JP2001297627A - Conductive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive material having superior electrical conductivity and thermal heat conductivity. SOLUTION: A conductive material includes a mixed conductive powder of 75 to 95 weight 5 composed of a nearly ball-shaped, composite conductive powder, in which the surface of the copper powder or the copper alloy powder is coated with silver or a silver alloy for the most part, and the powder having silver as a main ingredient with a flocculating characteristic, are included, and a binder composition of a matter such as epoxy resin containing 2.5 to 5 weight %. The diameters of the nearly ball-shaped, composite conductive powder of 10 μm or smaller and the powder having silver as a main ingredient of 0.5 μm or smaller preferably have a high thermal conductivity and larger electrical conductivity. A mix weight proportion of the nearly ball-shaped composite conductive powder and the powder, having silver as a main ingredient between 99:1 and 85:15, preferably has flow property, electrical conductivity, and thermal conductivity and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive material used for bonding of high conductivity and high thermal conductivity and a conductive material used for interlayer connection of a front and back circuit of a substrate.

[0002]

2. Description of the Related Art Conventionally, as a conductive material requiring thermal conductivity, a conductive material obtained by dispersing a highly thermally conductive metal powder or a highly thermally conductive inorganic powder in a binder composition such as an epoxy resin has been used. In addition, silver powder, aluminum powder, copper powder, and the like, which are high heat conductive metal powders, have been used as conductive materials that require electrical conductivity.

A conductive material used for bonding such as die bonding is required to have high thermal conductivity as well as conductivity. Therefore, silver powder is often used in a large proportion. However, when the mixing ratio of the silver powder is large, there is a disadvantage that the silver powder is expensive and the conductive material is also expensive. Further, when the size of the scale is large and thin, the hiding power is large, and there is a disadvantage that voids are apt to remain when the solvent is dried.

Further, in applications such as die bonding, fluidity when the conductive material is extruded by applying pressure from a syringe or the like and viscous behavior in which the extruded conductive material does not easily flow out are required. On the other hand, the multilayer wiring board by the build-up method is required to have high filling property (fluidity), high conductivity, and high reliability.

[0005]

The first, second, third and fourth aspects of the present invention provide a conductive material excellent in high electrical conductivity and high thermal conductivity. A fifth aspect of the present invention provides a conductive material having high resistance reliability and good through-hole filling properties, in addition to the first, second, third, and fourth aspects of the invention.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a substantially spherical composite conductive powder in which the surface of a copper powder or a copper alloy powder is substantially coated with silver or a silver alloy and a powder mainly containing silver having cohesiveness. The present invention relates to a conductive material containing a mixed conductive powder and a binder composition. Further, the present invention relates to a conductive material in which the average particle size of the powder having silver as a main component having a cohesive property is 1/3 or less of the substantially spherical composite conductive powder. Further, the present invention relates to a conductive material in which the average particle diameter of the substantially spherical composite conductive powder is 10 μm or less, and the average particle diameter of the powder mainly containing cohesive silver is 0.5 μm or less.

[0007] The present invention also relates to a conductive material in which a powder containing silver having a cohesive property as a main component is a lump. further,
The present invention relates to a conductive material in which the mixing ratio of the substantially spherical composite conductive powder and the powder containing silver as a main component is 99: 1 to 85:15 in terms of weight ratio. About materials.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a substantially spherical composite conductive powder whose inside is coated with copper or copper alloy powder and whose surface is coated with silver or silver alloy is used.
Even if the surface of copper powder or copper alloy powder is completely coated with silver or silver alloy or contains an alloy layer in which copper powder or copper alloy powder inside and silver or silver alloy on the surface are mixed There is no particular problem as long as a part of the copper powder or copper alloy powder inside is exposed between silver or silver alloy coated with 50% or more of the particles in the conductive powder. Note that as the copper alloy powder, an alloy powder of copper and tin, copper and zinc, or the like can be used. As the silver alloy, an alloy of silver and palladium, silver and platinum, or the like can be used.

In order to coat the surface of copper powder or copper alloy powder with silver or silver alloy, there are methods such as displacement plating, electroplating, and electroless plating. It is preferable to coat by a displacement plating method because of its high adhesion and low lining cost. The coating amount of silver or silver alloy on the surface of copper powder or copper alloy powder is in the range of 5 to 25% by weight based on copper powder or copper alloy powder from the viewpoints of migration resistance, cost, and improvement in conductivity. Preferably, the range is 10 to 23% by weight.

As the composite conductive powder, a powder having a substantially spherical shape is used and does not need to be completely spherical. For example, a substantially spherical composite conductive powder having an aspect ratio of 1 to 1.5 and a long diameter having an average particle diameter of 1 to 20 μm is used. It is preferable to use powder, and it is preferable to use a substantially spherical composite conductive powder having an aspect ratio of 1 to 1.3 and a long diameter having an average particle diameter of 1 to 10 μm. The average particle size mentioned above can be measured by a laser scattering type particle size distribution measuring device. In the present invention, the measurement was performed using a master sizer (manufactured by Malvern) as the device.

The aspect ratio in the present invention refers to the ratio of the major axis to the minor axis (major axis / minor axis) of the conductive powder particles. In the present invention, the particles of the conductive powder are mixed well in the curable resin having a low viscosity, and the resin is cured while allowing the particles to settle by standing, and the obtained cured product is cut in the vertical direction. The shape of the particles appearing on the cut surface is observed under magnification with an electron microscope, and the major axis / minor axis of each particle is obtained for at least 100 particles, and the average value thereof is defined as the aspect ratio.

Here, the minor axis is selected so that a particle appearing on the cut surface is sandwiched by a combination of two parallel lines contacting the outside of the particle, and two of the combinations having the shortest interval are selected. The distance between the parallel lines. On the other hand, the major axis is the two parallel lines perpendicular to the parallel line that determines the minor axis, and is the distance between the two parallel lines that are the longest among the combinations of the two parallel lines that contact the outside of the particle. is there. The rectangle formed by these four lines is sized to fit the particle exactly inside it. The specific method used in the present invention will be described later.

The substantially spherical composite conductive powder immediately after the surface of the copper powder or copper alloy powder used in the present invention is substantially coated with silver or a silver alloy is in an agglomerated state. preferable. When a substantially spherical composite conductive powder in an agglomerated state that has not been pulverized is used, the packing density does not increase and the thermal conductivity or conductivity tends to be unable to be increased.

There is no particular limitation on the method of pulverization. For example, a shear force is applied to the substantially spherical composite conductive powder to loosen the agglomeration, or a mechanically weak force is applied to reduce the agglomeration of the particles without deforming the particles. It can be broken by removing it. The effect of the pulverization is that, for example, when silver or a silver alloy is coated on the surface of a copper powder or a copper alloy powder by a plating method, the bulk density of the substantially spherical composite conductive powder that is not pulverized is about 45 to 50% in relative density
Before and after, it can be increased to 60% or more by pulverization.

In the present invention, by using a substantially spherical composite conductive powder in which the surface of copper powder or copper alloy powder is substantially covered with silver or a silver alloy and is pulverized, the orientation when crushing on a flat substrate or the like can be improved. And good thermal conductivity can be maintained. If this is, for example, flaky composite conductive powder, it will not only hinder the evaporation of the solvent, but also cannot increase the thermal conductivity in the direction perpendicular to the substrate surface.

According to the present invention, in addition to the substantially spherical composite conductive powder having the surface of the copper powder or the copper alloy powder coated with substantially silver or silver alloy as described above, one of the substantially spherical composite conductive powder having an average particle diameter of one of the above-described ones. / 3
Hereinafter, a powder containing silver having a cohesive property as a main component is used. By this combination, fluidity, conductivity, and thermal conductivity are balanced, and bleeding and dripping of the conductive material can be prevented as long as fluidity is not impaired.

The silver-based powder having cohesive properties is
As described above, it is preferable to use powder having an average particle diameter of 1/3 or less of the pulverized substantially spherical composite conductive powder,
It is more preferred to use no more than 4 powders. If the powder exceeds 1/3, it is difficult to increase the filling rate of the pulverized substantially spherical composite conductive powder, and it tends to be impossible to increase the thermal conductivity.

There is no particular limitation on the shape of the powder containing silver having cohesive properties as a main component, but from the viewpoint of suppressing a rise in temperature when the blending amount is increased, it is preferably a lump or substantially spherical. The powder containing silver as a main component having cohesiveness contains silver powder in an amount of 50% by weight or more, and additionally contains copper powder, nickel powder, alloy powder of silver and palladium, and alloy powder of silver and copper. Is used.

In addition to the particle diameters of the conductive powder described above, if the substantially spherical composite conductive powder is 10 μm or less and the powder containing silver as a main component is 0.5 μm or less, high thermal conductivity and excellent conductivity are obtained. More preferably, the substantially spherical composite conductive powder is 8 μm or less, and the silver-based powder is more preferably 0.4 μm or less, and the substantially spherical composite conductive powder is 6.5 μm or less, and the powder is mainly silver. Is more preferably 0.2 μm or less.

The compounding ratio of the substantially spherical composite conductive powder and the powder containing silver as a main component is such that the weight ratio of the substantially spherical composite conductive powder: powder containing silver as a main component is 99: 1 to 85:15. It is preferable in terms of fluidity, electrical conductivity, thermal conductivity, and the like.
8:12 is more preferable, and 98: 2 to 90:10.
Is more preferable.

As the binder composition, epoxy resin,
Thermosetting resins such as phenolic resins, melamine resins, unsaturated polyester resins, and urethane resins, and, if necessary, thermoplastic resins such as saturated polyester resins and phenoxy resins that impart flexibility. In addition, the thermoplastic resin used as needed is 15% with respect to the binder composition.
It is preferable that the content is not more than weight%.

As the binder composition, those containing a curing agent, a curing accelerator, a coupling agent for improving the wettability with a metal, a surfactant and the like in addition to the above components are used. The content of the curing agent is preferably in the range of 0.2 to 10% by weight based on the binder composition, and the content of the curing accelerator is preferably 0.1 to 10% by weight based on the binder composition. Preferably, the content of the coupling agent and the content of the surfactant are within the range of 0.1 to 0.1% based on the binder composition.
It is preferably in the range of 01 to 1% by weight.

The solvent is added as needed, and when it is added, a higher alcohol and its ester, a carbitol type and its ester are appropriately selected and added according to the working temperature. The smaller the amount of addition, the better, but depending on the application, it may be contained at 2% by weight or more based on the conductive material. For example, when a conductive material containing a solvent is filled in a through-hole and then heated and pressed, the solvent can be volatilized by preliminary drying after filling, and densification can be achieved by pressure hardening. It may be contained.

The mixing ratio of the mixed conductive powder and the binder composition is preferably in the range of 75 to 95% by weight of the mixed conductive powder and 5 to 25% by weight of the binder composition.
5 to 20% by weight of the binder composition with respect to 0 to 95% by weight
Is more preferable. The conductive material according to the present invention can be obtained by uniformly mixing and dispersing a material containing the mixed conductive powder and the binder composition by using a grinder, a kneader, a three-roll mill, or the like.

[0025]

The present invention will be described below with reference to examples.

Example 1 Bisphenol A type epoxy resin (oiled shell epoxy)
80 parts by weight of an aliphatic diglycidyl ether (trade name: ED, manufactured by Asahi Denka Kogyo Co., Ltd.)
-503) 8 parts by weight, 2-phenyl-4-methyl-5-
8 parts by weight of hydroxymethylimidazole (trade name: Curesol 2P4MHZ, manufactured by Shikoku Chemicals Co., Ltd.) and 4 parts by weight of dicyandiamide were added and uniformly mixed to obtain a binder composition.

Next, spherical copper powder (trade name: SFR-Cu, manufactured by Nippon Atomize Processing Co., Ltd.) having an average particle size of 5.1 μm produced by an atomizing method was washed with dilute hydrochloric acid and pure water. 80 g of AgCN and 75 of NaCN
g was subjected to displacement plating so that the amount of silver was 18% by weight with respect to the spherical copper powder, washed with water and dried to obtain silver-plated copper powder.

Thereafter, 1500 g of the silver-plated copper powder obtained above and 4 kg of zirconia balls having a diameter of 2 mm were put into a 6-liter ball mill container and rotated for 120 minutes.
The aspect ratio is 1.1 on average and the average diameter of the major axis is 5.3.
A μm-disintegrated substantially spherical silver-plated copper powder was obtained. Five particles of the obtained substantially spherical silver-plated copper powder were taken out and quantitatively analyzed by a scanning Auger electron spectrometer to examine the exposed area of the copper powder. The average area was 7% in the range of 3 to 10%. Was.

To 55 g of the above-obtained binder composition, 425 g of the pulverized substantially spherical silver-plated copper powder obtained above, and silver powder having a particle size of 0.1 μm or less and agglomerated into a dendritic form ((stock) ) Sylvest E-20, manufactured by Tokuriki Chemical Laboratory)
20 g and 15 g of diethylene glycol ethyl ether having a boiling point of 202 ° C. as a solvent were added, and the mixture was uniformly mixed and dispersed with a three-roll mill and a stirrer to obtain a conductive material.
The content of the solvent was 2.9% by weight based on the conductive material.
The blending ratio of the binder composition and the mixed conductive powder (pulverized substantially spherical silver-plated copper powder and agglomerated dendritic silver powder) was 11% by weight for the binder composition and 8 for the mixed conductive powder.
It was 9% by weight.

Next, a 1.6 mm-thick paper phenol laminate (manufactured by Hitachi Chemical Co., Ltd., trade name: MCL
The test pattern 1 shown in FIG. 1 was printed on −437F (SRD)), and heat-treated in air at 80 ° C. for 1 hour and at 165 ° C. for 1 hour to obtain a wiring board. In FIG. 1, reference numeral 2 denotes a paper phenol laminate. As a result of evaluating the characteristics of the obtained wiring board, the maximum specific resistance of the conductor was 45 μm.
Ω ・ m, minimum value is 33μΩ ・ m, average is 37μΩ ・ m
Met.

The specific method of measuring the aspect ratio in this embodiment will be described below. 8 g of a base material (No. 10-8130) of a low-viscosity epoxy resin (manufactured by Buehler) and 2 g of a curing agent (No. 10-8132) are mixed, and 2 g of conductive powder is mixed and dispersed well, and the mixture is left as it is. After degassing in vacuo at a temperature of 30 ° C., the particles were allowed to stand at 30 ° C. for 10 hours to settle and harden the particles. Thereafter, the obtained cured product was cut in the vertical direction, the cut surface was magnified 1000 times with an electron microscope, and the long diameter / short diameter of 150 particles that appeared on the cut surface was obtained. Ratio.

Example 2 To 45 g of the binder composition obtained in Example 1, 440 g of the crushed substantially spherical silver-plated copper powder obtained in Example 1, and the particle size used in Example 1 was 0.1 μm or less. 15 g of aggregated and dendritic silver powder and 15 g of the solvent used in Example 1 were added, and the mixture was uniformly mixed and dispersed with a three-roll mill and a stirrer to obtain a conductive material. The content of the solvent was 2.9% by weight with respect to the conductive material, and the mixing ratio of the binder composition and the mixed conductive powder was 9% by weight of the binder composition and 9% by weight of the mixed conductive powder.
It was 1% by weight. Hereinafter, as a result of fabricating a wiring board through the same steps as in Example 1 and evaluating the characteristics, the specific resistance of the conductor was 41 μΩ · m at the maximum, 33 μΩ · m at the minimum, and 35 μΩ · m on average. Was.

Example 3 The exposed area of copper was 6% on average, and the average long diameter was 5.4.
Except that μm-disintegrated substantially spherical silver-plated copper powder was used,
A conductive material was obtained through the same materials as in Example 1 and the same steps as in Example 1. Hereinafter, as a result of fabricating a wiring board through the same steps as in Example 1 and evaluating the characteristics, the specific resistance of the conductor was 40 μΩ · m at the maximum value, 31 μΩ · m at the minimum value, and 3 on the average.
It was 5 μΩ · m.

Example 4 45 g of the pulverized substantially spherical silver-plated copper powder obtained in Example 1 was added to 45 g of the binder composition obtained in Example 1, and the particle size used in Example 1 was 0.1 μm or less. 10 g of the aggregated and dendritic silver powder and 15 g of the solvent used in Example 1 were added, and the mixture was uniformly mixed and dispersed with a three-roll mill and a stirrer to obtain a conductive material. The content of the solvent was 2.9% by weight with respect to the conductive material, and the mixing ratio of the binder composition and the mixed conductive powder was 9% by weight of the binder composition and 9% by weight of the mixed conductive powder.
It was 1% by weight. Hereinafter, as a result of fabricating a wiring board through the same steps as in Example 1 and evaluating the characteristics, the specific resistance of the conductor was 43 μΩ · m at the maximum, 33 μΩ · m at the minimum, and 36 μΩ · m on average. Was.

Next, the wiring boards obtained in Examples 1, 2, 3 and 4 were left in a thermo-hygrostat at 85 ° C. and 85% relative humidity for 500 hours, and the resistance change rate was measured. −
0.5%.

Comparative Example 1 45 g of the spherical copper powder used in Example 1 and 15 g of the solvent used in Example 1 were added to 45 g of the binder composition obtained in Example 1.
Was added and uniformly mixed and dispersed with a three-roll mill and a stirrer to obtain a conductive material. Hereinafter, as a result of fabricating a wiring board through the same steps as in Example 1 and evaluating the characteristics, the specific resistance of the conductor was 87 μΩ · m at the maximum and 56 μΩ · m at the minimum.
And the average was 69 μΩ · m. When the obtained wiring board was left in a thermo-hygrostat at 85 ° C. and 85% relative humidity for 500 hours, and the resistance change rate was measured, it was found to be 157% on average, and the resistance was largely changed.

[0037]

The conductive material according to the first, second, third and fourth aspects is excellent in high electrical conductivity and high thermal conductivity, and is an industrially suitable electrically conductive material. The conductive material according to claim 5 is a conductive material having high resistance reliability and good filling property in through holes, in addition to the invention according to claims 1, 2, 3 and 4.

[Brief description of the drawings]

FIG. 1 is a plan view showing a test pattern formed on a paper phenol laminate.

[Explanation of symbols]

 1 Test pattern 2 Paper phenol laminate

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) C09J 11/04 C09J 11/04 201/00 201/00 F term (reference) 4E351 BB01 BB31 DD04 DD05 DD52 EE15 EE16 GG16 4J040 DB001 EB031 EB131 ED111 EF001 HA066 HA076 JB02 JB10 KA03 KA07 KA32 LA08 LA09 NA20 5E343 AA14 BB24 BB25 BB52 BB72 BB76 BB77 BB79 DD02 FF02 GG16 5G301 DA03 DA06 DA42 DA53 DA55 DA57 DA57 DA57 DA57 DA57 DA57 DA57 DA57 DA57 DA57 DA57 DA57 DA57 DA57 DA57 DA57

Claims (5)

[Claims] 1. A mixed conductive powder and a binder composition comprising a substantially spherical composite conductive powder in which the surface of a copper powder or a copper alloy powder is substantially coated with silver or a silver alloy and a powder mainly containing silver having cohesiveness. A conductive material comprising: 2. The conductive material according to claim 1, wherein the average particle diameter of the powder containing silver having cohesive properties as a main component is 1/3 or less of the substantially spherical composite conductive powder. 3. The substantially spherical composite conductive powder has an average particle size of 10 μm.
The conductive material according to claim 1, wherein the average particle diameter of the powder containing silver having cohesive properties as a main component is 0.5 m or less. 4. The conductive material according to claim 1, wherein the powder containing silver having cohesive properties as a main component is in a lump. 5. The compounding ratio of the substantially spherical composite conductive powder and the powder containing silver as a main component is such that the weight ratio of the substantially spherical composite conductive powder: powder containing silver as a main component is 99: 1 to 85: The conductive material according to claim 1, 2, 3, or 4.