1. Enhanced protection for enhanced PCB performance
Conformal Coatings
Enhanced protection for enhanced PCB performance

2. Introduction
Why Coat?

3. CONFORMAL COATINGS
A newly manufactured printed circuit board will generally perform well but performance will quickly deteriorate.
Common causes of deterioration and PCB failure include:
Atmospheric moisture
Contamination of the surface with airborne ionic material
Electrostatic attraction of dust to the surface
Corrosive environments, such as salt fog
Conformal coatings can be applied to a PCB giving protection against the environment, extending the life of the board and therefore can be used in a vast array of electronic applications.
Military
Industrial
Automotive
Domestic
Aerospace

4. CONFORMAL COATINGS
Conformal coatings are thin coatings, typically microns, which ‘conform’ to the contours of a PCB.
The ideal conformal coating will have performance requirements that include:
Good electrical properties
Low moisture permeability
Good mechanical durability
Excellent adhesion properties
Good thermal resistance
Additional properties such as flame retardance or chemical resistance may also be required.

5. CONFORMAL COATING TERMINOLOGY
Different chemistries utilised in conformal coating technology require different types of cure. It is important to understand the terms used in conformal coating in under to understand cure schedules:
‘Tack Free’ – this is the time at which the coating is no longer tacky but slight indentations may be left in the coating when pressed firmly
‘Touch Dry’ – this is the time at which the coating is dry enough to touch without leaving any fingerprints on the surface of the coating
It is important to note that some coatings are very soft and can feel tacky even when fully cured. The touch dry time in these cases is more a reference to when you can move the board without affecting the coating
‘Cure Time’ – this is the time at which the coating is fully cured and will offer protection
It is also important to note that most coatings actually reach their optimum cure level after around 7 days but they will provide protection prior to this

6. CONFORMAL COATING APPLICATION
Conformal coatings can be brushed, dipped or sprayed depending on the requirements. Customers often specify their desired application method.
Brushing:
Advantages
Disadvantages
Cost effective
Uneven coating
Ideal for small scale production
Difficult to get under components
Selective coating
Only one side at a time can be coated

7. CONFORMAL COATING APPLICATION
Dip Coating:
Advantages
Disadvantages
Ideal for medium scale production
Initial capital outlay
Uniform coating thickness
Masking essential for connectors
Easy to operate machinery
Special extraction may be required
Both sides can be coated at the same time
Suitable for higher viscosity materials
Coating can penetrate under components
Operator training required but not difficult

8. CONFORMAL COATING APPLICATION
Spraying – aerosol or manual spray gun:
Advantages
Disadvantages
Cost effective
Overspray can occur
Ideal for bench top work and repair
Difficult to get under components
Ideal for small to medium scale production
Special extraction may be required
Convenient
Only one side at a time can be coated

9. SPRAYING

10. CONFORMAL COATING APPLICATION
Selective Spraying:
Advantages
Disadvantages
No masking required
Initial capital outlay
Uniform thickness
Low under component penetration – requires good flow properties with the coating
Automated process – good for inline procedures
Special extraction may be required – but can be linked to the machine easily
Ideal for all scales of production
Requires a trained operator to set the software

11. SELECTIVE COATING

12. SELECTIVE COATING

13. Application Conditions
Temperature – Affects viscosity and evaporation rate
Humidity – Contaminates dip coat tanks, blooming in hand spray and affects curing / pot life.
Ventilation – Affects operators

14. Product Choice
Coating Options

15. Considerations for Choice
As there are many different applications for conformal coatings, there are also a number of elements that must be considered as part of the selection process:
Coating properties
Adhesion
Flexibility
Temperature range
Mechanical durability
Electrical performance
Environmental performance
Flame retardance
Mould resistance
Application
Viscosity/application
Touch dry time
Full cure time
Curing conditions
Is re-work required?
Cost
Quality
Approvals required?

16. CONFORMAL COATING TYPES
Conformal coatings are available in a number of different chemistry types and also cure via different mechanisms.
The different types of conformal coating include:
Solvent-based – Evaporation Cure
Solvent-based – Heat Cure
Low VOC/Water-based – Evaporation/Heat Cure
Non-VOC – Moisture Cure
UV Cure – Dual Cure: Moisture/Heat
Common conformal coating chemistries include:
Acrylic
Polyurethane
Silicone
Modified-silicone

17. DCA (SCC3) MODIFIED SILICONE COATING
DCA is a flexible, transparent & unique modified silicone conformal coating specifically designed for the protection of electronic circuitry.
Key Features:
Resistant to most solvents, lubricants and chemicals associated with most aerospace and automotive applications.
Excellent adhesion under various climatic conditions to a variety of substrates, including high altitude/decompression
Fluoresces under UV light for ease of inspection.
Extreme operating temperature range (-70˚C to +200˚C)
Excellent electrical properties

18. DCA (SCC3) MODIFIED SILICONE COATING
DCA is a solvent based coating and can be sprayed, dipped or brushed.
For optimum properties, DCA should be heat cured (2hrs at RT, 90˚C advised). If RT cured then the solvent resistance will be significantly reduced.
Should be used with DCT thinners and removed with CCRG – Electrolube Conformal Coating Remover Gel
Approvals
Def-Stan 59/47 – Standard now obsolete
UL746 – File Number E138403

19. DCA (SCC3) MODIFIED SILICONE COATING
The DCA (SCC3) Range includes:
DCA-FD – Fast-dry version
DCA-HT – With improved high temperature performance
DCR – Opaque red version
DCB – Opaque black version
DCRT – Opaque red, high viscosity version
DCE – Thixotropic gel version (dam and fill applications)
Unique range of products based on a silicone modified alkyd
Avoids issues associated with silicone migration
Easier processing than standard silicones
Performance compares with many silicone conformal coatings

20. TFA – TOLUENE FREE ACRYLIC COATING
TFA is a flexible and transparent acrylic conformal coating for the protection of electronic circuitry.
It has been formulated to meet many of today’s commercial applications, meeting both Military and IPC standards.
Key Features:
Toluene free product.
Fluoresces under UV light for ease of inspection.
Wide operating temperature range (-65˚C to +125˚C)
Excellent Dielectric properties
Clear coating with excellent resistance to yellowing when exposed
to UV light

21. TFA – TOLUENE FREE ACRYLIC COATING
TFA is a solvent based coating and can be sprayed, dipped or brushed.
Should be used with DCT thinners and removed with CCRG – Electrolube Conformal Coating Remover Gel
Approvals
UL746 Approved
IPC-CC-830 approved
Automatically meets MIL C
Also available: AFA – Aromatic Free Acrylic

22. VOCs – THE NEED TO CHANGE
VOCs or Volatile Organic Compounds are carbon based compounds which vaporise easily under ambient conditions VOCs contribute towards the formation of ground level ozone Such pollution can have many detrimental effects on the environment, damaging forests and vegetation In addition, some materials classed as VOCs can act as irritants and over exposure can lead to a variety of health problems

23. EU Solvents Emissions Directive
VOC DEFINITION
EU Solvents Emissions Directive
“Any organic compound having at 20˚C a vapour pressure of 0.01kPa or more, or having corresponding volatility under the particular conditions of use”

24. UVCL - UV Cure Extremely rapid initial cure schedule
Ideal for high volume production
In-line process, curing equipment required
Very high level of protection; highly cross-linked coating
Excellent chemical and solvent resistance
Using a dual cure system can ensure that in shadowed areas under components the coating still cures and protects the PCB
Moisture
Heat
UV cure coatings are available as 100% solids materials
Non-VOC options

25. WBPS – WATER-BASED COATING
WBPs is a water-based conformal coating, based on polymeric materials which has been specifically formulated for the protection of electronic circuitry.
It offers an excellent blend of both physical and electrical properties in a more environmentally and user friendly package when compared to conventional solvent based conformal coatings.
Non-flammable and contains very low levels of VOC’s.
WBP is for dipping/brushing applications whilst WBPS (Sprayable) has been specifically formulated for use in selective film coater equipment.

26. WBPS – WATER-BASED COATING
Key Features:
Environmentally friendly and eliminates hazards associated with solvent based conformal coatings
Excellent solvent resistance.
Very low VOC content
NMP (N-Methyl pyrrolidone) free.
Fluoresces under UV light for ease of inspection.
Excellent adhesion on a wide variety of substrates.
Excellent Dielectric properties and resistant to mould growth.

27. PUC – POLYURETHANE COATING
PUC is a tough, flexible, modified polyurethane conformal coating and is specifically designed for the protection of electronic circuitry, particularly in harsh conditions.
Key Features
Excellent adhesion to a wide variety of substrates.
Fluoresces under UV light for ease of inspection.
Good resistance to a wide variety of chemicals including acids and alkalis.
Wide operating temperature range.
Excellent mechanical properties including abrasion resistance
Solvent-based, can be sprayed, dipped or brushed
Should be used with PTH thinners and removed with CCRG

28. OTHER COATINGS
Modified Silicone – LFCC, FSC (Modified with acrylic; up to 125˚C)
Acrylic – HPA (MIL Approved), APL, AFA, APLSP (Sprayable version), TRV
Water-Based – WBP (Dipping Version)
Polyester – CPL
Surface Modifier – TFCF (Fluorinated)

29. CHOOSING THE RIGHT PRODUCT
High Temperature – DCA (SCC3) Range
Excellent Clarity – TFA or an Acrylic Coating
Chemical Resistance – PUC or DCA (SCC3) Range
Cosmetic Appearance – CPL (no UV trace)
Low Solvent Content – WBP or WBPs
Reworkable – Acrylic Coatings or FSC
UL Approved – DCA and TFA
UV Cure - UVCL

30. Polyester
CPL
Modified Silicone
DCA
FSCP
FSC
UV Cure
UVCL
Polyurethane
PUC
PUCAF
Opaque
DCRT
DCR
DCB
Acrylic
HPA
TFA
APL
AFA
Water-Based
WBP
WBPs

31. Electrolube Conformal Coating Selector Chart
Is low/non VOC required?
YES
DCA (UL746)
UVCL (IPC-CC-830)
UVCL
WBP(s)
WBP(s)
PUC
PUCAF NO
YES
HPA (MIL-I-46058C)
TFA (IPC-CC-830/UL746)
AFA (UL746)
FSC (IEC61086)
Is optical clarity required? NO
Is chemical resistance
required?
YES
Is an approval
required?
YES
YES NO NO
Is an approval
required?
YES
Is a fast touch dry
time required?
YES
Is the operating temperature
below -55°C?
DCA/WBP(s)
YES NO NO NO
APL
YES
Is easy removal for
re-work required?
Is the operating temperature
above 130°C?
DCA NO

32. Conformal Coatings
Potential Problems

33. Adhesion Loss
Incorrect curing could cause adhesion loss. This could be due to insufficient curing, i.e. the coating has not finished cross-linking.
It could also be a problem with removing masking material – ideally this should be done when the coating is still soft.

34. Conformal Coatings
Rework Considerations

35. Coating Removal Products
For acrylics, a solvent based product like Electrolube ULS is ideal for quick and clean removal of the coating.
For coatings with a higher chemical resistance, a product such as Electrolube RRS will be required.
For localised rework, a remover gel like Electrolube CCRG is ideal.

36. OTHER PRODUCTS
In order for conformal coatings to be applied correctly some complimentary products are required:
Thinners – where applicable conformal coatings are diluted to the required viscosity,
Electrolube have a range of thinners suitable for this process
Masking – PCM and PCS are coating masks suitable for covering connectors during
the coating process

37. For further information please visit www.electrolube.com
Thank You
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