WO2015186704A1 - 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 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 anisotropic conductive paste and anisotropic conductive film are widely known. In the anisotropic conductive material, conductive particles are dispersed in a binder resin.

In order to obtain various connection structures, for example, the anisotropic conductive material may be connected between a flexible printed circuit board and a glass substrate (FOG (Film on Glass)), or connected between a semiconductor chip and a flexible printed circuit board (COF ( (Chip on Film)), connection between a semiconductor chip and a glass substrate (COG (Chip on Glass)), connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)), and the like.

For example, when electrically connecting the electrode of the flexible printed circuit board and the electrode of the glass epoxy substrate by the anisotropic conductive material, an anisotropic conductive material containing conductive particles is disposed on the glass epoxy substrate. To do. Next, a flexible printed circuit board is laminated, and heated and pressurized. As a result, the anisotropic conductive material is cured, and the electrodes are electrically connected via the conductive particles to obtain a connection structure.

As an example of the anisotropic conductive material, the following Patent Document 1 includes a resin layer containing a thermosetting resin, solder powder, and a curing agent, and the solder powder and the curing agent include the resin layer. An adhesive tape present therein is disclosed. This adhesive tape is in the form of a film, not a paste.

Further, Patent Document 1 discloses a bonding method using the above-mentioned adhesive tape. Specifically, a first substrate, an adhesive tape, a second substrate, an adhesive tape, and a third substrate are laminated in this order from the bottom to obtain a laminate. At this time, the first electrode provided on the surface of the first substrate is opposed to the second electrode provided on the surface of the second substrate. Moreover, the 2nd electrode provided in the surface of the 2nd board | substrate and the 3rd electrode provided in the surface of the 3rd board | substrate are made to oppose. Then, the laminate is heated and bonded at a predetermined temperature. Thereby, a connection structure is obtained.

WO2008 / 023452A1

The adhesive tape described in Patent Document 1 is a film, not a paste. For this reason, 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 easily placed in a region (space) where no electrode is formed. Solder powder disposed in a region where no electrode is formed does not contribute to conduction between the electrodes.

Also, even if the anisotropic conductive paste contains solder powder, the solder powder may not be efficiently disposed on the electrodes (lines).

An object of the present invention is to provide a conductive paste that can efficiently arrange solder particles on electrodes and can improve conduction reliability between the electrodes. Moreover, this invention is providing the manufacturing method of the connection structure and connection structure using the said electrically conductive paste.

According to a wide aspect of the present invention, the solder includes a thermosetting component, a flux, and a plurality of solder particles, and the viscosity at the melting point of the flux is 0.1 Pa · s or more and 3 Pa · s or less. A conductive paste is provided in which the viscosity at the melting point of the particles is 0.1 Pa · s or more and 5 Pa · s or less.

In a specific aspect of the conductive paste according to the present invention, the melting point of the flux is 80 ° C. or more and 190 ° C. or less, and 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 according to the present invention, the content of the flux is 0.1 wt% or more and 5 wt% or less in 100 wt% of the conductive paste.

In a specific aspect of the conductive paste according to the present invention, the conductive paste does not contain a filler or contains a filler in less than 0.25% by weight in 100% by weight of the conductive paste.

In a specific aspect of the conductive paste according to the present invention, the solder particles are surface-treated so that carboxyl groups exist on the outer surface.

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

According to a wide aspect of the present invention, 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 the first The connection target member and a connection part connecting the second connection target member are formed, and the connection part is formed of the above-described conductive paste, and the first electrode and the second electrode A connection structure is provided in which an electrode is electrically connected by a solder portion in the connection portion.

According to a wide aspect of the present invention, using the conductive paste described above, the step of disposing the conductive paste on the surface of the first connection target member having at least one first electrode on the surface; On the surface opposite to the first connection target member side of the paste, the second connection target member having at least one second electrode on the surface is formed by the first electrode and the second electrode. The first connection target member and the second connection target member are disposed so as to face each other, and by heating the conductive paste to a temperature equal to or higher than the melting point of the solder particles and equal to or higher than the curing temperature of the thermosetting component. And a step of electrically connecting the first electrode and the second electrode with a solder portion in the connection portion. , How to manufacture connection structures There is provided.

In a specific aspect of the method for manufacturing a connection structure according to the present invention, in the step of arranging the second connection target member and the step of forming the connection portion, no pressure is applied, and the conductive paste includes The weight of the second connection target member is added.

It is preferable that the second connection target member is a resin film, a flexible printed board, a rigid flexible board, or a flexible flat cable.

The conductive paste according to the present invention includes a thermosetting component, a flux, and a plurality of solder particles, and the viscosity at the melting point of the flux is 0.1 Pa · s or more and 3 Pa · s or less. Since the viscosity at the melting point is 0.1 Pa · s or more and 5 Pa · s or less, when the electrodes are electrically connected, the solder particles can be efficiently disposed on the electrodes. The conduction reliability can be increased.

FIG. 1 is a partially cutaway front sectional view schematically showing a connection structure obtained using a conductive paste according to an embodiment of the present invention. FIGS. 2A to 2C are diagrams for explaining each step of an example of a method of manufacturing a connection structure using the conductive paste according to the embodiment of the present invention. FIG. 3 is a partially cutaway front sectional view showing a modified example of the connection structure. FIGS. 4A, 4B, and 4C are images showing an example of a connection structure using a conductive paste that is not included in the embodiment of the present invention. FIGS. 4A and 4B are images. FIG. 4C is a cross-sectional image, and FIG. 4C is a planar image.

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

The conductive paste according to the present invention includes a thermosetting component, a flux, and a plurality of solder particles. In the conductive paste according to the present invention, the viscosity at the melting point of the flux is 0.1 Pa · s or more and 3 Pa · s or less. In the conductive paste according to the present invention, the solder particles have a viscosity at the melting point of 0.1 Pa · s to 5 Pa · s.

In the conductive paste according to the present invention, since the above-described configuration is adopted, when the electrodes are electrically connected, a plurality of solder particles are easily collected between the electrodes, and the plurality of solder particles are placed on the electrodes (lines). Can be arranged efficiently. Moreover, it is difficult for some of the plurality of solder particles to be disposed in a region (space) where no electrode is formed, and the amount of solder particles disposed in a region where no electrode is 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 laterally adjacent electrodes that should not be connected, and to improve insulation reliability. Such an effect is obtained when the oxide paste 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 melt, the conductive paste This is considered to be because the viscosity of this is moderate.

The conductive paste according to the present invention can be suitably used for the following manufacturing method of the connection structure according to the present invention.

In the method for manufacturing a connection structure according to the present invention, a conductive paste, a first connection target member, and a second connection target member are used. The conductive material used in the method for manufacturing a connection structure according to the present invention is not a conductive film but a conductive paste. The conductive paste includes 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.

In the method for manufacturing a connection structure according to the present invention, the step of disposing the conductive paste according to the present invention on the surface of the first connection target member, and the first connection target member side of the conductive paste include: On the opposite surface, the step of disposing the second connection object member so that the first electrode and the second electrode face each other, the melting point of the solder particles or higher, and the thermosetting component By heating the conductive paste above the curing temperature, a connection portion connecting the first connection target member and the second connection target member is formed by the conductive paste, and the first And electrically connecting the second electrode and the second electrode with a solder portion in the connection portion. In the manufacturing method of the connection structure according to the present invention, in the step of arranging the second connection target member and the step of forming the connection portion, no pressure is applied, and the second connection is applied to the conductive paste. The weight of the target member is preferably added. In the method for manufacturing a connection structure according to the present invention, in the step of arranging the second connection target member and the step of forming the connection portion, the conductive paste has a weight force of the second connection target member. It is preferable not to apply a pressure higher than.

In the manufacturing method of the connection structure according to the present invention, since the above-described configuration is adopted, the plurality of solder particles are easily collected between the first electrode and the second electrode, and the plurality of solder particles are collected on the electrode ( Line). Moreover, it is difficult for some of the plurality of solder particles to be disposed in a region (space) where no electrode is formed, and the amount of solder particles disposed in a region where no electrode is formed can be considerably reduced. 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 laterally adjacent electrodes that should not be connected, and to improve insulation reliability.

Thus, in order to efficiently arrange a plurality of solder particles on the electrode and to considerably reduce the amount of solder particles arranged in the region where the electrode is not formed, a conductive paste is used instead of a conductive film. The inventors have found that they need to be used.

Further, conductive particles having base material particles and a solder layer disposed on the surface of the base material particles are known as particles different from the solder particles. Compared to the case where such conductive particles are used, when solder particles are used, the melting point of the flux and the melting point of the solder particles are in a specific range, so that the solder particles are arranged on the electrodes. The effect of improving accuracy is increased.

Furthermore, in the step of arranging the second connection target member and the step of forming the connection portion, if the weight of the second connection target member is added to the conductive paste without applying pressure, the connection portion is Solder particles arranged in a region (space) where no electrode is formed before being formed are more easily collected between the first electrode and the second electrode, and a plurality of solder particles are separated into electrodes (lines). The inventors have also found that they can be arranged efficiently above. In the present invention, a configuration in which a conductive paste is used instead of a conductive film and a configuration in which the weight of the second connection target member is added to the conductive paste without applying pressure are used in combination. This has a great meaning in order to obtain the effects of the present invention at a higher level.

In addition, WO2008 / 023452A1 describes that it is preferable to pressurize with a predetermined pressure at the time of bonding from the viewpoint of efficiently moving the solder powder to the electrode surface, and the pressurizing pressure further ensures the solder area. For example, it is described that the pressure is set to 0 MPa or more, preferably 1 MPa or more. Further, even if the pressure intentionally applied to the adhesive tape is 0 MPa, the member disposed on the adhesive tape It is described that a predetermined pressure may be applied to the adhesive tape by its own weight. In WO2008 / 023452A1, it is described that the pressure applied intentionally to the adhesive tape may be 0 MPa, but there is no difference between the effect when the pressure exceeding 0 MPa is applied and when the pressure is set to 0 MPa. Not listed.

If a conductive paste is used instead of a conductive film, the thickness of the connecting portion can be adjusted as appropriate depending on the amount of the conductive paste applied. On the other hand, in the conductive film, in order to change or adjust the thickness of the connection portion, it is necessary to prepare a conductive film having a different thickness or to prepare a conductive film having a predetermined thickness. There is.

Hereinafter, the present invention will be clarified by describing specific embodiments and examples of the present invention with reference to the drawings.

First, FIG. 1 schematically shows a connection structure obtained by using a conductive paste according to an embodiment of the present invention in a partially cutaway front sectional view.

The connection structure 1 shown in FIG. 1 is a connection that connects a first connection target member 2, a second connection target member 3, and the first connection target member 2 and the second connection target member 3. Part 4. The connection portion 4 is formed of a conductive paste containing a thermosetting component, a flux, and a plurality of solder particles. In this conductive paste, the viscosity at the melting point of the flux and the viscosity at the melting point of the solder particles are within a specific range.

The connecting portion 4 includes a solder portion 4A in which a plurality of solder particles are gathered and joined to each other, and a cured product portion 4B in which a thermosetting component is thermally cured.

The first connection object member 2 has a plurality of first electrodes 2a on the 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. In the connection portion 4, no solder exists in a region (cured product portion 4B portion) different from the solder portion 4A gathered between the first electrode 2a and the second electrode 3a. In an area different from the solder part 4A (hardened product part 4B part), there is no solder separated from the solder part 4A. If the amount is small, the solder may be present in a region (cured product portion 4B portion) different from the solder portion 4A gathered 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 molten solder particles are wetted and spread on the surface of the electrode to solidify to form a solder portion 4 </ b> A. For this reason, the connection area of 4 A of solder parts and the 1st electrode 2a, and 4 A of solder parts, and the 2nd electrode 3a becomes large. That is, by using the solder particles, the solder portion 4A, the first electrode 2a, and the solder portion are compared with the case where the conductive outer surface is made of a metal such as nickel, gold or copper. The contact area between 4A and the second electrode 3a increases. For this reason, the conduction | electrical_connection reliability and connection reliability in the connection structure 1 become high. In general, the flux contained in the conductive paste is gradually deactivated by heating.

In addition, in the connection structure 1 shown in FIG. 1, all of the solder portions 4A are located in the facing region between the first and second electrodes 2a and 3a. 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 the solder part 4XA and the hardened | cured material part 4XB. As in the connection structure 1X, most of the solder portions 4XA are located in regions where the first and second electrodes 2a and 3a are opposed to each other, and a part of the solder portion 4XA is first and second. You may protrude to the side from the area | region which electrode 2a, 3a has opposed. The solder part 4XA protruding laterally from the region where the first and second electrodes 2a and 3a are opposed is a part of the solder part 4XA and is not a solder separated from the solder part 4XA. In the present embodiment, the amount of solder away from the solder portion can be reduced, but the solder away from the solder portion may exist in the cured product portion.

If the amount of solder particles used is reduced, the connection structure 1 can be easily obtained. If the amount of the solder particles used is increased, it becomes easy to obtain the connection structure 1X.

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

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

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

Moreover, the 2nd connection object member 3 which has the 2nd electrode 3a on the surface (lower surface) is prepared. Next, as shown in FIG. 2B, in the conductive paste 11 on the surface of the first connection target member 2, on the surface of the conductive paste 11 opposite to the first connection target member 2 side, The 2nd connection object member 3 is arrange | positioned (2nd process). On the surface of the conductive paste 11, the second connection target member 3 is disposed 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 above the melting point of the solder particles 11A and above the curing temperature of the thermosetting component 11B (third step). That is, the conductive paste 11 is heated to a temperature lower than the melting point of the solder particles 11A and the curing temperature of the thermosetting component 11B. At the time of this heating, the solder particles 11A that existed in the region where no electrode is formed gather between the first electrode 2a and the second electrode 3a (self-aggregation effect). In this 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. Also, the solder particles 11A are melted and joined together. Further, the thermosetting component 11B is thermoset. As a result, as shown in FIG. 2C, the connection portion 4 connecting the first connection target member 2 and the second connection target member 3 is formed with the conductive paste 11. The connection part 4 is formed by the conductive paste 11, the solder part 4A is formed by joining a plurality of solder particles 11A, and the cured part 4B is formed by thermosetting the thermosetting component 11B. Since the solder particles 11A move quickly, the first electrode 2a and the second electrode are moved after the movement of the solder particles 11A not located between the first electrode 2a and the second electrode 3a starts. It is not necessary to keep the temperature constant until the movement of the solder particles 11A is completed.

In this embodiment, no pressure is applied in the second step and the third step. In the present embodiment, the weight of the second connection target member 3 is added to the conductive paste 11. For this reason, when the connection part 4 is formed, the solder particles 11A are effectively collected between the first electrode 2a and the second electrode 3a. In addition, if pressure is applied in at least one of the second step and the third step, the action of the solder particles trying to collect between the first electrode and the second electrode is hindered. The tendency to become higher. This has been found by the inventors.

In this way, the connection structure 1 shown in FIG. 1 is obtained. The second step and the third step may be performed continuously. Moreover, after performing the said 2nd process, the laminated body of the obtained 1st connection object member 2, the electrically conductive paste 11, and the 2nd connection object member 3 is moved to a heating part, and said 3rd said You may perform a process. In order to perform the heating, the laminate may be disposed on a heating member, or the laminate may be disposed in a heated space.

The heating temperature in the third step is not particularly limited as long as it is higher than the melting point of the solder particles and higher than the curing temperature of the thermosetting component. The heating temperature is preferably 130 ° C. or higher, more preferably 160 ° C. or higher, preferably 450 ° C. or lower, more preferably 250 ° C. or lower, and still more preferably 200 ° C. or lower.

In addition, the said 1st connection object member should just have at least 1 1st electrode. The first connection target member preferably has a plurality of first electrodes. The said 2nd connection object member should just have at least 1 2nd electrode. The second connection target member preferably 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 semiconductor chips, capacitors, and diodes, and resin films, printed boards, flexible printed boards, flexible flat cables, rigid flexible boards, glass epoxies. Examples thereof include electronic components such as circuit boards such as substrates and glass substrates. The first and second connection target members are preferably electronic components.

It is preferable that at least one of the first connection target member and the second connection target member is a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. The second connection target member is preferably a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. Resin films, flexible printed boards, flexible flat cables, and rigid flexible boards have the property of being highly flexible and relatively lightweight. When a conductive film is used for connection of such a connection object member, there exists a tendency for a solder particle not to gather on an electrode. On the other hand, since the conductive paste according to the present invention is used, even if a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board is used, the solder particles can be efficiently collected on the electrode. And the reliability of conduction between the electrodes can be sufficiently enhanced. When using a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board, the reliability of conduction between electrodes by not applying pressure compared to the case of using other connection target members such as a semiconductor chip. The improvement effect can be obtained more effectively.

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. When the connection object 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. 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. In addition, when the said electrode is an aluminum electrode, the electrode formed only with aluminum may be sufficient and the electrode by which the aluminum layer was laminated | stacked on the surface of the metal oxide layer may be sufficient. Examples of the material for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal element include Sn, Al, and Ga.

The distance D1 of the connecting portion at the position where the first electrode and the second electrode face each other is preferably 5 μm or more, more preferably 20 μm or more, preferably 50 μm or less, more preferably 75 μm or less. When the distance D1 is equal to or greater than the lower limit, the connection reliability between the connection portion and the connection target member is further increased. When the distance D1 is less than or equal to the above upper limit, solder particles are more likely to gather on the electrodes when the connection portion is formed, and the conduction reliability between the electrodes is further enhanced.

In order to arrange the solder particles more efficiently on the electrode, the viscosity η1 at 25 ° C. of the conductive paste is preferably 10 Pa · s or more, more preferably 50 Pa · s or more, and further preferably 100 Pa · s or more, preferably Is 800 Pa · s or less, more preferably 600 Pa · s or less, and still more preferably 500 Pa · s or less.

The viscosity can be appropriately adjusted depending on the type and amount of the compounding component. Further, the use of a filler can make the viscosity relatively high. However, since the filler may inhibit the movement of the solder particles, the filler content is preferably small.

In order to arrange the solder particles more efficiently on the electrode, the viscosity η2 at the melting point of the flux of the conductive paste is 0.1 Pa · s or more and 3 Pa · s or less. From the viewpoint of more efficiently arranging the solder particles on the electrode, the viscosity η2 is preferably 0.15 Pa · s or more, more preferably 0.2 Pa · s or more, preferably 2 Pa · s or less, more preferably 1 Pa · s or less.

In order to more efficiently arrange the solder particles on the electrode, the viscosity η3 at the melting point of the solder particles of the conductive paste is 0.1 Pa · s or more and 5 Pa · s or less. From the viewpoint of more efficiently arranging the solder particles on the electrode, the viscosity η3 is preferably 0.15 Pa · s or more, more preferably 0.2 Pa · s or more, preferably 3 Pa · s or less, more preferably 1 Pa · s or less.

From the viewpoint of more efficiently arranging the solder particles on the electrode, the ratio of the viscosity η1 to the viscosity η2 (η1 / η2) is preferably 15 or more, more preferably 50 or more, preferably 3000 or less, more preferably Is 2500 or less.

From the viewpoint of more efficiently arranging the solder particles on the electrode, the ratio of the viscosity η1 to the viscosity η3 (η1 / η3) is preferably 10 or more, more preferably 40 or more, preferably 2500 or less, more preferably Is 2000 or less.

From the viewpoint of more efficiently arranging the solder particles on the electrode, the ratio of the viscosity η2 to the viscosity η3 (η2 / η3) is preferably 0.1 or more, more preferably 0.3 or more, preferably 10 Below, more preferably 1 or less.

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

The conductive paste includes a thermosetting component, a flux, and a plurality of solder particles. The thermosetting component preferably includes a curable compound (thermosetting compound) that 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 a conductive outer surface. As for the said solder particle, both a center part and an electroconductive outer surface are formed with the solder. From the viewpoint of more efficiently arranging the solder on the electrode, the solder particles are preferably surface-treated so that carboxyl groups exist on the outer surface. The solder particles are preferably blended into the conductive paste after being surface-treated so that carboxyl groups exist on the outer surface.

The solder is preferably a metal (low melting point metal) having a melting point of 450 ° C. or lower. The solder particles are preferably metal particles (low melting point metal particles) having a melting point of 450 ° C. or lower. The low melting point metal particles are particles containing a low melting point metal. The low melting point metal is a metal having a melting point of 450 ° C. or lower. The melting point of the low melting point metal is preferably 300 ° C. or lower, more preferably 160 ° C. or lower. The solder particles include tin. In 100% by weight of the metal contained in the solder particles, the content of tin is preferably 30% by weight or more, more preferably 40% by weight or more, still more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the content of tin in the solder particles is equal to or higher than the lower limit, the connection reliability between the solder portion and the electrode is further enhanced.

The tin content is determined using a high-frequency inductively coupled plasma emission spectrometer (“ICP-AES” manufactured by Horiba, Ltd.) or a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu). It can be measured.

By using the above solder particles, the solder is melted and joined to the electrodes, and the solder portion conducts between the electrodes. For example, since the solder portion and the electrode are not in point contact but in surface contact, the connection resistance is lowered. In addition, the use of solder particles increases the bonding strength between the solder portion and the electrode. As a result, peeling between the solder portion and the electrode is further less likely to occur, and the conduction reliability and the connection reliability are effectively increased.

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. Of these, the low melting point metal is preferably tin, a tin-silver alloy, a tin-silver-copper alloy, a tin-bismuth alloy, or a tin-indium alloy because of its excellent wettability with respect to the electrode. More preferred are a tin-bismuth alloy and a tin-indium alloy.

The solder particles are preferably a filler material having a liquidus line of 450 ° C. or lower based on JIS Z3001: Welding terms. Examples of the composition of the solder particles include metal compositions containing zinc, gold, silver, lead, copper, tin, bismuth, indium and the like. Of these, a tin-indium system (117 ° C. eutectic) or a tin-bismuth system (139 ° C. eutectic) which is low-melting and lead-free is preferable. That is, the solder particles preferably do not contain lead, and preferably contain tin and indium, or contain tin and bismuth.

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

The average particle diameter of the solder particles is preferably 0.5 μm or more, more preferably 1 μm or more, still more preferably 3 μm or more, particularly preferably 5 μm or more, preferably 100 μm or less, more preferably 40 μm or less, and even more preferably 30 μm. Hereinafter, it is more 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 arranged on the electrode. 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 the 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 and calculating an average value.

The content of the solder particles in 100% by weight of the conductive paste 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, preferably 80% by weight or less, more preferably 60% by weight or less, and 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, it is possible to more efficiently arrange the solder particles on the electrodes, and it is easy to arrange many solder particles between the electrodes, The conduction reliability is further increased. From the viewpoint of further improving the conduction reliability, it is preferable that the content of the solder particles is large.

(Compound curable by heating: thermosetting component)
Examples of the thermosetting compound include oxetane compounds, epoxy compounds, episulfide compounds, (meth) acrylic compounds, phenolic compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. Among these, an epoxy compound is preferable 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 the form of particles.

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. Is 98% by weight or less, more preferably 90% by weight or less, and particularly preferably 80% by weight or less. From the viewpoint of further improving the impact resistance, it is preferable that the content of the thermosetting component is large.

(Thermosetting agent: thermosetting component)
The thermosetting agent thermosets the thermosetting compound. Examples of the 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 generator. As for the said thermosetting agent, only 1 type may be used and 2 or more types may be used together.

Among these, an imidazole curing agent, a polythiol curing agent, or an amine curing agent is preferable because the conductive paste can be cured more rapidly at a low temperature. Moreover, since a storage stability becomes high when the curable compound curable by heating and the thermosetting agent are mixed, a latent curing agent is preferable. The latent curing agent is preferably a latent imidazole curing agent, a latent polythiol curing agent or a latent amine curing agent. In addition, the said thermosetting agent may be coat | covered with polymeric substances, such as a polyurethane resin or a polyester resin.

The imidazole curing agent is not particularly limited, and 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2, 4-Diamino-6- [2'-methylimidazolyl- (1 ')]-ethyl-s-triazine and 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s- Examples include triazine isocyanuric acid adducts.

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

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

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

Examples of the thermal cation curing agent include iodonium cation curing agents, oxonium cation curing agents, and sulfonium cation curing agents. Examples of the iodonium-based cationic curing agent include bis (4-tert-butylphenyl) iodonium hexafluorophosphate. Examples of the oxonium-based cationic curing agent include trimethyloxonium tetrafluoroborate. Examples of the sulfonium-based cationic curing agent include tri-p-tolylsulfonium hexafluorophosphate.

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

The reaction initiation temperature of the thermosetting agent is preferably 50 ° C or higher, more preferably 70 ° C or higher, still more preferably 80 ° C or higher, preferably 250 ° C or lower, more preferably 200 ° C or lower, still more preferably 150 ° C or lower, Especially preferably, it is 140 degrees C or less. When the reaction start temperature of the thermosetting agent is not less than the above lower limit and not more than the above upper limit, the solder particles are more efficiently arranged on the electrode. The reaction initiation temperature of the thermosetting agent is particularly preferably 80 ° C. or higher and 140 ° C. or lower.

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

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

The content of the thermosetting agent is not particularly limited. The content of the thermosetting agent is preferably 0.01 parts by weight or more, more preferably 1 part by weight or more, preferably 200 parts by weight or less, more preferably 100 parts by weight with respect to 100 parts by weight of the thermosetting compound. Part or less, more preferably 75 parts by weight or less. When the content of the thermosetting agent is at least the above lower limit, it is easy to sufficiently cure the conductive paste. When the content of the thermosetting agent is not more than the above upper limit, it is difficult for an excess thermosetting agent that did not participate in curing after curing to remain, and the heat resistance of the cured product is further enhanced.

(flux)
The conductive paste contains a flux. By using flux, the solder can be more effectively placed 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, an organic acid, and pine resin. Etc. As for the said flux, only 1 type may be used and 2 or more types may be used together.

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 pine resin include activated pine resin and non-activated pine resin. The flux is preferably an organic acid having two or more carboxyl groups, pine resin. The flux may be an organic acid having two or more carboxyl groups, or pine resin. By using an organic acid having two or more carboxyl groups, pine resin, the conduction reliability between the electrodes is further enhanced.

The above rosins are rosins whose main component is abietic acid. The flux is preferably rosins, and more preferably abietic acid. By using this preferable flux, the conduction reliability between the electrodes is further enhanced.

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, particularly preferably 100 ° C. or higher, preferably 200 ° C. or lower, more preferably 190 ° C. or lower. More preferably, it is 160 ° C. or less, more 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 more effectively exhibited, and the solder particles are more efficiently arranged on the electrode. As a result, the connection resistance between the electrodes is reduced, and the connection reliability is also increased. The active temperature (melting point) of the flux is preferably 80 ° C. or higher and 190 ° C. or lower, and more preferably 100 ° C. or higher and 190 ° C. or lower. The activation temperature of the flux is particularly preferably 80 ° C. or higher and 140 ° C. or lower, and more preferably 100 ° C. or higher and 140 ° C. or lower.

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

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

From the viewpoint of more efficiently arranging 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, preferably 5 ° C or higher, more preferably 10 ° C or higher. Is more preferable.

From the viewpoint of more efficiently arranging the solder on the electrode, the melting point of the flux is preferably higher than the reaction start temperature of the thermosetting agent, more preferably 5 ° C or higher, more preferably 10 ° C or higher. More preferably.

The flux may be dispersed in the conductive paste or may be adhered on the surface of the solder particles.

Since the melting point of the flux is higher than the melting point of the solder, the solder particles can be efficiently aggregated on the electrode portion. This is because, when heat is applied at the time of joining, when the electrode formed on the connection target member is compared with the portion of the connection target member around the electrode, the thermal conductivity of the electrode portion is that of the connection target member portion around the electrode. Due to the fact that it is higher than the heat traditional rate, it is caused by the rapid temperature rise of the electrode part. At the stage where the melting point of the solder particles is exceeded, the inside of the solder particles dissolves, but the oxide film formed on the surface does not reach the melting point (activation temperature) of the flux and is not removed. In this state, since the temperature of the electrode portion first reaches the melting point (activation temperature) of the flux, the oxide film on the surface of the solder particles preferentially on the electrode is removed, and the solder particles are placed on the surface of the electrode. Can spread wet. Thereby, solder particles can be efficiently aggregated on the electrode.

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

The above-mentioned thermal cation curing agent can be used as the flux that releases cations by heating.

In 100% by weight of the conductive paste, the content of the flux is preferably 0.5% by weight or more, preferably 30% by weight or less, more preferably 25% by weight or less. The conductive paste may not contain a flux. When the flux content is not less than the above lower limit and not more than the above upper limit, it becomes more difficult to 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 is more effective. Can be removed.

(Filler)
A filler may be added to the conductive paste. The filler may be an organic filler or an inorganic filler. However, since the filler may inhibit the movement of the solder particles, the filler content is preferably small.

It is preferable that the conductive paste does not contain a filler or contains a filler in less than 5% by weight in 100% by weight of the conductive paste. In 100% by weight of the conductive paste, the content of the filler is preferably 0% by weight (not contained) or more, preferably 5% by weight or less, more preferably 2% by weight or less, still more preferably 1% by weight or less, even more. Preferably it is less than 0.25 wt%, particularly preferably 0.1 wt% 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 are more efficiently arranged on the electrode. It is particularly preferred that the conductive paste does not contain a filler or contains less than 0.25% by weight of filler in 100% by weight of the conductive paste, and most preferably the conductive paste does not contain a filler. If the filler content is less than 0.25% by weight, the solder particle migration inhibition by the filler is sufficiently small, and if the filler content is 0.1% by weight or less, the solder particle migration inhibition by the filler is inhibited. Pretty small.

(Other ingredients)
If necessary, the conductive paste is, for example, a filler, an extender, a softener, a plasticizer, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, and a lubricant. In addition, various additives such as an antistatic agent and a flame retardant may be included.

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

Polymer A:
Synthesis of reaction product (polymer A) of bisphenol F with 1,6-hexanediol diglycidyl ether and bisphenol F type epoxy resin:
72 parts by weight of bisphenol F (containing 4,4′-methylene bisphenol, 2,4′-methylene bisphenol and 2,2′-methylene bisphenol in a weight ratio of 2: 3: 1), 1,6-hexanediol 70 parts by weight of glycidyl ether and 30 parts by weight of bisphenol F type epoxy resin (“EPICLON EXA-830CRP” manufactured by DIC) were placed in a three-necked flask and dissolved at 150 ° C. under a nitrogen flow. Thereafter, 0.1 part by weight of tetra-n-butylsulfonium bromide, which is a catalyst for addition reaction of a hydroxyl group and an epoxy group, was added, and an addition polymerization reaction was performed at 150 ° C. for 6 hours under a nitrogen flow to obtain a reactant (polymer). A) was obtained.

By confirming that the addition polymerization reaction has progressed by NMR, the reaction product (Polymer A) contains a hydroxyl group derived from bisphenol F, 1,6-hexanediol diglycidyl ether, and an epoxy group of bisphenol F type epoxy resin. It was confirmed that it has a structural unit bonded to the main chain and has an epoxy group at both ends.

The weight average molecular weight of the reaction product (polymer A) obtained by GPC was 10,000, and the number average molecular weight was 3,500.

Polymer B: both ends epoxy group rigid skeleton phenoxy resin, “YX6900BH45” manufactured by Mitsubishi Chemical Corporation, weight average molecular weight 16000

Thermosetting compound 1: Resorcinol type epoxy compound, “EX-201” manufactured by Nagase ChemteX Corporation, washed after crystallization at low temperature

Thermosetting compound 2: Bisphenol F type epoxy resin, “EPICLON EXA-830CRP” manufactured by DIC, used after being crystallized at low temperature

Thermosetting agent 1: Pentaerythritol tetrakis (3-mercaptobutyrate), “Karenz MT PE1” manufactured by Showa Denko KK

Latent epoxy thermosetting agent 1: T & K TOKA's “Fujicure 7000”

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

Flux 2: Succinic acid, manufactured by Wako Pure Chemical Industries, Ltd., melting point (active temperature) 186 ° C.

Flux 3: Abietic acid, manufactured by Wako Pure Chemical Industries, Ltd., melting point (activation temperature) 174 ° C.

Solder particles 1 (SnBi solder particles, melting point 139 ° C., “DS10” manufactured by Mitsui Kinzoku Co., Ltd.) are subjected to the following surface treatment, average particle diameter 13 μm)

Surface treatment of solder particles:
200 g of solder particles, 40 g of adipic acid, and 70 g of acetone are weighed in a three-necked flask, and 0.3 g of dibutyltin oxide, which is a dehydration condensation catalyst between the hydroxyl groups of the solder particles and the carboxyl groups of adipic acid, is added. The reaction was carried out at 4 ° C for 4 hours. Thereafter, the solder particles were collected by filtration.

The collected solder particles, 50 g of adipic acid, 200 g of toluene, and 0.3 g of para-toluenesulfonic acid are weighed in a three-necked flask and allowed to react at 120 ° C. for 3 hours while evacuating and refluxing. It was. At this time, the reaction was carried out while removing water produced by dehydration condensation using a Dean-Stark extraction device.

Thereafter, the solder particles were collected by filtration, washed with hexane, and dried. Thereafter, the obtained solder particles were crushed with a ball mill, and then a sieve was selected so as to obtain a predetermined CV value. The obtained solder particles were surface-treated so that carboxyl groups were present on the outer surface.

Solder particles 2 (SnBi solder particles, melting point 139 ° C., “DS30” manufactured by Mitsui Kinzoku Co., Ltd.) surface-treated in the same manner as the solder particles 1, average particle diameter 32 μm

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

Phenoxy resin (“YP-50S” manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.)

(Examples 1 to 4, 6 to 9)
(1) Preparation of anisotropic conductive paste The components shown in Table 1 below were blended in the blending amounts shown in Table 1 to obtain anisotropic conductive paste. In the anisotropic conductive paste obtained, the thermosetting compound was dispersed in the form of particles.

(2) Production of first connection structure (L / S = 50 μm / 50 μm) Glass epoxy substrate (FR-4 substrate) having a copper electrode pattern (copper electrode thickness 10 μm) having an L / S of 50 μm / 50 μm on the upper surface (First connection object member) was prepared. Moreover, the flexible printed circuit board (2nd connection object member) which has a copper electrode pattern (copper electrode thickness 10 micrometers) whose L / S is 50 micrometers / 50 micrometers on the lower surface was prepared.

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

The anisotropic conductive paste immediately after fabrication was applied to the upper surface of the glass epoxy substrate so as to have a thickness of 50 μm to form an anisotropic conductive paste layer. Next, the flexible printed circuit board was 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 board is added 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 cured at 190 ° C. to obtain a first connection structure.

(3) Production of second connection structure (L / S = 75 μm / 75 μm) Glass epoxy substrate (FR-4 substrate) having a copper electrode pattern (copper electrode thickness 10 μm) having L / S of 75 μm / 75 μm on the upper surface (First connection object member) was prepared. Moreover, the flexible printed circuit board (2nd connection object member) which has a copper electrode pattern (copper electrode thickness 10 micrometers) whose L / S is 75 micrometers / 75 micrometers on the lower surface was prepared.

2nd connection structure was obtained like manufacture of the 1st connection structure except having used the above-mentioned glass epoxy board and flexible printed circuit board from which L / S differs.

(4) Production of third connection structure (L / S = 100 μm / 100 μm) Glass epoxy substrate (FR-4 substrate) having a copper electrode pattern (copper electrode thickness 10 μm) with L / S of 100 μm / 100 μm on the upper surface (First connection object member) was prepared. Moreover, the flexible printed circuit board (2nd connection object member) which has a copper electrode pattern (copper electrode thickness 10 micrometers) whose L / S is 100 micrometers / 100 micrometers on the lower surface was prepared.

3rd connection structure was obtained like manufacture of the 1st connection structure except having used the above-mentioned glass epoxy board and flexible printed circuit board from which L / S differs.

(Example 5)
Electrode size (L) / inter-electrode space (S) is 100 μm / 100 μm (for the third connection structure), 75 μm / 75 μm (for the second connection structure), 50 μm / 50 μm (first connection structure) 5 mm square semiconductor chip (thickness 400 μm) and a glass epoxy substrate (size 30 × 30 mm, thickness 0.4 mm) having electrodes facing it. First, second, and third connection structures were obtained in the same manner as in Example 1 except that a semiconductor chip and a glass epoxy substrate were used.

(Comparative Examples 1, 2, 5)
(1) Preparation of anisotropic conductive paste The components shown in Table 2 below were blended in the blending amounts shown in Table 2 to obtain anisotropic conductive paste. 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 phenoxy resin (“YP-50S” manufactured by Nippon Steel & Sumikin Chemical Co., Ltd.) was dissolved in methyl ethyl ketone (MEK) so that the solid content was 50% by weight to obtain a solution. Ingredients other than the phenoxy resin shown in Table 2 below were blended with the blending amounts shown in Table 2 below and the total amount of the above solution, and after stirring for 5 minutes at 2000 rpm using a planetary stirrer, a bar coater was used. It was coated on a release PET (polyethylene terephthalate) film so that the thickness after drying was 30 μm. An anisotropic conductive film was obtained by removing MEK by vacuum drying at room temperature.

The 1st, 2nd, 3rd connection structure was obtained like Example 1 except having used an anisotropic conductive film.

(Comparative Example 4)
Electrode size (L) / inter-electrode space (S) is 100 μm / 100 μm (for the third connection structure), 75 μm / 75 μm (for the second connection structure), 50 μm / 50 μm (first connection structure) 5 mm square semiconductor chip (thickness 400 μm) and a glass epoxy substrate (size 30 × 30 mm thickness 0.4 mm) having electrodes facing it. The first, second, and third connection structures were obtained in the same manner as in Comparative Example 1 except that this semiconductor chip and glass epoxy substrate were used.

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

(2) Connection distance (inter-electrode spacing)
By observing a cross section of the obtained first connection structure, the distance D1 (interval between electrodes) of the connection portion at the position where the upper and lower electrodes face each other was evaluated.

(3) Solder placement accuracy on electrodes In the cross section (cross section in the direction shown in FIG. 1) of the obtained first connection structure, it is separated from the solder portion disposed between the electrodes in 100% of the total area of the solder. Thus, the area (%) of the solder remaining in the cured product was evaluated. In addition, the average of the area in five cross sections was computed. The placement accuracy of the solder on the electrode was determined according to the following criteria.

[Judgment criteria for placement accuracy of conductive particles on electrode]
OO: The area of the solder (solder particles) remaining in the cured product away from the solder portion arranged between the electrodes in the total area of 100% of the solder appearing in the cross section is 0% or more and 1% or less ○: Out of 100% of the total area of the solder appearing in the cross section, the area of the solder (solder particles) remaining in the cured product away from the solder portion disposed between the electrodes exceeds 1% and is 10% or less Δ: The area of the solder (solder particles) remaining in the cured product away from the solder portion arranged between the electrodes exceeds 100% in the total area of 100% of the solder appearing in the cross section, and is 30% or less X: Out of the total area of 100% of the solder appearing in the cross section, the area of the solder (solder particles) remaining in the cured product away from the solder portion disposed between the electrodes exceeds 30%

(4) Connection reliability between upper and lower electrodes In the obtained first, second and third connection structures (n = 15), the connection resistance between the upper and lower electrodes was measured by the four-terminal method, respectively. . The average value of connection resistance was calculated. Note that the connection resistance can be obtained by measuring the voltage when a constant current is passed from the relationship of voltage = current × resistance. The conduction reliability was determined according to the following criteria.

[Judgment criteria for conduction reliability]
○○: Average value of connection resistance is 8.0Ω or less ○: Average value of connection resistance exceeds 8.0Ω and 10.0Ω or less △: Average value of connection resistance exceeds 10.0Ω and 15.0Ω or less × : Average connection resistance exceeds 15.0Ω

(5) Insulation reliability between adjacent electrodes After the first, second, and third connection structures (n = 15) obtained were left in an atmosphere of 85 ° C. and 85% humidity for 100 hours. 5V was applied between the adjacent electrodes, and the resistance value was measured at 25 locations. Insulation reliability was judged according to the following criteria.

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

The results are shown in Tables 1 and 2 below.

From the difference between the results of Example 1 and Comparative Example 1 and the difference between the results of Example 5 and Comparative Example 4, when the second connection target member is a flexible printed circuit board, the second connection target member is It can be seen that the effect of improving the conduction reliability by using the conductive paste of the present invention can be obtained more effectively than in the case of a semiconductor chip.

It was confirmed that the same results were obtained even when a resin film, a flexible flat cable, and a rigid flexible substrate were used instead of the flexible printed substrate.

Further, FIGS. 4A, 4B and 4C show an example of a connection structure using a conductive paste not included in the embodiment of the present invention. 4A and 4B are cross-sectional images, and FIG. 4C is a planar image. 4A, 4B, and 4C, a plurality of solders (solder particles) remaining in the cured product away from the solder portions disposed between the electrodes exist on the side of the solder portions. You can see that On the other hand, in this invention, it can avoid that the solder (solder particle | grains) which remain | separated from the solder part arrange | positioned between electrodes and remain | survived in hardened | cured material does not exist.

DESCRIPTION OF SYMBOLS 1,1X ... Connection structure 2 ... 1st connection object member 2a ... 1st electrode 3 ... 2nd connection object member 3a ... 2nd electrode 4, 4X ... Connection part 4A, 4XA ... Solder part 4B, 4XB ... Cured part 11 ... Conductive paste 11A ... Solder particles 11B ... Thermosetting component

Claims (12)

1. Including a thermosetting component, a flux, and a plurality of solder particles;
   The viscosity at the melting point of the flux is 0.1 Pa · s or more and 3 Pa · s or less,
   The electrically conductive paste whose viscosity in melting | fusing point of the said solder particle is 0.1 Pa.s or more and 5 Pa.s or less.
2. The conductive paste according to claim 1, wherein the melting point of the flux is 80 ° C or higher and 190 ° C or lower.
3. The conductive paste according to claim 2, wherein the melting point of the flux is 100 ° C or higher and 190 ° C or lower.
4. The conductive paste according to any one of claims 1 to 3, wherein the content of the flux is 0.1 wt% or more and 5 wt% or less in 100 wt% of the conductive paste.
5. The conductive paste according to any one of claims 1 to 4, which does not contain a filler or contains the filler in less than 0.25% by weight in 100% by weight of the conductive paste.
6. The conductive paste according to any one of claims 1 to 5, wherein the solder particles are surface-treated so that carboxyl groups are present on the outer surface.
7. The conductive paste according to any one of claims 1 to 6, wherein a melting point of the flux is higher than a melting point of the solder particles.
8. A first connection target member having at least one first electrode on its surface;
   A second connection target member having at least one second electrode on its surface;
   A connecting portion connecting the first connection target member and the second connection target member;
   The connection part is formed of the conductive paste according to any one of claims 1 to 7,
   A connection structure in which the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.
9. The connection structure according to claim 8, wherein the second connection target member is a resin film, a flexible printed board, a rigid flexible board, or a flexible flat cable.
10. Using the conductive paste according to any one of claims 1 to 7, disposing the conductive paste on a surface of a first connection target member having at least one first electrode on the surface;
    On the surface opposite to the first connection target member side of the conductive paste, a second connection target member having at least one second electrode on the surface, the first electrode and the second electrode And a step of arranging so as to face each other,
    By connecting the first connection target member and the second connection target member by heating the conductive paste above the melting point of the solder particles and above the curing temperature of the thermosetting component, And a step of electrically connecting the first electrode and the second electrode with a solder portion in the connection portion, the method comprising: forming the conductive paste;
11. The weight of the second connection target member is added to the conductive paste without applying pressure in the step of arranging the second connection target member and the step of forming the connection part. Method for manufacturing the connection structure of the present invention.
12. The method for manufacturing a connection structure according to claim 10 or 11, wherein the second connection target member is a resin film, a flexible printed board, a rigid flexible board, or a flexible flat cable.

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