Application of Infrared Welding Technology in Fully Automatic Tabber-Stringers

Author:

xiaolanjing

Fully automatic tabber-stringers are used in solar module production for the process of welding solar cells into cell strings. Since the welding quality of solar cells directly affects module performance, the selection of welding method is particularly important.

Solar cell welding methods are divided into two categories: contact welding and non-contact welding.

Contact welding, also known as soldering iron welding, uses the heat of a soldering iron tip for welding. This traditional method has many drawbacks: poor temperature uniformity, frequent cleaning required for the soldering iron tip, and long welding cycles.

Non-contact welding mainly includes hot air welding, electromagnetic induction welding, and infrared welding. Among these, infrared welding technology is the most widely applied due to its unique advantages. This article mainly discusses infrared welding technology and its specific application in tabber-stringer equipment.

I. Infrared Welding Technology

1. Infrared Heating Lamp

It consists of a quartz glass tube and a tungsten filament. The tungsten filament is inserted into a gas-filled quartz tube; under AC voltage, the tungsten filament heats up and warms the gas inside the quartz tube, thereby generating infrared radiation. When infrared rays are absorbed by an object, the object is heated. The back of the lamp has a reflective layer that concentrates light toward one side, reducing energy waste. The filament, supported by tungsten wire within uniform sections, is less prone to sagging.

2. Advantages and Disadvantages of Infrared Welding

Advantages: High heating efficiency, low heat loss, low equipment maintenance cost; directly heats the object without heating the surrounding air, and provides the optimal wavelength suitable for the heating target.

Disadvantages: Infrared is a radiation technology, which carries the inherent weakness of radiation technologies — the risk of over-temperature; temperature differences between solder joints caused by variations in thermal characteristics.

II. Application of Infrared Welding Technology in Tabber-Stringer Equipment

1. Infrared Radiation Module

The tabber-stringer adopts a half-gold-plated infrared radiation module for near-infrared radiation welding. In addition, an infrared thermometer is installed; through the sensing of the infrared temperature sensor, temperature can be fed back in real time, facilitating system temperature control and maintaining the temperature at a relatively stable value.

The infrared radiation module mainly consists of a half-gold-plated reflective film infrared lamp, a cooling fan, mounting fixtures for the module, insulating ceramic parts, and a reflector hood. The infrared lamp adopts a half-gold-plated coating that concentrates and reflects infrared heat in the same direction, achieving a reflection efficiency of up to 95%. The module uses 5 heating lamps arranged at equal intervals (single lamp power: 1.5 kW, maximum module power: 7.5 kW) with a unified reflector hood. The heat source can effectively cover the entire cell area, providing good temperature uniformity. (See Figure 1)

The equipment adopts two identical infrared welding modules, configured with two heating zones: preheating and welding. The preheating temperature is controlled at 120–160°C, and the welding temperature is controlled at 230–260°C. When a solar cell is conveyed into the infrared welding zone, the infrared lamps radiate infrared rays of a specific wavelength in the direction perpendicular to the soldering ribbon, rapidly raising the temperature of the ribbon and the silver busbars on the cell. After temperature rise, welding is performed simultaneously on both the front and rear sides of the cell.

2. Principle of Infrared Welding Temperature Control

The principle of infrared welding temperature control is as follows: after the infrared temperature sensor captures the temperature, it feeds the data back to the infrared thermometer, which outputs the temperature parameters to the input terminal of the PLC temperature control module. The PLC temperature control module adjusts the 4–20 mA output current based on the difference between the measured temperature and the set temperature, and controls the output power of infrared heating by regulating the power of the bidirectional thyristor. The output power of the infrared heating lamp is directly proportional to the heating temperature. (See Figure 2)

The infrared welding method can essentially ensure uniform temperature distribution across the zone, effectively resolving the issue of cold solder joints on solar cells. The welding process is completed in one pass, also improving equipment efficiency.

Due to the physical characteristics of solar cells — being thin, brittle, and prone to cracking — implementing an automatic welding process is relatively difficult. Infrared welding offers advantages such as cleanliness, pollution-free operation, high efficiency, energy savings, and ease of maintenance, making it currently the most mature and stable welding method. This approach not only ensures welding quality but also greatly improves production efficiency. The welding appearance is more aesthetically pleasing compared to spot welding, and it further reduces the issues of cold solder joints and micro-cracks during solar cell welding.

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Fusing Challenges in Large-Format Engineering Printers: Technical Principle Analysis of Multi-Lamp Zone Temperature Control

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Fusing Challenges in Large-Format Engineering Printers: Technical Principle Analysis of Multi-Lamp Zone Temperature Control