| 摘要 |
PROBLEM TO BE SOLVED: To prevent a drill from being damaged by removing disturbance factors etc., and accurately detecting whether the drill comes into contact with a desired conductor layer, and also preventing a harmonic current from flowing to the drill, when a bore hole is made down to a desired conductor layer of a substrate by drilling with a spindle.SOLUTION: There is provided a descent distance information detection mechanism having a high-frequency AC power supply, a bypass circuit including at least a reactor, a canceling circuit, and a current transformer for high harmonic which has an input winding and a canceling winding having the same number of turns and connected in opposite winding directions, and one or more output windings. Magnetic flux generated at the input winding owing to disturbance factors and magnetic flux generated at the canceling winding by the canceling circuit cancel each other, and no current is generated on an output winding side of the current transformer, so descent distance information on a spindle can be precisely determined, and the bypass circuit prevents a harmonic current etc., from flowing to a drill, thereby preventing the drill from being damaged.SELECTED DRAWING: Figure 1 |
