Fusion of ultrasound & X-ray data for inspection of modern microelectronic
packages Ryan S.H. Yang
05/09/2012
Supervisors:
David M. Harvey, Guang-Ming Zhang
Sponsorship
• Sponsored by a Doctoral Training Award from IeMRC (Innovative electronics Manufacturing Research Centre) for 3 years.
• Collaborators:-
• Delphi Electronics and Safety. Delphi is a leading global supplier of electronics and technologies for automotive, commercial vehicle and other market segments.
• Sonoscan Inc. - Scanning Acoustic Microscopy manufacturer.
• Systegration Ltd. – X-ray system technical support
Outline
• Introduction • Reliability of electronics • Solder joint Image Features • Experimental procedures • Results and Discussion • Conclusions
Introduction 1910
Ford Model T
Introduction
McLaren MP4-12C
2013
Introduction
• Research have shown that electronics can be amount to more than 23% of the total manufacturing cost.
• >80% of automotive innovation now stems from electronics.
Reliability of Electronics Required Operation Temperature
• For example, “How long will the ECU last?”
• Among the reliability concern, solder joint reliability is one of the most critical issue, in many cases they are the weakest link in terms of product reliability.
Reliability of Electronics
b
a a
b
a
b
cooling heating CTE a < CTE b
• Plastic Deformation • Imposes cyclic strain • Crack initiate and
Growth
Reliability of Electronics
• CTE mismatch and cyclic fatigue failure are unavoidable.
• Inspection techniques are often used to monitor the solder joint behaviour and through life performance.
• Acoustic Micro Imaging and X-ray imaging are principle Non-Destructive Testing techniques. Both techniques can penetrate through the component to image the hidden solder joints.
• However, due to some intrinsic properties of each inspection tool, the capability of monitoring the solder joints fatigue failure is discounted.
Reliability of Electronics
• AMI is an effective approach for detecting gap-type defects due to strong reflections of ultrasound at a solid-air interface.
• X-ray inspection is able to identify volumetric defects which are hard to detect by AMI.
• Fusion of Acoustic and X-ray image features offers a complimentary method for automatic inspection and monitoring.
• This research integrates multi-inspection technologies into an innovative monitoring system to study solder joint through life performance.
Solder Joint Image Features
Ability to detect fatigue failures, i.e. thin laminar cracks.
Non-destructive test.
Ability to monitor actual product through-life.
Output (A-scan & Image) Input
Scan motion
Ultrasound wave
De-ionised water
Flip chip
Bump to Board
Interface
Chip to Bump Interface
Front surface
A-scan Focus motion
Main Bang
Acoustic Micro Imaging or C-SAM
Solder Joint Image Features Ultrasound image analysis
Solder Joint Image Features Histogram of bump before and after ATC test
Solder Joint Image Features
rvoid = Dvoid/2
rbump = Dbump /2
Image intensity (range 0-255)
Bonding area (Pixels)
Solder void (Percentage)
Solder joint with void
Experimental Procedures
• Organic FR4 test board of 0.8mm thickness
• 14 flip chips on both sides of the board
• Die Thickness = 725μm
• die size = 3948μm × 8898μm
• 109 solder bumps
• Ball height = 125μm
• Accelerated thermal cycling test
Thermal profiling -40 degC to +132 degC
500 cycle test, 100 cycle test, informed selection of 96 cycle tests
Total test time > 700 hours
Experimental Procedures
• Accelerated Thermal cycling (ATC) tests were carried out for 96 cycles. Test
boards were investigated every 8 cycles by performing AMI and x-ray
imaging.
• Ultrasound scanning
• 2 boards x 14 flip chips x 13 scan cycles x 4 image each = 1456 images
• Total data acquisition time >242 hours
• X-ray scanning
• 2 boards x 4 flip chips x 13 scan cycles x 10 image each = 1040 images
• Total data acquisition time >170 hours
• Micro-sectioning on 2 flip chips with 109 solder joints
• 109 x 2 x 2 image each = 436 SEM images
• Total sectioning time >160 hours
Experimental Procedures
Hough Transform
Solder joint detection
ROI segmentation
Image feature extraction
Results and Discussion
Results and Discussion • Mean intensity and detected area for healthy joint, fractured joint and
joint with void against number of thermal cycles. • From the plots, it can be perceived that the solder joint begins to fail
around 32 cycles, and has failed completely at 48 cycles.
Results and Discussion • A scatter plot of a flip chip with 109 solder joints where the x-axis is
the mean intensity and the y-axis is the area of the extracted region.
Results and Discussion • Naïve Bayes Classification result for the state of solder joints. A
diagonal line denotes the classification boundary. • Classification for a solder joint from healthy to failed states.
Results and Discussion • By setting the void percentage of individual solder joint at 3%, joints
having voiding could be detected.
Results and Discussion • Number of cycles to failure and void measurement for a row of solder
joints. Bump #52 with high void percentage reduces the confidence of the result.
• Bump #100 has a failure beyond 96 cycles, which denotes a healthy joint. This joint was an interesting case as it had failed, but was masquerading as a healthy joint in the ultrasound measurement system used.
Results and Discussion • A 3D failure distribution for all 109 solder joints for a flip chip on the test
board was constructed. • The similarity of the plot patterns illustrates the evidence of strong co-
relationship between both monitoring and prediction results.
Monitoring Results Simulation / Prediction Results
Results and Discussion • Different failure distribution patterns were observed for flip chips
located at different board locations.
Conclusions
• For ATC or other environmental testing, robust, reliable tools are essential for monitoring the through life performance of solder joints.
• Multi-inspection of solder joints using AMI and X-ray shows promise, particularly for difficult cases of joints having voiding
• The results obtained enable lifetime monitoring of solder joint’s performance, and facilitate the testing procedures to ensure reliable and high quality modern microelectronic systems.
• If we can improve the reliability and durability of electronics products, we can reduce environmental impact, through their longer lifetimes and associated reduction in manufacturing costs.
Thank you for your Attention!!
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