wire bonder ultrasonic energy calibration

1. why need to calibrate ultrasonic energy?
1. suppose there are hundreds of machines in the plant running to produce the same product, with same parameters, than it is important to keep the energy output of each machine are very close, let's say, within acceptable variance. since there are must be some variations of the transducer dimensions, resistance of EFO wires and output of EFO boxes, the output of ultrasonic energy could be effected by these variations.
2. when ultrasonic energy calibration is required?
1. when changing transducer, EFO wires, FEO box
3. practical method of ultrasonic energy calibration
1. Gap sensor
1. using a sensor with laser beam, to measure the displacement of capillary tip under different input setting
2. ball shear test
1. use a DOE matrix, with different inputs of ultrasonic energy, measure the ball shear value of each group and compare the data.
3. peeling test
1. use a DOE matrix, with different inputs of ultrasonic energy, do the peeling test, check when the ball start to lift, or peeling.
4. Easy way from KNS: on-bonder personality factor (OBPF) 
1. use standard p-part, leadframe, wire, bonding with special designed capillary and bonding program, bond at least 800 wires, and calculate the current factor