IGBT Modules - Technologies, Driver and Application (Second Edition) - page 83

provide ahigh level of reliability in power cycling.
IMS (isolated metal substrate) performs the same role as a DCB substrate in a power
electronics component, although the IMS does not have nearly the breadth of
application in power electronics as the DCB. Mainly because of the very poor thermal
conductivity of the polymer insulator (1 to
) and the coefficient of expansion,
which ismuch greater than that of the semiconductor chip at
ppm 54
2.2.3 Baseplate
In the lower power range, IGBTmodules without a baseplate aremore frequently used
(DCB or IMS modules). While those in the medium and high power range almost all
have a baseplate. The baseplate is usually made of copper and is 3mm to 8mm thick,
with a nickel coating of 3µm to 10µm. Alternatively other baseplate materials such as
AlSiC (aluminium silicon carbide) or, less frequently, Cu/Mo (copper molybdenum)
alloys, can beused.
Fig. 2.5
Assembly examples
The baseplate is not usually flat. It is curved, either convexor concave. This curvature is
deliberate, in order to ensure optimal thermal contact with the cooling medium, as the
baseplate expands in the subsequent application as the temperature increases. This
expansion is different from the expansion of a DCB. A bi-metal effect occurs. The
approach of the manufacturers who have understood this inevitable effect is to make a
baseplate that shows optimal thermal transfer resistance to the cooling medium in hot
1...,73,74,75,76,77,78,79,80,81,82 84,85,86,87,88,89,90,91,92,93,...548
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