JP2013209575A - Electroconductive adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroconductive adhesive that satisfies high thermal conductivity required for electroconductive adhesives, is capable of stably bonding a semiconductor element to a substrate and exhibits high thermal stress.SOLUTION: An electroconductive adhesive comprises (a) a conductive filler, (b) an adduct produced by reacting a polyoxyalkylenediamine, which has a molecular weight of 500-5,000, and a bisphenol type epoxy resin, which is in a liquid state at 25°C, at 50-150°C so that the equivalent ratio of epoxy groups to amino groups becomes 10-40, (c) a resol type phenol resin that is in a liquid state at 25°C, and (d) a curing accelerator. The amount of the resol type phenol resin is preferably 10-50 pts.wt. based on 100 pts.wt. of the adduct. The adduct may be produced by first reacting the polyoxyalkylenediamine and the bisphenol type epoxy resin and subsequently adding more bisphenol type epoxy resin.

Description

  The present invention relates to a conductive adhesive, and more particularly to a conductive adhesive that has both heat resistance and flexibility and can stably bond a semiconductor element to a substrate.

  Solder such as tin-lead solder has been used as a method for bonding semiconductor elements to lead frames, substrates, etc. In recent years, lead-free solder that does not cause environmental pollution, and substrate thinning and multilayering have been used. Attention has come to be paid to conductive adhesives that can be mounted at low temperatures, suitable for modularization.

In general, conductive adhesives are made by mixing a resin having a binder function with a metal having a conductive function (conductive filler), applied by dispensing or screen printing, etc., and heat is applied after mounting a component thereon. In addition, it is bonded by being cured.
In such a conductive adhesive, the binder resin component that holds the metal is a major factor that determines the adhesive performance of the conductive adhesive. A typical example of the binder resin is an epoxy resin, and an imidazole-based curing agent. It is cured [see, for example, Patent Document 1]. Furthermore, the improvement of the performance of the conductive adhesive was studied, for example, the conductive adhesive that suppressed fine cracks generated in the binder resin portion during the high-temperature treatment of the joining process (see Patent Document 2), and the reworkability was improved. Conductive adhesives that meet various requirements such as conductive adhesives (see Patent Document 3) and conductive adhesives that improve workability by extending the tack-free time (see Patent Document 4) have been proposed. This is mainly achieved by improving the binder resin component.

  When the semiconductor adhesive is fixed on the substrate, the conductive adhesive is sandwiched between the substrate and the semiconductor element and heated to fix them. When an epoxy resin is used as the binder resin, this heating is usually performed at around 200 ° C. for about 30 to 90 minutes in order to advance the curing of the epoxy resin. After heating at the temperature and time required for curing, the temperature is returned to room temperature, but during this cooling process, the expansion coefficient of the substrate and the epoxy resin are different, so the binder resin sandwiched between the substrate and the semiconductor element is distorted. It may take up and the adhesion may not be perfect. In order to eliminate such distortion, the binder resin needs to be flexible with respect to thermal stress. However, the binder resin that has been used so far cannot satisfy both high flexibility and high thermal conductivity at the same time, and has high bondability, thermal conductivity, and die bond bonding that requires thermal stress relaxation. There is a need for a conductive adhesive suitable for such applications.

JP-A-8-176408 JP 2004-359830 A JP 2005-132854 A JP 2007-197498 A

  An object of the present invention made in view of such problems is to provide a conductive material exhibiting high thermal stress that can stably adhere a semiconductor element to a substrate while satisfying high thermal conductivity required as a conductive adhesive. It is in providing an adhesive.

  The conductive adhesive of the present invention that has solved the above problems comprises: a) a conductive filler; b) a polyoxyalkylene diamine having a number average molecular weight of 500 to 5000 and a bisphenol type epoxy resin that is liquid at 25 ° C. An adduct formed by reacting at an epoxy group equivalent ratio of 10 to 40 at 80 to 200 ° C., c) a resol type phenol resin that is liquid at 25 ° C., and d) a curing accelerator. .

  At this time, it is preferable that a resol type phenol resin shall be 10-50 weight part with respect to 100 weight part of addition bodies.

  The adduct is reacted with polyoxyalkylenediamine having a molecular weight of 500 to 5000 and a bisphenol type epoxy resin that is liquid at 25 ° C. at 80 to 200 ° C. with an equivalent ratio of epoxy groups to amino groups of 5 to 25, After returning to room temperature, the bisphenol-type epoxy resin is additionally added, and finally the equivalent ratio of epoxy groups to amino groups may be 10 to 40.

  The conductive adhesive of the present invention relaxes strain in various harsh environments such as high temperature and high humidity, high temperature aging, heat cycle, etc. due to the high thermal stress characteristics of the conductive adhesive after heat curing and bonding Therefore, strong adhesion is possible in the long term.

About the conductive adhesive-2, the result (Table 4) of the aging test in the atmosphere of temperature 85 degreeC and relative humidity 85% is shown with the graph. About the conductive adhesive-2, the result (Table 4) of the aging test in the atmosphere of temperature 150 degreeC is shown with the graph. About the conductive adhesive-2, the result (Table 4) of the heat cycle test which makes temperature -50 degreeC and 150 degreeC 1 cycle (1 hour) is shown with the graph.

  The conductive adhesive of the present invention comprises a) a conductive filler, b) a polyoxyalkylene diamine having a number average molecular weight (hereinafter simply referred to as “molecular weight”) of 500 to 5000, and a bisphenol type epoxy resin that is liquid at 25 ° C. Is an adduct formed by reacting at 50 to 150 ° C. with an equivalent ratio of epoxy group to amino group of 3 to 15 (hereinafter, simply referred to as “adduct” unless otherwise specified). And c) a resol type phenol resin that is liquid at 25 ° C., and d) a curing accelerator.

1. Details of each ingredient:
Hereinafter, each component will be described in detail.
a) Conductive filler:
The conductive filler is a component that contributes to conductivity in the conductive adhesive, and is a metal powder such as gold, silver, palladium, copper, aluminum, nickel, and further, a metal powder such as copper, nickel, aluminum. Also included are gold, silver and palladium coated on the surface.

The shape of the conductive filler is not particularly limited, such as a spherical shape or a flake shape. However, if a part of the flake shape is partially spherical, the spherical shape enters the gap in the flake shape and the conductivity is reduced. It becomes better and more preferable. In addition, when two or more types having different particle diameter ranges are used in combination with a spherical shape, it is preferable that the metal powder having a small particle diameter is embedded in the gap between the metal powder having a large particle diameter.
The average particle diameter (D50) of the conductive filler is preferably 1 to 10 μm, more preferably 2 to 6 μm. Although a particle size smaller than 1 μm can be used, a high cost is required to obtain a fine powder. As a calculation method of the average particle diameter (D50), the average particle diameter (D50) is calculated from a volume integrated particle diameter 50% value measured using a general particle size distribution measurement method such as a laser method or a sedimentation method.

  The conductive filler is preferably 80 to 92% by weight in the final conductive adhesive. If it is less than 80% by weight, the conductivity is inferior, and if it exceeds 92% by weight, the conductivity is good, but the adhesiveness as a conductive adhesive tends to be poor because there are relatively few components to adhere. .

b) Adducts:
The adduct is produced by a reaction between polyoxyalkylene diamine and a bisphenol type epoxy resin.
b-1) polyoxyalkylenediamine;
The polyoxyalkylene diamine used for the production of the adduct has a structure in which amino groups are arranged at both ends of the polyoxyalkylene, and is represented by the general formula [1]. In the formula, R is an alkylene group, preferably 2 to 6 carbon atoms, more preferably 2 or 3, and n is a repeating unit.

The molecular weight of the polyoxyalkylene diamine is 500 to 5000, preferably 900 to 4000. Therefore, n in the formula is a number that satisfies the molecular weight of the polyoxyalkylene diamine within the above range. R in the formula may be an alkylene group having the same carbon number in one molecule, or a mixture of oxyalkylenes having different carbon numbers in one molecule (for example, polyoxyethyleneoxy Propylenediamine). Moreover, you may mix 2 or more types of polyoxyalkylene diamine from which the structure of R in a formula differs (for example, mixing of polyoxyethylene diamine and polyoxypropylene diamine).
These polyoxypropylene diamines are known, for example, commercially available from Huntsman under the name “Jeffamine”, and these can also be used.

  The molecular weight of the polyoxyalkylene diamine can generally be determined as an average molecular weight (number average molecular weight) from the amine value by measuring the amine value. In the present invention, the polyoxyalkylene diamine has a molecular weight of 500 to 5000, preferably 900 to 4000. Alkylene diamines are used. When the molecular weight obtained by this method is less than 500, the flexibility is lowered and the heat-resistant adhesive is not flexible, and there is a tendency to crack and impair the conductivity. However, the heat resistance of the intended heat resistant adhesive tends to decrease.

b-2) bisphenol type epoxy resin;
Bisphenol-type epoxy resin is a general term for compounds in which two OH groups of bisphenols are each substituted with a compound having a terminal epoxy group (oxirane ring), and is typically obtained by reacting bisphenols with epichlorohydrin. The chemical structure of the type epoxy resin is represented by the formula [2] (wherein n is a repeating unit).

  Bisphenols include bisphenol A [4,4′-dihydroxy-2,2′-diphenylpropane], bisphenol F [4,4′-dihydroxy-2,2′-diphenylmethane], and bisphenol AD [4,4′-dihydroxy. -2,2'-diphenylethane], bisphenol C [4,4'-isopropylidenebis (2-methylphenol)], bisphenol S [4,4'-dihydroxy-2,2'-diphenylsulfoxide], There are bisphenolfluorene, 4,4 ′-(1-phenylethylidene) bisphenol, and one or more are selected. In particular, an epoxy resin using bisphenol A (bisphenol A type epoxy resin) and an epoxy resin using bisphenol F (bisphenol F type epoxy resin) are preferably used.

  The bisphenol type epoxy resin used for the production of the adduct is liquid at 25 ° C., and preferably has an epoxy gram equivalent of 150 to 250 g / eq (eq represents an equivalent) and a viscosity at 25 ° C. of 3000. It is a low viscosity type of 10000 mPa · s. In the conductive adhesive of the present invention, a so-called “solvent” is not used, and a solid or high-viscosity type is difficult to produce a conductive adhesive, is liquid at room temperature, and has low viscosity. It is convenient to have it.

  Bisphenol type epoxy resins are known, for example, commercially available products from ADEKA Corporation, Dainippon Ink & Chemicals, Inc. (DIC) Corporation, etc., and these can be arbitrarily selected and used.

  The reaction between polyoxyalkylene diamine and bisphenol-type epoxy resin is the reaction between the amino group of polyoxyalkylene diamine and the epoxy group of bisphenol-type epoxy resin, which can be easily brought into contact with each other at room temperature or higher. proceed.

This adduct is an intermediate in the conductive adhesive of the present invention, and the adduct should have fluidity. Therefore, the adduct is required to be produced under mild conditions. In the molecular structure, polyoxyalkylenediamine has two primary amino groups (—NH ₂ ) in the molecule, and the first hydrogen (H) of the two hydrogen atoms of each amino group is an epoxy. First, a bisphenol-type epoxy resin is added to both ends of the polyoxyalkylenediamine to form an epoxy compound at both ends, and the second hydrogen of the amino group, and the hydroxyl group formed by the addition. Since the reaction of (—OH) hydrogen is relatively slow, it is considered that a large amount of hydrogen remains unreacted even if it partially reacts with an epoxy group depending on the production conditions of the adduct.

  From this point of view, the reaction between the polyoxyalkylene diamine and the bisphenol type epoxy resin is 10 to 40, preferably 15 to 30 in terms of the equivalent ratio of the epoxy group of the bisphenol type epoxy resin to the amino group of the polyoxyalkylene diamine. Stir at a temperature of 80 to 200 ° C., preferably 120 to 180 ° C. for 4 to 6 hours. If it is less than 80 degreeC, reaction may be inadequate, and when it exceeds 200 degreeC, reaction will advance excessively and the fluidity | liquidity of an adduct will be lose | eliminated.

  In a typical embodiment, polyoxyalkylene diamine is made into a liquid state at 40 to 60 ° C., and the bisphenol type epoxy resin is dissolved therein while stirring and heated to 50 to 80 ° C. and held for 30 minutes to 1 hour. Next, the temperature is gradually raised to 160 ° C., and the mixture is stirred for 4 hours.

The adduct thus produced is in a form having a plurality of epoxy groups in one molecule. Further, this adduct may be further mixed with a bisphenol type epoxy resin. In this case, bisphenol is reacted at an equivalent ratio of 2 or more with respect to the amino group of the above polyoxyalkylenediamine, preferably 5 to 25 at an equivalent ratio of 40 to 200 ° C., preferably 50 to 150 ° C., and returned to room temperature. A type epoxy resin is added, and finally the equivalent ratio of epoxy groups to amino groups is set to 10-40.
A part of the bisphenol-type epoxy resin added to the reaction and the bisphenol-type epoxy resin added later are not adducts, but here they are collectively treated as “adducts” for the sake of explanation.

  The amount of the adduct used is preferably 10 to 25 parts by weight with respect to 100 parts by weight of the conductive filler. Preferably it is used at 10 to 15 parts by weight. If it is less than 10 weight part, the adhesiveness of a conductive adhesive may be inferior, and when it exceeds 25 weight part, electroconductivity may fall.

c) Resol type phenol resin:
The resol type phenol resin functions as a curing agent that reacts the hydroxyl group of the resol type phenol resin with the epoxy group remaining in the adduct to make the adduct molecule a network structure.

  A resol type phenol resin is produced by a reaction between phenols and aldehydes. Here, phenols are phenol, cresol, xylenol, ethylphenol, butylphenol, octylphenol, allylphenol, bisphenol A, bisphenol F, bisphenol S, resorcin, catechol and other phenols, halogenated phenol, phenylphenol, aminophenol, etc. The aldehydes are formaldehyde, paraformaldehyde, trioxane, furfural, acetaldehyde and the like.

Resole-type phenolic resins vary in degree of polymerization or degree of crosslinking depending on the type of compound of each of phenols and aldehydes, compounding ratio, reaction temperature, reaction time, catalyst, etc. However, a novolac type phenol resin that is liquid at 25 ° C. is selected for the conductive adhesive of the present invention because of the advantage in use as a conductive adhesive. The reaction between phenols and aldehydes is generally a solid resin called novolak when an acidic catalyst is used, but a liquid resin called liquid resol is used when an alkaline catalyst is used. Therefore, the resol type phenol resin used in the present invention is preferably obtained using an alkaline catalyst.
A typical chemical structure of a resol type phenol resin is represented by the following formula [2].

  The resol-type phenolic resin has a function of causing the hydroxyl group to react with the epoxy group at the end of the adduct to crosslink and cure the molecular chain of the adduct, and the molecular weight of the resol-type phenolic resin itself must be increased. There is no. Specifically, a resol type phenol resin produced from phenol and formalin is preferably selected to have a viscosity at 25 ° C. of 1500 to 3500 mPA · s and an OH gram equivalent of 100 to 150 g / eq.

  Resol type phenol resins are available from Meiwa Kasei Co., Ltd. as “MEH-8010” (phenol gram equivalent 130 g / eq.), “MEH-8000H” (phenol gram equivalent 141 g / eq.), “MEH-8005” (phenol gram). Equivalents of 135 g / eq.) And “MEH-8015” (phenol gram equivalent of 134 g / eq.) Are commercially available and can be used.

  The amount of the resol type phenol resin used is selected in relation to the above adduct, but is generally preferably 10 to 50 parts by weight, more preferably 20 to 40 parts by weight with respect to 100 parts by weight of the adduct. If it is less than 10 parts by weight, the curing may be insufficient and the heat resistance of the conductive adhesive may be inferior, and the thermal conductivity may be lowered even when the curing is sufficient. If it exceeds 50 parts by weight, the high elasticity of the conductive adhesive may not be obtained.

d) Curing accelerator:
The curing accelerator has a function of accelerating the crosslinking reaction by the reaction between the epoxy group of the adduct and the hydroxyl group of the resol type phenol resin, and one that is generally used is arbitrarily selected. Phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-ethyl-4-methylimidazole, 1-cyano-2-ethyl-4-methylimidazole, 4,4 ′ There are imidazole derivatives such as methylenebis (2-ethyl-5-methylimidazole) and 2-heptadecylimidazole, tertiary amines such as benzyldimethylamine, and triphenylphosphine (TPP). These curing accelerators may be used alone or in combination of two or more.

  The blending amount of the curing accelerator is selected in relation to the reaction between the adduct and the resol type phenol resin. Here, it is preferably 1 to 5 parts by weight, more preferably 2 to 3 parts per 100 parts by weight of the adduct. Parts by weight. This range is selected in consideration of the function as a conductive adhesive.

e) Other:
The conductive adhesive of the present invention may optionally include a plasticizer such as glycidyl neodecanoate and a coupling agent such as γ-glycidoxypropyltrimethoxysilane as other components. Moreover, an acid additive such as adipic acid, a rheology control agent such as fine powdered silane, an organic solvent for dissolving the solid adduct, and the like can be optionally added. However, by using a resol type phenolic resin that is liquid at 25 ° C. in the present invention, each component of the conductive adhesive can be made uniform without using an organic solvent that dissolves the solid adduct. It becomes possible to avoid poor performance such as generation of voids due to residual solvent.
The selection of other components and the amount used are arbitrarily determined within a range that does not hinder the performance of the conductive adhesive of the present invention.

2. Production of conductive adhesive:
As described above, the conductive adhesive of the present invention is prepared in advance by reaction of polyoxyalkylenediamine and bisphenol type epoxy resin, and using the adduct, conductive filler, resol type phenol resin, curing Manufactured with an accelerator. The order of mixing is not particularly limited. Mixing is preferably performed at room temperature to a low temperature of 50 ° C. or lower. At this point, even if some hydroxyl groups and some epoxy groups in the mixture may react, the proportion is relatively low. When the mixing temperature is increased, this reaction rate is increased, which may hinder subsequent application to the bonding object.

  In the above, the adduct was produced in advance, but polyoxyalkylene diamine, bisphenol type epoxy resin, resol type phenol resin, curing accelerator, conductive filler, and other optional components may be mixed to form a conductive adhesive. In this case, after applying a conductive adhesive between the objects to be bonded, it is heated at 50 to 80 ° C. for 0.5 to 2 hours, and then the temperature is increased to finally reach 120 to 200 ° C. Hold for 4 hours. That is, in this case, the first hydrogen (H) of the primary amino group in the polyoxyalkylenediamine molecule preferentially reacts with the epoxy group of the bisphenol-type epoxy resin particularly in the initial state of 50 to 80 ° C. Thus, an adduct is substantially formed.

  The conductive adhesive of the present invention configured with the composition described above has a soft segment of a polyoxyalkylene group having a relatively flexible molecular structure in the molecule, and both ends of the soft segment are bisphenol type epoxy resin, Further, it is sandwiched between hard segments cured by cross-linking by reaction with a resol type phenolic resin. The soft segment mainly determines the flexibility of the conductive adhesive, and the hard segment mainly determines the heat resistance. As described above, the conductive adhesive of the present invention is capable of satisfying flexibility as well as heat resistance by optimizing the molecular structure of the soft segment and the hard segment, and further their composition ratio. is there.

  After the conductive adhesive of the present invention is applied between objects to be bonded, it is heated to be cured and bonded. Specifically, adhesion is achieved by curing at 130-220 ° C. for 15-120 minutes. That is, a conductive adhesive is applied on one of the objects to be bonded, for example, a substrate, and another object to be bonded, for example, a semiconductor element is placed on the substrate, and the conductive adhesive is placed under this curing condition. Cured and adhesion between the objects to be bonded is achieved. As the material for the surface of the supporting substrate as the object to be bonded, it is used for precious metal surface substrates such as gold and palladium plating, metal surface substrates plated with nickel, silver or their alloys on copper substrates, rigid substrates for printed circuit boards, etc. And a glass epoxy substrate.

1) Component a) conductive filler used in the examples:
A flake-shaped silver powder (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) having an average particle size (D50) of 4-7 μm was used.

b) Adduct of polyoxyalkylenediamine and bisphenol type epoxy resin:
b-1) polyoxyalkylenediamine;
Polyethylenediamine; molecular weight 900 [manufactured by Huntsman, “Jeffamine ED900” (trade name)],
Polypropylenediamine; molecular weight 2000 [manufactured by Huntsman, “Jeffamine D2000” (trade name)],
Polypropylene diamine; molecular weight 4000 [manufactured by Huntsman, “Jeffamine D4000” (trade name)],
Were used respectively.

b-2) Bisphenol type epoxy resin:
Bisphenol A type epoxy resin; liquid at room temperature, epoxy gram equivalent = 173 g / eq, viscosity = 3500-5500 mPa · s (25 ° C.) [Dainippon Ink Chemical Co., Ltd., “EPICLON EXA-850CRP” (trade name)] ,
Bisphenol F type epoxy resin; liquid at room temperature, epoxy gram equivalent = 160 g / eq, liquid, viscosity = 1100-1500 mPa · s (25 ° C.) [Dainippon Ink Chemical Co., Ltd., “EEPICLON EXA-830CRP” (trade name) )],
Were used respectively.

b-3) Synthesis of adduct:
A bisphenol-type epoxy resin was added to polyoxyalkylenediamine, heated to 80 ° C. with stirring and held for 1 hour, further heated to 160 ° C. and stirred for 4 hours for synthesis. As a comparative example, the blending amount of polyoxyalkylenediamine and bisphenol type epoxy resin was out of the scope of the present invention to obtain an adduct.

  The compositions of the adducts produced as Examples and Comparative Examples are shown in Tables 1 and 2. In addition, in the adducts 5 and 6, after the synthesis of the adduct, a bisphenol type epoxy resin is further added at the time of adjusting the conductive adhesive. For convenience of explanation, it is shown as an additional body here.

c) resol type phenol resin;
Resol type formaldehyde resin: “MEH-8000H” (trade name) manufactured by Meiwa Kasei Co., Ltd. was used. Viscosity = 1500-3500 mPa · s (25 ° C.), hydroxyl group equivalent = 141 g / OH group was used.

d) a curing accelerator;
2-Phenyl-4-methyl-5-hydroxymethylimidazole [manufactured by Shikoku Kasei Kogyo Co., Ltd., “Curazole 2P4MHZ” (trade name)] was used.

2) Mixing ratio of conductive adhesive Silver powder as conductive filler, adduct shown in Tables 1 and 2, bisphenol A type epoxy resin or bisphenol F type epoxy resin as resol type phenolic resin, 2-phenyl as curing accelerator -4-methyl-5-hydroxymethylimidazole was mixed and kneaded at room temperature for 5 minutes with a three-roll (manufactured by Inoue Seisakusho) and a rotation and revolution kneading apparatus (manufactured by Shinky, “AR-250” (model number)) Adhesive. Table 3 shows the composition of the conductive adhesive used for the evaluation.

3) Evaluation method of conductive adhesive a) Storage elastic modulus: 5 × the conductive adhesive composition on a support substrate treated with Teflon (registered trademark) so that the film thickness after curing is 0.5 mm. The sample was applied in a shape of 40 mm, heat-treated at 160 ° C. for 60 minutes, peeled from the supporting substrate, and used as a cured product of a conductive adhesive for testing, and used as a sample for evaluating storage elastic modulus.
This sample was measured under the following conditions using a dynamic viscoelasticity measuring apparatus (“EXSTAR DMS6100” (trade name) manufactured by SII), and the storage elastic modulus at 25 ° C. was defined as the elastic modulus.
・ Jig: Tensile ・ Distance between chucks: 20 mm
・ Rise rate: 3 ° C / min ・ Measurement frequency: 1 Hz
・ Sample size: 0.5mm (width) x 40mm (length)
Die shear strength: 200 mm / sec. Using an adhesive strength measuring instrument [manufactured by Dage, “Series 4000” (product name)]. The die shear strength at 25 ° C. was measured.

b) Thermal conductivity: A conductive adhesive composition was applied in a circular shape with a diameter of 1 cm on a Teflon (registered trademark) -treated support base so that the film thickness after curing was 1 mm. The sample was subjected to heat treatment for minutes, peeled off from the supporting substrate, and used as a test product for evaluating thermal conductivity as a cured product of a conductive adhesive for testing. This sample was obtained by a laser flash method using a thermal conductivity measuring instrument (manufactured by Osaka City Industrial Research Institute).

c) Die shear strength: A conductive adhesive composition was applied to a silver-plated Ni-Cu frame so that the film thickness after curing was about 0.03 mm, and a 2 × 2 mm silicon chip as a supporting substrate was applied. The sample was mounted and heat-treated at 160 ° C. for 60 minutes to obtain a sample for die shear strength evaluation. This sample was measured at 200 mm / sec. Using an adhesive strength measuring device [manufactured by Dage, “Series 4000” (product name)]. The die shear strength at 25 ° C. was measured.
The evaluation is performed by performing an aging test (in the air) for a predetermined time in an atmosphere of 85 ° C. and 85% relative humidity and 150 ° C. for a predetermined time, cooling at −50 ° C. and heating at 150 ° C. for 30 minutes, A cycle (1 hour) was repeated, and a heat cycle test (in the atmosphere) was repeated for a predetermined time, and the die shear strength was measured over time. )

d) Volume resistivity: A conductive adhesive composition is applied on a glass supporting substrate so that the film thickness after curing is about 0.03 mm with a width of 5 mm and a length of 60 mm using a masking substrate. The sample was subjected to heat treatment at 160 ° C. for 60 minutes to obtain a sample for volume resistivity evaluation. The volume resistivity of this sample body was measured using a resistor [manufactured by HIoki Corporation, “Milliohm Hitester 3540” (product name)].
Evaluation is performed in an atmosphere of 85 ° C. and a relative humidity of 85%, and an aging test (under the atmosphere) for a predetermined time in an atmosphere of 150 ° C., cooling at −50 ° C. and heating at 150 ° C. are alternately repeated every 30 minutes. A heat cycle test (in the atmosphere) performed for a predetermined time was performed, and the volume resistivity was measured over time.

4) Measurement results Table 3 shows the measurement results of thermal conductivity and storage elastic modulus for each of the cured bodies of the conductive adhesives 1 to 10.

  About the conductive adhesive-2 which is an Example, the aging test (under air | atmosphere) which hold | maintains a hardening body in the atmosphere of temperature 85 degreeC, relative humidity 85%, and temperature 150 degreeC, -50 degreeC and 150 degreeC A heat cycle test (in the atmosphere) in which heating was alternately repeated every 30 minutes was performed, and die shear strength and volume resistivity in each test were measured over time. Table 4 shows the measurement results. FIG. 1 shows the measurement results of the die shear strength and the volume resistance value depending on the holding time in an atmosphere having a temperature of 85 ° C. and a relative humidity of 85%.

  For each of the conductive adhesives-9 and 10 as comparative examples, the die shear strength and the volume resistance value immediately after returning the cured body to room temperature and after holding it in an atmosphere of 85 ° C. and 85% relative humidity for 1000 hours Was measured. Table 5 shows the measurement results.

Regarding the conductive adhesives -1 to 8 which are the embodiments, the thermal conductivity is as high as 1 W / mK or higher, the storage elastic modulus is all 1000 MPa or lower, and it is confirmed that it has a low elasticity and a function of reducing thermal stress. It was.
It was confirmed that the volume resistance value under various conditions performed for the conductive adhesive-2 was kept low and excellent in long-term reliability (adhesion peeling due to deterioration hardly occurred). Regarding the conductive adhesive compositions-9 and 10 which are comparative examples, either the volume resistance value or the die shear strength is greatly changed after the initial value and 1000 hours, and it is confirmed that the long-term reliability is inferior. It was done.
From this result, the conductive adhesive of the present invention has low elasticity after adhesive curing and has a high function of reducing thermal stress. Therefore, the adhesive layer does not peel off and therefore has sufficient adhesive strength as an adhesive. In addition, it was confirmed to have a high thermal conductivity.

  The conductive adhesive of the present invention exhibits high thermal stress while satisfying high thermal conductivity, and can stably adhere a semiconductor element to a substrate even through a harsh thermal history, greatly contributing to the electronic industry. .

Claims (3)

  a) a conductive filler, b) a polyoxyalkylenediamine having a number average molecular weight of 500 to 5000 and a bisphenol-type epoxy resin that is liquid at 25 ° C., the equivalent ratio of epoxy groups to amino groups is 10 to 40, and 50 to 150 A conductive adhesive comprising: an adduct formed by reaction at ° C; c) a resol-type phenolic resin that is liquid at 25 ° C; and d) a curing accelerator.   The conductive adhesive according to claim 1, wherein the resol type phenolic resin is 10 to 50 parts by weight with respect to 100 parts by weight of the adduct.   The adduct is reacted with polyoxyalkylene diamine having a number average molecular weight of 500 to 5000 and bisphenol type epoxy resin which is liquid at 25 ° C. at 50 to 150 ° C. with an equivalent ratio of epoxy groups to amino groups of 5 to 25. The conductive adhesive according to claim 1, wherein the bisphenol-type epoxy resin is additionally added after returning to room temperature, and finally the equivalent ratio of the epoxy group to the amino group is set to 10 to 40.

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