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Aluminum as Heat Sink Material

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Aluminum is an extremely versatile metal, so it is no wonder that it is a commonly used for heat sink applications. The transfer of heat in order to cool a device or maintain a certain temperature is an important property of modern metals, and aluminum is one of the prime choices for engineers and designers. Today, we will be looking at why aluminum makes such an excellent option for heat sinks and which of its properties make it particularly desirable in this regard.

Aluminum is a prized material for several reasons. Its light weight and high strength-to-weight ratio are two of the first characteristics that come to mind. Aluminum also has excellent corrosion resistance, is extremely durable, conducts electricity and offers amazing formability. That is not to mention its recyclability and other sustainability features.

When it comes to electronics and other modern devices, one key property is what really makes aluminum indispensable: its remarkable thermal conductivity. This is critical for equipment and applications that must maintain a certain temperature or remove excess heat; aluminum’s conductivity is a natural property that arises from its chemistry.

What makes aluminum so good at conducting heat?

When looking at a material’s ability to conduct heat, this is usually measured in what is known as watts per meter-kelvin, which can be denoted as (W/(m⋅K)), or as centimeter-kelvin (W/(cm⋅K)). There is also the English system using British Thermal Units, which measures thermal conductivity as BTU/(h⋅ft⋅°F).

No matter how you measure it, the chart of metals that are best at conducting heat will generally start with silver. It has a conductivity of 406 W/(m⋅K). Next on the list is copper at 385 W/(m⋅K), gold offers 314 W/(m⋅K) and then aluminum at 237 W/(m⋅K).

Other common metals, like iron and steel, have much lower numbers; stainless steel measures 16 W/(m⋅K). Why is aluminum so high on the list? Without going too deeply into the chemistry, the basic reason that metals are good conductors of heat is that they have free electrons that will start to move as they get heated; that movement (the heat) will get transferred through the metal more quickly than other substances.

Metals with more free electrons are more likely to conduct heat well, such as aluminum. A good rule of thumb is that if a metal is good at conducting electricity, it will also be good at conducting heat.

Let us compare the metals on the list above to better understand why the best option will be aluminum. First, silver and gold are much more expensive and less practical than aluminum; also, silver tends to corrode quickly when used as a conductor.

That leaves copper and aluminum, and while copper is the better conductor, it is also heavier and more expensive. If all that matters for your application is the amount of conductivity, regardless of price and weight, then copper might be your best material. If you require a lightweight, cost-effective material for your heat sink, aluminum is a good option.

What is a heat sink and why is it so important in modern engineering?

A heat sink is a kind of passive heat exchanger. It can transfer heat that has been generated by a device into a fluid medium, normally air but sometimes a liquid coolant. This allows the heat to dissipate away from the equipment.

In modern mechanical devices, which can include everything from an engine to electronics, the regulation of heat can be extremely important. A heat sink helps ensure that the device does not overheat. In computers, for instance, heat sinks are useful for keeping the CPU and other important chipsets from becoming too hot.

A heat sink usually must have a large surface area to maximize the transfer of the heat into the surrounding air. Aluminum’s many advantages (lightweight, cost-effective, formable) make it a key component for heat sinks in mobile phones, LED lights, televisions and more. The ability to economically extrude aluminum into profiles with multiple “fins” increases the heat sink’s surface area and its’ ability to transfer heat.

When designing the heat sink, engineers need to consider several factors: air velocity, surrounding materials, surface treatment, and the shape of the device. Even the adhesive or fastener used to connect the heat sink can have an impact on its effectiveness.

Which alloys are particularly well suited for heat sinks?

One thing that you should know is that pure metals make better heat conductors than alloyed metals. Working with aluminum, pure aluminum is impractical because it is generally too soft, and certain alloys work better as heat sinks than others.

Alloy 1050 is an excellent heat conductor, as high as 229 W/(m⋅K) but tends to be soft. While trading off a bit of conductivity, stronger alloys such as 6060, 6061 and 6063 can still be effective. They will exhibit thermal conductivity values between 166 and 201 W/(m⋅K). Even the temper of the alloy will affect the amount of heat conducted, so it is important to know exactly how much conductivity you need and check it against the properties of the alloy under consideration.

Your Technical Services Professional

When trying to match a material for an application, it makes sense to work with an experienced material supplier who knows the particulars of heat sinks and conductivity. At Clinton Aluminum, our knowledgeable professionals are strongly committed to working with our customers through every step of their procurement process. That means we can help advise you on which alloys might work best with your application.

Contact us today to learn more about which aluminum alloy is right for you.

 

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