A field-tested look at the LPM process, material selection, partner evaluation, and common pitfalls
Electronic products face an ever-growing list of environmental threats — moisture ingress, chemical exposure, mechanical vibration, and temperature swings — that can degrade performance or cause catastrophic failure. As devices shrink and find their way into harsher settings, manufacturers need encapsulation methods that seal out the elements without damaging sensitive components. Low pressure molding has emerged as one of the most effective answers, combining gentle processing conditions with rapid cycle times and durable protection.
This guide walks through how low pressure molding for waterproof electronics works, where it delivers the most value, and what to look for when choosing a manufacturing partner.
Low pressure molding (LPM) is an encapsulation process that uses thermoplastic hot-melt adhesives — typically polyamide or polyolefin-based compounds — to surround and seal electronic assemblies. Unlike traditional high-pressure injection molding, LPM operates at low injection pressures (generally 1.5 to 40 bar) and moderate temperatures (around 180–220 °C). The molten material flows gently around components, filling cavities and forming a solid, watertight shell within seconds to minutes.
The process consists of three straightforward steps:
Because the pressure and temperature stay well below the thresholds that could damage electronics, LPM is particularly suited to assemblies that include fragile components, fine-pitch devices, or wire bonds.
Engineers evaluating protection methods often compare LPM against potting, conformal coating, gasket sealing, and laser welding. Each technique has its place, but LPM offers a compelling balance of speed, protection level, and component safety.
| Method | Cycle Time | Pressure on Components | Typical IP Rating |
|---|---|---|---|
| Low Pressure Molding | Seconds to minutes | Low (1.5–40 bar) | Up to IP67 / IP68 |
| Potting | Hours to overnight | Low (no pressure) | Up to IP68 |
| Conformal Coating | 30–60 min (incl. bake) | Negligible | IP54–IP65 |
| Gasket Sealing | Assembly-dependent | None | Up to IP67 |
Potting compounds typically require extended curing times — anywhere from hours to a full day at room or elevated temperature. Conformal coating involves multiple steps including masking, spraying, and baking. LPM, by contrast, completes the encapsulation cycle in a matter of seconds to a few minutes, dramatically reducing per-unit processing time and enabling higher-volume production.
High-pressure injection molding can crack brittle components or deform thin PCB substrates. Potting generates exothermic heat during curing that may stress temperature-sensitive parts. LPM's low pressure and controlled temperature keep thermal and mechanical stress to a minimum, making it safe for MEMS sensors, LED modules, battery management circuits, and other delicate assemblies.
A properly executed LPM enclosure achieves ingress protection ratings up to IP67 and IP68, meaning the device is dust-tight and can withstand continuous immersion in water. The thermoplastic material bonds directly to the component surfaces and connector leads, eliminating the gaps and leak paths that gasket-based seals can develop over time.
Unlike potting, which often wastes material in mixing cups and overflow, LPM injects only the required volume into each mold cavity. The thermoplastic adhesives are also free of solvents, reducing volatile organic compound (VOC) emissions in the production environment.
LPM's versatility makes it valuable across a wide range of sectors. Farway Electronic, a Shenzhen-based EMS provider operating low pressure molding for automotive electronics and other demanding applications, lists the following fields as core LPM use cases:
Not every contract manufacturer offers low pressure molding, and among those that do, capabilities vary widely. The following criteria help identify a partner capable of delivering consistent, high-quality encapsulation.
A capable LPM partner should operate multiple injection molding machines to handle parallel projects and volume scaling. Farway, for example, runs four low-pressure injection molding machines alongside its SMT, DIP, conformal coating, and testing lines in a 2,000-square-metre facility in LongGang, Shenzhen. This integrated setup allows encapsulation to happen on the same site as board assembly and testing, reducing handling risk and lead time.
Effective LPM begins long before the first shot of material. The partner should offer mold design consultation, material selection guidance, and prototype tooling to validate the encapsulation design before committing to production tooling. Farway's engineering team covers electronic, structural, and BOM engineering, supporting customers from NPI (new product introduction) through DFX (design for excellence) reviews and into mass production.
Encapsulation quality directly affects product reliability, so the partner's quality management framework matters. Look for certifications relevant to your industry:
| Standard | Scope |
|---|---|
| ISO 9001 | General quality management |
| ISO 13485 | Medical device quality management |
| IATF 16949 | Automotive industry quality management |
| ISO 14001 | Environmental management |
Farway holds all four certifications, along with UL, RoHS, SGS, and REACH compliance within its product certification scope. Its assembly work follows the IPC-A-610 standard.
Waterproofing claims must be verified, not assumed. A full-service partner should offer environmental testing alongside encapsulation — including high- and low-temperature reliability testing, thermal imaging inspection, and functional testing under load. Farway's testing capabilities span SPI, AOI, X-ray, ICT, FCT, thermal imaging, and oscilloscope-based testing, providing end-to-end verification that high reliability low pressure molding pcba meets both electrical and environmental specifications.
Different applications call for different thermoplastic adhesive formulations. Polyamide-based materials offer excellent adhesion and a wide operating temperature range, while polyolefin-based compounds provide superior chemical resistance. The partner should help ｓｅｌｅｃｔ the material that matches your operating environment, regulatory requirements, and cost targets.
When LPM is integrated into a one-stop manufacturing flow, the path from design to finished product becomes shorter and more controllable. A typical workflow at an integrated EMS provider like Farway looks like this:
By keeping every step under one roof, the manufacturer maintains full traceability — from material lot numbers to test records — and can resolve issues faster than a fragmented supply chain allows.
Even with capable equipment, LPM projects can stumble on a few recurring issues. Knowing them in advance helps smooth the path to production.
Low pressure molding gives electronics manufacturers a fast, gentle, and reliable way to protect sensitive assemblies from water, dust, chemicals, and mechanical stress. When the process is integrated into a full-service manufacturing operation — combining board fabrication, assembly, testing, and encapsulation under one quality system — the benefits multiply: shorter lead times, tighter traceability, and fewer handoffs that can introduce defects.
Farway Electronic brings together four LPM machines, certified quality systems spanning automotive and medical standards, and a complete PCBA-to-finished-product production chain in its Shenzhen facility. For teams seeking durable electronic encapsulation coating backed by in-house testing and engineering support, the company offers a practical path from prototype to volume production.
To discuss your waterproofing requirements, contact Farway Electronic at sales@farway.hk or visit the low pressure molding service page.
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