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LED, BGA, and QFN Inspection - X-Ray Inspection for SMT Quality Assurance and Control

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In this presentation we will cover the manufacturing of the most challenging surface mount parts to assemble and inspect today: LEDs, BGAs, and QFNs. The presentation will focus on the pitfalls of manufacturing and inspecting PCBs with these devices and solution to the technical challenges encountered by luminaire integrators and contract manufacturers. This presentation is targeted at manufacturing, process, and quality personnel responsible for designing; implementing and/or controlling the surface mount device application and inspection process. Those personnel responsible for training operators and technicians to perform assembly inspection or control the manufacturing process would also benefit from this presentation.

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LED, BGA, and QFN Inspection - X-Ray Inspection for SMT Quality Assurance and Control

  1. 1. www.creativeelectron.com Copyright © 2015 Creative Electron X-Ray Inspection for SMT Quality Assurance and Control
  2. 2. www.creativeelectron.com Copyright © 2015 Creative Electron The X-Ray Machine You Didn’t Know Existed! The first inline/offline hybrid x-ray inspection, designed to meet the needs of the high mix/low volume manufacturers
  3. 3. www.creativeelectron.com Copyright © 2015 Creative Electron TruView 6 & the Power of Crowdsourcing
  4. 4. www.creativeelectron.com Copyright © 2015 Creative Electron Schedule for this presentation Introduction to x-ray technology Where SMT problems come from? Case studies - assembly and inspection of: LED BGA PTH QFN How to use statistical analysis to diagnose your SMT line
  5. 5. www.creativeelectron.com Copyright © 2015 Creative Electron How do we image the X-rays? When X-rays hit certain materials, they cause them to fluoresce. In this process, the energy of the X-ray is absorbed and re-emitted as visible light. Usually this light is very faint and needs to be amplified, else very sensitive detectors need to be used. Flat Panel Detector. Photo byTeledyne Technologies. Image intensifier. Photo by Hamamatsu Corporation
  6. 6. www.creativeelectron.com Copyright © 2015 Creative Electron How do we get a magnified image? 8 Just like light,X-rays travel in straight lines. Unlike light,we cannot use a lens, so we use geometric magnification. The magnification is increased by moving the sample closer to the X-ray source (and vice versa).
  7. 7. www.creativeelectron.com Copyright © 2015 Creative Electron Field of View The electron beam generated by the cathode is rapidly accelerated against the anode. Upon colliding with the anode, a cone-shaped beam of x-rays is generated As the x-ray beam moves farther from the anode target, the diameter of the beam increases proportionally.The angle of the x-ray cone beam, α, is determined by the angle of the anode target Diameter of the x-ray beam increases as it moves away from the source Magnification is a function of the distances between source, sample, and detector
  8. 8. www.creativeelectron.com Copyright © 2015 Creative Electron Where Are Defects Introduced?
  9. 9. www.creativeelectron.com Copyright © 2015 Creative Electron Defects associated with paste application Excess solder Solder bridges Insufficient solder Solder Paste Application Defects
  10. 10. www.creativeelectron.com Copyright © 2015 Creative Electron Component Placement Defects Defects associated with component placement Misalignment Polarity (tantalum) Missing component
  11. 11. www.creativeelectron.com Copyright © 2015 Creative Electron Reflow Oven Defects Defects associated with the Reflow oven Voiding Bridging Solder balls Excess solder Insufficient solder
  12. 12. www.creativeelectron.com Copyright © 2015 Creative Electron Statistical Process Control Manufacturing process quality assurance. Solder joint measurement data,collected during x-ray test, can be statistically analyzed to identify manufacturing drifts,trends and other relevant process quality issues.
  13. 13. www.creativeelectron.com Copyright © 2015 Creative Electron Other PCB Issues Under X-Ray: QFN Short
  14. 14. www.creativeelectron.com Copyright © 2015 Creative Electron Other PCB Issues Under X-Ray: Blown Trace
  15. 15. www.creativeelectron.com Copyright © 2015 Creative Electron PCB broken trace
  16. 16. www.creativeelectron.com Copyright © 2015 Creative Electron Broken Wirebonds
  17. 17. www.creativeelectron.com Copyright © 2015 Creative Electron Other PCB Issues Under X-Ray: Misaligned Cap
  18. 18. www.creativeelectron.com Copyright © 2015 Creative Electron Other PCB Issues Under X-Ray: Tombstoning
  19. 19. www.creativeelectron.com Copyright © 2015 Creative Electron Other PCB Issues Under X-Ray: Missing Cap
  20. 20. www.creativeelectron.com Copyright © 2015 Creative Electron Wire Crimp Defect
  21. 21. www.creativeelectron.com Copyright © 2015 Creative Electron Wire Crimp Defect
  22. 22. www.creativeelectron.com Copyright © 2015 Creative Electron Manufacturing Inspection Case studies LED BGA PTH QFN
  23. 23. www.creativeelectron.com Copyright © 2015 Creative Electron Typical LED luminaire fabricated by GMC
  24. 24. www.creativeelectron.com Copyright © 2015 Creative Electron LED Voiding This relationship shows us the operating temperature of the LED grows exponentially with the void area. For this reason it is critical to keep the voiding area to a minimum.
  25. 25. www.creativeelectron.com Copyright © 2015 Creative Electron Typical samples prior to quality inspection; prior to adoption of x-ray imaging
  26. 26. www.creativeelectron.com Copyright © 2015 Creative Electron First samples after implementation of quality program and inspection
  27. 27. www.creativeelectron.com Copyright © 2015 Creative Electron Summary of results for luminaire “A” SinkPAD IITM substrate Prior to quality program Initial samples after implementation of quality program Voiding Luminaire “A” Mean 40% Std Deviation 15 Voiding Luminaire “A” Mean 8% Std Deviation 0.9
  28. 28. www.creativeelectron.com Copyright © 2015 Creative Electron How GMC improved SMT assembly quality? • Substrate surface cleanness • Substrate and LED metallization • Reflow oven temperature profile • Paste selection, dispensing, and storage • LED and substrate handling and storage
  29. 29. www.creativeelectron.com Copyright © 2015 Creative Electron Current quality inspection program Use x-ray inspection to set proper manufacturing parameters for each product. Use voiding area a key metric to determine process variation Use LED information to determine maximum operating temperature to achieve expected lifespan Measure temperature as a function of voiding area to determine maximum voiding allowed Set plan to continuously measure voiding area with x- ray to verify conformity of manufacturing process
  30. 30. www.creativeelectron.com Copyright © 2015 Creative Electron Medical device assembly GMC started assembling medical device probes for radiotherapy RMAs have reached $25k per month Design has never worked well…
  31. 31. www.creativeelectron.com Copyright © 2015 Creative Electron Medical device probe assembly Complex construction 2 reflow cycles: first for FPGA, second for sensor Lot’s of connectivity problems with the FPGA, likely due to the second reflow Sensor FPGA PCB
  32. 32. www.creativeelectron.com Copyright © 2015 Creative Electron Sensor side assembly Bare PCB PCB with sensors removed
  33. 33. www.creativeelectron.com Copyright © 2015 Creative Electron Simplified assembly – 1 sensor, 1 FPGA Sensor FPGA PCB
  34. 34. www.creativeelectron.com Copyright © 2015 Creative Electron X-ray of assembly – 1 sensor, 1 FPGA
  35. 35. www.creativeelectron.com Copyright © 2015 Creative Electron X-ray of assembly – 1 sensor, 1 FPGA
  36. 36. www.creativeelectron.com Copyright © 2015 Creative Electron X-ray of assembly – 1 sensor, 1 FPGA
  37. 37. www.creativeelectron.com Copyright © 2015 Creative Electron X-ray of assembly – 1 sensor, 1 FPGA
  38. 38. www.creativeelectron.com Copyright © 2015 Creative Electron X-ray of assembly – 1 sensor, 1 FPGA
  39. 39. www.creativeelectron.com Copyright © 2015 Creative Electron BGA inspection with dual energy imaging
  40. 40. www.creativeelectron.com Copyright © 2015 Creative Electron BGA Opens
  41. 41. www.creativeelectron.com Copyright © 2015 Creative Electron BGA Head In Pillow Visual Inspection
  42. 42. www.creativeelectron.com Copyright © 2015 Creative Electron BGA Head In Pillow X-Ray Inspection
  43. 43. www.creativeelectron.com Copyright © 2015 Creative Electron BGA inspection – ball size analysis Gradient in ball sizes indicate planarity issues with the assembly Different ball sizes also cause voiding discrepancies in the assembly Small Large
  44. 44. www.creativeelectron.com Copyright © 2015 Creative Electron BGA Co-planarity Inspection
  45. 45. www.creativeelectron.com Copyright © 2015 Creative Electron Planarity issues with FPGA assembly Sensor FPGA PCB
  46. 46. www.creativeelectron.com Copyright © 2015 Creative Electron Fixing the problem • Epoxy on the corners of the FPGA • Underfill also an option Sensor FPGA PCB
  47. 47. www.creativeelectron.com Copyright © 2015 Creative Electron Plated Thru Hole
  48. 48. www.creativeelectron.com Copyright © 2015 Creative Electron Plated Thru Hole per IPC-A610
  49. 49. www.creativeelectron.com Copyright © 2015 Creative Electron Measuring PTH Fill with X-Rays
  50. 50. www.creativeelectron.com Copyright © 2015 Creative Electron Measuring PTH Fill with X-Rays – Side View
  51. 51. www.creativeelectron.com Copyright © 2015 Creative Electron Measuring PTH Fill with X-Rays – Top View
  52. 52. www.creativeelectron.com Copyright © 2015 Creative Electron Data processing board • High volume production - thousands of boards per week • Intermittent issues with QFN parts
  53. 53. www.creativeelectron.com Copyright © 2015 Creative Electron QFN assembly with excess voiding
  54. 54. www.creativeelectron.com Copyright © 2015 Creative Electron Problem QFN assembly – open pin
  55. 55. www.creativeelectron.com Copyright © 2015 Creative Electron Detail of open pin in QFN package
  56. 56. www.creativeelectron.com Copyright © 2015 Creative Electron Excessive Pad Voiding A B
  57. 57. www.creativeelectron.com Copyright © 2015 Creative Electron Another QFN problem: improper alignment
  58. 58. www.creativeelectron.com Copyright © 2015 Creative Electron Quality control inspection with x-ray • Problem of open pins of QFN traced to dirty stencil • Review of stencil cleaning process was done. Proper procedures were not being followed • Training of cleaning staff was repeated to assure they follow all steps • Since proper stencil cleaning procedures were followed, no more issues of this nature were found.
  59. 59. www.creativeelectron.com Copyright © 2015 Creative Electron For more information Contact us: www.creativeelectron.com Chat with us live at our website Email us at info@creativeelectron.com Call us at 760.752.1192 Learn more at X-Ray University http://creativeelectron.com/x-ray-university/
  60. 60. www.creativeelectron.com Copyright © 2015 Creative Electron Thanks for your time!

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