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Chip Cards

The chip card is a microcontroller or memory card with a full-blown processor structure, packaged in a plastic card. Thanks to modern semiconductor integration technology, chip cards have the same size as credit cards, and are not thicker than any magnet strip card. This article is intended as an introduction to chip card technology.

Chip cards with a variety of appearances and functions have been around since the middle of the nineteen seventies. Today, they are used increasingly in, for instance, telephone booths (though not yet in the UK) and personnel identification and work time logging systems in large plants and office buildings. In some cases, they are also used for electronic financial transactions. In the near future, further measures towards application-independent, international, standardization of the chip card is sure to give a tremendous boost to the number of applications. This will be helped by much reduced productions cost, which goes hand in hand with high production volumes. Also, a combined chipcard/magnet strip card will soon be unveiled.

The primary function of a chip card is to help identify the rightful owner, or, with non- personalized cards, to grant the user a certain service for which a remuneration is due that is within the limits of the ‘value’ of the card. In this respect, chip cards are the successors of the widespread ‘flexible friend’, the magnet strip card issued by banks and credit card organizations. The requirements as regards physical and electrical characteristics of the chip card are laid down in ISO standard 7816, part 3.

Construction of a chip card

The generic name ‘chip card’ is used to cover the following products:

  • Smart Card
  • Memory Card
  • Processor Card
  • Intelligent Card
  • IC card

These different names already hint at differences as regards function and internal construction. According to the ISO 7816 standard, the name ‘IC Card’ should be used to denote all members of the chip card family.

Magnet strip cards with their passive function and small memory capacity (342 bytes) are easily read, copied and forged. By contrast, chip cards, by virtue of their much larger memory capacity (up to 32 KByte), built-in intelligence and access lock, offer a much higher degree of safety against unauthorized use. Yet, they are relatively cheap to produce.

Production

The chip card has the same size as a bank or credit card: 85.6x54x0.76 mm. For mobile telephones and other applications where space is restricted, so-called ‘Plug-in SIM®’ cards are available with a size of 18x28x0.76 mm. The chip proper has a size of 10×10 mm2, and is embedded in plastic carrier material. Because of the flexibility of the card and other external factors, the carrier ‘floats’ inside a clearance in the plastic carrier.

The chip carrier element is produced by covering both sides of a foil with copper foil. Next, the contacts and the layout are etched, and subsequently through-contacted. Onto this composite foil, an equalizing foil is laminated, from which the clearances for the chip contacts are punched. The chip is secured on to the equalizing foil with the aid of silicon rubber cement, connected to the conducting foil, and subsequently covered by another foil. The rear side of the conducting foil contains the contacts, which later form the contacts to the outside world.

A further layer of foil, which has clearances of the size of the contact elements, is secured at the contact element side of the conducting foil. The finished carrier element is punched out of a larger sheet, and inserted into the card, which consists of several layers of PVC foil. These make the card resistant against high temperatures, high humidity, and chemicals. However, direct heat transfer to the card, as well as electrical noise at the chip contacts (ESD) and excessive strain caused by bending, should be avoided.