In modern electronics manufacturing, protecting delicate components from moisture, vibration, dust, and thermal stress is no longer optional — it is a design requirement. Among the available protection methods, low pressure molding with overmolding capability has emerged as a preferred solution for manufacturers who need reliable encapsulation without risking damage to sensitive circuit boards, sensors, and connectors. This article explores what this technology offers, why it stands out compared to alternatives, and what to look for when choosing a manufacturing partner that provides low pressure molding with overmolding service.
Low pressure molding (LPM) is an encapsulation process that uses thermoplastic hot-melt adhesives — typically polyamide (PA) or polyolefin (PO) based materials — injected at low pressure to protect electronic assemblies. The injection pressure generally ranges from 3.5 to 14 bar (approximately 50 to 200 psi), which is a fraction of what conventional injection molding requires. When combined with overmolding capability, the process goes a step further: it allows a second material to be molded over an existing substrate or component, creating a unified, sealed, and mechanically robust part in a single operation.
The material is heated to a relatively moderate temperature (180–240°C) and flows gently around the inserted component. Because aluminum molds are used and remain comparatively cool, heat is drawn away quickly from the encapsulated electronics, keeping solder joints and temperature-sensitive elements within safe limits. Once cooled, the material bonds directly to the substrate through natural adhesion — no primers, curing agents, or additional bonding steps are needed.
The defining advantage of low pressure molding is right in the name: low pressure. Traditional high-pressure injection molding operates at 1,700 bar or more, which can crack fragile components, dislodge fine-pitch parts, or warp thin PCB substrates. Low pressure molding reduces injection force by over 99%, making it safe for encapsulating populated circuit boards, bare wire bonds, delicate sensors, and MEMS devices. This is why industries that deal with low pressure molding for sensitive electronics — from medical devices to automotive control modules — have adopted the process as standard practice.
Properly designed low pressure overmolded parts can achieve IP67 or IP68 ingress protection ratings, meaning they are dust-tight and can withstand continuous immersion in water. The thermoplastic material forms a seamless, void-free enclosure around the component, blocking moisture, chemical exposure, salt spray, and corrosive gases. For products deployed outdoors, in engine compartments, or in industrial washdown environments, this level of sealing is critical for long-term reliability.
Low pressure molding with overmolding consolidates multiple manufacturing steps into one. Instead of separately potting a board, applying a conformal coating, adding a mechanical housing, and sealing cable entries, the overmolding process achieves encapsulation, sealing, strain relief, and structural support in a single molding cycle. Cycle times typically range from 15 to 60 seconds, and because no curing is required (the thermoplastic solidifies by cooling), parts are ready for downstream assembly or testing immediately after ejection.
Aluminum molds used in low pressure molding are significantly less expensive and faster to machine than the hardened steel tooling required for high-pressure injection molding. This makes LPM particularly cost-effective for low-to-medium volume production runs and prototyping. Material waste is also minimal — the thermoplastic hot-melt adhesives are reworkable and recyclable, and runners and flash can often be reground and reused. For manufacturers running multiple product variants or iterating on designs, this flexibility translates directly into shorter lead times and lower per-unit costs.
Overmolding capability opens up design possibilities that single-material processes cannot match. A manufacturer can combine a rigid substrate with a soft overmold layer for vibration damping, add integrated strain relief at cable exits, or encapsulate a PCB while leaving specific connectors or antenna regions exposed. The range of available materials — from rigid polyamides to soft polyolefins and TPU — allows engineers to tune hardness (Shore A 30 to Shore D 60), chemical resistance, thermal performance (−40°C to 150°C), and even biocompatibility for medical applications.
Did you know? Some polyamide-based hot-melt materials used in low pressure molding are up to 80% bio-based and fully reworkable. This means encapsulated parts can be heated and opened for prototyping, field repairs, or component recovery — something that is practically impossible with two-part epoxy potting compounds.
Material selection is central to the success of any low pressure overmolding project. The three main families of materials each serve distinct purposes:
Low pressure molding with overmolding capability serves a broad spectrum of industries, each with distinct protection requirements:
To understand why low pressure molding with overmolding is often the preferred choice, it helps to compare it with two common alternatives: traditional potting and high-pressure injection molding.
| Factor | Low Pressure Molding | Potting (Epoxy Resin) | High-Pressure Injection Molding |
|---|---|---|---|
| Injection Pressure | 3.5–14 bar | N/A (pour or dispense) | 1,700+ bar |
| Cycle Time | 15–60 seconds | Hours (curing required) | Seconds (high volume) |
| Mold Material | Aluminum (lower cost) | Silicone or plastic shells | Hardened steel (high cost) |
| Component Safety | Safe for delicate electronics | Safe but slow | Risk of damage to fragile parts |
| Environmental Sealing | IP65–IP68 | Good, but void-prone | Variable (depends on design) |
| Reworkability | Yes (thermoplastic, reheatable) | No (thermoset, permanent) | No (high-pressure bond) |
| Typical Use Case | PCBs, sensors, connectors, cable assemblies | Large enclosures, low-volume potting | Structural plastic parts, high-volume housings |
As the comparison shows, low pressure molding occupies a sweet spot: it delivers the speed and repeatability of injection molding without the high forces that endanger sensitive components, and it avoids the long curing times and permanence of epoxy potting.
Not all electronics manufacturers offer low pressure molding in-house. Many outsource encapsulation to third parties, which adds lead time, communication overhead, and quality risk. When a manufacturing partner has overmolding capability integrated into its own production line, several advantages follow:
Farway Electronic, based in LongGang, Shenzhen, operates a 2,000-square-metre manufacturing facility equipped with four dedicated low-pressure injection molding machines. The company's PCBA low pressure injection coating service covers the full production chain — from technical consulting and engineering support through product and mold development to volume production.
Applications supported by Farway's low pressure molding line include medical and industrial sensors, LED lighting modules, mobile-phone and power batteries, connector harnesses, circuit boards, and microswitches. The company holds ISO 9001, ISO 13485 (medical devices), and IATF 16949 (automotive) certifications, ensuring that overmolded products meet industry-specific quality management requirements.
What sets Farway apart is its integrated one-stop manufacturing model. Customers can have their PCBs fabricated, components sourced and inspected, SMT and DIP assembly completed, conformal coating applied, low pressure overmolding performed, and finished products tested and assembled — all within the same facility. This eliminates the coordination overhead and quality variability that come with multi-vendor supply chains, particularly for products that require both PCBA and encapsulation under controlled conditions.
Farway has served more than 100 industry customers across over 20 countries and regions, with experience in transportation, new energy, security, medical, and communication applications. Whether the requirement is a prototype run of a new sensor design or medium-volume production of waterproof connector assemblies, the company's low pressure molding line is configured to handle both with the same process controls.
Low pressure molding with overmolding capability offers a compelling combination of component safety, environmental protection, production efficiency, and cost effectiveness. For electronic products that must survive harsh conditions — whether in automotive engine bays, medical environments, outdoor installations, or industrial settings — it provides a single-step encapsulation solution that outperforms both potting and high-pressure molding in most real-world scenarios.
Choosing the right manufacturing partner is just as important as choosing the right process. A partner with in-house overmolding capability, integrated testing, and relevant industry certifications can significantly reduce development time, improve product reliability, and simplify supply chain management. Farway Electronic's combination of PCBA manufacturing expertise, four low-pressure molding machines, and ISO/IATF-certified quality systems makes it a practical choice for companies seeking end-to-end electronics manufacturing with encapsulation under one roof.
Looking for a reliable partner for your next overmolding project? Explore Farway's low pressure molding services or contact the team to discuss your requirements.
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