Manufacturers of photovoltaic (PV) modules are increasingly turning to automation as a competitive factor. Perfectly soldered joints contribute to the efficiency of PV modules. Consistently high product quality and shorter cycle times lead to a permanent reduction in costs. As in other industrial sectors, image processing is becoming an important function for more and more companies. In a fully automated soldering system from Mondragon Assembly of Stahringen, Germany, the Cognex In-Sight® vision system optimizes the process of soldering the cross-links between photovoltaic modules. Important factors in creating a perfect soldered joint are the largest possible contact area, the high strength of the compound and a small contact resistance. Together, these three criteria largely determine the conductivity and current flow, thus ensuring a high degree of efficiency in the completed solar module.
Parallel workflow saves time
Before the In-Sight vision system can set the precise positioning of the soldered joints, the cross-links made of galvanized copper are inserted into the system as approximately 5 mm wide strips. A stretching station prevents the formation of wave-shaped and crescent-shaped deformations. Using a pneumatic string cutter, they are cut down to match the typical product specifications. A vacuum pad gripper then successively places the cross-link strips individually on a clipboard, until they form the completed connection diagram of the circuits. Then the cross-links are in turn transferred by means of pneumatic grippers to the photovoltaic module. This approach offers the advantage of parallel soldering and positioning and thus saves even more time.
Soldered jointly reliably detected
The entire process takes place simultaneously on the front and back of the module. On each side, two induction soldering heads equipped with the In-Sight vision system move over the work areas. Supported by red dome lighting, they recognize the predefined soldered joints. Simultaneously, the vision systems inspect the individual target positions which are stored in type-specific recipes. The actual and target positions are compared, and the deviation is transmitted to the control. If the tolerance limits have been complied with, the flux material is sprayed on and soldered, whereas rejected sites are reworked manually. The quality inspection of the soldered joints themselves is performed by the automated soldering machine.
Vision system accelerates production
The In-Sight vision system creates significant time saving compared to manual production. Mondragon Assembly achieved cycle times of only 80 seconds for cells with three busbars and modules with six strings. In addition to the rapid functioning as a standalone system, the easy handling of the compact In-Sight image processing system speeds up the use of the equipment. Even without detailed knowledge in the field of image processing or programming, it can be configured easily and quickly for pending tasks in production. Using its spreadsheet interface, the implementation of simpler applications can be done especially quickly. Complex applications are solved by powerful vision tools. A wide range of development, management and monitoring tools is offered by the graphical development platform In-Sight Explorer. Based on the familiar Windows® environment, it provides for shorter development cycles for vision applications, increased functional reliability and high system flexibility.
Advantage of worldwide availability
In addition to high product quality, Cognex offers Mondragon Assembly the advantage of a seamlessly integrated global service and logistics network. Cognex’s In-Sight Explorer is so easy to use that even less well-trained employees can operate the equipment without knowledge in the field of image processing systems. A further advantage is the implementation of In-Sight vision systems as a standalone solution, whereby they can also be used easily without central control. The use of a central server becomes unnecessary, making is possible to do repair and maintenance work even without specialist IT personnel. In this way, the vision-based soldering system for cross-links of photovoltaic modules ensures especially application-oriented operation, in addition to fast cycle times and consistently high quality in the soldered joints.