3

Table 1: Thermal Board Configurations. Note: *Single device, **Dual devices.

R

If readers are interested in the test conditions and method, they are encouraged to refer to appen-

dix B for details.

0

0.2

0.4

0.6

0.8

1

40

60

80

100

120

140

2oz COPPER MOU NT ING PAD AREA (in )

2

4.5"x5" FR-4 Board

T

= 25 C

S till Air

A

o

Top Cu*

Bottom Cu*

1/2T op+1/2Bottom Cu*

Top Cu**

* S ingle device

** Dual devices

Figure 3.

surface placement.

Plots in figure 3 show the relationship of R

placement on the board. It is apparent that increasing copper mounting pad area considerably

lowers R

device. In addition, placing all the copper on the top side of the board further reduces R

By substituting the thermal resistance, ambient temperature, and the maximum junction tempera-

ture rating into equation 2.1, the steady-state maximum power dissipation curves can be obtained

and are shown in figure 4.

A 20% increase in the power handling can be achieved by increasing the copper pad area on top

that no additional board space is required. For maximum performance, it is recommended to put

extra copper on the bottom of the board connected to the top pad by through-hole thermal vias.

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