HEAT SINK MATERIAL
The thermal conductivity of the heat sink’s material has major impact on cooling performance. Thermal conductivity is measured in W/mK; higher values mean better conductivity.
Alloys have lower thermal conductivity than pure metals, but may better mechanical or chemical (corrosion) properties.
- It has thermal conductivity of 205 W/mk, which is good (as a comparison: steel has about 50 W/MK). The production of aluminium heat sinks is inexpensive; they can be made using extrusion Due to its softness, aluminium can also be milled quickly; die – casting and evem cold forging are also possible. Aluminum is also very light (thus, an aluminium heat sink will put less stress on its mounting when the units is moved around)
- Copper’s thermal conductivity is about twice as high as aluminium – almost 400 W/mk. This makes it an excellent material for heat sinks; but its disadvantages include high weight, high price, and less choice as far as production methods are concerned. Cooper heat sinks can be milled, die-cast, or made of copper plates bonded together, extrusion is not possible.
- To combine the advantages of aluminium and copper, heat sinks can be made of aluminium and copper, which helps lead the heat away to the outer parts of the heat sink. The first heat sink for PC CPUs with an embedded copper piece was the Alpha p7125 (for first – generation Slot A Athlon (CPUs), keep in mind that a copper embedding is only useful if it is tightly bonded to the alminum part for good thermal transfer. This is the not always the case, especially not with inexpensive coolers. If the thermal transfer between the copper and the aluminium is poor, the copper embedding may do more harm than good.
The copper core helps the heat move to the upper parts of the heat sink.
- Silver has an even higher thermal conductivity than copper, but only by about 10 &. This does not justify the much higher price for heat sink production however, pulverized silver is a common ingredient in High end thermal compounds.
Bounder Fin / Folder Fin
Instead of extruding, forging, or milling fins, it is also possible to simply use copper (or aluminium) plates as fins, and bond them on a base plate. If each fin is made of a separate plate, we refer to such heat sinks as boned fin heat sinks, if all fins are made if one large plate that is folded to form the fins, we have a folded fin heat sink. Advantages of such heat sink designs include high surface, and low weight however, the performance is only good if the bonding is done properly.