Pad, paste or phase change?
Three materials, three jobs. Getting this choice right is worth more degrees than any amount of shopping for a bigger W/mK number.
| Thermal pad | Thermal paste | Phase change | |
|---|---|---|---|
| Gap it can fill | Fixed 0.5 – 3.0 mm | Microscopic only | 0.2 mm, self-levelling |
| Conductivity here | 12 – 15 W/mK | 3.8 – 8.5 W/mK | Paste-class once melted |
| Goes on | Peel and lay flat | Pea, line or spread | Drop in dry, heat once |
| Comes off | In one piece | Wipe with alcohol | Scrape after cooling |
| Reusable | Usually yes | No | No |
| Made for | VRM blocks, VRAM, M.2 drives | CPU and GPU dies under a cold plate | Laptops and set-and-forget builds |
The single question that decides everything
Is there a gap you can see, or are the two surfaces already touching?
If they touch — a processor lid under a cold plate, a bare die under a heatsink — you want paste. Two machined surfaces look flat and are not; at the scale that matters they are a landscape of ridges with air trapped between them, and air is one of the best insulators in the building. Paste displaces that air. It is not a filler and it is not glue: the thinner the layer, the better the result, because the paste itself conducts heat far worse than the metal on either side of it.
If there is a visible gap — memory packages under a backplate, a VRM block, an M.2 drive under a shield — you want a pad. Here the material has to be thick enough to touch both sides and soft enough not to hold them apart, which is why the range steps in half-millimeters and why measuring is the whole job.
The two awkward cases
Sometimes the gap is not the same height everywhere. A backplate that sits over memory packages and a choke at once is two different measurements, and one sheet cannot be right for both. Buy the two thicknesses, cut each to the component it covers, and lay them side by side rather than compromising on an average that touches neither properly.
The other case is hardware you do not want to open again. Phase-change film goes in dry, melts once on the first heat cycle and then stays put for years without the pump-out that eventually thins a paste joint under hard cycling. That is the trade: a slightly fussier install for a joint you can forget about.
Two things that are always wrong. Stacking thin pads to reach a thickness, and using so much paste that it runs off the die. Both add thermal barriers to a joint whose entire purpose is to remove them.
The compounds in this range
Three compounds — GC-2, GC-4 and the nano-diamond GC-5 — shown in the syringe sizes GELID sells them in, from the everyday tube to the one you keep for reseating a graphics card.
Phase change
HeatPhase Ultra, cut for Intel and AMD lids, for joints that should be installed once and then left alone.
Questions people actually ask
Can I use thermal paste instead of a thermal pad?
Only if the two surfaces already touch. Paste fills the microscopic roughness between machined metal; it cannot bridge a visible gap. Squeezed into a half-millimeter void it slumps, runs and leaves air behind, which is the one thing a thermal interface exists to remove.
How much thermal paste do I actually need?
For a mainstream desktop CPU, a pea-sized blob or a thin line down the middle. A one-gram syringe covers roughly four to six standard applications; the 3.5-gram tube is for people who reseat often or who are doing a graphics card, where the die is smaller but the job is fiddlier.
Does higher W/mK always mean lower temperatures?
Not by much once you are past the basics. Contact quality, mounting pressure and the thickness of the layer swamp the difference between a 8 W/mK compound and a 12 W/mK one. The number matters most when everything else is already right.
Do GELID pads need to be cut to shape?
Yes, and that is the point. They ship as rectangles from small squares up to long strips, and you trim them with scissors or a craft knife. Cut slightly oversize: a pad that squeezes out at the edges has definitely made contact.
Are thermal pads reusable?
Usually. A GP-series pad that has been compressed once will still work if you peel it off carefully and it has not torn or picked up dust. Paste is not reusable — clean it off with isopropyl alcohol and start again.
What is phase-change material and why is it solid?
HeatPhase Ultra sits as a dry, handleable film at room temperature and softens into a paste-thin layer the first time the chip gets hot, filling the surface roughness and then staying put. It does not pump out over heat cycles the way some pastes do, which is why laptop makers use it.
Which one for a laptop?
Phase change on the die, pads on the heat pipes and VRM. Paste is fine too, but laptops heat-cycle hard and are annoying to open, so the material that stays where you put it is worth the extra step.
Which one for a graphics card memory block?
A pad, almost always, and the thickness is the whole question. Measure it — the manufacturer’s original pads are frequently a different height from what the internet tells you.
Know the gap already?
Put the number into the finder and see every GELID sheet that fits it.
Open the thermal pad finder