1. Conformal Coating Training

2. Coating Conformal What is a conformal coating? What does it do?
Why coat?
What types are there?
How to select?
How to apply?
How to test?

3. Coating Conformal What is a Conformal Coating?
A thin protective film that “conforms” to the varied profiles of an electronic circuit assembly.
A breathing membrane that will filter moisture and dirt to protect the assembly from environments.

4. Coating Conformal Why Coat? Provide Protection From:
Insulation and Dielectric Failures
Moisture
Heat
Corrosion
Fungus
Dust, Conductive particles
IMPROVED CIRCUIT RELIABILITY

5. Coating Conformal What Does It Do? It should provide...
4/27/2017
Conformal
Coating
What Does It Do?
It should provide...
Good insulation
Good dielectric properties
Good moisture resistance
Good flexibility so as not to stress components...
Ability to be Repaired... 5

6. Coating Conformal What Coating Types Are Available? Coating Type
MIL Spec Thickness
Acrylics
25-75µ ( ”)
Polyurethanes
Epoxies
Silicones
50-200µ ( ”)

7. Coating Conformal How To Select? Applicable Standards & Specifications
4/27/2017
Conformal
Coating
How To Select?
Applicable Standards & Specifications
US MIL-I-46058C
IPC-CC-830B
UL - Underwriters Labs 746E
Electrical Properties
Insulation resistance, dielectric constant
Thermal Properties
Operating temperature range, thermal expansion (CTE) 7

8. Coating Conformal Acrylic Strengths and Weaknesses
5 Strengths of Coating Type
5 Weaknesses of Cure Type
ACRYLIC
Ease of rework
Simple drying process
Good moisture resistance
High fluorescence level
Ease of viscosity adjustment
Solvent Evaporation
High VOC potential
Difficult to maintain viscosity
Requires close monitoring of solvent concentration, hence Creates a 2-part scenario
Flammability
High probability of reversion under temperature and humidity stress conditions
Heat Cure
Cure is dependent on thickness
Component mass affects time and temperature of cure process
Susceptible to cure inhibition
Shrinkage (3% - 10%), potential for damaging fragile (e.g., glass) components
Should be used with caution for low temperature components
UV Cure
Incomplete cure in shadowed areas
Pungent odour, potential skin irritant
Can become very brittle at higher temperature
Difficult to rework
Type of UV and intensity affect cure
Acrylic
Strengths
and
Weaknesses

9. Coating Conformal Epoxy Strengths and Weaknesses
5 Strengths of Coating Type
5 Weaknesses of Cure Type
EPOXY
Useful to about 150oC [302oF]
Harder durometer, abrasion resistance
CTE closer to epoxy PCB substrate
Higher Tg
Good dielectric properties
Solvent Evaporation
Higher chloride contamination potential
Process intensive, difficult to maintain viscosity, complex mix ratios
Potential for high stress during temperature cycling conditions
Difficult to rework
High probability of reversion under temperature and humidity stress conditions
Heat Cure
Cure is dependent on thickness
Component mass affects time and temperature of cure process
Selective coating quality (edge definition) could be impacted
Shrinkage (3% - 10%), potential for damaging fragile (e.g., glass) components
Should be used with caution for low temperature components
UV Cure
Incomplete cure in shadowed areas
Pungent odour, potential skin irritant
Can become very brittle at higher temperature
Type of UV and intensity affect cure
Catalyzed
Cure inhibition
Short work life
Contamination sensitive
Pungent odour
Epoxy
Strengths
and
Weaknesses

10. Coating Conformal Polyurethanes Strengths and Weaknesses
5 Strengths of Coating Type
5 Weaknesses of Cure Type
POLYURETHANE
Good dielectric properties
Good moisture resistance
Solvent resistance
Less reversion potential
Abrasion resistance
Solvent Evaporation
Moisture affects cure rate and desires properties
Long complete cure time (up to 30 days)
Health and safety concerns
Potential for high stress during temperature cycling conditions
High probability of reversion under temperature and humidity stress conditions
Heat Cure
Cure is dependent on thickness
Component mass affects time and temperature of cure process
High VOC potential
Should be used with caution for low temperature components
Reacts violently with presence of water
UV Cure
Incomplete cure in shadowed areas
Pungent odour, potential skin irritant
Can become very brittle at higher temperature
Difficult to rework
Type of UV and intensity affect cure
Polyurethanes
Strengths
and
Weaknesses

11. Coating Conformal Silicone Strengths and Weaknesses
5 Strengths of Coating Type
5 Weaknesses of Cure Type
SILICONES
Stable over wide temperature range (in general, -40oC to 200oC) [104oF to 392oF]
Flexible, provides dampening and impact protection
Good moisture, humidity, and UV/sun light resistance
High dielectric strength
Low surface energy to enable effective penetration under components
Room Temperature Vulcanization (RTV)
Requires humidity (minimum 20% RH) to cure and only intermittent solvent resistance
Low abrasion resistance
Short pot life
TCE is ppm/oC
If proper housekeeping is not followed, there is a potential for cross contamination
UV Cure
Incomplete cure in shadowed areas
Potential skin irritant
Only intermittent solvent resistance
Catalyzed (Addition)
Potential for cure inhibition
Adhesion may be difficult
Silicone
Strengths
and
Weaknesses

12. Coating Conformal How To Apply? Brushing Dipping – Manual / Automated
Spraying – Aerosol / Manual / Automated
Flow-Coat – Automated

13. Coating BRUSH Application Conformal Brushing?
Best suited for repair and rework
Keep the brush “loaded”
Flow the coating - DO NOT PAINT!
BRUSH Application

14. Coating DIP Application Conformal Dip
Slow speed dip - < 30cm/min (12”/min) – Minimizes air entrapment under components
Slower Removal Rate - < 10cm/min (4”/min) – The slower the speed, the thinner the coating
ALWAYS dip board in vertical position, not horizontal
DIP Application

15. Coating DIP Application Conformal Dip
Coating penetrates under components and behind component legs
Coating is applied to both sides simultaneously
Coating thickness controlled by dipping speed & viscosity control
Can be done by hand for small assemblies but best done by machine
DIP Application

16. Coating DIP Application Conformal “Double Dipping”
Single Dip – Possibility of Sharp Edges being exposed
Double Dip Solves this Problem

17. Coating DIP Application Conformal Automated Dipping
Controls dip speed in and out
Maximizes coverage
Reduces waste
Minimizes Evaporation of Coating Bath
DIP Application

18. Coating SPRAY Application Conformal Spray?
Coating is thinned with solvent for application
Hand Spray
HumiSeal Aerosol products
Automated Equipment
Asymtek / Nordson
PVA
SPRAY Application

19. Coating SPRAY Application Conformal Spraying – Aerosol/Hand
Remember cured coating thickness should be 25 - 75 ( ”) and material is diluted
Need multiple passes each at 90 degrees and multiple coats, 2 to 3 minimum
Always spray assembly in horizontal with spray gun at ~45 degree angle to board surface
SPRAY Application

20. Coating SPRAY Application Conformal Spraying – Hand/Auto
Relatively Simple
2-Part Materials may be used
Better Tip and Edge Coverage
Reduced Masking
SPRAY Application

21. Coating SPRAY Application Conformal AEROSOLS
1B73, 1B15H, 1A33 and 1A27
Packaged in 12-oz cans
Good for small users and rework
Lower solids content than liquid products
SPRAY Application

22. Conformal
Coating
Selective Spray Equipment
SPRAY Application

23. Conformal
Coating
Automated Atomized Spray
SPRAY Application

24. Conformal
Coating
FLOW Coating

25. Coating Conformal How To Test? Visual Inspection With UV Light
Check Coating Uniformity

26. Coating Conformal Humiseal Conformal Coatings Widest product selection
> 50 years experience
Greatest pool of technical knowledge
ISO 9001 Registered
Mil-I-46058C, IPC-CC-830 and UL746E compliant products
VOC compliant materials

27. Coating HumiSeal Acrylic (AR) Products Conformal EASY TO APPLY
Most forgiving of contamination
Dry at room temperatures
Have desirable electrical and physical properties
Fungus resistant
Long pot life
No exotherm during drying- heat sensitive components
Does not shrink
EASY TO REPAIR
VOC and VOC HAPS-free versions available
HumiSeal Acrylic (AR) Products

28. Coating HumiSeal Urethane (UR) Products Conformal
Excellent chemical and humidity resistance
Outstanding dielectric properties for extended periods
Excellent chemical resistance
Available as single - or two-component
Variety of cure types
Moderately repairable
Chemical strippers
Heat
VOC and VOC HAPS-free versions available
HumiSeal Urethane (UR) Products

29. Coating HumiSeal Silicone (SR) Products Conformal
Excellent for high temperature service
Good thermal endurance – heat generating devices
Humidity and corrosion resistance
One component, 100% solids – no VOC issues
Thermal or moisture cure
Lower abrasion resistance- softer
High CTE
Mechanically repairable
Not solvent-soluble / Do not vaporize with heat
New Silicone Digesters
HumiSeal Silicone (SR) Products

30. Coating HumiSeal Epoxy (ER) 2A53 Conformal
Two components: 2A53A + 2A53B
High abrasion and chemical resistance
Might be considered “indestructible”
Good electrical properties
Good component anchoring
Very Difficult to Repair
Hard to physically remove
Not removed by solvent
Chemical strippers will attack substrates
HumiSeal Epoxy (ER) 2A53

31. Coating HumiSeal 1B51 Series (Synthetic Rubber) Conformal
High flexibility
Excellent electrical properties
High humidity & corrosion resistance
Good thermal stability, low outgassing
High cohesive strength – tough
Low CTE
Stabile Modulus at lower temps
Must be repaired mechanically
Not solvent soluble / requires aggressive stripper
Does not vaporize with heat
HumiSeal 1B51 Series (Synthetic Rubber)

32. Coating HumiSeal Ancillary Products Conformal TempSeal Strippers
Thinners
HumiSeal Ancillary Products

33. Coating Troubleshooting Conformal
Conformal Coating is a Simple Process
Clean
Masking
Coating Application
Dry / Cure
Remove Masking
But if product is not processed correctly…
Troubleshooting

34. Coating Troubleshooting Conformal Surface Cleanliness
Poor surface cleanliness is most common cause of coating problems
Adhesion loss
Electrical failures
Coating voids
IPC specifications recommend ionic cleanliness level of < 1.5 g/cm2 NaCl equivalence
Troubleshooting
Surface Cleanliness

35. Coating Troubleshooting Conformal Coating Thickness
Need to keep within recommended ranges
Too Thick
Incomplete drying / solvent entrapment
Bubbles
Longer cure times
Shrinking or cracking
Decreased coating properties
Too Thin
Inadequate Protection!
Troubleshooting
Coating Thickness