A heat sink is a passive thermal component, usually made of aluminum or copper, that absorbs heat from a hot electronic part such as a CPU, GPU, voltage regulator or SSD controller and spreads it over a large finned surface where it can be released into the air. In power and cooling within hardware, it is the basic building block of almost every cooling solution, from a bare aluminum block on a chipset to a large tower cooler with heat pipes.
A heat sink does not create cold. It lowers the thermal resistance between the chip and the ambient air, so the chip can dissipate its power at a lower temperature. Paired with a fan it becomes an active cooler; without one it relies on natural convection.
How a heat sink moves heat
Heat travels from the chip to the air through a chain of steps, and each step adds thermal resistance, measured in kelvin per watt (K/W). The chip temperature equals the ambient temperature plus the dissipated power multiplied by the total resistance of the chain.
| Step | Mechanism | Main design factor |
|---|---|---|
| Die to heat spreader | Conduction through solder or paste | Chip packaging, not user-controlled |
| Spreader to base | Conduction through thermal interface material | Paste quality and mounting pressure |
| Base to fins | Conduction, often through heat pipes or a vapor chamber | Material and heat pipe count |
| Fins to air | Convection and a small share of radiation | Fin area and airflow |
For example, a cooler with a total resistance of 0.2 K/W dissipating 150 W raises the chip about 30 K above the air inside the case. Halving the resistance halves that rise, which is why fin area, airflow and contact quality are the levers that matter.
Heat pipes are sealed copper tubes containing a small amount of fluid that evaporates at the hot end and condenses at the cool end. They carry heat to distant fins with an effective conductivity far above solid copper. A vapor chamber applies the same principle in a flat form, spreading heat evenly under a large base.
Materials and construction
The choice of material is a trade-off between thermal conductivity, weight and cost. Many coolers combine materials: a copper base and heat pipes with thin aluminum fins.
| Material | Thermal conductivity | Strengths | Weaknesses |
|---|---|---|---|
| Aluminum alloys | About 150-235 W/m·K | Light, cheap, easy to extrude | Lower conductivity |
| Copper | About 385-400 W/m·K | Excellent heat spreading | Heavy, more expensive, harder to shape |
| Copper base with aluminum fins | Mixed | Good balance of performance and weight | Joint quality affects results |
| Graphite sheets | Very high in-plane, low through-plane | Thin, used in phones and laptops | Poor at moving heat outward |
Manufacturing methods include extrusion for simple aluminum profiles, skived fins cut from a solid block, stacked fins soldered or pressed onto heat pipes, and die-cast shapes for complex enclosures. Soldered joints conduct heat better than press-fit ones.
Types of heat sinks in computers
Heat sinks appear in many forms inside a computer. The right type depends on the power to be dissipated and the space and airflow available.
| Type | Typical heat load | Where it is used |
|---|---|---|
| Passive plate or block | A few watts | Chipsets, VRMs, M.2 SSDs |
| Low-profile active cooler | About 35-95 W | Small form factor PCs |
| Tower cooler with heat pipes | About 120-250 W | Desktop CPUs |
| Dual-tower cooler | About 200-300 W | High-end desktop CPUs |
| GPU cooler with vapor chamber | About 200-450 W | Graphics cards |
| Fanless chassis heat sink | About 10-65 W | Silent PCs and industrial systems |
Liquid cooling is a related but different approach: a cold plate absorbs heat and a pump carries it to a radiator, which is itself a heat sink with a fan. The radiator simply moves the fin area to a more convenient place in the case.
Choosing and installing a heat sink
A heat sink is sized by the power the chip actually dissipates, not only by its nominal TDP, because modern processors can exceed TDP for long periods under boost. Physical fit is just as important: cooler height, RAM clearance and socket mounting must all match.
- Match the heat load: choose a cooler rated with margin for the processor’s sustained boost power.
- Check clearances: tower height against case width, and fin overhang against tall memory modules.
- Apply thermal paste correctly: a thin, even layer; too much paste insulates rather than conducts.
- Use even mounting pressure: tighten screws gradually in a cross pattern.
- Remove protective film from the base before installation, a frequent and costly oversight.
- Plan case airflow: a heat sink only works if fresh air reaches the fins and warm air can leave.
Symptoms of an inadequate heat sink
When cooling is insufficient, the chip protects itself through thermal throttling, reducing clock speed to stay within its temperature limit. The table below links typical symptoms to causes and fixes.
| Symptom | Likely cause | Remedy |
|---|---|---|
| Temperatures rise quickly under load | Poor contact or dried paste | Remount with fresh paste |
| Slow, steady rise over minutes | Fins saturated, weak airflow | Increase airflow or use a larger cooler |
| High temperatures after months | Dust clogging the fins | Clean the fins and filters |
| Uneven core temperatures | Uneven mounting pressure | Re-tighten mounting evenly |
| Loud fan at idle | Aggressive fan curve | Adjust the fan curve in firmware |
The short version
A heat sink is a piece of metal with many thin fins that sits on top of a hot chip. The metal pulls heat out of the chip, and the fins give that heat a large surface to escape into the air.
It works like a radiator in a room. More fins and more airflow carry more heat away. A heat sink does not make anything cold. It simply keeps the chip from overheating so it can run at full speed.
Where it makes a difference
A video editor notices that long exports on a desktop with a 125 W processor run much slower than benchmarks suggest. Monitoring software shows the CPU reaching about 100 °C within a minute and dropping its clock speed. The system uses a small low-profile cooler designed for roughly 65 W.
The editor replaces it with a tower cooler with six heat pipes and a 120 mm fan, applies fresh paste and adds a rear exhaust fan to the case. Under the same export, the processor now settles around 78 °C without throttling. The export finishes noticeably faster, and the system is quieter because the larger fins need less fan speed to move the same heat.