28-09-2012, 01:08 PM
Design of Heat Sinks
design of heat sinks.ppt (Size: 1.16 MB / Downloads: 40)
Semiconductor Heat Sinks
Thermal Physics of Semiconductor Heat Sinks (SHS) is an interesting and urgent topics of semiconductor devices cooling.
While in the long ago passed years of easy-happy Semiconductor Heat Sinks solutions.
Those were practically of the single uniform design as, for example, this one for the 486X chipset from the early 90s.
The continuous more and more stiff and demanding interest in the heat to be evacuated from the electronic devices, more effectively, brought up the newer styles for SHS.
Specially designed forced convection along the short fins or
Guided directed air flux down the longitudinal fins
Geometrical & Thermal Design Constraints
The most important factor for the airflow available is the maximum volume the heat sink can occupy.
Wmax, Lmax, and Hmax
The design must accommodate the component specifications, such as the power dissipated (P) and the maximum junction temperature (Tjmax).
The maximum heat sink weight, also play a role in the design.
Another important factor during the design phase is the maximum allowable cost of the thermal solution
Types of Heat Sinks
Thermal conductivity and cooling surface area must always be weighed against material and manufacturing costs.
Most heat sinks are made from aluminum, because of its low thermal resistance, light weight, and low cost.
Copper is also used for heat sinks; although lower in thermal resistance than aluminum, its cost and greater weight make it less desirable for many applications.
Stamped heat sinks : made from a single sheet of metal, which is cut and bent to give the desired thermal properties.
Extruded heat sinks : are very cost effective and provide good thermal performance.
Many basic shapes can be provided off-the-shelf.
Heat Sink Castings : provide a cost-effective solution for high-volume, stable applications.
Bonded-fin heat sinks : are made by bonding fins, fabricated from sheet metal or through extrusion, to an extruded base.
This process increases the surface area over a similar extruded piece, reducing the thermal resistance by A 1/2to 2/3.