Thermal Pads vs Thermal Paste: The Best Choice for Mounting Your Heatsinks

 Effectively transferring heat away from sensitive electronics components requires mounting specialized heatsinks to spread thermal energy.

A thermally conductive layer gets inserted between the IC surface and heatsink base for the best heat transfer rates into the fins/spreaders.

The two most common interface layer types used are:

Thermal Paste - Viscous silicone greases filled with thermally conductive particles to fill microscopic gaps. Requires precise manual application for even coverage.

Thermal Pads - Solid phase change films that conform when pressure gets applied without messy applications. Just peel and stick.

So should you employ messy pastes or convenient pads when installing heatsinks onto ICs, GPUs, PCBs and other hot electronics?

We’ll compare thermal interface materials focusing on:

• Thermal performance differences
• Ease of application
• Longevity and maintenance
• Cost considerations

By the end, you’ll know whether thermal grease pastes or attached pads serve as the best choice when mounting heatsinks for cooling needs.

Let’s get started!

Thermal Paste Overview

Thermal paste has reigned supreme for many years as the interface material of choice when heat sinking electronics components. These silicone or ceramic based compounds filled with thermally conductive particles:

• Fill microscopic air pockets between mounting surfaces
• Improve thermal transfer compared to just metal-on-metal
• Available as spreads, loose fillers, or consolidated pastes

By filling air gaps that act as insulation, thermal pastes effectively act like solder allowing heat energy to flow between objects. This lets heatsinks pull more heat from contact areas.

Common brand name pastes include Arctic Silver, Noctua NT-H1, and Thermal Grizzly Kryonaut. Better formulations leverage advances like diamond particulate filler or liquid metal alloys for minimal interface resistance.

Now let’s examine thermal pad based alternatives...

Thermal Pad Overview

Thermal pads offer another solid state conductive layer option without messy grease application. Pads consist of:

• Rubberized conformal fill material
• Fiberglass reinforcing
• Conductive filler additive like ceramic or graphite

Pads get manufactured into standardized shapes/sizes, or provided die-cut for particular IC packages. Simply peel off the release liner, stick pad directly onto components that need cooling, and then fasten heatsinks atop.

No mess or precise manual spreading needed. Conforming properties fill voids nicely. Popular brands include Bergquist Gap Pad VO Ultra Soft, Fujipoly SARCON, and Laird Tflex HD.

With both materials providing thermally conductive junctions understood—let’s compare how they differ in key categories.

Thermal Performance: Pastes vs Pads

First and foremost, the effectiveness at transferring thermal energy plays a huge role choosing between pastes and pads.

In general, traditional thermal pastes edge out pads slightly regarding absolute cooling capabilities. The following factors contribute advantages with paste materials:

Particle Density - Pastes get formulated with higher possible loadings of thermally conductive filler particles like silver, carbon, diamond or ceramics (~65%+ by weight). Pads peak around 10-20% filler concentrations. This gives pastes higher conductivities (15+ W/mK) over pads (5 W/mK).

Conformability – The wet liquid or semi-solid nature of pastes coats mating surfaces better at a microscopic level despite surface roughness or flatness imperfections. Pads can develop small voids reducing conductance.

Contact Pressure – Excessive mounting pressures may squeeze pads causing reduced performance. Pastes tolerate pressure levels across a wider range.

However, for normal mounted components under standard installation practices, thermal pads perform nearly comparably (+/- 5-10%) while bringing other advantages...

Ease of Application: Pads Win

Applying traditional thermal paste properly for peak performance requires meticulous care and skill:

1. Clean mating surfaces with alcohol
2. Cut correct size blob onto component centre
3. Use spreader to evenly distribute thinly
4. Avoid trapped bubbles for good surface contact
5. Reapply if voids get noticed

This process guarantees proper coverage while avoiding excess overflow or uneven regions if done quickly before curing sets in. A steady hand stays necessary working the viscous material into place.

In contrast, thermal pads deploy rapidly with zero skill needed thanks to peel and stick application directly onto parts requiring cooling prior to heatsink attachment. No mess, preparation, tools, or practice required. Just peel, stick, mount heatsink.

Long Term Reliability Favors Pads

Both pastes and pads effectively conduct when first applied. But material durability and drying determines long term performance.

Thermal pastes inevitably dry and crack over time - decreasing effectiveness requiring reapplication after 1-2 years. Cycling between temperature extremes accelerates breakdowns shortening lifespans further as volatiles evaporate out.

Comparatively, insulating polymer binders give thermal pads much longer stable usable lifespans over 5-10 years. The solid pad material resists drying plus handles temperature fluctuations better. Less risks of pump-out and adhesive breakdown too.

Cost Comparison: Pastes Generally Cheaper

Both application types deliver excellent thermally conductive junctions cost effectively. But differences exist:

• Thermal Pastes - only need tiny amounts making grams stretch a long ways. Cost ~$5-$20 per use.
• Thermal Pads – collecting die cut shapes for various sizes adds costs. However still affordable in bulk averaging $1-$5 per pad.

If using frequently across vast production volumes with many one-off sized components, pastes tend to cost less overall. But for small volumes or large standardized ICs, pre-cut pads better suit.

Now let’s shift into collateral factors influencing the pastes versus pad decision.

Other Considerations Between Pastes and Pads

Beyond core performance versus application comparisons, a few other factors potentially sway decisions:

Heatsink Mounting Method – Permanent epoxy affixed heatsinks work fine with pads. But spring clip mounted sinks seeing frequent mounting/dismounting would gradually degrade thermal pads. Pastes handle this with reapplication.

Electrical Isolation – Sometimes electrical isolation becomes necessary between components and heatsinks tied to chassis ground. Thermal pads commonly utilize dielectric films ideal for this unlike conductive pastes.

Phase Change Needs – Applications seeing extreme heat spikes may leverage phase change materials for thermal load buffering. Encasing these inside pads creates self-contained thermal solutions.

Adhesive Requirements – When heatsink or component mounting methods require supplemental mechanical adhesives or epoxy, thermal pastes already include suitable binders. Pads then add unnecessary stickiness.

Consider unique application needs influencing optimal materials.

Now let’s shift into summarizing key decider factors.

Thermal Paste vs. Pad Summary

Consideration	Thermal Paste	Thermal Pads
Thermal Conductance	Higher (~15+ W/m*K)	Moderate (~3-8 W/m*K)
Application Method	Messy meticulous spreading	Clean peel and stick
Long Term Reliability	Dries and cracks over time	Stable performance for years
Electrical Isolation	Typically electrically conductive	Optional insulated versions
Customization/Versatility	Any shapes/sizes	Relies on die-cut supply
Costs	Cheap <$1 per use	Moderate $<5 per pad

For most common heatsink mounting needs onto CPUs, GPUs or power electronics - thermal pads make the easiest and most reliable long term choice. Unique high performance demands may necessitate thermal pastes with higher conductivities and thinner bond lines. But convenience wins out for generic needs.

Conclusion

Smoothing heat transfer from electronics into heatsinks using thermal interface materials boosts cooling efficiencies compared to just direct solid contact. Both conductive pastes and pads facilitate this critical junction role.

Thermal pastes reign supreme minimizing thermal resistances thanks to extreme filler concentrations that get manually spread into microscopic voids. But convenience and longevity favors thermal pads peel and stick approach despite slightly reduced conductance.

For steadfast set-it-and-forget-it heatsink bonding demands, thermal pads take the crown for hassle free deployment that lasts. However, exotic cooling pursuits pursuing every last degree drop may need traditional pastes ultimate capabilities.

Either way, leveraging thermally conductive junction layers pushes cooling potentials further when managing electronics heat generation limits. Confidently select between handy pads ready for simple integration or highest performance pastes needing skilled application depending on thermal needs and longer term maintenance appetites.

And that wraps up our in-depth assessment covering considerations, tradeoffs, and recommendations choosing