News Article
Laser joining of solar cells
Researchers at the Fraunhofer Institute for Laser Technology ILT have developed a non-contact soldering system in which the temperature is constantly monitored. If the temperature deviates beyond set limits, the system automatically adjusts it to an acceptable value.
Researchers at the Fraunhofer Institute for Laser Technology ILT have developed a non-contact soldering system in which the temperature is constantly monitored. If the temperature deviates beyond set limits, the system automatically adjusts it to an acceptable value. Instead of an electrode, a laser beam is used for the soldering operation. A single solar cell produces a relatively low output. Tiny strips of metal are used to link cells together. If the laser soldering temperature is too high, the solder joint may fracture. This new system provides automatic temperature regulation.
To obtain sufficient power to operate a pocket calculator, parking ticket dispenser or photovoltaic module, sunlight has to be captured simultaneously by an array of cells. They are connected in series using tiny strips of metal known as stringers. Each stringer has to be positioned in precisely the right spot, and then its solder coating is melted using a hot electrode. When the solder sets, it forms a stable bond with the metallic coating on the silicon. The amount of heat induced in the stringer and the silicon depends on the contact between the soldering electrode and the stringer. Applying too much energy causes thermal stress which in the worst case could destroy the solder joint, leaving a break in the electrical circuit that makes the solar module unfit for use.
The next project is to develop a faster, more reliable method of connecting solar cells by means of laser welding, whereas soldering only involves melting the solder, in laser welding the stringer itself is melted.
To obtain sufficient power to operate a pocket calculator, parking ticket dispenser or photovoltaic module, sunlight has to be captured simultaneously by an array of cells. They are connected in series using tiny strips of metal known as stringers. Each stringer has to be positioned in precisely the right spot, and then its solder coating is melted using a hot electrode. When the solder sets, it forms a stable bond with the metallic coating on the silicon. The amount of heat induced in the stringer and the silicon depends on the contact between the soldering electrode and the stringer. Applying too much energy causes thermal stress which in the worst case could destroy the solder joint, leaving a break in the electrical circuit that makes the solar module unfit for use.
The next project is to develop a faster, more reliable method of connecting solar cells by means of laser welding, whereas soldering only involves melting the solder, in laser welding the stringer itself is melted.
