JP2007234830A - Conductive bonding structure of flexible wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive bonding structure which can carry out the mutual conductive bonding of flexible wiring boards securing necessary bonding strength, being advantageous in thinning and making compact, and being excellent in reliability. <P>SOLUTION: In a second flexible wiring board 16 on which LED 14 is COF-mounted, a lead extension 16b is formed with a lead wire 1621 extended therein in the both sides of the connection lug array in which the second connection lug 1622 is juxtaposed, one pair of engaging ears 1611, 1611 is formed extending an insulation base film 161 in a first flexible wiring board 11 conductive-bonded to a liquid crystal display, a first connection lug 1122 of a LED current carrying wiring pattern 112 is juxtaposed corresponding to the second connection lug 1622 in the both side portions of the connection lug array portion, and one pair of locking hole portions 1111, 1111 are drilled into which the engaging ear 1611 is engaged/inserted. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive bonding structure for conductively connecting flexible wiring boards.

  In recent years, an image display module using a flat display panel (hereinafter referred to as FPD (Flat Panel Display)) such as a liquid crystal display panel or an organic electroluminescence display panel is advantageous in reducing the thickness of an applied device. It is widely used as a display for mobile devices such as PDAs (Personal Digital Assistance). However, the demand for miniaturization and thinning is extremely strict for displays of mobile devices, and further thinning of the FPD module is also demanded.

Conventionally, a mounting structure using a flexible wiring board disclosed in Patent Document 1 has been proposed as a mounting structure for promoting the reduction in size and thickness of electronic devices such as FPD modules.
JP 2004-356111 A

  In the mounting structure shown in Patent Document 1, the flexible wiring boards are used as much as possible to achieve a significant reduction in thickness, and the flexible wiring boards are conductively connected to each other by soldering to prevent peeling of solder joints that are easily peeled off. As a means, a metal clamping member with a spring or the like interposed is used.

  However, when the holding member as described above is used to electrically connect the flexible wiring boards, it becomes difficult to reduce the thickness of the eyelids promoted by using the flexible wiring boards.

  The adverse effect on the thinning by the sandwiching member is a major drawback in the FPD module in which the demand for small and thinning is extremely severe as described above.

  An object of the present invention is to provide a conductive bonding structure that is advantageous for miniaturization and thinning and that is excellent in reliability, capable of ensuring a necessary bonding strength between flexible wiring boards and conducting bonding.

  The conductive junction structure of the flexible wiring board of the present invention is flexible to the first wiring of the first flexible wiring board in which a plurality of wirings made of a conductor are formed on the surface of a base film made of a flexible insulating film material. A conductive junction structure of a flexible wiring board for conducting and connecting a corresponding second wiring of a second flexible wiring board in which a plurality of wirings made of a conductor are formed on the surface of a base film made of an insulating film material, On both sides of the terminal arrangement portion where the second connection terminal of the second wiring in the second flexible wiring board is arranged, engaging pieces are formed by protruding the edge of the base film, The engaging piece is inserted into both sides of the terminal arrangement portion where the first connection terminal of the first wiring is arranged in the first flexible wiring board. Stop holes are respectively drilled, and the second connection terminals corresponding to the first connection terminals overlap with each other and the two connection terminals are electrically connected to each other in a state where the engagement pieces corresponding to the locking holes are inserted. It is characterized by being connected.

  According to the conductive bonding structure of the flexible wiring board of the present invention, at least one pair of engaging pieces and locking holes are provided in the pair of flexible wiring boards to be conductively bonded, and the engaging pieces corresponding to the locking holes are inserted. By doing so, the conductive connection state between the connection terminals is maintained, so that an appropriate conductive joint state between the flexible wiring boards can be maintained for a long time without using a dedicated peeling prevention member. Miniaturization and thinning are promoted without reducing reliability.

  In the conductive junction structure of the flexible wiring board of the present invention, it is preferable that the first connection terminal and the second connection terminal corresponding to each other are conductively connected by soldering, thereby reducing the size and thickness of the applied device. Further promoted.

  Further, in the conductive junction structure of the flexible wiring board according to the present invention, the second flexible wiring board is a wiring board that conductively connects the liquid crystal display panel and its drive control circuit board, and the first flexible wiring board is the above-described wiring board. A liquid crystal display module that is effectively applied to a liquid crystal display module, which is a wiring board for energizing a light source of a backlight that irradiates light to the liquid crystal display panel, thereby promoting a reduction in size and thickness and providing sufficient reliability. A display module is obtained.

  FIG. 1A is a schematic cross-sectional view showing a liquid crystal display module as an embodiment of the present invention, FIG. 1B is a partially enlarged cross-sectional view showing a main part Q thereof, and FIG. It is a partial expansion top view of a liquid crystal display module.

  As shown in FIG. 1, the housing of the present liquid crystal display module includes a storage case 1 having a shape obtained by removing a top plate of a flat rectangular parallelepiped box, and a cover case 2 having the same shape from which a bottom plate has been removed. Being done. Both of these cases 1 and 2 are formed by processing a metal plate. A display window 202 for observing the display is formed in the top plate 201 of the cover case 2.

  A frame 3 is disposed in the casing. The frame 3 according to the present embodiment includes a front chamber 3a and a rear chamber 3b, which are formed in a rectangular parallelepiped with a flat space outer shape, in two stages. That is, a partition shelf 302 protrudes over the entire inner surface of the side plate 301 that forms a frame surrounding the rectangular space, and the front chamber 3a and the rear chamber 3b are separated from each other by using the partition shelf 302 as a boundary. The front chamber 3a and the rear chamber 3b are connected in two stages, and are communicated with each other by a space 3c surrounded by a partition shelf 302.

  A liquid crystal display panel 4 is accommodated in the front chamber 3 a of the frame 3. The liquid crystal display panel 4 is formed by bonding a pair of glass substrates 5 and 6 on which electrodes (not shown) are formed with a predetermined gap therebetween by a frame-shaped sealing material (not shown) with the respective electrode formation surfaces facing each other. The liquid crystal (not shown) is sealed between the glass substrates 5 and 6 surrounded by the frame-shaped sealing material. A pair of front and rear polarizing plates 7 and 8 are attached to the outer surfaces of the glass substrates 5 and 6 opposite to the liquid crystal sealing side, respectively.

  The area of the pair of glass substrates 5 and 6 in the liquid crystal display panel 4 of this example is larger in the rear glass substrate 6 than in the front glass substrate 5 on the display surface side, and the glass substrates 5 and 6 having different sizes. Are joined so that one edge of the rear glass substrate 6 protrudes from the corresponding edge of the front glass substrate 5. On the protruding edge 601 of the rear glass substrate 6, wirings drawn from the respective electrodes and connection terminals (not shown) at respective ends thereof are arranged to form driving circuit portions. A driver LSI 9 as a drive circuit element is mounted on COG (Chip On Glass). A first flexible wiring board 11 (FPC: Flexible Printed Circuit) is conductively joined to the input terminal area of the drive circuit section.

  In the rear chamber 3b of the frame 3, a sidelight type planar illumination device 12 is accommodated. The sidelight type planar illumination device 12 of the present embodiment has a light emitting diode (hereinafter referred to as an LED (hereinafter referred to as LED)) as a point light source on one end surface 131 of a transparent light guide plate 13 having a rectangular shape substantially corresponding to the liquid crystal display panel 4 to be irradiated. 14), and a light reflecting sheet 15 is installed on the rear surface 133 of the light guide plate 13 opposite to the front surface 132 facing the liquid crystal display panel 4. On the rear surface 133 of the light guide plate 13 where the light reflecting sheet 15 is installed, concentric concavities and convexities for uniformly reflecting the light emitted from the LEDs 14 and entering the light guide plate 13 from the light incident end surface 131 toward the front surface 132. A pattern (not shown) is formed.

  As shown in FIG. 2, in the present embodiment, two LEDs 14, 14 are arranged, and these LEDs are connected to the second flexible wiring in a state where each light emitting surface is in close contact with the light incident end surface 131 of the light guide plate 13. It is directly mounted on the substrate 16 by the COF (Chip On Film) method. As shown in the member explanatory diagram of FIG. 3, the second flexible wiring board 16 includes an LED array portion 16a in which two LEDs 14 and 14 are arranged in parallel at a predetermined interval, and a lead extension extending perpendicularly therefrom. It consists of the exit part 16b.

  In addition, the second flexible wiring board 16 is formed by forming an energization wiring pattern 162 made of a conductive material for energizing the LEDs 14 on the surface of the flexible insulating base film 161. The second flexible wiring board 16 of this embodiment is formed by patterning a conductive wiring pattern 162 made of copper foil on the surface of an insulating base film 161 made of polyimide resin by photolithography.

  A second connection terminal 1622 is formed at each distal end portion of the four second lead wires 1621 formed on the surface of the lead extension portion 16b of the energization wiring pattern 162.

  Then, both ends of the insulating base film 161 are extended to a tip end portion of the second flexible wiring board 16 where the second connection terminals 1622 of the lead extension portion 16b are arranged in parallel, and a pair of engagement ear portions. 1611 and 1611 are formed.

  On the other hand, as shown in FIG. 3, the first flexible wiring board 11 has the LED wiring pattern 112 on the surface of the insulating base film 111 so as to correspond to the energization wiring pattern 162 of the second flexible wiring board 16. Is formed. In this LED wiring pattern 112, first connection terminals 1122 are formed at the respective tips of the four first lead wirings 1121 so as to correspond to the second connection terminals 1622, and each of the first connection terminals 1122 is formed. A solder coating (not shown) is applied to the surface.

  Similarly to the second flexible wiring board 16, the first flexible wiring board 11 is also formed by patterning an LED wiring pattern 112 made of copper foil on the surface of an insulating base film 111 made of a polyimide resin film by photolithography.

  Locking holes 1111 are formed in both side portions of the connection terminal array portion where the first connection terminals 1122 are arranged in parallel with the engagement ear portions 1611 of the second flexible wiring board 16. Yes. Each locking hole 1111 is formed in an oval shape having a length L1 substantially equal to the length L2 of the engagement ear portion 1611. Further, by leaving the copper foil at the periphery of each locking hole 1111 when the wiring pattern of the LED wiring pattern 112 or the like is etched, a flange ring 113 for hole reinforcement is formed over the entire periphery of each locking hole 1111.

  Here, an operation procedure for conducting and joining the second flexible wiring board 16 to the first flexible wiring board 11 will be described.

  First, as shown in FIG. 2, the frame 3 is similarly inserted into the pair of locking holes 1111 of the first flexible wiring board 11 that is conductively joined to the tip of the protruding edge 601 of the liquid crystal display panel 4 and is drawn out of the frame 3. The corresponding engaging ears 1611 of the second flexible wiring board 16 drawn out are respectively inserted. At this time, by appropriately curving the lead extension portion 16b of the second flexible wiring board 16, each engagement ear portion 1611 can be easily inserted into the corresponding locking hole 112, and after insertion, the insulating base As the lead extension portion 16b substantially returns to its original flat shape due to the elasticity of the film 161 itself, each engagement ear portion 1611 is fully engaged in the corresponding locking hole 1111 as shown in FIG. The combined state (hereinafter referred to as the maximum engagement state) is maintained.

  The maximum engagement state is a state in which the second connection terminals 1622 of the second flexible wiring board 16 accurately overlap the corresponding first connection terminals 1122 of the first flexible wiring board 11 in the intended arrangement (hereinafter referred to as terminals). It is called a consistent state. That is, the distance D1 between the respective locking holes 112 in the first flexible wiring board 11 and the ears of the lead extending portions 16b in the second flexible wiring board 16 so that the desired terminal alignment state can be obtained in the maximum engagement state. Each dimension of the root-to-base distance D2 is set.

  Thus, the accurate position between the first connection terminal 1122 and the second connection terminal 1622 corresponding to each other can be obtained by simply inserting the engagement ears 1611 corresponding to the pair of locking holes 1111. The alignment can be easily performed, and accordingly, the number of man-hours for manufacturing the liquid crystal display module is reduced.

  After the alignment of the first connection terminal 1122 and the second connection terminal 1622, the connection terminals 1122 and 1622 are connected by soldering. At this time, since the surface of the first connection terminal 1122 is preliminarily coated with a solder film, as shown in FIG. 1B, the two connection terminals 1122 and 1622 sufficiently interpose the solder P therebetween. And a strong conductive connection. In order to further increase the strength of the conductive connection, it is preferable to apply a solder coating to the surface of the second connection terminal 1622 as well.

  In the sidelight type planar illumination device 12 configured as described above, the light emitted from the LED 14 enters the light guide plate 13 from the opposite end surface 131, and this incident light is concentric unevenness on the rear surface 133. When incident on the pattern, the light is totally reflected toward the front surface 132 and emitted from the front surface 132 in a planar shape. There is also light that exits from the light guide plate 13 after entering the concentric pattern, but the emitted light is reflected by the light reflecting sheet 15 and reentered into the light guide plate 13. Thereby, the utilization efficiency of the emitted light from LED14 is raised significantly.

  As shown in FIG. 1, two optical sheets, a light diffusion sheet 17 and a prism sheet 18, are superimposed on the front surface 132 of the light guide plate 13 in that order. The light diffusion sheet 17 is installed in order to make the luminance distribution of the irradiation light emitted from the light guide plate 12 planar, and the prism sheet 18 is installed to align the emission direction of the irradiation light in the front direction.

  Then, the planar lighting device 12 on which the two optical sheets 17 and 18 are superposed is housed in a predetermined position in the rear chamber 3b while being supported by the rear panel 19. The rear panel 19 is fitted and attached to the frame 3 so as to close the bottom surface of the frame rear chamber 3b.

  A drive control circuit board 20 is installed on the inner surface of the bottom plate 101 in the storage case 1 on the rear surface side of the rear panel 19. The drive control circuit board 20 controls the driving of the entire liquid crystal display module, and the first flexible wiring board 11 that is conductively joined to the end of the glass substrate 6 of the liquid crystal display panel 4 is connected to the connector 21. It is electrically connected through. In this electrical connection, as described above, the second flexible wiring board 16 on which the LEDs 14 are mounted is soldered to the first flexible wiring board 11, and then the first flexible wiring board 11 is folded back to the frame rear chamber 3b side. It is only necessary to insert the folded tip portion into the connector 21.

  As described above, in the liquid crystal display module of this embodiment, the second flexible wiring board 16 for driving the LEDs 14 is soldered to the first flexible wiring board 11 for driving the liquid crystal display panel 4, so that the mounting structure As a result, the liquid crystal display module can be reduced in size and thickness. In the joining of the flexible wiring boards 11 and 16, a pair of locking holes 1111 is provided on one side, and a pair of engagement ears 1611 are provided on the other side corresponding to the locking holes 1111. Since the engagement ear portion 1611 is inserted and the corresponding first and second connection terminals 1112 and 1622 are positioned so as to properly overlap with each other, the positioning operation between the connection terminals is simplified, and the liquid crystal display Module manufacturing man-hours are reduced. In addition, since the insulating base films 111 and 161 in the solder joint portions of the flexible wiring boards 11 and 16 are coupled to each other by engaging and inserting the engagement ear portions 1611 into the locking holes 1111, the external force applied to the solder joint portions. Peeling action due to is suppressed, and the reliability of solder bonding is improved.

In addition, this invention is not limited to the said embodiment.
For example, the combination of the shape of the engagement piece and the locking hole is not limited to the combination of the rectangle and the ellipse as in the above embodiment, and various combinations of shapes are possible. The modification shown in FIG. 4A is a combination of an oblong locking hole 40 and a trapezoidal engagement piece 30, and the modification shown in FIG. These locking holes 60 are combined. Like the engagement pieces 30 and 50 of these modified examples, the engagement pieces 30 and 50 are formed in a shape in which there is a portion whose width gradually increases toward the distal end side, and the maximum width Wm of each engagement piece 30 and 50 corresponds to the corresponding engagement piece. By setting the dimension larger than the length L of the stop holes 40, 60, the detachment of the engaging pieces 30, 50 from the locking holes 40, 60 is suppressed, and the reliability of the solder joint is further increased. improves. Note that. When the engagement pieces 30 and 50 are inserted into the locking holes 40 and 60, the engagement pieces 30 and 50 can be easily inserted by bending them so that the maximum width Wm is reduced.

  In addition, the present invention is not limited to the case where the connection terminals are conductively connected to each other by a solder bonding method, but the case where the connection terminals are conductively connected using another connection member such as an anisotropic conductive adhesive, or by ultrasonic welding or laser welding. The present invention can also be applied effectively when using other various conductive connection methods such as conductive connection.

  In addition, the conductive bonding structure of the flexible wiring board of the present invention is not limited to the conductive bonding between the flexible wiring boards in the liquid crystal display module, but can be widely applied to the conductive bonding between flexible wiring boards in other various electronic devices. Of course.

(A) is typical sectional drawing which shows the liquid crystal display module as one Embodiment of this invention, (b) is typical sectional drawing which expanded and showed the Q section. It is the partially expanded top view which abbreviate | omitted the housing | casing and showed the principal part by developing the said liquid crystal display module. It is explanatory drawing which decomposed | disassembled and showed the structural member of Q part in the said liquid crystal display module. (A), (b) is a structure explanatory drawing which shows the modification of the principal part in the said embodiment, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Storage case 2 Cover case 3 Frame 4 Liquid crystal display panel 5, 6 Glass substrate 7, 8 Polarizing plate 9 Driver LSI
11 1st flexible wiring board 111 Insulation base film 1111 Locking hole 112 LED energization wiring pattern 1122 1st connection terminal 12 Planar illumination device 13 Light guide plate 14 LED
15 light reflection sheet 16 second flexible wiring board 161 insulation base film 1611 engagement ear 162 lead wiring pattern 1622 second connection terminal 17 light diffusion sheet 18 prism sheet 19 rear panel 20 drive control circuit board 21 connectors 30 and 50 engagement Piece 40, 60 Locking hole

Claims (3)

A conductor on the surface of a base film made of a flexible insulating film material on a first wiring of a first flexible wiring board in which a plurality of wires made of a conductor are formed on the surface of a base film made of a flexible insulating film material A conductive junction structure of a flexible wiring board for conductively connecting a corresponding second wiring of a second flexible wiring board formed with a plurality of wirings comprising:
On both sides of the terminal arrangement portion where the second connection terminal of the second wiring is arranged in the second flexible wiring board, an engagement piece is formed by protruding the edge of the base film, respectively.
Locking holes through which the engagement pieces are inserted are respectively formed on both sides of the terminal arrangement portion where the first connection terminal of the first wiring is arranged on the first flexible wiring board,
In a state where the engagement piece corresponding to the locking hole is inserted, the second connection terminal corresponding to the first connection terminal overlaps and the connection terminals are electrically connected to each other. Conductive bonding structure of wiring board.   The conductive connection structure for a flexible wiring board according to claim 1, wherein the first connection terminal and the second connection terminal corresponding to each other are conductively connected by solder.   The second flexible wiring board is a wiring board that conductively connects the liquid crystal display panel and its drive control circuit board in the liquid crystal display module, and the first flexible wiring board irradiates the liquid crystal display panel with light. The conductive junction structure for a flexible wiring board according to claim 1 or 2, wherein the conductive wiring board is a wiring board for energizing a light source of a backlight.

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