Method for forming wire on plastic carrier

Abstract

The invention relates to the technical field of photovoltaic electrodes, and particularly discloses a method for forming a wire on a plastic carrier. In particular to a method comprising the following steps: preparing a hard plastic carrier, printing patterned metal line segments on one surface of the carrier, removing impurities on the metal line segments on the carrier, chemically plating a copper layer, and removing an oxide layer and an electroplating copper layer on the copper layer; in this way, the grid line used on the photovoltaic cell can be successfully formed on the plastic carrier.

Description

Technical Field

[0001] The invention relates to photovoltaic electrodes, and in particular to a method for forming a conductive line on a plastic carrier. Background Art

[0002] Silicon-based cells with monocrystalline silicon or polycrystalline silicon as substrate materials are the most important and widely used cell types in the current photovoltaic industry, with a market share of over 70%. Photoelectric effect is generated by irradiating silicon-based cells with light; and through the PN junction structure on the surface of the cell, directional transmission of free electrons is achieved, thereby forming current and completing photovoltaic power generation. Therefore, how to maximize the number of free electrons generated by silicon-based cells and how to maximize the collection of free electrons on the surface of silicon-based cells are the most important factors affecting the power generation efficiency of battery components.

[0003] The traditional cell production process mainly involves printing conductive silver paste on the cell surface through screen printing, and solidifying the silver paste through high-temperature sintering (above 500°C) to form secondary grid lines and main grid lines on the cell surface, thereby collecting free electrons on the cell surface. With the iterative upgrade of battery components and the improvement of battery efficiency, the width of the grid line has also been reduced from about 100um in the early days to a line width below 100um or even below 50um; the reduction in line width reduces the shielding of incident light, which also means that the illuminated area of ​​the cell surface can be further increased, thereby improving the power generation efficiency of the cell. For example, the latest generation of SHJ (silicon-based heterojunction) series batteries, according to research, has a reported grid line width of about 15um, and the conversion rate of mass-produced batteries can reach more than 25%.

[0004] The reduction in grid line width and the inability of the TCO (transparent conductive oxide) layer on the surface of the new generation SHJ series batteries to undergo high-temperature processing above 200°C make it impossible to use existing traditional high-temperature silver paste on this type of battery cells.

[0005] Its alternative is low-temperature silver paste; the resistivity of low-temperature silver paste is generally higher than that of copper or silver, especially in the narrow line width state, its resistivity will be too high, thus affecting the battery conversion rate. At the same time, the double-sided printing of this type of battery cell can easily make the cost of using its silver paste significantly higher than other types of battery cells. It is of great significance to develop metal electrode grid line materials with higher conductivity and lower cost to replace the existing silver paste materials with excessively high electrode grid line resistance caused by low-temperature silver paste.

[0006] In the above-mentioned traditional electrode structure, because the grid lines are mainly made of silver paste, and the grid lines are directly formed on the surface of the battery, some batteries cannot be used for high-temperature processing due to their own characteristics. In addition, the use of expensive silver paste not only increases the cost of the entire electrode structure, but also makes the manufacturing industry, which is already in an era of low profits, even worse. At the same time, because of the current technology, the electrode structure is inevitably unable to be separated from the battery, so that it is too much subject to the physical limitations of the battery cell itself. Summary of the invention

[0007] In order to solve the above problems, the present invention proposes a method for forming a conductive line on a plastic carrier. After the manufacturing is completed, the conductive line can be adhered to the battery surface as needed, and then the plastic sheet serving as the carrier can be removed.

[0008] The present invention solves the above problems by providing a method for forming a conductive line on a plastic carrier, comprising:

[0009] Prepare a hard plastic carrier;

[0010] Printing patterned metal line segments on a surface of the plastic carrier;

[0011] Selectively plating a chemical copper layer on the metal line segment;

[0012] removing the oxide layer on the chemical copper layer; and

[0013] The electroplated copper layer is located outside the chemical copper layer.

[0014] Another object of the present invention is that the material of the metal wire segment includes one of silver paste, copper paste, silver-aluminum paste, silver-copper paste, titanium paste or copper-titanium paste or a mixture thereof.

[0015] Another object of the present invention is to further include a pretreatment step, wherein the pretreatment includes an acid washing step implemented with an acidic solution and an alkaline washing step implemented with an alkaline solution.

[0016] Another object of the present invention is to further include a step of increasing the roughness of the chemical copper layer, which is performed after the step of removing the oxide layer on the chemical copper layer and before electroplating an electroplated copper layer on the chemical copper layer.

[0017] Another object of the present invention is that the plastic carrier is selected from PET or a film.

[0018] Another object of the present invention is that the pickling step is carried out with sulfuric acid and the alkaline liquid is sodium carbonate.

[0019] Another object of the present invention is that the selective electroless plating of a chemical copper layer on the metal wire segment means that when the metal wire segment contains a conductive material and the content of the conductive material is below 30% WT, a chemical copper layer is electrolessly plated on the metal wire segment.

[0020] Another object of the present invention is that the plastic carrier is selected from PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCT (polyethylene 1,4-cyclohexanedimethanol terephthalate), PC (polycarbonate), PETG (polyethylene terephthalate-1,4-cyclohexanedimethanol ester), PMMA (polymethyl methacrylate), COC (cyclic olefin copolymer) or PVA (polyvinyl alcohol), EVA, POE or a composite film of EVA and POE.

[0021] Another object of the present invention is to further include a step of forming a protective layer, which is to form a protective layer on the outer side of the electroplated copper layer.

[0022] Another object of the present invention is that the protective layer is selected from one of nickel, tin, potassium-containing metals, gold, silver, palladium, bismuth, indium tin alloy or tin-bismuth alloy, or a mixture thereof.

[0023] The present invention is described in the following detailed description in a non-limiting manner; the described parts are merely embodiments of the present invention and have no direct impact on the scope of the present invention. Therefore, the following description should not be interpreted in a limiting manner. DETAILED DESCRIPTION

[0024] The present invention aims to provide a method for forming a conductive line on a plastic carrier. When implementing the present invention, firstly, a plastic carrier is prepared, and the plastic carrier can be a thermoplastic polyester with a certain optical transmittance; it can be selected from PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCT (polyethylene 1,4-cyclohexanedimethanol terephthalate), PC (polycarbonate), PETG (polyethylene terephthalate-1,4-cyclohexanedimethanol ester), PMMA (polymethyl methacrylate), COC (cycloolefin copolymer) or PVA (polyvinyl alcohol), preferably polyethylene terephthalate (PET). At the same time, it can also be a film of another thermoplastic polyester, preferably ethylene-vinyl acetate (EVA), POE, or a composite film of EVA and POE or other similar materials. It is worth noting that the plastic carrier can be a layer of hard plastic with release function. In another embodiment, a layer of UV de-viscosity adhesive can be coated on the surface of the carrier to achieve the effect of detaching from the battery surface during use.

[0025] After printing the conductive paste, such as silver paste, copper paste, silver-aluminum paste, silver-copper paste, titanium paste or copper-titanium paste or a mixture thereof, directly onto the plastic carrier in a patterned manner to print the conductive metal wire segments, the carrier is alkali-washed with an alkaline solution such as sodium carbonate as needed, and then the carrier is acid-washed with an acidic solution such as sulfuric acid to remove impurities such as oxides on the plastic carrier and / or the metal wire segments. Furthermore, after cleaning the plastic carrier containing the metal wire segments, it can be determined whether to perform a chemical copper plating step depending on the amount of a conductive material contained in the conductive paste. After experiments, it was found that, generally, when the content is below 30WT (weight ratio), the conductive material content is low and is not suitable for direct electroplating; and when it is above the above numerical range, it is suitable for direct electroplating because the resistance is small, and the chemical plating step is no longer required, so chemically plating a chemical copper layer on the metal wire segments is a selective step.

[0026] The process of chemical plating is to put the treated plastic carrier into copper plating solution for copper deposition. The copper plating temperature is 30-50℃ and the chemical plating time is 60-1800S (seconds); after taking the plastic carrier out of the solution, rinse it with deionized water for 2-5min (minutes). The copper plating solution can be made of [Tiancheng Chemical] 36B base agent 70-100ml / L, 36C additive 40-60ml / L, 36S stabilizer 1-3ml / L, 36pH adjuster 20-40ml / L, 36R copper plating reducing agent 10-16ml / L, and the rest is deionized water.

[0027] Put the plastic carrier after chemical copper plating into the pickling solution, pickle for 10-120 seconds at room temperature, and rinse with deionized water for 2-5 minutes. The pickling solution is a mixture of 1-10% sulfuric acid and deionized water. By putting the plastic carrier into the pickling solution, the oxide layer on the chemical copper layer can be removed. At the same time, the roughness of the chemical copper layer can be increased due to the corrosive effect of the acidic solution, which is beneficial to the future electroplating steps.

[0028] The pickled plastic carrier is placed in the electroplating solution for electroplating at a temperature of 20-30°C and a current density of 1.0-20.0A / dm 2 The electroplating time is 5-60 minutes. After taking out and rinsing with deionized water for 2-5 minutes, a complete wire with good conductivity can be obtained on the plastic carrier after cooling and drying, forming a complete electrode that can be used for photovoltaic cells.

[0029] Of course, after the wires are completely formed on the plastic carrier, since the outermost layer is a copper layer, and it is a well-known fact that copper is very easy to oxidize in the natural environment, in order to prevent the oxidation of the wires, a protective layer must be formed on the outside of the wires, that is, the exposed part, and the formation method can also be selected to be electroplating; wherein, the material of the protective layer can be selected from nickel, tin, potassium-containing metal, gold, silver, palladium, bismuth, indium tin alloy or tin-bismuth alloy, or a mixture thereof.

[0030] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the description should be regarded as illustrative rather than restrictive.

Claims

1. A method for forming a conductive line on a plastic carrier, characterized in that: Included: Prepare a hard plastic carrier; Printing patterned metal line segments on a surface of the plastic carrier; Selectively plating a chemical copper layer on the metal line segment; removing the oxide layer on the chemical copper layer; as well as The electroplated copper layer is located outside the chemical copper layer.

2. The method for forming a conductive line on a plastic carrier according to claim 1, wherein: The material of the metal line segment includes silver paste, copper paste, silver-aluminum paste, silver-copper paste, titanium paste or copper-titanium paste or a mixture thereof.

3. The method for forming a conductive line on a plastic carrier according to claim 1, wherein: The method further comprises a pretreatment step, wherein the pretreatment step comprises an acid washing step implemented with an acidic liquid and an alkaline washing step implemented with an alkaline liquid.

4. The method for forming a conductive line on a plastic carrier according to claim 1, 2 or 3, wherein: The method also includes a step of increasing the roughness of the chemical copper layer, which is performed after removing the oxide layer on the chemical copper layer and before electroplating an electroplated copper layer on the chemical copper layer.

5. The method for forming a conductive line on a plastic carrier according to claim 1, wherein: The plastic carrier is selected from PET or a film.

6. The method for forming a conductive line on a plastic carrier as claimed in claim 3, wherein: The pickling step is performed with sulfuric acid, and the alkaline solution is sodium carbonate.

7. The method for forming a conductive line on a plastic carrier according to claim 1 or 2, wherein: The selectively plating a chemical copper layer on the metal line segment means that when the metal line segment contains a conductive material and the content of the conductive material is below 30% WT, a chemical copper layer is plated on the metal line segment.

8. The method for forming a conductive line on a plastic carrier as claimed in claim 1, wherein: The plastic carrier is selected from PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PCT (polyethylene 1,4-cyclohexanedimethanol terephthalate), PC (polycarbonate), PETG (polyethylene terephthalate-1,4-cyclohexanedimethanol ester), PMMA (polymethyl methacrylate), COC (cycloolefin copolymer), PVA (polyvinyl alcohol), EVA, POE or a composite film of EVA and POE.

9. The method for forming a conductive line on a plastic carrier as claimed in claim 1, wherein: The method also includes a step of forming a protective layer, which is to form a protective layer on the outer side of the electroplated copper layer.

10. The method for forming a conductive line on a plastic carrier as claimed in claim 9, wherein: The protective layer is selected from nickel, tin, potassium-containing metal, gold, silver, palladium, bismuth, indium-tin alloy, tin-bismuth alloy, or a mixture thereof.