Preparation process of alloy conductor capable of improving electric conductivity

Abstract

The invention discloses a preparation process of an alloy conductor capable of improving electric conductivity. The preparation process comprises the following steps: enabling the alloy conductor to pass through a passivation tank; after passivation, the conductor passes through a dust-free air blowing box, 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 box and is coated with a conductive adhesive layer; enabling the alloy conductor coated with the conductive adhesive layer to pass through electrostatic powder spraying equipment, and spraying silver powder on the conductive adhesive layer; according to the invention, the surface of the linear conductor is coated with a silver colloid composite layer on line through the processes of silver powder spraying, mechanical coating, curing and the like, so that the conductivity of the linear conductor is improved; and in addition, a large amount of waste water cannot be generated in the mode, only a small amount of waste water is generated in the passivation process, and compared with the electrosilvering process, the waste liquid treatment mode generated in the chemical silvering process is simpler, and the emission requirement can be met more easily.

Description

Technical Field

[0001] The invention relates to a preparation process of an alloy conductor, in particular to a preparation process of an alloy conductor with improved electrical conductivity. Background Art

[0002] There are many processes for improving the conductivity of alloy conductors in the existing technology, such as electroplating silver process, chemical silver plating process, PVD physical vapor deposition process, hot dip silver plating and nano silver paste coating process. The above methods can improve the conductivity of copper substrate; however, these processes are relatively complicated and have corresponding disadvantages. Although the electroplating silver process is relatively mature and the coating is relatively uniform and has strong adhesion, it needs to be pickled in the early stage. The waste liquid after the pickling process needs to be treated by water treatment equipment before it can be discharged, and the plating solution contains cyanide. Cyanide plating solution is toxic, so it also needs environmental protection treatment. Cyanide-free plating solution is expensive and requires high process stability. Therefore, its production is less environmentally friendly. In order to improve environmental protection, a large amount of environmental protection treatment equipment needs to be invested. In addition, the porosity of the electroplated silver coating is high, and its long-term corrosion resistance is not high. Although the chemical silver plating process is better than the electroplating silver method in terms of environmental protection, its waste liquid contains formaldehyde, ammonia, silver ions and organic matter, and still requires multi-step treatment. In addition, the silver recovery rate is high. If the recovery rate does not meet the relevant regulatory requirements, it will lead to wastewater discharge. The problem of excessive discharge is more important. Not only is its production cost high, but the utilization rate of silver is also low. In addition, due to the poor stability of the plating solution, real-time monitoring is required, so its plating speed is slow, which is not conducive to improving production efficiency. The PVD physical vapor deposition process is generally suitable for high-end products such as products in the aerospace field. Its process is not suitable for the production of general cable conductors because its equipment investment is large, the equipment occupies a large amount of factory space, and the wire has to pass through the vacuum chamber continuously, and the production speed is also slow. The problem of the hot-dip silver process is that it needs to be carried out in a high-temperature environment, which easily leads to annealing and softening of the copper substrate. In addition, the silver consumption of this method is very large, so its production cost is extremely high. The emerging process of nano-silver paste coating is more suitable for the fields of flexible electronics and printed circuits, but not for the field of power cable conductors. The biggest problem is its poor performance in improving conductivity. Based on the above problems, the present invention proposes a preparation process for alloy conductors with improved conductivity, which basically does not produce a large amount of wastewater and coats a layer of silver glue composite layer on the surface of the linear conductor through spraying, mechanical coating and curing processes to improve the conductive performance of the linear conductor. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention proposes a process for preparing an alloy conductor with improved conductivity, which includes: a process of passing the alloy conductor through a passivation tank to form a protective film on the surface of the alloy conductor; After passivation, the conductor passes through a dust-free air blowing box to remove a large amount of moisture on the surface of the conductor, and then passes through an electric drying device for drying; The process of passing the dried alloy conductor through a conductive adhesive storage box to be coated with a conductive adhesive layer; passing the alloy conductor coated with the conductive adhesive layer through an electrostatic powder spraying device to spray silver powder on the conductive adhesive layer; The alloy conductor with silver powder adhered to it enters a pre-curing oven for pre-curing and rounding, and also includes a process in which the rounded conductor enters a complete drying and curing box for complete curing and is shaped by a multi-mode shaping wheel after curing. After the alloy conductor is shaped, it is wound by a winding device.

[0004] Preferably, the process of coating the conductive adhesive layer also includes passing the alloy conductor formed with the conductive adhesive layer through an inner ring toothed mold so that the conductive adhesive forms a gear shape with teeth on the alloy conductor, and after the gear shape with teeth is formed, spraying silver powder on the conductive adhesive layer through electrostatic powder spraying equipment so that silver powder adheres to the teeth and the teeth.

[0005] Preferably, the inner ring gear mold is arranged between the conductive glue storage box and the box containing silver powder.

[0006] Preferably, before the alloy conductor with silver powder adhered to it enters the complete drying and curing box, it must first pass through an inner conical rounding die to round the gear-shaped conductive adhesive layer, so that the gear-shaped conductive adhesive is squeezed and filled into the tooth groove, thereby coating the silver powder in the tooth groove on the alloy conductor, forming a silver adhesive composite layer on the alloy conductor.

[0007] Preferably, the multi-mode shaping wheel is a plurality of 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 previous guide wheel.

[0008] Preferably, the silver powder is selected from a combination of one or more of silver-coated copper powder, spherical silver powder, and flaky silver powder.

[0009] Preferably, the conductive adhesive is selected from silver-filled silicone conductive adhesive or epoxy-based conductive adhesive.

[0010] Preferably, the alloy conductor is a linear conductor made of silver-copper alloy, chromium-zirconium-copper alloy or oxygen-free copper alloy among copper alloys.

[0011] Preferably, the thickness of the conductive adhesive layer is 5-30 μm, the viscosity is 3000-5000 mPa·s, and the amount of the silver powder is 0.1-0.25 g / m.

[0012] Preferably, the temperature in the pre-curing process is 25-80°C, and the temperature in the full curing process is 120-180°C.

[0013] The technical effects of the present invention are as follows: a silver paste composite layer is coated on the surface of a linear conductor online through processes such as silver powder spraying, mechanical coating and curing, thereby improving the conductive performance of the linear conductor; and this method does not generate a large amount of wastewater, only a small amount of wastewater is generated during the passivation process. Moreover, compared with the waste liquid treatment method generated by the electroplating silver process and the chemical silver plating process, it is simpler and easier to meet the discharge requirements.

[0014] Through the pre-curing process, the conductive adhesive is partially cured 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 flexibility for subsequent rounding and shaping.

[0015] The conductive adhesive is formed into a gear shape with teeth on the alloy conductor through an inner ring toothed die, so that a large amount of silver powder is sprayed in the tooth grooves and on the teeth when the silver powder is sprayed. Moreover, the adhesive layer at the tooth grooves formed by the inner ring toothed die is thinner, so that the silver powder is closer to the alloy conductor. When it passes through the inner conical rounding die, because the channel in the die presents a conical structure from the input end to the output end, the inner diameter of the channel in the die gradually decreases, so that the toothed conductive adhesive contacts the channel in the die. Therefore, the toothed conductive adhesive is squeezed by the gradually decreasing inner diameter of the channel, so that it fills the tooth grooves and then wraps the silver powder in the tooth grooves on the linear conductor. By combining silver powder and conductive adhesive, cracks and pores on the surface of the wire can be filled, thereby increasing the effective conductive area and improving the conductive performance. Moreover, when the conductive adhesive uses silver-filled silicone conductive adhesive, the antioxidant performance of the copper wire can also be improved.

[0016] The purpose of shaping through the multi-mode shaping wheel is to make use of the fact that the width of the wire groove on the rear guide wheel is smaller than the width of the wire groove on the front guide wheel, so that the concentricity of the rounded linear conductor can be kept consistent after being squeezed, thereby improving the consistency of the shape and size of the linear conductor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the planar structure of the inner ring gear mold; Figure 2 It is a structural diagram of the inner conical rounding mold. DETAILED DESCRIPTION

[0018] Next, we will further explain the preparation process of an alloy conductor with improved conductivity described in the present invention with reference to the accompanying drawings.

[0019] In one embodiment, see Figure 1-Figure 2When preparing the alloy conductor, a copper wire made of a silver-copper alloy is selected as a linear conductor and passed through a passivation tank to form a protective film on the surface of the linear conductor; then it passes through a dust-free air blowing box, and a large amount of moisture on the surface of the conductor is blown away by the air blowing nozzle in the dust-free air blowing box, and then it is dried by an electric drying device. The electric drying device has been disclosed in the utility model patent with publication number CN212434357U and publication date January 29, 2021. Therefore, the electric drying device is not described in detail in this patent. The dried linear conductor is passed through a storage box of silver-filled silicone conductive adhesive to be coated with a conductive adhesive layer. The alloy conductor coated with the conductive adhesive layer is then passed through an inner ring toothed die to form a gear-shaped structure with teeth on the linear conductor. The gear-shaped linear conductor with teeth is then passed through an electrostatic powder spraying device to spray silver-coated copper powder onto the conductive adhesive layer, so that silver powder adheres to the teeth and the grooves. The silver powder is selected from silver-coated copper powder or a mixture of 70% silver-coated copper powder and 30% spherical silver powder by weight. It should be noted that the spray guns of the electrostatic powder spraying device should be arranged in a ring around the wheel-shaped linear conductor at a distance of 150-250 mm from the linear conductor to ensure uniform silver powder spraying. The humidity in the environment should be controlled during spraying, preferably ≤50% RH to prevent oxidation of the silver powder. In addition, the viscosity of the silver-filled silicone conductive adhesive should be maintained at 3000-5000 mPa·s. The linear conductor with silver powder adhered to it is placed in a pre-curing oven for pre-curing. During the pre-curing process, the temperature is 25~30℃ because it uses silver-filled silicone conductive adhesive. If epoxy-based conductive adhesive is used, the temperature is 60~75℃. The adhesive layer is partially cured through the pre-curing process to ensure that the adhesive layer has initial mechanical strength to fix the silver powder, while retaining a certain flexibility for subsequent rounding and shaping.

[0020] The pre-cured linear conductor passes through an inner conical shrinking die to shrink the gear-shaped conductive adhesive layer. During the shrinking process, the gear-shaped conductive adhesive layer contacts the channel in the inner conical shrinking die, so that the gear-shaped conductive adhesive is squeezed and filled into the tooth groove, thereby coating the silver powder in the tooth groove on the linear conductor, and coating the alloy conductor with a layer of uncured silver adhesive composite layer; the linear conductor forming the silver adhesive composite layer is completely cured in a second oven, and after curing, it is shaped by a multi-mode shaping wheel and then wound by a winding device; the temperature in the second oven should be maintained at 80-120°C during drying and curing, and when epoxy-based conductive adhesive is used, 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 0.1-0.15g / m; the thickness of the conductive adhesive layer is 15-25μm.

[0021] In another embodiment, when copper wire made of chromium-zirconium-copper alloy is selected as the linear conductor, the conductive adhesive suitable therefor should be epoxy-based conductive adhesive, and all silver powders should be spherical silver powders. This is because the conductivity of most copper wires made of chromium-zirconium-copper alloy is lower than that of copper wires made of silver-copper alloy, while the conductivity of epoxy-based conductive adhesive and spherical silver powder are respectively higher than that of silver-filled silicone conductive adhesive and silver-coated copper powder. The amount of silver powder used is 0.2-0.25 g / m. Due to the increase in the amount of silver powder used, in order to better cover the silver powder, the thickness of the conductive adhesive layer is 20-30 μm.

[0022] The inner conical rounding die and the inner ring gear die used in the above two embodiments should be provided with a water cooling mechanism to prevent frictional overheating from causing the conductive adhesive to block the die.

[0023] The production process and preparation principle of the present invention are completely different from those of the prior art. In the present invention, conductive glue is first applied to the conductor, and then the conductive glue is formed into a gear shape. The purpose is to enable the silver powder to adhere to the tooth groove and contact the linear conductor. Then, the silver powder is coated on the linear conductor by using an inner conical mold to round it. Because both silver powder and conductive glue are conductive, the conductive performance of the linear conductor can be improved. In addition, the production cost is lower and more environmentally friendly than the prior art.

[0024] The protection scope of the present invention is not limited to the above embodiment and its variations. Conventional modifications and replacements made by those skilled in the art based on the contents of this embodiment are all within the protection scope of the present invention.

Claims

1. A process for preparing an alloy conductor with improved electrical conductivity, characterized by: The process of passing the alloy conductor through the passivation tank to form a protective film on the surface of the alloy conductor; After passivation, the conductor passes through a dust-free air blowing box to remove a large amount of moisture on the surface of the conductor, and then passes through an electric drying device for drying; The process of coating the dried alloy conductor with a conductive adhesive layer by passing it through a conductive adhesive storage box; A process in which an alloy conductor coated with a conductive adhesive layer is passed through an electrostatic powder spraying device to spray silver powder onto the conductive adhesive layer; The alloy conductor with silver powder adhered to it enters a pre-curing oven for pre-curing and rounding. The rounded conductor also enters a second oven for complete curing and is shaped by a multi-mode shaping wheel after curing. After the alloy conductor is shaped, it is wound by a winding device.

2. The process for preparing an alloy conductor with improved electrical conductivity according to claim 1, wherein: The process of coating the conductive adhesive layer also includes passing the alloy conductor formed with the conductive adhesive layer through an inner ring toothed mold so that the conductive adhesive forms a gear shape with teeth and grooves on the alloy conductor. After the gear shape with teeth and grooves is formed, silver powder is sprayed on the conductive adhesive layer through an electrostatic powder spraying device so that the silver powder adheres to the teeth and grooves.

3. The process for preparing an alloy conductor with improved electrical conductivity according to claim 2, wherein: Before the alloy conductor with silver powder adhered to it enters the complete drying and curing box, it must first pass through the inner conical rounding die to round the gear-shaped conductive adhesive layer, so that the gear-shaped conductive adhesive is squeezed and filled into the tooth groove, thereby coating the silver powder in the tooth groove on the alloy conductor, forming a silver adhesive composite layer on the alloy conductor.

4. The process for preparing an alloy conductor with improved electrical conductivity according to claim 1, wherein: The multi-mode shaping wheel is a plurality of 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 previous guide wheel.

5. The process for preparing an alloy conductor with improved electrical conductivity according to claim 1, wherein: The silver powder is selected from a combination of silver-coated copper powder and spherical silver powder.

6. The process for preparing an alloy conductor with improved electrical conductivity according to claim 1, wherein: The conductive adhesive is selected from silver-filled silicone conductive adhesive or epoxy-based conductive adhesive.

7. The process for preparing an alloy conductor with improved electrical conductivity according to claim 1, wherein: The alloy conductor is selected from a silver-copper alloy or a linear conductor made of chromium-zirconium-copper among copper alloys.

8. The process for preparing an alloy conductor with improved electrical conductivity according to claim 1, wherein: The thickness of the conductive adhesive layer is 5-30 μm, the viscosity is 3000-5000 mPa·s, and the amount of the silver powder is 0.1-0.25 g / m.

9. The process for preparing an alloy conductor with improved electrical conductivity according to claim 1, wherein: The temperature in the pre-curing process is 25-80°C, and the temperature in the full curing process is 80-180°C.

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