AN533

Surface mount packages

17/22

Figure 16.

Relative variation of thermal impedance junction to ambient versus pulse

duration

Figure 17.

2.3

depending on the performance required in the design. Four techniques are commonly used:

●

FR4 - Copper

●

IMS (Insulated Metal Substrate)

●

FR4 board with copper filled through holes + HEATSINK

●

IMS + HEATSINK.

1E-3

1E-2

1E-1

1E+0

1E+1

1E+2

0.01

0.10

1.00

tp(s)

Zth(j-a)/ Rth(j-a)

1E-3

1E-2

1E-1

1E+0

1E+1

1E+2 5E+2

0.01

0.10

1.00

tp(s)

Zth(j-a) / Rth(j-a)

SOT-23

SOT-223

0.001

0.01

0.1

1

10

100

1,000

0.1

0.2

0.5

1

2

5

10

20

50

Zth(j-a)

INFINITE HEATSINK

IMS FLOATING IN AIR

FR4

die

package

board

board/air

influence of the various mounting elements