Heat Sink Buying Guide

Heat sinks are a widely used method of cooling for parts or components that can become hot while in use. Many types of electronics and mechanical devices or machinery use heat sinks to help them dissipate the heat they generate.

So, what does a heat sink do? The simple answer is that it gradually transfers heat energy away from whatever component is generating it. More broadly, using a heat sink improves performance and extends the life of the component(s) in question, allowing them to run better, longer, and more efficiently.

Strictly speaking, the definition of a heat sink can include any substance or device that absorbs or dissipates heat - especially when the heat is unwanted or detrimental to performance. After all, in extreme cases, electrical or mechanical heat build-up could cause complete system failures, fires, explosions, or injury.

In practice, the term ‘heat sink’ typically refers to various kinds of electronics cooling, where it might also be referred to as a heat spreader, or simply a cooler. Coolers of this type are a form of radiator because they radiate the heat they collect out into the atmosphere and away from the source.

Heat sinks are used to absorb and dissipate the high temperatures created by many different sorts of electronic and mechanical devices. In fact, any system that generates heat as a by-product of normal running might make use of a heatsink-type device to help important parts stay cooler. Examples can include mechanical, fuelled, electronic, friction, chemical, solar, or nuclear processes.

There are various heat sink types in common use, and they can look quite different from one model to the next. However, most types do still have a number of key features or characteristics in common.

As mentioned above, there are several different types of heat sinks. However, they are almost always made from metal, most often copper or aluminium.

One of the most common designs for a heat sink is the familiar ‘fin’ layout. There are also alternative versions that use pins, stamping, and various other moulding techniques to increase both surface area and the overall rate of heat transfer.

The majority of heat sinks are passive. This means that they will naturally conduct heat away from the source without any further equipment or processes required, as long as they remain in direct contact with the particular part or component in question.

However, additional cooling measures (such as powered fans) can often be attached to a heatsink, making the dissipation much more effective. Products that employ such techniques are generally referred to as active heat sinks.

A helpful comparison between some of the more widely used heat sink types can be seen in the following sections.

In a CLC setup, a pump continually pulls a fixed volume of water/coolant around a sealed and enclosed network of tubes. The liquid flows through a block attached directly to the component being cooled, where it absorbs heat through a contact plate. It’s then channelled to a radiator or heatsink, where a secondary thermal transfer takes place between the water and the surrounding air. In this way, the liquid is cooled before looping back around again, and so on.

Whether powered by fans or pumps, active cooling heat sinks are widely used as a temperature control system in electronics, protecting and enhancing the performance of various chips, LEDs, ICs and other modules. They are especially important in computers, as CPUs and graphics cards, in particular, will often get very warm under load.

Insufficient cooling can have a drastic impact on electrical performance, either through physical damage to circuits or due to a process known as ‘thermal throttling’. The latter occurs when a PC or other ‘smart’ system detects rising temperatures and attempts to limit heat build-up by aggressively restricting the power available to key components.

As noted above, there is a wide variety of constructions, designs and manufacturing techniques used in making heatsinks for computers, motherboards and other devices. Common options include:

• Extruded heat sinks - the metal is simply forced into the required shape; extremely common in a wide range of applications
• Forged heat sinks - relies on a die or mould to set the metal in the form needed; often cheaper for mass production
• Bonded heat sinks - fins are individually attached to the base in a dense array, ideal for bespoke or space-limited applications
• Stamped heat sinks - among the cheapest to mass-produce, but generally less powerful and effective as coolers
• CNC machined heat sinks - often among the more expensive options as the metal is precision-cut from a solid block, meaning much more material goes to waste
• Skived or zipper fin heat sinks - a highly effective (and, again, typically more expensive) manufacturing process, using a dedicated machine to cut the fins and then push them up into position; identified by a slight curve at the fin base

Most of these techniques offer alternate ways of achieving the classic finned or pinned heatsink layout. Typically, the choice will come down to striking the best balance for an individual supplier between quality, performance, cost, and sales volume.

We’ve already touched on the importance of heatsinks for cooling vital PC components such as CPUs and GPUs. Some other examples of everyday heat sink uses include:

• Motherboard heatsinks
• Solid-state and relay heat sinks
• Power transistor heat sink
• PCB  heat sinks
• External/internal laptop heatsinks
• Heat sinks for amplifiers

When asking yourself ‘What type of heat sink should I buy?’, the answer will almost always come down to the specifics of your setup and cooling needs. Identifying some basic details about your intended application is the first step in knowing how to choose heat sinks.

Key considerations for the best choice of heat sink include:

• What sort of power draw the component in question will be using.This is often referred to as the TDP (thermal design power, or thermal design profile).TDP is often used as a basic indication of a component’s power consumption, especially with CPUs (processors) and GPUs (video cards). TDP ratings specify the maximum heat a component can use in watts.It’s typically a good indicator of how hot a particular part has the potential to get under load
• How cool the component ideally needs to be kept in order to perform optimally
• How much space is available to install a cooler, heat spreader, or heat sink - they’re available in a wide variety of sizes, from tiny module heat sinks to much larger installations
• Which type of heat sink design or layout will give you the best thermal performance for your system specs
• Whether you need an active heat sink or a passive radiator
• How much you’re willing to spend on a cooler

You can find some typical applications of the various types of heat sinks in the table below.

How Do You Fit a Heat Sink?

Almost every individual type, make and model of heatsink has its own particular mounting mechanism, although the majority will look reasonably similar from one product to the next.

In most cases, the installer will need to attach the base plate of the cooler tightly to the surface of the component they’re cooling. This is usually done via a manual clamping or screw-down assembly. There’s a broad array of heatsink mounting accessories available for various models, including spring clips, spring mount rivets, screws, and adhesive tapes.

Nearly all heat sinks, especially those intended for use in computers and motherboards, will require an application of thermal paste between the component and the heat plate of the cooler.

Thermal paste (also called TIM or thermal grease) is a heat-conducting substance that improves thermal transfer between two metal plates. It helps to fill in any small gaps left by tiny imperfections in either surface, resulting in far better overall cooling performance. Over time it can dry and crack, requiring periodic reapplication.

Why are Heat Sinks Used in Power Amplifiers?

As with many other types of electrical equipment, the active elements in a power amplifier - specifically the transistors - can generate a surprising amount of heat as they conduct current. Just like PC components, these parts have an operational temperature limit that can’t be exceeded without risk of damage, failure, or (at the very least) severely impeded performance.

Buying a good heatsink suitable for the job helps to protect delicate electronics and the people using them while ensuring you get the best results from your devices.

Does Raspberry Pi Need a Heatsink?

Not typically, no - provided you’re using your Raspberry Pi set up within the limits it was designed for. While certain updated models are seen as using slightly increased power draw, the majority of chips used in RasPi builds (such as BCM2835) were created to function reasonably without one.

That said, additional cooling never hurts with 99% of electronics, and you may see improved performance by lowering temperatures on almost any enclosed system. There are commands you can run to check the operating temperature of a Raspberry Pi while under load.

Can I Change a Heat Sink Myself?

In most cases, yes - it’s certainly fairly common practice in computer maintenance. Provided you’ve carefully read and understood the instructions and steps required to install a given model of computer heat sink or cooler, you should have little difficulty in mounting the heatsink to the desired component.

If you’re unsure about how to change a heatsink or uncertain if you even need to do so, it’s always best to talk to an expert for professional help and advice.