JP6082843B2 - Conductive paste and connection structure - Google Patents

Description

  The present invention relates to a conductive paste including a plurality of solder particles. The present invention also relates to a connection structure using the conductive paste.

  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.

  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, Patent Document 1 described below describes an anisotropic conductive material including conductive particles and a resin component that cannot be cured at the melting point of the conductive particles. Specifically, the conductive particles include tin (Sn), indium (In), bismuth (Bi), silver (Ag), copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd ), Gallium (Ga), silver (Ag), thallium (Tl), and the like, and alloys of these metals.

  In Patent Document 1, a resin heating step for heating the anisotropic conductive resin to a temperature higher than the melting point of the conductive particles and at which the curing of the resin component is not completed, and a resin component curing step for curing the resin component The electrical connection between the electrodes is described. Patent Document 1 describes that mounting is performed with the temperature profile shown in FIG. In Patent Document 1, the conductive particles melt in a resin component that is not completely cured at a temperature at which the anisotropic conductive resin is heated.

  Patent Document 2 below discloses an adhesive tape that includes a resin layer containing a thermosetting resin, solder powder, and a curing agent, and the solder powder and the curing agent are present in the resin layer. Yes. This adhesive tape is in the form of a film, not a paste.

  Patent Document 2 discloses an adhesion method using the 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.

Patent Document 3 below discloses an anisotropic conductive material in which conductive particles are dispersed in an insulating binder. The minimum melt viscosity [η ₀ ] of this anisotropic conductive material is 1.0 × 10 ^{2 to} 1.0 × 10 ⁶ mPa · sec. In this anisotropic conductive material, 1 <[η ₁ ] / [η ₀ ] ≦ 3 ([η ₀ ] is the minimum melt viscosity of the anisotropic conductive material, and [η ₁ ] is the temperature T ₀ indicating the minimum melt viscosity. (Melt viscosity at a temperature T ₁ lower by 30 ° C.).

  The following Patent Documents 4 and 5 disclose an anisotropic conductive material including a thermosetting binder, solder particles having a melting point of 180 ° C. or lower or 160 ° C. or lower, and a flux component. As the flux component, a compound represented by the following formula (101) or (102) is used. Moreover, the anisotropic conductive material of patent document 4 contains an epoxy resin and a cation hardening initiator essential as the said thermosetting binder. Patent Documents 4 and 5 describe that the flux component and the solder particles are coordinated by chelate.

In the above formula (101) and the above formula (102), R _{1 to} R ₄ represent a hydrogen atom, an alkyl group, or a hydroxyl group, and X has a lone electron pair or a double bond π electron that can coordinate with a metal. Represents an atomic group, and Y represents an atom or atomic group forming a main chain skeleton. In Patent Document 5, Y in the above formula (101) and the above formula (102) is an alkyl group.

  The following Patent Document 6 discloses a solder ball having a surface coated with at least two kinds of organic acids having 10 to 25 carbon atoms and having a carboxyl group. In this solder ball, the carboxyl group of the organic acid is chelated with the surface of the solder ball.

  Patent Document 7 below discloses a solder powder in which at least one of a fatty acid and a dicarboxylic acid is chemically bonded to the surface and coated. Patent Document 7 discloses a conductive adhesive (anisotropic conductive material) containing the solder powder, a resin, and a curing agent.

  Patent Document 8 below discloses conductive particles having solder on a conductive surface, and a group containing a carboxyl group is covalently bonded to the surface of the solder.

JP 2004-260131 A WO2008 / 023452A1 JP 2009-32657 A JP 2011-63727 A WO2009 / 001448A1 JP 2008-272779 A JP 2010-126719 A WO2013 / 125517A1

  In the case of conventional anisotropic conductive paste containing solder powder or conductive particles having a solder layer on the surface, the solder powder or conductive particles may not be efficiently disposed on the electrodes (lines). In the conventional solder powder or conductive particles, the moving speed of the solder powder or conductive particles onto the electrode may be slow.

  Further, when the electrodes are electrically connected by the method described in Patent Document 1 using the anisotropic conductive material described in Patent Document 1, conductive particles including solder are efficiently formed on the electrodes (lines). May not be placed. Moreover, in the Example of patent document 1, in order to move a solder fully at the temperature more than melting | fusing point of solder, it is hold | maintained at fixed temperature, and the manufacturing efficiency of a connection structure becomes low. When mounting is performed with the temperature profile shown in FIG. 8 of Patent Document 1, the manufacturing efficiency of the connection structure is lowered.

  Moreover, the adhesive tape of patent document 2 is a film form, and is not 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 2, 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.

  In Patent Document 2, there is no specific description of the conductive particles used for the anisotropic conductive material. In the Example of patent document 3, the copper layer is formed on the surface of the resin particle, and the electroconductive particle in which the solder layer is formed on the surface of this copper layer is used. The central part of the conductive particles is composed of resin particles. In addition, when the anisotropic conductive material described in Patent Documents 2 and 3 is used, the conductive particles are difficult to be efficiently disposed on the electrodes (lines), and a positional shift between the upper and lower electrodes to be connected may occur. There are things to do.

  In Patent Document 7, at least one of fatty acid and dicarboxylic acid is chemically bonded to the surface. Moreover, in patent document 7, in order to obtain solder powder, it is made to react at 40-60 degreeC, without using a catalyst. Therefore, fatty acids and dicarboxylic acids are not covalently bonded to the surface of the solder powder. Even if such a solder powder described in Patent Document 7 is used, fatty acid or dicarboxylic acid can be easily removed from the surface of the solder powder, the connection resistance between the electrodes becomes high, or the generation of voids cannot be sufficiently suppressed. There are things to do.

  An object of the present invention is to provide a conductive paste capable of efficiently arranging solder particles on electrodes, preventing positional displacement between the electrodes, and improving conduction reliability between the electrodes. is there. Moreover, the objective of this invention is providing the connection structure using the said electrically conductive paste.

  According to a wide aspect of the present invention, the solder particles include a plurality of solder particles and a binder, and the solder particles are particles in which both the center portion and the outer surface of the conductive portion are solder, A group having at least one carboxyl group is covalently bonded to the surface via an ether bond, an ester bond or a group represented by the following formula (X), and the melting point of the solder is −10 ° C. or higher. The minimum value of the viscosity of the conductive paste in the temperature region below the melting point is 100 mPa · s or more, and the maximum value of the viscosity of the conductive paste in the temperature region of the solder melting point −10 ° C. or more and the melting point of the solder or less is 2000 mPa · s. A conductive paste is provided that is:

  In a specific aspect of the conductive paste according to the present invention, the binder is not completely cured at the melting point of the solder particles.

  In a specific aspect of the conductive paste according to the present invention, a group having at least one carboxyl group is covalently bonded to the surface of the solder of the solder particle via the group represented by the formula (X). .

  On the specific situation with the electrically conductive paste which concerns on this invention, the said binder contains a thermosetting compound and a thermosetting agent.

  On the specific situation with the electrically conductive paste which concerns on this invention, the said thermosetting compound contains a crystalline thermosetting compound.

  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 90 weight% in 100 weight% of electrically conductive paste.

  According to a wide aspect of the present invention, a first connection target member having a first electrode on the surface, a second connection target member having a second electrode on the surface, the first connection target member, and the A connection portion connecting the second connection target member, wherein the material of the connection portion is the conductive paste described above, and the first electrode and the second electrode are electrically connected by the solder particles. A connection structure is provided which is connected in a connected manner.

  The conductive paste according to the present invention includes a plurality of solder particles and a binder, and the solder particles are particles in which both the central portion and the outer surface of the conductive portion are solder, and the solder surface of the solder particles A group having at least one carboxyl group is covalently bonded via an ether bond, an ester bond or a group represented by the above formula (X), and the melting point of the solder is −10 ° C. or higher and the melting point of the solder. The minimum value of the viscosity of the conductive paste in the following temperature region is 100 mPa · s or more, and the maximum value of the viscosity of the conductive paste in the temperature region of the melting point of the solder is −10 ° C. or more and the melting point of the solder or less is 2000 mPa · s or less. Therefore, the solder particles can be efficiently arranged on the electrodes, the positional displacement between the electrodes can be prevented, and the conduction reliability between the electrodes can be improved. Can.

FIG. 1 is a cross-sectional view schematically showing a connection structure obtained using a conductive paste according to an embodiment of the present invention. 2A to 2C are cross-sectional views for explaining each step of an example of a method of manufacturing a connection structure using the conductive paste according to the embodiment of the present invention. FIG. 3 is a cross-sectional view showing a modification of the connection structure.

  Details of the present invention will be described below.

(Conductive paste)
The conductive paste according to the present invention includes a plurality of solder particles and a binder. The solder particles are particles in which both the central portion and the outer surface of the conductive portion are solder. In the solder particles, both the central portion and the outer surface of the conductive portion are formed of solder. A group having at least one carboxyl group is covalently bonded to the surface of the solder of the solder particle via an ether bond, an ester bond or a group represented by the following formula (X). The minimum value of the viscosity of the conductive paste in the temperature region R above the melting point of the solder −10 ° C. (temperature lower by 10 ° C. than the melting point of the solder) and below the melting point of the solder is 100 mPa · s or more. The maximum value of the viscosity of the conductive paste in the temperature region R of 10 ° C. or higher and lower than the melting point of the solder is 2000 mPa · s or lower. In the following formula (X), the right end and the left end represent a binding site.

  The solder particles are different from particles obtained by simply coating the solder particles with a compound having a carboxyl group. In the solder particles, not only a carboxyl group is present on the surface of the solder, but also at least one carboxyl group is present on the surface of the solder via an ether bond, an ester bond or a group represented by the formula (X). The group it has is bonded. The solder particles are also different from solder particles in which a compound having a carboxyl group has a chelate coordination (coordination bond) on the surface of the solder.

  In the present invention, since the above-described configuration is provided, 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 separated into electrodes (lines). Can be efficiently placed on top. 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. In the present invention, it is possible to efficiently move the solder particles that are not located between the opposing electrodes between the opposing electrodes. 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. Furthermore, it is possible to prevent positional deviation between the electrodes. In the present invention, when the second connection target member is superimposed on the first connection target member to which the conductive paste is applied, the alignment of the electrode of the first connection target member and the electrode of the second connection target member is performed. Even when the first connection target member and the second connection target member are overlapped with each other in a state of being shifted, the shift is corrected, and the electrodes of the first connection target member and the second connection target member are corrected. The electrode can be connected (self-alignment effect). In order to obtain such an effect, using specific solder particles and controlling the viscosity of the conductive paste within a specific range in consideration of the melting point of the solder particles greatly contributes.

  In addition, when using conductive particles including base particles not formed of solder and a solder layer disposed on the surface of the base particles, the conductive particles are not formed on the electrodes. It becomes difficult to gather, and since the solder bonding property between the conductive particles is low, the conductive particles that have moved onto the electrode easily move out of the electrode. For this reason, the effect of suppressing the displacement between the electrodes is also reduced. In the present invention, it is also possible to use solder particles instead of conductive particles including base particles and solder layers arranged on the surfaces of the base particles in order to efficiently move the solder particles between the opposing electrodes. Greatly contributes.

  In the solder particles, a group having at least one carboxyl group is covalently bonded to the surface of the solder via an ether bond, an ester bond or a group represented by the formula (X). Generation of voids in the body can also be suppressed. As a result of suppressing the generation of voids, connection reliability in the connection structure is increased. Furthermore, an increase in connection resistance in the connection structure due to the void can be suppressed. Further, it becomes difficult to form an oxide film on the surface of the solder, and the oxide film on the surface of the electrodes can be effectively eliminated when connecting the electrodes.

  Further, before dispersing the solder particles in the binder, a group having at least one carboxyl group is formed on the surface of the solder in the solder particles via an ether bond, an ester bond or a group represented by the formula (X). Bonding is preferred. Solder particles in which a group having at least one carboxyl group is bonded to the surface of the solder via an ether bond, an ester bond or a group represented by the formula (X) are dispersed in a binder, and a conductive paste is obtained. It is preferable to obtain. Before dispersing the solder particles in the binder, a group having at least one carboxyl group is bonded to the surface of the solder in the solder particles via an ether bond, an ester bond or a group represented by the formula (X). Therefore, the oxide film on the surface of the solder and the surface of the electrode can be effectively eliminated even if the flux is not blended in the conductive paste or the amount of the flux added to the conductive paste is small. Generation | occurrence | production of the void in a connection structure can be suppressed further by not mix | blending a flux or reducing the usage-amount of a flux.

  In the above solder particles, the thickness of the covering portion in which a group having at least one carboxyl group is bonded to the surface of the solder via an ether bond, an ester bond or a group represented by the formula (X) is increased. Can do. As a result, the solder particles and the oxide film on the surface of the electrode can be effectively eliminated, and the connection resistance between the electrodes can be reduced. Moreover, in the said solder particle, the electric charge of the surface of a solder particle can be made small by reducing the hydroxyl group of the surface of a solder particle by introduction | transduction of said group. As a result, solder particles are easily collected efficiently during conductive connection.

  In order to arrange the solder particles on the electrode more efficiently, the group represented by the above formula (X) preferably constitutes a urethane bond.

  From the viewpoint of effectively exhibiting the effects of the present invention, it is preferable that the binder is not completely cured at the melting point of the solder particles. The phrase “curing is not completed at the melting point of the solder particles” means that the binder has a fluidity at the melting point of the solder particles.

  In order to arrange the solder particles on the electrode more efficiently, the minimum value of the viscosity of the conductive paste in the temperature region R is preferably 150 mPa · s or more, more preferably 200 mPa · s or more. In order to arrange the solder particles more efficiently on the electrode, the maximum value of the viscosity of the conductive paste in the temperature region R is preferably 1500 mPa · s or less, more preferably 1000 mPa · s or less.

  The viscosity of the conductive paste in the temperature region R is measured using “STRESSTECH” manufactured by EOLOGICA, under conditions of a rotor diameter of 20 mm, oscillation strain control, and a temperature increase rate from 23 ° C. to 10 ° C./min.

  From the viewpoint of more efficiently arranging the solder particles on the electrodes, more effectively suppressing the displacement between the electrodes, and further improving the conduction reliability and the insulation reliability between the electrodes, The viscosity is preferably 100 Pa · s or higher, more preferably 150 Pa · s or higher, preferably 600 Pa · s or lower, more preferably 500 Pa · s or lower.

  The viscosity of the conductive paste at 25 ° C. is measured under the conditions of 25 ° C. and 5 rpm using an E-type viscometer (“TVE22L” manufactured by Toki Sangyo Co., Ltd.).

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

  The conductive paste and the binder preferably contain a thermoplastic component or a thermosetting component. The said electrically conductive paste and the said binder may contain the thermoplastic component and may contain the thermosetting component. The conductive paste and the binder preferably include a thermosetting component. The conductive paste and the binder preferably contain a thermosetting compound and a thermosetting agent.

  Hereinafter, each component contained in the conductive paste will be described.

(Solder particles)
The solder particles have solder on the outer surface of the conductive part. The solder particles are particles in which both the central portion and the outer surface of the conductive portion are solder.

  From the viewpoint of effectively reducing the connection resistance in the connection structure and effectively suppressing the generation of voids, a group containing a carboxyl group is covalently bonded to the surface of the solder via an ether bond or an ester bond. It is preferable.

  Hydroxyl groups exist on the surface of the solder. By covalently bonding this hydroxyl group and a group containing a carboxyl group, a stronger bond can be formed than in the case of bonding by other coordination bond (chelate coordination) or the like, so the connection resistance between the electrodes is reduced, And the solder particle which can suppress generation | occurrence | production of a void is obtained.

  In the solder particles, the bonding form between the surface of the solder and the group containing a carboxyl group may not include a coordination bond, and may not include a bond due to a chelate coordination.

  From the viewpoint of effectively reducing the connection resistance in the connection structure and effectively suppressing the generation of voids, the solder particles are compounds having a functional group capable of reacting with a hydroxyl group and a carboxyl group (hereinafter referred to as Compound X). Is preferably obtained by reacting a hydroxyl group on the surface of the solder with a functional group capable of reacting with the hydroxyl group. In the above reaction, a covalent bond is formed. By reacting a hydroxyl group on the surface of the solder with a functional group capable of reacting with the hydroxyl group in the compound X, solder particles in which a group containing a carboxyl group is covalently bonded to the surface of the solder can be easily obtained. It is also possible to obtain solder particles in which a group containing a carboxyl group is covalently bonded to the surface of the solder via an ether bond or an ester bond. By reacting a hydroxyl group on the surface of the solder with a functional group capable of reacting with the hydroxyl group, the compound X can be chemically bonded to the surface of the solder in the form of a covalent bond.

  Examples of the functional group capable of reacting with the hydroxyl group include a hydroxyl group, a carboxyl group, an ester group, and a carbonyl group. A hydroxyl group or a carboxyl group is preferred. The functional group capable of reacting with the hydroxyl group may be a hydroxyl group or a carboxyl group.

  Examples of the compound having a functional group capable of reacting with a hydroxyl group include levulinic acid, glutaric acid, succinic acid, malic acid, oxalic acid, malonic acid, adipic acid, 5-ketohexanoic acid, 3-hydroxypropionic acid, 4-aminobutyric acid, 3-mercaptopropionic acid, 3-mercaptoisobutyric acid, 3-methylthiopropionic acid, 3-phenylpropionic acid, 3-phenylisobutyric acid, 4-phenylbutyric acid, decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, Examples include 9-hexadecenoic acid, heptadecanoic acid, stearic acid, oleic acid, vaccenic acid, linoleic acid, (9,12,15) -linolenic acid, nonadecanoic acid, arachidic acid, decanedioic acid, and dodecanedioic acid. Glutaric acid or glycolic acid is preferred. Only 1 type may be used for the compound which has the functional group which can react with the said hydroxyl group, and 2 or more types may be used together. The compound having a functional group capable of reacting with the hydroxyl group is preferably a compound having at least one carboxyl group.

  The compound X preferably has a flux action, and the compound X preferably has a flux action in a state of being bonded to the solder surface. The compound having a flux action can remove the oxide film on the surface of the solder and the oxide film on the surface of the electrode. The carboxyl group has a flux action.

  Examples of the compound having a flux action include levulinic acid, glutaric acid, succinic acid, 5-ketohexanoic acid, 3-hydroxypropionic acid, 4-aminobutyric acid, 3-mercaptopropionic acid, 3-mercaptoisobutyric acid, and 3-methylthiopropionic acid. , 3-phenylpropionic acid, 3-phenylisobutyric acid and 4-phenylbutyric acid. Glutaric acid or glycolic acid is preferred. As for the compound which has the said flux effect | action, only 1 type may be used and 2 or more types may be used together.

  From the viewpoint of effectively reducing the connection resistance in the connection structure and effectively suppressing the generation of voids, the functional group capable of reacting with the hydroxyl group in the compound X is preferably a hydroxyl group or a carboxyl group. The functional group capable of reacting with the hydroxyl group in the compound X may be a hydroxyl group or a carboxyl group. When the functional group capable of reacting with the hydroxyl group is a carboxyl group, the compound X preferably has at least two carboxyl groups. By reacting a part of the carboxyl groups of the compound having at least two carboxyl groups with a hydroxyl group on the surface of the solder, solder particles in which a group containing a carboxyl group is covalently bonded to the surface of the solder can be obtained.

  The solder particle manufacturing method includes, for example, a step of using solder particles to mix the solder particles, a compound having a functional group capable of reacting with a hydroxyl group and a carboxyl group, a catalyst, and a solvent. In the method for producing solder particles, solder particles in which a group containing a carboxyl group is covalently bonded to the surface of the solder can be easily obtained by the mixing step.

  In the method for producing solder particles, it is preferable that the solder particles are used to mix and heat the solder particles, a compound having a functional group capable of reacting with the hydroxyl group and a carboxyl group, the catalyst, and the solvent. . By the mixing and heating process, solder particles in which a group containing a carboxyl group is covalently bonded to the surface of the solder can be obtained more easily.

  Examples of the solvent include alcohol solvents such as methanol, ethanol, propanol and butanol, acetone, methyl ethyl ketone, ethyl acetate, toluene and xylene. The solvent is preferably an organic solvent, and more preferably toluene. As for the said solvent, only 1 type may be used and 2 or more types may be used together.

  Examples of the catalyst include p-toluenesulfonic acid, benzenesulfonic acid and 10-camphorsulfonic acid. The catalyst is preferably p-toluenesulfonic acid. As for the said catalyst, only 1 type may be used and 2 or more types may be used together.

  It is preferable to heat at the time of the mixing. The heating temperature is preferably 90 ° C or higher, more preferably 100 ° C or higher, preferably 130 ° C or lower, more preferably 110 ° C or lower.

  From the viewpoint of effectively reducing the connection resistance in the connection structure and effectively suppressing the generation of voids, the solder particles are a step of reacting the isocyanate with a hydroxyl group on the surface of the solder using an isocyanate compound. It is preferable that it is obtained through this. In the above reaction, a covalent bond is formed. By reacting the hydroxyl group on the surface of the solder with the isocyanate compound, it is possible to easily obtain solder particles in which the nitrogen atom of the group derived from the above-mentioned formula isocyanate group is covalently bonded to the surface of the solder. By reacting the isocyanate compound with a hydroxyl group on the surface of the solder, a group derived from the isocyanate group can be chemically bonded to the surface of the solder in the form of a covalent bond.

  Moreover, a silane coupling agent can be easily reacted with a group derived from an isocyanate group. Since the solder particles can be easily obtained, the group having at least one carboxyl group is introduced by a reaction using a silane coupling agent having a carboxyl group, or a silane coupling agent is used. After the reaction, it is preferably introduced by reacting a group having at least one carboxyl group with a group derived from a silane coupling agent. The solder particles are preferably obtained by reacting the isocyanate compound with a hydroxyl group on the surface of the solder using the isocyanate compound and then reacting a compound having at least one carboxyl group.

  From the viewpoint of effectively reducing the connection resistance in the connection structure and effectively suppressing the generation of voids, the compound having at least one carboxyl group preferably has a plurality of carboxyl groups.

  Examples of the isocyanate compound include diphenylmethane-4,4'-diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), and isophorone diisocyanate (IPDI). Isocyanate compounds other than these may be used. After reacting this compound on the surface of the solder, the residual isocyanate group, and a compound having reactivity with the residual isocyanate group and having a carboxyl group are reacted, and expressed on the solder surface by the formula (X). A carboxyl group can be introduced through the group.

  As said isocyanate compound, you may use the compound which has an unsaturated double bond and has an isocyanate group. Examples include 2-acryloyloxyethyl isocyanate and 2-isocyanatoethyl methacrylate. After reacting the isocyanate group of this compound on the surface of the solder, the surface of the solder is reacted with a compound having a functional group having reactivity with the remaining unsaturated double bond and having a carboxyl group. A carboxyl group can be introduced through the group represented by the formula (X).

  Examples of the silane coupling agent include 3-isocyanatopropyltriethoxysilane (“KBE-9007” manufactured by Shin-Etsu Chemical Co., Ltd.) and 3-isocyanatepropyltrimethoxysilane (“Y-5187” manufactured by MOMENTIVE). . As for the said silane coupling agent, only 1 type may be used and 2 or more types may be used together.

  Examples of the compound having at least one carboxyl group include levulinic acid, glutaric acid, succinic acid, malic acid, oxalic acid, malonic acid, adipic acid, 5-ketohexanoic acid, 3-hydroxypropionic acid, 4-aminobutyric acid, 3 -Mercaptopropionic acid, 3-mercaptoisobutyric acid, 3-methylthiopropionic acid, 3-phenylpropionic acid, 3-phenylisobutyric acid, 4-phenylbutyric acid, decanoic acid, dodecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, 9 -Hexadecenoic acid, heptadecanoic acid, stearic acid, oleic acid, vaccenic acid, linoleic acid, (9,12,15) -linolenic acid, nonadecanoic acid, arachidic acid, decanedioic acid and dodecanedioic acid. Glutaric acid, adipic acid or glycolic acid is preferred. As for the compound which has at least 1 said carboxyl group, only 1 type may be used and 2 or more types may be used together.

  After reacting the isocyanate compound with the hydroxyl group on the surface of the solder using the isocyanate compound, the carboxyl group of the compound having a plurality of carboxyl groups is reacted with the hydroxyl group on the surface of the solder. A group having at least one of can be left.

  In the method for producing solder particles, using the solder particles and using an isocyanate compound, after reacting the isocyanate compound with a hydroxyl group on the surface of the solder, reacting a compound having at least one carboxyl group. Solder particles in which a group having at least one carboxyl group is bonded to the surface of the solder via the group represented by the above formula (X) are obtained. In the method for producing solder particles, solder particles in which a group containing a carboxyl group is introduced on the surface of the solder can be easily obtained by the above-described steps.

  Specific methods for producing the solder particles include the following methods. Solder particles are dispersed in an organic solvent, and a silane coupling agent having an isocyanate group is added. Thereafter, a silane coupling agent is covalently bonded to the solder surface using a reaction catalyst between a hydroxyl group and an isocyanate group on the solder surface of the solder particles. Next, a hydroxyl group is generated by hydrolyzing the alkoxy group bonded to the silicon atom of the silane coupling agent. The produced hydroxyl group is reacted with a carboxyl group of a compound having at least one carboxyl group.

  Moreover, the following method is mentioned as a specific manufacturing method of the said solder particle. Solder particles are dispersed in an organic solvent, and a compound having an isocyanate group and an unsaturated double bond is added. Thereafter, a covalent bond is formed using a reaction catalyst between a hydroxyl group and an isocyanate group on the solder surface of the solder particles. Thereafter, the unsaturated double bond introduced is reacted with a compound having an unsaturated double bond and a carboxyl group.

  As reaction catalysts for hydroxyl groups and isocyanate groups on the solder surface of solder particles, tin-based catalysts (dibutyltin dilaurate, etc.), amine-based catalysts (triethylenediamine, etc.), carboxylate catalysts (lead naphthenate, potassium acetate, etc.), and And trialkylphosphine catalysts (triethylphosphine, etc.).

  From the viewpoint of effectively reducing the connection resistance in the connection structure and effectively suppressing the generation of voids, the compound having at least one carboxyl group is a compound represented by the following formula (1): Is preferred. The compound represented by the following formula (1) has a flux action. Moreover, the compound represented by following formula (1) has a flux effect | action in the state introduced into the surface of solder.

  In said formula (1), X represents the functional group which can react with a hydroxyl group, R represents a C1-C5 bivalent organic group. The organic group may contain a carbon atom, a hydrogen atom, and an oxygen atom. The organic group may be a divalent hydrocarbon group having 1 to 5 carbon atoms. The main chain of the organic group is preferably a divalent hydrocarbon group. In the organic group, a carboxyl group or a hydroxyl group may be bonded to a divalent hydrocarbon group. Examples of the compound represented by the above formula (1) include citric acid.

  The compound having at least one carboxyl group is preferably a compound represented by the following formula (1A) or the following formula (1B). The compound having at least one carboxyl group is preferably a compound represented by the following formula (1A), and more preferably a compound represented by the following formula (1B).

  In said formula (1A), R represents a C1-C5 bivalent organic group. R in the above formula (1A) is the same as R in the above formula (1).

  In said formula (1B), R represents a C1-C5 bivalent organic group. R in the above formula (1B) is the same as R in the above formula (1).

  A group represented by the following formula (2A) or the following formula (2B) is preferably bonded to the surface of the solder. A group represented by the following formula (2A) is preferably bonded to the surface of the solder, and more preferably a group represented by the following formula (2B) is bonded. In the following formula (2A), the left end represents a binding site.

  In said formula (2A), R represents a C1-C5 bivalent organic group. R in the above formula (2A) is the same as R in the above formula (1). In the following formula (2B), the left end represents a binding site.

  In said formula (2B), R represents a C1-C5 bivalent organic group. R in the above formula (2B) is the same as R in the above formula (1).

  From the viewpoint of improving the wettability of the solder surface, the molecular weight of the compound having at least one carboxyl group is preferably 10,000 or less, more preferably 1000 or less, and even more preferably 500 or less.

  The molecular weight means a molecular weight that can be calculated from the structural formula when the compound having at least one carboxyl group is not a polymer and when the structural formula of the compound having at least one carboxyl group can be specified. Further, when the compound having at least one carboxyl group is a polymer, it means a weight average molecular weight.

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

  The zeta potential of the solder particles is preferably 0 mV or more, more 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, particularly preferably 0.5 mV. It is as follows. 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 less than 0 mV, the aggregation of solder particles on the electrode may be insufficient during mounting.

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

  The tin content is determined using a high frequency inductively coupled plasma 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. The low melting point metal is preferably tin, a tin-silver alloy, a tin-silver-copper alloy, a tin-bismuth alloy, or a tin-indium alloy because of its excellent wettability with respect to the electrode. More preferred are a tin-bismuth alloy and a tin-indium alloy.

  The solder particles are preferably a filler material having a liquidus line of 450 ° C. or lower based on JIS Z3001: welding terms. Examples of the composition of the solder particles include metal compositions containing zinc, gold, silver, lead, copper, tin, bismuth, indium and the like. A tin-indium system (117 ° C eutectic) or a tin-bismuth system (139 ° C eutectic) that has a low melting point and is free of lead 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, calculating an average value, or performing laser diffraction particle size distribution measurement.

  The coefficient of variation of the particle diameter of the solder particles is preferably 5% or more, more preferably 10% or more, 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 shape of the solder particles is not particularly limited. The solder particles may have a spherical shape or a shape other than a spherical shape such as a flat shape.

  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 90% by weight or less, more preferably 80% by weight or less, still more preferably 60% by weight or less, and particularly 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.

(Thermoplastic component)
The thermoplastic component is preferably a thermoplastic compound. Examples of the thermoplastic compound include phenoxy resin, urethane resin, (meth) acrylic resin, polyester resin, polyimide resin, and polyamide resin. As for the said thermoplastic compound, only 1 type may be used and 2 or more types may be used together.

  The content of the thermoplastic compound in 100% by weight of the conductive paste is preferably 20% by weight or more, more preferably 40% by weight or more, still more preferably 50% by weight or more, preferably 99% by weight or less, more preferably It is 98 weight% or less, More preferably, it is 90 weight% or less, Most preferably, it is 80 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 compound: thermosetting component)
The thermosetting compound is a compound that can be cured by heating. 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. From the viewpoint of further improving the curability and curability and viscosity of the conductive paste and further improving the connection reliability, an epoxy compound is preferable.

  From the viewpoint of efficiently arranging the solder particles on the electrodes, effectively suppressing misalignment between the electrodes, and further improving the conduction reliability and insulation reliability between the electrodes, the thermosetting compound is crystalline. It is preferable that a thermosetting compound is included.

  From the viewpoint of arranging solder particles more efficiently on the electrodes, more effectively suppressing displacement between the electrodes, and further improving the conduction reliability and insulation reliability between the electrodes, the above crystalline thermosetting The active compound is preferably solid at 25 ° C.

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

  From the viewpoint of arranging solder particles more efficiently on the electrodes, more effectively suppressing misalignment between the electrodes, and further improving the conduction reliability and insulation reliability between the electrodes, the above crystalline thermosetting The molecular weight of the functional compound is preferably 300 or more, more preferably 350 or more, preferably 500 or less, more preferably 400 or less.

  The molecular weight means a molecular weight that can be calculated from the structural formula when the thermosetting compound is not a polymer and when the structural formula of the thermosetting compound can be specified. Moreover, when the said thermosetting compound is a polymer, a weight average molecular weight is meant.

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

  An aromatic epoxy compound is mentioned as said epoxy compound. Crystalline epoxy compounds such as resorcinol-type epoxy compounds, naphthalene-type epoxy compounds, biphenyl-type epoxy compounds, and benzophenone-type epoxy compounds are preferred. From the viewpoint of more efficiently arranging the solder particles on the electrodes, more effectively suppressing the displacement between the electrodes, and further improving the conduction reliability and the insulation reliability between the electrodes, the epoxy compound and the above The crystalline epoxy compound is preferably a resorcinol type epoxy compound, a naphthalene type epoxy compound, a biphenyl type epoxy compound or a benzophenone type epoxy compound, more preferably a benzophenone compound, and 2,4-bis (glycidyloxy) benzophenone. Or 4,4′-bis (glycidyloxy) benzophenone. By using the above-mentioned preferable epoxy compound, the first connection target member and the second connection are high when the connection target member is pasted and when the viscosity is high and acceleration is applied by impact such as conveyance. The positional deviation with respect to the target member can be suppressed, and the viscosity of the conductive paste can be greatly reduced by the heat at the time of curing, and the aggregation of the solder particles can be efficiently advanced.

  “Crystallinity” in the crystalline thermosetting compound means a state in which molecular chains are regularly arranged, and the crystalline thermosetting compound has a glass transition temperature and a melting point.

  From the viewpoint of arranging solder particles more efficiently on the electrodes, more effectively suppressing displacement between the electrodes, and further improving the conduction reliability and insulation reliability between the electrodes, the above crystalline thermosetting The functional compound is particularly preferably a benzophenone type epoxy compound, and most preferably 2,4-bis (glycidyloxy) benzophenone or 4,4′-bis (glycidyloxy) benzophenone.

  The (meth) acrylic compound is a compound having a (meth) acryloyl group. Examples of the (meth) acrylic compound include epoxy (meth) acrylate compounds. A compound in which a (meth) acryloyl group is introduced into the epoxy compound with (meth) acrylic acid or the like is preferable.

  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.

  In 100% by weight of the conductive paste, the content of the crystalline thermosetting compound is preferably 20% by weight or more, more preferably 40% by weight or more, still more preferably 50% by weight or more, preferably 99% by weight or less. More preferably, it is 98 weight% or less, More preferably, it is 90 weight% or less, Most preferably, it is 80 weight% or less.

  The content of the crystalline thermosetting compound is preferably 10% by weight or more, more preferably 30% by weight or more, still more preferably 50% by weight or more, particularly preferably in 100% by weight of the total thermosetting compound. Is 70% by weight or more, preferably 100% by weight or less.

(Thermosetting agent: thermosetting component)
The thermosetting agent thermosets the thermosetting compound. Examples of the thermosetting agent include imidazole curing agents, amine curing agents, phenol curing agents, polythiol curing agents, and other thiol curing agents, acid anhydrides, thermal cation initiators (thermal cation curing agents), and thermal radical generators. It is done. As for the said thermosetting agent, only 1 type may be used and 2 or more types may be used together.

  An imidazole curing agent, a thiol curing agent, or an amine curing agent is preferred 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 thiol 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 thiol curing agent is not particularly limited, and examples thereof include trimethylolpropane tris-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, and dipentaerythritol hexa-3-mercaptopropionate. .

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

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

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

  From the viewpoint of more efficiently arranging the solder on the electrode, the reaction initiation temperature of the thermosetting agent is preferably 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.

  From the viewpoint of effectively increasing the storage stability of the conductive paste and making it difficult for components other than solder particles to flow during connection between the electrodes, the flux is preferably solid at 25 ° C.

  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 active temperature (melting point) of the flux is preferably 50 ° C. or higher, more preferably 70 ° C. or higher, further preferably 80 ° C. or higher, preferably 200 ° C. or lower, more preferably 190 ° C. or lower, even more preferably 160 ° C. or lower. More preferably, it is 150 ° C. or less, and still more preferably 140 ° C. or less. When the activation temperature of the flux is not less than the above lower limit and not more than the above upper limit, the flux effect is more effectively exhibited, and the solder particles are more efficiently arranged on the electrode. The active temperature (melting point) of the flux is preferably 80 ° C. or higher and 190 ° C. or lower. The activation temperature (melting point) of the flux is particularly preferably 80 ° C. or higher and 140 ° C. or lower.

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

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

  From the viewpoint of more efficiently arranging the solder on the electrode, the melting point of the flux is preferably higher than the melting point of the solder in the solder particles, preferably 5 ° C or higher, more preferably 10 ° C or higher. Is more preferable.

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

  The 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.

  The content of the filler in 100% by weight of the conductive paste is preferably 0% by weight or more, preferably 5% by weight or less, more preferably 2% by weight or less, and further 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.

(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.

(Connection structure and method of manufacturing connection structure)
A connection structure according to the present invention includes a first connection target member having at least one first electrode on the surface, a second connection target member having at least one second electrode on the surface, and the first The connection object member and the connection part which has connected the said 2nd connection object member are provided. In the connection structure according to the present invention, the material of the connection portion is the conductive paste described above. The connection part is formed of the conductive paste described above. The connection part is a cured product of the conductive paste. In the connection structure according to the present invention, the first electrode and the second electrode are electrically connected by a solder portion in the connection portion.

  The manufacturing method of the connection structure according to the present invention includes 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 using the conductive paste described above. The second connection target member having at least one second electrode on the surface of the conductive paste opposite to the first connection target member side is provided with the first electrode and the second connection target. A step of arranging the electrodes to face each other, and a connection for connecting the first connection target member and the second connection target member by heating the conductive paste to a temperature equal to or higher than the melting point of the solder particles. Forming a portion with the conductive paste, and electrically connecting the first electrode and the second electrode with a solder portion in the connection portion. Preferably, the conductive paste is heated above the curing temperature of the thermosetting component.

  In the connection structure according to the present invention and the method for manufacturing the connection structure according to the present invention, since a specific conductive paste is used, a plurality of solder particles are likely to gather between the first electrode and the second electrode. A plurality of solder particles can be efficiently arranged 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.

  In addition, it is necessary to use a conductive paste instead of a conductive film in order to efficiently arrange a plurality of solder particles on an electrode and to considerably reduce the amount of solder particles arranged in a region where no electrode is formed. The present inventor has found that

  In the present invention, another method of efficiently collecting a plurality of solder particles between the electrodes may be further employed. As a method for efficiently collecting a plurality of solder particles between electrodes, when heat is applied to the conductive paste between the first connection target member and the second connection target member, the viscosity of the conductive paste by heat is applied. The method of generating the convection of the electrically conductive paste between a 1st connection object member and a 2nd connection object member etc. is mentioned because it falls. In this method, a method of generating convection due to a difference in heat capacity between the electrode on the surface of the connection target member and the other surface member, a method of generating convection as water vapor from the heat of the connection target member, and the first Examples include a method of generating convection due to a temperature difference between the connection target member and the second connection target member. Thereby, the solder particles in the conductive paste can be efficiently moved to the surface of the electrode.

  In the present invention, a method of selectively aggregating solder particles on the surface of the electrode may be further employed. As a method of selectively agglomerating solder particles on the surface of the electrode, there is a connection target member formed by an electrode material having good wettability of molten solder particles and another surface material having poor wettability of molten solder particles. A method of selectively adhering molten solder particles that have reached the surface of the electrode to the electrode and then melting and adhering another solder particle to the molten solder particles, and an electrode material with good thermal conductivity And other surface materials with poor thermal conductivity are selected, and when heat is applied, the temperature of the electrode is raised relative to the other surface members to selectively In this method, the solder particles are selectively agglomerated on the electrodes by using solder particles that have been treated so as to have a positive charge with respect to the negative charges existing on the electrode formed of metal. Method of, and, the electrode having a hydrophilic metal surface, the resin other than the solder particles in the conductive paste by a hydrophobic, a method to aggregate selectively solder particles on the electrode, and the like.

  The thickness of the solder part between the electrodes is preferably 10 μm or more, more preferably 20 μm or more, preferably 100 μm or less, more preferably 80 μm or less. Solder wet area on the surface of the electrode (area where the solder is in contact with 100% of the exposed area of the electrode, electrically connected to the first electrode and the first electrode before forming the connecting portion) The area where the solder part is in contact with the second electrode with respect to the exposed area of 100% is preferably 50% or more, more preferably 60% or more, and still more preferably 70% or more, preferably 100% or less.

  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 added, or pressure is applied in at least one of the step of arranging the second connection target member and the step of forming the connection portion, and the second connection target member It is preferable that the pressure of pressurization is less than 1 MPa in both the step of disposing and the step of forming the connecting portion. By not applying a pressure of 1 MPa or more, the aggregation of solder particles is considerably promoted. From the viewpoint of suppressing the warpage of the connection target member, in the method for manufacturing a connection structure according to the present invention, at least one of the step of arranging the second connection target member and the step of forming the connection portion is performed. The pressure of pressurization may be less than 1 MPa in both the step of performing pressure and arranging the second connection target member and the step of forming the connection portion. When pressurization is performed, the pressurization may be performed only in the step of arranging the second connection target member, or the pressurization may be performed only in the step of forming the connection portion. Pressurization may be performed in both the step of arranging the connection target member and the step of forming the connection portion. The case where the pressure is less than 1 MPa includes the case where no pressure is applied. When pressurizing, the pressure of pressurization is preferably 0.9 MPa or less, more preferably 0.8 MPa or less. When the pressure of the pressurization is 0.8 MPa or less, the aggregation of the solder particles is further promoted more remarkably than when the pressure of the pressurization exceeds 0.8 MPa.

  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, and in the step of arranging the second connection target member and the step of forming the connection portion, the conductive paste exceeds the weight force of the second connection target member. It is preferable that no pressure is applied. In these cases, the uniformity of the amount of solder can be further enhanced in the plurality of solder portions. Furthermore, the thickness of the solder part can be increased more effectively, and a plurality of solder particles can be easily collected between the electrodes, and the plurality of solder particles can be arranged more efficiently on the electrodes (lines). it can. Moreover, it is difficult for some of the plurality of solder particles to be arranged in a region (space) where no electrode is formed, and the amount of solder particles arranged in a region where no electrode is formed can be further reduced. Therefore, the conduction reliability between the electrodes can be further enhanced. In addition, the electrical connection between the laterally adjacent electrodes that should not be connected can be further prevented, and the insulation reliability can be further improved.

  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 inventor has also found that the arrangement can be made more efficient. 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, WO2008 / 023452A1 recognizes nothing about the importance of using a paste-like conductive paste instead of a film.

  Moreover, if a conductive paste is used instead of a conductive film, it becomes easy to adjust the thickness of the connection part and the solder part 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. In addition, the conductive film has a problem that the melt viscosity of the conductive film cannot be sufficiently lowered at the melting temperature of the solder, and the aggregation of the solder particles is hindered.

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

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

  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 by the conductive paste described above. In this embodiment, the said electrically conductive paste contains the said thermosetting compound and the said thermosetting agent.

  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, a plurality of solder particles gather between the first electrode 2 a and the second electrode 3 a, and after the plurality of solder particles melt, After the electrode surface wets and spreads, it solidifies to form the solder portion 4A. 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, 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 seen. Sometimes, 50% or more (more preferably 60% or more, still more preferably 70% or more, particularly preferably 80% or more) out of 100% of the area where the first electrode and the second electrode face each other. , Most preferably 90% or more), the solder portion in the connection portion is preferably disposed.

  From the viewpoint of further improving the conduction reliability, the first electrode and the second electrode are opposed to each other in a direction orthogonal to the stacking direction of the first electrode, the connection portion, and the second electrode. When the matching portion is viewed, the portion where the first electrode and the second electrode face each other is 70% or more (more preferably 80% or more, more preferably 90%) of the solder portion in the connection portion. In particular, it is preferable that 95% or more, most preferably 99% or more) is disposed.

  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 (third step). Preferably, the conductive paste 11 is heated above the curing temperature of the thermosetting component 11B (binder). 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 conductive paste further has a specific composition, so that the solder particles 11A are disposed between the first electrode 2a and the second electrode 3a. To gather effectively. 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. If the solder particles 11A are sufficiently moved, 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, it is preferable that no pressure is applied in the second step and the third step. In this case, 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 inventor.

  However, pressurization may be performed as long as the interval between the first electrode and the second electrode can be secured. As a means for ensuring the gap between the electrodes, for example, a spacer corresponding to the desired gap between the electrodes may be added so that at least one, preferably three or more spacers are arranged between the electrodes. Examples of the spacer include inorganic particles and organic particles. The spacer is preferably an insulating particle.

  Moreover, in this embodiment, since pressurization is not performed, when the second connection target member is superimposed on the first connection target member to which the conductive paste is applied, the electrode of the first connection target member Even when the first connection target member and the second connection target member are overlapped in a state where the alignment of the electrodes of the second connection target member is shifted, the shift is corrected and the first connection target member is corrected. Can be connected to the electrode of the second connection target member (self-alignment effect). This is because the molten solder self-aggregated between the electrode of the first connection target member and the electrode of the second connection target member is the electrode of the first connection target member and the electrode of the second connection target member. As the area where the solder and the other components of the conductive paste are in contact with each other is minimized, the area becomes more stable in terms of energy. Because. At this time, it is desirable that the conductive paste is not cured and that the viscosity of components other than the solder particles of the conductive paste is sufficiently low at that temperature and time.

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

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

  The said 1st, 2nd connection object member is not specifically limited. Specifically as said 1st, 2nd connection object member, electronic components, such as a semiconductor chip, a semiconductor package, LED chip, LED package, a capacitor | condenser, a diode, and a resin film, a printed circuit board, a flexible printed circuit board, flexible Examples thereof include electronic components such as circuit boards such as flat cables, rigid flexible boards, glass epoxy boards, and glass boards. The first and second connection target members are preferably electronic components.

  At least one of the first connection target member and the second connection target member is preferably a semiconductor chip, a resin film, a flexible printed circuit board, a rigid flexible circuit board, or a flexible flat cable. A substrate, a flexible flat cable, or a rigid flexible substrate is more preferable. The second connection target member is preferably a semiconductor chip, a resin film, a flexible printed board, a rigid flexible board, or a flexible flat cable, and more preferably a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. preferable. 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, by using a conductive paste, even if a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board is used, it is possible to efficiently collect the solder particles on the electrodes, thereby ensuring conduction reliability between the electrodes. The nature can be sufficiently enhanced. When using a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid flexible circuit board, compared to the case of using other connection target members such as a semiconductor chip, the conduction reliability between the electrodes by not applying pressure is improved. The improvement effect can be obtained more effectively.

  Peripherals, area arrays, and the like exist in the form of the connection target member. As a feature of each member, in the peripheral substrate, the electrodes are present only on the outer peripheral portion of the substrate. In the area array substrate, there are electrodes in the plane.

  Examples of the electrode provided on the connection target member include metal electrodes such as a gold electrode, a nickel electrode, a tin electrode, an aluminum electrode, a copper electrode, a molybdenum electrode, a silver electrode, a SUS electrode, and a tungsten electrode. When the connection object member is a flexible printed board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, a silver electrode, or a copper electrode. When the connection target member is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, a silver electrode, or a tungsten electrode. 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.

  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.

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

Synthesis of 2,4-bis (glycidyloxy) benzophenone:
In a three-necked flask, 27 g of 2,4-dihydroxybenzophenone, 230 g of epichlorohydrin, 70 g of n-butanol and 1 g of tetraethylbenzylammonium chloride were added and stirred and dissolved at room temperature. Thereafter, the temperature was raised to 70 ° C. under stirring in a nitrogen atmosphere, and 45 g of an aqueous sodium hydroxide solution (concentration: 48 wt%) was added dropwise under reduced pressure. The dropping was performed over 4 hours. Then, it was made to react at 70 degreeC for 2 hours, using a Dean-Stark tube, removing a water | moisture content. Thereafter, unreacted epichlorohydrin was removed under reduced pressure.

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

  Then, it cooled to room temperature and wash | cleaned with the pure water until the washing | cleaning liquid became neutral. The organic layer was collected by filtration, and the remaining water and the mixed solvent were removed under reduced pressure to obtain a reaction product.

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

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

-Differential scanning calorimetry (DSC) measuring device and measuring conditions Device: “X-DSC7000” manufactured by Hitachi High-Tech Science Co., sample amount: 3 mg, temperature condition: 10 ° C./min

  -Melt viscosity at 150 ° C .: Measured using an ICI cone plate viscometer manufactured by MST Engineering in accordance with ASTM D4287

  ・ Measurement of epoxy equivalent: Measured according to JIS K7236: 2001

  Measurement of molecular weight: Measured using a GC-MS apparatus (“JMS K-9” manufactured by JEOL Ltd.)

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

Synthesis of 4,4′-bis (glycidyloxy) benzophenone:
In a three-necked flask, 27 g of 4,4′-dihydroxybenzophenone, 230 g of epichlorohydrin, 70 g of n-butanol, and 1 g of tetraethylbenzylammonium chloride were stirred and dissolved at room temperature. Thereafter, the temperature was raised to 70 ° C. under stirring in a nitrogen atmosphere, and 45 g of an aqueous sodium hydroxide solution (concentration: 48 wt%) was added dropwise under reduced pressure. The dropping was performed over 4 hours. after that. The reaction was carried out at 70 ° C. for 2 hours using a Dean-Stark tube while removing moisture. Thereafter, unreacted epichlorohydrin was removed under reduced pressure.

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

  Then, it cooled to room temperature and wash | cleaned with the pure water until the washing | cleaning liquid became neutral. The organic layer was collected by filtration, and the remaining water and the mixed solvent were removed under reduced pressure to obtain a reaction product.

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

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

  Thermosetting compound 3: Epoxy group-containing acrylic polymer, “MARPROOF G-0150M” manufactured by NOF Corporation

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

  Latent epoxy thermosetting agent 1: “Fujicure 7000” manufactured by T & K TOKA

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

Method for producing solder particles 1-3:
Solder particles 1:
SnBi solder particles (“DS-10” manufactured by Mitsui Kinzoku Co., Ltd., average particle size (median diameter) 12 μm) and glutaric acid (a compound having two carboxyl groups, “glutaric acid” manufactured by Wako Pure Chemical Industries, Ltd.) By using p-toluenesulfonic acid as a catalyst and stirring for 8 hours while dehydrating in a toluene solvent at 90 ° C., solder particles 1 in which a carboxyl group-containing group is covalently bonded to the surface of the solder were obtained.

  In the obtained solder particles 1, the CV value was 20%, the surface zeta potential was 1.2 mV, and the molecular weight Mw of the polymer constituting the surface was 2000.

Solder particles 2:
200 g of SnBi solder particles (“DS-10” manufactured by Mitsui Kinzoku Co., Ltd., average particle size (median diameter) 12 μm), 10 g of a silane coupling agent having an isocyanate group (“KBE-9007” manufactured by Shin-Etsu Chemical Co., Ltd.), and 70 g of acetone. Weighed into a three-necked flask. While stirring at room temperature, 0.25 g of dibutyltin dilaurate, which is a reaction catalyst for the hydroxyl group and isocyanate group on the surface of the solder particles, was added, and the mixture was heated at 60 ° C. for 30 minutes under stirring in a nitrogen atmosphere. Thereafter, 50 g of methanol was added, and the mixture was heated at 60 ° C. for 10 minutes under stirring in a nitrogen atmosphere.

  Then, it cooled to room temperature, the solder particle was filtered with the filter paper, and solvent removal was performed at room temperature for 1 hour by vacuum drying.

  Put the solder particles in a three-necked flask, add 70 g of acetone, 30 g of monoethyl adipate, and 0.5 g of monobutyltin oxide which is a transesterification reaction catalyst, and let it react at 60 ° C. for 1 hour in a nitrogen atmosphere with stirring. It was.

  Thereby, the ester group of the monoethyl adipate was made to react with the silanol group derived from a silane coupling agent by the transesterification, and was covalently bonded.

  Thereafter, 10 g of adipic acid was added and reacted at 60 ° C. for 1 hour, whereby adipic acid was added to the residual ethyl ester group not reacted with the silanol group of monoethyl adipate.

  Then, cool to room temperature, filter the solder particles with filter paper, wash the solder particles with hexane on the filter paper, unreacted, and adhere to the surface of the solder particles by non-covalent bonds, residual monoethyl adipate After removing adipic acid, the solvent was removed by vacuum drying at room temperature for 1 hour.

  After the obtained solder particles were crushed with a ball mill, a sieve was selected so as to obtain a predetermined CV value.

  The molecular weight of the polymer formed on the solder surface was determined by using 0.1N hydrochloric acid, dissolving the solder, collecting the polymer by filtration, and determining the weight average molecular weight by GPC.

  Thereby, solder particles 2 were obtained. In the obtained solder particles 2, the CV value was 20%, the surface zeta potential was 0.9 mV, and the molecular weight Mw of the polymer constituting the surface was 9800.

Solder particles 3:
In the step of obtaining the solder particles 2, the solder particles 3 were obtained in the same manner except that monoethyl adipate was changed to monoethyl glutarate and adipic acid was changed to glutaric acid.

  In the obtained solder particles 3, the CV value was 20%, the surface zeta potential was 0.92 mV, and the molecular weight Mw of the polymer constituting the surface was 9600.

  Solder particles A: SnBi solder particles (“DS-10” manufactured by Mitsui Kinzoku Co., Ltd., average particle diameter (median diameter) 12 μm)

(Zeta potential measurement)
0.05 g of the obtained solder particles were put in 10 g of methanol and subjected to ultrasonic treatment to uniformly disperse, thereby obtaining a dispersion. The zeta potential was measured by electrophoretic measurement using this dispersion and “Delsamax PRO” manufactured by Beckman Coulter.

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

  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 = 42 wt%: 58 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. In this way, a 1 μm thick copper layer is formed on the surface of the resin particles, and a 3 μm thick solder layer (tin: bismuth = 42 wt%: 58 wt%) is formed on the surface of the copper layer. Conductive particles 1 were prepared.

(Examples 1 to 4, 6, 7 , Reference Example 5 and Comparative Examples 1 to 3)
(1) Preparation of anisotropic conductive paste The components shown in Table 1 below were blended in the blending amounts shown in Table 1 to obtain anisotropic conductive paste.

(2) Production of first connection structure (L / S = 50 μm / 50 μm) Glass epoxy substrate having a copper electrode pattern (copper electrode thickness 12 μm) having an L / S of 50 μm / 50 μm and an electrode length of 3 mm on the upper surface (FR-4 substrate) (first connection target member) was prepared. Moreover, the flexible printed circuit board (2nd connection object member) which has a copper electrode pattern (thickness of a copper electrode 12 micrometers) of L / S 50 micrometers / 50 micrometers and electrode length 3mm on the lower surface was prepared.

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

  On the upper surface of the glass epoxy substrate, the anisotropic conductive paste immediately after production is applied by screen printing using a metal mask so that the thickness is 100 μm on the electrode of the glass epoxy substrate, and anisotropic conductive A paste layer was formed. Next, the flexible printed circuit board was laminated on the upper surface of the anisotropic conductive paste layer so that the electrodes face each other. At this time, no pressure was applied. The weight of the flexible printed board is added to the anisotropic conductive paste layer. Thereafter, while heating the anisotropic conductive paste layer to 190 ° C., the solder is melted, and the anisotropic conductive paste layer is cured at 190 ° C. for 10 seconds. Obtained.

(3) Production of second connection structure (L / S = 75 μm / 75 μm) Glass epoxy substrate having a L / S of 75 μm / 75 μm and an electrode length of 3 mm on a copper electrode pattern (copper electrode thickness 12 μm) on the upper surface (FR-4 substrate) (first connection target member) was prepared. In addition, a flexible printed circuit board (second connection target member) having a L / S of 75 μm / 75 μm and an electrode length of 3 mm on the lower surface of a copper electrode pattern (copper electrode thickness 12 μm) 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 having a copper electrode pattern (copper electrode thickness 12 μm) with L / S of 100 μm / 100 μm and electrode length of 3 mm on the upper surface (FR-4 substrate) (first connection target member) was prepared. Moreover, the flexible printed circuit board (2nd connection object member) which has a copper electrode pattern (thickness of copper electrode 12 micrometers) of L / S of 100 micrometers / 100 micrometers and electrode length 3mm 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.

(Evaluation)
(1) Viscosity 1
The viscosity (η25) at 25 ° C. of the anisotropic conductive paste was measured using an E-type viscometer (“TVE22L” manufactured by Toki Sangyo Co., Ltd.) at 25 ° C. and 5 rpm.

(2) Viscosity 2
The minimum value and the maximum value of the viscosity of the conductive paste were measured in a temperature range (mp-10 to mp) from the melting point of the solder to −10 ° C. or more and below the melting point of the solder. Specifically, measurement was performed using a rheometer (“STRESSTECH” manufactured by EOLOGICA) under the conditions of a rotor diameter of 20 mm, oscillation strain control, and a temperature rising rate of 10 ° C./min.

(3) Thickness of solder part By observing a cross section of the obtained first connection structure, the thickness of the solder part located between the upper and lower electrodes was evaluated.

(4) Solder placement accuracy on electrode 1
In the obtained first, second, and third connection structures, a 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 provided. When viewed, the ratio X of the area where the solder portion in the connection portion is arranged in the area of 100% of the portion where the first electrode and the second electrode face each other was evaluated. The solder placement accuracy 1 on the electrode was determined according to the following criteria.

[Criteria for solder placement accuracy 1 on electrode]
○○: Ratio X is 70% or more ○: Ratio X is 60% or more and less than 70% Δ: Ratio X is 50% or more and less than 60% X: Ratio X is less than 50%

(5) Solder placement accuracy on electrode 2
In the obtained first, second, and third connection structures, the first electrode and the second electrode are opposed to each other in a direction orthogonal to the stacking direction of the first electrode, the connection portion, and the second electrode. When looking at the mating part, the ratio Y of the solder part in the connecting part arranged in the part where the first electrode and the second electrode face each other in 100% of the solder part in the connecting part was evaluated. . The solder placement accuracy 2 on the electrode was determined according to the following criteria.

[Criteria for solder placement accuracy 2 on electrode]
◯: Ratio Y is 99% or more ○: Ratio Y is 90% or more and less than 99% △: Ratio Y is 70% or more and less than 90% X: Ratio Y is less than 70%

(6) Conduction reliability between upper and lower electrodes In the obtained first, second, and third connection structures (n = 15), the connection resistance per connection portion between the upper and lower electrodes is 4 respectively. It was measured by the terminal method. 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 connection resistance is 50 mΩ or less ○: Average connection resistance exceeds 50 mΩ, 70 mΩ or less △: Average connection resistance exceeds 70 mΩ, 100 mΩ or less ×: Average connection resistance exceeds 100 mΩ Or there is a bad connection

(7) Insulation reliability between adjacent electrodes in the horizontal direction The obtained first, second and third connection structures (n = 15) were left in an atmosphere of 85 ° C. and 85% humidity for 100 hours. Then, 5V was applied between the electrodes adjacent to the horizontal direction, 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) Position shift between upper and lower electrodes In the obtained first, second, and third connection structures, the first electrode and the second electrode are stacked in the stacking direction of the first electrode, the connection portion, and the second electrode. Whether the center line of the first electrode and the center line of the second electrode were aligned when the portion facing the two electrodes was viewed, and the distance of the positional deviation were evaluated. The positional deviation between the upper and lower electrodes was determined according to the following criteria.

[Criteria for misregistration between upper and lower electrodes]
○: Misalignment is less than 15 μm ○: Misalignment is 15 μm or more and less than 25 μm Δ: Misalignment is 25 μm or more and less than 40 μm ×: Misalignment is 40 μm or more

  Details and results are shown in Table 1 below.

  The same tendency was observed when a resin film, a flexible flat cable, and a rigid flexible board were used instead of the flexible printed board.

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

Claims (8)

Including a plurality of solder particles and a binder,
The solder particles are particles in which both the central portion and the outer surface of the conductive portion are solder,
A group having at least one carboxyl group is covalently bonded to the surface of the solder of the solder particles via an ether bond, an ester bond or a group represented by the following formula (X),
The minimum value of the viscosity of the conductive paste in the temperature region of the solder melting point −10 ° C. or higher and the solder melting point or lower is 100 mPa · s or higher, and the solder melting point −10 ° C. or higher and the solder melting point or lower. The conductive paste in which the maximum value of the viscosity of the conductive paste is 1500 mPa · s or less.

  The conductive paste according to claim 1, wherein the binder is not completely cured at the melting point of the solder particles.   3. The conductive paste according to claim 1, wherein a group having at least one carboxyl group is covalently bonded to a surface of the solder of the solder particle via a group represented by the formula (X).   The electrically conductive paste of any one of Claims 1-3 in which the said binder contains a thermosetting compound and a thermosetting agent.   The electrically conductive paste of Claim 4 in which the said thermosetting compound contains a crystalline thermosetting compound.   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 80 weight% in 100 weight% of electrically conductive paste. A first connection object member having a first electrode on its surface;
A second connection target member having a second electrode on its surface;
A connection portion connecting the first connection target member and the second connection target member;
The material of the connection part is the conductive paste according to any one of claims 1 to 7,
A connection structure in which the first electrode and the second electrode are electrically connected by the solder particles.

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