2- Available Conformal Coatings Chemistries and Technologies

Introduction Conformal coating definition Chemistries available: Pros/Cons Technologies available: Pros/Cons

What is a Conformal coating? Thin plastic protective film “Conforms” to the varied profile of an electronic circuit assembly. Membrane that filters water vapour and solid debris Protects the assembly from corrosion in harsh environments.

What is a Conformal Coating? Nominally, the coating should be 25µ to 200µ Too thick may cause problems such as solvent entrapment, bubbling, shrinkage and cracking. Too thin means inadequate protection

The correct Conformal Coating should provide: Good dielectric properties –Insulation resistance –Moisture resistance –Breakdown voltage Good flexibility so as not to stress components... Chemical resistance against anticipated environment Good adhesion to substrate Repairability

Conformal Coating What does it do? It seals contamination IN AS WELL AS OUT. –Remember, the coating is the last of many chemical processes. –A chemical residue ‘Soup’!. –Do I need to clean? Probably !

Why is Conformal Coating Used? Extended Warranties on Consumer Electronics Automotive and Military, Safety Features

Increased demand on coating Automotive electronics will soon represent 40% of the cost of a car A great number of safety features are electronically controlled (ABS, Airbag, Servo steering,…)

Main Conformal Coating Chemistries Acrylic (AR) Polyurethane (PU) Silicone (SR)

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

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

Acrylic Conformal Coatings AR Examples of use include: Engine management Air bag controllers Avionics Communication Equipment Elevator Controls

Polyurethane Conformal Coatings PU Very good solvent resistance 1 and 2K systems Easy to apply Longer cure times Difficult to repair

Polyurethane Conformal Coatings PU Especially suitable for: –Salt Spray protection –Applications where solvent resistance required –Directly mounted assemblies –Reparability is not an issue

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

Silicone Conformal Coatings SR OVERKILL for all but specialist applications Used in: Huge, industrial drilling/mining equipment High temperature electronics Under bonnet electronics

Technologies available Solvent-based Water-Based Solvent less Silicones Solvent less UV Curable

Solvent-Based Advantages –Full range of chemistries available –Easy to process –Good wetting –‘Quasi Cleaning’ –Fast Cure Disadvantages –Flammable –Odour –Extraction Required –VOC Emissions

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

Solvent-less 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

Solventless UV curable: Benefits –Very fast curing –High volume processing –High temperature performance –Great flexibility at low temperature –Excellent adhesion and chemical resistance Reliable secondary cure mechanism

Solventless UV curable: –Improve protection of your boards –Reduce floor space –Improve productivity –Reduce solvent consumption –ISO and other environmental legislation –Safer material to use –Easily processable with automated equipment –Mil-I-46058C & UL approval

Summary: Technologies / Chemistries COATING TYPES ARPUSRSBWBUV Application Easiness Dependant on tech Drying / Curing Time Chemical Resistance 144Dependant on chem. 5 Moisture Protection Reworkability Environmental Friendly Dependant on tech Main featuresGeneral purpose Chem. Resis. High temp.Most common Manual application High volume Higher number = better properties SB = Solvent Based AR = Acrylic PU = Polyurethane WB = Water Based SR = Silicone UV = UV curable

Thank you for your attention! Any questions ?