Conformal coating has long been the default answer for protecting circuit boards from moisture, dust, and mild chemical exposure. It works well for consumer gadgets and industrial controls. Medical devices, however, raise the stakes. Implantable and wearable sensors face direct contact with bodily fluids. Handheld diagnostic tools are wiped down with aggressive disinfectants dozens of times per day. In these scenarios a thin coating layer — measured in micrometres — can degrade, pinhole, or delaminate long before the product reaches the end of its intended service life.
Low pressure molding takes a fundamentally different approach. Instead of painting a film onto the board surface, it surrounds sensitive components with a solid, three-dimensional thermoplastic shell — typically 1 to 3 millimetres thick — that bonds directly to the PCB and its connectors. The result is a sealed, cushioned assembly that resists water ingress, mechanical shock, and chemical attack far more aggressively than any spray-on layer. For products that must meet ingress-protection ratings of IP67 or above, this difference is decisive.
The process sounds intricate but follows a clean, repeatable sequence. A polyamide or polyolefin hot-melt adhesive — formulated to flow at roughly 180 to 220 degrees Celsius — is melted and injected into a steel or aluminium mould at pressures of only 1.5 to 40 bar. That pressure range is roughly one-tenth to one-fiftieth of what a conventional injection-moulding machine uses, which is why delicate wire bonds, sensors, and MEMS die survive without damage.
Because the material bonds chemically to the board substrate and mechanically around component bodies, there are no air gaps for moisture to wick through. The cycle time — typically under two minutes — is also dramatically faster than the multi-hour cure required for two-part epoxy potting compounds.
Not every medical PCB needs full encapsulation. The strongest case for low pressure molding for electronics emerges in applications where the device will encounter liquid, vibration, or handling stress that a coating alone cannot manage. Common medical use cases include:
In each of these scenarios the common thread is that failure is not merely inconvenient — it can compromise patient safety or trigger a costly recall. That is why design teams in the medical sector increasingly treat encapsulation as a reliability investment rather than a manufacturing cost line.
Both techniques have their place on a production floor, and the best manufacturers offer both. The decision hinges on the severity of the operating environment, the required protection rating, and the cost ceiling for the product.
| Factor | Conformal Coating | Low Pressure Molding |
|---|---|---|
| Protection thickness | 25–75 micrometres (thin film) | 1–3 mm (solid shell) |
| Typical IP rating achievable | IP54–IP65 | IP67–IP68 |
| Mechanical shock resistance | Low — coating does not cushion | High — thermoplastic absorbs impact |
| Cycle time per board | Minutes to hours (includes curing) | Under 2 minutes (no separate cure) |
| Rework difficulty | Moderate — coatings can be stripped | Difficult — shell must be cut away |
| Best-suited use case | Indoor electronics, mild environments | Wet, harsh, or safety-critical environments |
The takeaway is not that one method replaces the other. Many medical products use conformal coating on the main PCB for baseline protection and reserve encapsulation for the sub-assemblies that face the harshest exposure. A manufacturing partner that offers both processes under one roof lets the design team make that trade-off without splitting the build across vendors.
Selecting a supplier for medical encapsulation involves more than comparing machine specifications. The right partner brings together material expertise, mould-design capability, quality-system discipline, and an understanding of medical-industry compliance. When evaluating candidates, product teams should ask:
These questions matter because medical-device recalls are most often traced not to a single failed component but to a protection scheme that was not validated for the real operating environment. A partner that can run the full sequence — from board assembly through encapsulation to functional testing — shortens the validation path and keeps accountability in one place.
Farway Electronic, a ShenZhen-based EMS provider established in 2018, illustrates what an integrated medical-encapsulation workflow looks like in practice. The company operates four low-pressure injection-moulding machines alongside two SMT lines, two DIP through-hole lines, a conformal-coating spraying line, and two finished-product assembly lines within a 2,000-square-metre LongGang facility. That equipment mix allows a medical-device customer to move from bare PCB through SMT placement, DIP soldering, conformal coating, low pressure encapsulation for medical devices, functional testing, and final box-build assembly without changing suppliers.
The quality-system layer is equally relevant for medical work. Farway holds ISO 13485 for medical device quality management alongside ISO 9001, IATF 16949, and ISO 14001, and builds to the IPC-A-610 PCBA assembly standard. Its PCBA test capability spans AOI, X-ray inspection, ICT, FCT functional testing, thermal imaging, and high- and low-temperature reliability testing — the inspection toolkit needed to confirm that an encapsulated medical board performs identically before and after the moulding step.
The most common mistake product teams make with low pressure molding is treating it as a late-stage add-on. Waiting until the PCB design is frozen before engaging the encapsulation partner often forces compromises — a connector that should have been repositioned, a component that sits too close to the mould parting line, or a board outline that does not leave room for the mould draft angle. The fix is to bring the molding engineer into the DFX review as early as the schematic stage.
Equally important is material selection. Polyamide-based hot melts dominate the market, but hardness, colour, and biocompatibility rating all vary by formulation. A supplier that stocks multiple material families — and can guide the choice based on the device's expected chemical exposure, temperature range, and regulatory class — saves weeks of trial-and-error prototyping.
Finally, plan for inspection. Encapsulation hides what it protects, which means X-ray and functional testing become essential rather than optional. A partner that can run these checks on the same floor where the moulding happens catches defects in minutes, not weeks.
If your next medical device needs encapsulation that holds up to real-world conditions — not just lab simulations — talk to a partner that can run the full build under one quality system. Farway Electronic's integrated SMT, DIP, conformal coating, low pressure molding, and PCBA testing capabilities are built for exactly that. Contact the engineering team at farway.hk/contact to discuss your project, request a quotation, or schedule a process-capability review.
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