Flexible circuit board and connect structure thereof

The present invention relates to a connect structure of a flexible circuit board where a plurality of conductors wired to a flexible print circuit board are divided, being connected to a flexible circuit member.

For example, a door of an automobile is provided with various electric equipment such as a power window driving mechanism, a door mirror driving mechanism, a door lock mechanism, a speaker or the like. In order to perform electrical connection for the electric equipment, many harnesses are wired. In this case, as a method for simplifying the wiring of the harnesses, collective wiring is conducted using a flexible print circuit board (FPC) on which a plurality of conductors have been printed. The plurality of conductors on the flexible print circuit board are respectively divided at a portion of the board reaching each electric equipment. Each of the divided conductor groups is connected to a flexible circuit member for branching, and each flexible circuit member connected/branched is connected to target electric equipment. In this case, as the flexible circuit member to be connected to the flexible print circuit board, a flexible and flat lead wire is used.

An object of the invention is to provide a connect structure of a flexible circuit member where a plurality of flexible circuit members are easily drawn out from a flexible circuit board and where small-sizing of the flexible circuit board and overlapping arrangement of a plurality of flexible circuit members are allowed so that the simplification of fixing work of the flexible circuit members is achieved.

In view of a first aspect, the invention is directed to a flexible circuit board. The board includes a flexible base member having an enclosed opening with a first edge part. The circuit board includes a circuit wired to the base member. The circuit includes the first circuit part terminating at the first edge part for electrical connection.

Preferably, the base member has a second edge part away from the opening. The circuit includes a second circuit part terminating at the second edge part for electrical connection.

Preferably, the second circuit part extends alongside the first circuit part.

Preferably, the opening is configured in a rectangular shape.

Preferably, the opening has a recess from the first edge part, extending alongside the first circuit part.

In view of a second aspect of the invention, the invention is directed to a connect structure. The connect structure includes a flexible first circuit member including conductors wired thereto. The conductors include a first conductor group. The first circuit member defines an opening having a first edge part. The first conductor group terminates at the first edge part. The connect structure includes a flexible second circuit member electrically connected to first conductor group at the first edge part.

Preferably, the first circuit member has a second edge part. The conductors include a second conductor group terminating at the second edge. The connect structure includes a flexible third circuit member electrically connected to the second conductor group at the second edge part.

Preferably, the second and third circuit members are overlapped each other in a direction.

Preferably, the opening includes recesses from both ends of the first edge part, extending alongside the first conductor group.

These and other features, aspects, and advantage of the present invention will become better under stood with reference to the following description, appended claims, and accompanying drawings where:

FIG. 1 is a perspective view showing a state before a flexible print circuit board and a flexible circuit member are accommodated in an electronic control unit, to which an interconnect structure of a flexible circuit member of a first embodiment of the present invention is applied;

FIG. 2 is a perspective view of a connection fixture for the connection of a circuit member to the board according to the first embodiment of the present invention;

FIG. 3 is a sectional view of a state where the circuit member is connected to the board according to the first embodiment of the present invention;

FIG. 4 is a perspective view showing a state before the board and the circuit member are connected to each other according to the first embodiment of the present invention;

FIG. 5 is a perspective view of a state showing a midway where the flexible circuit member connected to the board is wired from a back surface of the board to a surface thereof according to the first embodiment;

FIG. 6 is a perspective view showing a modified embodiment of the board according to the first embodiment of the present invention; and

FIG. 7 is a perspective view showing a state before a board and a circuit member are connected to each other according to a second embodiment of the present invention.

As shown in FIG. 1, in a interconnect structure of a flexible circuit member according to this embodiment, as one example, a flexible print circuit board (FPC) 10 A for a control board is connected with flat and flexible first and second lead wires 20 and 30 each serving as a flexible circuit member. This flexible print circuit board 10 A is formed by bringing a conductive foil such as a copper foil in close contact with a surface of a base film, as known in general. The surface of the base film is covered with a cover film in an insulating manner. Using the conductive foil, a wiring pattern is printed in a desired shape by an etching process, a plating process or the like. On the other hand, the first and second lead wires 20 and 30 are respectively formed as flexible flat cables, where a conductive foil such as a copper foil is sandwiched in a base film using adhesive.

As shown in FIG. 4, the board 10 A is wholly formed in a rectangular shape having a width W 0 . The first and second lead wires 20 and 30 are respectively formed in strip shapes having widths W 1 and W 2 (W 1 >W 2 ).

Also, a plurality of copper foils 11 a to 11 h serving as conductors are wired to the entire board 10 A. Four copper foils 11 a to 11 d of these copper foils are arranged on a central portion. Two copper foils 11 e and 11 f and two copper foils 11 g and 11 h are respectively arranged on both side edge portions. Then, the copper foils 11 a to 11 d on the central portion are defined as a first conductor group (one of conductor groups), and the first lead wire (one of flexible circuit members) 12 is connected to the first conductor group 12 . The copper foils 11 e to 11 h on both the side edge portions are defined as a second conductor group (the other of conductor groups) 13 , and the second lead wire (the other of flexible circuit bodies) 30 is connected to the second conductor group 13 .

As shown in FIG. 4, four copper foils 21 a to 21 d are arranged in first lead wire 20 so as to correspond to the copper foils 11 a to 11 d of the first conductor group 12 . Four copper foils 31 a to 31 d are arranged in the second lead wire 30 so as to correspond to the copper foils 11 e to 11 h of the second conductor group 13 .

Furthermore, as shown in FIG. 4, U-shaped cut-out in plan view is formed at a portion of the board 10 A which is close to one end thereof. A terminal end 12 a of the first conductor group 12 is defined at a formation part 14 d, as a first edge part, of the U-shaped cut-out 14 in plan view. The first lead wire 20 , as a second circuit member, is connected to the terminal end 12 a. Also, a tongue (end) 15 , as a second edge part, is formed integrally at a central portion of one end of the flexible print circuit board 10 A. The second conductor group 13 is collected to this tongue 15 to define a terminal end 13 a. The second lead wire 30 , as a third circuit member, is connected to the terminal end 13 a.

As shown in FIG. 1, when the copper foils 11 a to 11 d on the board 10 A and the copper foils 21 a to 21 d of the first lead wire 20 corresponding thereto are mutually connected to each other, connection fixtures, each of which is so-called “piercing terminal” 40 shown in FIG. 2, are used. This piercing terminal 40 comprises a rectangular primary part 41 formed of such a conductor as a copper plate and a plurality of piercing claws 42 provided on both sides of the primary part perpendicularly thereto. Then, insulating films of connection ends on the copper foils 11 a to 11 d and the copper foils 21 a to 21 d are cut and removed (shown with oblique lines in Figure), and the copper foils of the connection ends are exposed in advance. Then, the piercing terminals 4 are arranged to extend over ends of one copper foils 11 a to 11 d and the other copper foils 21 a to 21 d to be connected. The piercing claws 42 are pierced into both side portions of the copper foils and the respective piercing claws 42 are caulked in opposing directions to each other. At this time, a case that the terminals 40 are fitted to the connection ends from back surfaces (back surface in Figure) thereof has been illustrated, but the present invention is not limited to this case. The terminals 40 may be fitted from a surface (surface in Figure) of the connection ends.

Also, the copper foils 11 e to 11 h on the flexible print board 10 A and the copper foils 31 a to 31 d of the second wire 30 are mutually connected to each other. In this case, after insulating films of one copper foils 11 e to 11 h and the other copper foils 31 a to 31 d are cut and removed (shown with oblique lines in Figure) like the first lead wire, the terminals 40 are attached to extend over respective connection ends.

As shown in FIG. 4, the cut-out 14 is wholly formed in a U-shape in plan view. The cut-out 14 has a primary opening 14 a formed so as to extend in a width (W 0 ) of the flexible print board 10 A. This cut-out 14 has recess openings 14 b and 14 c which are formed so as to be continuous from both ends of the primary opening 14 a and which extend towards a side where the first conductor group 12 has been arranged perpendicularly to the primary opening. As shown in FIG. 4, the primary opening 14 a is formed so as to have a relatively large gap or width (S 1 ). Also, the recess opening 14 b is formed so as to have a gap or width (S 2 ) smaller than that of the primary opening 14 a.

Then, in order to the first and second lead wires 20 and 30 to the flexible print board 10 A, first, as shown in FIG. 4, in a state where the first lead wire 20 is disposed below the flexible print board 10 A, the connection end of the first lead wire 20 is connected to the terminal end 12 a of the first conductor group 12 , using the terminals 40 . Next, in a state where the connection end of the second conductor group 13 is caused to match with the tongue 15 , the second lead wire 30 is connected to the terminal end 13 a of the second conductor group 13 , using the terminals 40 . Thereby, as shown in FIG. 1, the first lead wire 20 and the second lead wire 30 are connected to the flexible print circuit board 10 A such the former is positioned on an upper side and the later is positioned on a lower side. These first and second lead wires 20 and 30 are overlapped up and down in the same direction to be drawn out.

Thus, as shown in FIG. 1, the board 10 A connected with the first and second lead wires 20 and 30 together with the connection ends of the first and second lead wires 20 and 30 is accommodated in an electronic control unit 50 . This control unit 50 is provided with an upper casing 50 a made of synthetic resin and a lower casing 50 b made of synthetic resin. This unit 50 is wholly formed to conform to the board 10 A, and it is formed at its one end with a drawing-out opening 51 for drawing out the first and second lead wires 20 and 30 .

As shown in FIG. 3, the upper casing 50 a is put on the outer periphery of the lower casing 50 b. An accommodating part 52 for accommodating the flexible print board 10 A is formed between both the casings. When the upper casing 50 a and the lower casing 50 b are mated with each other, protrusions 53 protruded from the lower casing 50 b are fitted into a fitting holes 53 a of the upper casing 50 a to be positioned. Furthermore, lock claws (engagement part) 54 , protruded from side faces of the lower casing 50 b, are engaged with lock holes (engagement part) 54 a of the upper casing 50 a so that the lower casing is prevented from falling off. At this time, the protrusions 53 are positioned at corners C 1 and C 2 on both sides of the end of the flexible print circuit board 10 A. The protrusion 53 are inserted into insertion holes 16 formed in the corners C 1 and C 2 so that the board 10 A is prevented from falling off against pulling force acting on the first and second lead wires 20 and 30 .

Also, a receiving groove 55 for receiving the terminals 40 which have connected the first and second lead wires 20 and 30 to the board 10 A is formed in the lower casing 50 b. A front groove 55 b and a rear groove 55 c are formed in the this receiving groove 55 so as to sandwich a shallow shelf which has the same depth as the thickness of one of the first and second lead wires 20 and 30 and which is positioned at a central portion of the receiving groove 55 . As shown in FIG. 1, in a case that the first lead wire 20 is arranged below the second lead wire 30 , the piercing terminals 40 connecting this first lead 20 is received in the rear groove 55 c. As described below, the front groove 55 b receives the piercing terminals 40 connecting the second lead wire 30 when the second lead wire 30 is wired below the first lead wire 20 .

As explained above, in the connection structure of a flexible circuit member according to the present embodiment, such a structure is employed that the first lead wire 20 is connected to the board 10 A and the second lead wire 30 is connected to the board 10 A. That is, the cut-out 14 formed in an intermediate portion to the board 10 A serves as the terminal end 12 a of the first conductor group 12 , so that this terminal end 12 a is connected with the first lead wire 20 . Accordingly, the first lead wire 20 connected to the first conductor group 12 is drawn out as if it is branched from the intermediate portion of the board 10 A in a direction of the thickness thereof. Furthermore, the second lead wire 30 connected to the second conductor group 13 is drawn out as if it is branched from one end of the board 10 A in a direction of extension of the board. Accordingly, it becomes possible to draw out the first lead wire 20 and the second lead wire 30 in such a manner as overlapping up and down in the same direction. These lead wires 20 and 30 can be prevented from being positioned side by side in a conventional manner.

Accordingly, even in a case that the width (W 1 +W 2 ) of the first lead wire 20 plus the second lead wire 30 is larger than the width W 0 of the board 10 A, the total width of the first and second lead wires 20 and 30 to be drawn out from the flexible print board 10 A is not the summed width of the respective widths W 1 and W 2 of the first and second lead wires 20 and 30 , but it becomes a wider one of the first and second lead wires. Namely the width W 1 of the first lead wire 20 becomes the width for drawing-out in this embodiment. For this reason, a down-sizing is achieved by reducing the width W 0 of the board 10 A. Restriction on the widths of the first and second lead wires 20 and 30 is relaxed largely, and the degree of freedom for wiring or circuit design is expanded.

Also, the first and second lead wires 20 and 30 are drawn out in a manner overlapping up and down in the same direction, so that the lead wires 20 and 30 protruding from the control unit 50 , respectively, can be collectively fixed by fixing means 60 such as a tape, a clip or the like, thereby facilitating a fixing work at that time.

Furthermore, since the cut-out 14 is wholly formed in a U shape in plan view by the primary opening 14 a and the recess openings 14 b, the terminal end 12 a of the first conductor group 12 can be bent freely in the direction of the thickness of the board 10 A through the recess openings 14 b. Therefore, when the first lead wire 20 is connected to the first conductor group 12 , the terminal end 12 a can be pulled out from the board 10 A in the connection direction, in the back surface direction in this embodiment, to be connected, so that the connecting work is easily and accurately performed.

In addition, the case that the first and second lead wires 20 and 30 connected to the board 10 A are wired such that the first lead wire 20 is positioned below the second lead wire 30 has been illustrated. In the wired state, the lead wire 20 may be arranged on an upper side of the second lead wire 30 according to mounting position of electric equipment to be respectively connected. In this case, as shown in FIG. 5, while the first lead wire 20 is further being bent in a curved state, the tip end thereof is caused to pass through the generally U-shaped cut-out 14 . Accordingly, when the first lead wire 20 is caused to pass through the board 10 A from the back surface to the surface thereof (or from the surface to the back surface), the opening area of the cut-out 14 is enlarged through the recess openings 14 b, so that wiring changing work is performed smoothly.

Incidentally, in the first embodiment, the case that one lead wire is connected to the cut-out side of the board has been shown. The present invention is not limited to this embodiment, but such a structure can be employed that a plurality of lead wires are connected to the cut-out side of the board. Also, as a modified embodiment of the first embodiment shown in FIG. 6, such a structure can be employed that a central connection part (the terminal end 13 a of the second conductor group 13 ) of one end of a flexible print board 10 B does not project.

FIG. 7 is a perspective view showing a state before a flexible print board 10 C and the flexible circuit member 20 are connected to each other according to a second embodiment of the present invention.

This second embodiment is different from the first embodiment in that the terminal end (connection part) 13 a of the second conductor group 13 is not provided at the central portion of one end of the board 10 C and the second conductor group 13 extends continuously from a central portion of one end of the board 10 C so that a flexible circuit member part 17 with a narrow width (W 2 ) is formed integrally in a projecting manner.

Then, a cut-out 14 is formed at a predetermined portion of the board 10 C. This embodiment is similar to the first embodiment regarding a point that a terminal end 12 a of a first conductor group 12 is defined at the formation part 14 d of the cut-out 14 and a flat and flexible first lead wire (flexible circuit member) 20 is connectable to this terminal end 12 a. The first lead wire 20 is drawn out from the board 10 C with a small width in such a manner that the flexible circuit member part 17 and the first lead wire 20 overlap each other. Thereby, the down-sizing of the board 10 C can be achieved unlike the conventional art where a plurality of circuit members are arranged side by side at one end of the board 10 C. The limitations on the first lead wire 20 and the circuit member part 17 is relaxed largely to expand the degree of freedom for wiring or circuit design.

As explained above, since it is unnecessary to arrange a plurality of flexible circuit members at an end of a flexible print board side by side in the conventional manner, a down-sizing of the board is achieved. The limitations on the widths of the circuit member and the circuit member part of the end side of the board are largely relaxed and the degree of freedom for wiring or circuit design is expanded.

A plurality of circuit members are drawn out from a board with a small width such that they overlap one anther. Thereby, it is unnecessary to arrange a plurality of circuit members at an end of a board side by side so that the down-sizing of the board can be achieved. By relaxing limitations on widths of respective circuit members, the degree of freedom for wiring or circuit design is expanded.

It becomes possible to fix a plurality of flexible circuit members collectively so that fixing work for them is easily and securely performed.

A terminal end of one of the conductor groups provided within the U-shaped cut-out is bent freely in a direction of the thickness of a board through an recess openings. Thereby, connection of one of the conductive groups and one of the circuit members is easily and accurately performed. Also, one of circuit members connected to one of conductor groups of a board is replaced to a surface side or a back surface side of the board up and down through the cut-out, so that wiring workability of circuit members is further improved.

The entire contents of Japanese Patent Applications P2000-333448 (filed Oct. 31, 2000) are incorporated herein by reference.

Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings. The scope of the invention is defined with reference to the following claims.