All about Thermal Pads – An Introductory Guide

Thermal pads are essential in PC building for enhancing heat dissipation and maintaining safe component temperatures. This guide will provide a comprehensive overview of thermal pad terminology, types, usage recommendations, and frequently asked questions.

What Are Thermal Pads?

Thermal pads for CPU are materials engineered to transfer heat away from computer components. They comprise thermally conductive fillers like ceramic, graphite, or metal powders suspended in a polymer base. This forms a pliable, heat-absorbing material.

Thermal pads conform to microscopic ridges and valleys between mating surfaces. This displaces trapped air pockets that impede heat transfer. The conformal contact facilitates thermal conduction from hot components to heatsinks so the heat can dissipate.

How Do Thermal Pads Work?

Thermal pads work through the physics of conductive heat transfer. As electrons flow through powered components, they produce heat as a byproduct. The thermally conductive fillers in the pad absorb this heat.

The pad’s material matrix then spreads the heat laterally across the pad’s surface area rather than allowing hotspots to form. This distributes the heat so it can conduct through the pad’s thickness to the heatsink.

The heatsink draws heat away from the pad’s surface through its conductive metal fins. Finally, airflow from a fan or liquid cooling carries the heat away into the surrounding environment.

Key Terminology

• Thermal Conductivity – The thermal pad material properties allow it to conduct heat, which is measured in W/mK. Higher values equate to better heat transfer capability.
• TIM (Thermal Interface Material) – Substances like pads, pastes, or liquids are applied between components and heatsinks to improve heat transfer.
• Thermal Resistance – A material’s resistance to conductive heat flow. Measured in °C-in2/W. Lower values equal better cooling efficacy.
• Bond Line Thickness – The thickness of a TIM layer between surfaces. Thinner bond lines improve heat transfer.
• Thermal Impedance – A material’s overall resistance to heat flow, including contact resistance. Measured in °C/W.

Thermal Pad Materials

Thermal pads consist of a polymer base matrix filled with conductive filler ingredients such as:

• Ceramic particles – aluminum oxide, boron nitride, silicon carbide
• Graphite and graphene flakes
• Carbon fibers or nanotubes
• Metallic particles – aluminum, magnesium, nickel
• Thermal phase change materials

Higher percentages and thermally conductive types of fillers increase the pad’s efficacy. Common polymer bases include silicone, acrylic, rubber, or fiberglass.

Thermal Pad vs Thermal Paste

Thermal Pad Thickness Considerations

Choosing the proper thermal pad thickness is vital for optimal heat transfer:

• Thicker pads can conform better and accommodate unevenness
• Thinner pads reduce bond line thickness for heat to transfer through

Consider the pad pressure to reach proper deflection levels. For GPUs, 1.0-1.5mm pads are common. CPUs and M.2 SSDs use 0.5-2.0mm pads.

Applying Thermal Pads

Follow these best practices when installing thermal pads:

• Clean surfaces with isopropyl alcohol first
• Carefully remove all plastic film before application
• Avoid stretching or tearing pads to retain thickness
• Apply gradual pressure to conform the pad without gaps
• Use shims if the heatsink has uneven pressure distribution
• Replace old pads – don’t just reapply them

Thermal Pad Performance Factors

Consider these metrics when selecting a thermal pad product:

• Thermal Conductivity – Higher W/mK values transfer heat better
• Thermal Impedance – Lower °C/W indicates better real-world performance
• Temperature Range – Must withstand component operating temps
• Dielectric Strength – Important if electrically isolating pads
• Cold Flow – Prevents pump out after time
• Compressive Strength – Resists thinning under pressure