Tool cutting method for workpiece having a plurality of LED chips sealed by sealing member

A tool cutting method for cutting a workpiece composed of a substrate, a plurality of light-emitting diode chips mounted on said substrate, and a sealing member for covering said light-emitting diode chips, said sealing member including a fluorescent material, said sealing member of said workpiece being cut by tool cutting means to thereby reduce the thickness of said sealing member to a finished thickness providing a desired brightness of light emitted from said light-emitting diode chips, said tool cutting method comprising:

• a correlation table preparing step of preparing a correlation table indicating the correlation between the brightness of light emitted from said light-emitting diode chips and the thickness of said sealing member;
• a brightness measuring step of measuring the brightness of light emitted from said light-emitting diode chips by applying a voltage to said light-emitting diode chips;
• a calculating step of calculating the thickness of said sealing member corresponding to said desired thickness from the brightness measured in said brightness measuring step and said correlation table;
• and
• a cutting step of cutting said sealing member by using said tool cutting means after performing said calculating step to reduce the thickness of said sealing member to said finished thickness providing said desired brightness of light emitted from said light-emitting diode chips.