Thermal Pad

A thermal pad is a pre-formed sheet of thermally conductive, pliable material — usually silicone loaded with ceramic or other conductive fillers — placed between a heat-producing component and its heatsink. Like thermal paste, its job is to displace insulating air from the contact interface; unlike paste, a pad arrives at a fixed thickness and conforms under clamping pressure rather than flowing like a grease. That one difference decides everything about where each belongs.

Pad versus paste

The two solve different problems, and the physics is unforgiving about which is which. Thermal paste excels at tight, flat interfaces — a bare die against a machined heatsink base — where clamping squeezes it into a film mere tens of microns thick; since an interface's thermal resistance scales with thickness, that thin film is hard to beat. A pad shines where there is a real gap to bridge or surfaces at different heights: it spans distances measured in fractions of a millimetre to several millimetres that paste physically cannot fill without slumping out. Pads are also forgiving to install — peel, place, clamp, done, with no coverage judgment calls — and many are electrically insulating, adding protection where a sink passes near exposed traces. The trade-off is honest: even a good pad presents higher thermal resistance than a well-applied thin paste layer, so putting a thick pad where a thin paste film belongs needlessly raises chip temperature.

Durability under mining conditions

Mining hardware runs hot continuously for years and cycles thermally at every restart and curtailment — the exact regime that degrades greases. Quality pads do not dry out, crack, or migrate the way paste can under repeated cycling, and they are immune to the pump-out effect that slowly squeezes paste from a joint that flexes with temperature. For gap-filling duty on a machine expected to run unattended for years, that stability is precisely the point: the pad performing in year four roughly as it did on day one.

Where pads live on a hashboard

On ASIC boards the division of labor is consistent. The primary chip-to-heatsink joints stay on paste — repair benches use dense silicone compounds specified for the job — because those junctions carry the most heat and reward the lowest resistance. Pads take the supporting roles: coupling voltage-regulator stages, inductors, and other secondary components that sit at different heights into a shared sink or the chassis, and generally bridging every interface too uneven for grease. During hashboard rework, treat pads as consumables: once compressed, a pad takes a set and does not reliably re-conform, so anything disturbed during heatsink removal should be replaced, not reused — the same discipline as reapplying paste after any joint is broken. Thickness must match the design gap; substituting a thicker or thinner pad than the original changes clamping force across the whole stack, and both extremes end in hot components.

The repair-bench rule

Choose by geometry, not habit: flat and tight gets thin paste, gapped or uneven gets the correctly sized pad, and every disturbed interface gets fresh material before power-on. If a board arrives with overheating that traces to crumbling pads or bare interfaces from a previous owner's shortcut, that is a routine fix — and if the diagnosis is beyond the home bench, start a repair with us and it gets done right.

When ordering replacements, three numbers matter. Thickness must match the mechanical gap the designer intended — measure the old pad or the gap itself rather than guessing. Thermal conductivity, quoted in W/mK, spans an order of magnitude across the market from bargain sheets to premium gap fillers; secondary components are forgiving, but anything dissipating real watts deserves the better material. Hardness (compressibility) determines how fully the pad conforms and how much force the assembly needs — an overly stiff pad on a large sink can bow a board, and a board bowed under clamping stress is a future solder-joint failure. Reputable industrial brands publish all three figures; unbranded sheets often perform far below their listed specs, which is a poor place to save money on a machine that runs continuously. Cut pads cleanly, keep protective films on until placement, and never stack two thin pads to fake one thick one — every added interface adds resistance.