JP2017163029A - Electronic component mounting method, board, electronic circuit, surface light source device, display device, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce positional deviation of an electronic component mounted on a board.SOLUTION: An electronic component mounting method for mounting an electronic component at a predetermined position of a board by solder joint has a coating step of applying an adhesive to a reception part arranged to overlap the electronic component at least partially, in the plan view, when the electronic component is mounted at a predetermined position, and having an opening, so as to be able to flow thereinto, an electronic component arrangement step of arranging the electronic component at a predetermined position, an adhesive hardening step of hardening the adhesive and fixing the electronic component at the predetermined position, and a solder joining step executed simultaneously with or after the adhesive hardening step, and solder joining the electronic component to the board.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electronic component mounting method, a substrate, an electronic circuit, a surface light source device, a display device, and an electronic apparatus.

  Various electronic components are mounted on a substrate mounted on an electronic device. For example, in a liquid crystal display, an LED (Light Emitting Diode) chip is mounted on a substrate mounted as a light source of an edge light type backlight using a light guide plate.

  FIG. 1 is a diagram illustrating a conventional example of a substrate on which an LED chip is mounted. FIG. 1A is a plan view showing a part of the surface of the substrate 100. The substrate 100 includes lands 3 at both ends of the opening 2A. The terminal 4a of the LED chip 4 is joined to the land 3 by solder.

  FIG.1 (b) is a conceptual diagram of the AA cross section of the board | substrate 100 shown by Fig.1 (a). The substrate 100 is composed of layers laminated in the order of the conductive foil 13, the plating 12, the adhesive layer 11, and the coverlay 10 on the front surface and the back surface of the base material 14.

  The land 3 and the wiring between the lands are formed by the conductor foil 13. The wiring pattern of the conductor foil 13 is formed by an etching method or the like. The plating 12 prevents oxidation and corrosion of the conductor foil 13 and improves solderability. The coverlay 10 protects both sides of the substrate 100, and the land 3 is formed in the opening 2A. The base material 14 and the coverlay 10 are flexible insulating films.

  The LED chip 4 is mounted on the substrate 100 by placing on the land 3 to which the solder 5 is applied and melting the solder 5. When the LED chip 4 is placed on the land 3, a positional shift may occur, and a technique for detecting a positional shift of an electronic component mounted on a substrate and performing alignment is known (for example, see Patent Document 1). reference).

JP 2015-119134 A

  The displacement of the electronic components mounted on the board is not limited to occur when the electronic parts are placed on the lands on the board, but the amount of solder applied to the lands, the surface tension due to the solder at the time of melting, the deformation of the board It may also occur due to such causes. Even if the electronic component is simply temporarily fixed to the substrate with an adhesive, the electronic component may be displaced in the direction perpendicular to the substrate surface due to, for example, variations in the amount of adhesive applied.

In recent years, in a liquid crystal display, a substrate on which an LED chip is mounted is used as a light source of an edge light type backlight using a light guide plate. For example, when a gap is formed between the LED chip mounted on the substrate and the light guide plate, a part of the incident light may not enter the light guide plate and the luminance efficiency may decrease. A decrease in luminance efficiency also leads to an increase in power consumption. Further, the positional deviation of the LED chip also causes a poor appearance near the incident light of the liquid crystal display. As described above, the optical performance of the LED is not sufficiently exhibited due to the positional deviation of the LED chip.

  Therefore, an object of the present application is to provide a technique for reducing the positional deviation of an electronic component mounted on a substrate.

  In order to solve the above-described problems, in the present invention, when an electronic component is mounted at a predetermined position on a substrate by solder bonding, a receiving portion having an opening through which an adhesive can flow is provided between lands for bonding terminals of the electronic component. The adhesive applied so as to be able to flow into the receiving portion is cured to fix the electronic component at a predetermined position on the substrate.

  Specifically, the present invention relates to an electronic component mounting method for mounting an electronic component at a predetermined position on a substrate by solder bonding, and at least a part of the electronic component in plan view when the electronic component is mounted at a predetermined position. Are applied so that the adhesive can flow into a receiving portion having an opening, the electronic component placement step for placing the electronic component in a predetermined position, and the adhesive is cured to place the electronic component in a predetermined position. An adhesive curing step for fixing to the substrate, and a solder joining step that is performed simultaneously with the adhesive curing step or after the adhesive curing step, and solders the electronic component to the substrate.

  According to such an electronic component mounting method, the electronic component is fixed at a predetermined position on the substrate with an adhesive before soldering. Therefore, the displacement of the electronic component due to the surface tension at the time of melting the solder is reduced. The “predetermined position” is a position at which the electronic component can appropriately function or perform on the substrate surface.

  In addition, when an adhesive is applied to the substrate surface, it is conceivable that a positional deviation in the direction perpendicular to the surface of the substrate occurs due to variations in the amount of adhesive applied. However, according to the electronic component mounting method described above, when the electronic component is placed at a predetermined position on the substrate, the excess adhesive flows into the receiving portion, thereby reducing the displacement due to the variation in the coating amount. Further, since the electronic component is fixed by an adhesive, it is expected that the bonding strength to the substrate is improved.

  The adhesive is a thermosetting adhesive that cures at a temperature lower than the melting point of the solder. In the adhesive curing process and the solder joining process, the adhesive is applied to the receiving portion, and the electronic component is placed at a predetermined position. This may be performed by raising the temperature of the substrate to a temperature at which solder bonding is possible. According to such an electronic component mounting method, the thermosetting adhesive is cured before the solder is melted, and the electronic component is fixed at a predetermined position on the substrate. The

  The adhesive is a UV curable adhesive that is cured by a chemical reaction caused by ultraviolet (UV) irradiation. In the adhesive curing process and the solder bonding process, the adhesive is applied to the receiving portion and the electronic component is placed in a predetermined position. It may be executed by irradiating the arranged substrate with ultraviolet rays, and then raising the temperature of the substrate to a temperature at which solder bonding is possible. If the adhesive is a UV curable adhesive, the curing speed is faster than that of the thermosetting adhesive, and the working time can be shortened. Further, curing at a low temperature is possible, and temperature adjustment for curing the adhesive is not necessary.

  The electronic component may be an electronic component that emits light. If the above-mentioned electronic component emits light, the incident light from the electronic component is mounted at a position where the light enters the light guide plate at an appropriate angle, thereby reducing the light incident loss to the light guide plate and improving the luminance efficiency. Can be suppressed. Therefore, reduction of power consumption is also expected. The electronic component may be an LED chip.

In addition, the present invention is a substrate used in the above electronic component mounting method, and when the electronic component is mounted at a predetermined position, the electronic component is disposed so as to at least partially overlap with the electronic component in plan view. A receiving portion having an inflow opening is provided. The receiving part can be formed in various shapes depending on conditions such as the viscosity of the adhesive, the coating amount, the position and size of the electronic component.

  The receiving portion may have a plurality of holes (hereinafter also referred to as through holes) formed on the bottom surface of the opening. If the receiving portion is formed in this way, even if the capacity of the opening into which the adhesive flows is insufficient due to the restriction of the shape of the cover lay, the additional capacity for the adhesive to flow in can be reduced due to the through hole. Securement is possible.

  The receiving part may be formed from a plurality of holes. If the receiving portion is formed in this way, even if it is difficult to provide an opening in the cover lay between lands due to downsizing of electronic components, it is possible to secure a capacity for the adhesive to flow in through a plurality of through holes. Is possible.

  A plurality of holes may penetrate to the back surface of the substrate. If the receiving portion is formed in this way, even an adhesive having lower fluidity can be easily flowed in due to characteristics such as viscosity of the adhesive.

  The opening or a part of the plurality of holes may be arranged outside in a plan view of the outer shape of the electronic component mounted at a predetermined position. If the receiving portion is formed in this way, the strength in the shear direction between the electronic component and the substrate can be improved.

  Further, the present invention may be an electronic circuit configured by mounting electronic components on the above-described substrate. According to such an electronic circuit, the function or performance of an electronic component that requires mounting accuracy can be appropriately exhibited.

  The present invention may also be a surface light source device that includes the electronic circuit described above and uses an electronic component mounted on the electronic circuit as a light source.

  The present invention may also be a display device that includes the surface light source device described above and a display panel that receives light emitted from the surface light source device.

  Further, the present invention may be an electronic device including the above display device.

  According to the present invention, it is possible to reduce displacement of electronic components mounted on a substrate.

FIG. 1 is a diagram illustrating a conventional example of a substrate on which an LED chip is mounted. FIG. 2 is a plan view illustrating the surface of the substrate according to the embodiment. FIG. 3 is a conceptual diagram of a cross section between BB of the substrate shown in FIG. FIG. 4 is a graph illustrating temperature changes during solder reflow. FIG. 5 is a diagram illustrating a substrate according to the first modification. FIG. 6 is a diagram illustrating a substrate according to the second modification. FIG. 7 is a conceptual diagram of a cross section of the substrate in which the coverlay on the back surface of the through hole is opened in the second modification. FIG. 8 is a plan view illustrating a substrate according to the third modification. FIG. 9 is a cross-sectional view illustrating the configuration of a backlight including the substrate according to the embodiment. FIG. 10 is a perspective view illustrating the configuration of a liquid crystal display using a backlight as a light source.

  Hereinafter, embodiments of the present invention will be described. The embodiment described below exemplifies one aspect of the present invention, and does not limit the technical scope of the present invention to the following aspect.

Embodiment
The electronic component according to the present embodiment is described as a surface-mounted LED chip 4. The substrate according to the present embodiment is described as a double-sided substrate. The electronic component is not limited to the LED chip 4, and may be an electronic component that emits light other than the LED, an image sensor, other electronic components, or an electronic component that is connected by leads. Further, the substrate may be a substrate having a single-sided structure or a structure of three or more layers, and may be a flexible printed circuit board (FPC, Flexible Printed Circuits) that is flexible and deformable.

(Configuration overview)
FIG. 2 is a plan view illustrating the surface of the substrate according to this embodiment. In the present embodiment, an example in which the LED chip 4 is mounted on a substrate will be described as an example of an electronic component. In the following description, the LED chip 4 side in the normal direction of the substrate is the upper side. In each plan view, the LED chip 4 mounted on the substrate is indicated by a dotted line. The substrate 1A forms a pair of openings 2 on the surface at both ends of the position where the LED chip 4 is mounted. A land 3 is formed in each opening 2. Terminals 4 a at both ends of the LED chip 4 are disposed on the land 3.

  Between the pair of lands, a receiving portion 6 is formed by an opening on the surface of the substrate 1A. The receiving portion 6 is formed so that an adhesive applied to the substrate 1A can flow when the LED chip 4 is disposed on the substrate 1A. The receiving portion 6 is preferably formed at a position spaced 0.1 mm or more downward from the outer shape of the LED chip 4.

For example, the adhesive is applied in such an amount as to form a hemisphere having a radius of about 0.25 mm, and the volume of the adhesive in this case is 0.03 mm ³ . The application volume of the adhesive is assumed to be 0.01 to 0.1 mm ³ . The volume of the receiving portion 6 may be, for example, about opening area × height = (0.7 mm × 1.4 mm) × 0.03 mm. In addition, the volume of the receiving part 6 is not limited to the illustrated value. Moreover, the shape of the opening of the receiving portion 6 is not limited to the substantially rectangular shape illustrated in FIG. 2, and may be a round shape or other shapes according to the terminals of the electronic component to be mounted.

  FIG. 3 is a conceptual diagram of a cross section between BB of the substrate shown in FIG. FIG. 3A is a conceptual diagram of a cross section between B and B in a state where the adhesive 7 is applied to the surface of the substrate 1A before the LED chip 4 is mounted. As with the substrate 100 shown in FIG. 1B, the substrate 1 </ b> A is composed of layers laminated in the order of the conductive foil 13, the plating 12, the adhesive layer 11, and the coverlay 10 on the front surface and the back surface of the base material 14. Composed. The adhesive layer 11 and the coverlay 10 have an opening 2 that opens at a position where the land 3 is formed. Further, the adhesive layer 11 and the cover lay 10 are opened between the lands to form the receiving portion 6.

  The land 3 and the wiring between the lands are formed by the conductor foil 13. The wiring pattern of the conductor foil 13 is formed by an etching method or the like. The plating 12 covers the conductor foil 13 to prevent the conductor foil 13 from being oxidized or corroded or to improve the solderability. The coverlay 10 protects both surfaces of the substrate 1A. Solder 5 is applied to the land 3 formed in the opening 2. An adhesive 7 is applied to the opening of the receiving portion 6.

FIG. 3B shows a conceptual diagram of a cross section between B and B in a state where the LED chip 4 fixed by the adhesive 7 is mounted on the substrate 1A by solder bonding. Each layer laminated | stacked on the surface and back surface of 1 A of board | substrates is the same as that of Fig.3 (a). In addition, in each drawing, the same component is referred with the same code | symbol, and the description is abbreviate | omitted.

  In FIG. 3A, when the LED chip 4 is placed on the land 3 to which the solder 5 is applied, the adhesive 7 applied to the receiving portion 6 is brought into contact with and bonded to the LED chip 4. At this time, the surplus adhesive 7 flows into the receiving portion 6, and the LED chip 4 is disposed at the target position. The target position is determined in advance with an allowable tolerance as a position for exhibiting the function of the LED chip 4 as a light source. The LED chip 4 is fixed at the target position by curing the adhesive 7 before the solder 5 is melted. The target position corresponds to the “predetermined position” in the present invention.

  After the adhesive 7 is cured, the solder 5 is melted to form a fillet, whereby the LED chip 4 is bonded to the land 3.

(Electronic component mounting)
The electronic component is mounted on the substrate 1 </ b> A by being fixed to a target position on the substrate 1 </ b> A by the adhesive 7 and then bonded to the land 3 by the solder 5. Examples of the soldering method include a reflow method in which cream solder is applied to the lands 3 as the solder 5 and an electronic component is placed thereon, and then heat is applied to melt the solder 5.

  Here, an example in which the LED chip 4 is mounted on the substrate 1A shown in FIG. 2 as an example of an electronic component will be described. First, the cream solder 5 is applied to the land 3 of FIG. An adhesive 7 is applied to the receiving portion 6. The adhesive 7 may be applied so as to be able to flow into the receiving portion 6 in a region around the opening of the receiving portion 6.

  Next, both terminals 4 a of the LED chip 4 are placed on the pair of lands 3, respectively. At this time, the surplus adhesive 7 flows into the receiving portion 6 so that the LED chip 4 is disposed at a target position on the substrate 1A. By curing the adhesive 7, the LED chip 4 is fixed at a target position on the substrate 1A. Next, the cream solder 5 is melted and soldering is performed. When soldering is normally performed, a fillet is formed around each terminal 4a due to the surface tension of the solder or the like. Since the LED chip 4 is fixed at the target position by the adhesive 7, it is expected that no positional deviation will occur.

  FIG. 4 is a graph illustrating temperature changes during solder reflow. The horizontal axis represents time, and the vertical axis represents temperature. The heating of the substrate 1 </ b> A is started after the solder 5 and the adhesive 7 are applied and the electronic component is placed on the land 3.

  The substrate 1A is heated to a temperature T1, for example, with a temperature increase of 1 to 5 degrees per second. The substrate 1A is preheated at a temperature T1 from time t1 to time t2. The preheating process alleviates a rapid temperature change with respect to the electronic component and promotes good fillet formation. Preheating is performed in a temperature range of 180 to 200 degrees for a time within 120 seconds, for example.

  After the preheating step, the substrate 1A is further heated to the temperature T2 by a temperature increase of 1 to 5 degrees per second, for example. When the adhesive 7 is a thermosetting resin, the adhesive 7 starts to cure during the time t2 to t3 when the temperature rises to T2, and before the melting of the solder 5 starts, the electronic component is Curing proceeds to the extent that it is fixed at the target position.

In the reflow process from time t3 to time t4, the solder 5 melts to form a fillet, and the electronic components such as the LED chip 4 are soldered to the substrate 1A. The reflow is performed, for example, at a temperature of 220 ° C. or more and for a time within 60 seconds. The reflow is preferably performed at a temperature of 260 ° C. or lower, and the heating at 260 ° C. is preferably within 10 seconds. In addition, the range of time and temperature in the preheating process and the reflow process is not limited to the above, and may be changed according to conditions such as the type of solder 5 and the adhesive 7 used or the amount of application.

  Further, the adhesive 7 is not limited to a thermosetting resin that cures before the solder 5 is melted by heating. The adhesive 7 may be an adhesive that can be cured before the solder 5 is melted. For example, the adhesive 7 may be a UV curable resin. When the adhesive 7 is a UV curable resin, the adhesive 7 can be cured by irradiating ultraviolet rays before the solder 5 is melted.

[Modification 1]
In the present embodiment, the receiving portion 6 is formed by the opening of the cover lay 10. On the other hand, in the first modification, the receiving portion 6 has a plurality of through holes on the bottom surface of the opening portion of the cover lay 10 to reach the cover lay 10 on the back surface side.

  FIG. 5 is a diagram illustrating a substrate according to the first modification. FIG. 5A is a plan view showing a part of the surface of the substrate 1B. The substrate 1B shown in FIG. 5 is the same as the substrate 1A shown in FIG. 2 except for the receiving portion 6B.

  The receiving portion 6B of the substrate 1B according to Modification 1 is formed between the pair of lands 3 by an opening on the surface of the substrate 1B, and a plurality of through holes 6a are provided on the bottom surface. In the example of FIG. 5A, three through holes 6a are formed.

FIG.5 (b) is a conceptual diagram of the cross section between CC of the board | substrate 1B shown by Fig.5 (a). Each layer laminated | stacked on the surface and back surface of the board | substrate 1B is the same as that of Fig.3 (a). When the electronic component is placed on the substrate 1B, if the volume of the adhesive 7 flowing into the receiving portion 6B is larger than the volume secured by the opening of the cover lay 10, the excess adhesive 7 is put into the through hole 6a. Inflow. A plurality of through holes may be provided as holes having a diameter of about 0.2 mm and a volume of about 0.002 mm ³ , for example. The through hole may be a hole penetrating the base material 14 and the conductor foil 13 on the back surface side. In addition, the size of the through hole is an example, and is not limited to the above, and may be any shape and volume that allow the surplus adhesive 7 to flow.

  Even if the capacity of the opening portion of the cover lay 10 is smaller than the volume of the remaining adhesive 7 due to the restriction of the shape of the cover lay 10, the excess adhesive 7 flows into the through hole, thereby Can be arranged at predetermined positions on the substrate 1B.

[Modification 2]
In the present embodiment, the receiving portion 6 is formed by the opening of the cover lay 10. In the first modification, the receiving portion 6B is formed by a plurality of through holes 6a reaching the opening of the cover lay 10 and the cover lay 10 on the back surface side. On the other hand, in the modified example 2, the receiving part 6 is formed by a plurality of through holes 6a.

  FIG. 6 is a diagram illustrating a substrate according to the second modification. FIG. 6A is a plan view showing a part of the surface of the substrate 1C. The substrate 1C shown in FIG. 6 is the same as the substrate 1A shown in FIG. 2 except for the opening 2 and the receiving portion 6.

  The substrate 1 </ b> C according to the modification 2 has an opening 2 </ b> C including a pair of lands 3. In the opening 2C, a plurality of through holes 6a are provided between a pair of lands. When it is difficult to form the opening of the cover lay 10 due to downsizing of the electronic component, the surplus adhesive 7 can be received by the plurality of through holes 6a. In the example of FIG. 6A, ten through holes 6a are formed.

  FIG. 6B is a conceptual diagram of a cross section between DD of the substrate 1 </ b> C shown in FIG. Each layer laminated | stacked on the surface and back surface of the board | substrate 1C is the same as that of FIG.5 (b) except the opening part of the coverlay 10 of the surface. No opening is formed by the coverlay 10 between the pair of lands on the substrate 1C. When the electronic component is placed on the substrate 1C, the excess adhesive 7 flows into the through hole 6a.

  FIG. 7 is a conceptual diagram of a cross section of a substrate in which the coverlay on the back surface of the through hole 6a is opened in the second modification. A plan view of the substrate 1D shown in FIG. 7 is the same as FIG. Moreover, each layer laminated | stacked on the surface and back surface of board | substrate 1D is the same as that of FIG.6 (b) except the point which has the adhesive layer 11 and coverlay 10 of a back surface.

  When the receiving part 6 is formed by a plurality of through holes 6a, it is considered that the adhesive 7 is unlikely to flow into the through holes 6a depending on various conditions such as the viscosity and the coating amount of the adhesive. The substrate 1D shown in FIG. 7 can promote the inflow of the adhesive 7 by opening the coverlay 10 on the back surface and penetrating the through hole 6a in the back surface. In this case, the adhesive 7 that has flowed to the back surface is attached to the back surface stage by, for example, attaching a slightly peelable adhesive film to the adhesive 7 flowing out from the through hole 6a that penetrates the back surface. Adhesion and the like can be prevented. The film may be peeled after the adhesive 7 is cured at a temperature lower than the melting point of the solder. Moreover, when the said film has heat resistance which satisfies reflow conditions, you may peel after reflow.

[Modification 3]
In Modification 3, the receiving part is formed at a position where the side part of the electronic component to be mounted and the substrate are fixed. FIG. 8 is a plan view illustrating a substrate 1E according to the third modification. The substrate 1E shown in FIG. 8 is the same as the substrate 1A shown in FIG. 2 except for the position of the receiving portion 6E.

  In FIG. 8, the receiving portion 6E of the substrate 1E is formed at a position where the side surface opposite to the light emitting surface of the LED chip 4 which is an example of the electronic component is disposed. When the LED chip 4 is placed on the substrate 1E, the adhesive 7 applied to the receiving portion 6E fixes the side surface of the LED chip 4 and the substrate 1E to fix the LED chip 4 at a target position on the substrate 1E. By fixing the side surface of the LED chip 4 to the substrate 1E with the adhesive 7, it is expected that the strength in the shear direction with respect to the light emitting surface of the LED chip 4 is improved. The receiving portion 6E is not limited to the shape shown in FIG. 8, and is formed at a position where the side surface of the electronic component is disposed by the through hole or the combination with the through hole described in the first or second modification. Also good.

〔application〕
According to the substrate 1A to the substrate 1E (hereinafter also collectively referred to as the substrate 1) provided by the embodiment described above, the positional deviation when the LED chip 4 is mounted on the substrate 1 is reduced. By mounting the LED chip 4 at a position where light can be incident at an appropriate angle with respect to the light guide plate, it is possible to provide the substrate 1 with reduced light incident loss.

  In addition, a surface light source device such as a backlight using light emitted from the LED chip 4 mounted on the substrate 1 as a light source can be provided. FIG. 9 is a cross-sectional view illustrating the configuration of a backlight including the substrate 1 according to the embodiment. FIG. 9 shows a cross-sectional view of main components of an edge light type backlight 20 for a liquid crystal display. The backlight 20 includes a substrate 1, a light source unit 21, a light guide plate 22, a frame 23, a reflection sheet 24, a diffusion sheet 25, and prism sheets 26 and 27.

The light source unit 21 is the substrate 1 according to the embodiment in which the plurality of LED chips 4 are mounted such that the respective light emitting surfaces are oriented in the same direction and incident light is appropriately incident on the light guide plate 22. Each LED chip 4 is mounted at a target position without being displaced during reflow.

  The light guide plate 22 is a plate-shaped light guide formed of a transparent material such as polycarbonate resin, and guides light introduced from the light source 21 into the light guide plate 22 to the entire surface using total reflection. Is designed to emit light uniformly. In order for the backlight 20 to guide the light from the light source unit 21 to the light guide plate 22, the light emission surface of each LED chip 4 in the light source unit 21 faces the side surface of the light guide plate 22 and enters the light guide plate 22. Is assembled so as to be in a positional relationship where it is totally reflected on both surfaces so as not to leak.

  The frame 23 is a frame-shaped member formed of polycarbonate resin or the like, and is fitted on the outer peripheral surface of the light guide plate 22. The frame 23 takes light leaking from the outer peripheral surface of the light guide plate 22 into the light guide plate using reflection from the frame 23. The reflection sheet 24 is a film that reflects light in the light guide plate 22 that has been transmitted through the back surface of the light guide plate 22, so that the light is again taken into the light guide plate 22 and prevents light from leaking from the back surface of the light guide plate 22.

  The diffusion sheet 25 is a sheet that diffuses and uniformizes the light emitted from the surface of the light guide plate 22. The prism sheets 26 and 27 are sheets for collecting the light diffused by the diffusion sheet 25 and increasing the luminance when the backlight 20 is viewed from the surface.

  In the backlight 20 configured as described above, light emitted from the light source unit 21 enters the light guide plate 22 and sequentially passes through the light guide plate 22, the diffusion sheet 25, and the prism sheets 26 and 27. Emits light from the surface side of the. According to such a backlight 20, since the LED chip 4 as the light source unit 21 is mounted at a target position where the incident light loss is reduced, an improvement in luminance efficiency can be expected. Further, the backlight 20 can be a surface light source device in which power consumption is suppressed due to a reduction in incident light loss.

  Furthermore, a display device such as a liquid crystal display provided with such a backlight 20 can be provided. FIG. 10 is a perspective view illustrating the configuration of a liquid crystal display using the backlight 20 as a light source. FIG. 10 shows the main components of the liquid crystal display 30. The liquid crystal display 30 is configured such that a liquid crystal panel 31 overlaps the light exit surface of the backlight 20 described above.

  The liquid crystal panel 31 is a display panel that displays light by receiving light emitted from the backlight 20 and applying a voltage to the liquid crystal 32 to increase or decrease the light transmittance. The liquid crystal panel 31 includes a liquid crystal 32 sandwiched between glass plates 33a and 33b and further sealed between a pair of polarizing plates 34a and 34b. The light emitted from the backlight 20 passes through each component in the order of the polarizing plate 34a, the glass plate 33a, the liquid crystal 32, the glass plate 33b, and the polarizing plate 34b.

  In the liquid crystal display 30 configured in this manner, the LED chip 4 is accurately mounted at the target position of the substrate 1, and the light incident loss from the light source unit 21 to the light guide plate 22 is reduced, thereby improving the luminance efficiency. It can be expected that power consumption is suppressed.

  Furthermore, electronic devices, such as a smart phone, a digital camera, a tablet terminal, provided with such a liquid crystal display 30 can be provided. Such an electronic device can be expected to provide a display with improved luminance efficiency and reduced power consumption.

1A, 1B, 1C, 1D, 1E Substrate 2, 2C Opening 3 Land 4 LED chip 4a Terminal 5 Solder 6, 6B, 6E Receiving part 6a Through hole 7 Adhesive 10 Coverlay 11 Adhesive layer 12 Plating 13 Conductive foil 14 Base Material 20 Backlight (Surface light source device)
21 light source part 22 light guide plate 30 liquid crystal display (display device)
31 LCD panel

Claims (16)

An electronic component mounting method for mounting an electronic component at a predetermined position on a substrate by solder bonding,
An application step of applying an adhesive so as to be able to flow into a receiving portion that is arranged so that at least a portion thereof overlaps with the electronic component when seen in a plan view when the electronic component is mounted at the predetermined position;
An electronic component arranging step of arranging the electronic component at the predetermined position;
An adhesive curing step of curing the adhesive and fixing the electronic component in the predetermined position;
Executed at the same time as the adhesive curing step or after the adhesive curing step, and a solder joining step for solder joining the electronic component to the substrate;
An electronic component mounting method comprising: The adhesive is a thermosetting adhesive that cures at a temperature lower than the melting point of the solder,
The adhesive curing step and the solder bonding step are performed by raising the temperature of the substrate on which the adhesive is applied so as to flow into the receiving portion and the electronic component is disposed at the predetermined position to a temperature at which solder bonding is possible. The electronic component mounting method according to claim 1, wherein the electronic component mounting method is executed. The adhesive is a UV curable adhesive that is cured by a chemical reaction by irradiation with ultraviolet rays (UV, ultraviolet),
The adhesive curing step and the solder joining step irradiate the substrate on which the adhesive is applied so as to flow into the receiving portion and the electronic component is disposed at the predetermined position, and then the substrate is soldered. 2. The electronic component mounting method according to claim 1, wherein the electronic component mounting method is performed by raising the temperature to a temperature capable of performing the following.   The electronic component mounting method according to claim 1, wherein the electronic component is an electronic component that emits light.   The electronic component mounting method according to claim 1, wherein the electronic component is an LED (Light Emitting Diode) chip. A board for mounting an electronic component at a predetermined position of a board by soldering,
A substrate comprising: a receiving portion having an opening through which an adhesive can flow and is disposed so as to at least partially overlap the electronic component when seen in a plan view when the electronic component is mounted at the predetermined position.   The substrate according to claim 6, wherein the receiving portion has a plurality of holes formed in a bottom surface of the opening.   The substrate according to claim 6, wherein the receiving portion is formed of a plurality of holes.   The substrate according to claim 7 or 8, wherein the plurality of holes penetrates to the back surface of the substrate.   10. The device according to claim 6, wherein the opening or a part of the plurality of holes is arranged outside in a plan view of an outer shape of the electronic component mounted at the predetermined position. Board.   An electronic circuit comprising the substrate according to any one of claims 6 to 10 and the electronic component mounted thereon.   The electronic circuit according to claim 11, wherein the electronic component is an electronic component that emits light.   The electronic circuit according to claim 11, wherein the electronic component is an LED chip. It has an electronic circuit according to any one of claims 11 to 13,
A surface light source device using the electronic component mounted on the electronic circuit as a light source. A surface light source device according to claim 14,
A display panel that receives light emitted from the surface light source device;
A display device comprising:   An electronic apparatus comprising the display device according to claim 15.

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