Heat Sink Information

What is Heatsink ?
Heatsink or Heat Sink is a device  usually made of aluminum alloy material, used to dissipate heat from a hot component,such as CPU. Heatsink has many different types and uses, such as CPU heatsink,VGA heatsink, Mainboard Heatsink.

What material could be used for heatsink ?
The selection of material for heatsink depend on the thermal conductivity of heatsink material.The unit for thermal conductivity is W/mk, higher value means better conductivity.  There's four material suitable for making heatsink, they are silver, copper,aluminum and steel. Thermal conductivity for steel is only about 50W/mk, 205W/mk for Aluminum, 400W/mk for Copper,and 440W/mk for Silver. The Silver has highest value, but it will be too expensive for a ordinary use of heatsink, so it is not practical to use silver to make heatsink. Copper is good for making heatsink, its thermal conductivity is just only 10% less than silver but  about 2 times higher than of aluminum,but it also has its disadvantage, it is of high price and has high weight, compared to the same size of aluminum heatsink, copper heatsink has exceed the maxinium weight limit for CPU heatsink, and the production method has less choice,Copper heatsinks can be milled, die-cast, or made of copper plates bonded together; extrusion is not possible. Aluminum heat sink is the most commonly used heatsink in current market, Aluminum is rather cheap, has low melting point, and it can be easily extruded,the production method for aluminum heatsink is relatively simple and easy, this is why aluminum heat sink is the most common one in our current market. Copper has better thermal conductivity and aluminum has better thermal dissipating property, so people find out a better solution for making heat sink by combined aluminum and copper together, use copper plate to contact the heat sources, and use aluminum parts to dissipate the heat.

What characteristics make a heat sink a good one? There's a number of factors to consider:

• High heat sink surface. It's at the surface of the heatsink where the thermal transfer takes place. Therefore, heat sinks should be designed to have a large surface; this goal can be reached by using a large amount of fine fins, or by increasing the size of the heat sink itself.
• Good aerodynamics. Heat sinks must be designed in a way that air can easily and quickly float through the cooler, and reach all cooling fins. Especially heatsinks having a very large amount of fine fins, with small distances between the fins may not allow good air flow. A compromise between high surface (many fins with small gaps between them) and good aerodynamics must be found. This also depends on the fan the heat sink is used with: A powerful fan can force air even through a heat sink with lots of fine fins with only small gaps for air flow - whereas on a passive heat sink, there should be fewer cooling fins with more space between them. Therefore, simply adding a fan to a large heat sink designed for fanless usage doesn't necessarily result in a good cooler.
• Good thermal transfer within the heat sink. Large cooling fins are pointless if the heat can't reach them, so the heat sink must be designed to allow good thermal transfer from the heat source to the fins. Thicker fins have better thermal conductivity; so again, a compromise between high surface (many thin fins) and good thermal transfer (thicker fins) must be found. Of course, the material used has a major influence on thermal transfer within the heat sink. Sometimes, heat pipes are used to lead the heat from the heat source to the parts of the fins that are further away from the heat source.
• Perfect flatness of the contact area. The part of the heat sink that is in contact with the heat source must be perfectly flat. A flat contact area allows you to use a thinner layer of thermal compound, which will reduce the thermal resistance between heat sink and heat source. Good mounting method. For good thermal transfer, the pressure between heatsink and heat source must be high. Heatsink clips must be designed to provide a strong pressure, while still being reasonably easy to install. Heat Sink mountings with screws/springs are often better than regular clips. Thermoconductive glue or sticky tape should only be used in situations where mounting with clips or screws isn't possible. 

Heatsink surface Treatment
Surface treatment for Aluminum heatsink is oftenly anodization (anoic oxidation ) or caustic wash (Alkali Corrosion). If the heatsink surface treatment is anodization, the heatsink could be colorated in many different colors.It has no difference about which color to be colorated with the heatsink, because the heatsink get rid of heat by  convection.
Surface treatment for copper heatsink could be plated with silver or gold, but this is not necessary if heatsink is working is a dry environment.If the heatsink used in a humidity environment galvanization is necessary

Heatsink Production Method
Aluminum heatsink is oftenly produced by extrusion, this method is quite simple and easy. But this method has a disadvantage, the thickness and height of the fins could not  exceed 1:18 in inverse proportion. Copper heatsink and aluminum heatsink could be made by die-casting. If the heatsink require very fine and high fins, another method called Cold Forging is required. If heatsink need to made be with their thickness and height of fin exceed 1:18 in inverse proportion, Milled/Cut Method is required, this could be achieved by CNC machine. 

 

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