MTB33N10E

http://onsemi.com

7

RECOMMENDED FOOTPRINT FOR SURFACE MOUNTED APPLICATIONS

Surface mount board layout is a critical portion of the

total design. The footprint for the semiconductor packages

must be the correct size to ensure proper solder connection

interface between the board and the package. With the

correct pad geometry, the packages will self align when

subjected to a solder reflow process.

mm

inches

0.33

8.38

0.08

2.032

0.04

1.016

0.63

17.02

0.42

10.66

0.12

3.05

0.24

6.096

POWER DISSIPATION FOR A SURFACE MOUNT DEVICE

The power dissipation for a surface mount device is a

function of the drain pad size. These can vary from the

minimum pad size for soldering to a pad size given for

maximum power dissipation. Power dissipation for a

thermal resistance from the device junction to ambient, and

The values for the equation are found in the maximum

ratings table on the data sheet. Substituting these values

one can calculate the power dissipation of the device. For a

50°C/W

= 2.5 Watts

the recommended footprint on a glass epoxy printed circuit

board to achieve a power dissipation of 2.5 Watts. There are

other alternatives to achieving higher power dissipation

from the surface mount packages. One is to increase the

area of the drain pad. By increasing the area of the drain

pad, the power dissipation can be increased. Although one

can almost double the power dissipation with this method,

one will be giving up area on the printed circuit board

which can defeat the purpose of using surface mount

area is shown in Figure 16.

Figure 16. Thermal Resistance versus Drain Pad

2.5 Watts

A, Area (square inches)

Board Material = 0.0625″

G−10/FR−4, 2 oz Copper

°

60

70

50

40

30

20

16

14

12

10

8

6

4

2

0

3.5 Watts

5 Watts