Inside of a credit card

By silviodc, 18 April 2019

What do you mean? Inside of a credit card?
It’s just a sheet of plastic. There is nothing inside, you might think.
But credit cards embed actually a tiny computer!
The golden chip you see on the front, is basically the same as the simcard in your phone. Just running different software.

Opening the card

I had an old credit card which I had to get rid of, and followed the banks advise to cut it in half.
Intrigued by the opportunity, I simply cut right through the middle of the chip. And yes, its very satisfying to do so 😀

The actual chip is under the central contact plate. The dark lines are simply separating the pins from each other.

View from below, where I could get rid of the hard plastic cover and parts of the glue. The big contacts on the sides are for the contact less payment antenna
here you can see a literal cross section of the chip and its contacts


The above image beautifully explains what is hard to see in the real life image. The ATM gets in contact with the card, provides power and a clock signal and then starts communication with the card.

While credit cards only store the information about your account and the reader checks then online if you can pay, there are also cards where you can actually store money offline in the chip. This has the advantage that the reader does not need an internet connection. (Great if you are at a festival) You see this most commonly in old cigarette vending machines.

This smart cards do not have to have open contacts and can also work contact less, like in your passport.

They can have up to 256 kB storage capacity and can even run lightweigt Java applications (Java Card)

Modern credit cards also embedd an antenna for the contact less payments, but it is a little harder to get it out.

Here is an X-ray of a credit card where you can see it very clearly:

(found on the blog of Robin Minto)


One of the embossed letters on the credit card, 800x magnified

The microscopic camera used for the images is this one: USB WiFi Mikroskop Kamera