Electronic – Why does smart card antenna follow a “snake” pattern when approaching the chip


This image is from this post which shows MasterCard plastic card being dissolved in acetone to have the circuitry extracted for further analysis (TL;DR further analysis failed because of chip protective features). Wires are a bit off because acetone made them unbind from the plastic.

Smart card wiring

Note the area close to the chip – two wires approach the chip and each of them follows a "snake" pattern – down, then up, then down, then up again, that repeats at least four times.

What's the purpose of this "snake" pattern?

Best Answer

The module is connected to the antenna using conductive adhesive. At the backside of the module there are two pads that are glued to the antenna. For this reason the antenna needs some pads as well or a meander-shaped region that serves the same purpose.

A more detailed discussion can be found here: http://arxiv.org/pdf/1507.06427.pdf.