JP2008140596A - Surface illumination device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface illumination device capable of easily and surely carrying out inspection of mounting positions on a printed circuit board of a point light source such as an LED. <P>SOLUTION: In the surface illumination device equipped with an FPC assembly 20 composed of LEDs 50 and an FPC 21 on which the LED 50 are mounted, and a light guide plate, conductive patterns formed in the FPC 21 include a pair of lands 33, 34 corresponding to a pair of electrode terminals 53, 54 of the LEDs 50, and wiring patterns 32a to 32c connected to the respective lands 33, 34 constituting the pair of the lands 33, 34, the LEDs 50 are mounted on the FPC 21 so that their light-emitting faces 50a become nearly perpendicular to a mounting face of the FPC 21, the FPC assembly 20 is arranged so that the light-emitting faces 50a of the LEDs 50 is opposite to a light incident face of the light guide plate, and at positions corresponding to the rear faces 50b of the light-emitting faces 50a of the LEDs 50 on the mounting face of the FPC 21, marks 39 for inspecting the mounting positions are installed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sidelight type planar illumination device, and more particularly to a planar illumination device used as illumination means of a liquid crystal display device.

  Conventionally, as an auxiliary light source for a liquid crystal display device, there is a sidelight type planar illumination device in which a primary light source is disposed on a side end surface of a light guide plate (hereinafter, a side end surface on which a primary light source is disposed is also referred to as a light incident surface). It is widely used in the field of liquid crystal display devices having a relatively small display area. In particular, liquid crystal display devices for small mobile terminals such as mobile phones are white light sources that are excellent in handling, easy to miniaturize, and have high impact resistance as the primary light source for such planar lighting devices. A point light source (hereinafter, also simply referred to as an LED) such as an LED is frequently used.

  FIG. 6 is an exploded perspective view schematically showing a configuration example of a sidelight type planar illumination device using LEDs as a primary light source. In FIG. 6, the planar lighting device 100 includes an FPC assembly 120 including an LED 50 and a flexible printed circuit board (hereinafter also referred to as FPC) 121 on which the LED 50 is mounted, a light guide plate 11, and a rear surface 11 b side of the light guide plate 11. The reflection plate 15 is disposed, and the diffusion plate 12 and the prism plates 13 and 14 are sequentially stacked on the surface 11 a side of the light guide plate 11. In the planar lighting device 100, the LED 50 has one light emitting surface 50 a that is substantially perpendicular to the mounting surface 121 a of the FPC 121. In the FPC assembly 120, the mounting surface 121 a of the FPC 121 has the light guide plate 11. The light emitting surface 50a of the LED 50 is disposed and fixed so as to face the light incident surface 11c that is one side end surface of the light guide plate 11.

  Here, the light guide plate 11 is a plate-like light guide formed by preferably injection-molding a translucent resin such as a polycarbonate resin. Generally, the rear surface 11b and / or the front surface 11a of the light guide plate 11 are both. Are formed with optical path changing means (not shown) for changing the traveling direction of light. The reflection plate 15 reflects light leaking from the back surface 11b of the light guide plate 11 to re-enter the light guide plate 11, and the diffusion plate 12 diffuses and equalizes light emitted from the surface 11a of the light guide plate 11. It is. The prism plates 13 and 14 collect light and improve the front luminance of the planar illumination device 100. Each prism plate 13 and 14 has a prism row formed in one direction. The layers are stacked so that their directions are orthogonal to each other.

  Further, in the planar illumination device 100, the light incident surface 11c of the light guide plate 11 diffuses incident light from the LED 50 to the light guide plate 11 so that the light emitting surface 50a of the LED 50 faces the light incident surface 11c. A light incident prism portion 19 including a plurality of prisms extending in the thickness direction is formed.

  In the planar illumination device 100 configured as described above, the light incident from the light incident surface 11c propagates toward the other side end surface 11d while being totally reflected in the light guide plate 11, and during that time, by the optical path changing means. The light whose path has been changed is emitted from the surface 11a. In this case, for example, when the optical path conversion means is a dot-shaped optical path conversion pattern, the area density of the pattern is sparse on the light incident surface 11c side, and the end By making the surface 11d side dense, planar uniform light emission is realized.

  In such a planar illumination device, it is one of the important issues to promote higher brightness, and as one means for that purpose, it is necessary to increase the output of each LED by increasing the drive current. Conceivable. However, in general, it is known that a decrease in luminance and a decrease in lifetime occur due to heat generated by light emission, and in order to maintain a stable luminance while maintaining the drive current of the LED within an allowable limit, It is desirable to take some heat dissipation measures for the FPC assembly. Therefore, the present applicant has previously proposed a planar illumination device having an FPC as shown in FIG. 7 (see Patent Document 1).

  The FPC 121 shown in FIG. 7 has a conductive pattern formed on a base film 131 made of polyimide or the like, for example, using copper foil or the like, and a coverlay film 141 made of polyimide or the like is similarly laminated on the upper layer. Is formed. The conductive pattern includes, for example, a pair of land portions 133 and 134 where a pair of electrode terminals (not shown) of the LED 50 shown in FIG. 6 are respectively disposed, and a wiring pattern 132 connected to each land portion 133 and 134. It is included. Furthermore, the wiring pattern 132 includes relay portions 136 and 135 that are formed to be wider than at least the land portions 133 and 134. The wiring pattern 132 and the land portions 133 and 134 are connected to the relay portions 136 and 135. It is connected via. And from the opening part 142 provided in the coverlay film 141, the land parts 133 and 134 and some relay parts 136 and 135 connected to the land parts 133 and 134 are exposed.

  In the LED 50, the electrode terminals and the land portions 133 and 134 are usually connected by a reflow process using cream solder, and are electrically connected to the wiring pattern 132 and positioned and fixed to the FPC 121. It is. At that time, the land parts 133 and 134 are usually formed in a shape and dimensions substantially corresponding to the electrode terminals, and thus, in the reflow process, utilizing the self-alignment action due to the surface tension of the molten solder, The LED 50 can be positioned.

  The FPC 121 shown in FIG. 7 connects the land parts 133 and 134 and the wiring pattern 132 via relay parts 136 and 135 having a larger area than the land parts 133 and 134, thereby forming a conductive pattern coverlay film 141. In addition to preventing disconnection of the portion exposed from the opening 142 of the LED and improving the peel strength of the land portions 133 and 134, the heat generated from the LED 50 and transmitted to the land portions 133 and 134, Even when the output of the LED 50 is increased by efficiently dissipating heat from the relay units 136 and 135, the temperature rise is suppressed, thereby contributing to higher luminance and luminance stability of the planar lighting device.

JP 2006-310123 A

  On the other hand, in order to promote higher brightness of the planar lighting device, it is desirable to improve and stabilize the light coupling efficiency between the LED and the light guide plate together with the higher output of the LED as described above. In particular, it is necessary to strictly control the distance between the light emitting surface of the LED and the light incident surface of the light guide plate. Therefore, for example, in the planar lighting device 100 having the configuration shown in FIG. 6, first, the FPC assembly in which the position of the LED 50 in the front-rear direction (Y direction shown in FIG. 6) of the LED 50 is positioned with high accuracy. 120, and the FPC assembly 120 is accurately assembled at a predetermined position with respect to the light guide plate 11, so that the light emitting surface 50a of the LED 50 and the light incident surface 11c of the light guide plate 11 are formed. It achieves strict control of the spacing.

  In particular, when a plurality of LEDs 50 are mounted on a single FPC 121 as in the planar lighting device 100 shown in FIG. 6, when the FPC assembly 120 is assembled to the light guide plate 11, the light emitting surfaces of the plurality of LEDs 50. Since the distance between the LED 50a and the light incident surface 11c of the light guide plate 11 cannot be finely adjusted individually for each LED, higher accuracy is achieved with respect to the position in the front-rear direction of each LED 50 fixed on the FPC 121. It will be required.

  In order to satisfy such a requirement, in addition to improving the mounting accuracy of the LED 50 on the FPC 121 by strict management of the reflow process, usually, after mounting the LED 50 on the FPC 121, It is necessary to perform inspection to select the FPC assembly 120 that satisfies the standard regarding the positional accuracy of the LED 50 and use only the selected FPC assembly 120 in the subsequent process.

  Such an inspection of the mounting position is based on, for example, one side (for example, the side 121b) extending in parallel with the arrangement direction (X direction) of the land parts 133 and 134 among the sides constituting the outer edge of the FPC 121. From 121b to the light emitting surface 50a of the LED 50 mounted on the FPC 121 (or at least a part of the light emitting surface 50a and the portion arranged in parallel with the side 121b when the LED 50 is normally mounted). This can be implemented by measuring the distance (in the Y direction) and determining whether the measured distance is within a predetermined standard range.

  However, in this inspection method based on the outer shape of the FPC 121, the measured value of the distance includes the manufacturing tolerance variation of the FPC 121 outer shape (that is, the dimensional variation from the one side 121b as the measurement reference to the land portions 133 and 134). ) Is included, and there is a problem that it is difficult to determine the quality of the mounting position of the LED 50 in the front-rear direction with sufficient accuracy. In addition, the tasks involved in the inspection process are relatively complex, such as measuring distances and comparing measured distances with standard values. When it is carried out by visual inspection (using an appropriate measuring instrument, etc.), the work man-hours in the inspection process are increased, and thus the manufacturing cost of the surface illumination device is increased, and there is a possibility that the inspection work may be misidentified. There is also a problem.

  Furthermore, although the FPC 121 shown in FIG. 7 has a certain effect for preventing the disconnection of the conductive pattern in the opening 142 as described above, for example, the land parts 133 and 134 (or the relay parts 136 and 135). In the fillet formed by the solder solidified above, the stress concentrates on the location where the thickness of the solder changes abruptly, resulting in breakage in the corresponding location of the land portions 133 and 134 (or the relay portions 136 and 135). In some cases, there is room for further improvement in terms of preventing disconnection of the conductive pattern.

  This invention is made | formed in view of the said subject, and provides the planar illuminating device which can implement easily and reliably the inspection of the mounting position on the printed circuit boards of point light sources, such as LED. Objective.

  The present invention further provides a planar illumination device capable of improving the mounting accuracy of a point light source such as an LED on a printed circuit board and effectively preventing disconnection of a wiring pattern around the point light source. For the purpose.

  In order to achieve the above object, a planar illumination device according to the present invention is a planar illumination device comprising a point light source, a printed circuit board assembly including a printed circuit board on which the point light source is mounted, and a light guide plate. The conductive pattern formed on the printed circuit board includes a pair of land portions corresponding to a pair of electrode terminals of the point light source and a wiring pattern connected to each land portion constituting the pair of land portions. The point light source is mounted on the printed circuit board such that a light emitting surface thereof is substantially perpendicular to a mounting surface of the printed circuit board, and the printed circuit board assembly includes the light emission of the point light source. The surface is disposed so as to face the light incident surface of the light guide plate, and a mounting position inspection mark is provided at a position corresponding to the back surface of the light emitting surface of the point light source on the mounting surface of the printed circuit board. Established And wherein the are.

  Here, in the following description, the light emitting surface side of the point light source is the front, the back side of the light emitting surface is the rear, and the front-rear direction of the printed circuit board is the point when the point light source is normally mounted on the printed circuit board. The direction in which the light emitting surface of the shaped light source faces is defined as the front, and the direction in which the rear surface of the light emitting surface faces is defined as the rear.

  In the planar illumination device according to the present invention, the point light source is mounted on the printed circuit board so that the light emitting surface thereof is substantially perpendicular to the mounting surface of the printed circuit board, and the printed circuit board assembly includes the point light source. The light emitting surface of the light guide plate is arranged to face the light incident surface of the light guide plate, and a mounting position inspection mark is provided at a position corresponding to the back surface of the light emitting surface of the point light source on the mounting surface of the printed circuit board. Therefore, after mounting the point light source on the printed circuit board, when performing the mounting position inspection, the point on the basis of whether or not the mounting position inspection mark looks in accordance with a predetermined inspection standard. It is possible to easily and reliably determine the quality of the mounting position of the shaped light source in the front-rear direction of the printed circuit board.

  In order to improve the light coupling efficiency between the light guide plate and the point light source by strictly controlling the distance between the light emitting surface of the LED and the light incident surface of the light guide plate, the present invention provides a printed circuit board for the point light source. Focusing on the fact that the mounting position accuracy in the front-rear direction is critically important, mounting position inspection marks are provided on the mounting surface of the printed circuit board corresponding to the back surface of the light emitting surface of the point light source This means that it is possible to reduce the man-hours required for the mounting position inspection process and improve the reliability thereof, thereby contributing to higher brightness and improved yield of the surface illumination device. is there.

  The mounting position inspection mark can be formed by any appropriate means including printing, but is preferably provided as a part of the conductive pattern. In other words, the mounting position inspection mark is preferably formed together with the wiring pattern included in the conductive pattern and the pair of land portions in the same process as the mounting pattern inspection mark. Can be placed with high accuracy with respect to other conductive patterns (particularly, a pair of lands corresponding to a pair of electrode terminals of a point light source), and reliability of mounting position inspection based on mounting position inspection marks Can be improved.

  In one embodiment of the present invention, the back surface of the point light source is a plane that is substantially parallel to the light incident surface of the light guide plate when the point light source is normally mounted on the printed circuit board. The mounting position inspection mark is formed in a belt-like shape extending in the extending direction of the straight line at a nominal position of the mounting surface of the printed circuit board as viewed from above the plane of the point light source. Is.

  In the planar illumination device according to the present invention, in order to improve the light coupling efficiency between the light guide plate and the point light source by strictly controlling the distance between the light emitting surface of the point light source and the light incident surface of the light guide plate As described above, the mounting position accuracy of the point light source in the front-rear direction of the printed circuit board is important. In other words, the mounting position accuracy in the direction orthogonal to the front-rear direction of the printed circuit board (hereinafter also referred to as the left-right direction) is important. There is a relatively large tolerance.

  From such a viewpoint, at least a part of the back surface of the point light source forms a plane parallel to the light incident surface of the light guide plate in a normal mounting state of the point light source on the printed circuit board, and The point light source is formed by forming the mounting position inspection mark in a strip shape extending in the direction of the straight line at the nominal position of the straight line that forms the top view of the plane of the point light source on the mounting surface of the printed circuit board. The positional deviation in the front-rear direction of the printed circuit board can be easily and reliably visually recognized as the positional deviation in the band width direction of the mounting position inspection mark, and the coupling efficiency between the point light source and the light guide plate Since the positional deviation in the left-right direction that does not have a sensitive effect coincides with the extension direction of the band, it does not appear as a visible positional deviation with respect to the mounting position inspection mark, and the mounting has a relatively simple configuration. While using marks location test, the mounting position inspection mark, without causing a rise in unwanted failure rate, it can be effectively used as a criterion for selectively testing only the position accuracy required.

  More preferably, the mounting position inspection mark has a front edge and a rear edge extending in parallel to the plane of the back surface of the point light source, and a band width with a distance between the front edge and the rear edge. As for the formation position of the mounting position inspection mark, the nominal position on the straight printed circuit board forming the top view of the plane of the point light source is included within the range of the band width ( Typically, the nominal position coincides with the central axis of the belt extension direction), and the belt width is set as an allowable range for the positional deviation of the point light source in the front-rear direction of the printed circuit board. May be.

  In this case, in the mounting position inspection process, when the printed circuit board is viewed from the mounting surface side, the straight line that forms the top view shape of the flat surface of the back surface of the mounted point light source is the mounting position inspection mark. If it is not included in the band width, in other words, at least part of the front edge of the mounting position inspection mark is visible outside the outline of the point light source, or after the mounting position inspection mark. If at least a part of the edge is not covered with the outline of the point light source, the mounting position can be determined as a misalignment defect. Such mounting position inspection is performed especially when a worker in charge performs visual inspection (using a microscope or the like if necessary) to determine whether or not the mounting position of the point light source is good. This is advantageous in that it can be immediately discriminated by visual recognition.

  Here, the shape of the mounting position inspection mark formed in a band shape in the band extending direction can be set to any appropriate shape in consideration of various conditions. For example, when the nominal position of the plane of the back surface of the point light source exists between a pair of land portions, the mounting position inspection mark is isolated from each land portion between the pair of land portions. It may be formed in a strip shape. Alternatively, similarly, when the nominal position of the plane of the back surface of the point light source is between the pair of land portions, the mounting position inspection mark is opposed to each land portion constituting the pair of land portions. It may be constituted by a pair of lead portions that are drawn from one side and extend toward the other land portion and face each other at a predetermined interval.

  In one embodiment of the present invention, the conductive pattern includes auxiliary wiring that connects each land portion constituting the pair of land portions and the wiring pattern, bypassing a place where they are directly connected. The auxiliary wiring has a lead-out portion that is led out from one opposite side of each land portion constituting the pair of land portions and extends toward the other land portion, and for the mounting position inspection At least a part of the mark consists of a lead-out portion of the auxiliary wiring.

  According to the mounting position inspection mark having such a configuration, the conduction pattern connects each land portion and the wiring pattern constituting the pair of land portions, bypassing a place where they are directly connected. Including the auxiliary wiring, the auxiliary wiring is drawn out from one opposite side of each land portion constituting the pair of land portions, and has a lead portion extending toward the other land portion, respectively. While making effective use of the wiring space on the printed circuit board, the mounting position inspection mark is easily visible and reliable, and as described below, the mounting accuracy of the point light source on the printed circuit board is improved. In addition, it is possible to improve the reliability of conduction near the point light source on the printed circuit board.

In general, a pair of electrode terminals of a point light source are provided on both lateral sides of the point light source in the left-right direction, and are directly connected to each land portion constituting a pair of land portions corresponding to the pair of electrode terminals. The wiring pattern is connected to any one of the land portions outside the point light source in the left-right direction. On the other hand, the lead-out portion of the auxiliary wiring that is drawn out from one side of each land portion facing each other and extends toward the other land portion is drawn out from one side of each land portion in the left-right direction of the point light source. Thus, it extends inside the point light source.
Therefore, at the time of solder reflow in the mounting process of the point light source, the cream solder applied to the land part is melted, and each electrode is caused by the solder flowing from the land part toward the wiring pattern toward the outside of the point light source. For the force acting on the terminal, the force acting on each electrode terminal by the solder that is drawn from one side of each land portion facing each other and flows to the lead portion of the auxiliary wiring that extends toward the other land portion, It will act in the direction of cancellation.
As a result, for example, the symmetry between the forces acting on each electrode terminal is broken by the solder flowing in the wiring pattern directly connected to each land portion, and even when torque is generated to rotate the point light source. Since the size is suppressed, the occurrence of the positional deviation of the point light source in the solder reflow process can be reduced.

  In particular, when the point light source has a light emitting portion that is made of a light-transmitting resin that seals the LED chip and is exposed without having an exterior, such a point light source is When mounted on a flexible printed circuit board so that the light emitting part protrudes from the outer shape, the center of gravity of the point light source is biased forward, so the force acting on each electrode terminal as described above It reacts more sensitively to the breaking of symmetry between them, and misalignment due to rotation or the like is likely to occur. Therefore, the above-described positional shift reducing effect of the auxiliary wiring according to one embodiment of the present invention is a point light source having a light emitting portion that is made of a light-transmitting resin that seals the LED chip and is exposed without having an exterior. When mounted on a printed circuit board such that the light emitting portion protrudes from the outer shape of the printed circuit board, a particularly remarkable effect is obtained.

  Furthermore, this auxiliary wiring duplicates the connection between the land portion and the wiring pattern by connecting each land portion constituting the pair of land portions and the wiring pattern, bypassing the place where they are directly connected. At the same time, the auxiliary wiring itself is less likely to be broken for the following reasons, so that the reliability of the continuity of the wiring around the point light source on the printed circuit board is improved.

  Generally, the solder that solidifies on the land portion forms a curved surface shape (so-called fillet) whose thickness changes from the height of the side surface of the electrode terminal to the land portion, and in that case, stress is applied to the location where the thickness of the solder changes rapidly. As a result, the disconnection is likely to occur at the corresponding portion of the land portion (or the wiring pattern directly connected to the land portion). However, since the lead-out portions of the auxiliary wirings that are drawn from the opposite sides of each land portion and extend toward the other land portion extend inside the point light source, they are usually point light sources. Even if the electrode terminals provided on both sides on the outer side in the left-right direction are not in contact with each other, or even if a part of the electrode terminals have a portion that wraps around the inside of the point light source along the bottom surface, There is no side surface that rises sufficiently high from the lead-out portion of the auxiliary wiring. Therefore, when the solder that has flowed to the lead-out portion of the auxiliary wiring is solidified, a clear fillet is not formed there, and stress concentration as described above does not occur. Therefore, the auxiliary wiring is directly connected to each land portion, for example. Even if the wiring pattern is narrower than the wiring pattern to be connected, disconnection hardly occurs.

  Therefore, preferably, the line width of the lead-out portion of the auxiliary wiring can be narrower than the side length of the land portion from which the lead-out portion is led out. In this configuration, the shape of the land portion can be maintained in a shape that does not impair the self-alignment function during solder reflow, so that the mounting position in the left-right direction of the point light source is determined by the light from the light guide plate and the point light source. This is advantageous from the viewpoint of coupling efficiency in positioning with sufficient accuracy.

  The auxiliary wiring according to one embodiment of the present invention is particularly preferable when the printed circuit board on which the point light source is mounted is a flexible printed circuit board (FPC). In this FPC, typically, a conductive pattern is formed by, for example, copper foil on a base film made of polyimide or the like, and a coverlay film made of polyimide or the like is laminated and bonded to the upper layer. The cover lay film is provided with a pair of land portions, a wiring pattern directly connected to each land portion, and an opening for exposing a part of the auxiliary wiring.

  In the case of FPC, stress caused by deformation such as bending becomes a major factor of disconnection of the conductive pattern, and disconnection is likely to occur particularly in the conductive pattern exposed from the opening not protected by the coverlay film. However, since the auxiliary wiring according to one embodiment of the present invention extends inward of the external shape of the point-like light source to be mounted on each land portion, an opening portion where stress concentration due to bending of the FPC is likely to occur. After mounting the point light source, it is possible to minimize the influence of the FPC deformation on the auxiliary wiring after mounting the point light source. More effective.

  In a preferred aspect of the present invention, the mounting position inspection mark is isolated from each land portion constituting the pair of land portions corresponding to the pair of electrode terminals of the point light source and the auxiliary wiring drawn from each land portion. It is composed of a strip-shaped portion formed and a portion consisting of a lead-out portion of the auxiliary wiring led out from each land portion, and the strip-shaped portion is pointed by the band width between the front edge and the rear edge. And defining the allowable range of the positional deviation in the front-rear direction of the light source, and at least the trailing edge of the auxiliary wiring is formed on the same surface as the rear edge of the strip-shaped portion. It functions as a part of the mounting position inspection mark.

  Alternatively, the mounting position inspection mark according to a preferred aspect of the present invention is extended from the portion of the auxiliary wiring drawn out from each land portion and from the portion of the auxiliary wiring extended at a predetermined interval. And a pair of opposing extension portions, and the pair of extension portions are allowed to be displaced in the front-rear direction by the band width between the front edge and the rear edge. And at least a rear edge thereof is formed on the same surface as a rear edge of the pair of extension portions, thereby functioning as a part of the mounting position inspection mark. To do.

  Furthermore, in one aspect of the present invention, a portion of the wiring pattern that is directly connected to each land portion constituting the pair of land portions is formed as a pattern wider than each land portion, The wiring pattern is directly connected to each land portion by overlapping one corner of the wide pattern and one corner of each land portion.

  According to this configuration, the portion directly connected to each land portion constituting the pair of land portions of the wiring pattern is formed as a pattern wider than each land portion, so the peel strength of the land portion is improved. In addition, by efficiently dissipating the heat generated from the point light source, the temperature rise of the point light source is suppressed, and this contributes to higher brightness and brightness stability of the planar illumination device. Furthermore, the wiring pattern is directly connected to each land portion by overlapping one corner of the wide pattern and one corner of each land portion, so that the shape of each land portion is changed during solder reflow. Since the self-alignment function can be maintained in a shape that is not impaired, the point light source can be positioned with high accuracy.

  Furthermore, the portion directly connected to each land portion constituting the pair of land portions of the wiring pattern is formed as a pattern wider than each land portion, which means that the printed circuit board on which the point light source is mounted In the case of FPC, it is particularly advantageous in preventing disconnection of a portion of the conductive pattern exposed from the opening of the coverlay film. In this case, preferably, the outline of one corner of the wide pattern directly connected to each of the land portions of the wiring pattern is two adjacent sides among the sides constituting the opening of the cover lay film of the flexible printed circuit board. It is desirable that the one side extends in a direction substantially perpendicular to one of the two adjacent sides and one side extends in a direction substantially perpendicular to the other of the two adjacent sides. On the other hand, a more effective shape can be obtained.

  Since the present invention is configured as described above, it is possible to easily and surely inspect the mounting position of a point light source such as an LED on a printed circuit board, and to improve the light coupling efficiency between the point light source and the light guide plate. By improving and stabilizing, it contributes to higher brightness of the planar lighting device and improved productivity. In addition, according to the invention, the accuracy of mounting a point light source such as an LED on a printed circuit board is improved, and the disconnection of the wiring pattern around the point light source is effectively prevented, thereby achieving high brightness and reliability. It becomes possible to provide a high planar illumination device.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. However, the drawings are for explanation, and do not necessarily accurately reflect actual shapes and dimensions. FIG. 1 is an exploded perspective view showing a main part of a planar illumination device 10 according to the first embodiment of the present invention. The planar illumination device 10 has substantially the same configuration as that of the planar illumination device 100 shown in FIG. 6, and only the configuration of the FPC assembly 20 is different. The FPC assembly 20 will be described in detail below.

  FIG. 2 is a plan view showing the configuration of the FPC assembly 20 in the present embodiment, FIG. 2A is a plan view showing an FPC 21 that is a printed circuit board in the present embodiment, and FIG. It is a top view which shows FPC assembly 20 which is the printed circuit board assembly in embodiment. FIG. 2C is a plan view showing the LED 50 that is the point light source in the present embodiment and is mounted on the FPC 21 to constitute the FPC assembly 20.

  As shown in FIG. 2C, the LED 50 does not have a substrate part 51, an LED chip (not shown) mounted on the substrate part 51, and a lamp house (exterior), and seals the LED chip. And a light emitting part 52 formed so as to expose the translucent resin. A pair of electrode terminals 53 and 54 for supplying current to the LED chip are provided on both sides of the substrate part 51. Yes. Further, the outer shape of the translucent resin constituting the light emitting portion 52 has a light emitting surface 50a provided with a cylindrical surface protruding forward in the light emitting direction of the LED 50 (in the direction of arrow A shown in FIG. 2C). The back surface 50b forms a plane orthogonal to the front of the light emission direction of the LED 50. Preferably, the LED 50 has a layer in which yttrium, aluminum, and garnet (YAG) fine particles activated by cerium, which is a yellow light emitting phosphor, are mixed in a translucent resin constituting the light emitting unit 52. The LED chip is a blue light emitting element in which a light emitting layer in which nitride compound semiconductors such as GaN and GaAIN are stacked is formed on a sapphire substrate, and is absorbed by blue light from the LED chip and YAG fine particles. It is a pseudo white LED that generates white light by mixing with yellow light that is emitted by converting a part of blue light into a long wavelength.

  As shown in FIG. 2A, the FPC 21 forms a conductive pattern on a base film 31 made of polyimide or the like, for example, using copper foil or the like, and a coverlay film 41 (also made of polyimide or the like) on the upper layer. 2 (a) is stacked and bonded together, and the conductive pattern formed on the base film 31 is formed by the pair of electrode terminals 53 and 54 of the LED 50. A pair of land portions 33 and 34 to be mounted, wiring patterns 32a to 32c directly connected to each land portion 33 and 34, and each land portion 33 and 34 and wiring patterns 32a to 32c are directly connected to each other. Auxiliary wirings 37 and 38 that bypass and connect portions to be connected and a mounting position inspection mark 39 are included.

  Here, the cover lay film 41 is provided avoiding the connection terminal portion 23 for connecting the FPC 21 to an external drive circuit, and has an opening 42 at the mounting position of the LED 50, from the opening 42. The pair of land portions 33, 34, a part of the wiring patterns 32a to 32c directly connected to each land part 33, 34, a part of the auxiliary wirings 37, 38, and the mounting position inspection mark 39 are exposed. . In the present embodiment, the portions directly connected to the land portions 33 and 34 of the wiring patterns 32 a to 32 c are formed as patterns 35 and 36 having a width wider than at least the land portions 33 and 34.

  In the FPC assembly 20 according to the present embodiment, the two LEDs 50 are arranged with a pair of electrode terminals 53 and 54 on a corresponding pair of land portions 33 and 34, respectively, as shown in FIG. The light emitting surface 50a of the LED 50 and the back surface 50b thereof are mounted so as to be substantially perpendicular to the mounting surface (XY plane) of the FPC 21, and the light emitting portion 52 of each LED 50 is disposed in front of the FPC 21. It arrange | positions so that it may protrude from the edge 21a. The FPC assembly 20 configured as described above is arranged and fixed so that the light emitting surface 50a of the LED 50 faces the light incident surface 11c of the light guide plate 11 as shown in FIG.

  In the planar illumination device 10 according to the present embodiment, a cutout portion that conforms to the outer shape of the light emitting portion 52 of the LED 50 is formed at a position where the light emitting surface 50a of the LED 50 faces the light incident surface 11c of the light guide plate 11. The LED 50 may be arranged by fitting the light emitting portion 52 to the notch portion 12d, and the light incident prism portion 19 including a plurality of prisms extending in the thickness direction of the light guide plate 11 is as described above. It may be formed on the inner surface of the notch.

  Next, with reference to FIG. 3 and FIG. 4, the detail of a structure of the conduction | electrical_connection pattern in FPC21 in this embodiment, and its effect | action and effect are demonstrated.

  In the present embodiment, the wide patterns 35 and 36 in which the wiring patterns (for example, 32a and 32b) are directly connected to the land portions 33 and 34 are exposed from the openings 42 as shown in FIG. The portion is substantially parallel to one side 35a, 36a extending in a direction substantially orthogonal to one of the two adjacent sides 42a, 42b constituting the opening 42 and the other 42b of the two adjacent sides 42a, 42b constituting the opening 42. The wide pattern 35, 36 and each land part 33, 34 are (virtual) intersections of the two sides 33a, 33b of the land part 33. One corner overlaps one corner which is a (virtual) intersection of the two sides 35a and 35b of the wide pattern portion 35, and similarly, a (virtual) intersection of the two sides 34a and 34b of the land portion 34. And some corner, two sides 36a of the wide pattern portion 36, 36b (hypothetical) intersections and corner a is directly connected to overlap. The corners of the land portions 33 and 34 that are directly connected to the wide patterns 35 and 36 of the wiring pattern are present outside the LED 50 in the left-right direction (X direction).

  On the other hand, the auxiliary wirings 37 and 38 connected to the respective land portions 33 and 34 are drawn out from the opposite sides 33c and 34c of the respective land portions 33 and 34 and directed toward the other land portions 34 and 33, respectively. The extending portions 37a and 38a are extended, and the land portions 33 and 34 and the wide patterns 35 and 36 of the wiring patterns (for example, 32a and 32b) overlap and are directly connected according to a substantially U-shaped pattern. It is connected to each wiring pattern (for example, 32a, 32b) while detouring one corner (see FIG. 2A).

  By configuring the shape of each land portion 33, 34 and the wide patterns 35, 36 and the connection manner thereof as described above, even if stress due to bending of the FPC 21 is applied in all directions, the wide pattern 35 is formed. , 36 does not have a bending direction that easily breaks, so that the portions exposed from the opening 42 of the conductive pattern (particularly, the sides 42a, 42a, 42b constituting the opening 42 and the wide patterns 35, 36 are in contact with each other). The disconnection at (part) can be effectively prevented.

  Here, due to the shape of the FPC 21 in the present embodiment, the FPC 21 is likely to bend with a crease in the short side direction (Y direction), and therefore, particularly in the conductive pattern exposed from the opening 42 of the cover lay film 41. In general, the shape extending along the longitudinal direction (X direction) of the FPC 21 is considered to be disadvantageous to the stress caused by bending.

  However, the lead-out portions 37a and 38a of the auxiliary wirings 37 and 38 in the present embodiment extend from the lands 33 and 34 inward of the outer shape of the LED 50 mounted on the FPC 21 (see FIG. 3B). Therefore, the lead portions 37a and 38a exist due to the presence of the edge portions 42a and 42a separated from the edges 42a and 42a of the opening 42 where stress concentration is likely to occur, and the rigidity of the LED 50 after the LED 50 is mounted. In the region, it is difficult to cause a disconnection because, for example, a bending in which the short direction (Y direction) of the FPC 21 is a crease hardly occurs.

  According to the study by the present inventors, the auxiliary wiring 37, even under severe conditions in which the land portions 33, 34, or the wide patterns 35, 36, or the portions where they are overlapped and directly connected are generated. It has been confirmed that no disconnection occurs in 38, and the auxiliary wirings 37 and 38 in this embodiment double the conduction paths between the land portions 33 and 34 and the wiring patterns 32a to 32c to improve their reliability. It functions effectively as a means to make it happen.

  Further, as shown in FIG. 3B, the LED 50 is mounted on the FPC 21 by arranging the pair of electrode terminals 53 and 54 on the corresponding pair of land portions 33 and 34. These are electrically connected and positioned and fixed by a reflow process using cream solder.

  Therefore, it is desirable that the land portions 33 and 34 are formed in a shape and size substantially corresponding to the electrode terminals 53 and 54, so that the self-alignment effect due to the surface tension of the molten solder is effective in the reflow process. Therefore, the LED 50 can be positioned with high accuracy. In relation to this point, the shapes of the land portions 33 and 34 and the wiring patterns 32a to 32c and the connection modes thereof in the present embodiment are disconnected without substantially damaging the contours forming the shapes of the land portions 33 and 34. This is advantageous because it can be prevented. For the same reason, it is desirable that the line widths of the leading portions 37a and 37b of the auxiliary wirings 37 and 38 are narrower than the lengths of the sides 33c and 34c of the land portions 33 and 34 from which the auxiliary wirings 37 and 38 are drawn. .

  Furthermore, since the wide patterns 35 and 36 in the present embodiment are formed so as to have an area larger than that of the land portion, heat generated by the LED 50 and transmitted to the electrode terminals 53 and 54 is generated. It also functions as a heat dissipation part.

Next, another operation of the auxiliary wirings 37 and 38 in this embodiment will be described.
As shown in FIG. 4, when the LED 50 is mounted by solder reflow, the cream solder (A) applied to the land portions 33 and 34 is melted, and the wiring pattern is passed from each land portion 33 and 34 through a corner directly connected. A force in the α direction mainly acts on each of the electrode terminals 53 and 54 by the flowing solder and flowing into the electrode terminals 53 and 54.

  As described above, the LED 50 is positioned by self-alignment by the force acting on the electrode terminals 53 and 54. On the other hand, the symmetry of the force acting on the electrode terminals 53 and 54 due to some factor. In the case of collapse, a torque for rotating the LED 50 is generated, and there is a possibility that displacement due to the rotation occurs.

  However, in the present embodiment, since there are auxiliary wirings 37 and 38 having lead-out portions 37a and 38a drawn from the sides 33c and 34c of the land portions 33 and 34, the solder that has flowed through the auxiliary wirings 37 and 38 is present. The force acting on the electrode terminals 53 and 54 in the β direction cancels the force acting on the electrode terminals 53 and 54 in the α direction. As a result, the symmetry between the forces acting on the electrode terminals 58 and 57 is broken by the solder flowing from the land portions 33 and 34 to the wiring patterns 32a and 32b, and a torque is generated to rotate the LED 50. However, since the size thereof is suppressed, the occurrence of positional deviation of the LED 50 in the solder reflow process can be reduced.

  In particular, when the LED 50 to be used is mounted on the FPC 21 so that the light emitting portion 52 protrudes from the outer shape of the FPC 21 as in the FPC assembly 20 in the present embodiment, the center of gravity of the LED 50 is forward. Since it is biased, it reacts more sensitively to the breaking of symmetry between the forces acting on the electrode terminals 53 and 54 as described above, and misalignment due to rotation or the like is likely to occur. The effect of reducing misalignment due to the configuration having the auxiliary wirings 37 and 38 according to the present invention functions particularly effectively for such an LED 50 and its mounting form on the FPC 21.

  Here, the reason why the auxiliary wirings 37 and 38 are less likely to be disconnected will be described as follows. Generally, the solder solidified on the land portions 33 and 34 is the surface of the land portions 33 and 34 (or the wide patterns 35 and 36) from the height of the side surface of the electrode terminal (for example, the electrode terminals 53 and 54 of the LED 50). In this case, a curved surface shape (so-called fillet) whose thickness changes is formed, and at this time, stress concentrates on a place where the thickness of the solder changes rapidly, whereby land portions 33 and 34 (or wide patterns 35 and 36) are formed. Disconnections are likely to occur at the corresponding locations.

  On the other hand, since the auxiliary wirings 37 and 38 are drawn out from the sides 33c and 34c of the land portions 33 and 34 and extend inside the outer shape of the LED 50, the electrode terminals 53 and 54 are connected to the auxiliary wirings 37 and 38, respectively. There is no side surface that rises at a sufficient height from the surface of the auxiliary wirings 37 and 38. Accordingly, when the solder that has flowed through the auxiliary wirings 37 and 38 is solidified, a clear fillet is not formed on the auxiliary wirings 37 and 38, and the stress concentration as described above does not occur.

  The FPC 21 in the present embodiment has the above-described configuration and enables the LED 50 to be mounted with high accuracy. In general, in order to improve and stabilize the light coupling efficiency between the LED 50 and the light guide plate 11. In addition, in order to strictly control the distance between the light emitting surface 50a of the LED 50 and the light incident surface 11c of the light guide plate 11, after mounting the LED 50 on the FPC 21, the mounting position is inspected to relate to the positional accuracy of the LED 50. It is necessary to sort out the FPC assembly 20 that satisfies the standard, and use only the sorted FPC assembly 20 in the subsequent process. The mounting position inspection mark 39 of the FPC 21 in the present embodiment is useful for inspecting the mounting position of the LED 50, and the configuration, operation, and effect thereof will be described below.

  First, in the present embodiment, the back surface 50b of the LED 50 is located with respect to the light incident surface 11c of the light guide plate 11 when the FPC assembly 20 is assembled to the light guide plate 11 in a normal mounting state of the LED 50 to the FPC 21. Are parallel planes. The mounting position inspection mark 39 in this embodiment is formed in a strip shape isolated from the land portions 33, 34 between the pair of land portions 33, 34, as shown in FIG. ing.

  The formation position of the mounting position inspection mark 39 will be described in detail with reference to FIG. 3B showing a state where the LED 50 is normally mounted on the FPC 21. That is, the mounting position inspection mark 39 is a front edge extending parallel to the back surface 50b of the LED 50 along the straight line extension direction at a nominal position of the mounting surface of the FPC 21 as viewed from above the back surface 50b of the LED 50. The nominal position of a straight line having 39a and a rear edge 39b when the back surface 50b of the LED 50 is viewed from above is included in the range of the band width d defined by the front edge 39a and the rear edge 39b. The band width d is set as an allowable range for the positional deviation of the LED 50 in the front-rear direction (Y direction) of the FPC 21. Preferably, the nominal position of the straight line when the rear surface 50b of the LED 50 is viewed from above is the mounting position. It may coincide with the central axis in the longitudinal direction (X direction) of the inspection mark 39.

  By using such mounting position inspection mark 39, in the mounting process of the LED 50 on the FPC 21, for example, the FPC 21 is translated in the front-rear direction (Y direction) or rotated within the mounting surface (XY plane) of the FPC 21. For example, when the FPC 21 is displaced in the front-rear direction (Y direction) at the mounting position of the LED 50, the mounted LED 50 when the FPC 21 is viewed from the mounting surface side in the position inspection process after the mounting process. It is possible to easily and reliably determine whether the mounting position is good or not based on whether or not the straight line forming the top view shape of the back surface 50b is included in the band width d of the mounting position inspection mark 39. .

  In particular, even when such an inspection work is performed visually by a worker (using a microscope or the like if necessary), at least a part of the front edge 39a of the mounting position inspection mark 39 is dotted. Whether the LED 50 and the mounting position inspection mark 39 are visible or not visible is determined by determining whether the rear edge 39b of the mounting position inspection mark is covered by the outer shape of the LED 50. Therefore, the number of man-hours required for the mounting position inspection process can be reduced, and the reliability of the inspection can be improved.

  In the planar illumination device 10 according to the present invention, the light coupling efficiency of the light guide plate 11 and the LED 50 is improved by strictly controlling the distance between the light emitting surface 50a of the LED 50 and the light incident surface 11c of the light guide plate 11. For this purpose, the mounting position accuracy of the LED 50 in the front-rear direction (Y direction) of the FPC 21 is important. In other words, there is a relatively large allowable range for the mounting position accuracy of the FPC 21 in the left-right direction (X direction). .

  From this point of view, the mounting position inspection mark 39 according to the present embodiment can easily and reliably set the positional displacement of the FPC 21 in the front-rear direction (Y direction) as the positional displacement of the mounting position inspection mark 39 in the band width d direction. The positional deviation in the left-right direction (X direction) that is visible and does not have a sharp influence on the coupling efficiency between the LED 50 and the light guide plate 11 is a visible positional deviation with respect to the mounting position inspection mark 39. As the mounting position inspection mark 39 having a relatively simple configuration is used, the mounting position inspection mark 39 can be provided with the required positional accuracy without causing an unnecessary increase in the defective rate. It can be effectively used as a standard for selectively inspecting only.

  Further, the portion of the FPC 21 that is not covered with the cover lay film 41 may be subjected to any appropriate surface treatment such as solder plating, electrolytic gold plating, electrolytic gold flash plating, and rust prevention treatment. However, when the surface treatment of the mounting position inspection mark 39 is performed by rust prevention treatment, if the mounting position inspection mark 39 becomes difficult to see due to so-called blackening after reflow in the mounting process, the mounting position inspection mark 39 39 may be provided with a lead pad for plating (not shown) for performing electrolytic gold plating or the like.

  In the above-described first embodiment of the present invention, the connection form between the land lines 33 and 34 and the wiring patterns 32a to 32c via the auxiliary wirings 37 and 38 and the wide patterns 35 and 36 is as follows. As described above, although it is suitable for improving the accuracy of the mounting position and ensuring the reliability of conduction, the structure of the mounting position inspection mark 39 according to the present invention and the inspection process of the mounting position accuracy using it However, it is not necessarily an essential component.

  Next, a planar lighting device according to another embodiment of the present invention will be described with reference to FIG. Since the embodiment described below is different from the first embodiment described above only in the mode of the mounting position inspection mark provided on the FPC 21, the description of the overlapping parts is omitted in the following description. The mounting position inspection mark in each embodiment will be described.

  FIG. 5A is a plan view showing a mounting position inspection mark 60 of the surface illumination device according to the second embodiment of the present invention. The mounting position inspection mark 60 includes a strip-shaped portion 61 formed isolated from the land portions 33, 34 and the auxiliary wirings 62, 63 drawn from the land portions 33, 34, and the land portions 33. , 34 is composed of a portion composed of the lead-out portions 62a, 63a of the auxiliary wirings 62, 63. The strip-shaped portion 61 defines an allowable range of positional deviation in the front-rear direction (Y direction) of the LED 50 by the band width between the front edge 61a and the rear edge 61b, and the auxiliary wiring 62. , 63 have at least rear edges 62c, 63c formed on the same surface as the rear edge 61b of the strip-shaped portion 61, thereby functioning as a part of the mounting position inspection mark 60. Is. At this time, the front edges 62b and 63b of the lead portions 62a and 63a of the auxiliary wirings 62 and 63 are not necessarily formed on the same surface as the front edge 61a of the strip-shaped portion 61, and the auxiliary wirings 62 and 63 are not necessarily formed. On the other hand, it may be formed at an appropriate position in order to secure a necessary line width from the viewpoint of improving the reliability of conduction and the mounting accuracy.

  FIG. 5B is a plan view showing a mounting position inspection mark 70 of the surface illumination device according to the third embodiment of the present invention. The mounting position inspection mark 70 is extended from the lead wire portions 73a and 74a of the auxiliary wires 73 and 74 drawn from the land portions 33 and 34 and the lead wire portions 73a and 74a of the auxiliary wires 73 and 74, respectively. And a portion composed of a pair of extension portions 71 and 72 facing each other at a predetermined interval. The pair of extension portions 73 and 74 define an allowable range of positional deviation in the front-rear direction (Y direction) of the LED 50 according to the band width between the front edges 71a and 72a and the rear edges 71b and 72b. In addition, the lead-out portions 73a and 74a of the auxiliary wirings 73 and 74 have at least rear edges 73c and 74c formed on the same surface as the rear edges 71b and 72b of the pair of extension portions 71 and 72. It functions as a part of the mounting position inspection mark 70. At this time, the front edges 73b and 74b of the lead portions 73a and 74a of the auxiliary wirings 73 and 74 are not necessarily formed on the same surface as the front edges 71a and 72a of the pair of extension portions 71 and 72. The wirings 73 and 74 may be formed at appropriate positions in order to secure a necessary line width from the viewpoint of improving the reliability of conduction and the mounting accuracy.

  In the second and third embodiments described above, the wiring space on the FPC 21 is effectively used by using at least a part of the auxiliary wirings 62, 63, 73, 74 as mounting position inspection marks 60, 70. On the other hand, it is possible to improve the visibility and reliability of the mounting position inspection marks 60 and 70, improve the mounting accuracy of the LED 50 on the FPC 21, and improve the reliability of conduction of the FPC 21 near the LED 50. It becomes possible.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to embodiment mentioned above. For example, the mounting position inspection mark according to the present invention is preferably provided as a part of the conductive pattern formed on the printed circuit board from the viewpoint of position accuracy, but is provided by any means including printing. It may be. Further, the point light source according to the present invention may be provided with a lamp house formed from, for example, a heat-resistant white resin, and / or the mounting form of the point light source on the printed circuit board is as follows: The entire outer shape of the point light source may be arranged and mounted on the mounting surface of the printed board. Further, the configurations of the conductive pattern and the mounting position inspection mark according to the present invention are not necessarily limited to the flexible printed circuit board, but can be applied to any appropriate printed circuit board.

  Further, the configuration of the planar illumination device according to the present invention is not limited to the configuration of the planar illumination device 10 shown in FIG. 1, but the shape of the light guide plate 11 and its main surfaces 11 a and 11 b and the side end surfaces 11 c, The structure such as 11d or the presence or absence of use of the reflecting plate 15, the diffusing plate 12, and the prism plates 13 and 14 can be arbitrarily selected. In the present embodiment, the FPC assembly 20 drives the LEDs 50 in series, but it goes without saying that the present invention is not limited to the number of LEDs used and the connection form. Furthermore, the inspection of the mounting position using the mounting position inspection mark according to the present invention is not only performed by visual inspection by a worker, but also by any appropriate automatic inspection system including an imaging unit and an image processing unit. Needless to say, it can be suitably implemented.

It is a disassembled perspective view which shows the principal part of the planar illuminating device in the 1st Embodiment of this invention. It is a top view which shows the FPC assembly of the planar illuminating device shown in FIG. 1, (a) is a top view which shows FPC, (b) is a top view which shows FPC assembly, (c) is mounted on FPC. It is a top view which shows LED. FIG. 3 is an enlarged view showing the vicinity of a land portion of the FPC assembly shown in FIG. 2, (a) is a plan view showing the FPC, and (b) is a plan view showing a state in which the LEDs are normally mounted. . FIG. 3 is an enlarged plan view showing the vicinity of a land portion of the FPC shown in FIG. 2A in order to explain an operation of the auxiliary wiring in the present embodiment. (A) is a top view which shows the mounting position inspection mark of the planar illuminating device in the 2nd Embodiment of this invention, (b) is the mounting position of the planar illuminating device in the 3rd Embodiment of this invention. It is a top view which shows the mark for a test | inspection. It is a disassembled perspective view which shows the structural example of the conventional planar illuminating device. It is a top view which shows one structural example of conventional FPC.

Explanation of symbols

10: planar illumination device, 11: light guide plate, 11c: light incident surface, 20: FPC assembly (printed circuit board assembly), 21: FPC (printed circuit board), 32a, 32b, 32c: wiring pattern, 33, 34 : A pair of lands, 37, 38: auxiliary wiring, 39: mounting position inspection mark, 50: LED (point light source), 50a: light emitting surface, 50b: back surface

Claims (5)

In a planar lighting device comprising a point light source and a printed circuit board assembly comprising a printed circuit board on which the point light source is mounted, and a light guide plate,
The conductive pattern formed on the printed circuit board includes a pair of land portions corresponding to the pair of electrode terminals of the point light source, and a wiring pattern connected to each land portion constituting the pair of land portions,
The point light source is mounted on the printed circuit board so that the light emitting surface thereof is substantially perpendicular to the mounting surface of the printed circuit board, and the printed circuit board assembly includes the light emitting surface of the point light source. , Arranged to face the light incident surface of the light guide plate,
A planar illumination device, wherein a mounting position inspection mark is provided at a location corresponding to a back surface of the light emitting surface of the point light source on the mounting surface of the printed circuit board.   The planar illumination device according to claim 1, wherein the mounting position inspection mark is provided as a part of the conduction pattern.   The back surface of the point light source has a plane that is substantially parallel to the light incident surface of the light guide plate in a normal mounting state of the point light source on the printed circuit board. 2. The inspection mark is formed in a belt-like shape extending in an extending direction of the straight line at a nominal position of a straight line when the plane of the point light source is viewed from above on the mounting surface of the printed circuit board. Or the planar illumination device of 2.   The conduction pattern includes an auxiliary wiring that connects each land portion constituting the pair of land portions and the wiring pattern, bypassing a place where they are directly connected, and the auxiliary wiring includes the pair of land portions. Each of the land portions constituting the land portion has a lead portion extending from one opposite side to the other land portion, and at least a part of the mounting position inspection mark is a lead of the auxiliary wiring It consists of a part, The planar illuminating device of any one of Claim 1 to 3 characterized by the above-mentioned. A portion of the wiring pattern that is directly connected to each land portion constituting the pair of land portions is formed as a wider pattern than each land portion, and the wiring pattern is formed of the wide pattern. 5. The planar illumination device according to claim 1, wherein the planar lighting device is directly connected to each land portion by overlapping one corner and one corner of each land portion. 6.

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