2D Xray Inspection

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2-D X-ray Inspection Lead-free Solders

• Dr. David Bernard
• Product Manager X-ray Systems

Dage Precision Industries Limited Rabans Lane,
Aylesbury, Bucks., HP19 8RG, UK Tel [phone]
Fax [phone] d.bernard_at_dage-group.com www.da
ge-group.com
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Why X-ray Inspect?Optical image
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Why X-ray Inspect?x-ray image overlay on optical
image
Lead-free sample
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Why need an oblique angled view?

• The solder ball shape can obscure pad detail if
  only look from above
• May see truncation at top and bottom of ball as
  evidence of good reflow BUT...
• Different oblique views can be needed to confirm
  analysis
• Looks OK in one orientation but not in another,
  or vice versa!
• Angled views usually show ball shape variation
  better and can remove objects from other board
  levels from interfering with analysis

Lead-free images
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Why need an oblique angled view?
NORMAL VIEW
Not a lead-free image
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Why need an oblique angled view?
OBLIQUE VIEW
Not a lead-free image
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Implications of Lead-freeon X-ray Inspection
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X-ray of Lead-free Soldered Boards
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X-ray of Lead-free Soldered Boards

• Traditional solder SnPb (6337)
• Most common lead-free solder
• SnAgCu (SAC alloy)
• 97 Sn
• This and other lead-free solders have high Z
  material
• Sufficient radiation absorption to cast a shadow
  at the detector (image intensifier)
• Slightly different x-ray tube conditions (power
  kV) may be necessary than with traditional solder
  but inspection capabilities should not be
  compromised

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Example Images
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Popcorning Bridging
PossibleFaults
BGA
Opens
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Voiding and location within Sample
Not a lead-free image
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Voiding in Pads or Die Attach

• Calculating the void percentage may be critical
  for automotive and other high temperature / high
  power applications where a poor joining area
  within the connection or die attach could provide
  easy failure paths.
• Criteria needed?
• lt x of total pad / die area?
• No one void gt y of total?

Lead-free image
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Lead-free Board
Lead-free images
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Flip Chip on Lead-free Board
Normal View
Oblique View
Oblique View
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Lead-free Board
Oblique View
Lead-free images
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Conclusion

• Much less experience with lead-free solders
• Higher temperatures used
• Closer to critical temperatures PCB / components
• Bad News
• Learning curve to climb
• Trials / Mistakes / Errors will be made
• Good News (!)
• Your 2-D x-ray inspection system should see them