IGBT Modules - Technologies, Driver and Application (Second Edition) - page 80

modules with blocking voltages of up to 1.2kV and currents of up to typically 40A have
solutions in which the package consists of a moulded compound. Parallel to these
solutions, in the same power range and at higher voltages and currents, there are
solutions for IGBTmodules that comprise a plastic frame and lid as well as silicone gel.
This latter construction is now the most frequently used by all manufacturers. Older
generations of IGBTmodules still in use were constructed with a plastic frame and lid,
silicone gel and a final epoxy layer. There is also a variant, known as press-pack case,
which is based on the package concept used for highperformance thyristors.
Fig. 2.3
Construction of a standard IGBTmodulewith baseplate
2.2.1 Plastic frame
The frame for all IGBT module concepts is made of plastic. So these plastics must
match a high requirements specification. Firstly, the package plastics must be
mechanically stable and demonstrate high tensile strength over the entire temperature
range. Also critical are the temperatures which, in traction applications, for example,
range from a minimum of as low as -55°C to a maximum of >125°C under electrical
operation. In addition, many IGBT components, particularly in the low and medium
power range, are soldered into printed circuit boards. During the soldering process,
temperatures of >250°C are transferred to the plastic frame via the soldered connection
of the IGBT component. The component package must also be able to withstand this
processwithout becoming damaged.
Thirdly, the plastic must be an electrical insulator. A high CTI value (chapter
required in order to keep the creepage distances (present in the package) short and to
permit ahighdegree of pollution duringoperation.
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