Schmalz Wafer Gripper SWG

J. Schmalz GmbH’s new development, the Schmalz Wafer Gripper SWG, is particularly suitable for the extremely fast, precise and damage-free handling of highly sensitive wafer and solar cells.

The SWG has decisive advantages compared with manual grippers, mechanical grippers, conventional vacuum grippers or floating suction pads employing Bernoulli’s principle regarding process safety, damage minimisation and cycle times.

DESCRIPTION

The latest technology for handling wafers and solar cells utilises conventional vacuum grippers or floating suction pads employing Bernoulli’s principle. However, these types of gripper both have considerable disadvantages: When using conventional vacuum grippers, chemical contamination and high mechanical strain occur at contact surfaces. Meanwhile floating suction pads carry the disadvantages of a considerably lower cycle speed of t > 1 second, of relatively imprecise positioning and uncontrolled blow-off of nuisance particles into the process room. The Schmalz Wafer Gripper SWG, is capable to eliminate disadvantages of previous handling concepts.

Applications:

• Extremely fast, reliable, precise and gentle handling of silicon wafers and cells
• Fully or partially automated production of silicon PV cells with maximum process stability,         
• production line uptime, cell efficiency and line output
• Loading and unloading of stacks and conveyor belts
• High accuracy positioning during and after the visual inspection process
• “In flight” check for broken wafers during handling

INNOVATIVE ASPECT

There are not many industries in which integrated automation plays as great a role as it does in photovoltaic production. All process steps are seamlessly integrated with one another – particularly the loading and unloading of wafers and cells. When choosing handling technology, the decisive criteria are the technology’s effect on the stability of round-the-clock production processes and on damage minimisation. These criteria influence system output and the effectiveness of the fully integrated photovoltaic modules. Moving by hand and mechanical gripping come with major disadvantages.

For this reason, vacuum grippers are the preferred equipment in all areas of photovoltaic production – particularly with the fast handling afforded by parallel kinematics and robot systems. However, not every vacuum gripper is suitable for all the process steps involved in handling photovoltaic components, namely gripping, moving, optical measurement, positioning, stacking, and releasing:

• First, wafers and cells made from crystalline silicon are extremely thin, typically 200–120 µm, and therefore are extremely fragile. 
• Second, parts of the production process take place under clean room or wet chemical conditions, placing special demands on the production and handling facilities. 
• Third, the highly competitive solar industry is being forced to continuously improve its production efficiency, partly due to the declining price paid for solar electricity fed back into the grid.

The latest technology for handling wafers and solar cells utilises conventional vacuum grippers or floating suction pads employing Bernoulli’s principle. However, these types of gripper both have considerable disadvantages. While conventional vacuum grippers 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. The Solution therefore must be the Schmalz Wafer Gripper SWG:

It provides a unique combination of the advantages of the two solutions described above while eliminating their disadvantages. Based on a new handling concept, the SWG offers new levels of process safety and damage minimisation and reaches the magical cycle time of 1 second.

The SWG grips the entire surface of the wafer without leaving a mark and meets the highest standards of acceleration and process speed. The SWG also provides accurate, reliable handling when working with wafers that are smaller than the contact surface of the gripper. Because the air and ultra-small particles are completely extracted, production can be carried out under clean room conditions.

The SWG gripper has been tested by renowned manufacturers and is now available as a series product. It is available for common robot flange connections and includes complete vacuum generation. Customer requirements regarding loading conditions and distance measurement can be accommodated. Due to its light and compact construction, the SWG has already been able to achieve cycle times of under 1 second when handling wafers using parallel kinematic systems from renowned manufacturers.

Construction

• Low weight plastic components
• Modular design of contact surface, vacuum generator, blow-off unit, robot interface, sensors and optional features
• Gripper sizes available for standard cell sizes 125 mm and 156 mm, semi square
• Various contact surfaces available
• Integrated pneumatic vacuum generation with high throughput and controlled air discharge

The SWG has decisive advantages compared to the other technologies:

• Extremely fast and accurate handling with a magical cycle time of less than 1 second, extremely short suction time of less than 0,02 seconds
• Minimal shearing forces and minimal risk of conchoidal fractures due to low vacuum level (the wafer “jumps” with a distance of 2 mm towards the contact surface)
• Precise positioning and minimal cycle times due to fast blow-off function
• "In-flight"-breakage control by optional backlighting of the whole wafer due to modular construction with different contact surfaces, absorbability elements and sensor technology
• Minimal surface contamination of the raw wafer and avoidance of blind spots due to special gripper contact surface made of PEEK (Polyetheretherketon). Alternatively, contact surfaces made of POM (Polyoxymethylen) or PMMA (Polymethylmethacrylat) (in case of optional backlighting-function) are available
• Secure gripping and holding of deformed or broken wafers due to high holding forces even in case of partial utilisation or leakage
• Exact positioning while visual inspection and position measuring
• Completely flexible connectivity of sensors for part presence detection or distance measurement
• Optional instalment of additional vacuum grippers in different positions for gripping convex and concave wafers or to cushion bounces during gripping
• Optional instalment of additional backlights 
• Available for common robot flange connections
• Including complete vacuum generation as a standard
• Provision for customer requirements regarding loading conditions and distance measurement can be accommodated

BENEFITS

Product Highlights and Consumer Advantages:

• Large contact area between wafer and gripper with maximum holding force
• High speed, high accuracy handling for cycle times < 1 second 
• Moderate air consumption 
• Less operating cost than Bernoulli grippers
• Low vacuum level 
• Minimal torsional forces and minimal conchoidal fracture risk, therefore less throw-outs
• High throughput vacuum generation 
• Reliable gripping and handling even of deformed and broken wafers
• Controlled air discharge 
• No contamination of working range with silicon dust or fragments
• Rapid venting of vacuum chamber 
• Precise positioning and very short cycle times
• Gripper surface optionally made of PEEK (Polyetheretherketone) 
• Minimal surface contamination and reduction of blind spots
• Modular concept with various surface materials, sensors and optional shock absorption elements 
• Optional breakage detection through backlit gripper surface

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