System for regulating the applied blade-to-boule force during the slicing of wafers

In a wafer saw for slicing thin wafers from a boule of source material in which said saw has a saw blade which revolves at high speed for slicing wafers from said boule;

• said saw holds said boule stationary during the slicing of each wafer;
• said saw translates said revolving saw blade to cause the cutting surface of said blade to penetrate said stationary boule to slice a wafer from said boule by removing boule material which attaches said wafer to the remainder of said boule and said boule and said saw has a control system for controlling the rate of translation of said blade, the improvement comprising:
• means for regulating the blade-to-boule force urging said blade of said saw into said boule during the slicing of wafers to improve the as-sawn quality of the wafers, said means for regulating comprising:
• force sensing means for sensing the blade-to-boule force urging said blade of said saw into said boule;
• said force sensing means comprising a transducer fixed to said stationary boule for sensing said blade-to-boule force;
• force reference means for establishing a desired pattern of blade-to-boule force;
• force comparator means for determining whether said sensed blade-to-boule force exceeds said desired blade-to-boule force and for determining whether such sensed blade-to-boule force is less than said desired blade-to-boule force by more than a desired force-hysteresis amount;
• control means for decreasing the feedrate of said saw blade into said boule when said force comparator means produces an output indicating that said sensed blade-to-boule force is greater than said desired blade-to-boule force and for increasing said feedrate when said comparator means produces an output indicating that said sensed blade-to-boule force is less than said desired blade-to-boule force by an amount which is greater than said desired force hysteresis amount.