Researchers at the Daegu Gyeongbuk Institute of Science and Technology (DGIST) in South Korea have developed an ultrasound transducer with a screw-threaded focusing lens that can reveal micro-defects inside semiconductor chips previously hidden by the sensor's own internal noise. The work was published in NDT & E International.
Ultrasound inspection is a central method for finding microscopic cracks and voids inside semiconductors without damaging the device, offering better penetration than X-rays or optical inspection in many cases. The problem lay in the small lens of industrial equipment: waves reflected inside it converged and formed edge noise that degraded the image.
The solution from the team led by Professor Chang Jin Ho was inspired by the wedge-shaped structures of anechoic chambers, which prevent sound reflections. The researchers engraved closely spaced, slanted, screw-thread-shaped grooves onto the smooth side surface of the lens. When waves hit those inclined surfaces, they scatter in many directions instead of converging to create noise.
Through computer simulations, the team set the specifications it considers ideal: a thread height of 500 micrometres and an inclination angle of 30 degrees, combining noise suppression with ease of fabrication. Because the change requires only machining the lens's outer surface, without altering the sensor's size or internal components, the technology can be applied to existing compact industrial equipment.
In tests on automotive power modules, the new transducer revealed microstructures and defects previously obscured by noise, such as metal wires about one-quarter the thickness of a human hair and microscopic bubbles, with clarity rivalling conventional computed tomography (CT). The study's co-first authors are postdoctoral researcher Kang Sungwoo and student Park Hyunkyu.
The focus now is validation on real process defects, in joint research with semiconductor manufacturers, to accelerate next-generation non-destructive testing systems. The most immediate field of application is high-reliability power semiconductors used in electric vehicles and aerospace, where an internal flaw can compromise performance and safety.
Image credit: Daegu Gyeongbuk Institute of Science and Technology (DGIST), via Tech Xplore.
Sources: Tech Xplore, Asia Research News, BrightSurf and NDT & E International paper (DOI).
Transparency: this article was produced with the help of artificial intelligence, based on cross-checking public posts and internet sources listed above. Please consult the original sources to confirm the details.
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