Can I Put Thermal Paste on Thermal Pads?

If there is one common mistake some systems designers makes is putting thermal paste on thermal pads.

This is not right – you cannot use these thermal interface materials together. It will reduce heat transfer, thereby compromising the cooling performance.

Let’s explore this in detail, so that you don’t make this mistake in your next project.

Why it is Not Recommended

· Increased Thermal Resistance

Applying thermal paste over a thermal pad traps heat rather than transferring it quickly. Heat transfers best through direct, solid metal-to-metal contact even a small increase in thermal resistance can affect system efficiency and long-term reliability.

Moreover, use either a thermal pad or thermal paste according to the equipment manufacturer’s specifications. Adding the two materials will produce uneven contact, forcing heat to pass through more materials before reaching the cooling surface.

· Creates Trapped Air Pockets

Adding thermal paste is unlikely to improve performance in industrial thermal management because the two materials may not bond evenly. When the heat sink is installed, the paste may spread unevenly, preventing the pad from compressing as designed. This leads to leaving microscopic air pockets in between that reduce heat transfer, increasing operating temperatures, maintenance costs, and affecting system reliability.

· Possibility of Slippage

Applying thermal paste over a thermal pad is unnecessary and increases the possibility of contamination without improving cooling performance. It increases the risk of paste spilling beyond the intended contact area, resulting in assembly errors, maintenance costs, and electrical issues.

Moreover, non-conductive paste can also attract dust when forced onto nearby electronic components, making future maintenance more difficult and affecting manufacturing efficiency.

· Affect the Compression on Thermal Pads

For manufacturers, OEMs, and maintenance teams, maintaining the correct compression of thermal pads is important. Thermal paste can prevent thermal pads from compressing evenly causing some areas to be over-compressed while others remain under-compressed.

Thermal pads have a specific thickness that allows the pad to fill gaps evenly. Adding thermal paste on top creates uneven pressure during installation, preventing the thermal pad from compressing uniformly. Improper compression may lead to inconsistent contact, reduced heat transfer, localized hot spots, and lower cooling reliability in electrical equipment.

· Will Alter Intended Thermal Interface

Thermal pads are designed to transfer heat across larger gaps, adding paste doesn’t boost their performance. They are thicker and generally have lower thermal conductivity and adding paste can prevent the thermal pad from compressing evenly. This results in reduced heat transfer and inconsistent pressure across the surface.

In short, both thermal paste and thermal pads offer excellent solutions, and mixing them introduces performance risks without any benefit. Their performance and applications differ and selecting the correct thermal interface material for your gap size and thermal requirements can extend your product’s lifespan.

FAQs

How do you choose the correct thermal interface material?

In most cases, you should choose a thermal interface material (TIM) based on gap size, compression ratio, operating temperature, electrical insulation and long-term reliability.

For instance, thermal paste works well in CPUs, where the gap thickness is 0.02 to 0.1 mm. On the other hand, you can apply thermal pads in LED modules, EV batteries, power supply systems and telecommunication equipment.

Can thermal paste replace thermal pads?

Thermal paste cannot replace thermal pads in every application. It can only replace a thermal pad when the gap between the heat source and the heat sink is extremely small and the surfaces fit tightly together.

What is the difference between thermal paste and thermal pads?

When should you replace thermal pads?

• When the pad is damaged.
• When upgrading cooling hardware.
• During heat sink removal.
• After long-term operation.
• If the device overheats.
• During major maintenance.

Need Help in Choosing the Right Thermal Interface Material

As your experienced OEM thermal pad supplier in China, our engineers will help you in the TIM selection process. Once we receive your application requirements, our team will evaluate the thermal conductivity targets, operating temperature, gap size and compression requirements. With this, Gallop will recommend a custom solution – contact us now.