FLEX CIRCUIT HAVING REPAIRABLE CONNECTOR TAIL

Abstract: A repairable flex circuit (1), comprising: a generally flexible, electrically insulative substrate (2) having a first edge (3) thereof, and a plurality of electrically conductive circuit traces (5) arranged on the substrate. Each circuit trace has an end thereof terminating at a first connector element (8) proximate the first edge (3), and at least one second connector element (13) spaced apart from the first connector element, with each of said first and second connector elements being a plated through hole, a plated blind via, or a solder pad.

Description: FLEX CIRCUIT HAVING REPAIRABLE CONNECTOR TAIL The present invention relates generally to flexible printed circuits ("flex circuits"), and more particularly to approaches for repairing flex circuits. FIG. 1 illustrates a typical application of flex circuits, wherein a connector tail portion of a flex circuit 987 is electrically connected to an electronic assembly 34, which may be an electronic module, a circuit board, another flex circuit, an electrical connector, or any other electrical/electronic device, component, or assembly to which it is desired to connect a flex circuit. (Although not shown here, the flex circuit itself may be populated with electronic components, or may be part of an electrical wiring/bus system, or the like.) Connection of the flex circuit 987 to the electronic assembly 34 is most typically carried out by soldering. Use of flex circuits rather than conventional round- wire wire harnesses has become increasingly more commonplace, especially in the computer, automotive, aviation, and aerospace industries. However, one drawback of using flex circuitry is the difficulty of servicing the electronic assemblies 34 connected by the flex. That is, if a particular asse bly 34 fails and needs to be replaced, it is difficult to remove the assembly 34 from the overall circuit and connect back in a replacement assembly, without damaging the flex circuit or requiring tedious and expensive procedures for effecting replacement. It would be desirable, therefore, to provide a way of allowing flex circuits to be used while at the same time providing for an easy, effective, and inexpensive way of allowing for replacement of failed electronic assemblies 34. The present invention provides a flex circuit with a repairable connector tail portion. An article according to the present invention comprises: a generally flexible, electrically insulative substrate having a first edge thereof, and a plurality of electrically conductive circuit traces arranged on the substrate. Each circuit trace has an end thereof terminating at a first connector element thereof proximate the first edge, and at least one second connector element thereof spaced apart from the first connector element, with each of said first and second connector elements being a plated through hole, a plated blind via, or a solder pad. It is an advantage that the present invention provides a connector portion for a flex circuit which facilitates both (1) connection of the flex circuit to an electronic module, another flex circuit, or the like, and (2) disconnection and reconnection of the flex circuit, such as may be needed to facilitate repairs. Another advantage is that the present; invention may be easily incorporated into the designs of most existing flex circuits . The present invention will now be described further, by way of example, with reference to the accompanying drawings, m which: FIG. 1 is a plan view of a flex circuit and an electronic assembly prior to connection therebetween according to the prior art; FIGS. 2-3 are plan views of a flex circuit connector tail according to the present invention, respectively before and after connection with an electronic assembly; FIGS. 4-5 are plan views of the circuit connection shown in FIG. 3 after cutting along a cutting line thereof, respectively before and after replacing the electronic assembly; FIGS. 6-7 are plan views of the circuit connection shown in FIG. 3 after cutting along an alternate cutting line thereof, respectively before and after replacing the flex circuit; and FIG. 8 is a plan view of an alternative embodiment of the present invention. Referring now to the drawings, FIGS. 2-8 show a repairable flex circuit 1 according to the present invention, comprising: a generally flexible, electrically insulative substrate 2 having a first edge 3 thereof, and a plurality of electrically conductive circuit traces 5 arranged on the substrate. Each circuit trace has an end thereof terminating at a first connector element 8 proximate the first edge 3, and at least one second connector element 13 spaced apart from the first connector element, with each of said first and second connector elements being a plated through hole, a plated blind via, or a solder pad. To assist the reader in understanding the present invention, all reference numbers used herein are summarised in the table below, along with the elements they represent: 1 = Repairable flex circuit/connector tail 1 ' = Replacement flex circuit/connector tail 2 = Substrate of connector tail 3 = First edge of connector tail 5 = Circuit traces on/within connector tail 8 = First connector element 13 = Second connector element 21 = Cutting line between first/second connector elements 34 = Electronic assembly connected to connector tail 55 = Connector elements of electronic assembly 89 = Overlapping mechanical/electrical connection area 144 = Straight alignment line of connector elements 233 = Zigzagged alignment line of connector elements 377 = Newly cut (next) first edge 610 = Alternative cutting line 987 = Flex circuit/connector tail according to prior art ' = Replacement part (indicated by "prime" mark) A = Connector element segment of flex/tail B = Connectorless segment of flex/tail The first and second connector elements 8/13 of the flex circuit connector tail 1 should be exposed (i.e., not covered over by the flex circuit's insulating polymer layer) so as to be readily interconnectable with the pins, plated through holes, solder pads, or other connector features 55 of the electronic assembly 34 to which the connector tail 1 is to be connected. The interconnection between the connector tail 1 and the assembly 34 is preferably effected by soldering, but may also be effected by ultrasonic welding, heat staking, crimping, pinning, laser bonding, or the like. Regardless of the processing method selected, interconnection is made by aligning the flex tail 1 and the electronic assembly 34 such that the connector elements 55 of the assembly 34 overlap (or are overlapped by) the connector tail's first connector elements 8, as illustrated at reference numeral 89 in FIG. 3. Once the respective connector elements 8/55 of the connector tail 1 and electronic assembly 34 are thusly aligned, the overlapping elements 8/55 may be connected together. When soldering is used and the connector elements 8/55 are plated through holes, it may be desirable to insert a pin through each pair of overlapping through holes 8/55 prior to soldering, in order to assist in alignment and solder joint strengthening. While the connector elements 8/13 may be arranged across the connector tail 1 in a wide variety of ways, it is preferred that they be generally evenly distributed along the length of each circuit trace 5. Also, prior to any repair (described below) , preferably each trace 5 terminates proximate the first edge 3 at a first connector element 8. Additionally, it should be apparent that the connector elements 8/13 on the connector tail 1 should be arranged so as to matchingly correspond with the respective connector elements 55 of the electronic assembly 34; that is, the pattern and spacing of the connector tail's connector elements 8/13 should essentially mirror that of the corresponding assembly's connector elements 55. This is desired so that proper alignment of the overlapping connector elements can be achieved. For example, each of the first and second connector elements 8/13 may be aligned -- with respect to all corresponding other of the first and second connector elements -- either (1) along a generally straight line 144 running transverse to the length of the traces 5 (see FIG. 8), or (2) along a generally zigzagged line 233 running transverse to the traces (see FIGS. 2-7). With the respective connector elements of the flex circuit 1 and the electronic assembly 34 aligned and connected as described above, the connector tail 1 of the present invention serves to electrically and mechanically connect together the traces 5 of the flex circuit with the corresponding traces of the electronic assembly. If either the flex circuit 1 or the electronic assembly 34 needs to be subsequently detached (e.g., because of a component failure associated with one of the circuits) , the connector tail 1 may be cut so as to present a second set of connector elements 13 to which a new flex circuit 1' or electronic assembly 34' may be connected. The replacement process is illustrated m FIGS. 4-5, where the replacement of the assembly 34 is illustrated. The replacement process is begun by cutting the connector tail 1 along a cutting line 21 which runs transverse to the traces 5 between the first connector elements 5 and the ad acent set of second connector elements 13, as shown in FIG. 4. This essentially presents these second connector elements 13 so as to be the connector elements closest to the newly cut first edge 377. Then, the connector tail 1 and the replacement assembly 34 ' may be aligned such that the replacement assembly's connector elements 55 ' overlap (or are overlapped by) the connector tail's second connector elements 13 proximate the newly cut first edge 377, as illustrated m FIG. 5. Alternatively, rather than disconnecting the original electronic assembly 34 and replacing it with a new one 34 ' , as illustrated m FIGS. 4-5, it is also possible to replace the original lex circuit 1 with a new one 1 ' , as shown m FIGS. 6-7. Here, the replacement is facilitated by cutting along cutting line 610, rather than along cutting line 21. After this cut is made, a small connector element segment ("A") of the connector tail remains attached to the electronic assembly 34, while the main connectorless tail segment ("B") may be discarded. Upon cutting along the cutting line 610, a set of second connector elements 13 is presented ad acent the newly cut edge, to which a new replacement connector tail 1 ' may be attached as described above and illustrated m FIG. 7. As this foregoing description illustrates, the specially configured connector tail of the present invention may not only be used to initially connect together the flex circuit 1 and an electronic assembly 34, but may also be beneficially used to remove either the flex circuit 1 or the assembly 34 from the overall circuit connection and easily replace it with a new one l'/34' . If the connector tail 1 is provided with only one set of second connector elements 13, then only one repair/replacement may be performed after the initial connection; however, if more than one set of second connector elements 13 are provided, then a like number of repairs may be made. The number of second connector element sets 13 provided should be determined according to how often repair of the circuit is anticipated. Various other modifications to the present invention may occur to those skilled m the art to which the present invention pertains. For example, although the foregoing examples illustrate only two circuits being connected together at any given time (e.g., 1 and 34), the present invention may in fact be used to connect together more than two circuits at a time, as illustrated m FIG. 8. Also, it should be noted that while the flex circuit 1 of the present invention is best constructed using conventional flex circuit structure (i.e., wherein the substrate 2 is made of polyester, polyimide, polyetherimide, or the like, and the circuit traces 5 are made of copper, carbon, aluminium, solder, conductive ink, or the like) , it is not required that the electronic assembly 34 or the area surrounding its connector elements 55 be made of flex. In fact, the present invention is equally applicable to electronic assemblies 34 made of rigid FR-4 epoxy/glass, ceramic (e.g., alumina), etched tri-layer-metal construction, and so on. Additionally, although the word "connector tail" has been used throughout to describe the specially designed connector element arrangement of the present invention, the arrangement of the connector elements 8/13 does not necessarily have to be provided on a "tail" portion that extends outward from the general periphery of the flex circuit. Thus, the use of the word "tail" refers more to a portion of a flex circuit on which first and second connector elements 8/13 are arrayed according to the present invention, as opposed to defining and limiting the geometric shape of this portion per se .

Claims: CLAIMS 1. A repairable flex circuit, comprising: a generally flexible, electrically insulative substrate (2) having a first edge (3) thereof; and a plurality of electrically conductive circuit traces (5) arranged on said substrate (2); wherein each circuit trace (5) terminates at a first connector element (8) thereof proximate said first edge (3); wherein each circuit trace further includes at least one second connector element (13) thereof spaced apart from said first connector element (8) ; wherein each of said first and second connector elements (8,13) is a plated through hole, a plated blind via, or a solder pad. 2. A repairable flex circuit according to claim 1, wherein said first and second connector elements of each circuit trace are generally evenly distributed therealong. 3. A repairable flex circuit according to claim 1, wherein said circuit traces run generally parallel to one another. 4. A repairable flex circuit according to claim 1, wherein each of said first and second connector elements is aligned, with respect to all corresponding other of said first and second connector elements, along a generally straight line running transverse to the length of said circuit traces. 5. A repairable flex circuit according to claim 1, wherein each of said first and second connector elements is aligned, with respect to all corresponding other of said first and second connector elements, along a generally zigzagged line running transverse to the length of said circuit traces. 6. A repairable flex circuit according to claim 1, wherein said substrate is made of polyester, polyimide, or polyetherimide, and said circuit traces are made of copper, carbon, aluminium, solder, or conductive ink. 7. A repairable flex circuit, comprising: a generally flexible, electrically insulative substrate having a first edge thereof; and a plurality of electrically conductive circuit traces arranged on said substrate, wherein each circuit trace terminates at a first connector element thereof proximate said first edge and at least one second connector element thereof spaced apart from said first connector element, wherein each of said first and second connector elements is a plated through hole, a plated blind via, or a solder pad; wherein each of said first and second connector elements is aligned, with respect to all corresponding other of said first and second connector elements, along a generally zigzagged line running transverse to the length of said circuit traces. 8. A method for repairing an electrical circuit, comprising the steps of: providing an electrical assembly, including: a flex circuit having a connector tail portion thereof, wherein the connector tail portion has a first edge thereof and a plurality of circuit traces arranged thereon or therewithin, wherein each circuit trace terminates at a first connector element thereof proximate the first edge and includes at least one second connector element thereof spaced apart from the first connector element, wherein each first and second connector element is a plated through hole, a plated blind via, or a solder pad; and a first electrical component having a second edge thereof and a plurality of circuit traces terminating proximate the second edge; wherein the connector tail portion and first electrical component are arranged such that their respective first and second edges contactedly overlap each other, with the respective circuit traces of the connector tail portion and first electrical component being mechanically and electrically connected to each other at each first connector element ; cutting the connector tail portion thereacross between the first connector elements and the second connector elements, thereby severing the first electrical component and attached first connector elements from the connector tail portion and second connector elements, thereby presenting a third edge of the connector tail portion proximate the second connector elements; arranging a second electrical component substantially similar to the first electrical component such that a fourth edge thereof contactedly overlaps the third edge of the connector tail portion; and mechanically and electrically connecting together the respective circuit traces of the second electrical component and the connector tail portion at the second connector elements . 9. A method according to claim 8, wherein each of the first and second connector elements is aligned, with respect to all corresponding other of the first and second connector elements, along a generally straight line running transverse to the length of the circuit traces on the connector tail portion. 10. A method according to claim 8, wherein each of the first and second connector elements is aligned, with respect to all corresponding other of the first and second connector elements, along a generally zigzagged line running transverse to the length of the circuit traces on the connector tail portion.

Inventors: ACHARI ACHYUTA, BAKER JAY DEAVIS, LI DELIN, NATION BRENDA JOYCE, TRUBLOWSKI JOHN, ACHARI, ACHYUTA, BAKER, JAY, DEAVIS, LI, DELIN, NATION, BRENDA, JOYCE, TRUBLOWSKI, JOHN
Applicants: FORD MOTOR CO, FORD MOTOR COMPANY, FORD MOTOR COMPANY LIMITED
Application year: 2000
Main classification: H05K1
IPC codes: H05K1, H05K3