PROCESS FOR MANUFACTURING OF A TRANSPONDER AND A TRANSPONDER MANUFACTURED BY MEANS OF THE PROCESS

Abstract: The invention refers to a process for manufacturing of a transponder and a transponder manufactured by means of a process. The transponder consists of an elongated coil carrier (2), preferably a ferrite core, with a coil (4) wound on the coil carrier's shell surface (22) which forms the transponder's antenna. The coil's wire ends (12, 13) are connected to an IC circuit (3), which in a conventional manner contains memory circuits for storage of a unique code and some form of power source, preferably a condenser. In accordance with the invention the transponder's end section is provided with two separate electrically conductive coatings (10, 11), which extend over subsections on both the coil carrier's end-head (20) and the shell surface (22). The IC circuit (3) is mounted on the end-head (20) and the respective wire ends (12, 13) are connected to the part of the coating (10, 11) which reaches down over the shell surface (22). The design sets low requirements for positioning accuracy of the IC circuit and the coil wire ends, which simplifies mass production of the transponder.

Description: PROCESS FORMANUFACTURING OFA TRANSPONDERAND A TRANSPONDER MANUFACTURED BYMEANS OFTHE PROCESS The present invention refers to a process for the manufacturing of a transponder in accordance with the introduction to claim 1, and a transponder manufactured by means of the process in accordance to what is indicated in more detail in the introduction to claim 7. STATE OF THE TECHNOLOGY The invention refers to transponders which are used to identify different objects with an unique code for the object. The transponder conventionally incorporates an antenna and an IC circuit. The antenna, which is used to receive and transmit, can be implemented in a number of different ways, e.g. by means of placing a wire on a flat supporting body in a zigzag pattern, or by winding a coil shaped antenna round a core. A coil shaped antenna wound on a ferrite core provides a very good antenna effect, and it is this type of antenna which the transponder in accordance with the invention uses. The IC circuit contains circuits which store a code, or sequence of codes, including some form of power source to be able to send the messages. A simple type of transponder can incorporate a condenser which can be charged up by the signals received from the antenna. In other types of transponders the condenser can be excluded, where instead the energy stored in the coil/antenna is utilised by an IC circuit to send back the messages. These transponders are for example used in so-called immobilizer systems in vehicles, where the ignition key contains a transponder and an unique code, which is verified before the engine can be started. A process for automatic manufacturing of a transponder is previously known by virtue of US,A,5,025,550, where the transponder's IC circuit is soldered to a flexible circuit board, which circuit board is moulded into an insert in such a way that the circuit board's connection extrudes from the insert. The insert is then mounted on a transponder core with a wound on coil, whereupon the coil's wire ends are soldered to the connection extruding from the insert. An additional manufacturing process for a transponder is known by virtue of WO 96/29618, in which process a substrate which supports an IC circuit is placed into a wire winding tool, which wire winding tool constitutes a work platform for all subsequent manufacturing stages. It is also mentioned that the IC circuit can be mounted on the transponder core, whereupon the coil's wire ends are connected directly to the IC circuit. Another wire winding process for a transponder is also known by virtue of DE,C, where the ends of the coil's wire windings are fixed in position with a rotating worktable. The positioning of the wire ends is arranged here at a distance from the core of the transponder, resulting is a transponder with an IC circuit separate from the core (with the exception of coil's wire connections). In EP,A,677,887 a so-called "pot-core" transponder is shown, which can be mounted recessed in the surrounding material, where the IC circuit is mounted on the outside of the cup-shaped housing which encloses the transponder, and where the coil is arranged on a core centred in the housing. The coil's wire ends are connected to the IC circuit arranged on the end-head by means of guiding the respective wire ends through two diametrically opposed slots in the cup-shaped housing, whereupon the wire ends are connected to the IC circuit on the exterior bottom end of the housing. OBJECTIVE OF THE INVENTION The objective of the invention is to simplify the manufacturing of a transponder, so that the transponder can manufactured more quickly, with fewer assembly stages, lower tolerance requirements during assembly and winding of the coil's wire ends, and also that the number of component parts is minimised. This hereby achieves a transponder with low manufacturing costs and high yield from the production process. Another objective is to permit manufacturing where the antenna windings do not require to be applied directly on the IC circuit, which reduces mechanical stress on the IC circuit and subsequent cassation of the transponder as a result therefrom. Yet another objective of a more profitable manufacturing process is that the ready-made coil, mounted on a core, can easily be tested before the IC circuit is mounted. Defective coils can then be rejected before the IC circuit is mounted. This considerably reduces the number of assembled transponders which require cassation, due to that the coil's inductive characteristics vary during production and constitute the biggest source of faults for rejected transponders. SHORT DESCRIPTION OF THE INVENTION The process in accordance with the invention for manufacturing of a transponder is characterised by claim 1, and a transponder manufactured by means of the process is characterised by claim 7. By means of the process in accordance with the invention and the transponder manufactured thereby, it is possible to mass produce transponders at low cost with a high yield rate from the production process. Other characteristics and advantages of the invention are indicated in the characteristic parts of dependent claims and the subsequent description of exemplified design examples. The descriptions of design examples refer to figures indicated in the following list of figures. LIST OF FIGURES Figure 1, shows a transponder in accordance with the invention; Figures 2a-2c, show how a transponder core in accordance with the invention can be prepared prior to mounting of an IC circuit and winding of wire on the coil; Figures 3a-3c, show the manufacturing stages for a first advantageous assembly process for a complete transponder, Figure 3d, shows an IC circuit with its connection points, Figures 4a-4d, show the manufacturing stages for a second advantageous assembly process for a complete transponder, and; Figure 5, shows a third advantageous assembly process of a complete transponder. DESCRIPTION OF DESIGN EXAMPLE Figure 1 shows a transponder in accordance with the invention. The transponder consists of a coil carrier 2 elongated along a lengthwise axis 19, which coil carrier is dimensionally limited by a shell surface 22 the generatrix of which is parallel to the coil carrier's lengthwise axis 19 and two end-head surfaces 20, 21 essentially arranged orthogonally with the coil carrier's lengthwise axis. The coil carrier is preferably manufactured of ferrite, either in the form of an electrically conductive or non electrically conductive ferrite material. The coil carrier has a cylindrical form in the design example shown in figure 1, but may also be manufacturing of bar-shaped material with a multi-faceted cross-section. A thin gauge coil wire 5 is wound on the shell surface 22 of the coil carrier 2, which forms an antenna. A coil 4 is wound on the coil carrier, with a thin gauge coil wire 5. The coil forms the antenna which is required to receive and transmit respective signals. By signal is also meant the ability of the transponder to influence the field built up by the transmitter, which field changes can be detected. An IC circuit 3 is connected to the wire ends 12, 13 of the coil in order to achieve a functional transponder. The coil carrier is coated with a first and second electrically conductive coating, 10 and 11, to bring the wire ends 12, 13 in contact with the respective connections 31, 32 (see figure 3d), which coatings are insulated in relation to each other. The first and second electrically conductive coatings, 10 and 1 1, both have an extension over at least one part of the coil carrier's shell surface 22 and at least one part of one of the coil carrier's end-head surfaces, in figure 1 end-head surface 20. The coatings form two essentially similar and in relation to each other insulated but electrically conductive coatings on the end parts, where each electrically conductive coating covers a crescent-shaped part of the coil carrier's end-head and connecting surfaces on the shell surface. Only a lesser part of the shell surface 22 is coated, seen lengthwise from the coated end-head surface 20 less than 20 %, preferably only a few per cent of the coil carrier's length, and covering only one sector segment of the shell surface less than 160- 170 degrees. Each crescent-shaped coating on the end-head shall cover less than 50 % of the end- head's total surface, preferably in the magnitude of 30-40 %. The antenna wire's first and second wire ends, 12 and 13, are connected to the first and second coating, 10 and 1 1, on the coil carrier's shell surface 22. The IC circuit 3 is mounted on the coated end-head so that its first and second connection point, 31 and 32, are connected to the first and second coating, 10 and 1 1, on the coil carrier's 2 end-head surface 20. The figures 2a-2c show a simple manufacturing process where the coil carrier is provided with a first and second coating, 10 and 1 1. In the event that an electrically conductive ferrite core is used as a coil carrier 2 , then in the first stage, figure 2a, an electrically insulating coating 23 shall be applied on the coil carrier's end section. This can preferably be implemented by means of a simple dip process where the coil carrier is dipped in an insulation liquid, which insulation liquid leaves a film on the end section which can be brought to a solid state with some form of hardening process, e.g. air, IR, or heat treatment. In a second stage, figure 2b, an electrically conductive coating 24 is applied in a similar way. In a third stage, figure 2c, the end section is processed so that one part 25 of the electrical coating is removed across the end section of the end-head, in such a way that two essentially similar and insulated in relation to each other but electrically conductive coatings 10, 11 are formed on the end section, where each electrical coating covers a crescent-shaped part of the coil carrier's end-head and connecting surfaces on the shell surface. The processing of the electrically conductive coating, with the objective of achieving two separate coatings, can be conducted in a number of ways. Mechanical processing, etching, or some other similar process can be used. As an alternative to the dip process the coatings can be applied by means of a spray tool, injection moulding or electrostatic surface treatment, where the surfaces which are not to be coated are masked. The coil carrier 2 can be provided with a guide slot 29 with the objective of localising the coil carrier for subsequent assembly. The figures 3a-3c show how a transponder is assembled on a coil carrier 2 which is covered with a first and second coating, 10 and 1 1, in figure 3a. In a first stage the IC circuit 3 is mounted across the end-head 20. The IC circuit is shown in figure 3d seen from below, and is provided with two connection points 31 and 32. The IC circuit can be connected in a number of ways. Solder material can be applied on the coatings 10 and 1 1, after which soldering can be conducted with IR soldering or some other similar method. Alternatively the IC circuit can be provided with solder on the connection points 31 and 33. In the next stage the coil carrier 2 and the mounted IC circuit 3 can be provided with their coil winding in a coil winding station, where the coil wire's 5 ends 12 and 13 are connected to the first and second coating, 10 and 1 1, on the coil carrier's shell surface 22. The coil wire's 5 ends 12 and 13 can be connected in a number of ways. Solder material can be applied on the coatings 10 and 1 1, after which soldering is conducted by IR soldering or some other similar method. Alternatively the ends 12, 13 can be provided with solder on the connecting points 14, 15. Figures 4a-4d show an alternative assembly sequence, where the coil wire is first wound on the coil carrier, figure 4b, after which the IC circuit is mounted on the coil carrier 2 and the coil wound on it, figure 4c. This assembly sequence allows the antenna made on the coil carrier to be tested in terms of inductance for verification that the inductance lies within the given acceptance interval, which testing and verification is conducted before the IC circuit is anchored to the coil carrier. Defective coils can then be rejected before the IC circuit is mounted. This reduces to a considerable extent the number of assembled transponders which are rejected, since the coil's inductive properties vary during production, and constitute the biggest fault source for scrapped transponders. Figure 5 shows an alternative method of assembling the transponder. An electrically conductive glue is applied here, preferably epoxy glue, in two strings, 33 and 34, on the coil carrier's end section. Each string is applied in a thin strip from the one half of the end-head 20 and down over the shell surface 22. The strings 33, 34 are applied so that a sufficient insulation distance is achieved between the strings. In the event that the coil carrier is an electrically conductive ferrite core, an insulation layer 23 shall also be applied in the same way as shown in figure 2a. This technique enables a rapid assembly process, where the coil winding can be applied in a first stage, after which the glue strings are applied and the coil wire ends 12, 13 are connected to the glue strings on the shell surface and the IC circuit 3 is pressed firmly to the glue strings on the end-head surface 20. Where coil wire is used which has protective paint, the protective paint shall be removed on the ends with a suitable process. During soldering and other similar processes the protective paint is removed in the heating process. In yet another alternative method for manufacturing of the transponder it is possible to start from a core corresponding to figure 2b. Thereafter the coil is wound and the coil ends are attached to the conductive coating 24, in essentially diametrical surfaces on the shell surface's coating. The slot 25 can be formed in a next stage, and an IC circuit is mounted over the slot 25. The assembled transponder 1 can in a conventional manner be provided with protective paint and then be moulded into a glass cylinder. This glass cylinder can then be moulded into the object which shall be given an unique code. The invention can be varied in a number of ways within the framework for the claims. The most important thing is that no extra conductor substrates are required, and that the actual coil carrier constitutes the supporting body for the electrical conductor connections between the IC circuit and the coil winding. The design example shown in figure 2c also implies that the tolerance requirements during the mounting of the IC circuit to the end-head are set very low. The IC circuit can be permitted rotational positioning round the axis 19 within a very large angular range, in practice exceeding ± 45 degrees, from a centred normal position. In a similar way the positioning of the wire ends 12, 13 can permit rotational positioning round the axis 19 within a very large angular range over the shell surface. These low tolerance requirements for positioning of the wire ends and the IC circuit imply that the assembly process can be conducted at high speed, with multi-stage operation machines, e.g. of the type shown in WO 96/29618, where the need for adjustments in the machine is dramatically reduced with a design of the transponder in accordance with the invention. In that the attachment surfaces for the IC circuit and coil's wire ends lie on perpendicular surfaces in relation to each other, and that the coil's wire ends are attached in the same plane as the coil winding, the application and connection of the wire during winding is simplified , while the IC circuit does not run the risk of being affected by the wire application tool.

Claims: CLAIMS 1. Process for manufacturing of a transponder, which transponder consists of a coil carrier elongated along a lengthwise axis, and which coil carrier is dimensionally limited by a shell surface the generatrix of which is parallel to the coil carrier's lengthwise axis and two end-head surfaces essentially arranged orthogonally with the coil carrier's lengthwise axis, on which coil carrier a coil shaped antenna is wound, including an IC circuit connected to the coil's wire ends c h a r a c t e r i s e d b y that - a first and second electrically conductive coating are applied on the coil carrier, which coatings are insulated in relation to each other, - where the first and second coating both have an elongation over at least one part of the coil carrier's shell surface and at least one part of the coil carrier's end-head surface, - whereupon the antenna wire's first and second wire ends are applied by means of an anchoring process to a permanent conductive contact to the first and second coatings on the coil carrier's shell surface, - and that the IC circuit's first and second connection points are applied by means of an anchoring process to a permanent electrically conductive contact to the first and the second coatings on the coil carrier's end-head surface. 2 Process for manufacturing of a transponder in accordance with claim 1 c h a r a c t e r i s e d b y that the electrical coatings on the coil carrier are formed by a stepwise process where - in a first stage one end part of the coil carrier is coated in its entirety with an electrically conductive coating, where the named end part consists of an end-head and a lesser part of the shell surface which connects to the named end-head, - whereupon by means of a machine process a part of the electrical coating is removed across the end part of the end-head, in such a way that two essentially similar and insulated in relation to each other but electrically conductive coatings are formed on the end part, where each electrical coating covers a crescent-shaped part of the coil carrier's end-head and the connecting surfaces on the shell surface. 3. Process for manufacturing of a transponder in accordance with claim 2 c h a r a c t e r i s e d b y that before the electrical coating is applied to the coil carrier an electrically insulating layer is applied on the coil carrier's end part with an elongation on the coil carrier corresponding in extent to at least the subsequent coating of the electrically conductive coating and localisation on the coil carrier. 4. Process for manufacturing of a transponder in accordance with one of the previous claims characterised by that the anchoring process for at least one of the IC circuit's connecting points and/or the antenna wire's first and second wire ends consists of a soldering process. 5. Process for manufacturing of a transponder in accordance with one of the previous claims characterised by that the anchoring process for at least one of the IC circuit's connection points and/or the antenna wire's first and second wire ends consists of a gluing process, where and electrically conductive glue is used, preferably an electrically conductive glue of the epoxy type. 6. Process for manufacturing of a transponder in accordance with any of claims 4 or 5 characterised by that in a first stage the antenna wire is wound on the coil carrier followed by anchoring of the wire ends , and that in a second separate stage the IC circuit is anchored to the coil carrier, whereby the antenna made on the coil carrier can be tested in terms of inductance for verification that the inductance lies within the given acceptance interval, which testing and verification is conducted before the IC circuit is anchored to the coil carrier. 7. Transponder for unique identification of objects, which transponder consists of - a coil carrier (2) elongated along a lengthwise axis (19), which coil carrier is dimensionally limited by a shell surface (22) the generatrix of which is parallel to the coil carrier's lengthwise axis (19) and two end-head surfaces (20, 21) essentially arranged orthogonally to the lengthwise axis of the coil carrier, - a coil shaped antenna (4) wound on the coil carrier's shell surface (22), and - an IC circuit (3) connected to the coil's wire ends (12, 13) characterised by that - a first and second electrically conductive coating (10 and 11) are applied on the coil carrier (2), which coatings are insulated in relation to each other, - where the first and second coating both have an elongation over at least one part of the coil carrier's shell surface (22) and at least one part of the coil carrier's end-head surface (20), - the antenna wire's first and second wire ends (12 and 13) are connected to the first and second coating (10, 11) on the coil carrier's shell surface (22), - and that the IC circuit's first and second connecting points (31 and 33) are connected to the first and second coating on the coil carrier's end-head surface (20). 8. Transponder in accordance with claim 7 characterised by that the respective coating (10, 11) covers less than 50 % of the end-head surface (20), preferably in the magnitude of 30-40 %, and that the respective coating (10, 11) covers less than 20 % of the shell surface, seen lengthwise from the covered end-head surface (20), and preferably only a few per cent of the coil carrier's length, and only covering a sector segment of the shell surface (22) of less than 160-170 degrees. 9. Transponder in accordance with claim 8 characterised by that the coil carrier (2) is a ferrite core, and that if the ferrite core is electrically conductive there is an electrically insulating layer (23) between the ferrite core and the electrically conductive coatings (10, 11). 10. Transponder in accordance with claim 9 characterised by that the electrically conductive coatings (10, 11) consist of an electrically conductive glue (33, 34), to which glue the IC circuit (3) and the wire ends (12, 13) are attached before the glue hardens.

Inventors: JOHANSSON HANS, LINDQVIST FRANK, LINDQVIST HENRIK, JOHANSSON, HANS, LINDQVIST, FRANK, LINDQVIST, HENRIK
Applicants: FYRTECH MICROELECTRONICS AB, JOHANSSON HANS ARNE VALENTIN, LINDQVIST FRANK, LINDQVIST HENRIK, JOHANSSON, HANS, LINDQVIST, FRANK, LINDQVIST, HENRIK
Application year: 1998
Main classification: G01V15
IPC codes: G01V15, G06K19