Triangular conductive wire and preparation method therefor

Abstract

A triangular conductive wire and a preparation method therefor, which belong to the technical field of solar cells. The triangular conductive wire comprises a conductive wire substrate, two reflective coatings and a soldering layer, wherein the reflective coatings are respectively arranged on two reflective faces of the conductive wire substrate; an included angle between the two reflective faces of the conductive wire substrate is (60±1)°; a non-illuminated face of the conductive wire substrate is provided with a concave face, and the soldering layer is arranged on the surface of the concave face; the soldering layer is made of a low-temperature tin-based alloy, the melting point of which is 135°C-148°C; and the cross section of the conductive wire substrate is in the shape of a regular triangle that has a single inwards concave side and has three R corners with radii less than 15 μm. The triangular conductive wire is structurally different from conventional triangular conductive wires. A concave face is provided on the non-illuminated face, and the soldering layer is arranged on the surface of the concave face, such that problems such as solder overflow, solder balls and pseudo soldering can be prevented from occurring during the process of soldering the triangular conductive wire to a cell; and the low-temperature tin-based alloy with a melting point of 135°C-148°C is used to make the soldering layer, such that the triangular conductive wire can be soldered to the cell within 200°C, which is 40°C lower than a conventional soldering temperature, thereby significantly reducing the risks of cell hidden cracking and fragmentation.

Description

A triangular conductive wire and its preparation method Technical Field

[0001] The invention belongs to the technical field of solar cells, and in particular to a triangular conductive wire and a preparation method thereof. Background Art

[0002] Photovoltaic conductive filament, also known as tinned copper ribbon or tin-coated copper ribbon, is a crucial component of photovoltaic modules, serving as a connection within the photovoltaic cell package. It conducts the electrical energy converted from sunlight on the photovoltaic cell and transmits it to the electrical equipment, playing a crucial role in conducting and concentrating electricity. This generated electricity requires advanced metallization (or interconnection) technology to minimize losses. For modules, achieving higher power gain through more efficient metallization and interconnection technologies, alongside high-efficiency cells, is crucial. Conventional modules typically utilize flat conductive filaments with a planar surface. This results in nearly all sunlight incident perpendicularly on the filament surface being reflected and lost, resulting in low module utilization. Triangular conductive filaments offer higher reflectivity than flat or circular filaments, resulting in significant optical gain and higher module power. The R angle of conventional triangular conductive wire is generally greater than 30μm. Due to the large proportion of the arc transition area, the reflective ability is weakened. In addition, due to the use of traditional tin-lead alloy as the plating layer, the welding temperature is high, and the surface tin solder layer is easy to flow during the string soldering process, which is prone to problems such as tin overflow, tin beads, cold solder joints, hidden cracks and fragments. Summary of the Invention

[0003] Purpose of the invention: To provide a triangular conductive wire and a preparation method thereof to solve the above-mentioned problems existing in the prior art.

[0004] In a first aspect, the present invention provides a triangular conductive wire, comprising a conductive wire substrate, two reflective coatings, and a welding layer;

[0005] The reflective coating is respectively provided on the two reflective surfaces of the conductive thread substrate, and the angle between the two reflective surfaces of the conductive thread substrate is 60±1°;

[0006] The backlight surface of the conductive wire substrate is provided with a concave surface, and the welding layer is provided on the concave surface. The material of the welding layer is a low-temperature tin-based alloy with a melting point of 135° C. to 148° C.;

[0007] The cross-section of the conductive thread substrate is a regular triangle with one side concave inward, and the three R angles are less than 15 μm.

[0008] Preferably, the conductive wire substrate is made by rolling copper wire or copper-clad aluminum wire with a wire diameter of 0.1mm to 0.5mm through a precision rolling mill.

[0009] Preferably, the two reflective surfaces and the backlight surface of the conductive thread substrate are subjected to ultrasonic polishing.

[0010] Preferably, the roughness Ra value of the two reflective surfaces and the backlight surface of the conductive thread substrate is less than 0.03 μm.

[0011] Preferably, the reflective coating is made by magnetron sputtering silver or aluminum, or by electroplating silver.

[0012] Preferably, the roughness Ra value of the reflective coating is less than 0.5 μm.

[0013] Preferably, the reflective coating has a thickness of 0.1 μm to 1 μm.

[0014] Preferably, the curvature of the concave surface is 10° to 30°, and the chord length corresponding to the curvature accounts for 60% to 75% of the length of the bottom side of the cross section of the conductive thread substrate.

[0015] Preferably, the thickness of the welding layer is 10 μm to 25 μm.

[0016] Preferably, the low-temperature tin-based alloy is prepared by the following method:

[0017] Sn-10wt%Zn and Sn-10wt%P were prepared by vacuum induction furnace melting and used as intermediate alloys.

[0018] Metal-based graphene is prepared by hydrazine hydrate method and used as an intermediate alloy;

[0019] The master alloy and other metals are blended according to target composition, and the low-temperature tin-based alloy is prepared in a vacuum induction melting furnace. The low-temperature tin-based alloy has the following composition: Sn: 38%-53%, Bi: 50%-65%, Cu: 0.1%-0.8%, Zn: 0.2%-1%, P: 0.08%-0.25%, and graphene: 0.1%-0.2%.

[0020] Preferably, the metal-based graphene is prepared by a hydrazine hydrate method, comprising:

[0021] Add 1 g of graphene with an average diameter of 30 nm to 50 nm to 50 ml of 2% copper sulfate solution and disperse it evenly with ultrasound. Then, add 2 ml of 2% hydrazine hydrate solution dropwise to the above solution, stir magnetically for 40 minutes, and then centrifuge and dry for later use.

[0022] In a second aspect, the present invention provides a method for preparing a triangular conductive wire, which is used to prepare any triangular conductive wire described in the first aspect, comprising:

[0023] The round wire substrate is rolled using a precision rolling mill to form a conductive wire substrate having a cross-sectional shape of an equilateral triangle with one side concave.

[0024] annealing the conductive filament substrate for later use;

[0025] Ultrasonic polishing equipment is used to polish the two reflective surfaces and the backlight surface of the conductive wire substrate;

[0026] Silver or aluminum is plated on the two reflective surfaces of the conductive wire substrate using magnetron sputtering or electroplating technology to form a reflective coating;

[0027] Using local tin plating equipment, a low-temperature tin-based alloy is hot-dip plated on the concave surface of the conductive wire substrate to form a soldering layer. Technical Solutions

[0028] Type your technical solution description paragraph here. Beneficial effects

[0029] In summary, the beneficial effects of the present invention are:

[0030] 1. The conductive wire base material is copper wire or copper-clad aluminum wire. Copper-clad aluminum wire has low density and low price. After the wire diameter is enlarged, it has the same conductivity as copper wire, which reduces the cost by at least 20% compared with copper wire.

[0031] 2. This triangular conductive wire structure is different from the traditional triangular conductive wire. A concave surface is set on the backlight side, and a welding layer is set on the concave surface to prevent problems such as tin overflow, tin beads, and cold soldering during the welding process between the triangular conductive wire and the battery cell.

[0032] 3. The cross-section of the triangular conductive wire is a single-sided concave equilateral triangle, and the three R angles are less than 15μm. Therefore, the arc transition area accounts for a small proportion, the reflective efficiency is high, and it has a better component power gain effect.

[0033] 4. A low-temperature tin-based alloy with a melting point of 135°C ~ 148°C is used as the welding layer, which can be welded to the battery cell within 200°C, which is 40°C lower than the traditional welding temperature, greatly reducing the risk of hidden cracks and fragments of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] FIG1 is a schematic diagram of a triangular conductive wire provided by the present invention.

[0035] The accompanying drawings are marked as follows: 1. conductive wire substrate; 2. reflective coating; 3. welding layer; 4. concave surface. Modes for Carrying Out the Invention DETAILED DESCRIPTION

[0036] In the following description, numerous specific details are provided to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without one or more of these details. In other instances, certain technical features well known in the art are not described to avoid confusion with the present invention. Example 1

[0037] As shown in Figure 1, the triangular conductive wire disclosed in this embodiment includes a conductive wire substrate 1, two reflective coatings 2, and a welding layer 3. The reflective coatings 2 are respectively arranged on the two reflective surfaces of the conductive wire substrate 1. The angle between the two reflective surfaces of the conductive wire substrate 1 is 60±1°. The backlight surface of the conductive wire substrate 1 is provided with a concave surface 4, and the welding layer 3 is arranged on the surface of the concave surface 4. The material of the welding layer 3 is a low-temperature tin-based alloy with a melting point of 135°C~148°C. The cross-sectional shape of the conductive wire substrate 1 is a single-sided concave equilateral triangle, and the three R angles are less than 15μm. A concave surface 4 is provided on the backlight surface, and a welding layer 3 is provided on the surface of the concave surface 4, which can prevent problems such as tin overflow, tin beads, and cold solder joints from occurring during the welding process between the triangular conductive wire and the battery cell. The cross-section of the triangular conductive wire is a single-sided concave equilateral triangle, and the three R angles are less than 15μm, so the arc transition area accounts for a small proportion, the reflective efficiency is high, and the component power gain effect is better. A low-temperature tin-based alloy with a melting point of 135℃~148℃ is used as the welding layer 3, and can be welded to the battery cell within 200℃, which is 40℃ lower than the traditional welding temperature, greatly reducing the risk of hidden cracks and fragments in the battery cell.

[0038] As shown in FIG1 , the conductive wire substrate 1 is made of copper wire or copper-clad aluminum wire with a wire diameter of 0.1 mm to 0.5 mm, which is rolled by a precision rolling mill. Copper-clad aluminum wire has a low density and is inexpensive. By increasing the wire diameter, it has a conductivity comparable to that of copper wire, reducing costs by at least 20% compared to copper wire.

[0039] Specifically, the tensile strength of copper wire is >250MPa, elongation is >23%, and conductivity is 100%IACS; the tensile strength of copper clad aluminum wire is >230Mpa, elongation is >15%, and conductivity is >45%IACS.

[0040] As shown in FIG1 , the two reflective surfaces and the backlight surface of the conductive thread substrate 1 are subjected to ultrasonic polishing to reduce surface roughness.

[0041] As shown in FIG1 , the roughness Ra values ​​of the two light-reflecting surfaces and the backlight surface of the conductive thread substrate 1 are less than 0.03 μm.

[0042] As shown in FIG1 , the reflective coating 2 is made by magnetron sputtering of silver or aluminum or by electroplating of silver.

[0043] Specifically, when the reflective coating 2 is made of silver or aluminum by magnetron sputtering, the thickness is 0.1 μm to 0.3 μm; when the reflective coating 2 is made of silver by electroplating, the thickness is 0.3 μm to 1 μm.

[0044] As shown in FIG1 , the roughness Ra value of the reflective coating 2 is less than 0.5 μm, which can ensure that the surface of the reflective coating 2 is smooth, thereby improving the reflective performance of the triangular conductive wire.

[0045] As shown in FIG1 , the thickness of the reflective coating 2 is 0.1 μm to 1 μm, so as to protect the conductive thread substrate 1 from being oxidized and corroded by oxygen in the air.

[0046] As shown in FIG1 , the arc of the concave surface 4 is 10° to 30°, and the chord length corresponding to the arc accounts for 60% to 75% of the length of the bottom side of the cross section of the conductive fiber substrate 1 .

[0047] As shown in FIG1 , the thickness of the welding layer 3 is 10 μm to 25 μm, which can ensure that the conductive wire is firmly welded to the battery cell.

[0048] In this embodiment, the low-temperature tin-based alloy is prepared by the following method:

[0049] Sn-10wt%Zn and Sn-10wt%P were prepared by vacuum induction furnace melting and used as intermediate alloys.

[0050] Metal-based graphene is prepared by hydrazine hydrate method and used as an intermediate alloy;

[0051] The above master alloy and other metals are mixed according to the target composition, and a low-temperature tin-based alloy is prepared in a vacuum induction melting furnace. The composition of the low-temperature tin-based alloy is: Bi: 59.7%, Cu: 0.45%, Zn: 0.6%, P: 0.1%, and graphene: 0.15%.

[0052] Specifically, the metal-based graphene is prepared by the hydrazine hydrate method, including:

[0053] Add 1 g of graphene with an average diameter of 30 nm to 50 nm to 50 ml of 2% copper sulfate solution and disperse it evenly with ultrasound. Then, add 2 ml of 2% hydrazine hydrate solution dropwise to the above solution, stir magnetically for 40 minutes, and then centrifuge and dry for later use.

[0054] The melting point of the low-temperature tin-based alloy prepared in this embodiment is 145°C.

[0055] It should be noted that the above alloy is an alloy composed of Cu, Zn, P elements and graphene added to the Sn-Bi binary alloy. The addition of a small amount of Zn element and graphene can improve the conductivity of the alloy. However, Zn has a stronger binding ability with O than other elements, and will first oxidize to form a Zn-containing oxide film on the surface of the alloy. The passivation ability of this film is weak and far inferior to that of the Al2O3 film. As the temperature and time increase, the oxidation weight gain curve shows a linear growth law. By adding a trace amount of P element to the alloy and utilizing its skin effect, a continuous protective layer of the skin film is formed on the surface of the molten alloy during the preparation and use of the alloy. This protective layer can prevent the solder alloy from continuing to directly contact with the surrounding air, protecting the solder alloy from further oxidation, thereby achieving the purpose of inhibiting the activity of Zn in the alloy and enhancing the oxidation resistance of the alloy. Example 2

[0056] The difference from Example 1 is that the low-temperature tin-based alloy composition of this embodiment is: Sn: 41.77%, Bi: 57.2%, Cu: 0.31%, Zn: 0.45%, P: 0.08%, and graphene: 0.2%.

[0057] The low-temperature tin-based alloy prepared in this embodiment has a melting point of 137°C. Example 3

[0058] The difference from Example 1 is that the low-temperature tin-based alloy composition of this embodiment is: Sn: 48.72%, Bi: 50.25%, Cu: 0.38%, Zn: 0.4%, P: 0.09%, and graphene: 0.16%.

[0059] The low-temperature tin-based alloy prepared in this embodiment has a melting point of 148°C. Example 4

[0060] The method for preparing the triangular conductive wire disclosed in this embodiment is used to prepare the triangular conductive wire, comprising:

[0061] A precision rolling mill is used to roll a copper wire substrate with a wire diameter of 0.2 mm into a conductive wire substrate with a cross-sectional shape of a single-sided concave equilateral triangle. The side length of the triangle is 0.25 mm, the three R angles are 10 μm, 10 μm, and 12 μm respectively, the angle between the two reflective surfaces is 59°, and the arc of the concave surface is 20°.

[0062] annealing the conductive filament substrate for later use;

[0063] Ultrasonic polishing equipment is used to polish the two reflective surfaces and the backlight surface of the conductive wire substrate. After polishing, the roughness Ra value of the two reflective surfaces and the backlight surface is 0.02 μm.

[0064] Silver is plated on the two reflective surfaces of the conductive wire substrate by magnetron sputtering to form a reflective coating with a thickness of 0.3 μm;

[0065] A local tin plating device is used to hot-dip plate a low-temperature tin-based alloy on the concave surface of the conductive wire substrate to form a soldering layer with a thickness of 12 μm. Example 5

[0066] The method for preparing the triangular conductive wire disclosed in this embodiment is used to prepare the triangular conductive wire, comprising:

[0067] A copper wire substrate with a wire diameter of 0.4 mm was rolled using a precision rolling mill to form a conductive wire substrate with a cross-sectional shape of a single-sided concave equilateral triangle. The triangle side length was 0.5 mm, the three R angles were 15 μm, 15 μm, and 20 μm, respectively. The angle between the two reflective surfaces was 59°, and the concave surface had a curvature of 20°.

[0068] annealing the conductive filament substrate for later use;

[0069] Ultrasonic polishing equipment is used to polish the two reflective surfaces and the backlight surface of the conductive wire substrate. After polishing, the roughness Ra value of the two reflective surfaces and the backlight surface is 0.02 μm.

[0070] Silver is plated on the two reflective surfaces of the conductive wire substrate by magnetron sputtering to form a reflective coating with a thickness of 0.3 μm;

[0071] A local tin plating device is used to hot-dip plate a low-temperature tin-based alloy on the concave surface of the conductive wire substrate to form a soldering layer with a thickness of 12 μm. Example 6

[0072] The method for preparing the triangular conductive wire disclosed in this embodiment is used to prepare the triangular conductive wire, comprising:

[0073] A precision rolling mill is used to roll a copper-clad aluminum wire substrate with a wire diameter of 0.27mm to make it a conductive wire substrate with a cross-sectional shape of a single-sided concave equilateral triangle. The side length of the triangle is 0.34mm, the three R angles are 10μm, 10μm, and 12μm respectively, the angle between the two reflective surfaces is 59°, and the arc of the concave surface is 20°.

[0074] annealing the conductive filament substrate for later use;

[0075] Ultrasonic polishing equipment is used to polish the two reflective surfaces and the backlight surface of the conductive wire substrate. After polishing, the roughness Ra value of the two reflective surfaces and the backlight surface is 0.03 μm.

[0076] The two reflective surfaces of the conductive wire substrate are plated with silver using an electroplating process to form a reflective coating with a thickness of 0.5 μm.

[0077] A local tin plating device is used to hot-dip plate a low-temperature tin-based alloy on the concave surface of the conductive wire substrate to form a soldering layer with a thickness of 15 μm.

[0078] In this embodiment, the copper-clad aluminum wire has a strength of 241 MPa, an elongation of 14.2%, and a conductivity of 55% IACS. Comparative Example 1

[0079] The difference between Comparative Example 1 and Example 4 is that a flat conductive wire with a wire diameter of 0.25 mm and a silver plating thickness of 0.3 μm is used as the interconnection ribbon. Comparative Example 2

[0080] The difference between Comparative Example 2 and Example 5 is that a commercially available triangular conductive wire with a cross-sectional side length of 0.5 mm and an R angle greater than 35 μm is used as the interconnecting ribbon.

[0081] The conductive filaments obtained in Examples 4-6 and Comparative Examples 1-2 were used to make small modules, each using 9BB half-cell HJT cells of the same power. The module length and width were both 200 mm. According to IEC 61215:2016, under standard test conditions (STC), the performance parameters of each conductive filament and the module power are shown in the following table:

[0082] Number Width*Thickness / Triangle side length ( / mm) R angle ( / μm) Tensile strength ( / MPa) Elongation ( / %) Electrical resistance ( / Ω·mm 2 / m)Module power (W) Example 4 0.25 10,10,12 25 5 26.2 0.0 17 37.48 Example 5 0.50 15,15,20 25 3 28.6 0.0 17 17.41 Example 6 0.34 10,10,12 23 5 14.2 0.0 3 137.44 Comparative Example 1 0.25*0.1-25 8 28.9 0.0 17 27.32 Comparative Example 2 0.5*0.1 36,36,40 26 128.10 17 17.38

[0083] It should be noted that copper-clad aluminum wire has lower conductivity than copper wire. According to relevant parameters, copper-clad aluminum alloy wire can achieve conductivity comparable to copper wire after being enlarged to a certain diameter. For example, a copper-clad aluminum wire with a conductivity of 55% and a diameter of 0.27mm can have the same conductivity as a copper wire with a conductivity of 100% and a diameter of 0.2mm.

[0084] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all fall within the scope of protection of the present invention.

Claims

1. A triangular conductive wire, characterized in that: It includes a conductive wire substrate, two reflective coating layers, and a welding layer; The reflective coating is respectively provided on the two reflective surfaces of the conductive thread substrate, and the angle between the two reflective surfaces of the conductive thread substrate is 60±1°; The backlight surface of the conductive wire substrate is provided with a concave surface, and the welding layer is provided on the concave surface. The material of the welding layer is a low-temperature tin-based alloy with a melting point of 135° C. to 148° C.; The cross-section of the conductive thread substrate is a regular triangle with one side concave inward, and the three R angles are less than 15 μm.

2. The triangular conductive wire according to claim 1, characterized in that: The conductive wire substrate is made by rolling copper wire or copper-clad aluminum wire with a wire diameter of 0.1mm-0.5mm through a precision rolling mill.

3. The triangular conductive wire according to claim 1, characterized in that: The two reflective surfaces and the backlight surface of the conductive thread substrate are processed by ultrasonic polishing.

4. The triangular conductive wire according to claim 3, characterized in that: The Ra values of the roughness of the two reflective surfaces and the backlight surface of the conductive thread substrate are less than 0.03 μm.

5. The triangular conductive wire according to claim 1, characterized in that: The reflective coating is made by magnetron sputtering silver or aluminum, or by electroplating silver.

6. The triangular conductive wire according to claim 5, characterized in that: The roughness Ra value of the reflective coating is less than 0.5 μm.

7. The triangular conductive wire according to claim 5, characterized in that: The thickness of the reflective coating is 0.1 μm to 1 μm.

8. The triangular conductive wire according to claim 1, characterized in that: The concave surface has an arc angle of 10° to 30°, and a chord length corresponding to the arc accounts for 60% to 75% of the length of the bottom side of the conductive thread substrate cross section.

9. The triangular conductive wire according to claim 1, characterized in that: The thickness of the welding layer is 10 μm to 25 μm.

10. The triangular conductive wire according to claim 1, characterized in that: The low-temperature tin-based alloy is prepared by the following method: Sn-10wt%Zn and Sn-10wt%P were prepared by vacuum induction furnace melting and used as intermediate alloys. Metal-based graphene is prepared by hydrazine hydrate method and used as an intermediate alloy; The master alloy and other metals are blended according to target composition, and the low-temperature tin-based alloy is prepared in a vacuum induction melting furnace. The low-temperature tin-based alloy has the following composition: Sn: 38%-53%, Bi: 50%-65%, Cu: 0.1%-0.8%, Zn: 0.2%-1%, P: 0.08%-0.25%, and graphene: 0.1%-0.2%.

11. The triangular conductive wire according to claim 10, characterized in that: The metal-based graphene is prepared by a hydrazine hydrate method, comprising: Add 1g of graphene with an average diameter of 30nm~50nm to 50ml of 2% copper sulfate solution and disperse it evenly with ultrasound; Then, 2 ml of 2% hydrazine hydrate solution was added dropwise to the above solution, magnetically stirred for 40 min, and then centrifuged and dried for later use.

12. A method for preparing a triangular conductive wire, for producing the triangular conductive wire according to any one of claims 1 to 9, characterized in that: include: The round wire substrate is rolled using a precision rolling mill to form a conductive wire substrate having a cross-sectional shape of an equilateral triangle with one side concave. annealing the conductive filament substrate for later use; Ultrasonic polishing equipment is used to polish the two reflective surfaces and the backlight surface of the conductive wire substrate; Silver or aluminum is plated on the two reflective surfaces of the conductive wire substrate using magnetron sputtering or electroplating technology to form a reflective coating; Using local tin plating equipment, a low-temperature tin-based alloy is hot-dip plated on the concave surface of the conductive wire substrate to form a soldering layer.

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