Customer’s Application
The client is a manufacturer of industrial electronics, specialising in the design of compact, high-power-density DC-DC converter mod ules for use in factory automation and robotic systems. The application involves the full potting and encapsulation of the converter’s printed circuit board (PCB) using advanced electronic potting compounds designed for demanding industrial environments. This PCB is densely populated with high-heat-flux components, including power MOSFETs, inductors, and control ICs, all within a sealed, compact metal enclosure to ensure long-term electronic component protection.
The Engineering Challenge
The relentless industry drive towards miniaturisation creates a significant thermal management crisis for power electronics designers, which highlights the growing importance of thermal management for PCBs.
- High Heat Density: As power modules become smaller while handling more power, the components are packed more tightly together. This drastically reduces the surface area and air gaps available for natural convective cooling, leading to the formation of intense localised hotspots on components like MOSFETs. These hotspots can quickly exceed the safe operating temperature of the silicon, leading to performance degradation and premature failure, making effective PCB heat dissipation essential.
- High Thermal Resistance: Heat generated at the semiconductor junction must travel through a series of material layers to escape to the ambient environment: from the silicon die, through the component package, through the potting material, and finally to the device’s external heatsink or chassis. Air, a thermal insulator, trapped within the enclosure presents a major barrier in this path. High thermal resistance at any point in this chain will cause the junction temperature to rise to dangerous levels, increasing reliance on advanced thermal interface materials.
- Electrical Insulation Requirement: While the primary goal is to conduct heat, the potting compound must simultaneously act as a superior electrical insulator. It must prevent arcing and short circuits between high-voltage traces, component leads, and the grounded metal chassis, ensuring reliable PCB protection under continuous operation.
- Void-Free Encapsulation: The potting material must have excellent flow characteristics to penetrate the tight spaces under and around all components on the dense PCB. Any trapped air voids will act as insulating pockets, preventing heat from escaping and creating localised thermal failures. Selecting appropriate heat dissipation materials for electronic systems becomes critical to avoid such risks.
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Kohesi Bond offers proven thermally conductive potting solutions.
The Kohesi Bond Solution | Custom Engineered Certainty
The solution to this challenge lies in a specialised epoxy that possesses a seemingly contradictory set of properties: it must be an excellent thermal conductor while also being an excellent electrical insulator and provide good flow properties. This balance is often achieved through engineered PCB thermal management solutions tailored for compact assemblies.
- High Thermal Conductivity: The primary requirement is a high thermal conductivity, or K-value (e.g., > 1.2 W/m·K). This creates a low-resistance path for heat to flow away from the hot components and into the heatsink. This property is achieved by loading the epoxy resin with specialised thermally conductive but electrically insulating fillers, such as aluminium oxide, aluminium nitride, or boron nitride, forming a highly reliable thermal epoxy compound.
- High Dielectric Strength: To ensure electrical safety, the material must exhibit a high dielectric strength (e.g., > 430 V/mil), providing robust insulation against high voltages while functioning as a dependable heat-resistant potting compound.
- Low Viscosity and Good Flow: A low-viscosity, easily flowable epoxy is essential to ensure complete impregnation of the entire PCB assembly. This eliminates voids and maximises the surface area contact between the potting material and the heat-generating components, which is critical for effective thermal transfer. Vacuum potting techniques are often recommended to assist in this process, particularly when integrating high-performance thermal interface materials into compact electronic assemblies.
- Low Coefficient of Thermal Expansion (CTE): A low CTE helps to minimise the mechanical stress placed on the components and their solder joints during the thermal cycles of powering the device on and off.
- Strong Adhesion: The epoxy must adhere well to all surfaces within the assembly — the FR-4 PCB material, the various component packages, and the aluminium or copper housing, to create a stable and reliable thermal and mechanical interface. This performance is strengthened through advanced epoxy bonding adhesive chemistry engineered for durability.
To meet the application’s rigorous thermal management demands, Kohesi Bond’s experts custom-formulated KB 1040 CTE-LO. This specialised, two-component epoxy is engineered for exceptionally high thermal conductivity (1.4–1.5 W/m/K) and optimized flow properties to ensure seamless, void-free potting. Beyond its thermal performance, KB 1040 CTE-LO acts as a superior insulator, boasting a high dielectric strength of 450 volts/mil to prevent electrical leakage and arcing in high-density circuits.
Related Products
B 1040 CTE LO
Kohesi Bond KB 1040 CTE-LO is an exclusive two component epoxy system suitable for bonding, sealing, coating and encapsulation applications. Know more
It delivers superior mechanical strength and a remarkably low coefficient of thermal expansion (CTE), ensuring long-term dimensional stability. Furthermore, KB 1040 CTE-LO exhibits outstanding adhesion to diverse plastics, metals, and ceramics, maintaining structural integrity and high-performance electrical insulation even under extreme thermal cycling and mechanical stress.
The Result
The implementation of KB 1040 CTE-LO yielded immediate improvements in the DC-DC converter’s performance. Thermal imaging under full load revealed a 50°C reduction in peak MOSFET temperatures compared to the previous air-cooled design. This superior thermal management allowed the module to operate at a 30% higher power output without exceeding design limits, providing a significant competitive advantage.
Most importantly, eliminating overheating-related failures substantially increased the product’s Mean Time Between Failures (MTBF), drastically reducing warranty claims. By utilising an advanced epoxy loaded with specialised ceramic fillers, Kohesi Bond engineered a material that achieves the “paradoxical” goal of high thermal conductivity while maintaining a high dielectric strength. This ensures the converter remains perfectly insulated even as it efficiently dissipates heat. Kohesi Bond’s engineered certainty is safeguarding the client’s reputation for robustness in demanding industrial environments.
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. |
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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!
