Conformal coating protects a board surface from moisture, dust, and mild chemical exposure, and for many indoor products it is sufficient. But coating is thin, typically tens to a few hundred micrometres, and it cannot seal connectors, cable outlets, or sensor ports against sustained water ingress. When a product is deployed in automotive wheel wells, outdoor telecom enclosures, medical sensors that undergo sterilisation, or battery packs exposed to humidity, the assembly needs a thicker, three-dimensional barrier that fully surrounds the electronics.
That barrier is what encapsulation provides. It mechanically locks the board inside a solid or semi-solid material, blocking liquid water, dampening vibration, relieving strain on solder joints and wire harnesses, and insulating conductors from each other. For products that must meet ingress protection ratings, encapsulation is usually mandatory rather than optional. The question is not whether to encapsulate, but which method to use.
Potting and low pressure injection molding pcba both enclose a board in a protective material, but they do it differently. Potting pours a liquid resin, usually a two-part epoxy or polyurethane, into a housing around the board and then waits for it to cure in an oven. The process is simple in concept but slow in execution, and the cured resin is difficult to remove for rework.
Low pressure molding takes a different route. A thermoplastic hot-melt adhesive, typically based on polyamide or polyolefin, is melted in a reservoir and injected into a mould at low pressure, generally in the range of 1.5 to 40 bar. The material flows around the board and solidifies as it cools, usually within seconds. There is no mixing, no vacuum settling, and no oven cure. Because the injection pressure is low and the material temperature is comparatively modest, the process can mould directly around fragile components, connectors, and wire harnesses without damaging them.
The step reduction is not the only advantage. Each characteristic of the process maps to a concrete production benefit:
The moulding material is the single largest determinant of how the encapsulated assembly performs in the field. The two dominant chemistries are polyamide and polyolefin hot-melt adhesives, each available in hardness grades ranging from soft, rubber-like compounds to rigid structural materials.
| Material | Strengths | Typical Use |
|---|---|---|
| Polyamide | Wide operating temperature range, excellent adhesion to many substrates, good chemical resistance, high dielectric strength | Automotive sensors, industrial connectors, cable overmolds |
| Polyolefin | Lower processing temperature, softer grades available, good flexibility at low temperatures, lower cost | Consumer electronics, battery packs, medical sensors |
Hardness is chosen based on whether the encapsulant needs to act as a structural housing, in which case a harder grade is selected, or as a flexible gasket around moving parts, where a softer grade is preferred. Additives can introduce UV resistance, colour coding, optical clarity, or enhanced thermal stability for products exposed to sustained heat.
The versatility of low pressure molding is reflected in the breadth of its applications. Because the process can seal around electronics, cables, and mechanical features in a single shot, it serves product categories that would otherwise need multiple protection methods combined.
In each of these fields, the decision to encapsulate rather than coat is driven by the severity of the operating environment and the cost of field failure. A coated board that fails in service often cannot be repaired on site; an encapsulated board is designed not to fail in the first place.
Not every product needs full encapsulation, and not every encapsulated product needs low pressure molding. The selection depends on the ingress protection target, the volume, the rework requirement, and the available equipment.
| Factor | Conformal Coating | Potting | Low Pressure Molding |
|---|---|---|---|
| Ingress protection | Up to IP54 typical | Up to IP67/IP68 | Up to IP68 |
| Cycle time | Minutes per board | Hours, oven cure required | Seconds to minutes |
| Rework | Depends on chemistry | Difficult, often destructive | Heat-removable, reworkable |
| VOC emissions | Solvent-based types emit VOCs | Some systems emit VOCs | None, solid thermoplastic |
| Equipment investment | Low to moderate | Moderate | Higher, requires mould tooling |
For products that only face humidity and dust, conformal coating remains the most economical choice. For products that need full immersion protection but run in low volumes with frequent design changes, potting may still be pragmatic. For medium-to-high volume products that need reliable sealing, fast cycle times, and the option to rework, low pressure molding is increasingly the preferred route. A capable finished product assembly partner can help evaluate which method fits a given product before tooling investment is committed.
Farway Electronic, a Shenzhen-based EMS provider, operates four low-pressure injection moulding machines as part of its one-stop PCBA manufacturing service. The company positions low pressure molding as a complement to its smt pcb assembly, DIP through-hole welding, conformal coating, and finished-product assembly lines, so boards move from bare PCB to encapsulated, tested, and packaged product within a single facility.
Farway's low pressure molding service covers the full project cycle, from technical consulting and engineering through product and mould development to volume production. The moulding line is designed for sensitive electronic components and supports applications including medical and industrial sensors, LED lighting, mobile-phone and power batteries, connector harnesses, circuit boards, and microswitches. This breadth matters because encapsulation quality depends as much on mould design and material selection as on the injection equipment itself.
Because the moulding step sits inside a broader manufacturing flow, encapsulated boards proceed directly to PCBA testing, including ICT, FCT, thermal imaging, and functional verification under IPC-oriented controls. Farway also offers a one-year free-repair commitment for eligible non-external defects arising during standard customer use, which reflects confidence in the protection the encapsulation provides.
Like any moulding process, low pressure injection has its own failure modes. Recognising them early prevents scrap and rework downstream.
Setting up low pressure molding in-house is feasible for high-volume, single-product lines, but it requires equipment capital, mould tooling expertise, material knowledge, and a qualified testing capability to verify sealing performance. For most product teams, the economics favour outsourcing to an EMS partner that already runs the equipment and can integrate encapsulation with the rest of the PCBA process.
A partner with an established moulding line brings several advantages: documented process parameters, trained operators, mould maintenance discipline, and the ability to run prototype, medium-volume, and mass-production batches on the same equipment family. This is particularly important for products targeting automotive, medical, or industrial certifications, where encapsulation consistency is audited as part of supplier qualification rather than checked only at final inspection.
Low pressure molding only delivers its intended protection when the material, mould design, process parameters, and downstream testing are all controlled. For teams that need reliable encapsulation across prototype, medium-volume, and mass-production runs, working with an experienced EMS partner removes the guesswork.
Farway Electronic operates four low-pressure injection moulding machines backed by ISO-certified quality systems, IPC-standard assembly controls, and integrated testing from SMT through finished-product assembly. To discuss your encapsulation requirements or request a quotation, contact the engineering team at sales@farway.hk.
Whether you are sealing a medical sensor, an automotive connector harness, or a waterproof consumer device, the principles are the same: choose the right material, design the mould around the sensitive features, control the injection parameters, and verify sealing against recognised standards. Done well, low pressure molding turns a vulnerable board assembly into a product built to survive its working environment for the full duration of its service life.
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