The increasing demand for high-performance and compact power electronics places significant requirements on the thermal management of modern semiconductor technologies. In particular, silicon carbide (SiC) and gallium nitride (GaN) semiconductors offer considerable advantages over conventional silicon solutions, including higher voltage resistance, lower switching losses, and improved efficiency at elevated temperatures. However, this higher power density also results in increased cooling needs. Innovative solutions are needed.
Top-Side Cooling:
Efficient Head Dissipation
With top-side cooling, heat is dissipated directly through the top of the semiconductor chip - instead of through the bottom as before. This reduces thermal resistance, improves temperature distribution, and leads to longer service life and higher efficiency for the entire system.
Therefore, top-side cooling is an interesting and innovative solution for developers, which we will explore in depth in our webinar with Kerafol on October 16.
Use this opportunity to learn more about the advantages and applications of top-side cooling and KERAMOLD®, and ask your questions directly to us and our partner Kerafol. Register here for the webinar on October 16:
Variants of Top-Side Cooling
We offer various versions of top-side cooling - including the TO263-7 in both isolated and non-isolated versions, as well as the TOLT.
| Top-Side Cooling TO263-7 (non-isolated) | Top-Side Cooling TO263-7 (isolated) | Top-Side Cooling TOLT (non-isolated) | |
|---|---|---|---|
 |  |  | |
| Voltage | 750V + 1200V | 750V + 1200V | 750V |
| RDson | From 18mΩ | From 16mΩ | From 9mΩ |
Additional chips are also available.
More information can be found on our homepage:
Go to SemiQ Website Go to PNJ Website
Challenges of Conventional TIMs for Top-Side Cooling
To optimize heat dissipation in top-side cooling, so-called TIMs - thermal interface materials - must meet several requirements: They should have high thermal conductivity, minimize thermal contact resistance, provide electrical insulation (where the cooling surface of the semiconductor is not already isolated), and offer high mechanical stability and reliability.
Conventional Thermal Interface Materials Compared
Thermal Pastes
Thermal pastes are characterized by their low bond-line thickness (BLT), resulting in very low thermal resistance. However, they are not always electrically insulating and are not suitable for compensating mechanical tolerances. Additionally, some commercially available pastes tend to exhibit the so-called pump-out effect during intensive power cycles, where the material moves out of the contact area due to repeated thermal stress, degrading heat dissipation.
The KP100 from Kerafol offers a new solution thanks to its specially formulated filling. The datasheet for this new paste will soon be available on our homepage.
Phase-Change-Material
Phase-change materials (PCM) melt at higher operating temperatures, thereby reducing their contact resistance. They require special mounting methods and are suitable for applications with very low mechanical tolerances where electrical insulation is not required.
Go to datasheet for PCMs 16125c from Kerafol
Gap Filler Liquids
The use of gap filler liquids has become a popular solution, especially for higher quantities. The combination of high thermal conductivity, low material costs, and easy automation via dispensing systems offers many advantages.
Unlike the previously mentioned product groups, gap filler liquids are also electrically insulating. Their application in liquid form requires no pressure and eliminates any mechanical stress on the heat source. The subsequent curing process does require additional time in production, but enables an efficient and stable thermal connection - even with larger mechanical tolerances and layer thicknesses.
The silicone-free GFU 15 stands out for its easy processing at room temperature, high electrical insulation, and good thermal conductivity for applications with large manufacturing tolerances, while GFL 3030 and GFL 3040 offer very high thermal performance and cost-effective processing, especially for demanding thermal requirements.
Discover all gap filler liquids
The Gamechanger: KERAMOLD®
KERAMOLD® is a specially developed TPE-based granulate that is highly thermally conductive and electrically insulating. It combines the advantages of various material groups in the field of TIMs (thermal interface materials). In the overmolding process, KERAMOLD® is applied directly to the PCB or semiconductor chip, creating a custom-fit, thermally conductive, and electrically insulating protective layer - without any curing process.
| Type | Thermal Conductivity (W/mK) | Thermal Resistance (K/W) | Color | Breakdown Voltage (kV) | Hardness (Shore A) |
|---|---|---|---|---|---|
| Keramold 15 | 1.5 | 1.66 | Orange | > 16 | 65-80 |
| Keramold 20 | 2.0 | 0.63 | Grey | 3.0 | 15-30 |
| Keramold 20N | 2.0 | 0.63 | Grey | 3.0 | 30-45 |
| Keramold 25 | 2.5 | 0.50 | Red | > 16 | 40-60 |
Application Areas for Top-Side Cooling with KERAMOLD®
Top-side cooling presents several mechanical, electrical, and thermal challenges simultaneously. Thanks to its excellent insulation properties combined with high mechanical flexibility, KERAMOLD® is particularly suitable for use with non-isolated top-side cooling semiconductors in high-voltage applications with moderate mechanical tolerances, which can be bridged with relatively low contact pressure.
- Minimized Contact Resistance: The overmolding process can minimize the contact resistance between the KERAMOLD® material and the semiconductor. The high softness and elasticity of the material contribute to this, as it falls within the low Shore A range - unlike conventional plastics.
- High Thermal Conductivity: Thanks to special fillers, KERAMOLD® products achieve thermal conductivity of over 2.5 W/mK in the Z-direction (through-plane) and over 3.2 W/mK in the X/Y-direction (in-plane) - significantly higher than conventional plastics. A material with 3.5 W/mK (KERAMOLD35) is already in development. Improved heat dissipation and additional heat spreading enable more efficient cooling of hot spots and potentially more compact heat sink designs.
- Custom Fit: The 3D shape of the TIM not only improves heat transfer but also facilitates the management of leakage currents. Not only the contact surface of the semiconductor, but also, for example, the pins are connected and encapsulated. Material utilization is very high and reproducible with this method.
KERAMOLD® has a CTI value of >600 V, belongs to insulation class I, and can help reduce component spacing.
- Excellent Mechanical Strength: Overmolding with soft and elastic TPE additionally protects the semiconductor from mechanical stresses such as vibration, CTE mismatch, moisture, and environmental influences - extending the lifespan of electronic components.
- Efficient Manufacturing Process: Overmolding with KERAMOLD® results in shorter process times in manufacturing. In comparison, curing of 2K materials such as potting or gap filler materials takes significantly longer. The manufacturing quality and repeatability of overmolding are very high.
Your All-in-One Solution:
Complete encapsulation of the PCB and SiC semiconductor eliminates the need for additional materials and process steps such as potting or conformal coating. The KERAMOLD® material was developed not only for heat transfer but also for protection of the electronic assembly.
Are you interested in top-side cooling and KERAMOLD®?
On October 16, we will be hosting our webinar together with experts Wolfgang Höfer and Simon Gumbel from Kerafol. Dive deeper into the topic with us and get all your questions about top-side cooling and KERAMOLD® answered!
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