Electronics potting compounds are used to protect printed circuit boards and electronic components when the device must continue to function in the presence of:
- moisture,
- contaminants,
- vibrations,
- mechanical shocks,
- temperature fluctuations,
- and other critical operating conditions.
However, not all printed circuit board resins respond in the same way to these operating conditions. Epoxy, polyurethane, and silicone encapsulants have different characteristics, and the choice must be based on the application, the operating environment, and the performance requirements of the electronic system.
What are potting resins and electronic encapsulants?
Electronic encapsulants are materials used to insulate and protect boards, circuits, and electronic components from conditions that could compromise their performance and reliability.
Through the potting process, the material surrounds the component or assembly and creates more robust protection than a simple surface coating. For this reason, electronic potting resins are used primarily when the device is intended for demanding operating conditions.
What is meant by potting and encapsulation
The term potting generally refers to the filling of a container or an electronic assembly with a compound that, after curing, encapsulates the system.
Encapsulation, on the other hand, can also involve individual components or specific areas of the device.
In practice, the two terms belong to the same technological field and share a common goal: to create a protective barrier between the electronics and the operating environment.
Resin and encapsulant therefore do not refer to a single chemical. There are epoxy, polyurethane, and silicone formulations single-component and two-component, rigid or flexible, dielectric, thermally conductive, and formulated for specific application requirements.
What is potting used for?
A printed circuit board does not necessarily operate in a controlled environment. Temperature, humidity, contaminants, vibrations, and shocks can all act simultaneously on the materials and interfaces within the assembly.
A resin for protecting electronics can help to:
- electrically insulate components and connections;
- protect against water, humidity, and contaminants;
- mitigate the effects of vibrations and mechanical shocks;
- protect against chemicals;
- support the management of temperature variations;
- in specific formulations, facilitate heat transfer.
The level of protection is one of the aspects that distinguishes potting from conformal coating. The latter creates a thin film that follows the contour of the PCB, whereas in potting, the amount of material used is significantly greater and can go so far as to completely encapsulate the assembly.
This does not mean that one technology is always preferable to the other. They are different solutions, to be chosen based on the geometry, the level of protection required, the possibility of rework, and the expected operating conditions.
Which resins are used for printed circuit boards
For potting and electronic encapsulation, three main families of materials are used:
Epoxy encapsulants
Epoxy encapsulants generally feature formulations characterized by good electrical, adhesion, and mechanical and chemical resistance.
However, within the same family, there are significant differences in performance. Rigid systems are available for high mechanical protection, more flexible formulations designed to minimize stress on components, thermally conductive products, and one- or two-component systems.
For this reason, it is incorrect to automatically associate “epoxy” with a single set of properties.
The Electrolube product line, on the other hand, includes a variety of solutions. ER2188 is a general-purpose epoxy resin with good electrical properties, adhesion, and chemical and water resistance, while ER2220 combines environmental protection with thermal dissipation capabilities.
| Product | Type | Main characteristics |
| Electrolube ER2188 | Epoxy | General-purpose use, good chemical and water resistance, adhesion and electrical properties |
| Electrolube ER2220 | Epoxy | PCB encapsulation, environmental protection, heat dissipation and flame-retardant formulation |
Single-component epoxy encapsulants can be advantageous when you want to eliminate the mixing step, while two-component epoxy encapsulants allow for a wide range of combinations of stiffness, flexibility, thermal conductivity, and workability.
Polyurethane encapsulants
Polyurethane encapsulants represent another widely used family in electronic protection.
The available formulations can offer high toughness, flexibility, and resistance to water and moisture. These characteristics make them particularly attractive when the system must withstand mechanical stresses or when an excessively rigid structure would risk transferring stress directly to the components.
Even within the polyurethane family, performance can vary significantly depending on the formulation. Some products prioritize resistance to water and marine environments, while others emphasize chemical resistance, reworkability, thermal management, or lighting applications.
| Product | Type | Main characteristics |
| Electrolube UR5041 | Polyurethane | High toughness, tear resistance and seawater resistance |
| Electrolube UR5118 | Polyurethane | Good electrical properties, low water absorption, high toughness and seawater resistance |
| Electrolube UR5634 | Polyurethane | Low viscosity, suitable for LED encapsulation, resistant to water and mould growth |
| Electrolube UR5635 | Polyurethane | Low viscosity and a formulation suitable for LED applications in various environmental conditions |
Flexibility is therefore not the only parameter that defines a polyurethane encapsulant. When selecting a product, the chemical basis of the formulation, the operating environment, and the expected exposure to water, humidity, solvents, and temperature must also be evaluated.
Silicone encapsulants
Silicone encapsulants are particularly suitable when reliability must be maintained despite significant variations in operating conditions.
The structure of silicones allows for a combination of thermal stability and low elastic modulus. The material can therefore deform by absorbing part of the stress generated by differences in thermal expansion between PCBs, copper, components, ceramics, plastics, and metals.
This behavior becomes particularly important in systems subjected to repeated thermal cycles, vibrations, and shocks.
The product line includes both DOWSIL™ encapsulants and SYLGARD™ products, with formulations designed for different requirements: low stress, thermal conductivity, optical transparency, low outgassing, or applications in harsh environmental conditions.
| Product | Type | Main characteristics |
| DOWSIL™ 93-500 | Two-part silicone | Low outgassing according to ASTM E-595, physical and electrical stability, and a wide operating temperature range. Specifically designed for aerospace applications |
| DOWSIL™ CN-8760 | Thermally conductive silicone | Low viscosity, 1:1 mix ratio, room-temperature cure and moderate heat dissipation |
| DOWSIL™ EE-3200 GEL | Low-stress silicone | Reduced stress on components, moderate heat dissipation and good primerless adhesion |
| DOWSIL™ EI-2888 | Optically clear, primerless silicone | Low viscosity, good primerless adhesion and high optical performance for lighting applications |
| DOWSIL™ TC-6020 | Two-part, thermally conductive silicone | Medium viscosity, good dielectric properties and good heat dissipation |
| SYLGARD™ 170 | Two-part silicone | Low viscosity, flexibility over a wide temperature range and moderate thermal conductivity |
| SYLGARD™ 184 | Optically clear, two-part silicone | Good dielectric properties, high transparency and flexibility over a wide temperature range |
| SYLGARD™ 567 | Two-part silicone | 1:1 mix ratio, low viscosity, heat cure and good dielectric properties |
| SYLGARD™ Q3-3600 | Two-part, thermally conductive silicone | Low-viscosity encapsulant, good thermal conductivity, long working time and heat cure |
This variety also makes it possible to find encapsulants with high optical transparency for lighting applications, as well as formulations designed for thermal management or the protection of power electronics.
However, silicones are not a universal solution. Compared to some organic materials, they may exhibit lower initial adhesion, higher costs, and greater gas permeability. In applications that are highly sensitive to contamination, the volatility of the formulations must also be evaluated.
The choice must therefore take these aspects into account alongside the advantages offered in terms of elasticity and long-term stability.
Comparison of the 3 technologies
The characteristics of the individual formulation can significantly alter the behavior of the material, but some general differences help guide the selection process.
| Criterion | Epoxies | Polyurethanes | Silicones |
| Rigidity | From flexible to highly rigid, depending on the formulation | Generally greater deformation capability than epoxy systems | Low modulus and high elasticity |
| Adhesion | Generally high | Good adhesion | May require surface pretreatment or the use of a primer |
| Chemical resistance | Can be very high | Generally good | Depends on the formulation |
| Water and moisture | Highly resistant formulations available | Numerous formulations designed for humid environments or immersion | High stability in humid environments |
| Thermal cycling | Flexible and low-stress systems available | Good ability to absorb stress in flexible formulations | Particularly suitable for managing stress and differences in thermal expansion |
| Severe operating temperatures | Very good | Generally no higher than 130°C | One of the main strengths of silicone technology, with excellent performance at both low and high temperatures |
| Reworkability | Very difficult in rigid systems | Possible with some soft formulations | Generally possible |
| Thermal management | Thermally conductive versions available | Thermally conductive versions available | Wide availability of thermally conductive systems |
The correct approach, therefore, is not to ask which is “the best resin,” but how the material should behave throughout the device’s operational life.
High initial adhesion, for example, is not sufficient if, during thermal cycles, the material transfers excessive stress to the interfaces. Similarly, high flexibility is not necessarily an advantage when the application requires high structural rigidity.
Applications of resins for electronics
Resins for electronic circuits are used in a wide variety of systems. Geometries, temperatures, environmental conditions, and electrical requirements vary, so the material to be selected also varies.
Mechanical and environmental protection
In potting, the resin can fully or partially encapsulate the circuit and its components.
Generally, the primary objective is to protect the electronics from the external environment and provide mechanical protection for the electronic device against impacts, vibrations, and shocks.
Electrical insulation
Many encapsulants have dielectric properties and are designed to electrically insulate components and connections.
However, the resin for electrical insulation must be evaluated in conjunction with the other requirements of the application. Dielectric strength and insulation resistance are fundamental, but the material must maintain its characteristics even after exposure to the conditions expected during service.
Humidity, temperature, and contaminants can, in fact, affect the system’s electrical reliability over time.
Electrical windings and motors
Resins are also used to protect electrical windings, stators, rotors, and electric motors, where they can be applied through impregnation or encapsulation processes.
In addition to insulation, these applications may require thermal resistance, protection against moisture and fluids, and in high-power-density systems a greater ability to transfer heat.
The resin must therefore be selected by considering both the manufacturing process and the motor’s operating conditions.
Heat dissipation
Miniaturization, the increase in component density on the circuit board, and the growing use of power modules make thermal management an increasingly important factor.
A thermally conductive encapsulant can combine circuit protection with heat transfer to the housing or to a heat sink.
It is not sufficient to compare only the nominal value of thermal conductivity: geometry, thickness, filler content, interfaces, and the application process all influence the system’s actual performance.
Lighting and optical applications
In LED applications and lighting, the optical behavior of the material can also be a decisive factor.
The product line includes highly transparent polyurethane and silicone potting compounds and formulations developed to maintain optical performance under demanding operating conditions.
In these systems, transparency, material stability, the curing process, and behavior at operating temperatures must all be considered together.
How to choose a potting resin
The selection of an electronics resin should be based on the actual conditions under which the device will operate.
Temperature and thermal cycles
It is not enough to consider only the maximum temperature.
A device that continuously cycles between low and high temperatures can be subjected to significant stress due to the differing coefficients of thermal expansion of the materials comprising the assembly.
Modulus of elasticity, flexibility, and long-term behavior therefore become design parameters just as important as the nominal temperature range.
Humidity, water, and chemicals
It is essential to precisely identify which substances will come into contact with the resin.
Water, saltwater, oils, fuels, solvents, and other agents do not produce the same corrosive and aging effects; nor do two products belonging to the same chemical family necessarily offer the same resistance.
Mechanical stresses
Vibrations, shocks, and device movements require careful consideration when selecting the material and assessing its ability to absorb such stresses.
An encapsulant that is too rigid can transfer stresses to interfaces and components, while a more flexible formulation can reduce stresses in dynamic applications.
Electrical properties
For dielectric encapsulants, dielectric strength, insulation, and the stability of these properties over the device’s lifetime must be considered.
It is not just the initial value that matters, but the ability to maintain it after exposure to actual operating conditions.
Thermal management
When the PCB or components generate significant amounts of heat, the resin can become an integral part of the thermal path.
In this case, a thermally conductive formulation must be evaluated, and the system must be considered as a whole, not just the single value listed in the technical data sheet.
Manufacturing process
The resin must also be compatible with the manufacturing process.
Parameters to evaluate include:
- single-component or two-component;
- mixing ratio;
- viscosity and ability to fill cavities and complex geometries;
- pot life and gel time;
- curing at room temperature or under heat;
- any need for primers or surface pretreatments;
- any need for degassing;
- ability to automate mixing and dispensing;
- future need to rework the circuit.
A technically sound material that is incompatible with the manufacturing process cannot be used correctly.
Resins and potting compounds: the MD Poland offering
The MD Poland product line includes electronic potting compounds based on various technologies and brands, including:
- DOWSIL™,
- SYLGARD™,
- Electrolube,
The availability of different chemical families allows us to start not from a predetermined technology, but from the project’s requirements.
An effective selection takes into account:
- actual operating conditions;
- temperature and thermal cycles;
- materials present in the PCB and in the electronic device assembly;
- exposure to water, humidity, and chemicals;
- vibrations and mechanical stresses;
- electrical insulation;
- heat dissipation;
- geometry and quantity of material to be dispensed;
- manufacturing process.
MD Poland supports companies in selecting the most suitable technology and formulation and in defining the application process, evaluating material, application, and operating conditions together.
Discover the range of resins and encapsulants for electronics or contact the experts at MD Poland to identify the right solution for your application.
