1. Field of the Invention
This invention is directed to a method for making laminated plastic cards which incorporate electronic elements such as integrated circuit microchips.
2. Background of the Invention
Laminated electronic cards are widely used in the radio-frequency identification (RFID) field for applications which include remotely readable electronic key cards and identification cards. Each electronic card may contain a radio-frequency transponder system which typically includes a transponder microchip with associated elements such as tuning capacitors and a radio-frequency antenna. The electronic components of the card are contained between two or more sheets of plastic laminated to each other by application of heat and pressure to top and bottom exterior surfaces of the card assembly.
In existing card lamination processes the electronic components are supplied to the card manufacturer on a continuous roll of polyester which may be 2 inches wide by 1000 feet in length, with the electronic circuits spaced along the roll at, e.g. two inch intervals. Each electronic circuit may include a radio-frequency antenna circuit printed on the polyester sheet, an integrated circuit such as a flip chip integrated circuit electrically connected to the antenna, and any other components such as a tuning capacitor that may be required for the operation of the particular circuit. The electronic circuit as supplied on the roll is complete and ready for insertion into a card.
This is accomplished by punching out from the roll portions of polyester sheet carrying each electronic circuit to obtain an inlay or insert which are picked up and placed one-by-one by a robotic device onto a blank first sheet of plastic. The individual inlays are held in place on this blank sheet by means of a pre-applied adhesive or by laser welding. The electronic circuit inlays are then covered with a second sheet of plastic placed over the first sheet of plastic. These two sheets of plastic range between 2 and 10 mils in thickness and together make up the core of the laminated cards. Additional sheets may be placed over the first and second sheets, for example, graphics layers and protective clear overlays. The multiple sheets are then laminated to each other by application of sufficient heat and pressure to cause partial fusion of the contacting surfaces of the adjacent sheets. The first and second plastic sheets are typically of vinyl which is not compatible with the polyethylene carrier sheet of the electronic circuit inlay. That is, the vinyl does not make a dependable lamination bond with the polyethylene. For this reason, the polyethylene sheet is limited to an interior portion of the card, leaving a sufficient border around the inlay, e.g. a ⅛th or ¼ inch width, of the first and second sheets of vinyl to bond to each other around the electronics inlay. 
The process just described is cumbersome because of the number of operations involved, including separation of the electronics inlays from the supply roll, transferring each inlay to the plastic sheet and fastening the inlay to the plastic sheet.
In applicant's prior application Ser. No. 09/299,944, now U.S. Pat. No. 6,248,199, a method for the continuous extrusion of electronic cards with inlaid electronic circuits or devices was disclosed. While continuous extrusion addresses some of the shortcomings of the prior art, it requires specialized extrusion equipment.
A simpler and faster method of making electronic cards is still needed which makes use of machinery and processes familiar to the industry such as lamination processes and equipment.