Preliminary
Heatsinking TO-220Packages
The thermal resistance of a TO-220 package can be
reduced by attaching it to a heat sink or a copper plane
on a PC board. If a copper plane is to be used, the
values of
θ
JA
will be same as shown in next section for
TO-263 package.
Heatsinking TO-263 and SOT-223 Packages
The TO-263 and SOT-223 packages use the copper
plane on the PCB as a heatsink. The tab of these
packages are soldered to the copper plane for heat
sinking. Fig.4 shows a curve for
θ
JA
of TO-263 package
for different copper area sizes, using a typical PCB with
1 ounce copper and no solder mask over the copper
area for heat sinking.
RT9172
1
square
inch
produces
very
little
As shown in the figure, increasing the copper area
beyond
improvement. The minimum value for
θ
JA
for the TO-
263 package mounted to a PCB is 32
°
C/W.
θ
JA
vs. Copper (1 Ounce) Area for TO-263
200
180
160
T
RMAX
= T
JMAX
- T
AMAX
4W
140
120
100
80
60
40
20
0
0
0.5
1
1.5
2
2.5
3
2.5W
1W
Copper Foil Area (SQ. IN.)
Fig. 4
DS9172-03 April 2002
www.richtek-ic.com.tw
9
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
