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

performance

of

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

copper layer of the PC board. This leads to a

reduction of thermal resistance to 35

of the 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

drawback 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

®

RBO40-40G / RBO40-40M / RBO40-40T

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