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Heatsink paste is a product designed to increase thermal conductivity between a processor and a heatsink used to draw heat away from the processor. Heatsinks are an important cooling component in an electronics system, designed to keep the processor from overheating while it is working. Heatsink paste or a similar thermal conductor is usually applied at the factory when products are manufactured, and people who build their own electronics use heatsink paste in their work as well.
As a processor works, it can become extremely hot. If there is no way for the heat to dissipate, the heat can build up and eventually damage the processor, causing the system to fail. Heatsinks are installed in close proximity to processors to conduct the heat and typically a fan is mounted near the heatsink to vent the heat, keeping the system as cool as possible. However, the space between the processor and the heatsink can create a highly inefficient energy transfer, as air does not conduct heat well. Heatsink paste is used to close that gap with a conductive substance.
On the macroscopic level, the heatsink and the processor can look like they are securely butted up against each other, with no gaps for air. However, on a microscopic level, the surfaces are coarse. The coarse surfaces do not meet up, allowing air gaps to be present. Heatsink paste, made with various conductive materials like metals suspended in a silicone paste, fills these gaps.
This substance is greasy and slightly fluid. Only a very thin layer is needed to conduct heat effectively away from the processor. Numerous manufacturers produce an array of brands and may sell them under generic labels as “thermal paste” or some variant thereof. The products usually come in applicators to make it easy for people to apply small dots of heatsink paste to electronics components.
When working with heatsink paste, it is a good idea to wear gloves. While the product is not harmful to touch in most cases, it is greasy and difficult to remove. Wearing gloves will help people keep their hands clean. If an applicator is not available, a toothpick or similar object can be used to scoop up small amounts of heatsink paste and deposit them. It is important to avoid overapplying, as a little bit of paste goes a long way. If too much is applied, when the heatstink and processor are nestled back together, the paste can squeeze out between them and make a mess.