Heat sink for RF power amplifiers

What is the crieteria of Heat sink selection for the High power RF amplifier and what is its related calculation?

hi,
i have designed 30W power amplifer before. what we did was use heat sink and thermal grease. to be honest with you, i just used heat sink which was available/used for many projects before!

to select heat sink, you may consult with the manufacturer try to get data on PA power slump. material of heat sink and the shape might affect heat sinking properties.

the criteria is simple. You ask your device manufacturer what temperature the semiconductor junctions have to stay below to yield a desired lifetime. For example, they might say "you need to keep the device junctions below 140 deg C if you want the mean lifetime to be 10 years."

then you look at your environment, and size the heat sink and any auxiliary cooling items (like a fan, water cooling, etc) to not, on the average, exceed that junction temperature.

You will need to know the packaging thermal resistance of the devices to calculate this.

parameters to be known:

-the power dissipated in the active device(RF power transistor)

-maximum junction temperature of the device( from data sheet of the device)

-the ambient temperature of the final device , that is going to work in

-the thermal resistance parameter of the device(Rth-device) (from data sheet)

if these parametes are known , then the heat sink design can be done.

thanks....


can u send me the link of design equation for the same .

http://www.triquint.com/products/d/m...nd-qfn-package

thanks a lot..