A conformal-coating specification defines the areas to protect, the areas to keep clear, the selected coating system and the evidence needed to accept the finished assembly. Naming a coating family by itself leaves important manufacturing decisions unresolved. Start with the product environment and the surfaces that must remain accessible or electrically connected.
Translate the environment into requirements
Describe the expected exposure to moisture, contamination, chemicals and temperature. Identify the product’s cleaning, servicing and rework needs. The engineering team should select a coating system and verification plan that address those conditions and the actual assembly materials. Do not assume that a coating alone establishes enclosure protection, electrical safety or a particular service life.
Check compatibility with components, labels, connectors, adhesives and prior cleaning processes. Review the coating manufacturer’s instructions for application and cure. Where the assembly contains sensitive sensors, switches or adjustable parts, define how their operation will be protected and checked after processing.
Create an unambiguous masking drawing
| Drawing element | Information to include |
|---|---|
| Coated areas | Identify the board side and the required coverage boundaries. |
| Keep-out areas | Mark contacts, test points, mechanical fits and components that must remain uncoated. |
| Boundary tolerance | State the allowed transition at each critical masked edge. |
| Material identification | Specify the approved coating product and how alternates may be evaluated. |
| Acceptance evidence | Define coverage, cure and other checks appropriate to the selected process. |
A photograph with loosely drawn arrows may help explain the intent, but it should not be the only controlled definition for a repeat build. Use reference designators, dimensions or clear drawing features so that another operator can identify the same boundary.
Place coating correctly in the assembly sequence
Agree when programming, inspection and electrical testing occur. Some test access may be covered after coating, while some functional behavior may need to be checked after the coating process. Record which failures can be reworked, how coating removal is controlled and what inspection or retest follows a repair.
For example, an assembly may require exposed programming contacts during initial production but protection of those contacts in the finished product. Resolve that sequence explicitly. Leaving an operator to infer whether the contacts should be masked or covered can create inconsistent finished units.
Include these items in the RFQ
- The released assembly drawing and component list.
- The approved material or the engineering process for selecting it.
- A controlled coating and masking drawing for both board sides.
- The required acceptance checks and record format.
- Quantity, handling constraints and any permitted rework process.
Available equipment, approved materials, qualification evidence and processing limits for this project are [NEEDS CLIENT INPUT]. No factory certification or claim of being the first supplier to provide a process is asserted here.
Use the conformal-coating service requirements and functional-test checklist to define the complete scope. Request a coating scope review