Technical Report: Ultrasonic Vibration Measurement of Wire Laser Doppler Vibrometer (Part 3)

Ono Sokki LV-1800 Laser Doppler Vibrometer
XYZ Magnetic Stand with Stage -Ono Sokki LV-0030 + LV-0015 + LV-0016
Large tripod Ono Sokki
Tripod mounting plate (magnetic iron plate) Ono Sokki LV-0018A
Digital oscilloscope (OSC) or equivalent high-speed storage oscilloscope (with 1MB or more of memory)
BNC-to-BNC cable x 1, probe x 1 (alligator clip-to-BNC cable, etc., depending on the equipment)
90° Reflective Mirror (Used when measuring lead frames) Ono Sokki LV-0301

Attach the tripod mounting plate to the tripod, and then secure the magnetic stand with the XYZ stage to it.
Remove the sensor head from the LV-1800 unit and attach it to the magnetic stand.
The voltage signal from the transducer's ultrasonic transmitter* is extracted from the wire bonder and connected to OSC CH 1.
*This may vary depending on the manufacturer. Please refer to the Bonder manual.
The speed output from the LV-1800 is input to OSC CH 2.

Turn on the power. Perform a warm-up for at least 20 minutes.
Manually move the capillary to the bonding location where you want to measure.
Shine the laser beam onto the capillary and adjust the lens focal length and microstage so that the reflection level indicator lights up stably in the green range (without blinking). At this time, confirm that the "ERROR" indicator on the sensor and main unit does not light up or blink.

*Item ③ is the most technically demanding part of the entire process. The relative vibration between the bonder body and the sensor has such a minor impact on the measurement results that it cannot be observed from the capillary vibration data due to the frequency components of its vibration velocity. However, if the bonder or the floor on which the tripod is placed lacks strength and vibrates significantly, it is difficult to stably illuminate the top of the capillary cylinder with laser light, making it impossible to maintain a stable level indicator and obtain data with a good signal-to-noise ratio. As a countermeasure, the effect of vibration can be reduced by placing an optical vibration isolation table under the tripod.

The laser focal point on the capillary should be as close to the tip as possible. However, depending on the type of capillary, the tip may bend under load, so it is recommended to set the focal point at the point where it begins to taper. It is important to note that if the focal point is changed significantly with each measurement, the data correlation will be lost, so the XYZ stage should be adjusted so that it is nearly identical.
For vibrations above 60kHz, select a velocity range of 1 m/s/V. *We recommend using the velocity output rather than the displacement output of Laser Doppler Vibrometer. With the displacement output, small vibration displacements from the floor are picked up simultaneously, but with the vibration velocity output, the vibration velocity of the capillary and the vibration velocity of the floor are significantly different, so this effect will not be reflected in the data.
Leave both the HPF and LPF filters turned off.

A vibrator has the characteristic of generating large vibrations at a specific frequency (resonant frequency), but since the frequency can change depending on the conditions, a feedback circuit is installed in the oscillator that drives the vibrator to control the frequency. In addition, vibrations propagated by the metal horn are amplified, so the amplitude at the tool tip is about a few micrometers under no load. To perform stable bonding, it is necessary to stabilize the vibration amplitude at the tool tip. For this reason, the need to directly measure the vibration at the tool tip is increasing year by year.

Turn on the power.
Display only the waveforms you want to show.
- CH Key
- Lighting
Let the input coupling be AC.
- INPUT key
- AC
Set the probe's attenuation ratio^.

* Observe the attenuation ratio of the probe and set the attenuation ratio.
- INPUT key
- Probe
- 1:1 or 1:10
Set the voltage axis sensitivity to optimal (around 2 V/div).
- V/DIV Key
- Rotary knob
Set trigger mode to single
- MODE key
- SINGLE
Set the trigger level and trigger source to CH 1 (approximately 0.5 V).
- LEVEL/SOURCE Key
- CH 1
- Rotary knob
Set the trigger position to (-4 div).
- POSITION/DELEY Key
- -4 div
Set storage capacity to 1 MB or more.
- ACQ Key
- Length
- 1M
Set the time axis for each bonding time to (1 ms/div to 10 ms/div).
- TIME/DIV knob
Put the OSC into a trigger-waiting state.
- START/STOP key

Once the setup is complete, perform a manual test oscillation. At that time, confirm that the OVER or ERROR indicator on the LV-1800 does not light up. If OVER lights up, the speed range is too low or the settings are incorrect and the light output is insufficient. Look at the OSC display, and if the waveform exceeds 10 V per amplitude, the range is inappropriate. Change to a range that does not exceed 10 V. If oscillation occurs but no data is displayed, it is possible that the start button was not pressed or the trigger level setting is incorrect. Readjust the trigger level so that the US oscillation waveform can be displayed.

The waveform can be magnified at any point.
- POSITION key
- Use the rotary knob to bring the area you want to enlarge to the center of the screen.
- Select the magnification using the ZOOM key or rotary knob.
Display the spectrum
- Turn on the SHIFT key, then press the FFT key.
- Select the waveform you want to display spectrally using Trace.
- Turn on FFT.
Read each waveform using the cursor (two cursor positions are available).
- CURSOR key
- Turn on the CURSOR
- Rotary knob
Print it out
- COPY key