STAR Module
Thru-scan imaging uses a transducer on either side of the sample. The top transducer pulses very high frequency ultrasound into the sample; the bottom transducer reads the exiting ultrasound. Gap-type defects (cracks, delaminations, disbonds) block ultrasound from reaching the bottom transducer. The image shows internal structure and the acoustic shadow of the defect- but not its depth.
Reflection-mode imaging, by contrast, uses a single topside transducer which pulses ultrasound and receives return echoes. Internal features and defects are imaged, but the varying arrival time of return echoes indicates their depth.
Thru-scan imaging tells a failure analyst that a defect is present, while reflection mode imaging tells the analyst the defect's vertical position. STAR makes it unnecessary for the analyst to lose time by switching from one mode to the other and having to flip the sample over to rescan it.
In a plastic integrated circuit (IC) package, the die attach might be delaminated from the top side of the die paddle- a serious defect. Alternately, molding compound might be delaminated from the bottom side of the die paddle- a less troublesome anomaly. Using the two-mode STAR system, the analyst can:
- tell that a defect exists, and
- instantly evaluate its location and significance.
Sonoscan, 530 E. Green St., Bensenville, IL 60106. Tel: 630-766-7088. Fax: 630-766-4603.