Conformal Coatings

Conformal coatings protect printed circuit boards and other electronic assemblies from environmental damage. Applied by spraying, dipping, brushing or vapor deposition, conformal coatings “conform” to the contours of a printed circuit board, sealing the board’s components. Conformal coatings are typically applied at 25-250 μm (micrometers or microns.) The thickness will vary based on the particular chemistry and the level of protection needed. Conformal coatings serve as protection against moisture, dust, chemicals, temperature extremes and other hazards that could result in damage or failure of the electronics to function.

In order to inspect the electronics, most conformal coatings are transparent. Some types contain a fluorescing dye, so that when viewed under a UV light they will fluoresce brightly. This helps with inspection to be sure the coating fully encapsulates the assembly without voids, bubbles or pinholes.

Types of Conformal Coatings

There are 5 major types of conformal coatings on the market today, differentiated by their base polymer chemistry. These are acrylic, epoxy, polyurethane, silicone and paralene. Each chemistry has its own particular set of strengths and weaknesses and are available from a number of suppliers worldwide. Each type is further subdivided by features such as cure method (for example: air, oven or UV), application method (spray, dip, brush), and properties (high temperature, high flexibility, UV resistance and so on). A 6th type of chemistry is a relative newcomer, the so-called nano conformal coatings. Here fluorine-containing materials are put into a vacuum deposition chamber along with a part to be coated. The fluorine containing material is then deposited on, theoretically every surface of the part, interior and exterior providing a nanometer thick protection from water, chemicals, etc. The major types of conformal coatings are summarized here:

Type Base Chemistry Application Method Advantages
Acrylic Acrylic Acid Spraying

Dipping

Brushing

Ease of rework
Simple drying process
Good moisture resistance
Epoxy  

 

Epichlorohydrin

Spraying

Dipping

Brushing

Relatively Hi temp
High hardness
Abrasion resistance
Low CTE
Higher Tg (Glass transition)
Good dielectric properties
Polyurethane Urethane + Polyol

Spraying
Dipping
Brushing
Good dielectric properties
Good moisture resistance
Solvent resistance
Less reversion potential
Abrasion resistance
Silicone  

Siloxane

Spraying

Dipping

Brushing

Hi and Low temp performance
Flexible
Good moisture resistance
High dielectric strength
Hydrophobic
Paralene Paralene C

Vapor

Deposition

Excellent uniformity
Chemical inertness
Low outgassing
Low dielectric constant
Hydrophobic grades

Coating Performance

Conformal coatings are particularly important in automotive, military, aerospace, marine, lighting, industrial and green energy applications where exposure to the elements is significant. But the use of electronics in industrial, domestic and mobile applications is driving the need for greater protection through the use of conformal coatings. 

Various industrial and military specifications categorize conformal coatings by their design and performance criterion. These specifications assist users to select the appropriate coating for their application. Specifications include:

  • IPC-CC-830B
  • MIL-I-46058
  • UL746E

NanoSlic as a Conformal Coating

NanoSlic offers a new approach to conformal coating technology. Its hydrophobic /oleophobic surface and ceramic chemistry provide a unique combination of properties and offers advanced environmental protection.

  • Hydrophobic and oleophobic, provides “water-proof” protection
  • Applied easily by dipping, spraying. Does not require complicated vapor deposition equipment
  • Thin coatings of 2-4 μ makes it possible to penetrate and encapsulate “hidden” areas
  • One part formula does need pre-mixing
  • Room temperature formation means coatings are effectively stress-free
  • Cure can be accelerated with heat
  • Adheres strongly to most materials, including stainless steel
  • Chemically inert and stable and provides excellent barrier
  • Coatings easily pass a 100hr salt-spray test.
  • Excellent electrical properties
  • Transparent but also available with UV fluorescing dye
  • Coatings provide surface lubrication with high abrasion resistance

Will Nanoslic Work for Your Application? Let’s find out.