Digital Signal Processing Reference
In-Depth Information
12
The Manufacture
of Transponders and
Contactless Smart Cards
12.1 Glass and Plastic Transponders
A transponder is made up of two components: the electronic data carrier and the
housing. Figure 12.1 gives a simplified representation of the manufacturing process
for an inductively coupled transponder.
12.1.1 Module manufacture
In accordance with the normal semiconductor manufacturing procedure, the
microchip
is produced on a so-called
wafer
. This is a slice of silicon, which may be 6 inches
in diameter, upon which several hundred microchips are produced simultaneously by
repeated doping, exposure, etching and washing of the surface.
In the next stage of production, the microchips on the wafer are contacted using
metal points and then each of the chips is individually tested for functionality. The
chips have additional contact fields for this purpose, which give direct access — i.e.
without going through the HF interface — to the chip's memory and security electron-
ics. The chips are placed in so-called
test mode
during this procedure, which permits
unlimited direct access to all functional groups upon the chip. The functional test can
therefore be performed significantly more intensively and comprehensively than would
be possible later on, when communication can only taken place via the contactless
technology.
All defective chips are marked with a red ink dot at this stage, so that they can
be identified and separated out in the subsequent stages of production. The test mode
can also be used to programme a unique
serial number
into the chip, if the chip has
an EEPROM. In read-only transponders, the serial number is programmed by cutting
through predefined connecting lines on the chip using a laser beam.
After the successful completion of the test programme the test mode is deactivated
by permanently breaking certain connections (so-called fuses) on the chip by a strong
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