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COATING
SOLUTIONS
Common Slot Die Coating Defects
Chatter
Causes:
-Fluctuations in flow rate
-Mechanical vibrations
-Coating bead Oscillations
Solution: Minimize or eliminate vibration and/or oscillation
-Fluctuations in flow rate
-Mechanical vibrations
-Coating bead Oscillations
Solution: Minimize or eliminate vibration and/or oscillation
Ribbing
Cause: Instability in the coating bead
Solution: Reduce the coating gap
Solution: Reduce the coating gap
Air Entrainment
Cause: Air is drawn in at the dynamic wetting line
Solutions: -Utilize vacuum systems
-Apply an electrostatic field
-Ensure surface energy compatibility with surface tension (using corona, plasma, flame, or primer treatments)
Solutions: -Utilize vacuum systems
-Apply an electrostatic field
-Ensure surface energy compatibility with surface tension (using corona, plasma, flame, or primer treatments)
Air Entrapment
Cause: Air in the fluid before it reaches the pump
Solutions: -Allow time for air to dissipate
-Implement cone flow
-Use a dampening chamber
-Apply sonic techniques
Solutions: -Allow time for air to dissipate
-Implement cone flow
-Use a dampening chamber
-Apply sonic techniques
Dewetting
Cause: Surface tension gradient
Solutions:
-Use a vacuum system
-Apply an electrostatic field
-Ensure surface energy compatibility with surface tension
Solutions:
-Use a vacuum system
-Apply an electrostatic field
-Ensure surface energy compatibility with surface tension
Streaks
Causes: -Presence of particles
-Bubbles
-Non-uniform wetting at the slot exit
Solutions: -Clean the surface
-Simulate and adjust the process
-Bubbles
-Non-uniform wetting at the slot exit
Solutions: -Clean the surface
-Simulate and adjust the process
Particles
Causes:
-Contamination
-Gel formation
Solutions:
-Clean the affected area
-Minimize recirculation zones
-Contamination
-Gel formation
Solutions:
-Clean the affected area
-Minimize recirculation zones
Chevrons
Causes: -Acoustic waves in the vacuum chamber
-Close proximity to the substrate
Solutions: -Measure frequency and clean/replace as necessary
-Adjust vacuum level
-Move closer to the substrate
-Close proximity to the substrate
Solutions: -Measure frequency and clean/replace as necessary
-Adjust vacuum level
-Move closer to the substrate
Hashmarks
Cause: A gravity-driven defect in curtain coating
Solution: Adjust flow rate and line speed to control fluid impact
Solution: Adjust flow rate and line speed to control fluid impact
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