A process for producing an alloy conductor having improved electrical conductivity

Abstract

The application discloses a preparation process of an alloy conductor with improved conductivity, which comprises the following steps: the alloy conductor passes through a passivation tank; after being passivated, the alloy conductor passes through a dust-free air blowing tank, and a large amount of moisture on the surface of the conductor is removed through air blowing, and then the conductor is dried through an electric drying device; the dried alloy conductor passes through a conductive adhesive storage tank to coat a conductive adhesive layer; the alloy conductor coated with the conductive adhesive layer passes through an electrostatic powder spraying device to spray silver powder on the conductive adhesive layer; and the alloy conductor with the adhered silver powder enters a pre-solidification oven to be pre-solidified. The application improves the conductive performance of the linear conductor by spraying silver powder, mechanically coating and solidifying on the surface of the linear conductor to form a silver adhesive composite layer. Moreover, the method does not produce a large amount of waste water, only a small amount of waste water is produced in the passivation process, and the waste liquid treatment mode is simpler and easier to meet the discharge requirements compared with the electroplating silver process and the chemical silver plating process.

Description

Technical Field

[0001] This invention relates to the preparation process of alloy conductors, and more specifically to a preparation process for alloy conductors with improved conductivity. Background Technology

[0002] There are many existing technologies for improving the conductivity of alloy conductors, such as electroplating silver, electroless silver plating, PVD physical vapor deposition, hot-dip silver plating, and nano-silver paste coating. All of these methods can improve the conductivity of the copper substrate; however, these processes are relatively complex and each has its own drawbacks. While electroplating silver is a mature process that produces a uniform and strong coating, it requires initial acid pickling. The wastewater from this pickling process needs to be treated by water treatment equipment before discharge, and the electroplating solution contains cyanide. Cyanide plating solutions are toxic and require environmentally friendly treatment, while cyanide-free solutions are more expensive and require high process stability. This results in poorer environmental performance, necessitating significant investment in environmental treatment equipment to improve environmental friendliness. Furthermore, electroplating produces a porous silver coating with low long-term corrosion resistance. While chemical silver plating is more environmentally friendly than electroplating, its wastewater contains formaldehyde, ammonia, silver ions, and organic matter, requiring multi-step treatment. High silver recovery rates are also crucial; failure to meet regulatory requirements can lead to wastewater discharge problems. The problems with excessive silver content are more significant than simply high production costs and low silver utilization. Furthermore, the poor stability of the plating solution necessitates real-time monitoring, resulting in slow plating speeds and hindering production efficiency. PVD (Physical Vapor Deposition) is generally suitable for high-end products like those in the aerospace field, but it's unsuitable for general cable conductor production due to its large equipment investment, space requirements, and slow production speed caused by the continuous passage of wires through a vacuum chamber. Hot-dip silver plating requires high temperatures, which can soften the copper substrate during annealing, and it consumes a large amount of silver, leading to extremely high production costs. Nano-silver paste coating, an emerging technology, is more suitable for flexible electronics and printed circuits, but not for power cable conductors, primarily due to its poor conductivity improvement. To address these issues, this invention proposes a process for preparing alloy conductors with improved conductivity. This process generates minimal wastewater and, through spraying, mechanical coating, and curing, coats the surface of the linear conductor with a silver paste composite layer, thereby improving its conductivity. Summary of the Invention

[0003] To solve the above-mentioned technical problems, this invention patent proposes a process for preparing an alloy conductor with improved conductivity, which includes: a process of passing the alloy conductor through a passivation groove to form a protective film on the surface of the alloy conductor.

[0004] After passivation, the conductor passes through a clean air blowing box to remove a large amount of moisture from its surface, and then is dried by an electric drying device.

[0005] The process of passing the dried alloy conductor through a conductive adhesive storage box to coat it with a conductive adhesive layer; the process of passing the alloy conductor coated with the conductive adhesive layer through an electrostatic powder spraying device to spray silver powder onto the conductive adhesive layer.

[0006] The process includes the pre-curing of the alloy conductor with silver powder adhering to it in a pre-curing oven and the rounding process. It also includes the process of the rounded conductor entering a complete drying and curing oven for complete curing and the process of shaping it after curing using a multi-mode shaping wheel. After the alloy conductor is shaped, it is wound up by a winding device.

[0007] Preferably, the process of coating the conductive adhesive layer also includes passing the alloy conductor with the conductive adhesive layer through an inner ring tooth mold to form a gear shape with toothed grooves on the alloy conductor, and then passing the gear shape with toothed grooves through an electrostatic powder spraying device to spray silver powder onto the conductive adhesive layer, so that silver powder adheres to both the inside of the toothed grooves and the teeth.

[0008] Preferably, the inner ring tooth mold is disposed between the conductive adhesive storage box and the box containing silver powder.

[0009] Preferably, before the alloy conductor with silver powder adhering to it enters the complete drying and curing box, it needs to pass through the inner conical rounding mold to round the gear-shaped conductive adhesive layer. This allows the gear-shaped conductive adhesive to be squeezed and filled into the tooth groove, thereby coating the silver powder in the tooth groove onto the alloy conductor and forming a silver adhesive composite layer on the alloy conductor.

[0010] Preferably, the multi-mode shaping wheel consists of several guide wheels with wire grooves, and the width of the wire groove on each subsequent guide wheel is smaller than the width of the wire groove on the preceding guide wheel.

[0011] Preferably, the silver powder is selected from one or more combinations of silver-coated copper powder, spherical silver powder, and flake silver powder.

[0012] Preferably, the conductive adhesive is selected from silver-filled silicone conductive adhesive or epoxy-based conductive adhesive.

[0013] Preferably, the alloy conductor is a wire conductor made from silver-copper alloy, chromium-zirconium copper alloy, or oxygen-free copper alloy.

[0014] Preferably, the conductive adhesive layer has a thickness of 5-30 μm, a viscosity of 3000-5000 mPa·s, and the amount of silver powder used is 0.1-0.25 g / m.

[0015] Preferably, the temperature in the pre-curing process is 25–80°C, and the temperature in the complete curing process is 120–180°C.

[0016] The technical advantages of this invention are as follows: It improves the conductivity of linear conductors by coating a layer of silver paste composite on the surface of the linear conductor through processes such as silver powder spraying, mechanical coating and curing; moreover, this method does not generate a large amount of wastewater, only a small amount of wastewater is generated during the passivation process, and the wastewater treatment method is simpler and easier to meet the discharge requirements compared with the wastewater generated by electroplating silver process and chemical silver plating process.

[0017] The conductive adhesive is partially cured by a pre-curing process before the rounding mold is formed, ensuring that the adhesive layer has initial mechanical strength to fix the silver powder and prevent the silver powder from falling off during the rounding process, while retaining a certain degree of flexibility for subsequent rounding and shaping.

[0018] The conductive adhesive is formed into a gear-like shape with toothed grooves on the alloy conductor using an inner ring toothed mold. This allows for the application of a large amount of silver powder to both the grooves and the teeth during silver powder spraying. The adhesive layer at the grooves formed by the inner ring toothed mold is thinner, making the silver powder adhere more closely to the alloy conductor. When the conductive adhesive passes through an inner conical rounding mold, the conical structure of the channel from the inlet to the outlet gradually reduces the inner diameter of the channel. This causes the toothed conductive adhesive to come into contact with the channel, creating a compressive force that fills the grooves and coats the silver powder within them onto the conductor. By combining silver powder and conductive adhesive, cracks and pores on the wire surface can be filled, increasing the effective conductive area and improving conductivity. Furthermore, using silver-filled silicone conductive adhesive can also improve the oxidation resistance of the copper wire.

[0019] The purpose of shaping with multi-mode shaping wheels is to utilize the fact that the width of the wire groove on the subsequent guide wheel is smaller than the width of the wire groove on the previous guide wheel, so that the concentricity of the rounded linear conductor can be kept consistent after being compressed, thereby improving the consistency of the shape and size of the linear conductor. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the planar structure of an inner ring tooth mold;

[0021] Figure 2 This is a schematic diagram of the structure of an inner conical rounding mold. Detailed Implementation

[0022] The following description, in conjunction with the accompanying drawings, further illustrates the preparation process of an alloy conductor for improving conductivity as described in this invention patent.

[0023] In one embodiment, see Figures 1-2In preparing the alloy conductor, copper wire made of silver-copper alloy is selected as the linear conductor and passed through a passivation groove to form a protective film on the surface of the linear conductor; then it passes through a dust-free air blowing box, and air is blown through the air nozzles in the dust-free air blowing box to remove a large amount of moisture from the surface of the conductor, and then it is dried by an electric drying device. The electric drying device has been published in a utility model patent with publication number CN212434357U and publication date January 29, 2021. Therefore, the electric drying device will not be described in this patent.

[0024] After drying, the linear conductor is passed through a storage box coated with a conductive adhesive layer of silver-filled silicone conductive adhesive. Then, the alloy conductor coated with the conductive adhesive layer is passed through an inner ring-tooth mold, forming a gear-like structure with grooves on the linear conductor. The gear-like linear conductor with grooves is then passed through an electrostatic powder coating device to spray silver-coated copper powder onto the conductive adhesive layer, ensuring that silver powder adheres to both the grooves and the teeth. The silver powder used is either silver-coated copper powder or a mixture of 70% silver-coated copper powder and 30% spherical silver powder by weight. It is important to note that at least three spray guns of the electrostatic powder coating device should be arranged in a ring around the wheel-like linear conductor, with a distance of 150-250 mm from the linear conductor to ensure uniform silver powder coating. The humidity of the environment must be controlled during spraying, preferably ≤50% RH, to prevent silver powder oxidation. Additionally, the viscosity of the silver-filled silicone conductive adhesive must be maintained at 3000-5000 mPa·s.

[0025] The wire conductor with silver powder adhering to it is placed in a pre-curing oven for pre-curing. Since silver-filled silicone conductive adhesive is used, the pre-curing temperature is 25~30℃. If epoxy conductive adhesive is used, the pre-curing temperature is 60~75℃. The pre-curing process partially cures the adhesive layer, ensuring that the adhesive layer has the initial mechanical strength to fix the silver powder, while retaining a certain degree of flexibility for subsequent rounding and shaping.

[0026] The pre-cured linear conductor passes through an inner conical rounding mold to round the gear-shaped conductive adhesive layer. During the rounding process, the gear-shaped conductive adhesive layer contacts the channel inside the inner conical rounding mold, causing the gear-shaped conductive adhesive to be squeezed and filled into the tooth grooves. This coats the silver powder in the tooth grooves onto the linear conductor, resulting in an uncured silver paste composite layer covering the alloy conductor. The linear conductor with the silver paste composite layer is then fully cured in a second oven. After curing, it is shaped by a multi-mold forming wheel and then wound up by a winding device. The temperature in the second oven should be maintained at 80–120°C during drying and curing. When using epoxy-based conductive adhesive, the temperature in the second oven should be maintained at 120–180°C. The amount of silver powder used in the above process should be controlled at 0.1–0.15 g / m. The thickness of the conductive adhesive layer is 15–25 μm.

[0027] In another embodiment, when copper wire made of chromium-zirconium-copper alloy is selected as the linear conductor, the conductive adhesive used should be epoxy-based conductive adhesive, and all silver powder should be spherical silver powder. This is because the conductivity of copper wire made of most chromium-zirconium-copper alloys is lower than that of copper wire made of silver-copper alloys, while the conductivity of epoxy-based conductive adhesive and spherical silver powder is higher than that of silver-filled silicone conductive adhesive and silver-coated copper powder, respectively. The amount of silver powder used is 0.2 to 0.25 g / m. Due to the increased amount of silver powder, the thickness of the conductive adhesive layer is 20-30 μm to ensure better coating of the silver powder.

[0028] The inner conical rounding mold and the inner ring tooth mold used in the above two embodiments should be equipped with a water-cooling heat dissipation mechanism to avoid overheating due to friction, which could cause the conductive adhesive to clog the mold.

[0029] The production process and preparation principle of this invention are completely different from those of the prior art. In this invention, conductive adhesive is first coated onto the conductor, and then the conductive adhesive is formed into a gear shape. The purpose is to allow silver powder to adhere in the grooves and contact the linear conductor. Then, the silver powder is coated onto the linear conductor by using an inner conical mold to round it off. Since both silver powder and conductive adhesive are conductive, the conductivity of the linear conductor can be improved. Moreover, the production cost is lower and more environmentally friendly than that of the prior art.

[0030] The scope of protection of this invention patent is not limited to the above embodiments and their variations. Conventional modifications and substitutions made by those skilled in the art based on the content of these embodiments are all within the scope of protection of this invention patent.

Claims

1. A process for preparing an alloy conductor with improved conductivity, characterized by: The process of passing an alloy conductor through a passivation trench to form a protective film on the surface of the alloy conductor, wherein the alloy conductor is selected from silver-copper alloys or wire conductors made of chromium-zirconium copper. After passivation, the conductor passes through a clean air blowing box to remove a large amount of moisture from its surface, and then is dried by an electric drying device. The process of passing the dried alloy conductor through a conductive adhesive storage box and coating it with a conductive adhesive layer; The process involves passing an alloy conductor coated with a conductive adhesive layer through an electrostatic powder coating device to spray silver powder onto the conductive adhesive layer. During the silver powder spraying process, the humidity in the environment must be controlled to be ≤50% RH to prevent the silver powder from oxidizing. The process includes a pre-curing process where the alloy conductor with silver powder adheres to it enters a pre-curing oven for pre-curing and a rounding process. It also includes a process where the rounded conductor enters a second oven for complete curing and a process where it is shaped by a multi-die forming wheel after curing. After the alloy conductor is shaped, it is wound up by a winding device. The pre-curing process partially cures the conductive adhesive layer before the rounding die, ensuring the adhesive layer has initial mechanical strength to fix the silver powder and prevent it from falling off during rounding, while retaining a certain degree of flexibility for subsequent rounding. The process of coating the conductive adhesive layer also includes passing the alloy conductor with the conductive adhesive layer through an inner ring toothed die to form a gear-shaped conductive adhesive with grooves on the alloy conductor. After forming the gear-shaped conductive adhesive, silver powder is sprayed onto the conductive adhesive layer using an electrostatic powder spraying device, ensuring that silver powder adheres to both the grooves and the teeth. Before entering the second oven, the alloy conductor with silver powder adheres to it must first pass through an inner conical rounding die to round the gear-shaped conductive adhesive layer, causing the gear-shaped conductive adhesive to be squeezed. After pressing, the conductive adhesive is filled into the toothed grooves, thereby coating the silver powder inside the grooves onto the alloy conductor, forming a silver paste composite layer on the alloy conductor. The conductive adhesive is selected from silver-filled silicone conductive adhesive or epoxy-based conductive adhesive. An inner ring toothed mold forms a gear-shaped conductive adhesive with toothed grooves on the alloy conductor, ensuring that a large amount of silver powder is sprayed onto both the grooves and the teeth during silver powder spraying. The adhesive layer at the grooves formed by the inner ring toothed mold is thinner, allowing the silver powder to adhere more closely to the alloy conductor. When it passes through an inner conical rounding mold, the channel within the mold has a conical structure from the inlet to the outlet, causing the inner diameter of the channel to gradually decrease. This brings the toothed conductive adhesive into contact with the channel within the mold, creating a compressive force that fills the toothed conductive adhesive into the grooves, thus coating the silver powder inside the grooves onto the wire conductor. By combining silver powder and conductive adhesive, cracks and pores on the wire surface are filled, thereby increasing the effective conductive area and improving conductivity.

2. The preparation process of an alloy conductor with improved conductivity as described in claim 1, characterized in that: The multi-mode shaping wheel consists of several guide wheels with wire grooves, and the width of the wire groove on each subsequent guide wheel is smaller than the width of the wire groove on the preceding guide wheel.

3. The preparation process of an alloy conductor with improved conductivity as described in claim 1, characterized in that: The silver powder is selected from one or more combinations of silver-coated copper powder and spherical silver powder.

4. The preparation process of an alloy conductor with improved conductivity as described in claim 1, characterized in that, The conductive adhesive layer has a thickness of 5-30 μm and a viscosity of 3000-5000 mPa·s, and the amount of silver powder used is 0.1-0.25 g / m.

5. The preparation process of an alloy conductor with improved conductivity as described in claim 1, characterized in that, The temperature in the pre-curing process is 25–80°C, and the temperature in the complete curing process is 80–180°C.

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