What are some thermally conductive media?

1. Thermal Grease

Thermal grease is currently the most widely used thermally conductive medium. It is a paste-like substance made from silicone oil as the base material, with the addition of thermally conductive powders, thixotropic agents, and other fillers. It is produced through processes such as heating and depressurization, and grinding. It is amorphous and has a certain viscosity, providing excellent adhesion. It can completely fill the coated area without gaps and is not easily detached from the chip. Furthermore, thermal grease has no noticeable grainy texture, preventing scratches on the chip; the coating is thin, resulting in low thermal resistance. Its operating temperature is generally -50℃ to 180℃, and it possesses good thermal conductivity, high-temperature resistance, aging resistance, and oil leakage prevention.

During the heat dissipation process, after being heated to a certain condition, the thermal grease becomes semi-fluid, fully filling the gaps between the CPU and the heatsink, resulting in a tighter bond and enhanced heat conduction. Under normal circumstances, thermal grease is insoluble in water, not easily oxidized, and also possesses certain lubricating and electrical insulating properties.

2. Thermally Conductive Silicone

Like thermally conductive grease, thermally conductive silicone is made by adding thermally conductive powder to silicone oil and processing it. However, unlike thermally conductive grease, thermally conductive silicone can be cured, and the cured material is hard. Its thermal conductivity is slightly lower than that of thermally conductive grease. Currently, there are two types of thermally conductive silicone on the market:

(1) One type has adhesive properties after curing. In professional terms, it is a single-component thermally conductive adhesive. Manufacturers generally use this silicone as an adhesive between heat sinks and heat-generating objects. Its advantage is its very strong adhesion, but this is also its disadvantage. When we need to repair it, after a lot of effort to separate the bonded equipment and the heat sink, we often find a lot of solid silicone residue on the contact surfaces of the two. This silicone is quite difficult to remove completely. Because thermally conductive adhesive has both thermal conductivity and heat dissipation effects, it is suitable for bonding between two flat surfaces.

(2) The other type is a glossy solid after curing, which is a thermally conductive potting compound. As the name suggests, thermally conductive silicone sealant, because it requires potting, is not as viscous as adhesive but rather has a fluid, "flowing water" quality, making it suitable for use on large-area circuit boards with very high application efficiency. Most manufacturers use it on heat-generating components with uneven surfaces. Consider this: besides "flowing water," which can penetrate uneven areas completely, what other thermally conductive medium has this ability to enter irregular spaces? Therefore, for electronic components like power supplies with complex circuits, thermally conductive potting compound is the most suitable for heat dissipation. Its heat dissipation efficiency is higher than adhesive, but the solidified product is more brittle, and the residue is easier to remove.

In summary, regardless of the specific application, thermally conductive silicone sealant has strong thermal conductivity, but it can easily "stick" components to heat sinks. Therefore, it is necessary to recommend the appropriate silicone sealant based on the actual situation.

3. Thermally Conductive Putty

Temperature conductive putty is a new type of thermally conductive medium. It is a gel-like substance made from silicone resin as a base material, with added thermally conductive fillers and binders in a certain proportion, and processed through a special process. It possesses superior resistance to high and low temperatures, excellent weather resistance, radiation resistance, and superior dielectric properties. Like thermal grease, thermal putty is a paste, but unlike amorphous thermal grease, it can be molded into specific shapes, similar to modeling clay. This makes it very convenient to disassemble; any residue adhering to the heatsink can be wiped clean with a tissue, avoiding the drying and dripping problems of thermal grease. Therefore, it is equally suitable for use between electronic components and heat sinks/casings on both flat and uneven surfaces, ensuring tight contact, reducing thermal resistance, and quickly and effectively lowering the temperature of electronic components, thereby extending their lifespan and improving their reliability.

4. Graphite Pads

This thermally conductive medium is relatively rare and is generally used on objects with low heat generation. It uses graphite composite materials and undergoes certain chemical treatments, resulting in excellent thermal conductivity, making it suitable for heat dissipation systems of electronic chips, CPUs, and other products. In early boxed Intel P4 processors, the material attached to the bottom of the heatsink was a graphite thermal pad called M751. The advantage of this thermal medium is its non-stickiness, preventing the CPU from being pulled off the socket when the heatsink is removed.

5. Thermal Pads

Thermal pads possess excellent thermal conductivity and high-grade voltage resistance and insulation. With a thermal conductivity of 1.0~4.0 W/m*K and a voltage breakdown value exceeding 4000 volts, they are a viable alternative to thermal grease. The material itself has a certain degree of flexibility, allowing it to fit well between power devices and heatsinks or machine casings, achieving optimal heat conduction and dissipation, meeting the current requirements of the electronics industry for thermal materials. These products can be cut to any size to meet the needs of automated production and product protection. Thermal pads range in thickness from 0.5mm to 5mm, with a maximum thickness of 15mm for special requirements. They are specifically designed for heat transfer through gaps, filling these gaps to facilitate heat transfer between heat-generating and heat-dissipating components. They also provide shock absorption, insulation, and sealing, meeting the design requirements for miniaturization and ultra-thin devices. This makes them a highly versatile and practical new material.

6. Phase Change Thermal Conductive Materials

Phase change materials are primarily used in high-performance devices requiring low thermal resistance and high thermal conductivity. They are used in microprocessors and power devices requiring low thermal resistance to ensure excellent heat dissipation. Phase change thermal conductive materials undergo a phase change at 45℃-58℃ and flow under pressure to fill irregular gaps between the heat-generating element and the heat sink, displacing air and forming an excellent thermal interface.