Wire bonder ultrasonic vibration measurement by laser Doppler vibrometer
8.Measurement procedure of wire bonding
8-1 System configuration
- Laser Doppler vibrometer LV-1710 (Ono Sokki)
- Magnet stand LV-0030 + Fine-positioning XY stage LV-0015 + Fine-positioning Z stage LV-0016 (Ono Sokki)
- Tripod LV-0017A (Ono Sokki)
- Steel plate with tripod LV-0018A （Magnetizable steel plate, Ono Sokki）
- Digital oscilloscope DL-1640 (Yokogawa Electric Corporation) or High-speed storage oscilloscope equivalent to the DL-1640 (1M or more memory installed)
- BNC−BNC cable×1, probe×1 （crocodile clip – BNC cable if necessary）
- 90°bending mirror（used when measuring lead frame）
8-2 System setup procedure
- Attach the steel plate on the tripod, and fix the magnet stand with fine-positioning XYZ stage.
- Take the LV sensor head out from the main unit and attach it to the magnet stand.
- Take the voltage signal of the transducer's ultrasonic transmitter* from the wire bonder and connect it to CH1 of the OSC.
* It depends on the manufacture. Refer to the bonder manual.
- Input the speed output from LV-1710 to CH2 of OSC.
8-3 Sensor operation procedure
- Turn the power ON. Take time to warm-up at least 20 minutes.
- Manually move the capillary to the bonding position where you want to measure.
- Apply laser light to the capillary, and operate the focal length of the lens and the microstage so that the reflection level indicator lights stably in the range of green (so that it does not blink).
At this time, check that the “ERROR” on the sensor / main unit does not light up or blink.
*This is the most technical part of the whole work. The effect of the relative vibration of the bonder body and sensor on the measurement result is so slight that it cannot easily be observed from the vibration data of the capillary by referred the frequency component of the vibration speed.
· When the level indicator cannot be hold stably so data with high S/N cannot be obtained.
(When the bonder or the floor on which the tripod is mounted dos not enough strength etc.
laser light cannot stably be irradiated to the top of the capillary cylinder.)
As a countermeasure, pulling the optical vibration isolation table under the tripod is recommended to reduce the influence of vibration.
- Set the laser focus position at the tip of capillary.
The focal position is preferably the tip of the capillary as much as possible. However, the tip might deflect with loads depending on the type of capillary. In that case, set the position where the taper begins to taper as the focal position. It is important to set so that focus positions are almost the same at each measurement so adjust with the XYZ stage. If the focal position is changed significantly, the data cannot be correlated.
- Set the velocity range
Tentatively try “1 (m/s)/V” when the vibration region is more than 60kHz.
· The velocity output is recommended to select as output setting.
*Set to displacement output:
The ratio between the displacement amplitude of background vibration superposed from the floor to sensor and the displacement amplitude of capillary is small. Not easy to confirm capillary behavior.
*Set to velocity output :
The ratio between the velocity amplitude of background vibration superposed from the floor to sensor and the velocity amplitude of capillary is large. Waveform can be observed with large S/N ratio.
- Set the filter
Turn off both HPF and LPF.
8-4 Temporary Setup Procedure of oscilloscope
Observe the actual signal and adjust the voltage range appropriately.
The vibration waveform of laser Doppler vibrometer is memorized by one shot trigger using a digital oscilloscope. The oscillation waveform of ultrasonic sound is used as a reference. The analysis is performed by expanding an arbitrary waveform part offline.
- Turn the power ON
- Display only the waveform required
· CH key
· Light on
- Set input coupling to AC
· INPUT key
- Set the damping ratio of probe*
*Refer to the probe damping ratio before the set.
· INPUT key
· １:１ or １:１０
- Set the optimum voltage axis sensitivity (about 2 V / div)
· V／DIV key
· Rotary knob
- Set the trigger mode to single.
· MODE key
- Set the trigger level and trigger source to CH1 (about 0.5V)
· LEVEL／SOURCE key
· CH 1
· Rotary knob
- Set the trigger position to (-4 div).
· POSITION／DELEY keyー
· -4 div
- Set storage memory capacity to 1 M or more
· ACQ key
- Set the time axis for each bonding time（1ms/div to 10ms/div）
· TIME／DIV knob
- Put the OSC in the trigger wait state.
· START／STOP key
8-5 Test oscillation for wire bonder
After completing the setting, try the test oscillation manually.
- Check that the LV-1710 OVER or ERROR is not lit.
OVER is lit: The speed range is too low or the light intensity is insufficient because of bad setting.
If the waveform of half amplitude exceeds 10V at OSC display, the range is not appropriate. Change the range under 10V.
- When data is not displayed
The start button may not be pressed, or the trigger level setting may be inappropriate. Set the trigger level again so that the US oscillation waveform is displayed.
8-6 Oscilloscope Analysis Procedure
- Enlarge and display the waveform at any position
· POSITION key
· Bring the position you want to enlarge to the center of the screen by using the rotary knob.
· ZOOM key
· Select the magnification with the rotary knob.
- Display spectrum
· Lights up SHIFT and select FFT key
· Select the waveform you want to display as a spectrum by using Trace
· Turn ON the FFT
- Read each waveform with the cursor (two places can be set)
· CURSOR key
· Turn ON the CURSOR
· Rotary knob
- Print out
· COPY key
- Hatano, T. (1990.11) ”Jidousyayou IC no cyouonpa bonding” : Ultrasonic Technology Vol.2 No.11（’90.11）
- Hamada, K. (1991.4) ”Cyouonpa IC you bonda”: Ultrasonic Technology Vol.3 No.4（’91.4）
- Matsumura, K. (1992.2) ”IC you cyouonpa boru bonda”: Ultrasonic Technology Vol.4 No.2（’92.2）
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