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Conformal Coating Types Reference: AR, ER, SR, UR, XY

Choosing a conformal coating means trading barrier performance against rework effort and process cost. This table lists the five IPC-CC-830 type codes with typical strengths, limits and rework difficulty, so you can discuss options with a coating supplier or write a clear drawing note.

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Type code	Chemistry	Typical application	Typical strengths	Typical limits	Rework
AR	Acrylic	Spray, dip, brush	Easy to apply, good moisture resistance, low cost	Limited solvent and abrasion resistance	Easiest: dissolves in common solvents, soldering through the film is common
ER	Epoxy	Spray, dip, brush (often two-part)	Hard film, good chemical and abrasion resistance	Stresses components in thermal cycling, difficult to remove	Hard: usually needs mechanical or aggressive chemical removal
SR	Silicone	Spray, dip, brush	Wide temperature range, flexible, good in humidity	Softer film, poor solvent resistance, can contaminate other processes	Moderate: specialised removers or mechanical removal
UR	Urethane	Spray, dip, brush	Good chemical and abrasion resistance, good moisture barrier	Can be hard to remove, some types sensitive to moisture during cure	Moderate to hard: chemical strippers or solder through for thin films
XY	Paraxylylene (parylene)	Vacuum vapor deposition	Very thin, uniform, pinhole-free film, excellent barrier	Needs special equipment and masking, higher cost	Hard: usually micro-abrasion, laser or plasma methods
Standard	IPC-CC-830	Qualification and performance of electrical insulating compound for printed wiring assemblies	Defines type codes AR, ER, SR, UR, XY	Not an application standard
Standard	IPC-A-610 (conformal coating section)	Acceptance criteria for coverage and thickness	Used for inspection	Check your class
Standard	IPC-HDBK-830	Guidelines for design, selection and application of conformal coating	Handbook for process engineers	Guidance rather than requirements
Inspection	UV tracer	Many coatings contain a UV tracer for inspection	Lets inspectors see coverage under UV light	Does not measure thickness
Thickness	Acrylic, epoxy, urethane	Commonly specified as a range in micrometers	Per IPC-CC-830 and the drawing	Measure wet film or cured film per method
Masking	Connectors, test points, heat sinks	Keep out of connectors and mating surfaces	Defined by the drawing	Check before application

Traits are general trends, not data sheet values, and actual products within a family differ. Defense programs often require a coating on a Qualified Products List or a specific coating called out by drawing. Always follow the drawing, the supplier data sheet and the customer specification.

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How to use the table

Search for a chemistry, such as silicone or parylene, or for a word like rework. Compare the rows against your environment. A deployed radio in a humid, wide-temperature setting may favor silicone or parylene, while a lab unit may be fine with acrylic. The table is a conversation starter, and the actual product must be qualified for your assembly and your customer. Export the comparison to attach to a design review.

Selection factors

Think about service temperature range, humidity or salt exposure, chemical contact, vibration, repair needs and the cure or application method available at your facility. Hard coatings can add stress to fragile parts through thermal cycling, while soft ones may give little abrasion protection. Defense electronics often need repair and rework late in the build, which pushes many teams to acrylic or to careful masking. Parylene gives excellent protection but needs a specialist vendor.

Match the coating to the environment in the test plan
Verify compatibility with fluxes, cleaners and adhesives
Define keep-out areas on the drawing
Specify inspection under UV and thickness method

Common mistakes

Frequent problems include coating over residues that were never cleaned, which causes delamination and electrochemical migration, and using the wrong film thickness. Another mistake is skipping a masking plan, which leads to coated connectors. Keep a coating record for each lot with material lot, cure profile and inspector, so that field returns can be traced. Coatings qualified to IPC-CC-830 prove the material, not your application process.

Frequently Asked Questions

What do AR, ER, SR, UR and XY stand for?

They are IPC-CC-830 type codes: AR for acrylic, ER for epoxy, SR for silicone, UR for urethane and XY for paraxylylene, commonly called parylene. The standard qualifies the materials by type.

Which coating is easiest to rework?

Acrylic is generally the easiest because it dissolves in common solvents and can often be soldered through. Epoxy and parylene are the hardest to remove. Real products vary, so check the supplier's removal guidance.

Is parylene always the best choice?

Not always. It gives a thin, uniform barrier but needs vacuum deposition equipment, careful masking and often an outside vendor. For many assemblies a spray-applied coating is enough and cheaper to process and repair.

Does this table replace the standard?

No. It summarizes general characteristics. IPC-CC-830 and IPC-HDBK-830 are the references, and your drawing and customer specification decide the approved material and the acceptance criteria.

Netray can help link coating batches and process records to serial numbers in your ERP. Ask us when you want that kept on your own servers.

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