Conformal coating application on electronic boards to specification
Conformal coating application is the process by which an already assembled electronic board receives a thin film that follows the contour of its components. What defines the process is not the material: it is how far the coating reaches, which areas it must not touch and with what criterion the result is accepted. This page explains how it is defined. The supply of already coated boards is handled as a service under conformal coating.
What it involves
What conformal coating application covers and what it does not
Unlike potting, which embeds the area in resin, conformal coating leaves the board recognisable and, depending on the material, repairable. It is applied on the assembled board, not on a bare board: the coating has to coexist with the components that are already soldered and with those that will be handled later. That is why conformal coating application always starts with the same two questions: which surface is covered and what has to stay intact.
- Full coverage or limited to the areas your documentation indicates
- Faces of the board that are coated and faces that are not
- Areas that must stay free of coating
- Material and curing system when the project specifies them
- Surface condition required before application, if the process requires it
Process control
Verifiable criteria of conformal coating application
The acceptance criterion for conformal coating application is agreed in writing before the order and depends on the material and the assigned manufacturer. On receipt only what was specified is checked: this list does not describe what we offer, but what has to be settled with you before the batch is launched.
- How far the coating reaches and where it stops
- That the masked areas have stayed free of material
- Appearance of the coating: continuity and absence of build-ups
- That curing has finished before handling or packing
- What sampling is applied to the batch received
How this process is coordinated
How conformal coating application is defined
The masking is defined with your documentation before the board leaves for the manufacturer. Changing it afterwards costs considerably more than agreeing it beforehand.
You define areas
You state which areas are coated and which stay free, on a drawing or on a marked board.
We agree material and method
We review the requirement and coordinate with the network which material and which application method fit your board and your volume.
Coated sample
You validate coverage, masking limits and behaviour in your assembly or repair process.
Application to series
The approved criterion is kept in writing and maintained in later deliveries.
Critical points
What must be decided before conformal coating application
The most common mistake is not choosing the wrong material: it is not defining properly what must NOT be coated. These four decisions are the ones that condition conformal coating application.
Areas that must stay free
Connectors, contact surfaces, test points or adjustment areas, when your documentation excludes them. There is no universal list: the project sets it.
Expected exposure level
What the equipment will be subjected to in service according to what your project declares. The requirement comes from there, not from a catalogue of finishes.
Repairability after coating
If the board must be able to be touched up or repaired later, the material chosen conditions that possibility.
Acceptance criterion
How it is checked that the coverage reaches where it should, that the masking has been respected and that curing has finished. It is what is verified on the batch on receipt.
Related information
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What this process actually covers
This process is carried out by manufacturers in our network selected for each project; Justicia Marin defines the requirement with you, coordinates the supply and verifies the batch received. We have no workshop, machinery or laboratory of our own, and we issue no certifications: certificates are those of the manufacturer or supplier that carries out the process. The specific means available and the level of control that can be achieved are confirmed in writing in the quote before the order. We do not attribute a standardised protection rating or an accredited resistance to this process in a generic way: the real behaviour depends on the material, the thickness and the masking, and is defined for each project.
Where this capability ends: if a volume has to be filled or embedded instead of covering the surface, that is potting and encapsulation. If what has to be covered is a cable or harness on the outside, it is cable harness protection. Curing is carried out according to the system and process specified, and checking under UV light is only possible when the material chosen allows it. As a technical reference of the sector, IPC-A-610 treats coverage and thickness of the coating as acceptance criteria of the assembly, and devotes a separate section to potting.
Questions about the process
Conformal coating application: frequently asked questions
- How does conformal coating application on a circuit board work?
- First the board is prepared and the areas that must stay free are masked. Then the manufacturer applies the coating, for example by spraying, dipping or selective application, and lets it cure according to the specified system. Finally, coverage and masking are checked before the board is packed. The criterion for each step is fixed in the quote, so conformal coating application is repeatable.
- Which application methods are there?
- The most common are manual or automatic spraying, dipping, brushing and selective application with a robot. The choice depends on the board, the material, the free areas and the volume. We agree with the manufacturer which method gives the requested result repeatably and record that.
- How is it checked that the coating has been applied correctly?
- Many coating materials contain a UV indicator, so that coverage and free areas are visible under UV light. A sampled thickness measurement can also be agreed. References such as IPC-HDBK-830 help to fix acceptance; that criterion is set in the quote before the order and checked on sample and batch.
- What is the difference from the conformal coating service page?
- Here we describe the process itself: masking, application, curing and acceptance. The conformal coating service is about the complete supply of coated boards: which protection your application needs, how the choice is made and how the project is supported from enquiry to recurring supply.
- Which parts are usually masked?
- Connectors, pin strips, test points, switch and contact surfaces, potentiometers, heat sinks and areas that will still be soldered later. Which these are on your board is determined by your documentation. State them unambiguously on a drawing or a marked sample, because changing afterwards costs far more.
- Who coats the boards?
- A specialised manufacturer that we choose based on material, application method, volume and the agreed checks. Justicia Marin fixes the areas and the criterion with you, coordinates the sample and checks the batch received. We do not have a coating line of our own.
- Which data do you need?
- The type of board, the sides and areas that must be coated, the areas that must stay free, any requirements for material, layer thickness and repairability, the expected environment and the quantity. With a marked board or a drawing we can fix the process fastest.
Does your board work outside a clean environment?
Ask us about the right coating.
Tell us the type of board, the areas that must stay free and the expected environment so that we can prepare a proposal.
What you can send us
- Bill of materials or part numbers (Excel, PDF or text)
- Drawing or schematic for custom assemblies (PDF, DXF or similar)
- Estimated quantity and expected repeat orders
- Your priority: competitive price, certification or lead time
- Required standards or documentation
- Target delivery date
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