The latest technology for handling wafers and solar cells utilises conventional vacuum suction pads or floating suction pads employing Bernoulli’s principle. However, these types of grippers both have considerable disadvantages. While conventional vacuum suction pads allow very high transverse acceleration, and therefore short cycle times, chemical contamination and high mechanical strain occur at contact surfaces. Although the chemical and mechanical effects of floating suction pads are much lower, they carry the disadvantages of a considerably lower cycle speed, relatively imprecise positioning, and uncontrolled blow-off of nuisance particles into the process room.
Not only do these disadvantages affect the system output, they also negatively influence the effectiveness of the fully integrated photovoltaic modules. With its new gripping concept, the Schmalz wafer gripper successfully eliminates these disadvantages. The SWG grips the entire surface of the wafer and is therefore especially gentle. Hundreds of suction holes minimise the effect of the force on the wafer and prevent the formation of micro fractures. Optional damping elements can further reinforce this positive effect. The PEEK (polyetheretherketone) contact surface allows for handling without leaving marks or surface contamination.
At the same time, the SWG meets the highest demands for acceleration and process speed. Specially designed for the production of photovoltaics, the Schmalz wafer gripper achieves cycle times of under a second. The large contact surface between the wafer and the gripper offers significant advantages over conventional grippers. For one, they provide maximum holding forces, guaranteeing slip-free handling of wafers, even during complex, highly dynamic process steps with high transverse acceleration. In addition, even deformed or damaged wafers can be securely gripped and reliably removed from the process room. This leads to a lasting increase in process stability. Additionally, since the drawn-in air can be expelled in a controlled manner, the production can take place under clean room conditions.
The SWG also provides innovations in process monitoring. Intelligent sensor modules enable even complex inspection tasks to be easily integrated into the handling process. Such tasks include vacuum-coverage monitoring, detection of double coverage, distance monitoring and break detection.
The aforementioned product characteristics make the SWG suitable for all handling and testing procedures involved in the partially or fully automated manufacture of solar cells. In particular, this includes the removal of wafers from stacks and belts, buffering and bifurcation, and exact positioning of wafers during and after visual inspection. The SWG is available in two different surface geometries for the common cell sizes of 5" and 6".
J. Schmalz GmbH has its headquarters in Glatten in Germany's Black Forest and is one of the world's leading suppliers of vacuum technology. Its portfolio includes high-quality products and services in the areas of automation, handling and clamping technology. Founded in 1910, the company has a long tradition of offering innovative and efficient vacuum solutions to customers from various industries. In 2008, the company had a total of 570 employees at the headquarters in Glatten and its 16 overseas subsidiaries.