Black Anodized Aluminum Heat Sink Extrusion

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Heat sink is an essential component in electronic and mechanical applications, it absorb the heat from heat source and transferring the heat to the air or liquid.

As different applications have different power and heat density, accordingly there are various heat sink types, for material clarified, some heat sinks are made from aluminum, and some are made from copper; For process the heat sinks can be clarified to extrusions, skiving fins, zipper fins, cold forging heat sinks. But the most commonly heat sink type is aluminum extruded heat sink, and the heat sink extrusions are usually anodized, black anodized is the most commonly surface finish.

In the process of heat sink manufacturing, we all know that the heat sink should be anodized, but it is not clear whether black or white is better. Here are some analysis:

In fact, the key point to this problem is the problem of emissivity. In industry, the chemical potions used in white and black anodizing are different, so are their surface properties the same? We assume the same. Both are 0.85. There are two cases to discuss:

 1,The heat sink is not exposed to the air: such as notebooks, PC power supplies. In this case, the problem is simple, it doesn't matter whether the heat sink is white or black, because their emissivity is the same, whether it is forced heat sink or natural heat dissipation, the amount of radiant heat exchange on the surface is the same.

2, The heat sink is exposed to the air: such as industrial computers, LED street lights. Then solar radiation needs to be considered. Let's do a thought experiment: two heat sinks anodized with the same absorption rate, one reflecting all visible light is white, and one absorbing all visible light is black. Which of them has a higher temperature under the exposure of pure visible light (such as LED lights)? The answer is, of course, that black is relatively high, because it absorbs all visible light, absorbs energy, and has no mechanical energy, so the internal energy must increase. What about putting white and black in the sun? Visible light does no work on white, and electromagnetic waves of other wavelengths (infrared, ultraviolet) are both white and black, so the temperature of white is still lower than that of black.

So how to select the color of the anodized heat sink extrusions? it depends on the environment of the applications, if the devices are not exposed to the outside directly, the black anodized aluminum heat sink extrusion would be better, and if it's installed in the outside, the clear anodized heat sink is an optimized option.

We know that aluminum readily reacts with oxygen to form a very thin oxide layer in air.This naturally-formed protective film prevents rusting, making aluminum somewhat resistant to corrosion.

However, this film is very thin and can corrode due to chemical reactions caused by the environment, so a protective surface treatment is required, anodizing is one such protection.

Anodizing is a surface treatment process, in which non-ferrous metals such as aluminum, magnesium and titanium are electrolyzed as anodes in an acidic electrolyte to form a dense oxide film on the surface of the material to resist corrosion and improve wear resistance. For decoration, etc. The anodic oxide film is usually transparent and the microscopic is porous structure, the diameter of these pores is 100Å-300Å (1Å=0.1nm), in fact there are astonishing 5-70 billion holes per cubic centimeter. Knowing these holes, we can easily understand color anodizing.

For example, if every hole in the oxide film is filled with red dye, it will produce red anodization and create a colored surface that will remain until the oxide film itself wears off. In the same way with other color dyes, corresponding color anodization can be formed. So, black anodizing, is actually on the anodized surface, filled with black pigment.

What's the benefits of black anodized aluminum heat sink extruison?

1, Extruded heat sink is the most cost efficient heat sink type;

2, Aluminum is a excellent thermal conductor, so the aluminum heat sink extrusion can meet most of electronic components like LED, BGA, FPGA,etc.

3, Aluminum has a good malleability, it's easy to manufacture;

4, High production efficiency;

5, The anodizing can improve the corrosion protection, wear protection;

6, Anodizing can increase the electrical isolation and surface emissivity.

Heat sink images

Sinda Thermal can supply varieties of heat sinks with competitive price and high quality standard, we offer the custom extruded heat sink with different extrusion width, height and length, There is no MOQ in Sinda Thermal, 1pcs order is available, and we can provide very fast delivery time since all the manufacturing process are completed in house, also we own thousands of existing extrusion tooling dies for selection. Our factory has passed through ISO9000,ISO9001, we are qualified to manufacturing every type of heat sink includes skived fins heat sink, cold forging heat sink, zipper fin soldering heat sink with heat pipe or vapor chamber, liquid cooling cold plate, please feel free to contact us if you have any thermal issues.

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