Method for producing copper-based powder for electrode paste and method for producing multilayer ceramic elements

Abstract

The technical gist of the present invention is that it comprises a first step of mixing copper or copper oxide powder with zinc powder to produce a mixed powder, a second step of heat-treating the mixed powder in a reducing atmosphere to produce a copper-zinc alloy powder, a third step of heat-treating the copper-zinc alloy powder in an oxidizing atmosphere to produce a copper oxide-zinc oxide alloy powder, a fourth step of pulverizing the copper oxide-zinc oxide alloy powder to produce a pulverized copper oxide-zinc oxide alloy powder, and a fifth step of heat-treating the pulverized copper oxide-zinc oxide alloy powder in a reducing atmosphere to re-reduce the pulverized copper oxide-zinc oxide alloy powder into a copper-zinc alloy powder, thereby alloying copper and zinc.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a copper-zinc alloy powder for a multilayer ceramic element capable of simultaneous firing, a copper-zinc alloy powder produced therefrom, an electrode paste containing the same, and a multilayer ceramic element.

Background Art

[0002] Although ceramic elements have fast responsiveness and precision and can be miniaturized and lightened, their displacement is smaller than that of electric elements and shows limitations. Therefore, in order to overcome this, a multilayer ceramic element in which thin ceramics with electrodes formed thereon are stacked in multiple layers has been developed.

[0003] A multilayer ceramic element is manufactured by first forming a ceramic material into a thin ceramic form, forming an electrode on the surface of the ceramic with a conductor material, and then stacking a large number of them. At this time, since the stacked ceramics are weak in strength, they are hardened firmly through heat treatment.

[0004] Regarding electrode materials, silver (Ag) has a very low melting point of 961°C, so it is used as silver palladium (AgPd) or silver platinum (AgPt) by being solid-dissolved with palladium (Pd) or platinum (Pt) having a high melting point. However, since noble metals such as palladium are very expensive, although the proportion of relatively inexpensive silver is increased and used as an electrode material, there are decisive difficulties in mass-producing multilayer ceramic elements for economic reasons.

[0005] There are cases where copper (Cu) or nickel (Ni) is used as an electrode material. In "Multilayer Ceramic Component (KR10-1580350B1)", a multilayer ceramic component that can adjust the content or size of a co-material added to an internal electrode layer and utilize the high sintering driving force of the co-material to enhance the connectivity of the internal electrode, and copper or nickel is applied as the internal electrode.

[0006] However, a common problem is that segregation, where copper or nickel elements precipitate in specific areas during the alloying process of copper and nickel, easily occurs, leading to a tendency for copper and nickel to separate. Even by altering the sintering behavior of copper to overcome this problem, there have been limitations in manufacturing multilayer ceramic elements. In particular, nickel is used as an electrode material for secondary batteries, and its high price makes its use difficult. Therefore, there is a need to develop technologies for copper-based alloy powders, electrode pastes containing these alloys, and multilayer ceramic elements that can maintain stable electrical conductivity using a metal cheaper than nickel. [Overview of the project] [Problems that the invention aims to solve]

[0007] This invention was made to solve the aforementioned problems, and its technical objective is to provide a method for producing copper-zinc alloy powder for multilayer ceramic elements that can be co-fired so that copper and zinc are alloyed and electrical conductivity is stably maintained, the copper-zinc alloy powder produced therefrom, an electrode paste containing the same, and a multilayer ceramic element. [Means for solving the problem]

[0008] To solve the above technical problems, the present invention provides a method for producing copper-zinc alloy powder for multilayer ceramic elements that can be fired simultaneously, comprising: a first step of mixing copper or copper oxide powder and zinc powder to produce a mixed powder; a second step of heat-treating the mixed powder in a reducing atmosphere to produce copper-zinc alloy powder; a third step of heat-treating the copper-zinc alloy powder in an oxidizing atmosphere to produce copper oxide-zinc alloy powder; a fourth step of pulverizing the copper oxide-zinc alloy powder to produce pulverized copper oxide-zinc alloy powder; and a fifth step of heat-treating the pulverized copper oxide-zinc alloy powder in a reducing atmosphere to re-reduce the pulverized copper oxide-zinc alloy powder back into copper-zinc alloy powder, characterized in that copper and zinc are alloyed.

[0009] In the present invention, the first step is characterized by mixing the copper or copper oxide powder and the zinc powder in a weight ratio of 5 to 9.9:0.1 to 5.

[0010] In the present invention, the second step is characterized by heat-treating the mixed powder in a hydrogen or hydrogen / nitrogen mixed gas atmosphere at a temperature of 500 to 650°C.

[0011] In the present invention, the third step is characterized by heat-treating the copper-zinc alloy powder in an oxygen or air atmosphere at a temperature of 500 to 900°C.

[0012] In the present invention, the fifth step is characterized by heat-treating the pulverized copper oxide-zinc oxide alloy powder in a hydrogen or hydrogen / nitrogen mixed gas atmosphere at a temperature lower than the heat treatment temperature of the second step.

[0013] To solve the other technical problems mentioned above, the present invention provides a copper-zinc alloy powder characterized by being manufactured by the method described above.

[0014] To solve the aforementioned technical problems, the present invention provides an electrode paste characterized by comprising an organic vehicle formed by mixing an organic solvent and a binder, and the copper-zinc alloy powder.

[0015] To solve the aforementioned technical problems, the present invention provides a multilayer ceramic element characterized by forming a ceramic laminate by printing the electrode paste onto a ceramic tape, heat-treating it in an oxidizing atmosphere, and then heat-treating it in a reducing atmosphere.

[0016] In the present invention, the ceramic element is formed by the steps of: heat-treating the ceramic laminate in an oxidizing atmosphere at 100 to 650°C to burn out the binder and degrease it, then heat-treating it in an oxidizing atmosphere at 800 to 1,100°C to sinter it, and then heat-treating the sintered ceramic laminate in a reducing atmosphere at 100 to 300°C.

Advantages of the Invention

[0017] According to the present invention by the means for solving the above problems, by using dissimilar metals of copper and zinc and enabling co-firing even in an oxidizing atmosphere and controlling the shrinkage rate between the dissimilar metals, it is possible to manufacture a copper-zinc alloy powder capable of preventing shrinkage and delamination. Since it is alloyed with zinc compared to pure copper and has a dense structure, there is an effect that the heat resistance can be improved up to 1,050 °C.

[0018] In particular, the copper-zinc alloy powder of the present invention has a stable electrical conductivity compared to bulk copper and expensive silver palladium (AgPd) materials. Therefore, it can be utilized as an electrode of a laminated ceramic element after manufacturing an electrode paste instead of expensive silver palladium (AgPd), resulting in an effect of enhancing economic efficiency.

Brief Description of the Drawings

[0019] [Figure 1] It is a flowchart showing a method for manufacturing a copper-zinc alloy powder according to the present invention. [Figure 2] It is a flowchart showing a method for manufacturing an electrode paste and a laminated ceramic element according to the present invention. [Figure 3] It is a schematic diagram showing a method for manufacturing an electrode of a laminated ceramic element according to the present invention. [Figure 4] It is a SEM photograph showing the surface change of the copper-zinc alloy powder. [Figure 5] It is a graph showing a comparison of the electrical conductivity by electrode materials. ]>

Modes for Carrying Out the Invention

[0020] While the present invention is capable of undergoing various modifications and has various forms, specific embodiments will be described in detail in the following text. However, this is not intended to limit the present invention to the specific disclosed forms, and it should be understood to include all modifications, equivalents, or alternatives within the spirit and technical scope of the present invention.

[0021] The terms used in this application are merely used to describe specific embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates a different meaning. In this application, terms such as "comprising" or "having" are intended to specify the existence of a combination of features, numbers, steps, components, etc. described in the specification, and it should be understood that they do not pre-exclude the existence or addition possibility of one or more other combinations of features, numbers, steps, components, etc.

[0022] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by those having ordinary knowledge in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and should not be interpreted in an ideal or overly formal sense unless clearly defined in this application.

[0023] Details of well-known functions and configurations that are repeated here and may unnecessarily obscure the gist of the present invention will be omitted. Embodiments of the present invention are provided to more fully explain the present invention to those having ordinary knowledge in the art.

[0024] The present invention relates to a method for producing copper-zinc alloy powder for multilayer ceramic elements that can be fired simultaneously. Figure 1 is a flowchart of the method for producing copper-zinc alloy powder according to the present invention. Referring to Figure 1, the copper-zinc alloy powder of the present invention is produced by a first step (S10) of mixing copper or copper oxide powder and zinc powder to produce a mixed powder, a second step (S20) of heat-treating the mixed powder in a reducing atmosphere to produce copper-zinc alloy powder, a third step (S30) of heat-treating the copper-zinc alloy powder in an oxidizing atmosphere to produce copper oxide-zinc oxide alloy powder, a fourth step (S40) of pulverizing the copper oxide-zinc oxide alloy powder to produce pulverized copper oxide-zinc oxide alloy powder, and a fifth step (S50) of heat-treating the pulverized copper oxide-zinc oxide alloy powder in a reducing atmosphere to re-reduce the pulverized copper oxide-zinc oxide alloy powder back into copper-zinc alloy powder, characterized in that copper and zinc are alloyed.

[0025] According to the manufacturing method described above, the first step is to mix copper or copper oxide powder with zinc powder to produce a mixed powder (S10).

[0026] The copper or copper oxide powder and the zinc powder can be mixed in a weight ratio of 5 to 9.9:0.1 to 5. If the copper or copper oxide powder is less than 5 by weight, or if the zinc powder is more than 5 by weight, it is difficult to adjust the mixture in terms of improving electrical conductivity. If the copper or copper oxide powder is more than 9.9 by weight, or if the zinc powder is less than 0.1 by weight, it may cause shrinkage or delamination between the copper and zinc, which is undesirable.

[0027] Next, the second step is to heat-treat the mixed powder in a reducing atmosphere to produce copper-zinc alloy powder (S20).

[0028] The mixed powder is heat-treated at a temperature of 500 to 650°C in a hydrogen or hydrogen / nitrogen gas atmosphere. Since the melting point of zinc is approximately 419°C, the temperature must be above the minimum melting point of zinc for copper-zinc alloying, and a temperature of 500°C or higher is preferable for process efficiency. Reducing heat treatment at temperatures below 500°C has the disadvantage of taking a long time for copper-zinc alloying, while temperatures exceeding 650°C may cause alteration of the physical properties of the copper-zinc alloy powder due to the high temperature. Because copper has a high melting point of 1,085°C, heat treatment at a temperature of 500 to 650°C in a reducing atmosphere can create an alloy powder form in which zinc, with a lower melting point of approximately 419°C, melts and encases the surface of the copper. However, the oxidation rate of zinc is relatively faster than that of copper, and in this case, an oxide film can form on the surface of the alloy powder.

[0029] Next, the third step is to heat-treat the copper-zinc alloy powder in an oxidizing atmosphere to produce copper oxide-zinc oxide alloy powder (S30).

[0030] The copper-zinc alloy powder is heat-treated in an oxygen or air atmosphere at a temperature of 500 to 900°C. The heat treatment must be performed in an oxygen or air atmosphere at a minimum of 500°C or higher to allow for oxidation of the copper-zinc alloy powder; temperatures exceeding 900°C are undesirable as they lead to over-oxidation of copper and zinc.

[0031] Next, the fourth step is to grind the copper oxide-zinc oxide alloy powder to produce the ground copper oxide-zinc oxide alloy powder (S40).

[0032] The copper oxide-zinc oxide alloy powder is ground to a particle size of 0.5 to 10 μm. For application as an electrode in a multilayer ceramic element, it can be ground to particles with a particle size of 0.5 to 10 μm, but preferably it can be ground to have a particle size of 1 to 5 μm, and more preferably to have a particle size of 1 μm or less.

[0033] Next, the fifth step is to heat-treat the pulverized copper oxide-zinc oxide alloy powder in a reducing atmosphere to re-reduce the pulverized copper oxide-zinc oxide alloy powder back into copper-zinc alloy powder (S50).

[0034] When the pulverized copper oxide-zinc oxide alloy powder is heat-treated and stabilized in a hydrogen or hydrogen / nitrogen gas atmosphere at a temperature relatively lower than the heat treatment temperature of the second step, the oxide film formed on the surface of the copper-zinc alloy powder is removed. In the case of heat treatment, it may be carried out at 100 to 300°C. If the temperature is below 100°C, a lot of time is consumed and a large amount of hydrogen / nitrogen gas must be used for the oxide form of copper oxide or zinc oxide to be completely reduced to the metallic form, which has a drawback in the process. Temperatures above 300°C cannot be said to be stable temperatures for re-reduction to copper-zinc alloy powder.

[0035] On the other hand, electrode paste and multilayer ceramic elements can be manufactured using the copper-zinc alloy powder produced by the above method. Figure 2 is a flowchart showing the method for manufacturing electrode paste and multilayer ceramic elements according to the present invention, and Figure 3 is a schematic diagram showing the electrode manufacturing method for multilayer ceramic elements according to the present invention.

[0036] The electrode paste can consist of an organic vehicle formed by mixing an organic solvent and a binder, and copper-zinc alloy powder produced by the method described above. In this case, the pulverized copper oxide-zinc alloy powder from step 4 can be used as the copper-zinc alloy powder mixed with the organic vehicle. Specifically, the pulverized copper oxide-zinc alloy powder and the organic vehicle can be placed in a mixer in a 1:1 weight ratio and primary mixed at 600-1,000 rpm, followed by secondary mixing in a three-roll mill, and then filtered to obtain the electrode paste.

[0037] The organic vehicle plays a role in holding the copper oxide-zinc oxide alloy powder together for aggregation. One or more organic solvents can be selected from the group consisting of PGME (propylene glycol monomethyl ether), terpineol (α, b, d, g), dihydroterpineol, and dihydroterpinyl acetate. The binder can be prepared by dissolving ethyl cellulose at 20% by weight in ethanol, and PVB (polyvinyl butyral) can also be used if necessary. During the preparation of the organic vehicle, additional materials such as DOP (di-2-ethylhexyl phthalate) plasticizer, BYK-111 (dispersant), and borosilicate glass frit may also be added.

[0038] Such organic vehicles can be manufactured by mixing an organic solvent and a binder in a weight ratio of 5-9:1-5. If the organic solvent is less than 4 by weight, homogeneous mixing of the binder cannot be achieved, and if the organic solvent is more than 9 by weight, the use of too much organic solvent may impair the physical properties of the organic vehicle. If the binder is less than 1 by weight or more than 5 by weight, it is undesirable for electrode paste formation.

[0039] To manufacture a multilayer ceramic element using such an electrode paste, the electrode paste is screen printed onto a sheet-shaped ceramic tape to form a ceramic laminate, which is then heat-treated in an oxidizing atmosphere and then in a reducing atmosphere.

[0040] The multilayer ceramic element is manufactured by first heat-treating the ceramic laminate in an oxidizing atmosphere at 100-650°C to burn out the binder and degrease it via organic burnout, then heat-treating it in an oxidizing atmosphere at 800-1,100°C to sinter it, followed by heat-treating the sintered ceramic laminate in a reducing atmosphere at 100-300°C to stabilize it, thereby reducing the metal oxide to metal. In other words, through the re-reduction heat treatment, oxygen and hydrogen in copper oxide-zinc oxide combine to form water, which evaporates and reduces the mixture back to copper-zinc.

[0041] Therefore, in the conventional manufacturing of multilayer ceramic elements, after printing electrode paste onto ceramic tape and stacking it, degreasing and sintering (oxygen partial pressure pO2 < 10) are performed from the beginning in a reducing atmosphere (N2, H2). -13 (atm) and re-oxidation heat treatment (oxygen partial pressure pO2 < 10 -6 Unlike the previous method, which required specialized equipment and involved cumbersome processes such as gas injection, the multilayer ceramic element according to the present invention has the advantage of being able to be degreased and fired simultaneously in an atmospheric environment, and can be easily manufactured simply by applying heat treatment in a reducing atmosphere in the post-processing step.

[0042] The following describes embodiments of the present invention in more detail. However, the following embodiments are merely illustrative to aid in understanding the present invention, and the scope of the present invention is not limited to these embodiments.

[0043] <Example 1> Manufacturing of copper-zinc alloy powder Copper oxide powder (Cu2O2, CuO) and zinc (Zn) powder were prepared. The copper(I) oxide powder and zinc powder were mixed in ethanol in a weight ratio of 9:1 and wet-mixed to ensure uniform mixing. The uniformly mixed solution was dried at room temperature or high temperature below 100°C to obtain a uniformly mixed copper-zinc powder.

[0044] A uniformly mixed copper-zinc powder was subjected to a reducing heat treatment at 600°C in a pure hydrogen atmosphere or a hydrogen / nitrogen gas mixture atmosphere to form a copper-zinc alloy powder.

[0045] Copper-zinc alloy powder was heat-treated at a temperature of 600°C in an air or oxygen atmosphere to form copper oxide-zinc oxide alloy powder.

[0046] The obtained copper oxide (CuO)-zinc oxide (ZnO) alloy powder was ground using zirconia balls by ball milling for 24 hours to obtain copper oxide-zinc oxide alloy powder with an average diameter of 0.5 to 10 μm.

[0047] The pulverized copper oxide-zinc oxide alloy powder was heat-treated in a hydrogen or hydrogen / nitrogen gas atmosphere at a suitable temperature range of 100-300°C, lower than that of the reduction heat treatment, thereby reducing the pulverized copper oxide-zinc oxide alloy powder back to copper-zinc alloy powder.

[0048] Manufacturing of electrode paste Organic vehicles were prepared by mixing organic solvents and binders in a weight ratio of 5-9:1-5. Different viscosity characteristics were observed depending on the mixing ratio. Terpineol was used as the organic solvent, and the binder was prepared by dissolving 20% ​​by weight of ethyl cellulose in ethanol.

[0049] The pulverized copper oxide-zinc oxide alloy powder and the manufactured organic vehicle were mixed in a 1:1 weight ratio at 700-1,000 rpm for 20 seconds or more to produce an electrode paste.

[0050] Manufacturing of multilayer ceramic elements To obtain copper-zinc electrodes, the electrode paste was printed onto a substrate, heat-treated at 550°C in an air atmosphere to burn out the binder and degrease it, then heat-treated at 950°C in an air atmosphere to sinter it, and then re-reduction heat treatment was performed at a temperature of 100-300°C in a hydrogen / nitrogen mixed gas atmosphere to reduce the copper oxide-zinc oxide to copper-zinc. Through the heat treatment process, oxygen and hydrogen in the copper oxide-zinc oxide combined to form water, which evaporated and was reduced to copper-zinc.

[0051] Figure 4 is an SEM image showing the surface changes of copper-zinc alloy powder. This confirms that copper-based alloying occurs through the degreasing, sintering, and reduction post-treatment processes of the multilayer ceramic element.

[0052] <Comparative Example 1> In Comparative Example 1, a multilayer ceramic element was manufactured using the same process as in Example 1, but instead of a copper-zinc alloy, bulk copper (Bulk Cu) was used as the electrode material.

[0053] <Comparative Example 2> In Comparative Example 2, a multilayer ceramic element was manufactured using the same process as in Example 1, but instead of a copper-zinc alloy, AgPd was used as the electrode material.

[0054] Figure 5 is a graph comparing the electrical conductivity of different electrode materials. Referring to Figure 5, Comparative Example 1 has an electrical conductivity of 10 8 (Ω·M) -1 Comparative Example 2 is close to 10 7 (Ω·M) -1 While similar, it can be confirmed that the copper-zinc alloy electrode in the multilayer ceramic element of Example 1 has a relatively higher electrical conductivity than that of Comparative Example 2. This indicates that in the multilayer ceramic element to which the copper-zinc alloy of the present invention is applied as an electrode, shrinkage and delamination between copper and zinc do not occur, and electrical conductivity is stably maintained.

[0055] In summary, the present invention is characterized by the fact that, by mixing copper or copper oxide powder with zinc powder, heat-treating it in a reducing atmosphere, then in an oxidizing atmosphere, and then going through a grinding process before heat-treating it in a reducing atmosphere, copper and zinc are alloyed, the metal oxide film can be removed, and electrical conductivity can be stably maintained.

[0056] These characteristics allow for the simultaneous firing of dissimilar metals, copper and zinc, even in an oxidizing atmosphere. By controlling the shrinkage rate between the dissimilar metals, it is possible to manufacture copper-zinc alloy powder that prevents shrinkage and delamination. This offers the advantage of being able to manufacture electrode pastes and multilayer ceramic elements using this powder.

[0057] Furthermore, the copper-zinc alloy powder of the present invention maintains stable electrical conductivity compared to bulk copper (Bulk Cu) and silver-palladium (AgPd) materials, which is significant because it can be used as an electrode in multilayer ceramic elements instead of expensive nickel, thereby improving cost-effectiveness.

[0058] The above description is merely illustrative of the technical concept of the present invention, and a person with ordinary skill in the art to which the present invention pertains can make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed herein are for illustrative purposes only, not to limit the technical concept of the present invention, and the scope of the technical concept of the present invention is not limited by such embodiments. The scope of protection of the present invention should be interpreted by the claims, and all technical concepts within an equivalent scope should be interpreted as being included in the scope of rights of the present invention.

Claims

1. A first step is to produce a mixed powder by mixing copper or copper oxide powder with zinc powder, A second step involves heat-treating the mixed powder in a reducing atmosphere to produce copper-zinc alloy powder, A third step involves heat-treating the aforementioned copper-zinc alloy powder in an oxidizing atmosphere to produce copper oxide-zinc oxide powder, A fourth step involves grinding the aforementioned copper oxide-zinc oxide powder to produce the ground copper oxide-zinc oxide powder, A method for producing copper-based powder for electrode paste, characterized by comprising a fifth step of heat-treating the pulverized copper oxide-zinc oxide powder in a reducing atmosphere to re-reduce the pulverized copper oxide-zinc oxide powder back into copper-zinc alloy powder.

2. The first step is, A method for producing copper-based powder for electrode paste according to claim 1, characterized by mixing the copper or copper oxide powder and the zinc powder in a weight ratio of 5:5 to 9.9:0.

1.

3. The second step described above is: A method for producing copper-based powder for electrode paste according to claim 1, characterized by heat-treating the mixed powder in a hydrogen or hydrogen / nitrogen mixed gas atmosphere at a temperature of 500 to 650°C.

4. The previous third step is, A method for producing copper-based powder for electrode paste according to claim 1, characterized by heat-treating the copper-zinc alloy powder in an oxygen or air atmosphere at a temperature of 500 to 900°C.

5. The fifth step described above is: The method for producing copper-based powder for electrode paste according to claim 1, characterized in that the pulverized copper oxide-zinc oxide powder is heat-treated in a hydrogen or hydrogen / nitrogen mixed gas atmosphere at a temperature lower than the heat treatment temperature of the second step.

6. A first step of mixing copper or copper oxide powder with zinc powder to produce a mixed powder, A second step involves heat-treating the mixed powder in a reducing atmosphere to produce copper-zinc alloy powder, A third step involves heat-treating the aforementioned copper-zinc alloy powder in an oxidizing atmosphere to produce copper oxide-zinc oxide powder, A fourth step involves grinding the aforementioned copper oxide-zinc oxide powder to produce the ground copper oxide-zinc oxide powder, A method for producing copper-based powder for electrode paste, characterized by containing the following:

7. A step of producing an electrode paste by mixing an organic vehicle formed by mixing an organic solvent and a binder with copper-based powder for electrode paste produced by the method for producing copper-based powder for electrode paste described in claim 1 or claim 6, The steps include printing the electrode paste onto a ceramic material to form a ceramic laminate, degreasing it by heat treatment in an oxidizing atmosphere, and then sintering it by heat treatment in an oxidizing atmosphere, The steps include heat-treating the sintered ceramic laminate in a reducing atmosphere, A method for manufacturing a multilayer ceramic element, characterized by including [the following].

8. The method for manufacturing a multilayer ceramic element according to claim 7, characterized in that the ceramic material is a ceramic tape.

9. The degreasing is performed by heat-treating the ceramic laminate in an oxidizing atmosphere at 100 to 650°C to burn out the binder. The aforementioned sintering is performed by heat treatment at 800 to 1,100°C in an oxidizing atmosphere. The method for manufacturing a multilayer ceramic element according to claim 7, characterized in that the heat treatment in the reducing atmosphere is performed at a temperature of 100 to 300°C.

Images