High reliability contact structure for series connected component-subgrid based on microbumps and surface treatment

Abstract

This invention relates to a high-reliability contact structure for a tandem connector-sub-gate based on micro-bumps and surface treatment. It includes a P-region main gate and an N-region main gate mounted on a solar cell; multiple P-region sub-gates disposed on the P-region main gate and multiple N-region sub-gates disposed on the N-region main gate; and a tandem connector mounted on the P-region and N-region sub-gates. The tandem connector has an array of micro-bumps on the side facing the P-region and N-region sub-gates. The P-region and N-region sub-gates have micro-groove structures at corresponding positions that match the micro-bumps, and the micro-groove structures are filled with a conductive composite material layer. This novel structure forms a three-dimensional mechanical interlock by embedding micro-bumps into micro-grooves, improving connection strength and peel resistance, increasing the contact area to reduce contact resistance, and employing a low-temperature hot-pressing process to achieve reliable connection. It is suitable for high-efficiency photovoltaic cell interconnection. This invention improves the mechanical stability and conductive reliability of the electrode connection.

Description

Technical Field

[0001] This utility model relates to the field of solar cell electrode interconnection technology, specifically a high-reliability contact structure for a tandem connector-sub-gate based on micro-bumps and surface treatment. Background Technology

[0002] The high-reliability contact structure of the sub-busbar is a key connection part of the solar cell electrode system. It is used to realize the electrical conduction between the series connector and the P-region sub-busbar and N-region sub-busbar on the cell. By optimizing the physical morphology and material combination of the contact interface, the structure undertakes the functions of current collection and transmission, improves the mechanical stability and conductivity of the connection, and ensures the electrical continuity and environmental tolerance of the photovoltaic module in long-term operation.

[0003] Common tandem connectors and sub-gate contact structures typically employ planar welding or conductive adhesive bonding, resulting in surface or line contact. Lacking a microstructural interlocking mechanism, the actual contact area is limited, and the interface bonding relies primarily on the adhesion of the solder or adhesive layer. When subjected to temperature cycling or mechanical stress, stress concentration easily occurs at the interface, leading to fatigue cracking of the solder joints or adhesive layer. Furthermore, the smooth surface of the sub-gate lacks an anchoring structure, failing to effectively prevent slippage or peeling of the tandem connector. Consequently, the mechanical bonding strength is low, and the peel resistance is insufficient.

[0004] Meanwhile, the contact interface is a planar structure, which limits the actual conduction area. The current is concentrated in a local area, resulting in excessively high current density. This can easily lead to local overheating and electromigration. Over long-term operation, the contact resistance gradually increases, causing power loss and hot spot risks.

[0005] When using traditional tin-lead solder for welding, high-temperature melting is required, which can easily cause thermal stress deformation of the battery cell, damage the passivation layer or cause the main grid to crack, affecting the intrinsic performance of the battery. The thermal expansion coefficients of the solder joint or conductive adhesive layer and the copper strip and silver paste do not match, and repeated thermal stress is generated in the day and night temperature difference or climate cycle, which accelerates the interface delamination or desoldering. The planar structure has high requirements for assembly precision, and even a small misalignment will lead to poor contact or cold solder joint, affecting the yield.

[0006] In addition, metal ions in solder may undergo electrochemical migration in humid and hot environments, inducing leakage or short circuits and reducing the long-term reliability and environmental tolerance of components. Utility Model Content

[0007] To address the shortcomings of existing technologies, this invention provides a high-reliability contact structure for the tandem connector-sub-gate based on micro-bumps and surface treatment. The micro-bumps and micro-grooves form a three-dimensional interlock, increasing the contact area and reducing resistance. Conductive adhesive filler forms a composite interface, and the multi-layer metal structure enhances conductivity. It is suitable for low-temperature processes and solves the problems of common tandem connector-sub-gate contact structures, such as weak planar contact bonding, easy desoldering and peeling, current concentration leading to overheating, high-temperature welding damaging the battery, easy thermal stress delamination, high assembly precision requirements, high risk of ion migration in humid and hot environments, and poor reliability.

[0008] To achieve the above objectives, this utility model provides the following technical solution: a high-reliability contact structure for a series connector-sub-gate based on micro-bumps and surface treatment, including a P-region main gate and an N-region main gate mounted on the battery cell; it also includes a plurality of P-region sub-gates disposed on the P-region main gate and a plurality of N-region sub-gates disposed on the N-region main gate;

[0009] It also includes a connector installed on the P-region subgate and the N-region subgate. The connector has an array of microbumps on the side facing the P-region subgate and the N-region subgate. The P-region subgate and the N-region subgate have microgroove structures at corresponding positions that match the microbumps, and the microgroove structures are filled with a conductive composite material layer.

[0010] Furthermore, the micro-bumps are hemispherical with a height of 10–50 μm, a diameter of 20–80 μm, and a distribution density of 80–150 per cm².

[0011] Furthermore, the microgroove structure is formed on the surface of the P-region subgate and N-region subgate by laser etching. The depth of the microgroove structure is 5–20 μm, the width is 10–30 μm, and the microgroove structure is distributed in an interlaced grid pattern with a density of 50–200 per mm².

[0012] Furthermore, the conductive composite material layer is a conductive adhesive containing silver nanoparticles. During the hot pressing process, the conductive adhesive fills the microgroove structure and contacts the microbumps, forming a metal-polymer composite interface after curing.

[0013] Furthermore, the connector is made of copper foil substrate, and the micro-bumps on the surface of the connector are composed of multiple layers of copper, nickel and silver metal.

[0014] Furthermore, the P-region subgate and N-region subgate are fine wire electrodes formed by sintering silver-based conductive paste or copper-based conductive paste, and the linewidth of the P-region subgate and N-region subgate is less than 100 μm.

[0015] Furthermore, the temperature of the hot-press connection is 150–180°C and the pressure is 10–20N. Under these conditions, the microbumps undergo plastic deformation and embed into the microgroove structure. When the serial connector is hot-pressed with the P-region sub-gate and the N-region sub-gate, the microbumps embed into the microgroove structure and form an electrical and mechanical connection with the conductive composite material layer.

[0016] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0017] 1. By setting micro-bumps on the connector and matching micro-groove structures on the sub-gate, a three-dimensional interlocking connection is formed, which improves the mechanical bonding strength of the contact interface and enhances the anti-peeling ability. The micro-bumps and micro-groove structures work together to increase the actual contact area and reduce the current density per unit area, which helps to reduce the contact resistance and improve the electrical performance.

[0018] 2. The microgroove structure is filled with conductive adhesive containing silver nanoparticles. During hot pressing, the gaps are fully filled to form a metal-polymer composite conductive path, which improves connection stability and conductivity reliability. Copper foil substrate and multilayer metal microbumps of copper, nickel and silver are used to balance high conductivity, solderability and oxidation resistance, which improves long-term operation stability. The overall structure is adapted to low temperature hot pressing process to avoid the impact of high temperature welding on battery performance, and is suitable for high-efficiency battery technology routes. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of this utility model;

[0020] Figure 2 This is a partial three-dimensional structural diagram of the present utility model;

[0021] Figure 3 This is a schematic diagram of the disassembled three-dimensional structure of this utility model;

[0022] Figure 4 This is a three-dimensional structural diagram of the location of the connector in this utility model;

[0023] Figure 5 This utility model Figure 2 A magnified three-dimensional structural diagram of location A.

[0024] In the figure: 1. P-region main gate; 2. N-region main gate; 3. P-region sub-gate; 4. N-region sub-gate; 5. Connector; 6. Microbump; 7. Microgroove structure; 8. Conductive composite material layer. Detailed Implementation

[0025] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0026] Please see Figures 1-5The high-reliability contact structure of the micro-bumps 6 and the surface-treated connecting piece 5 in this embodiment includes a P-region main grid 1 and an N-region main grid 2 mounted on the battery cell; it also includes a plurality of P-region sub-grids 3 disposed on the P-region main grid 1 and a plurality of N-region sub-grids 4 disposed on the N-region main grid 2.

[0027] In this embodiment, by setting micro-bumps 6 on the tandem connector 5 and setting matching micro-groove structures 7 on the sub-gate, a three-dimensional interlocking connection is formed, which improves the mechanical bonding strength and anti-peeling ability, increases the contact area to reduce current density and contact resistance, and improves electrical performance. The micro-groove is filled with conductive adhesive containing silver nanoparticles, and after hot pressing, a metal-polymer composite interface is formed. The copper foil substrate and the multilayer metal micro-bumps 6 of copper, nickel and silver are used to enhance conductivity and oxidation resistance. The overall structure is adapted to the low-temperature hot pressing process and is suitable for high-efficiency battery technology.

[0028] Please see Figures 1-5 In this embodiment, in order to achieve three-dimensional fitting between the micro-bumps 6 and the micro-groove structure 7 and improve mechanical strength and electrical performance, the serial connector 5 installed on the P-region sub-gate 3 and the N-region sub-gate 4 in this embodiment has an array of micro-bumps 6 on the side of the serial connector 5 facing the P-region sub-gate 3 and the N-region sub-gate 4. The P-region sub-gate 3 and the N-region sub-gate 4 have micro-groove structures 7 at corresponding positions that match the micro-bumps 6, and the micro-groove structure 7 is filled with a conductive composite material layer 8.

[0029] In this embodiment, the connector 5 is used to realize the electrical connection between adjacent battery cells. The micro-bumps 6 on its surface are embedded in the microgroove structure 7 during the hot pressing process to form a mechanical interlock and improve the connection strength. The micro-bumps 6 and the microgroove structure 7 cooperate to increase the actual contact area, reduce the contact resistance, and improve the electrical performance. The P-region sub-gate 3 and N-region sub-gate 4 serve as current collection electrodes and are responsible for transmitting photogenerated carriers to the connection interface. The microgroove structure 7 is set on the sub-gate to accommodate the micro-bumps 6, providing positioning and anchoring functions and enhancing the anti-peeling ability. The conductive composite material layer 8 fills the inside of the microgroove, wrapping the gap between the micro-bumps 6 and the groove wall to form a stable conductive path, suppress interface oxidation, and improve the long-term reliability of the connection.

[0030] It should be noted that the microbumps 6 are hemispherical, with a height of 10–50 μm and a diameter of 20–80 μm, with a distribution density of 80–150 bumps / cm². The microgroove structure 7 is formed on the surfaces of the P-region sub-gate 3 and the N-region sub-gate 4 by laser etching. The depth of the microgroove structure 7 is 5–20 μm, and the width is 10–30 μm. The microgroove structure 7 is distributed in an interlaced grid pattern (interlaced grid pattern means that the microgrooves are arranged in a crisscrossing grid pattern on the surface of the sub-gate, with adjacent microgrooves staggered to enhance multi-directional shear resistance), with a density of 50–200 bumps / mm². The hemispherical structure of the microbumps 6 is conducive to uniform deformation and smooth embedding into the microgrooves during hot pressing, with a height of 10 to 50 micrometers, ensuring... Sufficient material volume participates in plastic flow, with a diameter of 20 to 80 micrometers, matching the microgroove size for a tight fit. The distribution density is 80 to 150 per square centimeter, ensuring uniform stress in the connection area and increasing the number of conductive points. The microgroove structure 7 is formed by laser etching, exhibiting high precision and good consistency. The depth is 5 to 20 micrometers, avoiding damage to the underlying functional layer. The width is 10 to 30 micrometers, adapting to the size of the microbumps 6 for stable accommodation. The staggered grid distribution enhances multi-directional shear resistance, with a density of 50 to 200 per square millimeter, improving contact point coverage and reducing local current density. The microbumps 6 and the microgroove structure 7 work together to form a mechanical interlock, significantly improving peel strength and electrical contact reliability.

[0031] Please see Figures 1-5 In this embodiment, in order to fill the microgrooves with conductive adhesive and combine them with the multilayer metal microbumps 6 to enhance connection reliability and adapt to low-temperature processes, the conductive composite material layer 8 in this embodiment is a conductive adhesive containing silver nanoparticles. During the hot pressing process, the conductive adhesive fills the microgrooves structure 7 and contacts the microbumps 6, forming a metal-polymer composite interface after curing. The hot pressing temperature is 150–180°C and the pressure is 10–20N. Under these conditions, the microbumps 6 undergo plastic deformation and embed into the microgrooves structure 7. When the serial connector 5 is hot-pressed with the P-region sub-gate 3 and the N-region sub-gate 4, the microbumps 6 embed into the microgrooves structure 7 and form an electrical and mechanical connection with the conductive composite material layer 8.

[0032] In this embodiment, the conductive composite material layer 8 uses a conductive adhesive containing silver nanoparticles, which can flow and fully fill the microgroove structure 7 during hot pressing, contacting the microbumps 6. After curing, it forms a metal-polymer composite interface, enhancing the continuity of the conductive path and the interface bonding strength, and improving the connection stability. The microbumps 6 are composed of multiple layers of copper, nickel, and silver metals, possessing good conductivity, solderability, and oxidation resistance. Under hot pressing conditions, they are prone to plastic deformation, working together with the conductive adhesive to fill the groove and improve the contact quality. The connector 5 serves as the carrier substrate for the microbumps 6, transmitting pressure and maintaining structural integrity during the connection process. The P-region sub-gate 3 and N-region sub-gate 4 serve as current collecting electrodes, participating in the interlocking connection and conducting current. The hot pressing process is carried out at a temperature of 150 to 180 degrees Celsius and a pressure of 10 to 20 Newtons, allowing the materials to fully deform and bond, achieving a reliable connection at low temperatures and avoiding high-temperature damage to the battery structure.

[0033] It should be added that the microbumps 6 are formed on the copper foil substrate by electroplating to form a multilayer metal stack of copper / nickel / silver, and the morphology is defined by a photoresist template; the conductive composite material layer 8 is coated with conductive adhesive containing silver nanoparticles into the microgroove structure 7 by dispensing or printing.

[0034] It should be noted that the tandem connector 5 is a copper foil substrate, the micro-bumps 6 on the surface of the tandem connector 5 are composed of multiple metal layers of copper, nickel and silver, the P-region sub-gate 3 and the N-region sub-gate 4 are fine wire electrodes formed by sintering silver-based conductive paste or copper-based conductive paste, and the linewidth of the P-region sub-gate 3 and the N-region sub-gate 4 is less than 100μm.

[0035] The working principle of the above embodiments is as follows:

[0036] In use, the P-region main grid 1 and N-region main grid 2 are first mounted on the solar cell, and multiple P-region sub-grids 3 and N-region sub-grids 4 are then set on them. Next, a microgroove structure 7 is formed on the surface of the P-region sub-grids 3 and N-region sub-grids 4 by laser etching. Simultaneously, an array of microbumps 6 is fabricated on the side of the connector 5 facing the sub-grids. The microbumps 6 are composed of a multilayer copper-nickel-silver metal stack, are hemispherical, with a height of 10 to 50 micrometers, a diameter of 20 to 80 micrometers, and a distribution density of 80 to 150 bumps per square centimeter. The microgroove structure 7 has a depth of 5 to 20 micrometers and a width of 10 to 30 micrometers, and is distributed in an interlaced grid pattern with a density of 50 to 200 bumps per square millimeter. Then, the microgroove structure 7 is further processed... The groove structure 7 is filled with conductive adhesive containing silver nanoparticles as a conductive composite material layer 8. The serial connector 5 is aligned with the positions of the P-region sub-gate 3 and the N-region sub-gate 4 and assembled. A pressure of 10 to 20 Newtons is applied at a temperature of 150 to 180 degrees Celsius for thermo-pressing connection. At this time, the micro-bumps 6 undergo plastic deformation and embed into the micro-groove structure 7. The conductive adhesive flows and wraps the interface between the micro-bumps 6 and the micro-groove during the heating and pressurization process. After cooling and curing, a metal-polymer composite interface is formed, realizing electrical and mechanical connection. Finally, a high-reliability contact between the serial connector 5 and the sub-gate is completed. This process avoids the impact of high-temperature welding on the battery performance and is suitable for the low-temperature interconnection process of high-efficiency photovoltaic cells.

[0037] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0038] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-reliability contact structure for a tandem connector-sub-gate based on micro-bumps and surface treatment, comprising a P-region main gate (1) and an N-region main gate (2) mounted on a solar cell; characterized in that: It also includes multiple P-region sub-gates (3) set on the P-region main gate (1) and multiple N-region sub-gates (4) set on the N-region main gate (2). It also includes a connector (5) installed on the P-region sub-gate (3) and the N-region sub-gate (4). The connector (5) has an array of micro-bumps (6) on the side facing the P-region sub-gate (3) and the N-region sub-gate (4). The P-region sub-gate (3) and the N-region sub-gate (4) have micro-groove structures (7) that match the micro-bumps (6) at corresponding positions. The micro-groove structures (7) are filled with a conductive composite material layer (8).

2. The high-reliability contact structure of the tandem connector-sub-gate based on micro-bumps and surface treatment according to claim 1, characterized in that: The micro-bumps (6) are hemispherical with a height of 10–50 μm and a diameter of 20–80 μm, with a distribution density of 80–150 per cm².

3. The high-reliability contact structure of the tandem connector-sub-gate based on micro-bumps and surface treatment according to claim 1, characterized in that: The microgroove structure (7) is formed on the surface of the subgate (3) in the P region and the subgate (4) in the N region by laser etching. The depth of the microgroove structure (7) is 5–20 μm and the width is 10–30 μm. The microgroove structure (7) is distributed in an interlaced grid pattern with a density of 50–200 per mm².

4. The high-reliability contact structure of the tandem connector-sub-gate based on micro-bumps and surface treatment according to claim 1, characterized in that: The conductive composite material layer (8) is a conductive adhesive containing silver nanoparticles. During the hot pressing process, the conductive adhesive fills the microgroove structure (7) and contacts the microbumps (6), forming a metal-polymer composite interface after curing.

5. The high-reliability contact structure of the tandem connector-sub-gate based on micro-bumps and surface treatment according to claim 1, characterized in that: The connector (5) is a copper foil substrate, and the micro-bumps (6) on the surface of the connector (5) are composed of multiple layers of copper, nickel and silver metal.

6. The high-reliability contact structure of the tandem connector-sub-gate based on micro-bumps and surface treatment according to claim 1, characterized in that: The P-region sub-gate (3) and the N-region sub-gate (4) are fine wire electrodes formed by sintering silver-based conductive paste or copper-based conductive paste, and the linewidth of the P-region sub-gate (3) and the N-region sub-gate (4) is less than 100 μm.

7. The high-reliability contact structure of the tandem connector-sub-gate based on micro-bumps and surface treatment according to claim 1, characterized in that: The temperature of the hot-press connection is 150–180°C and the pressure is 10–20N. Under these conditions, the micro-bumps (6) undergo plastic deformation and embed into the micro-groove structure (7). When the serial connector (5) is hot-pressed with the P-region sub-gate (3) and the N-region sub-gate (4), the micro-bumps (6) embed into the micro-groove structure (7) and form an electrical and mechanical connection with the conductive composite material layer (8).

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