Dry-contact technique for high-resolution ultrasonic imaging

Area of Science:

• Materials Science
• Non-Destructive Testing
• Acoustics

Background:

• Traditional ultrasonic imaging often requires sample wetting, which can be impractical or undesirable.
• Achieving high-resolution imaging necessitates efficient acoustic coupling between the transducer and the sample.

Purpose of the Study:

• To investigate the efficiency of dry-contact ultrasonic transmission for high-resolution imaging.
• To develop a method for forming a dry-contact interface without wetting the sample.
• To model and assess signal loss during dry-contact ultrasonic transmission.

Main Methods:

• A dry-contact interface was created using a thin film between water and the sample.
• Air evacuation between the film and sample applied pressure to the interface.
• A transmission model was developed to evaluate signal loss.
• Various films were tested to determine optimal transmission properties.

Main Results:

• Higher frequency ultrasound was effectively transmitted into the sample by selecting an optimum film.
• The optimal film maintained displacement continuity between the film and sample.
• Successful ultrasonic imaging was achieved on package delamination and ball-grid-array interfaces.

Conclusions:

• Dry-contact ultrasonic transmission is feasible for high-resolution imaging without sample wetting.
• Film selection is critical for efficient ultrasound coupling and signal integrity.
• The developed method enables non-destructive evaluation of packaged electronic components.