A novel approach for flip chip solder joint quality inspection: laser ultrasound and interferometric system

A novel, noncontact, nondestructive approach for flip chip solder joint quality inspection is presented. In this technique, a pulsed laser generates ultrasound on the chip's surface, exciting the whole chip into a vibration motion. An interferometer was used to measure the vibration displacemen...

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Bibliographic Details
Published in:IEEE transactions on components and packaging technologies 2001-12, Vol.24 (4), p.616-624
Main Authors: Sheng Liu, Erdahl, D., Ume, I.C., Achari, A., Gamalski, J.
Format: Article
Language:English
Subjects:
Algorithms
BGA
Chips
Displacement measurement
Error analysis
Flip chip
Flip chip solder joints
Inspection
Lasers
Optical pulse generation
Semiconductor device measurement
Solders
Surface emitting lasers
Ultrasonic imaging
Ultrasonic variables measurement
Vibration
Vibration measurement
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Summary:A novel, noncontact, nondestructive approach for flip chip solder joint quality inspection is presented. In this technique, a pulsed laser generates ultrasound on the chip's surface, exciting the whole chip into a vibration motion. An interferometer was used to measure the vibration displacement of the chip's surface. Because changes in solder joint quality produce a different vibration response, a value, "error ratio," is used to measure the difference between a good chip and a chip with defects. An automatic signal-processing algorithm to calculate the error ratio was developed and implemented, as well as a frequency analysis algorithm. The inspection system was characterized, and results are presented for two cases of flip chips with missing solder balls. Results indicate that a laser ultrasonic/interferometeric system offers great promise for solder bump inspection in flip chip, BGA, chip scale, and micro BGA packages.
ISSN:1521-3331
1557-9972
DOI:10.1109/6144.974950