TW201606797A - Conductive paste, connected structure and method for producing connected structure - Google Patents

Abstract

Provided is a conductive paste which is capable of efficiently disposing solder particles on an electrode and enhancing conduction reliability between electrodes. A conductive paste according to the present invention contains a thermosetting component, a flux and a plurality of solder particles. This conductive paste has a viscosity of from 0.1 Pa.s to 3 Pa.s (inclusive) at the melting point of the flux, and a viscosity of from 0.1 Pa.s to 5 Pa.s (inclusive) at the melting point of the solder particles.

Description

Conductive paste, connection structure, and manufacturing method of connection structure

The present invention relates to a conductive paste comprising solder particles. Moreover, the present invention relates to a connection structure using the above-described conductive paste and a method of manufacturing the connection structure.

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

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

When the electrode of the flexible printed circuit board and the electrode of the glass epoxy substrate are electrically connected to each other by the anisotropic conductive material, an anisotropic conductive material containing conductive particles is placed on the glass epoxy substrate. Next, a flexible printed circuit board is laminated to perform heating and pressurization. Thereby, the anisotropic conductive material is cured, and the electrodes are electrically connected via the conductive particles to obtain a bonded structure.

In an example of the anisotropic conductive material, Patent Document 1 discloses a resin layer containing a thermosetting resin, a solder powder, and a curing agent, and the solder powder and the curing agent are present in the resin layer. In the middle of the belt. The subsequent strip is membranous and Not mushy.

Further, Patent Document 1 discloses a method of using the above-described subsequent tape. Specifically, the first substrate, the subsequent tape, the second substrate, the adhesive tape, and the third substrate are sequentially laminated from the bottom to the top to obtain a laminated body. At this time, the first electrode provided on the surface of the first substrate faces the second electrode provided on the surface of the second substrate. Further, the second electrode provided on the surface of the second substrate faces the third electrode provided on the surface of the third substrate. Further, the laminate is heated at a specific temperature to be followed. Thereby, the connection structure is obtained.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] WO2008/023452A1

The adhesive tape described in Patent Document 1 has a film shape and is not a paste. Therefore, it is difficult to efficiently arrange the solder powder on the electrodes (lines). For example, in the adhesive tape described in Patent Document 1, a part of the solder powder is also easily disposed in a region (gap) where the electrode is not formed. The solder powder disposed in the region where the electrode is not formed does not contribute to the conduction between the electrodes.

Further, even in the case of an anisotropic conductive paste containing solder powder, the solder powder is not efficiently disposed on the electrode (line).

It is an object of the present invention to provide a conductive paste which can efficiently dispose solder particles on an electrode and improve the conduction reliability between electrodes. Moreover, the present invention provides a connection structure using the above-described conductive paste and a method of manufacturing the connection structure.

According to a broad aspect of the present invention, there is provided a conductive paste comprising a thermosetting component, a flux, and a plurality of solder particles, and having a viscosity of 0.1 Pa at a melting point of the flux. s above and 3Pa. Below s, the viscosity at the melting point of the above solder particles Is 0.1Pa. s above and 5Pa. s below.

In a specific aspect of the conductive paste of the present invention, the melting point of the flux is 80 ° C or more and 190 ° C or less. In another specific aspect, the melting point of the flux is 100 ° C or more and 190 ° C or less.

In a specific aspect of the conductive paste of the present invention, the flux is contained in an amount of 0.1% by weight or more and 5% by weight or less based on 100% by weight of the conductive paste.

In a specific aspect of the conductive paste of the present invention, the conductive paste contains no filler or contains less than 0.25% by weight of the filler in 100% by weight of the conductive paste.

In a specific aspect of the conductive paste of the present invention, the solder particles are surface-treated in such a manner that a carboxyl group is present on the outer surface.

In a specific aspect of the conductive paste of the present invention, the melting point of the flux is higher than the melting point of the solder particles.

According to a broad aspect of the present invention, a connection structure comprising: a first connection member having at least one first electrode on a surface thereof, and a second connection member having at least one second electrode on a surface thereof And a connection portion that connects the first connection target member to the second connection target member; and the connection portion is formed by the conductive paste, wherein the first electrode and the second electrode are connected by the connection The solder portion of the portion is electrically connected.

According to a broad aspect of the present invention, a method of manufacturing a connection structure comprising: disposing the conductive paste on a surface of a first connection member having at least one first electrode on its surface using the conductive paste; a step of arranging a second connection member having at least one second electrode 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 the step of heating the conductive paste to a temperature equal to or higher than a melting point of the solder particles and a hardening temperature of the thermosetting component to form the first connection member and the second connection by the conductive paste formation a connecting portion to which the target member is connected, and the first electrode is connected And the step of electrically connecting the second electrode to the solder portion in the connection portion.

In a specific aspect of the method for producing a connection structure according to the present invention, in the step of disposing the second connection member and the step of forming the connection portion, applying the second to the conductive paste without applying pressure The weight of the connected object component.

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

The conductive paste of the present invention contains a thermosetting component, a flux, and a plurality of solder particles, and has a viscosity of 0.1 Pa under the melting point of the flux. s above and 3Pa. Below s, the viscosity at the melting point of the above solder particles is 0.1 Pa. s above and 5Pa. s or less, when the electrodes are electrically connected to each other, the solder particles can be efficiently disposed on the electrodes, and the conduction reliability between the electrodes can be improved.

1, 1X‧‧‧ connection structure

2‧‧‧1st connection object component

2a‧‧‧1st electrode

3‧‧‧2nd connection object component

3a‧‧‧2nd electrode

4, 4X‧‧‧ Connection Department

4A, 4XA‧‧‧ solder department

4B, 4XB‧‧‧ Hardened Parts

11‧‧‧Electrical paste

11A‧‧‧ solder particles

11B‧‧‧ thermosetting ingredients

Fig. 1 is a partially cross-sectional front 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 2(c) are views for explaining respective steps of an example of a method of manufacturing a bonded structure using a conductive paste according to an embodiment of the present invention.

Fig. 3 is a partial cross-sectional front cross-sectional view showing a modification of the connection structure.

4(a), 4(b) and 4(c) are views showing an example of a connection structure using a conductive paste which is not included in the embodiment of the present invention, and Figs. 4(a) and 4(b) are cross-sectional images. Fig. 4(c) is a top view image.

Hereinafter, the details of the present invention will be described.

The conductive paste of the present invention contains a thermosetting component, a flux, and a plurality of solder particles. The conductive paste of the present invention has a viscosity of 0.1 Pa under the melting point of the above flux. s above and 3Pa. s below. The conductive paste of the present invention is viscous under the melting point of the above solder particles The degree is 0.1Pa. s above and 5Pa. s below.

According to the conductive paste of the present invention, when the electrodes are electrically connected to each other, a plurality of solder particles are easily collected between the electrodes, and a plurality of solder particles can be efficiently disposed on the electrodes (wires). on. Further, it is difficult to arrange one of the plurality of solder particles in a region (gap) in which the electrode is not formed, and the amount of the solder particles disposed in the region where the electrode is not formed can be extremely reduced. Therefore, the conduction reliability between the electrodes can be improved. Further, it is possible to prevent electrical connection between electrodes adjacent to each other in the lateral direction, and to improve insulation reliability. The reason for obtaining such an effect is that when the oxide film on the surface of the solder particles is removed at the melting point of the flux, the viscosity of the conductive paste is moderate, and when the solder particles are melted, the viscosity of the conductive paste is moderate.

The conductive paste of the present invention can be suitably used in the following method for producing a bonded structure of the present invention.

In the method for producing a connection structure according to the present invention, a conductive paste, a first connection member, and a second connection member are used. The conductive material used in the method for producing the bonded structure of the present invention is a conductive paste, not a conductive film. The conductive paste contains a thermosetting component, a flux, and a plurality of solder particles. The first connection target member has at least one first electrode on the surface. The second connection target member has at least one second electrode on the surface.

A method of manufacturing a connection structure according to the present invention includes: a step of disposing a conductive paste of the present invention on a surface of the first connection member; and a surface of the conductive paste opposite to a side of the first connection member; a step of arranging the second connection member so that the first electrode and the second electrode face each other; and heating the conductive paste to a temperature higher than a melting point of the solder particles and a hardening temperature of the thermosetting component A connection portion that connects the first connection target member and the second connection target member is formed by the conductive paste, and the first electrode and the second electrode are electrically connected by a solder portion of the connection portion. The steps of sexual connection. The manufacturer of the connection structure of the present invention In the method, in the step of arranging the second connection member and the step of forming the connection portion, the weight of the second connection member is applied to the conductive paste without applying pressure. In the method of manufacturing the connection structure of the present invention, it is preferable that the step of arranging the second connection member and the step of forming the connection portion do not apply the weight of the second connection member to the conductive paste. Pressure of pressure.

In the manufacturing method of the connection structure of the present invention, since the above-described configuration is adopted, a plurality of solder particles are easily collected between the first electrode and the second electrode, and a plurality of solder particles can be efficiently disposed on the electrode (line). on. Further, it is difficult to arrange one of the plurality of solder particles in a region (gap) in which the electrode is not formed, and the amount of the solder particles disposed in the region where the electrode is not formed can be extremely reduced. Therefore, the conduction reliability between the first electrode and the second electrode can be improved. Further, it is possible to prevent electrical connection between electrodes adjacent to each other in the lateral direction, and to improve insulation reliability.

As described above, the inventors of the present invention have found that in order to efficiently arrange a plurality of solder particles on the electrode and to extremely reduce the amount of the solder particles disposed in the region where the electrode is not formed, it is necessary to use a conductive paste instead of the conductive film.

Further, as the particles different from the solder particles, conductive particles having a substrate particle and a solder layer disposed on the surface of the substrate particle are known. When the solder particles are used, when the solder particles are used, the melting point of the flux and the melting point of the solder particles are within a specific range, and the arrangement accuracy of the solder particles on the electrodes is improved. Become bigger.

Furthermore, the inventors of the present invention have found that, in the step of arranging the second connection member and the step of forming the connection portion, the weight of the second connection member is applied to the conductive paste without applying pressure. The solder particles disposed in the region (gap) where the electrode is not formed before the formation of the connection portion are more likely to be further collected between the first electrode and the second electrode, and the plurality of solder particles can be efficiently disposed on the electrode (line). . In the present invention, the conductive paste is used instead of the conductive film, and the conductive paste is applied without pressurization. The combination of the weights of the second connection target members is employed, and this case has a great significance for obtaining the effect of the present invention at a higher level.

Further, in WO 2008/023452 A1, it is described that the solder powder is poured onto the surface of the electrode to efficiently move it, and it is preferable to pressurize it at a specific pressure at the time of the subsequent step, and it is described that it is formed in a sure manner. From the viewpoint of the solder region, the pressurization pressure is, for example, 0 MPa or more, preferably 1 MPa or more, and further describes that the weight of the member placed on the succeeding belt can be self-weight even if the pressure applied to the adhesive tape is 0 MPa. And apply specific pressure to the belt. In WO 2008/023452 A1, although the pressure applied to the subsequent tape is described as being 0 MPa, there is no description about the difference between the effect of applying a pressure exceeding 0 MPa and the case of setting it to 0 MPa.

Further, if a conductive paste is used instead of the conductive film, the thickness of the joint portion can be appropriately adjusted by the amount of the conductive paste applied. On the other hand, the conductive film has a problem that in order to change or adjust the thickness of the connection portion, a conductive film of a different thickness must be prepared, or a conductive film of a specific thickness must be prepared.

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described with respect to the specific embodiments and examples of the invention.

First, in Fig. 1, a connection structure obtained by using a conductive paste according to an embodiment of the present invention is schematically shown in a partial cross-sectional front cross-sectional view.

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 object member 2 and the second connection object member 3. The connecting portion 4 is formed of a conductive paste containing a thermosetting component, a flux, and a plurality of solder particles. The viscosity of the conductive paste at the melting point of the flux and the viscosity at the melting point of the solder particles are within a specific range.

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

The first connection target member 2 has a plurality of first electrodes 2a on the surface (upper surface). 2nd company The object 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. Further, in the connection portion 4, solder is not present in a region (a portion of the cured 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 cured portion 4B). In addition, in a small amount, solder may be present in a region (a portion of the cured portion 4B) different from the solder portion 4A that is collected between the first electrode 2a and the second electrode 3a.

As shown in FIG. 1, in the connection structure 1, after a plurality of solder particles are melted, the melt of the solder particles is wetted and diffused on the surface of the electrode, and then solidified to form the 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 is increased. In other words, by using the solder particles, the solder portion 4A and the first electrode 2a, and the solder portion 4A and the second electrode 3a are used as compared with the case where the conductive outer surface is a conductive particle of a metal such as nickel, gold or copper. The contact area becomes large. Therefore, the conduction reliability and the connection reliability of the connection structure 1 become high. Further, the flux contained in the conductive paste is generally gradually deactivated by heating.

Further, in the connection structure 1 shown in Fig. 1, all of the solder portions 4A are located in the opposing regions between the first and second electrodes 2a and 3a. The connection structure 1X of the modification shown in FIG. 3 differs from the connection structure 1 shown in FIG. 1 only in the connection portion 4X. The connecting portion 4X has a solder portion 4XA and a cured portion 4XB. As in 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 opposed to the region between the first and second electrodes 2a and 3a. Extend to the side. The solder portion 4XA that protrudes laterally from the region opposite to the first and second electrodes 2a and 3a is a part of the solder portion 4XA, and is not solder separated from the solder portion 4XA. Further, in the present embodiment, the amount of solder separated from the solder portion can be reduced, but the solder separated from the solder portion may be present in the cured portion.

When the amount of use of the solder particles is reduced, the connection structure 1 is easily obtained. If more welding When the amount of the particles is used, the joined structure 1X is easily obtained.

Next, an example of a method of manufacturing the bonded structure 1 using the conductive paste of one embodiment of the present invention will be described.

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

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

Moreover, the second connection member 3 having the second electrode 3a on the front surface (lower surface) is prepared. Then, as shown in Fig. 2 (b), the conductive paste 11 on the surface of the first connection member 2 is placed on the surface opposite to the first connection member 2 side of the conductive paste 11 The connection target member 3 is connected (the second step). The second connection member 3 is placed on the surface of the conductive paste 11 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 equal to or higher than the melting point of the solder particles 11A and the hardening temperature of the thermosetting component 11B (third step). That is, the conductive paste 11 is heated to a temperature lower than the lower temperature of the melting point of the solder particles 11A and the hardening temperature of the thermosetting component 11B. At the time of this heating, the solder particles 11A existing in the region where the electrode is not formed are collected between the first electrode 2a and the second electrode 3a (self-aggregation effect). In the present embodiment, since the conductive paste is used instead of the conductive film, the solder particles 11A are effectively collected between the first electrode 2a and the second electrode 3a. Further, the solder particles 11A are melted and joined to each other. Further, the thermosetting component 11B is thermally cured. As a result, as shown in FIG. 2( c ), the connection portion 4 that connects the first connection member 2 and the second connection member 3 is formed by the conductive paste 11 . The connection portion 4 is formed by the conductive paste 11, and solder is formed by bonding a plurality of solder particles 11A. In the portion 4A, the cured portion 4B is formed by thermally curing the thermosetting component 11B. Since the solder particles 11A move rapidly, the solder particles 11A may be transferred between the first electrode 2a and the second electrode 3a after the movement of the solder particles 11A between the first electrode 2a and the second electrode 3a is started. Do not keep the temperature fixed until the end of the move.

In the present embodiment, no pressurization is performed in the second step and the third step. In the present embodiment, the weight of the second connection member 3 is applied to the conductive paste 11. Therefore, at the time of formation of the connection portion 4, the solder particles 11A are effectively collected between the first electrode 2a and the second electrode 3a. In addition, when pressurization is performed in at least one of the second step and the third step, the tendency of the solder particles to be concentrated between the first electrode and the second electrode is suppressed. This situation was discovered by the inventors and the like.

In this way, the connection structure 1 shown in Fig. 1 is obtained. Furthermore, the second step and the third step described above can be continuously performed. Further, after the second step, the obtained first connection member 2, the conductive paste 11 and the second connection member 3 may be moved to the heating unit, and the third step may be performed. 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 the heated space.

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 130 ° C or higher, more preferably 160 ° C or higher, more preferably 450 ° C or lower, more preferably 250 ° C or lower, and still more preferably 200 ° C or lower.

In addition, the first connection target member may have at least one first electrode. Preferably, the first connection target member has a plurality of first electrodes. The second connection target member may have at least one second electrode. Preferably, the second connection target member has a plurality of second electrodes.

The first and second connection target members are not particularly limited. Specific examples of the first and second connection target members include electronic components such as a semiconductor wafer, a capacitor, and a diode, and a resin film, a printed circuit board, a flexible printed circuit board, and a flexible flat cable. Electronic components such as rigid flexible substrates, glass epoxy substrates, and circuit boards such as glass substrates. Preferably, the first and second connection target members are electronic components.

At least one of the first connection target member and the second connection target member is preferably a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate. Preferably, the second connection member is a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate. The resin film, the flexible printed circuit board, the flexible flat cable, and the rigid flexible substrate have high flexibility and relatively lightweight properties. When a conductive film is used for the connection of such a connection target member, there is a tendency that solder particles are less likely to accumulate on the electrode. On the other hand, since the conductive paste of the present invention is used, even if a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate is used, solder particles can be efficiently collected on the electrodes, and the electrodes can be sufficiently increased. Continuity reliability. When a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate is used, it is possible to more effectively obtain an electrode between the electrodes which is not subjected to pressurization as compared with the case of using another member to be connected such as a semiconductor wafer. Improve the effect of continuity reliability.

Examples of the electrode provided on the connection target member include metal electrodes such as a gold electrode, a nickel electrode, a tin electrode, an aluminum electrode, a copper electrode, a silver electrode, a molybdenum electrode, a SUS electrode, and a tungsten electrode. In the case where the connection target member is a flexible printed circuit board or a flexible flat cable, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, a silver electrode or a copper electrode. In the case where 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. Further, in the case where the electrode is an aluminum electrode, it may be an electrode formed only of aluminum, or an electrode having an aluminum layer on a surface layer 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, Ga, and the like.

The distance D1 between the first electrode and the connecting portion at a position facing the second electrode is preferably 5 μm or more, more preferably 20 μm or more, and is preferably 50 μm or less, and more preferably 75 μm or less. When the distance D1 is equal to or higher than the lower limit, the connection reliability between the connection portion and the connection target member is further improved. When the distance D1 is equal to or less than the above upper limit, the solder particles are more likely to accumulate on the electrode when the connection portion is formed, and the conduction reliability between the electrodes is further improved.

In order to further efficiently dispose the solder particles on the electrode, the viscosity η1 of the conductive paste at 25 ° C is preferably 10 Pa. Above s, more preferably 50Pa. s or more, and further preferably 100 Pa. Above s, preferably 800 Pa. Below s, more preferably 600Pa. s is below, and further preferably 500 Pa. s below.

The above viscosity can be appropriately adjusted by the type of the blending component and the blending amount. Further, the viscosity can be relatively increased by using a filler. However, since the filler suppresses the movement of the solder particles, it is preferred that the filler be contained in a small amount.

In order to further efficiently dispose the solder particles on the electrode, the viscosity η2 of the conductive paste under the melting point of the flux is 0.1 Pa. s above and 3Pa. s below. The viscosity η2 is preferably 0.15 Pa from the viewpoint of further efficiently disposing the solder particles on the electrode. Above s, more preferably 0.2Pa. Above s, preferably 2 Pa. Below s, more preferably 1Pa. s below.

In order to further efficiently dispose the solder particles on the electrode, the viscosity η3 of the conductive paste at the melting point of the solder particles is 0.1 Pa. s above and 5Pa. s below. The viscosity η3 is preferably 0.15 Pa from the viewpoint of further efficiently disposing the solder particles on the electrode. Above s, more preferably 0.2Pa. Above s, preferably 3 Pa. Below s, more preferably 1Pa. s below.

The ratio (η1/η2) of the viscosity η1 to the viscosity η2 is preferably 15 or more, more preferably 50 or more, and more preferably 3,000 or less, from the viewpoint of further efficiently disposing the solder particles on the electrode. More preferably, it is 2,500 or less.

The ratio (η1/η3) of the viscosity η1 to the viscosity η3 is preferably 10 or more, and more preferably 40 or more, from the viewpoint of further efficiently disposing the solder particles on the electrode. It is preferably 2,500 or less, more preferably 2,000 or less.

The ratio of the viscosity η2 to the viscosity η3 (η2/η3) is preferably 0.1 or more, more preferably 0.3 or more, and more preferably 10 or less, from the viewpoint of further efficiently disposing the solder particles on the electrode. More preferably 1 or less.

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

The conductive paste contains a thermosetting component, a flux, and a plurality of solder particles. It is preferable that the thermosetting component contains a curable compound (thermosetting compound) which can be cured by heating, and a thermosetting agent.

Hereinafter, other details of the present invention will be described.

(solder particles)

The solder particles have solder on the conductive outer surface. The central portion of the solder particles and the conductive outer surface are each formed of solder. From the viewpoint of further efficiently disposing the solder on the electrode, the solder particles are preferably surface-treated such that a carboxyl group is present on the outer surface. The solder particles are preferably surface-treated in such a manner that a carboxyl group is present on the outer surface, and then formulated into a conductive paste.

The above solder is preferably a metal having a melting point of 450 ° C or less (low melting point metal). The solder particles are preferably metal particles (low melting point metal particles) having a melting point of 450 ° C or lower. The low melting point metal particles are particles containing a low melting point metal. The low melting point metal means a metal having a melting point of 450 ° C or less. The melting point of the low melting point metal is preferably 300 ° C or lower, more preferably 160 ° C or lower. Further, the solder particles contain tin. The content of tin in the 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 particularly preferably 90% by weight or more. When the content of tin in the solder particles is at least the above lower limit, the connection reliability between the solder portion and the electrode is further improved.

Furthermore, the above tin content can be used in high frequency inductively coupled plasma luminescence spectroscopic analysis The measurement was carried out by using "ICP-AES" manufactured by Horiba, Ltd., or a fluorescent X-ray analyzer ("EDX-800HS" manufactured by Shimadzu Corporation).

By using the above-described solder particles, the solder is melted and bonded to the electrodes, and the solder portion electrically conducts between the electrodes. For example, since the solder portion and the electrode are easily surface-contacted rather than in point contact, the connection resistance is lowered. Moreover, by using the solder particles, the bonding strength between the solder portion and the electrode is improved, and as a result, it is difficult to further cause peeling of the solder portion and the electrode, and the conduction reliability and the connection reliability are effectively improved.

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

The solder particles are preferably a filler material based on JIS Z3001: the liquidus of the welding term is 450 ° C or less. Examples of the composition of the solder particles include a metal composition containing zinc, gold, silver, lead, copper, tin, antimony, indium, or the like. Among them, a tin-indium-based (117 ° C eutectic) or a tin-lanthanide (139 ° C eutectic) having a low melting point and no lead is preferable. That is, the solder particles preferably do not contain lead, preferably contain tin and indium, or contain tin and antimony.

In order to further improve the bonding strength between the solder portion and the electrode, the solder particles may further comprise nickel, copper, lanthanum, aluminum, zinc, iron, gold, titanium, phosphorus, lanthanum, cerium, cobalt, lanthanum, manganese, chromium, molybdenum, Metal such as palladium. Further, from the viewpoint of further improving the bonding strength between the solder portion and the electrode, the solder particles preferably contain nickel, copper, ruthenium, aluminum or zinc. From the viewpoint of further improving the bonding strength between the solder portion and the electrode, the content of the metal for improving the bonding strength is preferably 0.0001% by weight or more, preferably 1% by weight or less, based on 100% by weight of the solder particles.

The average particle diameter of the solder particles is preferably 0.5 μm or more, and more preferably 1 μm or more. Further, it is preferably 3 μm or more, more preferably 5 μm or more, more preferably 100 μm or less, still more preferably 40 μm or less, further preferably 30 μm or less, further preferably 20 μm or less, particularly preferably 15 μm or less, and most preferably 10 μm or less. . When the average particle diameter of the solder particles is not less than the above lower limit and not more than the above upper limit, the solder particles can be more efficiently disposed on the electrode. The average particle diameter of the solder particles is preferably 3 μm or more and 30 μm or less.

The "average particle diameter" of the above solder particles means a number average particle diameter. The average particle diameter of the solder particles can be determined, for example, by observing an arbitrary 50 solder particles by an electron microscope or an optical microscope and calculating an average value.

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, and particularly preferably 20% by weight or more, based on 100% by weight of the conductive paste. It is 30% by weight or more, preferably 80% by weight or less, more preferably 60% by weight or less, still more preferably 50% by weight or less. When the content of the solder particles is not less than the above lower limit and not more than the above upper limit, the solder particles can be more efficiently disposed on the electrode, and a large amount of solder particles can be easily disposed between the electrodes, and the conduction reliability can be further improved. From the viewpoint of further improving the conduction reliability, it is preferred that the content of the solder particles is large.

(a compound that can be hardened by heating: a thermosetting component)

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. a formate compound, a polyoxymethylene compound, a polyimine compound, and the like. Among them, an epoxy compound is preferred from the viewpoint of further improving the curability and viscosity of the conductive paste and further improving the connection reliability.

In the conductive paste, the thermosetting compound is preferably dispersed in a particulate form.

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, based on 100% by weight of the conductive paste. More preferably, it is 98% by weight or less, further preferably 90% by weight. More preferably, it is 80% by weight or less. From the viewpoint of further improving the impact resistance, it is preferred that the content of the thermosetting component is large.

(thermosetting agent: thermosetting component)

The above-mentioned thermosetting agent thermally hardens the above-mentioned thermosetting compound. Examples of the above-mentioned thermosetting agent include an imidazole curing agent, an amine curing agent, a phenol curing agent, a polythiol curing agent, an acid anhydride, a thermal cation initiator, and a thermal radical generating agent. These thermosetting agents may be used alone or in combination of two or more.

Among them, an imidazole hardener, a polythiol hardener or an amine hardener is preferred because the conductive paste can be further hardened at a low temperature. Further, since the storage stability is improved when the curable compound which can be cured by heating is mixed with the above-mentioned thermosetting agent, a latent curing agent is preferable. The latent hardener is preferably a latent imidazole hardener, a latent polythiol hardener or a latent amine hardener. Further, the thermosetting agent may be coated with a polymer material such as a polyurethane resin or a polyester resin.

The imidazole curing agent is not particularly limited, and examples thereof include 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, and trimellitic acid 1-cyanoacetate. 2-phenylimidazolium, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-average-three And 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-average-three An isocyanuric acid addition product or the like.

The polythiol curing agent is not particularly limited, and examples thereof include trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptobutyrate), and pentaerythritol tetrakis(3-mercaptopropionate). And dipentaerythritol hexa(3-mercaptopropionate) and the like.

The solubility parameter of the above-mentioned polythiol curing agent is preferably 9.5 or more, preferably 12 or less. The above solubility parameters are calculated by the Fedors method. For example, the solubility parameter of trimethylolpropane tris(3-mercaptopropionate) is 9.6, and the solubility parameter of dipentaerythritol hexakis(3-mercaptopropionate) is 11.4.

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

Examples of the thermal cation hardening agent include a lanthanoid cation curing agent, an oxonium cation curing agent, and a lanthanoid cation curing agent. The ruthenium-based cation hardener may, for example, be bis(4-tert-butylphenyl)phosphonium hexafluorophosphate. Examples of the oxonium-based cationic curing agent include trimethyloxonium tetrafluoroborate. Examples of the ruthenium-based cation hardener include tri-p-tolylphosphonium hexafluorophosphate.

The thermal radical generating agent 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 ditributyl peroxide and methyl ethyl ketone peroxide.

The reaction initiation temperature of the above-mentioned thermosetting agent is preferably 50 ° C or more, more preferably 70 ° C or more, further preferably 80 ° C or more, preferably 250 ° C or less, more preferably 200 ° C or less, and still more preferably 150 Below °C, it is particularly preferably below 140 °C. When the reaction initiation temperature of the thermal curing agent is not less than the above lower limit and not more than the above upper limit, the solder particles can be more efficiently disposed on the electrode. The reaction initiation temperature of the above-mentioned thermosetting agent is particularly preferably 80 ° C or more and 140 ° C or less.

The reaction initiation temperature of the thermal curing agent is preferably lower than the melting point of the solder in the solder particles, more preferably 5 ° C or lower, and further preferably from the viewpoint of further efficiently disposing the solder on the electrode. It is 10 ° C or lower.

The reaction initiation temperature of the above-mentioned thermosetting agent means a temperature at which the onset of the exothermic peak by DSC (differential scanning calorimetry) is raised.

The content of the above-mentioned thermosetting agent is not particularly limited. The content of the thermal curing agent is preferably 0.01 parts by weight or more, more preferably 1 part by weight or more, more preferably 200 parts by weight or less, still more preferably 100 parts by weight or less, based on 100 parts by weight of the thermosetting compound. It is preferably 75 parts by weight or less. When the content of the thermosetting agent is at least the above lower limit, the conductive paste is easily cured sufficiently. If the content of the thermosetting agent is below the above upper limit, after hardening It is difficult to leave the remaining heat hardener which is not involved in hardening, and the heat resistance of the cured product is further improved.

(flux)

The above conductive paste contains a flux. The solder can be further efficiently disposed on the electrode by using a flux. The flux is not particularly limited. As the flux, a flux which is generally used for solder bonding 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, a phosphoric acid, a derivative of phosphoric acid, an organic halide, an anthracene, and an organic acid. And turpentine and so on. The flux may be used alone or in combination of two or more.

Examples of the molten salt include ammonium chloride and the like. Examples of the organic acid include lactic acid, citric acid, stearic acid, glutamic acid, and glutaric acid. Examples of the rosin include activated rosin and inactivated rosin. The 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 a rosin. By using an organic acid or rosin having two or more carboxyl groups, the conduction reliability between the electrodes is further improved.

The above rosin is a rosin mainly composed of rosin acid. The flux is preferably rosin, more preferably rosin acid. By using the preferred flux, the conduction reliability between the electrodes is further improved.

The active temperature (melting point) of the flux is preferably 50 ° C or higher, more preferably 70 ° C or higher, still more preferably 80 ° C or higher, and particularly preferably 100 ° C or higher, preferably 200 ° C or lower, more preferably 190 ° C. Hereinafter, it is more preferably 160 ° C or less, further preferably 150 ° C or less, and still more preferably 140 ° C or less. When the activation temperature of the flux is not less than the above lower limit and not more than the above upper limit, the flux effect is further effectively exhibited, and the solder particles are more efficiently disposed on the electrode. As a result, the connection resistance between the electrodes is lowered, and the connection reliability is also improved. The active temperature (melting point) of the above flux is preferably 80 ° C or more and 190 ° C or less, more preferably 100 ° C or more and 190 ° C or less. The above flux has an active temperature of 80. Above °C and below 140 °C, more preferably from 100 °C to 140 °C.

Examples of the flux having a melting point of 80 ° C or more and 190 ° C or less include succinic acid (melting point 186 ° C), glutaric acid (melting point 96 ° C), adipic acid (melting point 152 ° C), and pimelic acid (melting point 104). °C), dicarboxylic acid such as suberic acid (melting point 142 ° C), benzoic acid (melting point 122 ° C), malic acid (melting point 130 ° C) and the like.

Further, the flux has a boiling point of 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 in the solder particles, more preferably 5 ° C or higher, and further preferably 10 ° C higher. the above.

The melting point of the flux is preferably higher than the reaction initiation temperature of the thermal curing agent, more preferably 5 ° C or higher, and further preferably 10 high, from the viewpoint of further efficiently disposing the solder on the electrode. Above °C.

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

By making the melting point of the flux higher than the melting point of the solder, the solder particles can be efficiently condensed on the electrode portion. The reason for this is that when heat is applied during bonding, when the electrode formed on the member to be connected is compared with the portion of the member to be connected around the electrode, the thermal conductivity of the electrode portion is higher than that of the member to be connected around the electrode. The thermal conductivity is such that the temperature of the electrode portion rises faster. At the stage of exceeding the melting point of the solder particles, the inside of the solder particles is melted, but the oxide film formed on the surface is not removed because the melting point (active temperature) of the flux is not reached. In this state, since the temperature of the electrode portion first reaches the melting point (active temperature) of the flux, the oxide film on the surface of the solder particles on the electrode can be preferentially removed to wet the solder particles on the surface of the electrode. diffusion. Thereby, the solder particles can be efficiently condensed on the electrode.

The flux is preferably a flux that releases cations by heating. The solder particles can be further efficiently configured by using a flux that releases cations by heating On the electrode.

Examples of the flux that releases cations by heating include the above-mentioned thermal cation hardener.

The content of the flux is preferably 0.5% by weight or more, preferably 30% by weight or less, and more preferably 25% by weight or less based on 100% by weight of the conductive paste. The above conductive paste may also not contain a flux. When the content of the flux is not less than the above lower limit and not more than the above upper limit, it is difficult to further form an oxide film on the surface of the solder and the electrode, and the oxide film formed on the surface of the solder and the electrode can be further effectively removed.

(filler)

A filler may also be added to the above conductive paste. The filler may be an organic filler or an inorganic filler. However, since the filler suppresses the movement of the solder particles, it is preferred that the filler be contained in a small amount.

The conductive paste preferably contains no filler or contains less than 5% by weight of the filler in 100% by weight of the conductive paste. The content of the filler is preferably 0% by weight or less, preferably 5% by weight or less, more preferably 2% by weight or less, still more preferably 1% by weight or less, based on 100% by weight of the conductive paste. More preferably, it is less than 0.25% by weight, and particularly preferably 0.1% by weight or less. When the content of the filler is not less than the above lower limit, and not more than the above upper limit, or less than the above upper limit, the solder particles can be more efficiently disposed on the electrode. It is preferable that the conductive paste contains no filler or contains less than 0.25% by weight of the conductive paste in 100% by weight of the conductive paste, and it is preferable that the conductive paste does not contain a filler. When the content of the filler is less than 0.25% by weight, the movement of the solder particles due to the filler is sufficiently suppressed. When the content of the filler is 0.1% by weight or less, the movement of the solder particles due to the filler is suppressed to be relatively small.

(other ingredients)

The above conductive paste may also contain, for example, a filler, a bulking agent, a softener, a plasticizer, a polymerization catalyst, a hardening catalyst, a colorant, an antioxidant, a heat stabilizer, and a light stabilizer. Various additives such as a fixative, an ultraviolet absorber, a lubricant, an antistatic agent, and a flame retardant.

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

Polymer A:

Synthesis of a reaction of bisphenol F with 1,6-hexanediol diglycidyl ether and bisphenol F-type epoxy resin (Polymer A):

Bisphenol F (containing 4,3'-methylene bisphenol, 2,4'-methylene bisphenol, and 2,2'-methylene bisphenol in a weight ratio of 2:3:1) 72 30 parts by weight of a weight fraction, 1,6-hexanediol diglycidyl ether, and 30 parts by weight of a bisphenol F-type epoxy resin ("EPICLON EXA-830CRP" manufactured by DIC Corporation) were placed in a three-necked flask under a nitrogen stream. These were dissolved at 150 °C. Thereafter, 0.1 part by weight of tetra-n-butyl bromide as an addition reaction catalyst of a hydroxyl group and an epoxy group was added, and a polymerization reaction was carried out at 150 ° C for 6 hours under a nitrogen stream to obtain a reactant (polymerization). A).

It was confirmed by NMR that the addition polymerization reaction was carried out, and it was confirmed that the reactant (polymer A) had a hydroxyl group derived from bisphenol F and 1,6-hexanediol diglycidyl ether and a bisphenol F-type ring in the main chain. A structural unit in which an epoxy group of an oxy-resin is bonded and has an epoxy group at both ends.

The reactant (Polymer A) obtained by GPC had a weight average molecular weight of 10,000 and a number average molecular weight of 3,500.

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

Thermosetting compound 1: Resorcinol type epoxy compound, "EX-201" manufactured by Nagase ChemteX Co., Ltd., crystallized at a low temperature, and then used for cleaning.

Thermosetting compound 2: bisphenol F-type epoxy resin, "EPICLON EXA-830CRP" manufactured by DIC Corporation, crystallization after low temperature, and then used for cleaning

Thermal hardener 1: pentaerythritol tetrakis(3-mercaptobutyrate), "Karenz MT PE1" manufactured by Showa Denko

Latent epoxy heat hardener 1: "Fujicure 7000" manufactured by T & K TOKA

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

Flux 2: succinic acid, manufactured by Wako Pure Chemical Industries, Inc., melting point (activity temperature) 186 ° C

Flux 3: rosin acid, manufactured by Wako Pure Chemical Industries, Inc., melting point (activity temperature) 174 ° C

The particles obtained by the following surface treatment of the solder particles 1 (SnBi solder particles, melting point 139 ° C, "DS10" manufactured by Mitsui Metals Co., Ltd.), average particle diameter 13 μm)

Surface treatment of solder particles:

Weigh 200 g of solder particles, 40 g of adipic acid, and 70 g of acetone in a three-necked flask, and add 0.3 g of dibutyltin oxide as a dehydration condensation catalyst of a hydroxyl group on the surface of the solder particles and a carboxyl group of adipic acid at 60 ° C. The reaction was carried out for 4 hours. Thereafter, it is recovered by filtering the solder particles.

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 while refluxing, and then inverted at 120 ° C. It should be 3 hours. At this time, the reaction was carried out while removing water generated by dehydration condensation using a Dean-Stark extraction apparatus.

Thereafter, the solder particles were recovered by filtration, washed with hexane, and dried. Thereafter, the obtained solder particles were crushed by a ball mill, and the screen was selected so as to have a specific CV value. The obtained solder particles were subjected to surface treatment in such a manner that carboxyl groups were present on the outer surface.

The particles obtained by surface treatment of the solder particles 2 (SnBi solder particles, melting point 139 ° C, "DS30" manufactured by Mitsui Metals Co., Ltd.) in the same manner as the solder particles 1 have an average particle diameter of 32 μm.

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

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

(Examples 1 to 4, 6 to 9) (1) Production of anisotropic conductive paste

The components shown in the following Table 1 were blended in the amounts shown in Table 1 below to obtain an anisotropic conductive paste. Further, in the obtained anisotropic conductive paste, the thermosetting compound is dispersed in a particulate form.

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

A glass epoxy substrate (FR-4 substrate) (first connection target member) having a copper electrode pattern (copper electrode thickness: 10 μm) having an L/S of 50 μm/50 μm was prepared on the upper surface. In addition, a flexible printed circuit board (second connection target member) having a copper electrode pattern (copper electrode thickness: 10 μm) having an L/S of 50 μm/50 μm was prepared on the lower surface.

The overlapping area of the glass epoxy substrate and the flexible substrate was set to 1.5 cm × 4 mm, and the number of connected electrodes was set to 75 pairs.

Coating on the surface of the above glass epoxy substrate so as to have a thickness of 50 μm The anisotropic conductive paste is formed to form an 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 pressurization is performed. The weight of the above flexible printed substrate is applied to the anisotropic conductive paste layer. Then, while the temperature of the anisotropic conductive paste layer was 190 ° C, the solder was melted, and the anisotropic conductive paste layer was cured at 190 ° C to obtain a first bonded structure.

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

A glass epoxy substrate (FR-4 substrate) (first connection target member) having a copper electrode pattern (copper electrode thickness: 10 μm) having an L/S of 75 μm/75 μm was prepared on the upper surface. Further, a flexible printed circuit board (second connection target member) having a copper electrode pattern (copper electrode thickness: 10 μm) having an L/S of 75 μm/75 μm was prepared on the lower surface.

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

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

A glass epoxy substrate (FR-4 substrate) (first connection target member) having a copper electrode pattern (copper electrode thickness: 10 μm) having an L/S of 100 μm/100 μm was prepared on the upper surface. Further, a flexible printed circuit board (second connection target member) having a copper electrode pattern (copper electrode thickness: 10 μm) having an L/S of 100 μm/100 μm was prepared on the lower surface.

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

(Example 5)

The preparation electrode size (L) / inter-electrode spacing (S) is 100 μm / 100 μm (for the third connection structure), 75 μm / 75 μm (for the second connection structure), and 50 μm / 50 μm (for the first connection structure). A 5 mm square semiconductor wafer (thickness: 400 μm) and a glass epoxy substrate (having a size of 30 × 30 mm and a thickness of 0.4 mm) having electrodes opposed thereto. The first and second were obtained in the same manner as in the first embodiment except that the semiconductor wafer and the glass epoxy substrate were used. The third connection structure.

(Comparative Examples 1, 2, 5) (1) Production of anisotropic conductive paste

The components shown in the following Table 2 were blended in the amounts shown in Table 2 below to obtain an anisotropic conductive paste. 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.

(Comparative Example 3)

10 parts by weight of a phenoxy resin ("YP-50S" manufactured by Nippon Steel & Sumitomo Chemical Co., Ltd.) was dissolved in methyl ethyl ketone (MEK) so as to have a solid content of 50% by weight to obtain a solution. The components and all the amounts of the above-mentioned solutions other than the phenoxy resin shown in the following Table 2 shown in Table 2 below were blended, and stirred at 2000 rpm for 5 minutes using a planetary mixer, and then coated with a bar. The cloth machine was applied to a release PET (polyethylene terephthalate) film so as to have a thickness of 30 μm after drying. The MEK was removed by vacuum drying at room temperature, whereby an anisotropic conductive film was obtained.

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.

(Comparative Example 4)

The preparation electrode size (L) / inter-electrode spacing (S) is 100 μm / 100 μm (for the third connection structure), 75 μm / 75 μm (for the second connection structure), and 50 μm / 50 μm (for the first connection structure). A 5 mm square semiconductor wafer (thickness: 400 μm) and a glass epoxy substrate (having a size of 30 × 30 mm and a thickness of 0.4 mm) having electrodes opposed thereto. The first, second, and third connection structures were obtained in the same manner as in Comparative Example 1, except that the semiconductor wafer and the glass epoxy substrate were used.

(assessment) (1) Viscosity

Using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.), measured at 25 ° C and 5 rpm The viscosity of the anisotropic conductive paste at 25 ° C is η1. Further, the viscosity η2 of the anisotropic conductive paste at the melting point of the flux was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.) under the conditions of the melting point of the flux and 5 rpm. Further, the viscosity η3 of the anisotropic conductive paste at the melting point of the solder particles was measured under the conditions of the melting point of the solder particles and 5 rpm using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd.). The ratio (η1/η2), the ratio (η1/η3), and the ratio (η2/η3) were obtained from the obtained measured values.

(2) Distance of the connecting portion (interval between electrodes)

By taking a cross-sectional view of the obtained first connection structure, the distance D1 (the interval between the electrodes) of the connection portion where the upper and lower electrodes are opposed to each other is evaluated.

(3) Configuration accuracy of the solder on the electrode

In the cross section of the obtained first connection structure (cross section in the direction shown in FIG. 1), the area of the solder remaining in the hardened material separated from the solder portion disposed between the electrodes in 100% of the total area of the solder (%)to evaluate. Furthermore, the average of the areas among the five sections was calculated. The arrangement accuracy of the solder on the electrodes was determined based on the following criteria.

[Criteria for Judging the Arrangement Accuracy of Conductive Particles on Electrodes]

○○: The area of the solder (solder particles) remaining in the cured product separated from the solder portion disposed between the electrodes by 100% of the total area of the solder which is present in the cross section is 0% or more and 1% or less

○: 100% of the total area of the solder in the cross section, the area of the solder (solder particles) remaining in the cured material separated from the solder portion disposed between the electrodes is more than 1% and less than 10%.

Δ: The area of the solder (solder particles) remaining in the cured product separated from the solder portion disposed between the electrodes by 100% of the total area of the solder which is present in the cross section is more than 10% and is 30% or less.

×: The area of the solder (solder particles) remaining in the hardened material separated from the solder portion disposed between the electrodes by more than 30% of the total area of the solder which is present in the cross section is more than 30%

(4) Continuity reliability between upper and lower electrodes

The connection resistance between the upper and lower electrodes was measured by the four-terminal method for the obtained first, second, and third connection structures (n = 15). Calculate the average value of the connection resistance. Further, the connection resistance can be obtained by measuring the voltage at the time of flowing a fixed current based on the relationship of voltage=current×resistance. The conduction reliability was determined based on the following criteria.

[Determination of Conductivity Reliability]

○○: The average value of the connection resistance is 8.0 Ω or less.

○: The average value of the connection resistance exceeds 8.0 Ω and is 10.0 Ω or less.

△: The average value of the connection resistance exceeds 10.0 Ω and is 15.0 Ω or less.

×: The average value of the connection resistance exceeds 15.0 Ω

(5) Insulation reliability between adjacent electrodes

The first, second, and third connected structures (n = 15) obtained were placed in an environment of a temperature of 85 ° C and a humidity of 85% for 100 hours, and then 5 V was applied between adjacent electrodes at 25 sites. The resistance value was measured. The insulation reliability was determined based on the following criteria.

[Determination of 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 is less than 10 ⁵ Ω

The results are shown in Tables 1 and 2 below.

According to the difference between the results of the first embodiment and the comparative example 1 and the difference between the results of the fifth embodiment and the comparative example 4, when the second connection target member is a flexible printed circuit board, the second connection target member is a semiconductor wafer. In comparison with the case, the effect of improving the conduction reliability obtained by using the conductive paste of the present invention can be further effectively obtained.

It was confirmed that the same result can be obtained when a resin film, a flexible flat cable, and a rigid flexible substrate are used instead of the flexible printed substrate.

Further, an example of a connection structure using a conductive paste which is not included in the embodiment of the present invention is shown in FIGS. 4(a), 4(b) and 4(c). 4(a) and 4(b) are cross-sectional images, and FIG. 4(c) is a plan view image. In (a), (b), and (c) of FIG. 4, it is found that a plurality of solder (solder particles) remaining in the cured material separated from the solder portion disposed between the electrodes are present on the side of the solder portion. On the other hand, in the present invention, the solder (solder particles) remaining in the cured portion separated from the solder portion disposed between the electrodes can be prevented from being present.

1‧‧‧Connection structure

2‧‧‧1st connection object component

2a‧‧‧1st electrode

3‧‧‧2nd connection object component

3a‧‧‧2nd electrode

4‧‧‧Connecting Department

4A‧‧‧ solder department

4B‧‧‧ Hardened Parts

Claims (12)

A conductive paste comprising a thermosetting component, a flux, and a plurality of solder particles, and having a viscosity of 0.1 Pa at a melting point of the flux. s above and 3Pa. Below s, the viscosity at the melting point of the above solder particles is 0.1 Pa. s above and 5Pa. s below. The conductive paste of claim 1, wherein the flux has a melting point of 80 ° C or more and 190 ° C or less. The conductive paste of claim 2, wherein the flux has a melting point of 100 ° C or more and 190 ° C or less. The conductive paste according to any one of claims 1 to 3, wherein the flux is contained in an amount of 0.1% by weight or more and 5% by weight or less based on 100% by weight of the conductive paste. The conductive paste according to any one of claims 1 to 3, which does not contain a filler or contains less than 0.25% by weight of a filler in 100% by weight of the conductive paste. The conductive paste according to any one of claims 1 to 3, wherein the solder particles are surface-treated in such a manner that a carboxyl group is present on the outer surface. The conductive paste according to any one of claims 1 to 3, wherein the melting point of the flux is higher than the melting point of the solder particles. A connection structure comprising: a first connection member having at least one first electrode on a surface thereof; a second connection member having at least one second electrode on a surface; and a connection portion A connection object member is connected to the second connection object member; the connection portion is formed by the conductive paste according to any one of claims 1 to 7. The first electrode and the second electrode are electrically connected by a solder portion of the connection portion. The connection structure according to claim 8, wherein the second connection target member is a resin film, a flexible printed circuit board, a rigid flexible substrate, or a flexible flat cable. A method of manufacturing a connection structure, comprising: using the conductive paste according to any one of claims 1 to 7 to dispose the conductive paste on a surface of a first connection member having at least one first electrode on its surface a step of arranging a second connection target having at least one second electrode on a 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 a step of forming the first connection member and the second by the conductive paste by heating the conductive paste to a temperature equal to or higher than a melting point of the solder particles and a hardening temperature of the thermosetting component The connection portion to which the target member is connected is connected, and the first electrode and the second electrode are electrically connected by a solder portion of the connection portion. The method of manufacturing a connection structure according to claim 10, wherein in the step of arranging the second connection member and the step of forming the connection portion, the second connection member is applied to the conductive paste without applying pressure The weight. The method of manufacturing a connection structure according to claim 10, wherein the second connection target member is a resin film, a flexible printed circuit board, a rigid flexible substrate, or a flexible flat cable.