Heat sinks are most important components of electrical devices, they are used in everything be it any lighting equipment or automotive equipment.
For a heat sink to work properly and effectively it is necessary to look at some basic things. Such as finding a proper balance between different factors for performance purposes. Performance of a heat sink is greatly affected by following factors:
- The material used
- Protrusion design
- Air Velocity
- Surface
When it comes to the choice of material, Aluminum is the most common choice.
Why is Aluminum a better option than Copper?
Copper has a high conductivity ratio, as a matter-of-fact conductivity of copper is 60% more than that of Aluminum.
But Aluminum is versatile, it is low cost, low maintenance and lightweight. And its thermal conductivity is still better. This makes it a better option to be used as heat sinks.
Aluminum Heat Sinks
As mentioned earlier, Aluminum is the most used element for heat sinks. Specifically extruded aluminum heat sinks are considered to fit the needs of most devices.
Aluminum is lightweight metal; it is not overly priced, and it has relatively good conductivity.
Copper Heat Sinks
Copper has even better conductivity than Aluminum, it has conductivity at 406W/m•K. However, Copper is highly expensive and overweight.
Copper has double the conductivity of aluminum, but the metal is triple times more expensive than aluminum and not just expensive it is also a lot more overweight than aluminum, which is why aluminum is preferable to be used in heat sinks rather than copper.
However, Copper is still used when thermal conductivity is considered more important the price or the weight of the metal.
Thermal Management and Thermal Conductivity of Aluminum and Copper
All electricity-based devices produce heat, and they require thermal management to work efficiently for a longer period and for preventing failures in the system. Thermal management means a device cooling by the convection currents of hot air being replaced by the cooler air.
How efficiently a thermal management system works depends on how effectively a conducting system can carry away the heat outside the device. To construct a heat sink most popular materials which are used are aluminum and Copper. Both elements have thermal properties and are ideal for the construction of a heat sink.
Thermal Conductivity is the estimate of heat flow per unit cross-sectional area through a medium
Substances with high thermal conductivity are listed below:
THERMAL CONDUCTIVITY = k = W/(m k)
MATERIAL @25C
Diamond 1000
Silver 429
Copper 401
Gold 310
Lithium 301
Beryllium 218
aluminum 205
Tungsten 174
Graphite 168
Pinchbeck 159
Magnesium 156
It is obvious that we are not able to construct a heat sink using Diamond because firstly it is a precious metal and secondly it is too expensive to be used to build a thermal management system. Instead of using expensive metals such as Gold, Diamond or Silver it is reasonable to use Copper and aluminum for the construction of a heat sink. Both the metals are efficient in thermal conduction.
Mechanical Properties Affecting Material Selection
Density of the material is as important as the cost or the efficiency. Copper may be twice as efficient in thermal conductivity, but it is also triple times denser than aluminum, which brings us to conclusion that a copper heat sink with equal heat flow with weigh 50% more than an aluminum heat sink. Adding the cost, copper is triple times expensive than aluminum.
Aluminum extrusion is a much easier process than Copper extrusion. Although copper can be extruded but the process is much more complex, and it is a difficult task to extrude the shape of a heat sink. It requires the metal to be heated at high temperatures, possibly damaging, or reducing the life of the extrusion equipment. Die costs for extruding aluminum is high but machining copper into extrusion shapes is much more costly.
Thermal Conductivity of Aluminum Alloys
The table above shows that Aluminum has Thermal Conductivity of 205 W/m.K. When aluminum is alloyed with other elements, such as silicon, Magnesium, iron, thermal conductivity then depends directly on the form of alloy.
1050A, aluminum alloy, has one of the higher thermal conductivities at 229 W/m•K. But the alloy is mechanically soft. Alloys, 6060 and 6063 are most used with conductivity at 209 and 201.
Alloys are selected based on their mechanical properties, which includes corrosion resistance, tensile strength, and hardness.
Alloy 6060 has a thermal conductivity of 209 W/m.K, it is used for complex cross sections and it also responds well to anodizing processes. Which is why it is considered as a good choice for heat sinks.
Primarily used aluminum alloys for high efficiency liquid cooled plates are 1050A (TC 222W/m.K) and 6082 (TC 180W/m.K).
Making the Right Choices for Your Project
Whichever alloy you choose, remember that there is more to heat dispersal than alloy choice.
The difference in thermal conductivity between 6000 series alloys is relatively minimal. So, maximizing the surface area of the heat sink and optimizing airflow over it are key to enhancing performance.
In your design, be sure the heat sink conforms as tightly as possible to the hot component and leaves the smallest possible gap. This will help ensure the success of your project.
Making Right Alloy Choices
It is key to remember that whichever alloy you are going to use, heat dispersal is more important than alloy
There are about 6000 alloy series and the difference in their thermal conductivity is minimal. Therefore, focusing on maximizing the surface area of the heat sink and balancing the air flow is the key for enhanced performance.
While you are building heat sinks it is important to make sure that the heat sink conforms to the hot device as tightly as possible leaving minimum gaps.
Conclusion
At the end of the day the choice of the material depends on you, but as the facts mention aluminum is considered as the smart choice for the heat sinks. It is affordable, efficient, and lightweight.
