JP6745300B2 - Surface illumination device and mounting method - Google Patents

Description

The present invention relates to a planar lighting device and a mounting method.

Conventionally, in a mounting method in which a pad serving as an electrode provided on a mounting surface of a substrate and a terminal provided on a side surface or a bottom surface of a light source or other electronic component are joined by reflow of solder printed on the pad, an electronic component A technique is known in which the mounting surface and the electronic component are bonded to each other via an adhesive or solder arranged at a position different from that of the terminal to prevent the electronic component from tilting or shifting the mounting position during reflow.

Japanese Unexamined Patent Publication No. 9-260429 JP, 2011-66112, A JP, 2017-163029, A

However, in the conventional technique, there is still a possibility that the device is mounted in a state of being inclined with respect to the pad. For example, when the electronic component is a light source, it is mounted in a state in which it is tilted from the original angle with respect to the pad, and if the optical axis of the light source deviates from the original direction, the desired illumination performance may not be realized. As described above, due to the sophistication of performance required for electronic parts, further improvement of mounting accuracy is expected.

The present invention has been made in view of the above, and an object thereof is to provide a planar lighting device and a mounting method capable of improving mounting accuracy.

In order to solve the problems described above and achieve the object, a planar lighting device according to an aspect of the present invention includes a plurality of pads, a light source, and an adhesive member. The plurality of pads are provided on the main surface of the wiring board. The light source has a terminal housed in each of a plurality of cavities arranged on any surface other than the light emitting surface, and the pad and the terminal are joined via the solder housed in the cavity. The adhesive member is disposed between the main surface and the light source and adheres the main surface and the light source. The terminal is arranged on one end side in the lateral direction of the light source in plan view. The center of the adhesive member is arranged only on one end side in plan view.

According to one aspect of the present invention, mounting accuracy can be improved.

FIG. 1 is a front view showing an example of the external appearance of the planar lighting device according to the embodiment. FIG. 2 is a cross-sectional view of the planar lighting device according to the embodiment. FIG. 3 is a diagram showing the appearance of the LED. FIG. 4 is a diagram showing the appearance of the LED. FIG. 5 is a diagram showing the appearance of the LED. FIG. 6 is a diagram showing the appearance of the LED. FIG. 7 is a diagram for explaining an example of a light source mounting method 1. FIG. 8 is a diagram for explaining an example of a light source mounting method 2. FIG. 9 is a diagram for explaining an example of the light source mounting method 3. FIG. 10 is a diagram for explaining an example of a light source mounting method 4.

Hereinafter, a planar lighting device and a mounting method according to embodiments will be described with reference to the drawings. Note that the dimensional relationship of each element in the drawings, the ratio of each element, and the like may differ from reality. Even between the drawings, there may be a case where the dimensional relationships and ratios are different from each other. In each drawing, in order to make the description easy to understand, a three-dimensional orthogonal coordinate system in which the light emission direction of the planar lighting device is the positive Z-axis direction may be illustrated.

FIG. 1 is a front view showing an example of the external appearance of the planar lighting device according to the embodiment. As shown in the example of FIG. 1, the planar lighting device 1 according to the embodiment has a substantially rectangular shape in a top view. One end side of the planar lighting device 1 in the longitudinal direction (X-axis direction) is covered with a light shielding sheet 10 including a first light shielding sheet 10a and a second light shielding sheet 10b. The other end side of the planar lighting device 1 in the longitudinal direction is covered with the light shielding sheet 100.

Then, the planar lighting device 1 emits light from a light emitting region (also referred to as a light emitting area) R which is not covered with the light shielding sheets 10 and 100. That is, the light-shielding sheets 10 and 100 define the light emitting region R. The planar lighting device 1 according to this embodiment is used as a backlight of a liquid crystal display device. Such a liquid crystal display device is used, for example, in a smartphone.

Further, as shown in FIG. 1, the width of the light shielding sheet 10 is wider than that of the light shielding sheet 100. This is because the light-shielding sheet 100 covers a light guide plate, a diffusion sheet, and a prism sheet, which will be described later, which are present in the lower portion of the light-shielding sheet 100 on the Z-axis negative direction side, whereas the light-shielding sheet 10 lowers the light-shielding sheet 10. This is to cover a relatively wide area that further includes an LED (Light Emitting Diode), an FPC (Flexible Printed Circuit), and the like, which will be described later, in addition to a light guide plate, a diffusion sheet, and a prism sheet, which will be described later, in FIG.

Next, the configuration of the planar lighting device 1 according to the embodiment will be described with reference to FIG. FIG. 2 is a cross-sectional view of the planar lighting device according to the embodiment. FIG. 2 shows a cross section of the planar lighting device 1 taken along the line AA of FIG. 1 as viewed from the Y-axis positive direction side.

As shown in FIG. 2, the planar lighting device 1 includes a first light shielding sheet 10a, a second light shielding sheet 10b, a frame 11, an LED 12, a light guide plate 13, an FPC 14, a prism sheet 15, and a diffusion sheet. 16, a first connecting member 17, a second connecting member 18, and a pad 50.

The frame 11 is, for example, a housing made of a metal material or a resin material, has a side wall 11a and a bottom portion 11b, and has an LED 12, a light guide plate 13, an FPC 14, a prism sheet 15, and a diffusion sheet 16. The first connecting member 17, the second connecting member 18, and the pad 50 are accommodated.

The LED 12 is, for example, a point light source, and in the present embodiment, the plurality of LEDs 12 are arranged along the Y-axis direction which is the lateral direction of the planar lighting device 1. Further, the LED 12 is, for example, a pseudo white LED including a blue LED and a phosphor.

The LED 12 has a light emitting surface 12a, a bottom surface 12b that intersects (for example, is orthogonal to) the light emitting surface 12a, a back surface 12c that is a surface opposite to the light emitting surface 12a, and a side surface that intersects the light emitting surface 12a and the bottom surface 12b. 12d (see FIG. 3). The light emitting surface 12a is a surface that emits light toward the X-axis positive direction on the light guide plate 13 side described later. The bottom surface 12b is a surface facing a mounting surface 14a of the FPC 14 described later.

A recess (cavity) is formed on the bottom surface 12b at a position corresponding to the terminal (electrode terminal) of the LED 12, and the solder 60 is poured into the cavity, so that the terminal of the LED 12 and the FPC 14 described below are connected to the pad 50 described below. Are joined through. That is, the LED 12 is a side-view type LED in which the bottom surface 12b intersecting the light emitting surface 12a is mounted on the FPC 14.

Next, the LED 12 will be further described with reference to FIGS. 3 to 6 are views showing the appearance of the LED 12. 3 and 4 show perspective views of the LED 12. Further, FIG. 5 shows a view of the LED 12 viewed from the bottom surface 12b side which is the Z axis negative direction side. FIG. 6 shows a view of the LED 12 viewed from the back surface 12c side, which is the negative side of the X axis.

As shown in FIG. 3, one LED 12 has a substantially rectangular parallelepiped shape in a plan view in which the Y-axis direction is the longitudinal direction and the X-axis direction is the lateral direction. Has two light emitting surfaces 12a having substantially the same area. The number of light emitting surfaces 12a included in one LED 12 is not limited to two, and may be one or three or more. Further, the two light emitting surfaces 12a may not be substantially the same in area and may be different from each other.

As shown in FIGS. 4 to 6, in the LED 12, a cavity 120 is formed in a part of a corner portion where the bottom surface 12b and the back surface 12c intersect, and a terminal 120a is provided on the inner surface of this recess. It can be said that the cavity 120 is a part of the bottom surface 12b (or the back surface 12c), that is, the terminal 120a is provided on the bottom surface 12b (or the back surface 12c).

Specifically, the terminal 120a is provided on the peripheral surface of the cavity 120 having a combination of a semi-cylindrical shape and a semi-conical shape, and the solder 60 is poured into the cavity 120 to be electrically connected to the FPC 14. The cavity 120 in which the terminal 120a is provided is not limited to the shape in which the semi-cylindrical shape and the semi-conical shape are combined, and may be any recessed shape.

The LED 12 may be a top-view type LED whose back surface 12c is mounted on the FPC 14. The cavity 120 that houses the terminal 120a is not limited to being formed at the intersection of the bottom surface 12b and the back surface 12c of the LED 12, and may be, for example, the back surface 12c or any surface other than the light emitting surface 12a. ..

Further, as shown in FIG. 5, in the LED 12, the terminal 120a housed in the cavity 120 is arranged on one end side closer to the X axis negative direction than the center line 12m of the LED 12 in the X axis direction (short direction) in plan view. The light emitting surface 12a may be formed on the other end side closer to the positive direction of the X axis.

Returning to FIG. 2, the light guide plate 13 is, for example, a plate-shaped member made of a transparent material (for example, polycarbonate resin), and is formed in a substantially rectangular shape when viewed from the Z axis negative direction side in a top view. The light guide plate 13 has two main surfaces 13a and 13b and a side surface 13c.

The side surface 13c is a light incident surface (hereinafter, referred to as a light incident surface 13c) which faces the light emitting surface 12a of the LED 12 and on which the light emitted from the light emitting surface 12a is incident. That is, the planar lighting device 1 according to the embodiment is a so-called edge light type lighting device in which a plurality of LEDs 12 are arranged along the edge of the light guide plate 13 (light incident surface 13c).

The main surface 13a is a main surface that intersects with the light incident surface 13c, and is an emission surface (hereinafter referred to as an emission surface 13a) from which the light incident from the light incident surface 13c is emitted. The main surface 13b is a main surface on the opposite side of the emission surface 13a (hereinafter referred to as the opposite surface 13b). On the opposite surface 13b, for example, an optical path changing pattern including a plurality of dots is formed. Thereby, the traveling direction of the light traveling in the light guide plate 13 is changed, and more light is emitted from the emission surface 13a.

The light guide plate 13 may be provided with a wedge portion on the side surface 13c side, for example. Specifically, the light guide plate 13 may be provided with a wedge portion in which the thickness of the light guide plate 13 gradually decreases from the side surface 13c side toward the X-axis positive direction which is the longitudinal direction of the light guide plate 13.

The FPC 14 is a flexible substrate (wiring substrate) on which the LEDs 12 are mounted, for example. The FPC 14 is an example of a substrate, and may be a rigid (rigid) substrate. The FPC 14 has, for example, a strip shape whose longitudinal direction is the Y-axis direction, and has a mounting surface 14a which is a main surface on which a plurality of LEDs 12 are arranged along the longitudinal direction. A metal pattern such as wiring is formed on the FPC 14, and a pad 50, which will be described later, connected to the metal pattern is arranged on the mounting surface 14a.

Further, the FPC 14 is connected to a drive circuit (not shown), and the LED 12 is controlled to be lit by the drive circuit. Although the FPC 14 is provided on the bottom portion 11b side of the frame 11, it may be provided on the emission surface 13a side of the light guide plate 13. Specifically, the FPC 14 may be arranged on the top surface side on the Z axis positive direction side opposite to the bottom surface 12b of the LED 12. When using a top-view type LED as the light source, the FPC may be arranged on the side wall 11 a of the frame 11.

The prism sheet 15 controls the light distribution of the light diffused by the diffusing sheet 16 described below, and emits the light subjected to the light distribution control in the light emission direction that is the Z-axis positive direction.

The diffusion sheet 16 is provided on the emission surface 13a side of the light guide plate 13 and diffuses the light emitted from the emission surface 13a. Specifically, for example, the diffusion sheet 16 is arranged so as to cover the emission surface 13a and diffuses the light emitted from the emission surface 13a.

The first connecting member 17 and the second connecting member 18 are, for example, a single-sided tape or a double-sided tape. The first connecting member 17 connects the LED 12 and the light guide plate 13 optically or structurally. Specifically, the first connecting member 17 connects the light emitting surface 12a of the LED 12 and the light entering surface 13c of the light guide plate 13.

The second connecting member 18 is a member that is arranged so as to be sandwiched between the FPC 14 and the opposite surface 13 b of the light guide plate 13, and fixes the light guide plate 13 to the FPC 14. For example, one surface of the second connecting member 18 is attached to at least a part of the mounting surface 14a of the FPC 14 near the light guide plate 13, and is attached to at least a portion of the opposite surface 13b of the light guide plate 13 near the LED 12. Attached.

A plurality of pads 50 are provided on the mounting surface 14a of the FPC 14. The plurality of pads 50 are linearly arranged along the Y-axis direction that is the longitudinal direction of the FPC 14. The pad 50 is, for example, a conductive electrode made of a metal material such as gold foil or copper foil, and is a portion joined to the terminal 120a (see FIGS. 4 to 6) of the LED 12 via the solder 60.

Then, each of the plurality of pads 50 is bonded to each of the plurality of terminals 120a of the LED 12. That is, one LED 12 is bonded to the same number of pads 50 as the number of terminals 120a. That is, in this embodiment, one LED 12 is bonded to the three pads 50.

Further, only the pad 50 is provided on the mounting surface 14a of the FPC 14, and a wiring electrically connected to the pad 50 is provided on the back surface side (not shown) opposite to the mounting surface 14a, and the wiring drives the LED 12. Connected to the drive circuit.

<LED mounting method 1>
Next, mounting methods 1 to 4 of the LED 12 will be described with reference to FIGS. 7 to 10. FIG. 7: is a figure for demonstrating an example of the mounting method 1 of a light source (LED). 7A is a top view of the FPC 14 and the LED 12, and FIG. 7B is a view of the FPC 14 and the LED 12 corresponding to FIG. 7A as seen from the back surface 12c side. Note that FIGS. 8 to 10 are also illustrated from the same viewpoint as FIG. 7. Further, in FIGS. 7 to 10, in order to simplify the illustration and the description, the case where the number of the cavities 120 and the terminals 120a arranged in the longitudinal direction of the LED 12 is two is shown as an example.

As shown in FIG. 7, first, in step 1-1, the pad 50 is arranged on the mounting surface 14 a of the LED 12 in the FPC 14.

Next, in step 1-2, the solder 60 is printed (applied) on the surface of the pad 50, respectively. The solder 60 may contain, for example, about 50% flux.

In step 1-2, the adhesive 51 is applied on the mounting surface 14a. In this case, the adhesive 51 can be arranged, for example, so as to overlap with the midpoint of a line segment connecting the centers 50C of the two pads 50 in a top view (plan view), and in particular, the center 51C of the adhesive 51. However, they can be arranged so as to overlap with the midpoint of a line segment connecting the centers 50C of the two pads 50 in a top view (plan view). However, the application position of the adhesive agent 51 is not limited to these, and for example, the adhesive agent 51 may be arranged at a position overlapping at least the LED 12 in a top view (plan view). Further, the adhesive 51 may be arranged in two or more places. In addition, the solder 60 and the adhesive 51 may be applied first, or simultaneously.

Next, in step 1-3, the LED 12 is arranged while controlling the position and the attitude. Here, the size of the pad 50 arranged on the mounting surface 14a in the step 1-1 is larger than the size of the cavity 120 of the LED 12. In addition, the center 51C of the adhesive 51 applied in step 1-2 (see step 1-2) is arranged on one end side which is closer to the back surface 12c than the center line 12m in the lateral direction of the LED 12 in plan view. There is. Specifically, the adhesive 51 is disposed between the pads 50 having the centers 51C adjacent to each other, more specifically, between the terminals 120a (cavities 120) adjacent to each other. In the illustrated example, the pad 50 is arranged such that the end portion of the pad 50 on the light emitting surface 12a side is located closer to the light emitting surface 12a than the center line 12m, but the present invention is not limited to this, and for example, the center line 12m May be arranged closer to the back surface 12c, or may be arranged near the center line 12m so as to substantially coincide with the center line 12m. On the other hand, the end of the pad 50 on the side opposite to the light emitting surface 12a (that is, the back surface 12c side) may be arranged near the back surface 12c so as to substantially match the back surface 12c of the LED 12 in a plan view.

The solder 60 printed in step 1-2 is arranged so as to overlap the cavity 120 in a plan view. Specifically, the width b of the solder 60 in the longitudinal direction of the LED 12 is smaller than the width a of the cavity 120 in the longitudinal direction of the LED 12. Further, with respect to the lateral direction of the LED 12, the end of the solder 60 on the light emitting surface 12a side is arranged closer to the back surface 12c than the end of the cavity 120 on the light emitting surface 12a side. In other words, the solder 60 is not printed between the bottom surface 12b (see FIG. 6) of the LED 12 (excluding the cavity 120) and the mounting surface 14a of the FPC 14. Therefore, the LED 12 is arranged on the pad 50 and the adhesive 51 without riding on the solder 60. Then, the adhesive 51 is deformed according to the posture of the LED 12 arranged on the pad 50, and is arranged between the mounting surface 14 a and the LED 12.

Next, in step 1-4, the temperature is raised to the melting point of the solder 60 or higher for reflow of the solder 60. Here, the adhesive 51 has a thermosetting property that cures at a temperature lower than the melting point of the solder 60. Therefore, when the temperature rises and reaches the temperature at which the adhesive 51 is cured, the adhesive 51 starts to cure before the solder 60 melts and flows. The adhesive 51 shrinks at a predetermined shrinkage rate so as to narrow the gap between the LED 12 and the pad 50 by curing, and becomes the adhesive member 51a. At this time, depending on the arrangement of the adhesive member 51a, the LED 12 may be fixed in a state in which it is tilted from a desired posture, but as described in step 1-3, the center 51C (see step 1-2) is When the adhesive 51 is arranged on one end side which is closer to the back surface 12c than the center line 12m in the lateral direction of the LED 12 in a plan view, the contracting force of the adhesive 51 is stably transmitted to the LED 12, and The position and the posture can be more stably held by the pad 50 and the adhesive member 51a. Furthermore, when the adhesive 51 or the center 51C of the adhesive 51 is arranged so as to overlap with the midpoint of the line segment connecting the centers 50C of the two pads 50 in plan view as described in Step 1-2, the adhesive 51 The contraction force of is stably transmitted to the LED 12. Further, as described in Step 1-3, the center 51C of the adhesive 51 (adhesive member 51a) is arranged between the adjacent pads 50, and more preferably between the adjacent terminals 120a, so that the pad 50 with respect to the terminal 120a can be formed. The position and orientation of the LED 12 are likely to be stably held regardless of the size or the application state of the solder 60.

When the temperature further rises and reaches the melting point temperature of the solder 60, the solder 60 melts. The melted solder 60 is accommodated in the cavity 120 of the LED 12, and the terminal 120a and the pad 50 are bonded to each other. At this time, the melted solder 60 basically does not enter between the LED 12 and the pad 50, but may intrude slightly depending on the surface condition of the pad 50 and the like.

Further, as described above, when the solder 60 before melting contains the flux, the volume of the solder 60 accommodated in the cavity 120 becomes smaller than the volume of the solder 60 before melting, and the inside of the cavity 120 is soldered. It may not be possible to fill 60. Therefore, for example, as illustrated in Step 1-3, the solder 60 may be applied so as to extend to the back surface 12c side to a position where it does not overlap the cavity 120 in a plan view. At this time, the end portion of the solder 60 may be arranged on the pad 50, and may further extend to the mounting surface 14a.

As described above, according to the light source (LED) mounting method 1, the pad 50 holds the attitude of the LED 12 before the adhesive 51 is cured, and the pad 50 and the adhesive member 51a maintain the attitude of the LED 12 after the adhesive 51 is cured. To do. Further, the solder 60, which causes a change in volume during reflow, does not participate in maintaining the attitude of the LED 12. Therefore, the mounting accuracy of the LED 12 on the FPC 14 is improved.

The distance between the bottom surface 12b (see FIG. 6) of the LED 12 mounted by the light source (LED) mounting method 1 and the pad 50 is basically 0. Even if the solder 60 slightly invades between the LED 12 and the pad 50, for example, the particle diameter of the particles contained in the solder 60 is generally 20 μm or less (preferably 10 μm or less, more preferably 5 μm or less). Can be In this manner, there is no substantial gap between the bottom surface 12b of the LED 12 and the pad 50, and the bottom surface 12b of the LED 12 and the pad 50 are in close contact with each other (substantial gap is 0). The positional accuracy (dimensional accuracy) in the height direction (Z-axis direction) can be improved. The LED 12 may be held so that the distance between the bottom surface 12b of the LED 12 and the pad 50 exceeds 20 μm.

<LED mounting method 2>
FIG. 8 is a diagram for explaining an example of a light source (LED) mounting method 2. As shown in FIG. 8, first, in step 2-1, the pad 50 and the support member 70 are arranged on the mounting surface 14 a of the LED 12 in the FPC 14. The support member 70 is an insulating member having a predetermined thickness. As the support member 70, for example, a resin member that is less likely to change in volume during reflow can be used. The support member 70 may be a metal member or other conductive member that is insulated from the LED 12 and the mounting surface 14a.

Next, in step 2-2, the solder 60 is printed (applied) on the surface of the pad 50, and the adhesive 51 is applied on the mounting surface 14a. The position where the adhesive 51 is applied may be, for example, a position overlapping the LED 12 in a top view (plan view), and may be the same as step 1-2 in FIG. 7. The process 2-2 is the same as the process 1-2 of FIG. 7 except for the position where the adhesive 51 is applied, and thus detailed description thereof will be omitted.

Next, in step 2-3, the LED 12 is arranged while controlling the position and the attitude. The LED 12 is arranged on the pad 50, the adhesive 51 and the support member 70 without riding on the solder 60. For example, when the pad 50 and the support member 70 have different thicknesses, the LED 12 is arranged in an attitude corresponding to the difference in the thickness. The adhesive 51 is deformed according to the attitude of the LED 12, and is arranged between the mounting surface 14a and the LED 12.

Next, in step 2-4, in order to reflow the solder 60, the temperature is raised so as to be equal to or higher than the melting point of the solder 60. When the temperature at which the adhesive 51 is hardened is reached, the adhesive 51 starts to harden before the solder 60 melts and flows. When the temperature further rises and reaches the melting point temperature of the solder 60, the solder 60 melts. The melted solder 60 is accommodated in the cavity 120 of the LED 12, and the terminal 120a and the pad 50 are bonded to each other. At this time, the melted solder 60 does not enter or slightly penetrates between the LED 12 and the pad 50. Step 2-4 is the same as step 1-4 in FIG. 7, and thus detailed description will be omitted.

As described above, according to the light source (LED) mounting method 2, the pad 50 and the support member 70 maintain the posture of the LED 12 before the adhesive 51 is cured, and after the adhesive 51 is cured, the pad 50, the support member 70, and the pad 50. The adhesive member 51a holds the attitude of the LED 12. Further, the solder 60, which causes a change in volume during reflow, does not participate in maintaining the attitude of the LED 12. Therefore, the mounting accuracy of the LED 12 on the FPC 14 is improved. Although FIG. 8 illustrates an example in which the height of the support member 70 is larger than the height of the pad 50, the present invention is not limited to this. For example, the height of the support member 70 may be smaller than the height of the pad 50, and the height of the support member 70 and the pad 50 may be the same. The LED 12 is held in a posture corresponding to the heights of the support member 70 and the pad 50.

Further, the distance between the bottom surface 12b (see FIG. 6) of the LED 12 mounted by the light source (LED) mounting method 2 and the pad 50 can be, for example, 20 μm or less. The LED 12 may be held so that the distance between the bottom surface 12b of the LED 12 and the pad 50 exceeds 20 μm.

In the present mounting method 2, for example, the interval between the adjacent pads 50 is small, and the adhesive 51 cannot be arranged between the adjacent pads 50. For example, the adhesive is closer to the light emitting surface 12a side than the pads 50 in a plan view. The LED 12 can be appropriately held even when the 51 must be arranged. In such a case, the LED 12 is likely to tilt so that the distance from the light emitting surface 12a side to the mounting surface 14a is smaller than that on the back surface 12c due to contraction accompanying the curing of the adhesive 51. At this time, if the support member 70 is previously arranged on the mounting surface 14a, the inclination of the LED 12 due to the curing of the adhesive 51 can be suppressed. Although the support member 70 is illustrated as two members in FIG. 8, the support member 70 is not limited to this and may be formed as one continuous member, for example. Further, in FIG. 8, a part of the support member 70 is arranged so as not to overlap with the LED 12 in a plan view, but the present invention is not limited to this, and the entire region of the support member 70 is arranged so as to overlap with the LED 12 in a plan view. May be.

<LED mounting method 3>
FIG. 9 is a diagram for explaining an example of a light source (LED) mounting method 3. As shown in FIG. 9, first, in step 3-1, the pad 55 is arranged on the mounting surface 14 a of the LED 12 in the FPC 14. The pad 55 is a composite member in which a coating layer 57 (solder layer) is laminated on the pad layer 56. As the pad layer 56, for example, the pad 50 described in FIGS. 7 and 8 can be used. Further, as the coating layer 57, tin plating or solder coating can be used, for example. The coating layer 57 has a smaller content of flux than the solder 60, and has a small volume change during reflow.

Next, in step 3-2, the solder 60 is printed (applied) on the surface of the pad 55, and the adhesive 51 is applied on the mounting surface 14a. The adhesive 51 can be arranged, for example, in the same manner as in step 1-2 of FIG. 7 or step 2-2 of FIG.

Next, in step 3-3, the LED 12 is arranged while controlling the position and the attitude. The pad 55 arranged in the step 3-1 and the solder 60 printed in the step 3-2 are arranged so as to overlap the cavity 120 in a plan view. Specifically, the width of the pad 55 and the solder 60 in the longitudinal direction of the LED 12 is smaller than the width of the cavity 120 in the longitudinal direction of the LED 12. Further, the ends of the pads 55 and the solder 60 on the light emitting surface 12a side are arranged closer to the back surface 12c than the end of the cavity 120 on the light emitting surface 12a side in the lateral direction of the LED 12. Therefore, the LED 12 is arranged so that the solder 60 is in contact with the cavity 120 or the terminal 120a. The adhesive 51 is deformed according to the attitude of the LED 12, and is arranged between the mounting surface 14a and the LED 12. At this time, when the LED 12 is arranged such that a part of the pad 55 is housed in the cavity 120, the thickness of the adhesive 51 becomes smaller than the thickness of the pad 55. In particular, when a part of the pad layer 56 of the pad 55 is accommodated in the cavity 120 as illustrated, the thickness of the adhesive 51, that is, the distance between the mounting surface 14 a and the LED 12 is smaller than the thickness of the pad layer 56. Narrows.

Next, in step 3-4, in order to reflow the solder 60 and the coating layer 57, the temperature is raised so as to be equal to or higher than the melting points of the solder 60 and the coating layer 57. When the temperature at which the adhesive 51 hardens is reached, the adhesive 51 hardens before the solder 60 and the coating layer 57 melt, and an adhesive member 51a having high dimensional stability is produced. When the temperature further rises and reaches the melting point temperature of the solder 60 and the coating layer 57, the solder 60 and the coating layer 57 melt. The melted solder 60 and the coating layer 57 are contained in the cavity 120 of the LED 12 as the solder 60a mixed to an unidentifiable degree, and the terminal 120a and the pad layer 56 are bonded to each other. At this time, the melted solder 60a does not enter or slightly penetrates between the LED 12 and the pad layer 56.

As described above, according to the light source (LED) mounting method 3, the pad 55 holds the attitude of the LED 12 before the adhesive 51 is cured, and the adhesive member 51a moves the LED 12 after the adhesive 51 is cured. Hold. Therefore, the mounting accuracy of the LED 12 on the FPC 14 is improved.

Further, according to the light source (LED) mounting method 3, the coating layer 57 is arranged in advance in anticipation that the volume of the solder 60 decreases before and after melting. Thereby, the connection between the terminal 120a and the pad layer 56 via the solder 60a composed of the component derived from the solder 60 and the coating layer 57 becomes more reliable.

The distance between the bottom surface 12b (see FIG. 6) of the LED 12 mounted by the light source (LED) mounting method 3 and the pad layer 56 can be set to, for example, 20 μm or less. In particular, when a part of the pad layer 56 is housed in the cavity 120, the distance between the bottom surface 12b of the LED 12 and the pad layer 56 is 0 or less, that is, the distance between the bottom surface 12b of the LED 12 and the mounting surface 14a is set to the pad layer 56. The thickness can be equal to or less than that (substantial gap is 0). Further, it is possible to reliably suppress the infiltration of the solder into the interface between the bottom surface 12b of the LED 12 and the mounting surface 14a of the FPC 14. As a result, the positional accuracy of the LED 12 in the height direction is further enhanced. The LED 12 may be held so that the distance between the bottom surface 12b of the LED 12 and the pad layer 56 exceeds 20 μm.

<LED mounting method 4>
FIG. 10 is a diagram for explaining an example of a light source (LED) mounting method 4. As shown in FIG. 10, first, in step 4-1, the pad 50 and the support member 70 are arranged on the mounting surface 14 a of the LED 12 in the FPC 14. Since step 4-1 is the same as step 2-1 shown in FIG. 8, detailed description thereof will be omitted.

Next, in step 4-2, the solder 60 is printed (applied) on the surface of the pad 50, and the adhesive 51 is applied on the mounting surface 14a. The step 4-2 is the same as the step 2-2 of FIG. 8 except for the area where the solder 60 is applied.

Next, in step 4-3, the LED 12 is arranged while controlling the position and the posture. Since the size of the solder 60 in plan view is larger than the cavity 120 of the LED 12, the LED 12 is arranged on the adhesive 51, the solder 60, and the support member 70. The adhesive 51 is deformed according to the attitude of the LED 12, and is arranged between the mounting surface 14a and the LED 12. At this time, since the solder 60 is arranged on the surface of the pad 50, the thickness of the adhesive 51 becomes larger than the thickness of the pad 50.

Next, in step 4-4, the temperature is raised so as to be equal to or higher than the melting point of the solder 60 in order to reflow the solder 60. When the temperature at which the adhesive 51 hardens is reached, the adhesive 51 hardens before the solder 60 melts and flows, and the adhesive member 51a is generated. When the temperature further rises and reaches the melting point temperature of the solder 60, the solder 60 melts. The melted solder 60 is accommodated in the cavity 120 of the LED 12, and the terminal 120a and the pad 50 are bonded to each other.

As described above, according to the light source (LED) mounting method 4, the solder 60 and the support member 70 hold the attitude of the LED 12 before the adhesive 51 is cured, and the adhesive member 51a and the support member 70 are cured after the adhesive 51 is cured. The support member 70 holds the attitude of the LED 12. Therefore, the mounting accuracy of the LED 12 on the FPC 14 is improved.

According to the light source (LED) mounting method 4, a solder 60 larger than the cavity 120 is applied in advance in anticipation that the volume of the solder 60 decreases before and after melting. Thereby, the connection between the terminal 120a and the pad 50 via the solder 60 becomes more reliable.

Further, the distance between the bottom surface 12b (see FIG. 6) of the LED 12 mounted by the light source (LED) mounting method 4 and the mounting surface 14a can be made larger than the thickness of the pad 50. For example, the LED 12 is arranged in a posture according to the thickness of the support member 70 and the distance between the mounting surface 14a and the upper surface of the solder 60 applied on the pad 50 in step 4-2. That is, by changing the thickness of the solder 60 applied on the pad 50 or the thickness and arrangement of the support member 70, the LED 12 can be arranged in a posture according to the changed thickness and arrangement. Therefore, for example, when it is attempted to change the thickness of the second connecting member 18 according to the adhesive strength required for the second connecting member 18 for fixing the FPC 14 shown in FIG. By setting the thickness of the support member 70 in accordance with the thickness of the LED 12, the LED 12 can be held in a stable position at a predetermined height direction (Z-axis direction) position. The thickness of the support member 70 may be smaller or larger than the distance between the mounting surface 14a and the upper surface of the solder 60 applied on the pad 50 in step 4-2.

The method of mounting the light source (LED) according to the embodiment has been described above. As described above, according to the light source (LED) mounting method according to the embodiment, the LED 12 is held by the member having higher dimensional stability than the solder 60 before and after the reflow, so that the mounting accuracy is improved.

In the mounting methods 1 to 4 of the light source (LED) shown in FIGS. 7 to 10, the solder 60 or 60 a is described as being housed so as to fill the cavity 120. However, the pad 50 or the pad layer 56 and the terminal 120 a. A gap may be formed in the cavity 120 as long as they are properly connected.

Further, although the adhesive 51 has been described as having thermosetting properties, it may be formed of any material as long as it can be cured at a temperature lower than the melting point of the solder 60, for example, it may be cured at room temperature before reflow. Good.

Although the pad 50 and the support member 70 are shown as separate members in FIG. 8 or FIG. 10, they may be formed as one continuous member.

Further, in the mounting method 3 of the light source (LED) shown in FIG. 9, for example, the supporting member 70 shown in FIG. 8 may be used. As a result, the mounting accuracy of the LED 12, which is an example of the electronic component, can be further improved.

Further, although the method of mounting the light source (LED 12) in the planar lighting device 1 has been described above, any method of mounting any electronic component may be used as long as it has terminals housed in each of a plurality of cavities. Good.

Further, the present invention is not limited to the above embodiment. The present invention also includes those configured by appropriately combining the constituent elements described above. Further, further effects and modified examples can be easily derived by those skilled in the art. Therefore, the broader aspect of the present invention is not limited to the above-described embodiment, and various modifications can be made.

1 surface illumination device, 12 LED, 14 FPC, 14a mounting surface, 50, 55 pad, 51 adhesive, 51a adhesive member, 60 solder, 70 support member, 120 cavity, 120a terminal

Claims (12)

A plurality of pads provided on the main surface of the wiring board,
A light source having a terminal housed in each of a plurality of cavities arranged on any surface other than the light emitting surface, wherein the pad and the terminal are joined via the solder housed in the cavity,
An adhesive member that is disposed between the main surface and the light source, and that adheres the main surface and the light source,
The terminal is arranged on one end side in the lateral direction of the light source in a plan view,
The planar illumination device in which the center of the adhesive member is disposed only on the one end side in a plan view. A plurality of pads provided on the main surface of the wiring board,
A light source having a terminal housed in each of a plurality of cavities arranged on any surface other than the light emitting surface, wherein the pad and the terminal are joined via the solder housed in the cavity,
An adhesive member arranged between the main surface and the light source, for bonding the main surface and the light source ,
A support member disposed between the main surface and the light source ,
The planar illumination device in which the support member is arranged only on the other end side opposite to the one end side in the lateral direction of the light source in which the terminals are arranged . Distance between the said surface of the light source pad is 20μm or less, the planar lighting device according to claim 1 or 2. The one end side is a side opposite to the light emitting surface of the light source,
The planar lighting device according to claim 1. The planar illumination device according to claim 1 , wherein a center of the adhesive member is arranged between adjacent terminals. The adhesive member is planar lighting device according to arranged so as to overlap with the midpoint of a line segment connecting the two centers of the pad adjacent in plan view, any one of claims 1-5. The pad is smaller than the region overlapping with the cavity in a plan view, the planar lighting device according to any one of claims 1-6. A method of mounting an electronic component, wherein terminals accommodated in each of a plurality of cavities arranged in a longitudinal direction on one surface of an electronic component are connected to a plurality of pads provided on a main surface of a wiring board. ,
Applying a paste solder to each of the pads,
Placing a thermosetting adhesive on the main surface,
Arranging the electronic component on the adhesive so that the cavities overlap with at least a part of the solder applied to each of the pads in plan view,
Fixing the electronic component via an adhesive member obtained by curing the adhesive at a temperature lower than the melting temperature of the solder;
The terminals of the electronic component which is fixed by melting the solder seen including a step of joining said pads,
The terminal is arranged on one end side in the lateral direction of the electronic component in plan view,
The mounting method , wherein the center of the adhesive member is arranged only on the one end side in a plan view . The mounting method according to claim 8 , wherein the melted solder is accommodated in the cavity and cured. Said been the solder applied on the pad, extending to a position which does not overlap with the cavity in a plan view, mounting method according to claim 8 or 9. Said pad, said has a solder layer on a main surface of the electronic component and the opposing mounting method according to any one of claims 8-10. The adhesive shrinks to narrow the distance between the said electronic component pad by curing, mounting method according to any one of claims 8-11.

Images