No Energy Wasted

Fig.1: Some temperatures are recorded by Speedway modules near measurement points within the processing area; Picture: Wago

Since it is relatively cost-efficient, mono and polycrystalline silicon is primarily used in solar panel semiconductors. In particular, polycrystalline silicon cells (pre-processed silicon wafers) demonstrate a good price/performance ratio. Nevertheless, silicon cells account for approx. 60 percent  of the total cost of a solar module. Soldering is one of the different production steps involved in making a solar panel from individual silicon cells. Somont (based in Umkirch near Freiburg, Germany) specializes in developing and manufacturing stringer soldering machines, which solder individual cells into cell bands or strings. Since a single cell is only 180 to 280 µm thick, machine soldering requires careful handling and a strictly-controlled soldering process. Somont has developed a handling system that removes cells from the magazine without touching the edges and places them softly on the feed conveyor. Then, with the help of a camera, the cells are aligned and fed into the soldering station. There, appropriately fitted soldering bands are used to solder cells into strings of 10. This process electrically connects the upper sides of the cells with one another. Somont uses a proprietary „soft touch“ soldering process. It ensures that only as much energy is transmitted to the cells as is necessary for a high-quality soldered connection.

Offset I/O modules reduce line lengths

Fig. 2: Within Certus One, IP67 modules record signals from the Speedway system (on-site as needed or collected in the lower cabinet of the machine

Certus One and Rapid stringers allow the company to offer its customers modular systems that can be adapted to customer requirements as dictated by production capacity and handling. The Speedway 767 and X-Com systems provide the necessary degree of freedom for this. The main argument for using these systems is their great flexibility. The IP67 system designed for installation without switch cabinets consists of a coupler with eight digital inputs and up to 64 separate I/O modules. Using data and power supply cable, these are offset from the coupler and enable needs-based signal detection close to the sensors. Distance between modules can be up to 50 m with a total spread of up to 500 m. „We use Profibus couplers with analog I/O modules to collect process data. Depending on sensor position and accessibility, we place the modules within the processing area or in the more protected area below it.

This enables us to reduce overall system cost. Thanks to simple line structure, the number of lines is reduced,“ explains Marc Fey, who is responsible for electrical design work at Somont. For monitoring the soldering process, for example, Pt100 sensors on the soldering heads (max. 3) record temperatures. Values are recorded by analogue input modules that are installed in a cable duct within the processing area and then transmitted to the superordinate controller by the Profibus coupler. The controller, in turn, regulates the six heating elements for the soldering process, 13 pre-heating elements, and six band heating elements. For the soldering process, cells are first pre-heated to 120 °C and then soldered at 240 °C. The pre- and post-heating system ensures material friendly temperature control.

Fig. 3: A Profibus coupler with more than 30 I/O modules relays signals from sensors to the superordinate controller

Depending on the stage of expansion, the Certus system can process up to 4,800 cells in an hour. A standard solar panel requires 60 cells. Thus, the system delivers strings for up to 80 solar panels per hour. „Under some circumstances, a machine breakdown can  cause production downtime and thus considerable financial damage. Compared to this, the cost…