In our previous post, we explored the critical thermal problem facing modern AI hardware. Now, let’s get into the specifics of the solution. For the engineers tasked with designing and building these powerful systems, selecting the right Thermal Interface Material (TIM) is not a matter of guesswork; it’s a precise engineering decision that directly impacts performance and reliability.
While the market offers a variety of TIMs—from thermal greases to phase-change materials—thermal pads have become a go-to solution for many industrial and high-performance computing applications. Their consistent thickness, ease of application, and clean, reliable performance offer significant advantages on the assembly line.
Here’s what you need to know to make an informed choice.
Key Properties of Thermal Pads, Explained
- Thermal Conductivity (W/mK) This is the most critical metric you will evaluate. Thermal conductivity measures a material’s ability to conduct heat. The higher the value, the more efficiently the material will transfer heat away from the component. For high-power AI processors, you’ll typically need a pad with a thermal conductivity of 5 W/mK or higher, and for the most demanding applications, you may even require materials exceeding 15 W/mK.
- Hardness & Compressibility A thermal pad’s primary job is to fill microscopic air gaps between two surfaces. A pad that is too hard will not conform to surface irregularities, leaving air gaps that impede heat transfer. A soft, compressible pad, on the other hand, will conform to the surface with minimal pressure, ensuring maximum contact and a highly efficient thermal path. This is particularly important for components with uneven surfaces or applications where mounting pressure is a concern.
- Electrical Properties (Conductivity vs. Insulation) Not all thermal pads are created equal when it comes to electricity. You must choose a material that fits your circuit design.
- Electrically Insulative Pads: These are the most common choice and are essential for applications where the component and heat sink are at different electrical potentials. They prevent short circuits and are used for applications like MOSFETs, voltage regulators, and other components on a circuit board.
- Electrically Conductive Pads: These pads contain conductive fillers (like graphite or metallic particles) and are used for grounding or EMI shielding purposes while also transferring heat.
- Thickness & The “Thin to Win” Principle When it comes to TIMs, thickness is a major factor. The “Thin to Win” principle states that a thinner thermal interface material will generally have lower thermal resistance. While thicker thermal gap fillers are necessary to bridge large gaps (often found in power supplies or multi-board systems), you should always aim for the thinnest pad possible that can still effectively fill the gap and provide a stable connection.
Application-Specific Guidance
- For High-Power GPUs and CPUs: Focus on high thermal conductivity (8+ W/mK) and good compressibility to ensure a flawless connection to the heat sink.
- For Memory Chips (VRAM) & Power Delivery Components: A moderately conductive and conformable pad is often sufficient. Here, the focus is on covering multiple smaller chips and dissipating heat across the board.
- For Large-Gap Applications: If you’re working with a system with significant air gaps, you’ll need a highly compressible thermal gap filler.
At NEDC, we understand that selecting the right material is a complex process. Our engineering team works with a vast portfolio of advanced thermal materials from leading manufacturers. We can not only help you choose the ideal material but also provide custom die-cut pads to your exact specifications, ensuring your project achieves optimal thermal performance.