claims 1 to 6, wherein the average particle diameter of the solder particles is 1 μm or more and 60 μm or less. The conductive paste according to any one of claims 1 to 6, wherein the content of the solder particles is 10% by weight or more and 80% by weight or less. A connection structure includes: a first connection target member having at least one first electrode on a surface; a second connection target member having at least one second electrode on a surface; and a connection portion that connects the first 1 The connection target member is connected to the second connection target member; the connection portion is a hardened material of the conductive paste according to any one of claims 1 to 17; and the first electrode and the second electrode system use the connection portion. The solder part is electrically connected. The connection structure according to claim 18, wherein the second connection target member is a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate. For example, if the connection structure of claim 18 or 19 is viewed in a direction in which the first electrode, the connection portion, and the second electrode are stacked, the portion where the first electrode and the second electrode oppose each other is described above. The solder portion of the connection portion is disposed in at least 50% of the area of the first electrode and the second electrode facing each other at 100%. For example, the connection structure of claim 18 or 19, wherein the first electrode and the second electrode are opposed to each other in a direction orthogonal to the lamination direction of the first electrode, the connection portion, and the second electrode. In some cases, at least 70% of the solder portion of the connection portion is disposed at a portion where the first electrode and the second electrode face each other. A method for manufacturing a connection structure, comprising the steps of using the conductive paste according to any one of claims 1 to 17 to dispose the conductive paste on the surface of a first connection target member having at least one first electrode on the surface. ; A second connection target member having at least one second electrode on the surface is arranged on the surface of the conductive paste opposite to the first connection target member side so that the first electrode and the second electrode face each other; And forming a connection portion that connects the first connection target member and the second connection target member by using the conductive paste by heating the conductive paste to a temperature above the melting point of the solder particles and a temperature above the curing temperature of the thermosetting component. And the first electrode and the second electrode are electrically connected by a solder portion of the connection portion. For example, the method for manufacturing a connection structure of claim 22, wherein in the step of disposing the second connection target member and the step of forming the connection portion, the conductive paste is applied to the conductive paste without applying pressure to the second connection target member. Or pressurizing in at least one of the step of disposing the second connection object member and the step of forming the connection portion, and both of the step of disposing the second connection object member and the step of forming the connection portion In both cases, the pressurized pressure did not reach 1 MPa. For example, the manufacturing method of the connection structure of claim 23, wherein in the step of arranging the second connection target member and the step of forming the connection portion, the conductive paste is applied with the weight of the second connection target member without being pressurized. . The method for manufacturing a connection structure according to any one of claims 22 to 24, wherein the second connection target member is a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate. According to the method for manufacturing a connection structure according to any one of claims 22 to 24, a connection structure is obtained in which the connection structure is viewed in a laminated direction of the first electrode, the connection portion, and the second electrode. In a portion where the first electrode and the second electrode face each other, a solder portion in the connection portion is disposed at 50% or more of an area of 100% of an area where the first electrode and the second electrode face each other. According to the method for manufacturing a connection structure according to any one of claims 22 to 24, a connection structure is obtained in which the connection structure is orthogonal to a laminated direction of the first electrode, the connection portion, and the second electrode. When observing a portion of the first electrode and the second electrode facing each other in a direction, more than 70% of the solder portion of the connection portion is arranged at a portion of the first electrode and the second electrode facing each other.