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Conformal Coatings. Enhanced protection for enhanced PCB performance. Introduction. Why Coat?. 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:

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conformal coatings
Conformal Coatings

Enhanced protection for enhanced PCB performance

slide2

Introduction

Why Coat?

conformal coatings1
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

conformal coatings2
CONFORMAL COATINGS
  • Conformal coatings are thin coatings, typically 25-75 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 retardanceor chemical resistance may also be required.
slide5

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

conformal coating application
CONFORMAL COATING APPLICATION
  • Conformal coatings can be brushed, dipped or sprayed depending on the requirements. Customers often specify their desired application method.
  • Brushing:
conformal coating application2
CONFORMAL COATING APPLICATION
  • Spraying – aerosol or manual spray gun:
conformal coating application3
CONFORMAL COATING APPLICATION
  • Selective Spraying:
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

Application Conditions
slide14

Product Choice

Coating Options

considerations for choice
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?
conformal coating types
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
dca scc3 modified silicone coating
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
dca scc3 modified silicone coating1
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, 2hrs @ 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
dca scc3 modified silicone coating2
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
tfa toluene free acrylic coating
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
tfa toluene free acrylic coating1
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-46058-C
    • Also available: AFA – Aromatic Free Acrylic
slide22

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

voc definition
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”
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

UVCL - UV Cure
wbps water based coating
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.
wbps water based coating1
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.
puc polyurethane coating
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
slide28

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)

slide29

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
slide30

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

slide31

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

slide32

Conformal Coatings

Potential Problems

adhesion loss
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.
slide34

Conformal Coatings

Rework Considerations

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.

Coating Removal Products
slide36

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
thank you
Thank You

For further information please visit www.electrolube.com