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!!