Silicon, the predominant material used for the manufacture of photovoltaic cells, is made in two forms, Multi-Crystal and Mono-Crystal. Cast multi-crystalline ingots or grown single crystalline ingots are converted into wafers which eventually capture the sun’s rays and produce electricity.
After the ends of the cast or grown silicon ingots are “cropped” using either an annular or reciprocating saw, they are then converted into a block shape using a process known as “squaring”. Similar to cropping, squaring is an abrasive sawing process. Squaring saws or “squarers” convert the ingots into blocks. Modern squarers use diamond-coated wire cooled by a specialized coolant lubricant to perform the task of sawing. Older squarers had utilized silicon carbide slurry as an abrasive. This slurry is fed onto wires which then perform the task of sawing. Conversion to the newer type diamond-coated technology allows for a two-fold reduction in process time. Also, the newer fixed diamond wire process is much cleaner and produces less waste allowing for simpler and more environmentally friendly processing.
After the ingot is squared into a block, the edges are beveled or edge-ground using a diamond grinding wheel cooled and lubricated to avoid creation of high temperatures and chipping of the surface.
After the “squared” block has been beveled it is mounted on a beam. The beam is then fed into a traditional silicon carbide slurry fed wire saw and sawn into thin wafers. After the “wafering” process is complete the wafers are rinsed free of gross amounts of slurry/silicon residue “swarf” and demounted from the beam. After demounting, the wafers are cleaned in a combination of ultrasonic and spray-cleaning apparatus. The wafers are then sold to a customer as “as cut” wafers or the wafers remain in the factory for further processing (texturing, etching, etc.) depending on the factory’s capabilities. Eventually, the silicon wafer is converted into a photovoltaic cell converting light to electricity.