When a moisture sensor fails inside an automotive control unit, or a medical device PCB shorts out after minimal field exposure, the root cause often traces back to inadequate environmental protection. Engineers have long relied on potting and conformal coating to guard circuit boards, but neither method is ideal for every assembly.
low pressure molding for sensitive electronics has emerged as a middle ground that delivers robust encapsulation without subjecting delicate components to the thermal and mechanical stress of conventional injection molding. This guide walks through how the process works, where it fits best, and what OEM procurement teams should evaluate when selecting a supplier.
What Is Low Pressure Molding and Why It Matters
Low pressure molding (LPM) is a process in which a thermoplastic adhesive compound, typically a polyamide or polyolefin-based material, is melted at relatively low temperatures (generally 180 to 220 degrees Celsius) and injected into a mold cavity at pressures far below those used in standard injection molding. The molten material flows around the electronic assembly, fills the cavity, and solidifies into a seamless protective shell.
The key distinction from traditional injection molding is the pressure level. Standard injection molding operates at pressures that can easily exceed 1,000 bar, which would crush fragile solder joints, bond wires, and sensor membranes. LPM, by contrast, typically works in the range of 20 to 60 bar, low enough that populated PCBAs, connectors, and microswitches survive the encapsulation cycle intact.
Compared to potting: Potting uses liquid resins that require long curing times, sometimes hours per batch, and often involve messy cleanup and shrinkage. LPM completes a cycle in seconds, not hours, because the material solidifies by cooling rather than chemical curing.
Where LPM Outperforms Other Protection Methods
No single protection method fits every product. The table below compares the three most common approaches so engineering and procurement teams can match the method to the application:
| Factor |
Conformal Coating |
Potting |
Low Pressure Molding |
| Typical thickness |
25 to 75 microns (thin film) |
Full enclosure, several mm |
Full or partial enclosure, 1 to 5 mm |
| Processing time per part |
Minutes to tens of minutes (including drying) |
Hours (curing dependent) |
Seconds to minutes |
| Pressure on components |
Negligible (spray or dip) |
Negligible (liquid pour) |
Low (20 to 60 bar) |
| Waterproofing level |
Moderate (moisture barrier, not submersible) |
High (full seal) |
High (full seal, IP67 and above achievable) |
| Best suited for |
Dense PCB assemblies needing thin protection |
Large enclosures, high-voltage units |
Small to medium assemblies needing fast, reliable sealing |
For products that demand genuine waterproofing, not just moisture resistance,
low pressure molding for waterproof electronics offers a compelling balance. It achieves the sealing performance of potting while cutting cycle time dramatically, which translates into lower per-unit cost at production volumes.
Industry Applications: From Automotive Sensors to Medical Devices
LPM has found adoption across sectors where electronics must survive harsh environments in compact form factors. Below are several application areas where the technology delivers clear value.
Automotive Electronics
Modern vehicles pack dozens of electronic control units, sensors, and connectors into environments that cycle between extreme cold and engine-bay heat, all while exposed to road spray, salt, and vibration. Window-lifter controllers, anti-pinch modules, tire pressure sensors, and in-cabin comfort modules are common candidates for LPM encapsulation. The process seals the PCB against moisture ingress while absorbing vibration that would otherwise fatigue solder joints over millions of thermal cycles.
For OEMs sourcing automotive electronics manufacturing, working with an
automotive electronics low pressure molding supplier that holds IATF 16949 certification is essential. The standard requires documented process control, failure mode analysis, and traceability that automotive OEMs mandate in their supplier qualification processes.
Medical Devices
Medical sensors, wearable monitors, and implantable-grade electronics demand protection that is both biologically compatible and hermetically reliable. LPM materials are available in medical-grade formulations that meet USP Class VI and ISO 10993 biocompatibility standards. The low processing temperature is particularly valuable for medical assemblies that incorporate temperature-sensitive batteries or delicate sensor membranes.
A manufacturing partner with ISO 13485 certification demonstrates that its quality management system is structured around the documentation, risk management, and traceability requirements specific to medical device production.
Industrial Sensors and LED Lighting
Industrial environments expose electronics to dust, chemical splashes, and wide temperature swings. Pressure sensors, flow meters, and LED driver modules benefit from LPM because the encapsulant forms a continuous barrier with no seams or gaps. LED lighting applications, in particular, value the optical clarity and thermal stability of certain LPM compounds, which protect the driver circuitry without interfering with light output.
What to Evaluate When Selecting an LPM Manufacturing Partner
Choosing the right supplier involves more than comparing price per part. The following factors directly affect product reliability, production lead time, and long-term partnership viability.
1. Equipment and Capacity
Ask how many low-pressure injection molding machines the facility operates and what tonnage range they cover. A shop running only one machine is a single point of failure; a facility with multiple machines can absorb maintenance downtime and scale with your volume growth. Equally important is whether the supplier can produce custom molds in-house or relies on third-party tool shops, which adds lead time and communication overhead.
2. Material Expertise and Sourcing
LPM compounds from brands such as Henkel Technomelt and Bostik Born2Bond have different hardness, adhesion, and temperature ratings. A capable partner should advise on material selection based on your application environment, not simply run whatever compound you specify. They should also maintain controlled material storage to prevent moisture absorption, which degrades molding quality.
3. Engineering Support from Concept to Production
The most common LPM defects, incomplete fill, voids, and wire sweep, originate in mold design and process parameter setup. A supplier that offers mold-flow analysis, prototype tooling, and parameter optimization during the NPI phase will catch these issues before they reach mass production. Look for a partner whose engineering team can participate in DFM reviews and suggest design modifications that improve moldability.
4. Quality System and Traceability
At minimum, the supplier should hold ISO 9001 certification. For regulated industries, industry-specific certifications (IATF 16949 for automotive, ISO 13485 for medical) are non-negotiable. Beyond the certificate itself, ask how the supplier traces materials, process parameters, and inspection results to specific production lots, because this traceability is what enables effective root-cause analysis if a field failure occurs.
5. Integrated Manufacturing Capabilities
LPM rarely exists in isolation. The encapsulated assembly usually starts as a bare PCB, goes through SMT and DIP soldering, receives functional testing, and then moves to molding. A partner that handles all of these steps under one roof eliminates handoff delays, reduces logistics risk, and maintains consistent quality documentation across the entire build. This is where a one-stop electronics manufacturer provides measurable advantage over a molding-only shop.
A Real-World Manufacturing Setup
To illustrate what a capable LPM operation looks like in practice, consider Farway Electronic, a Shenzhen-based EMS provider established in 2018. The company operates a 2,000-square-metre production facility in LongGang, Shenzhen, equipped with four low-pressure injection molding machines alongside two SMT lines, two DIP plug-in lines, a conformal coating line, and two finished-product assembly lines.
Farway's low-pressure molding service covers technical consulting, product and mould development, and volume production. Application areas documented on the company's service pages include medical and industrial sensors, LED lighting, mobile-phone and power batteries, connector harnesses, circuit boards, and microswitches. The company holds ISO 9001, ISO 13485, IATF 16949, and ISO 14001 certifications, and works to IPC-A-610 assembly standards.
Critically, Farway integrates LPM into a full manufacturing chain that spans PCB fabrication, component sourcing, SMT, DIP, conformal coating, PCBA testing, and box-build assembly. This means an OEM can move from bare board to encapsulated, tested, packaged product without managing multiple vendors or shipping partially assembled boards between facilities.
Production scale: Farway reports serving more than 100 industry customers across more than 20 countries and regions, with order capacities ranging from single-piece prototypes through medium and large production batches.
Common Pitfalls to Avoid
Even with the right partner, projects can go off track. The following issues appear frequently enough to warrant attention during the planning phase:
Designing the PCB without considering mold draft angles, which leads to demolding difficulty and damaged components.
Specifying a single material hardness for all application areas, when in reality different zones of the same assembly may need different durometers.
Skipping prototype tooling to save upfront cost, only to discover fill problems at mass production when changes are far more expensive.
Neglecting to define acceptance criteria for encapsulation quality (void size, coverage area, adhesion) before production starts, leading to subjective pass/fail disputes.
Assuming that a waterproof LPM seal eliminates the need for conformal coating underneath, when in fact the two methods protect against different failure modes and are often complementary.
Choosing the Right Partner for Your Next Encapsulation Project
Low pressure molding is a mature, proven technology, but its success depends heavily on the manufacturing partner executing it. The right partner brings material expertise, in-house tooling, integrated production capabilities, and the quality certifications your industry demands. If your next project involves protecting sensitive electronics in automotive, medical, industrial, or consumer applications, it is worth discussing your requirements with a manufacturer that can handle the full production chain, not just the molding step. Farway Electronic offers exactly this kind of integrated, certification-backed manufacturing capability from its Shenzhen facility. To discuss your project specifications, request a quotation, or learn more about low-pressure molding capabilities, contact Farway at sales@farway.hk or visit the company's website for detailed service information.
