Conductive composition, conductive sheet, connection structure, and method for manufacturing connection structure

Abstract

The present invention provides a conductive composition that is less likely to protrude from a connection position between substrates during mounting of an electronic component. A conductive composition according to an embodiment of the present invention contains conductive particles and a resin. When a complex viscosity η is measured for the conductive composition by increasing the temperature from 25°C under conditions of a temperature increase rate of 10°C / min, a minimum complex viscosity η0 is 2000 mPa·s to 500000 mPa·s, and formula (1) is satisfied for the complex viscosity η0 (mPa·s) and a complex viscosity η1 (mPa·s) at a temperature (T0 - 30°C) that is 30°C lower than a temperature T0 at which the complex viscosity η0 is exhibited.　(1): η1 / η0 > 3.7

Description

Conductive composition, conductive sheet, connecting structure, and method for manufacturing the connecting structure.

[0001] The present invention relates to a conductive composition, a conductive sheet, a connecting structure, and a method for manufacturing the connecting structure.

[0002] The mounting of electronic components is performed, for example, by electrically connecting two wiring circuit boards. Conventionally, anisotropic conductive compositions are used to connect two wiring circuit boards. When heated while placed between the two wiring circuit boards, the anisotropic conductive composition exhibits conductivity in the stacking direction of the two wiring circuit boards, while ensuring insulation in the direction perpendicular to the stacking direction (plane direction).

[0003] An anisotropic conductive composition is known to be a combination of solder particles and a thermosetting resin (for example, Patent Document 1). When this anisotropic conductive composition is heated, the solder particles melt and aggregate between the electrodes of one wiring circuit board and the electrodes of the other wiring circuit board. Subsequently, as the molten solder cools and solidifies, these electrodes are electrically connected. In areas where there are no electrodes, the aggregation of solder particles does not proceed, and the insulating properties of the resin are maintained. Through this mechanism, anisotropy is exhibited in which the electrical properties differ in the stacking direction and the planar direction of the two wiring circuit boards.

[0004] International Publication No. 2023 / 145487

[0005] When a heating process is performed to electrically connect two wiring circuit boards, the conductive composition typically softens first and then hardens. According to the inventors' research, when the conductive composition softens, it tends to protrude from the connection point between the boards. If the conductive composition protrudes significantly from the connection point, it becomes necessary to avoid the protruding conductive composition when mounting other electronic components, which tends to reduce the mounting density of electronic components.

[0006] The object of the present invention is to provide a conductive composition that is less likely to protrude from the connection points between substrates when mounting electronic components.

[0007] [1] The conductive composition according to an embodiment of the present invention is a conductive composition comprising conductive particles and a resin, wherein when the complex viscosity η of the conductive composition is measured by raising the temperature from 25°C at a heating rate of 10°C / min, the minimum complex viscosity η0 is 2000 mPa·s to 500000 mPa·s, and the following formula (1) holds true for the complex viscosity η0 (mPa·s) and the complex viscosity η1 (mPa·s) at a temperature 30°C lower than the temperature T0 at which the complex viscosity η0 is observed (T0-30°C): η1 / η0 > 3.7 (1) [2] In the conductive composition described in [1] above, the ratio of the complex viscosity η1 to the complex viscosity η0, η1 / η0, may be 50 or less. [3] In the conductive composition described in [1] or [2] above, the temperature T0 may be 100°C or higher. [4] In the conductive composition according to any of [1] to [3] above, the maximum temperature T at which the complex viscosity η is 500,000 mPa·s or less MAX and the lowest temperature T MIN The difference T MAX -T MINThe temperature may be 85°C or lower. [5] In the conductive composition according to any one of [1] to [4] above, the conductive particles may be solder particles. [6] In the conductive composition according to any one of [1] to [5] above, the resin may include at least one selected from the group consisting of epoxy resin, (meth)acrylic resin, phenoxy resin and phenol resin. [7] In the conductive composition according to any one of [1] to [6] above, the resin may include epoxy resin. [8] In the conductive composition according to [7] above, the weight-average molecular weight of the epoxy resin may be less than 10,000. [9] In the conductive composition according to [7] or [8] above, the epoxy resin may include repeating units having a glycidyl group.

[10] In the conductive composition according to any one of [7] to [9] above, the epoxy resin may have at least one selected from the group consisting of a dicyclopentadiene skeleton, a biphenyl skeleton, a naphthalene skeleton, a phenol skeleton and a cresol skeleton.

[11] In the conductive composition described in any of [7] to

[10] above, the content of the epoxy resin as a solid in the resin may be 50% by weight or more.

[12] In the conductive composition described in any of [1] to

[11] above, the epoxy equivalent of the resin may be 200 g / eq. or more.

[13] In the conductive composition described in any of [1] to

[12] above, the resin may include a polymer resin having a weight-average molecular weight of 10,000 or more.

[14] In the conductive composition described in

[13] above, the content of the polymer resin in the resin may be 20% by weight or less.

[15] The conductive composition described in any of [1] to

[14] above may further include a flux.

[16] In the conductive composition described in

[15] above, the first acid dissociation constant pKa1 of the flux may be 3.0 to 5.0.

[17] In the conductive composition described in

[15] or

[16] above, the amount of flux may be 2.0 to 10 parts by weight per 100 parts by weight of the conductive particles.

[18] A conductive sheet according to an embodiment of the present invention is made from the conductive composition described in any of [1] to

[17] above.

[19] A connection structure according to an embodiment of the present invention comprises: a first substrate on which a first electrode is disposed; a second substrate on which a second electrode is disposed; and a connecting member connecting the first substrate and the second substrate, wherein the connecting member is formed from a conductive composition described in any of [1] to

[17] above.

[20] A method for manufacturing a connection structure according to an embodiment of the present invention is a method for manufacturing a connection structure according to

[19] above, comprising: arranging the conductive composition between the first substrate and the second substrate; and heating the conductive composition to form the connecting member.

[0008] According to embodiments of the present invention, it is possible to provide a conductive composition that is less likely to protrude from the connection points between substrates when mounting electronic components.

[0009] This is a graph illustrating the relationship between temperature and complex viscosity η for a conductive composition. This is a schematic cross-sectional view of a conductive sheet according to one embodiment of the present invention. This is a schematic cross-sectional view of a connecting structure according to one embodiment of the present invention. This is a diagram illustrating the manufacturing method of the connecting structure shown in Figure 3. This is a diagram illustrating the manufacturing method of the connecting structure shown in Figure 3.

[0010] ≪1. Conductive Composition≫ The conductive composition according to the embodiment of the present invention comprises conductive particles and a resin. When the complex viscosity η of the conductive composition is measured by raising the temperature from 25°C at a heating rate of 10°C / min, the minimum complex viscosity η0 is between 2000 mPa·s and 500000 mPa·s. Furthermore, the following equation (1) holds true for the above complex viscosity η0 (mPa·s) and the complex viscosity η1 (mPa·s) at a temperature 30°C lower than the temperature T0 at which the complex viscosity η0 is observed (T0-30°C). η1 / η0 > 3.7 (1)

[0011] According to the inventors' studies, conductive compositions whose complex viscosity η0 and ratio η1 / η0 satisfy the above-mentioned numerical range tend to have a narrow numerical range for the temperature at which they soften. As a result, when a heating process is performed to electrically connect two wiring circuit boards, the time during which the conductive composition is softened tends to be shorter than in conventional methods. Conductive compositions that soften for a short time during the heating process tend to be less likely to spill out from the connection position between the boards. Furthermore, because this conductive composition softens for a short time during the heating process, it is easier to maintain the dispersibility of the conductive particles, and as a result, the uniformity of the accumulation on the electrodes on the board tends to improve. In other words, this conductive composition tends to improve the integration when electrically connecting two boards.

[0012] The complex viscosity η of a conductive composition can be measured by the following method. First, a sample for measurement composed of the conductive composition is prepared. The sample for measurement is disc-shaped, with a base diameter of 25.0 mm and a thickness of 320 ± 50 μm. The sample for measurement is preferably dry. In this specification, "dry" means that the solvent content remaining in the sample for measurement is 1000 wt ppm or less, preferably 500 wt ppm or less. The sample for measurement is preferably substantially solvent-free. The sample for measurement may also be obtained by punching out a disc-shaped laminate of multiple conductive sheets made using the conductive composition. Next, dynamic viscoelasticity measurement is performed on the sample for measurement under the following measurement conditions. Measurement conditions Measurement environment: atmospheric atmosphere Strain value: 0.5% Measurement frequency: 1 Hz Temperature range: 25°C to 300°C Heating rate: 10°C / min Shape: parallel plate 25.0 mmφ

[0013] From the results of the dynamic viscoelasticity measurements described above, a temperature-complex viscosity profile (e.g., Figure 1) is created. From this profile, the minimum complex viscosity η0 (the minimum value of complex viscosity η) and the complex viscosity η1 at a temperature 30°C lower than the temperature T0 at which complex viscosity η0 is observed (T0-30°C) can be identified.

[0014] Figure 1 is a graph illustrating the relationship between temperature and complex viscosity η for the above-mentioned measurement sample (conductive composition). This graph schematically shows the relationship between temperature and complex viscosity η and does not limit the physical properties of the conductive composition. As can be seen from the graph in Figure 1, when the above-mentioned measurement sample is heated and its temperature rises, the complex viscosity η usually gradually decreases. Then, at temperature T0, the complex viscosity η reaches its minimum value (complex viscosity η0). Furthermore, when the measurement sample is heated to a temperature higher than T0, its complex viscosity η increases.

[0015] The complex viscosity η0 is, as described above, between 2,000 mPa·s and 500,000 mPa·s. The complex viscosity η0 is preferably 400,000 mPa·s or less, and may also be 300,000 mPa·s or less, 200,000 mPa·s or less, 100,000 mPa·s or less, 90,000 mPa·s or less, 80,000 mPa·s or less, 70,000 mPa·s or less, and even 60,000 mPa·s or less. The lower limit of the complex viscosity η0 is preferably 3000 mPa·s or more, but may also be 4000 mPa·s or more, 5000 mPa·s or more, 6000 mPa·s or more, 7000 mPa·s or more, 8000 mPa·s or more, 9000 mPa·s or more, 10000 mPa·s or more, 20000 mPa·s or more, 30000 mPa·s or more, 40000 mPa·s or more, and even 50000 mPa·s or more.

[0016] The temperature T0 at which the complex viscosity η0 is observed is, for example, 80°C or higher, and may also be 90°C or higher, 100°C or higher, 110°C or higher, 115°C or higher, or even 120°C or higher. When the temperature T0 is high, the two wiring circuit boards tend to be easily connected without applying large pressure to them during the heating process for electrically connecting them. The upper limit of the temperature T0 is, for example, 250°C or lower, and may also be 230°C or lower, 200°C or lower, 180°C or lower, 150°C or lower, 140°C or lower, or even 130°C or lower.

[0017] When the conductive composition contains solder particles as conductive particles, it is preferable that the temperature T0 is lower than the melting point P of the solder particles. The difference between temperature T0 and the melting point P |T0-P| is, for example, 0°C to 150°C, and may also be 30°C to 130°C, or even 50°C to 100°C.

[0018] The ratio η1 / η0 of the complex viscosity η1 (mPa·s) to the complex viscosity η0 (mPa·s) is greater than 3.7 as described above, and may be 3.8 or greater, 3.9 or greater, 4.0 or greater, 4.3 or greater, 4.5 or greater, 4.8 or greater, 5.0 or greater, 5.3 or greater, 5.5 or greater, 5.8 or greater, 6.0 or greater, 6.3 or greater, 6.5 or greater, 6.8 or greater, 7.0 or greater, 7.3 or greater, 7.5 or greater, 7.8 or greater, 8.0 or greater, 8.3 or greater, and even 8.5 or greater. The upper limit of the ratio η1 / η0 is, for example, 50 or less, and may be 40 or less, 30 or less, 20 or less, 18 or less, 15 or less, 13 or less, 10 or less, and even 9.0 or less. When the ratio η1 / η0 is 50 or less, there is a tendency for these substrates to be easily bonded together via the conductive composition during the heating process for electrically connecting two wiring circuit boards. The ratio η1 / η0 may be between 4.0 and 20. By adjusting the ratio η1 / η0 to an appropriate value, the amount of conductive composition that protrudes from the connection points between substrates during the heating process described above tends to be further reduced.

[0019] The value of the complex viscosity η1 at temperature (T0–30°C) is not particularly limited as long as the ratio η1 / η0 is greater than 3.7. The complex viscosity η1 may be, for example, 10,000 mPa·s to 10,000,000 mPa·s, 50,000 mPa·s to 5,000,000 mPa·s, or even 100,000 mPa·s to 1,000,000 mPa·s.

[0020] As described above, the conductive composition of this embodiment tends to have a narrow temperature range in which it softens. For example, the maximum temperature T at which the complex viscosity η of the conductive composition is 500,000 mPa·s or less. MAX and the lowest temperature T MIN The difference T MAX -T MINis preferably 85°C or lower, may be 70°C or lower, 65°C or lower, 60°C or lower, 55°C or lower, 50°C or lower, or even 45°C or lower. The difference T MAX -T MIN has a lower limit of, for example, 5°C or higher, and may be 10°C or higher, 15°C or higher, 20°C or higher, 25°C or higher, 30°C or higher, 35°C or higher, or even 40°C or higher.

[0021] The above maximum temperature T MAX is typically higher than the temperature T0, and is, for example, 100°C or higher, may be 110°C or higher, 120°C or higher, or even 130°C or higher. The maximum temperature T MAX has an upper limit of, for example, 300°C or lower, and may be 250°C or lower, 230°C or lower, 200°C or lower, 180°C or lower, or even 150°C or lower.

[0022] The above minimum temperature T MIN is typically lower than the temperature T0, and is, for example, 120°C or lower, may be 110°C or lower, 100°C or lower, or even 95°C or lower. The minimum temperature T MIN has a lower limit of, for example, 60°C or higher, and may be 70°C or higher, 80°C or higher, or even 90°C or higher.

[0023] <1-1. Conductive particles> As described above, the conductive composition contains conductive particles. The conductive particles are not particularly limited as long as they are particles having conductivity. Only one type of conductive particles may be used, or two or more types may be used.

[0024] Examples of the conductive particles include: metal particles such as solder particles, nickel particles, gold-plated nickel particles, copper particles, silver particles, metal crystal nanoparticles, and particles obtained by coating a metal surface with another metal; and particles obtained by coating resin particles formed of styrene resin, urethane resin, melamine resin, epoxy resin, acrylic resin, phenol resin, styrene-butadiene resin or the like with a conductive thin film of gold, nickel, silver, copper, solder or the like.

[0025] The conductive particles are preferably solder particles. There may be only one type of solder particle or two or more types. From the viewpoint of environmental protection, the material of the solder particles is preferably lead-free solder material that does not contain lead. Solder particles typically have a self-assembly function. Therefore, when the conductive particles are solder particles, there is a tendency for the two wiring circuit boards to be easily connected in the heating process for electrically connecting them without applying a large amount of pressure to these boards.

[0026] The solder particles preferably contain tin (Sn). Solder particles containing tin tend to accelerate the hardening of the resin through metal catalytic action. In the solder particles, tin may exist in elemental form or form an alloy with other metals. Examples of tin alloys include tin-bismuth alloy (Sn-Bi), tin-silver-copper alloy (Sn-Ag-Cu), tin-silver alloy (Sn-Ag), and tin-bismuth-indium alloy (Sn-Bi-In).

[0027] When solder particles contain a tin-silver-copper alloy, the tin content in the tin-silver-copper alloy may be, for example, 90% by weight or more, and may be 95% by weight or more. The silver content in the tin-silver-copper alloy may be, for example, 10% by weight or less, and may be 5% by weight or less. The copper content in the tin-silver-copper alloy may be, for example, 1% by weight or less, and may be 0.5% by weight or less.

[0028] When the solder particles contain a tin-bismuth alloy, the tin content in the tin-bismuth alloy may be, for example, 80% by weight or less, or 50% by weight or less. The bismuth content in the tin-bismuth alloy may be, for example, 20% by weight or more, or 50% by weight or more.

[0029] The melting point P of the solder particles is, for example, 70°C or higher, and may be 100°C or higher, 120°C or higher, 150°C or higher, 180°C or higher, or even 200°C or higher. The melting point P of the solder particles is, for example, 350°C or lower, and may be 330°C or lower, 300°C or lower, 280°C or lower, 260°C or lower, or even 240°C or lower. The melting point can be measured by differential scanning calorimetry (DSC).

[0030] The shape of the conductive particles is not particularly limited as long as they are particulate, and examples include spherical, ellipsoidal, flaky, and fibrous shapes. Spherical conductive particles are preferred. The average particle diameter (average primary particle diameter) of the conductive particles is, for example, 20 μm or less, and may be 10 μm or less, 8 μm or less, 5 μm or less, or even 3 μm or less. Conductive particles with a small average particle diameter are suitable for the fabrication of miniaturized, low-profile connecting structures. The average particle diameter of the conductive particles may be, for example, 0.1 μm or more, or 0.5 μm or more. In this specification, the average particle diameter can be specified as the median diameter (D50) in the particle size distribution measured by a laser diffraction particle size distribution analyzer or the like.

[0031] The content of conductive particles in the conductive composition is, for example, 20% by weight or more, and may be 30% by weight or more, 40% by weight or more, 50% by weight or more, or even 60% by weight or more. The above content may be, for example, 80% by weight or less, and may be 70% by weight or less.

[0032] Furthermore, conductive particles (especially solder particles) may have an oxide film formed on their surface, but it is preferable that no oxide film is formed. The oxide film on conductive particles can be removed, for example, by performing an acid treatment on the conductive particles before preparing the conductive composition. Details of the method for removing the oxide film will be explained in section 1-6. Method for producing conductive compositions.

[0033] <1-2. Resin> As described above, the conductive composition includes a resin. As the resin, any resin known in the field of anisotropic conductive compositions can be used, such as thermosetting resins and thermoplastic resins. It is preferable that the resin includes a thermosetting resin.

[0034] The resin preferably contains at least one selected from the group consisting of epoxy resin, (meth)acrylic resin, phenoxy resin, and phenolic resin, and is particularly preferably epoxy resin. In this specification, "(meth)acrylic" means "acrylic and / or methacrylic".

[0035] The epoxy equivalent weight of the resin is, for example, 100 g / eq. or more, may be 150 g / eq. or more, 180 g / eq. or more, 200 g / eq. or more, 225 g / eq. or more, 230 g / eq. or more, 250 g / eq. or more, or even 280 g / eq. or more. A resin having a relatively large epoxy equivalent weight facilitates adjusting the temperature T0, which exhibits the complex viscosity η0 mentioned above, to an appropriate value. The epoxy equivalent weight is, for example, 3000 g / eq. or less, may be 2000 g / eq. or less, 1000 g / eq. or less, 800 g / eq. or less, 500 g / eq. or less, 400 g / eq. or less, or even 300 g / eq. or less. Here, epoxy equivalent weight means the weight of the resin per equivalent of epoxy groups contained in the resin. When the conductive composition contains two or more types of resins each having an epoxy group, the average epoxy equivalent weight of these resins may satisfy the above numerical range.

[0036] (1-2-a. Epoxy Resin) The epoxy resin may be of only one type, or may be of two or more types. Typically, the epoxy resin described in the section (1-2-a. Epoxy Resin) has a weight average molecular weight of less than 10,000 and is not classified as a polymer resin described later.

[0037] Typically, the epoxy resin is thermosetting. In other words, the epoxy resin typically has at least one epoxy group (particularly a glycidyl group) per molecule. As for the epoxy equivalent weight of the epoxy resin, the numerical range described above for the resin can be incorporated herein by reference.

[0038] Preferably, the epoxy resin contains a repeating unit having an epoxy group (particularly a glycidyl group) in its molecule. The repeating unit having an epoxy group is represented by, for example, the following formula (1).

[0039] In the above formula (1), A is a divalent linking group. A preferably contains a ring structure. Examples of the ring structure include aliphatic rings such as a dicyclopentadiene ring; and aromatic rings such as a benzene ring, a biphenyl ring, and a naphthalene ring. The ring structure may or may not further have a substituent. The ring structure may be directly bonded to the benzene ring adjacent to A in formula (1), or may be bonded via a linking group such as an alkylene group.

[0040] As shown in formula (1), the benzene ring adjacent to A has a glycidyl group. This benzene ring may further have a substituent other than the glycidyl group. Examples of said other substituent include alkyl groups such as a methyl group.

[0041] The epoxy resin preferably has at least one selected from the group consisting of a dicyclopentadiene skeleton, a biphenyl skeleton, a naphthalene skeleton, a phenol skeleton, and a cresol skeleton in its molecule, more preferably has at least one selected from the group consisting of a dicyclopentadiene skeleton, a biphenyl skeleton, and a naphthalene skeleton, and particularly preferably has a dicyclopentadiene skeleton. According to the epoxy resin having the aforementioned rigid skeleton, the ratio η1 / η0 described above tends to be easily adjusted to a high value for the conductive composition.

[0042] The dicyclopentadiene skeleton is, for example, represented by the following formula (2).

[0043] In the above formula (2), * indicates a bonding site to another structure. Specifically, formula (2) shows a dicyclopentadiene ring functioning as a divalent linking group. This dicyclopentadiene ring may or may not have a substituent. Examples of the epoxy resin having a dicyclopentadiene skeleton include those in which A is represented by formula (2) in the repeating unit of the above formula (1).

[0044] Furthermore, examples of epoxy resins having a biphenyl skeleton include those in which A is a biphenyl ring in the repeating unit of formula (1) above. Examples of epoxy resins having a naphthalene skeleton include those in which A is a naphthalene ring in the repeating unit of formula (1) above.

[0045] The epoxy resin included in the conductive composition of this embodiment is not limited to those described above. For example, the conductive composition may include other epoxy resins other than the epoxy resin having the repeating unit of formula (1) described above.

[0046] Specific examples of epoxy resins (thermosetting epoxy resins) include bisphenol-type epoxy resins (e.g., bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, and bisphenol S-type epoxy resin), novolac-type epoxy resins (e.g., phenol novolac-type epoxy resin, cresol novolac-type epoxy resin, and biphenyl-type epoxy resin), naphthalene-type epoxy resin, fluorene-type epoxy resin (e.g., bisarylfluorene-type epoxy resin), triphenylmethane-type epoxy resin (e.g., trishydroxyphenylmethane-type epoxy resin), and dicyclopentadiene-type epoxy resin.

[0047] The conductive composition preferably contains at least one epoxy resin selected from the group consisting of dicyclopentadiene-type epoxy resins, biphenyl-type epoxy resins, and naphthalene-type epoxy resins, and is particularly preferably a dicyclopentadiene-type epoxy resin. However, the conductive composition may also contain other epoxy resins (for example, bisphenol A-type epoxy resins, cresol novolac-type epoxy resins, phenol novolac-type epoxy resins, etc.).

[0048] Commercially available dicyclopentadiene-type epoxy resins include "EPICLON HP-7200HHH" from DIC Corporation and "XD-1000" from Nippon Kayaku Co., Ltd. Commercially available biphenyl-type epoxy resins include "NC-3000-H" and "NC-3500" from Nippon Kayaku Co., Ltd. Commercially available naphthalene-type epoxy resins include "NC-7000-H" from Nippon Kayaku Co., Ltd. Commercially available bisphenol-type epoxy resins include "jER828" from Mitsubishi Chemical Corporation and "NPES907" from Nanya Plastics Co., Ltd. Commercially available cresol novolac-type epoxy resins include "EOCN-1020-70" from Nippon Kayaku Co., Ltd. Commercially available phenol novolac-type epoxy resins include "EPPN-502H" from Nippon Kayaku Co., Ltd.

[0049] The weight-average molecular weight of the epoxy resin is, for example, less than 10,000, and may be 9,000 or less, 8,000 or less, 7,000 or less, 6,000 or less, 5,000 or less, or even 4,000 or less. Epoxy resins with a small weight-average molecular weight tend to make it easier to adjust the minimum complex viscosity η0 of the conductive composition to a small value. The above weight-average molecular weight is, for example, 100 or more, and may be 300 or more, 500 or more, 800 or more, or even 1,000 or more. The weight-average molecular weight can be measured by GPC (gel permeation chromatography).

[0050] The curing temperature of the epoxy resin is, for example, 150°C to 280°C, but may also be 160°C to 260°C, or even 170°C to 250°C. When the conductive particles are solder particles, it is preferable that the curing temperature of the epoxy resin be above the melting point P of the solder particles.

[0051] In the conductive composition, the epoxy resin may be liquid or solid. The conductive composition of this embodiment preferably contains a solid epoxy resin. The conductive composition may contain a liquid epoxy resin together with the solid epoxy resin, or in place of the solid epoxy resin. In this specification, "liquid" means a substance in a liquid state that is flowable at atmospheric pressure (101.325 kPa) and 25°C, and "solid" means a substance in a solid state that is not flowable at atmospheric pressure and 25°C.

[0052] The softening point of the solid epoxy resin is, for example, 40°C or higher, and may be 60°C or higher, or even 80°C or higher. The softening point is, for example, 200°C or lower, and may be 180°C or lower, 150°C or lower, or even 140°C or lower. When the conductive particles are solder particles, it is preferable that the softening point is lower than the melting point P of the solder particles. The softening point can be measured using a thermomechanical analyzer.

[0053] The epoxy resin content in the conductive composition is, for example, 10% by weight or more, and may be 20% by weight or more, 25% by weight or more, or even 30% by weight or more. The above content may be, for example, 60% by weight or less, 50% by weight or less, or even 40% by weight or less.

[0054] The content ratio R1 of solid epoxy resin in the resin contained in the conductive composition is, for example, 40% by weight or more, and may be 50% by weight or more, 60% by weight or more, 65% by weight or more, and even 70% by weight or more. When the content ratio R1 is high, the properties of the solid epoxy resin are more easily reflected in the conductive composition, and there is a tendency to adjust the above-mentioned ratio η1 / η0 to a high value for the conductive composition. The content ratio R1 is, for example, 95% by weight or less, and may be 90% by weight or less, 85% by weight or less, and even 80% by weight or less.

[0055] (1-2-b. Polymer Resin) The conductive composition preferably contains a polymer resin having a weight-average molecular weight of 10,000 or more. The polymer resin is suitable for adjusting the complex viscosity η of the conductive composition to an appropriate value. There may be only one type of polymer resin or two or more types.

[0056] Examples of polymeric resins include epoxy resins and (meth)acrylic resins, which have a weight-average molecular weight of 10,000 or more. Epoxy resins with a weight-average molecular weight of 10,000 or more are sometimes called phenoxy resins.

[0057] The epoxy resin used as a polymer resin may be thermosetting or thermoplastic. A thermosetting epoxy resin typically has at least one epoxy group (particularly a glycidyl group) in one molecule. In this case, the epoxy equivalent of the epoxy resin may be, for example, 3000 g / eq. or more, 5000 g / eq. or more, and even 8000 g / eq. or more. The epoxy equivalent may also be, for example, 50000 g / eq. or less, and 10000 g / eq. or less.

[0058] Specific examples of epoxy resins are those exemplified in section (1-2-a. Epoxy Resins). The epoxy resin used as the polymer resin is preferably a bisphenol-type epoxy resin (particularly bisphenol A-type epoxy resin or bisphenol F-type epoxy resin). Examples of commercially available bisphenol-type epoxy resins used as polymer resins include the product names "jER1256" and "jER4250" manufactured by Mitsubishi Chemical Corporation.

[0059] The (meth)acrylic resin used as the polymer resin is preferably thermoplastic. Examples of commercially available (meth)acrylic resins include "Teisan Resin SG-70L" manufactured by Nagase ChemteX Corporation and "ARUFON UH-2170" manufactured by Toagosei Co., Ltd.

[0060] The weight-average molecular weight of the polymer resin is 10,000 or more, as described above, but may be 20,000 or more, 30,000 or more, or even 40,000 or more. The above weight-average molecular weight may be, for example, 2 million or less, but may be 1 million or less, 500,000 or less, 300,000 or less, or even 100,000 or less.

[0061] The polymer resin may be thermosetting or thermoplastic. If the polymer resin is thermosetting, the curing temperature of the polymer resin may be, for example, 120°C to 280°C, 160°C to 260°C, or even 170°C to 250°C. If the conductive particles are solder particles, the curing temperature of the polymer resin is preferably above the melting point P of the solder particles.

[0062] In the conductive composition, the polymer resin may be liquid, but it is preferably solid. When the conductive particles are solder particles, the glass transition temperature of the solid polymer resin is preferably lower than the melting point P of the solder particles. The glass transition temperature is, for example, 50°C to 150°C, and may also be 80°C to 120°C.

[0063] The content of polymer resin in the conductive composition is, for example, 0.1% by weight or more, and may be 0.5% by weight or more, 1.0% by weight or more, 2.0% by weight or more, and even 3.0% by weight or more. The above content is, for example, 20% by weight or less, and may be 15% by weight or less, 10% by weight or less, and even 5.0% by weight or less.

[0064] The content ratio R2 of the polymer resin in the resin contained in the conductive composition is, for example, 30% by weight or less, and may be 25% by weight or less, 20% by weight or less, 15% by weight or less, or even 10% by weight or less. When the content ratio R2 is low, it tends to be easier to adjust the minimum complex viscosity η0 of the conductive composition to a small value. The content ratio R2 is, for example, 0.1% by weight or more, and may be 0.5% by weight or more, 1.0% by weight or more, 5.0% by weight or more, or even 8.0% by weight or more.

[0065] (1-2-c. Other Resins) The conductive composition may contain other resins besides those described above. Examples of other resins include urea resin, melamine resin, diallyl phthalate resin, silicone resin, polyester resin (e.g., polyethylene terephthalate), polyimide resin, polyurethane resin, polyolefin (e.g., polyethylene, polypropylene, ethylene-propylene copolymer), polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl chloride, polystyrene, polyacrylonitrile, polyamide, polycarbonate, polyacetal, polyphenylene oxide, polyphenylene sulfide, polysulfone, polyethersulfone, polyetheretherketone, polyallylsulfone, polyaminobismaleimide, polyamideimide, polyetherimide, bismaleimide triazine resin, polymethylpentene, fluorinated resin, liquid crystal polymer, olefin-vinyl alcohol copolymer, ionomer, polyarylate, acrylonitrile-ethylene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, butadiene-styrene copolymer, and the like.

[0066] The content of other resins in the conductive composition may be, for example, 10% by weight or less, 5% by weight or less, 1% by weight or less, or even 0.1% by weight or less. The conductive composition may be substantially free of other resins.

[0067] <1-3. Flux> The conductive composition preferably further contains flux. Flux tends to remove oxide films that may be present on the surface of conductive particles. Flux also tends to remove oxide films that may be present on the surface of electrodes that the conductive composition contacts when the conductive composition is used to connect two wiring circuit boards. There may be only one type of flux or two or more types.

[0068] The flux is preferably an organic acid, and more preferably a carboxylic acid compound. Examples of carboxylic acid compounds include monocarboxylic acid compounds, dicarboxylic acid compounds, and tricarboxylic acid compounds, with dicarboxylic acid compounds being preferred.

[0069] Examples of monocarboxylic acid compounds include aliphatic monocarboxylic acids and aromatic monocarboxylic acids. Examples of aromatic monocarboxylic acids include 2-phenoxybenzoic acid.

[0070] Examples of dicarboxylic acid compounds include aliphatic dicarboxylic acids and aromatic dicarboxylic acids. Aliphatic dicarboxylic acids include linear saturated dicarboxylic acids, branched saturated dicarboxylic acids, linear unsaturated dicarboxylic acids, and branched unsaturated dicarboxylic acids.

[0071] Examples of linear saturated dicarboxylic acids include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid. Examples of branched saturated dicarboxylic acids include 3,3-dimethylglutaric acid and 3-methyladipic acid. Examples of linear unsaturated dicarboxylic acids include fumaric acid.

[0072] Examples of tricarboxylic acid compounds include 1,3,5-pentanetricarboxylic acid and tricarbaryl acid.

[0073] From the viewpoint of improving connection reliability, the flux is preferably an aliphatic dicarboxylic acid (especially a linear saturated dicarboxylic acid or a branched saturated dicarboxylic acid), more preferably glutaric acid, adipic acid, pimelic acid, 3-methyladipic acid, or 3,3-dimethylglutaric acid, and particularly preferably 3,3-dimethylglutaric acid.

[0074] The flux may also be a salt of an organic acid (especially a dicarboxylic acid compound).

[0075] The first acid dissociation constant pKa1 of the flux is, for example, 3.0 or higher, and may be 3.3 or higher, or even 3.5 or higher. The upper limit of the first acid dissociation constant pKa1 is, for example, 5.0 or lower, and may be 4.8 or lower, 4.5 or lower, 4.3 or lower, or even 4.0 or lower. The first acid dissociation constant pKa1 may be between 3.0 and 5.0. If the first acid dissociation constant pKa1 of the flux is within the above range, it is easy to adjust the temperature T0 at which the above complex viscosity η0 is observed to an appropriate value.

[0076] In this specification, the "acid dissociation constant" is the value in water at 25°C. The first acid dissociation constant pKa1 of flux can be determined by the following method. First, prepare 20 mL of an aqueous solution of flux (concentration 0.5 mol / L). Add an aqueous solution of sodium hydroxide (concentration 0.5 mol / L) dropwise to this aqueous solution and perform a neutralization titration. In the neutralization titration, the first hydrogen ion (H) from the flux is determined. + The acid dissociation constant when ) dissociates can be considered as the first acid dissociation constant pKa1. The above neutralization titration is performed under a temperature of 25°C.

[0077] The flux content in the conductive composition is, for example, 1% to 10% by weight, and may also be 3% to 7% by weight.

[0078] The flux content in the conductive composition may be, for example, 1.0 part by weight or more, 2.0 parts by weight or more, or even 5.0 parts by weight or more, per 100 parts by weight of conductive particles. The above content may be, for example, 20 parts by weight or less, or 10 parts by weight or less, per 100 parts by weight of conductive particles. The above content may be 2.0 parts by weight to 10 parts by weight per 100 parts by weight of conductive particles. If the flux content is within the above range, it is easy to adjust the temperature T0 at which the above complex viscosity η0 is observed to an appropriate value.

[0079] <1-4. Curing Agent> The conductive composition may further contain a curing agent. The curing agent can react with a resin component, such as epoxy resin, to accelerate its curing. There may be only one type of curing agent, or two or more types.

[0080] Examples of curing agents include acid anhydride-based curing agents, amine-based curing agents, phenol-based curing agents, cationic initiators, imidazole catalysts, and DICY (dicyandiamide).

[0081] The amount of curing agent in the conductive composition is, for example, less than 20 parts by weight per 100 parts by weight of the resin component, and may be less than 10 parts by weight, less than 5 parts by weight, less than 3 parts by weight, or even less than 1 part by weight. The conductive composition does not need to contain a curing agent.

[0082] <1-5. Other Additives> The conductive composition may further contain other additives in addition to the components described above. Examples of other additives include solvents and curing aids. Examples of solvents include organic solvents such as methyl ethyl ketone.

[0083] The content of other additives in the conductive composition may be, for example, 10% by weight or less, 5% by weight or less, 1% by weight or less, or even 0.1% by weight or less. The conductive composition may be substantially free of other additives. If the conductive composition contains a solvent, the solid content concentration of the conductive composition may be, for example, 50% by weight to 80% by weight, or 60% by weight to 75% by weight.

[0084] <1-6. Method for Producing Conductive Compositions> Conductive compositions according to embodiments of the present invention can be prepared, for example, by stirring and mixing the above-mentioned conductive particles, resin, and, if necessary, a solvent. After preparing the conductive composition, the solvent may be removed from the conductive composition by heat treatment or the like.

[0085] Before preparing the conductive composition, any oxide film formed on the surface of the conductive particles may be removed beforehand. The oxide film can be removed, for example, by acid treatment, in which the conductive particles are brought into contact with an acid treatment agent. The acid treatment agent may be one type or two or more types.

[0086] The acid treatment agent is preferably a carboxylic acid treatment agent having a carboxyl group. Examples of carboxylic acid treatment agents include monocarboxylic acid treatment agents, dicarboxylic acid treatment agents, and trifunctional or more carboxylic acid treatment agents, with dicarboxylic acid treatment agents being preferred. The dicarboxylic acid treatment agent is preferably an aliphatic dicarboxylic acid treatment agent, and is particularly preferably malic acid.

[0087] ≪2. Conductive Sheet≫ The conductive sheet according to the embodiment of the present invention is composed of the conductive composition described above. More specifically, the conductive sheet has the same composition as the conductive composition, except that it does not contain a solvent (or has a low solvent content). However, the conductive sheet may contain a small amount of solvent derived from the conductive composition. When the conductive composition contains a thermosetting resin, the thermosetting resin is typically present in an uncured state in the conductive sheet. The conductive sheet of this embodiment can typically function as an anisotropic conductive sheet.

[0088] <2-1. Structure of the Conductive Sheet> An example of a conductive sheet according to an embodiment of the present invention is shown in Figure 2. Figure 2 shows the conductive sheet 1 placed on the release liner 15. Another aspect of the present invention is to provide a laminate 150 comprising the conductive sheet 1 and the release liner 15. When the conductive sheet 1 is used, the release liner 15 is peeled off from the conductive sheet 1.

[0089] As shown in Figure 2, the conductive sheet 1 has, for example, a matrix 3 and conductive particles 5 dispersed in the matrix 3. More specifically, the matrix 3 surrounds the conductive particles 5. In the matrix 3, the conductive particles 5 may be spaced apart from each other or partially aggregated. In this embodiment, it is preferable that the matrix 3 contains the above-mentioned resin.

[0090] As the release liner 15, the release liner described in section 2-2, "Method for Manufacturing Conductive Sheets," can be used. In the example shown in Figure 2, the conductive sheet 1 is placed on one release liner 15. However, the conductive sheet 1 may be placed between two release liners 15.

[0091] <2-2. Method for Manufacturing a Conductive Sheet> A conductive sheet according to an embodiment of the present invention can be manufactured, for example, by the following method. First, the above-mentioned conductive composition is prepared. Next, the conductive composition is applied to a release liner to form a coating film. A conductive sheet can be formed by drying the coating film. The drying conditions for the coating film are not particularly limited, and for example, the drying temperature is 40°C to 100°C and the drying time is 1 minute to 60 minutes.

[0092] Known materials can be used as the release liner. Examples of the base material for the release liner (hereinafter referred to as "liner base material") include resin films. Examples of resins that make up the resin film include polyester such as polyethylene terephthalate, acetate resin, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. Preferably, the resin that makes up the resin film is polyester such as polyethylene terephthalate. The thickness of the release liner is, for example, 1 μm to 100 μm.

[0093] The peel-off liner may include layers other than the liner substrate. The peel-off liner may include a release layer. For example, the peel-off liner includes a liner substrate and a release layer formed on one side of the liner substrate. In the peel-off liner, the release layer may be on the side of the coating film.

[0094] <2-3. Physical Properties of Conductive Sheets> The thickness of the conductive sheet is, for example, 50 μm or less, and may be 25 μm or less, 15 μm or less, or even 10 μm or less. The thickness of the conductive sheet is, for example, 1 μm or more.

[0095] ≪3. Connection Structure≫ <3-1. Configuration of the Connection Structure> An example of a connection structure according to an embodiment of the present invention is shown in Figure 3. The connection structure 100 shown in Figure 3 comprises a first substrate 20, a second substrate 30, and a connecting member 10. A first electrode 21 is arranged on the first substrate 20, and a second electrode 31 is arranged on the second substrate 30. The connecting member 10 is formed from the conductive composition described above and connects the first substrate 20 and the second substrate 30. The first substrate 20, the connecting member 10, and the second substrate 30 are arranged in this order in the stacking direction Y.

[0096] The first substrate 20 is typically a wiring circuit board. The first substrate 20 has, for example, a flat plate shape and a pair of main surfaces (the surfaces of the first substrate 20 that have the largest surface area). Of the pair of main surfaces, the first electrode 21 is arranged on the main surface facing the connecting member 10.

[0097] Examples of materials for the first substrate 20 include insulating materials and semiconductor materials. The thickness of the first substrate 20 is, for example, 5 μm to 1000 μm.

[0098] The first electrodes 21 are arranged in a pattern on the first substrate 20, for example. For example, the first electrodes 21 may be arranged in a dot pattern. In this case, the shape of the first electrodes 21 is typically columnar (such as cylindrical or prismatic). In this embodiment, a plurality of columnar first electrodes 21 may be arranged in an evenly aligned plane direction X perpendicular to the stacking direction Y. Figure 3 shows an example in which two first electrodes 21 are arranged on the first substrate 20.

[0099] Examples of materials for the first electrode 21 include metals such as gold, copper, and nickel.

[0100] The thickness of the first electrode 21 is, for example, 0 μm to 20 μm, and may be 0.001 μm to 5 μm. At least a portion of the first electrode 21 may be embedded in the first substrate 20. In this case, the thickness of the portion of the first electrode 21 that protrudes from the first substrate 20 is considered to be the thickness of the first electrode 21. That is, if the first electrode 21 does not protrude from the first substrate 20 and the surface of the first electrode 21 coincides with the surface of the first substrate 20, the thickness of the first electrode 21 is 0 μm.

[0101] When the first electrode 21 is cylindrical, the diameter of the first electrode 21 in plan view is, for example, 1 μm to 200 μm, and may be 1 μm to 100 μm, 1 μm to 50 μm, or even 1 μm to 20 μm.

[0102] The distance (pitch) between two adjacent first electrodes 21 in the planar direction X is, for example, 3 μm to 400 μm, and may be 5 μm to 200 μm, 7 μm to 100 μm, or even 10 μm to 40 μm.

[0103] The second substrate 30 is typically a wiring circuit board. However, the second substrate 30 may also be a chip component such as a mini / micro LED. The second substrate 30 has, for example, a flat plate shape and a pair of main surfaces. The second electrode 31 is placed on the main surface of the pair of main surfaces that faces the connecting member 10.

[0104] The material and thickness of the second substrate 30 are as described above for the first substrate 20.

[0105] The second electrodes 31 are arranged in a pattern on the second substrate 30, for example. For example, the second electrodes 31 may be arranged in a dot pattern. In this case, the shape of the second electrodes 31 is typically columnar (such as cylindrical or prismatic). In this embodiment, a plurality of columnar second electrodes 31 may be arranged evenly aligned in the planar direction X. Figure 3 shows an example in which two second electrodes 31 are arranged on the second substrate 30.

[0106] The material and dimensions of the second electrode 31, such as its thickness, are as described above for the first electrode 21.

[0107] Preferably, the distance (pitch) between two adjacent second electrodes 31 in the planar direction X is the same as the distance (pitch) between two adjacent first electrodes 21 in the planar direction X. In other words, it is preferable that the second electrodes 31 face the first electrodes 21, and that these electrodes 21 and 31 are aligned along the stacking direction Y. More specifically, it is preferable that the second electrodes 31 overlap the first electrodes 21 in a plan view.

[0108] The connecting member 10 has a conductive portion 6 and an insulating portion 7. The conductive portion 6 is in direct contact with the first electrode 21 arranged on the first substrate 20 and the second electrode 31 arranged on the second substrate 30, and electrically connects them. The conductive portion 6 makes it possible to exhibit conductivity in the stacking direction Y.

[0109] It is preferable that the conductive portion 6 overlaps the first electrode 21 and the second electrode 31 in a plan view. If the first electrode 21 and the second electrode 31 are arranged in a pattern, it is preferable that the conductive portion 6 is also arranged in a pattern. For example, the conductive portion 6 may be arranged in a dot pattern. In this case, the shape of the conductive portion 6 is typically columnar (such as cylindrical or prismatic). In this embodiment, a plurality of columnar conductive portions 6 may be arranged evenly aligned in the planar direction X. Figure 3 shows an example in which two conductive portions 6 are arranged within the connecting member 10.

[0110] The conductive portion 6 is formed by the aggregation of conductive particles. Therefore, the conductive portion 6 typically contains a material derived from the conductive particles. If the conductive particles are solder particles, the conductive portion 6 may be formed by the melting and aggregation of the solder particles.

[0111] The insulating portion 7 surrounds the conductive portion 6 and fills the space between the first substrate 20 and the second substrate 30 where the conductive portion 6 is not present. The insulating portion 7 is in direct contact with the surface of the first substrate 20 where the first electrode 21 is not placed, and with the surface of the second substrate 30 where the second electrode 31 is not placed. The insulating portion 7 can function as an adhesive portion that adheres to the first substrate 20 and the second substrate 30, respectively. The insulating portion 7 ensures insulation in the plane direction X.

[0112] The insulating portion 7 is formed by the curing of a resin such as epoxy resin, as described later. Typically, the insulating portion 7 includes a material derived from the matrix of the conductive sheet.

[0113] The thickness of the connecting member 10 is, for example, 50 μm or less, and may be 25 μm or less, 15 μm or less, or even 5 μm or less. The thickness of the connecting member 10 is, for example, 1 μm or more.

[0114] <3-2. Method for Manufacturing a Connecting Structure> A method for manufacturing a connecting structure 100 according to an embodiment of the present invention includes, for example, placing a conductive composition (typically a conductive sheet 1 composed of the conductive composition) between a first substrate 20 and a second substrate 30, and heating the conductive composition to form a connecting member 10.

[0115] The connecting structure 100 can be manufactured in detail by the following method. First, as shown in Figure 4A, a conductive sheet 1 made of a conductive composition is placed between the first substrate 20 and the second substrate 30. At this time, it is preferable that the conductive sheet 1 is in contact with both the first electrode 21 and the second electrode 31.

[0116] Next, the conductive sheet 1 is heated. The conductive sheet 1 is typically heated by the following first heating. If the conductive particles 5 are solder particles, it is preferable to heat the conductive sheet 1 by first heating and second heating. In the first heating, the conductive sheet 1 is heated to a temperature above the softening point of the resin in the conductive sheet 1 (for example, solid epoxy resin or solid polymer resin). If the conductive particles 5 are solder particles, it is preferable that the temperature of the first heating is below the melting point P of the solder particles. As a result of the first heating, the conductive sheet 1 softens and the first electrode 21 and the second electrode 31 each become embedded in the conductive sheet 1 (Figure 4B). As a result, the first electrode 21 and the second electrode 31 each become embedded in the conductive sheet 1. The conductive sheet 1 comes into contact with the surface of the first substrate 20 where the first electrode 21 is not placed and the surface of the second substrate 30 where the second electrode 31 is not placed.

[0117] The heating temperature in the first heating stage is, for example, 180°C or lower, and may be 100°C or lower, 80°C or lower, or even 70°C or lower. The above heating temperature is, for example, 40°C or higher.

[0118] In the first heating stage, pressure may be applied to the laminate of the first substrate 20, the conductive sheet 1, and the second substrate 30 in the stacking direction Y to cause them to be pressed together (thermocompressed). The pressure applied to the laminate in the first heating stage may be, for example, 0.001 MPa to 10 MPa, 0.005 MPa to 5 MPa, or even 0.01 MPa to 1 MPa.

[0119] As described above, if the conductive particles 5 are solder particles, it is preferable to perform a second heating on the conductive sheet 1. The second heating is typically performed after the first heating. In the second heating, the conductive sheet 1 is heated to a temperature above the melting point P of the conductive particles (solder particles) 5. Due to the second heating, the conductive particles (solder particles) 5 in the conductive sheet 1 melt and aggregate (self-aggregate) between the first electrode 21 and the second electrode 31. This forms a conductive portion 6 that electrically connects the first electrode 21 and the second electrode 31. At this time, the resin constituting the matrix 3 of the conductive sheet 1 hardens while surrounding the conductive portion 6, thereby forming an insulating portion 7. In this way, the connecting member 10 is formed from the conductive sheet 1 by the first and second heating, and a connecting structure 100 (Figure 3) can be obtained. Note that if the conductive particles 5 are not solder particles, the above second heating is not necessarily required.

[0120] The heating temperature for the second heating step is, for example, 70°C or higher, and may be 100°C or higher, 120°C or higher, 130°C or higher, 150°C or higher, or even 200°C or higher. The heating temperature is, for example, 380°C or lower, and may be 350°C or lower, 330°C or lower, 300°C or lower, 280°C or lower, or even 270°C or lower.

[0121] The second heating step may be performed using a pressure oven. A pressure oven allows the conductive sheet 1 to be heated under pressure in a sealed space. This tends to suppress the volatilization of some of the components of the conductive sheet 1 and the generation of voids. Examples of pressure ovens include automatic heating and pressurizing equipment, pressurizing ovens, voidless pressurizing ovens, autoclaves, and vacuum pressurizing reflow apparatus.

[0122] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way to these examples. Where "parts" is mentioned, it means "parts by weight" unless otherwise specified, and where "%" is mentioned, it means "percent by weight" unless otherwise specified.

[0123] (Example 1) First, a dicyclopentadiene type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., trade name "XD-1000", epoxy equivalent 245-260 g / eq, solid (25°C)) was dissolved in methyl ethyl ketone to prepare a varnish (solid content concentration 60% by weight).

[0124] Next, 200 parts by weight of solder particles (manufactured by Mitsui Mining & Smelting Co., Ltd., product name "SAC305 ST-3", Sn 96.5% by weight, Ag 3.0% by weight, Cu 0.5% by weight, melting point 218°C, spherical shape, average primary particle diameter 3 μm) as conductive particles, 80 parts by weight (calculated on solid content) of the above varnish made of solid epoxy resin, 20 parts by weight (calculated on solid content) of varnish (manufactured by Mitsubishi Chemical Corporation, product name "jER1256B40", solid content concentration 40% by weight) obtained by dissolving bisphenol A type epoxy resin (weight-average molecular weight 45000, epoxy equivalent 8500 g / eq, solid (25°C)) in methyl ethyl ketone, and 3,3-dimethylglutaric acid (Changzhou Liren Medical) as a flux. The conductive composition of Example 1 was obtained by mixing 15 parts by weight of (manufactured by Technology Co., Ltd.) with methyl ethyl ketone, which is a diluent, so that the solid content was 40% by volume, and stirring.

[0125] (Examples 2-8 and Comparative Example 1) Conductive compositions of Examples 2-8 and Comparative Example 1 were obtained by the same method as in Example 1, except that the types and contents of the materials used were changed as shown in Tables 1 and 2. In Examples 2-8 and Comparative Example 1, solid epoxy resins, polymer resins, fluxes, etc., were dissolved in a solvent such as methyl ethyl ketone beforehand as needed to prepare a varnish, and the varnish was mixed with other materials to prepare the conductive composition. Solder particles were used as conductive particles in all of these examples and comparative examples.

[0126] <First Acid Dissociation Constant pKa1 of Flux> The first acid dissociation constant pKa1 of the flux used in the examples and comparative examples was determined by the following method. First, the flux was dissolved in deionized water to prepare 20 mL of an aqueous solution of flux (concentration 0.5 mol / L). An aqueous solution of sodium hydroxide with a concentration of 0.5 mol / L (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., product name: 0.5 mol / L sodium hydroxide solution) was added dropwise to this aqueous solution and a neutralization titration was performed. The neutralization titration was performed under temperature conditions of 25°C. During the neutralization titration, the first acid dissociation constant pKa1 was determined using a pH meter (manufactured by AS ONE, pH meter (pen type), Code No: 1-062-01, Model: AS600).

[0127] <Average Epoxy Equivalents> For the resins used in the examples and comparative examples, the average epoxy equivalent was calculated based on the epoxy equivalent of each resin and its content.

[0128] <Measurement of Complex Viscosity> The complex viscosity η of the conductive compositions of the examples and comparative examples was measured by the following method. First, the conductive composition was applied to a release liner using an applicator to form a coating film. Multiple conductive sheets with a thickness of 50 μm were prepared by drying the coating film at 60°C for 5 minutes. Multiple conductive sheets were laminated to prepare a laminate with a thickness of 320 ± 50 μm, and a measurement sample with a bottom diameter of 25.0 mm was obtained by punching out this laminate into a disc shape. This measurement sample was set in a rheometer (manufactured by Anton Paar, product name "MCR302e"), and dynamic viscoelasticity measurement was performed under the following measurement conditions. Measurement conditions Measurement environment: atmospheric atmosphere Strain value: 0.5% Measurement frequency: 1 Hz Temperature range: 25°C to 300°C Heating rate: 10°C / min Shape: parallel plate 25.0 mmφ

[0129] Next, a temperature-complex viscosity profile was created from the results of dynamic viscoelasticity measurements. From this profile, the minimum complex viscosity η0 and the complex viscosity η1 at a temperature 30°C lower than the temperature T0 at which complex viscosity η0 is observed (T0-30°C) were identified. Furthermore, the highest temperature T at which the complex viscosity η is 500,000 mPa·s or less was identified. MAX and minimum temperature T MINThey also identified it.

[0130] <Integration Test> Using the conductive compositions of the examples and comparative examples, connection structures were fabricated by the following method, and the amount of conductive composition overflow and the solder integration were evaluated. Note that solder integration is an indicator of the reliability of the electrical connection in the connection structure.

[0131] (Fabrication of connecting structure) First, the conductive composition was applied to the release surface of the release liner using an applicator to form a coating film. In Example 1, a polyethylene terephthalate (PET) liner (manufactured by Toyobo Co., Ltd., product name "TN-200", thickness 50 μm) was used as the release liner. In Examples 2 to 8 and Comparative Example 1, a polyethylene terephthalate (PET) liner (manufactured by Higashiyama Film Co., Ltd., product name "HY-NS40", thickness 38 μm) was used as the release liner.

[0132] Next, conductive sheets were fabricated by drying the coating film using a constant temperature bath. Specifically, in Example 1 and Comparative Example 1, the coating film was dried at 60°C for 5 minutes to obtain conductive sheets with a thickness of 5 μm. In Examples 2 to 8, the coating film was dried at 80°C for 5 minutes to obtain conductive sheets with a thickness of 20 μm. The thickness of the conductive sheets was adjusted by the thickness of the coating film, taking into account the average primary particle size of the solder particles used.

[0133] Next, a dummy wafer with an Au electrode (10 mm x 10 mm) and alkali-free glass (20 mm x 20 mm) were prepared. In Example 1 and Comparative Example 1, a dummy wafer with an electrode of 10 μm square and an electrode end-to-end distance of 10 μm was used. In Examples 2 to 8, a dummy wafer with an electrode of 50 μm square and an electrode end-to-end distance of 50 μm was used. Next, the release liner was peeled off the fabricated conductive sheet, and the conductive sheet was placed between the dummy wafer and the alkali-free glass.

[0134] Next, a first heating (thermocompression bonding) was performed on the laminate of the dummy wafer, conductive sheet, and alkali-free glass. In Comparative Example 1, the first heating was performed for 2 seconds at a temperature of 40°C and a pressure of 0.3 MPa. In Examples 1 to 8, the first heating was performed for 2 seconds at a temperature of 65°C and a pressure of 0.3 MPa.

[0135] Next, the laminate was placed in a vacuum pressure reflow apparatus (SST Vacuum Reflow System, product name "Model1200 Table Top Furnace"), vacuuming was performed, and then a second heating was carried out. For Examples 1 to 7 and Comparative Example 1, which used SAC305 solder particles, the second heating was performed under the following conditions: pressurized to 4.5 atmospheres with nitrogen, heating rate of 200°C / min, maximum temperature of 260°C, and holding time of 30 seconds. For Example 8, which used SnBi58 solder particles, the second heating was performed under the following conditions: pressurized to 4.5 atmospheres with nitrogen, heating rate of 100°C / min, maximum temperature of 170°C, and holding time of 30 seconds. As a result, a connecting member was formed from the conductive sheet, and a connecting structure was obtained.

[0136] (Evaluation of conductive composition overflow) The amount of conductive composition overflow was evaluated for the fabricated connection structure using the following method. First, the connection structure was observed in a plan view from the dummy wafer side using an optical microscope (digital microscope, manufactured by Keyence Corporation, product name "VHX-8000"). The observation of the connection structure was performed under a magnification of 300x.

[0137] For one of the four end faces defining the outer shape of the dummy wafer, the distance between that end face and the end of the conductive composition that protruded beyond that end face was measured. The above measurement was performed on all end faces, and the average of the obtained distances was identified as the amount of conductive composition overhang.

[0138] (Evaluation of Solder Integration) The solder integration of the fabricated connection structure was evaluated using the following method. First, the connection structure was observed from the alkali-free glass side using an optical microscope (digital microscope, manufactured by Keyence Corporation, product name "VHX-8000"). The connection structure was observed at a magnification of 500x in four different field-of-view areas.

[0139] Next, for the 35 electrodes within the observation field, electrodes that were completely covered with solder were evaluated as pass, and those with part or all of their surface exposed were evaluated as fail. The ratio of electrodes evaluated as pass was considered the solder density, and evaluation was performed based on the following criteria: • Evaluation Criteria 4: Solder density is 95% or higher. 3: Solder density is 90% or higher but less than 95%. 2: Solder density is 80% or higher but less than 90%. 1: Solder density is less than 80%.

[0140] <Solder Connection Evaluation> Using the conductive compositions of Examples 2 and 4, connection structures were fabricated using the following method, and the solder connections were evaluated.

[0141] First, a conductive composition was applied to a release liner (polyethylene terephthalate (PET) liner, manufactured by Higashiyama Film Co., Ltd., product name "HY-NS40", thickness 38 μm) using an applicator to form a coating film. A conductive sheet with a thickness of 20 μm was prepared by drying the coating film at 80°C for 5 minutes.

[0142] Next, two dummy wafers with Au electrodes (10 mm x 10 mm, electrode square 50 μm, electrode edge-to-edge distance 50 μm) were prepared. At this time, a high-precision die bonding apparatus (Finetech, product name "FINEPLACER lambda 2") was used to adjust the position of the electrodes of the opposing wafers so that they were aligned via a conductive sheet.

[0143] Next, the laminate was placed in a vacuum pressure reflow apparatus (SST Vacuum Reflow System, product name "Model1200 Table Top Furnace"), and then vacuum was applied. Subsequently, it was pressurized to 4.5 atmospheres with nitrogen and heated under the conditions of a heating rate of 200°C / min, a maximum temperature of 260°C, and a holding time of 60 seconds. As a result, connecting members were formed from the conductive sheets, and a connecting structure was obtained.

[0144] The obtained connection structures were embedded in resin, and the laminated cross-section was exposed by mechanical polishing. The laminated cross-section was observed with an optical microscope (name "VHX-7000", manufactured by Keyence Corporation), and the solder connection between opposing electrodes was evaluated based on the following criteria: • Evaluation Criteria 2: Solder connection between opposing electrodes was observed. 1: Solder connection between opposing electrodes was not observed.

[0145]

[0146]

[0147] The abbreviations in Tables 1 and 2 are as follows: SAC305 ST-3: Manufactured by Mitsui Mining & Smelting Co., Ltd., product name "SAC305 ST-3", Sn 96.5% by weight, Ag 3.0% by weight, Cu 0.5% by weight, melting point 218°C, spherical shape, average primary particle diameter 3 μm SAC305 STC-7: Manufactured by Mitsui Mining & Smelting Co., Ltd., product name "SAC305 STC-7", Sn 96.5% by weight, Ag 3.0% by weight, Cu 0.5% by weight, melting point 218°C, spherical shape, average primary particle diameter 8 μm SnBi58 STC-7: Manufactured by Mitsui Mining & Smelting Co., Ltd., product name "Sn42Bi58 STC-7", Sn 42% by weight, Bi 58% by weight, melting point 139°C, spherical shape, average primary particle diameter 8 μm jER828: Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name "jER828", epoxy equivalent weight 184-194 g / eq, liquid (25°C)) XD1000: Dicyclopentadiene type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product name "XD-1000", epoxy equivalent weight 245-260 g / eq, solid (25°C)) NC7000H: Naphthalene type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product name "NC-7000-H", epoxy equivalent weight 223-238 g / eq, solid (25°C)) NC3000H: Biphenyl type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product name "NC-3000-H", epoxy equivalent weight 280-300 g / eq, solid (25°C)) EOCN102070: Cresol novolac type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., product name "EOCN-1020-70", epoxy equivalent 191-207 g / eq, solid (25°C)) NPES907: Bisphenol A type epoxy resin (manufactured by Nanya Plastics Co., Ltd., product name "NPES907", epoxy equivalent 1500-1600 g / eq, solid (25°C), softening point 120-130°C) jER1256: Varnish obtained by dissolving bisphenol A type epoxy resin (weight-average molecular weight 45000, epoxy equivalent 8500 g / eq, solid (25°C)) in methyl ethyl ketone (manufactured by Mitsubishi Chemical Corporation, product name "jER1256B40", solid content concentration 40% by weight) Note that the content of each component listed in Tables 1-2 is the value excluding the solvent (solid content equivalent).

[0148] As can be seen from Tables 1 and 2, the minimum complex viscosity η0 ranged from 2,000 mPa·s to 500,000 mPa·s, and the conductive compositions of the examples in which the equation η1 / η0 > 3.7 holds true for complex viscosity η0 and complex viscosity η1 showed smaller amounts of overflow measured by the above method compared to the comparative examples.

[0149] The conductive composition of the present invention can be used for connecting wiring circuit boards.

Claims

1. A conductive composition comprising conductive particles and a resin, wherein, when the complex viscosity η of the conductive composition is measured by raising the temperature from 25°C at a heating rate of 10°C / min, the minimum complex viscosity η0 is between 2000 mPa·s and 500000 mPa·s, and the following equation (1) holds true for the complex viscosity η0 (mPa·s) and the complex viscosity η1 (mPa·s) at a temperature 30°C lower than the temperature T0 at which the complex viscosity η0 is observed (T0-30°C): η1 / η0 > 3.7 (1) 2. The conductive composition according to claim 1, wherein the ratio of the complex viscosity η1 to the complex viscosity η0, η1 / η0, is 50 or less.

3. The conductive composition according to claim 1, wherein the temperature T0 is 100°C or higher.

4. The maximum temperature T at which the complex viscosity η is 500,000 mPa·s or less. MAX and the lowest temperature T MIN The difference T MAX -T MIN The conductive composition according to claim 1, wherein the temperature is 85°C or lower.

5. The conductive composition according to claim 1, wherein the conductive particles are solder particles.

6. The conductive composition according to claim 1, wherein the resin comprises at least one selected from the group consisting of epoxy resin, (meth)acrylic resin, phenoxy resin, and phenolic resin.

7. The conductive composition according to claim 1, wherein the resin comprises an epoxy resin.

8. The conductive composition according to claim 7, wherein the weight-average molecular weight of the epoxy resin is less than 10,000.

9. The conductive composition according to claim 7, wherein the epoxy resin comprises repeating units having glycidyl groups.

10. The conductive composition according to claim 7, wherein the epoxy resin has at least one selected from the group consisting of a dicyclopentadiene skeleton, a biphenyl skeleton, a naphthalene skeleton, a phenol skeleton, and a cresol skeleton.

11. The conductive composition according to claim 7, wherein the content ratio of the epoxy resin in the solid portion of the resin is 50% by weight or more.

12. The conductive composition according to claim 1, wherein the epoxy equivalent of the resin is 200 g / eq. or more.

13. The conductive composition according to claim 1, wherein the resin comprises a polymer resin having a weight-average molecular weight of 10,000 or more.

14. The conductive composition according to claim 13, wherein the content of the polymer resin in the resin is 20% by weight or less.

15. The conductive composition according to claim 1, further comprising flux.

16. The conductive composition according to claim 15, wherein the first acid dissociation constant pKa1 of the flux is 3.0 to 5.

0.

17. The conductive composition according to claim 15, wherein the flux content is 2.0 to 10 parts by weight per 100 parts by weight of the conductive particles.

18. A conductive sheet comprising a conductive composition according to any one of claims 1 to 17.

19. A connecting structure comprising: a first substrate on which a first electrode is disposed; a second substrate on which a second electrode is disposed; and a connecting member connecting the first substrate and the second substrate, wherein the connecting member is formed from a conductive composition according to any one of claims 1 to 17.

20. A method for manufacturing a connecting structure according to claim 19, comprising: arranging the conductive composition between the first substrate and the second substrate; and heating the conductive composition to form the connecting member.

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