JP2016076494A - Conductive paste, connection structure, and method for manufacturing connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste capable of efficiently arranging solder particles on electrodes to improve conduction reliability between the electrodes.SOLUTION: A conductive paste 11 comprises a thermosetting component 11B and a plurality of solder particles 11A, and the zeta potential on the surface of the solder particles 11A is plus. The solder particle 11a includes an anionic polymer disposed on the surface of a solder particle 11A body. The dielectric constant of a component excluding the solder particles 11A in the conductive paste 11 is preferably 3.4 or more and 6 or less, the viscosity of the conductive paste 11 at 25°C is preferably 10-800 Pa s, and the average particle diameter of the solder particles 11A is desirably 1-40 μm.SELECTED DRAWING: Figure 2

Description

  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 pastes and anisotropic conductive films are widely known. In the anisotropic conductive material, conductive particles are dispersed in a binder resin.

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

  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 in a film form and not in a paste form. 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.

  Moreover, even if it is the anisotropic conductive paste containing solder powder, solder powder may not be efficiently arrange | positioned on an electrode (line).

  The objective of this invention is providing the electrically conductive paste which can arrange | position a solder particle efficiently on an electrode and can improve the conduction | electrical_connection reliability between 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, there is provided a conductive paste comprising a thermosetting component and a plurality of solder particles, wherein the surface of the solder particles has a positive zeta potential.

  On the specific situation with the electrically conductive paste which concerns on this invention, the said solder particle has a solder particle main body and the anion polymer arrange | positioned on the surface of the said solder particle main body.

  On the specific situation with the electrically conductive paste which concerns on this invention, the dielectric constant measured using the component except the said solder particle in an electrically conductive paste is 3.4 or more and 6 or less.

  On the specific situation with the electrically conductive paste which concerns on this invention, the viscosity in 25 degreeC is 10 Pa.s or more and 800 Pa.s or less.

  On the specific situation with the electrically conductive paste which concerns on this invention, the minimum value of the viscosity in the temperature range below the melting point of the said solder particle is 0.1 Pa.s or more and 10 Pa.s or less.

  On the specific situation with the electrically conductive paste which concerns on this invention, the average particle diameter of the said solder particle is 1 micrometer or more and 40 micrometers or less.

  On the specific situation with the electrically conductive paste which concerns on this invention, content of the said solder particle is 10 to 60 weight% in 100 weight% of said electrically conductive paste.

  On the specific situation with the electrically conductive paste which concerns on this invention, the CV value of the particle diameter of the said solder particle is 5% or more and 40% or less.

  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. , Manufacturing method of connection structure It 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.

  When the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connection portion, and the second electrode, the first electrode and the second electrode It is preferable that the solder part in the connection part is arranged in 50% or more of the area of 100% of the part facing the two electrodes. At least one side surface of the first electrode and the second electrode is inclined inward, and the inner angle at the tip of the inclined portion of the inclined electrode is not less than 20 degrees and not more than 80 degrees. Preferably there is. The second connection target member is preferably a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board.

  The conductive paste according to the present invention contains a thermosetting component and a plurality of solder particles, and since the zeta potential of the surface of the solder particles is positive, the solder particles are electrically connected when the electrodes are electrically connected. It can arrange | position efficiently on an electrode and can improve the conduction | electrical_connection reliability between electrodes.

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. 2A to 2C are diagrams for explaining each step of an example of a method for 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. FIG. 4 is a schematic front view for explaining an example of the shape of the electrode. 5A, 5B, and 5C are images showing an example of a connection structure using the conductive paste included in the embodiment of the present invention. FIGS. 5A and 5B are cross-sectional views. FIG. 5C is a planar image. 6A, 6B, and 6C are images showing an example of a connection structure using a conductive paste that is not included in the embodiment of the present invention, and FIGS. 6A and 6B are images. FIG. 6C is a cross-sectional image, and FIG. 6C is a planar image.

  Details of the present invention will be described below.

  The conductive paste according to the present invention includes a thermosetting component and a plurality of solder particles. In the conductive paste according to the present invention, the zeta potential on the surface of the solder particles is positive. The zeta potential on the surface of general solder particles is not positive. In the conductive paste according to the present invention, the zeta potential on the surface of the solder particles is used with a positive value.

  In the conductive paste according to the present invention, since the above-described configuration is adopted, when the electrodes are electrically connected, the plurality of solder particles are likely to gather between the upper and lower electrodes, and the plurality of solder particles are collected. It can arrange | position efficiently on an 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 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. In order to obtain such an effect, the positive zeta potential on the surface of the solder particles contributes greatly. Solder particles having a positive zeta potential on the surface of the solder particles tend to gather together.

  In addition, since the zeta potential on the surface of the solder particles is positive, when the electrode of the connection target member is a metal, the charge on the surface of the electrode becomes negative, so it is estimated that the solder particles are likely to aggregate on the electrode. The The zeta potential of the solder particles is preferably 1 mV or less. When the zeta potential of the solder particles is 1 mV or less, when the viscosity of the conductive paste is reduced by heat or the like, the repulsion between the solder particles is small, so that the solder particles are more likely to aggregate.

  The electrically conductive paste which concerns on this invention can be used suitably for the manufacturing method of the connection structure which concerns on the following this invention.

  In the manufacturing method of the connection structure according to the present invention, the conductive paste, the first connection target member, and the 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 plurality of solder particles and a thermosetting component. 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.

  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.

  In addition, when a conductive paste is used instead of a conductive film, the thickness of the connection portion can be appropriately adjusted 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 part 4 is formed of a conductive paste containing a thermosetting component and a plurality of solder particles. In this conductive paste, the zeta potential on the surface of the solder particles is positive.

  The connection 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 target 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 melt of the solder particles wets and spreads on the surface of the electrode and is solidified 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. Note that the conductive paste may contain a flux. When the flux is used, the flux is generally deactivated gradually by heating.

  In addition, in the connection structure 1 shown in FIG. 1, all the solder parts 4A are located in the area | region which the 1st, 2nd electrodes 2a and 3a oppose. 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.

  From the viewpoint of further improving the conduction reliability, in the connection structures 1 and 1X, the first electrode 2a and the second electrode 3a are arranged in the stacking direction of the first electrode 2a, the connection portion 4, and the second electrode 3a. When the portion facing each other is viewed at 50% or more, preferably 75% or more of 100% of the area of the facing portion between the first electrode 2a and the second electrode 3a, the connecting portion 4, It is preferable that the solder portions 4A and 4XA in 4X are arranged.

  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 1st connection object member 2 which has the 1st electrode 2a on the surface (upper surface) is prepared. Next, as shown in FIG. 2A, a conductive paste 11 including a thermosetting component 11B and a plurality of solder particles 11A is disposed on the surface of the first connection target member 2 (first Process). 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 the present 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.

  From the viewpoint of further improving the conduction reliability, in the connection structures 1 and 1X, the first electrode 2a and the second electrode 3a are arranged in the stacking direction of the first electrode 2a, the connection portion 4, and the second electrode 3a. When the portion facing each other is seen, the solder portions 4A in the connection portions 4A, 4X are not less than 50% in the area 100% of the portions facing the first electrode 2a and the second electrode 3a. It is preferable to obtain a connection structure 1, 1X in which 4XA is arranged.

  The heating temperature in the third step is not particularly limited as long as it is not lower than the melting point of the solder particles and not lower 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, after the said 3rd process, a 1st connection object member or a 2nd connection object member can be peeled from a connection part for the purpose of correction of a position or re-production. The heating temperature for performing this peeling is preferably not lower than the melting point of the solder particles, more preferably not lower than the melting point (° C.) of the solder particles + 10 ° C. The heating temperature for performing this peeling may be the melting point (° C.) of the solder particles + 100 ° C. or less.

  As the heating method in the third step, a method of heating the entire connection structure using a reflow furnace or an oven above the melting point of the solder particles and the curing temperature of the thermosetting component, or a connection structure The method of heating only the connection part of a body locally is mentioned.

  As a tool used for the method of heating locally, a hot plate, a heat gun for applying hot air, a soldering iron, an infrared heater, and the like can be given.

  In addition, when heating locally with a hot plate, the metal directly under the connection is made of a metal with high thermal conductivity, and other places where heating is not preferred are made of a material with low thermal conductivity such as a fluororesin. The upper surface of the hot plate is preferably formed.

  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 said 1st, 2nd connection object member is not specifically 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.

A preferable combination of the first and second connection target members includes a combination of an electronic component such as a capacitor and a diode and a circuit board. In this combination, the bottom area of the electronic component (surface area on the side connected by solder) is preferably 8000 μm ² or less. In this combination, it is preferable that the electrode is not formed on the side surface of the electronic component, and the electrode is formed only on the bottom surface (the surface on the side connected by the solder) of the electronic component. By applying the conductive paste to the entire bottom surface of the electronic component, the Manhattan phenomenon in which only one of the electronic components rises can be suppressed, and high connection reliability can be obtained by the solder aggregated between the electrodes. it can.

  A preferable combination of the first and second connection target members includes a combination of a semiconductor chip or a semiconductor package and a circuit board. In this combination, it is preferable that only the electrode is formed on the connection surface of the semiconductor chip or the semiconductor package, and no bump is formed. By making a connection using the conductive paste, bumps can be formed by agglomeration of solder particles in the conductive paste between the opposing electrodes, and the formed bumps can cure the thermosetting component. A connection structure reinforced with objects can be obtained.

  A preferable combination of the first and second connection target members includes a combination of a cable line and a circuit board. A highly reliable connection structure that can be connected by agglomerating solder particles so as to cover the cable wires arranged on the electrodes of the circuit board, and the thermosetting component covering the periphery is cured. Can be obtained.

  A preferable combination of the first and second connection target members includes a combination of a circuit board and a circuit board. For example, when there is a semiconductor component on the back surface opposite to the connection surface of the first connection target member, the second connection target member can be connected without applying pressure. Thereby, generation | occurrence | production of the defect of the semiconductor component located in the back surface opposite to the connection surface of a 1st connection object member can be suppressed, and a favorable connection structure can be obtained.

  In addition, as a preferable combination of the first and second connection target members, as a measure against EMI, a combination of a shield cover or a shield case, which is a metal cover disposed on a substrate such as a cellular phone, and a circuit board Is mentioned. After mounting electronic components other than the shield cover and shield case on the circuit board, the shield cover or shield case and circuit board are connected at a lower temperature compared to ordinary lead-free solder by connecting using the above conductive paste. Can be connected, and thermal damage to electronic components other than the already mounted shield cover or shield case can be reduced.

  In addition, a first connection target member having a metal first electrode (wiring) on the outer periphery and a second connection target member having a second electrode (wiring) opposed to the first electrode (wiring) Combinations are listed. The first connection target member and the second connection target member are bonded to each other with the conductive paste and heated, whereby the first connection target member and the second connection target member are opposed to each other. A connection structure in which the electrodes are connected with solder and the periphery thereof is hardened with a cured product of a thermosetting component is obtained. Thereby, it can prevent that water and water vapor | steam penetrate | invade into the inside where the 1st connection object member and the 2nd connection object material were pasted together from the outer peripheral part.

  Moreover, as a preferable combination of the first and second connection target members, a combination of a camera module board mounted on a mobile phone or the like and a flexible printed board or the like may be mentioned. With this combination, it is possible to perform mounting without damaging the optical system of the camera module because it is possible to heat from the flexible substrate side and mount without applying pressure from the lens side of the camera module. .

  As an example of the construction method, a conductive paste is applied to one connection target member, the thermosetting component is semi-cured by heat or light, and then bonded to the other connection target member. A method of bonding and adhering at a temperature higher than the melting temperature is mentioned. When semi-curing the thermosetting component, if the thermosetting component is semi-cured under the condition above the melting point temperature of the solder, the solder will aggregate on the electrode of the applied member to be connected, forming a bump. Can be made. By semi-curing the thermosetting component, the first electrode of the first connection target member and the second electrode of the second connection target member can be accurately aligned, and the connection reliability is improved. be able to.

  As another example of the construction method, a conductive paste is applied on the wiring of the circuit board and heated to the melting point of the solder or higher, thereby aggregating the solder on the wiring and forming a wiring having a thickness in the height direction. A method for forming wiring is also included. Since this method can improve the cross-sectional area of the wiring, it is useful for forming a wiring through which a high current flows.

  As still another example of the construction method, a conductive paste is applied on a circuit board on which vias are formed, or a semiconductor component such as a semiconductor chip or a wafer, and the solder is heated to a temperature higher than the melting point of the solder so that the solder is formed in the vias. The method of filling is mentioned. Accordingly, the front and back surfaces of the circuit board and the semiconductor component can be made conductive, and a highly reliable connection structure can be obtained by reinforcing the periphery of the via with a cured product of a thermosetting component.

  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. The first and second connection target members may be a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board.

  Examples of the electrodes provided on the connection target member include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, silver electrodes, molybdenum electrodes, SUS electrodes, and tungsten electrodes. 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.

  As shown in FIG. 4, at least one side surface of the first electrode 2a of the first connection target member 2Y and the second electrode 3a of the second connection target member 3Y is inclined inward. Preferably it is. It is preferable that both side surfaces of the first electrode 2a and the second electrode 3a are inclined inward. When the side surface of the electrode is inclined inward, the electrode width becomes narrower from the side opposite to the electrode connection side toward the electrode connection side. The internal angle (C in FIG. 4) at the tip of the inclined portion of the inclined electrode is preferably 20 degrees or more, preferably less than 90 degrees, more preferably 85 degrees or less, and even more preferably 80 degrees or less. When the electrode having the inclined surface as described above is used, the solder particles are more easily collected on the electrode. This is thought to be because the side surface of the electrode is less likely to hinder the movement of the solder particles. In particular, the inclined structure exhibits a great effect in order to gather solder particles.

  The distance D1 of the connecting portion at the position where the first electrode and the second electrode face each other is preferably 3 μm or more, more preferably 5 μm or more, preferably 40 μm or less, more preferably 30 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. Further, from the viewpoint of further improving the conduction reliability between the electrodes, the distance D1 is preferably 10 μm or more, more preferably 12 μm or more.

  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 said viscosity can be suitably adjusted with the kind and compounding quantity of a compounding component. Further, the use of a filler can make the viscosity relatively high.

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

  The minimum value of viscosity of the conductive paste (minimum melt viscosity value) in a temperature range of 25 ° C. or higher and the melting point of the solder particles (solder) is preferably 0.1 Pa · s or higher, more preferably 0. .2 Pa · s or more, preferably 10 Pa · s or less, more preferably 1 Pa · s or less. When the minimum value of the viscosity is not less than the above lower limit and not more than the above upper limit, the solder particles can be arranged more efficiently on the electrode.

  The minimum value of the above viscosity is STRESSTECH (manufactured by EOLOGICA), etc., strain control 1 rad, frequency 1 Hz, heating rate 20 ° C./min, measurement temperature range 40 to 200 ° C. (however, the melting point of solder particles is 200 ° C. In the case of exceeding the upper limit of the temperature, the melting point of the solder particles is taken into account). From the measurement result, the minimum value of the viscosity in the temperature region of the solder particle melting point or lower is evaluated.

  The dielectric constant measured using the component excluding the solder particles is preferably 3.4 or more, more preferably 3.5 or more, still more preferably 4 or more, preferably 6 or less, more preferably 5 or less. The component excluding the solder particles may be obtained by removing the solder particles from the conductive paste, or may be obtained by adding a compounding component excluding the solder particles in the conductive paste. When the zeta potential on the surface of the solder particles is positive and the dielectric constant of the component excluding the solder particles is not less than the lower limit and not more than the upper limit, the solder particles are more likely to collect on the electrode.

  The dielectric constant is measured using a dielectric measuring device (Toyo Technica Co., Ltd., 126096W type) under the conditions of a sample size diameter of 20 mm, a thickness of 100 μm, an applied voltage of 0.2 MV / m, a response speed of 8 ms, and a measurement frequency of 100 MHz. Is possible.

  From the viewpoint of more efficiently disposing the solder particles on the electrode, the minimum value of the viscosity of the conductive paste (the value of the minimum melt viscosity) in the temperature range of 25 ° C. or higher and the melting point of the solder particles or lower is 0 ° C. It is preferable that the dielectric constant measured using the component excluding the solder particles is not less than the above lower limit and not more than the above upper limit.

  The conductive paste includes a thermosetting component 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. The conductive paste preferably contains a flux.

  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. The zeta potential on the surface of the solder particle is positive.

  Since it is easy to add the zeta potential on the surface, the solder particles preferably have a solder particle body and an anionic polymer disposed on the surface of the solder particle body. The solder particles are preferably obtained by surface-treating the solder particle body with an anionic polymer or a compound that becomes an anionic polymer. As for the said anion polymer and the compound used as the said anion polymer, only 1 type may respectively be used and 2 or more types may be used together. The anionic polymer is a polymer having an acidic group.

  As a method of surface-treating the solder particle body with an anionic polymer, as an anionic polymer, for example, a (meth) acrylic polymer copolymerized with (meth) acrylic acid, synthesized from a dicarboxylic acid and a diol and having carboxyl groups at both ends Polyester polymer, polymer obtained by intermolecular dehydration condensation reaction of dicarboxylic acid and having carboxyl groups at both ends, polyester polymer synthesized from dicarboxylic acid and diamine and having carboxyl groups at both ends, and modified poval having carboxyl groups ( A method of reacting a carboxyl group of an anionic polymer with a hydroxyl group on the surface of a solder particle body using “GOHSEX T” manufactured by Nippon Synthetic Chemical Co., Ltd., etc.

The anionic portion of the anionic polymer, the carboxyl group and the like, in otherwise, tosyl _{p-H 3 CC 6 H 4} S (= O) 2-) and a sulfonate ion group ^{(-SO 3-)} And phosphate ion group (—PO ⁴⁻ ) and the like.

  As another method for the surface treatment, a compound having a functional group that reacts with a hydroxyl group on the surface of the solder particle body and further having a functional group that can be polymerized by an addition or condensation reaction is used. The method of polymerizing on the surface of a particle main body is mentioned. Examples of the functional group that reacts with the hydroxyl group on the surface of the solder particle body include a carboxyl group, and examples of the functional group that polymerizes by addition and condensation reactions include a hydroxyl group, a carboxyl group, an amino group, and a (meth) acryloyl group. It is done.

  As another method of surface treatment, the surface of the solder particle body is modified with a compound having a functional group that reacts with a hydroxyl group on the surface of the solder particle body and having a polymerizable functional group, and then an anion. You may surface-treat with a polymer. Examples of the compound having a functional group that reacts with a hydroxyl group on the surface of the solder particle body and further having a polymerizable functional group include a silane coupling agent having an isocyanate group. It is preferable that the solder particles are obtained using a silane coupling agent having an isocyanate group.

  The weight average molecular weight of the anionic polymer is preferably 2000 or more, more preferably 3000 or more, preferably 10,000 or less, more preferably 8000 or less. When the weight average molecular weight is not less than the above lower limit and not more than the above upper limit, a sufficient amount of charge and flux properties can be introduced on the surface of the solder particles. Thereby, it is easy to control the zeta potential on the surface of the solder particles within a suitable range, and the oxide film on the surface of the electrode can be effectively removed when the connection target member is connected.

  When the weight average molecular weight is not less than the above lower limit and not more than the above upper limit, it is easy to dispose an anionic polymer on the surface of the solder particle body, and it is easy to make the zeta potential on the surface of the solder particle positive. The solder particles can be arranged on the electrodes even more efficiently.

  The weight average molecular weight indicates a weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

  The weight average molecular weight of the polymer obtained by surface-treating the solder particle body with a compound that becomes an anionic polymer is obtained by dissolving the solder in the solder particles and removing the solder particles with dilute hydrochloric acid or the like that does not cause decomposition of the polymer. It can be determined by measuring the weight average molecular weight of the remaining polymer.

  Regarding the introduction amount of the anionic polymer on the surface of the solder particles, the acid value per 1 g of the solder particles is preferably 1 mgKOH or more, more preferably 2 mgKOH or more, preferably 10 mgKOH or less, more preferably 6 mgKOH or less.

  The acid value can be measured as follows. 1 g of solder particles is added to 36 g of acetone and dispersed with an ultrasonic wave for 1 minute. Thereafter, phenolphthalein is used as an indicator and titrated with a 0.1 mol / L potassium hydroxide ethanol solution.

  The solder is preferably a low melting point metal having a melting point of 450 ° C. or lower. The solder particles are preferably 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 optical 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 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. Especially, since it is excellent in the wettability with respect to an electrode, it is preferable that the said low melting metal is a tin, a tin-silver alloy, a tin-silver-copper alloy, a tin-bismuth alloy, and a tin-indium alloy. 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. Among them, 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 a number average particle diameter. The average particle diameter of the solder particles is obtained, for example, by observing 50 arbitrary solder particles with an electron microscope or an optical microscope and calculating an average value.

  The coefficient of variation of the particle diameter of the solder particles is preferably 5% or more, more preferably 10% or more, preferably 40% or less, more preferably 30% or less. When the variation coefficient of the particle diameter 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. However, the coefficient of variation of the particle diameter of the solder particles may be less than 5%.

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

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

  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.

  The zeta potential on the surface of the solder particles is positive. The zeta potential is measured as follows.

Zeta potential measurement method:
0.05 g of solder particles are put in 10 g of methanol and subjected to ultrasonic treatment or the like to uniformly disperse to obtain a dispersion. The zeta potential can be measured by electrophoretic measurement using this dispersion and “Delsamax PRO” manufactured by Beckman Coulter.

  Examples of the method for measuring the zeta potential of solder particles already dispersed in the conductive paste include the following. For example, in a solvent that can dissolve the components other than the solder particles of the conductive paste, dissolve the components other than the solder particles in the conductive paste, separate the solder particles by precipitation or centrifugation, and then wash with methanol. , And can be measured by the above method. At this time, it is preferable to perform washing with a solvent capable of washing the additive and the surfactant in the conductive paste.

  Specifically, 1 g of conductive paste is added to 50 g of methyl ethyl ketone (MEK), and the mixture is dispersed with ultrasonic waves at 23 ° C. for 1 minute, and then the solder particles are collected with a filter paper. Thereafter, the solder particles are washed with methanol, 0.05 g of the solder particles are weighed, put into 10 g of methanol, and subjected to ultrasonic treatment or the like to uniformly disperse to obtain a dispersion. Using this dispersion and using “Delsamax PRO” manufactured by Beckman Coulter, the zeta potential can be measured at 23 ° C. by electrophoretic measurement. It is not necessary to adjust the pH.

  The zeta potential of the solder particles is preferably more than 0 mV, preferably 10 mV or less, more preferably 5 mV or less, even more preferably 1 mV or less, still more preferably 0.7 mV or less, and particularly preferably 0.5 mV or less. If the zeta potential is less than or equal to the above upper limit, solder particles tend to collect during conductive connection. When the zeta potential is 0 mV or less, the aggregation of solder particles on the electrode may be insufficient during mounting.

(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 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, and examples thereof include trimethylolpropane tris-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, and dipentaerythritol hexa-3-mercaptopropionate. .

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

  The thermal radical generator 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 higher than the melting point of the solder in the solder particles, more preferably 5 ° C. or more, more preferably 10 It is more preferable that the temperature is higher than ° C.

  The reaction start temperature of the thermosetting agent means a 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 preferably 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 rosin is a rosin composed mainly of 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 melting point of the flux is preferably 50 ° C. or higher, more preferably 70 ° C. or higher, still more preferably 80 ° C. or higher, preferably 200 ° C. or lower, more preferably 160 ° C. or lower, even more preferably 150 ° C. or lower, still more preferably. 140 ° C. or lower. When the melting point 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. The melting point of the flux is preferably 80 ° C. or higher and 190 ° C. or lower. The melting point of the flux is particularly preferably 80 ° 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 lower than the melting point of the solder in the solder particles, more preferably 5 ° C. or more, more preferably 10 ° C. or more. Is more preferable.

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

  The said flux may be disperse | distributed in the electrically conductive paste and may adhere on the surface of the solder particle.

  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.

  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. By adding the filler, the distance at which the solder particles aggregate can be suppressed, and the solder particles can be uniformly aggregated on all the electrodes of the substrate.

  In 100% by weight of the conductive paste, the filler content is preferably 0% by weight (not contained) or more, preferably 5% by weight or less, more preferably 2% by weight or less, and still more preferably 1% by weight or less. When the content of the filler 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.

(Compound with high dielectric constant)
A compound having a high dielectric constant such as a compound having a hydroxyl group, a thiol group or a carboxyl group, an amine compound, and an imidazole compound may be added to the conductive paste. The compound having a high dielectric constant may be a curing agent having a high dielectric constant.

  The content of the compound having a high dielectric constant (such as a high dielectric constant curing agent) in 100% by weight of the conductive paste is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, and preferably 40 parts by weight or less. The amount is preferably 30 parts by weight or less. The compound having a high dielectric constant is preferably a compound having a functional group that reacts with an epoxy group. The compound having a high dielectric constant has a dielectric constant of 4 or more, preferably 5 or more, and preferably 7 or less.

(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.

(Other details of conductive paste)
The conductive paste is preferably an anisotropic conductive paste.

  In 100% by weight of the conductive paste, the content of the thermosetting component is preferably 10% by weight or more, more preferably 20% by weight or more, still more preferably 30% by weight or more, and further preferably 40% by weight or more. More preferably, it is 50% by weight or more, particularly preferably 55% by weight or more, most preferably 70% by weight or more, preferably 99.99% by weight or less, more preferably 99.9% by weight or less. When the content of the thermosetting component is not less than the above lower limit and not more than the above upper limit, the conductive particles are efficiently arranged between the electrodes, and the connection reliability of the connection target member connected by the conductive paste is further increased. Become.

  In 100% by weight of the conductive paste, the content of the solder particles is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, preferably 80% by weight or less, more preferably 60% by weight or less, Preferably it is 45 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 conduction reliability between the electrodes is further enhanced.

  Since the conduction reliability can be improved by the specific solder particles in the present invention, when the line (L) where the electrode is formed is 50 μm or more and less than 150 μm, The content of the solder particles is preferably 20% by weight or more, more preferably 30% by weight or more, preferably 55% by weight or less, more preferably 45% by weight or less.

  Since the conduction reliability can be enhanced by the specific solder particles in the present invention, when the space (S) where the electrode is not formed is 50 μm or more and less than 150 μm, The content of the solder particles is preferably 30% by weight or more, more preferably 40% by weight or more, preferably 70% by weight or less, more preferably 60% by weight or less.

  In addition, since the conduction reliability can be enhanced by the specific solder particles in the present invention, when the line (L) where the electrode is formed is 150 μm or more and less than 1000 μm, the conductive paste is 100% by weight. The solder particle content is preferably 30% by weight or more, more preferably 40% by weight or more, preferably 70% by weight or less, more preferably 60% by weight or less.

  Since the conduction reliability can be improved by the specific solder particles in the present invention, when the space (S) where the electrode is not formed is 150 μm or more and less than 1000 μm, The content of the solder particles is preferably 30% by weight or more, more preferably 40% by weight or more, preferably 70% by weight or less, more preferably 60% by weight or less.

  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 a 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 an addition reaction catalyst between 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. A) was obtained.

  By confirming that the addition polymerization reaction has progressed by NMR, the reaction product (polymer A) is composed of 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 reaction product (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: both end 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

  Thermosetting compound 2: Naphthalene type epoxy compound, “HP-4032D” manufactured by DIC

  High dielectric constant curing agent: pentaerythritol tetrakis (3-mercaptobutyrate)

  Thermosetting agent: “Karenz MT PE1” manufactured by Showa Denko KK

  Flux: Adipic acid, manufactured by Wako Pure Chemical Industries

Method for producing solder particles 1-6, 9:
Solder particles having anionic polymer 1: 200 g of solder particle main body, 40 g of adipic acid, and 70 g of acetone are weighed in a three-necked flask, and then dehydration condensation between the hydroxyl group on the surface of the solder particle main body and the carboxyl group of adipic acid 0.3 g of dibutyltin oxide as a catalyst was added and reacted at 60 ° 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 paratoluenesulfonic acid were weighed in a three-necked flask and reacted at 120 ° C. for 3 hours while evacuating and refluxing. . 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.

Solder particles having anionic polymer 2:
Solder particles were obtained in the same manner as the solder particles having anionic polymer 1 except that adipic acid was changed to glutaric acid when forming the anionic polymer 1.

(Zeta potential measurement)
Moreover, 0.05 g of solder particles having the anion polymer 1 or the anion polymer 2 were put in 10 g of methanol and subjected to ultrasonic treatment to uniformly disperse the obtained solder particles, thereby obtaining a dispersion. The zeta potential was measured by electrophoretic measurement using this dispersion and “Delsamax PRO” manufactured by Beckman Coulter. During the measurement, the liquid temperature was 23 ° C., and the pH was not adjusted.

(Weight average molecular weight of anionic polymer)
The weight average molecular weight of the anionic polymer 1 on the surface of the solder particles was obtained by dissolving the solder using 0.1N hydrochloric acid, collecting the polymer by filtration, and determining by GPC.

(CV value of solder particles)
The CV value was measured with a laser diffraction particle size distribution analyzer (“LA-920” manufactured by Horiba, Ltd.).

  Solder particles 1 (SnBi solder particles, melting point 139 ° C., solder particles main body selected from Mitsui Kinzoku “ST-3”), surface-treated solder particles having anionic polymer 1, average particle diameter 4 μm, CV value 7%, zeta potential on the surface: +0.65 mV, polymer molecular weight Mw = 6500)

  Solder particles 2 (SnBi solder particles, melting point 139 ° C., solder particles main body selected from Mitsui Kinzoku Co., Ltd. “ST-5”, surface-treated solder particles having anionic polymer 1, average particle diameter 6 μm, CV value 10%, surface zeta potential: +0.61 mV, polymer molecular weight Mw = 6800)

  Solder particle 3 (SnBi solder particle, melting point 139 ° C., solder particle body selected from Mitsui Kinzoku “DS10”, surface-treated solder particle having anionic polymer 1, average particle diameter 13 μm, CV value 20% Surface zeta potential: +0.48 mV, polymer molecular weight Mw = 7000)

  Solder particles 4 (SnBi solder particles, melting point 139 ° C., solder particles main body selected from “10-25” manufactured by Mitsui Kinzoku Co., Ltd.), surface-treated solder particles having anionic polymer 1, average particle diameter 25 μm, CV value 15%, surface zeta potential: +0.4 mV, polymer molecular weight Mw = 8000)

  Solder particle 5 (SnBi solder particle, melting point 139 ° C., solder particle body selected from “ST-3” manufactured by Mitsui Kinzoku Co., Ltd., surface treated anionic polymer 2 solder particle, average particle diameter 4 μm, CV value 7%, surface zeta potential: +0.7 mV, polymer molecular weight Mw = 7000)

  Solder particles 6 (SnBi solder particles, melting point 139 ° C., solder particles selected from “10-25” manufactured by Mitsui Kinzoku Co., Ltd.), surface-treated solder particles having anionic polymer 2, average particle diameter 25 μm, CV value 15 %, Surface zeta potential: +0.5 mV, polymer molecular weight Mw = 7500)

  Solder particles 7 (SnBi solder particles, melting point 139 ° C., particles selected from Mitsui Kinzoku “10-25”, average particle diameter 22 μm, CV value 14%, surface zeta potential: −27 mV)

  Solder particles 8 (SnBi solder particles, melting point 139 ° C., particles selected from Mitsui Kinzoku “20-40”, average particle size 38 μm, CV value 20%, surface zeta potential: −25 mV)

Also, the following solder particles 9 were produced by changing only the surface treatment amount from the solder particles 1.
Solder particle 9 (SnBi solder particle, melting point 139 ° C., solder particle body selected from “ST-3” manufactured by Mitsui Kinzoku Co., Ltd., surface-treated solder particle having anionic polymer 1, average particle diameter 4 μm, CV value 7%, zeta potential on the surface: +0.1 mV, polymer molecular weight Mw = 6500)

  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

Production method of conductive particles 1:
Divinylbenzene resin particles having an average particle diameter of 10 μm (“Micropearl SP-210” manufactured by Sekisui Chemical Co., Ltd.) were subjected to electroless nickel plating to form a base nickel plating layer having a thickness of 0.1 μm on the surface of the resin particles. Next, the resin particles on which the base nickel plating layer was formed were subjected to electrolytic copper plating to form a 1 μm thick copper layer. Furthermore, electrolytic plating was performed using an electrolytic plating solution containing tin and bismuth to form a solder layer having a thickness of 3 μm. Thus, a 1 μm thick copper layer is formed on the surface of the resin particles, and a 3 μm thick solder layer (tin: bismuth = 43 wt%: 57 wt%) is formed on the surface of the copper layer. Conductive particles 1 were prepared.

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

(Examples 1-12 and 15-17)
(1) Preparation of anisotropic conductive paste The components shown in Tables 1 and 2 below were blended in the blending amounts shown in Tables 1 and 2 to obtain anisotropic conductive pastes.

(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) with 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. Note that the side surfaces of both the electrode of the glass epoxy substrate and the electrode of the flexible printed board are inclined inward, and the inner angle C at the tip of the inclined portion of the inclined electrode is 75 degrees.

  The overlapping area of the glass epoxy substrate and the flexible printed circuit board 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 a temperature of 185 ° C., the solder was melted and the anisotropic conductive paste layer was cured at 185 ° 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.

  A 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 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) having 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.

  A 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 13)
The electrode size / interelectrode space (L / S) is 100 μm / 100 μm (for the third connection structure), 75 μm / 75 μm (for the second connection structure), 50 μm / 50 μm (for the first connection structure) ) And a glass epoxy substrate (size 30 × 30 mm, thickness 0.4 mm) having a 5 mm square semiconductor chip (thickness 400 μm) and an electrode facing it, Second and third connection structures were obtained.

(Example 14)
When obtaining the first, second, and third connection structures, except that the inclined structures were eliminated on both sides of the electrodes of the glass epoxy board and the flexible printed board (inner angle C was 90 degrees). In the same manner as in Example 1, first, second, and third connection structures were obtained.

(Comparative Examples 1-4)
(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 4)
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.

  Except having used the anisotropic conductive film, it carried out similarly to Example 1, and obtained the 1st, 2nd, 3rd connection structure.

(Comparative Example 5)
Copper electrode patterns (copper electrode thickness) with L / S of 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 semiconductor chip having 10 μm) on the lower surface was prepared.

  First, second, and third connection structures were obtained in the same manner as in Comparative Example 1 except that the flexible printed circuit board was changed to a semiconductor chip.

(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.).

(2) Minimum melt viscosity The minimum melt viscosity of the anisotropic conductive paste in the temperature range from 25 ° C. to the melting point of the solder particles or the melting point of the solder on the surface of the conductive particles was measured.

(3) Dielectric constant In the blending components shown in Tables 1 and 2 below, a blend was prepared by blending components excluding solder particles in the conductive paste. Using this composition, using a dielectric measuring device (Toyo Technica, 126096W type), sample size diameter 20 mm, thickness 100 μm, applied voltage 0.2 MV / m, response speed 8 ms, measurement speed 115 times / second. The dielectric constant was measured under the conditions described above.

(4) Distance of connection part (interval between electrodes)
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.

(5) 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.

[Criteria for solder placement accuracy on electrodes]
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%

(6) Conduction 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

(7) Insulation reliability between adjacent electrodes The obtained first, second and third connection structures (n = 15) 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

(8) Solder placement accuracy on the electrode When the portion where the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connection portion, and the second electrode is viewed, The area A (%) in which the solder part in the connection part is arranged was evaluated in the area of 100% of the part where the electrode and the second electrode face each other. 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.

[Criteria for solder placement accuracy on electrodes]
◯: The area A is 75% or more and 100% or less ◯: The area A is 50% or more and less than 75% Δ: The area A is 30% or more and less than 50% X: The area A is less than 30%

(9) Impedance measurement The differential impedance of adjacent electrodes was measured by the TDR method using a Tektronix "DSA8200 impedance measurement device" and a Tektronix "P80318" as a probe. In the third connection structure, the difference in impedance at locations connected by the anisotropic conductive paste was obtained with respect to the differential impedance (90Ω) of the substrate and FPC. Impedance measurement was determined according to the following criteria.

[Criteria for impedance measurement]
○○: The differential impedance of the connected part is less than −5Ω ○: The differential impedance of the connected part is −5Ω or more and less than −10Ω Δ: The differential impedance of the connected part is −10Ω or more, −15Ω Less than ×: The differential impedance of the connected part is -15Ω or more

  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 13 and Comparative Example 5, 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.

  The same was true when a resin film and a flexible flat cable were used instead of the flexible printed circuit board.

  FIGS. 5A, 5B, and 5C show an example of a connection structure using the conductive paste included in the embodiment of the present invention. 5A and 5B are cross-sectional images, and FIG. 5C is a planar image. 5A, 5B, and 5C, it can be seen that there is no solder (solder particles) remaining in the cured product away from the solder portions arranged between the electrodes.

  Further, FIGS. 6A, 6B and 6C show an example of a connection structure using a conductive paste not included in the embodiment of the present invention. 6A and 6B are cross-sectional images, and FIG. 6C is a planar image. 6 (a), 6 (b), and 6 (c), there are a plurality of solders (solder particles) left in the cured product apart from the solder portions arranged between the electrodes, on the side of the solder portions. You can see that In addition, it confirmed that the connection structure similar to the connection structure shown to FIG. 6 (a), (b) and (c) was obtained even if it pressurized in the process of forming a connection part.

DESCRIPTION OF SYMBOLS 1,1X ... Connection structure 2, 2Y ... 1st connection object member 2a ... 1st electrode 3, 3Y ... 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 (17)

A thermosetting component and a plurality of solder particles;
A conductive paste having a positive zeta potential on the surface of the solder particles.   The conductive paste according to claim 1, wherein the solder particles have a solder particle main body and an anionic polymer disposed on a surface of the solder particle main body.   The electrically conductive paste of Claim 1 or 2 whose dielectric constant measured using the component except the said solder particle in an electrically conductive paste is 3.4 or more and 6 or less.   The electrically conductive paste of any one of Claims 1-3 whose viscosity in 25 degreeC is 10 Pa.s or more and 800 Pa.s or less.   The conductive paste according to any one of claims 1 to 3, wherein a minimum value of viscosity in a temperature range of 25 ° C or higher and lower than a melting point of the solder particles is 0.1 Pa · s or higher and 10 Pa · s or lower. .   The electrically conductive paste of any one of Claims 1-5 whose average particle diameter of the said solder particle is 1 micrometer or more and 40 micrometers or less.   The electrically conductive paste of any one of Claims 1-6 whose content of the said solder particle is 10 to 60 weight% in 100 weight% of electrically conductive paste.   The electrically conductive paste of any one of Claims 1-7 whose CV value of the particle diameter of the said solder particle is 5% or more and 40% or less. 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 portion is formed of the conductive paste according to any one of claims 1 to 8,
A connection structure in which the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.   When the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connection portion, and the second electrode, the first electrode and the second electrode 10. The connection structure according to claim 9, wherein the solder portion in the connection portion is arranged in 50% or more of the area of 100% of the portion facing the two electrodes.   At least one side surface of the first electrode and the second electrode is inclined inward, and the inner angle at the tip of the inclined portion of the inclined electrode is not less than 20 degrees and not more than 80 degrees. The connection structure according to claim 9 or 10, wherein there is a connection structure.   The connection structure according to any one of claims 9 to 11, wherein the second connection target member is a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. Using the conductive paste according to claim 1, 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;   When the first electrode and the second electrode face each other in the stacking direction of the first electrode, the connection portion, and the second electrode, the first electrode and the second electrode The manufacturing method of the connection structure of Claim 13 which obtains the connection structure by which the solder part in the said connection part is arrange | positioned in 50% or more in 100% of the area of the part which opposes two electrodes. .   15. 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 portion. The manufacturing method of the connection structure of description.   At least one side surface of the first electrode and the second electrode is inclined inward, and the inner angle at the tip of the inclined portion of the inclined electrode is not less than 20 degrees and not more than 80 degrees. The manufacturing method of the connection structure of any one of Claims 13-15 which exists.   The manufacturing method of the connection structure of any one of Claims 13-16 whose said 2nd connection object member is a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible substrate.