KR102605910B1 - Conductive materials and connection structures - Google Patents

Abstract

A conductive material that can selectively arrange solder in conductive particles on an electrode and improve conduction reliability is provided. The electrically conductive material according to the present invention includes a plurality of conductive particles having solder in the outer surface portion of the electrically conductive portion, and a thermosetting component, and the conductive particles and the thermosetting component are heated at a temperature increase rate of 10°C/min from 25°C, respectively. When differential scanning calorimetry is performed by heating with There is overlap in .

Description

Conductive materials and connection structures

The present invention relates to a conductive material containing conductive particles containing solder. Furthermore, the present invention relates to a bonded structure using the above-mentioned electrically conductive material.

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

The anisotropic conductive material is used to obtain various connection structures, for example, connection between a flexible printed board and a glass substrate (Film on Glass (FOG)), connection between a semiconductor chip and a flexible printed board (Chip on Film (COF)), It is used for the connection between a semiconductor chip and a glass substrate (COG (Chip on Glass)), and the connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)).

When, for example, an electrode of a flexible printed circuit board and an electrode of a glass epoxy substrate are electrically connected by the anisotropic conductive material, the anisotropic conductive material containing conductive particles is disposed on the glass epoxy substrate. Next, flexible printed boards are laminated, heated and pressed. In this way, the anisotropic conductive material is cured and the electrodes are electrically connected via the conductive particles to obtain a connected structure.

As an example of the anisotropic conductive material, Patent Document 1 below describes an anisotropic conductive material containing conductive particles and a resin component whose curing is not complete 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), and gallium. Metals such as (Ga) and thallium (Tl) and alloys of these metals are exemplified.

In Patent Document 1, through a resin heating step of heating the anisotropic conductive resin to a temperature that is higher than the melting point of the conductive particles and at which curing of the resin component is not completed, and a resin component curing step of curing the resin component, the electrode Electrically connecting them is described. Additionally, Patent Document 1 describes mounting with a temperature profile shown in FIG. 8 of Patent Document 1. In Patent Document 1, the conductive particles are melted within the resin component at which curing is not completed at the 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. This adhesive tape is in the form of a film and not a paste.

Japanese Patent Publication No. 2004-260131 WO 2008/023452 A1

In conventional solder powders or anisotropic conductive materials containing conductive particles having a solder layer on the surface, the solder powder or conductive particles may not be efficiently disposed on the electrode (line).

Additionally, when the anisotropic conductive material described in Patent Document 1 is used to electrically connect electrodes by the method described in Patent Document 1, conductive particles containing solder may not be efficiently disposed on the electrodes (lines). Additionally, in the example of Patent Document 1, the temperature is maintained at a constant temperature to sufficiently move the solder at a temperature above the melting point of the solder, which lowers the manufacturing efficiency of the connection structure. If mounting is performed with the temperature profile shown in FIG. 8 of Patent Document 1, the manufacturing efficiency of the connection structure decreases.

In addition, the adhesive tape described in Patent Document 2 is in the form of a film and is not in the form of a paste. In an adhesive tape having a composition as described in Patent Document 2, it is difficult to efficiently arrange solder powder on the electrode (line). For example, in the adhesive tape described in Patent Document 2, a part of the solder powder is likely to be disposed even in areas (spaces) where electrodes are not formed. Solder powder disposed in areas where electrodes are not formed does not contribute to conduction between electrodes.

The purpose of the present invention is to provide a conductive material that can selectively arrange solder in conductive particles on an electrode and improve conduction reliability. Furthermore, an object of the present invention is to provide a bonded structure using the above-described electrically conductive material.

According to a broad aspect of the present invention, the outer surface portion of the conductive portion includes a plurality of conductive particles having solder and a thermosetting component, and the conductive particles and the thermosetting component are heated at a temperature increase rate of 10°C/min from 25°C, respectively. When differential scanning calorimetry is performed by heating with In overlapping, conductive materials are provided.

In certain specific situations of the electrically conductive material according to the present invention, the total amount of heat generated from curing of the thermosetting component in a temperature range below the endothermic peak top temperature resulting from melting of the solder in the electrically conductive particles is It is smaller than the total amount of heat generated from curing of the thermosetting component in a temperature range equal to or higher than the endothermic peak top temperature resulting from melting of the solder.

In a certain aspect of the conductive material according to the present invention, the first exothermic peak top temperature resulting from curing of the thermosetting component is on the lower temperature side than the endothermic peak top temperature resulting from melting of the solder in the conductive particles, Additionally, there is a second exothermic peak top temperature resulting from curing of the thermosetting component at a temperature higher than the endothermic peak top temperature resulting from melting of the solder in the conductive particles.

In a specific aspect of the conductive material according to the present invention, the absolute value of the difference between the endothermic peak top temperature and the first exothermic peak top temperature is 3°C or more and 60°C or less, and the endothermic peak top temperature and the second exothermic peak top temperature are 3°C or more and 60°C or less. The absolute value of the difference from the exothermic peak top temperature is 5°C or more and 60°C or less.

In a specific situation of the conductive material according to the present invention, the peak end temperature on the high temperature side of the endothermic peak is lower than the peak end temperature on the high temperature side of the exothermic peak on the highest temperature side.

In a certain aspect of the conductive material according to the present invention, the peak end temperature on the high temperature side of the endothermic peak is lower than the peak end temperature on the high temperature side of the exothermic peak on the highest temperature side, and the low temperature side of the endothermic peak is lower than the peak end temperature on the high temperature side of the exothermic peak on the highest temperature side. The peak onset temperature on the side is higher than the peak onset temperature on the low temperature side of the exothermic peak on the lowest temperature side.

In a specific aspect of the electrically conductive material according to the present invention, the electrically conductive particles are solder particles.

In a certain situation of the electrically-conductive material which concerns on this invention, a carboxyl group exists on the outer surface of the said electroconductive particle.

In a specific aspect of the electrically conductive material according to the present invention, the electrically conductive material is in a liquid state at 25°C and is an electrically conductive paste.

According to a broad aspect of the present invention, there is provided a first connection target member having at least one first electrode on its surface, a second connection target member having at least one second electrode on its surface, the first connection target member, and the above A connection portion connecting a second connection target member is provided, the connection portion is a cured product of the above-described conductive material, and the first electrode and the second electrode are electrically connected by a solder portion in the connection portion. A connection structure is provided.

In a specific aspect of the connection structure according to the present invention, when the portions of the first electrode and the second electrode facing each other are viewed in the lamination direction of the first electrode, the connection portion, and the second electrode, the first electrode It is preferable that the solder portion in the connection portion is disposed in 50% or more of 100% of the area of the portion where the electrode and the second electrode face each other.

The electrically conductive material according to the present invention includes a plurality of conductive particles having solder in the outer surface portion of the electrically conductive portion, and a thermosetting component, and the conductive particles and the thermosetting component are heated at a temperature increase rate of 10°C/min from 25°C, respectively. When differential scanning calorimetry is performed by heating with Since they overlap, solder in the conductive particles can be selectively disposed on the electrode, and conduction reliability can be improved.

Figure 1 is a schematic diagram showing an example of the relationship between an endothermic peak derived from melting of solder in conductive particles and an exothermic peak derived from curing of a thermosetting component in differential scanning calorimetry.
FIG. 2 is a cross-sectional view schematically showing a bonded structure obtained using a conductive material according to an embodiment of the present invention.
3(a) to 3(c) are cross-sectional views for explaining each step of an example of a method of manufacturing a bonded structure using a conductive material according to an embodiment of the present invention.
Fig. 4 is a cross-sectional view showing a modified example of the bonded structure.
Fig. 5 is a cross-sectional view showing a first example of conductive particles that can be used in an electrically conductive material.
Fig. 6 is a cross-sectional view showing a second example of conductive particles that can be used in electrically conductive materials.
Fig. 7 is a cross-sectional view showing a third example of conductive particles that can be used in electrically conductive materials.

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

(Challenge Materials)

The electrically conductive material according to the present invention contains a plurality of conductive particles and a binder. The electrically conductive particles have an electrically conductive portion. The electrically conductive particles have solder on the outer surface of the electrically conductive portion. Solder is included in the conductive portion and is part or all of the conductive portion.

The electrically conductive material according to the present invention contains a thermosetting component as the binder. The thermosetting component preferably contains a thermosetting compound and a thermosetting agent.

In the present invention, when differential scanning calorimetry is performed by heating at a temperature increase rate of 25°C to 10°C/min, a temperature range showing an endothermic peak resulting from melting of the solder in the conductive particles, and a temperature range of the thermosetting component Temperature regions showing exothermic peaks resulting from curing overlap at least in part.

Specifically, the thermosetting component is heated at a temperature increase rate of 10°C/min and differential scanning calorimetry (DSC) is performed. Additionally, the conductive particles are heated at a temperature increase rate of 10°C/min and differential scanning calorimetry (DSC) is performed. This measurement may be performed using a conductive material. As schematically shown in FIG. 1, in this DSC, in the conductive material according to the present invention, a temperature region showing an endothermic peak P3 resulting from melting of the solder in the conductive particles, and curing of the thermosetting component The temperature regions representing the exothermic peaks P1 and P2 derived from overlap at least in part.

In the present invention, since the above-described structure is provided, solder in conductive particles can be selectively disposed on the electrode. When the electrodes are electrically connected, the solder in the conductive particles tends to collect between the upper and lower opposing electrodes, and the solder in the conductive particles can be efficiently disposed on the electrodes (lines). Moreover, it becomes difficult for the cured product of the thermosetting component to remain between the electrode and the solder portion, and the contact area between the electrode and the solder portion can be increased.

Additionally, it is difficult for a part of the solder in the conductive particles to be placed in the area (space) where the electrode is not formed, and the amount of solder placed in the area where the electrode is not formed can be significantly reduced. In the present invention, solder not located between opposing electrodes can be efficiently moved between opposing electrodes. Therefore, the reliability of conduction between electrodes can be improved. In addition, electrical connection between horizontally adjacent electrodes that should not be connected can be prevented, thereby improving insulation reliability.

As shown in FIG. 1, the total heat generation amount (1) derived from curing of the thermosetting component in a temperature range below the endothermic peak top P3t temperature resulting from melting of the solder in the conductive particles is It is preferable that the total calorific value (2) derived from curing of the thermosetting component in a temperature range equal to or higher than the endothermic peak top P3t temperature resulting from melting of the solder is smaller than the total calorific value (2). The total calorific value (1) is preferably 1/2 or less, more preferably 1/5 or less of the total calorific value (2). Since the total calorific value (1) is relatively small, the thickness of the conductive material can be sufficiently secured before the solder melts, and the positions of the plurality of conductive particles can be brought closer together. As a result, the plurality of conductive particles can be moved further on the electrode. there is. In particular, when mounting on the surface of a semiconductor chip, etc., resin flows from the center to the outer periphery, so a difference is likely to occur in the amount of solder on the electrodes in the center and the outer periphery, but the total amount of heat generated from curing of the thermosetting component By adjusting within the above range, it becomes possible to uniformly mount the amount of solder on the electrodes in the center and the outer peripheral portion, and the variation in the amount of solder on the electrodes can be effectively suppressed. Since the total calorific value (2) is relatively large, after melting of the solder, the solder placed on the electrode can be deposited on the electrode, allowing the amount of solder on the electrode to be further increased.

As shown in FIG. 1, the first exothermic peak top P1t temperature resulting from curing of the thermosetting component is on the lower temperature side than the endothermic peak top P3t temperature resulting from melting of the solder in the conductive particles, and the above It is preferable that the second exothermic peak top P2t temperature resulting from curing of the thermosetting component is on a higher temperature side than the endothermic peak top P3t temperature resulting from melting of the solder in the conductive particles. In this case, the positions of the plurality of conductive particles can be brought closer together, and the solder melts quickly after the positions of the plurality of conductive particles become closer. As a result, the plurality of conductive particles can be moved further onto the electrode.

The absolute value of the difference between the endothermic peak top P3t temperature and the first exothermic peak top P1t temperature is preferably 3°C or higher, more preferably 5°C or higher, further preferably 8°C or higher, and preferably 60°C. Below, more preferably 58°C or below, further preferably 55°C or below. In this case, the positions of the plurality of conductive particles can be brought closer together, and the solder melts quickly after the positions of the plurality of conductive particles become closer. As a result, the plurality of conductive particles can be moved further onto the electrode.

The absolute value of the difference between the endothermic peak top P3t temperature and the second exothermic peak top P2t temperature is preferably 5°C or higher, more preferably 8°C or higher, further preferably 10°C or higher, and preferably 60°C. Below, more preferably 58°C or below, further preferably 55°C or below. In this case, after the molten solder is disposed on the electrode, the solder can be applied to the electrode to further increase the amount of solder on the electrode.

From the viewpoint of more efficiently disposing the solder on the electrode, as shown in FIG. 1, the peak height of the exothermic peak at the first exothermic peak top P1t temperature is greater than that at the second exothermic peak top P2t temperature. It is preferable that it is smaller than the peak height of the exothermic peak.

The exothermic peak top P1t and P2t temperatures and the endothermic peak top P3t temperature represent the temperature at which the calorific value or endothermic amount in the exothermic peak P1, P2 or endothermic peak P3 is highest. The exothermic peaks P1 and P2 refer to the portion where the calorific value begins to rise from the baseline B (the temperature at that portion is the exothermic start temperature), and the calorific value decreases after reaching the exothermic peak tops P1t and P2t, and the calorific value decreases. It starts to increase again or represents the part where the calorific value reaches baseline B. The endothermic peak P3 refers to the endothermic amount falling from the part where the endothermic amount begins to rise from the baseline B (the temperature at that part is the endothermic start temperature), and after reaching the endothermic peak top P3t, the endothermic amount decreases, and the endothermic amount reaches the baseline B. It represents the part up to this point. In order to ensure that the exothermic peak top P1t and P2t temperatures and the endothermic peak top P3t temperature satisfy the above-mentioned relationship, the type of thermosetting compound in the thermosetting component, the type of thermosetting agent, and the composition of the solder in the conductive particles are appropriately adjusted. Just adjust it.

From the viewpoint of more efficiently disposing the solder on the electrode, the peak end temperature on the high temperature side of the endothermic peak resulting from melting of the solder in the conductive particles is the exothermic temperature on the highest temperature side resulting from curing of the thermosetting component. It is preferable that it is lower than the peak end temperature on the high temperature side of the peak. The peak end temperature on the high temperature side of the endothermic peak resulting from melting of the solder in the conductive particles is the temperature leading to the baseline B on the high temperature side of the endothermic peak P3 in FIG. 1. The peak end temperature on the high temperature side of the highest temperature side exothermic peak resulting from curing of the thermosetting component is the temperature leading to the base line B on the high temperature side of the exothermic peak P2 in FIG. 1.

From the viewpoint of more efficiently disposing the solder on the electrode, the peak onset temperature on the low temperature side of the endothermic peak resulting from melting of the solder in the conductive particles is the exothermic temperature on the lowest temperature side resulting from curing of the thermosetting component. It is preferable that it is higher than the peak onset temperature on the low temperature side of the peak. The peak onset temperature on the low-temperature side of the endothermic peak resulting from melting of the solder in the conductive particles is the temperature leading to the baseline B on the low-temperature side of the endothermic peak P3 in FIG. 1. The peak onset temperature on the low-temperature side of the lowest-temperature exothermic peak resulting from curing of the thermosetting component is the temperature leading to the base line B on the low-temperature side of the exothermic peak P1 in FIG. 1.

From the viewpoint of more efficiently disposing the solder on the electrode, the peak end temperature on the high temperature side of the endothermic peak resulting from melting of the solder in the conductive particles is the above. The peak start temperature on the low-temperature side of the endothermic peak derived from melting of the solder in the conductive particles is lower than the peak termination temperature on the high-temperature side of the highest-temperature exothermic peak resulting from curing of the thermosetting component. It is preferable that the peak onset temperature of the lowest temperature side exothermic peak resulting from curing of the thermosetting component is higher than the peak onset temperature on the low temperature side.

In order to arrange solder on the electrode more efficiently, the conductive material is preferably in a liquid state at 25°C, and is preferably a conductive paste.

In order to more efficiently place the solder on the electrode, the viscosity (η25) at 25°C of the conductive material is preferably 20 Pa·s or more, more preferably 25 Pa·s or more, and preferably 600 Pa·s or less. , more preferably 550 Pa·s or less. The viscosity of the conductive material at 25°C affects the movement speed of the conductive particles or solder at the initial stage of conductive connection.

In order to more efficiently place the solder on the electrode, the ratio of the viscosity (η25) of the conductive material at 25°C to the viscosity (η100) of the conductive material at 100°C is preferably 10 or more, more preferably is 80 or more, more preferably 100 or more, preferably 2500 or less, more preferably 2000 or less. The viscosity of the electrically conductive material at 100°C affects the movement speed of the conductive connection medium of the electrically conductive particles or solder. If the ratio (η25/η100) is equal to or greater than the lower limit and equal to or lower than the upper limit, the conductive particles or solder move efficiently from the initial stage to the middle stage during conductive connection.

The viscosity was measured using STRESSTECH (manufactured by EOLOGICA), etc. under conditions of strain control of 1 rad, frequency of 1 Hz, temperature increase rate of 20°C/min, and measurement temperature range of 25 to 200°C. possible.

In addition, the viscosity after holding the conductive material for 10 seconds at the exothermic peak top P1t temperature resulting from curing of the thermosetting component is preferably 1 Pa·s or more, more preferably 3 Pa·s or more, and preferably 10 Pa·s. s or less, more preferably 8 Pa·s or less. In addition, the viscosity after holding the conductive material for 10 seconds at the exothermic peak top P2t temperature resulting from curing of the thermosetting component is preferably 100 Pa·s or more, more preferably 110 Pa·s or more, and preferably 10000 Pa·s. s or less, more preferably 9500 Pa·s or less.

The above-mentioned electrically conductive material can be used as a conductive paste, a conductive film, etc. It is preferable that the above-mentioned conductive material is an anisotropic conductive material. It is preferable that the electrically conductive paste is an anisotropic electrically conductive paste. It is preferable that the conductive film is an anisotropic conductive film. The above-mentioned conductive material is suitably used for electrical connection of electrodes. It is preferable that the said electrically-conductive material is a circuit connection material.

Hereinafter, each component contained in the above-mentioned conductive material will be described.

(Conductive particles)

The electrically conductive particles electrically connect electrodes of connection target members. The electrically conductive particles have solder on the outer surface of the electrically conductive portion. The conductive particles may be solder particles. The solder particles are formed of solder. The solder particles have solder on the outer surface portion of the conductive portion. The solder particles are particles in which both the center portion of the solder particle and the outer surface portion of the conductive portion are solder. As for the solder particles, both the center portion and the outer surface portion of the conductive portion are formed of solder. The said electroconductive particle may have a substrate particle and an electroconductive part arrange|positioned on the surface of the said substrate particle. In this case, the conductive particles have solder on the outer surface portion of the conductive portion.

Furthermore, compared to the case where the above solder particles are used, when conductive particles including base particles not formed of solder and solder portions disposed on the surface of the base particles are used, it becomes difficult for the conductive particles to gather on the electrode, causing the conductive particles to separate from each other. Since solder bondability is low, conductive particles that have moved onto the electrode tend to move outside the electrode, and the effect of suppressing misalignment between electrodes also tends to be low. Therefore, it is preferable that the conductive particles are solder particles.

From the viewpoint of effectively lowering the connection resistance in the connection structure and effectively suppressing the generation of voids, it is preferable that a carboxyl group or an amino group is present on the outer surface of the conductive particles (outer surface of the solder), and the presence of a carboxyl group is preferable. It is preferable that an amino group is present. It is preferable that a group containing a carboxyl group or an amino group is covalently bonded to the outer surface of the conductive particle (outer surface of solder) through a Si-O bond, an ether bond, an ester bond, or a group represented by the following formula (X), , it is more preferable that a group containing a carboxyl group or an amino group is covalently bonded through an ether bond, an ester bond, or a group represented by the following formula (X). The group containing a carboxyl group or an amino group may contain both a carboxyl group and an amino group. In addition, in the following formula (X), the right end and left end represent binding sites.

Hydroxyl groups exist on the solder surface. By covalently bonding a group containing a hydroxyl group to a carboxyl group, a stronger bond can be formed than when bonding through other coordination bonds (chelate coordination), etc., thus lowering the connection resistance between electrodes and suppressing the generation of voids. Possible conductive particles are obtained.

In the above-described conductive particles, the form of bond between the solder surface and the group containing the carboxyl group does not need to include a coordination bond, nor does it need to include a bond by chelate coordination.

From the viewpoint of effectively lowering the connection resistance in the connection structure and effectively suppressing the generation of voids, the above-mentioned conductive particle is a compound (hereinafter sometimes referred to as compound It is preferable to obtain it by reacting the hydroxyl group on the solder surface with a functional group that can react with the hydroxyl group. In this reaction, a covalent bond is formed. By reacting a hydroxyl group on the solder surface with a functional group capable of reacting with the hydroxyl group in the compound It is also possible to obtain conductive particles in which a group containing a carboxyl group or an amino group is covalently bonded through an ester bond. By reacting a functional group capable of reacting with the hydroxyl group on the solder surface, the compound

Functional groups capable of reacting with the hydroxyl group include hydroxyl group, carboxyl group, ester group, and carbonyl group. Hydroxyl or carboxyl groups are preferred. The functional group capable of reacting with the hydroxyl group may be a hydroxyl group or a carboxyl group.

Compounds having a functional group capable of reacting with a hydroxyl group include levulinic acid, glutaric acid, glycolic acid, succinic acid, malic acid, oxalic acid, malonic acid, adipic acid, 5-ketohexanoic acid, 3-hydroxypropionic acid, and 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, pentadecane Acids, 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 dodecanediic acid. Examples include miscalculation. Glutaric acid or glycolic acid is preferred. Only one type of compound having a functional group capable of reacting with the hydroxyl group may be used, or two or more types may be used in combination. 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 A compound having a flux action can remove the oxide film on the solder surface and the oxide film on the electrode surface. The carboxyl group has a flux action.

Compounds having a flux effect include levulinic acid, glutaric acid, glycolic acid, succinic acid, 5-ketohexanoic acid, 3-hydroxypropionic acid, 4-aminobutyric acid, 3-mercaptopropionic acid, and 3-mercaptoisobutyric acid. , 3-methylthiopropionic acid, 3-phenylpropionic acid, 3-phenyl isobutyric acid, and 4-phenylbutyric acid. Glutaric acid or glycolic acid is preferred. Only one type of compound having the above flux action may be used, or two or more types may be used in combination.

From the viewpoint of effectively lowering the connection resistance in the connected structure and effectively suppressing the generation of voids, it is preferable that the functional group capable of reacting with the hydroxyl group in the compound X is a hydroxyl group or a carboxyl group. The functional group capable of reacting with the hydroxyl group in the compound When the functional group capable of reacting with the hydroxyl group is a carboxyl group, it is preferable that the compound X has at least two carboxyl groups. By reacting some of the carboxyl groups of a compound having at least two carboxyl groups with hydroxyl groups on the solder surface, conductive particles in which a group containing a carboxyl group is covalently bonded to the solder surface are obtained.

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

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

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. Only one type of the above catalyst may be used, and two or more types may be used in combination.

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

From the viewpoint of effectively lowering the connection resistance in the connection structure and effectively suppressing the generation of voids, the conductive particles are preferably obtained through a process of using an isocyanate compound and reacting the isocyanate compound with the hydroxyl group on the solder surface. do. In this reaction, a covalent bond is formed. By reacting the hydroxyl group on the solder surface with the above-mentioned isocyanate compound, conductive particles in which the nitrogen atom of the group derived from the isocyanate group is covalently bonded to the solder surface can be easily obtained. By reacting the isocyanate compound with the hydroxyl group on the solder surface, the group derived from the isocyanate group can be chemically bonded to the solder surface in the form of a covalent bond.

Additionally, a silane coupling agent can be easily reacted with a group derived from an isocyanate group. Since the above-described conductive particles can be easily obtained, the group containing the carboxyl group is introduced through a reaction using a silane coupling agent having a carboxyl group, or the carboxyl group is added to a group derived from the silane coupling agent after reaction using a silane coupling agent. It is preferable that it is introduced by reacting at least one compound. The conductive particles are preferably obtained by using the isocyanate compound to react with a hydroxyl group on the solder surface, and then reacting the isocyanate compound with a compound having at least one carboxyl group.

From the viewpoint of effectively lowering the connection resistance in the connected structure and effectively suppressing the generation of voids, it is preferable that the compound having at least one carboxyl group 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 solder surface, the remaining isocyanate group is reacted with a compound that is reactive with the remaining isocyanate group and also has a carboxyl group, so that a carboxyl group can be introduced to the solder surface through the group represented by the formula (X). .

As the isocyanate compound, a compound having an unsaturated double bond and an isocyanate group may be used. Examples include 2-acryloyloxyethyl isocyanate and 2-isocyanatoethyl methacrylate. After reacting the isocyanate group of this compound with the solder surface, reacting with a compound having a functional group reactive to the remaining unsaturated double bond and also having a carboxyl group, a carboxyl group is formed on the solder surface through the group represented by the above formula (X). can be introduced.

As the silane coupling agent, 3-isocyanate propyltriethoxysilane (“KBE-9007” manufactured by Shin-Etsu Silicone Co., Ltd.), 3-isocyanate propyltrimethoxysilane (“Y-5187” manufactured by MOMENTIVE Co., Ltd.), etc. can be mentioned. As for the said silane coupling agent, only one type may be used, and two or more types may be used together.

Examples of the compounds having at least one carboxyl group include levulinic acid, glutaric acid, glycolic 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. etc. can be mentioned. Glutaric acid, adipic acid or glycolic acid are preferred. Only one type of the compound having at least one carboxyl group may be used, or two or more types may be used in combination.

Using the isocyanate compound, a hydroxyl group on the solder surface is reacted with the isocyanate compound, and then a part of the carboxyl group of a compound having a plurality of carboxyl groups is reacted with a hydroxyl group on the solder surface, thereby allowing groups containing a carboxyl group to remain.

In the method for producing the conductive particles, conductive particles are used, and an isocyanate compound is used to react the isocyanate compound with the hydroxyl group on the solder surface, and then react with a compound having at least one carboxyl group, and then apply the above-described compound to the solder surface. Conductive particles to which a group containing a carboxyl group is bonded are obtained through the group represented by formula (X). In the method for producing conductive particles, conductive particles having a group containing a carboxyl group introduced into the solder surface can be easily obtained through the above process.

Specific methods for producing the electrically conductive particles include the following methods. Conductive 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 the hydroxyl group and the isocyanate group on the solder surface of the conductive particles. Next, the alkoxy group bonded to the silicon atom of the silane coupling agent is hydrolyzed to generate a hydroxyl group. The resulting hydroxyl group is reacted with the carboxyl group of a compound having at least one carboxyl group.

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

Catalysts for the reaction between the hydroxyl group and the isocyanate group on the solder surface of the conductive particles include tin-based catalysts (dibutyltin dilaurate, etc.), amine-based catalysts (triethylenediamine, etc.), and carboxylate catalysts (lead naphthenate, potassium acetate, etc.) ), and trialkylphosphine catalysts (triethylphosphine, etc.).

From the viewpoint of effectively lowering the connection resistance in the connected structure and effectively suppressing the generation of voids, the compound having at least one carboxyl group is preferably a compound represented by the following formula (1). The compound represented by the following formula (1) has a flux effect. Additionally, the compound represented by the following formula (1) has a flux effect when introduced into the solder surface.

In the above formula (1), X represents a functional group capable of reacting with a hydroxyl group, and R represents a divalent organic group having 1 to 5 carbon atoms. 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. The compound represented by the formula (1) includes, for example, 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 the above formula (1A), R represents a divalent organic group having 1 to 5 carbon atoms. R in the above formula (1A) is the same as R in the above formula (1).

In the formula (1B), R represents a divalent organic group having 1 to 5 carbon atoms. R in the formula (1B) is the same as R in the formula (1).

It is preferable that a group represented by the following formula (2A) or the following formula (2B) is bonded to the solder surface. It is preferable that the group represented by the following formula (2A) is bonded to the solder surface, and it is more preferable that the group represented by the following formula (2B) is bonded. In addition, in the following formula (2A) and the following formula (2B), the left end represents a binding site.

In the formula (2A), R represents a divalent organic group having 1 to 5 carbon atoms. R in the above formula (2A) is the same as R in the above formula (1).

In the formula (2B), R represents a divalent organic group having 1 to 5 carbon atoms. R in the formula (2B) is the same as R in the formula (1).

From the viewpoint of increasing the wettability of the solder surface, the molecular weight of the compound having at least one carboxyl group is preferably 10000 or less, more preferably 1000 or less, and still more preferably 500 or less.

The molecular weight refers to 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. In addition, when the compound having at least one carboxyl group is a polymer, it means the weight average molecular weight.

In order to effectively increase the cohesiveness of the conductive particles during conductive connection, it is preferable that the conductive particles have a conductive particle body and an anionic polymer disposed on the surface of the conductive particle body. The conductive particles are preferably obtained by surface treating the conductive particle body with an anionic polymer or a compound that becomes an anionic polymer. The conductive particles are preferably surface-treated with an anionic polymer or a compound that becomes an anionic polymer. Only one type of the anionic polymer and the compound forming the anionic polymer may be used, or two or more types may be used in combination. The anionic polymer is a polymer having an acidic group.

A method of surface treating the conductive particle body with an anionic polymer includes, for example, (meth)acrylic polymer copolymerized with (meth)acrylic acid, polyester synthesized from dicarboxylic acid and diol and having carboxyl groups at both ends. Polymers, polymers obtained by intermolecular dehydration condensation reaction of dicarboxylic acids and having carboxyl groups at both ends, polyester polymers synthesized from dicarboxylic acids and diamines and having carboxyl groups at both ends, and modified poly having carboxyl groups. A method of reacting the carboxyl group of the anionic polymer with the hydroxyl group on the surface of the conductive particle body using vinyl alcohol (“Gosenex T” manufactured by Nippon Kosei Chemical Co., Ltd.) or the like can be cited.

Examples of the anionic moiety of the anionic polymer include the carboxyl group, and others include tosyl group (pH ₃ CC ₆ H ₄ S(=O) ₂ -), sulfonic acid ion group (-SO ₃ ^- ), and phosphate ion group ( -PO ₄ ^- ), etc. may be mentioned.

In addition, as another method of surface treatment, a compound having a functional group that reacts with a hydroxyl group on the surface of the conductive particle body and a functional group that can be polymerized through addition and condensation reactions is used, and this compound is applied on the surface of the conductive particle body. A method of polymerizing is included. Functional groups that react with the hydroxyl group on the surface of the conductive particle main body include carboxyl groups and isocyanate groups, and functional groups that polymerize by addition and condensation reactions include hydroxyl groups, carboxyl groups, amino groups, and (meth)acryloyl groups. .

The weight average molecular weight of the anionic polymer is preferably 2000 or more, more preferably 3000 or more, preferably 10000 or less, and more preferably 8000 or less. If the weight average molecular weight is equal to or greater than the lower limit and equal to or lower than the upper limit, a sufficient amount of charge and flux can be introduced into the surface of the conductive particles. As a result, the cohesion of the conductive particles can be effectively increased during conductive connection, and the oxide film on the electrode surface can be effectively removed when connecting the member to be connected.

If the weight average molecular weight is equal to or greater than the lower limit and equal to or lower than the upper limit, it is easy to arrange the anionic polymer on the surface of the conductive particle body, the cohesiveness of the solder particles can be effectively increased during conductive connection, and the conductive particles can be further placed on the electrode. Can be deployed efficiently.

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

The weight average molecular weight of the anionic polymer can be determined by dissolving the solder in the conductive particles, removing the conductive particles with diluted hydrochloric acid or the like, which does not cause decomposition of the anionic polymer, and then measuring the weight average molecular weight of the remaining anionic polymer.

Regarding the amount of anionic polymer introduced onto the surface of the conductive particles, the acid value per 1g of conductive particles is preferably 1 mgKOH or more, more preferably 2 mgKOH or more, preferably 10 mgKOH or less, more preferably Typically, it is less than 6mgKOH.

The acid value can be measured as follows. 1 g of conductive particles was added to 36 g of acetone and dispersed by ultrasonic waves for 1 minute. Thereafter, titration is performed with 0.1 mol/L potassium hydroxide ethanol solution using phenolphthalein as an indicator.

Next, specific examples of conductive particles will be described with reference to the drawings.

Fig. 5 is a cross-sectional view showing a first example of conductive particles that can be used in an electrically conductive material.

The conductive particles 21 shown in FIG. 5 are solder particles. The conductive particles 21 are formed entirely of solder. The conductive particles 21 do not have substrate particles in their cores and are not core-shell particles. As for the conductive particles 21, both the center portion and the outer surface portion of the conductive portion are formed with solder.

Fig. 6 is a cross-sectional view showing a second example of conductive particles that can be used in electrically conductive materials.

The electroconductive particle 31 shown in FIG. 6 is provided with the substrate particle 32 and the electrically conductive part 33 arrange|positioned on the surface of the substrate particle 32. The conductive portion 33 covers the surface of the substrate particle 32. The electrically conductive particles 31 are coated particles in which the surface of the substrate particle 32 is covered with the electrically conductive portion 33 .

The conductive portion 33 has a second conductive portion 33A and a solder portion 33B (first conductive portion). The conductive particles 31 include a second conductive portion 33A between the substrate particles 32 and the solder portion 33B. Therefore, the conductive particles 31 include the substrate particles 32, the second conductive portion 33A disposed on the surface of the substrate particle 32, and the solder portion disposed on the outer surface of the second conductive portion 33A. (33B) is provided.

Fig. 7 is a cross-sectional view showing a third example of conductive particles that can be used in electrically conductive materials.

As described above, the conductive portion 33 in the conductive particles 31 has a two-layer structure. The conductive particle 41 shown in FIG. 7 is a single-layer conductive portion and has a solder portion 42. The electroconductive particle 41 includes a substrate particle 32 and a solder portion 42 disposed on the surface of the substrate particle 32.

Examples of the substrate particles include resin particles, inorganic particles excluding metal particles, organic-inorganic hybrid particles, and metal particles. It is preferable that the said substrate particle is a substrate particle excluding a metal, and it is preferable that it is a resin particle, an inorganic particle excluding a metal particle, or an organic-inorganic hybrid particle. The substrate particles may be copper particles. The substrate particle may have a core and a shell disposed on the surface of the core, or may be a core-shell particle. The core may be an organic core, and the shell may be an inorganic shell.

As a resin for forming the resin particles, various organic substances are suitably used. Resins for forming the resin particles include, for example, polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; Acrylic resins such as polymethyl methacrylate and polymethyl acrylate; Polycarbonate, polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester. Resin, saturated polyester resin, polyethylene terephthalate, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyamidoimide, polyetheretherketone, polyethersulfone, divinylbenzene polymer, and divinylbenzene-based copolymer. etc. can be mentioned. Examples of the divinylbenzene-based copolymer include divinylbenzene-styrene copolymer and divinylbenzene-(meth)acrylic acid ester copolymer. Since the hardness of the resin particles can be easily controlled to an appropriate range, the resin for forming the resin particles is preferably a polymer obtained by polymerizing one or two or more types of polymerizable monomers having an ethylenically unsaturated group.

When the resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, examples of the polymerizable monomer having an ethylenically unsaturated group include non-crosslinkable monomers and crosslinkable monomers.

Examples of the non-crosslinkable monomer include styrene-based monomers such as styrene and α-methylstyrene; Carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; Methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth) Alkyl (meth)acrylate compounds such as acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; oxygen atom-containing (meth)acrylate compounds such as 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate; Nitrile-containing monomers such as (meth)acrylonitrile; Vinyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, and propyl vinyl ether; Acid vinyl ester compounds such as vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate; Unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene; and halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene.

Examples of the crosslinkable monomer include tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, and trimethylolpropane tri(meth)acrylate. Latex, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate polyfunctional (meth)acrylate compounds such as polyester, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; Triallyl (iso) cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, and γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilyl. and silane-containing monomers such as styrene and vinyltrimethoxysilane.

The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group by a known method. Examples of this method include a method of performing suspension polymerization in the presence of a radical polymerization initiator, and a method of polymerizing the monomer by swelling it with a radical polymerization initiator using non-crosslinked seed particles.

When the substrate particles are inorganic particles other than metal or organic-inorganic hybrid particles, examples of the inorganic material for forming the substrate particles include silica, alumina, barium titanate, zirconia, and carbon black. It is preferable that the inorganic material is not a metal. The particles formed from the above silica are not particularly limited, but examples include particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, and then performing baking as necessary. there is. Examples of the organic-inorganic hybrid particles include organic-inorganic hybrid particles formed of a crosslinked alkoxysilyl polymer and an acrylic resin.

When the substrate particles are metal particles, examples of metals for forming the metal particles include silver, copper, nickel, silicon, gold, and titanium. When the substrate particles are metal particles, it is preferable that the metal particles are copper particles. However, it is preferable that the substrate particles are not metal particles.

The particle diameter of the substrate particle is preferably 0.1 μm or more, more preferably 1 μm or more, further preferably 1.5 μm or more, particularly preferably 2 μm or more, preferably 100 μm or less, more preferably is 50 μm or less, more preferably 40 μm or less, further preferably 20 μm or less, further preferably 10 μm or less, particularly preferably 5 μm or less, and most preferably 3 μm or less. If the particle diameter of the substrate particle is more than the above lower limit, the contact area between the conductive particles and the electrode increases, so the reliability of conduction between electrodes can be further improved, and the connection resistance between electrodes connected through the conductive particles can be further lowered. You can. If the particle diameter of the substrate particle is below the above upper limit, the conductive particles are easily compressed, the connection resistance between electrodes can be further lowered, and the gap between electrodes can be further reduced.

When the substrate particle is spherical, the particle diameter of the substrate particle represents the diameter, and when the substrate particle is not spherical, it represents the maximum diameter.

It is especially preferable that the particle diameter of the said substrate particle is 2 micrometers or more and 5 micrometers or less. If the particle diameter of the substrate particles is within the range of 2 μm or more and 5 μm or less, the space between electrodes can be made smaller, and even if the thickness of the conductive portion is increased, small conductive particles can be obtained.

The method of forming an electrically conductive portion on the surface of the substrate particle and the method of forming a solder portion on the surface of the substrate particle or the surface of the second electrically conductive portion are not particularly limited. Methods for forming the conductive portion and the solder portion include, for example, electroless plating, electroplating, physical collision, mechanochemical reaction, physical vapor deposition, or physical adsorption. and a method of coating the surface of the base particle with a paste containing metal powder or a metal powder and a binder. Methods using electroless plating, electroplating, or physical impact are suitable. Examples of the physical vapor deposition method include vacuum deposition, ion plating, and ion sputtering. In addition, in the method using physical collision, for example, Theta Composer (manufactured by Tokuju Kosakusho Co., Ltd.) is used.

The melting point of the substrate particles is preferably higher than the melting points of the conductive portion and the solder portion. The melting point of the substrate particles is preferably greater than 160°C, more preferably greater than 300°C, further preferably greater than 400°C, and particularly preferably greater than 450°C. Additionally, the melting point of the substrate particles may be less than 400°C. The melting point of the substrate particles may be 160°C or lower. The softening point of the substrate particles is preferably 260°C or higher. The softening point of the substrate particles may be less than 260°C.

The conductive particles may have a single-layer solder portion. The conductive particles may have multiple layers of conductive portions (solder portion, second conductive portion). That is, in the above-described conductive particles, two or more layers of conductive portions may be laminated. When the conductive portion has two or more layers, the conductive particles preferably have solder on the outer surface of the conductive portion.

The solder is preferably a metal with a melting point of 450°C or lower (low melting point metal). The solder portion is preferably a metal layer (low melting point metal layer) with a melting point of 450°C or lower. The low melting point metal layer is a layer containing a low melting point metal. The solder in the conductive particles is preferably a metal particle (low melting point metal particle) with 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 refers to a metal with 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. Additionally, it is preferable that the solder in the conductive particles contains tin. Among 100% by weight of metal contained in the solder portion and 100% by weight of metal contained in the solder in the conductive particles, the tin content is preferably 30% by weight or more, more preferably 40% by weight or more, and further. Preferably it is 70% by weight or more, particularly preferably 90% by weight or more. If the content of tin contained in the solder in the conductive particles is more than the above lower limit, the reliability of conduction between the conductive particles and the electrode increases further.

In addition, the tin content was determined using a high-frequency inductively coupled plasma emission spectrometer (“ICP-AES” manufactured by Horiba Seisakusho Co., Ltd.) or a fluorescence X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Seisakusho Co., Ltd.). It can be measured.

By using conductive particles having the solder on the outer surface portion of the electrically conductive portion, the solder is melted and bonded to the electrode, allowing the solder to conduct electricity between the electrodes. For example, since the solder and the electrode are likely to make surface contact rather than point contact, the connection resistance is lowered. In addition, the use of conductive particles having solder on the outer surface of the conductive portion increases the bonding strength between the solder and the electrode, making it more difficult for the solder and the electrode to peel off, effectively increasing conduction reliability.

The low melting point metal constituting the solder portion and the solder particles is not particularly limited. The low melting point metal is preferably tin or an alloy containing tin. The alloy may include tin-silver alloy, tin-copper alloy, tin-silver-copper alloy, tin-bismuth alloy, tin-zinc alloy, tin-indium alloy, etc. In terms of excellent wettability to the electrode, the low melting point metal is preferably tin, tin-silver alloy, tin-silver-copper alloy, tin-bismuth alloy, or tin-indium alloy. It is more preferable that it is a tin-bismuth alloy or a tin-indium alloy.

The material constituting the solder (solder portion) is preferably a filler material with a liquidus line of 450°C or lower based on JIS Z3001: Welding Terminology. Examples of the composition of the solder include metal compositions containing zinc, gold, silver, lead, copper, tin, bismuth, indium, etc. A tin-indium system (eutectic at 117°C) or a tin-bismuth system (eutectic at 139°C) that has a low melting point and is lead-free is preferred. That is, the solder preferably does not contain lead, and is preferably a solder containing tin and indium, or a solder containing tin and bismuth.

In order to further increase the bonding strength between the solder and the electrode, the solder in the conductive particles contains nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium, cobalt, bismuth, and manganese. , may contain metals such as chromium, molybdenum, and palladium. Additionally, from the viewpoint of further increasing the bonding strength between the solder and the electrode, it is preferable that the solder in the conductive particles contains nickel, copper, antimony, aluminum, or zinc. From the viewpoint of further increasing the bonding strength between the solder and the electrode in the solder portion or the conductive particles, the content of these metals for increasing the bonding strength is preferably 0.0001% by weight based on 100% by weight of solder in the conductive particles. or more, and preferably 1% by weight or less.

The melting point of the second conductive portion is preferably higher than the melting point of the solder portion. The melting point of the second conductive portion is preferably greater than 160°C, more preferably greater than 300°C, still more preferably greater than 400°C, even more preferably greater than 450°C, and particularly preferably Exceeding 500°C, most preferably exceeding 600°C. Because the solder portion has a low melting point, it melts during conductive connection. It is preferable that the second conductive portion does not melt during conductive connection. The conductive particles are preferably used by melting the solder, preferably by melting the solder portion, and are preferably used by melting the solder portion without melting the second conductive portion. Since the melting point of the second conductive portion is higher than the melting point of the solder portion, only the solder portion can be melted without melting the second conductive portion during conductive connection.

The absolute value of the difference between the melting point of the solder portion and the melting point of the second conductive portion exceeds 0°C, preferably 5°C or higher, more preferably 10°C or higher, further preferably 30°C or higher, particularly preferably is 50°C or higher, most preferably 100°C or higher.

The second conductive portion preferably includes metal. The metal constituting the second conductive portion is not particularly limited. Examples of the metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium, and cadmium, and alloys thereof. . Additionally, as the metal, tin-doped indium oxide (ITO) may be used. Only one type of the above metal may be used, and two or more types may be used together.

The second conductive portion is preferably a nickel layer, a palladium layer, a copper layer, or a gold layer, more preferably a nickel layer or a gold layer, and still more preferably a copper layer. The conductive particles preferably have a nickel layer, a palladium layer, a copper layer, or a gold layer, more preferably have a nickel layer or a gold layer, and even more preferably have a copper layer. By using conductive particles having these preferable conductive parts for the connection between electrodes, the connection resistance between electrodes is further lowered. Additionally, solder portions can be formed much more easily on the surfaces of these preferable conductive portions.

The thickness of the solder portion is preferably 0.005 μm or more, more preferably 0.01 μm or more, preferably 10 μm or less, more preferably 1 μm or less, and even more preferably 0.3 μm or less. If the thickness of the solder portion is more than the above lower limit and less than the above upper limit, sufficient conductivity is obtained, and the conductive particles do not become too hard and are sufficiently deformed during connection between electrodes.

The average particle diameter of the conductive particles is preferably 0.5 μm or more, more preferably 1 μm or more, further preferably 3 μm or more, preferably 100 μm or less, more preferably 50 μm or less, even more preferably Typically, it is 40 μm or less, particularly preferably 30 μm or less. If the average particle diameter of the conductive particles is equal to or greater than the lower limit and equal to or less than the upper limit, the solder in the conductive particles can be placed on the electrodes more efficiently, and it is easy to place a large amount of solder in the conductive particles between the electrodes. As a result, conduction reliability is further improved.

The “average particle diameter” of the electrically conductive particles represents the number average particle diameter. The average particle diameter of the conductive particles is determined by, for example, observing 50 arbitrary conductive particles with an electron microscope or an optical microscope and calculating the average value.

The shape of the conductive particles is not particularly limited. The shape of the conductive particles may be spherical or may be a shape other than a spherical shape, such as a flat shape.

Among 100% by weight of the electrically conductive material, the content of the conductive particles is preferably 1% by weight or more, more preferably 2% by weight or more, further preferably 10% by weight or more, particularly preferably 20% by weight or more. Preferably it is 30% by weight or more, preferably 80% by weight or less, more preferably 60% by weight or less, and even more preferably 50% by weight or less. If the content of the conductive particles is more than the lower limit and less than the upper limit, the solder in the conductive particles can be placed on the electrodes more efficiently, and it is easy to place a large amount of solder in the conductive particles between the electrodes. Continuity reliability is further improved. From the viewpoint of further improving conduction reliability, it is preferable that the content of the conductive particles is higher.

(thermosetting compound)

The thermosetting compound is a compound that can be cured by heating. Examples of the thermosetting compounds include oxetane compounds, epoxy compounds, episulfide compounds, (meth)acrylic compounds, phenol compounds, amino compounds, unsaturated polyester compounds, polyurethane compounds, silicone compounds, and polyimide compounds. From the viewpoint of further improving the curability and viscosity of the electrically conductive material and further improving connection reliability, an epoxy compound or an episulfide compound is preferable, and an epoxy compound is more preferable. The electrically conductive material preferably contains an epoxy compound. As for the said thermosetting compound, only 1 type may be used, and 2 or more types may be used together.

From the viewpoint of further suppressing corrosion of the electrode and keeping the connection resistance even lower, the thermosetting compound preferably contains a thermosetting compound having a nitrogen atom, and preferably contains a thermosetting compound having a triazine skeleton. do.

Examples of the thermosetting compound having the nitrogen atom include triazine triglycidyl ether, and the TEPIC series (TEPIC-G, TEPIC-S, TEPIC-SS, TEPIC-HP, TEPIC-L, TEPIC) manufactured by Nissan Chemical Industries, Ltd. -PAS, TEPIC-VL, TEPIC-UC), etc.

Examples of the epoxy compound include aromatic epoxy compounds. Crystalline epoxy compounds such as resorcinol-type epoxy compounds, naphthalene-type epoxy compounds, biphenyl-type epoxy compounds, and benzophenone-type epoxy compounds are preferable. An epoxy compound that is solid at room temperature (23°C) and has a melting temperature below the melting point of solder is preferred. The melting temperature is preferably 100°C or lower, more preferably 80°C or lower, and preferably 40°C or higher. In the step of joining the connection target members by using the above-mentioned preferred epoxy compound, the viscosity is high, and when acceleration is applied due to impact such as conveyance, positional deviation of the first connection target member and the second connection target member can be suppressed. Moreover, the viscosity of the conductive material can be greatly reduced by the heat during curing, and agglomeration of the solder can be promoted efficiently.

Among 100% by weight of the electrically conductive material, the content of the thermosetting compound is preferably 20% by weight or more, more preferably 40% by weight or more, further preferably 50% by weight or more, and preferably 99% by weight or less. More preferably, it is 98 weight% or less, further preferably 90 weight% or less, and particularly preferably 80 weight% or less. If the content of the thermosetting compound is more than the lower limit and less than the upper limit, the solder in the conductive particles can be placed on the electrodes more efficiently, positional misalignment between the electrodes is further suppressed, and the reliability of conduction between the electrodes is further improved. It can be raised higher. From the viewpoint of further improving impact resistance, it is preferable that the content of the thermosetting compound is higher. From the viewpoint of further improving the curability and viscosity of the conductive material and further improving connection reliability, the content of the epoxy compound in 100% by weight of the conductive material is preferably 10% by weight or more, more preferably 15% by weight. It is more than weight%, Preferably it is 50 weight% or less, More preferably, it is 30 weight% or less.

(thermal curing agent)

The thermosetting agent thermocures the thermosetting compound. Examples of the thermal curing agent include imidazole curing agents, phenol curing agents, thiol curing agents, amine curing agents, acid anhydride curing agents, thermal cationic initiators (thermal cationic curing agents), and thermal radical generators. As for the said thermosetting agent, only 1 type may be used, and 2 or more types may be used together.

The imidazole curing agent is not particularly limited and includes 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, and 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-triazine isocyanuric acid adduct, etc. can be mentioned.

The thiol curing agent is not particularly limited and includes trimethylolpropane tris-3-mercaptopropionate, pentaerythritol tetrakis-3-mercaptopropionate, and dipentaerythritol hexa-3-mercaptopropionate. etc. can be mentioned.

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

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

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

The thermal radical generator is not particularly limited and includes 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 start temperature of the thermosetting agent is preferably 50°C or higher, more preferably 70°C or higher, further preferably 80°C or higher, preferably 250°C or lower, more preferably 200°C or lower, even more preferably Typically, it is 150°C or lower, particularly preferably 140°C or lower. If the reaction start temperature of the thermosetting agent is equal to or higher than the lower limit and equal to or lower than the upper limit, the solder is disposed on the electrode more efficiently. It is particularly preferable that the reaction start temperature of the thermosetting agent is 80°C or higher and 140°C or lower.

From the viewpoint of more efficiently disposing the solder on the electrode, the reaction start temperature of the thermosetting agent is preferably higher than the melting point of the solder in the conductive particles, more preferably 5°C or higher, and 10°C or higher. It is more desirable.

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

The content of the thermosetting agent is not particularly limited. With respect to 100 parts by weight of the thermosetting compound, the content of the thermosetting agent is preferably 0.01 part 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 or less. , more preferably 75 parts by weight or less. If the content of the thermosetting agent is more than the above lower limit, it is easy to sufficiently cure the conductive material. If the content of the thermosetting agent is below the above upper limit, it becomes difficult for excess thermosetting agent that was not involved in curing to remain after curing, and the heat resistance of the cured product further increases.

(flux)

The electrically conductive material preferably contains flux. By using flux, solder can be placed on the electrode more effectively. The flux is not particularly limited. As the flux, a flux generally used in solder joints and the like can be used. The above-mentioned conductive material does not need to contain flux.

Examples of the flux include zinc chloride, mixtures of zinc chloride and inorganic halides, mixtures of zinc chloride and inorganic acids, molten salts, phosphoric acid, derivatives of phosphoric acid, organic halides, hydrazine, organic acids, and pine resin. Only one type of the above flux may be used, or two or more types may be used together.

Examples of the molten salt include ammonium chloride. Examples of the organic acids include lactic acid, citric acid, stearic acid, glutamic acid, and glutaric acid. Examples of the resin include activated resin and deactivated resin. The flux is preferably an organic acid or resin having two or more carboxyl groups. The flux may be an organic acid having two or more carboxyl groups, or pine resin may be used. By using an organic acid or rosin having two or more carboxyl groups, the reliability of conduction between electrodes is further improved.

The rosin is a type of rosin containing abietic acid as its main component. The flux is preferably rosin, and more preferably abietic acid. By using this preferred flux, the reliability of conduction between electrodes is further improved.

The activation 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. More preferably, it is 160°C or lower, even more preferably 150°C or lower, and even more preferably 140°C or lower. If the activation temperature of the flux is equal to or higher than the lower limit and equal to or lower than the upper limit, the flux effect is exerted more effectively, and the solder is disposed on the electrode more efficiently. The activation temperature (melting point) of the flux is preferably 80°C or higher and 190°C or lower. It is particularly preferable that the activation temperature (melting point) of the flux is 80°C or higher and 140°C or lower.

The flux whose activation temperature (melting point) is 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), and pimelic acid (melting point 104°C). ), dicarboxylic acids such as suberic acid (melting point 142°C), benzoic acid (melting point 122°C), and malic acid (melting point 130°C).

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

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

From the viewpoint of more efficiently disposing 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 more higher, and even more preferably 10°C or more higher.

The flux may be dispersed in the conductive material or may adhere to the surface of the conductive particles.

Since the melting point of the flux is higher than the melting point of the solder, the solder can be efficiently coagulated in the electrode portion. This means that when heat is applied at the time of joining, when comparing the electrode formed on the connection target member and the portion of the connection target member around the electrode, the thermal conductivity of the electrode portion is higher than the thermal conductivity of the connection target member portion around the electrode. This is due to the rapid temperature rise of the part. At the stage where the melting point of the solder in the conductive particles is exceeded, the solder in the conductive particles is dissolved, but the oxide film formed on the surface is not removed because it has not reached the melting point (activation temperature) of the flux. In this state, since the temperature of the electrode portion first reaches the melting point (activation temperature) of the flux, the oxide film on the solder surface on the conductive particles that reached the electrode is removed preferentially, and the conductive particles are removed by the activated flux. By neutralizing the electric charge on the solder surface, the solder can spread on the surface of the electrode. Thereby, the solder can be efficiently aggregated on the electrode.

The flux is preferably a flux that releases positive ions when heated. By using a flux that releases positive ions when heated, solder can be placed on the electrode even more efficiently.

Examples of the flux that releases positive ions by heating include the thermal cationic initiator.

Among 100% by weight of the electrically conductive material, the content of the flux is preferably 0.5% by weight or more, preferably 30% by weight or less, and more preferably 25% by weight or less. If the flux content is more than the above lower limit and below the above upper limit, it becomes more difficult for an oxide film to form on the surface of the solder and the electrode, and the oxide film formed on the surface of the solder and the electrode can be removed more effectively.

(other ingredients)

The electrically conductive material may, if necessary, contain various additives such as fillers, extenders, softeners, plasticizers, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, and flame retardants. It may include .

(Connection structure and method of manufacturing the connection structure)

The connection structure according to the present invention includes a first connection target member having at least one first electrode on its surface, a second connection target member having at least one second electrode on its surface, the first connection target member, and the above A connection portion connecting the second connection target member is provided. In the connection structure according to the present invention, the material of the connection part is the above-described conductive material, and the connection part is a cured product of the above-mentioned conductive material. 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 includes the steps of using the above-described conductive material to dispose the conductive material on the surface of a first connection target member having at least one first electrode on the surface, and the first electrode of the conductive material. 1 A step of arranging a second connection target member having at least one second electrode on the surface on a surface opposite to the connection target member side so that the first electrode and the second electrode face each other, and the conductive particles By heating the conductive material above the melting point of the solder, a connection portion connecting the first connection target member and the second connection target member is formed by the conductive material, and the first electrode and the second connection target member are formed by heating the conductive material above the melting point of the solder. A step of electrically connecting two electrodes using a solder portion in the connection portion is provided. Preferably, the conductive material is heated above the curing temperature of the thermosetting component and thermosetting compound.

In the bonded structure and the manufacturing method of the bonded structure according to the present invention, since a specific conductive material is used, the solder in the plurality of conductive particles is likely to collect between the first electrode and the second electrode, and the solder is applied to the electrode (line ) can be placed efficiently on top. Additionally, it is difficult for a part of the solder to be placed in the area (space) where the electrode is not formed, so the amount of solder placed in the area where the electrode is not formed can be significantly reduced. Accordingly, the reliability of conduction between the first electrode and the second electrode can be improved. In addition, electrical connection between horizontally adjacent electrodes that should not be connected can be prevented, thereby improving insulation reliability.

In addition, in order to efficiently arrange the solder in the plurality of conductive particles on the electrode and to significantly reduce the amount of solder placed in the area where the electrode is not formed, it is preferable to use a conductive paste rather than a conductive film. .

The thickness of the solder portion between electrodes is preferably 10 μm or more, more preferably 20 μm or more, preferably 100 μm or less, and more preferably 80 μm or less. The solder wet area (area in contact with solder out of 100% of the exposed area of the electrode) on the surface of the electrode is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. In other words, it is 100% or less.

In the method of manufacturing a connected structure according to the present invention, in the step of disposing the second connection target member and the step of forming the connection portion, no pressurization is performed, and the weight of the second connection target member is applied to the conductive material. Preferably, in the step of arranging the second connection target member and the step of forming the connection portion, a pressing pressure exceeding the force of the weight of the second connection target member is not applied to the conductive material. It is desirable. In these cases, the uniformity of the solder amount in the plurality of solder portions can be further improved. In addition, the thickness of the solder portion can be increased more effectively, and a large amount of solder from the plurality of conductive particles is more likely to collect between the electrodes, so that the solder from the plurality of conductive particles can be transferred onto the electrode (line) more efficiently. It can be placed. In addition, it is difficult for a part of the solder in the plurality of conductive particles to be placed in the area (space) where the electrode is not formed, so the amount of solder in the conductive particles placed in the area where the electrode is not formed can be further reduced. You can. Therefore, the reliability of conduction between electrodes can be further improved. In addition, electrical connection between horizontally adjacent electrodes that should not be connected can be further prevented, and insulation reliability can be further improved.

Additionally, 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 applied to the conductive material without applying pressure, the electrode will form before the connection portion is formed. The solder placed in this unformed area (space) becomes more likely to gather between the first electrode and the second electrode, making it possible to place the solder in a plurality of conductive particles on the electrode (line) more efficiently. I also found out that it can be done. In the present invention, a combination of 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 applied to the conductive paste without applying pressure includes the following: It is of great significance to obtain the effect at a higher level.

In addition, WO 2008/023452 A1 describes that from the viewpoint of efficiently moving solder powder by flowing it to the surface of the electrode, applying pressure to a predetermined pressure during adhesion is sufficient, and the applied pressure allows the area of solder to be more reliably located. From the viewpoint of formation, it is described that the pressure is, for example, 0 MPa or more, preferably 1 MPa or more, and even if the pressure intentionally applied to the adhesive tape is 0 MPa, the self-weight of the member disposed on the adhesive tape causes pressure to be applied to the adhesive tape. It is described that a certain pressure may be applied. In WO 2008/023452 A1, it is described that the pressure intentionally applied to the adhesive tape may be 0 MPa, but the difference in effect between applying a pressure exceeding 0 MPa and 0 MPa is not described at all. Additionally, in WO 2008/023452 A1, the importance of using a conductive paste in the form of a paste rather than a film is not recognized at all.

Additionally, if a conductive paste is used instead of a conductive film, it becomes easy to adjust the thickness of the connection portion and the solder portion depending on the amount of conductive paste applied. On the other hand, with conductive films, there is a problem that in order to change or adjust the thickness of the connection portion, a conductive film with a different thickness must be prepared or a conductive film with a predetermined thickness must be prepared. In addition, in a conductive film, compared to a conductive paste, the melt viscosity of the conductive film cannot be sufficiently lowered at the melting temperature of the solder, and the cohesion of the solder tends to be inhibited.

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

FIG. 2 is a cross-sectional view schematically showing a bonded structure obtained using a conductive material according to an embodiment of the present invention.

The connection structure 1 shown in FIG. 2 includes a first connection target member 2, a second connection target member 3, and a first connection target member 2 and a second connection target member 3. It is provided with a connecting portion (4) that is connected. The connection portion 4 is formed of the above-described electrically conductive material. In this embodiment, the electrically conductive material contains solder particles as electrically conductive particles.

The connection portion 4 has a solder portion 4A in which a plurality of solder particles are gathered and joined together, and a cured portion 4B in which a thermosetting component is thermoset.

The first connection target member 2 has a plurality of first electrodes 2a on its surface (upper surface). The second connection target member 3 has a plurality of second electrodes 3a on its surface (lower surface). The first electrode 2a and the second electrode 3a are electrically connected by a 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 addition, in the connection portion 4, there is no solder in a region (cured portion 4B portion) different from the solder portion 4A gathered between the first electrode 2a and the second electrode 3a. . In a region different from the solder portion 4A (cured portion 4B portion), there is no solder spaced apart from the solder portion 4A. Additionally, if it is a small amount, solder may be present in an area (cured material portion 4B portion) different from the solder portion 4A gathered between the first electrode 2a and the second electrode 3a.

As shown in FIG. 2, in the connection structure 1, a plurality of solder particles gather between the first electrode 2a and the second electrode 3a, and after the plurality of solder particles are melted, the solder particles The melt spreads on the surface of the electrode and then solidifies, forming the solder portion 4A. For this reason, the connection areas between the solder portion 4A and the first electrode 2a and the solder portion 4A and the second electrode 3a increase. That is, by using solder particles, compared to the case of using conductive particles in which the outer surface portion of the conductive portion is a metal such as nickel, gold, or copper, the solder portion 4A, the first electrode 2a, and the solder portion 4A ) and the contact area between the second electrode 3a increases. For this reason, the conduction reliability and connection reliability in the connection structure 1 increase.

Additionally, the conductive material may contain flux. When flux is used, the flux is generally gradually deactivated by heating.

In addition, in the connection structure 1 shown in FIG. 2, all solder portions 4A are located in opposing areas between the first and second electrodes 2a and 3a. The connected structure 1X of the modified example shown in FIG. 4 is different from the connected structure 1 shown in FIG. 2 only in the connection portion 4X. The connection portion 4X has a solder portion 4XA and a cured portion 4XB. Like the connection structure 1X, most of the solder portion 4XA is located in the area where the first and second electrodes 2a and 3a face each other, and a portion of the solder portion 4XA is located at the first and second electrodes 2a and 3a. It may protrude laterally from the opposing areas of the electrodes 2a and 3a. The solder portion 4XA protruding laterally from the opposing area of the first and second electrodes 2a and 3a is a part of the solder portion 4XA and is not solder spaced apart from the solder portion 4XA. . Additionally, in this embodiment, the amount of solder spaced apart from the solder portion can be reduced, but the solder spaced apart from the solder portion may be present in the cured portion.

If the amount of solder particles used is reduced, it becomes easier to obtain the connection structure 1. If the amount of solder particles used increases, it becomes easier to obtain the bonded structure 1X.

From the viewpoint of further improving conduction reliability, when viewing the opposing portions of the first electrode and the second electrode in the stacking direction of the first electrode, the connection portion, and the second electrode, the first electrode and the second electrode 50% or more (more preferably 60% or more, further preferably 70% or more, particularly preferably 80% or more, most preferably 90% or more) of 100% of the area of the opposing portion of the second electrode. , it is preferable that the solder portion in the connection portion is disposed.

From the viewpoint of further improving conduction reliability, when viewing the opposing portions of the first electrode and the second electrode in the stacking direction of the first electrode, the connection portion, and the second electrode, the first electrode and the second electrode With regard to the ratio of the area where the solder portion in the connection portion is disposed in 100% of the area of the opposing portion of the second electrode, the difference between the ratio of the area at the central electrode and the ratio of the area at the outer peripheral electrode is preferably is less than 15%, more preferably less than 10%, and even more preferably less than 5%.

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

First, the first connection target member 2 having the first electrode 2a on its surface (upper surface) is prepared. Next, as shown in FIG. 3(a), the electrically conductive material 11 containing the thermosetting component 11B and a plurality of solder particles 11A is disposed on the surface of the first connection target member 2. (1st process). The electrically-conductive material 11 used is a thermosetting component 11B and contains a thermosetting compound and a thermosetting agent.

The conductive material 11 is disposed on the surface of the first connection target member 2 on which the first electrode 2a is installed. After the conductive material 11 is disposed, the solder particles 11A are disposed on both the first electrode 2a (line) and the area (space) in which the first electrode 2a is not formed.

The method of disposing the conductive material 11 is not particularly limited, and includes application using a dispenser, screen printing, and ejection using an inkjet device.

Additionally, a second connection target member 3 having the second electrode 3a on its surface (lower surface) is prepared. Next, as shown in FIG. 3(b), in the conductive material 11 on the surface of the first connection target member 2, the first connection target member 2 side of the conductive material 11 and Arranges the second connection target member 3 on the opposite surface (second process). The second connection target member 3 is disposed on the surface of the conductive material 11 from the second electrode 3a side. At this time, the first electrode 2a and the second electrode 3a are opposed to each other.

Next, the conductive material 11 is heated above the melting point of the solder particles 11A (third process). Preferably, the conductive material 11 is heated above the curing temperature of the thermosetting component 11B (binder). During this heating, the solder particles 11A existing in the area where the electrode is not formed gather between the first electrode 2a and the second electrode 3a (self-aggregation effect). When a conductive paste is used instead of a conductive film, the solder particles 11A are effectively collected between the first electrode 2a and the second electrode 3a. Additionally, the solder particles 11A are melted and joined together. Additionally, the thermosetting component (11B) is thermoset. As a result, as shown in FIG. 3(c), the connection portion 4 connecting the first connection target member 2 and the second connection target member 3 is formed with the conductive material 11. do. The connection portion 4 is formed by the conductive material 11, the solder portion 4A is formed by joining a plurality of solder particles 11A, and the thermosetting component 11B is thermoset to form the cured portion 4B. is formed

In this embodiment, it is preferable not to apply pressure in the second process and the third process. In this case, the weight of the second connection target member 3 is applied to the conductive material 11. For this reason, when forming the connection portion 4, the solder particles 11A are effectively gathered between the first electrode 2a and the second electrode 3a. Additionally, in at least one of the second process and the third process, when pressure is applied, the tendency for solder particles to gather between the first electrode and the second electrode is inhibited.

Moreover, in this embodiment, since pressurization is not performed, when the second connection target member is superimposed on the first connection target member coated with a conductive material, the electrode of the first connection target member and the electrode of the second connection target member In a state where the alignment is misaligned, even when the first connection target member and the second connection target member overlap, the misalignment can be corrected to connect the electrode of the first connection target member and the electrode of the second connection target member. (self-alignment effect). This means that the molten solder that self-aggregated between the electrode of the first connection target member and the electrode of the second connection target member is the solder between the electrode of the first connection target member and the electrode of the second connection target member and the conductive material. This is because the direction in which the area in contact with other components is the smallest becomes energetically stable, and a force acts on the connection structure, which is the alignment, which is the connection structure that has the minimum area. At this time, it is preferable that the conductive material is not hardened and that the viscosity of components other than the conductive particles of the conductive material are sufficiently low at the temperature and time.

In this way, the connection structure 1 shown in FIG. 2 is obtained. Additionally, the second process and the third process may be performed continuously. Furthermore, after performing the second step, the obtained laminate of the first connection target member 2, the conductive material 11, and the second connection target member 3 is moved to the heating unit, and the third process is performed. It's okay too. In order to perform the heating, the laminate may be placed on a heating member, or the laminate may be placed 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 even more preferably 200°C or lower. .

As a heating method in the third step, a method of heating the entire connected structure to a temperature higher than the melting point of the solder and the curing temperature of the thermosetting component using a reflow furnace or an oven, or a method of heating only the connection portion of the connected structure locally A method of heating is possible.

The first and second connection target members are not particularly limited. The first and second connection target members specifically include electronic components such as semiconductor chips, semiconductor packages, LED chips, LED packages, condensers and diodes, and resin films, printed boards, flexible printed boards, and flexible flat cables, Electronic components such as circuit boards such as rigid flexible substrates, glass epoxy substrates, and glass substrates can be mentioned. It is preferable that the first and second connection target members are electronic components.

It is preferable that at least one of the first connection target member and the second connection target member is a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. It is preferable that the second connection target member is a resin film, a flexible printed board, a flexible flat cable, or a rigid flexible board. Resin films, flexible printed boards, flexible flat cables, and rigid flexible boards have the properties of being highly flexible and relatively lightweight. When a conductive film is used to connect such connection target members, solder tends to have difficulty gathering on the electrode. In contrast, by using a conductive paste, even if a resin film, flexible printed board, flexible flat cable, or rigid flexible board is used, the solder can be efficiently collected on the electrodes, thereby sufficiently increasing the reliability of conduction between the electrodes. When using a resin film, flexible printed board, flexible flat cable, or rigid flexible board, the effect of improving the conduction reliability between electrodes is further improved by not applying pressure compared to when using other connection target members such as semiconductor chips. obtained effectively.

The shape of the connection target member includes a periphery, an area array, etc. As a characteristic of each member, in the peripheral substrate, electrodes exist only on the outer periphery of the substrate. In an area array substrate, electrodes exist within the surface.

Examples of electrodes provided on the connection target member include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes. When the connection target member is a flexible printed circuit board, the electrode is preferably a gold electrode, nickel electrode, tin electrode, silver electrode, or 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 electrode is an aluminum electrode, it may be an electrode formed only of aluminum, or an electrode in which an aluminum layer is laminated on the surface of a metal oxide layer. Examples of materials 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 elements include Sn, Al, and Ga.

Hereinafter, the present invention will be described in detail through examples and comparative examples. The present invention is not limited to the following examples.

Polymer A:

Synthesis of the reactant (polymer A) of bisphenol F, 1,6-hexanediol diglycidyl ether, and bisphenol F type epoxy resin:

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

NMR confirmed that the addition polymerization reaction had progressed, and the reactant (polymer A) had a structure in which a hydroxyl group derived from bisphenol F, 1,6-hexanediol diglycidyl ether, and an epoxy group of bisphenol F-type epoxy resin were bonded. It was confirmed that it had a unit in the main chain and also had epoxy groups at both ends.

The weight average molecular weight of the reactant (polymer A) obtained by GPC was 10000 and the number average molecular weight was 3500.

Thermosetting compound 1: Resorcinol type epoxy compound, “EX-201” manufactured by Nagase Chemtex.

Heat curing agent 1: Thiol heat curing agent, “Carens MT” manufactured by Showa Denko.

Thermosetting agent 2: Microcapsule type thermosetting agent, “HXA3922HP” manufactured by Asahi Kasei E-Materials.

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

Flux 1: Glutaric acid, manufactured by Wako Pure Chemical Industries, Ltd.

Coupling agent 1: Silane coupling agent, “KBE-9007” manufactured by Shin-Etsu Silicone Co., Ltd.

Solder particle 1:

Manufacturing method of solder particle 1:

SnBi solder particles (“ST-5” manufactured by Mitsui Kinzoku Co., Ltd., average particle diameter (median diameter) 5 μm) and glutaric acid (a compound having two carboxyl groups, “Glutaric Acid” manufactured by Wako Pure Chemical Industries, Ltd.) , using p-toluenesulfonic acid as a catalyst, and stirring for 8 hours while dehydrating at 90°C in a toluene solvent to obtain solder particles 1 in which a group containing a carboxyl group is covalently bonded to the surface of the solder.

The obtained solder particle 1 had a CV value of 20%, and the molecular weight of the polymer constituting the surface was Mw = 2000.

(Examples 1 to 6 and Comparative Examples 1 and 2)

(1) Production of anisotropic conductive paste

The components shown in Table 1 below were mixed in the amounts shown in Table 1 below to obtain an anisotropic electrically conductive paste.

(2) Fabrication of the first connection structure (area array substrate)

As the first connection target member, copper electrodes of 250 μm at a 400 μm pitch are arranged in an area array on the surface of the semiconductor chip main body (size 5 × 5 mm, thickness 0.4 mm), and a passivation film (poly E) is placed on the outermost surface. A semiconductor chip with a mid-thickness of 5 μm and an opening diameter of the electrode portion of 200 μm) was prepared. The number of copper electrodes per semiconductor chip is 10 x 10, for a total of 100.

As the second connection target member, a copper electrode is disposed on the surface of the glass epoxy substrate main body (size 20 x 20 mm, thickness 1.2 mm, material FR-4) so as to have the same pattern as the electrode of the first connection target member. A glass epoxy substrate was prepared, with a solder resist film formed in the area where the copper electrode was not placed. The level difference between the surface of the copper electrode and the surface of the solder resist film is 15 μm, and the solder resist film protrudes beyond the copper electrode.

The anisotropic conductive paste immediately after production was applied to the upper surface of the glass epoxy substrate using a dispenser to form an anisotropic conductive paste layer. The method of applying the anisotropic conductive paste layer was performed so that the diameter was 2.5 mm at the center of the glass epoxy substrate. Next, the semiconductor chip was stacked on the upper surface of the anisotropic conductive paste layer so that the electrodes faced each other. The weight of the semiconductor chip is applied to the anisotropic conductive paste layer.

The temperature of the anisotropic conductive paste layer was heated to 139°C (melting point of solder) 5 seconds after the start of temperature increase. Furthermore, 15 seconds after the start of the temperature increase, the anisotropic conductive paste layer was heated so that the temperature was 160°C, the anisotropic conductive paste was cured, and a bonded structure was obtained. During heating, no pressurization was performed.

(3) Fabrication of the second connection structure (peripheral substrate)

As the first connection target member, on the surface of the semiconductor chip main body (size 5 × 5 mm, thickness 0.4 mm), copper electrodes of 250 μm at a pitch of 400 μm are disposed (around) on the outer periphery of the chip, and passivation is applied to the outermost surface. A semiconductor chip on which a film (polyimide, 5 μm thick, electrode opening diameter 200 μm) was formed was prepared. The number of copper electrodes is 36 in total (10 x 4 sides) per semiconductor chip.

As the second connection target member, a copper electrode is disposed on the surface of the glass epoxy substrate main body (size 20 x 20 mm, thickness 1.2 mm, material FR-4) so as to have the same pattern as the electrode of the first connection target member. The step difference between the surface of the copper electrode where the solder resist film is formed in the area where the copper electrode is not disposed and the surface of the solder resist film is 15 μm, and the solder resist film protrudes beyond the copper electrode.

The anisotropic conductive paste immediately after production was applied to the upper surface of the glass epoxy substrate using a dispenser to form an anisotropic conductive paste layer. The method of applying the anisotropic conductive paste layer was performed so that the diameter was 2.5 mm at the center of the glass epoxy substrate. Next, the semiconductor chip was stacked on the upper surface of the anisotropic conductive paste layer so that the electrodes faced each other. The weight of the semiconductor chip is applied to the anisotropic conductive paste layer.

The temperature of the anisotropic conductive paste layer was heated to 139°C (melting point of solder) 5 seconds after the start of temperature increase. Furthermore, 15 seconds after the start of the temperature increase, the anisotropic conductive paste layer was heated so that the temperature was 160°C, the anisotropic conductive paste was cured, and a bonded structure was obtained. During heating, no pressurization was performed.

(evaluation)

(1) Viscosity

The viscosity (η25) at 25°C and the viscosity (η100) at 100°C of the anisotropic conductive paste were measured using STRESSTECH (manufactured by EOLOGICA), strain control 1rad, frequency 1Hz, temperature rise. Measurements were made under conditions of a speed of 20°C/min and a measurement temperature range of 25 to 200°C.

(2) Measurement of exothermic peak P1 and endothermic peak P2 by DSC

The thermosetting components in the anisotropic conductive pastes of Examples and Comparative Examples were blended. Using a differential scanning calorimetry device (“Q2000” manufactured by TA Instruments), the obtained thermosetting component was heated at a temperature increase rate of 10°C/min, and exothermic peaks P1 and P2 resulting from curing of the thermosetting component were measured.

Additionally, using a differential scanning calorimetry device (“Q2000” manufactured by TA Instruments), the conductive particles were heated at a temperature increase rate of 10°C/min, and the endothermic peak P3 resulting from melting of the solder in the conductive particles was measured. did.

Table 1 below shows the results of 1) to 9) below.

1) Whether or not there is overlap between the temperature region representing the endothermic peak P3 resulting from melting of the solder in the conductive particles and the temperature region representing the exothermic peak P1 resulting from curing of the thermosetting component.

2) Whether or not there is overlap between the temperature region representing the endothermic peak P3 resulting from melting of the solder in the conductive particles and the temperature region representing the exothermic peak P2 resulting from curing of the thermosetting component.

3) Exothermic peak top P1t temperature resulting from curing of thermosetting components

4) Exothermic peak top P2t temperature resulting from curing of thermosetting components

5) Endothermic peak top P3t temperature resulting from melting of solder in conductive particles

6) Absolute value of the difference between the endothermic peak top P3t temperature and the exothermic peak top P1t temperature

7) Absolute value of the difference between the endothermic peak top P3t temperature and the exothermic peak top P2t temperature

8) Total heat generation resulting from curing of the thermosetting component in the temperature range below the endothermic peak top P3t temperature (low temperature side)

9) Total heat generation resulting from curing of the thermosetting component in a temperature range above the endothermic peak top P3t temperature (high temperature side)

Table 1 below also shows the results of 10) and 11) below.

10) The peak end temperature ( relationship with Y1); In Table 1, written as X1<Y1, X1=Y1, or X1>Y1.

11) The low-temperature peak onset temperature ( relationship with Y2); In Table 1, written as X2<Y2, X2=Y2, or X2>Y2.

In the evaluations 1) and 2) above, “-” shown as a result indicates that no peak exists. In the evaluation of 10) and 11) above, “-” shown as a result indicates no evaluation.

(3) Accuracy of placement of solder on electrode 1

In the obtained connection structure, when the first electrode and the connection portion at the center are viewed from the stacking direction of the second electrode, the opposing portions of the first electrode and the second electrode are viewed from the opposing portions of the first electrode and the second electrode. The ratio The placement accuracy of solder on the electrode was determined based on the following criteria.

[Judgment criteria for solder placement accuracy 1 on electrodes]

○○: Ratio

○: Ratio X is 80% or more and less than 90%

△: Ratio X is 60% or more and less than 80%

×: Ratio X is less than 60%

(4) Solder placement accuracy 2 on the electrode

In the obtained connection structure, when looking at the portions of the first electrode and the second electrode facing each other in the lamination direction of the first electrode in the outer peripheral portion, the connection section, and the second electrode, among 100% of the solder portion in the connection section, the first electrode and The ratio Y of the solder portion in the connection portion disposed in the opposing portion of the second electrode was evaluated. The placement accuracy 2 of the solder on the electrode was determined based on the following standards.

[Judgment criteria for solder placement accuracy 2 on electrodes]

○○: Ratio

○: Ratio X is 80% or more and less than 90%

△: Ratio X is 60% or more and less than 80%

×: Ratio X is less than 60%

(5) Solder placement accuracy within the board 3

In the obtained connection structure, when the portions of the first electrode and the second electrode are viewed in the direction of stacking the first electrode, the connection portion, and the second electrode, the area of the portions of the first electrode and the second electrode are opposed to each other. Regarding the ratio of the area where the solder part in the connection part is disposed in 100%, the difference Z between the ratio of the area of the electrode in the center and the ratio of the area of the electrode in the outer peripheral part was evaluated. The solder placement accuracy 3 in the board was determined based on the following standards.

[Judgment criteria for solder placement accuracy 3 within the board]

○○: Tea Z is less than 5%

○: Tea Z is 5% or more and less than 10%

△: Tea Z is 10% or more, less than 15%

×: Tea Z is 15% or more

(6) Continuity reliability between upper and lower electrodes

In the obtained connected structures (n=15 pieces), the connection resistance between the upper and lower electrodes was measured using the four-terminal method. The average value of the connection resistance was calculated. Additionally, from the relationship of voltage = current x resistance, the connection resistance can be obtained by measuring the voltage when a constant current is passed. Continuity reliability was determined based on the following criteria.

[Judgment criteria for continuity reliability]

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

○: The average value of connection resistance is greater than 8.0Ω and less than 10.0Ω.

△: The average value of connection resistance is greater than 10.0Ω and less than 15.0Ω.

×: Average value of connection resistance exceeds 15.0Ω

The results are shown in Table 1 below.

The same trend was observed even when flexible printed boards, resin films, flexible flat cables, and rigid flexible boards were used.

1, 1X: connection structure
2: Absence of first connection target
2a: first electrode
3: Absence of second connection target
3a: second electrode
4, 4X: Connection
4A, 4XA: Solder
4B, 4XB: Hard cargo section
11: Challenge materials
11A: Solder particles (conductive particles)
11B: Thermoset component
21: Conductive particles (solder particles)
31: Conductive particles
32: substrate particles
33: Conductive portion (conductive portion with solder)
33A: Second conduction section
33B: Solder
41: Conductive particles
42: Solder

Claims (11)

Containing a plurality of conductive particles containing solder and a thermosetting component in the outer surface portion of the conductive portion,
When the conductive particles and the thermosetting component are each heated from 25°C at a temperature increase rate of 10°C/min and differential scanning calorimetry is performed, a temperature range showing an endothermic peak resulting from melting of solder in the conductive particles. and the temperature region showing the exothermic peak resulting from curing of the thermosetting component overlaps at least in part,
The total calorific value derived from curing of the thermosetting component in a temperature range below the endothermic peak top temperature resulting from melting of the solder in the conductive particles is the endothermic peak top temperature derived from melting of the solder in the conductive particles. A conductive material that is smaller than the total calorific value resulting from curing of the thermosetting component in the above temperature range. The method according to claim 1, wherein the first exothermic peak top temperature resulting from curing of the thermosetting component is on a lower temperature side than the endothermic peak top temperature resulting from melting of the solder in the conductive particles, and further, in the conductive particles, A conductive material that has a second exothermic peak top temperature resulting from curing of the thermosetting component on a higher temperature side than the endothermic peak top temperature resulting from melting of the solder. The method according to claim 2, wherein the absolute value of the difference between the endothermic peak top temperature and the first exothermic peak top temperature is 3°C or more and 60°C or less, and the difference between the endothermic peak top temperature and the second exothermic peak top temperature is 3°C or more and 60°C or less. A conductive material whose absolute difference is 5℃ or higher and 60℃ or lower. The conductive material according to any one of claims 1 to 3, wherein the peak end temperature of the endothermic peak on the high temperature side is lower than the peak end temperature of the exothermic peak on the highest temperature side. The method according to any one of claims 1 to 3, wherein the peak end temperature on the high temperature side of the endothermic peak is lower than the peak end temperature on the high temperature side of the exothermic peak on the highest temperature side, and the peak end temperature on the high temperature side of the endothermic peak is lower than the peak end temperature on the high temperature side of the endothermic peak. , a conductive material in which the peak onset temperature on the low temperature side is higher than the peak onset temperature on the low temperature side of the exothermic peak on the lowest temperature side. The electrically conductive material according to any one of claims 1 to 3, wherein the electrically conductive particles are solder particles. The electrically conductive material according to any one of claims 1 to 3, wherein a carboxyl group is present on the outer surface of the electrically conductive particles. The electrically conductive material according to any one of claims 1 to 3, which is liquid at 25°C and is a conductive paste. A first connection target member having at least one first electrode on its surface,
a second connection target member having at least one second electrode on its surface;
It has a connection part connecting the first connection target member and the second connection target member,
The connection portion is a cured product of the electrically conductive material according to any one of claims 1 to 3,
A connection structure in which the first electrode and the second electrode are electrically connected by a solder portion in the connection portion. The method of claim 9, wherein when the opposing portions of the first electrode and the second electrode are viewed in the stacking direction of the first electrode, the connection portion, and the second electrode, the first electrode and the second electrode are A connection structure in which a solder portion in the connection portion is disposed in 50% or more of 100% of the area of the portions facing each other. delete

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