Registers – Records – Conductive
Patent
1994-07-25
1996-07-09
Hajec, Donald T.
Registers
Records
Conductive
902 26, G06K 19067
Patent
active
055346863
DESCRIPTION:
BRIEF SUMMARY
The invention relates to chip cards such as memory cards or microprocessor-based cards.
These cards are used in a growing number of applications, and an essential factor in their success lies in the possibility of manufacturing them at low cost. For example, for applications to commercial transactions involving small sums of money (for example prepaid phone cards, prepaid parking cards, etc.), it is very important that the cost of manufacture of the card should be low as compared with the commercial value of the services provided by the card.
To manufacture a chip card, a micromodule comprising an integrated circuit chip, a connector with several contacts and connection wires between the chip and the connector are mounted in a plastic carrier (the card itself). The connector of the chip card is constituted by the connector of the micromodule.
It is noted that, in the manufacture of the micromodule, the operations of assembling the chip in the micromodule cost a great deal more than the chip itself. The ratio may go up to 4:1.
To reduce the overall cost of the card, it is therefore advantageous to optimize the operations of assembling the chip in the micromodule, even if this makes the circuits of the chip more complex. The documents WO-A-604 171, EP-A-0 287 175 and FR-A-2 608 293 presents embodiments such as these.
Among the approaches envisaged, there is that of reducing the number of contacts of the connector, and hence of the number of connection wires (which are soldered by the so-called wire-bonding technique) between the chip and the connector. cards have a maximum of eight contacts according to the ISO standard 7816. Often, only five or six of these contacts are actually used.
If there could be a change to having only two contacts, the cost would be considerably reduced. Furthermore, reducing the number of contacts would mean reducing the risk of electrostatic discharges which can damage the chips. A reduction is also obtained in the surface area of the chip (a large portion of which is used solely to place the contact pads which have to receive the connection wires with the connector), the cost of the chip being thereby reduced accordingly. Finally, if only two contacts are used, it is possible to envisage applications of chip cards in formats other than those of credit cards which constitute the most common format of presently used chip cards (these are flat cards of about 5 cm by 8 cm with a thickness of about 1 millimeter). For example, it is possible to envisage chip coins (having a format similar to that of a coin) or chip keys (having a format similar to that of a key). In these formats, it would be particularly advantageous to have only two contacts, in order to eliminate, to the greatest possible extent, the requirements of the accurate positioning of the card in the reader.
However, it is of course not easy to propose a card having only two contacts because it is necessary firstly to supply the card with power and secondly to enable two-way communication between the card and the reader into which it is inserted. For example, the phone cards presently used in France have seven useful contacts that may be called VCC, VSS, VPP, CLK, I/O, RST, FUSE, plus one unused contact (PROG). These contacts correspond respectively to:
I/O: data output for reading in a memory of the card;
FUSE: contact for general activation and reinitialization; and
RST: this contact defines whether the operation is an incrementation operation (RST=0) or a programming operation (RST=1) on a leading edge of the clock signal CLK.
It will easily be understood that it is not easy to obtain the same functions with two contacts only.
However, attempts have been made to propose cards that work with two contacts only. The proposals made are based essentially on the use of the ground contact VSS and the supply contact VCC with an amplitude modulation of the voltage present at the contact VCC. The permanent presence of a supply voltage gives the supply power of the card. The modulation of this voltage represents the information ele
REFERENCES:
patent: 4272758 (1981-06-01), Giraud
patent: 4621190 (1988-11-01), Saito et al.
patent: 4948954 (1990-08-01), Dias
Kowalski Jacek
Sureaud Jean
Filipek Jeffrey R.
Gemplus Card International
Hajec Donald T.
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