Process for cleaning residual ink after development of photosensitive ink and ensuring development morphology of groove

Abstract

The invention belongs to the technical field of copper electroplating processes, and discloses a process for cleaning residual ink after photosensitive ink development and ensuring groove development morphology. According to the cleaning process for residual ink after photosensitive ink development, the residual ink at the bottom of a groove after graphical development is cleaned, morphology change caused by over-display of the groove is prevented, the quality and consistency of an electroplated layer are ensured, and the method comprises the step of adding an acid pickling step to remove residual developing agents or ink after the development process, so that the residual ink is removed. And on one hand, a developing solution can be neutralized to prevent excessive display, and on the other hand, residues can be removed to optimize the electroplating effect.

Description

Technical Field

[0001] The present invention relates to the technical field of copper electroplating technology, and in particular to a process for cleaning residual ink after photosensitive ink development and ensuring groove development morphology, and more particularly to a method for adding a pickling step after graphic development before copper electroplating to clean residual ink and neutralize the previous developer to prevent over-development. Background Art

[0002] Low-temperature silver paste is one of the main raw materials for heterojunction batteries. After technical breakthroughs, domestic low-temperature silver paste can be used on a large scale in the mass production of heterojunction batteries. With the gradual expansion of global photovoltaic installed capacity, the consumption of silver paste has gradually received attention from the industry. At present, the global annual production of metallic silver is about 30,000 tons, and the production situation has been relatively stable in the past 10 years. At present, global photovoltaic silver accounts for about 10% of global silver production. If the global photovoltaic installed capacity reaches more than 1000GW, it is expected that silver consumption will reach more than 50% of global silver production (assuming silver electrodes, without considering the replacement of silver by factors such as silver-clad copper). If the industry adheres to the existing technical route, it will be a high probability event for silver prices to get out of control. Therefore, the cost reduction of heterojunction batteries requires new ways to replace silver. At present, electroplated copper has replaced silk-screen silver as an electrode, which has been a consensus in the industry.

[0003] In the photovoltaic industry, copper electroplating is an important step in manufacturing high-efficiency solar cells. The traditional electroplating process includes the printing, exposure, and development of a graphic photosensitive ink before copper electroplating, which is used to form the desired electroplating pattern on the substrate. After development, a certain amount of developer or ink residue usually remains on the surface of the substrate and the bottom of the groove. These residues may have a negative impact on the quality of the copper plating during the subsequent electroplating process, such as forming an uneven plating layer or reducing the adhesion of the copper layer. Traditional cleaning methods often fail to effectively remove these residues, so an improved process method is needed to improve the quality and consistency of the electroplated copper pattern. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the above-mentioned background technology and provide a cleaning process for residual ink after photosensitive ink development. The improved method provided by the present invention ensures the quality and consistency of the electroplating layer by cleaning the residual ink at the bottom of the groove after graphic development and ensuring the groove development morphology. The method includes adding an acid washing step after the development process to remove the residual developer or ink, and can neutralize the previous developer to prevent over-development and ensure the groove morphology, thereby optimizing the electroplating effect.

[0005] To achieve the purpose of the present invention, the cleaning process of residual ink after the photosensitive ink is developed in the present invention comprises the following steps: (1) Place the silicon wafer in an alkaline solution at 50-90°C for reaction. Through the anisotropic etching mechanism of alkali on silicon, a pyramid light-trapping structure is formed on the surface of the silicon wafer. The size of the surface pyramid is 0.5um-10um, and the surface reflectivity of the silicon wafer is between 5%-30%. Then, the front and back sides of the silicon wafer are cleaned with HF solution to remove surface metal ion contamination. At this time, a velvet structure on the front and back sides is formed. (2) Using PECVD chemical deposition method, a layer of intrinsic amorphous silicon and a layer of phosphorus-doped n-type amorphous silicon are sequentially deposited on the front side, and a layer of intrinsic amorphous silicon and a layer of boron-doped p-type amorphous silicon are sequentially deposited on the back side; (3) Using PVD or RPD physical method to deposit a layer of TCO conductive film or multiple layers of TCO conductive films with different refractive indices on the front and back of the silicon wafer, with a total film thickness of 50nm-200nm and a refractive index of 1.6-2.5; (4) Deposit a 10-500 nm metal seed layer on the front and back sides by sputtering; (5) Printing photosensitive ink or wet film on the front side by screen printing; (6) The ink is baked after screen printing, and the film thickness after the ink is dried is 8~20 microns; (7) Printing photosensitive ink or wet film on the back side by screen printing in the same manner as step (5); (8) Graphic exposure of ink on the front and back sides; (9) Development: spray and soak the front and back ink surfaces with developer solution, and the unexposed parts of the front and back are developed; (10) After leaving the developing tank, it is not dried and immediately put into the pickling tank for pickling; (11) After pickling, rinse thoroughly with deionized water or tap water to remove the pickling solution and its residues, and then dry until there is no moisture at all to form a groove pattern with a copper bottom on the front and back sides; (12) After cleaning, the copper is sent to the electroplating tank for copper electroplating to form a high-quality copper pattern; (13) Use NaOH or KOH solution to remove the ink on the front and back sides, thereby forming a battery cell with grid lines on the front and back sides.

[0006] Furthermore, in some embodiments of the present invention, the alkali solution in step (1) is a KOH or NaOH solution; preferably, the mass concentration of the alkali solution is 0.5%-10%.

[0007] Furthermore, in some embodiments of the present invention, the thickness of the intrinsic amorphous silicon sequentially deposited on the front side in step (2) is 2nm-20nm, and the thickness of the phosphorus-doped amorphous silicon is 2nm-20nm.

[0008] Furthermore, in some embodiments of the present invention, the thickness of the intrinsic amorphous silicon deposited on the back side in step (2) is 2nm-20nm, and the thickness of the boron-doped amorphous silicon is 2nm-20nm.

[0009] Furthermore, in some embodiments of the present invention, the metal seed layer in step (4) is pure copper metal, or an alloy metal containing copper, nickel, and molybdenum.

[0010] Furthermore, in some embodiments of the present invention, in the step (5) screen printing, the ink viscosity is 1000-15000 cps, the screen printing plate is 100-350 mesh, the screen plate film thickness is 10-20 microns, and the gauze thickness is 30-60 microns.

[0011] Furthermore, in some embodiments of the present invention, the baking temperature in step (6) is 70-110° C., and the baking time is 2-20 min.

[0012] Furthermore, in some embodiments of the present invention, the patterned exposure in step (8) is performed by LDI or mask projection exposure; preferably, the exposure energy of the patterned exposure in step (8) is 30 mj~100 mj, and the line width range is 5 um~100 um.

[0013] Furthermore, in some embodiments of the present invention, the developer in step (9) is one or more of potassium carbonate, sodium carbonate, potassium hydroxide, and sodium hydroxide solution; preferably, the mass concentration of the developer solution is 0.5% to 5%.

[0014] Furthermore, in some embodiments of the present invention, the spraying and soaking time in step (9) is 30 seconds to 2 minutes.

[0015] Furthermore, in some embodiments of the present invention, the composition of the pickling solution in step (10) includes an acidic component and an auxiliary agent. Preferably, the acidic component is an organic acid, preferably acetic acid or citric acid. Preferably, the volume concentration of the acidic component is 0.5% to 10%; preferably, the auxiliary agent is a surfactant. Preferably, the volume concentration of the auxiliary agent is 0.1% to 1%.

[0016] Furthermore, in some embodiments of the present invention, the pickling temperature in step (10) is in the range of 25°C to 60°C, and the pickling time is in the range of 1 minute to 10 minutes; the pickling method is immersion or spray immersion.

[0017] Furthermore, in some embodiments of the present invention, the line width of the groove pattern in step (11) ranges from 5 um to 100 um.

[0018] Furthermore, in some embodiments of the present invention, the mass concentration of the NaOH or KOH solution in step (13) is 2% to 10%.

[0019] Prior art solutions usually involve using traditional cleaning steps after development, such as deionized water rinsing or using tap water detergent to remove development residues. These methods can clean the bottom of the groove to a certain extent, but may not completely remove all residual ink, resulting in unstable electroplating quality. The method of the present invention adds an acid washing step after development, which can neutralize the developer to prevent over-development and remove residues. The mechanism of acetic acid cleaning oily substances is as follows: (1) Solubility: Acetic acid can interact with some polar components in oils and fats (such as acids, alcohols, etc.), thereby helping to decompose and dissolve oils and fats; (2) Emulsification: Acetic acid can act as an emulsifier to a certain extent, dispersing grease in water and making it easier to clean; (3) Stain removal effect: The acidic properties of acetic acid can help remove certain stains and deposits.

[0020] (4) Neutralizing the developer: Acetic acid is neutralized with the alkaline developer to prevent residual ink from forming at the bottom of the groove, thereby preventing over-development and ensuring the groove morphology.

[0021] Especially when the line width of the groove is less than 15um, the residual ink and developer at the bottom of the line are not easy to be washed out of the groove by water due to the small line width. The use of acid washing can prevent the developer from crossing the line to ensure the development morphology, and it can also more easily dissolve and emulsify the residual ink at the bottom and then wash it out of the groove. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the SEM image of the bottom of the groove in the normal development process using the traditional cleaning step in the prior art, with a lot of residual ink; Figure 2 In the groove morphology image of the normal development process using the traditional cleaning step, the bottom widening is obvious; Figure 3 The cleaning process of the present invention is used, the volume concentration of the acidic component is 1%, and the residual ink at the bottom of the groove is greatly improved; Figure 4 In the figure, the cleaning process of the present invention is used, the volume concentration of the acidic component is 1%, and the groove morphology has a good morphology; Figure 5 The cleaning process of the present invention is used, the volume concentration of the acidic component is 3%, and there is no residual ink at the bottom of the groove; Figure 6 The groove pattern with copper bottom formed on the front and back sides in the process step (11) of the present invention (line width range 5um~100um); Figure 7 The high-quality copper pattern is formed after the copper electroplating treatment in the process step (12) of the present invention; Figure 8 The solar cell with grid lines on the front side is formed in the process step (13) of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through the practice of the present invention. It should be understood that the following description is only used to explain the present invention and is not intended to limit the present invention.

[0024] As used herein, the terms "comprises," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0025] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0026] When amount, concentration or other value or parameter is expressed as range, preferred range or a series of upper preferred value and lower preferred value limit range, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when disclosing range "1 to 5", described range should be interpreted as including range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc. When numerical range is described in this article, unless otherwise stated, the range is intended to include its end value and all integers and fractions within the range.

[0027] Singular forms include plural references unless the context clearly indicates otherwise. "Optional" or "either" means that the subsequently described event or incident may or may not occur, and that the description includes instances where the event occurs and instances where it does not.

[0028] Approximate terms in the specification and claims are used to modify quantities, indicating that the present invention is not limited to the specific quantity, but also includes acceptable and modified parts close to the quantity without causing changes in the relevant basic functions. Accordingly, the use of "about", "approximately", etc. to modify a numerical value means that the present invention is not limited to the exact numerical value. In some examples, the approximate terms may correspond to the accuracy of the instrument for measuring the numerical value. In the specification and claims of this application, range limitations can be combined and / or interchanged, and if not otherwise stated, these ranges include all subranges contained therein.

[0029] The indefinite articles "a" and "an" before the elements or components of the present invention have no limitation on the quantity requirements (i.e. the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and the elements or components in the singular form also include the plural form, unless the quantity obviously refers to the singular form only.

[0030] In addition, the descriptions of the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" described below mean that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0031] In the specific embodiment of the present invention, except that the volume concentration of the acidic component in the pickling solution has a significant impact on the cleaning effect, the fluctuations of the process parameters of other steps within the range will not have a significant impact on the final process effect.

[0032] Example 1 Step 1: Place the silicon wafer in a 9% concentration, 80°C KOH solution for 3 minutes to react. A pyramid light-trapping structure is formed on the surface of the silicon wafer through the anisotropic etching mechanism of alkali on silicon. The size of the surface pyramid is 0.5um-10um, and the surface reflectivity of the silicon wafer is between 5%-30%. Then, the front and back sides of the silicon wafer are cleaned with HF solution to remove surface metal ion contamination. At this time, a velvet structure on the front and back sides is formed. Step 2: A layer of intrinsic amorphous silicon and a layer of phosphorus-doped n-type amorphous silicon are sequentially deposited on the front side by using a PECVD chemical deposition method, wherein the thickness of the intrinsic amorphous silicon is 2nm-20nm, and the thickness of the phosphorus-doped amorphous silicon is 2nm-20nm. A layer of intrinsic amorphous silicon and a layer of boron-doped p-type amorphous silicon are also deposited on the back side at one time, wherein the thickness of the intrinsic amorphous silicon is 2nm-20nm, and the thickness of the boron-doped amorphous silicon is 2nm-20nm. Step 3: Use PVD method to deposit multiple layers of TCO conductive films with different refractive indices on the front and back of the silicon wafer, where the total film thickness is 50nm-200nm and the refractive index is 1.6-2.5; Step 4: Deposit a 10-500nm metal seed layer on both the front and back sides by sputtering. The metal seed layer is pure copper metal. Step 5: Print photosensitive ink or wet film (negative) on the front side by screen printing, with ink viscosity of 1000~15000cps, screen printing screen of 100~350 mesh, screen film thickness of 10~20 microns, and yarn thickness of 30~60 microns; Step 6: After the ink is screen-printed, the baking temperature is 70~110℃, the baking time is 2~20min, and the film thickness after the ink is dried is 8~20 microns; Step 7: In the same way, print photosensitive ink or wet film (negative) on the back of the battery by screen printing. The ink viscosity is 1000~15000cps, the screen printing screen is 100~350 mesh, the screen film thickness is 10~20 microns, and the yarn thickness is 30~60 microns; Step 8: Graphic exposure of ink on the front and back sides (LDI or mask projection exposure), exposure energy 30mj~100mj, line width range 5um~100um; Step 9: Development: Use 1% sodium carbonate developer solution to spray and soak the front and back ink surfaces for 1 minute, and the unexposed parts of the front and back are developed; Step 10: After exiting the developer tank, rinse thoroughly with deionized water or tap water without drying to remove the developer solution and its residues, and use airflow drying or other appropriate drying methods to dry until there is no moisture at all, forming a groove pattern with copper bottom on the front and back sides (line width range 5um~100um). The specific SEM of the groove bottom is as follows Figure 1 As shown, there is a lot of residual ink and the morphology is as follows Figure 2 As shown, the bottom is widened more; Step 11: After cleaning, it is sent to the electroplating tank for copper electroplating to form a high-quality copper pattern; Step 12: Use KOH solution (6% concentration) to remove the ink on the front and back sides, thus forming a battery cell with grid lines on the front and back sides.

[0033] Example 2 Step 1: Place the silicon wafer in a 9% concentration, 80°C KOH solution for 3 minutes to react. A pyramid light-trapping structure is formed on the surface of the silicon wafer through the anisotropic etching mechanism of alkali on silicon. The size of the surface pyramid is 0.5um-10um, and the surface reflectivity of the silicon wafer is between 5%-30%. Then, the front and back sides of the silicon wafer are cleaned with HF solution to remove surface metal ion contamination. At this time, a velvet structure on the front and back sides is formed. Step 2: A layer of intrinsic amorphous silicon and a layer of phosphorus-doped n-type amorphous silicon are sequentially deposited on the front side by using a PECVD chemical deposition method, wherein the thickness of the intrinsic amorphous silicon is 2nm-20nm, and the thickness of the phosphorus-doped amorphous silicon is 2nm-20nm. A layer of intrinsic amorphous silicon and a layer of boron-doped p-type amorphous silicon are also deposited on the back side at one time, wherein the thickness of the intrinsic amorphous silicon is 2nm-20nm, and the thickness of the boron-doped amorphous silicon is 2nm-20nm. Step 3: Use PVD method to deposit multiple layers of TCO conductive films with different refractive indices on the front and back of the silicon wafer, where the total film thickness is 50nm-200nm and the refractive index is 1.6-2.5; Step 4: Deposit a 10-500nm metal seed layer on both the front and back sides by sputtering. The metal seed layer is pure copper metal. Step 5: Print photosensitive ink or wet film (negative) on the front side by screen printing, with ink viscosity of 1000~15000cps, screen printing screen of 100~350 mesh, screen film thickness of 10~20 microns, and yarn thickness of 30~60 microns; Step 6: After the ink is screen-printed, the baking temperature is 70~110℃, the baking time is 2~20min, and the film thickness after the ink is dried is 8~20 microns; Step 7: In the same way, print photosensitive ink or wet film (negative) on the back of the battery by screen printing. The ink viscosity is 1000~15000cps, the screen printing screen is 100~350 mesh, the screen film thickness is 10~20 microns, and the yarn thickness is 30~60 microns; Step 8: Graphic exposure of ink on the front and back sides (LDI or mask projection exposure), exposure energy 30mj~100mj, line width range 5um~100um; Step 9: Development: Use 1% sodium carbonate developer solution to spray and soak the front and back ink surfaces for 1 minute, and the unexposed parts of the front and back are developed; Step 10: After exiting the developing tank, do not dry it, and immediately enter the pickling tank for pickling by immersion or spray immersion. After development, soak the exposed substrate in a pickling solution. The pickling solution consists of acetic acid and an auxiliary agent. The acetic acid concentration is 1% (volume ratio). The auxiliary agent is a surfactant, and the concentration of the auxiliary agent is 0.5% (volume ratio). The pickling temperature range is 30°C and the time is 2 minutes. The specific SEM of the bottom of the groove is as follows Figure 3 As shown, there is less residual ink and the morphology is as Figure 4 As shown, the morphology is good; Step 11: After pickling, rinse thoroughly with deionized water or tap water to remove the pickling solution and its residues, use airflow drying or other appropriate drying methods to dry until there is no moisture at all, forming a groove pattern with copper bottom on the front and back sides (line width range 5um~100um); Step 12: After cleaning, it is sent to the electroplating tank for copper electroplating to form a high-quality copper pattern; Step 13: Use KOH solution (6% concentration) to remove the ink on the front and back sides, thus forming a battery cell with grid lines on the front and back sides.

[0034] Example 3 Step 1: Place the silicon wafer in a 9% concentration, 80°C KOH solution for 3 minutes to react. A pyramid light-trapping structure is formed on the surface of the silicon wafer through the anisotropic etching mechanism of alkali on silicon. The size of the surface pyramid is 0.5um-10um, and the surface reflectivity of the silicon wafer is between 5%-30%. Then, the front and back sides of the silicon wafer are cleaned with HF solution to remove surface metal ion contamination. At this time, a velvet structure on the front and back sides is formed. Step 2: A layer of intrinsic amorphous silicon and a layer of phosphorus-doped n-type amorphous silicon are sequentially deposited on the front side by using a PECVD chemical deposition method, wherein the thickness of the intrinsic amorphous silicon is 2nm-20nm, and the thickness of the phosphorus-doped amorphous silicon is 2nm-20nm. A layer of intrinsic amorphous silicon and a layer of boron-doped p-type amorphous silicon are also deposited on the back side at one time, wherein the thickness of the intrinsic amorphous silicon is 2nm-20nm, and the thickness of the boron-doped amorphous silicon is 2nm-20nm. Step 3: Use PVD method to deposit multiple layers of TCO conductive films with different refractive indices on the front and back of the silicon wafer, where the total film thickness is 50nm-200nm and the refractive index is 1.6-2.5; Step 4: Deposit a 10-500nm metal seed layer on both the front and back sides by sputtering. The metal seed layer is pure copper metal. Step 5: Print photosensitive ink or wet film (negative) on the front side by screen printing, with ink viscosity of 1000~15000cps, screen printing screen of 100~350 mesh, screen film thickness of 10~20 microns, and yarn thickness of 30~60 microns; Step 6: After the ink is screen-printed, the baking temperature is 70~110℃, the baking time is 2~20min, and the film thickness after the ink is dried is 8~20 microns; Step 7: In the same way, print photosensitive ink or wet film (negative) on the back of the battery by screen printing. The ink viscosity is 1000~15000cps, the screen printing screen is 100~350 mesh, the screen film thickness is 10~20 microns, and the yarn thickness is 30~60 microns; Step 8: Graphic exposure of ink on the front and back sides (LDI or mask projection exposure), exposure energy 30mj~100mj, line width range 5um~100um; Step 9: Development: Use 1% sodium carbonate developer solution to spray and soak the front and back ink surfaces for 1 minute, and the unexposed parts of the front and back are developed; Step 10: After exiting the developing tank, do not dry it, and immediately enter the pickling tank for pickling by immersion or spray immersion. After development, expose it and soak it in the pickling solution. The pickling solution consists of acetic acid and an auxiliary agent. The concentration of acetic acid is 3% (volume ratio). The auxiliary agent is a surfactant and the concentration of the auxiliary agent is 0.5% (volume ratio). The pickling temperature is 30°C and the time is 2 minutes. Step 11: After pickling, rinse thoroughly with deionized water or tap water to remove the pickling solution and its residues, use airflow drying or other appropriate drying methods to dry until there is no moisture at all, and form a groove pattern with copper bottom on the front and back sides (line width range 5um~100um) (such as Figure 6 As shown in the figure), the specific SEM of the bottom of the groove is as follows Figure 5 As shown, the residual ink is significantly reduced compared with the first two embodiments; Step 12: After cleaning, it is sent to the electroplating tank for copper electroplating to form high-quality copper patterns (such as Figure 7 shown); Step 13: Use KOH solution (concentration 6%) to remove the ink on the front and back sides, thus forming a battery cell with grid lines on the front and back sides (such as Figure 8 as shown).

[0035] Example 4 Step 1: Place the silicon wafer in a 2.5% concentration, 60°C KOH solution for 20 minutes to react. A pyramid light-trapping structure is formed on the surface of the silicon wafer through the anisotropic etching mechanism of alkali on silicon. The size of the surface pyramid is 0.5um-10um, and the surface reflectivity of the silicon wafer is between 5%-30%. Then, the front and back sides of the silicon wafer are cleaned with HF solution to remove surface metal ion contamination. At this time, a velvet structure on the front and back sides is formed. Step 2: A layer of intrinsic amorphous silicon and a layer of phosphorus-doped n-type amorphous silicon are sequentially deposited on the front side by using a PECVD chemical deposition method, wherein the thickness of the intrinsic amorphous silicon is 2nm-20nm, and the thickness of the phosphorus-doped amorphous silicon is 2nm-20nm. A layer of intrinsic amorphous silicon and a layer of boron-doped p-type amorphous silicon are also deposited on the back side at one time, wherein the thickness of the intrinsic amorphous silicon is 2nm-20nm, and the thickness of the boron-doped amorphous silicon is 2nm-20nm. Step 3: Use PVD method to deposit a layer of TCO conductive film on the front and back of the silicon wafer, where the total film thickness is 50nm-200nm and the refractive index is 1.6-2.5; Step 4: Deposit a 10-500nm metal seed layer on both the front and back sides by sputtering. The metal seed layer is pure copper metal, or alloy metals including copper, nickel, molybdenum, etc. Step 5: Print photosensitive ink or wet film (negative) on the front side by screen printing, with ink viscosity of 1000~15000cps, screen printing screen of 100~350 mesh, screen film thickness of 10~20 microns, and yarn thickness of 30~60 microns; Step 6: Bake the ink after screen printing at a temperature of 70-110°C for 2-20 minutes. The film thickness after the ink is dried is 8-20 microns. Step 7: In the same way, print photosensitive ink or wet film (negative) on the back of the battery by screen printing. The ink viscosity is 1000~15000cps, the screen printing screen is 100~350 mesh, the screen film thickness is 10~20 microns, and the yarn thickness is 30~60 microns; Step 8: Graphic exposure of ink on the front and back sides (LDI or mask projection exposure), exposure energy 30mj~100mj, line width range 5um~100um; Step 9: Development: Use 1.5% potassium carbonate developer solution to spray and soak the front and back ink surfaces for 2 minutes, and the unexposed parts of the front and back are developed; Step 10: After exiting the developing tank, the substrate is immediately put into the pickling tank for pickling by immersion or spray immersion without drying. After development, the exposed substrate is soaked in a pickling solution. The pickling solution comprises acetic acid and an auxiliary agent. The concentration of the acid component is 4% (volume ratio). The auxiliary agent is a surfactant. The concentration range of the auxiliary agent is 0.5% (volume ratio). The pickling temperature is 30°C and the time is 3 minutes. Step 11: After pickling, rinse thoroughly with deionized water or tap water to remove the pickling solution and its residues, use airflow drying or other appropriate drying methods to dry until there is no moisture at all, forming a groove pattern with copper bottom on the front and back sides (line width range 5um~100um); Step 12: After cleaning, it is sent to the electroplating tank for copper electroplating to form a high-quality copper pattern; Step 13: Use NaOH solution (concentration 5%) to remove the ink on the front and back sides, thus forming a battery cell with grid lines on the front and back sides.

[0036] Example 5 Step 1: Place the silicon wafer in a KOH or NaOH solution with a concentration of 8% and a temperature of 50°C for 5 minutes to form a pyramid light-trapping structure on the surface of the silicon wafer through the anisotropic etching mechanism of alkali on silicon. The size of the surface pyramid is 0.5um-10um, and the surface reflectivity of the silicon wafer is between 5%-30%. Then, use HF solution to clean the front and back of the silicon wafer to remove surface metal ion contamination. At this time, a velvet structure on the front and back is formed. Step 2: A layer of intrinsic amorphous silicon and a layer of phosphorus-doped n-type amorphous silicon are sequentially deposited on the front side by using a PECVD chemical deposition method, wherein the thickness of the intrinsic amorphous silicon is 2nm-20nm, and the thickness of the phosphorus-doped amorphous silicon is 2nm-20nm. A layer of intrinsic amorphous silicon and a layer of boron-doped p-type amorphous silicon are also deposited on the back side at one time, wherein the thickness of the intrinsic amorphous silicon is 2nm-20nm, and the thickness of the boron-doped amorphous silicon is 2nm-20nm. Step 3: Use the RPD physical method to deposit multiple layers of TCO conductive films with different refractive indices on the front and back of the silicon wafer, where the total film thickness is 50nm-200nm and the refractive index is 1.6-2.5; Step 4: Deposit a 10-500nm metal seed layer on both the front and back sides by sputtering. The metal seed layer is pure copper metal, or alloy metals including copper, nickel, molybdenum, etc. Step 5: Print photosensitive ink or wet film (negative) on the front side by screen printing, with ink viscosity of 1000~15000cps, screen printing screen of 100~350 mesh, screen film thickness of 10~20 microns, and yarn thickness of 30~60 microns; Step 6: After the ink is screen-printed, the baking temperature is 70~110℃, the baking time is 2~20min, and the film thickness after the ink is dried is 8~20 microns; Step 7: In the same way, print photosensitive ink or wet film (negative) on the back of the battery by screen printing. The ink viscosity is 1000~15000cps, the screen printing screen is 100~350 mesh, the screen film thickness is 10~20 microns, and the yarn thickness is 30~60 microns; Step 8: Graphic exposure of ink on the front and back sides (LDI or mask projection exposure), exposure energy 30mj~100mj, line width range 5um~100um; Step 9: Development: Use 3% sodium hydroxide developer solution to spray and soak the front and back ink surfaces for 30 seconds, and the unexposed parts of the front and back are developed; Step 10: After exiting the developing tank, the substrate is immediately put into the pickling tank for pickling by immersion or spray immersion without drying. After development, the exposed substrate is soaked in a pickling solution. The pickling solution includes citric acid and an auxiliary agent. The concentration of the acid component is 5% (volume ratio). The auxiliary agent is a surfactant. The concentration of the auxiliary agent is 1% (volume ratio). The pickling temperature range is 40°C and the time is 2 minutes. Step 11: After pickling, rinse thoroughly with deionized water or tap water to remove the pickling solution and its residues, use airflow drying or other appropriate drying methods to dry until there is no moisture at all, forming a groove pattern with copper bottom on the front and back sides (line width range 5um~100um); Step 12: After cleaning, it is sent to the electroplating tank for copper electroplating to form a high-quality copper pattern; Step 13: Use KOH solution (6% concentration) to remove the ink on the front and back sides, thus forming a battery cell with grid lines on the front and back sides.

[0037] The process of the present invention can reduce the residual ink at the bottom of the groove after development, improve the bonding strength of the copper grid line, and reduce the risk of grid detachment. As shown in the following table, after acid washing, the grid detachment ratio is greatly reduced, and the bottom contact resistance is also reduced. The relevant values ​​of Examples 4-5 are not substantially different from those of Example 3, and are significantly better than Example 1. The relevant values ​​of Example 2 are worse than those of Example 3, but significantly better than Example 1.

[0038] Those skilled in the art will easily understand that the above descriptions are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A process for cleaning residual ink after photosensitive ink development and ensuring groove development morphology, characterized in that: The process comprises the following steps: (1) Place the silicon wafer in an alkaline solution at 50-90°C for reaction. Through the anisotropic etching mechanism of alkali on silicon, a pyramid light-trapping structure is formed on the surface of the silicon wafer. The size of the surface pyramid is 0.5um-10um, and the surface reflectivity of the silicon wafer is between 5%-30%. Then, the front and back sides of the silicon wafer are cleaned with HF solution to remove surface metal ion contamination. At this time, a velvet structure on the front and back sides is formed. (2) Using PECVD chemical deposition method, a layer of intrinsic amorphous silicon and a layer of phosphorus-doped n-type amorphous silicon are sequentially deposited on the front side, and a layer of intrinsic amorphous silicon and a layer of boron-doped p-type amorphous silicon are sequentially deposited on the back side; (3) Using PVD or RPD physical method to deposit a layer of TCO conductive film or multiple layers of TCO conductive films with different refractive indices on the front and back of the silicon wafer, with a total film thickness of 50nm-200nm and a refractive index of 1.6-2.5; (4) Deposit a 10-500 nm metal seed layer on the front and back sides by sputtering; (5) Printing photosensitive ink or wet film on the front side by screen printing; (6) The ink is baked after screen printing, and the film thickness after the ink is dried is 8~20 microns; (7) Printing photosensitive ink or wet film on the back side by screen printing in the same manner as step (5); (8) Graphic exposure of ink on the front and back sides; (9) Development: spray and soak the front and back ink surfaces with developer solution, and the unexposed parts of the front and back are developed; (10) After leaving the developing tank, it is not dried and immediately put into the pickling tank for pickling; (11) After pickling, rinse thoroughly with deionized water or tap water to remove the pickling solution and its residues, and then dry until there is no moisture at all to form a groove pattern with a copper bottom on the front and back sides; (12) After cleaning, the copper is sent to the electroplating tank for copper electroplating to form a high-quality copper pattern; (13) Use NaOH or KOH solution to remove the ink on the front and back sides, thereby forming a battery cell with grid lines on the front and back sides.

2. The process for cleaning residual ink after developing photosensitive ink and ensuring groove development morphology according to claim 1, characterized in that: The alkali solution in step (1) is KOH or NaOH solution; preferably, the mass concentration of the alkali solution is 0.5%-10%.

3. The process for cleaning residual ink after developing photosensitive ink and ensuring groove development morphology according to claim 1, characterized in that: In the step (2), the thickness of the intrinsic amorphous silicon deposited on the front side is 2nm-20nm, and the thickness of the phosphorus-doped amorphous silicon is 2nm-20nm; preferably, the thickness of the intrinsic amorphous silicon deposited on the back side in the step (2) is 2nm-20nm, and the thickness of the boron-doped amorphous silicon is 2nm-20nm.

4. The process for cleaning residual ink after photosensitive ink development and ensuring groove development morphology according to claim 1, characterized in that: In the step (4), the metal seed layer is pure copper metal, or an alloy metal containing copper, nickel and molybdenum; preferably, in the step (5), the ink viscosity in screen printing is 1000-15000 cps, the screen printing plate is 100-350 mesh, the screen film thickness is 10-20 microns, and the yarn thickness is 30-60 microns.

5. The process for cleaning residual ink after photosensitive ink development and ensuring groove development morphology according to claim 1, characterized in that: In the step (6), the baking temperature is 70-110° C. and the baking time is 2-20 min.

6. The process for cleaning residual ink after photosensitive ink development and ensuring groove development morphology according to claim 1, characterized in that: The patterned exposure in step (8) is performed by LDI or mask projection exposure. Preferably, the exposure energy of the patterned exposure in step (8) is 30 mj~100 mj, and the line width range is 5 um~100 um.

7. The process for cleaning residual ink after photosensitive ink development and ensuring groove development morphology according to claim 1, characterized in that: The developer in step (9) is one or more of potassium carbonate, sodium carbonate, potassium hydroxide and sodium hydroxide solution; preferably, the mass concentration of the developer solution is 0.5% to 5%; preferably, the spraying and soaking time in step (9) is 30s to 2min.

8. The process for cleaning residual ink after photosensitive ink development and ensuring groove development morphology according to claim 1, characterized in that: The pickling solution in step (10) comprises an acidic component and an auxiliary agent. Preferably, the acidic component is an organic acid, preferably acetic acid or citric acid. Preferably, the volume concentration of the acidic component is 0.5% to 10%. Preferably, the auxiliary agent is a surfactant. Preferably, the volume concentration of the auxiliary agent is 0.1% to 1%.

9. The process for cleaning residual ink after photosensitive ink development and ensuring groove development morphology according to claim 1, characterized in that: The pickling temperature in step (10) is in the range of 25°C to 60°C, and the pickling time is in the range of 1 minute to 10 minutes; the pickling method is immersion or spray immersion.

10. The process for cleaning residual ink after photosensitive ink development and ensuring groove development morphology according to claim 1, characterized in that: The line width of the groove pattern in step (11) is in the range of 5 um to 100 um; preferably, the mass concentration of the NaOH or KOH solution in step (13) is in the range of 2% to 10%.

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