Horizontal electroplating method of solar cell silicon wafer

Abstract

The invention relates to a horizontal electroplating method for a solar cell silicon wafer, and relates to the field of solar cell electroplating. According to the technical scheme, the dynamic close fit between the cathode conductive roller and the upper surface of the solar cell silicon wafer is realized through the gravity self-adaptive structure, so that the contact resistance between the cathode conductive roller and the solar cell silicon wafer is remarkably reduced, and the current conduction stability is improved; the problem of uneven coating thickness caused by poor contact in the traditional electroplating process is fundamentally solved, the mechanical stress concentration is effectively avoided, the hidden crack and fragment risk of the solar cell silicon wafer is greatly reduced, and the collaborative improvement of the electroplating efficiency, quality and cost control is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cell electroplating, and particularly relates to a horizontal electroplating method for silicon wafers of solar cells. Background Art

[0002] In the manufacturing process of crystalline silicon solar cells, the electroplating of the lower surface metallization is a key link for realizing efficient carrier collection. With the development of high-efficiency cell technologies such as PERC and TOPCon, the requirement for the conductivity uniformity of the back grid lines has been raised to the accuracy level of ±5 μm. At the same time, the trend of thinning (thickness ≤ 150 μm) has significantly enhanced the mechanical stress sensitivity of the contact devices. The existing industrial solutions generally adopt the electroplating technology with the cathode contacting the upper surface and electroplating the lower surface. However, due to the edge electric field effect, the electroplating of the lower surface still needs to conduct current through the upper surface cathode. This indirect conduction mode poses strict requirements on the stability of the contact interface. The industry standard requires that the contact resistance fluctuation of the cathode contact be maintained at < ±5% and the mechanical damage rate be < 0.1% during continuous production, which poses double challenges to the material properties and structural design of the contact devices.

[0003] On the one hand, the cathode brush solution in the prior art has an inherent defect of dynamic contact instability: the discrete structure of the cathode brush generates large fluctuations, which in turn causes the over-tolerance of the coating thickness and easily leads to the attenuation of the fill factor of the cell.

[0004] On the other hand, the fixed cathode conductive roller solution in the prior art exposes fatal defects in the application of thinning: when the thickness of the silicon wafer ≤ 150 μm, the edge stress generated by the fixed cathode conductive roller is very easy to exceed the fracture strength of the silicon wafer, which in turn leads to a soaring of the hidden crack rate and a significant increase in the fragmentation rate compared with the conventional process. The geometric mismatch in the contact area further deteriorates the current density uniformity. Summary of the Invention

[0005] The purpose of the present invention is to provide a horizontal electroplating method for silicon wafers of solar cells to solve the problems existing in the above-mentioned prior art.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows: A horizontal electroplating method for silicon wafers of solar cells, the method comprising: The silicon wafer of the solar cell moves horizontally after contacting the supporting roller; In response to the silicon wafer of the solar cell moving into the electroplating solution tank, the lower surface of the silicon wafer of the solar cell contacts the electroplating solution in the electroplating solution tank, and the upper surface of the silicon wafer of the solar cell contacts the cathode conductive roller arranged above the electroplating solution tank; Connect the negative electrode of the power supply to the cathode conductive roller, connect the anode in the electroplating solution tank to the positive electrode of the power supply. After turning on the power supply, electroplating occurs on the lower surface of the silicon wafer of the solar cell. Wherein, the cathode conductive roller includes an axial center part and a conductive sleeve part located outside the axial center part, and the conductive sleeve part is dynamically and tightly attached to the upper surface of the silicon wafer of the solar cell by its own weight adaptively.

[0007] In a possible implementation manner, the axial center part includes an axial center, the conductive sleeve part includes an axial center ring sleeved on the outer periphery of the axial center and a conductive outer sleeve located outside the axial center ring, and the conductive outer sleeve is elastically connected to the axial center ring through an elastic member; The conductive outer sleeve is of a single-layer or multi-layer structure; The conductive outer sleeve is a single whole, or consists of multiple pieces arranged at axial intervals; Wherein, when the conductive outer sleeve is of a single-layer structure, the axial center is electrically connected to the conductive outer sleeve; when the conductive outer sleeve is of a multi-layer structure, the axial center is electrically connected to at least the outermost layer of the conductive outer sleeve.

[0008] In a possible implementation manner, the conductive outer sleeve is elastically connected to the axial center ring through a plurality of cylindrically helical compression springs distributed radially, and the cylindrically helical compression springs are made of stainless steel and the surfaces are nickel-plated.

[0009] In a possible implementation manner, the conductive outer sleeve is elastically connected to the axial center ring through a plurality of wavy spring washers distributed radially.

[0010] In a possible implementation manner, the conductive outer sleeve is elastically connected to the axial center ring through a plurality of micro conical disc springs distributed radially.

[0011] In a possible implementation manner, the conductive outer sleeve is elastically connected to the axial center ring through a plurality of elastic rubber columns distributed radially.

[0012] In a possible implementation manner, the conductive outer sleeve is elastically connected to the axial center ring through a plurality of elastic sheets distributed radially, and the elastic sheets are stainless steel elastic sheets or polymer compound elastic sheets.

[0013] In a possible implementation manner, the conductive outer sleeve is elastically connected to the axial center ring through a plurality of elastic sponges distributed radially.

[0014] In a possible implementation manner, the conductive outer sleeve is elastically connected to the axial center ring through a single cylindrically helical compression spring arranged axially.

[0015] In a possible implementation, the supporting roller rotates synchronously with the cathode conductive roller, and the linear velocity difference between the two does not exceed ±0.1 m / min.

[0016] In a possible implementation, the electroplating solution in the electroplating solution tank is a solution containing copper ions.

[0017] In a possible implementation, the electroplating solution in the electroplating solution tank is a solution containing nickel ions.

[0018] In a possible implementation, the electroplating solution in the electroplating solution tank is a solution containing tin ions.

[0019] In a possible implementation, the electroplating solution in the electroplating solution tank is a solution containing silver ions.

[0020] In a possible implementation, the surface of the supporting roller is wrapped with a layer of polymer elastic material to prevent scratching the silicon wafer of the solar cell.

[0021] In a possible implementation, in response to the electroplating process of the silicon wafer of the solar cell, the electroplating solution is circulated and filtered to remove impurities in the electroplating solution.

[0022] In a possible implementation, in response to the completion of the electroplating of the silicon wafer of the solar cell, the silicon wafer of the solar cell is washed and dried.

[0023] The beneficial effects brought by the technical solution provided by the present invention at least include: This technical solution realizes the dynamic close fit between the cathode conductive roller and the upper surface of the silicon wafer of the solar cell through the gravity adaptive structure, significantly reduces the contact resistance between the cathode conductive roller and the silicon wafer of the solar cell and improves the current conduction stability, fundamentally solves the problem of uneven coating thickness caused by poor contact in the traditional electroplating process, effectively avoids mechanical stress concentration, greatly reduces the risk of hidden cracks and fragmentation of the silicon wafer of the solar cell, and realizes the coordinated improvement of electroplating efficiency, quality and cost control. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and are used to explain the present invention together with the embodiments of the present invention, and do not constitute a limitation to the present invention.

[0025] Figure 1 The flowchart shows the horizontal electroplating method of the silicon wafer of the solar cell provided by an exemplary embodiment of the present invention.

[0026] Figure 2 The schematic diagram shows the process structure when the silicon wafer of the solar cell provided by an exemplary embodiment of the present invention is horizontally electroplated.

[0027] Figure 3 Shows a schematic radial cross - section of a cathode conductive roller provided by an exemplary embodiment of the present invention.

[0028] Figure 4 Shows a schematic axial cross - section of a cathode conductive roller provided by an exemplary embodiment of the present invention.

[0029] Figure 5 Shows a schematic structural view of a cathode conductive roller provided by an exemplary embodiment of the present invention; wherein, Figure 5 (a) is an axonometric view, Figure 5 (b) is a radial cross - section view.

[0030] Figure 6 Shows a schematic structural view of another cathode conductive roller provided by an exemplary embodiment of the present invention; wherein, Figure 6 (a) is an axonometric view, Figure 6 (b) is a radial cross - section view.

[0031] Figure 7 Shows a schematic structural view of another cathode conductive roller provided by an exemplary embodiment of the present invention.

[0032] Figure 8 Shows a schematic axial cross - section of another cathode conductive roller provided by an exemplary embodiment of the present invention.

[0033] In the figure: 1, silicon wafer of solar cell; 2, electroplating solution tank; 3, supporting roller; 4, cathode conductive roller; 41, axis center; 42, axis center ring; 43, conductive outer sleeve; 431, rigid outer sleeve; 432, flexible outer sleeve; 44, elastic member; 5, anode; 6, power supply. Detailed implementation manners

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] Among them, the same components are denoted by the same reference numerals. It should be noted that the terms "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to the directions in the attached drawings of the present invention specification, and the terms "bottom surface" and "top surface", "inner" and "outer" respectively refer to facing or away from a specific component. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention specification, "a plurality of" means two or more.

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0037] Embodiment 1 Figure 1 The flowchart of the horizontal electroplating method of a solar cell silicon wafer provided by an exemplary embodiment of the present invention is shown. Figure 2 The process structure diagram during horizontal electroplating of a solar cell silicon wafer provided by an exemplary embodiment of the present invention is shown. The horizontal electroplating method of the solar cell silicon wafer specifically includes: Step 101, after the solar cell silicon wafer 1 contacts the supporting roller 3, it moves in the horizontal direction.

[0038] In the embodiments of the present application, before electroplating, a series of pretreatment operations need to be performed on the solar cell silicon wafer to ensure the electroplating effect. For example, the lower surface of the solar cell silicon wafer is cleaned to remove impurities such as oil stains and dust on the surface. Chemical cleaning methods can be used, such as pickling with a dilute hydrochloric acid solution. The pickling time depends on the pollution degree of the solar cell silicon wafer, generally 1 - 3 minutes. After pickling, it is thoroughly rinsed with deionized water to ensure that there is no residual acid solution on the surface. At the same time, the surface roughness of the solar cell silicon wafer needs to be detected and adjusted. Appropriate surface roughness helps to improve the adhesion of the electroplating layer.

[0039] Step 102, in response to the solar cell silicon wafer 1 moving into the electroplating solution tank 2, the lower surface of the solar cell silicon wafer 1 contacts the electroplating solution in the electroplating solution tank 2, and the upper surface of the solar cell silicon wafer 1 contacts the cathode conductive roller 4 provided above the electroplating solution tank 2; wherein, the cathode conductive roller 4 includes an axis part and a conductive sleeve part located outside the axis part, and the conductive sleeve part adaptively and dynamically fits tightly with the upper surface of the solar cell silicon wafer 1 by its own weight.

[0040] In the embodiments of the present application, the supporting roller not only needs to drive the silicon wafer of the solar cell to move smoothly, but also needs to ensure the stability of the silicon wafer of the solar cell during the movement. The material selection of the supporting roller needs to consider wear resistance and corrosion resistance, and generally stainless steel material can be selected. Preferably, the surface of the supporting roller is wrapped with a layer of polymer elastic material to prevent scratching the silicon wafer of the solar cell. The thickness of the polymer elastic material layer is generally 1-3 millimeters to ensure that it can not only prevent scratching the silicon wafer of the solar cell, but also provide sufficient supporting force. The rotation speed of the supporting roller needs to be accurately controlled according to the requirements of the electroplating process and match the rotation speed of the cathode conductive roller to ensure the uniform movement of the silicon wafer of the solar cell.

[0041] Step 103, connect the cathode conductive roller 4 to the negative pole of the power supply 6, connect the anode 5 in the electroplating solution tank 2 to the positive pole of the power supply 6. After turning on the power supply 6, electroplating occurs on the lower surface of the silicon wafer 1 of the solar cell.

[0042] In the embodiments of the present application, the way that the conductive sleeve part of the cathode conductive roller adaptively and dynamically fits tightly with the upper surface of the silicon wafer of the solar cell by its own weight is one of the key innovations of the present invention. The self-weight design of the conductive sleeve part in the cathode conductive roller needs to be accurately calculated according to the size, thickness of the silicon wafer of the solar cell and the requirements of the electroplating process to ensure that it can not only provide sufficient pressure for good electrical contact, but also will not cause excessive pressure on the silicon wafer of the solar cell and cause damage, so as to realize that the cathode conductive roller can adaptively adjust according to the tiny undulations on the surface of the silicon wafer of the solar cell during the fitting process and ensure the contact uniformity of the entire upper surface.

[0043] Furthermore, Figure 3 Fig. shows a schematic radial cross-sectional view of a cathode conductive roller provided by an exemplary embodiment of the present invention. Figure 4 Fig. shows a schematic axial cross-sectional view of a cathode conductive roller provided by an exemplary embodiment of the present invention. The shaft center part includes a shaft center 41, the conductive sleeve part includes a shaft center ring 42 sleeved on the outer periphery of the shaft center 41, and a conductive outer sleeve 43 located outside the shaft center ring 42. The conductive outer sleeve 43 is elastically connected to the shaft center ring 42 through an elastic member 44. The conductive outer sleeve 43 is composed of a single-layer conductive outer sleeve. The shaft center 41 is electrically connected to the conductive outer sleeve 43. The single-layer conductive outer sleeve can be a rigid conductive material, such as a stainless steel sleeve; it can also be a non-rigid conductive material, such as a conductive rubber tube.

[0044] In one example, Figure 5 Fig. shows a schematic structural view of a cathode conductive roller provided by an exemplary embodiment of the present invention; wherein, Figure 5 (a) is an axonometric view, Figure 5(b) is a radial sectional view. In this example, the elastic member 44 is an elastic sheet, which can be a stainless - steel elastic sheet or a polymer compound elastic sheet.

[0045] In another example, the central axis ring 42 and the conductive outer sleeve 43 are elastically connected by a plurality of cylindrically helical compression springs evenly distributed in the radial direction. The material of the cylindrically helical compression spring is stainless steel and its surface is nickel - plated. Stainless steel has good corrosion resistance and strength, and nickel - plating further improves the corrosion resistance and wear resistance of the spring. Parameters such as the wire diameter, number of turns, and elastic coefficient of the cylindrically helical compression spring need to be calculated and selected according to the actual working conditions to ensure that it can provide appropriate elastic force. For example, the wire diameter is generally between 0.5 - 1.2 mm, the effective number of turns is 5 - 8 turns, and the elastic coefficient is between 0.8 - 1.5 N / mm.

[0046] In another example, the central axis ring 42 and the conductive outer sleeve 43 are elastically connected by a plurality of wave - shaped spring washers evenly distributed in the radial direction. The wave - shaped spring washer has unique elastic characteristics and can provide large elastic deformation in a small space. Parameters such as its waveform height and wave - peak spacing will affect its elastic performance. The waveform height is generally between 0.3 - 0.8 mm, and the wave - peak spacing is between 1.2 - 2.0 mm.

[0047] In another example, the central axis ring 42 and the conductive outer sleeve 43 are elastically connected by a plurality of micro - conical disc springs evenly distributed in the radial direction. The micro - conical disc spring has a high load - bearing capacity and good elastic stability. Parameters such as its outer diameter, cone angle, and combination method need to be optimized according to actual requirements. The outer diameter is generally between 6 - 10 mm, the cone angle is between 18° - 25°, and the combination method can be 3 - 5 pieces stacked in opposition.

[0048] In another example, the central axis ring 42 and the conductive outer sleeve 43 are elastically connected by a plurality of elastic rubber columns evenly distributed in the radial direction. The Shore hardness of the elastic rubber column needs to be selected according to the thickness and characteristics of the solar cell silicon wafer. For thinner solar cell silicon wafers, soft rubber columns with a Shore hardness between 50 - 60 HA can be selected; for thicker solar cell silicon wafers, hard rubber columns with a Shore hardness between 70 - 80 HA can be selected. At the same time, the dynamic compression set of the elastic rubber column should be less than 10% to ensure its long - term use stability.

[0049] In another example, the central axis ring 42 and the conductive outer sleeve 43 are elastically connected by a plurality of elastic sponges evenly distributed in the radial direction. The elastic sponge is usually made of polyurethane or silicon - based materials with excellent aging resistance and insulation properties. Its porous structure can provide buffering and shock - absorption performance, effectively reducing the impact of mechanical vibration on the conductive components.

[0050] In the embodiments of the present application, a servo motor is selected to drive the shaft center, which can accurately control the rotation speed of the shaft center and can be flexibly adjusted according to different stages of the electroplating process.

[0051] In the embodiments of the present application, the gravity exerted by the cathode conductive roller on the silicon wafer of the solar cell is determined by the number of elastic members, the specifications of the elastic members, the wall thickness of the conductive outer sleeve, and the material of the conductive outer sleeve.

[0052] Optionally, the cross-sectional shape of the shaft center 41 includes but is not limited to one of a circle, an ellipse, a triangle, a quadrilateral, a pentagon, a hexagon, and an octagon.

[0053] Optionally, the shaft center 41 can be composed of a single material or more than one material. For example, an insulating material or a conductive material can be coated on the shaft center 41.

[0054] Optionally, the cross-sectional shape of the shaft center ring 42 includes but is not limited to one of a circle, an ellipse, a triangle, a quadrilateral, a pentagon, a hexagon, and an octagon.

[0055] It is worth mentioning that the supporting roller rotates synchronously with the cathode conductive roller, and the linear velocity difference between the two does not exceed ±0.1 m / min. To achieve this precise synchronous rotation, a servo motor can be used in conjunction with an absolute encoder to achieve synchronous control of the supporting roller and the cathode conductive roller through the CAN bus.

[0056] Furthermore, the power supply 6 uses a pulse power supply, and the parameter settings of the pulse power supply have an important impact on the electroplating effect. The frequency range of the pulse power supply is generally adjustable between 100 - 2000 Hz, the duty cycle is between 20 - 80%, the forward current density is between 2 - 8 A / dm², the reverse current density is between 0.5 - 2 A / dm², and the pulse rise time is less than 50 μs. By reasonably adjusting these parameters, the quality and uniformity of the electroplated layer can be improved. The material of the anode 5 is generally selected as titanium-based coated with precious metal oxides, such as IrO2 - Ta2O5, to ensure its good electrical conductivity and corrosion resistance. The area ratio of the anode to the cathode (S_A / S_C) needs to be controlled between 1:1 and 2:1 to ensure uniform current distribution during the electroplating process. Optionally, the power supply 6 can also use a DC power supply.

[0057] In one example, the electroplating solution in the electroplating solution tank 2 is a solution containing copper ions. The copper ion concentration is generally between 10 - 30 g / L, the temperature of the electroplating solution needs to be controlled between 25 - 35 °C, and the pH value is controlled between 2.5 - 4.5. To ensure the stability of the electroplating solution and the electroplating effect, appropriate additives, such as brighteners and leveling agents, can also be added to the electroplating solution to improve the quality of the coating.

[0058] In another example, the electroplating solution in the electroplating bath 2 is a solution containing nickel ions. The nickel ion concentration is generally between 8 - 25 g / L. Also, the temperature and pH value of the electroplating solution need to be controlled. Meanwhile, in order to improve the quality of the coating, corresponding additives can be added. Moreover, 0.5 - 3 g / L of boric acid can be added to the electroplating solution as a buffer to maintain the chemical stability of the electroplating solution.

[0059] In another example, the electroplating solution in the electroplating bath 2 is a solution containing tin ions. The tin ion concentration is usually controlled at 15 - 40 g / L to ensure the coating thickness and uniformity. The electroplating solution temperature needs to be maintained at 20 - 35 °C, and the pH value is adjusted to the weakly acidic range of 1.5 - 3.5 to inhibit the hydrolysis of tin ions and improve the deposition efficiency. Organic brighteners (such as aldehyde compounds) can be added to improve the surface gloss of the coating. At the same time, a small amount of antioxidant (such as ascorbic acid) is added to prevent the oxidation of tin ions. For different substrates (such as copper, steel), complexing agents (such as citric acid or tartaric acid) can also be introduced to adjust the reduction rate of tin ions to ensure the coating adhesion and compactness.

[0060] In another example, the electroplating solution in the electroplating bath 2 is a solution containing silver ions. The silver ion concentration is generally set at 5 - 20 g / L to balance the coating thickness and material cost. The electroplating solution temperature is controlled at 25 - 40 °C, and the pH value is maintained at 4.5 - 7.0 (the range from neutral to weakly alkaline) to avoid the reaction of silver ions with chloride ions to form precipitates under acidic conditions. The additives include brighteners (such as sulfur-containing organic compounds) to enhance the mirror effect of the coating, conductive salts (such as potassium nitrate) to enhance the conductivity of the solution, and stabilizers (such as potassium cyanide or thiosulfate) to prevent the agglomeration of silver ions. For the electroplating of precision electronic components, a small amount of ammonia water is often added as a buffer to maintain the pH stability of the solution. At the same time, by controlling the current density (0.5 - 2 A / dm²), a uniform and dense silver layer is ensured, which has excellent conductivity and antioxidant properties.

[0061] Specifically, in response to the electroplating process of solar cell silicon wafers, the electroplating solution is circulated and filtered to remove impurities in the electroplating solution. Exemplarily, a two-stage filtration device is used for the circulation filtration of the electroplating solution. The primary filter element has a precision of 10 μm (PP cotton), and the secondary filter element has a precision of 1 μm (ceramic membrane). The circulation flow rate is controlled at 5 - 15 L / min. At the same time, the temperature difference of the electroplating solution needs to be controlled within ±1 °C. Through circulation filtration, the cleanliness of the electroplating solution can be guaranteed, and the quality of the electroplated layer can be improved.

[0062] More specifically, in response to the completion of electroplating of the solar cell silicon wafers, the solar cell silicon wafers are washed with water and dried. Exemplarily, deionized water is used for the water wash, and a three-stage countercurrent rinsing is set to ensure that the residual electroplating solution on the surface of the solar cell silicon wafers is thoroughly cleaned, and the conductivity of the rinsed water is controlled to be <5 μS / cm. The drying process uses temperature gradient control. First, pre-drying is carried out at 60 °C, then main drying is carried out at 80 °C, and finally cooling is carried out at 50 °C. The total drying time is 8 - 15 minutes, and the wind speed is controlled at 0.5 - 1.2 m / s to ensure uniform drying of the surface of the solar cell silicon wafers and avoid defects such as water marks.

[0063] Example 2 This example is basically the same as Example 1, except that: Figure 6 Fig. shows a schematic structural diagram of another cathode conductive roller provided by an exemplary embodiment of the present invention; wherein, Figure 6 (a) is an axonometric view, Figure 6 (b) is a radial cross-sectional view. In this example, the conductive outer sleeve 43 is composed of a layer of rigid outer sleeve 431 and a layer of flexible outer sleeve 432, and the flexible outer sleeve 432 is electrically connected to the axis 41. According to specific application requirements, the conductive outer sleeve 43 can be composed of more than two layers of conductive outer sleeves, and the axis 41 is electrically connected to at least the outermost layer of the conductive outer sleeve 43; the axis 41 can be electrically connected to any layer of the conductive outer sleeve 43, or to all layers of the conductive outer sleeve 43, but must be electrically connected to the outermost layer of the conductive outer sleeve 43.

[0064] Example 3 This example is basically the same as Example 1, except that: Figure 7 Fig. shows a schematic axial cross-sectional view of another cathode conductive roller provided by an exemplary embodiment of the present invention. In this example, the elastic member 44 is an axially arranged cylindrical helical compression spring, and the spring connects the conductive outer sleeve 43 and the axis ring 42. The spring is a stainless steel spring or a polymer compound spring.

[0065] Example 4 This example is basically the same as Example 1, except that: Figure 8 Fig. shows a schematic axial cross-sectional view of another cathode conductive roller provided by an exemplary embodiment of the present invention. In this example, the cathode conductive roller 4 is realized as having a plurality of conductive sleeve portions corresponding to the axis portion. A plurality of spaced-apart conductive outer sleeves 43 are provided on the outer periphery of the axis 41. Both inner ends of each conductive outer sleeve 43 are connected to an axis ring 42 through an elastic member 44, and the axis ring 42 is sleeved on the axis 41.

[0066] It is worth mentioning that in the above embodiments, the power supply is transmitted to the conductive outer sleeve through the axis.

[0067] In summary, the technical solution realizes the dynamic close fitting of the cathode conductive roller and the upper surface of the solar cell silicon wafer through the gravity adaptive structure, significantly reduces the contact resistance between the cathode conductive roller and the solar cell silicon wafer, and improves the current conduction stability. Fundamentally, it solves the problem of uneven coating thickness caused by poor contact in the traditional electroplating process, effectively avoids mechanical stress concentration, greatly reduces the risk of solar cell silicon wafer cracking and fragmentation, and realizes the coordinated improvement of electroplating efficiency, quality and cost control.

[0068] In the embodiments disclosed in the present invention, terms such as "installation", "connection", "connection", "fixation" and the like should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "connection" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments disclosed in the present invention can be understood according to specific circumstances.

[0069] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A horizontal electroplating method for solar cell silicon wafers, characterized in that: The method comprises: The solar cell silicon wafer moves in the horizontal direction after contacting the supporting roller; In response to the solar cell silicon wafer moving into the electroplating tank, the lower surface of the solar cell silicon wafer contacts the electroplating solution in the electroplating tank, and the upper surface of the solar cell silicon wafer contacts the cathode conductive roller disposed above the electroplating tank; Connecting the cathode conductive roller to the negative pole of the power supply, connecting the anode in the electroplating liquid tank to the positive pole of the power supply, and after turning on the power supply, electroplating occurs on the lower surface of the solar cell silicon wafer; The cathode conductive roller comprises an axial portion and a conductive sleeve portion located outside the axial portion, and the conductive sleeve portion dynamically and tightly fits with the upper surface of the solar cell silicon wafer in an adaptive manner by its own weight.

2. The horizontal electroplating method of solar cell silicon wafer according to claim 1, characterized in that: The axial portion includes an axial center, and the conductive sleeve portion includes an axial ring sleeved on the outer periphery of the axial center, and a conductive outer sleeve located outside the axial ring, and the conductive outer sleeve is elastically connected to the axial ring through an elastic member; The conductive outer sleeve is a single-layer or multi-layer structure; The conductive outer sleeve is a whole piece, or is composed of a plurality of pieces arranged at intervals in the axial direction; Wherein, when the conductive outer sleeve is a single-layer structure, the axis is electrically connected to the conductive outer sleeve; when the conductive outer sleeve is a multi-layer structure, the axis is electrically connected to at least the outermost layer of the conductive outer sleeve.

3. The horizontal electroplating method of solar cell silicon wafer according to claim 2, characterized in that: The conductive outer sleeve is elastically connected to the shaft ring via a plurality of radially distributed cylindrical helical compression springs. The cylindrical helical compression springs are made of stainless steel, and the surface is nickel-plated.

4. The horizontal electroplating method for solar cell silicon wafers according to claim 2, characterized in that: The conductive outer sleeve is elastically connected to the shaft ring via a plurality of radially distributed wave-shaped spring washers.

5. The horizontal electroplating method of solar cell silicon wafer according to claim 2, characterized in that: The conductive outer sleeve is elastically connected to the shaft ring through a plurality of radially distributed micro conical disc springs.

6. The horizontal electroplating method of solar cell silicon wafer according to claim 2, characterized in that: The conductive outer sleeve is elastically connected to the shaft ring via a plurality of radially distributed elastic rubber columns.

7. The horizontal electroplating method for solar cell silicon wafers according to claim 2, characterized in that: The conductive outer sleeve is elastically connected to the shaft ring through a plurality of radially distributed elastic sheets, and the elastic sheets are stainless steel elastic sheets or polymer compound elastic sheets.

8. The horizontal electroplating method for solar cell silicon wafers according to claim 2, characterized in that: The conductive outer sleeve is elastically connected to the shaft ring via a plurality of radially distributed elastic sponges.

9. The horizontal electroplating method for solar cell silicon wafers according to claim 2, characterized in that: The conductive outer sleeve is elastically connected to the shaft ring via an axially arranged cylindrical helical compression spring.

10. The horizontal electroplating method for solar cell silicon wafers according to any one of claims 1 to 9, characterized in that: The supporting roller rotates synchronously with the cathode conductive roller, and the linear speed difference between the two does not exceed ±0.1m / min.

11. The horizontal electroplating method for solar cell silicon wafers according to claim 1, characterized in that: The electroplating solution in the electroplating solution tank is a solution containing copper ions.

12. The horizontal electroplating method for solar cell silicon wafers according to claim 1, characterized in that: The electroplating solution in the electroplating solution tank is a solution containing nickel ions.

13. The horizontal electroplating method for solar cell silicon wafers according to claim 1, characterized in that: The electroplating solution in the electroplating solution tank is a solution containing tin ions.

14. The horizontal electroplating method for solar cell silicon wafers according to claim 1, characterized in that: The electroplating solution in the electroplating solution tank is a solution containing silver ions.

15. The horizontal electroplating method for solar cell silicon wafers according to claim 1, characterized in that: The surface of the supporting roller is coated with a layer of polymer elastic material to prevent the solar cell silicon wafer from being scratched.

16. The horizontal electroplating method for solar cell silicon wafers according to claim 1, characterized in that: In response to the solar cell silicon wafer electroplating process, the electroplating solution is circulated and filtered to remove impurities in the electroplating solution.

17. The horizontal electroplating method for solar cell silicon wafers according to claim 1, characterized in that: In response to the completion of electroplating of the solar cell silicon wafer, the solar cell silicon wafer is washed and dried.

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