CLP200M Datasheet, PDF (19/21 Pages) STMicroelectronics – OVERVOLTAGE AND OVERCURRENT PROTECTION FOR TELECOM LINE

A new technology available today is IMS - an Insu-
lated Metallic Substrate. This offers greatly en-
hanced thermal characteristics for surface
mount components. IMS is a substrate consisting
of three different layers, (I) the base material which
is available as an aluminium or a copper plate, (II)
a thermal conductive dielectrical layer and (III) a
copper foil, which can be etched as a circuit layer.
Using this material a thermal resistance of 8°C/W
with 40 cm² of board floating in air is achievable
(see fig. 4). If even higher power is to be dissipated
Fig 4 : Mounting on metal backed board
CLP200M
an external heatsink could be applied which leads
to an Rth(j-a) of 3.5°C/W (see Fig. 5), assuming
that Rth (heatsink-air) is equal to Rth (junction-
heatsink). This is commonly applied in practice,
leading to reasonable heatsink dimensions. Often
power devices are defined by considering the
maximum junction temperature of the device. In
practice , however, this is far from being exploited.
A summary of various power management capa-
bilities is made in table 1 based on a reasonable
delta T of 70°C junction to air.
Fig 5 : Mounting on metal backed board with an
external heatsink applied
Copper foil
In su l ati o n
Aluminium
Copper foil
FR4 board
Aluminium
heatsink
The PowerSO-10 concept also represents an at-
tractive alternative to C.O.B. techniques. Pow-
erSO-10 offers devices fully tested at low and high
temperature. Mounting is simple - only conven-
tional SMT is required - enablingthe users to get rid
of bond wire problems and the problem to control
the high temperature soft soldering as well. An op-
timized thermal management is guaranteed
through PowerSO-10 as the power chips must in
any case be mounted on heat spreaders before
being mounted onto the substrate.
TABLE 1 : THERMAL IMPEDANCE VERSUS SUBSTRATE
PowerSo-10 package mounted on
1.FR4 using the recommended pad-layout
2.FR4 with heatsink on board (6cm²)
3.FR4 with copper-filled through holes and external heatsink applied
4. IMS floating in air (40 cm²)
5. IMS with external heatsink applied
(*) Based on a delta T of 70 °C junction train.
Rth (j-a)
50 °C/W
35 °C/W
12 °C/W
8 °C/W
3.5 °C/W
P Diss (*)
1.5 W
2.0 W
5.8 W
8.8 W
20 W
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