When working with a central processing unit (CPU), it’s important to consider the specifications around a heat sink that’s suitable for your unique application. Many times, thermal interface material is needed to ensure that all materials involved are thermally compatible with each other.
What is a thermal interface material?
Thermal interface materials (TIMs) are typically placed between two or more heat-sensitive manufacturing components to protect those components from heat-related adverse reactions. It’s important to understand which type of thermal interface material your application needs, where it is needed and how it should be applied. Some materials require very specific placement and pressure during installation. The two TIMs covered in this article are thermal pads and thermal paste.
Deciding Between Thermal Pads and Thermal Paste
Two of the most common thermal interface materials used include both thermal pads and thermal paste (commonly known as thermal grease). While both materials provide similar thermal management properties, they are used in widely different cases based on the nature by which they must be applied. Nonetheless, it’s important that both materials are in-touch with the heatsink or another heat-producing component during and after application, ensuring that all air gaps to external environments are sealed.
Thermal pads are notoriously easy to apply – many experts noting that pads are far less maintenance to apply than thermal paste. Simply put, the pads need to be laid onto their application with relative pressure.
Thermal pads are sometimes included with the heat-producing component to bypass the pad adhesion, making the manufacturer’s job even easier. Similarly, thermal pads are far less likely to shift out of their initial position compared to thermal paste.
They have a standardized heat dissipation capacity across the surface of the pad compared to the thermal paste’s liquid state, making that standardization more challenging to achieve. Upon application, the pad will react to the heat-producing component’s temperature by softening and therefore enabling the pad to fill interfacial gaps in the surface of the application.
As there are two sides of every coin, thermal pads also come with their own disadvantages depending on the application at hand. As thermal pads adhere to the heatsink, the pad will oftentimes mold to one of the heat-producing surfaces it touches.
Therefore, thermal pads must be replaced if the heatsink or other components nearby are moved.
Thermal pads cannot be used more than once, and if removed, each component must be handled with extreme caution – especially once the pad has adhered to other components of the application.
Thermal paste offers a similar solution to thermal pads, but being a liquid, the paste can be used in several ways that a thermal pad cannot. The paste is applied via dispenser (syringe, tube, etc.) directly to the central processing unit (CPU) or the heatsink, filling even the smallest interfacial air gaps to ensure efficient thermal transfer and conservation.
Though the paste is applied as a liquid, it solidifies over time to create a bond much stronger than that of the thermal pad. Therefore, applications using thermal paste are more durable and tend to have a longer lifespan.
Another key benefit of using thermal paste is the efficiency of the material. Very little paste is needed, as the heat transfer capacity is inversely correlated with the amount of thermal interface material used.
In other words, the TIM is most effective when a very thin layer is used, as opposed to using a more generous amount of the material. Of course, it’s important that enough of the material is used to fill all necessary gaps.
While the thermal paste certainly has several desirable properties – especially compared to their pad counterparts – it’s important to understand the potential risks associated with a material that requires manual application techniques.
Depending on the application, thermal paste may not be the best option for you. As the paste is manually applied as a liquid, it can be challenging to ensure an even coating.
Similarly, when applying the paste, it’s crucial to ensure that the entire surface area is covered as needed, and enough paste is used. While less it typically more when it comes to thermal paste, using too little will not adequately fill any air gaps that may be present.
The liquid state of thermal paste can lead to a mess and wasted material, so caution and precision are key.