EUPEC - Europäische Gesellschaft für Leistungshalbleiter mbH & Co KG
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 GERS Testers
Eupec manufactures IGBTs (insulated gate bipolar transistor), which are
used in railway technology for switching voltages greater 1,000 V at
currents of several hundreds of amperes. Eupec commissioned SYS TEC to
develop testing equipment, the GERS tester, for use in the production
process, in order to improve quality and yield in IGBT manufacturing.
Using this testing device, IGBTs are subjected to a gate – emitter
test. The control circuit of a functional IGBT is characterized by a
capacitance. The gate-emitter-path is generally shorted in defective
control circuits; nevertheless, even open gate – emitter paths must be
detected. Therefore, the load curve of the gate is evaluated with the
help of a micro-controller. The capacitance of the test piece is in the
range of 0.5 and 300 nF. To do this, points from the IGBT's charge
curve and compared to pre-defined values. The peak currents at
discharging of the capacitance are in the mA range. The leakage
currents in a charged capacitance are a few nA. The test device is
capable of picking up these low current levels. In addition, substrate
resistances are situated upstream of the gates and affect the switching
behavior of the IGBTs. These, too, are tested for function by a
measurement. Using one test construct it is possible to evaluate of up
to 10 substrates. The test device can be operated, in addition to
manual operation, also from a PC in a remote mode via RS232. The test
results are displayed on an LCD display. Data transfer to the PC is
done via an RS232 interface. The test devices were manufactured in
small series at SYS TEC.
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