HOW DIAMOND WIRE WORKS
Today diamond wire sawing is preferred by majority of solar silicon manufacturers, crystal growers, advanced ceramic manufacturers over other technologies/ cutting methods. diamond Wire saw operates similarly to horizontal hack saw, where head containing a pack of blades lengths of plain edge stainless or spring steel mounted parallel to head travel oscillates back and forth over the work piece or pieces which are mounted on a bed. The bed can be fed up into the blades at selected pressures. The diamond wire provides cutting or lapping action between the blades and material.
The wire saw allows slicing of hundreds of wafers simultaneously with the same continuous wire. In the past abrasives slurry wire saws were the main method used for cutting these ultra hard and brittle materials. Copper plated piano wires was used to trap abrasive particles (such as alumina or SiC) suspended in mechanical oil or water based coolant. To provide the cutting action and lubrication of the moving wire. The wire diameter used was smaller than 0.15mm and cutting kerf is about 0.19mm and 0.15mm and smaller. Abrasive slurry grit ranged from 1000 to 250 grit.
Viscosity and continuous mixing of the slurry must be maintained in order to produces consistent results. The improvement in diamond wire manufacturing technology and reduction in cost has made diamond wire cutting and industry standard. Diamond wire bonded with diamond offers many advantages in terms of faster cutting speed (frequently triple the speed) and improved surface finish quality (less secondary operations such as polishing).
Using Diamond Wire is much cleaner and faster process Today most Diamond Wire is wound around 2, 3,or 4 grooved mandrels in order to allow multiple loops for simultaneous slicing of the same ingot. When the looped wire is running across the ingot, the diamond particles on the surface of the wire will slowly lap/ grind off silicon on micro level (bit by bit). The cutting action is done by reciprocating motion. The wire is used once, and replaced with a new roll.
Typically this type of wire saw can travel at surface speed of 6 mm/sec. The wire moves forward for abut 300mm and this is retraced for abut 200mm. Net advance of the new wire is at an average speed of 2 m/sec with about 100 m new wire passed through each cycle. The wire can run continuously for more than 300 km long. More than 500 slices can be sawn simultaneously. In a production environment 8” (200mm) silicon boul can be cut in less than 8 hours and 12” (300mm) boul in less than 12 hours.