Conductive adhesive

Abstract

To provide a conductive adhesive having high flowability and having conductivity.SOLUTION: A conductive adhesive contains (A) conductive particles, (B) a solvent, (C) a thermosetting resin, and (D) silica particles with an average particle size of 1-50 nm. When the total of the (A) conductive particles, (B) solvent, (C) thermosetting resin, and (D) silica particles is 100 pts.wt., the content of the (D) silica particles is 1-20 pts.wt. and (B) solvent is 0.5-15 pts.wt. The (A) conductive particles may be silver particles.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a conductive adhesive used, for example, for fixing electronic components. [Background technology]

[0002] In electronic and electrical devices, it is necessary to fix tiny electronic components such as camera modules and light emitting diodes (LEDs). Conductive adhesives are used to fix tiny electronic components.

[0003] For example, Patent Document 1 describes a composition for an adhesive or encapsulant, which contains a siloxane polymer having a molecular weight of 300 to 150,000 g / mol and a viscosity of 1000 to 100000 mPa·sec at 25°C measured with a 5 rpm viscometer, and a curing agent that promotes curing of the siloxane polymer when irradiated with ultraviolet light. Patent Document 1 also describes that this material can be used in an LED device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2017-525834 Summary of the Invention [Problem to be solved by the invention]

[0005] Conductive adhesives are used in electronic and electrical devices to secure tiny electronic components such as camera modules and light emitting diodes (LEDs).

[0006] For example, when a camera module is attached to a device, a bracket is used to store it. A method called active alignment is used to attach the camera module.

[0007] In the active alignment method, first, the position of the camera module is adjusted relative to the bracket, and then the camera module is fixed to the bracket with a temporary fixing adhesive. Specifically, the temporary fixing adhesive is introduced, the position of the camera module is adjusted and determined, and then the temporary fixing adhesive is cured with UV light to fix the camera module in the specified position relative to the bracket.

[0008] Next, a conductive adhesive is applied between the camera module and the bracket. By applying the conductive adhesive, electrical conductivity can be obtained between the camera module and the bracket, so that the camera module can be grounded to the bracket.

[0009] Finally, the gap between the camera module and the bracket is filled by introducing a bracket fill adhesive, and the camera module is finally fixed. Since the size of the gap between the camera module and the bracket is small, the bracket fill adhesive needs to have high fluidity. Therefore, the active alignment method requires three types of adhesives: a temporary fixing adhesive, a conductive adhesive, and a bracket fill adhesive.

[0010] In recent years, there has been an increasing demand for injecting adhesive into small gaps for bonding camera modules. Conventionally, adhesives for injecting into small gaps have been limited to insulating adhesives. Conductive adhesives have low fluidity because they contain a large amount of conductive filler (e.g., metal particles) for imparting conductivity. Therefore, conductive adhesives have not been used as adhesives for injecting into small gaps.

[0011] On the other hand, in order to reduce the manufacturing costs of electronic devices and electric devices, it is necessary to mount electronic components more easily. If the conductive adhesive has high fluidity, it may be possible to replace the conductive adhesive and the adhesive for the bracket fill in the above-mentioned active alignment method with one type of conductive adhesive. In other words, by using a conductive adhesive with high fluidity, it may be possible to perform two processes, the process of grounding the camera module to the bracket and the process of finally fixing the camera module, in one process, and it is expected that the manufacturing cost will be reduced.

[0012] Therefore, an object of the present invention is to provide a conductive adhesive that has high fluidity and electrical conductivity. [Means for solving the problem]

[0013] In order to solve the above problems, the present invention has the following configuration.

[0014] (Configuration 1) Configuration 1 of the present invention is a conductive adhesive containing (A) conductive particles, (B) a solvent, (C) a thermosetting resin, and (D) silica particles having an average particle size of 1 to 50 nm.

[0015] According to the first aspect of the present invention, a conductive adhesive having high fluidity and electrical conductivity can be obtained. In particular, a conductive adhesive that can maintain high fluidity even after being jet-dispensed can be provided.

[0016] (Configuration 2) A second aspect of the present invention is the conductive adhesive of the first aspect, which comprises 1 to 20 parts by weight of (D) silica particles, based on 100 parts by weight of the total of (A) the conductive particles, (B) the solvent, (C) the thermosetting resin, and (D) the silica particles.

[0017] The conductive adhesive according to configuration 2 of the present invention contains a predetermined amount of silica particles, and thus has a given electrical conductivity and high fluidity.

[0018] (Configuration 3) Configuration 3 of the present invention is the conductive adhesive of configuration 1 or 2, in which (D) silica particles are premixed with (C) the thermosetting resin.

[0019] As in the third aspect of the present invention, the silica particles are mixed in advance with the thermosetting resin, so that the silica particles can be mixed with the conductive particles more uniformly. Also, the conductive adhesive can have higher fluidity.

[0020] (Configuration 4) A fourth aspect of the present invention is the conductive adhesive of any one of the first to third aspects, which comprises 0.5 to 15 parts by weight of (B) the solvent when the total of (A) the conductive particles, (B) the solvent, (C) the thermosetting resin, and (D) the silica particles having an average particle size of 1 to 50 nm is 100 parts by weight.

[0021] According to configuration 4 of the present invention, the conductive adhesive contains a predetermined amount of solvent, which makes it easy to handle as a conductive adhesive and more reliably ensures the fluidity of the conductive adhesive.

[0022] (Configuration 5) A fifth aspect of the present invention is the conductive adhesive of any one of the first to fourth aspects, wherein the (A) conductive particles are silver particles.

[0023] According to the fifth aspect of the present invention, since the electrical conductivity of silver is higher than that of other metals, a conductive adhesive with higher electrical conductivity can be obtained.

[0024] (Configuration 6) A sixth aspect of the present invention is the conductive adhesive of any one of the first to fifth aspects, wherein the (B) solvent contains an aromatic hydrocarbon.

[0025] According to configuration 6 of the present invention, the solvent contains an aromatic hydrocarbon, which makes it possible to obtain superior handleability as a conductive adhesive and more reliably obtain the fluidity of the conductive adhesive.

[0026] (Configuration 7) A seventh aspect of the present invention is the conductive adhesive of any one of the first to sixth aspects, wherein the thermosetting resin (C) comprises an epoxy resin or an acrylic resin.

[0027] According to the seventh aspect of the present invention, the thermosetting resin contains an epoxy resin or an acrylic resin, so that the electronic component to be fixed can be fixed more reliably.

[0028] (Configuration 8) An eighth aspect of the present invention is a conductive adhesive for a camera module, comprising the conductive adhesive of any one of the first to seventh aspects.

[0029] The conductive adhesive of the present invention has both high fluidity and a predetermined electrical conductivity, and therefore can satisfy the requirements for fluidity and electrical conductivity required when fixing a camera module.

[0030] (Configuration 9) A ninth aspect of the present invention is a jet-dispensing conductive adhesive comprising the conductive adhesive of any one of the first to seventh aspects.

[0031] The conductive adhesive of the present invention has high fluidity and can therefore be preferably used for jet dispensing. Effect of the Invention

[0032] According to the present invention, it is possible to provide a conductive adhesive having high fluidity and electrical conductivity. In particular, it is possible to provide a conductive adhesive that can maintain high fluidity even after the conductive adhesive is jet dispensed. [Brief description of the drawings]

[0033] [Figure 1] FIG. 2 is a schematic side view of a jig for measuring the fluidity of a conductive adhesive. [Diagram 2] FIG. 2 is a schematic diagram showing a jig for measuring the fluidity of a conductive adhesive, as viewed from above. [Diagram 3] FIG. 2 is a schematic diagram showing the arrangement of electrodes and a conductive adhesive for measuring the electrical resistance of the conductive adhesive. [Figure 4] FIG. 1 is a schematic cross-sectional view of an example of a jet dispenser. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the following embodiments are forms for embodying the present invention, and are not intended to limit the scope of the present invention.

[0035] The conductive adhesive according to an embodiment of the present invention is a conductive adhesive including (A) conductive particles, (B) a solvent, (C) a thermosetting resin, and (D) silica particles. The average particle size of the silica particles (D) is 1 to 50 nm. According to this embodiment, a conductive adhesive having high fluidity and conductivity can be obtained.

[0036] <(A) Conductive particles> The conductive adhesive of this embodiment includes conductive particles (A). The conductive particles are not particularly limited, and conductive metal particles can be used. The metal type of the metal particles can be silver (Ag), gold (Au), copper (Cu), nickel (Ni), palladium (Pd), platinum (Pt), tin (Sn), and alloys thereof. The conductive particles can be one type of metal particle or alloy particle alone, or two or more types of metal particles or alloy particles can be used in combination.

[0037] In an embodiment of the present invention, the conductive particles are preferably silver particles or alloy particles containing silver, and more preferably silver particles. The electrical conductivity of silver is higher than that of other metals. By using silver particles as the conductive particles, a conductive adhesive with higher electrical conductivity can be obtained.

[0038] The shape of the conductive particles is not particularly limited, and for example, spherical, granular, flake-like, or scaly conductive particles can be used.

[0039] The conductive particles have an average particle size of preferably 0.1 μm to 50 μm, more preferably 0.1 μm to 10 μm, still more preferably 0.1 μm to 7 μm, and most preferably 0.1 μm to 5 μm. The average particle size referred to here means the volume-based median diameter (d50) obtained by a laser diffraction scattering type particle size distribution measurement method.

[0040] The method for producing the conductive particles is not particularly limited, and the conductive particles can be produced, for example, by a reduction method, a pulverization method, an electrolysis method, an atomization method, a heat treatment method, or a combination thereof. For example, silver particles can also be produced by these production methods. Flake-shaped silver particles can be produced, for example, by crushing spherical or granular silver particles with a ball mill or the like.

[0041] <(B) Solvent> The conductive adhesive of this embodiment includes a solvent (B). Examples of the solvent include alcohols such as methanol, ethanol, and isopropyl alcohol (IPA), organic acids such as ethylene acetate, aromatic hydrocarbons such as solvent naphtha, cyclohexane, toluene, and xylene, N-alkylpyrrolidones such as N-methyl-2-pyrrolidone (NMP), amides such as N,N-dimethylformamide (DMF), ketones such as methyl ethyl ketone (MEK), cyclic carbonates such as terpineol (TEL) and butyl carbitol (BC), and water.

[0042] In the conductive adhesive of the present embodiment, the solvent (B) preferably contains an aromatic hydrocarbon. In order to more reliably obtain a conductive adhesive having excellent handling properties and flowability, it is preferable to use solvent naphtha or cyclohexane as the aromatic hydrocarbon.

[0043] The content of the solvent is not particularly limited. In order to more reliably obtain a conductive adhesive having excellent handling properties and flowability, the conductive adhesive preferably contains 0.5 to 15 parts by weight, more preferably 1 to 14 parts by weight, and even more preferably 2 to 13 parts by weight of the solvent (B) when the total of the conductive particles (A), the solvent (B), the thermosetting resin (C), and the silica particles (D) is taken as 100 parts by weight.

[0044] <(C) Thermosetting resin> The conductive adhesive of this embodiment contains a thermosetting resin (C). The thermosetting resin bonds and fixes the objects to be bonded together, and also bonds the inorganic materials in the conductive adhesive, that is, the conductive particles (A) and the silica particles (D).

[0045] Examples of the thermosetting resin that can be used include cellulose-based resins such as ethyl cellulose and nitrocellulose, acrylic resins, alkyd resins, saturated polyester resins, butyral resins, polyvinyl alcohol, hydroxypropyl cellulose, etc. These resins may be used alone or in combination of two or more.

[0046] The conductive adhesive of the present embodiment preferably contains an epoxy resin or an acrylic resin as the thermosetting resin (C). When the thermosetting resin contains an epoxy resin or an acrylic resin, the electronic component to be fixed can be fixed more reliably.

[0047] The content of the (C) thermosetting resin is preferably 30 to 80 parts by weight, more preferably 35 to 75 parts by weight, and even more preferably 40 to 70 parts by weight, based on 100 parts by weight of the (A) conductive particles. When the content of the thermosetting resin in the conductive adhesive is within the above range, it is possible to reliably bond and fix the objects to be bonded. In addition, it is possible to bond and fix the (A) conductive particles and (D) silica particles, which are inorganic materials in the conductive adhesive, and it is possible to maintain a predetermined conductivity due to the (A) conductive particles.

[0048] <(D) Silica particles> The conductive adhesive of this embodiment contains (D) silica particles having an average particle size of 1 to 50 nm. By having the average particle size of the silica particles be 1 to 50 nm, the conductive adhesive of this embodiment can have high fluidity. In particular, by containing silica particles having an average particle size of 1 to 50 nm, the conductive adhesive can maintain high fluidity even after jet dispensing. Jet dispensing is a supply method that applies a large impact to the conductive adhesive, but the nano-silica of the conductive adhesive of this embodiment is thought to have the effect of reducing the impact on the conductive adhesive during jet dispensing.

[0049] The shape of the silica particles can be spherical or a shape other than spherical. In order to maintain high fluidity, the shape of the silica particles contained in the conductive adhesive of the present embodiment is preferably spherical. The method for producing the silica particles is not particularly limited, and silica particles produced by a known method such as a thermal spraying method can be used.

[0050] The average particle size of the silica particles contained in the conductive adhesive of this embodiment is on the order of nanometers, making it difficult to measure the particle size by a laser diffraction scattering particle size distribution measurement method. The average particle size of the silica particles can be determined by taking a transmission electron microscope (TEM) photograph of the silica particles, measuring the particle sizes of 50 silica particles in the TEM photograph, and calculating the average value. The particle size of the silica particles can be determined by the maximum dimension of the silica particles in the TEM photograph. The particle size of the silica particles can be measured by using known image processing software.

[0051] The conductive adhesive of the embodiment of the present invention preferably contains 1 to 20 parts by weight, more preferably 1 to 10 parts by weight, and even more preferably 1 to 5 parts by weight of (D) silica particles, when the total of (A) conductive particles, (B) solvent, (C) thermosetting resin, and (D) silica particles is taken as 100 parts by weight. By containing a predetermined amount of silica particles, the conductive adhesive of the embodiment of the present invention can have a given conductivity and high fluidity.

[0052] The (D) silica particles contained in the conductive adhesive of the embodiment of the present invention are preferably premixed with the (C) thermosetting resin. By premixing the silica particles with the thermosetting resin as in the embodiment of the present invention, it is possible to obtain higher fluidity. Note that the form in which the silica particles are premixed with the thermosetting resin is sometimes called a master batch.

[0053] <Other ingredients> The conductive adhesive of the present embodiment may contain other additives, for example, dispersants, rheology modifiers, pigments, and the like.

[0054] <Viscosity of conductive adhesive> The initial viscosity (viscosity immediately after production) of the conductive adhesive of this embodiment is preferably 0.1 to 10 (Pa·s). The initial viscosity (viscosity immediately after production) of the conductive adhesive of this embodiment is preferably 0.1 to 10 (Pa·s) after 24 hours from immediately after production (viscosity after 24 hours). The ratio of the initial viscosity to the viscosity after 24 hours (referred to as "viscosity after 24 hours" / "initial viscosity" or "thickening rate after 24 hours") is preferably 0.9 to 1.4, more preferably 1.0 to 1.3. By having the initial viscosity, viscosity after 24 hours, and thickening rate after 24 hours of the conductive adhesive of this embodiment within a predetermined range, the conductive adhesive has high fluidity and can suppress the change in viscosity over time. Therefore, the conductive adhesive of this embodiment has good handleability as a product and can maintain high fluidity.

[0055] The viscosity of the conductive adhesive of this embodiment after jet dispensing is preferably 0.2 to 15 (Pa s), and more preferably 0.5 to 10 (Pa s). Since the viscosity of the conductive adhesive of this embodiment can be kept low even after jet dispensing, the conductive adhesive can be placed in a narrow gap by jet dispensing.

[0056] The viscosity of the conductive adhesive can be measured at a temperature of 25° C. and a rotation speed of 10 rpm using a Brookfield (B-type) viscometer.

[0057] <Method of manufacturing conductive adhesive> The conductive adhesive of this embodiment can be produced by mixing the above-mentioned components using, for example, a Raikai mill, a pot mill, a triple roll mill, a rotary mixer, a twin-shaft mixer, or the like.

[0058] <Applications of conductive adhesives> The use of the conductive adhesive of this embodiment will be described. The conductive adhesive of this embodiment can be used as a sealant and / or an electrode by applying it to a predetermined location. Any application method can be used, and the adhesive can be applied using a known method such as dispensing, jet dispensing, stencil printing, screen printing, pin transfer, stamping, etc.

[0059] After the conductive adhesive of this embodiment is applied to a predetermined position, the applied conductive adhesive can be cured by heat treatment. The heat treatment can be performed by increasing the temperature to 60 to 100°C in 20 to 40 minutes, and then maintaining the temperature after the increase for 50 to 70 minutes to cure the adhesive. Specifically, the temperature can be increased to 80°C in 30 minutes, and then maintained at 80°C for 60 minutes to cure the adhesive.

[0060] The conductive adhesive of the present embodiment can be used as a conductive adhesive for a camera module. The conductive adhesive of the present invention has both high fluidity and a predetermined electrical conductivity. Therefore, the conductive adhesive of the present invention can meet the requirements for fluidity and electrical conductivity required when fixing a camera module.

[0061] The conductive adhesive of the present embodiment can be preferably used as a conductive adhesive for jet dispensing. The conductive adhesive of the present embodiment has high fluidity even after jet dispensing. Therefore, it can be preferably used for fixing a camera module by jet dispensing.

[0062] FIG. 4 shows a schematic cross-sectional view of a jet dispenser (jet dispenser 50). The jet dispenser 50 has a needle 52 capable of reciprocating like a piston, a seal 54 (sealing member) for preventing the conductive adhesive 20 from leaking to the outside even when the needle 52 reciprocates, and a nozzle 56 for jet dispensing the conductive adhesive 20. As shown in FIG. 4(a), the needle 52 reciprocates with a stroke S, so that the conductive adhesive 20 is supplied to the jet dispenser 50 and jet dispensed from the nozzle 56. The nozzle 56 has a shape like a syringe needle with an inner diameter of 100 to 200 μm. As a result, as shown in FIG. 4(b), the conductive adhesive 20 jet-dispensed from the nozzle 56 is supplied to a predetermined object. The conductive adhesive of this embodiment has high fluidity even after jet dispensing, so that the conductive adhesive 20 can be supplied even to a narrow gap.

[0063] The jet dispenser 50 can perform several hundred jet dispense shots per second by the reciprocating motion of the needle 52. This results in a large impact being applied to the conductive adhesive 20. Even after such a large impact is applied, the conductive adhesive 20 of this embodiment can maintain its fluidity.

[0064] Jet dispensing is used to supply adhesive for fixing the camera module to the bracket. In recent years, there has been an increasing demand for injecting adhesive into a smaller gap in order to bond the camera module to the bracket. Specifically, the gap between the bracket and the camera module is several hundred μm (for example, 600 μm), and it is necessary to inject the adhesive over a length of several mm. If the conductive adhesive of this embodiment is jet dispensed after the camera module is fixed to the bracket by the temporary fixing adhesive, the conductive adhesive can be supplied (injected) into the small gap between the camera module and the bracket. The conductive adhesive of this embodiment has conductivity, and therefore has two functions: a conductive adhesive (an adhesive for earthing) and an adhesive for bracket fill (an adhesive for sealing). Therefore, the conductive adhesive of this embodiment can be used as one adhesive instead of two adhesives, the conductive adhesive and the adhesive for bracket fill.

[0065] As described above, by using the highly fluid and conductive conductive adhesive of this embodiment, it may be possible to perform the two steps of grounding the camera module to the bracket and finally fixing the camera module in a single step, which is expected to reduce manufacturing costs.

[0066] The electrical resistivity ρ of the conductive adhesive of this embodiment is 1×10 -4 ~5×10 -1 The conductive adhesive of the present embodiment is preferably used for the purposes of sealing and obtaining electrical conductivity, so there is no need to require high electrical conductivity.

[0067] The conductive adhesive of the present embodiment can be preferably used to fix minute elements, such as camera modules and image sensor modules, to predetermined locations in devices, since it can be supplied to small gaps. In addition, since the conductive adhesive of the present embodiment can be used for sealing and bonding narrow gaps, it can be used to form circuits and electrodes of electronic components, such as chip resistors and light-emitting diodes (LEDs), and to bond electronic components to substrates. EXAMPLES

[0068] Examples and comparative examples of the present invention will be described below. [Preparation of conductive adhesive] Conductive adhesives of the examples and comparative examples were prepared by mixing the following components in the ratios shown in Tables 1 to 3. The ratios of each component shown in Tables 1 to 3 are all shown in parts by weight.

[0069] (A) Silver particles (Silver particles 1) Flake particles, average particle size 6 μm (manufactured by METALOR, product name: EA-0001) (Silver particles 2) Spherical particles, average particle size 5 μm (manufactured by METALOR)

[0070] (B) Solvent (Solvent 1) Solvent naphtha (Maruzen Petrochemical Industry, SW1800) (Solvent 2) Cyclohexane (manufactured by Fujifilm Wako Pure Chemical Industries, product name: Cyclohexane)

[0071] (C) Thermosetting resin (Thermosetting resin 1) Bisphenol F type epoxy resin / bisphenol A type epoxy resin mixture (aromatic epoxy resin) (DIC Corporation, EXA835LV, epoxy equivalent 165) (Thermosetting resin 2) Aminophenol type liquid epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: jER630D)

[0072] (D) Nanosilica (Nanosilica 1) Average particle size: 10 nm, master batch processing (manufactured by Admatechs, product name: YA010AJGP) (Nanosilica 2) Average particle size: 50 nm, master batch processing (manufactured by Admatechs, product name: YA050C-SM1) (Nanosilica 3) Average particle size: 10 nm (Nippon Aerosil Co., Ltd., product name: R805) (Silica 4) Average particle size (D50) 1.5 μm (Admatechs, product name: SE5200 SEE)

[0073] In addition, nanosilica 1 and nanosilica 2 contain a resin component because they are masterbatch-treated. The blending amounts shown in Tables 1 to 3 indicate the blending amounts of only nanosilica excluding the resin component. The weight ratio of nanosilica in nanosilica 1 and nanosilica 2 is 90% by weight of the entire masterbatch, and the weight ratio of the resin component is 10% by weight of the entire masterbatch. For example, in the case of Example 1, the blending amount of nanosilica 1 is 3.8 parts by weight when silver particles 1 are 100 parts by weight, so 4.2 parts by weight of nanosilica 1 that has been masterbatch-treated is blended, and the resin component of nanosilica 1 is 0.42 parts by weight. The resin components of nanosilica 1 and nanosilica 2 are not listed in Tables 1 to 3.

[0074] Other Ingredients (Nano Ag) Average particle size: 100 nm, (METALOR, P620-24) (Hardening agent) Latent hardener (manufactured by T&K TOKA, product name: Fujicure FXR-1020)

[0075] The conductive adhesives used in the examples and comparative examples were produced by mixing the above-mentioned components in a planetary mixer, and then dispersing the mixture in a three-roll mill to form a paste.

[0076] [Method of measuring viscosity] The viscosity of the conductive adhesives of the Examples and Comparative Examples was measured using a Brookfield Type B viscometer at a temperature of 25° C. The viscosity was measured at a rotation speed of 10 rpm for each of the conductive adhesives of the Examples and Comparative Examples.

[0077] The "initial viscosity" in Tables 1 to 3 is the measured value when the viscosity was measured under the above conditions immediately after the conductive adhesive was produced. The "viscosity after 24 hours" in Tables 1 to 3 is the measured value when the viscosity was measured under the above conditions 24 hours after the "initial viscosity" was measured immediately after the conductive adhesive was produced. The "thickening ratio (times) after 24 hours" in Tables 1 to 3 is the ratio of the "viscosity after 24 hours" to the "initial viscosity" ("viscosity after 24 hours" / "initial viscosity"). If the thickening ratio (times) after 24 hours is too high, the conditions for applying the conductive adhesive change over time, which is not preferable for applying the conductive adhesive with good reproducibility. If the thickening ratio (times) after 24 hours is 1.5 times or less, it can be said that the viscosity increase is acceptable.

[0078] The "Post-JET Viscosity" in Tables 1 to 3 is the measured value when the conductive adhesive is jet-dispensed as specified, the jet-dispensed conductive adhesive is recovered, and the viscosity is measured under the above conditions. If the post-JET viscosity is 10,000 (Pa s) or less, it can be said that the conductive adhesive can be injected by jet dispensing into small gaps, for example, gaps of 600 μm.

[0079] [Method of measuring liquidity] The "fluidity (sec / mm)" in Tables 1 to 3 is an index showing the fluidity of the conductive adhesive 20 when jet-dispensed into a gap of 600 μm. Specifically, the flow rate of the conductive adhesive 20 was measured using a jig as shown in FIG. 1 (schematic view from the side) and FIG. 2 (schematic view from above). That is, as shown in FIG. 1 and FIG. 2, a glass plate 12 was placed on a stainless steel plate 14 via a spacer 16 so that the gap d was 600 μm, and the conductive adhesives 20 of the examples and comparative examples were placed near the opening of the gap (the part indicated by the arrow in FIG. 1) by jet-dispensing. The time t (sec) when the flow of the conductive adhesive 20 into the gap reached a predetermined flow distance L (mm) = 20 mm was measured, and the flow time t / L (sec / mm) per mm was calculated to determine the fluidity. The measurement of the fluidity was performed at 25°C. In the case of Comparative Example 1 and Comparative Example 2 shown in Table 1, the flow distance L did not reach 20 mm. Therefore, in the "fluidity" column in Table 1, "NG (Not Good)" is entered, and the distance at which the flow stopped is entered in parentheses. That is, in the case of the conductive adhesive of Comparative Example 1, the flow stopped at 6 mm, and in the case of the conductive adhesive of Comparative Example 2, the flow stopped at 1 mm.

[0080] [Method of measuring electrical resistance] The "resistance value (Ω)" in Tables 1 to 3 is the measured value of the electrical resistance when the conductive adhesive of the examples and comparative examples was cured. The electrical resistance was measured using electrodes 24 as shown in FIG. 3. That is, as shown in FIG. 3, a pair of strip-shaped electrodes 24 was arranged on the cured glass plate 12 so that the distance D between the electrodes 24 was 40 mm. The conductive adhesive of the examples and comparative examples was arranged on the glass plate 12 and the pair of electrodes 24 by stencil printing so that the width W was 10 mm, and cured. The temperature of the arranged conductive adhesive was raised to 80° C. for 30 minutes, and then the temperature was kept at 80° C. for 60 minutes to cure it. The film thickness of the conductive adhesive when cured was 20 μm. The electrical resistance value between the pair of cured electrodes 24 was measured by a resistance meter R to obtain the electrical resistance value of the examples and comparative examples. The film thickness was measured using a surface roughness and shape measuring instrument (model number: Surfcom 1500SD-2) manufactured by Tokyo Seimitsu Co., Ltd. The electrical resistance was measured using a digital multimeter (model number: 2001) manufactured by TFF Keithley Instruments, Inc.

[0081] As shown in Table 1, Comparative Examples 1 and 2 had problems with viscosity and fluidity after JET. That is, the conductive adhesive of Comparative Example 1, which does not have nanosilica, had a high viscosity after JET of 14.500 (Pa·s), and did not show good fluidity in the fluidity measurement. That is, as shown in Table 1, the conductive adhesive of Comparative Example 1 stopped flowing at 6 mm. Also, the conductive adhesive of Comparative Example 2, which has an average silica particle size of 1.5 μm, had a high viscosity after JET of 22.375 (Pa·s), and showed almost no fluidity in the fluidity measurement. That is, as shown in Table 1, the conductive adhesive of Comparative Example 2 stopped flowing at 1 mm. Also, as shown in Table 1, the conductive adhesive of Comparative Example 3, which has nano Ag instead of nanosilica, had a high viscosity of 13.375 after 24 hours, and the viscosity increase ratio after 24 hours was also a high ratio of 3.8 times.

[0082] In contrast, as shown in Tables 1 to 3, the viscosities after JET of the conductive adhesives of Examples 1 to 14 were 0.625 to 9.875 (Pa·s), which were lower than the viscosities of the conductive adhesives of Comparative Examples 1 and 2. The fluidity of the conductive adhesives of Examples 1 to 14 was 49 to 645 sec / mm, which showed higher fluidity than the conductive adhesives of Comparative Examples 1 and 2, which did not show fluidity. The viscosity of the conductive adhesives of Examples 1 to 14 after 24 hours was 0.375 to 7.875 (Pa·s), and the viscosity increase ratio after 24 hours was also 1.0 to 1.2 times, which was in a good range compared to the viscosity after 24 hours and the viscosity increase ratio (times) after 24 hours of the conductive adhesive of Comparative Example 3. The electrical resistance value was also in the range of 1.8 to 850 Ω (electrical resistivity ρ was 9.0×10 -4 ~4.25×10 -1 Ω·cm), which was an appropriate value for earthing purposes.

[0083] From the above, it is clear that the conductive adhesives of Examples 1 to 14 having a predetermined nanosilica exhibit high fluidity and do not increase in viscosity even after a predetermined time. Therefore, it is clear that the conductive adhesive of the present invention has high fluidity and is conductive. Therefore, it can be said that the conductive adhesive of the present invention can be preferably used as a jet-dispensing conductive adhesive for fixing, for example, a camera module.

[0084] [Table 1]

[0085] [Table 2]

[0086] [Table 3] [Explanation of symbols]

[0087] 12 Glass Plate 14 Stainless steel plate 16 Spacer 20 Conductive adhesive 22 Glass Plate 24 electrodes R resistance meter 50 Jet Dispenser 52 Needle 54 Seal (sealing material) 56 Nozzle S Stroke

Claims

1. A conductive adhesive comprising: (A) conductive particles; (B) a solvent; (C) a thermosetting resin; and (D) silica particles, The content of the (C) thermosetting resin is 30 to 80 parts by weight based on 100 parts by weight of the (A) conductive particles, (D) the average particle size of the silica particles is 1 to 50 nm; The conductive adhesive has a viscosity of 0.2 to 15 Pa·s after jet dispensing, as measured at a temperature of 25° C. and a rotation speed of 10 rpm using a Brookfield (B-type) viscometer.

2. 2. The conductive adhesive according to claim 1, comprising 1 to 20 parts by weight of (D) silica particles when the total of (A) the conductive particles, (B) the solvent, (C) the thermosetting resin, and (D) the silica particles is 100 parts by weight.

3. The conductive adhesive according to claim 1 or 2, wherein the silica particles (D) are premixed with the thermosetting resin (C).

4. The conductive adhesive according to any one of claims 1 to 3, comprising 0.5 to 15 parts by weight of the solvent (B) when the total of the conductive particles (A), the solvent (B), the thermosetting resin (C), and the silica particles (D) is 100 parts by weight.

5. The conductive adhesive according to claim 1 , wherein the conductive particles (A) are silver particles.

6. The conductive adhesive according to claim 1 , wherein the solvent (B) comprises solvent naphtha or cyclohexane.

7. The conductive adhesive according to claim 1 , wherein (C) the thermosetting resin comprises an epoxy resin or an acrylic resin.

8. A conductive adhesive for a camera module, comprising the conductive adhesive according to claim 1 .

9. A jet-dispensing conductive adhesive comprising the conductive adhesive of any one of claims 1 to 7.

Images