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Basic Concepts Of Conformal Coating
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Basic Concepts Of Conformal Coating

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  • 1. The Basic Concepts of Conformal Coating An examine of conformal coating materials available today and how they perform  
  • 2.
    • Summary
    • Definition of a Conformal coating
    • What the coating actually does
    • Why coatings are used
    • The types of coating available
    • How to select a coating
    • How a coating is applied
    • How to test for performance
  • 3.
    • Definition of a Conformal coating
    • It is a thin plastic protective film
    • “ conforms” to the surface of an electronic circuit assembly.
    • It is a breathing membrane that filters water vapour and solid debris
    • Protects the assembly from corrosion in harsh environments.
  • 4.
    • Definition of a Conformal coating
    • Nominally, the coating should be 0.001” to 0.008” thick (25 to 200µm)
    • Too thick may cause problems such as solvent entrapment, bubbling, shrinkage and cracking.
    • Too thin means inadequate protection
  • 5.
    • What the coating actually does
    • Improves reliability in humid environments
    • Reduces need to hermetically seal PCB
    • Reduces conductor spacing’s on PCB
    • Protects the PCB in aggressive environment
    • Protects the PCB against environmental particulates
  • 6.
    • What the coating actually does
    • Good dielectrics
      • Insulation & Moisture resistance
      • Breakdown voltage
    • Good flexibility so as not to stress components
    • Be Repairable
  • 7.
    • Is the coating waterproof?
    • NO! All coatings breathe. However, i t seals IN AS WELL AS OUT
    • Coatings permit air, which may contain moisture, to migrate in and out through the film.
    • If there is a soluble contaminant on the surface beneath the coating, then this may cause osmosis.
  • 8.
    • Why coatings are used
    • If your circuit is:
    • High-reliability and /or safety critical
    • Are operating in an aggressive environment
    • Fine line, fine pitch
    • There may be problems with long term reliability
  • 9.
    • Why coatings are used
    • Extended warranties on consumer electronics
    • Automotive, control drives, fire alarms and military / aerospace safety features & long term reliability
  • 10.
    • Increased demand on coating
    • Example is automotive electronics where it will soon represent 40% of the cost of the car
    • A great number of safety features are electronically controlled (ABS, airbag, servo)
  • 11.
    • The types of coatings available
    • Acrylics
    • Polyurethanes
    • Epoxies
    • Silicones
    • Paraxylylenes
    • Fluorocarbon
  • 12.
    • Acrylic Conformal Coatings
    • AR
    • Represent 80% of market
    • Single component materials
    • Excellent Moisture resistance
    • Easy to apply
    • Cure very quickly
    • Easy to repair by removal with solvent
  • 13.
    • Acrylic Conformal Coatings
    • AR
    • Especially suitable for:
      • Any application ‘in a box’
      • Boards with long service life
      • Any environment where water is main threat
      • Any environment without solvent exposure
  • 14.
    • Acrylic Conformal Coatings
    • AR
    • Examples of use include:
    • Engine management
    • Air bag controllers
    • Avionics
    • Communication Equipment
    • Elevator Controls
  • 15.
    • Polyurethane Conformal Coatings
    • UR
    • Very good solvent resistance
    • 1 and 2 part systems
    • Easy to apply
    • Longer cure times
    • Difficult to repair
  • 16.
    • Polyurethane Conformal Coatings
    • UR
    • Especially suitable for:
      • Salt Spray protection
      • Applications where solvent resistance required
      • Directly mounted assemblies
      • Reparability is not an issue
  • 17.
    • Silicone Conformal Coatings
    • SR
    • Excellent High Temperature Performance
    • Limited solvent resistance
    • Solventless Products
    • Harder to apply
    • Can be difficult to cure
    • Nearly impossible to repair
    • EXPENSIVE
  • 18.
    • Silicone Conformal Coatings
    • SR
    • OVERKILL for all but specialist applications
    • Used in:
    • Huge, industrial drilling/mining equipment
    • High temperature electronics
    • Under bonnet electronics
  • 19.
    • Epoxy Conformal Coatings
    • ER
    • Good moisture resistance
    • Good dielectric resistance
    • Excellent chemical resistance
    • Excellent temperature resistance
    • Poor flexibility
    • Poor to repair
  • 20.
    • Paraxylylene Conformal Coatings
    • XY
    • Excellent moisture resistance
    • Excellent dielectric resistance
    • Excellent chemical resistance
    • Excellent temperature resistance
    • High cost of process
    • Critical processing
  • 21.
    • Fluorocarbons
    • Good moisture resistance
    • Excellent dielectric resistance
    • Minimal chemical resistance
    • Good temperature resistance
    • Low cost of process / Expensive set up costs
    • No mar resistance
  • 22.
    • Typical Coating Thicknesses
    • Acrylics 0.001” - 0.003” 25/75µm
    • Polyurethanes 0.001” - 0.003” 25/75µm
    • Epoxies 0.001” - 0.003” 25/75µm
    • Silicones 0.002” - 0.008” 50/200µm
    • Paraxylylenes 0.0005” - 0.0007”
    • Fluorocarbon 0.0005” - 0.0007”
  • 23.
    • Technologies Available
    • Solvent-based
    • Water-Based
    • Solvent less Silicones
    • Solvent less UV Curable
  • 24.
    • Solvent-Based
    • Advantages
      • Full range of chemistries available
      • Easy to process
      • Good wetting
      • ‘ Quasi Cleaning’
      • Fast Cure
    • Disadvantages
      • Flammable
      • Odour
      • Extraction Required
      • VOC Emissions
  • 25.
    • Water-Based
    • Advantages
      • Most similar to solvent-based
      • Full range of chemistries available
      • Low odour
      • Non-flammable
      • Low VOC
    • Disadvantages
      • Longer cure times
      • Hard to apply by robotic equipment
      • More sensitive to contamination
  • 26.
    • Solventless Silicones
    • Advantages
      • Excellent high temp stability
      • Good flexibility
      • Low VOC
    • Disadvantages
      • Expensive
      • High Viscosity
      • Harder to apply by robotic equipment
      • Thick films required
      • More sensitive to contamination
      • Long cure times
  • 27.
    • Solventless UV Curable
      • Advantages
      • Very fast curing
      • High volume processing
      • High temperature performance
      • Great flexibility
      • Excellent adhesion and chemical resistance
      • Reliable secondary cure mechanism
    • Disadvantages
      • Hard to repair easily
      • Difficult in manual spray application
      • Unsuitable for dip applications
      • UV curing required
  • 28.
    • Summary: Technologies / Chemistries
    COATING TYPES AR PU SR SB WB UV Application Easiness Dependant on tech. Dependant on tech. 2 5 2 4 Drying / Curing Time 4 3 1 4 1 5 Chemical Resistance 1 4 4 Dependant on chem. Dependant on chem. 5 Moisture Protection 5 4 4 5 4 5 Reworkability 5 3 0 4 3 2 Environmental Friendly Dependant on tech. Dependant on tech. 5 1 5 5 Main features General purpose Chem. Resis. High temp. Most common Manual application High volume
  • 29. Humiseal Product Range & Codes
  • 30. Humiseal Product Code 1A33 1B31 1C49 1H20AR1 1B73 2A64 UV40
  • 31. Humiseal Product Code Solvent Based Number of part: 1 = 1 part system 2 = 2 part system 1 B31 2 A64
  • 32. Humiseal Product Code Solvent Based Number of part: 1 = 1 part system 2 = 2 part system 1 B 31 2 A 64 Chemistry: A = PU B or R= AR C = SR
  • 33. Humiseal Product Code Solvent Based Number of part: 1 = 1 part system 2 = 2 part system 1B 31 2A 64 Chemistry: A = PU B or R= AR C = SR Product number
  • 34. Humiseal Product Code Solvent Based (SB) Products 1B73 1B18 1B31 1R32 1R32A-2 1A33 1A68 1A20 2A64 Technology SB SB SB SB SB SB SB SB SB Chemistry AR AR AR AR AR PU PU PU PU Cure mechanism Solvent Evap. Solvent Evap. Solvent Evap. Solvent Evap. Solvent Evap. Oxygen Oxygen Moisture Moisture MIL Yes No Yes No No Yes No Yes Yes UL Yes Yes No No Yes No No Yes No Low cost equivalent 1B18 N/A 1R32 N/A N/A 1A68 N/A N/A N/A Comments Military Reference for AR Automotive Reference Military Reference for PU
  • 35. Humiseal Product Code Solvent Based 1H20 AR1 /S 1H20 UR5 /D Technology: 1H20 = water based Chemistry: AR = Acrylic UR = Polyurethane Application method: S = spraying D = dipping
  • 36. Humiseal Low VOC SB = Solvent Based AR = Acrylic PU = Polyurethane WB = Water Based SR = Silicone UV = UV curable Most widely used products Products UV40 UV40 250 1C49LV 1C51 1H20AR3/S 1H20AR3/D 1H20UR5/S 1H20UR5/D Technology UV UV SR SR WB WB Chemistry PU PU SR SR AR PU Cure mechanism UV+ Moisture UV+ Moisture Moisture Heat Air Oxygen MIL Yes No Yes Yes Pending Pending UL Yes Yes Yes Yes Pending Pending Low cost equivalent N/A N/A N/A N/A N/A N/A Comments Automotive reference Spray and dip grade Spray and dip grade
  • 37. Humiseal Thinners Most widely used products Products 503 535 505 521 604 600 Evaporation Rate (BuAc=1) 3.7 2.1 1.7 0.6 0.4 0.3 Flash point -1 7 14 27 11 47 Material 1B31, 1B73, 1A33 1B51 1R32 1B31, 1B73, 1A33 1B73 EPA 1R32A-2 Application method Dip, brush Dip, brush Dip, brush Spray, brush Spray, brush Spray, brush Comments Reference for dipping Reference for spraying Reduce bubbles
  • 38. Humiseal Strippers Most widely used products SB = Solvent Based AR = Acrylic PU = Polyurethane WB = Water Based SR = Silicone UV = UV curable Most widely used products Products 1080A 1020 1063 1072 Chemistry to remove SB AR WB AR PU PU Coatings 1B31, 1B73, 1R32A-2 1H20 AR3 1A33 1H20 UR5, UV40 Comments Replacing previous 1080 Replacing previous 1071
  • 39. Humiseal Product Range
    • SCH can provide:
      • A wide range of technologies and chemistries available
      • Expertise and technical support in product selection and application
      • Process solution for each challenging requirement
  • 40. Humiseal Product Range
    • ANY QUESTIONS....?