IBM developed a new process for etching Kapton polyimide film to enable flexible circuits. John Glenning led the development effort, which included defining a new etching chemistry using potassium hydroxide, developing photoresist that could withstand the etching, and building a pilot production line. Initial tests showed defects from redeposited etched Kapton and scalloping near circuit lines, but refinements to the rinsing and photoresist application addressed these issues. Understanding of how the etching was similar to developing polyamic acid helped optimize the process parameters.

1. Kapton Etch ProcessKapton Etch Process
DevelopmentDevelopment
1986 to 19881986 to 1988
John GlenningJohn Glenning
7/20/20137/20/2013
© 2011 John Glenning© 2011 John Glenning

2. Kapton Etch Process DevelopmentKapton Etch Process Development
IBM decided to enter the flexible circuit market
Flip-Chip Technology using thermal compression bonding to replace the C4 Chip
Attach Technology
© 2011 John Glenning© 2011 John Glenning

3. Kapton Etch Process DevelopmentKapton Etch Process Development
IBM decided to enter the flexible circuit market
Flip-Chip Technology using thermal compression bonding to replace the C4 Chip
Attach Technology
PRODUCTS FAMILIES:
Micro-electronic circuitry
Computer hard drives
High performance electric harnesses for the Department of Defense
Automotive harnesses
Aerospace
Industrial applications (flexible heaters, printer heads,…)
© 2011 John Glenning© 2011 John Glenning

4. Kapton Etch Process DevelopmentKapton Etch Process Development
Kapton
Kapton is a polyimide film developed by DuPont
© 2011 John Glenning© 2011 John Glenning

5. Kapton Etch Process DevelopmentKapton Etch Process Development
Kapton
Kapton is a polyimide film developed by DuPont
BENEFITS & STRENTHS:
Very durable
Flexible
Robust to vibration
Excellent electrical, thermal, chemical and mechanical properties
Can withstand extreme temperature
© 2011 John Glenning© 2011 John Glenning

6. Kapton Etch Process DevelopmentKapton Etch Process Development
Manufacturing Process
1. Metalize the Kapton surface using sputtering
© 2011 John Glenning© 2011 John Glenning

7. Kapton Etch Process DevelopmentKapton Etch Process Development
Manufacturing Process
1. Metalize the Kapton surface using sputtering
2. Pattern the electrical circuitry using photolithography, wet processing & plating
on both the top and bottom surfaces of the Kapton
© 2011 John Glenning© 2011 John Glenning

8. Kapton Etch Process DevelopmentKapton Etch Process Development
Manufacturing Process
1. Metalize the Kapton surface using sputtering
2. Pattern the electrical circuitry using photolithography, wet processing & plating
on both the top and bottom surfaces of the Kapton
3. Pattern the Kapton using photolithography and wet processing
© 2011 John Glenning© 2011 John Glenning

9. Kapton Etch Process DevelopmentKapton Etch Process Development
Manufacturing Process
1. Metalize the Kapton surface using sputtering
2. Pattern the electrical circuitry using photolithography, wet processing & plating
on both the top and bottom surfaces of the Kapton
3. Pattern the Kapton using photolithography and wet processing
4. Attach the semiconductor chip using thermal compression bonding
© 2011 John Glenning© 2011 John Glenning

10. Kapton Etch Process DevelopmentKapton Etch Process Development
Manufacturing Process
1. Metalize the Kapton surface using sputtering
2. Pattern the electrical circuitry using photolithography, wet processing & plating
on both the top and bottom surfaces of the Kapton
3. Pattern the Kapton using photolithography and wet processing
4. Attach the semiconductor chip using thermal compression bonding
5. Encapsulate the system, if required
© 2011 John Glenning© 2011 John Glenning

11. Kapton Etch Process DevelopmentKapton Etch Process Development
Manufacturing Process Development
All manufacturing technologies existed in IBM except for Kapton etch and thermal
compression bonding
© 2011 John Glenning© 2011 John Glenning

12. Kapton Etch Process DevelopmentKapton Etch Process Development
Manufacturing Process Development
All manufacturing technologies existed in IBM except for Kapton etch and thermal
compression bonding
Myself and another engineer were asked to join the development team a year before
the rest of the team was formed.
© 2011 John Glenning© 2011 John Glenning

13. Kapton Etch Process DevelopmentKapton Etch Process Development
Manufacturing Process Development
All manufacturing technologies existed in IBM except for Kapton etch and thermal
compression bonding
Myself and another engineer were asked to join the development team a year before
the rest of the team was formed.
I was responsible for developing the entire process for etching Kapton:
1. Develop a chemistry than can etch Kapton
2. Identify a photoresist system that can withstand the Kapton etch process
3. Develop post processing rinsing, cleaning and drying operations
© 2011 John Glenning© 2011 John Glenning

14. Kapton Etch Process DevelopmentKapton Etch Process Development
Chemistry
A literature searched identified two existing chemistries
1. Ethylenediamine: Highly carcinogenic
2. Hydrazine Hydrate: Rocket Fuel (very explosive)
© 2011 John Glenning© 2011 John Glenning

15. Kapton Etch Process DevelopmentKapton Etch Process Development
Chemistry
A literature searched identified two existing chemistries
1. Ethylenediamine: Highly carcinogenic
2. Hydrazine Hydrate: Rocket Fuel (very explosive)
Safety would not approve either chemistry unless it was demonstrated that no
alternative chemistries existed
© 2011 John Glenning© 2011 John Glenning

16. Kapton Etch Process DevelopmentKapton Etch Process Development
Chemistry
A literature searched identified two existing chemistries
1. Ethylenediamine: Highly carcinogenic
2. Hydrazine Hydrate: Rocket Fuel (very explosive)
Safety would not approve either chemistry unless it was demonstrated that no
alternative chemistries existed
Worked with Corporate R & D and identified highly concentrated potassium or
sodium hydroxide at elevated temperatures as potential chemistries.
© 2011 John Glenning© 2011 John Glenning

17. Kapton Etch Process DevelopmentKapton Etch Process Development
Process Refinement
Built a prototype line in a lab to build product at sizes larger then beakers
Immersion processes with heaters and spargers
© 2011 John Glenning© 2011 John Glenning

18. Kapton Etch Process DevelopmentKapton Etch Process Development
Process Refinement
Built a prototype line in a lab to build product at sizes larger then beakers
Immersion processes with heaters and spargers
Tested the process chemistries and temperature windows for etch rates based
on projected volumes and equipment size
Settled on 7M KOH at 95ºC
© 2011 John Glenning© 2011 John Glenning

19. Kapton Etch Process DevelopmentKapton Etch Process Development
Process Refinement
Built a prototype line in a lab to build product at sizes larger then beakers
Immersion processes with heaters and spargers
Tested the process chemistries and temperature windows for etch rates based
on projected volumes and equipment size
Settled on 7M KOH at 95ºC
Tested about 30 photoresist systems until we found one that completely
withstood the etching chemistry.
© 2011 John Glenning© 2011 John Glenning

20. Kapton Etch Process DevelopmentKapton Etch Process Development
Process Refinement
Built a prototype line in a lab to build product at sizes larger then beakers
Immersion processes with heaters and spargers
Tested the process chemistries and temperature windows for etch rates based
on projected volumes and equipment size
Settled on 7M KOH at 95ºC
Tested about 30 photoresist systems until we found one that completely
withstood the etching chemistry.
Developed a surface neutralization operation (HCl) and rinsing processes
© 2011 John Glenning© 2011 John Glenning

21. Kapton Etch Process DevelopmentKapton Etch Process Development
Building the Pilot Line
The rest of the team was formed
The final process would not be immersion. It would be spray. Spray processes
give much better mass transfer than immersion.
© 2011 John Glenning© 2011 John Glenning

22. Kapton Etch Process DevelopmentKapton Etch Process Development
Building the Pilot Line
The rest of the team was formed
The final process would not be immersion. It would be spray. Spray processes
give much better mass transfer than immersion.
Hydrochloric Acid neutralization step
© 2011 John Glenning© 2011 John Glenning

23. Kapton Etch Process DevelopmentKapton Etch Process Development
Building the Pilot Line
The rest of the team was formed
The final process would not be immersion. It would be spray. Spray processes
give much better mass transfer than immersion.
Hydrochloric Acid neutralization step
Three counter-current cascading water rinses
© 2011 John Glenning© 2011 John Glenning

24. Kapton Etch Process DevelopmentKapton Etch Process Development
Building the Pilot Line
The rest of the team was formed
The final process would not be immersion. It would be spray. Spray processes
give much better mass transfer than immersion.
Hydrochloric Acid neutralization step
Three counter-current cascading water rinses
Hot air dry
© 2011 John Glenning© 2011 John Glenning

25. Kapton Etch Process DevelopmentKapton Etch Process Development
Building the Pilot Line
The rest of the team was formed
The final process would not be immersion. It would be spray. Spray processes
give much better mass transfer than immersion.
Hydrochloric Acid neutralization step
Three counter-current cascading water rinses
Hot air dry
Write the equipment specifications, visit and identify vendors.
Awarded build and installation contracts.
Installed and debugged the process and the equipment .
© 2011 John Glenning© 2011 John Glenning

26. Kapton Etch Process DevelopmentKapton Etch Process Development
Initial Product Builds
Initial development run:
At 100x magnification, an unknown material was bridging circuits, which was
unacceptable.
Lab analysis determined the material to be partially etch Kapton which was
redeposited during the etching process
© 2011 John Glenning© 2011 John Glenning

27. Kapton Etch Process DevelopmentKapton Etch Process Development
Initial Product Builds
Initial development run:
At 100x magnification, an unknown material was bridging circuits, which was
unacceptable.
Lab analysis determined the material to be partially etch Kapton which was
redeposited during the etching process
Developed a rinsing chemistry that completely removed this material (0.5 M
potassium hydroxide at room temperature).
© 2011 John Glenning© 2011 John Glenning

28. Kapton Etch Process DevelopmentKapton Etch Process Development
Initial Product Builds
Excessive “scalloping” of the Kapton was observed near the circuit lines.
Product Manager determined this to be a defect and it need to be resolved.
© 2011 John Glenning© 2011 John Glenning

29. Kapton Etch Process DevelopmentKapton Etch Process Development
Initial Product Builds
Excessive “scalloping” of the Kapton was observed near the circuit lines.
Product Manager determined this to be a defect and it need to be resolved.
Root cause was determined to be a “tenting” of the laminated photoresist over
the circuit lines. This created a channel near the circuit lines and acted as a
capillary. The capillary effect drew etchant deep under the photoresist causing
this over etch.
© 2011 John Glenning© 2011 John Glenning

30. Kapton Etch Process DevelopmentKapton Etch Process Development
Initial Product Builds
Excessive “scalloping” of the Kapton was observed near the circuit lines.
Product Manager determined this to be a defect and it need to be resolved.
Root cause was determined to be a “tenting” of the laminated photoresist over
the circuit lines. This created a channel near the circuit lines and acted as a
capillary. The capillary effect drew etchant deep under the photoresist causing
this over etch.
It was decided that we would presoak the Photoresist-Kapton System with water
to fill the capillary. This solved the scalloping problem, but now we were over
etching the material.
© 2011 John Glenning© 2011 John Glenning

31. Kapton Etch Process DevelopmentKapton Etch Process Development
Initial Product Builds
Excessive “scalloping” of the Kapton was observed near the circuit lines.
Product Manager determined this to be a defect and it need to be resolved.
Root cause was determined to be a “tenting” of the laminated photoresist over
the circuit lines. This created a channel near the circuit lines and acted as a
capillary. The capillary effect drew etchant deep under the photoresist causing
this over etch.
It was decided that we would presoak the Photoresist-Kapton System with water
to fill the capillary. This solved the scalloping problem, but now we were over
etching the material.
It was determined this was caused by the water swelling the Kapton allowing for
more repaid penetration of the etchant. Kapton is very hydrophilic.
© 2011 John Glenning© 2011 John Glenning

32. Kapton Etch Process DevelopmentKapton Etch Process Development
Initial Product Builds
Excessive “scalloping” of the Kapton was observed near the circuit lines.
Product Manager determined this to be a defect and it need to be resolved.
Root cause was determined to be a “tenting” of the laminated photoresist over
the circuit lines. This created a channel near the circuit lines and acted as a
capillary. The capillary effect drew etchant deep under the photoresist causing
this over etch.
It was decided that we would presoak the Photoresist-Kapton System with water
to fill the capillary. This solved the scalloping problem, but now we were over
etching the material.
It was determined this was caused by the water swelling the Kapton allowing for
more repaid penetration of the etchant. Kapton is very hydrophilic.
Presoaking the Kapton with water tripled the etch rate.
© 2011 John Glenning© 2011 John Glenning

33. Kapton Etch Process DevelopmentKapton Etch Process Development
Understanding the Polyamic Acid Etching Process
In a previous project, I was developing the etching for polyamic acid, which is the
precursor of polymide. Polyamic acid is etched using 1 M KOH and 40ºC.
© 2011 John Glenning© 2011 John Glenning

34. Kapton Etch Process DevelopmentKapton Etch Process Development
Understanding the Polyamic Acid Etching Process
In a previous project, I was developing the etching for polyamic acid, which is the
precursor of polymide. Polyamic acid is etched using 1 M KOH and 40ºC.
Polymaic acid becomes polyimide by applying heat and the process is know as
imidization.
© 2011 John Glenning© 2011 John Glenning

35. Kapton Etch Process DevelopmentKapton Etch Process Development
Understanding the Polyamic Acid Etching Process
In a previous project, I was developing the etching for polyamic acid, which is the
precursor of polymide. Polyamic acid is etched using 1 M KOH and 40ºC.
Polymaic acid becomes polyimide by applying heat and the process is know as
imidization.
Spraying potassium hydroxide created potassium carbonate. Carbon dioxide is
absorbed during the spraying process and reacts with the potassium hydroxide
to create potassium carbonate.
2 KOH + CO2 → K2CO3 + H20
© 2011 John Glenning© 2011 John Glenning

36. Kapton Etch Process DevelopmentKapton Etch Process Development
Understanding the Polyamic Acid Etching Process
In a previous project, I was developing the etching for polyamic acid, which is the
precursor of polymide. Polyamic acid is etched using 1 M KOH and 40ºC.
Polymaic acid becomes polyimide by applying heat and the process is know as
imidization.
Spraying potassium hydroxide created potassium carbonate. Carbon dioxide is
absorbed during the spraying process and reacts with the potassium hydroxide
to create potassium carbonate.
2 KOH + CO2 → K2CO3 + H20
If the potassium carbonate concentration gets too high, the etching reaction will
shut down.
© 2011 John Glenning© 2011 John Glenning

37. Kapton Etch Process DevelopmentKapton Etch Process Development
Understanding the Polyamic Acid Etching Process
In the pilot line, I tested the entire range of potassium hydroxide, potassium
carbonate concentrations and etchant temperature to determine the effect on the
etching of Kapton
© 2011 John Glenning© 2011 John Glenning

38. Kapton Etch Process DevelopmentKapton Etch Process Development
Understanding the Polyamic Acid Etching Process
In the pilot line, I tested the entire range of potassium hydroxide, potassium
carbonate concentrations and etchant temperature to determine the effect on the
etching of Kapton:
1. The potassium hydroxide concentration determine the etch rate through the
Kapton Film
© 2011 John Glenning© 2011 John Glenning

39. Kapton Etch Process DevelopmentKapton Etch Process Development
Understanding the Polyamic Acid Etching Process
In the pilot line, I tested the entire range of potassium hydroxide, potassium
carbonate concentrations and etchant temperature to determine the effect on the
etching of Kapton:
1. The potassium hydroxide concentration determine the etch rate through the
Kapton Film
2. The potassium carbonate concentration determine the etch undercut of the
Kapton Film
© 2011 John Glenning© 2011 John Glenning

40. Kapton Etch Process DevelopmentKapton Etch Process Development
Understanding the Polyamic Acid Etching Process
In the pilot line, I tested the entire range of potassium hydroxide, potassium
carbonate concentrations and etchant temperature to determine the effect on the
etching of Kapton:
1. The potassium hydroxide concentration determine the etch rate through the
Kapton Film
2. The potassium carbonate concentration determine the etch undercut of the
Kapton Film
This was documented by a series of cross-section and this effect was
reproducible.
© 2011 John Glenning© 2011 John Glenning

41. Kapton Etch Process DevelopmentKapton Etch Process Development
Permanent Etch Mask Product Qualification
When planning for this product qualification, I expressed a concern to
management that we would fail Reliability Testing because of ionic entrapment in
the area between the permanent etch mask and the edge of the Kapton.
© 2011 John Glenning© 2011 John Glenning

42. Kapton Etch Process DevelopmentKapton Etch Process Development
Permanent Etch Mask Product Qualification
When planning for this product qualification, I expressed a concern to
management that we would fail Reliability Testing because of ionic entrapment in
the area between the permanent etch mask and the edge of the Kapton.
It was determined that they would go ahead with the Qualification because of the
schedule.
© 2011 John Glenning© 2011 John Glenning

43. Kapton Etch Process DevelopmentKapton Etch Process Development
Permanent Etch Mask Product Qualification
When planning for this product qualification, I expressed a concern to
management that we would fail Reliability Testing because of ionic entrapment in
the area between the permanent etch mask and the edge of the Kapton.
It was determined that they would go ahead with the Qualification because of the
schedule.
Product failed qualification due to Corrosion-Migration.
© 2011 John Glenning© 2011 John Glenning

44. Kapton Etch Process DevelopmentKapton Etch Process Development
Permanent Etch Mask Product Qualification
When planning for this product qualification, I expressed a concern to
management that we would fail Reliability Testing because of ionic entrapment in
the area between the permanent etch mask and the edge of the Kapton.
It was determined that they would go ahead with the Qualification because of the
schedule.
Product failed qualification due to Corrosion-Migration.
I presented my findings to Senior Management. It was agreed to rerun Product
Qualification with my alternative chemistry (7M KOH, 3M K2CO3 at 95ºC).
© 2011 John Glenning© 2011 John Glenning

45. Kapton Etch Process DevelopmentKapton Etch Process Development
Permanent Etch Mask Product Qualification
When planning for this product qualification, I expressed a concern to
management that we would fail Reliability Testing because of ionic entrapment in
the area between the permanent etch mask and the edge of the Kapton.
It was determined that they would go ahead with the Qualification because of the
schedule.
Product failed qualification due to Corrosion-Migration.
I presented my findings to Senior Management. It was agreed to rerun Product
Qualification with my alternative chemistry (7M KOH, 3M K2CO3 at 95ºC).
This time, they passed qualification.
© 2011 John Glenning© 2011 John Glenning

46. Kapton Etch Process DevelopmentKapton Etch Process Development
Permanent Etch Mask Product Qualification
When planning for this product qualification, I expressed a concern to
management that we would fail Reliability Testing because of ionic entrapment in
the area between the permanent etch mask and the edge of the Kapton.
It was determined that they would go ahead with the Qualification because of the
schedule.
Product failed qualification due to Corrosion-Migration.
I presented my findings to Senior Management. It was agreed to rerun Product
Qualification with my alternative chemistry (7M KOH, 3M K2CO3 at 95ºC).
This time, they passed qualification.
This became the Plan-of Record Process for Permanent Etch Masks
© 2011 John Glenning© 2011 John Glenning

47. Kapton Etch Process DevelopmentKapton Etch Process Development
Technology Transfer
I was a member of the Development-Manufacturing Team that transferred the
process to manufacturing
© 2011 John Glenning© 2011 John Glenning

48. Kapton Etch Process DevelopmentKapton Etch Process Development
Technology Transfer
I was a member of the Development-Manufacturing Team that transferred the
process to manufacturing
I was jointly responsible for the equipment design, build, installation and debug
with the Manufacturing Engineer for the Kapton Etch sector
© 2011 John Glenning© 2011 John Glenning

49. Kapton Etch Process DevelopmentKapton Etch Process Development
Technology Transfer
I was a member of the Development-Manufacturing Team that transferred the
process to manufacturing
I was jointly responsible for the equipment design, build, installation and debug
with the Manufacturing Engineer for the Kapton Etch sector
I was jointly responsible for the process scale-up
© 2011 John Glenning© 2011 John Glenning

50. Kapton Etch Process DevelopmentKapton Etch Process Development
Technology Transfer
I was a member of the Development-Manufacturing Team that transferred the
process to manufacturing
I was jointly responsible for the equipment design, build, installation and debug
with the Manufacturing Engineer for the Kapton Etch sector
I was jointly responsible for the process scale-up
IBM Qualifies Manufacturing processes using a 4 Level Stage Gate Process
© 2011 John Glenning© 2011 John Glenning

51. Kapton Etch Process DevelopmentKapton Etch Process Development
Technology Transfer
I was a member of the Development-Manufacturing Team that transferred the
process to manufacturing
I was jointly responsible for the equipment design, build, installation and debug
with the Manufacturing Engineer for the Kapton Etch sector
I was jointly responsible for the process scale-up
IBM Qualifies Manufacturing processes using a 4 Level Stage Gate Process
Development leads the first two Gates with Manufacturing in support
© 2011 John Glenning© 2011 John Glenning

52. Kapton Etch Process DevelopmentKapton Etch Process Development
Technology Transfer
I was a member of the Development-Manufacturing Team that transferred the
process to manufacturing
I was jointly responsible for the equipment design, build, installation and debug
with the Manufacturing Engineer for the Kapton Etch sector
I was jointly responsible for the process scale-up
IBM Qualifies Manufacturing processes using a 4 Level Stage Gate Process
Development leads the first two Gates with Manufacturing in support
Manufacturing leads the second two Gates with Development in support
© 2011 John Glenning© 2011 John Glenning

53. Kapton Etch Process DevelopmentKapton Etch Process Development
Technology Transfer
I was a member of the Development-Manufacturing Team that transferred the
process to manufacturing
I was jointly responsible for the equipment design, build, installation and debug
with the Manufacturing Engineer for the Kapton Etch sector
I was jointly responsible for the process scale-up
IBM Qualifies Manufacturing processes using a 4 Level Stage Gate Process
Development leads the first two Gates with Manufacturing in support
Manufacturing leads the second two Gates with Development in support
The process was successfully qualified
© 2011 John Glenning© 2011 John Glenning

54. Kapton Etch Process DevelopmentKapton Etch Process Development
Results
4 US Patents were issued for this Project
US Patent 4,846,929: Wet etching of thermally or chemically cured polyimide
US Patent 4,857,143: Wet etching of cured polyimide
US Patent 4,883,744: Forming a polymide pattern on a substrate
US Patent 5,203,955: Method for etching an organic polymeric material
In 1988, I was given an IBM Division Award for my work.
© 2011 John Glenning© 2011 John Glenning

55. New Product CommercializationNew Product Commercialization
End of Presentation
© 2011 John Glenning© 2011 John Glenning