How to apply Thermal Paste or Thermal Grease

Purpose of Thermal paste

The purpose of Thermal paste is to assist a heat sink in drawing away heat from a component. Most commonly custom thermal paste is used on a cpu, or processor.

How Thermal paste works

Thermal paste tries to fill imperfections present on any surface. Both your heat sink and cpu heat spreader will have tiny bumps and holes. These holes are filled with air. Air is bad for heat transfer.

However using too much can actually hurt heat transfer from your cpu to the heat sink. Thermal paste itself can act isolating. Furthermore a thick layer of thermal paste is likely to have a lot of tiny air bubbles. Again these will prevent perfect heat transfer.

Thermal paste application methods

Most common methods of applying thermal paste are the spread, cross, line and drop. Let’s check them out.

Spread: Don’t use it

The most recommended method for applying thermal paste is the spread. With the spread you are spreading the thermal paste or grease in an even thin layer on the entire surface of the heat sprayer. You can easily do this by using an old credit card.

Besides being very hard to get right this method also causes a lot of air to be trapped between the thermal paste. Therefore I cannot recommend it.

Cross: Don’t use it

Another method is to apply two lines in a cross shape. This method is rather easy.

This method has a high risk of applying too much thermal paste. Most thermal pastes are conductive. So if thermal paste touches the motherboard it can actually cause damage by shorting out circuits. I strongly suggest you avoid use this method.

Line: Good method

With the Line method a single stripe of thermal paste is applied to the heatspreader.

This method is very good. There is a very low chance of air bubbles. You will have to be carefull that no thermal paste leaks at the top and bottom sides.

Rice drop: Good method

The rice drop simply means putting a tiny dot of thermal paste on the center of the heatsprayer. Thanks to the pressure of the cooler the thermal paste will be spread and fill gaps where it is needed.

This method is excellent. There is very little risk of spilling. No air bubbles will form thanks to the pressure of the cooler.

The best method to apply Thermal Paste

Summarizing the different methods the line and rice drop are the best way to apply thermal compounds. Personally I prefer the rice drop because it limits the risk of spilling and it is extremely easy to get right. As a final suggestion you want to pay special attention to the point where you stop applying thermal paste. When you stop pressing the tube usually a tiny line will stick to your rice drop. So have some paper towels ready.

ps If something goes wrong you can always start over and remove the thermal paste with medicinal alcohol.