Design and performance of a thin, solid layer for high-resolution, dry-contact acoustic imaging

Area of Science:

• Materials Science
• Acoustics
• Non-Destructive Testing

Background:

• Traditional ultrasound imaging often requires water immersion, which can be impractical or undesirable for certain applications.
• Achieving high-frequency ultrasound transmission through solid interfaces presents challenges in signal attenuation and quality.

Purpose of the Study:

• To develop and validate a dry-contact ultrasound technique for improved high-frequency signal transmission.
• To enable high-quality acoustic imaging without the need for object immersion.
• To enhance spatial resolution and signal-to-noise ratio (SNR) for defect detection.

Main Methods:

• Development of a theoretical model for signal amplification and modulation to higher frequencies.
• Design and fabrication of thin, solid layers for ultrasound transmission.
• Experimental validation using high-frequency ultrasound through layer/silicon interfaces at ~0.1 MPa.
• Application to solder joint inspection in electronic packages.

Main Results:

• Demonstrated significantly improved spectral intensity in the 20-70 MHz range compared to water immersion.
• Observed modulation of peak spectral frequencies to higher ranges.
• Achieved higher spatial resolution and SNR in solder joint inspection.
• Successfully detected defective solder joints without wetting the package.

Conclusions:

• The proposed dry-contact technique effectively enhances high-frequency ultrasound transmission through thin solid layers.
• This method offers a viable alternative to water immersion, providing superior imaging performance.
• The technique shows promise for non-destructive testing applications, such as electronic package inspection.