CN108838507A - A kind of welding method of busbar - Google Patents

Abstract

The invention discloses a bus bar welding method, comprising: fixing the battery sheet on a welding base of an ultrasonic welding device, placing a welding strip on the battery sheet; heating the welding base, and the welding base conducts heat to the battery sheet, The battery sheet and the ribbon are welded together by an ultrasonic welding device, and an intermetallic compound layer is formed between the battery sheet and the ribbon. The welding method disclosed by the invention can solve the problem of uneven tension caused by the slow growth of the intermetallic compound layer and the uneven thickness, so that the welded product can meet the normal tension index of the battery, improve the reliability of the product, and reduce the defective rate of the product .

Description

A kind of welding method of bus bar

technical field

The invention relates to the field of production of photovoltaic cell components, in particular to a welding method applicable to the welding process of bus bars in solar cell panels.

Background technique

In a solar cell, a single solar cell cannot be directly used as a power source, but several single cells must be connected in series or in parallel and packaged into a module. From solar cells to battery modules, it is necessary to connect single-piece batteries to make them a whole, and welding is the key process. The welding method widely used at present is ultrasonic welding to weld the ribbon to the battery sheet. Taking aluminum ribbon welding as an example, the main body of the cell is a glass substrate, and the glass substrate is coated with a conductive thin film layer, such as a molybdenum thin film. The basic principle of this welding process is to make the aluminum strip and the semi-finished CIGS (a chalcopyrite crystal thin film solar cell with the best ratio of four elements: Cu, In, Ga, Se) glass molybdenum layer under the action of ultrasonic energy. An intermetallic compound (IMC, Intermetallic Compound) layer is formed between them. However, this ultrasonic welding process has at least the following disadvantages:

1. The growth of intermetallic compounds is too slow, which can easily cause uneven thickness of intermetallic compounds, which in turn causes uneven tension in the tensile test of battery failure analysis, which cannot meet the normal tensile index of the battery, poor product reliability, and high defect rate. question;

2. Oxygen is easily mixed with the conductive film layer during the bonding process to cause oxidation, resulting in poor bonding between the two, and may also cause the product to fail to weld or the reliability of the welded product to be poor;

3. The existing technology cannot realize automatic welding, the welding efficiency is low, the product defect rate is high, and the welding cost is high.

One or more of the problems described above are in dire need of improvement.

Contents of the invention

In view of the above-mentioned problems existing in the prior art, the purpose of one aspect of the present invention is to provide a bus bar welding method, which can form a uniform intermetallic compound layer between the welding strip and the battery sheet, effectively improving the product quality. reliability.

In order to achieve the above object, the invention provides a bus bar welding method, comprising:

Fix the battery sheet on the welding base of the ultrasonic welding device, place the welding ribbon on the battery sheet; heat the welding base, and the welding base will conduct heat to the battery sheet; use the ultrasonic welding device to weld the battery sheet and the welding ribbon together, An intermetallic compound layer is formed between the battery sheet and the welding strip, which solves the problem of uneven tension caused by the slow growth of the intermetallic compound layer and uneven thickness, so that the welded product meets the normal tension index of the battery and improves the product's durability. Reliability, reducing the defect rate of the product.

In some embodiments, fixing the battery sheet on the welding base includes: using a negative pressure forming device to generate negative pressure between the battery sheet and the welding base, so as to adsorb the battery sheet on the welding base.

In some embodiments, the negative pressure forming device includes a vacuum generator; a heating block capable of conducting heat is provided on the side of the welding base that carries the battery sheet, and a number of vacuum generators are provided on the side of the heating block close to the battery sheet. The open vacuum hole and the open end of the vacuum hole are aligned with the battery sheet.

In some embodiments, before heating the welding base, it also includes: passing a shielding gas at the welding contact surface between the battery sheet and the welding ribbon, so as to introduce the shielding gas into the gap between the battery sheet and the welding ribbon middle.

In some embodiments, the protective gas is one or a mixture of at least two of carbon dioxide, argon, helium and nitrogen.

In some embodiments, heating the welding base includes: detecting the temperature of the welding base, and turning on the heating device when it is detected that the temperature of the welding base is lower than a preset welding temperature.

In some embodiments, the soldering temperature preset value is 200°C-400°C.

In some embodiments, during welding, the ultrasonic welding device includes an ultrasonic transducer, the frequency of the ultrasonic transducer is 20kHz-200kHz, and the power of the ultrasonic transducer is 10-150w.

In some embodiments, the ultrasonic welding device includes a welding head, and the pressure of the welding head on the welding strip is 20-100 N, and the duration of the pressure is 10-50 ms.

In some embodiments, before the battery sheet is fixed on the welding base, the method further includes: transferring the battery sheet to the welding area through a transmission mechanism.

Compared with the prior art, the present invention provides a bus bar welding method. This method can form a layer of uniform intermetallic compound layer between the welding strip and the battery sheet, which solves the problem of slow growth of the intermetallic compound layer and the thickness of the intermetallic compound layer. The problem of uneven tension caused by unevenness makes the welded product meet the normal tension index of the battery, improves the reliability of the product, and reduces the defective rate of the product.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

This document provides a summary of various implementations or examples of the technology described in this disclosure, and is not a comprehensive disclosure of the full scope or all features of the technology disclosed.

Description of drawings

Fig. 1 is a schematic diagram of a state in which a cell is fixed on a welding base when a bus bar welding system is used to weld a bus bar according to an embodiment of the present invention;

Fig. 2 is a schematic structural view of a bus bar welding system according to an embodiment of the present invention;

Fig. 3 is a schematic diagram of the state in which the delivered battery slices are adsorbed on the heating block when the bus bar is welded by the bus bar welding system according to an embodiment of the present invention;

FIG. 4 is a schematic flowchart of a bus bar welding method according to an embodiment of the present invention.

Reference signs:

1-pressurizing device; 2-welding head; 3-ultrasonic transducer; 4-shielding gas supply device;

10-battery sheet; 20-welding strip; 30-molybdenum layer; 40-transmission mechanism; 50-intermetallic compound layer;

100-heating device; 101-welding base; 102-heating block; 103-vacuum generator; 104-heating element; 1021-vacuum hole.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present disclosure clearer, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Apparently, the described embodiments are some of the embodiments of the present disclosure, not all of them. Based on the described embodiments of the present disclosure, all other embodiments obtained by persons of ordinary skill in the art without creative effort fall within the protection scope of the present disclosure.

Unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have the usual meanings understood by those skilled in the art to which the present disclosure belongs. The words "comprising" or "comprising" and similar words used in the present disclosure mean that the elements or things appearing before the word include the elements or things listed after the word and their equivalents, without excluding other elements or things. Words such as "connected" or "connected" are not limited to physical or mechanical connections, and may also include electrical connections, whether direct or indirect. "Up", "Down", "Left", "Right" and so on are only used to indicate the relative positional relationship. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

To keep the following description of the embodiments of the present disclosure clear and concise, detailed descriptions of known functions and known components are omitted from the present disclosure.

In the current ultrasonic welding process of the bus bar in the solar cell module, the growth of the intermetallic compound layer is too slow, which may cause the problem of uneven tension. Therefore, in the present invention, an improved bus bar welding method is provided, and at the same time, the present invention also provides a welding system applied to the bus bar welding method.

First of all, please refer to accompanying drawing 2 and accompanying drawing 3 of the specification of the present invention, in this embodiment, provide a kind of specific structure of the welding system of the welding method that is applied to bus bar, wherein, welding system includes ultrasonic welding device and heating device The ultrasonic welding device can perform ultrasonic welding on the battery sheet 10 and the welding ribbon 20, thereby welding the battery sheet 10 and the welding ribbon 20 together. Specifically, the ultrasonic welding device includes a welding head 2 and a welding base 101, and the welding base 101 is located at the welding position. Below the head 2, it is used to carry and fix the battery sheet 10.

Fig. 1 shows a schematic diagram of the state where the battery sheet is fixed on the welding base when the bus bar welding system is used to weld the bus bar. During the ultrasonic welding process, the heating device 100 is used to carry and fix the battery sheet 10 on the welding base 101. for heating. Specifically, the heating device 100 includes a heating element 104 embedded in the welding base 101 for heating the welding base 101 capable of carrying and fixing the battery sheet 10 . Preferably, the heating element 104 can be implemented in the form of a heating rod pierced in the welding base 101 , which saves installation space and is low in cost. During the welding process, the heating rod is controlled to generate heat, which is then conducted to the welding base 101 to heat the welding base 101 .

Since the battery sheet 10 is always kept on the welding base 101 during the whole welding process, when the ultrasonic welding device is used to perform ultrasonic welding between the battery sheet 10 and the welding ribbon 20, the welding base 101 is continuously heated, so that the welding base 101 can be continuously heated. The growth of the intermetallic compound layer 50 is accelerated between the cell sheet 10 and the solder ribbon 20 . For example, when the battery sheet 10 and the welding ribbon 20 are welded by an ultrasonic welding device, the surface of the battery sheet 10 is coated with a molybdenum layer 30, and the welding ribbon 20 can be an aluminum strip. An intermetallic compound layer 50 is formed between the molybdenum layer 30 on the sheet 10 and the solder ribbon 20 . Those skilled in the art should understand that the formation of the intermetallic compound layer 50 between the solder strip 20 and the molybdenum layer 30 is only an exemplary illustration, and the molybdenum layer 30 still has other alternatives as a thin film conductive layer, such as ITO (tin-doped trioxide) Indium), AZO (aluminum-doped zinc oxide), etc., and the aluminum strip can also be replaced by copper strip, silver strip or silver aluminum alloy material according to needs. In this process, as for the heat source of the heating rod itself, it can be provided by other heating bodies, or it can be realized by the heating rod itself through electric heating.

Moreover, in some embodiments, it should be understood that in order to facilitate temperature control in the process, as a preference, the heating device 100 may further include: a temperature sensor (not shown in FIG. 1 ) and a control mechanism (not shown in FIG. 1 shown), wherein the temperature sensor is configured to detect the temperature of the welding base 101 in real time and feed back the detected temperature value to the control mechanism for temperature control, and the control mechanism is used to control the heating element 104 according to the temperature value of the welding base 101 detected by the temperature sensor opening and closing. In the process of heating control by the control mechanism, the heating element 104 is configured to be powered on and start to heat the welding base 101 continuously and evenly when the detected temperature of the welding base 101 is lower than the welding temperature preset value, and the heat will eventually pass through the welding base. 101 is conducted to the battery sheet 10, so that the temperature of the battery sheet 10 increases, thereby accelerating the formation of an intermetallic compound layer during welding. In this way, by introducing temperature control in the welding system, the battery sheet 10 can be kept above a certain temperature, which can effectively promote the growth of intermetallic compounds, and solve the problem of battery failure caused by the slow growth of intermetallic compounds and uneven thickness. In the analyzed tensile test, the uneven tensile force cannot meet the normal tensile index of the battery, which improves the stability of the process and the reliability of the product, reduces the defective rate of the product, and thus reduces the welding cost. As a further preference, the preset value of the welding temperature is usually controlled within the range of 200°C-400°C.

As shown in Figure 2, the ultrasonic welding device also includes an ultrasonic transducer 3, the ultrasonic transducer 3 is located on one side of the welding head 2, used to generate ultrasonic energy, and transmit the ultrasonic energy to the welding head 2 to drive the welding head 2 Oscillation along the extending direction of the ribbon 20 is generated. The energy in the vibration process will promote the generation of intermetallic compounds between the solder ribbon 20 and the thin film conductive layer (such as the molybdenum layer 30 ) on the battery sheet 10 , forming the intermetallic compound layer 50 . However, this oscillating process may also reduce the reliability of the connection between the battery sheet 10 and the soldering ribbon 20 . Therefore, in the technical solution of the present invention, the battery sheet 10 needs to be fixed and held on the welding base 101 . Those skilled in the art should understand that this purpose can be achieved by clamping, limiting and/or fixing methods realized by mechanical structures.

In order to ensure that the battery sheet 10 can be well heated while being fixed on the welding base 101, in some embodiments, as a preference, a heating block 102 is provided on the side of the welding base 101 carrying the battery sheet 10, and the heating block 102 carries And fix the battery sheet 10, at the same time, it can absorb the heat transferred from the welding base 101, and evenly transfer the heat to the battery sheet 10, so as to achieve the purpose of heating the battery sheet 10, thereby improving the reliability of the product.

In some embodiments, the battery sheet 10 can be adsorbed and fixed on the heating block 102 above the welding base 101 by negative pressure adsorption. The welding system provided by the embodiment of the present invention also includes a negative pressure forming device, such as a vacuum generator 103 as shown in FIG. 1 . In the embodiment using the vacuum generator 103, the side of the heating block 102 close to the battery sheet 10 is provided with several vacuum holes 1021 communicating with the vacuum generator 103, and the opening ends of the vacuum holes 1021 are aligned with the battery sheet 10, The negative pressure is formed at the vacuum hole 1021 by the vacuum generator 103 , so that the battery sheet 10 can be adsorbed on the heating block 102 .

In addition, during the process of welding the bus bars, pressing the welding head 2 against the welding strip 20 with a certain pressure can help to generate the intermetallic compound layer 50 between the welding strip 20 and the battery sheet 10 . Therefore, preferably, the ultrasonic welding device also includes a pressure device 1, the pressure device 1 is supported by the welding head 2 and can act independently relative to the welding head 2, pushes the welding head 2 to move, and is positioned on the welding base 101 during welding. The battery sheet 10 and the ribbon 20 apply pressure. As a further preference, the pressure applied by the welding head 2 to the welding strip 20 is 20-100 N, and the duration of the pressure is 10-50 ms.

In addition, in the traditional ultrasonic welding process, the bonding process between the welding ribbon 20 and the conductive film layer (such as the molybdenum layer) on the surface of the battery sheet 10 is easily mixed with oxygen and oxidized, resulting in poor bonding between the two. In order to avoid this problem, in some embodiments, as a preference, as shown in FIG. Shielding gas is introduced into the gap between the welding ribbons 20 . In this process, the composition of the shielding gas is an important factor. Preferably, the shielding gas is one or a mixture of at least two of carbon dioxide, argon, helium or nitrogen.

As a further preference, in some embodiments of the present invention, the welding system may further include a delivery mechanism 40 for delivering the cell sheet 10 to the area where the welding head 2 is located, and further to the heating block 102 below the welding head 2, In this way, the automation of the entire welding process can be further realized, the welding efficiency can be improved, mass production can be realized, and certain economic benefits can be brought.

The specific implementation of the welding system used in the welding process of the bus bar provided by the present invention has been introduced in detail above. The system can implement the ultrasonic welding process of the bus bar, accelerate the growth of the intermetallic compound layer, and improve the reliability of the obtained product. . At the same time, in some embodiments, it becomes possible to realize automatic welding in the process. The welding method of the bus bar of the present invention will be further described in detail in combination with the above technical content. Specifically, a bus bar welding method provided in an embodiment of the present invention, as shown in FIG. 4 , includes:

S1, fixing the battery sheet 10 on the welding base 101 of the ultrasonic welding device, and placing the welding ribbon 20 on the battery sheet 10;

S2, heating the welding base 101, and the welding base 101 conducts heat to the battery sheet 10;

S3, using an ultrasonic welding device to weld the battery sheet 10 and the welding ribbon 20 together, and an intermetallic compound layer 50 is formed between the battery sheet 10 and the welding ribbon 20 .

This method can accelerate the growth of the intermetallic compound layer 50 during the welding process, so that a uniform intermetallic compound layer is formed between the welding strip and the battery sheet, thereby solving the problem caused by the slow growth of the intermetallic compound and the uneven thickness. In the tensile test of battery failure analysis, the tensile force is uneven and cannot meet the normal tensile index of the battery, which improves the stability of the process and the reliability of the product, reduces the defective rate of the product, and thus reduces the welding cost.

In addition, in some embodiments, as a preference, fixing the battery sheet 10 on the welding base 101 includes: using a negative pressure forming device to generate negative pressure between the battery sheet 10 and the welding base 101, and adsorbing the battery sheet 10 on the welding base 101 on. Specifically, the negative pressure forming device includes a vacuum generator 103; a heating block 102 capable of conducting heat is provided on the side of the welding base 101 carrying the battery sheet 10, and several vacuum chambers are provided on the side of the heating block 102 close to the battery sheet 10. The generator 103 is connected to the vacuum hole 1021 , and the opening end of the vacuum hole 1021 is aligned with the battery sheet.

In some embodiments, as a preference, before heating the welding base 101, it also includes: passing a flowing protective gas at the welding contact surface between the battery sheet 10 and the welding ribbon 20, so as to introduce the protective gas into the battery In the gap between the sheet 10 and the ribbon 20. Wherein, the protective gas is one or a mixture of at least two of carbon dioxide, argon, helium and nitrogen.

In some embodiments, preferably, heating the welding base 101 includes: detecting the temperature of the welding base 101, when it is detected that the temperature of the welding base 101 is lower than the preset value of the welding temperature, turning on the heating device 100 to heat the welding base 101 for heating. This detection process can be collected in real time through the temperature sensor and fed back to the control mechanism. It can also be collected at a certain preset time interval as required, and the control mechanism compares the temperature fed back by the temperature sensor with the preset value of the welding temperature. When the comparison result shows that the temperature of the welding base 101 is lower than the preset value of the welding temperature, then The heating device 100 is started to heat the battery sheet 10 . In this process, generally, the soldering temperature preset value is 200°C-400°C.

During the ultrasonic welding of bus bars, the ultrasonic welding device is used as the main welding equipment, and usually includes an ultrasonic transducer 3, but the frequency and power of the ultrasonic transducer 3 are still important factors in process control. In the bus bar welding method provided by the present invention, preferably, the frequency of the ultrasonic transducer 3 is 20kHz-200kHz, and the power of the ultrasonic transducer 3 is 10-150w. On the other hand, in some embodiments, it is also possible to improve the reliability of products made by the process by controlling the pressure and pressing time of the welding head 2 against the welding strip 20 to the battery sheet 1, for example, an ultrasonic welding device The pressure of the welding head on the welding strip can be controlled as 20-100N, and the duration of the pressurization can be controlled as 10-50ms.

Furthermore, in order to improve the automation of the bus bar welding method and improve the welding efficiency, in some embodiments, preferably, before the battery piece 10 is fixed on the welding base 101, the battery piece 10 can be sent to the welding station through a transmission mechanism. area.

The above embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and the protection scope of the present invention is defined by the claims. Those skilled in the art can make various modifications or equivalent replacements to the present invention within the spirit and protection scope of the present invention, and such modifications or equivalent replacements should also be deemed to fall within the protection scope of the present invention.

Claims (10)

1. a kind of welding method of busbar, which is characterized in that including：

Cell piece is fixed on the welding pedestal of ultrasonic brazing unit, welding is placed on the cell piece；

The welding pedestal is heated, the welding pedestal conducts heat to the cell piece；

The cell piece and the welding are welded together using the ultrasonic brazing unit, the cell piece and the weldering Intermetallic compounds layer is formed between band.

2. the welding method of busbar as described in claim 1, which is characterized in that described that cell piece is fixed on welding pedestal On include：

Device is formed using negative pressure and generates negative pressure between the cell piece and the welding pedestal, the cell piece is adsorbed on On the welding pedestal.

3. the welding method of busbar as claimed in claim 2, which is characterized in that it includes vacuum hair that the negative pressure, which forms device, Raw device；

The side that the cell piece is carried on the welding pedestal is provided with the heat block that can conduct heat, and the heat block leans on The side of the nearly cell piece offers several vacuum holes being connected with the vacuum generator, and the vacuum hole Open end is directed at the cell piece.

4. the welding method of busbar as described in claim 1, which is characterized in that carry out heating it to the welding pedestal Before, further include：

It is passed through protective gas at welding contact surface between the cell piece and the welding, the protective gas is introduced Into the gap between the cell piece and the welding.

5. the welding method of busbar as claimed in claim 4, which is characterized in that the protective gas is carbon dioxide, argon One of gas, helium and nitrogen or at least two mixed gas.

6. the welding method of busbar as described in claim 1, which is characterized in that described to be heated to the welding pedestal Including：

The temperature for detecting the welding pedestal is opened when detecting the temperature of the welding pedestal lower than welding temperature preset value Open heating device.

7. the welding method of busbar as claimed in claim 6, which is characterized in that the welding temperature preset value be 200 DEG C- 400℃。

8. the welding method of busbar as described in claim 1, which is characterized in that the ultrasonic brazing unit includes ultrasound Wave transducer, the frequency of the ultrasonic transducer are 20kHz-200kHz, and the power of the ultrasonic transducer is 10- 150w。

9. the welding method of busbar as described in claim 1, which is characterized in that the ultrasonic brazing unit includes welding Head, the plumb joint are 20-100N to the pressure that the welding pressurizes, and the duration of pressurization is 10-50ms.

10. such as the welding method of the described in any item busbars of claim 1-9, which is characterized in that be fixed on weldering in cell piece Before connecing on pedestal, further include：

The cell piece is sent to welding region by transmission mechanism.