Effective thermal management is critical for computer functionality and longevity. As key heat generating components like CPUs and GPUs continue to advance in power and performance, there is an increasing need for high efficiency cooling solutions. The interface between these delicate electronics and their heatsinks is facilitated by thermal interface materials – specifically, thermal paste and thermal pads. But when should you choose pads over paste, or vice versa? This expert guide examines these interface options in-depth, providing everything you need to know to make the right choice.
What Are Thermal Pastes and Pads?
Before comparing pastes and pads, let‘s define what they are and how they work.
Thermal paste is a thermally conductive compound applied between the CPU/GPU and the heatsink. It is formulated to have high thermal conductivity, allowing efficient transfer of heat from the chip to the heatsink. Thermal paste is applied as a thick liquid or gel that then sets. Key properties include:
Thermal Conductivity: Measured in W/mK. Higher is better, with most quality pastes ranging from 3-20 W/mK.
Viscosity: Thickness of paste. Lower viscosity allows paste to fill microscopic gaps. High performance pastes aim for under 50,000 centipoises.
Composition: Various materials used including ceramics, metals, carbon, silicone. Impacts properties like conductivity, electrical insulation, and ease of use.
Thermal pads, meanwhile, are solid pad-like sheets made of thermally conductive material that is placed between surfaces. They conform to the components, facilitating heat transfer. Properties include:
Thermal Conductivity: Around 1-10 W/mK for most pads. High performance options reach 17 W/mK. Lower than typical pastes.
Thickness: Measured in mils (1/1000 inch) or mm. Thinner pads can enable better conductivity but thinner than ideal risks high thermal resistance.
Materials: Typically silicone, acrylic, graphite. Properties impact flexibility, durability, insulation, reusability.
Both pastes and pads serve as a thermal interface material (TIM) – improving conductivity from the heat generator (e.g. CPU die) to the heat spreader (e.g. heatsink). The TIM fills air pockets across uneven surfaces that would otherwise inhibit heat transfer. So which one performs this role best?
Thermal Paste vs Thermal Pads: Key Differences
While both products effectively move heat from chips to heatsinks, thermal pastes and pads vary significantly across some key metrics:
| Metric | Thermal Paste | Thermal Pad |
|---|---|---|
| Thermal Conductivity | Typically higher, around 7.5 W/mK avg. Specialized pastes reach 20+ W/mK. | Lower on average, 1-10 W/mK. High end around 17 W/mK. |
| Conformability | Excellent – paste can fill microscopic gaps | Poorer fit for uneven surfaces |
| Ease of Application | Needs care placing right amount of paste | Pads preformed to shape |
| Electrical Conductivity | Varies; metal-based pastes conductive | Most pads electrically insulative |
| Reusability | Not reusable | Can be reused if not adhered |
| Cost | Lower cost per use | Higher upfront cost |
Key differences that impact performance:
Thermal conductivity: Thermal pastes tend to be more thermally conductive, with specialty options reaching over 20 W/mK. The conforming nature of pastes also improves conductivity.
Conformability: The paste-like consistency enables superior fit to microscopic contours on surfaces. Pads conform poorly in comparison.
Ease of use: Pads are easier to initially place, while paste application takes more care. However paste lasts longer before needing replacement.
Composition: Metals improve conductivity but must be kept from circuits. Most pads are non-conductive.
Depending on use case and priorities, either pads or paste may be the better solution.
Thermal Paste vs Pads: Performance Comparison
So when applied properly, which thermal interface material actually cools PC components better?
Independent testing from sources like Tom‘s Hardware and Gamers Nexus sheds light on real world performance.
A Gamers Nexus test pitting thermal grizzly pads against Thermal Grizzly Kryonaut paste is insightful:
Chart via Gamers Nexus comparing CPU package temp using thermal pads vs quality thermal paste Source
The thermal paste offered superior cooling by a significant 5-10° C margin. Similarpaste-over-pad performance advantages are seen in Tom‘s Hardware testing:
Chart via Tom‘s Hardware showing lower temps with quality pastes Source
Why does the paste outperform? The conforming nature enables better fit with the microscopically uneven CPU and heatsink surfaces. This allows more effective conduction. Based on testing data, quality thermal paste clearly provides superior cooling to even high performance thermal pads.
However, performance metrics alone don‘t determine suitability. Pads offer their own advantages we‘ll explore next.
When To Use Thermal Pads Over Pastes
Thermal pads come out cooler in direct benchmarking. However, for some applications, thermal pads can still prove a smarter option:
Short term usage: For quick benchmarking or testing, pads avoid paste cure times and don‘t require cleaning off old paste. Just stick the pad on and later remove intact. Reusable for quick tests.
Electric insulation: Pastes with metal particles risk short circuiting motherboards if spilled. Non-conductive pads eliminate this hazard.
Simplicity: Paste application requires care – too little hurts cooling, too much makes a mess. Self adhesive pads are easier to apply for less involved users.
Reusability: As pads keep form, they don‘t need replacing each time a heatsink is reinstalled. Fresh paste is needed each reassembly.
For these niche use cases, thermal pad benefits can outweigh slightly poorer cooling. However for most users, thermal paste remains the top performing and recommended interface option.
Thermal Paste Selection Guidelines
With so many paste products available, choosing the right formula is vital. Follow these expert guidelines when selecting a CPU/GPU thermal paste:
Application environment: Factor in component TDP, overclocking, airflow. Higher demands need more extreme pastes.
conductivity: Around 7-13 W/mK offers the best balance. Too low hurts cooling, over 15 W/mK brings minimal gains for most.
Composition safety: Avoid electrically conductive metal pastes unless prepared to properly insulate circuits.
Viscosity: Under 50k centipoise enables spread into tiny gaps without being too thin or messy.
Real world tests: Prefer pastes like Noctua NT-H1 with proven superior cooling over spec sheet claims alone.
Application tools: Smooth spread requires the right tools – cotton swabs, spreaders, cleaning solution, and patience.
Curing considerations: "Burn in" paste by running system hot initially, and re-torque heatsink until paste fully sets.
Properly selecting and applying thermal paste enables CPUs, GPUs, and other components to run cooler, boosting system stability and component longevity.
Thermal Pad Selection Guidelines
While thermal pads underperform leading pastes in cooling ability, they still serve vital roles in some use cases. Here is how to best select a thermal pad:
Target Component: Match thickness to cooler used, component TDP and clearance space. Insufficient pads spike resistance.
Conformability: Softer pads like gelid extreme conform better to uneven surfaces. Rigid pads can air gap.
Phase Change: Some high end pads leverage phase change for drastically lower transient thermal resistance.
Adhesion method: Pads slipping can spike temperatures. Avoid messier glue with built in adhesion layers.
Composition safety: Many acrylic and silicone pads insulate electronically, avoiding short risk present in some pastes.
For applications like RAM cooling, SSD cooling or non-critical spots, thermal pad guidance ensures ideal fit.
Applying Thermal Compounds Correctly
With superior performing thermal paste selected and quality thermal pads on hand for niche roles, next comes proper application.
Applying thermal paste correctly is critical for enabling top cooling performance. Follow these professional tips:
Thermal Paste Application
- Start by cleaning CPU lid and heatsink base until shiny, residue-free metal exposed using isopropyl alcohol
- Place small ~rice grain size dot or thin line of paste in center of CPU (pea/X/line methods all effective)
- Use non-conductive spreaders as needed to evenly distribute to thin layer across full contact area
- Take care to keep paste only on CPU, avoiding overflow to sockets or board
- Mount heatsink according to manufacturer instructions, rotating evenly to squeeze out excess paste
- Initial boot allows paste to fully melt and set. Then re-torque heatsink mounts to ensure proper pressure applied.
Thermal Pad Application
- Confirm pad thickness matches clearance specs of the heatsink and component
- Thoroughly clean all contact surfaces, removing any old paste or pads
- Peel pad liner and firmly press pad against component, avoiding air pockets
- Use additional thermal adhesive if pad lacks sticky protective film
- Complete pad perimeter seals prevents lateral pump out premature failure
- Ensure pad remains firmly fixed to component through mounting and operation
Careful, conscientious application is essential, regardless of material used. Air gaps, overflow and loose pads cause hot spots that dramatically reduce cooler efficacy and component lifespan.
Maintaining Thermal Performance Long-Term
Thermal paste and pad performance degrades over time. Maintaining cooling efficacy requires properly replacing thermal material.
Thermal paste dries out and becomes less effective after 1-3 years of heat cycling. Routine replacement is key for sustained cooling, especially on high wear components like CPU and GPU dies. Clean off all old paste then reapply fresh material.
Thermal pads last longer, typically maintaining strong performance for 3-5 years before requiring swap out. Replacements are vital once pads get compressed or "pump out" over time.
Routinely checking core temperatures gives insight into cooling performance. Spikes over previously stable levels indicate possible thermal material degradation warranting refresh.
Conclusion
Thermal pastes and pads fill the tiny air gaps between computer components and coolers that hinder heat transfer away from hot electronics.
Thermal paste offers superior thermal conductivity and conformability compared to pads, directly translating to lower temperatures based on ample testing data.
For normal use cases, high performance thermal paste provides the best balance of cooling, ease of use, and affordability over long term operation.
Thermal pads better suit niche applications like temporary benchmarking and electrically sensitive components, thanks to traits like reusability and non-conductive materials.
By understanding thermal material properties and expert selection and application techniques, computer builders can help systems run reliably at peak temperatures for years. Thermal paste forms the ideal choice for most users, with thermal pads serving specialized roles.
