( 3 )

Heat Radiation Balance

(3-1)

TO-220 with heat sink

Where

θjc :

θjs :

The relation between temperature and heat radiation quantity is shown below.

(℃ )

The heat produced in the IC is radiated to ambience through the package and the heat

sink.

The quantity of the heat radiation depends on the heat source temperature, ambient

temperature and the thermal resistance of the package.

Heat radiation balance model of the TO-220 with heat sink is shown as below.

thermal resistance between IC chip (junction point) and the

package backside connecting to the heatsink.

thermal resistance between IC chip (junction point) and the

package surface.

thermal resistance between package backside and the heat sink

including the condidtion of insulator, silicon grease and

tighten torque.

thermal resistance of the heat sink

If the js is large enough compare with other thermal resistance, the js can be neglected and the

heat radiation model can be mentioned as below.

Tj

Ta

LOSS

P

Ambient

Temperature

Heat Source

(junction)

Temperature

JC

Heat Sink

IC

Package

Face Side

Resin

Chip

Package

Back Side

Tj

LOSS

P

Ta

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