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PCB potting is a controlled fill-and-cure process

PCB potting places an electronic assembly inside a defined cavity and fills the required region with a protective compound. The process can support environmental protection, insulation or mechanical stabilization, but its success depends on the complete construction: the resin, components, enclosure, interfaces and qualified application method. A smooth cured surface alone does not demonstrate a reliable potted assembly.

This page focuses on the engineering of the fill, mix, dispensing and cure sequence. It is distinct from the broader PCB encapsulation comparison, which helps select a protection strategy, and from PCB potting services, which is the route for a manufacturing quotation.

For early planning, calculate the cavity volume and subtract the solid volume below the intended fill line. Then use the exact mixed-compound density to estimate mass. Keep that geometric estimate separate from process waste, mixing limits and cure qualification. The worksheet makes these assumptions visible rather than presenting one unexplained resin quantity.

Define the fill before ordering material

A potting drawing should show the final enclosure, board position, fill level, protected regions and no-fill areas. Include the component side and any space underneath the board. Identify where air can escape as material enters. A plan view may look complete while leaving a trapped cavity beneath a large component or beside an internal wall.

State what displaces resin below the fill line. This can include the board, component bodies, supports, connector features and internal enclosure ribs. Do not subtract the complete volume of a tall component if part of it remains above the fill. For irregular geometry, use the controlled CAD volume or a validated physical measurement rather than forcing the design into a rectangular approximation.

An illustrative rectangular cavity measuring 100 脳 60 脳 10 mm has a gross volume of 60 mL. If the actual solids below the fill line displace 12 mL, the net fill is 48 mL. Adding a 10% issued-material overage gives 52.8 mL. These are example dimensions, not a recommended cavity or a universal waste allowance.

A second review should examine whether that geometry can be filled consistently. A narrow passage, a high component or a blocked vent may matter more than the total volume. Establish an observable fill condition and a repeatable fixture position before treating the estimate as a production instruction.

Calculate volume, mix mass and an optional allowance budget

Enter the internal dimensions, displaced volume and mixed-product density. The mixing input is explicitly a mass ratio: a value of 2 means two parts A for one part B by mass. If your supplier gives only a volume ratio, do not enter it as a mass ratio. Obtain the correct basis or the necessary component densities from the supplier.

The example above, using an illustrative mixed density of 1.5 g/mL, requires 79.2 g of issued mixture per unit. At a 2:1 mass ratio, that is 52.8 g of part A and 26.4 g of part B. For 100 units, the procurement arithmetic is 7.92 kg of mixed material. This does not authorize mixing all 7.92 kg in a single container.

Budget fields are optional. Leave all three cost allowances blank for a technical brief. If you enter a mixed-resin cost per kilogram, per-unit labor and a one-time setup allowance, also provide the source and currency. The subtotal covers only those entered items. It is uncalibrated planning arithmetic, not a current market price or an exact quote.

Select the exact compound for the actual assembly

Epoxy, polyurethane and silicone are common potting families, but the family name does not determine the complete behavior. Compare the actual formulation's cured properties, processing instructions and compatibility evidence. A flexible formulation may reduce some stresses but still require careful adhesion, environmental and containment review.

The and are useful starting points for obtaining exact product documents. A catalogue application is not proof that a material is approved for your board, voltage or enclosure.

Preserve the material identity in the bill of materials and work instruction. An alternate that has the same color or nominal hardness can still change flow, cure behavior, adhesion or thermal response. Define who approves substitutions and what evidence must be repeated.

Inspect and test before the board becomes inaccessible

Potting can make later inspection and repair difficult. Before application, verify the assembly state that will become hidden: component identity and orientation, required workmanship checks, programming status and the agreed electrical or functional tests. Record the results against the correct board revision and unit or lot identity.

Surface preparation must be compatible with the assembly and compound. Cleaning, drying and handling should follow the approved process and the exact material guidance. Do not apply a generic drying temperature or time copied from an unrelated assembly. Components, labels, plastics, moisture-sensitive parts and prior coatings may impose different limits.

Masking is a designed operation, not an improvised last step. Specify connector cavities, mating surfaces, vents, sensor openings, adjustment features and required test contacts. Check that temporary masks can be removed without damaging the cured edge or leaving contamination. If a permanent dam or gasket controls the fill, include it in the mechanical release.

Record the fixture orientation and reference surfaces. If the board sits at a different angle between trial and production, the same dispensed mass may produce a different fill level or trap air in a new location. A simple setup photo tied to the work instruction can help, but it should supplement rather than replace dimensional requirements.

Follow the material through five controlled stages

The sequence above is an explanatory model. The selected compound and validated production instruction determine the actual order, equipment settings and acceptance conditions. In particular, degassing may occur at different stages depending on the formulation and dispensing system; the animation is not a universal vacuum recipe.

Prepare and verify. Confirm the assembly, material identity, shelf-life status where applicable, enclosure and masking. Establish the pre-potting test result and the approved fill geometry.

Meter and mix. Use the specified ratio and mixing basis. For filled systems, follow the supplier's instructions for component preparation. Confirm that the dispensing system delivers a consistent mixture rather than assuming that equal pump motion means the correct ratio.

Manage air and dispense. Arrange the entry point and flow path so material can displace air instead of sealing it inside. Use the qualified degassing and dispensing method. Monitor changes in flow behavior and working time.

Cure within the qualified geometry. Respect the product-specific limits on batch size, fill depth and temperature history. A large mixing cup and a thin cavity can develop different thermal conditions even when they contain the same formulation.

Inspect, retest and release. Check the defined fill, exposed interfaces and relevant defects. Perform the agreed post-process verification and retain the process and material traceability.

A visible bubble is only one possible symptom

Voids can originate from introduced air, trapped pockets, moisture-related effects or process incompatibilities. Their significance depends on location and function. A small visible surface feature and a hidden gap in an intended thermal or insulating path may require different evaluation. Define the important regions before deciding how to inspect them.

Obtain the exact Electrolube product instructions through the . Review the grade-specific mixing, material-handling and cure conditions for the actual application. Do not turn a supplier example into a universal vacuum duration, heating schedule or humidity limit.

When a defect appears, retain the evidence and compare the actual process record with the approved conditions. Check the mixture, material handling, fill route, timing and geometry. Changing several parameters at once may hide the cause and make a successful trial difficult to repeat.

A surface inspection cannot establish that all internal regions are void-free. If the application needs evidence about hidden fill or interfaces, agree an appropriate qualification or inspection approach for that construction. State its sampling and limitations. Avoid promising a defect-free internal volume from an exterior photograph.

Separate working time, handling time and final properties

The period available for mixing and dispensing is not the same as the time at which a part can be moved, and neither necessarily equals the time at which the final properties are reached. Use the terminology and conditions in the exact technical data sheet. Record the temperature and geometry associated with those values.

Curing can generate heat. The reaction and heat dissipation depend on formulation and the amount and shape of material. Scaling a small trial to a large batch therefore requires review. Do not assume that multiplying all quantities leaves the temperature history unchanged.

Adhesion, inhibition or incomplete cure can also depend on contact with other materials. Evaluate the real enclosure, solder mask, labels, adhesives, residues and coatings in the proposed process. A witness sample mixed alongside the assembly may help monitor the batch, but it may not reproduce every interface or thermal condition inside the product.

The release record should identify the cure instruction revision and any required evidence before handling, testing or packaging. If production is interrupted, follow the approved recovery or disposition route. Reheating or adding a second layer without review can create a new process that has not been qualified.

Quote the complete operation, not only the resin

A useful enquiry includes the assembly and enclosure files, quantity, fill line, protected regions, keep-outs and target material. If the material is not yet selected, state the environment, thermal path and serviceability requirements. Include the required pre- and post-potting tests and the intended report.

The main cost drivers often include masking, preparation, dispensing access, cure space, material waste, inspection and rework risk. Separate prototype qualification from repeat production. A trial with extensive observations is a different scope from a stable released process.

For a complete assembly route, use PCB assembly. For the protection operation specifically, send the drawing and worksheet through PCB potting services or the direct Contact link. Downloaded quantities need to be reviewed against the actual CAD and material data; they do not automatically become an order.

PCB potting questions