Digital signal processing methods in a novel flip chip solder joint quality inspection system are presented. Laser ultrasound and interferometric system is a new approach for solder joint inspection. It has many advantages such as being noncontact, nondestructive, fast, accurate and low cost. Furthermore, it can be used on-line in assembly line or off-line during process development. In this system, signals recorded are ultrasound waveforms. Because noise is present, signal processing methods are developed to increase signal-to-noise ratio, and to extract solder joint quality information from those waveforms. Signals are analyzed both in frequency domain and time domain. In the frequency domain, digital filtering and Bartlett power spectrum estimation method are used, and defects can be detected from the frequency shifting. A series of experimental results are presented, showing that power spectrum estimation can greatly increase the signal-to-noise ratio than when only time domain averaging is used. This speeds up the data acquisition and analysis process. In the time domain, “error ratio” is used to measure the difference between a good chip and a chip with defect. Results indicate that error ratio method not only can detect whether a chip has solder joint defect or not, but can also locate that defect. Overall, signal processing plays a very important role in this flip chip quality inspection system.

Issue Section:
Technical Papers
Keywords:
flip-chip devices, reflow soldering, inspection, quality control, light interferometry, ultrasonic applications, spectral analysis, data acquisition, time-domain analysis, signal processing
Topics:
Errors, Flip-chip devices, Inspection, Signal processing, Signals, Solder joints, Flip-chip, Data acquisition, Vibration
1.
Edward
,
S.
,
1991
, “
X-Ray Systems Keep Pace with SMT
,”
Test Meas. World
,
11
(
3
), pp.
21
–
22
.
2.
Adams
,
T.
, 1995, “Acoustic Micro Imaging of Flip Chip Interconnects,” III-Vs Review, 8(5), Oct., pp. 50–52.
3.
Lau
,
J. H.
, and
Keely
,
C. A.
, 1989, “Dynamic Characterization of Surface-Mount Component Leads for Solder Joint Inspection,” IEEE Trans Surface-Mount Component Leads for Solder Joint Inspection, 12(4), Dec., pp. 594–602.
4.
Semmens
,
J. E.
, and
Kessler
,
L. W.
, 1997, “Further Investigation Into the Use of Acoustic Micro Imaging for Analyzing Flip Chip Integrity and Failure Modes,” Proc. SPIE, 6th Int. Conf. and Exhibit. on Multichip, Modules, Denver, CO, February 2–4, pp. 165–169.
5.
Liu, S., Erdahl, D., Ume, I. C., and Achari, A., 2000, “A Novel Method and Device for Solder Joint Quality Inspection by Using Laser Ultrasound,” Proc. Electronic Components and Technology Conference, Las Vegas, NV, May.
6.
Scruby, C. B., and Drain, L. E., 1990, Laser Ultrasonics: Techniques and Applications, Adam Hilger, New York, NY.
7.
Sanderson
,
T.
,
Ume
,
C.
, and
Jarzynski
,
J.
, 1998, “Experimental and Numerical Results for Intensity Modulated Laser Ultrasonic,” J. Acoust. Soc. Am., 104(4), Oct.
8.
Gorman, D. J., 1982, Free Vibration Analysis of Rectangular Plates, Elsevier North Holland.
9.
Oppenheim, A., and Schafer, R., 1998, Discrete-Time Signal Processing, 2nd Edition, Prentice-Hall, Englewood Cliffs, NJ.
Copyright © 2003
 by ASME
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