Electroconductive material, connection structure, and method for manufacturing connection structure

Abstract

Provided is an electroconductive material capable of enhancing bonding strength of an electrode part when electrodes are electrically connected, and improving conduction reliability of a connection structure obtained after repair.　This electroconductive material comprises solder particles, a solvent, an activator, and a binder resin. When a composition obtained by excluding the solder particles from the abovementioned electroconductive material is heated at a temperature increase rate of 3°C / second from 25°C to a solder particle melting point plus 20°C and is kept at the solder particle melting point plus 20°C for three minutes, the weight reduction rate is 50% or less; and when a composition obtained by excluding the solder particles from the electroconductive material is heated at a temperature increase rate of 50°C / second from 25°C to 400°C and kept at 400°C for 30 seconds, the weight reduction rate is 60% or more.

Description

Conductive material, connection structure, and method for manufacturing the connection structure

[0001] The present invention relates to a conductive material containing solder particles, a connection structure using the conductive material, and a method for manufacturing a connection structure using the conductive material.

[0002] Anisotropic conductive materials such as anisotropic conductive pastes and anisotropic conductive films are widely known, and in these anisotropic conductive materials, conductive particles are dispersed in a binder resin.

[0003] The anisotropic conductive material is used to obtain various connection structures, such as a connection between a flexible printed circuit board and a glass substrate (FOG (Film on Glass)), a connection between a semiconductor chip and a flexible printed circuit board (COF (Chip on Film)), a connection between a semiconductor chip and a glass substrate (COG (Chip on Glass)), and a connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)).

[0004] When an anisotropic conductive material containing solder particles is used to electrically connect, for example, electrodes between a flexible printed circuit board and a semiconductor chip (electronic component), the anisotropic conductive material containing solder particles is disposed on the flexible printed circuit board by screen printing or the like. Next, a semiconductor chip is stacked and heated by reflow or the like. When the conductive material is heated above the melting point of the solder particles, the solder particles melt and the solder condenses between the electrodes, electrically connecting the upper and lower electrodes. It is desirable that the solder particles be disposed between the upper and lower electrodes, and it is desirable that they not be disposed between adjacent horizontal electrodes. It is desirable that adjacent horizontal electrodes are not electrically connected.

[0005] Here, if electronic components, etc., are not properly connected, a repair operation may be performed in which only the improperly connected electronic components, etc. are removed and an attempt is made to reconnect the electrodes. In particular, in recent years, the particle size of solder particles has been decreasing due to the finer pitch of wiring and connectors, etc., on printed wiring boards, etc. When a conductive material containing solder particles is screen-printed on a fine-pitched printed wiring board, etc., the solder particles in the conductive material may be disposed in areas where no electrodes are formed. As a result, the amount of solder particles disposed between the upper and lower electrodes to be connected decreases, reducing the reliability of conductivity between the upper and lower electrodes to be connected or the reliability of insulation between adjacent lateral electrodes, resulting in improper connection of the electronic components, etc. For this reason, there is a need for the development of a conductive material with high repairability (the property of being able to easily remove only the improperly connected electronic components, etc., and reconnect the electrodes).

[0006] Patent Document 1 below discloses a mounting structure (connection structure) with improved repairability. The mounting structure is a mounting structure for semiconductor package components including a semiconductor package component having a plurality of first electrodes, a circuit board having a plurality of second electrodes, electrode bumps, a bonding member, and a resin member. In the mounting structure, the electrode bumps are disposed on the first electrodes, the bonding member is disposed on the second electrodes, and the resin member is disposed around the bonding member. In the mounting structure, the electrode bumps and the bonding member are electrically connected, thereby electrically connecting the first electrodes and the second electrodes. In the mounting structure, the bonding member and the resin member form a joint that bonds the electrode bumps and the second electrodes. In the mounting structure, the wetting height of the resin member disposed around the bonding member satisfies (outer wetting height)≦(inner wetting height)×0.8. Furthermore, Patent Document 1 discloses that the joint is a cured product obtained by curing a solder paste containing a solder material, a thermosetting resin, and a curing agent.

[0007] Japanese Patent Application Laid-Open No. 2018-181937

[0008] Conventional conductive materials described in Patent Document 1 and the like can improve repairability to a certain extent. However, with conventional conductive materials, it may be difficult to sufficiently remove residual components of the conductive material that adhere to the surfaces of electronic components, etc. that have not been properly connected. If electronic components, etc. with residual components of the conductive material adhered to their surfaces are reused, the residual components of the conductive material may inhibit the aggregation of solder particles in the newly placed conductive material. As a result, in the connection structure obtained after repair, the amount of solder particles placed between the upper and lower electrodes to be connected decreases, resulting in a problem of reduced reliability of conductivity between the upper and lower electrodes to be connected.

[0009] Furthermore, when electrodes are electrically connected using a conductive material that can be removed at low temperatures (for example, 180°C or lower), the conductive material is removed by heating such as reflow during mounting, which reduces the bond strength of the electrode portions (adhesion strength of the connection portions).If the bond strength of the electrode portions is low, the resulting connection structure will have a problem of low reliability of conduction between the upper and lower electrodes to be connected.

[0010] That is, when conventional conductive materials are used to electrically connect electrodes, it is difficult to increase the bonding strength of the electrode portions and to increase the electrical conductivity reliability of the connection structure obtained after repair.

[0011] An object of the present invention is to provide a conductive material that can increase the bonding strength of the electrode portions when electrically connecting electrodes and can increase the conduction reliability of the connection structure obtained after repair. Another object of the present invention is to provide a connection structure using the conductive material and a method for manufacturing a connection structure using the conductive material.

[0012] This specification discloses the following conductive material, connection structure, and method for manufacturing the connection structure.

[0013] Item 1. A conductive material comprising solder particles, a solvent, an activator, and a binder resin, wherein a composition of the conductive material excluding the solder particles is heated at a temperature rise rate of 3°C / sec from 25°C to a temperature 20°C above the melting point of the solder particles and held at the temperature 20°C above the melting point of the solder particles for 3 minutes, the weight loss rate is 50% or less, and a composition of the conductive material excluding the solder particles is heated at a temperature rise rate of 50°C / sec from 25°C to 400°C and held at 400°C for 30 seconds, the weight loss rate is 60% or more.

[0014] Item 2. The conductive material according to Item 1, wherein the binder resin has a weight loss rate of 20% or less when heated at a temperature rise rate of 3°C / sec from 25°C to a temperature 20°C higher than the melting point of the solder particles and held at the temperature 20°C higher than the melting point of the solder particles for 3 minutes, and a weight loss rate of 70% or more when heated at a temperature rise rate of 50°C / sec from 25°C to 400°C and held at 400°C for 30 seconds.

[0015] Item 3. The conductive material according to Item 1 or 2, wherein the boiling point of the solvent is 180° C. or higher and 400° C. or lower.

[0016] Item 4. The conductive material according to any one of Items 1 to 3, wherein the activator includes an aliphatic carboxylic acid or an aliphatic carboxylate.

[0017] Item 5. The conductive material according to Item 4, wherein the activator includes an aliphatic carboxylic acid.

[0018] Item 6. The conductive material according to any one of Items 1 to 5, wherein the solder particles have an average particle size of 10.0 μm or less.

[0019] Item 7. The conductive material according to any one of Items 1 to 6, wherein the content of the solder particles is 40% by weight or more and 70% by weight or less, based on 100% by weight of the conductive material.

[0020] Item 8. The conductive material according to any one of Items 1 to 7, which is a conductive paste.

[0021] Item 9. A connection structure comprising a first connection-target member having a first electrode on its surface, a second connection-target member having a second electrode on its surface, and a connection part connecting the first connection-target member and the second connection-target member, wherein the material of the connection part is the conductive material according to any one of items 1 to 8, and the first electrode and the second electrode are electrically connected by a solder part in the connection part.

[0022] Item 10. A method for manufacturing a connection structure, comprising the steps of: using the conductive material according to any one of Items 1 to 8 to place the conductive material on a surface of a first connection target member having a first electrode on its surface; placing a second connection target member having a second electrode on its surface on the surface of the conductive material opposite to the first connection target member side, so that the first electrode and the second electrode face each other; and heating the conductive material to a temperature equal to or higher than the melting point of the solder particles to form a connection section connecting the first connection target member and the second connection target member using the conductive material, and electrically connecting the first electrode and the second electrode by a solder section in the connection section.

[0023] The conductive material according to the present invention includes solder particles, a solvent, an activator, and a binder resin. In the conductive material according to the present invention, a composition of the conductive material excluding the solder particles is heated at a temperature increase rate of 3°C / sec from 25°C to a temperature 20°C above the melting point of the solder particles and held at the temperature 20°C above the melting point of the solder particles for 3 minutes, and exhibits a weight loss rate of 50% or less. In the conductive material according to the present invention, a composition of the conductive material excluding the solder particles is heated at a temperature increase rate of 50°C / sec from 25°C to 400°C and held at 400°C for 30 seconds, and exhibits a weight loss rate of 60% or more. Because the conductive material according to the present invention has the above configuration, when electrodes are electrically connected, the bonding strength of the electrodes can be increased and the electrical conductivity reliability of the connection structure obtained after repair can be improved.

[0024] Fig. 1 is a cross-sectional view schematically showing a connection structure obtained using a conductive material according to one embodiment of the present invention. Figures 2(a) to 2(c) are cross-sectional views for explaining an example of a method for producing a connection structure using a conductive material according to one embodiment of the present invention. Fig. 3 is a cross-sectional view showing a modified example of the connection structure.

[0025] The present invention will be described in detail below.

[0026] (Conductive Material) The conductive material according to the present invention includes solder particles, a solvent, an activator, and a binder resin. In the conductive material according to the present invention, the composition of the conductive material excluding the solder particles is heated at a temperature increase rate of 3°C / sec from 25°C to a temperature 20°C above the melting point of the solder particles and then held at the temperature 20°C above the melting point of the solder particles for 3 minutes, and the weight loss rate is 50% or less. In the conductive material according to the present invention, the composition of the conductive material excluding the solder particles is heated at a temperature increase rate of 50°C / sec from 25°C to 400°C and then held at 400°C for 30 seconds, and the weight loss rate is 60% or more.

[0027] Generally, an anisotropic conductive material containing solder particles is placed at a specific position on a substrate by screen printing or the like, and then heated by reflow or the like. When the anisotropic conductive material is heated to a temperature above the melting point of the solder particles, the solder particles melt and the solder condenses between the electrodes, electrically connecting the upper and lower electrodes.

[0028] Here, when electronic components, etc., are not properly connected, a repair operation may be performed in which only the improperly connected electronic components, etc. are removed and an attempt is made to reconnect the electrodes. In particular, in recent years, the particle size of solder particles has been reduced due to the finer pitch of wiring and connectors, etc., on printed wiring boards, etc. When a conductive material containing solder particles is screen-printed on a fine-pitched printed wiring board, etc., the solder particles in the conductive material may be disposed in areas where no electrodes are formed. As a result, the amount of solder particles disposed between the upper and lower electrodes to be connected may decrease, resulting in reduced electrical conductivity between the upper and lower electrodes to be connected or reduced insulation reliability between adjacent lateral electrodes. For this reason, there is a demand for conductive materials with improved repairability (the ability to easily remove only the improperly connected electronic components, etc., and reconnect the electrodes).

[0029] However, with conventional conductive materials, it can be difficult to sufficiently remove residual components of the conductive material that adhere to the surfaces of electronic components, etc. that have not been properly connected. If electronic components, etc. with residual components of the conductive material adhered to their surfaces are reused, the residual components of the conductive material will inhibit the aggregation of solder particles in the newly placed conductive material, resulting in a connection structure obtained after repair in which the amount of solder particles placed between the upper and lower electrodes to be connected will decrease, resulting in a problem of reduced reliability of conductivity between the upper and lower electrodes to be connected.

[0030] Furthermore, when electrodes are electrically connected using a conductive material that can be removed at low temperatures (for example, 180°C or lower; below the melting point of the solder particles), the conductive material is removed by heating such as reflow during mounting, which causes a problem of reduced bonding strength between the electrodes. If the bonding strength of the electrodes is low, there is a problem of reduced reliability of conduction between the upper and lower electrodes to be connected in the resulting connection structure.

[0031] That is, when conventional conductive materials are used to electrically connect electrodes, it is difficult to increase the bonding strength of the electrode portions and to increase the electrical conductivity reliability of the connection structure obtained after repair.

[0032] The present inventors have discovered that by using a conductive material whose weight loss rate satisfies a specific range when a composition excluding solder particles in the conductive material is heated under specific conditions, it is possible to prevent the conductive material from being removed by heating, such as during reflow mounting, and to increase the bonding strength of the electrode portion. Furthermore, the present inventors have discovered that by using a conductive material whose weight loss rate satisfies a specific range when a composition excluding solder particles in the conductive material is heated under specific conditions, it is possible to effectively remove residue components adhering to electronic components that have not been properly connected by heating during repair, and to reuse the electronic components for electrical connection. This invention can sufficiently improve the reliability of conductivity between electrodes to be connected.

[0033] In the present invention, the use of a conductive material that exhibits a weight loss rate that falls within a specific range when the composition excluding the solder particles in the conductive material is heated under specific conditions contributes greatly to achieving the above-described effects.

[0034] The conductive material according to the present invention has the above-mentioned configuration, and therefore when electrodes are electrically connected, the bonding strength of the electrode portion can be increased, and the electrical conductivity reliability of the connection structure obtained after repair can be improved.

[0035] Furthermore, with the conductive material according to the present invention, when connecting the electrodes, the solder particles tend to gather between the upper and lower opposing electrodes, allowing the solder particles to be arranged on the electrodes (lines). Furthermore, some of the solder particles are less likely to be arranged between horizontal electrodes that should not be connected, significantly reducing the amount of solder particles arranged between the horizontal electrodes that should not be connected. As a result, the present invention can effectively improve the reliability of conductivity between the upper and lower electrodes that should be connected, and can effectively improve the reliability of insulation between adjacent horizontal electrodes that should not be connected.

[0036] Furthermore, the present invention can prevent misalignment between electrodes. In the present invention, when a second connection target member is placed on a first connection target member having a conductive material disposed on its upper surface, even if the electrodes of the first connection target member and the second connection target member are misaligned, the misalignment can be corrected to connect the electrodes (self-alignment effect).

[0037] The conductive material has a weight loss rate of 50% or less when the composition excluding the solder particles is heated at a temperature rise rate of 3°C / sec from 25°C to a temperature 20°C above the melting point of the solder particles and then held at the temperature 20°C above the melting point of the solder particles for 3 minutes (heating test A) (hereinafter, sometimes referred to as "weight loss rate A of the composition excluding the solder particles"). The weight loss rate A of the composition excluding the solder particles can be calculated using the following formula:

[0038] Weight reduction rate A (%) of the composition excluding solder particles = (W1 - W2) x 100 / W1 W1: weight of the composition excluding solder particles in the conductive material before heating test A W2: weight of the composition excluding solder particles in the conductive material after heating test A

[0039] From the viewpoint of further increasing the bonding strength of the electrode portions when the electrodes are electrically connected, the weight loss rate A of the composition excluding the solder particles is preferably 45% or less, more preferably 40% or less, and even more preferably 30% or less. The lower limit of the weight loss rate A of the composition excluding the solder particles is not particularly limited. The weight loss rate A of the composition excluding the solder particles may be 0% or more, or may be 5% or more. The range of the weight loss rate A of the composition excluding the solder particles can be set by appropriately selecting the lower limit value and the upper limit value.

[0040] The weight loss rate A of the composition excluding the solder particles can be measured, for example, by the following method. The components of the conductive material excluding the solder particles are mixed to obtain a composition excluding the solder particles. Using a reflow simulator, 10 g (W1) of the composition excluding the solder particles before Heating Test A is heated from 25°C to the melting point of the solder particles + 20°C at a temperature increase rate of 3°C / sec, and the weight (W2) of the composition excluding the solder particles after holding at the melting point of the solder particles + 20°C for 3 minutes (Heating Test A) is measured. The weight loss rate A of the composition excluding the solder particles is calculated from W1 and W2. An example of the reflow simulator is the "core9046a" manufactured by Cores Corporation.

[0041] The conductive material has a weight loss rate of 60% or more when the composition excluding the solder particles is heated from 25°C to 400°C at a temperature increase rate of 50°C / sec and held at 400°C for 30 seconds (heating test B) (hereinafter, sometimes referred to as "weight loss rate B of the composition excluding the solder particles"). The weight loss rate B of the composition excluding the solder particles can be calculated using the following formula:

[0042] Weight reduction rate B (%) of the composition excluding solder particles = (W3 - W4) x 100 / W3 W3: Weight of the composition excluding solder particles in the conductive material before heating test B W4: Weight of the composition excluding solder particles in the conductive material after heating test B

[0043] From the viewpoint of further improving the electrical conductivity reliability of the connection structure obtained after repair, the weight loss rate B of the composition excluding the solder particles is preferably 65% ​​or more, more preferably 70% or more, and even more preferably 80% or more. The upper limit of the weight loss rate B of the composition excluding the solder particles is not particularly limited. The weight loss rate B of the composition excluding the solder particles may be 100% or less, or may be 99% or less. The range of the weight loss rate B of the composition excluding the solder particles can be set by appropriately selecting the lower limit value and the upper limit value.

[0044] The weight loss rate B of the composition excluding the solder particles can be measured, for example, by the following method. The components of the conductive material excluding the solder particles are mixed to obtain a composition excluding the solder particles. Using a hot plate, 10 g of the composition excluding the solder particles (W3) before Heating Test B is heated from 25°C to 400°C at a temperature increase rate of 50°C / sec, and the weight of the composition excluding the solder particles (W4) after holding at 400°C for 30 seconds (Heating Test B) is measured. The weight loss rate B of the composition excluding the solder particles is calculated from W3 and W4. An example of the hot plate is AS ONE Corporation's "PH131B."

[0045] Methods for adjusting the weight loss rates A and B of the composition excluding the solder particles to fall within a preferred range include a method using a preferred binder resin described below, a method adjusting the binder resin content, a method using a preferred solvent described below, and a method using a preferred activator described below.

[0046] From the viewpoint of more efficiently disposing the solder particles on the electrodes, the viscosity (η25) of the conductive material at 25° C. is preferably 30 Pa s or more, more preferably 50 Pa s or more, and is preferably 250 Pa s or less, more preferably 200 Pa s or less. The viscosity (η25) can be adjusted appropriately by the types and amounts of the blended components.

[0047] The viscosity (η25) can be measured, for example, using an E-type viscometer at 25° C. and 5 rpm. Examples of the E-type viscometer include "TVE22L" manufactured by Toki Sangyo Co., Ltd.

[0048] The conductive material can be used as a conductive paste, a conductive film, or the like. The conductive paste is preferably an anisotropic conductive paste, and the conductive film is preferably an anisotropic conductive film. From the viewpoint of more efficiently disposing solder on the electrodes, the conductive material is preferably a conductive paste. The conductive material is suitably used for electrical connection between electrodes. The conductive material is preferably a circuit connection material.

[0049] The environment in which the conductive material is used is not particularly limited, and the conductive material may be used in an environment of 25° C. and 50% RH, or in other environments.

[0050] Each component contained in the conductive material will be described below. In this specification, "(meth)acrylic" refers to acrylic and methacrylic.

[0051] <Solder Particles> The solder particles are formed of solder at both the center and the outer surface. The solder particles are particles in which both the center and the outer surface are solder. If conductive particles comprising a base particle formed of a material other than solder and a solder portion arranged on the surface of the base particle are used instead of the solder particles, the conductive particles are less likely to gather on the electrode. Furthermore, since the conductive particles have low solder bonding between the conductive particles, the conductive particles that have moved onto the electrode tend to easily move outside the electrode, and the effect of suppressing misalignment between electrodes also tends to be reduced.

[0052] The average particle diameter of the solder particles is preferably 40.0 μm or less. The average particle diameter of the solder particles is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, more preferably 30.0 μm or less, even more preferably 20.0 μm or less, even more preferably 15.0 μm or less, particularly preferably 8.0 μm or less, and most preferably 5.0 μm or less. When the average particle diameter of the solder particles is equal to or greater than the above lower limit and equal to or less than the above upper limit, the solder particles can be more efficiently arranged on the electrodes. When the average particle diameter of the solder particles is equal to or less than the above upper limit, the screen printability on fine-pitched substrates and the like can be further improved. In the conductive material according to the present invention, the smaller the average particle diameter of the solder particles, the more efficiently the solder particles can be arranged on the electrodes, effectively improving the conductivity reliability between upper and lower electrodes that should be connected and the insulation reliability between adjacent lateral electrodes that should not be connected. The range of the average particle diameter of the solder particles can be set by appropriately selecting the above lower limit and upper limit.

[0053] The average particle size of the solder particles is preferably a number-average particle size. The average particle size of the solder particles can be determined, for example, by observing 50 random solder particles with an electron microscope or an optical microscope and calculating the average particle size of each solder particle, or by performing laser diffraction particle size distribution measurement. In observation with an electron microscope or an optical microscope, the particle size of each solder particle is determined as the particle size in equivalent circle diameter. In observation with an electron microscope or an optical microscope, the average particle size of 50 random solder particles in equivalent circle diameter is approximately equal to the average particle size in equivalent sphere diameter. In laser diffraction particle size distribution measurement, the particle size of each solder particle is determined as the particle size in equivalent sphere diameter. The average particle size of the solder particles is preferably calculated by laser diffraction particle size distribution measurement.

[0054] The coefficient of variation (CV value) of the particle diameter of the solder particles is preferably 0% or more, more preferably 5% or more, and even more preferably 10% or more, and is preferably 40% or less, and more preferably 30% or less. When the coefficient of variation of the particle diameter of the solder particles is equal to or greater than the lower limit and equal to or less than the upper limit, the solder particles can be arranged on the electrode more efficiently. The coefficient of variation of the particle diameter of the solder particles may be less than 5%. The range of the coefficient of variation of the particle diameter of the solder particles can be set by appropriately selecting the lower limit and the upper limit.

[0055] The coefficient of variation (CV value) can be measured as follows.

[0056] CV value (%) = (ρ / Dn) × 100 ρ: Standard deviation of solder particle diameter Dn: Average value of solder particle diameter

[0057] The shape of the solder particles is not particularly limited, and may be spherical, may be a shape other than spherical, or may be flat or the like.

[0058] From the viewpoint of more efficiently disposing the solder particles on the electrodes, the specific gravity of the solder particles is preferably 4.0 or more, more preferably 5.0 or more, and even more preferably 6.0 or more. The specific gravity of the solder particles may be 20 or less, or may be 10 or less. The range of the specific gravity of the solder particles can be set by appropriately selecting the lower limit and the upper limit.

[0059] The specific gravity of the solder particles can be determined, for example, using "AccuPyc II 1340" manufactured by Shimadzu Corporation.

[0060] The solder in the solder particles is preferably a metal having a melting point of 450°C or less (low-melting-point metal). The solder particles are preferably metal particles having a melting point of 450°C or less (low-melting-point metal particles). The low-melting-point metal particles are particles containing a low-melting-point metal. The low-melting-point metal refers to a metal having a melting point of 450°C or less. The melting point of the low-melting-point metal is preferably 300°C or less, more preferably 260°C or less. The solder is preferably a low-melting-point solder having a melting point of less than 250°C.

[0061] From the viewpoint of further improving connection reliability, the melting point of the solder particles is preferably 100°C or higher, more preferably 150°C or higher, even more preferably 200°C or higher, and preferably 400°C or lower, more preferably 350°C or lower, even more preferably 300°C or lower, and particularly preferably 250°C or lower.

[0062] The melting point of the solder particles can be determined by differential scanning calorimetry (DSC). Examples of DSC devices include the "EXSTAR DSC7020" manufactured by SII Corporation.

[0063] Furthermore, the solder particles preferably contain tin. The tin content of 100% by weight of the metal contained in the solder particles is preferably 30% by weight or more, more preferably 40% by weight or more, even more preferably 70% by weight or more, and particularly preferably 90% by weight or more. When the tin content in the solder particles is equal to or greater than the lower limit, the electrical continuity reliability and connection reliability between the solder portion and the electrode are further improved. The tin content of 100% by weight of the metal contained in the solder particles may be equal to or less than 100% by weight, or may be less than 100% by weight. The range of the tin content of 100% by weight of the metal contained in the solder particles can be set by appropriately selecting the lower limit and the upper limit.

[0064] The tin content can be measured using a high-frequency inductively coupled plasma optical emission spectrometer (for example, "ICP-AES" manufactured by Horiba, Ltd.) or a fluorescent X-ray analyzer (for example, "EDX-800HS" manufactured by Shimadzu Corporation).

[0065] By using the solder particles, the solder melts and bonds to the electrodes, and the solder portion establishes electrical continuity between the electrodes. For example, the solder portion and the electrodes are more likely to have surface contact rather than point contact, which reduces connection resistance. Furthermore, the use of the solder particles increases the bonding strength of the electrodes, which makes it even less likely for the solder portion and the electrodes to peel off, resulting in even higher electrical continuity and connection reliability.

[0066] The low-melting point metal constituting the solder particles is not particularly limited. The low-melting point metal is preferably tin or an alloy containing tin. Examples of such alloys include a tin-silver alloy, a tin-copper alloy, a tin-silver-copper alloy, a tin-bismuth alloy, a tin-zinc alloy, a tin-indium alloy, and a tin-antimony alloy. Because of their excellent wettability with electrodes, the low-melting point metal is preferably tin, a tin-silver alloy, a tin-silver-copper alloy, a tin-bismuth alloy, a tin-indium alloy, or a tin-antimony alloy, and more preferably a tin-silver-copper alloy, a tin-bismuth alloy, a tin-indium alloy, or a tin-antimony alloy.

[0067] The solder particles are preferably filler metals with a liquidus temperature of 450°C or less, based on JIS Z3001: Welding Terminology. Examples of the composition of the solder particles include metal compositions containing zinc, gold, silver, lead, copper, tin, bismuth, and indium. A low-melting-point, lead-free tin-indium system (117°C eutectic) or tin-bismuth system (139°C eutectic) is preferred. In other words, the solder particles are preferably lead-free, and contain tin and indium, or tin and bismuth.

[0068] In order to further increase the bonding strength of the electrode portions, the solder particles may contain metals such as nickel, copper, antimony, aluminum, zinc, iron, gold, titanium, phosphorus, germanium, tellurium, cobalt, bismuth, manganese, chromium, molybdenum, and palladium. Furthermore, from the viewpoint of further increasing the bonding strength between electrodes, the solder particles preferably contain nickel, copper, antimony, aluminum, or zinc. From the viewpoint of further increasing the bonding strength between electrodes, the content of these metals is preferably 0.0001 wt % or more and preferably 1 wt % or less based on 100 wt % of the metals contained in the solder particles.

[0069] The content of the solder particles in 100% by weight of the conductive material is preferably 40% by weight or more, more preferably 50% by weight or more, even more preferably 55% by weight or more, particularly preferably 60% by weight or more, and most preferably 65% ​​by weight or more, and is preferably 90% by weight or less, more preferably 85% by weight or less, even more preferably 80% by weight or less, particularly preferably 75% by weight or less, and most preferably 70% by weight or less. When the content of the solder particles is equal to or greater than the lower limit and equal to or less than the upper limit, the solder particles can be more efficiently arranged on the electrodes, making it easier to arrange a large amount of solder between the electrodes, and further improving the conductivity reliability. From the viewpoint of further improving the conductivity reliability, a higher content of the solder particles is preferable.

[0070] <Solvent> Examples of the solvent include acetone, methanol, ethanol, butanol, 2-propanol, 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol, 2-(benzyloxy)ethanol, 2-phenoxyethanol, diethylene glycol monohexyl ether, propylene glycol monomethyl ether 2-acetate, 2-octanol, 2-acetoxy-1-methoxypropane, toluene, xylene, methyl ethyl ketone, N,N-dimethylformamide, methyl isobutyl ketone, N-methyl-pyrrolidone, n-hexane, cyclohexane, cyclohexanone, and naphtha, which is a mixture, etc. One of the solvents may be used alone, or two or more of them may be used in combination.

[0071] From the viewpoint of further increasing the bonding strength of the electrode portions when the electrodes are electrically connected, the solvent preferably contains 2-(benzyloxy)ethanol or 2-phenoxyethanol, and more preferably contains 2-phenoxyethanol.

[0072] From the viewpoint of further increasing the bonding strength of the electrode portions when the electrodes are electrically connected, the boiling point of the solvent is preferably higher than the melting point of the solder particles. The boiling point of the solvent is preferably the melting point of the solder particles + 10°C or higher, more preferably the melting point of the solder particles + 20°C or higher, even more preferably the melting point of the solder particles + 30°C or higher, and preferably the melting point of the solder particles + 150°C or lower, more preferably the melting point of the solder particles + 100°C or lower, and even more preferably the melting point of the solder particles + 80°C or lower. The boiling point of the solvent is preferably 10°C or higher than the melting point of the solder particles and 150°C or lower than the melting point of the solder particles. When the boiling point of the solvent is above the lower limit, the bonding strength between the electrodes can be further increased when the electrodes are electrically connected. When the boiling point of the solvent is below the upper limit, the conductivity reliability of the connection structure obtained after repair can be further improved.

[0073] The boiling point of the solvent is preferably 180°C or higher, more preferably 190°C or higher, even more preferably 200°C or higher, and preferably 400°C or lower, more preferably 380°C or lower, even more preferably 350°C or lower, particularly preferably 300°C or lower, and most preferably 250°C or lower. If the boiling point of the solvent is above the lower limit, the bonding strength of the electrode portions can be further increased when the electrodes are electrically connected. If the boiling point of the solvent is below the upper limit, the conductivity reliability of the connection structure obtained after repair can be further increased. In particular, if the boiling point of the solvent is below 250°C, the conductivity reliability of the connection structure obtained after repair can be significantly increased.

[0074] The content of the solvent in 100% by weight of the conductive material is preferably 5% by weight or more, more preferably 10% by weight or more, even more preferably 15% by weight or more, and preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less. When the content of the solvent is equal to or greater than the lower limit, the electrical conductivity reliability of the connection structure obtained after repair can be further improved. When the content of the solvent is equal to or less than the upper limit, the bonding strength of the electrode portion can be further improved when the electrodes are electrically connected.

[0075] The content of the solvent is preferably 50 parts by weight or more, more preferably 100 parts by weight or more, even more preferably 150 parts by weight or more, and preferably 300 parts by weight or less, more preferably 250 parts by weight or less, and even more preferably 200 parts by weight or less, relative to 100 parts by weight of the binder resin. When the content of the solvent is equal to or greater than the lower limit, the electrical conductivity reliability of the connection structure obtained after repair can be further improved. When the content of the solvent is equal to or less than the upper limit, the bonding strength of the electrode portion can be further improved when the electrodes are electrically connected.

[0076] <Activator> Examples of the activator include zinc chloride, a mixture of zinc chloride and an inorganic halide, a mixture of zinc chloride and an inorganic acid, a molten salt, an organic phosphorus compound, an organic halide, hydrazine, an amine compound, an organic acid, a salt of an organic acid, and pine resin. The activator may be used alone or in combination of two or more.

[0077] The molten salt may be ammonium chloride or the like.

[0078] Examples of the organic phosphorus compound include organic phosphonium salts, organic phosphoric acids, organic phosphate esters, organic phosphonic acids, organic phosphonic acid esters, organic phosphinic acids, and organic phosphinic acid esters.

[0079] Examples of the amine compound include cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, imidazole, benzimidazole, phenylimidazole, carboxybenzimidazole, benzotriazole, and carboxybenzotriazole.

[0080] The rosin is a rosin containing abietic acid as a main component, and examples of the rosin include abietic acid and acrylic-modified rosin.

[0081] The salt of the organic acid may be a neutralization reaction product (salt) of an organic acid and a basic compound. The salt of the organic acid is preferably a salt produced by the neutralization reaction of an organic acid and a basic compound. The conditions for the neutralization reaction are preferably a heating temperature of 25°C to 150°C and a heating time of 5 to 30 minutes. The organic acid preferably has the effect of cleaning the surface of a metal, and the basic compound preferably has the effect of neutralizing the organic acid.

[0082] The organic acid preferably includes an organic compound (carboxylic acid) having a carboxyl group. Examples of the organic acid include aliphatic carboxylic acids, alicyclic carboxylic acids, and aromatic carboxylic acids. Examples of the aliphatic carboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, citric acid, and malic acid. Examples of the alicyclic carboxylic acids include cyclohexylcarboxylic acid and 1,4-cyclohexyldicarboxylic acid. Examples of the aromatic carboxylic acids include isophthalic acid, terephthalic acid, trimellitic acid, and ethylenediaminetetraacetic acid. From the viewpoint of more efficiently distributing solder particles on electrodes, improving insulation reliability, and more effectively improving conduction reliability, the organic acid preferably includes glutaric acid, cyclohexylcarboxylic acid, or adipic acid.

[0083] The basic compound preferably includes an organic compound having an amino group (amine compound). Examples of the basic compound include diethanolamine, triethanolamine, methyldiethanolamine, ethyldiethanolamine, cyclohexylamine, dicyclohexylamine, benzylamine, benzhydrylamine, 2-methylbenzylamine, 3-methylbenzylamine, 4-tert-butylbenzylamine, N-methylbenzylamine, N-ethylbenzylamine, N-phenylbenzylamine, N-tert-butylbenzylamine, N-isopropylbenzylamine, N,N-dimethylbenzylamine, an imidazole compound, and a triazole compound. From the viewpoint of more efficiently disposing solder particles on the electrodes, improving insulation reliability, and more effectively improving conduction reliability, the basic compound preferably includes benzylamine.

[0084] Examples of the salts of the organic acids include benzylamine adipate, benzylamine glutarate, and cyclohexylamine succinate.

[0085] From the viewpoint of further increasing the electrical conductivity reliability of the connection structure obtained after repair and more efficiently disposing the solder particles on the electrodes, the activator preferably contains an organic acid or a salt of an organic acid, and more preferably contains an aliphatic carboxylic acid or an aliphatic carboxylate. From the viewpoint of further increasing the electrical conductivity reliability of the connection structure obtained after repair and more efficiently disposing the solder particles on the electrodes, the activator preferably contains glutaric acid, adipic acid, glutarate, or adipate.

[0086] From the viewpoint of further increasing the electrical conductivity of the connection structure obtained after repair and more efficiently disposing the solder particles on the electrodes, the activator more preferably contains an organic acid, and even more preferably contains an aliphatic carboxylic acid. From the viewpoint of further increasing the electrical conductivity of the connection structure obtained after repair and more efficiently disposing the solder particles on the electrodes, the activator particularly preferably contains glutaric acid or adipic acid.

[0087] The activator may be dispersed in the conductive material or may be attached to the surface of the solder particles.

[0088] The shape of the activator is not particularly limited. The activator may be spherical, may have a shape other than spherical, or may have a flat shape or the like. From the viewpoint of further improving screen printability, the shape of the activator is preferably spherical.

[0089] The particle size of the activator is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1.0 μm or more, and is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less. When the particle size of the activator is equal to or greater than the above lower limit and equal to or less than the above upper limit, the solder particles can be arranged on the electrode more efficiently.

[0090] The particle size of the activator is preferably an average particle size, and more preferably a number average particle size. The average particle size of the activator can be determined, for example, by observing 50 random activators with an electron microscope or an optical microscope and calculating the average particle size of each activator, or by performing laser diffraction particle size distribution measurement. In observation with an electron microscope or an optical microscope, the particle size of each activator is determined as the particle size in equivalent circle diameter. In observation with an electron microscope or an optical microscope, the average particle size of 50 random activators in equivalent circle diameter is approximately equal to the average particle size in equivalent sphere diameter. In laser diffraction particle size distribution measurement, the particle size of each activator is determined as the particle size in equivalent sphere diameter. The average particle size of the activator is preferably calculated by laser diffraction particle size distribution measurement.

[0091] The melting point (activation temperature) of the activator is preferably 50° C. or higher, more preferably 80° C. or higher, and even more preferably 100° C. or higher, and is preferably 300° C. or lower, more preferably 250° C. or lower, and even more preferably 200° C. or lower. When the melting point of the activator is equal to or higher than the above lower limit and equal to or lower than the above upper limit, the solder particles can be arranged on the electrodes more efficiently.

[0092] The melting point of the activator can be determined by differential scanning calorimetry (DSC). Examples of DSC equipment include the EXSTAR DSC7020 manufactured by SII.

[0093] The content of the activator in 100% by weight of the conductive material is preferably 1% by weight or more, more preferably 3% by weight or more, and even more preferably 5% by weight or more, and is preferably 30% by weight or less, and more preferably 25% by weight or less. When the content of the activator is equal to or more than the above lower limit and equal to or less than the above upper limit, oxide films are more unlikely to form on the surfaces of the solder particles and electrodes, and further, oxide films formed on the surfaces of the solder particles and electrodes can be more effectively removed.

[0094] The content of the activator relative to 100 parts by weight of the binder resin is preferably 10 parts by weight or more, more preferably 30 parts by weight or more, and preferably 100 parts by weight or less, more preferably 70 parts by weight or less. When the content of the activator is equal to or more than the above lower limit and equal to or less than the above upper limit, it becomes even more difficult for an oxide film to form on the surfaces of the solder particles and electrodes, and further, the oxide film formed on the surfaces of the solder particles and electrodes can be more effectively removed.

[0095] The content of the activator is preferably 1 part by weight or more, more preferably 5 parts by weight or more, and preferably 30 parts by weight or less, more preferably 20 parts by weight or less, relative to 100 parts by weight of the solder particles. When the content of the activator is equal to or more than the lower limit and equal to or less than the upper limit, it becomes even more difficult for an oxide film to form on the surfaces of the solder particles and electrodes, and further, the oxide film formed on the surfaces of the solder particles and electrodes can be more effectively removed.

[0096] <Binder Resin> The binder resin is not particularly limited. Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, and elastomers. Only one type of the binder resin may be used, or two or more types may be used in combination.

[0097] Examples of the vinyl resin include vinyl acetate resin and styrene resin. Examples of the thermoplastic resin include (meth)acrylic resin (also simply referred to as "acrylic resin"), polyolefin resin, ethylene-vinyl acetate copolymer, and polyamide resin. Examples of the curable resin include epoxy resin, urethane resin, polyimide resin, and unsaturated polyester resin. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin. The curable resin may be used in combination with a curing agent. Examples of the thermoplastic block copolymer include a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a hydrogenated product of a styrene-butadiene-styrene block copolymer, and a hydrogenated product of a styrene-isoprene-styrene block copolymer. Examples of the elastomer include a styrene-butadiene copolymer rubber and an acrylonitrile-styrene block copolymer rubber.

[0098] From the viewpoint of further improving the conduction reliability of the connection structure obtained after repair, the binder resin preferably contains a thermoplastic resin, and more preferably contains a (meth)acrylic resin.

[0099] The (meth)acrylic resin is not particularly limited. Examples of the (meth)acrylic resin include polymers of monomers such as (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isopropyl (meth)acrylate, and propyl (meth)acrylate. The (meth)acrylic resin may be a homopolymer of the above monomer, a copolymer of the above monomer, or a copolymer of the above monomer with another monomer. Only one type of the above (meth)acrylic resin may be used, or two or more types may be used in combination.

[0100] The binder resin is liquid or solid at room temperature (25°C), and when the binder resin is solid at room temperature, the thermal decomposition temperature of the binder resin is preferably equal to or higher than the melting point of the solder particles, more preferably higher than the melting point of the solder particles. By using the preferred binder resin, it is possible to prevent the conductive material from being removed by heating, such as in a reflow process during mounting, and it is possible to further increase the bonding strength between electrodes.

[0101] From the viewpoint of further increasing the conductivity reliability of the connection structure obtained after repair and more efficiently disposing the solder particles on the electrodes, the binder resin preferably contains a binder resin containing an oxygen atom or a nitrogen atom, and more preferably contains a binder resin containing an oxygen atom or a nitrogen atom in the side chain. From the viewpoint of further increasing the conductivity reliability of the connection structure obtained after repair and more efficiently disposing the solder particles on the electrodes, the binder resin preferably contains a binder resin containing a carboxyl group or an amino group, and more preferably contains a binder resin containing a carboxyl group or an amino group in the side chain. By using these preferred binder resins, residual components adhering to electronic components that have not been properly connected can be effectively removed by heating during repair, thereby improving the conductivity reliability of the connection structure obtained after repair.

[0102] The thermal decomposition initiation temperature of the binder resin is preferably the melting point of the solder particles + 10°C or higher, more preferably the melting point of the solder particles + 20°C or higher, even more preferably the melting point of the solder particles + 30°C or higher, and is preferably the melting point of the solder particles + 150°C or lower, more preferably the melting point of the solder particles + 100°C or lower, and even more preferably the melting point of the solder particles + 80°C or lower. The thermal decomposition initiation temperature of the binder resin is preferably 10°C or higher than the melting point of the solder particles, and preferably 150°C or higher than the melting point of the solder particles. When the thermal decomposition initiation temperature of the binder resin is above the lower limit, removal of the conductive material by heating, such as reflow, during mounting can be suppressed, thereby further increasing the bonding strength of the electrode portion. When the thermal decomposition initiation temperature of the binder resin is below the upper limit, residue components adhering to electronic components that were not properly connected can be effectively removed by heating during repair, thereby improving the conductivity reliability of the connection structure obtained after repair.

[0103] The thermal decomposition onset temperature of the binder resin is preferably 180°C or higher, more preferably 190°C or higher, even more preferably 200°C or higher, and preferably 400°C or lower, more preferably 380°C or lower, and even more preferably 350°C or lower. When the thermal decomposition onset temperature of the binder resin is equal to or higher than the lower limit, the conductive material can be prevented from being removed by heating such as reflow during mounting, and the bonding strength of the electrode portion can be further increased. When the thermal decomposition onset temperature of the binder resin is equal to or lower than the upper limit, residual components adhering to electronic components that have not been properly connected can be effectively removed by heating during repair, and the conductivity reliability of the connection structure obtained after repair can be improved.

[0104] The thermal decomposition onset temperature of the binder resin can be measured, for example, by the following method. Using a thermogravimetric differential thermal analyzer (TG-DTA), 10 g of binder resin is heated from 25°C to 1000°C at a heating rate of 10°C / min. In the obtained TG curve, the temperature at which the weight of the binder resin begins to decrease is defined as the thermal decomposition onset temperature. An example of the thermogravimetric differential thermal analyzer (TG-DTA) is the "NEXTA STA" manufactured by Hitachi High-Tech Science Corporation.

[0105] The binder resin is heated from 25°C to the melting point of the solder particles + 20°C at a temperature increase rate of 3°C / sec, and then held at the melting point of the solder particles + 20°C for 3 minutes (heating test A), and the weight loss rate is defined as the weight loss rate A of the binder resin. The weight loss rate A of the binder resin can be calculated using the following formula.

[0106] Weight reduction rate A (%) of binder resin = (W9 - W10) x 100 / W9 W9: Weight of binder resin before heating test A W10: Weight of binder resin after heating test A

[0107] From the viewpoint of further increasing the bonding strength of the electrode portions when the electrodes are electrically connected, it is preferable that the weight loss rate (weight loss rate A of the binder resin) when the binder resin is heated from 25°C to the melting point of the solder particles + 20°C at a temperature increase rate of 3°C / sec and then held at the melting point of the solder particles + 20°C for 3 minutes is 20% or less. From the viewpoint of further increasing the bonding strength of the electrode portions when the electrodes are electrically connected, the weight loss rate A of the binder resin is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. The lower limit of the weight loss rate A of the binder resin is not particularly limited. The weight loss rate A of the binder resin may be 0% or more or may be 5% or more. The range of the weight loss rate A of the binder resin can be set by appropriately selecting the lower limit and the upper limit.

[0108] The weight loss rate A of the binder resin can be measured, for example, by the following method. Using a reflow simulator, 10 g of binder resin (W9) is heated from 25°C to the melting point of the solder particles + 20°C at a temperature increase rate of 3°C / sec, and then held at the melting point of the solder particles + 20°C for 3 minutes (heating test A), and the weight (W10) of the binder resin is measured. The weight loss rate A of the binder resin is calculated from W9 and W10. An example of the reflow simulator device is the "core9046a" manufactured by Cores Corporation.

[0109] The weight loss rate when the binder resin is heated from 25°C to 400°C at a temperature increase rate of 50°C / sec and held at 400°C for 30 seconds (heating test B) is defined as the weight loss rate B of the binder resin. The weight loss rate B of the binder resin can be calculated by the following formula.

[0110] Weight reduction rate B of binder resin (%) = (W11 - W12) x 100 / W11 W11: Weight of binder resin before heating test B W12: Weight of binder resin after heating test B

[0111] From the viewpoint of further improving the electrical conductivity reliability of the connection structure obtained after repair, it is preferable that the weight loss rate (weight loss rate B of the binder resin) when the binder resin is heated from 25°C to 400°C at a temperature increase rate of 50°C / sec and held at 400°C for 30 seconds is 70% or more. From the viewpoint of further improving the electrical conductivity reliability of the connection structure obtained after repair, the weight loss rate B of the binder resin is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, and particularly preferably 85% or more. The upper limit of the weight loss rate B of the binder resin is not particularly limited. The weight loss rate B of the binder resin may be 100% or less, or may be 99% or less. The range of the weight loss rate B of the binder resin can be set by appropriately selecting the lower limit and the upper limit.

[0112] The weight loss rate B of the binder resin can be measured, for example, by the following method. Using a hot plate, 10 g of binder resin (W11) is heated from 25°C to 400°C at a temperature increase rate of 50°C / sec, and then held at 400°C for 30 seconds (heating test B), and the weight (W12) of the binder resin is measured. The weight loss rate B of the binder resin is calculated from W11 and W12. An example of the hot plate is "PH131B" manufactured by AS ONE Corporation.

[0113] From the viewpoint of further increasing the bonding strength of the electrode portion when the electrodes are electrically connected and further increasing the conductivity reliability of the connection structure obtained after repair, it is preferable that the weight reduction rate A of the binder resin is 20% or less and the weight reduction rate B of the binder resin is 70% or more.

[0114] The content of the binder resin in 100% by weight of the conductive material is preferably 1% by weight or more, more preferably 5% by weight or more, even more preferably 7% by weight or more, and is preferably 70% by weight or less, more preferably 50% by weight or less, even more preferably 30% by weight or less, and particularly preferably 20% by weight or less. When the content of the binder resin is equal to or more than the above lower limit and equal to or less than the above upper limit, when electrodes are electrically connected, the bonding strength of the electrode portions can be further increased, and the conductivity reliability of the connection structure obtained after repair can be further increased.

[0115] The content of the (meth)acrylic resin in 100% by weight of the conductive material is preferably 1% by weight or more, more preferably 5% by weight or more, even more preferably 7% by weight or more, and is preferably 70% by weight or less, more preferably 50% by weight or less, even more preferably 30% by weight or less, and particularly preferably 20% by weight or less. If the content of the (meth)acrylic resin is equal to or more than the above lower limit and equal to or less than the above upper limit, when electrodes are electrically connected, the bonding strength of the electrode portions can be further increased, and the conductivity reliability of the connection structure obtained after repair can be further increased.

[0116] The content of the binder resin relative to 100 parts by weight of the solder particles is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, even more preferably 13 parts by weight or more, and is preferably 50 parts by weight or less, more preferably 45 parts by weight or less, and even more preferably 40 parts by weight or less. When the content of the binder resin is equal to or more than the above-mentioned lower limit and equal to or less than the above-mentioned upper limit, when the electrodes are electrically connected, the bonding strength between the electrodes can be further increased, and the conductivity reliability of the connection structure obtained after repair can be further increased.

[0117] (Other Components) The conductive material may contain various additives, as needed, such as a filler, an extender, a softener, a plasticizer, a leveling agent, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a lubricant, an antistatic agent, and a flame retardant.

[0118] (Connection structure and method for manufacturing connection structure) The connection structure according to the present invention comprises a first connection-target member having a first electrode on its surface, a second connection-target member having a second electrode on its surface, and a connection portion connecting the first connection-target member and the second connection-target member. In the connection structure according to the present invention, the material of the connection portion is the conductive material described above. 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.

[0119] The thickness of the solder between the electrodes is preferably 10 μm or more, more preferably 20 μm or more, and preferably 100 μm or less, more preferably 80 μm or less. The solder wetted area on the surface of the electrode (the area in contact with the solder out of 100% of the exposed area of ​​the electrode) is preferably 50% or more, more preferably 70% or more, and preferably 100% or less.

[0120] A method for manufacturing a connection structure according to the present invention comprises the steps of: using the above-described conductive material to place the conductive material on the surface of a first connection-target member having a first electrode on its surface; and placing a second connection-target member having a second electrode on its surface, on the surface of the conductive material opposite to the first connection-target member, so that the first electrode faces the second electrode. A method for manufacturing a connection structure according to the present invention comprises the steps of heating the conductive material to a temperature equal to or higher than the melting point of the solder particles to form a connection portion connecting the first connection-target member and the second connection-target member using the conductive material, and electrically connecting the first electrode and the second electrode with a solder portion in the connection portion.

[0121] The connection structure according to the present invention uses a specific conductive material, which increases the bonding strength of the electrode portions of the connection structure and improves the electrical conductivity reliability of the connection structure after repair. Furthermore, the connection structure according to the present invention uses a specific conductive material, which makes it easier for solder particles to gather between the first electrode and the second electrode, allowing the solder particles to be efficiently arranged on the electrodes (lines). Furthermore, some of the solder particles are less likely to be arranged in areas (spaces) where no electrodes are formed, significantly reducing the amount of solder particles arranged in areas where no electrodes are formed. Therefore, the electrical conductivity reliability between the first electrode and the second electrode can be improved. Furthermore, electrical connection between laterally adjacent electrodes that should not be connected can be prevented, thereby improving insulation reliability.

[0122] Furthermore, in order to efficiently arrange the solder particles on the electrodes and significantly reduce the amount of solder particles arranged in areas where no electrodes are formed, it is preferable to use a conductive paste rather than a conductive film as the conductive material.

[0123] The thickness of the solder between the electrodes is preferably 10 μm or more, more preferably 20 μm or more, and preferably 100 μm or less, more preferably 80 μm or less. The solder wetted area on the surface of the electrode (the area in contact with the solder out of 100% of the exposed area of ​​the electrode) is preferably 50% or more, more preferably 60% or more, even more preferably 70% or more, and preferably 100% or less.

[0124] In the method for manufacturing a connection structure according to the present invention, it is preferable that no pressure is applied in the process of placing the second connection target member and the process of forming the connection portion, and that the weight of the second connection target member is applied to the conductive material. In the method for manufacturing a connection structure according to the present invention, it is preferable that no pressure exceeding the force of the weight of the second connection target member is applied to the conductive material in the process of placing the second connection target member and the process of forming the connection portion. In these cases, the uniformity of the solder amount in multiple solder portions can be further improved. Furthermore, the thickness of the solder portion can be more effectively increased, making it easier for solder particles to gather between electrodes and allowing the solder particles to be more efficiently arranged on the electrodes (lines). Furthermore, some of the solder particles are less likely to be arranged in areas (spaces) where no electrodes are formed, thereby further reducing the amount of solder arranged in areas where no electrodes are formed. Therefore, the reliability of conductivity between electrodes can be further improved. Moreover, electrical connection between laterally adjacent electrodes that should not be connected can be more effectively prevented, thereby further improving insulation reliability.

[0125] Furthermore, using a conductive paste instead of a conductive film makes it easier to adjust the thickness of the connection and solder joints by adjusting the amount of conductive paste applied. On the other hand, with a conductive film, changing or adjusting the thickness of the connection requires preparing conductive films of different thicknesses or conductive films of a specific thickness. Furthermore, compared with a conductive paste, with a conductive film, the melt viscosity of the conductive film cannot be sufficiently reduced at the melting temperature of the solder particles, which tends to inhibit the aggregation of the solder particles.

[0126] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

[0127] FIG. 1 is a cross-sectional view that schematically shows a connection structure obtained using a conductive material according to one embodiment of the present invention.

[0128] 1 includes a first connection target member 2, a second connection target member 3, and a connection portion 4 connecting the first connection target member 2 and the second connection target member 3. The connection portion 4 is formed from the conductive material described above. In this embodiment, the conductive material includes solder particles, a solvent, an activator, and a binder resin.

[0129] The connection portion 4 has a solder portion 4A in which solder particles are gathered and joined together, and a cured portion 4B in which a thermosetting compound is thermally cured.

[0130] 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 electrodes 2a and the second electrodes 3a are electrically connected by solder portions 4A. Therefore, the first connection target member 2 and the second connection target member 3 are electrically connected by solder portions 4A. In the connection portion 4, no solder particles are present in a region (hardened portion 4B) different from the solder portions 4A gathered between the first electrode 2a and the second electrode 3a. In a region (hardened portion 4B) different from the solder portions 4A, no solder particles are present apart from the solder portions 4A. In a small amount, solder particles may be present in a region (hardened portion 4B) different from the solder portions 4A gathered between the first electrode 2a and the second electrode 3a.

[0131] As shown in FIG. 1 , in the connection structure 1, solder particles gather between the first electrode 2a and the second electrode 3a. After the solder particles melt, the molten solder particles wet and spread over the surface of the electrodes, then solidify, forming a solder portion 4A. This increases the contact area between the solder portion 4A and the first electrode 2a, and between the solder portion 4A and the second electrode 3a. In other words, the use of solder particles increases the contact area between the solder portion 4A and the first electrode 2a, and between the solder portion 4A and the second electrode 3a, compared to when conductive particles whose outer surfaces are made of a metal such as nickel, gold, or copper are used. This also increases the electrical continuity and connection reliability of the connection structure 1. The activator is generally gradually deactivated by heating.

[0132] In the connection structure 1 shown in FIG. 1, all of the solder portions 4A are located in the opposing region between the first and second electrodes 2a, 3a. The modified connection structure 1X shown in FIG. 3 differs from the connection structure 1 shown in FIG. 1 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 opposing region between the first and second electrodes 2a, 3a, and some of the solder portion 4XA may extend laterally from the opposing region between the first and second electrodes 2a, 3a. The solder portion 4XA extending laterally from the opposing region between the first and second electrodes 2a, 3a is part of the solder portion 4XA and is not a solder particle separated from the solder portion 4XA. In this embodiment, the amount of solder particles separated from the solder portion can be reduced, but solder particles separated from the solder portion may be present in the cured portion.

[0133] 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 is increased, it becomes easier to obtain the connection structure 1X.

[0134] In the connection structure 1, 1X, when the portion where the first electrode 2a and the second electrode 3a face each other is viewed in the stacking direction of the first electrode 2a, the connection portion 4, 4X, and the second electrode 3a, the solder portions 4A, 4XA in the connection portion 4, 4X are preferably arranged in 50% or more of the 100% area of ​​the portion where the first electrode 2a and the second electrode 3a face each other. When the solder portions 4A, 4XA in the connection portion 4, 4X satisfy the above-mentioned preferred aspects, the electrical conductivity reliability can be further improved.

[0135] Next, with reference to FIG. 2, an example of a method for manufacturing the connection structure 1 using a conductive material according to one embodiment of the present invention will be described.

[0136] First, a first connection target member 2 having a first electrode 2a on its surface (upper surface) is prepared. Next, as shown in Fig. 2(a), a conductive material 11 containing solder particles 11A, a binder resin 11B, a solvent, and an activator is placed on the surface of the first connection target member 2 (first placement step). In this embodiment, the conductive material 11 is a conductive paste.

[0137] A conductive material 11 is placed on the surface of the first connection target component 2 on which the first electrode 2a is provided. After the conductive material 11 is placed, solder particles 11A are placed on both the first electrode 2a (lines) and the areas (spaces) where the first electrode 2a is not formed. Note that the conductive material may be placed only on the surface of the first electrode.

[0138] The method for disposing the conductive material 11 is not particularly limited, but examples thereof include application by a dispenser, screen printing, and ejection by an inkjet device.

[0139] Also, a second connection target member 3 having a second electrode 3a on its surface (lower surface) is prepared. Next, as shown in Fig. 2(b), a second connection target member 3 is placed on the surface of the conductive material 11 on the surface of the first connection target member 2, opposite the first connection target member 2 side of the conductive material 11 (second placement step). The second connection target member 3 is placed 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.

[0140] Next, the conductive material 11 is heated to a temperature equal to or higher than the melting point of the solder particles 11A (heating step). Preferably, the conductive material 11 is heated below the thermal decomposition end temperature of the binder resin 11B. During this heating, the solder particles 11A present in the area where no electrodes are 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 gather more effectively between the first electrode 2a and the second electrode 3a. Furthermore, the solder particles 11A melt and bond to each other. As a result, as shown in FIG. 2(c), a connection portion 4 connecting the first connection target member 2 and the second connection target member 3 is formed by the conductive material 11. The connection portion 4 is formed by the conductive material 11, and the solder particles 11A are bonded to form a solder portion 4A, and the binder resin 11B is thermally cured to form a cured portion 4B. If the solder particles 11A move sufficiently, it is not necessary to maintain a constant temperature from the time when the movement of the solder particles 11A that are not located between the first electrode 2a and the second electrode 3a begins until the movement of the solder particles 11A between the first electrode 2a and the second electrode 3a is completed.

[0141] It is preferable that no pressure be applied in the second arrangement step and the heating step. In this case, the weight of the second connection target member 3 is added to the conductive material 11. Therefore, when the connection portion 4 is formed, the solder particles 11A are more effectively gathered between the first electrode 2a and the second electrode 3a. Note that if pressure is applied in at least one of the second arrangement step and the heating step, the tendency of the solder particles 11A to gather between the first electrode 2a and the second electrode 3a is more likely to be inhibited.

[0142] When a second connection target member is placed on a first connection target member coated with a conductive material, the first and second connection target members may be placed together with the electrodes of the first and second connection target members misaligned. In this embodiment, since no pressure is applied, even if the first and second connection target members 2 and 3 are placed together with a slight misalignment between the first and second electrodes 2a and 3a, the slight misalignment can be corrected to connect the first and second electrodes 2a and 3a (self-alignment effect). This is because the molten solder self-aggregating between the first and second electrodes 2a and 3a is energetically more stable when the contact area between the solder and other components of the conductive material between the first and second electrodes 2a and 3a is minimized, and a force acts to create an aligned connection structure with the smallest contact area. At this time, it is desirable that the conductive material is not hardened and that the viscosity of the components of the conductive material other than the solder particles is sufficiently low at that temperature and for that time.

[0143] In this way, the connection structure 1 shown in Fig. 1 is obtained. The second arrangement step and the heating step may be performed consecutively. After the second arrangement step, the obtained laminate of the first connection-target member 2, the conductive material 11, and the second connection-target member 3 may be moved to a heating unit and the heating step may be performed. To perform the heating, the laminate may be placed on a heating member, or the laminate may be placed in a heated space.

[0144] The heating temperature in the heating step is preferably the melting point of the solder particles + 10° C. or more, more preferably the melting point of the solder particles + 20° C. or more, even more preferably the melting point of the solder particles + 30° C. or more, and is preferably the melting point of the solder particles + 150° C. or less, more preferably the melting point of the solder particles + 100° C. or less, and even more preferably the melting point of the solder particles + 80° C. or less. When the heating temperature in the heating step is equal to or greater than the lower limit and equal to or less than the upper limit, the bonding strength of the electrode portion of the connection structure can be further increased.

[0145] The heating temperature in the heating step is preferably 170° C. or higher, more preferably 180° C. or higher, and preferably 400° C. or lower, more preferably 350° C. or lower, and even more preferably 300° C. or lower. When the heating temperature in the heating step is equal to or higher than the lower limit and equal to or lower than the upper limit, the bonding strength of the electrode portion of the connection structure can be further increased.

[0146] Heating methods for the heating step include a method of heating the entire connection structure using a reflow furnace or an oven to a temperature above the melting point of the solder particles and below the end temperature of thermal decomposition of the binder resin, and a method of locally heating only the connection portion of the connection structure.

[0147] Examples of tools used for localized heating include a hot plate, a heat gun that applies hot air, a soldering iron, and an infrared heater.

[0148] Furthermore, when heating locally with a hot plate, it is preferable to form the top surface of the hot plate with a metal having high thermal conductivity directly below the connection part, and with a material having low thermal conductivity such as fluororesin for other areas where heating is not desirable.

[0149] If some of the electrodes in the obtained connection structure cannot be properly connected, only the connection target members that were not properly connected (particularly the second connection target member) may be removed, and an operation (repair) may be performed to attempt to connect the electrodes again. The method for manufacturing a connection structure according to the present invention may include a step of determining whether a repair step is necessary during or after the heating step. The method for manufacturing a connection structure according to the present invention may include a repair step after the heating step. The repair step may be performed when it is determined that a repair step is necessary in the step of determining whether a repair step is necessary.

[0150] In the repair step, it is preferable to remove the connection target components that could not be properly connected and the conductive material (particularly, a composition in the conductive material excluding solder particles) that has adhered to the connection target components that could not be properly connected. The repair step may include a step of removing the conductive material and a step of removing the connection target components that could not be properly connected.

[0151] In the repair process, it is preferable that the conductive material adhering to the connection target component that was not properly connected is removed by heating. In the repair process, it is preferable that the conductive material is heated to a temperature equal to or higher than the thermal decomposition end temperature of the binder resin. The heating temperature in the repair process is preferably equal to or higher than the thermal decomposition start temperature of the binder resin, and more preferably equal to or higher than the thermal decomposition end temperature of the binder resin. The heating temperature in the repair process is preferably 300°C or higher, more preferably 350°C or higher, even more preferably 400°C or higher, and preferably 550°C or lower, more preferably 500°C or lower, and even more preferably 450°C or lower. When the heating temperature in the repair process is equal to or higher than the lower limit and equal to or lower than the upper limit, the conductivity reliability of the connection structure obtained after repair can be further improved. The range of the heating temperature in the repair process can be set by appropriately selecting the lower limit and the upper limit.

[0152] The heating time in the repair step is not particularly limited. The heating time in the repair step is preferably 5 seconds or more, more preferably 10 seconds or more, and preferably 60 seconds or less, more preferably 45 seconds or less, and even more preferably 30 seconds or less. When the heating time in the repair step is equal to or greater than the lower limit and equal to or less than the upper limit, the electrical conductivity reliability of the connection structure obtained after repair can be further improved.

[0153] The method for removing the connection target components that could not be properly connected is not particularly limited. In the repair process, the connection target components that could not be properly connected may be removed by laser heating or hot plate heating.

[0154] In the method for manufacturing the connection structure, the first arrangement step, the second arrangement step, and the heating step may be performed again after the repair step. The method for manufacturing the connection structure may include a first arrangement step (1), a second arrangement step (1), a heating step (1), a repair step, a first arrangement step (2), a second arrangement step (2), and a heating step (2). In this way, a connection structure after repair is obtained.

[0155] The first and second connection target members are not particularly limited. Specific examples of the first and second connection target members include electronic components such as semiconductor chips, semiconductor packages, LED chips, LED packages, capacitors, and diodes, as well as electronic components such as resin films, printed circuit boards, flexible printed circuit boards, flexible flat cables, rigid-flexible boards, glass epoxy boards, and glass boards. The first and second connection target members are preferably electronic components.

[0156] At least one of the first and second connection target members is preferably a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid-flexible substrate. The second connection target member is preferably a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid-flexible substrate. Resin films, flexible printed circuit boards, flexible flat cables, and rigid-flexible substrates are highly flexible and relatively lightweight. When a conductive film is used to connect such connection target members, solder particles tend to be less likely to collect on the electrodes. In contrast, by using a conductive paste, solder particles can be efficiently collected on the electrodes, even when a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid-flexible substrate is used, thereby sufficiently improving the conductivity reliability between electrodes. When a resin film, a flexible printed circuit board, a flexible flat cable, or a rigid-flexible substrate is used, the effect of improving the conductivity reliability between electrodes by not applying pressure is more effectively achieved than when other connection target members such as semiconductor chips are used.

[0157] Examples of the electrodes provided on the connection target members 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 members are flexible printed circuit boards, the electrodes are preferably gold electrodes, tin electrodes, silver electrodes, or copper electrodes. When the connection target members are glass substrates, the electrodes are preferably copper electrodes or silver electrodes. When the electrodes are aluminum electrodes, they may be formed solely from aluminum, or may be electrodes 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 element include Sn, Al, and Ga.

[0158] In the connection structure according to the present invention, the first electrode and the second electrode are preferably arranged in an area array or peripheral arrangement. When the first electrode and the second electrode are arranged in an area array or peripheral arrangement, the effects of the present invention are more effectively achieved. The area array refers to a structure in which the electrodes are arranged in a grid pattern on the surface of the connection target component on which the electrodes are arranged. The peripheral arrangement refers to a structure in which the electrodes are arranged on the outer periphery of the connection target component. In a structure in which the electrodes are arranged in a comb-like pattern, it is sufficient for the solder particles to aggregate in a direction perpendicular to the combs, whereas in the area array or peripheral arrangement, the solder particles must aggregate uniformly over the entire surface on which the electrodes are arranged. Therefore, while conventional methods tend to result in uneven solder amounts, the method of the present invention allows the solder particles to aggregate uniformly over the entire surface.

[0159] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0160] Solder particles: Solder particles 1 ("Sn96.5Ag3.0Cu0.5 ST-3" manufactured by Mitsui Kinzoku Co., Ltd., SnAgCu solder particles, average particle diameter: 3.0 μm, melting point: 219°C, specific gravity: 7.4) Solder particles 2 ("Sn96.5Ag3.0Cu0.5 DS10" manufactured by Mitsui Kinzoku Co., Ltd., SnAgCu solder particles, average particle diameter: 10.0 μm, melting point: 219°C, specific gravity: 7.4) Solder particles 3 ("Sn96.5Ag3.0Cu0.5 Type5" manufactured by Mitsui Kinzoku Co., Ltd., SnAgCu solder particles, average particle diameter: 30.0 μm, melting point: 219°C, specific gravity: 7.4)

[0161] Solvent: 2-phenoxyethanol ("Phenyl Cellosolve" manufactured by TCI, boiling point: 237°C) 2-(benzyloxy)ethanol ("Benzyl Cellosolve" manufactured by TCI, boiling point: 256°C)

[0162] Activators: Glutaric acid (Wako "Glutaric acid", solid at 25°C, average particle size: 10 μm, melting point: 96°C) Adipic acid (Wako "Adipic acid", solid at 25°C, average particle size: 10 μm, melting point: 152°C) Glutaric acid benzylamine salt (Showa Chemical Industry Co., Ltd. "Glutaric acid benzylamine salt", solid at 25°C, average particle size: 10 μm, melting point: 110°C) Adipic acid benzylamine salt (Showa Chemical Industry Co., Ltd. "Adipic acid benzylamine salt", solid at 25°C, average particle size: 10 μm, melting point: 180°C)

[0163] Binder resins: Kyoeisha Chemical Co., Ltd. "Orikox KC-1300" ((meth)acrylic resin, weight loss rate A: 10%, weight loss rate B: 90%, thermal decomposition starting temperature: 290°C) Kyoeisha Chemical Co., Ltd. "Orikox KC-1700P" ((meth)acrylic resin, weight loss rate A: 8%, weight loss rate B: 85%, thermal decomposition starting temperature: 300°C) Kyoeisha Chemical Co., Ltd. "Orikox KC-7000F" ((meth)acrylic resin, weight loss rate A: 5%, weight loss rate B: 75%, thermal decomposition starting temperature: 330°C) Shin-Nakamura Chemical Co., Ltd. "EBECRYL3703" ((meth)acrylic resin, liquid at 25°C, weight loss rate A: 10%, weight loss rate B: 15%) "SR368" manufactured by Sartomer Corporation ((meth)acrylic resin, solid at 25°C, weight loss rate A: 5%, weight loss rate B: 15%, thermal decomposition temperature: 400°C)

[0164] (Examples 1 to 10 and Comparative Examples 1 and 2) (1) Preparation of conductive material (anisotropic conductive paste) The components shown in Tables 1 to 3 below were blended in the amounts shown in Tables 1 to 3 below to obtain conductive materials (anisotropic conductive pastes).

[0165] (Evaluation) (1) Weight Loss Rates A and B of Composition Excluding Solder Particles The components shown in Tables 1 to 3 below, excluding solder particles (components excluding solder particles among all components shown in Tables 1 to 3 below), were mixed in the same blending ratio as shown in Tables 1 to 3 below (adjusted to a total of 100 wt %) to obtain a composition excluding solder particles. Using a reflow simulator (Cores Corporation, "core9046a"), 10 g of the composition excluding solder particles (W1) before Heating Test A was heated at a temperature rise rate of 3°C / sec from 25°C to the melting point of the solder particles + 20°C, and then held at the melting point of the solder particles + 20°C for 3 minutes (Heating Test A), and the weight (W2) of the composition excluding the solder particles was measured. The weight loss rate A of the composition excluding the solder particles was calculated from W1 and W2. Furthermore, using a hot plate ("PH131B" manufactured by AS ONE Corporation), 10 g of the composition excluding the solder particles (W3) before Heating Test B was heated from 25°C to 400°C at a temperature increase rate of 50°C / sec, and held at 400°C for 30 seconds (Heating Test B), after which the weight (W4) of the composition excluding the solder particles was measured. From W3 and W4, the weight loss rate B of the composition excluding the solder particles was calculated.

[0166] (2) Bonding Strength of Electrode Portion The obtained conductive material was screen-printed onto a flexible printed circuit board (material: polyimide, thickness: 0.1 mm) having copper electrodes (electrode length: 3 mm, electrode thickness: 12 μm) with an L / S = 50 μm / 50 μm on its surface using a metal mask with dimensions of 80 μm × 80 μm and a thickness of 30 μm per opening, to form a conductive material layer. Next, a 500 μm thick, 4 mm square copper piece was placed on the upper surface of the conductive material layer to obtain a laminate. Thereafter, using a reflow simulator (Cores Corporation "Core9046a"), the obtained laminate was heated from 25 ° C. to the melting point of the solder particles + 20 ° C. at a heating rate of 3 ° C. / sec, and then held at the melting point of the solder particles + 20 ° C. for 3 minutes to obtain a test sample. The die shear strength of the obtained test sample was measured under the following conditions using a die shear tester ("Dage4000Plus" manufactured by Nordson Corporation). The bonding strength of the electrode portion was evaluated according to the following criteria.

[0167] [Conditions for measuring die shear strength] Temperature: 25°C Load cell used: Dage DS100 (for 100 kg) Measurement speed: 300 μm / s Descent speed: 300 μm / s Measurement height: 30 μm

[0168] [Criteria for determining the bond strength of the electrode portion] ◯: Die shear strength is 7.0 N or more ×: Die shear strength is less than 7.0 N

[0169] (3) Conduction reliability after repair (3-1) Fabrication of connection structure As a first connection target member, a glass epoxy substrate (material: FR-4, thickness: 0.6 mm) having copper electrodes (electrode length: 3 mm, electrode thickness: 12 μm) with L / S = 50 μm / 50 μm on its surface was prepared. As a second connection target member, an LED chip (length: 20 mm, width: 20 mm, thickness: 0.4 mm) having copper electrodes (electrode length: 3 mm, electrode thickness: 12 μm) with L / S = 50 μm / 50 μm on its surface was prepared.

[0170] The obtained conductive material was screen-printed on the glass epoxy substrate using a metal mask with openings measuring 80 μm × 80 μm and a thickness of 30 μm to form a conductive material layer (first placement step (1)). Next, an LED chip was stacked on the upper surface of the conductive material layer so that the electrodes faced each other (second placement step (1)). From this state, using a reflow simulator (Cores Corporation's "core9046a"), the resulting stack was heated from 25°C to the melting point of the solder particles + 20°C at a heating rate of 3°C / sec, and then held at the melting point of the solder particles + 20°C for 3 minutes (heating step (1)), thereby obtaining a connection structure. Note that no pressure was applied during heating.

[0171] (3-2) Reconnection (repair) of the resulting connection structure. Using a hot plate ("PH131B" manufactured by AS ONE Corporation), the resulting laminate was heated from 25°C to 400°C at a heating rate of 50°C / s, and held at 400°C for 30 seconds. After that, 50 LED chips were removed from the laminate (repair process). Next, in the same manner as in "(3-1) Preparation of Connection Structure," a metal mask was used to perform screen printing again on the glass epoxy substrate to form a conductive material layer (first placement process (2)). 50 LED chips were then stacked on the upper surface of the conductive material layer with their electrodes facing each other (second placement process (2)). From this state, using a reflow simulator ("core9046a" manufactured by CORS Corporation), the resulting laminate was heated from 25°C to the melting point of the solder particles + 20°C at a heating rate of 3°C / s, and held at the melting point of the solder particles + 20°C for 3 minutes (heating process (2)). This resulted in a repaired connection structure. No pressure was applied during any of the heating steps.

[0172] (3-3) Determination of Conduction Reliability After Repair For the resulting repaired connection structure, a voltage of 3 V was applied using a "CA150 Handy Cal" manufactured by Yokogawa Measurement Co., Ltd. to conduct an LED chip lighting test, and the number of LED chips that lit up among the 50 repaired LED chips was counted. The conduction reliability after repair was determined according to the following criteria.

[0173] [Criteria for evaluating the reliability of electrical continuity after repair] ◯: The number of lit LED chips is 40 or more. ○: The number of lit LED chips is 30 or more but less than 40. ×: The number of lit LED chips is less than 30.

[0174] (4) Screen Printability The obtained conductive material (anisotropic conductive paste) was screen printed on a glass slide using a metal mask with a dimension of 80 μm × 80 μm and a thickness of 30 μm per opening. For 50 printed patterns, the printed surface immediately after printing was observed with a laser microscope to calculate the volume of the conductive material applied to the glass slide, and the ratio X (%) of the volume of the conductive material applied to the glass slide to the volume per opening of the metal mask was calculated. Screen printability was evaluated according to the following criteria.

[0175] [Criteria for Screen Printability] ○○: The ratio X is 80% or more. ○: The ratio X is 60% or more and less than 80%. ×: The ratio X is less than 60%.

[0176] The results are shown in Tables 1 to 3 below.

[0177]

[0178]

[0179]

[0180] The results of the screen printability of both Example 7 and Example 8 were "good", but the value of the ratio X in the evaluation of the screen printability was higher in Example 7 than in Example 8. In other words, the screen printability of Example 7 was superior to that of Example 8.

[0181] REFERENCE SIGNS LIST 1, 1X... Connection structure 2... First member to be connected 2a... First electrode 3... Second member to be connected 3a... Second electrode 4, 4X... Connection portion 4A, 4XA... Solder portion 4B, 4XB... Hardened portion 11... Conductive material 11A... Solder particle 11B... Binder resin

Claims

1. A conductive material comprising solder particles, a solvent, an activator, and a binder resin, wherein the composition of the conductive material excluding the solder particles is heated at a heating rate of 3°C / sec from 25°C to the melting point of the solder particles + 20°C and held at the melting point of the solder particles + 20°C for 3 minutes, with a weight loss rate of 50% or less; and the composition of the conductive material excluding the solder particles is heated at a heating rate of 50°C / sec from 25°C to 400°C and held at 400°C for 30 seconds, with a weight loss rate of 60% or more.

2. The conductive material according to claim 1, wherein the weight loss rate when the binder resin is heated from 25°C to the melting point of the solder particles + 20°C at a heating rate of 3°C / sec and held at the melting point of the solder particles + 20°C for 3 minutes is 20% or less, and the weight loss rate when the binder resin is heated from 25°C to 400°C at a heating rate of 50°C / sec and held at 400°C for 30 seconds is 70% or more.

3. The conductive material according to claim 1 or 2, wherein the boiling point of the solvent is 180°C or higher and 400°C or lower.

4. The conductive material according to any one of claims 1 to 3, wherein the activator comprises an aliphatic carboxylic acid or an aliphatic carboxylate salt.

5. The conductive material of claim 4, wherein the activator comprises an aliphatic carboxylic acid.

6. The conductive material according to any one of claims 1 to 5, wherein the solder particles have an average particle size of 10.0 μm or less.

7. The conductive material according to any one of claims 1 to 6, wherein the content of the solder particles is 40% by weight or more and 70% by weight or less in 100% by weight of the conductive material.

8. The conductive material according to any one of claims 1 to 7, which is a conductive paste.

9. A connection structure comprising: a first member to be connected having a first electrode on its surface; a second member to be connected having a second electrode on its surface; and a connection part connecting the first member to be connected and the second member to be connected, wherein the material of the connection part is a conductive material as defined in any one of claims 1 to 8, and the first electrode and the second electrode are electrically connected by a solder part in the connection part.

10. A method for manufacturing a connection structure, comprising the steps of: using the conductive material according to any one of claims 1 to 8 to place the conductive material on the surface of a first connection target member having a first electrode on its surface; placing a second connection target member having a second electrode on its surface on the surface of the conductive material opposite to the first connection target member, so that the first electrode and the second electrode face each other; and heating the conductive material to a temperature equal to or higher than the melting point of the solder particles to form a connection part using the conductive material that connects the first connection target member and the second connection target member, and electrically connecting the first electrode and the second electrode with a solder part in the connection part.

Images