Building a PCB business card is a long-standing tradition among hardware hackers and something I hadn't tried yet, so naturally I had to give it a go.
While there are really a lot of different cool cards, one thing I have noticed is a tendency to try to cram in as many features as possible, which results in a really busy card where one has to search for the contact details, defeating its whole purpose.
With this in mind I decided that the most important factors would be usability and minimalism. After all, the card should facilitate, not hinder, the transmission of information.
To do so, one can read either the QR code or the NFC tag which both contain all the information in meCard and vCard formats respectively, so the fields are parsed automatically. Reading the QR, however, is a bit slower since it needs a few extra clicks (open QR app, add contact, select existing/new, etc), rather than simply approaching the card to the back of the phone.
The antenna design follows the equation
From the tag's datasheet, the NTAG216F, the input capacitance is 50pF , and NFC's operating frequency is of course 13.56MHz.
The antenna's inductance must thus be 2.75uH. One great tool to find the antenna's parameters is ST's eDesignSuite, where the inductance value is automatically updated when changes are made.
As for the physical appearance, since there is no standard business card size I chose to go with the dimensions of a credit card (85.60 mm × 53.98 mm). It also has a component count of 1, making it one of the least densely populated PCBs ever