Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/20—Conductive material dispersed in non-conductive organic material
  • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/12—Metallic powder containing non-metallic particles
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C9/00—Alloys based on copper
  • C22C9/01—Alloys based on copper with aluminium as the next major constituent
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
  • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
  • H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

• the present invention relates to a copper powder for conductive paste and a conductive paste using the same. Specifically, the present invention relates to a conductive powder that can be suitably used for forming an electric circuit, forming an external electrode of a ceramic capacitor, and the like, and more particularly to a copper powder that can be suitably used as a conductive filler of a baked conductive paste.
• the conductive paste is a fluid composition in which a conductive filler is dispersed in a vehicle composed of a resin binder and a solvent, and is widely used for forming an electric circuit, an external electrode of a ceramic capacitor, and the like.
• This type of conductive paste has a resin-cured type in which conductive fillers are pressure-bonded by curing the resin to ensure conduction, and organic components are volatilized by firing to sinter the conductive filler to ensure conduction. There are firing types.
• the former resin-curable conductive paste is generally a paste-like composition containing a conductive filler made of metal powder and an organic binder made of a thermosetting resin such as an epoxy resin, and is applied with heat.
• a thermosetting resin such as an epoxy resin
• the thermosetting resin is cured and shrunk together with the conductive filler, and the conductive fillers are pressure-bonded through the resin so as to be in contact with each other, thereby ensuring conductivity.
• This resin curable conductive paste can be processed in a relatively low temperature range from 100 ° C. to at most 200 ° C. and has little thermal damage, and is therefore mainly used for printed wiring boards and heat-sensitive resin boards.
• the latter baked conductive paste is a paste-like composition in which a conductive filler (metal powder) and glass frit are generally dispersed in an organic vehicle. Conductivity is ensured by volatilization of the vehicle and further sintering of the conductive filler. At this time, the glass frit has a function of adhering the conductive film to the substrate, and the organic vehicle functions as an organic liquid medium for enabling printing of the metal powder and the glass frit. Firing-type conductive paste cannot be used for printed wiring boards or resin materials because of its high firing temperature, but it can be reduced in resistance because it is sintered and the metal is integrated. It is used for external electrodes.
• Patent Document 1 proposes that a substance having a reducing action is blended in the conductive paste to suppress oxidation of the copper surface.
• Patent Document 2 proposes coating the particle surface with silver having oxidation resistance, and
• Patent Document 3 proposes coating with an inorganic oxide.
• Patent Document 4 discloses a copper alloy powder that is alloyed by adding at least one of Zn and Sn to Cu as a main component, and the content of Zn and / or Sn in the copper alloy powder is as follows. There is disclosed a copper alloy for conductive material paste, which is 0.02 to 1.2% by mass and the copper alloy powder contains 0.005 to 0.05% by mass of P.
• Patent Document 5 is characterized by containing 0.07 atomic% to 10 atomic% of Al inside the particles as copper powder for conductive paste that is fine in particle size but does not impair the balance of oxidation resistance and electrical conductivity.
• a copper powder for conductive paste is disclosed.
• JP-A-8-73780 Japanese Patent Laid-Open No. 10-152630 JP 2005-129424 A JP 2009-99443 A JP 2009-235556 A
• the present invention intends to provide a new copper powder for conductive paste that can maintain good oxidation resistance and obtain good conductivity.
• the present invention is a copper powder for conductive paste containing Al (aluminum) and P (phosphorus), wherein the Al concentration is higher than 10.0 atm% and lower than 65.0 atm%.
• Al aluminum
• P phosphorus
• the copper powder for conductive paste of the present invention can obtain good conductivity while maintaining oxidation resistance.
• Patent Document 5 Japanese Patent Application Laid-Open No. 2009-23556, applicant: Mitsui Kinzoku Mining Co., Ltd.
• the inventors added conductivity exceeding 10.0 atm% to the copper powder, and the conductivity was increased. He thought that not only was it damaged, but the oxidation resistance was too strong to fire in the atmosphere.
• the copper powder containing phosphorus containing Al in the range of more than 10.0 atm% and less than 65.0 atm% should be fired in the atmosphere at about 800-900 ° C.
• the oxidation resistance can be maintained even at this high temperature and the conductivity is excellent. This was surprising even in the light of common technical knowledge that the conductivity decreases as impurities are added to copper.
• the copper powder for conductive paste according to the present embodiment (hereinafter referred to as “main copper powder”) is a copper powder for conductive paste containing Al (aluminum) and P (phosphorus). Since copper powder having a composition containing Al and P may be used, metal elements other than Al and P may be contained, but typically Cu—P—Al type copper powder.
• the present copper powder is, for example, Ni, Ti, Fe, Co, Cr, Mg, Mn, Mo, W, Ta, In, Zr, Nb, B, Ge, Sn, You may contain the element component which consists of a combination of 1 type, or 2 or more types, such as Zn and Bi. By adding these, it is possible to adjust various characteristics required for the conductive paste, for example, to improve the sinterability by lowering the melting point.
• Al concentration It is important that the Al concentration of the constituent particles of the present copper powder (hereinafter referred to as “present copper powder particles”) is more than 10.0 atm% and not more than 65.0 atm%. If the Al concentration is higher than 10.0 atm%, the conductivity can be effectively increased. Specifically, in terms of the volume resistance value, it can be lower than 1.0 ⁇ 10 ⁇ 2 ⁇ ⁇ cm, and particularly lower than 2.0 ⁇ 10 ⁇ 3 ⁇ ⁇ cm. Thus, since the volume resistance value can be lowered, conduction can be ensured without forcibly and densely filling. On the other hand, if the Al concentration exceeds 70.0 atm%, the melting point is lowered and the oxidation resistance effect at high temperature is lost.
• the Al concentration of the present copper powder particles is particularly 20.0 atm% or more, especially 30.0 atm% or more, or particularly It is even more preferable that it is 60.0 atm% or less, especially 50.0 atm% or less.
• the P (phosphorus) concentration of the present copper powder particles is not particularly limited, but is 0.01 to 0.30 atm%, particularly 0.02 atm% or more, or 0.10 atm% or less, of which 0.02 atm%. It is preferable to contain at a rate of 0.06 atm% or less. If P (phosphorus) is contained in such a range, it has fine particle size and oxidation resistance, does not impair electrical conductivity, has small variations in shape and particle size, and can reduce the oxygen concentration.
• the D50 of the present copper powder is a request for fine powdering by fine pitching and high density firing by a specific resistance reduction request. From the viewpoint, it is preferably 0.1 ⁇ m to 10.0 ⁇ m, particularly 0.3 ⁇ m or more, or 5.0 ⁇ m or less, and more preferably 0.5 ⁇ m or more, or 3.0 ⁇ m or less.
• the present copper powder particles may be granular, particularly spherical, or may be formed by processing spherical particles.
• “granular” means a shape in which the aspect ratio (value obtained by dividing the average major axis by the average minor axis) is about 1 to 1.25, and the aspect ratio is about 1 to 1.1.
• the shape that is aligned with is called “spherical”.
• a state where the shapes are not aligned is called “indefinite shape”.
• the “granular” copper powder is preferable in that the mutual entanglement is reduced and the dispersibility in the paste is improved when used as a conductive material of the conductive paste.
• BET specific surface area of the copper powder particles (SSA) is preferably from 0.40 ⁇ 0.75m 2 / g, in particular 0.45 m 2 / g or more or 0 .70m 2 / g or less, in particular 0.50 m 2 / g or more among them, or, and even more preferably less 0.65 m 2 / g.
• the (initial) oxygen concentration of the copper powder is preferably 800 ppm to 5000 ppm.
• the oxygen concentration is in such a range, the conductivity and oxidation resistance of the conductive paste as the conductive material can be further improved.
• the (initial) oxygen concentration of the copper powder is preferably 800 ppm to 5000 ppm, more preferably 1000 ppm or more, or 4000 ppm or less, and particularly preferably 1200 ppm or more, or 3000 ppm or less.
• thermogravimetric / differential thermal analyzer The weight change rate ⁇ TG (%) in a predetermined temperature range by the thermogravimetric / differential thermal analyzer is an index indicating the oxidation resistance of the copper powder in the temperature range.
• the ⁇ TG between 40 and 800 ° C. can be 7.0% or less, particularly 4.0% or less, especially 3.0% or less.
• This copper powder can be produced by adding a predetermined amount of an Al component and other additive element components to molten copper in the form of a mother alloy or a compound, and then pulverizing it by a predetermined atomization method. it can.
• This type of copper powder can be applied to a wet reduction method in which a copper salt-containing solution or the like is deposited with a reducing agent, a vapor phase reduction method in which the copper salt is heated and vaporized and reduced in the gas phase, or a molten copper ingot. It can be produced by an atomizing method in which it is rapidly cooled with a refrigerant such as active gas or water to be powdered.
• the atomization method can reduce the residual concentration of impurities in the obtained copper powder as compared with the wet reduction method that is generally widely used, and also from the surface of the obtained copper powder particles. This has the advantage that the number of pores reaching the inside can be reduced. For this reason, the copper powder produced by the atomization method has the advantage that, when used as a conductive material of a conductive paste, the amount of gas generated during paste curing can be reduced and the progress of oxidation can be greatly suppressed. Yes.
• the water atomizing method can be preferably employed. Particles can be made finer by water atomization. By performing water atomization, dissolved oxygen in the water is taken into the particles, so that the oxygen concentration tends to increase. However, the water atomization method is preferable to the gas atomization method because the particle diameter can be reduced.
• the high pressure atomizing method is preferable because the particles can be produced finely and uniformly.
• the high pressure atomizing method is a method of atomizing at a water pressure of about 50 MPa to 150 MPa in the water atomizing method.
• the copper powder obtained by atomization may be reduced.
• the reduction treatment it is possible to further reduce the oxygen concentration on the surface of the copper powder that is easily oxidized.
• the reducing gas is not particularly limited, and examples thereof include hydrogen gas, ammonia gas, and butane gas.
• the reduction treatment is preferably performed at a temperature of 150 to 300 ° C., more preferably at a temperature of 170 to 210 ° C. This is because if the temperature is less than 150 ° C., the reduction rate becomes slow, and the treatment effect cannot be sufficiently exhibited, and if the temperature exceeds 300 ° C., it causes aggregation and sintering of copper powder. This is because when the temperature is 170 ° C. to 210 ° C., aggregation and sintering of copper powder can be reliably suppressed while efficiently reducing the oxygen concentration.
• the powdered copper powder is preferably classified. This classification can be easily carried out by separating coarse powder and fine powder using an appropriate classifier so that the target particle size is at the center.
• This copper powder can be used as it is, it can also be used after the copper powder is subjected to shape processing.
• a spherical particle powder (powder consisting of 80% or more of spherical particles) is mechanically processed into non-spherical particle powders such as flakes, scales, and flat plates (: 80% or more of non-spherical particles) Powder). More specifically, flaky particle powder (: 80% or more from flaky particles) is mechanically flattened (rolled or stretched) using a bead mill, ball mill, attritor, vibration mill, or the like. Shape powder). At this time, in order to process each particle independently while preventing aggregation and bonding between the particles, it is preferable to add a fatty acid such as stearic acid and an auxiliary agent such as a surfactant.
• a fatty acid such as stearic acid
• an auxiliary agent such as a surfactant.
• the copper powder that has been subjected to such shape processing can be used, or an original powder that is not subjected to shape processing can be mixed and used.
• this copper powder can control the sintering temperature characteristics according to the substrate, application, paste composition, etc.
• the copper powder for conductive paste especially for conductive paste fired at a high temperature of 500-900 ° C. Excellent as copper powder.
• the present invention can be applied very well to conductive materials such as conductive pastes for various electrical contact members such as conductor circuit formation by screen printing additive method and external electrodes of multilayer ceramic capacitors.
• This copper powder is suitable as a conductive filler used in, for example, a fired conductive paste. Therefore, for example, the copper powder can be blended in an organic vehicle to prepare a fired conductive paste.
• Copper powder for conductive paste using this copper powder as a conductive filler is suitable as a conductive paste for various electrical contact members such as for forming conductive circuits by screen printing additive method and for external electrodes of multilayer ceramic capacitors. Can be used for
• the copper powder for conductive paste of the present invention is used for internal electrodes of multilayer ceramic capacitors, chip parts such as inductors and resistors, single plate capacitor electrodes, tantalum capacitor electrodes, resin multilayer substrates, ceramic (LTCC) multilayer substrates, flexible Printed circuit boards (FPC), antenna switch modules, modules such as PA modules and high-frequency active filters, PDP front and back plates, electromagnetic shielding films for PDP color filters, crystalline solar cell surface electrodes and rear lead electrodes, conductive adhesives It can also be used for membrane switches such as EMI shield, RF-ID, and PC keyboard, anisotropic conductive film (ACF / ACP), and the like.
• chip parts such as inductors and resistors, single plate capacitor electrodes, tantalum capacitor electrodes, resin multilayer substrates, ceramic (LTCC) multilayer substrates, flexible Printed circuit boards (FPC), antenna switch modules, modules such as PA modules and high-frequency active filters, PDP front and back plates, electromagnetic shielding films for PDP color filters, crystalline solar
• Oxygen concentration (O 2 concentration)
• the oxygen concentration (also referred to as initial oxygen concentration) of the copper powder (sample) was analyzed using an oxygen / nitrogen analyzer (“EMGA-520 (model number)” manufactured by Horiba, Ltd.).
• BET specific surface area Using monosorb (trade name) manufactured by Yuasa Ionics Co., Ltd., “6.2 Flow Method (3.5)” of JIS R1626-1996 (Method for Measuring Specific Surface Area of Fine Ceramics Powder by Gas Adsorption BET Method)
• the BET specific surface area (SSA) was measured according to “one-point method”. At that time, a mixed gas of helium as a carrier gas and nitrogen as an adsorbate gas was used.
• Powder resistance Copper powder 15 g was put into a cylindrical container, and a measurement sample compression-molded at a press pressure of 40 ⁇ 10 6 Pa (408 kgf / cm 2 ) was formed, and Loresta AP and Loresta PD-41 type ( In each case, volume resistivity ( ⁇ ⁇ cm) was measured by Mitsubishi Chemical Corporation.
• Sintering start temperature was measured in nitrogen atmosphere using TMA / SS6000 which is a thermomechanical analyzer (TMA apparatus) manufactured by Seiko Instruments Inc., and evaluated according to the following criteria.
• TMA / SS6000 thermomechanical analyzer
• Sintering start temperature is 600 degreeC or more and 850 degrees C or less.
• ⁇ The sintering start temperature is higher than 850 ° C. and 900 ° C. or lower.
• X Sintering start temperature exceeded 900 degreeC, or it was less than 600 degreeC, or it did not sinter.
• Example preparation Example 1-4 and Comparative Example 1> A proper amount of Al as a pure metal and further a copper-phosphorus mother alloy (P15 wt%) are added to a molten metal (1350 ° C.) in which electrolytic copper (copper purity: Cu 99.95%) is dissolved, and stirred sufficiently. A 100 kg molten metal was prepared by mixing. Next, 100 kg of the molten metal was poured into the tundish in the water atomizing device (holding temperature 1300 ° C.), and the molten metal was dropped from the nozzle (caliber 5 mm) at the bottom of the tundish (flow rate 5 kg / min).
• Copper powder was manufactured by jetting water (water pressure: 100 MPa, water amount: 350 L / min) into the molten metal so as to form an inverted conical water flow shape from an injection hole having a diameter of 26 mm). Next, the obtained copper powder was classified by a classifier (“Turbo Classifier (trade name) TC-25 (model number)” manufactured by Nissin Engineering Co., Ltd.) to obtain a copper powder (sample). In Comparative Example 1, Al is not added.
• the gas atomizer (Nisshin Giken Co., Ltd., NEVA-GP2 type) chamber and raw material melting chamber were filled with argon gas, and then the raw material was heated and melted in a carbon crucible in the melting chamber to obtain a molten material (electro-copper) 1.74 g of metallic aluminum and a copper-phosphorus mother alloy (P15 wt%) were added to the molten metal in which the molten aluminum was dissolved to obtain 800 g of molten metal, which was sufficiently stirred and mixed. Thereafter, the molten metal was sprayed from a nozzle having a diameter of ⁇ 1.5 mm at 1250 ° C. and 3.0 MPa to obtain copper powder containing aluminum inside the particles. Thereafter, it was sieved with a 53 ⁇ m test sieve to obtain a final copper powder (sample).
• Example 1-4 As a result of observing and analyzing the copper powder obtained in Examples with an electron microscope or the like, most of them were spherical particles. Further, the copper powder obtained in Example 1-4 was mixed with the paste and fired, and as a result, it could be fired at about 800 to 900 ° C. in the atmosphere.
• the Al concentration is more than 10.0 atm% and less than or equal to 65.0 atm%, the conductivity can be increased, and the volume resistivity is particularly remarkable. It turns out that it can be lowered. Further, it has been confirmed that such an effect is not influenced by the P (phosphorus) concentration. Since the P (phosphorus) concentration affects the atomization and oxidation resistance, it can be considered that the P (phosphorus) content is preferably 0.01 to 0.3 atm%.
• the alloy crystal of Cu and Al is segregated on the particle surface, and there is no tendency for Al to concentrate on the particle surface. It can be considered that Cu and Al are alloyed inside the particles. Therefore, it can be considered that the copper powder of the present invention can be called an aluminum-copper alloy powder.

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• 2010
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