Stamped HEATSINKS ![]() |
Extruded HEATSINKS ![]() Another important characteristic of an extruded heat sink is its aspect ratio. A high aspect ratio leads to a better-performing heat sink. The aspect ratio of an extrusion is roughly the fin height divided by the fin spacing. Typical heat sinks have a 3:1 to 5:1 aspect ratio. Extrusions can go up to an 8:1 or 10:1 ratio. Generally, fin heights are limited to 3 in. or less; heat-sink widths range up to 18 in. |
Bonded Fin HEATSINKS ![]() So, in many applications, the performance of a bonded-fin heat sink compares with that of a good extruded heat sink. The advantage of the bonded fin's construction method is that its heat-sink base can hold much better dimensional tolerances, and, if the heat sink is very wide, the bonded fin's cost is comparable with that of an extrusion. In addition, fins taller than 3 in. are available, and their height can vary along the length of the heat sink. This height variation can even extend to leaving gaps in the fins where fins are not needed. In this case, bonded-fin technology can offer potential savings over an extrusion because it isn't necessary to remove any fin material. |
Convoluted (Folded) Fin HEATSINKS ![]() |
Zipper Fin HEATSINKS ![]() Zipper fin heatsinks are built using single sheets of formed metals, usually aluminum or copper metal, that are interlocked together mechanically. The resulting fin pack assembly allows engineers to design heatsinks with very high aspect ratios. Zipper fin heatsink can serve as an alternatives to folded fin heatsinks since their high thermal performance is equal to or slightly better than their folded fin heatsink counterpart. Zipper fin heatsinks have several other advantages over folded fin heatsinks, including lower tooling costs, faster lead times, the ability to use different metals within the fin pack, and the ability to design more complex heatsinks. |
FANSINKS ![]() |
Interface Materials The main purpose of an interface material is to fill the tiny air gaps between two dry surfaces. The flatter and smoother the surfaces, the thinner and softer the interface material required to fill the gaps. Because perfectly smooth and flat surfaces don't exist, you almost always get better performance from an interface material than from a bare metal-to-metal interface. Key characteristics of an interface material are thermal performance, compliance, adhesive properties, and reworkability. In some cases, electrical conductivity is also important. The materials include thermal compounds, solid-filled polymers, epoxies, and tapes. If your application is critical, weigh the costs of applying the material against the thermal performance you need. For example, if you must remove the heat sink from the component, choose a solid material. To get the best performance with the lightest weight, select a thermal compound. If the surface on which the heat sink must sit is uneven, a thicker conformable polymer is necessary to make up for height variations. For best performance, choose a polymer filled with a thermally conductive powder (alumina or metal, for example). Finally, if you use a clip, material adhesive properties are unimportant. Whatever material you choose, make sure that you can install it without air bubbles, because the point of using an interface material is to eliminate air pockets. Some materials are available preinstalled from heat-sink vendors, saving you the cost of dispensing or cutting to size and then applying it in your shop. |