For PCB encapsulation, hot melt low pressure molding (LPM) sits between a thin conformal coating and full potting: it encloses the board in a thick protective body like potting, but it sets on cooling in seconds instead of curing for hours. Choosing between the three methods depends on how harsh the environment is, how much mechanical protection the board needs, the production volume and whether the board must be repairable. This article compares the options and explains when PCB encapsulation hot melt makes sense.
Key takeaways
- Conformal coating is a thin film that protects against moisture and contamination but adds little mechanical strength.
- Potting fills a case with resin for strong protection, but cure time, mixing and a housing add cost and steps.
- Low pressure molding with polyamide hot melt gives potting-like protection with short cycles and no separate housing for many parts.
Why PCBs need protection
Printed circuit boards fail in the field mainly through moisture, condensation, contamination, corrosion, vibration and thermal shock. Moisture plus ionic residues can cause leakage currents and electrochemical migration between closely spaced conductors. Vibration fatigues solder joints, and heavy components can crack their joints if they are not supported. Outdoor lighting, vehicle electronics, sensors and industrial controls all face some combination of these stresses.
Encapsulation adds a barrier between the board and its environment. The three common approaches are conformal coating, potting and low pressure molding. They differ in how thick the barrier is, how it is applied and how long production takes.
Conformal coating, potting and LPM compared
The table below summarizes the general tendencies of each approach.
Three PCB protection methods at a glance (general tendencies)
| Point | Conformal coating | Potting / LPM |
|---|---|---|
| Layer | Thin film | Thick, fully enclosing |
| Mechanical protection | Low | High |
| Process time | Coat, then cure or dry | Potting: long cure; LPM: seconds |
| Housing | Needs separate housing | Potting: needs case; LPM: mold forms shape |
| Rework | Possible | Difficult (potting); limited (LPM) |
Actual performance depends on the material, design and process; confirm with tests on the real assembly.
Conformal coating is a thin polymer film, typically tens of micrometers thick, applied by spray, dip or selective coating. Common chemistries include acrylic, silicone, polyurethane and parylene. IPC-CC-830 is a widely referenced qualification standard for coating materials. Coatings are light and keep the board compact, but they offer little protection against impact or immersion and still require a housing.
Potting fills a case or shell around the board with liquid resin, usually epoxy, polyurethane or silicone, which then cures. It offers strong protection against moisture, vibration and impact. The drawbacks are long cure times, mix-ratio control, degassing to avoid voids, the cost and weight of the case and resin, and very difficult rework.
Low pressure molding places the board in a mold and injects molten hot melt, typically polyamide, at low pressure. The material flows around components, fills the mold and sets as it cools, so a finished part can come out in well under a minute. The mold forms the outer shape, so a separate housing is often unnecessary. For a closer look at cycle time and cost, see low pressure molding vs potting.
When PCB encapsulation hot melt is the right choice
PCB encapsulation hot melt by low pressure molding tends to fit well when:
- Volumes are medium to high, so the mold cost is spread over many parts and short cycles matter.
- The part is compact, such as a sensor, connector module, small controller or LED driver, where the molded body can also be the outer shell.
- Cables exit the board, because the same shot can seal the cable entry and form a strain relief.
- Solvent-free processing is preferred over two-part resins or solvent-based coatings.
It is less suitable for large boards with tall components, where the molten material would need long flow paths, or for products that must be repaired at board level. Very high continuous temperatures can also exceed what a thermoplastic can handle, in which case a cured system is considered.
Design for molding helps. Leave room for the material to flow around tall components, avoid sharp unsupported edges that could move under flow, and plan where the mold will clamp the board or cable. Our article on low pressure molding process parameters covers typical temperature, pressure and cycle ranges.
Choosing an encapsulation material
Whatever method you choose, check the material against the actual operating conditions:
| Requirement | What to check |
|---|---|
| Temperature range | Softening at high end, brittleness at low end |
| Water and dust | IP rating tests on the finished part (IEC 60529, ISO 20653 for vehicles) |
| Flame rating | UL 94 class required by the product |
| Adhesion | Bond to solder mask, component bodies, cable jackets and housings |
| Chemicals | Oils, fuels, cleaning agents, salt spray |
For hot melt LPM, adhesion to the cable jacket and to the solder mask is often the deciding factor for sealing performance, so trials should use the real board and cable. For flame retardancy without halogens, see halogen-free flame retardant hot melts. Our guide to connector sealing with polyamide hot melt covers related sealing tests.
LPM materials from SILVERSTAR CHEMICAL
SILVERSTAR CHEMICAL Co., Ltd. has produced its own polyamide hot melts in South Korea since 2011 and supplies them under the ERAMID brand. Its solvent-free polyamides for low pressure molding are used to protect PCBs, sensors, connectors and wire harnesses, with UL 94 V-0 flame-retardant grades and thermal stability grades up to 200°C, and offer shorter cycles than potting. The company handles raw material selection, formulation and quality inspection itself and can tailor viscosity and formulation to an application.
Product information is on the LPM solutions page, and company details are in the SILVERSTAR CHEMICAL company FAQ. Grade data is available on request.
Frequently Asked Questions
Q. What is PCB encapsulation hot melt?
It usually means low pressure molding: a polyamide hot melt is melted and injected at low pressure into a mold around the board, where it sets on cooling to form a protective body.
Q. Is low pressure molding better than potting?
Neither is better in every case. LPM offers short cycles and often removes the need for a housing; potting can suit large boards and very high continuous temperatures. The choice depends on part size, volume, environment and rework needs.
Q. Does conformal coating make a board waterproof?
Generally not for immersion. A coating protects against humidity and contamination, but full water and dust sealing usually needs a housing, potting or molding, confirmed by IP tests on the finished part.
Q. Can a molded PCB be reworked?
Rework is limited. The thermoplastic can be softened with heat, but removing it without damaging components is difficult, so LPM is best for boards that are not repaired at component level.
Q. Does SILVERSTAR CHEMICAL supply hot melt for PCB encapsulation?
Yes. Its ERAMID solvent-free polyamides for low pressure molding protect PCBs, sensors, connectors and wire harnesses, with UL 94 V-0 flame-retardant grades and thermal stability grades up to 200°C.
Share your board size, component heights, cable type and operating environment, and we will suggest a polyamide grade for molding trials. Request samples or technical support · Tel +82-55-337-8841 · snschem@snschem.kr
