Dual-interface smart card

A dual-interface smart card comprises an integrated circuit (IC) module coupled to a plastic card body. The IC module includes multiple downwardly facing, externally exposed contact pads that are electrically coupled to corresponding externally exposed sections of a radio frequency (RF) antenna incorporated into the card body. Each contact pad is electrically connected to the RF antenna by a pair of opposing, stapled-shaped, conductive elements, with one conductive element being permanently welded to the contact pad and the other permanently welded to the antenna. Each conductive element includes a pair of resilient spring arms that maintain electrical connection between the contact pad and the antenna even upon movement of the IC module relative to the card body. To provide further redundancy of connection between each contact pad and the antenna, the resilient spring arms of the opposing conductive elements are encapsulated with a supply of conductive filler material.

BACKGROUND

The present invention relates generally to the plastic card manufacturing industry and, more specifically, to the manufacture of dual-interface smart cards.

Smart cards are well known devices that include a plastic card body into which is embedded an integrated circuit (IC). The integrated circuit is designed to store data that can be used, inter alia, to provide the card with electronic identification, authentication, data storage and application processing capabilities. As a result, smart cards are widely used in commerce to provide information and/or application processing capabilities in connection with, but not limited to, bank cards, credit cards, health insurance cards, driver's licenses, transportation cards, loyalty cards and membership cards.

The card body for a smart card is typically constructed out of one or more layers of any durable plastic material, such as polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS) or polycarbonate. The dimensions of the card body are typically similar to the dimensions of a conventional credit card (i.e., 3.370 inches in length, 2.125 inches in width and 0.030 inches in thickness).

The integrated circuit (IC) is typically constructed as part of an integrated circuit (IC) module that includes a lead frame having a bottom surface on which the integrated circuit is fixedly mounted using a chip adhesive. The exposed portion of the IC is in turn encapsulated within a hard epoxy resin for protective purposes. As part of the smart card manufacturing process, the IC module is mounted, chip side down, into a fitted recess that is milled or otherwise formed into the top surface of the card body and is fixedly held in place using a hot melt adhesive.

Smart cards of the type as described above transmit data stored on the integrated circuit using either (i) a direct contact interface (the resultant products being commonly referred to in the art as contact smart cards), (ii) a contact-free interface (the resultant products being commonly referred to in the art as contactless smart cards) or (iii) a hybrid of the two aforementioned interfaces (the resultant products being commonly referred to in the art as dual-interface smart cards).

The contact interface for a dual-interface smart card is typically constructed as a plurality of gold-plated contact pads that are fixedly mounted onto the top surface of the lead frame and are arranged to form a total contact surface area of approximately 1 square centimeter. The underside of each contact pad is individually electrically connected to the integrated circuit by a corresponding gold-plated wire, the wires being encapsulated by a hard epoxy resin for protective purposes. As such, it is to be understood that the contact pads serve as an electrical interface for the IC when the smart card is inserted into an appropriate reader.

The contact-free interface for a dual-interface smart card is typically provided by a conductive antenna that is incorporated into the card body by any suitable means, such as through the use of embedding, etching, plating, printing or the like. Preferably, the antenna is arranged in a coiled, or spiraled, configuration around the IC module cavity and is, in turn, electrically connected to the integrated circuit, as will be described further in detail below. Accordingly, in response to an interrogation signal, information stored on the integrated circuit can be transmitted by the antenna as a radio frequency (RF) signal.

As noted above, the integrated circuit for a dual-interface smart card must be electrically connected to the antenna to effectively transmit data. Typically, a pair of opposing metal contact pads are mounted onto the underside of the lead frame, each contact pad being individually electrically connected to the integrated circuit by a corresponding gold-plated wire which is then encapsulated within a hard epoxy resin for protective purposes. The card body is then drilled, or routed, to the extent necessary so that the conductive component of the antenna is externally exposed at two separate locations.

Various techniques are known in the art for electrically connecting each contact pad formed on the underside of the IC module with a corresponding exposed portion of the antenna.

One such technique involves overfilling each routed hole with a conductive epoxy material that creates a convex protrusion or bump in direct alignment with each of the contact pads formed on the underside of the IC module. Accordingly, when the IC module is permanently affixed to the card body, an electrical connection is established between the integrated circuit and the antenna through the conductive epoxy.

The above-described method for electrically connecting the IC module to the antenna has been found in the industry to be largely unsatisfactory. Specifically, the conductive epoxy has been found to fragment, crack or otherwise break at one or both of its connection points in response to torsion or stress applied to the smart card during use and/or testing. As a result of the electrical disconnection of the IC module from the antenna, the smart card loses its RF signal transmission capabilities, which is highly undesirable.

In response, a number of alternative approaches for electrically connecting the IC module to the antenna have been implemented in the smart card manufacturing industry. However, these alternative approaches have been found to similarly suffer from a number of notable shortcomings including: (i) being considerably labor-intensive and time-consuming in nature, (ii) requiring the purchase of additional manufacturing equipment, and/or (iii) utilizing glues with limited shelf time.

Accordingly, it is an object of the present invention to provide a relatively inexpensive smart card that is flexible enough to support some stress but, at the same time, has the requisite structural integrity to maintain a strong physical connection of the IC module to the antenna.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new and improved dual-interface smart card.

It is another object of the present invention to provide a new and improved dual-interface smart card that is durable in nature and designed to maintain the requisite internal electrical connectivity between components in response to torsion and stress applied thereto.

It is yet another object of the present invention to provide a dual-interface smart card that has a limited number of parts and is cost-effective to manufacture.

Accordingly, as a feature of the present invention, there is provided a smart card, the smart card comprising (a) a card body, the card body comprising an antenna, (b) an integrated circuit (IC) module coupled to the card body, the IC module comprising an IC chip and a contact pad electrically coupled to the IC chip, and (c) a first conductive element for electrically coupling the IC module to the antenna, the first conductive element being permanently conductively coupled to one of the antenna and the contact pad, the first conductive element comprising a first resilient contact member that is adapted to electrically contact the other of the antenna and the contact pad, the first resilient contact member being adapted to flex to the extent necessary to maintain electrical contact with the other of the antenna and the contact pad upon movement of the IC module relative to the card body.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now toFIGS. 1 and 2, there are shown top plan and exploded, fragmentary, cross-section views of a first embodiment of a dual-interface smart card constructed according to the teachings of the present invention, the first embodiment dual-interface smart card being identified generally by reference numeral11. As will be described further below, smart card11is capable of transmitting stored electronic data using either a direct contact interface or a contact-free interface.

Dual-interface smart card11comprises a plastic card body13and an integrated circuit (IC) module15fixedly mounted into card body13, as will be described further below.

As seen most clearly inFIGS. 2 and 3, card body13is constructed out of a plurality of layers of any durable plastic material, such as polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS) or polycarbonate. The dimensions of card body13are preferably similar to the dimensions of a conventional credit card (i.e., 3.370 inches in length, 2.125 inches in width and 0.030 inches in thickness).

Card body13comprises a radio frequency (RF) inlay17that is disposed between a top print layer19and a bottom print layer21. In addition, a pair of opposing transparent overlays23and25is disposed on the top and bottom surfaces, respectively, of the stack. It should be noted that layers17,19,21,23and25are then permanently joined together by any conventional means, such as through a lamination process, to form the unitary card body13.

It should be noted that card body13is not limited to the number and arrangement of layers as described herein. Rather, it is to be understood that the number, construction and dimensions of the individual layers could be modified without departing from the spirit of the present invention as long as the overall dimensions of card body13remain generally the same (i.e., 3.370 inches in length, 2.125 inches in width and 0.030 inches in thickness).

RF inlay17includes a core layer27that is preferably constructed of a polyvinyl chloride (PVC) material that is approximately 350 μm in thickness, core layer27comprising a substantially flat top surface31and a substantially flat bottom surface33. As seen most clearly inFIG. 2, a radio frequency antenna35is incorporated into core layer27. Specifically, RF antenna35is preferably in the form of a 100 μm diameter copper wire that is embedded into top surface31and arranged in a coiled, or spiraled, configuration around the periphery of core layer27, the copper wire preferably being wrapped within an insulated sheath, or jacket (not shown). As will be described further in detail below, antenna35is electrically connected to IC module15to provide smart card11with RF transmission capabilities in the frequency range of approximately 13.56 MHz.

Each of top and bottom print layers19and21is preferably constructed out of a 200 μm thick white PVC material. As can be appreciated, layers19and21are adapted to receive printed matter to identify and decorate card11.

In addition, each of top and bottom overlays23and25is preferably constructed out of a 50 μm thick transparent PVC material. As can be appreciated, overlays23and25are designed to protect card body13from common environmental conditions.

As seen in bothFIGS. 2 and 3, card body13is shaped to define a generally rectangular module cavity, or recess,37that is dimensioned to fittingly receive module13(i.e., the cavity being approximately 13.4 mm in length by approximately 12.3 mm in width). Cavity37is formed into card body13by any conventional means, such as through a milling process, and extends down from the top surface of top print layer19to a depth that is nearly the entire thickness of core layer27. A narrow shelf, or mounting surface,39is formed into top print layer19around the periphery of cavity37in order to support IC module15, as will be described further below.

Referring now toFIG. 4, IC module15comprises a lead frame41that includes a top surface43and a bottom surface45. An integrated circuit chip47is in turn fixedly secured onto bottom surface45of lead frame41by a chip adhesive49.

A plurality of gold-plated contact pads51are fixedly mounted onto top surface43of lead frame41and are arranged to form a total contact surface area of approximately 1 sq cm. It should be noted that the underside of each contact pad51is electrically connected to IC chip47by a corresponding gold-plated wire53, thereby enabling a corresponding reader (not shown) to retrieve electronic data from IC chip47through contact pads51.

In addition, a pair of gold-plated contact pads55is fixedly mounted onto bottom surface45of lead frame41at opposite ends, each contact pad55being electrically connected to IC chip47by a corresponding gold-plated wire57. An encapsulation material59, such as a hard epoxy resin, is deposited over IC chip47as well as wires53and57to protect the sensitive components and ensure that adequate connectivity is maintained.

Referring back toFIG. 2, a pair of bores60(only one of which is shown inFIG. 2) is routed, or drilled, down into shelf39. As can be seen, each bore60is drilled a depth that is sufficient to expose a segment of the copper wire antenna35and a gap region that is approximately 213 um. As will be described in detail below, the exposed portion of antenna35is conductively coupled to each of contact pads55, thereby providing IC module15with RF transmission capabilities. Although not shown herein, it is to be understood that a conductive contact pad could be mounted onto the exposed segments of antenna35to facilitate connection therewith.

Preferably, smart card11is assembled in the following manner. Specifically, card body13is preferably formed from the plurality of laminates as described in detail above. In turn, card body13is shaped to define module cavity37by any conventional means, such as through a milling process. Furthermore, the pair of bores60is routed, or drilled, down into shelf39at a depth that is sufficient to expose a segment of the strands of copper wire antenna35.

IC module15is then mounted, chip47side down, onto shelf39with each contact pad55on the underside of lead frame41disposed in direct alignment with a corresponding exposed segment of RF antenna35, as shown inFIG. 2. Preferably, a hot melt (not shown) is utilized to permanently join IC module15to card body13to yield the unitary card11.

As a principal feature of the present invention, smart card11relies upon a novel means for connecting bottom contact pads55with the exposed segments of RF antenna35, the details of the connection means to be described in detail below. It is to be understood that the novel connection means provides smart card11with enough flexibility to support bending stress without compromising the requisite structural integrity of the internal physical connections, which is an object of the present invention.

Specifically, referring now toFIG. 2, the novel connection means utilizes first and second opposing conductive elements, or connectors,61-1and61-2as well as a supply of conductive filler material62(shown in dashed form inFIG. 6) that encapsulates at least a portion of elements61. For purposes of simplicity only, a single pair of conductive elements61is shown joining one contact pad55to exposed segments of RF antenna35. However, it is to be understood that an identical pair of conductive elements61and filler material62is preferably used to similarly join the other contact pad55to exposed segments of RF antenna35at a separate location.

As seen most clearly inFIGS. 5(a) and5(b), each conductive element61is preferably constructed out a length of thin wire (e.g., 100 micron in diameter) that is formed from a highly conductive material, such as gold, copper or aluminum. Although conductive element61is represented herein as wire that is generally circular in transverse cross-section, it is to be understood that alternate types of conductive elements (e.g., flattened, ribbon-type conductive elements) could be used in place thereof without departing from the spirit of the present invention.

Each conductive element61has a generally U-shaped, staple-like configuration with a straightened base portion, or support,63and a pair of resilient spring arms, or flexible contact members,65-1and65-2formed at opposite ends of base portion63. Spring arms65curve inward towards one another, as seen most clearly inFIG. 5(a). However, it should be noted that spring arms65extend laterally outward in opposing directions, as seen most clearly inFIG. 5(b), so as to provide conductive element61with a somewhat spiral, or helical, overall configuration. As can be appreciated, the outward lateral orientation of spring arms65serves to, inter alia, (i) expose base portion63as a region for conductive contact and (ii) prevent interference between spring arms65when a pair of conductive elements61is nested tightly together, as shown inFIG. 6.

It is to be understood that curvature of each spring arm65allows for its flexion downward upon receiving a suitable compressive force thereon, with each spring arm65resiliently returning to its original configuration upon withdrawal of such a compressive force. In this capacity, the resilient, spring-biased nature of each arm65enables each conductive element61to maintain direct contact with a complementary conductive item (e.g., antenna35, pad55and/or opposing element61) even when compression and separation forces are applied thereto. Because it has been found that the IC module in a conventional smart card is prone to movement relative to its card body, the utilization of spring-like contact arms65herein to maintain direct physical contact between IC module15and antenna35over time (i.e., even upon repeated movement of IC module15relative to card body13) serves as an important feature of the present invention.

It should be noted that each conductive element61is not limited to the slightly spiraled, staple-like configuration as represented herein. Rather, it is to be understood that each conductive element61could be alternatively configured without departing from the spirit of the present invention. However, it is preferred that modified versions of conductive elements61similarly utilize contact members with resilient characteristics. For example, rather than an arcuate design, each arm65could have an alternative configuration that enables direct electrical contact to be maintained between contact pad55and antenna35even upon slight movement of IC module15relative to card body13, such as a resilient coil, loop, tube, piston, sphere or the like, without departing from the spirit of the present invention.

It should also be noted that each conductive element61is represented herein as comprising two spring arms65to create redundancy in its points of physical connection. Accordingly, if one spring arm65should become disconnected from its opposing conductive item, it is to be understood that the direct contact established with the conductive element61can be adequately retained through its other arm65, which is highly desirable.

However, it should be noted that each conductive element61is not limited to a dual-arm construction. Rather, it is to be understood that the number of spring arms65for each conductive element61could be increased or decreased without departing from the spirit of the present invention. For example, each conductive element61could be alternatively include additional spring arms in order to increase the total number of connection points and overall contact surface area, thereby improving the reliability of the connection over time, which is highly desirable.

Referring back toFIG. 2, base portion63of first conductive element61-1is permanently welded to one or more strands of exposed RF antenna35by any conventional means, such as ultrasonic welding, with its opposing spring arms65directed upwards for electrical contact with contact pad55through either (i) direct contact with contact pad55and/or (ii) direct contact with second conductive element61-2(thereby resulting in the indirect contact with contact pad55). It should be noted that each spring arm65for first conductive element61-1preferably has a height H that is greater than the depth of routed bore60, thereby enabling each spring arm65to extend beyond shelf39and into direct conductive contact against opposing conductive element61-2and/or contact pad55when smart card11is in its fully assembled form, which is highly desirable.

Similarly, base portion63of second conductive element61-2is permanently welded to contact pad55by any conventional means, such as ultrasonic welding, with its opposing spring arms65directed downward towards for electrical contact with one or more strands of exposed RF antenna35through either (i) direct contact with antenna35and/or (ii) direct contact with first conductive element61-1(thereby resulting in the indirect contact with antenna35). Preferably, each spring arm65for second conductive element61-2similarly has a height H that is greater than the depth of routed bore60, thereby enabling each spring arm65to extend down into direct conductive contact against opposing conductive element61-1and/or one or more strands of exposed RF antenna35when smart card11is in its fully assembled form, which is highly desirable.

Preferably, conductive elements61-1and61-2are oriented in an offset relationship so that spring arms65do not interfere with one another as base portions63are drawn towards one another. As a result, conductive elements61-1and61-2can nest, or crash, tightly together, as shown inFIG. 6, with each spring arm65drawn firmly against one or more complementary conductive items (e.g., antenna35, pad55and/or a portion of an opposing conductive element61).

In addition, a supply of conductive filler material62is deposited into routed bore60so as to encapsulate at least a portion of spring arms65of first and second conductive element61-1and61-2. Filler material62is preferably constructed of a low durometer conductive silicone that is approximately 5 um in thickness. Due to its inherent softness, it is to be understood that conductive filler material62is able to receive substantial torsion forces without experiencing degradation of its physical structure (i.e., without cracking, fragmenting, breaking or the like). As a result, by permanently welding each conductive element61at one end and, in turn, encapsulating its opposite end with soft filler material62, it is to be understood that a strong connective bond is established between IC module15and RF antenna35that is able to withstand considerable torsion forces, which is highly desirable. In addition to its conductive properties, filler material62protects conductive elements61-1and61-2from oxidation and other forms of contamination that can jeopardize conductivity.

It should be noted that filler material62is not limited to a low durometer conductive silicone. Rather, it is to be understood that filler material62could be formed from any conventional conductive material with considerable softness and flexibility that enables it to withstand stress (e.g., mercury) without departing from the spirit of the present invention.

As a principal feature of the present invention, connective redundancy is utilized to conductively couple IC module15to antenna35. Specifically, each contact pad55is conductively coupled to one or more exposed strands of antenna35using both (i) the direct physical contact of each spring arm65against one or more complementary conductive items (e.g., antenna35, pad55and/or a portion of an opposing conductive element61) and (ii) conductive filler material62to encapsulate at least a portion of opposing conductive elements61. Stated another way, even when IC module15experiences significant motion relative to card body13, electrical connection is adequately maintained between IC module15and RF antenna35through either direct, physical, metal-on-metal spring contact and/or the use of conductive filler material62. As a result of the aforementioned connective redundancy, smart card11is rendered less susceptible to failure than traditional smart cards that rely upon a single means of electrically connecting an IC module to an RF antenna.

It should be noted that the details relating to the construction of smart card11are intended to be merely exemplary. Accordingly, it is to be understood that those skilled in the art shall be able to make numerous variations and modifications to smart card11without departing from the spirit of the present invention. All such variations and modifications are intended to be within the scope of the present invention as defined in the appended claims.

For example, referring now toFIG. 7, there is shown an exploded, fragmentary, cross-section view of a second embodiment of a dual-interface smart card constructed according to the teachings of the present invention, the second embodiment dual-interface smart card being identified generally by reference numeral111. As will be described further below, smart card111is capable of transmitting stored electronic data using either a direct contact interface or a contact-free interface.

As can be seen, smart card111is similar to smart card11in that smart card111comprises a plastic card body113that is shaped to define a module cavity, or recess, that is dimensioned to receive an integrated circuit (IC) module115.

Plastic card body113is similar to plastic card body13in that plastic card body113comprises a radio frequency (RF) inlay117that is disposed between a top print layer119and a bottom print layer121. In addition, a pair of opposing transparent overlays123and125is disposed on the top and bottom surfaces, respectively, of the stack. To form the unitary card body113, layers117,119,121,123and125are then permanently joined together by any conventional means, such as through a lamination process.

The principal distinction between plastic card body113and plastic card body13relates to the orientation of its associated RF inlay. Specifically, card body13is formed with RF inlay17disposed in its natural orientation (i.e., with flat top surface31facing upward). By comparison, card body113is formed with RF inlay117flipped upside down, or inverted, (i.e., with its flat top surface131facing downward and its flat bottom surface133facing upward). Accordingly, radio frequency antenna135, which is still preferably in the form of a 100 μm diameter copper wire, is effectively positioned along the underside of core layer127(i.e., adjacent bottom print layer121).

As seen most clearly inFIG. 8, RF antenna135is arranged as a plurality of concentric strands that extend along the periphery of core layer127. Preferably, one strand of antenna135is arranged in a dense configuration, such as a tightly wrapped coil, spiral or zig zag formation, to yield a contact terminal136that is aligned directly beneath a corresponding contact pad155in IC module115. In addition, although not shown herein, a conductive contact pad may be directly welded onto contact terminal136to further facilitate electrical connection. It should be noted that the dense configuration of contact terminal136ensures that when each of the pair of bores160(only one of which is shown inFIG. 7) is routed, or drilled, down into shelf139, a segment of the copper wire antenna is rendered exposed for contact.

Referring back toFIG. 7, smart card111is similar to smart card11in that smart card utilizes first and second opposing conductive elements161-1and161-2as well as a supply of conductive filler material (not shown) to encapsulate elements161. Specifically, each conductive element161is preferably constructed out a length of thin wire that is formed from a highly conductive material, such as gold or aluminum, and configured as a U-shaped staple with a generally straight base portion163and a pair of opposing, inwardly curved spring arms165.

Accordingly, the base portion163of first conductive element161-1is permanently welded to one or more strands of exposed RF antenna135with its spring arms165protruding in the upward direction towards contact pad155. Preferably, each spring arm165for conductive element161-1is of a length greater than the depth of routed bore160to promote contact with contact pad155and/or second conductive element161-2when smart card11is in its fully assembled form.

Similarly, base portion163of second conductive element161-2is permanently welded to contact pad155with its spring arms165protruding in the downward direction towards the one or more strands of exposed RF antenna135. Preferably, each spring arm165for second conductive element161-2is of a length greater than the depth of routed bore160to promote contact with exposed strands of RF antenna135and/or first conductive element161-1when smart card11is in its fully assembled form.

As noted briefly above, a supply of conductive filler material, which is preferably constructed of a low durometer silicone, is deposited into routed bore160so as to encapsulate the majority of the length of arms165for first and second conductive elements161-1and161-2. In this manner, the filler material serves to conductively couple first and second conductive elements161-1and161-2, thereby providing redundant electrical connection between IC module115and RF antenna135, which is a principal object of the present invention.

It should be noted that by inverting RF inlay117, the depth of routed bore160is lengthened considerably. As a result, the length, or area, of contact between first and second conductive elements161-1and161-2is substantially increased. Accordingly, by extending the area of contact between elements161, it is to be understood that a more robust, reliable and secure connection is established between IC module115and RF antenna135, which is highly desirable.