JP2007197498A - Conductive adhesive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive adhesive which has a long tack-free time and can improve workability, when semiconductor elements such as IC, or chip parts such as chip resisters and chip LED are adhered to lead frames, heat-releasing plates, or the like. <P>SOLUTION: This conductive adhesive comprising conductive powder (A), an epoxy resin (B) and a diluent (C) is characterized in that the contents of the components (A), (B) and (C) are 70 to 85 wt.%, 4 to 36 wt.% and 1 to 20 wt.%, respectively, and the diluent (C) is an organic compound having vapor pressure of ≤1.5 hPa at 20°C and vapor pressure of ≤15 hPa at 170°C. The diluent (C) preferably has viscosity of ≤0.1 Pa s at 25°C and a boiling point of ≥250°C, and includes aliphatic diol diglycidyl ethers, alicyclic diol diglycidyl ethers, and polyalkylene glycol diglycidyl ethers. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive adhesive, and more specifically, has a long tack-free time, and is used when a semiconductor element such as an IC and a chip component such as a chip resistor or a chip LED are bonded to a lead frame or a heat sink. The present invention relates to a conductive adhesive that can improve workability.

  In recent years, semiconductor elements such as ICs, LSIs, LEDs, and the like have been remarkably developed, and mass production is being performed. Accordingly, improvement of workability in mass production and reduction of manufacturing costs are important issues.

  Conventionally, as a method for bonding these semiconductor elements to a lead frame, a substrate, or the like, it has been mainstream to use a solder such as a gold-silicon eutectic solder or a tin-lead solder. However, the conventional methods are expensive in gold, cannot absorb the difference in thermal expansion between the semiconductor element and the lead frame or the substrate, and cracks are generated in the semiconductor element and the solder. A method using a conductive adhesive has become the mainstream because it lacks, the working temperature is relatively high, and the electrodes of semiconductor elements are easily contaminated.

  Commonly used conductive adhesive is composed of conductive powder, organic resin, diluent, catalyst (curing accelerator), etc., and conductive powder includes gold, silver, copper, carbon, etc. Is used. In addition, thermosetting resins such as epoxy resins and phenol resins are often used as organic resins.

These conductive adhesives are usually applied to lead frames and substrates by thick film screen printers or automatic coating equipment, and not only have excellent conductivity, adhesive strength and heat resistance, but also have a long tack-free time. Is required.
Here, the tack free time is one of the indexes representing the workability of the conductive adhesive, and the curing of the applied conductive adhesive proceeds at room temperature until the film is formed on the adhesive surface. Say time. In general, the time is required until a conductive adhesive is applied, the surface is traced with a metal needle, and the conductive adhesive does not adhere to the needle tip.
If the tack-free time of the conductive adhesive is short, connection failure may occur due to mounting of the semiconductor element and the chip component after the film is formed on the adhesive surface. On the other hand, if the tack free time is long, time can be afforded for the work, and therefore, a conductive adhesive having a long tack free time is preferred.

In the past, as a method for extending the tack-free time of a conductive adhesive, there has been proposed a solvent-free conductive adhesive that employs a component that does not require dilution of the epoxy resin with a solvent (for example, patent literature). 1). Here, in addition to conductive powder and epoxy resin, a modified resin mainly composed of bismaleimide and a triazine resin monomer, an aluminum compound, and a solventless conductive adhesive containing a silicon compound are described. .
However, according to such a conductive adhesive, it is expected that the tack-free time is lengthened to some extent. However, since there are many additive components, problems remain in terms of cost and productivity. Moreover, according to the examples, butyl carbitol acetate is blended and it is difficult to say that it is solvent-free.

Under such circumstances, the appearance of a conductive adhesive that has a sufficiently long tack-free time and is excellent in terms of cost and productivity even when there are few additive components has been desired.
Japanese Patent Laid-Open No. 62-285968

  In view of such circumstances, the object of the present invention is to achieve a long tack-free time and work when bonding a semiconductor element such as an IC and a chip component such as a chip resistor or a chip LED to a lead frame or a heat sink. An object of the present invention is to provide a conductive adhesive capable of improving the properties.

  The present inventor conducted extensive research to achieve the above object, and in a conductive adhesive containing silver powder, an epoxy resin and a diluent, a number of diluents were tested in order to increase the tack-free time. Tack-free time of conductive adhesive without impairing various properties such as adhesive strength and electrical resistance by selecting an organic compound whose vapor pressure at 20 ° C and 170 ° C is less than a specific value and blending it with a specific amount. Has been found to be able to be extended, and the present invention has been completed.

That is, according to the first invention of the present invention, in the conductive adhesive containing the conductive powder (A), the epoxy resin (B) and the diluent (C), the content of the three components is (A) Is 70 to 85% by weight, (B) is 4 to 36% by weight, (C) is 1 to 20% by weight, and the diluent (C) has a vapor pressure at 20 ° C. of 1.5 hPa or less, 170 There is provided a conductive adhesive characterized by being an organic compound having a vapor pressure at 15 ° C of 15 hPa or less.
According to a second aspect of the present invention, there is provided the conductive adhesive according to the first aspect, wherein the conductive powder (A) is silver.

On the other hand, according to the third invention of the present invention, in the first or second invention, the diluent (C) has a viscosity at 25 ° C. of 0.1 Pa · s or less. Is provided.
According to a fourth aspect of the present invention, there is provided the conductive adhesive according to any one of the first to third aspects, wherein the diluent (C) has a boiling point of 250 ° C. or higher. The
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the diluent (C) is an aliphatic diol diglycidyl ether, an alicyclic diol diglycidyl ether, or a polyalkylene glycol diester. A conductive adhesive is provided, which is any one selected from glycidyl ether.
Furthermore, according to the sixth invention of the present invention, in the fifth invention, the aliphatic diol diglycidyl ether is 1,6-hexanediol diglycidyl ether or 1,4-butanediol diglycidyl ether. A conductive adhesive is provided.

  On the other hand, according to the seventh aspect of the present invention, there is provided the conductive adhesive according to any one of the first to sixth aspects, wherein the tack free time is 60 minutes or more.

The conductive adhesive of the present invention contains a specific amount of a specific organic compound having a vapor pressure at 20 ° C. of 1.5 hPa or less and a vapor pressure at 170 ° C. of 15 hPa or less as a diluent. By using this conductive adhesive for bonding semiconductor elements such as ICs, chip resistors, chip components such as chip LEDs, and lead frames, heat sinks, etc. Connection failure caused by mounting the semiconductor element and the chip component after the film is formed on the adhesive surface can be reduced.
In addition, after applying the conductive adhesive, it is possible to extend the time until the semiconductor element and chip parts are mounted and heat-cured, which increases the batch processing amount of heat-curing and is expected to improve productivity. it can.

  Hereinafter, the conductive adhesive of the present invention will be described in detail. The conductive adhesive of the present invention is a conductive adhesive containing silver powder (A), epoxy resin (B), and diluent (C), and the vapor pressure at 20 ° C. is 1 as the diluent (C). It is characterized by containing a specific amount of a diluent having a vapor pressure of not more than 5 hPa and a vapor pressure at 170 ° C. of not more than 15 hPa.

  That is, in the present invention, the conductive adhesive is a conductive adhesive containing the conductive powder (A), the epoxy resin (B) and the diluent (C). 70 to 85 wt%, (B) is 4 to 36 wt%, (C) is 1 to 20 wt%, and the diluent (C) has a vapor pressure at 20 ° C of 1.5 hPa or less, 170 ° C. It is an organic compound having a vapor pressure of 15 hPa or less.

(A) Conductive powder The conductive powder in the present invention is not limited by its shape, and scale-like (flakes) and spherical simple substances, or a mixture thereof can be used. In the case of a conductive adhesive in which a mixture of spherical powder and flaky powder is blended, not only is the printability excellent, but the electrical resistance (sheet resistance value) of the adhesive film may be reduced to, for example, 300 mΩ or less.

  The average particle diameter of the conductive powder is not particularly limited. For example, in the case of an adhesive for a circuit board such as a semiconductor, the average particle diameter is 30 μm or less, preferably 20 μm or less, and particularly preferably 5 μm or less. When a fine spherical powder is used, the thixo ratio increases, so that it is suitable for a printing press, but is not suitable for an automatic coating apparatus. However, when scaly powder is mixed with spherical powder, the thixotropy is lowered moderately, resulting in a conductive adhesive suitable for an automatic coating apparatus. Therefore, it is preferable to select the conductive powder as appropriate depending on the method of applying the conductive adhesive.

  Moreover, the mixture ratio of electroconductive powder is set in the range of 70 to 85 weight% with respect to the composition whole quantity. When the conductive powder is less than 70% by weight, sufficient electrical conductivity cannot be obtained, and when it exceeds 85% by weight, the adhesive strength is remarkably lowered and the role as an adhesive is not fulfilled. The blending ratio of the conductive powder is particularly preferably 72 to 83% by weight.

  Silver, copper, nickel, or the like can be used as the conductive powder, but silver is most preferable. As silver, pure silver which does not contain lead is usually used, but an alloy containing tin, bismuth, indium, palladium or the like as a second component may be employed. However, the second component such as tin is desirably 5% by weight or less.

(B) Epoxy resin In the present invention, any known epoxy resin can be used as the epoxy resin, and there is no particular limitation.

  Examples of epoxy resins include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, novolac glycidyl ether, epoxidized soybean oil, mainly used for casting and adhesion of electronic materials. , 4-epoxy-6-methylcyclohexylmethylcarboxylate, 3,4-epoxycyclohexylmethylcarboxylate, and epoxy resin having a structure such as tetraglycidyldiaminodiphenylmethane. Since the present invention is a conductive adhesive, it is preferably liquid at room temperature. These epoxy resins may be used alone or in combination of a plurality of types.

  Moreover, if the object of adhesion is an electronic material, it is desirable that ionic impurities including chlorine ions are 800 ppm or less. In addition, you may mix | blend well-known thermosetting resins, such as a phenol resin and an unsaturated polyester resin, in the epoxy resin in the range which does not impair the objective of this invention.

  Moreover, the mixture ratio of an epoxy resin is set in the range of 4-36 weight% with respect to the composition whole quantity. If the epoxy resin is less than 4% by weight, sufficient adhesion cannot be obtained, and if it exceeds 36% by weight, the electrical conductivity is remarkably lowered. A particularly preferred proportion of the epoxy resin is in the range of 10 to 25% by weight.

The curing agent (curing accelerator) of the epoxy resin is not particularly limited as long as it can rapidly cure with the epoxy resin during heating (60 to 300 ° C.) and can satisfy long-term storage stability at room temperature. There is no.
In general, imidazoles such as 2-ethyl-4-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-heptadecyl imidazole, phenol novolak compound, dicyandiamide, acid anhydride tetrahydromethyl phthalic anhydride, hexahydrophthalic anhydride, methyl hymic anhydride, Lewis acid complex BF ₃ salt, and the like can be used. . These may be used alone or in combination. Since these curing agents (curing accelerators) have different performance depending on the type, the amount to be added cannot be defined, but an amount suitable for the stoichiometric composition with the epoxy resin is desirable.

  For example, it is known that the curing reaction of epoxy resin and 2-ethyl-4-methylimidazole is represented by the following chemical reaction formula, and when used as a single curing (acceleration) agent, 100 parts by weight of epoxy resin On the other hand, 2 to 6 parts by weight of 2-ethyl-4-methylimidazole is considered suitable. In addition, in the present invention, those which are recognized to have a curing accelerating action, such as amine salts and block isocyanates, can also be used.

(C) Diluent In the present invention, the diluent is a solvent for dissolving the resin component of the conductive adhesive, the vapor pressure at 20 ° C. is 1.5 hPa or less, and the vapor pressure at 170 ° C. is 15 hPa or less. Specific organic compounds are used.

  The diluent is not particularly limited depending on the type of the diluent as long as the vapor pressure at 20 ° C. is 1.5 hPa or less and the vapor pressure at 170 ° C. is 15 hPa or less and is compatible with the epoxy resin. . The vapor pressure at 20 ° C. must be 1.5 hPa or less, and the vapor pressure at 170 ° C. must be 15 hPa or less. If the vapor pressure is large at 20 ° C., the amount of volatilization during standing at room temperature is large. This is because the surface dries quickly, and if the vapor pressure is high at 170 ° C., the amount of volatilization during the curing reaction is large, and bubbles (voids) are generated in the cured product. When the vapor pressure at 20 ° C. exceeds 1.5 hPa or the vapor pressure at 170 ° C. exceeds 15 hPa, the tack-free time is long and sufficient adhesive strength cannot be obtained. The diluent preferably has a boiling point of 250 ° C. or higher. If the boiling point is less than 250 ° C., the resin volatilizes before sufficiently curing, and sufficient adhesive strength may not be obtained.

  The diluent is preferably liquid at room temperature and has a viscosity at 25 ° C. of 0.1 Pa · s or less. If the viscosity exceeds 0.1 Pa · s, printability and applicability may be deteriorated.

  In the present invention, a preferred diluent is any one selected from aliphatic diol diglycidyl ether, alicyclic diol diglycidyl ether, or polyalkylene glycol diglycidyl ether.

  Specific examples include aliphatic diol diglycidyl ethers such as 1,6-hexanediol diglycidyl ether and 1,4-butanediol diglycidyl ether, and alicyclic diol diglycidyl ethers such as cyclohexanedimethanol diglycidyl ether. be able to. 1,6-hexanediol diglycidyl ether is commercially available from Sakamoto Yakuhin Kogyo as SR-16H (viscosity at 25 ° C. is 0.025 Pa · s), SR-16HL (viscosity at 25 ° C. is 0.012 Pa · s), In addition, it is commercially available from Nagase ChemteX Corp. as Denacol EX-212L, and also as Yokkaichi Gosei Co., Ltd. Epo Gosei (registered trademark) HD. 1,4-butanediol diglycidyl ether is commercially available from Nagase ChemteX Corp. as Denacol EX-214L, and cyclohexanedimethanol diglycidyl ether is commercially available as EX-216L. Among these, those having a total chlorine content of 3% or less, more preferably 1% or less, and particularly preferably 0.2% or less are more preferable.

  Examples of the polyalkylene glycol diglycidyl ether include diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether. Diethylene glycol diglycidyl ether is commercially available from Sakamoto Yakuhin Kogyo as SR-2EG (viscosity at 25 ° C. of 0.022 Pa · s) and from Nagase ChemteX Corp. as Denacol EX-850L. Polyethylene glycol diglycidyl ether is commercially available from Sakamoto Pharmaceutical Co., Ltd. as SR-8EG (viscosity at 25 ° C. is 0.095 Pa · s) and SR-8EGS (viscosity at 25 ° C. is 0.060 Pa · s). For tripropylene glycol diglycidyl ether, SR-TPG from Sakamoto Pharmaceutical Co., Ltd. (viscosity at 25 ° C. is 0.03 Pa · s), for polypropylene glycol diglycidyl ether, SR-4PG (viscosity at 25 ° C. is 0.053 Pa · s). s). Among these, those having a total chlorine content of 3% or less, more preferably 1% or less, and particularly preferably 0.2% or less are more preferable.

  In the present invention, the diluent is blended in an amount of 1 to 20% by weight, preferably 3 to 10% by weight, based on the total amount of the composition. If the diluent is less than 1% by weight, the viscosity of the conductive adhesive may increase, and printability and applicability may be deteriorated. Conversely, if it exceeds 20% by weight, the viscosity becomes too low. , It may cause sagging and a decrease in adhesive strength during printing and application.

  The conductive adhesive of the present invention preferably has a longer tack-free time, and is preferably 60 minutes or longer, more preferably 120 minutes or longer, particularly 200 minutes or longer. The tack-free time is generally the time required to apply a conductive adhesive to a substrate, trace the surface with a metal needle and measure the surface until the conductive adhesive does not adhere to the needle tip. In the present invention, the tack free time is measured by the following method.

First, a conductive adhesive is applied on a 2.5 cm square copper substrate by screen printing. After coating, after standing for 0, 30, 60, 90, 120 minutes, place a 1.5 mm square silicon chip and leave it in an oven at 150 ° C. for 30 minutes to cure the conductive adhesive. Allow to cool. Thereafter, a force is applied to the silicon chip from the horizontal direction with respect to the substrate, and the force when the silicon chip is peeled is measured as an adhesive strength. Thus, the time when the average value measured at 10 points is reduced by 10% after application is defined as the tack-free time. If the tack free time is 60 minutes or more, it can be evaluated as good. On the other hand, if the tack free time is less than 60 minutes, the workability deteriorates, which is not preferable.
Although this evaluation method is not necessarily a general evaluation method, it is subject to actual use conditions in which a semiconductor element such as an IC and a chip resistor, a chip component such as a chip LED, and a lead frame or a heat sink are bonded. It can be said that it is a more suitable method.

  The conductive adhesive of the present invention is used when bonding a chip member such as a semiconductor element, a chip resistor, or a chip LED to a circuit board such as a lead frame, a printed wiring board (PWB), or a flexible printed board (FPC). Used when wiring above. Copper wiring is the mainstream for wiring on the circuit, but it can also be used for jumpers, through holes, and via holes.

  This adhesive is usually applied directly to a circuit board. In the manufacturing process and mounting process of components such as the above semiconductor elements, chip components, and wiring on the substrate, the conductive adhesive is repeatedly subjected to heat treatment at about 200 to 300 ° C. through a solder furnace and a wire bonding process. However, with the conductive adhesive of the present invention, neither conductivity nor adhesiveness is reduced.

  EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In addition, each sample of Experimental Examples 1-3 and Comparative Examples 1-7 was evaluated by the method shown below after kneading.

[Sample evaluation]
(1) Measurement of sheet resistance value A conductive adhesive was applied by screen printing in a rectangular shape having a width of 2 mm and a length of 5 mm so as to overlap the electrodes between the electrodes 2 mm apart on the alumina substrate. The conductive adhesive was cured by being left in an oven at 150 ° C. for 30 minutes, cooled to room temperature, and the resistance value between the electrodes was measured. When the average value measured at 10 points was less than 500 mΩ, it was judged as good (◯), and when it was 500 mΩ or more, it was judged as impossible (×).

(2) Measurement of adhesive strength A conductive adhesive was applied to a 2.5 cm square copper substrate by screen printing. A 1.5 mm square silicon chip was placed and allowed to stand in an oven at 150 ° C. for 30 minutes to cure the conductive adhesive and cooled to room temperature. Thereafter, a force was applied to the silicon chip from the horizontal direction with respect to the substrate, and the force when the silicon chip was peeled was measured as the adhesive strength. When the average value measured at 10 points was 25N (Newton) or more, it was judged as good (◯), and when it was less than 25N, it was judged as impossible (x).

(3) Measurement of heat resistance strength A conductive adhesive was applied on a 2.5 cm square copper substrate by screen printing. A 1.5 mm square silicon chip was placed and allowed to stand in an oven at 150 ° C. for 30 minutes to cure the conductive adhesive and cooled to room temperature. Thereafter, the substrate is allowed to stand for 30 seconds on a hot plate heated to 260 ° C., and a force is applied to the silicon chip from the horizontal direction against the substrate while being heated. As measured. If the average value measured at 10 points was 5N or more, it was judged as good (◯), and if it was less than 5N, it was judged as impossible (x).

(4) Measurement of tack free time A conductive adhesive was applied to a 2.5 cm square copper substrate by screen printing. After coating, after standing for 0, 30, 60, 90, 120 minutes, place a 1.5 mm square silicon chip and leave it in an oven at 150 ° C. for 30 minutes to cure the conductive adhesive. Until cooled. Thereafter, a force was applied to the silicon chip from the horizontal direction with respect to the substrate, and the force when the silicon chip was peeled was measured as the adhesive strength. The time when the average value measured at 10 points was reduced by 10% after application was defined as tack-free time. When the tack free time was 60 minutes or more, it was judged as good (◯), and when it was less than 1 hour, it was judged as impossible (x).

(5) Comprehensive evaluation If all the above four items are good (◯), it is judged as pass (◯), and even one that does not satisfy the condition is not acceptable (×).

(Examples 1-3)
Using the following silver powder component, epoxy resin component, curing agent / curing accelerator component, and diluent component as raw materials, blended according to the weight proportions in Table 1, prepared an adhesive composition, a three-roll kneader It was used and kneaded to obtain the conductive adhesive of the present invention.
As the silver powder, scaly silver powder having an average particle diameter of 1.45 μm (trade name: TC-25A, manufactured by Tokuru Chemical Laboratory Co., Ltd.) was used. As the epoxy resin, bisphenol A diglycidyl ether type epoxy resin (trade name: Epicoat 828, manufactured by Japan Epoxy Resin Co., Ltd.) was used. Further, dicyandiamide was used as a curing agent for the epoxy resin, and 2-phenyl-4,5-dihydroxymethylimidazole was used as a curing accelerator.
On the other hand, the diluent is SR-16H (1,6-hexanediol diglycidyl ether, vapor pressure 1.0 hPa (20 ° C.), vapor pressure 7.0 hPa (170 ° C.), and chlorine content 7.0% as diluent a1. , Boiling point 250 ° C. or higher, manufactured by Sakamoto Yakuhin Kogyo Co., Ltd., and SR-16HL (1,6-hexanediol diglycidyl ether, vapor pressure 1.0 hPa (20 ° C.), vapor pressure 7 as diluent a2. 0.0 hPa (170 ° C.), chlorine content 0.3%, boiling point 250 ° C. or higher, low chlorine product manufactured by Sakamoto Pharmaceutical Co., Ltd.).
Using this adhesive, printing was performed on an alumina substrate, and the volume resistivity was measured under the above conditions. Moreover, after dripping on the copper substrate and making it harden | cure, the adhesive strength and the hot strength were measured. The conductive adhesive of the present invention was dropped on the lead frame, the semiconductor chip was mounted, and after curing, the thermal conductivity was measured. Furthermore, the conductive adhesive of the present invention was printed on a substrate with a screen, and the printability was evaluated. The results are shown in Table 2.

(Comparative Examples 1-3)
As shown in Table 1, except that the type of the diluent component was changed, it was blended in the same manner as in the above examples, kneaded using a three-roll kneader, and a conductive adhesive for comparison was used. Obtained.
Note that n-butyl glycidyl ether (deer grade 1, vapor pressure 5.0 hPa (20 ° C.), boiling point 164 ° C., manufactured by Kanto Chemical Co., Ltd.) as diluent b, and isopropyl glycidyl ether (vapor pressure 12) as diluent c. 0.5 hPa (25 ° C.), boiling point 157 ° C., manufactured by Kanto Chemical Co., Ltd., 2-n-butoxyethanol (deer grade, vapor pressure 0.8 hPa (20 ° C.), vapor pressure 55.0 hPa (170 ° C.) as diluent d ), Boiling point 170.2 ° C., manufactured by Kanto Chemical Co., Inc.).
Using this adhesive, volume resistivity, adhesive strength, hot strength, and thermal conductivity were measured under the above conditions, and printability was further evaluated. The results are shown in Table 2.

(Comparative Examples 4-7)
As described in Table 1, the amount of silver powder or the like was changed (Comparative Examples 4 and 5) or the amount of the diluent a1 was changed (Comparative Examples 6 and 7). And it knead | mixed using a 3 roll type kneader, and obtained the conductive adhesive for a comparison.
Using this adhesive, volume resistivity, adhesive strength, hot strength, and thermal conductivity were measured under the above conditions, and printability was further evaluated. The results are shown in Table 2.

As is apparent from Table 2, the conductive adhesives of Examples 1 to 3 were 1,6-hexanediol diglycidyl ether (vapor pressure at 20 ° C. was 1.5 hPa or less and vapor pressure at 170 ° C. was 15 hPa. Hereinafter, it is understood that all of conductivity, adhesiveness, heat resistance, and workability (tack free time) are excellent.
On the other hand, Comparative Examples 1 and 2 were inoperable because the vapor pressure at 20 ° C. was 1.5 hPa or more. In Comparative Example 3, the vapor pressure at 170 ° C. of the diluent exceeded 15 hPa and the boiling point was as low as 170.2 ° C., so workability was not possible. Moreover, since the usage-amount of silver powder was not appropriate in Comparative Examples 4 and 5, electroconductivity was impossible or adhesiveness and heat resistance became improper. Further, in Comparative Examples 6 and 7, since the amount of 1,6-hexanediol diglycidyl ether used was not appropriate, the conductivity was not possible, or the adhesiveness and heat resistance were not possible.

Claims (7)

In the conductive adhesive containing the conductive powder (A), the epoxy resin (B) and the diluent (C),
The contents of the three components are (A) 70 to 85% by weight, (B) 4 to 36% by weight, (C) 1 to 20% by weight, and the diluent (C) is 20% by weight. A conductive adhesive, characterized in that it is an organic compound having a vapor pressure at 1.5 ° C of 1.5 hPa or less and a vapor pressure at 170 ° C of 15 hPa or less.   The conductive adhesive according to claim 1, wherein the conductive powder (A) is silver.   The conductive adhesive according to claim 1, wherein the diluent (C) has a viscosity at 25 ° C. of 0.1 Pa · s or less.   The conductive adhesive according to any one of claims 1 to 3, wherein the diluent (C) has a boiling point of 250 ° C or higher.   The diluent (C) is any one selected from aliphatic diol diglycidyl ether, alicyclic diol diglycidyl ether, and polyalkylene glycol diglycidyl ether. Conductive adhesive.   The conductive adhesive according to claim 5, wherein the aliphatic diol diglycidyl ether is 1,6-hexanediol diglycidyl ether or 1,4-butanediol diglycidyl ether.   The conductive adhesive according to any one of claims 1 to 6, wherein the tack-free time is 60 minutes or more.