Polyimide/Carbon Defects

1
Polyimide/Carbon Defects

• C. T. Mueller
• J. G. Coffer
• 6/21/2000

2
General Observations

• Two 6 sections of fiber from CDO384XB and
  CDO588XD examined
• 1 polyimide bubble (with hole in carbon layer) in
  CDO384XB
• 16 polyimide bubbles in CDO588XD
• most have a bright spot near carbon layer
• One 4 section from CDO731XB (non-carbon coated
  fiber) examined
• no polyimide bubbles found
• must clean to remove dirt (complete)
• small features found

3
Plans

• CDO588XD
• cut out section for FE-SEM inspection of
  polyimide surface
• 3 bubbles polyimide bubble (with hole in carbon
  layer)
• (complete -- see later charts)
• will remove polyimide after FE-SEM inspection to
  provide additional evidence (using optical
  microscope) that hole exists in carbon layer
• feature located directly beneath bubble in
  polyimide
• brighter than remaining background
• diffraction rings observed
• (complete -- see later charts)

4
Investigation of Hole in Carbon Coating

• Depth and Size
• bright light located at glass/carbon interface
  under backlit light illumination (transmission)
• size appears to be limited by optical resolution
  of microscope optics 400X 0.5 µm

pinhole or diffraction pattern I.e. Fresnel Zone
CDO384XB illumination transmission (light
behind the fiber), polarized
10 µm
5
Investigation of Polyimide Coating

• Lot information
• CDO384XB
• 1/21/99 run date
• two reels produced
• draw sheet This run was run using four coats
• CDO588XD
• 7/22/99
• at least four reels produced

Source Jeanette Plante
6
Location of Polyimide Defects

• Approximately uniformly located along the fiber

6 sample CDO588XD
7
Laboratory- Induced ESD Damage
Defect small compared to ESD damage

• Size of ESD burn appears to be random
• many large ones only a few small ones
• Smallest diameter burn to date
• 30 µm
• Electrical conditions
• breakdown voltage of 4 - 6 kV ( 6.7 - 10
  kV/mil)
• current limited to 100 - 150 µA
• planar electrodes (parallel E-fields)

3/22/2000
8
Noncarbon-Coated Fiber
fiber
9
Noncarbon-Coated Fiber
Reflection
10 µm
10
CDO588XD - Defect 1
FE-SEM
Optical
10 µm

• Polyimide present in both micrographs
• FE-SEM taken at 60 degrees to normal to surface
• No hole at surface of polyimide

11
Comparison to Re-spooled Fiber
Defect may actually have been seen earlier in
other fiber

• Carbon-coated fiber re-spooled at BiccGeneral in
  Nov. 99
• One polyimide defect in Loop 5
• center has 11 µm diameter dark area

3/22/2000
12
Polyimide Bubble -Carbon Pinhole

• CDO588XD - sample 2

Reflection
Transmission
10 µm
10 µm

• Polyimide present in both micrographs

13
Carbon

• CDO588XD - sample 2

• Reflection

• Polyimide has been etched off in sulfuric acid

• Multiple bright spots at carbon coating surface

10 µm
feature below polyimide bubble
100 x objective 0.3 µm resolution
10 µm

• Transmission

14
Conclusions

• Bubble defects are present in UNCABLED
  carbon-coated fiber
• Significantly more bubble defects found in
  CDO588XD vs. CDO384XB
• A distinct depression or dimple occurs in the
  polyimide directly above the location of the
  bubble feature
• Feature(s) exist in carbon coating
• below the polyimide bubbles
• AND elsewhere
• dimensions appear to be on the order of the
  resolution limit of the optical microscope (0.5
  µm)
• Now investigating Fresnel zones from photographs
• Features exist in non-carbon fiber