Thermally and electrically conductive adhesive composition

Abstract

The present invention relates to a thermally and electrically conductive adhesive composition, which includes (A) an electrically conductive filler, (B) an epoxy resin, (C) a reactive diluent, and (D) a curing agent, wherein the component (A) is a silver powder having an average particle diameter of 1 to 10 m, the component (B) has two or more epoxy functional groups and aromatic rings in each molecule, the component (C) is a compound having two or more glycidyl ether functional groups in an aliphatic hydrocarbon chain and also having a molecular weight of 150 to 600, and the component (D) is a compound having two or more phenol functional groups in each molecule, a compound having two or more aniline functional groups in each molecule, or a mixture of these compounds, and the content of each of the components (A), (B), (C), and (D) is within a specific range.

Claims

1. A thermally and electrically conductive adhesive composition, comprising (A) an electrically conductive filler, (B) an epoxy resin, (C) a reactive diluent, and (D) a curing agent, wherein the electrically conductive filler (A) is a pure silver powder having an average particle diameter of 1 to 10 m, and the content of the electrically conductive filler (A) is in a range of 85 to 94 mass % with respect to the total amount of the thermally and electrically conductive adhesive composition, the epoxy resin (B) has two or more epoxy functional groups and aromatic rings in each molecule, and the content of the epoxy resin (B) is in a range of 1 to 8 mass % with respect to the total amount of the thermally and electrically conductive adhesive composition, the reactive diluent (C) is butanediol diglycidyl ether or cyclohexanedimethanol diglycidyl ether, and the content of the reactive diluent (C) is in a range of 0.3 to 1.2 mass % with respect to the total amount of the thermally and electrically conductive adhesive composition, and the curing agent (D) is a compound having two or more phenol functional groups in each molecule, a compound having two or more aniline functional groups in each molecule, or a mixture of these compounds, and the content of the curing agent (D) is in a range of 0.2 to 3 mass % with respect to the total amount of the thermally and electrically conductive adhesive composition.

2. The thermally and electrically conductive adhesive composition according to claim 1, further comprising a rubber-based resin (E) which does not exhibit reactivity with the curing agent (D) in an amount ranging from 0.2 to 2 mass % with respect to the total amount of the thermally and electrically conductive adhesive composition.

3. The thermally and electrically conductive adhesive composition according to claim 1, wherein the TI value (thixotropic index) calculated from the measurement values at rotation speeds of 0.5 rpm and 5 rpm using a rotational viscometer of the thermally and electrically conductive adhesive composition excluding the electrically conductive filler (A) in the composition is from 1 to 3.

Description

EXAMPLES

(1) Hereinafter, the present invention will be further specifically described by way of Examples, however, the present invention is not limited to these Examples.

Examples 1 to 9 and Comparative Examples 1 to 3

(2) A. Preparation of Adhesive Composition

(3) The respective materials described in Table 1 were kneaded using a three roll, whereby an adhesive composition having a composition shown in Table 1 was prepared (the numerical value of each material indicates the mass % with respect to the total mass of the adhesive composition). The materials used are as follows. Incidentally, as for the order that the materials were kneaded, first, the component (A) and the component (E) were kneaded, and subsequently, the other various components were mixed and kneaded so that the respective components were uniformly dispersed. The resulting kneaded material was heated to 200 C. for 1 hour, and then left to cool to room temperature, whereby a cured body of the adhesive composition was obtained.

(4) (A) Electrically Conductive Filler

(5) silver powder (average particle diameter: 5.0 m, manufactured by Tanaka Kikinzoku Kogyo K.K.), tap density: 6.5 g/cm.sup.3 silver powder (average particle diameter: 1.5 m, manufactured by Tanaka Kikinzoku Kogyo K.K.), tap density: 4.7 g/cm.sup.3 silver powder (average particle diameter: 8.0 m, manufactured by Tanaka Kikinzoku Kogyo K.K.), tap density: 4.2 g/cm.sup.3
(B) Epoxy Resin bisphenol F-type epoxy resin (EPICRON EXA-830CRP, manufactured by DIC Corporation, in a liquid form at room temperature] phenol novolac-type epoxy resin (jER-152, manufactured by Mitsubishi Chemical Corporation, in a liquid form at room temperature) naphthalene-type epoxy resin (HP4032D, manufactured by DIC Corporation, in a liquid form at room temperature)
(C) Reactive Diluent 1,4-butanediol diglycidyl ether (molecular weight: 202.25) 1,4-cyclohexanedimethanol diglycidyl ether (molecular weight: 256.34)
(D) Curing Agent a compound having 2 or more phenol functional groups in each molecule (MEH8000H, manufactured by Meiwa Plastic Industries, Ltd.) a compound having 2 or more aniline functional groups in each molecule (4,4-diaminodiphenyl sulfone, manufactured by Tokyo Chemical Industry Co., Ltd.)
(E) Liquid Rubber-Based Resin acrylonitrile-butadiene rubber having a carboxyl group (CTBN-130013NA, manufactured by Ube Industries, Ltd.)
(Curing Accelerator) toluene bis dimethyl urea (manufactured by Carbon Scientific Co., Ltd.) imidazole-based curing accelerator (2P4MHZ, manufactured by Shikoku Chemicals Corporation)
(Solvent) -butyrolactone N-methylpyrrolidone
(Others) core-shell particles (AC-3355, manufactured by Aica Kogyo Company, Limited) silane coupling agent (Z-6040, manufactured by Dow Corning Toray Co., Ltd.)
B. Evaluation of Physical Properties of Adhesive Composition
1. Viscosity

(6) An adhesive composition was prepared excluding the electrically conductive filler (A), and the viscosity of the composition was measured. The viscosity was measured at a temperature of 25 C. using a cone-plate type viscometer as a rotational viscometer at a rotation speed of 0.5 ppm or 5 ppm using a 3R14 cone-plate. The result is shown in Table 1.

(7) 2. TI Value

(8) An adhesive composition was prepared excluding the electrically conductive filler (A), and the TI value of the composition was measured. The TI value was calculated by dividing the measurement value at a rotation speed of 0.5 ppm of the above-mentioned rotational viscometer by the measurement value at a rotation speed of ppm of the above-mentioned rotational viscometer. The result is shown in Table 1.

(9) 3. Measurement of Thermal Conductivity

(10) In order to evaluate the thermal conduction properties of the adhesive composition, the thermal conductivity of the adhesive composition was measured. The thermal conductivity (W/m.Math.K) was determined by measuring a thermal diffusivity a in accordance with ASTM E1461 using a laser flash method thermal constant measuring system (TC-7000, manufactured by ULVAC-RIKO, Inc.), calculating a specific gravity d at room temperature by a pycnometer method, and measuring a specific heat Cp at room temperature in accordance with JIS K7123 using a differential scanning calorimeter (DSC7020, manufactured by Seiko Electronics Co., Ltd.), and then, performing calculation according to the following formula. The result is shown in Table 1.
=adCp
4. Measurement of Volume Resistivity

(11) In order to evaluate the electrical properties of the adhesive composition, the volume resistivity of the adhesive composition was measured. The volume resistivity K (10.sup.4 .Math.cm) was determined by measuring the emerging resistance R by a DC four-terminal method using a DC voltage source monitor (R6243, manufactured by Advantest Corporation), and then, performing calculation according to the following formula from the width W, thickness T, and length L of a measurement sample. The result is shown in Table 1.
K=L/(RWT)
5. Measurement of Necking Rate

(12) After the adhesive composition was applied onto a 2 mm square silver-plated copper substrate by a dispenser, and thereafter, a 2 mm square silicon substrate was placed thereon so as to interpose the adhesive composition between the silicon substrate and the copper substrate. After performing a heat treatment at 200 C. for 1 hour, the necking rate was evaluated by observation of an SEM image of the vertical cross section of the cured body of the adhesive composition. Specifically, a 30 m square image was observed at arbitrary 5 sites of a substantially central portion of a cross-sectional image of the cured body of the adhesive composition, and the necking rate was calculated from the average of numerical values obtained by dividing the sum of the number of particles connected to each electrically conductive filler particle (1+the number of connected particles) by the number of electrically conductive filler particles (the following formula). The calculation result is shown in Table 1.
Necking rate (%)=100[1+the sum of the particles connected to each electrically conductive filler particle]/[the number of electrically conductive filler particles][Formula]

(13) TABLE-US-00001 TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 (A) Silver Average particle 91.6 91.6 91.6 91.6 91.6 91.6 85.3 91.6 powder diameter 5 m Average particle 13.5 diameter 1.5 m Average particle 80.0 diameter 8 m (B) Epoxy resin EXA-830CRP 3.1 2.2 1.6 1.3 2.5 2.2 1.4 4.8 3.1 JER-152 0.9 1.1 1.4 1.0 0.9 HP4032D (C) Reactive 1,4-Butanediol diglycidyl 1.0 1.0 1.2 1.5 1.1 1.0 0.5 4.0 diluent ether 1,4- 1.0 Cyclohexanedimethanol diglycidyl ether (E) Liquid CTBN1300x13NA 0.5 0.5 0.6 0.8 0.5 0.3 1.5 0.5 rubber- based resin Core-shell AC-3355 0.5 0.5 0.5 0.5 0.5 0.2 0.5 particles (D) Culing agent MEH8000H 0.4 0.4 0.4 0.4 0.4 0.3 0.4 4,4-diaminodiphenyl 0.6 1.5 sulfone Curing Toluene bis dimethyl 0.3 0.3 0.3 0.3 0.3 0.2 0.2 0.6 0.3 accelerator urea 2P4MHZ 0.1 0.1 0.1 0.1 0.1 0.1 0.3 0.1 Silane Z-6040 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.2 0.1 coupling agent Solvent -butyrolactone 2.4 2.4 2.5 2.5 2.4 2.4 3.4 1.8 2.4 N-methylpyrrolidone Viscosity 0.5 rpm (Pa .Math. s) 11.0 15.0 11.6 4.8 2.2 12.8 12 2.5 11.7 5 rpm (Pa .Math. s) 6.4 9.4 7.2 4.3 1.8 6.5 8 2.0 7.2 TI value 0.5/5 rpm 1.7 1.6 1.6 1.1 1.2 2.0 2 1.3 1.6 Thermal (W/m .Math. K) 67 55 38 30 21 63 73 19 56 conductivity Volume (10.sup.4 .Math. cm) 0.5 0.5 0.6 0.5 0.5 0.5 0.4 0.8 0.6 resistivity Necking rate (%) 260 220 185 175 170 225 255 150 240 Comp. Comp. Comp. Ex. 10 Ex. 11 Ex. 1 Ex. 2 Ex. 3 (A) Silver Average particle 91.6 85.3 91.6 85.3 83.5 powder diameter 5 m Average particle diameter 1.5 m Average particle diameter 8 m (B) Epoxy resin EXA-830CRP 2.1 7.0 2.7 0.8 9.1 JER-152 0.8 1.1 0.8 HP4032D 1.0 (C) Reactive 1,4-Butanediol diglycidyl 0.2 4.2 6.3 1.2 diluent ether 1,4- Cyclohexanedimethanol diglycidyl ether (E) Liquid CTBN1300x13NA 0.5 0.3 0.6 0.5 0.5 rubber- based resin Core-shell AC-3355 0.5 0.6 2.2 0.5 particles (D) Culing agent MEH8000H 0.4 1.5 0.5 0.5 2.5 4,4-diaminodiphenyl sulfone Curing Toluene bis dimethyl 0.3 0.2 0.3 0.2 0.3 accelerator urea 2P4MHZ 0.1 0.1 0.1 0.2 0.1 Silane Z-6040 0.1 0.1 0.1 0.1 0.1 coupling agent Solvent -butyrolactone 1.8 1.3 2.4 3.1 2.2 N-methylpyrrolidone 0.6 Viscosity 0.5 rpm (Pa .Math. s) 27.0 3.8 289.0 10.5 6.8 5 rpm (Pa .Math. s) 10.0 2.5 251.8 2.6 5.2 TI value 0.5/5 rpm 2.7 1.5 1.1 4.0 1.3 Thermal (W/m .Math. K) 58 17 3 5 conductivity Volume (10.sup.4 .Math. cm) 0.5 1.5 7.0 2.4 resistivity Necking rate (%) 215.0 160 101 130

(14) From the above results, it was confirmed that the adhesive composition of the present invention has high thermal conductivity and stable electrical conductivity.

(15) While the present invention has been described in detail with reference to specific embodiments, it is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

(16) Incidentally, the present application is based on Japanese Patent Application (Japanese Patent Application No. 2014-111769) filed on May 29, 2014 and the entire contents of which are incorporated herein by reference.