Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/11—Printed elements for providing electric connections to or between printed circuits
  • H05K1/118—Printed elements for providing electric connections to or between printed circuits specially for flexible printed circuits, e.g. using folded portions
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K1/00—Printed circuits
  • H05K1/02—Details
  • H05K1/11—Printed elements for providing electric connections to or between printed circuits
  • H05K1/115—Via connections; Lands around holes or via connections
  • H05K1/116—Lands, clearance holes or other lay-out details concerning the surrounding of a via
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
  • H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
  • H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
  • H05K3/341—Surface mounted components
  • H05K3/3431—Leadless components
  • H05K3/3436—Leadless components having an array of bottom contacts, e.g. pad grid array or ball grid array components

Definitions

• the instant invention relates to flexible printed circuits .
• Such cards usually comprise a body and a module.
• a module comprises a flexible printed circuit, which has a flexible substrate on which are formed electrical contacts. These contacts are to be connected to an integrated circuit (or ⁇ ⁇ ' ) of the card.
• the contacts serve to be connected to an external card reader. Using the card reader, it is possible to access data of the card, for example.
• the flexible printed circuit was provided with electrical zones, remote from the electrical contacts, but electrically connected there to.
• the electrical zone is to be welded to an electrical track of the card-receiving support.
• the card is fixed to the card-receiving support, the information can be accessed by the card- receiving support through the electrical zone which is electrically connected to the contact and hence to the chip,
• cards can still be removably used in conventional card-readers, where the contacts will be contacted to the card-reader .
• the instant invention has notably for object to improve such fixation.
• the flexible printed circuit comprises a flexible electrically- insulating substrate having opposed first and second faces.
• Electrical contacts are patterned on the first face. These contacts are designed to be placed in electrical contact with an electrical card-reading device. These electrical contacts are to be electrically connected to an integrated circuit of the contact-communication device .
• Each zone is associated to a respective contact.
• An electrical path is electrically connected both to a zone and an associated contact. At least part of the electrical path is patterned on the second face.
• the area where the solder paste is placed is circumscribed.
• the flow of the solder paste is more limited, and accuracy and repeatability of the fixation is enhanced, while ensuring all the functions of the device.
• the invention relates to a longer lasting flexible printed circuit .
• This flexible printed circuit for a contact-communication device.
• This flexible printed circuit comprises a flexible electrically- insulating substrate having a face.
• This flexible printed circuit further comprises a plurality of electrical contacts patterned on this face of the substrate. These electrical contacts are designed to be placed in electrical contact with an electrical card- reading device.
• the electrical contacts are also to be electrically connected to an integrated circuit of the contact- communication device.
• a plurality of electrical zones are patterned on a face of the substrate, each zone being associated to a respective contact.
• the electrical contact and associated zone together form a shape which is elongated along a respective direction.
• An electrical path electrically connects the zone to the associated contact.
• the electrical path is formed on a face of the substrate. It has a leg angled by at least 30° with respect to said direction.
• the electrical path does not extend along the direction of main stress due to the differential dilatation of the materials. Hence, the stresses encountered in the electrical path are lower, and the risk of failure lowered.
• FIG. 1 is a partial perspective exploded view of a system according to a first embodiment
• Fig. 2 is a partial top view of a flexible printed circuit for the system of Fig. 1,
• Fig. 3 is a view corresponding to Fig. 2 also showing in dotted lines the bottom face of the flexible printed circuit
• Fig. 4 is a view similar to Figs. 2 and 3 only showing the bottom face of the flexible printed circuit
• - Fig. 5 is a cross-sectional partial view along line V-V of Fig. 3,
• FIG. 6 is a lateral view of a system according to a second embodiment
• Fig. 7 is an enlarged view designated by sign 7 on Fig. 3,
• Fig. 8 is a top view of a band used for the manufacture of flexible printed circuit
• Fig. 9a and 9b are schematic side views illustrating differential thermal dilatation, respectively at rest and dilated.
• Fig. 9c is a schematic top view corresponding to
• Fig. 1 shows a system according to a first embodiment.
• the system comprises a connector (or card reader) 1 and a contact card 2 which is to be read in the card reader.
• the card is shown upside down with respect to the card reader. In use, the card 2 will be turned upside down, relative to the drawing of Fig. 1 to be placed in the card reader 1.
• the card 2 comprises a body 3 and a module 4 fixed to the body 3 by any suitable means. Details of the module 4 are not visible on Fig. 1. However, such a module 4 will at least comprise a flexible printed circuit 5.
• the flexible printed circuit will at least comprise a flexible substrate 6 on which are formed electrical contacts 7a-7h, which are to be described later in more details.
• the contacts 7a-7h are in electrical connection with an integrated circuit, or chip (not visible on Fig. 1) of the card.
• the chip is for example provided in the module 4, or elsewhere in the card 2.
• the card reader 1 may comprise a housing 8 of electrically insulating material, which receives electrical contacts 9a-9h, electrically insulated from one another. Each of these contacts comprise a contacting portion which will be placed in electrical contact with a respective electrical contact 7a-7h of the flexible printed circuit 5 when the card 2 is inserted in the card reader 1.
• each of the contacts 9a-9h of the card reader 1 is electrically connected to an electrical device (not shown) which needs to access to the data contained in the chip of the card, and/or write data therein.
• the card reader 1 can be connected to a printed circuit board 10 of this electrical device.
• the printed circuit board 10 may comprise tracks lla-lld which will each correspond to a respective one of the contacts 9a-9h (in the present case, where there are eight contacts, eight tracks may be provided, although only four are shown on the drawings) .
• the tracks lla-lld end with respective connection surfaces 11a' -lid'.
• the card 2 may be removably placed in the card reader 1.
• the flexible printed circuit 5 comprises a substrate 6 made of an electrically insulating material such as glass-epoxy of a suitable thickness, or other suitable materials.
• the substrate is provided as a thin plate having two opposed main faces 6a, 6b.
• the main face 6a is to be turned toward the contacts of the card reader in use.
• the main face 6b is globally parallel to the main face 6a.
• the main face 6a carries the electrical contacts 7a-7h of the flexible printed circuit 5. These contacts are electrically insulated from one another. These contacts are for example provided by electro- deposition and lamination processes.
• one of the electrical contacts for example the contact 7e, can be provided with a shape differing from that of the other contacts, so as to define the orientation of the flexible printed circuit with respect to the card.
• an electrical zone 13a-13h is associated, respectively, to each electrical contact 7a-7h.
• Each electrical zone 13a-13h is provided on the first main face 6a of the substrate. On this face, each zone 13a-13h, is separated from its associated electrical contact 7a-7h by a respective gap, so that there is no direct electrical connection between a zone and its associated contact on the first main face 6a.
• the zones 13a-13h are also electrically insulated from one another. For example, the zones 13a-13h are provided during the same manufacturing process as the electrical contacts 7a-7h.
• Fig. 4 now shows a bottom face 6b of the substrate.
• Fig. 4 is shown along the same orientation as Fig. 2, i.e. seen from over the substrate 6 and through it.
• Electrical paths 14a-14h are provided on the second face 6b. Each electrical path 14a-14h is associated both to a respective electrical contact 7a-7h, respectively, and to its associated electrical zone 13a- 13h, respectively.
• the electrical path 14a-14h are electrically insulated from one another on the second main face 6b. There are for example manufactured according to the same process as the contacts 7a-7h and the zones 13a- 13h.
• the electrical path 14c comprises a first region 15 which overlies the associated electrical contact 7c, and a second region 16 which overlies the associated zone 13c. The two regions 15 and 16 are electrically connected to one another on the second face. This description also applies to the other electrical paths in relation to their associated contact and zone.
• the first region 15 of the electrical path is electrically connected to the associated electrical contact 7e.
• This electrical connection is performed through the substrate 7.
• a through hole 17 is provided in the substrate, extending between the two main faces 6a, 6b. Electrical connection occurs for example by metallisation of this through hole 17.
• a blind plated through hole is provided.
• a similar method can be used to electrically connect the second region 16 to the electrical zone 13e through the substrate 6 by way of a through hole 18.
• the electrical connection between the two regions 15 and 16 of the electrical path 14 is performed out of the plane of Fig. 5.
• the chip 19 is also partly shown on Fig. 5.
• the chip 19 has an electrical connection terminal 19e which is electrically connected to the electrical contact 7e.
• the terminal 19e of the chip is electrically connected to the electrical path 14e, in particular its first region 15 which, itself, is electrically connected to the contact 7e.
• this connection is performed using an electrical conductor (wire 20) extending from the terminal 19e to the electrical path 14.
• this embodiment is illustrative only.
• the assembly of the flexible printed circuit 5 and of the chip 19 shown on Fig. 5 provides a module 4.
• the chip 19 is provided on the second main face 6b of the flexible printed circuit 6. It is fixed thereto by any suitable way.
• Fig. 1 shows an embodiment where the card 2 is removably inserted into a card reader 1.
• the card 2 is permanently fixed to the printed circuit board 10 of the electrical device.
• the tracks 11a, lie of the printed circuit board 10 are shown. These tracks are electrically connected by welding to a respective electrical zone 13a, 13e, directly overlying the respective track.
• the respective welds are shown as 21a, 21e on Fig. 6. Because the surface of the zones 13a-13h is relatively small, and is restricted, the weld has no risk of flowing along a metallisation of the first face 6a of the flexible printed circuit during soldering. Thus, the volume of necessary solder paste can be precisely controlled. Further, thanks to this method, no solder resist is used, so that the problems associated with solder resist are prevented .
• the electrical device will be able to access to the information of the chip of the card, since the track 11a, which is electrically connected through the soldering 21a with the zone 13a which, itself, is in electrical connection with the respective terminal area of the chip 19 through the flexible printed circuit.
• the same card 2 can be used either removably in a card reader 1, as shown on Fig. 1, or permanently as shown on Fig. 6.
• the geometry of an electrical path will be described, in relation to Fig. 7.
• This description is applied to the electrical path 14a, and its associated zone 13a and contact 7a, but could be transposed to the other electrical paths of the embodiment.
• the electrical contact 7a and its associated zone 13a together form an elongated shape along an axis X.
• the axis X can be defined as the main stress axis, when considering stress occurring in the device due to differential thermal dilatation of the two materials of the flexible printed circuit. Accordingly, the axis X can be considered as a main geometrical axis of the considered shape .
• Fig. 9a is a schematic cross-section of a composite comprising a material Ml and a material M2 assembled along an assembly surface S.
• material M2 will tend to expand more than material Ml while still being constrained by its fixation thereto. This will result in high shearing stress and strain at the interface between Ml and M2 which may, ultimately, lead to failure.
• the metallic material fails, its ability to conduct electrical current will be impaired. Such failure need not be global but may be provided as micro-cracks, which will worsen current flow. Further, these cracks may propagate when the card is submitted to repeated thermal stress (such as entering/leaving heated or air-conditioned buildings, ...) .
• Fig. 9c is a schematic top view showing that, for an elongated part, its dilatation will be maximal in its direction of main elongation ( i.e. its length increase will be greater than its width increase) .
• the electrical path is designed so as to withstand high stresses due to differential dilatation of the material of the substrate 6 and that (or those) of the electrical path 14a.
• no leg of the electrical path 14a is aligned with the direction X .
• the electrical path is sensibly V-shaped or U-shaped. It has a first leg 22 which extends sensibly along a first direction Xi . It has a second leg 23 which extends sensibly along a second direction X 2 . It has a third leg 24 which extends sensibly along a third direction X 3 .
• the second leg 23 may extend along a direction X 2 which is parallel to the direction X but offset with respect thereto along a direction (V) which is normal to the direction X and defines therewith the plane 6a of the substrate first face (in the present embodiment, this axis is of course also offset along the thickness direction of the substrate, since the path is not located on the same surface as the contact 7a and associated zone 13a) .
• the direction Xi extends between a point P i2 corresponding to the intersection of the first and second directions Xi , X 2 , and a center 25 of the connection region of the electrical path 14a with the electrical zone 13a. Projected in the plane of the drawing, the angle ⁇ can be measured between the axis X and the direction Xi .
• the third direction X 3 extends from a first point P 23 corresponding to the intersection of the second and third directions X 2 , X 3 and a center 26 of the connection region of the electrical path 14a to the electrical contact 7a.
• An angle ⁇ 2 is defined between the axis X and the direction X 3 .
• an angle of ⁇ of 30 degrees was enough to sufficiently improve the ability of the system to withstand stresses due to differential dilatation.
• An angle of ⁇ 2 of at least 30 degrees also provided good results. If the angle was lower, the system may not be able to sufficiently withstand stresses due to differential thermal dilatation.
• the length of the electrical path 14a would still be short, so that its cost will still be maintained reduced. Greater angles, such as angles of 60 degrees, as shown, or more, will further improve the ability to withstand these stresses, but to the additional cost of increasing the length of the electrical path 23 and thereby increasing its cost.
• the points 25 and 26 are aligned along the direction X.
• Fig. 8 now shows an example of an embodiment for the manufacture of such flexible printed circuits.
• Fig. 8 shows a part of a band 27 made of the material of the substrate, which is continuously processed in a roll-to- roll process.
• the band is driven by driven patterns 28 through a plurality of handling stations which each perform one step of the manufacturing process, such as patterning the contacts, zones and/or paths.
• the band can be virtually divided in a plurality of areas 29 each corresponding to a flexible printed circuit to be manufactured.
• the areas are arranged in an array of rows and columns.
• Each zone or contact to be metallised is in electrical connection (not visible) with a part which is at a given potential, so that metallisation of these contacts or zones can be performed. This is for example the role of the tails 30 which can be seen on Fig. 3 and 4.
• each formed flexible printed circuit will be separated from the band, for example by cutting along the dotted line 31 which is also visible on Fig. 3. This cutting will also insulate from one another the areas which have to be isolated from one another.

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• Engineering & Computer Science (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Combinations Of Printed Boards (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Family Cites Families (4)

• 2011
  • 2011-10-10 WO PCT/EP2011/067662 patent/WO2012055696A1/en active Application Filing
  • 2011-10-10 EP EP11767442.4A patent/EP2633744A1/de not_active Withdrawn

Non-Patent Citations (1)

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