JP7780693B2 - Method for producing solderable electrodes of base metal tin or base metal tin alloy by heat treatment under atmospheric pressure - Google Patents

Description

The present invention relates to a manufacturing method for sintering solderable base metal and alloy elements under air, and in particular, a heat treatment process is performed instead of an electroplating process, and more particularly, a method for creating electronic element electrodes without the need for a tin electroplating process, and a method for creating solderable electrodes that have high-performance properties while retaining solderability.

Existing technology 1 allows for high-temperature heat treatment of thick-film printed precious metals such as silver and silver-palladium alloys in air, but precious metals and alloy materials are very expensive.

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. However, 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.

According to existing technology 3, existing electronic components use either precious metals sintered under air as in existing technology 1 above, 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.

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.

As mentioned above, whether sintering a noble metal electrode in air or a base metal electrode in a restoring atmosphere, solderability is achieved by electroplating a tin layer on the surface of the electrode in a tin electroplating process, allowing it to be bonded to an electronic circuit board using 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 single tin layer.

As mentioned above, solder paste is primarily made up of both flux and powder. Solder paste is inexpensive and has good conductivity, but it oxidizes easily during heat treatment and tends to clump together, meaning it cannot be used as an electrode. It can only be used to connect silver or copper electrodes.

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 a higher viscosity, better wettability, and melts faster, becoming finer, but it oxidizes easily and is more expensive. Therefore, in practical terms, conventional solder pastes cannot be made solderable without an electroplating process.

The inventors have conducted careful research to overcome the above drawbacks and, utilizing scientific theory, have proposed this invention, which effectively overcomes the drawbacks and has a rational design.

The main objective of the present invention is to provide a method for producing electronic devices that can solve the above-mentioned problems of the prior art, utilize a heat treatment process instead of an electroplating process, and do not require a tin electroplating process, while still maintaining high performance characteristics while providing solderability to the electrodes.

To achieve the above objectives, the present invention provides a method for sintering solderable base metal and alloy elements under air, in which a printed thick-film base metal tin conductor paste film or a base metal tin alloy conductor paste film is sintered with 10 to 90% By adding 50% by weight of metallic aluminum powder, or by first printing a thick layer of base metal tin or base metal tin alloy conductive paste film, and then printing a thick layer of aluminum protective layer on top of it, and then heat treating it in air at 300-600°C, the highly aerobic properties of the metallic aluminum powder or aluminum protective layer are utilized to protect the base metal tin or base metal tin alloy conductive paste film, preventing it from oxidizing during sintering in high-temperature air. Furthermore, after the base metal tin or base metal tin alloy conductive paste film is oxidized during sintering in high-temperature air, the strong recovery properties of the metallic aluminum powder or aluminum protective layer allow the oxidized base metal tin or base metal tin alloy conductive paste film to recover to its original metal or alloy state, resulting in a thick-film base metal tin or base metal tin alloy electrode with solderability and a high melting point.

In accordance with 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.

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.

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.

To achieve the above objective, 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 base metal tin alloy formed by sintering according to the above-mentioned method.

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.

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

In the above-described 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.

In 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 conductor paste film or a base metal tin alloy conductor paste film, immersion plating with an aluminum protective layer, and then heat treating the element in air to remove the aluminum protective layer by sintering.

In the above embodiment of the present invention, the outer electrodes are formed by high-temperature sintering of the multilayer ceramic co-fired element, followed by direct immersion plating with a base metal tin conductor paste film or a base metal tin alloy conductor paste film, followed by immersion plating with an aluminum protective layer, followed by heat treatment in air to remove the aluminum protective layer by sintering.

To achieve the above objectives, the present invention provides a chip resistor having at least a front electrode and a back electrode connected to a resistive layer, wherein 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.

To achieve the above objectives, the present invention provides a method for manufacturing chip alloy resistors with a base metal alloy resistive layer. First, a single layer of thick-film base metal alloy resistive paste film is printed, and then a second layer of thick-film aluminum protective layer is printed on top of that. Following the chip resistor process, heat treatment is performed in air at 500-1400°C. The highly aerobic nature of the aluminum protective layer protects the base metal alloy resistive paste film from oxidation during sintering in high-temperature air. Furthermore, a heat dissipation layer with high thermal conductivity and insulating properties is formed on the aluminum protective layer, resulting in a thick-film base metal alloy resistive layer that is solderable and can maintain its resistive properties.

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.

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.

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.

According to the above embodiment of the present invention, after the folding step of the chip resistor process, highly conductive metal tin is sputtered to connect to the internal base metal alloy resistor layer and form an ohmic contact for side guiding. Then, the subsequent standard steps are completed according to the chip resistor process to produce the chip alloy resistor.

The features and technical content of the present invention will be explained in detail below with reference to the drawings. However, these drawings are for reference and explanation purposes only and the present invention is not limited thereby.

Figures 1 to 10 are, respectively, microstructural diagrams of the present invention when tin is added to aluminum and sintered, microstructural diagrams of the present invention when copper-tin is added to aluminum and sintered, microstructural diagrams of the present invention when an aluminum film is covered with a tin-copper film and sintered, microstructural diagrams 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, microstructural diagrams of the present invention when tin outer electrodes of a ceramic element are produced using the new process of the present invention, structural conceptual diagrams of the present invention when sintering tin outer electrodes using a multilayer ceramic element using the new process of the present invention, structural conceptual diagrams of the present invention when sintering tin outer electrodes directly using a multilayer ceramic element using the new process of the present invention, structural conceptual diagrams of the front and back tin electrodes of a chip resistor according to the present invention, microstructural diagrams of the present invention when sintering a protective layer of an alloy resistor under atmospheric conditions, and a side guide process and a conceptual diagram of the microstructural structure of the electrodes when sintering an alloy resistor under atmospheric conditions according to the present invention. As shown in the figure, the present invention is a method for sintering solderable base metal and alloy elements in air, by adding metallic aluminum powder to a printed thick-film base metal tin conductor paste film or base metal tin alloy conductor paste film, or by 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 a 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. This prevents oxidation during sintering in high-temperature air. Alternatively, after the base metal tin conductor paste film or base metal tin alloy conductor paste film is oxidized by sintering in high-temperature air, the strong recovery properties of the metal aluminum powder and the aluminum protective layer allow the oxidized base metal tin conductor paste film or base metal tin alloy conductor paste film to recover to its metal or alloy state. This allows base metal tin and tin alloys, which are easily oxidized by high-temperature sintering in air, to maintain their metal conductivity and alloy properties, resulting in a thick-film base metal tin electrode or base metal tin alloy electrode with solderability and an improved electrode melting point.

According to the present invention, metal electrodes can be soldered without the need for electroplating a single tin layer. Therefore, two methods are proposed for producing solderable electrodes using heat treatment instead of the electroplating process.

First, according to the present invention, a large amount of metal powder is added directly to the electrode. Furthermore, 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, which has a high oxidation enthalpy, is added to protect the tin from oxidation. Furthermore, due to the low melting point of the metal powder, other metals, such as copper metal powder, are added to form a copper-tin alloy, which raises its melting point.

Second, according to the present invention, tin is used directly 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. Furthermore, 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.

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

Tables 1 and 2 below show the resistance values and resistance characteristics after a thick conductive paste film was made by adding aluminum metal powder to metal powder, copper metal, and tin metal, then screen-printed onto the thick film and then subjected to a heat treatment of sintering at 300-600°C under air.

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

As can be seen from Table 2, when metal powder is mixed with copper powder, the antioxidant ability during heat treatment increases with the amount of metallic aluminum powder added. 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.

Figure 1 shows the microstructure (1000x microscope magnification) of the metal powder when aluminum metal powder is added and sintered at temperatures of 500°C and 600°C in air. It is clear that the highly aerobic aluminum metal powder allows the tin metal to maintain its high conductivity even when sintered at high temperatures in air.

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

Figure 3 shows the microstructure of an aluminum film or aluminum-related alloy (e.g., copper-aluminum) film printed on top of a printed metal tin film, sintered at 400°C in air. Figure (a) is a 1000x magnification microscopic structure image, and Figure (b) is an EDS layered image. Because metal aluminum film and aluminum-related alloy (e.g., copper-aluminum) film have high aerobicity and strong recovery properties, it is clear that the underlying metal tin film can maintain its high metal conductivity even when sintered at high temperatures in air.

[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.

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

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 electrode, 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, allowing the upper aluminum electrode to protect the lower tin or tin alloy electrode and prevent oxidation. The result is shown in Figure 5, where (a) is a 1000x magnification microscopic structural image, and (b) is an EDS layered image.

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 heat-treated at 300-600°C by sintering under air, the electrical and welding properties are excellent, resulting in excellent resistance characteristics.

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 a metal aluminum film or an aluminum-related alloy (e.g., copper-aluminum) film on top of that, and finally sintering it in air at 300-600°C. The metal tin film covered with the metal aluminum film or tin alloy film has extremely low resistance, while the voltage-dependent resistor with an alloy tin film electrode covered with a metal aluminum film has excellent voltage-dependent resistor properties.

[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.

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 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 using a nickel plating or tin electroplating process, resulting in structures such as those shown in Figures 6 and 7(a). To avoid the environmentally polluting effects of nickel plating or tin electroplating, the present invention forms a tin layer 15 or an aluminum protective layer 16 using tin immersion plating or aluminum immersion plating. The outer aluminum protective layer 16 is then removed by heat treatment and sintering at 300-600°C, forming a sintered tin layer outer 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.

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).

[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.

When fabricating the front and back electrodes connected to the chip resistor or resistive layer, a tin film 21 is first printed to connect the resistive film 22, followed by printing an aluminum protective layer 23, which is a single layer of aluminum or aluminum alloy film. Heat treatment at 300-600°C then forms the back tin electrode 24 and front tin electrode 25 that connect the resistive layer 26 and have high conductivity even when sintered in air, resulting in a structure like that shown in Figure 8(b) and (c). This provides stable resistor characteristics equivalent to the 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.

2. This 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 image when processed at the different temperatures shown in Figure (a).

(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 layer of 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 provides insulation and high thermal conductivity, as shown in Figure 9.

(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. Then, an aluminum protective layer 33 is printed on the alloy resistor paste film 32. This thick aluminum or aluminum alloy film (e.g., copper-aluminum) or aluminum oxide film completely covers the underlying alloy resistor paste film, protecting the alloy resistor paste film from oxidation during high-temperature heat treatment at 500-1400°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.

As explained above, the method of the present invention has the following technical features:

1. By printing a thick film of base metal powder (e.g., nickel or copper) with metal powder (10-50 wt%) and metallic aluminum powder (10-90 wt%) added, and then heat treating it in air at 300-600°C, 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 increased, resulting in a thick base metal electrode film that has solderability and high functional properties.

2. A layer of base metal conductor paste film, such as tin, or a base metal alloy conductor paste film, such as a tin alloy (e.g., 10 to 90 wt% tin-copper), is thick-film printed onto 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 top of the base metal conductor paste film or base metal alloy conductor 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.

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 addition ratio of copper, tin (10-50wt%), and aluminum (10-90wt%).

4. In addition to high conductivity, the outer electrodes of semiconductor ceramic NTC and PTC must also be solderable. They must also be able to form ohmic contacts with the semiconductor ceramic. This is achieved by adjusting the proportions of copper, nickel, tin (10-50 wt%), and aluminum (10-90 wt%) added, allowing thick-film electrodes with different work functions to form ohmic contacts, achieving conductive electrical properties and solderability.

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 then sintered by heat treatment (300-600°C) in air, removing the upper aluminum protective layer and forming a sintered tin or tin-copper layer in place of the electroplated tin layer.

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, followed by immersion plating with aluminum to protect the tin or tin-copper. The tin or copper-tin is then sintered by heat treatment in air (300-600°C). 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.

7. When creating a front electrode to connect 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 an 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 (500-1400°C).

8. First, an alloy resistor paste (e.g., copper-nickel, copper-manganese, or nickel-chromium (silicon)) film is printed, and then a thick aluminum film, an aluminum-related alloy [e.g., aluminum-copper (10-90 wt%)] film, or an aluminum-oxide mixture [e.g., aluminum-copper oxide (10-90 wt%)] film is printed on top of 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.

9. For the chip alloy resistors that can be sintered under air, as described above, after the folding process of the chip resistor process, when the side guides are made, an ohmic contact is formed between a highly conductive metal, such as copper, and the inner alloy resistor layer, such as copper-nickel, by sputtering, in order to derive the alloy resistor characteristics. Then, the subsequent standard processes for the chip resistor are carried out.

The technical features of this invention differ from existing technologies as follows:

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. 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 soldering properties while maintaining good electrical conductivity and adhesion.

In contrast to the above-mentioned existing technologies, the new 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 an aluminum-related alloy (e.g., copper-aluminum) film, which has high aerobicity and high recovery properties, and even when immediately subjected to high-temperature heat treatment in air, the functionality is not lost due to tin oxidation during sintering.

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

In contrast to the above, the new 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 it. This can replace the electroplated tin layer when creating 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, thereby reducing the electroplating pollution process and satisfying environmental, social, and corporate governance (ESG) requirements.

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, NTCs, PTCs, VDRs, and piezoelectric PZTs), so nitrogen-sintered copper electrodes cannot be used.

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 in air, making it possible to create copper electrodes using ceramic elements such as chip resistors, NTCs, PTCs, VDRs, and piezoelectric PZTs.

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

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 base metal alloy (e.g., copper-nickel, copper-manganese, nickel-chromium) resistors. Sintering in an air atmosphere oxidizes the oxide, resulting in properties equivalent to those sintered in a restoring atmosphere (e.g., copper-nickel, copper-manganese, and nickel-chromium).

As explained above, the present invention is a manufacturing method for sintering solderable base metal and alloy elements under air, which effectively overcomes the drawbacks of the prior art. By manufacturing electronic element electrodes using a heat treatment process instead of an electroplating process, the tin electroplating process is eliminated, 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.

However, the above description is a preferred embodiment of the present invention, and the scope of the present invention is not limited thereby.

All equivalent changes and modifications made based on the scope of the claims and the contents of the specification of the present invention are included within the scope of the claims of the present invention.

FIG. 1 is a microstructure diagram of the aluminum of the present invention when tin is added and sintered. FIG. 1 is a microstructure diagram of the aluminum of the present invention when copper tin is added and sintered. 1 is a microstructure diagram of the tin copper film of the present invention when it is covered with an aluminum film and sintered. 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. 1 is a microstructure diagram of the tin outer end electrode of a ceramic element fabricated by the novel process of the present invention. 1 is a structural conceptual diagram of a multilayer ceramic element when sintering tin outer electrodes in the novel process of the present invention. 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. 1 is a structural conceptual diagram of the front and back tin electrodes of a chip resistor according to the present invention. FIG. 1 is a microstructure diagram of the protective layer of the air-sintered alloy resistor according to the present invention; FIG. 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.

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 (10)

A printed thick-film base metal tin conductor paste film or base metal tin alloy conductor paste film is added with 10 wt% to 90 wt % of 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 : 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 pressure 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 : 3. The method for producing a solderable electrode of base metal tin or base metal tin alloy by heat treatment under atmospheric pressure according to claim 2 ,
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. The method for producing a solderable electrode of base metal tin or base metal tin alloy by heat treatment under atmospheric pressure according to claim 4 ,
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 : 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 . 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. The method for producing an outer electrode on the block-shaped ceramic element according to claim 6 or 7 ,
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 . A method for forming an outer electrode on a multilayer ceramic element, comprising the steps of:
The multilayer ceramic element is directly or immersion-plated with nickel , then immersion-plated with a base metal tin or a base metal tin alloy , and then immersion-plated with an aluminum protective layer , followed by heat treatment 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. The method for producing outer terminal electrodes in a multilayer ceramic element according to claim 9 ,
The method for forming an outer electrode on a multilayer ceramic element is characterized in that the multilayer ceramic element is a low temperature co-fired ceramic (LTCC), a multilayer ceramic capacitor (MLCC), a multilayer NTC (multilayer NTC) element, or a multilayer VDR (multilayer VDR) element.