Gear cutting – milling – or planing – Milling – Process
Reexamination Certificate
1999-02-05
2001-01-16
Howell, Daniel W. (Department: 3722)
Gear cutting, milling, or planing
Milling
Process
C029S825000, C409S186000, C409S193000
Reexamination Certificate
active
06174113
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority from prior French Patent Application No. 98-01423, filed Feb. 6, 1998, the entire disclosure of which is herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to smart cards, and more specifically to the manufacturing of a smart card with an antenna.
2. Description of Related Art
In conventional methods of manufacturing a smart card with an antenna, a smart card containing at least one metal winding is first manufactured. The metal winding is located some distance from the opposed faces of the card and the ends of the winding form electrical connection pads. A cavity is milled in the card to expose the connection pads, and then an electronic chip is fixed in the cavity and connected to the exposed pads. In order to mill the cavity, the milling tool is made to penetrate the card step-by-step and is withdrawn between steps in order to allow a visual inspection to determine if the connection pads have been exposed. By repeating this process, the desired cavities are formed in a series of smart cards.
Because the smart cards do not always have the same thickness, the typical antenna has a thickness of 35 or 70 microns, and the antenna is not always placed at the same distance from the faces of the card, the machining of cavities in a series of cards produces a high percentage of cards in which the pads of the antenna are not exposed or are completely machined (i.e., destroyed). Obviously, such incorrectly machined cards must be rejected. To limit the number of cards that are rejected, the operator must closely monitor the machining process to insure that the cavity is being correctly produced in each card, and must frequently carry out the repeated machining and inspection operations described above. The required machining time and high rejection rate cause conventional methods of manufacturing smart cards to have low productivity and high manufacturing costs.
SUMMARY OF THE INVENTION
In view of these drawbacks, it is an object of the present invention to remove the above-mentioned drawbacks and to provide an apparatus and method for machining smart cards that significantly reduce the rejection rate due to incorrect machining.
One embodiment of the machining method of the present invention is provided for use with a smart card of the type having at least one conducting winding at some distance from the opposed faces of the card, with the end portions of the winding forming electrical connection pads for an electronic chip. According to the method, an electric potential is generated in the winding. The milling tool is made to orthogonally penetrate the card in a region of at least one of the pads, and the electric potential of the milling tool is concomitantly monitored to detect a variation in electric potential that identifies a reference position of the milling tool with respect to the card and pad. The penetration of the milling tool is continued for a predetermined travel from the reference position so as to reach a machining position. In one preferred method, the milling tool is moved parallel to the card at the depth of the machining position in order to form a cavity in the smart card. In some methods, the electric potential is generated in the winding through the generation of an electromagnetic field in the environment of the card. In other methods, a point is inserted into the card to a level at which contact is made with the winding, and an electric potential source connected to the point generates the electric potential in the winding.
According to another embodiment of the present invention, a machining apparatus is provided for machining a cavity in a smart card. The machining apparatus includes a table for holding a card, a drive mechanism, and a milling tool. The drive mechanism rotates and feeds the milling tool, and a control circuit controls the drive mechanism. Additionally, an electromagnetic field generator is placed in the vicinity of the card. A detector detects a variation in the electric potential of the milling toot and delivers a reference signal to the control circuit when the variation exceeds a predetermined value. In an alternative embodiment of the machining apparatus, the electromagnetic field generator is omitted and a point is provided for insertion into the card to a level at which contact is made with the winding. The point is connected to an electric potential source.
Other objects, features, and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only and various modifications may naturally be performed without deviating from the present invention.
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Bernardo Jean-Manuel
Brechignac R{acute over (e)}mi
Bongini Stephen C.
Fleit Kain Gibbons Gutman & Bongini P.L.
Galanthay Theodore E.
Howell Daniel W.
STMicroelectronics S.A.
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