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A clean cut - End-to-end technology concept from Siemens optimizes wafer production
Thun/Switzerland. Meyer Burger (MB) based in Thun in Switzerland is among the world’s leading providers of innovative systems and processes based on semi-conductor technologies. One focus of the company’s activity is the production of wafers, which are sliced from silicon bricks using wire saws and further processed into solar cells. The “DW288 Series 3” diamond wire saw used for the process is equipped with Siemens technology. Optimum wire guidance and precisely coordinated end-to-end automation enable the machine to work with extremely thin cutting wires. This permits annual material savings per machine of around 100,000 US Dollars, resulting in lower unit costs per wafer.
As the name suggests, wafers are ultra-thin slices of material. These are sawn off silicon bricks, processed into products such as crystalline solar cells and used in microelectronics and photovoltaics applications. The company Meyer Burger (MB) based in Thun in Switzerland has specialized in systems and processes based on semi-conductor technologies and is a world leader in the manufacture of wafers. Over recent years, the method used to cut slices from the silicon bricks has changed: instead of cutting the material with a fluid known as slurry, diamond wires are now used which are more precise and less harmful to the material. The automation and drive concept of the machine used by MB to cut the wafers is provided by Siemens.
A hair’s breadth
The diamond wire management system (DWMS) used in the DW288 Series 3 diamond wire saw is based on separation of the storage spool area from the working area. The wire section currently in operation is guided and wound onto the spool in a single layer, meaning that the abrasive diamond wires being cyclically wound and unwound during the sawing process are no longer in contact with their neighboring wires. This increases the service life of the costly cutting wire by over 20 percent. This special wire guidance system and other optimization measures mean that the MB wire saw is able to use extremely thin cutting wires in comparison to customary machines in the industry. MB uses 70 micrometer (µm) wire on the machine as standard, allowing a precise, clearly defined cut. Wires as thin as 60 micrometers, around half the breadth of a human hair, are already being used with outstanding success. This is a field in which every micrometer counts, as reducing the kerf width by even as little as 10 µm can result in annual material savings per machine of around 100,000 US Dollars.
Everything from a single source
One of the improvements which has made this possible is synergetic optimization of the drive technology. “As the working wire is guided in a single layer by the diamond wire management system, the diameter of the spool always remains the same. This simplifies the control task of the winder, and makes greater control dynamics available for maintaining wire tension at a constant level,” explains Christoph Eggimann, Product Manager Wafering with responsibility for wire saws at MB’s Thun location. “Working with Siemens, we’ve developed an automation concept specifically optimized for this function in which the control system, drive controller and servo motors of the wire transfers as well as the I/O systems together form an end-to-end system from a single source.” Components used include a customer-specific touchpanel for convenient operation and a failsafe Simatic using WinAC RTX-F 2010 software, which also controls the machine’s safety response. Another key element is the drive control system, which was programmed using DCC (Drive Control Chart) directly in the Sinamics S120 drive controller. The sensitive wire is guided by 1FK7 servomotors. All the sensors and actuators required for the process are integrated using the IP20 protection-rated ET200SP I/O system and the IP65/67-rated ET200ecoPN. The use of Profinet makes for stable, simple communication.
Unprecedented level of material care
The DW288 Series 3 allows more dynamic cyclical acceleration and deceleration processes without causing additional stress on the wire. As a result, this machine boasts the lowest wire breakage rate on the market.
The company Meyer Burger (MB) based in Thun in Switzerland is a world leader in semiconductor-based systems. For the production of wafers, which are sliced from silicon bricks using wire saws, MB has developed the “DW288 Series 3” diamond wire saw equipped with Siemens technology.
High-precision cutting and sawing technology allows an exceptionally high number of wafers to be produced from a single silicon brick.
Highly developed diamond wire technology produces a higher yield of quality wafers from a silicon brick.
The “DW288 Series 3” is able to work with ultra-thin diamond wires, enabling annual material savings per machine of up to 100,000 US Dollars.