Almost every modern electronic device generates heat, whether we notice it or not. Without proper heat management, our electronic systems would either destroy themselves or, conversely, be severely limited in their computing capabilities.
The average TechSpot reader will think, of course, CPU and GPU cooling, but why does RAM usually not need fans to keep it cool? Why is there such a huge disparity between the performance of a mobile processor and a desktop processor, even though their dies are fairly similar in size? Why have recent performance gains from new chip generations started to slow down?
While transistor counts continue to grow, we’re increasingly running into the physical and thermal limits of silicon. Leakage current rises as transistors shrink, and the heat generated per square millimeter becomes harder to dissipate. In recent years, the industry has shifted toward advanced packaging techniques – like chiplets, 3D stacking, and interposers – to work around these limits rather than brute-force past them. Performance improvements are now less about shrinking transistors and more about clever architectural, interconnect, and thermal design strategies.
The bring proper answers to these kinds of questions that involve heat and the physics of how computers work on the nanoscale, this article will touch on the basic science of heat, how and why it is generated in electronics, and the various methods we have developed to control it.
The Basics of Heat: How Energy Moves Through Electronics
If you remember high school physics, heat is simply the random motion of the atoms and molecules that make up our world. When one molecule has higher kinetic energy than another, we say it is hotter. This heat can be transferred from one object to another when they come into contact, continuing until the two reach equilibrium. This means the hotter object will transfer some of its heat to the cooler object, with the end result being a temperature somewhere between the two.
The time it takes to transfer heat depends on the thermal conductivity of the materials involved. Thermal conductivity measures a material’s ability to conduct heat.
An insulator like Styrofoam has a relatively low thermal conductivity of around 0.03, while a conductor like copper has a high thermal conductivity of about 400. At the two extremes, a true vacuum has a thermal conductivity of 0, while diamond has the highest known thermal conductivity, exceeding 2,000.
One important thing to remember is that heat always flows toward colder areas, but technically, there’s no such thing as “cold” – we only perceive something as “cold” if it has less heat than its surroundings.
One important thing to remember is that heat always flows toward colder areas, but technically, there’s no such thing as “cold” – we only perceive something as “cold” if it has less heat than its surroundings. Another key definition we’ll need is thermal mass, which represents an object’s inertia against temperature fluctuations. With the same size furnace, it’s much easier to heat a single room than an entire house. This is because the thermal mass of a single room is much smaller than that of an entire house.
We can put all these concepts together with the simple example of boiling water. When you turn on the stove, the hot flame comes into contact with the cooler pot. Since the material making up the pot is a good thermal conductor, heat from the fire is transferred into the water until it boils.
The time it takes to boil depends on the method of heating, the pot material, and the amount of water. If you tried to boil a pot of water with a small lighter, it would take forever compared to using the large flame of a stove. This is because the stove has a much higher thermal output, measured in watts, than the small lighter.
Next, your water will boil faster if the pot has a higher thermal conductivity because more heat will be transferred to the water. If you were rich enough, a diamond pot would be the holy grail! Finally, we all know a small pot of water will boil faster than a much larger one. This is because with the smaller pot, there is less thermal mass to heat up.
Once you’re done cooking, you can let the water cool down naturally. When this happens, the heat from the water is released into the cooler room. Since the room has a much higher thermal mass than the pot, its temperature won’t change by much.
The Three Amigos (Sources) of Heat in Chips
Now that we understand how heat works and moves between objects, let’s talk about where it comes from in the first place. All digital electronics are made up of millions or even billions of transistors. For a more detailed look at how they work, check out Part 3 of our study on modern CPU design.
Essentially, transistors are electrically controlled switches that turn on and off billions of times a second. By connecting a bunch of them together, we can form the complex structures of a computer chip.
As these transistors operate, they dissipate power from three sources: switching, short-circuit, and leakage. Switching and short-circuit power are both considered dynamic sources of heat because they are influenced by the transistors turning on and off. Leakage power, on the other hand, is considered static since it remains constant and is not affected by the transistor’s operation.
We’ll start with switching power. To turn a transistor on or off, we have to set its gate to ground (logic 0) or Vdd (logic 1). It’s not as simple as just flipping a switch though since this input gate has a very small amount of capacitance. We can think of this as a tiny rechargeable battery. In order to activate the gate, we must charge the battery past a certain threshold level. Once we’re ready to turn the gate off again, we need to dump that charge to ground. Although these gates are microscopic, there are billions of them in modern chips and they are switching billions of times a second.
A small bit of heat is generated every time that gate charge is dumped to ground. To find the switching power, we multiply the activity factor (the average proportion of transistors switching at any given cycle), the frequency, the gate capacitance, and the voltage squared together.
Let’s look at short-circuit power now. Modern digital electronics use a technique called Complementary Metal Oxide Semiconductors (CMOS). Transistors are arranged in such a way that there is never a direct path for current to flow to ground. In the above example of a NOT gate, there are two complementary transistors. Whenever the top one is on, the bottom one is off and vice-versa. This ensures that the output is either at a 0 or 1 and is the inverse of the input.
As we switch transistors on and off however, there is a very short amount of time when both the transistors are conducting at the same time. When one set is turning off and another is turning on, they will both conduct when they reach the mid point. This is unavoidable and provides a temporary path for current to flow directly to ground. We can try to limit this by making the transistors between On and Off states faster, but can’t fully eliminate it.
As the operating frequency of a chip increases, there are more state changes and more instantaneous short-circuits. This increases the heat output of a chip. To find short-circuit power, we multiple the short-circuit current, operating voltage, and switching frequency together.
Both of these are examples of dynamic power. If we want to reduce it, the easiest way is to just decrease the frequency of the chip. That’s often not practical since it would slow down the performance of the chip. Another option is to decrease the chip’s operating voltage. Chips used to run at 5V and above while modern CPUs operate around 1V.
By designing the transistors to operate at a lower voltage, we can reduce the heat lost through dynamic power. Dynamic power is also the reason your CPU and GPU get hotter when you overclock. You are increasing the operating frequency and often the voltage, too. The higher these go, the more heat is generated each cycle.
The last type of heat generated in digital electronics is leakage power. We like to think of transistors as being either completely on or off, but that’s not how they work in reality. There will always be a tiny amount of current that flows through even when the transistor is in the non-conducting state. It’s a very complicated formula and the effect is only getting worse as we continue to shrink the transistors.
When they get smaller, there is less and less material to block the flow of electrons when we want them to be off. This is one of the main factors limiting the performance of new generations of chips as the proportion of leakage power keeps increasing each generation.
Also read: Sustainable Computing: Reduce, Reuse, Recycle. But… Is It Really That Simple?
The laws of physics have put us in a corner, and that corner is getting tighter. This is also why AI accelerators like NPUs and TPUs – which pack massive amounts of compute into tiny areas – pose major new thermal design challenges. These chips are often deployed in data centers where airflow and power budgets are limited, making efficient thermal strategies more important than ever.
Beyond performance, sustainability is also becoming a central concern. Data centers are increasingly exploring liquid immersion cooling, heat recycling, and low-GWP refrigerants to meet environmental targets while keeping power-hungry hardware under control. Green cooling tech isn’t just a future goal anymore – it’s actively being deployed in modern infrastructure.
Thermoelectric cooling, or Peltier devices, remain niche but have seen renewed interest in recent years. Some manufacturers have experimented with hybrid AIO + TEC solutions to push cooling performance beyond what traditional air or water can provide. While these setups still tend to be inefficient and power-hungry, improvements in thermoelectric materials could eventually make them more practical for specific use cases.
Likewise, vapor-compression chillers and phase-change systems are still primarily reserved for data centers and extreme overclocking. But there’s ongoing research into compact, efficient cooling solutions using advanced refrigerants and novel compressor designs that could one day bring sub-ambient cooling to more mainstream setups.
Take a Chill Pill: How We Keep Chips Cool – Cooling Techniques Explained
So we know where heat comes from in electronics – but what can we do with it? We need to get rid of it because if things get too hot, transistors can start to break down and become damaged.
Thermal throttling is a chip’s built-in method of cooling itself if we don’t provide adequate cooling. If the internal temperature sensors detect that it’s getting too toasty, the chip can automatically lower its operating frequency to reduce the amount of heat generated. However, this isn’t something you want to happen, and there are much better ways to deal with unwanted heat in a computer system.
Some chips don’t actually need fancy cooling solutions. Take a look around your motherboard and you’ll see dozens of small chips without heatsinks. How do they not overheat and destroy themselves? The reason is that they probably don’t generate much heat in the first place. Big, beefy CPUs and GPUs can dissipate hundreds of watts of power, while a small network or audio chip may only use a fraction of a watt.
In these cases, the motherboard itself or the chip’s outer packaging can serve as an adequate heatsink to keep the chip cool. Generally, though, once you get above about 1 watt of power dissipation, you need to start thinking about proper thermal management.
The name of the game here is keeping the thermal resistance between materials as low as possible. We want to create the shortest, most efficient path for heat to travel from the chip to the ambient air. This is why CPU and GPU dies come with integrated heat spreaders (IHS) on top. The actual silicon chip inside is much smaller than the size of the package, but by spreading the heat over a larger area, we can cool it more efficiently. It’s also important to use a good thermal compound between the chip and the cooler. Without this high-thermal-conductivity path, heat would have a much harder time flowing from the IHS to the heatsink.
There are two main forms of cooling: passive and active. Passive cooling uses a simple heatsink attached to the chip, relying on ambient airflow to carry the heat away. The material will be something with a high thermal conductivity and a large surface area, allowing it to transfer heat from the chip to the surrounding air efficiently.
Voltage regulators and memory chips can often get away with passive cooling since they don’t generate as much heat. Only high-end DDR5 modules and server memory typically require active cooling.
Likewise, the majority of mobile phone processors are passively cooled, although certain niche or gaming smartphones sometimes use vapor chambers or miniature active fans to manage higher thermal loads.
The higher the performance of a chip, the more power it generates – and the larger the heatsink required to keep it cool. This is why phone processors are less powerful than desktop-class processors: there simply isn’t enough cooling capacity to keep up.
Once you get into the tens of watts, you’ll likely start thinking about active cooling. This involves using a fan or another method to force air across a heatsink, allowing it to handle up to a few hundred watts. However, to take full advantage of this much cooling capacity, we need to ensure that heat is efficiently spread from the chip across the entire surface of the cooler. It wouldn’t be very useful to have a huge heatsink without an effective way to transfer heat to it.
This is where liquid cooling and heat pipes come in. Both perform the same essential task: transferring as much heat as possible from a chip to a heatsink or radiator. In a liquid cooling setup, heat is transferred from the chip to a water block using a high-thermal-conductivity thermal compound. The water block, often made of copper or another highly conductive material, then heats the liquid. This liquid stores the heat and carries it to the radiator, where it can be dissipated into the air. For smaller systems like laptops, which can’t fit a full liquid cooling setup, heat pipes are very common. Compared to a basic copper tube, a heat pipe setup can be 10-100x more efficient at transferring heat away from a chip.
A heat pipe is very similar to liquid cooling but employs a phase transition to increase thermal transfer. Inside a heat pipe, a liquid evaporates when heated, turning into vapor. The vapor travels along the pipe until it reaches the cooler end, where it condenses back into a liquid. The liquid then returns to the hot end through gravity or capillary action.
This evaporative cooling is the same principle behind why you feel cold when getting out of a shower or pool: the liquid absorbs heat as it evaporates and releases it when it condenses.
Now that we can transfer heat from the chip into a heat pipe or liquid, how do we efficiently dump that heat into the air? That’s where fins and radiators come in. A simple tube of water or a heat pipe will transfer some heat into the surrounding air, but not very much. To really cool things down, we need to increase the surface area exposed to the temperature gradient.
Thin fins in a heatsink or radiator spread the heat over a large surface area, allowing a fan to efficiently carry it away. The thinner the fins, the more surface area can fit into a given space. However, if the fins are too thin, they won’t make enough contact with the heat pipe to effectively transfer heat into the fins.
It’s a delicate balance – which is why, in some cases, a larger cooler can perform worse than a smaller, more optimized one. Gamers Nexus put together a great diagram (below) showing how this works in a typical heatsink:
Going Below Ambient: Advanced and Exotic Cooling
All of the cooling methods we’ve discussed so far work by the simple transfer of heat from a hot chip to the surrounding air. This means a chip can never get colder than the ambient temperature of the room it’s in. If we want to cool below ambient temperatures, or if we need to cool something massive like an entire data center, we need to apply some additional science. This is where chillers and thermoelectric coolers come in.
Thermoelectric cooling, also known as a Peltier device, is not very popular at the moment but has the potential to become very useful. These devices transfer heat from one side of a cooling plate to the other by consuming electricity. They use special thermoelectric materials that can create a temperature difference via an electric potential.
When a DC current flows through the device, heat is absorbed from one side and transferred to the other, allowing the “cool” side to drop below ambient temperature. Currently, these devices remain niche because they require a lot of energy to achieve significant cooling. However, researchers are working to develop more efficient versions for broader use.
Just as state transitions can transfer heat, changing the pressure of a fluid can also be used to move heat. This is the principle behind refrigerators, air conditioners, and most other large-scale cooling systems.
In these systems, a special refrigerant flows through a closed loop where it starts as a vapor, is compressed, condensed into a liquid, expanded, and evaporated back into a vapor. This cycle repeats continuously, transferring heat in the process. The compressor does require energy input, but a system like this can cool well below ambient temperatures. That’s how data centers and buildings stay cool even on the hottest days of summer.
Systems like these are typically second-order cooling systems when it comes to electronics: first, the heat from the chip is dumped into the room, and then the heat from the room is expelled to the outside via a vapor compression system.
However, extreme overclockers and performance enthusiasts may connect dedicated chillers directly to their CPUs for extra cooling performance. Temporary methods of extreme cooling are also possible using consumables like liquid nitrogen or dry ice.
Why Cooling Matters More Than Ever
Cooling is something all electronics require, but it can take many forms. The aim of the game is to move heat from the hot chip or system to the cooler surroundings. There’s no way to truly get rid of heat – all we can do is move it somewhere it won’t become a problem.
All digital electronics generate heat due to the nature of how their internal transistors operate. If that heat isn’t properly managed, the semiconductor material starts to break down, damaging the chip and shortening its lifespan.
Heat is the enemy of all electronics designers and remains one of the key limiting factors in pushing performance forward. We can’t simply make CPUs and GPUs bigger, because there’s no practical way to cool something that powerful. You just can’t get the heat out fast enough.
As computing demands continue to grow, managing heat efficiently is only becoming more critical – not just within a single chip, but across entire data centers, AI compute farms, and even future quantum systems. Thermal innovation is now at the heart of scaling technology itself.
Hopefully you’ll now have a greater appreciation for all the science that goes into keeping your electronics cool.
