Ultrasound is a sound wave with a frequency of more than 20KHz, which is outside the frequency that the human ear can hear (the frequency of sound that the human ear can hear: 16 HZ-20 KHZ). When the uniformity of the material changes, the acoustic impedance will change, and the amplitude and phase of the echo signal will change. The waveform data (such as peak value, time, etc.) are displayed with different colors or gray values, which can display the internal structure of the tested sample in real time.

Reflection scan mode:

A probe is used to transmit and receive ultrasonic waves simultaneously.

The scan modes are A-Scan, B-Scan, and C-Scan. In addition, there are D-Scan, X-Scan, G-Scan, and Z-Scan.

For specific layers, the image is clear.

Transmission scanning mode:

Similar to X-ray detection, the detection method using transmitted ultrasound as the signal.

The ultrasonic signal penetrates the entire sample under test, and a single scan can detect all interface defects.

The image is not as clear as the reflection.

Autofocus scanning technology

With traditional surface tracking techniques, in the face of large warped samples (such as thinned wafer bonding samples), severely warped locations cannot be detected due to defocus. With the application of autofocus scanning technology, the Z direction of the probe can be adjusted up and down in real time along with the fluctuation of the sample surface in the scanning process, and always focus on the specified interface inside the sample, so as to track the 2-5mm large warped sample surface.