Fast and Precise – with Due Care

Fig. 1: Handling of wafers demands speed and care (Picture: Stäubli)

The demands placed on automated handling in solar cell production push conventional solutions to their limits. Modern systems, such as are primarily used in the Far East, are expected to achieve an output of 3,000 wafers per hour. At the same time, the ultra-thin silicon wafers must be handled with the utmost care, as each seemingly insignificant disruption in the motion sequences of the robots inevitably leads to breakages. This is not only expensive for the systems operator; it can also have unpleasant repercussions for the systems manufacturer, who is normally expected to guarantee a breakage rate of less than 0.1 percent.

Made in Germany for the Far East

The Amberg-based systems integrator baumann nevertheless specializes in automated solutions for photovoltaics, offering standardized modules for loading and unloading the so-called wet benches. And German-made systems are in great demand in the Far East, where the business of loading and unloading modules is booming. The reason for this is their impressive performance, which sets new standards in the decisive factors of cycle time, breakage rate, and reliability. At the very heart of these systems is the high speed Scara made by Stäubli. The latest loading modules use the new TS60 Scara for the first time.
Baumann modules are designed for handling two different sizes of monocrystalline and polycrystalline wafers. The dimensions of the wafer can be either 125 × 125 mm or 156 × 156 mm. Changeover from one size to the other takes a maximum of ten minutes, thanks to sophisticated hardware and software solutions.

High-speed Scaras replace Delta kinematics

Fig. 2: A further point favoring the use of Scaras is their simple integration into the slender PV handling modules, where Delta kinematics would have a much greater footprint (Picture: Stäubli)

The wafers arrive at the loading modules via a single-track conveyor belt. Here, robots take the ultra-thin wafers and place them in precisely defined positions on the five roller tracks of the wet bench. In order to achieve the necessary cycle time – the system is designed for a maximum output of up to 3,000 wafers per hour – baumann favors an unconventional solution. The automation specialists deliberately chose not to use Delta robots for this application but to work with two very fast TS60 Scara robots.
Jörg Weigert, Project Manager at baumann, sums up why the company uses Scaras: “We are absolutely convinced by the performance of the Stäubli Scaras. The robots are fast, precise, and extremely reliable, even when they are in constant use over a multi-year period. The Scaras are simply unbeatable, particularly with regard to what really matters in these applications, namely robustness and reliability with minimum maintenance requirements.”
Jörg Weigert sees a further point favoring the use of Scaras in their simple integration into the slender PV handling modules. Because of the associated high levels of torque, Delta kinematics would require the module to be constructed on a disproportionately larger scale. This would run contrary to the philosophy of the manufacturer, which is to design systems to be as compact and reliable as possible.
In addition, this application necessitates the use of two robots – regardless of whether Delta or Scara kinematics apply – because of the conditions on the wet bench. The distances between the conveyor belt and the five roller tracks of the wet bench are simply too great to be serviced by one robot. Since two robots are used per module, the lower initial cost for the Scara represents a significa…

Facts for Decision Makers

Well balanced demands

• Clearly defined demands on the robots are met: shortest possible cycle times with lowest possible breakage rates.
• Scara robots are fast, precise, and extremely reliable, even when they are in constant use over a multi-year period.
• Refined programming together with specially developed grip technology
• ensures that the breakage rate is often significantly lower than the manufacturer’s guaranteed rate.

www.baumann-gmbh.de
www.staubli.com/robotics