CLP200M_03 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 R_th(j-a) of 3.5°C/W (see Fig. 5), assuming
that R_th (heatsink-air) is equal to R_th (junc-
tion-heatsink). This is commonly applied in prac-
tice, 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 ex-
ploited. A summary of various power management
capabilities is made in table 1 based on a reason-
able delta T of 70°C junction to air.
Fig 5 : Mounting on metal backed board with an
external heatsink applied
Copper foil
FR4 board
Copper foil
Insulation
ct(s) ^Aluminium
Aluminium
heatsink
Produ _{The PowerSO-10 concept also represents an at-}
te tractive alternative to C.O.B. techniques.
le ^{PowerSO-10 offers devices fully tested at low and}
o ^{high temperature. Mounting is simple - only con-}
s ventional SMT is required - enabling the users to
b _{get rid of bond wire problems and the problem to}
control the high temperature soft soldering as well.
An optimized 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.
) ^{- O} TABLE 1 : THERMAL IMPEDANCE VERSUS SUBSTRATE
t(s _{PowerSo-10 package mounted on}
uc _{1.FR4 using the recommended pad-layout}
rod 2.FR4 with heatsink on board (6cm²)
P _{3.FR4 with copper-filled through holes and external heatsink applied}
lete ^{4. IMS floating in air (40 cm2)}
so 5. IMS with external heatsink applied
Ob^{(*) Based on a delta T of 70 °C junction train.}
R_th (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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