KR20120021704A - Copper powder for conductive paste and conductive paste - Google Patents

Abstract

[PROBLEMS] To provide a copper powder having a fine particle size, which does not impair the balance between oxidation resistance and conductivity, and a copper powder for a conductive paste having a low variation in shape and particle size and a low oxygen concentration.
[Measures] A copper powder for conductive paste containing 0.05 atm-10 atm% of Bi in the particles is used.

Description

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

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a copper powder for conductive paste and a conductive paste using the same, and in particular, a variety of electrical products such as conductor circuits formed by screen printing additive method and external electrodes of multilayer ceramic capacitors. It is related with the copper powder suitable for the electrically-conductive material of the electrically conductive paste for contact members, etc., and the electrically conductive paste using the same.

Copper powder is widely used conventionally as the conductive material of the conductive paste for various electrical contact members, such as for conductor circuit formation by the screen printing additive method, the external electrode of a multilayer ceramic capacitor, etc. from the ease of handling. have.

The said electrically conductive paste can be obtained by mix | blending and kneading various additives, such as resin, such as an epoxy resin, and its hardening | curing agent, for example in copper powder. The copper powder used at this time is the wet reduction method which precipitates with a reducing agent from the solution containing a copper salt, the gaseous reduction method which heat-vaporizes a copper salt, and reduces it in a gaseous phase, or melted copper foil is an inert gas. It can manufacture by the atomizing method etc. which make it quench and powder into a refrigerant | coolant, such as water and the like.

In the method for producing a copper powder as described above, the atomizing method can reduce the residual concentration of impurities in the copper powder to be obtained, as compared with the wet reduction method which is generally widely used, and the surface of the particles of the copper powder to be obtained. It has the advantage that the pore from the inside to the inside can be reduced. 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. .

However, although the copper powder is suitable for the conductive material of the conductive paste due to its high conductivity, the finer the particle size, the lower the oxidation resistance, and in order to improve it, the surface of the particle is coated with silver having oxidation resistance or (Refer patent document 1), and measures, such as coating with an inorganic oxide (refer patent document 2), were employ | adopted.

Japanese Patent Application Laid-Open No. 10-152630 Japanese Patent Application Laid-Open No. 2005-129424

At the time of forming a circuit by a conductive paste etc., more refinement | miniaturization is calculated | required and the particle size of the electrically conductive powder used for an electrically conductive paste is inevitably refined | required these days. At the same time, in order to secure the stability and reliability of the paste properties, the shape and particle size unevenness must be small and the conductivity must be impaired. And if it only captures the improvement of oxidation resistance, it becomes possible to respond by the techniques, such as patent documents 1-2.

However, in the technologies such as Patent Literatures 1 and 2, depending on the coating technique, not only the components that impair conductivity other than copper are required, but also problems of peeling from the copper powder particles, which are core materials, are caused. . In addition, in order to reduce the nonuniformity of the shape and the particle size, it is desired that the particles to be formed are uniformly homogeneous and have a low oxygen concentration. However, it has not been found that such copper powder is still satisfactory.

SUMMARY OF THE INVENTION An object of the present invention is to provide a copper powder having a fine particle size, which does not impair the balance between oxidation resistance and conductivity, and a copper powder for conductive paste having a small nonuniformity in shape and particle size and having a low oxygen concentration. .

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining in order to solve the said subject, when the specific amount of Bi was contained in the particle | grains of a copper powder, it discovered that the said subject solved and completed this invention.

That is, the copper powder for electrically conductive pastes of this invention contains 0.05atm%-10atm% Bi in particle inside, It is characterized by the above-mentioned.

Moreover, 0.01 atm%-0.3 atm% may contain P (phosphorus) in particle inside, and it is preferable that Bi / P (atm ratio) is 4-200.

Furthermore, 0.1 atm% to 10 atm% of Ag may be contained in the particles, 0.1 atm% to 10 atm% of Si may be contained in the particles, and 0.1 atm% to 10 atm% of In may be contained in the particles. good.

And it is preferable that it was manufactured by the atomizing method.

Moreover, it is preferable that the difference of the weight change rate (Tg (%)) / specific surface area (SSA) in 240 degreeC and 600 degreeC is 1% / m <^2> / cm <^3> -30% / m <^2> / cm <^3> .

Another aspect of the present invention resides in a conductive paste containing the copper powder for conductive paste.

The copper powder for electrically conductive pastes of this invention is excellent in oxidation resistance, being fine in particle size, and the balance of electroconductivity is also balanced. In addition, since the irregularity of the shape and particle size is small and the oxygen content is low, the conductive material of the conductive paste for various electrical contact members such as the conductor circuit formation by the screen printing additive method or the external electrode of the multilayer ceramic capacitor is extremely It can be applied favorably.

1 is a photograph showing the SEM observation result of Example 2.

Although embodiment of copper powder for electrically conductive pastes by this invention is described, this invention is not limited to the following embodiment.

The copper powder for electrically conductive pastes concerning this invention contains 0.05atm%-10atm% Bi in particle inside, It is characterized by the above-mentioned.

It is important here not only to contain Bi, but to to contain a specific amount inside the particles.

That is, in the copper powder in which various substances or compounds which are less conductive than copper disclosed in the representative prior art, such as the said patent document, are coat | covered or affixed on the surface of the copper powder particle | grains which are core materials, although it is effective in improving oxidation resistance, The copper powder which is fine in a particle size and excellent in oxidation resistance cannot be obtained, without impairing electroconductivity which this invention requires.

Moreover, it is observed that Bi component contained in the copper powder for electrically conductive pastes which concerns on this invention exists in the crystal grain boundary of Cu, especially the grain surface of a particle surface, and the correlation with the refinement | miniaturization of particle | grains is also estimated.

Moreover, Bi content of the copper powder for electrically conductive pastes concerning this invention is 0.05atm%-10atm%, Preferably it is 0.5atm%-5atm%, More preferably, it is 0.5atm%-3atm%. If this content is less than 0.05 atm%, the effect which this invention requires cannot be expected. In addition, when it exceeds 10 atm%, not only the conductivity is impaired, but also an effect suitable for addition is not obtained.

Moreover, the copper powder for electrically conductive pastes which concerns on this invention can make a number average particle diameter into 0.5 micrometer-50 micrometers, and is suitable for the electrically conductive material etc. of the said electrically conductive paste for conductor circuit formation.

When the Bi component is contained in the copper powder particles, the effect of making the particles finer is particularly remarkable. For example, if the Bi content of about 0.05atm%? 3.0atm%, D ₅₀ is 5㎛? Of copper powder obtained by gas atomization it may be so 25㎛. Also D ₅₀ of copper powder obtained by water atomization is 1㎛? Can be so 5㎛. If it is copper powder of such Bi content, it will not damage electroconductivity at the time of use, as mentioned later. D ₅₀ is a volume cumulative particle diameter measured by a laser diffraction scattering particle size distribution analyzer or the like.

In addition, it is preferable that the copper powder for electrically conductive pastes which concerns on this invention not only has an effect to refine | miniaturize particle | grains, but also has characteristics, such as having a narrow particle size distribution and few granulations.

Specifically, the particle size distribution can have a coefficient of variation (SD / D ₅₀ ) obtained from D ₅₀ and a standard deviation value SD of about 0.2 to 0.6. Since such a copper powder can improve the dispersibility in the paste at the time of using for electrically conductive materials etc. of an electrically conductive paste, it is very preferable. Further, the assembly can be so 5㎛ the D ₅₀ of the copper powder obtained by gas atomization? If so the 25㎛, 10㎛ as D _90? 40㎛. In addition, if enough water 1㎛ the D ₅₀ of the copper powder produced by the atomization? 5㎛, it is possible to D ₉₀ with 5㎛? So 10㎛. Such a copper powder is excellent in the reliability of the fine circuit in the case of using it for the electrically-conductive material of an electrically conductive paste, etc., and is very preferable.

In addition to the Bi, the copper powder for the conductive paste according to the present invention preferably contains P (phosphorus) in the particles, preferably 0.01 atm% to 0.3 atm%, more preferably 0.02 atm to 0.1 atm%. When Bi and P coexist in copper powder and it exists in the range of such a specific amount, a particle size is fine, it has oxidation resistance, it does not impair conductivity, and also the shape and particle size nonuniformity are small, and low oxygen concentration is carried out. Characteristics improve. Moreover, it is preferable that P is distributed uniformly in the metal phase inside particle | grains.

Moreover, Bi / P (atm ratio) of the copper powder for electrically conductive pastes which concerns on this invention becomes like this. Preferably it is 4-200, More preferably, it is 10-100. If the Bi / P ratio is in such a range, the particle size is fine, oxidation resistance, high conductivity, small irregularity in shape and particle size, and easy to balance the characteristics of low oxygen concentration.

In addition, the copper powder for conductive pastes according to the present invention preferably contains Ag at 0.1 atm% to 10 atm%, more preferably 0.5 atm to 5 atm%, and most preferably 0.5 atm to 3 atm%. Do it. If it is the range of such a specific amount, electroconductivity can be improved more and the cost is also suppressed, maintaining oxidation resistance of the copper powder for electrically conductive pastes. Moreover, it is preferable that Ag is distributed uniformly in the metal phase inside particle | grains.

Further, the copper powder for conductive paste according to the present invention preferably contains Si in the particles of 0.1 atm% to 10 atm%, more preferably 0.5 atm to 5 atm%, and most preferably 0.5 atm to 3 atm%. Do it. If it is the range of such a specific amount, the oxidation resistance of a copper powder can be improved further. Moreover, it is preferable that Si distributes uniformly in the metal phase inside particle | grains.

The copper powder for conductive paste according to the present invention preferably contains In at 0.1 atm% to 10 atm%, more preferably at least 0.2 atm to 8 atm%, and most preferably at least 1 atm to 3 atm%. good. If it is the range of such a specific amount, the oxidation resistance of a copper powder can be improved further. Moreover, it is preferable that In distributes in the metal phase inside particle | grains.

In addition, when Bi, Ag, Si, P, and In are all contained, the particle size is fine, the shape and particle size nonuniformity are small, the oxidation resistance is significantly excellent, and the copper powder for the conductive paste is more excellent in conductivity.

In addition, although the copper powder for electrically conductive pastes concerning this invention can expect an effect, even if it is obtained by the wet reduction method, when the particle shape is uniform and when used as an electrically conductive paste, when considering the advantages, such as little gas generation, It is preferable that it is manufactured by the atomization method.

As for the atomizing method, there are a gas atomizing method and a water atomizing method. However, a gas atomizing method may be selected if the particle shape is to be equalized, and a water atomizing method may be selected if the particles are finer. Moreover, it is preferable if it is manufactured by the high pressure atomization method among the atomization methods. The copper powder obtained by such a high pressure atomization method is preferable because the particles are more uniform or finer. In this regard, 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, and at a gas pressure of about 1.5 MPa to 3 MPa in the gas atomizing method. Way.

In addition, the copper powder for electrically conductive pastes concerning this invention is the difference of the weight change rate (Tg (%)) / specific surface area (SSA) in 240 degreeC and 600 degreeC by a thermogravimetry-differential thermal analysis apparatus (hereinafter, (DELTA) ( TG / SSA)) is preferably 1% / m ² / cm ³ -30% / m ² / cm ³ , more preferably 1% / m ² / cm ³ -25% / m ² / cm ³ Is preferably.

According to this characteristic value (DELTA) (TG / SSA), the oxidation resistance of a copper powder can be seen. The temperature range of 240 ° C. to 600 ° C. is, for example, a heating temperature range when the main conductive paste is used, such as a conductive paste for firing external electrodes of a ceramic capacitor, and it is very important to have oxidation resistance in this region. When this (Δ) (TG / SSA) is the said preferable range, oxidation resistance is fully exhibited and it is suitable also in order to ensure high electrical conductivity.

Moreover, the copper powder for electrically conductive pastes which concerns on this invention is further at least 1 sort (s) of Ni, Al, Ti, Fe, Co, Cr, Mn, Mo, W, Ta, Zr, Nb, B, Ge, Sn, Zn, etc. By adding the above element component, the various characteristic improvement effect calculated | required by an electrically conductive paste can be made including reducing melting | fusing point and improving sintering property. Although the addition amount of these elements with respect to copper is suitably set from the electrically-conductive characteristic according to the kind of element to add, various other characteristics, etc., they are about 0.001 mass%-2 mass% normally.

Moreover, the copper powder for electrically conductive pastes which concerns on this invention is preferable in the shape of being granular, and especially in spherical form. Here, the granularity refers to a shape in which the aspect ratio (the value obtained by dividing the average long diameter divided by the average short diameter) is about 1 to 1.25, and the shape in which the aspect ratio is evenly about 1 to 1.1 is called spherical shape. In addition, the state in which the shape is not uniform is called indefinite shape. The copper powder which forms such a granule has little mutual entanglement, and when used for the electrically-conductive material of an electrically conductive paste etc., since the dispersibility in a paste improves, it is very preferable.

Moreover, the copper powder for electrically conductive pastes concerning this invention can ensure reliably, and can be suitable for the electrically-conductive material of an electrically conductive paste by making content oxygen concentration into 30 ppm 2500 ppm.

Next, the preferable specific manufacturing method of the copper powder for electrically conductive pastes which concerns on this invention is demonstrated.

The copper powder for electrically conductive pastes of this invention can be manufactured by adding a Bi component to molten copper in the form of a master alloy, a compound, etc. in predetermined amount, and then powdering it by the predetermined atomization method. .

According to the said manufacturing method, the copper powder which is fine in particle size and which does not impair the balance of oxidation resistance and electroconductivity, and the copper powder which is a nonuniformity of a shape and a particle size, and has a low oxygen concentration can be manufactured.

Although this reason is not accurate, it is estimated that Bi added to molten copper or a copper alloy catches oxygen in the produced | generated copper powder particle | grains, and suppresses oxidation so that electroconductivity may not be impaired.

Moreover, when P component is added to Bi component, surface tension of the molten metal at the time of atomization can be made small, and it is guessed that particle-shaped equalization and deoxygenation in a molten metal can be performed effectively. The P component may be added in a predetermined amount to the molten copper in the form of a master alloy or a compound, like the Bi component.

In addition, by adding an Ag component in addition to the Bi component, the conductivity can be further improved while ensuring oxidation resistance of the copper powder.

In addition to the Bi component, the oxidation resistance of the copper powder can be further improved by including the Si component and the In component.

Moreover, in the said manufacturing method, for the reason mentioned above, it is preferable to employ | adopt the high pressure atomization method. However, since the content yield of additive components other than copper may be low by the water atomization method compared with the gas atomization method, about Bi of the net amount in the target copper powder, It is necessary to add 1 to 10 times in the case, 1 to 100 times in the case of P, 1 to 10 times in the case of Ag, 1 to 10 times in the case of Si, and 1 to 10 times in the case of In.

In addition, in the said manufacturing method, after atomizing, you may reduce | reduce treatment. By this reduction treatment, the oxygen concentration on the surface of the copper powder which is easily prone to oxidation can be further reduced. The reduction treatment is preferably performed by gas 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.

Moreover, it is preferable to perform the said reducing process at the temperature of 150 degreeC-300 degreeC, and it is more preferable if it is especially performed at the temperature of 170 degreeC-210 degreeC. This is because if the temperature is less than 150 ° C, the reduction rate is slow, and the treatment effect cannot be sufficiently expressed. If the temperature exceeds 300 ° C, there is a fear that the copper powder may be aggregated or sintered. 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 concentration.

Moreover, in the said manufacturing method, it is preferable to classify after powdering. This classification can be performed easily by isolate | separating coarse powder and fine powder from the obtained copper powder using a suitable classification apparatus so that the target particle size may become a center. Here, it is preferable that the classifier such that 0.2? 0.6 coefficient of variation (SD / D ₅₀₎ described above.

The electrically conductive paste containing the copper powder for electrically conductive pastes of this invention manufactured by mixing and kneading | mixing and kneading various additives, such as resin, such as an epoxy resin, and its hardening | curing agent, to the copper powder as demonstrated above, Since the particle size is fine, the oxidation resistance and the conductivity are balanced, the shape irregularity is low, and the oxygen concentration is low. Therefore, for the formation of conductor circuits by the screen printing additive method, for external electrodes of multilayer ceramic capacitors, etc. It can be applied very favorably to the electrically-conductive material of the electrically conductive paste for various electrical contact members.

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, Flexible Printed Boards (FPC), Antenna Switch Modules, Modules such as PA Modules or High Frequency Active Filters, Electronic Shielding Films for PDP Front and Back Plates or PDP Color Filters, Crystalline Solar Surface Electrodes and Back-Out Electrodes, Conductive Adhesives, EMI Membrane switches such as shields, RF-IDs, and PC keyboards, and anisotropic conductive films (ACF / ACP) can also be used.

Hereinafter, the present invention will be further described based on the following Examples and Comparative Examples.

Example 1

After filling the chamber of a gas atomizing apparatus (made by Nisshin Kien Co., Ltd., NEVA-GP2 type) and a raw material dissolution chamber with nitrogen gas, the raw material was melted by the carbon crucible in a melting chamber, and it was set as the melt (electric copper 2.62g of metal bismuth was added to the molten metal which melt | dissolved, and it was set as 800g of molten metal, and fully stirred and mixed). Thereafter, the molten metal was sprayed at 1250 ° C. and 3.0 MPa from a nozzle having a diameter of 1.5 mm to obtain a copper powder containing bismuth in the particles. Then, it sieved with a 53 micrometer test sieve, and used as a final copper powder. The characteristics of the obtained copper powder are shown in Table 2.

(Examples 2-4)

A copper powder was obtained in the same manner as in Example 1 except that the metal bismuth addition amount was changed as shown in Table 1.

(Examples 5 to 11)

In addition to metal bismuth, copper-phosphorous master alloy (15 mass% of phosphorus grades) was also added except having added as shown in Table 1, and copper powder was obtained.

(Examples 12 and 13)

In addition to the metal bismuth and the copper-phosphorus master alloy, the copper powder was obtained in the same manner as in Example 1 except that electrical silver was added as shown in Table 1.

Example 14

A copper powder was obtained in the same manner as in Example 1 except that metal silicon (NIKSIL manufactured by Nippon Kenzoku Chemical Co., Ltd.) was added as well as the metal bismuth and copper-phosphorus mother alloy.

Example 15

In addition to the metal bismuth, a copper powder was obtained in the same manner as in Example 1 except that metal indium was added as shown in Table 1.

(Comparative Example 1-4)

Except having added the addition amount of the metal bismuth and / or copper-phosphorus master alloy as shown in Table 1, operation similar to Example 1 was performed and the copper powder was obtained.

[Table 1]

About the copper powder obtained by each Example and the comparative example, various characteristics were evaluated by the method shown below. The results are shown in Tables 2-6. In addition, when observed with 3500 times the scanning electron microscope (SEM) about the copper powder obtained in Example 2, as shown in FIG. 1, bismuth existed in the crystal grain boundary of the copper of a particle surface. In addition, the copper powder of the Example and the comparative example was contained inside particle | grains about Ag, Si, P, and In, respectively.

(1) bismuth, phosphorus, silver, silicon content

The sample was dissolved in acid and analyzed by ICP.

(2) oxygen concentration

The analysis was carried out by an oxygen-nitrogen analyzer (EMGA-520 (model number) manufactured by Horiba Seisakusho Co., Ltd.). The results are shown in Table 2. In addition, in order to evaluate the deterioration of oxidative resistance over time, using a SK-8000 manufactured by Sanyo Seiko, the temperature was raised to 200 ° C. at 10 ° C./min at an air flow rate of 8 L / min, and then 1 hour thereafter. The oxygen concentration of the retained sample was also measured. The results are shown in Table 5.

(3) Δ (TG / SSA)

Differential thermogravimetric simultaneous measurement apparatus (TG / DTA) (TG / DTA6300 high temperature type) Tg (%) in 40 degrees Celsius-600 degrees Celsius (heating rate: 10 degrees C / min, air flow rate: 200 mL / min) It measured by and calculated | required the difference of the weight change rate in 240 degreeC-600 degreeC. In addition, the specific surface area was calculated | required from the particle size distribution measured with the particle size measuring apparatus (The Nikki Micro Co., Ltd., microtrack MT-3000 type | mold), and was calculated arithmetically from both numerical values. In addition, TG / SSA (% / m ² / cm ³ ) at each temperature is shown in Table 3, and the TG / SSA is represented as TG / SSA of pure copper powder of Comparative Example 1 ([Tg / SSA] _Cu in Table). Table 4 shows the results obtained by dividing).

(4) particle shape

It observed with the scanning electron microscope.

(5) D ₅₀ , SD, SD / D ₅₀

The sample (0.2 g) was placed in pure water (100 mL) and irradiated with ultrasonic waves (3 minutes), and then dispersed by a particle size distribution measuring device (Microtrack (trade name) FRA (model number) manufactured by Nikkiso Kagaku Co., Ltd.). , Volume cumulative particle diameter D ₅₀ and standard deviation value SD and coefficient of variation (SD / D ₅₀ ) were obtained, respectively.

(6) powder resistance

15 g of the 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. (Manufactured by Co., Ltd.).

TABLE 2

[Table 3]

[Table 4]

As shown in Table 2-4, the copper powder of an Example is excellent in oxidation resistance compared with the comparative example which does not contain bismuth or does not contain bismuth and phosphorus, and especially it is excellent in the temperature range of 240 degreeC-600 degreeC. And it was found.

In addition, as shown in Table 2, the copper powder of the Example was spherical in shape, did not have nonuniformity, and also the size was fine. In particular, as the content of bismuth increased, the obtained copper powder was atomized.

Moreover, as shown in Table 5, when the copper powder of an Example was hold | maintained for a long time in the environment which is easy to oxidize, compared with the copper powder of a comparative example, it was remarkably excellent with time-resistant oxidation resistance.

TABLE 5

Moreover, as shown in Table 6, compared with the copper powder of the comparative example, the copper powder of an Example did not show a change in volume resistivity very much, and it was confirmed that it has favorable electroconductivity.

TABLE 6

Claims (9)

A copper powder for conductive paste, which contains 0.05atm% to 10atm% of Bi in the particles. The method of claim 1,
Copper powder for electrically conductive pastes containing 0.01atm%-0.3atm% of P (phosphorus) in particle inside. The method of claim 2,
Bi / P (atm ratio) is 4-200, The copper powder for electrically conductive pastes characterized by the above-mentioned. 4. The method according to any one of claims 1 to 3,
A copper powder for conductive paste, which contains 0.1 atm% to 10 atm% of Ag in the particles. 5. The method according to any one of claims 1 to 4,
The copper powder for conductive pastes containing 0.1 atm%-10atm% of Si in particle inside. The method according to any one of claims 1 to 5,
0.1 atm%-10atm% of In in a particle | grain inside, The copper powder for electrically conductive pastes characterized by the above-mentioned. The method according to any one of claims 1 to 6,
A copper powder for conductive paste, which is produced by an atomize method. The method according to any one of claims 1 to 7,
Copper powder for conductive paste, characterized in that the difference in weight change rate (Tg (%)) / specific surface area (SSA) at 240 ° C and 600 ° C is 1% / m ² / cm ^{3 to} 30% / m ² / cm ³ . The electrically conductive paste containing the copper powder for electrically conductive pastes in any one of Claims 1-8.

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