Customer’s Application
The client is a leading manufacturer of high-density, switch-mode AC-DC power supplies intended for use in medical diagnostic equipment and laboratory instrumentation. The application is the full potting and encapsulation of the power supply’s high-voltage PCB assembly using flame-retardant potting compounds. This process is not only for environmental protection but is also a mandatory step to meet stringent international safety and flammability standards.
The Engineering Challenge
For manufacturers of power electronics, safety and regulatory compliance are paramount design drivers requiring advanced flame-retardant materials.
- Fire Safety and Flammability: The highest priority is to prevent the start or propagation of a fire in the event of a catastrophic component failure, such as a shorted capacitor or an overloaded transformer. The materials used within the power supply, including the potting compound, must not act as fuel. Instead, they must be self-extinguishing to contain any thermal event.
- UL 94 V-0 Certification: To legally sell their products into key markets like North America and Europe, and specifically for medical and IT equipment applications, the final power supply unit must be tested and certified by a recognised body like Underwriters Laboratories (UL). A critical part of this certification is ensuring that the polymeric materials used meet the UL 94 V-0 flame retardancy rating standard. This is a non-negotiable requirement for market access.
- High Voltage Insulation: The potting epoxy must provide a robust dielectric barrier to prevent electrical arcing between high-voltage primary-side components and the low-voltage, user-accessible secondary side. It also increases the creepage and clearance distances, which are critical safety parameters in high-voltage design.
- Thermal Management: While flame retardancy is the primary goal, the potting compound must also be capable of conducting heat away from the heat-generating switching components. Effective thermal management reduces the operating temperature of the components, which in turn lowers the probability of a thermal failure that could initiate a fire in the first place.
Enhance PSU safety with Kohesi Bond’s flame-retardant potting solutions.
Built to support UL94 V-0 compliance and reliable performance.
The Kohesi Bond Solution | Custom Engineered Certainty
To mitigate the risk of catastrophic failure in high-voltage environments, Kohesi Bond custom-engineered an epoxy that was driven by the need to meet strict regulatory requirements and ensure the highest level of safety using a specialised UL 94 V-0 epoxy.
- UL 94 V-0 Rating: The single most critical property is that the epoxy must be officially recognised by UL as meeting the V-0 standard. This is the highest rating for flame retardancy for plastics, indicating that a vertical specimen stops burning within 10 seconds after the ignition source is removed, without any flaming drips. This certification must be documented on a UL “Yellow Card” for the specific material formulation and thickness used. Alternatively, independent testing of this epoxy can be conducted at UL or other accredited facilities to secure a UL 94 V-0 compliance certificate. This provides official proof of the material’s flame-retardant performance for regulatory submissions, though it does not constitute a formal UL Yellow Card certification.
- Halogen-Free Formulation: In line with modern environmental and safety regulations such as RoHS, the flame-retardant system should be halogen-free. This means it does not contain bromine or chlorine-based flame retardants, which can release toxic and corrosive gases when burnt.
- High Dielectric Strength: To ensure electrical safety and prevent faults, the material must possess a high dielectric strength and high volume resistivity.
- Good Thermal Conductivity: A thermally conductive formulation (e.g., > 0.8 W/m·K) is highly desirable to help dissipate heat, improve the power supply’s efficiency and reliability, and reduce the risk of a fire-initiating event.
- Low Exotherm Cure: Potting a relatively large volume like a power supply requires an epoxy system with a low exothermic reaction. This prevents excessive heat buildup during the curing process, which could damage the very electronic components the epoxy is intended to protect.
To meet these stringent safety and performance requirements, Kohesi Bond’s experts custom formulated KB 1631 FR-2, a specialised two part epoxy adhesive engineered for superior flame retardancy. This halogen-free formulation is designed to meet UL 94 V-0 standards, providing essential self-extinguishing properties associated with UL 94 V-0 certified materials that mitigate fire risks without releasing toxic or corrosive gases. Beyond its safety profile, KB 1631 FR-2 features a low-exotherm cure, making it ideal for potting the large volumes typical of power supply units while protecting sensitive internal components from excessive heat buildup during the curing process.
Related Products
KB 1631 FR-2
Kohesi Bond KB 1631 FR-2 is a two component, room temperature curing epoxy system. This flame retardant epoxy generates low smoke and contains a non-halogenated filler. Know More
This high-performance system offers a rare combination of good thermal conductivity and excellent electrical insulation, boasting high dielectric strength to prevent electrical leakage. KB 1631 FR-2 ensures long-term operational integrity through its robust mechanical strength and first-rate adhesion to various plastics, metals, and ceramics. Even in high-voltage environments subject to thermal stress, this epoxy maintains its structural and insulating properties, providing a reliable, compliant foundation for next-generation power electronics using a dependable UL 94 V-0 potting compound.
The Result
By encapsulating the power supply unit with KB 1631 FR-2, the manufacturer successfully passed all UL safety and flammability tests on the first attempt. This eliminated the need for costly redesigns and accelerated the time-to-market by several months. Beyond achieving UL 94 V-0 compliance, the epoxy’s thermal conductivity enhanced the unit’s long-term reliability, which unlocked high-value opportunities in the medical and data centre industries, leading to a projected 40% increase in sales.
For electronics OEMs, UL certification is a strategic business imperative that dictates global market access. By building their devices on a foundation of pre-certified materials like KB 1631 FR-2, manufacturers vastly simplify their own path to regulatory approval. Kohesi Bond provides more than a flame-retardant solution; it delivers guaranteed market access, reduced project risk, and faster revenue generation in an increasingly competitive landscape.
Technical Specifications Summary
| Parameter | Requirement | Significance |
| Thermal Conductivity (K) | > 1.2 W/m/K | Enables the efficient transfer of heat away from critical component hotspots. |
| Dielectric Strength | > 430 volts/mil | Prevents electrical arcing, short circuits, and ensures operational safety. |
| Volume Resistivity | > 1013 ohm-cm | Confirms the material’s high electrical insulation properties. |
| Viscosity (Mixed) | < 10,000 cps | Ensures complete, void-free filling around densely packed components for optimal thermal contact. |
| Service Temperature Range | -40°C to +120°C | Maintains mechanical and thermal stability above typical operating temperatures of industrial electronics. |
| Coefficient of Thermal Expansion (CTE) | < 25 ppm/°C | Ensures stress-free potting by matching expansion rates, protecting components and solder joints from cracking. |
Choose Kohesi Bond for high-quality industrial adhesive solutions.
Engineered for performance, compliance, and durability.
Utsav Shah is a 34-year-old entrepreneur with a passion for scientific discovery. Utsav’s journey began with a deep dive into materials science, earning degrees from USC and the Institute of Chemical Technology. He’s the visionary founder of Kohesi Bond, a top-rated adhesive manufacturer, and Cenerge Engineering Solutions, a leader in heat exchangers and cryogenic pumps. With over a decade of experience, Utsav consults across various industries, ensuring they have the perfect adhesive solution for their needs. Connect with him on LinkedIn!
