SUBSTRATES AND MOUNTING INFORMATION

The use of epoxy FR4 boards is quite common for

surface mounting techniques, however, their poor

thermal conduction compromises the

otherwise

outstanding thermal performanceof the PowerSO-

10. Some methods to overcome this limitation are

discussed below.

One possibility to improve the thermal conduction

is the use of large heat spreader areas at the cop-

per layer of the PC board. This leads to a reduction

of thermal resistance to 35

board heatsink (see fig. 2).

Use of copper-filled through holes on conventional

FR4 techniques will increase the metallization and

decrease thermal resistance accordingly. Using

a configurationwith 16 holes under the spreader of

the package with a pitch of 1.8 mm and a diameter

of 0.7 mm, the thermal resistance (junction -

heatsink) can be reduced to 12

°C/W (see fig. 3).

Beside the thermal advantage, this solution allows

multi-layer boards to be used. However, a draw-

back of this traditional material prevents its use in

very high power, high current circuits. For instance,

it is not advisable to surface mount devices with

currents greater than 10 A on FR4 boards. A

Power Mosfet or Schottky diode in a surface mount

power package can handle up to around 50 A if

better substrates are used.

Fig. 2 : Mounting on epoxy FR4 head dissipation by extending the area of the copper layer

Fig. 3 : Mounting on epoxy FR4 by using copper-filled through holes for heat transfer

FR4 board

Copper foil

FR4 board

Copper foil

heat transfer

heatsink

TLPxxM/G/G-1

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