Method for producing solderable electrodes of base metal tin or base metal tin alloy by heat treatment under atmospheric pressure

Abstract

To provide a fabrication method that allows sintering solderable base metal and alloy elements under air.SOLUTION: A solderable electrode can be manufactured by heat treatment instead of electroplating. This method directly adds a large amount of metal powder to the electrode, and also adds metallic aluminum powder with a high oxidation enthalpy to protect the tin from oxidation. Adding other metals, such as metallic copper powder, produces a copper-tin alloy to increase its melting point. This method also directly uses a tin-based electrode, and covers the tin electrode with an aluminum film to prevent it from oxidizing during heat treatment. Adding a suitable metal, such as copper, to the tin film produces a tin-copper alloy, thereby increasing the melting point of the electrode. This invention thus uses a heat treatment process instead of electroplating to produce electrodes for an electronic device without the need for a tin electroplating process, resulting in solderable electrodes with excellent solderability and high performance properties.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for producing solderable base metal and alloy elements by sintering them under air, and in particular, a method for producing electrodes for electronic elements by performing a heat treatment process instead of an electroplating process, and more particularly, a method for producing electrodes for electronic elements without the need for a tin electroplating process, and which can produce solderable electrodes while maintaining high performance properties. [Background technology]

[0002] According to existing technique 1, high-temperature heat treatment of thick-film printed precious metal silver or silver-palladium alloy can be performed in the atmosphere, but precious metals and alloy materials are very expensive.

[0003] According to existing technology 2, base metals such as copper, nickel, or copper-nickel alloys can be used in thick film printing instead of precious metals such as silver or silver-palladium alloys, but unless heat treatment is performed in a restoring atmosphere, the base metals such as copper, nickel, or copper-nickel alloys will oxidize and lose their properties. Therefore, while costs can be reduced by changing the material from precious metals to base metals, the heat treatment process must be changed from air sintering to restoring atmosphere sintering, which significantly increases process costs.

[0004] According to existing technology 3, existing electronic devices use either precious metals sintered under air as in existing technology 1 or base metals sintered under a restoring atmosphere as in existing technology 2 as electrodes, but can be further welded to a circuit board by electroplating with tin.

[0005] As described above, according to existing technologies, existing electronic devices can achieve the following three functions by fabricating electrodes: Function 1: Connect electronic elements to realize electronic element characteristics; Function 2: Connect electronic components in a tight mechanical connection; and Function 3: Connect to an electronic circuit board via soldering.

[0006] As described above, whether sintering a noble metal electrode in air or sintering a base metal electrode in a restoring atmosphere, solderability can be achieved by electroplating a tin layer on the surface of the electrode in a tin electroplating process, thereby allowing it to be bonded to an electronic circuit board with solder paste. However, because electroplating is a highly environmentally polluting process, there is a demand for solderable metal electrodes that do not require electroplating a tin layer.

[0007] As mentioned above, solder paste is mainly composed of flux and powder. Solder paste is inexpensive and has good conductivity, but it oxidizes easily during heat treatment and tends to clump together, so it cannot be used as an electrode and can only be used to connect silver or copper electrodes.

[0008] Because the welding effect of solder paste particles of different sizes is different, even if the quality is the same, solder paste with smaller particles has higher viscosity, better wettability, and melts faster to become fine particles, but it oxidizes easily and is more expensive. Therefore, in practical use, conventional electrodes cannot be made solderable without an electroplating process.

[0009] In order to overcome the above drawbacks, the inventors have conducted careful research and, by utilizing scientific principles, have proposed the present invention, which can effectively overcome the above drawbacks and has a rational design. DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0010] The main object of the present invention is to provide a method for producing an electronic device that can solve the above-mentioned problems of the prior art, utilizes a heat treatment process instead of an electroplating process, does not require a tin electroplating process, and can maintain high performance characteristics while providing solderability to the electrodes. [Means for solving the problem]

[0011] In order to achieve the above object, the present invention provides a method for sintering solderable base metal and alloy elements under air, and the method comprises the steps of: 10 to 90°C sintering a printed thick base metal tin conductor paste film or a base metal tin alloy conductor paste film; Alternatively, by adding wt% metallic aluminum powder, or by first printing one layer of thick base metal tin conductive paste film or base metal tin alloy conductive paste film, and then printing one layer of thick aluminum protective layer on top of it, and then heat treating it in the atmosphere at 300 to 600°C, the highly aerobic properties of the metallic aluminum powder or the aluminum protective layer can be utilized to protect the base metal tin conductive paste film or base metal tin alloy conductive paste film, preventing it from being oxidized during sintering in the high-temperature atmosphere. Alternatively, after the base metal tin conductive paste film or base metal tin alloy conductive paste film is oxidized during sintering in the high-temperature atmosphere, the strong restoration properties of the metallic aluminum powder or the aluminum protective layer can restore the oxidized base metal tin conductive paste film or base metal tin alloy conductive paste film to its original metal or alloy state, thereby providing solderability and increasing the melting point of the electrode, thereby obtaining a thick-film base metal tin electrode or base metal tin alloy electrode.

[0012] According to the above embodiment of the present invention, the base metal tin alloy conductor paste film is either a tin-copper alloy or a tin-nickel alloy.

[0013] According to the above embodiment of the present invention, the aluminum protective layer is one of an aluminum film, an aluminum alloy film, or an aluminum oxide film.

[0014] According to the above embodiment of the present invention, the aluminum alloy film is a copper aluminum alloy, and the aluminum oxide film is copper oxide.

[0015] In order to achieve the above object, the present invention provides a block-shaped ceramic element having at least outer electrodes located on both sides, the outer electrodes located on both sides being thick-film outer electrodes made of base metal tin or outer electrodes made of base metal tin alloy formed by sintering according to the above method.

[0016] According to the above embodiment of the present invention, the block-shaped ceramic element is a GPS ceramic antenna, a negative temperature coefficient (NTC) thermistor, a positive temperature coefficient (PTC) thermistor, a voltage dependent resistor (VDR), or a safety capacitor.

[0017] To achieve the above object, the present invention provides a multilayer ceramic co-fired element, which has at least an outer electrode, and the outer electrode is a thick-film outer electrode made of base metal tin or a base metal tin alloy, formed by sintering using the above method.

[0018] According to the above embodiment of the present invention, the multilayer ceramic element is a low temperature co-fired ceramic (LTCC), a multilayer ceramic capacitor (MLCC), a multilayer NTC element, or a multilayer VDR element.

[0019] According to the above embodiment of the present invention, the outer electrodes are formed by high-temperature sintering the multilayer ceramic co-fired element, nickel plating, immersion plating with a base metal tin conductive paste film or a base metal tin alloy conductive paste film, and then immersion plating with an aluminum protective layer, followed by heat treatment under air and sintering to remove the aluminum protective layer.

[0020] According to the above embodiment of the present invention, the outer electrodes are formed by sintering the multilayer ceramic co-fired element at high temperature, directly immersion plating a base metal tin conductive paste film or a base metal tin alloy conductive paste film, immersion plating an aluminum protective layer, and then heat treating the element in air to remove the aluminum protective layer by sintering.

[0021] In order to achieve the above object, the present invention is a chip resistor having at least a front electrode and a back electrode connected to a resistive layer, and the front electrode and back electrode are thick-film base-metal front tin electrodes or base-metal front tin alloy electrodes formed by sintering using the above methods, or are base-metal back tin electrodes or base-metal back tin alloy electrodes.

[0022] In order to achieve the above object, the present invention provides a method for manufacturing a chip alloy resistor having a base metal alloy resistance layer, in which a single layer of thick base metal alloy resistance paste film is first printed, and then a single layer of thick aluminum protective layer is printed on top of that, and then heat treated in the atmosphere at 500 to 1400°C according to the chip resistor process, and the highly aerobic nature of the aluminum protective layer protects the base metal alloy resistance paste film during sintering in the high-temperature atmosphere, preventing it from oxidizing, and a heat dissipation layer with high thermal conductivity and insulating properties is formed on the aluminum protective layer, thereby obtaining a thick base metal alloy resistance layer that has solderability and can maintain its resistance characteristics.

[0023] According to the above embodiment of the present invention, the base metal alloy resistor paste film is one of a copper-nickel film, a copper-manganese film, or a nickel-chromium (silicon) film.

[0024] According to the above embodiment of the present invention, the aluminum protective layer is one of an aluminum film, an aluminum alloy film, or an aluminum oxide film.

[0025] According to the above embodiment of the present invention, the aluminum alloy film is a copper aluminum alloy, and the aluminum oxide film is copper oxide.

[0026] According to the above embodiment of the present invention, after the folding process of the chip resistor process, a highly conductive metal tin is sputtered to connect to the internal base metal alloy resistor layer and form an ohmic contact so as to side guide, and then the subsequent standard process is completed according to the chip resistor process to fabricate the chip alloy resistor.

[0027] Hereinafter, the features and technical contents of the present invention will be described in detail with reference to the drawings. However, these drawings are for reference and explanation purposes only, and the present invention is not limited thereto. BEST MODE FOR CARRYING OUT THE INVENTION

[0028] Figures 1 to 10 are respectively a microstructural diagram of the present invention when tin is added to aluminum and sintered, a microstructural diagram of the present invention when copper tin is added to aluminum and sintered, a microstructural diagram of the present invention when an aluminum film is covered with a tin-copper film and sintered, a microstructural diagram of the present invention when an aluminum copper tin outer electrode of a ceramic element is produced using the new process of the present invention, a microstructural diagram of the present invention when the tin outer electrode of a ceramic element is produced using the new process of the present invention, a structural conceptual diagram of the present invention when a multilayer ceramic element is used to sinter tin outer electrodes, a structural conceptual diagram of the present invention when a multilayer ceramic element is used to directly sinter tin outer electrodes, a structural conceptual diagram of the front and back tin electrodes of a chip resistor according to the present invention, a microstructural diagram of the present invention when a protective layer of an alloy resistor is sintered in the atmosphere, and a side guide process and a microstructural conceptual diagram of the electrodes when an alloy resistor is sintered in the atmosphere according to the present invention. As shown in the figure, the present invention is a manufacturing method for sintering solderable base metal and alloy elements in air, and involves adding metallic aluminum powder to a printed thick-film base metal tin conductor paste film or base metal tin alloy conductor paste film, or first printing one layer of thick-film base metal tin conductor paste film or base metal tin alloy conductor paste film, and then printing one layer of thick-film aluminum protective layer on top of it, and then performing heat treatment at 300 to 600°C in air, utilizing the highly aerobic nature of the metallic aluminum powder or the aluminum protective layer to protect the base metal tin conductor paste film or base metal tin alloy conductor paste film. Furthermore, even if the base metal tin conductive paste film or base metal tin alloy conductive paste film is oxidized by sintering at high temperatures in the atmosphere, the strong recovery properties of the aluminum metal powder and the aluminum protective layer allow the oxidized base metal tin conductive paste film or base metal tin alloy conductive paste film to be restored to its metal or alloy state. Therefore, the base metal tin or tin alloy, which is easily oxidized by sintering at high temperatures in the atmosphere, can maintain its metal conductivity and alloy properties, thereby providing a thick-film base metal tin electrode or base metal tin alloy electrode with solderability and an improved electrode melting point.

[0029] According to the present invention, metal electrodes can be made solderable without the need to electroplate a single tin layer, and two methods are proposed for producing solderable electrodes using heat treatment instead of the electroplating process.

[0030] First, according to the present invention, a large amount of metal powder is directly added to the electrode, and since the metal electrode does not oxidize or melt into a liquid at the sintering temperature, it is necessary to prevent the metal powder from oxidizing during heat treatment in the atmosphere. Therefore, aluminum metal powder with a high oxidation formation enthalpy is added to protect the tin from oxidation, and since the metal powder has a low melting point, other metals, such as copper metal powder, are added to form a copper-tin alloy to improve its melting point.

[0031] Second, according to the present invention, tin is directly used as an electrode, and an aluminum film is directly coated on the tin electrode to prevent the tin electrode from being oxidized during heat treatment. In addition, to prevent the tin from melting into a liquid during heat treatment, a suitable metal such as copper is added to the tin film to form a tin-copper alloy, thereby increasing the melting point of the electrode.

[0032] The following examples are provided to illustrate the details and scope of the present invention, and the scope of the claims of the present invention is not limited thereby.

[0033] Tables 1 and 2 below show the resistance values ​​and resistance characteristics after thick conductive paste films are prepared by adding metallic aluminum powder to metallic copper and tin powder, then screen printing the thick films, and then sintering them in air at 300-600°C.

[0034] [Table 1]

[0035] As can be seen from Table 1, the oxidation resistance of the metal powder increases with the amount of aluminum metal powder added during heat treatment. By adding 40 wt% aluminum metal powder to 60 wt% metal powder, or by adding 30 wt% aluminum metal powder to 70 wt% metal powder, the tin-aluminum mixed conductor paste film can maintain high conductivity even when sintered at 600°C in air.

[0036] [Table 2]

[0037] As can be seen from Table 2, when metal powder is mixed with copper powder, the antioxidant ability during heat treatment increases with the addition of metallic aluminum powder. In particular, by adding 50 wt% metallic aluminum powder to 50 wt% metallic copper powder, or by adding 40 wt% metallic aluminum powder to 60 wt% metallic copper powder, the copper-aluminum mixed conductor paste film can maintain high conductivity even when sintered at 600°C in air.

[0038] Figure 1 shows the microstructure (1000x microscope magnification) of the metal powder when aluminum metal powder is added and sintered at 500°C and 600°C in air. It is clear that the aluminum metal powder has high aerobicity, and the tin can maintain its high electrical conductivity even when sintered at high temperatures in air.

[0039] Figure 2 shows the microstructure of aluminum powder mixed with copper powder at different sintering temperatures in air. Figure (a) shows the microstructure at 1000x magnification, Figure (b) shows the layered image taken with an energy dispersive spectrometer (EDS), and Figure (c) shows the material analysis. Due to the presence of highly aerobic aluminum powder, the resulting tin-copper alloys and tin and copper metals can maintain their high electrical conductivity even when sintered at high temperatures in air.

[0040] Figure 3 shows the microstructure of a printed tin metal film, sintered at 400°C under atmospheric conditions after an aluminum film or aluminum-related alloy (e.g., copper-aluminum) film is printed on top of it. Figure (a) is a 1000x magnification micrograph, and Figure (b) is an EDS layer image. Due to the high aerobicity and strong recovery properties of aluminum metal films and aluminum-related alloy (e.g., copper-aluminum) films, it is clear that the underlying tin metal film maintains its high metal conductivity even after high-temperature sintering under atmospheric conditions.

[0041] [Example 1] In a more specific embodiment of the present invention, the novel process can be applied to the outer electrodes of a ceramic block element, such as a GPS ceramic antenna, a negative temperature coefficient (NTC) thermistor, a positive temperature coefficient (PTC) thermistor, a voltage dependent resistor (VDR), or a safety capacitor.

[0042] According to the present invention, a conductive paste film made of a mixture of tin, aluminum, and copper is printed on both sides of the block-shaped ceramic element as the outer electrodes, and then heat-treated at 300 to 600°C under air, as shown in Figure 4.

[0043] In addition, tin electrodes are printed on both sides of the block-shaped ceramic element, and then an aluminum protective layer is printed on top of the tin electrodes, either on an aluminum film or an aluminum-related alloy (e.g., copper-aluminum) film. This is then heat-treated in air at 300-600°C, so that the upper aluminum electrode protects the lower tin or tin alloy electrode and prevents oxidation. This is shown in Figure 5, where (a) is a 1000x magnification microscopic structure diagram, and (b) is an EDS layer image.

[0044] Table 3 shows that when an aluminum-tin-related alloy (e.g., copper-tin-aluminum) film is thick-printed onto a block-shaped VDR element as the outer electrode, and then sintered under air to heat treat it at 300-600°C, the electrical and welding properties are excellent, resulting in excellent resistance characteristics.

[0045] [Table 3]

[0046] Table 4 shows the electrical and welding properties of a voltage-dependent resistor made by thick-printing a metal tin film or a tin alloy (e.g., tin-copper) film onto a disc-shaped voltage-dependent resistor, then thick-printing an aluminum metal film or an aluminum-related alloy (e.g., copper-aluminum) film on top of that, and finally heat-treating it by sintering at 300-600°C under air. The metal tin film covered with the aluminum metal film or tin alloy film has an extremely low resistance value, and the voltage-dependent resistor with an alloy tin film electrode covered with the aluminum metal film has excellent voltage-dependent resistor properties.

[0047] [Table 4]

[0048] [Example 2] According to a more specific embodiment of the present invention, the novel process can be applied to the outer electrodes of a multilayer ceramic element, such as a low temperature co-fired ceramic (LTCC), a multilayer ceramic capacitor (MLCC), a multilayer NTC element, or a multilayer VDR element.

[0049] 1. After high-temperature sintering of the multilayer ceramic co-fired element 11, a silver or copper paste immersion plating process is performed, followed by high-temperature sintering in air or nitrogen to form the outer terminal electrode 12. Conventionally, in order to weld the multilayer ceramic element to a circuit board, a nickel plating layer 13 or a tin electroplating layer 14 must be formed by a nickel plating or tin electroplating process, resulting in structures such as those shown in Figures 6 and 7(a). To avoid the environmental pollution caused by nickel plating or tin electroplating, the present invention uses tin immersion plating or aluminum immersion plating to form a tin layer 15 or an aluminum protective layer 16. The outer aluminum protective layer 16 is then removed by heat treatment and sintering at 300-600°C to form the sintered tin outer terminal electrode 17. By using the sintered tin layer instead of the conventional tin electroplating layer 14, structures such as those shown in Figures 6(b) and 6(c) can be obtained.

[0050] 2. After high-temperature sintering of the multilayer ceramic co-fired element 11, the tin layer 15 and aluminum protective layer 16 are formed directly by tin or aluminum immersion plating. Then, the outer aluminum protective layer 16 is removed by sintering heat treatment at 300-600°C. Instead of the sintered silver or copper outer electrodes, sintered tin outer electrodes 17 are formed. This not only allows connection to the internal electrodes 111, but also eliminates the need for a tin electroplating process and allows direct soldering onto a circuit board, resulting in the structures shown in Figures 7(b) and (c).

[0051] [Example 3] Chip resistor 1. The present invention applies a new process to chip resistor electrodes, as shown in Figure 8, where Figure (a) shows the conventional resistor terminal electrode structure, and Figures (b) and (c) show the new resistor terminal electrode structure of the present invention.

[0052] When manufacturing the front and back electrodes connected to the chip resistor or resistive layer, first, a tin film 21 connecting the resistive film 22 is printed, followed by printing an aluminum protective layer 23, which is a single layer of aluminum or aluminum alloy film. Heat treatment is then performed at 300-600°C, resulting in the formation of back tin electrodes 24 and front tin electrodes 25 that connect the resistive layer 26 and have high conductivity even when sintered in air, resulting in a structure as shown in Figure 8(b) and (c). This provides resistor characteristic stability equivalent to that of a front silver electrode 27, which has high conductivity when sintered in air. Furthermore, a nickel plating layer 28 and a tin electroplating layer 29, as shown in Figure 8(a), are formed without the need for an electroplating process.

[0053] 2. The present invention applies the new process to alloy chip resistors, as shown in Figure 9, where Figure (a) shows the microscopic structure at different temperatures (800°C / 10 min, 850°C / 10 min, 750°C / 10 min + 850°C / 10 min), and Figure (b) shows the EDS layer images of Figure (a) when processed at different temperatures.

[0054] (1) Protective layer First, a film of alloy resistor paste (e.g., copper-nickel, copper-manganese, nickel-chromium (silicon)) is printed, and then a thick aluminum film, aluminum alloy film (e.g., copper-aluminum), or aluminum oxide film is printed on the alloy resistor paste film as an aluminum protective layer. This protects the alloy resistor paste film from oxidation during high-temperature heat treatment at 500-1400°C, maintaining the high-performance resistance properties of the alloy resistor paste film. The aluminum protective layer on top forms insulation and has high thermal conductivity, as shown in Figure 9.

[0055] (2) Structure First, an alloy resistor paste (e.g., copper-nickel, copper-manganese, and nickel-chromium (silicon)) film 32 is printed on a substrate 31, and then an aluminum protective layer 33, which is a thick aluminum or aluminum alloy film (e.g., copper-aluminum) or aluminum oxide film that completely covers the underlying alloy resistor paste film, is printed on the alloy resistor paste film 32 to protect the alloy resistor paste film from oxidation during high-temperature heat treatment at 500 to 1400°C. Furthermore, to connect the alloy resistance layer 34, a highly conductive metal such as copper or tin is sputtered during the chip resistor folding process or side guide sputtering process, and the copper layer 35 or tin layer is used to connect the base metal alloy resistance layer 34 sintered in air. As shown in Figure 10, while a conventional chip alloy resistor made by copper sputtering further requires a nickel or tin electroplating process to form the element, a chip alloy resistor made by tin sputtering does not require nickel or tin electroplating to form the element. Figure 10 shows the structure of the side guide electrode of an alloy resistor sintered in air, where Figure (a) includes an etching process and Figure (b) does not. This novel structure allows chip resistors to be sintered in air, and its electrical properties are shown in Table 5.

[0056] [Table 5]

[0057] As described above, the method according to the present invention has the following technical features.

[0058] 1. By printing a thick film of base metal powder (e.g., nickel or copper) to which metal powder (10-50 wt%) and metallic aluminum powder (10-90 wt%) have been added, and then heat treating the resulting film at 300-600°C in air, oxidation of the base metals nickel, copper, and tin can be avoided, while at the same time the melting point of the tin alloy is improved, resulting in a thick base metal electrode film that has solderability and high functional properties.

[0059] 2. A layer of a base metal conductive paste film, such as tin, or a base metal alloy conductive paste film, such as a tin alloy (e.g., 10 to 90 wt% tin-copper), is thick-film printed on a ceramic substrate, and then a layer of thick-film printed aluminum protective layer of aluminum or an aluminum-related alloy (e.g., copper-aluminum) is printed on the base metal conductive paste film or base metal alloy conductive paste film. This prevents the base metal tin or copper from oxidizing and melting during heat treatment at 300 to 600°C in air, thereby producing a solderable tin or a thick-film base metal tin electrode film or tin alloy electrode film with high performance properties.

[0060] 3. The outer electrodes of dielectric ceramic safety capacitors and varistors require high conductivity as well as solderability. This can be achieved by adjusting the proportions of copper, tin (10-50wt%) and aluminum (10-90wt%) added.

[0061] 4. The outer electrodes of semiconducting ceramic NTC and PTC require high conductivity as well as solderability, and also need to form ohmic contact with the semiconducting ceramic. This can be achieved by adjusting the addition ratio of copper, nickel, tin (10-50wt%) and aluminum (10-90wt%), so that thick film electrodes with different work functions can form ohmic contact, thereby achieving conductive electrical properties and solderable electrodes.

[0062] 5. When manufacturing the outer electrodes of a multilayer ceramic co-fired element, after nickel plating, tin or copper-tin immersion plating is performed, and then aluminum is immersion plated to protect the tin. The tin or copper-tin is sintered by heat treatment (300-600°C) in air to remove the upper aluminum protective layer, and a sintered tin or tin-copper layer is formed in place of the tin electroplating layer.

[0063] 6. When manufacturing the outer electrodes of multilayer ceramic co-fired elements, instead of the existing high-temperature sintered silver electrodes or copper electrodes that require tin electroplating, tin or copper-tin immersion plating is performed, and then aluminum is immersion plated to protect the tin or tin-copper. The tin or copper-tin is sintered by heat treatment (300-600°C) in air. Then, instead of the existing outer electrodes made of sintered copper or silver and then nickel-plated or tin-plated, the upper aluminum protective layer is removed to form sintered tin or tin-copper outer electrodes.

[0064] 7. When fabricating a front electrode for connecting a chip resistor and a resistive layer, first print a layer of tin or copper-tin conductive paste film to connect the resistive film, then print an aluminum protective layer, which is a layer of aluminum film or an aluminum-related alloy (e.g., copper-aluminum) film, on top of that to protect the tin or copper-tin conductive paste film and prevent high-temperature oxidation, and then perform heat treatment (500 to 1400°C).

[0065] 8. First, a film of alloy resistor paste (such as copper-nickel, copper-manganese, or nickel-chromium (silicon)) is printed, and then a thick layer of aluminum film, aluminum-related alloy [such as aluminum-copper (10-90 wt%)] film, or aluminum-oxide mixture [such as aluminum-copper oxide (10-90 wt%)] film is printed on the alloy resistor paste film as an aluminum protective layer. This provides protection during heat treatment (500-1400°C), preventing oxidation of the copper-nickel-manganese series alloy resistor paste film and maintaining the high-performance resistance properties of the alloy resistor paste film. At the same time, the upper aluminum protective layer becomes a heat dissipation layer with insulating properties and high thermal conductivity after high-temperature sintering.

[0066] 9. For the chip alloy resistors that can be sintered under air, in order to obtain the properties of the alloy resistor, after the folding process of the chip resistor process, when the side guides are made, a highly conductive metal, such as copper, is sputtered to form an ohmic contact with the inner alloy resistor layer, such as copper-nickel, and then the subsequent standard processes for the chip resistor are carried out.

[0067] The present invention differs from existing technologies in the following technical features.

[0068] 1. Existing technology requires sintering in a restoring atmosphere (nitrogen or a nitrogen-hydrogen mixture) when heat treating base metal thick-film printed conductive copper, nickel, or copper-nickel alloy paste films. This prevents the base metal copper, nickel, or alloy from losing its functionality due to oxidation. Alternatively, sintering silver paste as the outer electrode in air provides good conductivity and adhesion, while also achieving good soldering properties.

[0069] In contrast to the above-mentioned existing technologies, the novel technology of the present invention protects base metal tin or tin alloys (e.g., copper-tin) by adding or covering them with aluminum powder or aluminum film, or aluminum-related alloy (e.g., copper-aluminum) film, which have high aerobicity and high recovery properties, and even if they are immediately subjected to high-temperature heat treatment in air, they do not lose their function due to tin oxidation during sintering.

[0070] 2. Existing multilayer ceramic elements are co-fired with the internal electrodes, and then the outer terminal electrodes are made through an immersion plating process, such as silver electrodes sintered under air or copper electrodes sintered in nitrogen, and then nickel or tin is plated through an electroplating process to protect the terminal electrodes and their good soldering properties.

[0071] In contrast to the above, the novel technology of the present invention protects a thick tin film with a thick aluminum film or an aluminum-related alloy (e.g., copper-aluminum) film, and then sinters the tin electrode instead of electroplating the tin electrode. This can replace the electroplated tin layer when forming the outer electrodes of a multilayer ceramic element, or can directly sinter tin outer electrodes instead of silver outer electrodes or copper outer electrodes of a multilayer ceramic element. This reduces the electroplating pollution process and satisfies environmental, social, and governance (ESG) requirements.

[0072] 3. When manufacturing the outer electrodes of existing ceramic elements, the properties of the sintered ceramic body change when the outer electrodes are sintered in a restoring atmosphere (e.g., chip resistors, NTC, PTC, VDR, and piezoelectric PZT), so nitrogen-sintered copper electrodes cannot be used.

[0073] In contrast to the above, the new technology of the present invention protects a thick copper electrode film with a thick aluminum film or an aluminum-related alloy (e.g., copper-aluminum) film and performs heat treatment under atmospheric conditions, so that copper electrodes can be fabricated using ceramic elements such as chip resistors, NTCs, PTCs, VDRs, and piezoelectric PZTs.

[0074] 4. Existing chip alloy resistors have a very low temperature coefficient of resistance, and are mainly made from air-sintered precious metal silver-palladium alloys or base metal copper-nickel alloys sintered under a restoring atmosphere of nitrogen (nitrogen and hydrogen).

[0075] In contrast to the above, the new technology of the present invention uses a thick aluminum film, an aluminum-related alloy (e.g., copper-aluminum) film, or an aluminum and oxide (e.g., copper oxide) film as a protective thick film when manufacturing a base metal alloy (e.g., copper-nickel, copper-manganese, nickel-chromium) resistor. In order to oxidize the base metal alloy, sintering is performed in an air atmosphere, thereby obtaining properties equivalent to those of base metal alloys sintered in a restoring atmosphere (e.g., copper-nickel, copper-manganese, and nickel-chromium).

[0076] As explained above, the present invention is a method for producing solderable base metal and alloy elements by sintering them under air, which effectively overcomes the drawbacks of the prior art. By producing electrodes for electronic elements using a heat treatment process instead of an electroplating process, the tin electroplating process is not required, and the electrodes become solderable electrodes with solderability and high performance properties. This makes the present invention more advanced and practical, and patent claims are filed in accordance with the law.

[0077] However, the above description is merely a preferred embodiment of the present invention, and the scope of the present invention is not limited thereto.

[0078] All equivalent changes and modifications made based on the claims and the contents of the specification of the present invention are included within the scope of the claims of the present invention. [Brief explanation of the drawings]

[0079] [Figure 1] FIG. 1 is a microstructure diagram of the aluminum of the present invention when tin is added and sintered. [Figure 2] FIG. 1 is a microstructure diagram of the aluminum of the present invention when copper tin is added and sintered. [Figure 3] 1 is a microstructure diagram of the tin copper film of the present invention when it is covered with an aluminum film and sintered. [Figure 4] 1 is a microstructure diagram of an aluminum copper tin outer electrode of a ceramic element fabricated by the novel process of the present invention. [Figure 5]1 is a microstructure diagram of the tin outer end electrode of a ceramic element fabricated by the novel process of the present invention. [Figure 6] 1 is a structural conceptual diagram of a multilayer ceramic element when sintering tin outer electrodes in the novel process of the present invention. [Figure 7] 1 is a structural conceptual diagram of a multilayer ceramic element in which tin outer electrodes are directly sintered in the novel process of the present invention. [Figure 8] 1 is a structural conceptual diagram of the front and back tin electrodes of a chip resistor according to the present invention. FIG. [Figure 9] 1 is a microstructure diagram of the protective layer of the air-sintered alloy resistor according to the present invention; FIG. [Figure 10] 1 is a schematic diagram of the side guide process of the air-sintered alloy resistor according to the present invention and the microstructure of its electrodes. [Explanation of symbols]

[0080] 11 Multilayer ceramic co-fired element 111 Internal electrode 12 Outer electrode 13 Nickel plating layer 14 Tin electroplating layer 15 Tin layer 16 Aluminum protective layer 17 Outer electrode of sintered tin layer 21 Tin Film 22 Resistive film 23 Aluminum protective layer 24 Backside tin electrode 25 Front tin electrode 26 Resistance layer 27 Front silver electrode 28 Nickel plating layer 29 Tin electroplating layer 31 PCB 32 Alloy Resistor Paste Film 33 Aluminum protective layer 34 alloy resistance layer 35 copper layer

Claims

1. A printed thick-film base metal tin conductor paste film or base metal tin alloy conductor paste film containing 10 wt% to 90 wt% metallic aluminum powder, When heat treatment is performed at 300 to 600°C under atmospheric conditions, the aluminum metal powder is easily oxidized, and the base metal tin conductor paste film or the base metal tin alloy conductor paste film is protected by the aluminum metal powder; The thick-film base metal tin electrode or base metal tin alloy electrode obtained by heat treatment of the base metal tin conductor paste film or the base metal tin alloy conductor paste film has solderability.

1. A method for producing a solderable electrode of base metal tin or a base metal tin alloy by heat treatment in air, comprising:

2. First, a layer of thick base metal tin conductor paste film or a layer of thick base metal tin alloy conductor paste film is printed, and then a layer of thick aluminum protective layer is printed thereon; The aluminum protective layer is easily oxidized when heat-treated at 300 to 600°C under atmospheric pressure, and the base metal tin conductive paste film or the base metal tin alloy conductive paste film is protected by the aluminum protective layer; The thick-film base metal tin electrode or base metal tin alloy electrode obtained by heat treatment of the base metal tin conductor paste film or the base metal tin alloy conductor paste film has solderability.

1. A method for producing a solderable electrode of base metal tin or a base metal tin alloy by heat treatment in air, comprising:

3. A method for producing a solderable electrode of base metal tin or a base metal tin alloy by heat treatment under atmospheric conditions according to claim 1 or claim 2, comprising: The base metal tin alloy conductor paste film is either a tin-copper alloy or a tin-nickel alloy.

1. A method for producing a solderable electrode of base metal tin or a base metal tin alloy by heat treatment in air, comprising:

4. A method for producing a solderable base metal tin or base metal tin alloy electrode by heat treatment under atmospheric conditions according to claim 2, comprising: The aluminum protective layer is either an aluminum film, an aluminum alloy film, or an aluminum oxide film.

1. A method for producing a solderable electrode of base metal tin or a base metal tin alloy by heat treatment in air, comprising:

5. A method for producing a solderable base metal tin or base metal tin alloy electrode by heat treatment under atmospheric conditions according to claim 4, comprising: the aluminum alloy film is a copper aluminum alloy; The aluminum oxide film is copper oxide 1. A method for producing a solderable electrode of base metal tin or a base metal tin alloy by heat treatment in air, comprising:

6. A method for producing an outer electrode on a block-shaped ceramic element, comprising the steps of: a thick base metal tin conductor paste film or a base metal tin alloy conductor paste film printed on the block-shaped ceramic element contains 10 wt% to 90 wt% of metallic aluminum powder; Heat treatment is carried out at 300 to 600°C in air. The block-shaped ceramic element is provided with outer electrodes of thick-film base metal tin electrodes or base metal tin alloy electrodes.

1. A method for producing an outer electrode on a block-shaped ceramic element.

7. A method for producing an outer electrode on a block-shaped ceramic element, comprising the steps of: First, a layer of thick base metal tin conductor paste film or a layer of thick base metal tin alloy conductor paste film is printed on the block-shaped ceramic element, and then a layer of thick aluminum protective layer is printed thereon; Heat treatment is carried out at 300 to 600°C in air. The block-shaped ceramic element is provided with outer electrodes of thick-film base metal tin electrodes or base metal tin alloy electrodes.

1. A method for producing an outer electrode on a block-shaped ceramic element.

8. A method for producing an outer electrode on the block-shaped ceramic element according to claim 6 or 7, comprising the steps of: The ceramic block element can be a GPS ceramic antenna, a negative temperature coefficient (NTC) thermistor, a positive temperature coefficient (PTC) thermistor, a voltage dependent resistor (VDR), or a safety capacitor.

1. A method for producing an outer electrode on a block-shaped ceramic element.

9. A method for forming an outer electrode on a multilayer ceramic element, comprising: The multilayer ceramic element is directly or immersion-plated with nickel, and then immersion-plated with base metal tin or a base metal tin alloy, and then immersion-plated with an aluminum protective layer, and then heat-treated at 300 to 600°C in air; The laminated ceramic element is provided with outer terminal electrodes of base metal tin electrodes or base metal tin alloy electrodes.

1. A method for forming an outer electrode on a multilayer ceramic element.

10. 10. The method for producing outer terminal electrodes in a multilayer ceramic element according to claim 9, The multilayer ceramic element is a low temperature co-fired ceramic (LTCC), a multilayer ceramic capacitor (MLCC), a multilayer NTC element, or a multilayer VDR element.

1. A method for forming an outer electrode on a multilayer ceramic element.

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