The Manufacture of Transponders and Contactless Smart Cards - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 329

Finally, a reflow soldering procedure, like the procedure used for fitting components
to SMD printed circuit boards, is available for the connection of an etched coil to a chip
module. In order to prevent short circuits (between the coil windings) in the vicinity
of the chip module as a result of the soldering process, the coil is first printed with
a solder resist (typically light green), keeping the antenna terminals free. A defined
quantity of soldering paste is deposited onto these connection areas by a dispenser.
After the chip module has been inserted into a stamped hole on the carrier foil provided
for this purpose and is thus fixed into position, heat is supplied to the terminals of the
chip module by a suitable soldering tool (soldering stamp). This causes the soldering
paste to melt, creating a permanent electrical and mechanical connection between the
chip module and the antenna coil (Figure 12.10).

Stamped out area

Antenna

Insulation

Section A-B

A B

Contactless
chi p module

Insulation

Antenna terminals

Soldering
paste

Antenna
terminal

Antenna

Figure 12.10 Soldered connection between the chip module and an etched antenna

12.2.3 Lamination

In the next step, the overlay and inlet foils are assembled and joined together with
precision. Finally, the foils are placed in a laminating machine. By the conduction

Pressure

Temperature

Overlay

Inlet

Figure 12.11 During the lamination procedure the PVC sheets are melted at high pressure and
temperatures up to 150 ◦ C