JP5059458B2 - Conductive powder, conductive paste, conductive sheet, circuit board and electronic component mounting circuit board - Google Patents

Description

  The present invention relates to a conductive powder, a conductive paste, a conductive sheet or a circuit board using a conductive paste used for conductivity or heat conduction, and an electronic component mounting circuit board.

  Conventionally, conductive powders combined with spherical or substantially spherical particles or flaky particles have been used as conductive pastes and conductive sheets used for electricity and heat conduction. (For example, refer nonpatent literature 1). In particular, in fields where high conductivity or high thermal conductivity is required, gold powder, silver powder, copper powder, aluminum powder, palladium powder or alloy powders thereof are used as conductive powder to increase conductivity and thermal conductivity. For this reason, the blending amount of the conductive powder has been increased.

The method for producing the highly filled conductive powder described in Non-Patent Document 1 is a method in which large and small spherical particles are combined and uniformly mixed, and the scaly particles and spherical particles or massive particles are combined. There is no description about obtaining highly filled conductive powder. Further, it is described that a relative packing density of 80% or more is theoretically obtained by arranging spherical particles regularly and further combining spherical particles having different particle diameters. However, the spherical silver powder that is commercially available has some aggregated particles. The silver powder having a particle size of 5 to 20 μm has a relative packing density of about 60%, and the silver powder having a particle size of about 1 μm. The relative packing density is about 50% at the highest, and even if they are mixed, the relative packing density remains around 60%.
Nikkan Kogyo Shimbun Co., Ltd., Powder Engineering Society Edition, Powder Engineering Handbook, First Edition, 1st Edition, February 1986 (Pages 101-107)

  In general, when an IC chip that generates heat is bonded using a conductive sheet, it is necessary to increase thermal conductivity and adhesive strength. Therefore, in the past, the conductive paste used for this purpose has been increased in conductivity by increasing the blending amount of the conductive powder. However, in the case of a normal conductive powder, if the blending amount is increased, the viscosity of the conductive paste is increased and pattern forming properties such as printability are deteriorated. On the other hand, when the ratio of the binder in the conductive paste is increased, the viscosity is decreased and the pattern formability is improved, but there is a disadvantage that the conductivity is deteriorated.

  In addition, when conductive paste is used as a heat conductive adhesive to increase the thermal conductivity in the penetration direction, even if the conductive powder is a paste made only of spherical particles, if the packing density of the conductive powder is low, the thermal conductivity is also low. There was a drawback that would become.

  When spherical conductive powder is used in these applications, the particles are spheres, so that contact with the plane to be connected becomes point contact due to electrical conductivity or thermal conductivity, and the contact efficiency between the particles and the plane is poor. In order to avoid this, if the particle shape is scale-like, the viscosity of the paste tends to increase, and the printability of the paste becomes poor. Also, the scale-like conductive particles in the paste formed on the base material tend to orient the scale-like surface perpendicular to the Z-axis (conducting direction) of the base material due to the viscous behavior of the paste during printing. Also, there is a disadvantage that the conductivity and thermal conductivity in the Z-axis direction are significantly lower than expected.

  Also, when these spherical conductive powders are used, when the particle layer is crushed by a press or the like, isotropic pressure is applied, the particles are slidable with each other, and the volume of the conductive powder is reduced. There was also a drawback that it was difficult to press against each other. In order to avoid such problems, it is necessary to have a method for measuring the ease with which conductive powder is filled, and it is suitable to measure the tap density as a characteristic corresponding to the state of filling while flowing, but the conductive In the case of an application in which the powder layer is pressed or pressed, it is not always appropriate to judge based on the tap density. Therefore, in addition to the tap density, it was considered that a measure for grasping the filling state when the conductive powder was clogged to the limit or the limit was useful.

  In addition, when silver powder is used as conductive powder, the conductivity is good, but migration resistance is poor, and when gold powder, palladium powder, or silver palladium alloy powder is used, migration resistance is good, but compared to using silver powder. Therefore, there is a drawback that the cost is significantly increased.

  Furthermore, when using a conductive paste as a conductive adhesive, the syringe-like syringe is pushed by an automatic machine to supply a desired amount of the conductive adhesive to a desired position, then moved to another position, and repeatedly from the syringe. Supply is done. In this case, if the thixotropy of the conductive adhesive is low, the paste is in a stringing state, and there is a problem that the conductive adhesive is applied to unnecessary portions.

  In general, in order to increase the thixotropy of the conductive adhesive, fine flaky particles are used in combination. However, when scale-like fine powder particles are used in combination, the fine particles are aggregated. Therefore, the paste to which these particles are added has a disadvantage that the viscosity increase is large and a highly filled conductive adhesive cannot be produced. In addition, when manufacturing a paste using mixed conductive powder with a low packing density, even when trying to manufacture a paste containing a high content of mixed conductive powder, adding mixed conductive powder to the binder causes the viscosity to be extremely high. Even if a mixing / dispersing device such as a three-roll mill or a raking machine is used, the viscosity is too high and the state becomes rugged. For this reason, there is a problem that it cannot be dispersed to form a paste.

  In order to produce a conductive powder composed of large particles or small particles having a large scale or low aspect ratio, large particles having a large particle size or a substantially spherical particle are weakly pulverized to roughly form large particles having a large particle shape or a low aspect ratio. Separately, after agglomeration of agglomerated small particles or nearly spherical particles, the small particles processed into a lump or scaly shape are produced, and both are mixed in the desired ratio. However, it has the trouble of making the large particles and the small particles separately and mixing them. In addition, when it is difficult to produce small particles, it is produced by a method of classifying a mixed powder consisting of large particles and small particles and collecting small particles. In this case, there is a disadvantage that the cost of the small particles is increased. there were.

  When a desired circuit pattern is formed on a substrate such as a film and chip components are connected on the circuit pattern, the circuit pattern is formed in advance, and after applying a conductive adhesive on the circuit pattern, Since chip components are connected via a conductive adhesive, there is a drawback that the number of processes increases. In addition, there are disadvantages such as deviation of the supply position of the conductive adhesive and bleeding due to a step of the circuit pattern.

Under such circumstances, the present inventor has intensively studied to solve the above-mentioned problems, and as a result, has completed the present invention with the following constitutional requirements.
[1] Gold powder, platinum powder, palladium powder, silver powder, copper powder, silver plating containing a dispersed conductive powder composed of polyhedral particles and substantially scaly particles, and bulk fine powder, and having a press density of 80% to 99.5% Conductive powder composed of copper powder, aluminum powder and alloy powder thereof.
[2] A conductive paste comprising the conductive powder of [1] and a binder.
[3] The conductive paste according to [2], wherein the conductive powder in the paste is in the range of 95 to 99.5% by weight and the binder is in the range of 0.5 to 5% by weight.
[4] The conductive paste according to [2] or [3], wherein the binder is a thermosoftening resin and has adhesiveness at normal temperature and pressure.
[5] A conductive sheet comprising the conductive powder of [1] and a binder.
[6] The conductive sheet according to [5], wherein the conductive powder in the sheet is in the range of 95 to 99.5% by weight and the binder is in the range of 0.5 to 5% by weight.
[7] The conductive sheet according to [5] or [6], wherein the binder is heat-softening and has adhesiveness at normal temperature and pressure.
[8] A circuit board in which a desired circuit pattern is formed on a substrate with the conductive paste of [2] to [4].
[9] The circuit board according to [8], wherein a plurality of circuit patterns are formed, and the circuit patterns formed on the substrate are connected.
[10] A desired circuit pattern is formed on a substrate with the conductive paste of [2] to [4], and an electronic component is connected via a part of the circuit pattern formed on the substrate. Electronic component mounting circuit board.
[11] The electronic component mounting circuit board according to [10], wherein a plurality of circuit patterns are formed, and the circuit patterns formed on the substrate are connected.

  In addition, the electroconductive powder which has the high press density used by this invention was not known conventionally.

  The conductive powder of the present invention has a characteristic that the press density is high. For this reason, a conductive paste or conductive sheet containing a high proportion of conductive powder can be formed with a small amount of binder. In addition, a circuit pattern formed with the conductive paste in which the amount of the binder is limited is good in conductivity, and has a characteristic that the conductivity becomes higher when pressed.

  In addition, since the binder itself is used that exhibits adhesiveness, the circuit itself formed on the base material exhibits adhesiveness, and the chip components and the like can be directly conductively connected to the circuit. For this reason, according to the present invention, it is possible to simultaneously perform circuit formation and adhesive application of chip parts, and the process can be simplified. Further, since the interlayer connection of a plurality of circuit formation substrates and the formation of the outermost circuit can be simultaneously performed, the process can be simplified.

  In addition, since the conductive powder is easily packed densely, the conductive powder is uniformly dispersed simply by preparing a uniform binder solution in advance, adding the conductive powder to this, and mixing for a short time. A paste can be produced, and a planar conductive sheet can be easily produced by printing or coating the paste on the sheet.

  Since the conductive fine particles are easily deformed and have the disadvantage of being easily agglomerated, mixing for a long time is necessary to break up the agglomeration, and fine powder such as soft silver is particularly deformed. For this reason, it is difficult to produce a conductive paste with good reproducibility, and there are drawbacks in that the properties such as viscosity, color tone, and conductivity are likely to vary, but the conductive paste of the present invention is manufactured in a short mixing time. Therefore, the deformation of fine particles and small particles is suppressed to the minimum. For this reason, high conductivity can be maintained.

  In addition, when a metal surface having irregularities and a silicon substrate are bonded with a conductive paste, the conductive powder is densely filled into fine irregularities on the surface of the metal plate, so that the contact efficiency is increased, and the conductivity and thermal conductivity are improved. Get higher.

Hereinafter, the best mode for carrying out the present invention will be described.
[Conductive powder]
The conductive powder of the present invention has a press density of 80% to 99.5%, a press density of 80% to 99.5%, a gold powder, a platinum powder, a palladium powder, a silver powder, a copper powder, a silver-plated copper powder, an aluminum powder, These alloy powders.

  The press density of the conductive powder of the present invention is 80% to 99.5%, preferably 85% to 99.5%. When the press density is within this range, it is possible to easily produce a printable conductive paste or conductive sheet even if the binder amount is reduced.

  The conductive powder of the present invention is a conductive powder having a press density of 80% to 99.5%, and preferably has a press density of 85% to 99.5%. When the press density is within this range, it is possible to easily produce a printable conductive paste even if the binder amount is reduced.

  As the conductive powder, gold powder, platinum powder, palladium powder, silver powder, copper powder, alloy powder thereof, silver-plated copper powder, or processed powder thereof is used. In the present invention, palladium powder, silver powder, copper powder, Silver-plated copper powder and aluminum powder are suitable.

When used for a conductive paste or a conductive sheet that takes advantage of conductivity and thermal conductivity, these conductive powders are used alone or in combination. The conductive powder having a press density in the predetermined range of the present invention is preferably a combination of a dispersed conductive powder composed of polyhedral particles and substantially scaly particles, and a lump of fine particles, and a combination of partially agglomerated lump or flakes. May be. In such a case, when the conductive powder or the conductive paste and the adherend are bonded, the contact state between the conductive powder and the adherend surface can be improved, which is preferable.

  In the present invention, being substantially monodispersed indicates a state in which most of the aggregated particles are pulverized. Polyhedron-shaped particles refer to polyhedrons whose surfaces are minute planes, polyhedrons composed of a plurality of planes and curved surfaces, and polyhedrons that can approximate a cube or a rectangular parallelepiped.

  Such polyhedral particles are pulverized and processed into shapes by agglomeration of raw conductive particles such as spherical particles, substantially spherical particles, and teardrop particles together with beads. Can be obtained. A high press density can be realized by combining a substantially monodispersed conductive powder having a large particle size and a conductive powder having a smaller particle size and agglomerated most of the particles. Moreover, the conductive powder may contain fine powder that is partially agglomerated. The size of the conductive powder is selected according to the application, but when used for the purpose of forming a circuit by a screen printing method, the average particle size of the large particles is preferably about 30 μm or less, more preferably 20 μm or less. In addition, when it consists only of large particle | grains, a press density becomes low, and when it is made a paste with few binders, smooth printing may be unable to be performed.

  For this reason, the conductive powder having a press density in the above-described range by combining substantially monodispersed large particles and small monodispersed particles can be made into a paste with a small amount of binder, and can be printed smoothly.

  The particle size of the lumpy or flaky fine powder is desirably used in combination with fine powder having an average particle size of 2 μm or less, preferably 1.5 μm or less, more preferably 1 μm or less, when used for applications that improve contactability. You may use together the nanoparticle of several tens nm level or a hundred nm level. When these nanoparticles are used in combination, it is easy to uniformly mix the nanoparticles and the conductive powder if the nanoparticles are added to the binder in advance, and then dispersed by uniform dispersion and then the conductive powder is added. This mixing method is particularly suitable when slurry-like nanoparticles are used.

The measurement method of the average particle diameter can be measured by a laser diffraction method.
By using the fine powder having such a particle size, the fine conductive powder in the conductive powder is rearranged so as to fit the irregularities of the surface of the adherend. It plays a role of filling gaps formed by conductive powders composed of particles. For this reason, the conductive connection between the electrode and the conductive circuit can be realized with a low contact resistance, and the thermal resistance of the adhesive interface can be reduced even with a heat conductive adhesive.

  The ratio of conductive powder (polyhedrally shaped particles and substantially scaly particles in a substantially monodispersed state) to fine powder (a fine powder such as a lump having a smaller particle size than that of the conductive powder and agglomerated mostly) is 95: 5 to 55:45, preferably 95: 5 to 60:40, and more preferably 95: 5 to 70:30. The conductive powder further includes an agglomerated powder of ultrafine powder, and the ultrafine powder constituting the agglomerated powder has an average primary particle size of 0.3 μm or less, and the ratio of the agglomerated powder of the conductive powder, the fine powder, and the ultrafine powder is by weight ratio. It may be 94.525: 4.975: 0.5 to 52.25: 42.75: 5.00. If the ratio of ultrafine powder aggregated powder is larger than this range, the number of contact points between particles will increase, and the aggregated powder of ultrafine powder will reduce the tap density of the conductive powder. It will reduce the sex. If the ratio of the ultrafine powder agglomerated powder is less than these ranges, the gap between the shape-processed conductive powders cannot be sufficiently filled, and the conductivity and thermal conductivity may be reduced due to insufficient contact between the particles. is there. The average primary particle size of the ultrafine powder constituting the aggregated powder is 0.3 μm or less, more preferably 0.2 μm or less, and even more preferably 0.15 μm or less. If the average primary particle size of the ultrafine powder constituting the agglomerated powder is larger than this, even if the silver ultrafine powder enters the gap formed between the fine powder, the large monodispersed particles, and the small particles, In some cases, the packing density cannot be increased, and instead the packing density is lowered.

In addition, the material which comprises fine powder and ultra fine powder can be exemplified by the conductive powder. Note that the fine powder and the ultrafine powder may be the same as or different from the large particles / small particles.
In the present invention, the press density is measured by the following method.

  Precisely weigh the conductive powder, put it in a cylinder with a constant cross section (the inner diameter of the cylinder is 10 to 20 mm), and the upper and lower sides of the conductive powder placed in the cylinder are approximately equal in diameter to the inner diameter of the cylinder. Is clamped with a movable thick disc (thickness of about 3 to 5 mm) and the disc is tightened with a micrometer.

  The press density is calculated from the mass of the conductive powder precisely weighed, the thickness of the conductive powder measured with a micrometer, and the diameter of the disk used for the measurement. The calculated density is divided by the true density of the conductive powder, and the calculated value is expressed in%.

The surface of the conductive powder of the present invention may be treated with a fatty acid treatment or a coupling agent.
Examples of the fatty acid include saturated fatty acids such as stearic acid, lauric acid, capric acid, and palmitic acid, and unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid, and sorbic acid. Examples of the coupling agent include titanate and silane coupling agents. If the amount of these surface treatment agents is large, the surface treatment agent may serve as a nucleus and the particles may aggregate together. The specific surface treatment amount is 0.5 wt% or less, 0.02 wt% or more, more preferably 0.3 wt% or less, 0.02 wt% or more, further preferably 0.25 wt%, based on the conductive powder. Below 0.02% by weight or more is desirable.

Production of conductive powder The conductive powder with high press density of the present invention is a substantially monodispersed polyhedral shape and substantially scaly large particles and small particles and fine particles placed in a container, and the container is moved to cause the conductive powder to flow, It can be easily obtained by pulverizing fine particles that are aggregated with substantially monodispersed polyhedral shapes and substantially scaly large particles and small particles and simultaneously mixing them. For example, it can be manufactured by the following manufacturing method.

Specifically, raw material conductive powder and beads having a small particle diameter are placed in a container, the container is moved to cause the raw material conductive powder and beads to flow, the conductive powder is pulverized into a monodispersed state, and polyhedral shaped particles and Shapes into substantially scaly particles. Put the shaped particles and relatively small cohesive particles in the same container, rotate the container containing only conductive powder without beads, etc., and mix only with the conductive particles. Large, substantially monodispersed particles can be obtained by uniformly mixing while pulverizing the aggregation of small particles. The conductive powder having a high press density can be obtained by appropriately controlling the particle size ratio between large particles and small particles and the volume ratio between particles.

  In addition, in order to increase the contact probability between particles or between the particle and the surface of the adherend, it is preferable that the shape of the particle is a polyhedron or a substantially scaly shape with a small aspect ratio. There is. At this time, if the shape of the large particles in the conductive powder is processed into a scaly shape having a large aspect ratio, the viscosity of the conductive paste is increased. Therefore, a large scaly shape having a small aspect ratio is preferable for the large particles. As the fine powder, a scaly or a lump is appropriately selected according to the use, and the combined use of the scaly fine particles is effective for improving the contact between the particles. Depending on the application, these particles can be used alone or in combination.

  In the present invention, in order to process the shape, when the raw material conductive powder and beads having a small particle diameter are put in a container, and the container is rotated to flow the raw material conductive powder and the beads, the raw material conductive powder is pulverized with the beads. Large particles in the raw material conductive powder are processed into polyhedral shapes or substantially scaly particles having a small aspect ratio, and small particles in the raw material conductive powder are processed into substantially scaly particles having a larger aspect ratio than the large particles. The fine particle size beads to be used preferably have an average particle size of 10 mm or less, more preferably 5 mm or less, and even more preferably 3 mm or less. As the material of the beads, since it is preferable that the mass of the beads is small, a ceramic such as glass, zirconia, or alumina having a density lower than that of the metal particles is suitable.

  If the diameter of the container containing the beads and the raw material conductive powder is large, the falling distance of the beads will increase, so the collision energy between the beads will be too large, and the shape will be processed without being sufficiently crushed. It is difficult to obtain high small particles.

  If the rotational speed of the container is too high, the collision energy between beads occurring in the container becomes too large, and the shape processing proceeds too much, making it difficult to obtain small particles with a high aspect ratio as described above. A low rotation speed is not preferable because it takes too much time for pulverization and shape processing. A suitable rotation speed is 10 to 100 rpm, preferably 30 to 80 rpm.

  The inner diameter of the container containing the beads and the raw conductive powder is preferably 10 cm to 80 cm, more preferably 10 cm to 60 cm, and even more preferably 10 cm to 40 cm. The bead filling volume is preferably about 20 to 80%, more preferably 30 to 70%, and still more preferably 40 to 70% of the effective volume of the container. If the filling volume of the beads is larger than this, the aggregated raw material conductive powder by the beads cannot be crushed smoothly, and the shape processing of the raw conductive powder may not proceed well. If the volume of the beads is smaller than this, the pulverization and shape processing of the raw material conductive powder may not be performed efficiently.

  The volume ratio of the filled volume of the beads to the raw material conductive powder is preferably 50:50 to 96: 4, more preferably 60:40 to 96: 4, and even more preferably 70:30 to 95: 5. It is. In addition, the volume of a bead and raw material electroconductive powder is calculated by a bulk density. When the ratio of the raw material conductive powder is less than this, there is a disadvantage that the processing efficiency is poor. Moreover, when raw material conductive powder exceeds this ratio, pulverization and shape processing of the raw material conductive powder may not be performed efficiently.

  In the present invention, the processing time when the beads and raw conductive powder are put into the container and the raw conductive powder is processed by rotating the container is the size of the container, the amount of beads charged, the amount of raw conductive powder charged, The optimum value is obtained while checking the tap density and particle shape change of the obtained conductive powder depending on the rotation speed and the like, but it may be about 1 hour to 100 hours.

There is no particular limitation on the method of mixing the dispersed conductive powder composed of processed polyhedral particles and substantially scaly particles and massive partially aggregated fine particles, but a method that avoids deformation of the particles is preferable, for example, V blender, ball Examples of the method include a ball mill without a (media) and a planetary mixer. The ball mill without a ball (media) is a method in which only the powder to be mixed is put into a ball mill container, the container is rotated without putting a ball for grinding, and the conductive powders are mixed. Moreover, when mixing each powder | flour, you may mix sequentially and the order in particular is not restrict | limited.

The mixing time is appropriately selected depending on the apparatus type, capacity, input amount of raw materials, and the like.
[Conductive paste]
The conductive paste of the present invention comprises at least one conductive powder selected from the group consisting of palladium powder, silver powder, copper powder, silver-plated copper powder, and aluminum powder having a press density of 80% to 99.5% and a binder. It is characterized by that. Such conductive powder is as described above.

  The ratio of the conductive powder to the binder in the conductive paste is 95 to 99.5% by weight of the conductive powder, and is composed of 0.5 to 5% by weight of the binder. Preferably, the conductive powder is 96 to 99.5% by weight. 0.5 to 4% by weight, more preferably 97 to 99.5% by weight of conductive powder and 0.5 to 3% by weight of binder. In the case where a conductive material composed of conductive powder and a binder is pressed and used, the amount of the binder can be further reduced. The conductive powder is composed of 98 to 99.5 wt% and the binder is 0.5 to 2 wt%. A printed circuit can be formed on a substrate even with a conductive material. Moreover, after forming this electrically conductive material on the base material which has peelability, this can be peeled and it can also be used as a sheet | seat for adhesion | attachment.

Conventionally, it is not known to control conductive powder at press density. Also, conductive powder with high press density is produced, and this feature is utilized to make a paste with a low binder content, thereby printing a circuit pattern. However, it has not been known that various methods such as pressing the pattern to enhance conductivity or using the pattern as an adhesive for chip parts can be performed at a practical level. These can be realized by using the conductive powder.
Binder As the binder of the present invention, a thermosetting resin or thermoplastic resin such as epoxy, phenol, polyester, polyurethane, phenoxy, polyester, and acrylic is selected according to the purpose together with a coupling agent, a curing agent, a diluent, and the like. Used, but not particularly limited. Among these, when a heat-softening resin is selected, a conductive paste is produced with a binder, a circuit pattern is formed on a substrate, and then the circuit resistance is subjected to a hot press treatment, whereby the circuit resistance value can be lowered. .

  A binder made of a thermosoftening resin having such an adhesive property means a resin that exhibits adhesiveness near room temperature (20 to 30 ° C.) and softens at least temporarily near 60 to 150 ° C. This corresponds to a thermosetting resin.

  For example, a solid epoxy resin having a softening temperature of 60 ° C. to 120 ° C. and a liquid epoxy resin mixed at room temperature can be used as the binder. The adhesiveness at this time can be adjusted by the ratio of the liquid resin to the solid resin.

  The paste of the present invention does not need to have strong adhesiveness in a normal state, and may have any adhesive strength that can temporarily bond chip parts and the like. This adhesive force can be suitably prepared by combining, for example, a resin that is sticky in a normal state and a resin that is a solid resin in a normal state and is softened by heating.

  Note that the conductive paste of the present invention can be prepared by mixing conductive powder and a binder, but usually a thermosetting resin or thermoplastic resin is dissolved and mixed in a solvent together with a curing agent, a coupling agent, and the like. When the binder solution is mixed with the mixed conductive powder to form a conductive paste, the surface treatment and mixing can be performed at a time, so that less energy is applied to the conductive powder and deformation of the powder can be suppressed. When the paste is printed on the substrate surface and the solvent is volatilized, a conductive paste printed matter exhibiting adhesiveness can be formed. When this conductive paste is applied on a peelable substrate and then dried by heating to volatilize the solvent, a conductive material having a desired form can be obtained.

  When the binder is a thermosetting resin that requires a curing agent such as an epoxy resin or a phenol resin, a curing agent such as an amine or an imidazole is added as necessary. Specifically, a known curing agent such as 2-phenyl-4-methyl-imidazole can be used without particular limitation.

  Further, titanate-based, silane-based, aluminate-based, etc. are used as coupling agents in order to improve the wettability between the binder and the conductive powder. The amount of the curing agent used varies depending on the type of the curing agent, but about 3 to 30 parts by weight per 100 parts by weight of the thermosetting resin is appropriate. Moreover, the usage-amount of a coupling agent should just be 1% or less with respect to paste weight, Preferably it is 0.5% or less.

  When the ratio of the liquid resin is increased, a circuit pattern having adhesiveness can be formed in a normal state, and thus the chip component can be directly bonded onto the pattern. Further, in order to produce a conductive sheet exhibiting heat-weldability, it is possible to perform heat-welding if a binder solution is produced using a solid resin having a heat softening temperature of 40 ° C. to 80 ° C. without using a liquid resin. A conductive sheet can be produced.

It is also possible to set the ratio of the liquid resin to 0 or low and use a solid resin that does not exhibit adhesiveness in a normal state as a binder depending on the application.
Solvent The paste of the present invention contains the above-described conductive powder and binder, but may contain a solvent as necessary. By using an appropriate amount of solvent in combination, the printability can be greatly improved, and a conductive paste that can be printed smoothly even with an extremely small amount of binder of less than 2% by weight can be obtained.

  The solvent used in the present invention preferably has a boiling point of 150 ° C. or higher, and preferably 175 ° C. or higher. Specifically, carbitols, higher alcohols, esters thereof, terpineol and the like can be used.

Since the conductive powder used in the present invention is in a uniformly dispersed state, when preparing a paste, it is easy to uniformly mix the conductive powder and the binder composition, and the time required for mixing and dispersing is short. In addition, the paste can be easily manufactured. For this reason, fine powder that easily deforms is contained, but since the deformation of the fine powder during the mixing process can be prevented, the viscosity, color tone, or characteristics of the conductive paste are stable and easy to reproduce. The approximate mixing time is about 1 to 10 minutes depending on the capacity of the mixer. In particular, when the conductive powder is as soft as silver, the shorter the mixing time, the better, and the effect of suppressing the shape deformation of the fine powder is great.

  Of the conductive powders used in the present invention, when the tap density is relatively high but the one having the property of relatively low press density is used, the filling amount of the conductive powder is compared when the paste is filled. Can be high. Furthermore, when pressing through holes filled with this paste, the press density is relatively low, so the conductive powder filling part can be easily crushed and the contact between the conductive powders can be increased. Can be obtained.

  Such a conductive paste of the present invention can be suitably used for circuit formation, and further for circuit formation or interlayer connection of circuit boards in which circuit patterns formed on a plurality of substrates are interlayer-connected.

  Furthermore, when the paste of the present invention is supplied between planes and sandwiched so that both planes are narrowed, the conductive powder remains between both planes, but the binder composition is extruded, so that the conductive powders between the planes contact each other. Also become stronger. Therefore, it is also useful as a paste using a conductive powder having a high press density as a thermal conductive grease used for increasing the thermal conductivity between both planes.

When the paste filled or applied as described above is crushed by a press to enhance conductivity, conductive powder having a high tap density and a low press density is preferable. Such characteristics can be controlled by selecting the raw material conductive powder when preparing the conductive powder and appropriately controlling the shape during the shape processing. The tap density (%) is a value obtained by dividing the density measured by tapping by the true density of the particle in%. In the present invention, the tap density of the particles is obtained by tapping 1,000 times with a stroke of 25 mm, and the tap density calculated from the volume and mass is taken as the packing density, which is the true density or theoretical density of the particles. It was calculated by dividing by.
Method for Producing Conductive Paste The conductive paste according to the present invention is a mixed conductive powder composed of a dispersed conductive powder composed of a binder component, shape-processed polyhedral-shaped particles and substantially scale-like particles, and massive partially aggregated fine particles in a solvent. Can be produced by adding a shearing force to the dispersed slurry and mixing them uniformly. As a device for applying a shearing force to the dispersion, there are a three-roll, a planetary mixer, a stirring blade, a raking machine, or a device for revolving and revolving the container to mix the material in the container with centrifugal force. An appropriate amount of a solvent may be added to the binder in advance, or a solvent may be added as necessary during mixing. If the viscosity at the time of mixing is too high, the mixing operation cannot be performed smoothly, so it is preferable to add a solvent to the binder in advance.
Use of conductive paste The conductive sheet of the present invention is characterized by containing a conductive powder having a press density of 80% to 99.5% and a binder. Such a conductive sheet is produced by printing the conductive paste on the surface of the substrate, and then drying, curing, or pressing as necessary.

  A well-known thing can be especially used as a base material without a restriction | limiting. For example, it may be a glass epoxy substrate or a release film. After printing the conductive paste on the surface of the release film, drying and curing it, and peeling the release film, it is possible to obtain only the conductive sheet. The conductive sheet thus obtained is in close contact with other substrates. You may let them.

  Since the conductive sheet of the present invention exhibits adhesion at room temperature, an IC chip or the like can be easily bonded. For example, if the conductive sheet is bonded on a wiring board and heated and cured, It becomes possible to adhere the IC chip through the conductive sheet.

Thus, if the electrically conductive sheet of this invention is used, what has conventionally required a complicated process can be easily manufactured.
The conductive paste can also be used for circuit formation, particularly for mounting circuit formation. For example, when a metal surface having irregularities and a silicon substrate are bonded with a conductive paste, if the silver fine powder having a particle size corresponding to the fine irregularities on the surface of the metal plate is used together, the silver fine powder is successfully filled into the irregularities on the metal surface. Therefore, the contact efficiency is increased, and the conductivity and thermal conductivity are increased.

The circuit board of the present invention is formed by forming a desired circuit pattern on a substrate with the conductive paste, and a plurality of circuit patterns are formed between the circuit patterns formed on the substrate. It may be connected. In the electronic component mounting circuit board of the present invention, a desired circuit pattern is formed on a substrate with the conductive paste, and the electronic component is connected via a part of the circuit pattern formed on the substrate. Thus, a plurality of circuit patterns may be formed, and the circuit patterns formed on the base material may be connected. These circuit patterns can be prepared by a known method using the conductive paste.
[Example]
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples at all.
Example 1
Preparation of conductive powder Silver powder having an average particle diameter of 5.0 μm was used as a raw material. This packing density was 51%.
The surface of the silver powder was treated with 0.1% by weight of stearic acid, and 500 g of this was weighed and placed in a ball mill having an internal volume of 2 liters. The ball mill is filled with 1 liter of alumina beads having a diameter of about 2 mm. The volume ratio of the beads to the conductive powder was beads: conductive powder = 11: 1. The diameter of the ball mill was about 12 cm. The ball mill is rotated at a rotational speed of 60 min ^-1
After time treatment, a shape-processed silver powder that is a substantially monodispersed conductive powder was obtained.

  As a result of observing the obtained shaped processed conductive powder with a particle size distribution measuring instrument and SEM, the average particle diameter is 6.2 μm, the average aspect ratio of large particles having a cumulative 30% diameter or more is 2.5, and the cumulative 30 The% diameter was 2.6 μm, and the average aspect ratio of the small particles was 7.2. The packing density of the treated conductive powder was 63%.

400 g of the above substantially monodispersed conductive powder and 100 g of easily dispersible bulk silver powder having an average particle diameter of 1.5 μm and a packing density calculated from the tap density of 52%, without the same balls as the ball mill having an internal volume of 2 liters The mixture was treated for 72 hours at a rotation speed of 50 min ⁻¹ to obtain mixed conductive powder. The filling density of the mixed conductive powder calculated from the tap density was 71%, and the press density was 89%.

Preparation of conductive paste Separately from the above, 50 parts by weight of bisphenol F type epoxy resin (trade name Epomic R110, manufactured by Mitsui Chemicals, Inc.) having an epoxy equivalent of 170 g / eq, an epoxy equivalent of 325 g / eq, and a softening temperature of 60 ° C. Bisphenol A type epoxy resin 45 parts by weight, 2-phenyl-4-methyl-imidazole (trade name Curesol 2P4MZ, manufactured by Shikoku Kasei Co., Ltd.) 4.5 parts by weight, titanate coupling agent 0.5 parts by weight and ethyl 100 parts by weight of carbitol was uniformly mixed to obtain a binder solution.

98 parts by weight of the mixed conductive powder and 4 parts by weight of the binder solution were uniformly mixed using a rake machine to obtain a conductive paste.
Circuit formation A circuit having a line length of 115 mm and a line width of 0.7 mm is printed on a glass epoxy substrate from which copper foil has been removed by etching, and then dried at 110 ° C. for 30 minutes, and then at 185 ° C. The volume resistivity of the circuit cured for 45 minutes was 6.8 μΩ · cm. Further, this paste was carefully printed and dried repeatedly so as not to contain voids, and laminated printed and dried to obtain a test piece having a thickness of 1.2 mm, which was cured to produce a heat conduction test piece. The thermal conductivity of this test piece was 25 Wm ⁻¹ K ⁻¹ .

Evaluation of the conductive sheet Further, the conductive paste was applied on a film having a release treatment on one side and dried at 100 ° C. to prepare a conductive sheet. Since the conductive sheet exhibits adhesiveness at room temperature, it can be bonded to the IC chip, and the conductive sheet is bonded onto the wiring board and heated to 185 ° C. in that state, so that the IC is placed on the wiring board via the conductive sheet. The chip could be glued.

The conductive sheet is cut into a shape having a width of 1 mm and a length of 300 mm, and a release-treated aluminum plate having a thickness of 2 mm is sandwiched between a polyimide film having a thickness of 25 microns and the polyimide film is further bonded to the aluminum plate. Heated to 110 ° C. while holding them for 10 minutes and heated, then applied 0.1 MPa while heated for 5 minutes, then cooled, peeled off the aluminum plate on one side, and carefully conductive sheet The aluminum plate in contact with was peeled off and further cured by heating at 185 ° C. for 45 minutes to obtain a cured conductive sheet. As a result, the volume resistivity of the obtained circuit was 4.6 μΩ · cm.
Example 2
Preparation of conductive powder Silver powder having an average particle diameter of 10.3 μm was used as a raw material. This packing density was 52%. The surface of the silver powder was treated with 0.2% by weight of stearic acid, and 1000 g of this was weighed and placed in a ball mill having an internal volume of 3 liters. The ball mill is filled with 1.5 liters of alumina beads having a diameter of about 2 mm. The volume ratio of the beads to the conductive powder was beads: conductive powder = 8: 1. The diameter of the ball mill was about 14 cm. The ball mill was treated at a rotation speed of 50 min ⁻¹ for 8 hours to obtain a shaped silver powder that was a substantially monodispersed conductive powder.

As a result of observing the resulting shape-processed conductive powder with a particle size distribution measuring instrument and SEM, the average particle size is 11.4 μm, and the average aspect ratio of large particles having a cumulative diameter of 30% or more is 2.8, The cumulative 30% diameter was 7.2 μm, and the average aspect ratio of the small particles was 5.5. The packing density of the treated conductive powder was 62%.

750 g of the above substantially monodispersed conductive powder and 250 g of easily dispersible bulk silver powder having an average particle size of 1.5 μm and a packing density calculated from the tap density of 52%, and having no ball having an internal volume of 2 liters as described in Example 1 The mixed conductive powder was obtained by processing for 48 hours at a rotation speed of 50 min ⁻¹ . The filling density of the mixed conductive powder calculated from the tap density was 76%, and the press density was 93%.

Preparation of Conductive Paste 99 g of this mixed conductive powder was added to 2 g of the binder solution described in Example 1 and 3 g of ethyl carbitol, and mixed uniformly for 2 minutes with a milling machine to obtain a conductive paste.

Circuit formation Various tests were conducted in the same manner as in Example 1 using this conductive paste.
The volume resistivity was measured by the same method as in Example 1 and found to be 5 μΩ · cm.

Evaluation of conductive sheet Separately from the above, 75 parts by weight of a semi-solid bisphenol A type epoxy resin having a heat softening temperature of 55 to 65 ° C, 20 parts by weight of a solid bisphenol A type epoxy resin having a heat softening temperature of 75 ° C to 85 ° C, and 2 parts -Phenyl-4-methyl-imidazole (manufactured by Shikoku Kasei Co., Ltd., trade name Curesol 2P4MZ) 4.5 parts by weight, titanate coupling agent 0.5 parts by weight and ethyl carbitol 100 parts by weight were mixed uniformly. A binder solution was obtained. 96 parts by weight of the mixed conductive powder and 8 parts by weight of the binder solution were mixed for 1 minute in a mixer that revolves while the container rotates to obtain a conductive paste. After the conductive paste was degassed in vacuum, it was applied on a release paper whose surface exhibited releasability by a doctor blade method, and then dried at 100 ° C. to prepare a conductive sheet having a thickness of 60 μm. This conductive sheet is weak at room temperature with a slight amount of solvent remaining, but can be bonded, and the cut piece can also be handled as a conductive sheet. When heated to around 70 ° C, it can be softened and strongly bonded, and further 165 ° C to 185 ° C. It was possible to cure and adhere to the conductive material when heated.
The volume resistivity of this cured conductive sheet was 9 μΩ · cm, and the thermal conductivity at 25 ° C. was 13 W / mK.
Example 3
Preparation of conductive powder Silver powder having an average particle size of 5.5 μm was used as a raw material. This packing density was 54%.
The surface of the silver powder was treated with 0.05% by weight of stearic acid, and 1500 g of this was weighed and placed in a ball mill having an internal volume of 5 liters. The ball mill is filled with 3 liters of alumina beads having a diameter of about 2 mm. The volume ratio of the beads to the conductive powder was beads: conductive powder = 11: 1. The diameter of the ball mill was about 14 cm. The ball mill was processed at a rotation speed of 50 min ⁻¹ for 4 hours to obtain a shaped silver powder that was a substantially monodispersed conductive powder.

As a result of observing the resulting shaped processed conductive powder with a particle size distribution measuring instrument and SEM, the average particle size is 6.5 μm, and the average aspect ratio of large particles having a cumulative 30% diameter or more is 2.5,
The cumulative 30% diameter was 3.3 μm, and the average aspect ratio of the small particles was 5.4. The packing density of the treated conductive powder was 65%.

350 g of the above substantially monodispersed conductive powder and 150 g of easily dispersible bulk silver powder having an average particle diameter of 1.5 μm and a packing density calculated from the tap density of 52%, and having no ball having an internal volume of 2 liters described in Example 1 The mixed conductive powder was obtained by processing for 48 hours at a rotation speed of 50 min ⁻¹ . The filling density of the mixed conductive powder calculated from the tap density was 73%, and the press density was 88%.

900 g of the above substantially monodispersed conductive powder and 100 g of easily dispersible bulk silver powder having an average particle diameter of 1.5 μm and a packing density calculated from the tap density of 52%, and having no ball having an internal volume of 2 liters described in Example 1 The mixed conductive powder was obtained by processing for 48 hours at a rotation speed of 50 min ⁻¹ . The filling density of the mixed conductive powder calculated from the tap density was 72%, and the press density was 89%.

Preparation of conductive paste 98 g of this mixed conductive powder was added to 4 g of the binder solution described in Example 1 and 3 g of ethyl carbitol, and mixed uniformly for 2 minutes with a milling machine to obtain a conductive paste.

Evaluation of circuit and conductive sheet Using this conductive paste, various tests were conducted in the same manner as in Example 1. As a result of measuring the volume resistivity by the same method as in Example 1, it was 8 μΩ · cm.
Example 4
Preparation of conductive powder Silver powder having an average particle diameter of 10.4 μm was used as a raw material. This packing density was 53%. The surface of this silver powder is treated with 0.05% by weight of stearic acid and weighed 2000 g.
It put into the ball mill of internal volume 10 liters. The ball mill is filled with 5 liters of alumina beads having a diameter of about 2 mm. The volume ratio of the beads to the conductive powder was beads: conductive powder = 14: 1. The diameter of the ball mill was about 24 cm. The ball mill was treated for 12 hours at a rotation speed of 30 min ⁻¹ to obtain a shaped silver powder which was a substantially monodispersed conductive powder.

As a result of observing the resulting shaped processed conductive powder with a particle size distribution measuring instrument and SEM, the average particle size is 11.3 μm, and the average aspect ratio of large particles having a cumulative 30% diameter or more is 2.3. The cumulative 30% diameter was 6.5 μm, and the average aspect ratio of the small particles was 5.3. The packing density of the treated conductive powder was 64%.

850 g of the above substantially monodispersed conductive powder and 150 g of easily dispersible bulk silver powder having an average particle diameter of 1.6 μm and a packing density calculated from the tap density of 54%, and having no ball having an internal volume of 2 liters described in Example 1 The mixed conductive powder was obtained by mixing for 36 hours at a rotation speed of 50 min ⁻¹ . The filling density of the mixed conductive powder calculated from the tap density was 77%, and the press density was 93%.

Preparation of conductive paste 95 g of this mixed conductive powder was added to 10 g of the binder solution described in Example 1, and the mixture was uniformly mixed for 2 minutes with a milling machine to obtain a conductive paste.

Evaluation of Circuit and Conductive Sheet Various tests were conducted in the same manner as in Example 1 using this conductive paste. As a result of measuring the volume resistivity by the same method as in Example 1, it was 10 μΩ · cm.
Example 5
Preparation of conductive powder Silver powder having an average particle diameter of 5.0 μm was used as a raw material. This packing density was 53%.
The surface of the silver powder was treated with 0.1% by weight of stearic acid, and 1000 g of this was weighed and placed in a ball mill having an internal volume of 3 liters. The ball mill is filled with 1.5 liters of alumina beads having a diameter of about 2 mm. The volume ratio of the beads to the conductive powder was beads: conductive powder = 8: 1. The diameter of the ball mill was about 14 cm. The ball mill was treated at a rotational speed of 60 min ⁻¹ for 6 hours to obtain a shaped silver powder that was a substantially monodispersed conductive powder.

As a result of observing the resulting shaped processed conductive powder with a particle size distribution measuring instrument and SEM, the average particle diameter is 6.1 μm, and the average aspect ratio of large particles having a cumulative 30% diameter or more is 2.4.
The cumulative 30% diameter was 2.7 μm, and the average aspect ratio of the small particles was 7.3. The packing density of the treated conductive powder was 63%.

400 g of the above substantially monodispersed conductive powder and 100 g of easily dispersible bulk silver powder having an average particle diameter of 1.5 μm and a packing density calculated from the tap density of 53% are the same as those in the ball mill having an internal volume of 2 liters. The mixture was treated for 72 hours at a rotation speed of 50 min ⁻¹ to obtain mixed conductive powder. The filling density of the mixed conductive powder calculated from the tap density was 72%, and the press density was 89%.

Preparation of Conductive Paste 97 g of this mixed conductive powder was added to 6 g of the binder solution described in Example 1, and the mixture was uniformly mixed for 2 minutes with a milling machine to obtain a conductive paste.

Evaluation of Circuit and Conductive Sheet Various tests were conducted in the same manner as in Example 1 using this conductive paste. As a result of measuring the volume resistivity by the same method as in Example 1, it was 10 μΩ · cm.
Example 6
Preparation of conductive powder An approximately spherical silver-plated copper powder having an average particle size of 5.5 μm and treated with 20% by weight of silver plating was used as a raw material. This packing density was 45%. The surface of this silver-plated copper powder was treated with 0.2% by weight of stearic acid, and 1000 g of this was weighed and placed in a ball mill having an internal volume of 3 liters. The ball mill is filled with 1.5 liters of glass beads having a diameter of about 2 mm. The volume ratio of the beads to the conductive powder was beads: conductive powder = 7: 1. The diameter of the ball mill was about 14 cm. The ball mill was treated for 4 hours at a rotation speed of 50 min ^-1 . As a result of observing the resulting shaped processed conductive powder with a particle size distribution measuring instrument and SEM, the average particle size was 6 μm, and the average aspect ratio of large particles having a cumulative 30% diameter or more was 2.4, and the cumulative 30 The% diameter was 5 μm, and the average aspect ratio of the small particles was 5.3. The packing density of the treated conductive powder was 64%. The conductive powder was stored in the atmosphere for 12 months, but no discoloration was observed.

480 g of the above substantially monodispersed conductive powder and 20 g of easily dispersible bulk silver powder having an average particle diameter of 1.5 μm and a packing density calculated from the tap density of 53% are the same as those in the ball mill having an internal volume of 2 liters. The mixture was treated for 72 hours at a rotation speed of 60 min ⁻¹ to obtain mixed conductive powder. The filling density of the mixed conductive powder calculated from the tap density was 69%, and the press density was 87%.

Preparation of Conductive Paste 97 g of this mixed conductive powder was added to 6 g of the binder solution described in Example 1, and the mixture was uniformly mixed for 2 minutes with a cracker to obtain a conductive paste. Various tests were conducted in the same manner as in Example 1 using this conductive paste. Further, 95 g of this mixed conductive powder was added to 10 g of the binder solution described in Example 1, and the mixture was uniformly mixed for 2 minutes with a rake machine to obtain a conductive paste.

Evaluation of Circuit and Conductive Sheet Various tests were conducted in the same manner as in Example 1 using this conductive paste. As a result of measuring the volume resistivity by the same method as in Example 1, it was 16 μΩ · cm.
Example 7
The average particle diameter of the conductive powder was 10.2 μm, and a substantially spherical silver-plated copper powder treated with 10% by weight of silver plating was used as a raw material. This packing density was 50%. The surface of the silver-plated copper powder was treated with 0.1% by weight of lauric acid, and 500 g of this was weighed and placed in a ball mill having an internal volume of 3 liters. The ball mill is filled with 1.0 liter of glass beads having a diameter of about 2 mm. The volume ratio of beads to conductive powder was bead: conductive powder = 9: 1. The diameter of the ball mill was about 14 cm. The ball mill was treated for 4 hours at a rotation speed of 50 min ^-1 . As a result of observing the resulting shape-processed conductive powder with a particle size distribution measuring instrument and SEM, the average particle size was 10.8 μm, and the average aspect ratio of large particles having a cumulative 30% diameter or more was 2.2. The cumulative 30% diameter was 4.8 μm, and the average aspect ratio of the small particles was 4.7. The packing density of the treated conductive powder was 64%. The conductive powder was stored in the atmosphere for 12 months, but no discoloration was observed.

450 g of the above substantially monodispersed conductive powder and 50 g of easily dispersible bulk silver powder having an average particle diameter of 1.5 μm are placed in a container having no internal ball of 2 liters described in Example 1 and rotated at 60 min ⁻¹ . The mixed conductive powder was obtained by treating at a speed for 36 hours. The filling density of the mixed conductive powder calculated from the tap density was 75%, and the press density was 92%.

Preparation of conductive paste 95 g of this mixed conductive powder was added to 10 g of the binder solution described in Example 1, and the mixture was uniformly mixed for 2 minutes with a milling machine to obtain a conductive paste.

Evaluation of Circuit and Conductive Sheet Various tests were conducted in the same manner as in Example 1 using this conductive paste. The printed circuit board was heated to 110 ° C. and heated and pressurized at a pressure of 0.1 MPa for 5 minutes. As a result, the volume resistivity of the circuit was 20 μΩ · cm.
Example 8
The average particle diameter of the conductive powder was 10.2 μm, and a substantially spherical silver-plated copper powder treated with 30% by weight of silver plating was used as a raw material. This packing density was 47%. The surface of the silver-plated copper powder was treated with 0.05% by weight of oleic acid, and 1000 g of this was weighed and placed in a ball mill having an internal volume of 5 liters. The ball mill is filled with 2.5 liters of glass beads having a diameter of about 2 mm. The volume ratio of beads to conductive powder was bead: conductive powder = 9: 1. The diameter of the ball mill was about 17 cm. The ball mill was treated at a rotational speed of 40 min ^-1 for 12 hours. As a result of observing the resulting shape-processed conductive powder with a particle size distribution measuring instrument and SEM, the average particle size is 11.2 μm, and the average aspect ratio of large particles having a cumulative 30% size or more is 2.6, The cumulative 30% diameter was 5.8 μm, and the average aspect ratio of the small particles was 5.8. The packing density of the treated conductive powder was 62%. The conductive powder was stored in the atmosphere for 12 months, but no discoloration was observed.

450 g of the above substantially monodispersed conductive powder and 50 g of easily dispersible bulk silver powder having an average particle diameter of 1.5 μm and a packing density calculated from the tap density of 53%, are the same as those in the ball mill having an internal volume of 2 liters. The mixture was treated for 72 hours at a rotation speed of 60 min ⁻¹ to obtain mixed conductive powder. The filling density of the mixed conductive powder calculated from the tap density was 74%, and the press density was 90%.

Preparation of Conductive Paste 99 g of this mixed conductive powder was added to 2 g of the binder solution described in Example 1 and 3 g of ethyl carbitol, and mixed uniformly for 2 minutes with a milling machine to obtain a conductive paste.

Evaluation of Circuit and Conductive Sheet Various tests were conducted in the same manner as in Example 1 using this conductive paste. The volume resistivity measured in the same manner as in Example 1 was 12 μΩ · cm.
Example 9
The average particle diameter of the conductive powder was 10.2 μm, and a substantially spherical silver-plated copper powder treated with 5% by weight of silver plating was used as a raw material. This packing density was 51%. The surface of the silver-plated copper powder was treated with 0.1% by weight of lauric acid, and 500 g of this was weighed and placed in a ball mill having an internal volume of 3 liters. The ball mill is filled with 1.5 liters of alumina beads having a diameter of about 2 mm. The volume ratio of the beads to the conductive powder was beads: conductive powder = 14: 1. The diameter of the ball mill was about 14 cm. The ball mill was treated for 4 hours at a rotation speed of 50 min ^-1 . As a result of observing the resulting shape-processed conductive powder with a particle size distribution measuring instrument and SEM, the average particle size is 10.8 μm, and the average aspect ratio of large particles having a cumulative diameter of 30% or more is 2.1, The cumulative 30% diameter was 4.7 μm, and the aspect ratio of the small particles was 4.6 on average. The packing density of the treated conductive powder was 64%. The conductive powder was stored in the atmosphere for 12 months, but no discoloration was observed.

400 g of the above substantially monodispersed conductive powder and 100 g of easily dispersible bulk silver powder having an average particle diameter of 1.5 μm and a packing density calculated from the tap density of 53% are the same as those in the ball mill having an internal volume of 2 liters. The mixture was treated for 72 hours at a rotation speed of 60 min ⁻¹ to obtain mixed conductive powder. The filling density of the mixed conductive powder calculated from the tap density was 76%, and the press density was 92%.

Preparation of conductive paste 98 g of this mixed conductive powder was added to 4 g of the binder solution described in Example 1 and 2 g of ethyl carbitol, and the mixture was uniformly mixed for 2 minutes with a milling machine to obtain a conductive paste.

Evaluation of Circuit and Conductive Sheet Various tests were conducted in the same manner as in Example 1 using this conductive paste. The volume resistivity measured in the same manner as in Example 1 was 13 μΩ · cm.
Example 10
Preparation of conductive paste 10 parts by weight of bisphenol F type epoxy resin (trade name Epomic R110, manufactured by Mitsui Chemicals, Inc.) having an epoxy equivalent of 170 g / eq, bisphenol A type epoxy having an epoxy equivalent of 325 g / eq and a softening temperature of 60 ° C. 85 parts by weight of resin, 4.5 parts by weight of 2-phenyl-4-methyl-imidazole (trade name Curesol 2P4MZ, manufactured by Shikoku Kasei Co., Ltd.), 0.5 parts by weight of titanate coupling agent and 100 parts by weight of ethyl carbitol Were uniformly mixed to obtain a binder solution.

  96 parts by weight of the mixed conductive powder described in Example 1 and 8 parts by weight of the above binder solution were uniformly mixed with a screening machine to obtain a conductive paste. Using this conductive paste, a desired pattern is printed on a polycarbonate film having a thickness of 125 μm, then dried at 100 ° C. for 45 minutes to evaporate the solvent, and a circuit thickness of about 30 μm is formed on the polycarbonate film. Formed.

A chip capacitor heated to 50 ° C. and an IC chip were pressed against and temporarily bonded to a component bonding portion on a circuit formed with electronic components . Thereafter, a polycarbonate film to which a chip capacitor and an IC chip are bonded is set in a mold, and a polycarbonate resin heated and melted at 240 ° C. is inserted into the mold at a pressure of 10 MPa, so that the IC chip and the chip capacitor are attached. An electronic component was fabricated by enclosing with polycarbonate.

The obtained IC chip and chip capacitor confirmed their predetermined functions.
Comparative Example 1
Preparation of conductive paste Using only the substantially monodispersed conductive powder (press density 70%) prepared in Example 1, the conductive paste was prepared using the binder described in Example 1. 10 g of the binder solution and 95 g of the conductive powder were mixed, and mixed for 2 minutes with a rake machine.

Evaluation of Circuit and Conductive Sheet The characteristics of this conductive paste were evaluated in the same manner as in Example 1. The printed circuit board was heated to 110 ° C. and heated and pressurized at a pressure of 10 MPa for 5 minutes. As a result, the volume specific resistance of the circuit was 35 μΩ · cm.
Comparative Example 2
Preparation of Conductive Paste 300 g of substantially monodispersed conductive powder prepared in Example 1 and 200 g of easily dispersible bulk silver powder having an average particle size of 1.5 μm and a packing density calculated from tap density of 53% are described in Example 1. The mixed conductive powder was produced by mixing by the method. The press density of the obtained mixed conductive powder was 74%.

Next, using the binder described in Example 1, 10 g of the binder solution and 95 g of the conductive powder were mixed for 2 minutes with a rake machine, but the viscosity was too high and stirring and mixing were difficult. For this reason, evaluation was not possible.
Comparative Example 3
Preparation of conductive paste Using only the substantially monodispersed conductive powder (press density 71%) prepared in Example 8, the conductive paste was prepared using the binder described in Example 1. 12 g of the binder solution and 94 g of the conductive powder were mixed, and mixed for 2 minutes with a rough machine.

Evaluation of Circuit and Conductive Sheet The characteristics of this conductive paste were evaluated in the same manner as in Example 1. The printed circuit board was heated to 110 ° C. and heated and pressurized at a pressure of 10 MPa for 5 minutes. As a result, the volume specific resistance of the circuit was 128 μΩ · cm.
Comparative Example 4
Preparation of conductive paste 300 g of substantially monodispersed conductive powder prepared in Example 8 and 200 g of easily dispersible bulk silver powder having an average particle diameter of 1.5 μm and a packing density calculated from the tap density of 53% are described in Example 1. The mixed conductive powder was produced by mixing by the method. The press density of the obtained mixed conductive powder was 74%. Next, using the binder described in Example 1, 10 g of the binder solution and 95 g of the conductive powder were mixed for 2 minutes with a scourer, but the viscosity was too high and stirring and mixing were difficult. For this reason, it was not possible to evaluate.

For Examples 2 to 9 and Comparative Examples 1 and 3, as in Example 1, the thermal conductivity was also evaluated.
The results are also shown in Table 1.

Claims (11)

Gold powder, platinum powder, palladium powder, silver powder, copper powder, silver-plated copper powder having a press density of 80% to 99.5%, including dispersed conductive powder composed of polyhedral particles and substantially scaly particles, and bulk fine powder, A conductive powder comprising an aluminum powder and an alloy powder thereof.   A conductive paste comprising the conductive powder according to claim 1 and a binder.   The conductive paste according to claim 2, wherein the conductive powder in the paste is in the range of 95 to 99.5% by weight and the binder is in the range of 0.5 to 5% by weight.   The conductive paste according to claim 2 or 3, wherein the binder is a thermosoftening resin and has adhesiveness under normal temperature and normal pressure. A conductive sheet comprising the conductive powder according to claim 1 and a binder. 6. The conductive sheet according to claim 5, wherein the conductive powder in the sheet is in the range of 95 to 99.5% by weight and the binder is in the range of 0.5 to 5% by weight.   The conductive sheet according to claim 5 or 6, wherein the binder is heat-softening and has adhesiveness at normal temperature and pressure.   A circuit board, wherein a desired circuit pattern is formed on a substrate with the conductive paste according to claim 2.   The circuit board according to claim 8, wherein a plurality of circuit patterns are formed, and the circuit patterns formed on the substrate are connected.   A desired circuit pattern is formed on a substrate with the conductive paste according to any one of claims 2 to 4, and an electronic component is connected through a part of the circuit pattern formed on the substrate. An electronic component mounting circuit board characterized by comprising:   The electronic component mounting circuit board according to claim 10, wherein a plurality of circuit patterns are formed, and the circuit patterns formed on the substrate are connected.