IllustrationConformal coating is a thin polymer film that protects a PCB from moisture and contamination and adds electrical insulation. IPC-CC-830C groups coatings by chemistry: acrylic, epoxy, silicone, polyurethane, parylene and others. Choose the chemistry for the environment, mask contacts, buttons and sensor openings, and check coverage under UV light.
Small devices live close to people. A wearable sees sweat and skin oils. A tracker on a pet collar or a bike sees rain, condensation and road salt. Conformal coating is a common way to help a board survive that, and an easy one to get wrong. A coating in the wrong place can block a charging contact, clog a pressure sensor or detune an antenna.
This is an engineering summary. We quote only the public table of contents and scope of IPC-CC-830C and give no thresholds from the paid standard.
What is conformal coating on a PCB, and what does it protect against?
A conformal coating is a thin insulating film applied over an assembled board, following the shape of the parts. IPC-CC-830C, revision C dated December 2018, is the IPC standard that qualifies coating materials. Its scope says the coating is intended to protect against moisture and contamination and provide electrical insulation, and is not a sole source of mechanical support (as of November 2026).
The same scope sets a limit. The standard covers materials qualification and conformance only. Application and performance in the end-use environment are outside its scope, and its tests run on standard test vehicles in place of real production boards. A product that says it meets IPC-CC-830C has passed material tests. Your board, your process and your housing still need their own checks.
The public table of contents lists the material tests, including fluorescence, flammability, dielectric withstanding voltage, moisture and insulation resistance, and thermal shock (IPC-CC-830C table of contents, as of November 2026).
Which conformal coating type fits your board?
IPC-CC-830C sorts coatings by cured chemistry and gives each a type letter: AR acrylic, ER epoxy, SR silicone, UR polyurethane, XY paraxylylene, UT ultra-thin and SC styrene block copolymer. A coating with a target thickness of 12.5 µm or less is Type UT whatever its chemistry. A hybrid takes the type of the chemistry with the highest share by weight (as of November 2026). Ask your supplier which type letter its product carries.
The table summarizes the trade-offs as AdvancedPCB lists them in its coating guide (AdvancedPCB, posted July 30, 2026, as of November 2026). The last column is our reading for small devices.
| Type | Strengths | Drawbacks | Where it fits |
|---|---|---|---|
| AR, acrylic | Easy to apply and rework, fast air dry, strong dielectric performance. | Moderate solvent and abrasion resistance. | Prototypes and boards you expect to repair. |
| SR, silicone | Moisture resistance, flexibility and a wide operating temperature range. | Harder to rework, longer cure times. | Boards that see humidity, condensation or wide temperature swings. |
| UR, polyurethane | Chemical and abrasion resistance, a strong moisture barrier. | Hard to remove. Solvent can be trapped if it is applied too thick. | Boards exposed to fuels, solvents or harsh cleaners. |
| ER, epoxy | Chemical resistance, mechanical durability and adhesion. | Rigid, and the hardest to remove. | Boards you never plan to rework. |
| XY, paraxylylene (parylene) | Nearly pinhole free and very uniform, strong dielectric performance. | Needs vacuum deposition equipment, costs more, and masking and rework are more complex. | Fine-pitch or high-voltage boards, and boards where a thin, even film matters. |
AdvancedPCB recommends silicone or parylene for high humidity or condensation, polyurethane or epoxy where fuels, solvents or harsh cleaners are present, and parylene or a controlled acrylic for high-voltage or fine-pitch assemblies (as of November 2026). MG Chemicals puts typical dry film thickness at 25.4 to 127 µm (MG Chemicals coating guidelines, as of November 2026).
Some sensors restrict chemistry. Bosch Sensortec's BME690 handling note says PCBs shall not be coated with materials containing or emitting siloxanes (BST-BME690-HS000-00, February 2025, as of November 2026). If your board carries that sensor, ask the coating maker in writing whether the product contains or emits siloxanes before you pick a silicone.
Does a wearable or tracker board need conformal coating?
Start with the enclosure. The housing seal keeps water and dust out. The coating protects the board from what still gets in: humidity that condenses inside the case, a seal that ages or leaks, or salt carried in on a damp gasket. Treat the coating as a second line of defense. An IP rating is earned by the sealed product in a test, and the coating alone does not give you one. For what those tests cover, see IP67 vs IP68 for wearables.
Signs your board needs it
- It is worn on skin or used outdoors, so sweat, rain or salt air can get inside over time.
- It moves between cold and warm places, which can form condensation inside a sealed housing.
- It has fine-pitch parts or high impedance circuits where a thin film of moisture can cause leakage.
- A vent, speaker port or charging contact opens a path from outside to the board.
When you may skip it
An indoor desk device with no vents and a stable temperature may not need coating. Coating adds a process step, masking labor and inspection, and makes rework harder. Decide from the environment the product will see, and test the choice. AdvancedPCB lists thermal cycling, 85°C and 85% RH humidity exposure, salt fog and mixed flowing gas among the environmental qualification tests used for coated assemblies (as of November 2026). Pick the ones that match your use.
What must stay uncoated, and how is it masked?
A dense wearable board packs contacts, sensors and an antenna into a few square centimeters. Every opening and contact needs a decision before the coating line runs. MG Chemicals says keep-out areas must be masked, with tape or a peelable mask, and that the mask should come off soon after application and before the coating has cured (as of November 2026).
| Keep-out area | Why it stays bare | Source or basis, as of November 2026 |
|---|---|---|
| Connectors, charging pads and pogo-pin contacts | A coating is an insulator, so it stops the contact from conducting. | SCS |
| Buttons, switches and other moving parts | Coating can stiffen or jam the moving part. | SCS and AdvancedPCB |
| Pressure, humidity and gas sensor vent holes | Liquid coating can flow into the opening and reach the MEMS element. | Bosch BME280 note: low-viscosity coatings or potting can enter the hole and damage the sensor element. |
| Microphone sound ports | The port is an open path to a MEMS die, the same risk as a sensor vent. | Our reasoning from the sensor case. Check your microphone maker's note. |
| Test points you will probe after coating | A coated pad cannot be probed without stripping it. | Our reasoning. Decide which tests run before coating. |
| Antenna feed and tuning parts | Coating adds dielectric material near the antenna and can shift its tuning. | Our reasoning from MG Chemicals' note that RF circuits need a low dielectric constant coating. |
| Optical windows, LEDs and photodiodes | A film or bubble in the light path changes what the sensor sees. | Our reasoning. Mask it or ask for a clear, bubble-free film. |
Sources: SCS, Masking for Parylene Deposition (July 7, 2021), Bosch Sensortec BME280 handling note BST-BME280-HS006-00 (May 2018), MG Chemicals on RF transparency and the AdvancedPCB guide above.
Sensors with openings
Bosch's BME280 note asks for the sensor hole to be covered during processing, for example with Kapton tape, and says no board wash should run once the sensor is on the board without that protection. It also asks you to avoid total and partial covering of the sensor with protective material such as epoxy resin, because contact with resin leads to an uneven stress distribution over the package. It names solvents such as acetone, ethanol and isopropyl alcohol as causes of humidity reading drift (as of November 2026). Ask your coating supplier which solvents its product releases while it cures.
Antennas
MG Chemicals says silicone coatings tend to have the lowest dielectric constant of the common chemistries, with acrylics, polyurethanes and UV-curable materials slightly higher. It reports values from 2 to 3.3 for many of its own products, measured per ASTM D150 (as of November 2026). Those values are for that maker's products. Either mask the antenna area or tune and measure the antenna on a coated board. For the antenna layout itself, see PCB antenna design for small devices.
Parylene masking
Parylene is applied by chemical vapor deposition, which AdvancedPCB says gives a uniform film that reaches beneath many components. SCS says it may be necessary to diagram the keep-out areas, and that parylene is exceptionally difficult to remove once bonded, so a masking error is costly (as of November 2026).
Conformal coating or potting electronics: which one?
Potting fills the space around the assembly with resin. RAMPF, a resin maker, says a cured potting compound replaces the air inside the housing, insulates live parts, conducts heat away from components and seals the assembly against moisture (RAMPF potting compounds, as of November 2026). The cost is weight, space and repair access.
| Question | Conformal coating | Potting |
|---|---|---|
| What it is | A thin film that follows the board contour. | A solid body of resin that fills the space around the assembly. |
| Thickness | Most coatings are applied at 25 to 75 µm (AdvancedPCB). RAMPF says typically well below 0.005 inch. | Fills the space around the parts, so the housing sets the thickness. |
| Weight and space | RAMPF says coating fits better when tight tolerances or low weight are the priority. | Adds resin mass and needs space in the housing. |
| Heat | RAMPF says a coating protects mainly against humidity and light contamination, and gives it no heat role. | RAMPF says a potting compound with thermally conductive fillers carries heat from the components to the housing wall. |
| Stress on parts | Thin film. Bosch still asks that resin stay off its stress-sensitive sensors. | RAMPF says sensitive parts and large temperature cycles call for a flexible, low-shrinkage system. |
| Inspection and repair | AdvancedPCB says coating allows easier inspection and repair. | AdvancedPCB says potting makes rework and part replacement much harder. |
| Sensors with openings | Mask the opening. | Bosch says to avoid total or partial covering of its sensors with protective material such as epoxy resin. |
Sources as of November 2026: AdvancedPCB guide, RAMPF potting page, Bosch BME690 note.
In our view, coating fits most wearables better. Weight and thickness are tight, and contacts and sensors need access. Potting suits a part of the product that must survive shock, vibration or immersion and will never be opened, such as a sealed sensor pod. RAMPF says polyurethane and silicone put little pressure on embedded parts, while rigid epoxy systems maximize mechanical strength instead (as of November 2026). If you pot, keep sensor openings out of the resin, as Bosch asks for its sensors, and plan how a failed unit will be analyzed.
How do you apply and inspect conformal coating?
Cleaning and application
AdvancedPCB says to remove flux residue, fingerprints and ionic contamination first, and points to IPC J-STD-001 for cleaning (as of November 2026). MG Chemicals says flux, grease or oil left on the surface can cause de-wetting, where the coating fails to spread over part of the board and floods the areas next to it.
Brushing suits prototypes and touch-up work. Spraying, manual or robotic, is common in production and needs masking and overspray control. Dipping gives full coverage but needs strong masking. Selective coating uses precision valves to place coating only where it is needed, which can cut the masking needed on dense boards (AdvancedPCB, as of November 2026). For a pilot build, ask your assembler which method and masking it would use.
UV inspection and thickness
A fluorescent tracer in the coating makes coverage easy to check, and IPC-CC-830C lists fluorescence among its material requirements. MG Chemicals describes the check simply: place the coated board under a black lamp and look for areas that fluoresce blue (as of November 2026). AdvancedPCB lists visual inspection under white and UV light for fluorescent coatings, and IPC-A-610 as the source of acceptance criteria for coated assemblies. Confirm which revision and class your assembler works to.
For thickness, AdvancedPCB lists eddy-current gauges, calibrated coupons, micrometers and, for parylene, weight gain. MG Chemicals notes that a digital coating thickness gauge works only on conductive substrates, so it cannot measure coating over solder mask, and that cross-section analysis is the most accurate method but destroys the sample (both as of November 2026). For adhesion, AdvancedPCB cites cross-hatch testing to ASTM D3359 where it applies.
What should you ask your hardware team?
Bring this list to the design review that freezes the board and the enclosure, and write the answers into the assembly drawing.
- Which IPC-CC-830C type is the coating, and which data sheet revision are we using?
- Does the board need coating at all, or does the enclosure seal already cover the environment we expect?
- Is there a masking drawing that lists every keep-out area: contacts, buttons, sensor vents, mic ports, test points, antenna parts?
- Which sensors on the board have maker rules about coatings, potting, solvents or siloxanes?
- Was the antenna tuned and the RF measured on a coated board?
- Is the coating fluorescent, who inspects coverage under UV light, and how is thickness measured?
- Which IPC-A-610 revision and class does the assembler use to accept coated boards?
Coating, masking and the enclosure seal sit inside the electronics and mechanical work. For how that work is organized, see engineering.
Questions about conformal coating
Is conformal coating waterproof?
No coating standard promises that. IPC-CC-830C says the coating is meant to protect against moisture and contamination and to insulate, and that the standard covers material qualification only. Performance in the end-use environment is outside its scope (IPC-CC-830C table of contents and scope, as of November 2026). Water resistance for the product comes from the enclosure and its test. See IP67 vs IP68 for wearables.
How thick is a conformal coating?
AdvancedPCB says most coatings are applied at 25 to 75 µm, and that parylene runs 0.2 to 2 mils, about 5 to 51 µm, as of November 2026 (source). IPC-CC-830C defines any coating with a target thickness of 12.5 µm or less as Type UT, ultra-thin, whatever its chemistry.
Can a coated board be repaired?
Yes, with effort that depends on the chemistry. AdvancedPCB calls acrylic generally the easiest to repair and says polyurethane and epoxy take much more effort to remove (as of November 2026). SCS says parylene is exceptionally difficult to remove once bonded (source).
How can Duobay help with coating and sealing decisions?
Duobay develops custom devices with a Shenzhen engineering team that covers mechanical, electrical, firmware, app and test work, so the board, the enclosure seal and the masking plan can be reviewed together. Prototypes and small batches are part of the work, and source files are assigned to you at every paid gate. Initial calls are free. Tell us about your device.
If you want a coating and masking plan checked against the sensors, contacts and antenna on your board, tell us about your device.
Sources. All pages accessed November 6, 2026. Material data and standards are revised, so confirm current values with your supplier before you decide.
- IPC, IPC-CC-830C Qualification and Performance of Electrical Insulating Compound for Printed Wiring Assemblies, December 2018, public table of contents and scope (link)
- AdvancedPCB, Conformal Coating: Complete Guide for PCB Protection (posted July 30, 2026) (link)
- MG Chemicals, Conformal Coating Guidelines (link)
- MG Chemicals, Conformal Coating Protect Mission-Critical Circuitry while Preserving RF Transparency (link)
- RAMPF, Potting Compounds and Encapsulation Resins for Electronics (link)
- Specialty Coating Systems, Masking for Parylene Deposition (July 7, 2021) (link)
- Bosch Sensortec, BME280 Handling, Soldering and Mounting Instructions, BST-BME280-HS006-00, revision 1.8, May 2018 (link)
- Bosch Sensortec, BME690 Handling, Soldering and Mounting Instructions, BST-BME690-HS000-00, revision 1.0, February 2025 (link)
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