KR20130101980A - Copper powder for electrically conductive paste, and electrically conductive paste - Google Patents

Abstract

The copper powder for electrically conductive pastes which can obtain favorable electroconductivity while maintaining oxidation resistance is provided. As a copper paste for electrically conductive paste containing Al (aluminum) and P (phosphorus), the copper powder for electrically conductive pastes whose Al concentration is more than 10.0 atm% and is 65.0 atm% or less is proposed.

Description

Copper powder for conductive paste and conductive paste {COPPER POWDER FOR ELECTRICALLY CONDUCTIVE PASTE, AND ELECTRICALLY CONDUCTIVE PASTE}

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 paste that can be favorably used for the formation of an electrical circuit, the formation of an external electrode of a ceramic capacitor, and the like, particularly a copper powder that can be suitably used as a conductive filler of a calcined 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, forming an external electrode of a ceramic capacitor, and the like.

This kind of conductive paste includes a resin curing type in which a conductive filler is squeezed by curing of the resin to secure conduction, and a firing type in which organic components are volatilized by firing to sinter the conductive filler to ensure conduction.

The former resin curable conductive paste is a paste composition containing a conductive filler made of a metal powder and an organic binder made of a thermosetting resin such as an epoxy resin. The thermosetting resin is electrically conductive by applying heat. It hardens | contracts and shrinks with a filler, and electrically conductive fillers are crimped | bonded through resin, and it is a contact state, and conductivity is ensured. This resin curable conductive paste can be treated in a relatively low temperature range from 100 ° C to 200 ° C, and has little thermal damage, and is therefore mainly used for printed wiring boards and heat-resistant resin substrates.

On the other hand, the latter calcined conductive paste is a paste-like composition generally obtained by dispersing a conductive filler (metal powder) and a glass frit in an organic vehicle, and the organic vehicle is volatilized by firing at 500 to 900 ° C. The conductive filler is secured by sintering the conductive filler. At this time, the glass frit has an action of adhering the conductive film to the substrate, and the organic vehicle acts as an organic liquid medium for enabling printing of the metal powder and the glass frit.

Since the baking type conductive paste has a high firing temperature, it cannot be used for printed wiring boards and resin materials, but since the metal is sintered to integrate, low resistance can be realized, for example, an external electrode of a multilayer ceramic capacitor, or the like. It is used.

In any of the resin curable conductive paste and the high temperature calcined conductive paste, although silver powder has been used abundantly as a conductive filler conventionally, since copper is cheaper, migration is less likely to occur, and copper powder is also excellent in soldering resistance. Electroconductive paste using this is becoming common. However, copper powder is easy to oxidize in air, and the oxide film on the surface of copper powder has the subject that the connection resistance will increase.

Therefore, regarding the copper powder used for an electrically conductive paste, the method of preventing the oxidation of the surface of copper powder is proposed variously conventionally.

For example, in patent document 1, it is proposed to mix | blend the substance which has a reducing effect in an electrically conductive paste, and to suppress oxidation of a copper surface.

Moreover, in patent document 2, coating the particle | grain surface with silver with oxidation resistance is proposed, and in patent document 3, coating with inorganic oxide is proposed.

Patent Document 4 is a copper alloy powder obtained by alloying at least one of Zn and Sn with Cu as a main component, and the content of Zn and / or Sn in the copper alloy powder is 0.02 to 1.2 mass%, and the copper The copper alloy for electrically conductive material pastes which contain P of 0.005-0.05 mass% is disclosed.

In addition, Patent Document 5 discloses a conductive paste copper powder containing 0.07 atomic% to 10 atomic% of Al in the particles as a finely grained copper powder which does not impair the balance between oxidation resistance and conductivity. A copper powder is disclosed.

Japanese Patent Application Laid-Open No. 8-73780 Japanese Patent Application Laid-Open No. 10-152630 Japanese Patent Application Laid-Open No. 2005-129424 Japanese Patent Laid-Open No. 2009-99443 Japanese Patent Laid-Open No. 2009-235556

As described above, various proposals have been made to increase the oxidation resistance of copper powder by adding various metal elements to copper. However, if impurities are added, the problem is that the conductivity is lower than that of copper powder not added. Was hugging.

Then, this invention is providing the new copper powder for electrically conductive pastes which can obtain favorable electroconductivity while maintaining oxidation resistance.

The present invention proposes a copper powder for conductive paste containing Al (aluminum) and P (phosphorus), wherein the Al concentration is more than 10.0 atm% and 65.0 atm% or less.

The copper powder for electrically conductive pastes of this invention can obtain favorable electroconductivity, maintaining oxidation resistance.

At the time of filing for patent document 5 (Japanese Patent Laid-Open No. 2009-23556, Applicant: Mitsui Ginjoku Kogyo Co., Ltd.), the inventors of the present invention found that when Al was added to the copper powder in an amount exceeding 10.0 atm%, the conductivity was impaired. In addition, it was thought that oxidation resistance was too strong and it cannot be baked in air | atmosphere. However, as a result of actually mixing in the paste and firing, the phosphorus-containing copper powder containing Al in an amount of more than 10.0 atm% and 65.0 atm% or less can be fired at about 800 to 900 ° C in air. It has been found that oxidation resistance can be maintained even at a high temperature and that the conductivity is excellent. This was surprising even in view of the common knowledge that the conductivity decreases as impurities are added to copper.

Next, although this invention is demonstrated based on embodiment example, this invention is not limited to embodiment described next.

<Copper powder for conductive paste>

The copper powder for electrically conductive pastes (henceforth a "main copper powder") which concerns on this embodiment is a copper powder for electrically conductive pastes containing Al (aluminum) and P (phosphorus). Since it should just be a copper powder of the composition containing Al and P, although metallic elements other than Al and P may be contained, they are typically Cu-P-Al copper powder.

This copper powder is, for example, Ni, Ti, Fe, Co, Cr, Mg, Mn, Mo, W, Ta, In, Zr, Nb, B, Ge, Sn, in addition to Al (aluminum) and P (phosphorus). , Zn, Bi, etc. may contain an element component consisting of one kind or a combination of two or more kinds.

By adding these, various characteristics required for an electrically conductive paste can be adjusted, for example, by reducing melting | fusing point and improving sintering property.

(Al concentration)

It is important that the Al concentration of the constituent particles of the copper powder (hereinafter referred to as "main copper powder particles") is more than 10.0 atm% and is 65.0 atm% or less.

If the Al concentration is more than 10.0 atm%, the conductivity can be effectively increased. Specifically, the volume resistivity value can be lower than 1.0 × 10 ⁻² Ω · cm, and particularly lower than 2.0 × 10 ⁻³ Ω · cm. In this way, the volume resistivity can be lowered, so that conduction can be secured without excessively fine filling.

On the other hand, when Al concentration exceeds 70.0 atm%, since melting | fusing point fall is seen and the oxidation resistance at high temperature is lost, it is important that it is 65.0 atm% or less.

As described above, in view of maintaining the effect of lowering the volume resistance value and maintaining the oxidation resistance at high temperature, the Al concentration of the present copper powder particles is particularly 20.0 atm% or more, especially 30.0 atm% or more, or particularly 60.0 atm% or less. Especially, it is further more preferable that it is 50.0 atm% or less.

(P concentration)

Although the P (phosphorus) concentration of this copper powder particle | grain is not specifically limited, 0.01-0.30atm%, especially 0.02atm% or more, or 0.10atm% or less, especially 0.02atm% or more, or 0.06atm% or less It is preferable to contain in the ratio of.

When P (phosphorus) is contained in such a range, it has fine particle size and oxidation resistance, there is little variation in shape and particle size, and the oxygen concentration can be made low, without impairing conductivity.

(D50)

D50 of the present copper powder, that is, D50 based on the volume-based particle size distribution measured by the laser diffraction scattering particle size distribution measurement method, is 0.1 from the viewpoint of high-density plasticity that requires micronization by fine pitching or the like and the demand for reducing specific resistance. It is preferable that they are micrometers-10.0 micrometers, and it is especially preferable that they are 0.3 micrometers or more, or 5.0 micrometers or less, especially 0.5 micrometers or more or 3.0 micrometers or less.

(Particle shape)

This copper powder particle may show a granular shape, especially spherical shape, or may be what shape-processes spherical particle.

Here, the "granular" refers to a shape having an aspect ratio (value obtained by dividing an average long diameter divided by an average short diameter) of about 1 to 1.25, and a shape having an aspect ratio of about 1 to 1.1 is specifically referred to as "sphere". do. On the other hand, the state where the shape is not prepared is called "negative shape".

The copper powder which forms a "granular" is preferable at the point which mutual entanglement decreases, and when used for the electrically-conductive material of an electrically conductive paste etc., the dispersibility in a paste improves.

(Specific surface area)

It is preferable that the BET specific surface area (SSA) of this copper powder particle is 0.40-0.75 m <2> / g from a viewpoint of adjusting the sintering start temperature suitably, Especially 0.45 m <2> / g or more or 0.70 m <2> / g or less, Especially, it is further more preferable that it is 0.50 m <2> / g or more or 0.65 m <2> / g or less.

(Oxygen concentration)

It is preferable that the (initial) oxygen concentration of this copper powder is 800 ppm-5000 ppm. If oxygen concentration is such a range, electroconductivity and oxidation resistance as an electrically-conductive material of an electrically conductive paste can be made into a more favorable range.

From this point of view, the (initial) oxygen concentration of the present 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.

(ΔTG)

The weight change rate (DELTA) TG (%) in a predetermined | prescribed temperature range by a thermogravimetric and differential thermal analysis apparatus is an index which shows the oxidation resistance of the copper powder in the temperature range.

Since this copper powder is excellent in oxidation resistance, (DELTA) TG between 40-800 degreeC can be made into 7.0% or less, especially 4.0% or less, especially 3.0% or less.

<Manufacturing method>

Next, the preferable specific manufacturing method of this copper powder is demonstrated.

The present copper powder is added to the molten copper by adding a predetermined amount of an Al component and other additional element components in the form of a mother alloy or a compound, and then powdered by a predetermined atomization method. It can manufacture.

This type of copper powder includes a wet reduction method in which a copper salt is precipitated from a solution containing a copper salt with a reducing agent, a gas phase reduction method in which the copper salt is heated and vaporized to be reduced in the gas phase, or a molten copper foil is used as an inert gas. It can manufacture by the atomizing method etc. which make it quench with a refrigerant | coolant, such as water, and powder. In these, the atomizing method can reduce the residual concentration of the impurity in the copper powder obtained compared with the wet reduction method generally used widely, and the pores which reach from the surface of the particle | grains of the copper powder obtained to the inside It has the advantage of making less. For this reason, when used for the electrically-conductive material of an electrically conductive paste, the copper powder manufactured by the atomizing method has the advantage that the gas generation amount at the time of paste hardening can be reduced, and progress of oxidation can be suppressed significantly. have.

As the atomizing method, a water atomizing method can be preferably employed. By atomizing a few, the refinement | miniaturization of a particle can be aimed at. Since the dissolved oxygen in the water is blown into the particles by the water atomization, the oxygen concentration tends to be higher. However, the water atomization method is preferable because the water atomization method can make the particle diameter smaller than the gas atomization method.

Among the several atomizing methods, 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 the atomization may be reduced. By the reduction treatment, it is possible to further reduce the oxygen concentration on the surface of the copper powder which is easily oxidized.

As such a reduction treatment, reduction with gas is preferable from the viewpoint of workability. Although the gas for a reduction process is not specifically limited, For example, hydrogen gas, ammonia gas, butane gas, etc. are mentioned.

It is preferable to perform the said reduction process at the temperature of 150-300 degreeC, and it is more preferable to carry out especially at the temperature of 170-210 degreeC. This is because if the temperature is less than 150 ° C, the reduction rate is slow, the treatment effect cannot be sufficiently expressed, and if the temperature exceeds 300 ° C, there is a fear of causing aggregation or sintering of the copper powder and the temperature It is because when it is 170 degreeC-210 degreeC, aggregation of a copper powder and sintering can be reliably suppressed, aiming at the reduction of the efficiency of oxygen density | concentration.

It is preferable to classify the copper powder after powdering.

This classification can be easily performed by separating coarse powder and fine powder so that the target particle size may be centered using a suitable classification apparatus.

(Shape processing)

Although this copper powder can also be used as it is, it can also be used after shape-processing this copper powder.

For example, spherical particle powder (powder composed of 80% or more of spherical particles) is mechanically processed to form non-spherical particle powder (flakes composed of non-spherical particles of 80% or more) such as flakes, flaky particles or flat plates. Can be processed.

More specifically, flake-shaped particle powder (by mechanically flattening (rolling or stretching) using a bead mill, a ball mill, an attritor, a vibration mill, or the like) 80% or more of the powder may be formed into a flake-like particle). At this time, in order to process each particle in the independent state, preventing particle aggregation and bonding, it is preferable to add fatty acids, such as stearic acid, and preparations, such as surfactant, for example.

And the copper powder which processed this shape can also be used, and can also mix and use this raw material which does not shape shape.

<Applications>

Since this copper powder can control a sintering temperature characteristic according to a board | substrate, a use, the compounding composition of a paste, etc., it is excellent as a copper powder for electrically conductive pastes, especially the copper powder for electrically conductive pastes baked at high temperature of 500-900 degreeC. For example, it can be applied very favorably to the electrically-conductive material of the electrically conductive paste for various electrical contact members, such as for conductor circuit formation by the screen printing additive method, or the external electrode of a multilayer ceramic capacitor.

This copper powder is suitable as a conductive filler used for a baking type electrically conductive paste, for example. Therefore, for example, the present copper powder may be blended in an organic vehicle to prepare a calcined conductive paste.

The copper powder for electrically conductive paste which used this copper powder as a conductive filler is suitable as an electrically conductive paste for various electrical contact members, such as for conductor circuit formation by the screen printing additive method, or the external electrode of a multilayer ceramic capacitor. Can be used.

In addition, the copper paste for the conductive paste of the present invention is an internal electrode of a multilayer ceramic capacitor, a chip component such as an inductor or a resistor, a single plate capacitor electrode, a tantalum capacitor electrode, a resin multilayer substrate, a ceramic (LTCC) multilayer substrate, a flexible printer substrate. (FPC), antenna switch module, module such as PA module or high frequency active filter, electronic shielding film for PDP front panel and back panel or PDP color filter, crystalline solar cell surface electrode and back extraction electrode, conductive adhesive, EMI shield, RF It can also be used for membrane switches such as ID, PC keyboards, and anisotropic conductive films (ACF / ACP).

<Description of fishing gear>

In this specification, when expressing with "X-Y" (X, Y is arbitrary numbers), unless otherwise indicated, it is "greater than X" or "preferably larger than X" with the meaning of "X or more and Y or less". Preferably less than Y ”.

In addition, when expressing as "X or more" (X is arbitrary number) or "Y or less" (Y is arbitrary number), the intention of the meaning of "it is preferable that it is larger than X" or "it is preferable that it is less than Y" Also includes.

[Example]

Hereinafter, the present invention will be further described based on the following examples and comparative examples.

About the copper powder obtained by the Example and the comparative example, various characteristics were evaluated by the method shown below.

(1) elemental concentration

The sample was dissolved in acid and analyzed by ICP.

(2) oxygen concentration (O ₂ concentration)

The oxygen concentration (also called initial oxygen concentration) of the copper powder (sample) was analyzed using the oxygen and nitrogen analyzer ("EMGA-520 (model number) by Horiba Seisakusho Co., Ltd.)."

(3) particle size distribution

0.2 g of copper powder (sample) was placed in 100 ml of pure water, irradiated with ultrasonic waves (3 minutes), and dispersed in a particle size distribution measuring device ("Micro Truck (brand name) FRA (model number)" manufactured by Nikkiso KK). By this, the volume cumulative particle diameter D50 was measured.

(4) BET specific surface area (SSA)

Using Monosorb (brand name) manufactured by Yuasa Ionics Co., Ltd., based on JIS R1626-1996 (Method of measuring specific surface area by gas adsorption BET method of fine ceramic powder) (6.2) The BET specific surface area (SSA) was measured. At this time, a mixed gas of helium, which is a carrier gas, and nitrogen, which is an adsorbate gas, was used.

(5) ΔTG

40 of copper powder (sample) using differential thermal thermogravimetry (TG / DTA) (manufactured by Seiko Instruments Co., Ltd., TG / DTA6300 high temperature type) (heating rate: 10 ° C / min, Air flow rate: 200 mL / min) The TG (%) at ° C to 800 ° C was measured, and TG (%) at the time of 40 ° C was taken as a reference value, and the difference (ΔTG) of the weight change rate (TG (%)) at 800 ° C from this reference value was determined. Saved.

(6) powder resistance

15 g of copper powder (sample) was placed in a normal container, and a measurement sample formed by compression molding at a press pressure of 40 × 10 ⁶ Pa (408 kgf / cm 2) was formed. The volume resistivity (ohm * cm) was measured by Kagaku Co., Ltd. product.

(7) Evaluation of Sinterability

Sintering start temperature was measured in nitrogen atmosphere using TMA / SS6000 which is a thermomechanical analyzer (TMA apparatus) by Seiko Instruments, Inc., and evaluated according to the following criteria.

(Double-circle): Sintering start temperature is 600 degreeC or more and 850 degrees C or less.

(Circle): Sintering start temperature is higher than 850 degreeC, and 900 degrees C or less.

X: Sintering start temperature is over 900 degreeC, or less than 600 degreeC, or does not sinter

<Preparation of Samples: Example 1-4 and Comparative Example 1>

To a molten metal (1350 ° C) in which electric copper (copper purity: 99.95% of copper) was dissolved, an appropriate amount of Al as a pure metal and a master alloy of copper-phosphorus (P15wt%) was added in an appropriate amount, followed by sufficient stirring and mixing to prepare a 100 kg molten metal. did.

Subsequently, 100 kg of the molten metal is injected into the tundish in the water atomizing device (holding temperature 1300 ° C), and the molten metal is dropped from the nozzle (diameter 5 mm) at the bottom of the tundish (flow rate 5 kg / min). Water injection from the jetting hole of a full cone nozzle (26 mm diameter) to jet water (water pressure of 100 MPa, water flow rate of 350 L / min) to form a reverse cone-shaped water flow; Copper powder was manufactured by doing.

Next, the obtained copper powder was classified by the classification apparatus ("Turbo Classifier (trade name) TC-25 (model number) by Nisshin Engineering Co., Ltd.)", and the copper powder (sample) was obtained.

In Comparative Example 1, Al was not added.

Comparative Example 2

Based on Example 1 of Unexamined-Japanese-Patent No. 2009-235556, the copper powder was produced as follows.

After filling the chamber and the raw material dissolution chamber of a gas atomizing device (made by Nisshingiken Co., Ltd. type, NEVA-GP2 type) with argon gas, the raw material was melted in a carbon crucible in the melting chamber to obtain a melt (electric copper) 1.74 g of metal aluminum and a master alloy of copper-phosphorus (P15wt%) were added to the molten metal which melt | dissolved, and it was set as 800 g of molten metal, and fully stirred and mixed). Then, the molten metal was sprayed at 1250 degreeC and 3.0 Mpa from the nozzle of diameter 1.5mm, and the copper powder containing aluminum inside particle | grains was obtained. Then, it sifted by 53 micrometer test sheave and obtained the final copper powder (sample) for the underbody.

[Table 1]

As a result of observing and analyzing the copper powder obtained in the Example with the electron microscope, most were spherical particle.

Moreover, when the copper powder obtained in Example 1-4 was mixed with the paste and baked, it could be baked in about 800-900 degreeC in air | atmosphere.

Examining the examples and comparative examples and the test results thus far, it is found that when the Al concentration is higher than 10.0 atm% and lower than 65.0 atm%, the conductivity can be increased, and in particular, the volume resistivity can be significantly lowered. Could.

Moreover, it is confirmed that such an effect is not influenced by P (phosphorus) concentration. Since P (phosphorus) concentration affects micronization and oxidation resistance, it can be considered that it is preferable to contain P (phosphorus) content in the ratio of 0.01-0.3 atm%.

Moreover, the copper powder of the comparative example 2 did not sinter in the evaluation test of sinterability. This is inferred to be caused by too large a particle size.

When analyzing the copper powder obtained in Example 1-4, the tendency that the alloy crystals of Cu and Al segregate on the particle surface, and the tendency of Al to concentrate on the particle surface is not recognized. Therefore, Cu and Al alloy in the particles. I can think of doing it. Therefore, it is thought that the copper powder of this invention can also be called aluminum-copper alloy powder.

Claims (7)

A copper paste for conductive paste containing Al (aluminum) and P (phosphorus), wherein the Al concentration is more than 10.0 atm% and is 65.0 atm% or less. The method of claim 1,
The copper powder for electrically conductive pastes whose D50 by the volume reference particle size distribution obtained by the laser diffraction scattering particle size distribution measuring method is 0.1 micrometer-10.0 micrometers. 3. The method according to claim 1 or 2,
Oxygen concentration is 800 ppm-5000 ppm, The copper powder for electrically conductive pastes characterized by the above-mentioned. 4. The method according to any one of claims 1 to 3,
Content of P (phosphorus) is 0.01 to 0.30 atm%, The copper powder for electrically conductive pastes characterized by the above-mentioned. 5. The method according to any one of claims 1 to 4,
The copper powder for electrically conductive pastes which was manufactured by the water atomization method. The copper powder for electrically conductive pastes formed by shape-processing the copper powder in any one of Claims 1-5. The electrically conductive paste containing the copper powder for electrically conductive pastes in any one of Claims 1-6.