阅读说明：本技术 光射出装置以及光射出装置的制造方法 (Light emitting device and method for manufacturing light emitting device ) 是由 香山贵彦 大泽隆士 于 2018-12-27 设计创作，主要内容包括：为了提供提高表面安装型LED相对于被卷圆成截头圆锥形状或者圆筒形状的布线基板的安装密度而实现高亮度,并且在将布线基板弯曲时不产生不良情况的可靠性高的照明装置,具备：布线基板,其弯曲成规定形状,具有可挠性；多组焊盘,它们在弯曲的所述布线基板上以至少一部分沿着周向形成列的方式排列设置；以及多个表面安装型LED,它们分别固定于所述多组焊盘,在将在弯曲后的所述布线基板上所述多组焊盘形成列的部分的周长度设为L,将周长度L中的所述多组焊盘的周向的长度的总和s所占的比例设为y＝s/L,将在弯曲后的所述布线基板上所述多组焊盘形成列的部分的曲率设为x的情况下,满足y≤-1.04x+1.80。(In order to provide a highly reliable lighting device which achieves high luminance by increasing the mounting density of surface mount type LEDs on a wiring board which is rolled into a truncated cone shape or a cylindrical shape and which does not cause a trouble when the wiring board is bent, the lighting device is provided with: a wiring substrate which is bent into a predetermined shape and has flexibility; a plurality of sets of pads arranged in a row at least partially along a circumferential direction on the bent wiring substrate; and a plurality of surface-mount LEDs each fixed to the plurality of sets of pads, wherein y is equal to or less than-1.04 x +1.80, where L is a circumferential length of a portion of the wiring substrate where the plurality of sets of pads are formed in a row after the bending, y is s/L is a ratio of a sum s of circumferential lengths of the plurality of sets of pads in the circumferential length L, and x is a curvature of the portion of the wiring substrate where the plurality of sets of pads are formed in a row after the bending.)

1. A light emitting device is characterized by comprising:

a wiring substrate which is bent into a predetermined shape and has flexibility;

a plurality of sets of pads arranged in a row at least partially along a direction of bending, i.e., a circumferential direction, on the wiring substrate after bending; and

a plurality of surface mount type LEDs respectively fixed to the plurality of sets of pads,

when the circumferential length of the portion of the wiring substrate where the plurality of sets of pads are formed in the row after the bending is set to L, the ratio of the sum s of the circumferential lengths of the plurality of sets of pads in the circumferential length L is set to y which is s/L, and the curvature of the portion of the wiring substrate where the plurality of sets of pads are formed in the row after the bending is set to x,

meets the requirement that y is less than or equal to-1.04 x + 1.80.

2. A light exit device as claimed in claim 1,

the predetermined shape is a truncated cone shape, a partial truncated cone shape, a cylindrical shape, a partial cylindrical shape, or a semi-cylindrical shape.

3. A light exit device as claimed in claim 1,

the light emitting device is formed to satisfy y ≦ -24.8x + 1.63.

4. A light exit device as claimed in claim 1,

the light emitting device is configured to satisfy y ≦ 0.745.

5. A light exit device as claimed in claim 4,

the light emitting device is configured to satisfy y ≦ 0.72.

6. A light exit device as claimed in claim 3,

the light emitting device is configured to satisfy y of 0.35. ltoreq. y.

7. A light exit device as claimed in claim 1,

the plurality of sets of pads are arranged in a plurality of rows in the circumferential direction of the wiring substrate which is rolled, and the surface-mount type LEDs are arranged corresponding to the pads,

y is less than or equal to-1.04 x +1.80 in each row.

8. A method of manufacturing a light emitting device, the light emitting device comprising: a wiring substrate which is bent into a predetermined shape and has flexibility; a plurality of sets of pads arranged in a row along a curved circumferential direction on the wiring substrate after the bending; a plurality of surface-mount LEDs fixed to the plurality of sets of pads, respectively, wherein the method for manufacturing the light emitting device is characterized in that,

when the circumferential length of the portion of the wiring substrate where the plurality of sets of pads are formed in the row after the bending is set to L, the ratio of the sum s of the circumferential lengths of the plurality of sets of pads in the circumferential length L is set to y which is s/L, and the curvature of the portion of the wiring substrate where the plurality of sets of pads are formed in the row after the bending is set to x,

meets the requirement that y is less than or equal to-1.04 x + 1.80.

Technical Field

The present invention relates to a light emitting device in which a surface mount type LED is fixed to a wiring substrate bent into a predetermined shape, and a method of manufacturing the same.

Background

This type of light emitting device was originally developed by the present applicant (see patent document 1), and conventionally, for example, a lead terminal of a shell LED was inserted into a through hole provided in a flexible wiring board formed in a partially circular band shape, and soldered, and then the wiring board was rolled so that end edges thereof abutted against each other, and bent in a truncated cone shape.

In recent years, surface-mount LEDs having higher power than shell LEDs have been applied to light emitting devices, and attempts have been made to emit light with high brightness.

However, when the surface mounting type LEDs are soldered to the wiring substrate at the same mounting density as the shell type LEDs, various problems occur. For example, if the wiring substrate is formed into a truncated cone shape or a cylindrical shape by rolling the wiring substrate after soldering a plurality of surface mount LEDs to the wiring substrate in a flat state, cracks may occur in the solder portion due to the bending of the wiring substrate. Further, since the allowance for the bending of the portion of the wiring substrate where the surface-mount LED is fixed by solder is small, if the wiring substrate is bent greatly, the wiring substrate itself may be cracked.

These problems are caused by the following: the surface-mount LED has a larger area to be fixed to the wiring board by solder than the shell LED, and has a larger area in which the wiring board is hard to bend due to the rigidity of the surface-mount LED itself.

Alternatively, even if the surface mount LED is soldered after the wiring substrate is rounded to have a truncated cone shape or a cylindrical shape, if the mounting density of the surface mount LED is too high with respect to the bending condition of the wiring substrate, the surface mount LED may not be soldered in a sufficient area with respect to the wiring substrate and may be easily detached.

Therefore, in order to prevent the occurrence of such a problem and to provide a light emitting device with low reliability, the mounting density has to be greatly reduced compared to the shell LED.

Further, if the mounting density is reduced, the portion of the wiring substrate where the surface-mount LED is not mounted becomes large, and when the wiring substrate is bent, the bending is absorbed by the portion, so that the above-described problem does not occur. However, if the mounting density is excessively reduced in consideration of safety, it is difficult to irradiate light with high brightness.

Even when the mounting density of the surface-mount LED on the wiring board is low, if the bending of the wiring board is excessively increased, the allowable limit of the wiring board itself is exceeded, and cracking or disconnection of the wiring may occur, which may cause a failure.

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a highly reliable light emitting device in which a surface mount LED is mounted on a wiring board bent into a predetermined shape with high density, thereby achieving high luminance, and in which no problem occurs even in a bent state.

Means for solving the problems

That is, the present invention provides a light emitting device including: a wiring substrate which is bent into a predetermined shape and has flexibility; a plurality of sets of pads arranged in a row along a direction of bending, i.e., a circumferential direction, on the wiring substrate after bending; and a plurality of surface-mount LEDs each fixed to the plurality of sets of pads, wherein y is equal to or less than-1.04 x +1.80, where L is a circumferential length of a portion of the wiring substrate where the plurality of sets of pads are formed in a column after the wiring substrate is bent, y is s/L is a ratio of a sum s of the circumferential lengths of the plurality of sets of pads in the circumferential length L, and x is a curvature of the portion of the wiring substrate where the plurality of sets of pads are formed in a column after the wiring substrate is bent.

Further, the present invention provides a method of manufacturing a light emitting device, including: a wiring substrate which is bent into a predetermined shape and has flexibility; a plurality of sets of pads arranged in a row along a direction of bending, i.e., a circumferential direction, on the wiring substrate after bending; and a plurality of surface mount type LEDs fixed to the plurality of sets of pads, respectively, wherein y is equal to or less than-1.04 x +1.80, where L is a circumferential length of a portion of the wiring substrate where the plurality of sets of pads are formed in a row after the bending, s is a ratio of y to s/L which is a total of circumferential lengths of the plurality of sets of pads in the circumferential length L, and x is a curvature of a portion of the wiring substrate where the plurality of sets of pads are formed in a row after the rolling.

The inventors of the present invention have made extensive studies and found a relationship between a curvature of a portion of a rolled wiring board on which a surface-mount LED is mounted and an upper limit of a mounting density at which no defect occurs in the rolled wiring board, and have realized a light emitting device and a method of manufacturing the same of the present invention for the first time.

In addition, if the mounting density of the surface mount LED is set so as to satisfy the above formula, for example, in a ring-shaped light emitting device in which a wiring board is bent after the surface mount LED is mounted on the wiring board to form a curved surface such as a truncated cone shape or a cylindrical shape, it is possible to prevent defects such as occurrence of solder cracks in the bent wiring board or cracking of the wiring board while increasing the mounting density as much as possible. Further, even in the case where the surface mount LED is fixed after the wiring substrate is bent to have, for example, a truncated cone shape or a cylindrical shape, the mounting density can be increased, and the surface mount LED can be prevented from being detached after completion, or the wiring substrate can be prevented from being cracked, or the wiring can be prevented from being disconnected.

Therefore, by using the surface-mount LED, a light emitting device having higher luminance and higher reliability than the conventional case of mounting the shell LED can be realized.

Examples of specific shapes of the light emitting device that can provide surface mounting reliability by the present invention include a truncated cone shape, a partial truncated cone shape, a cylindrical shape, a partial cylindrical shape, and a semi-cylindrical shape.

In order to satisfy the upper limit of the mounting density of the light emitting device that can achieve high reliability regardless of the value of the curvature x, y may be set to 0.745 or less. In order to further improve the reliability so that the surface-mount LED does not fall off even when an impact or the like is applied thereto, the surface-mount LED may be configured to satisfy y ≦ -24.8x +1.63 or y ≦ 0.72.

The lower limit of the mounting density is satisfied to realize a luminance of a conventional quality or higher as a ring-shaped light emitting device, and the lower limit of the mounting density is preferably 0.35. ltoreq. y.

If the plurality of sets of pads are arranged in a plurality of rows in the circumferential direction of the wiring substrate to be rounded, and the surface mount type LEDs are arranged corresponding to the pads of the respective sets, and y is equal to or less than-1.04 x +1.80 in each row, it is possible to realize an optimum mounting density in each row, realize high luminance, and prevent occurrence of defects.

ADVANTAGEOUS EFFECTS OF INVENTION

Thus, the light emitting device of the present invention satisfies y ≦ -1.04x +1.80, and therefore, can realize high luminance by increasing the mounting density of the surface mount type LED to a near limit, and ensure high reliability in which defects are less likely to occur.

Drawings

Fig. 1 is a schematic longitudinal sectional view of a light emitting device according to an embodiment of the present invention.

Fig. 2 is a schematic exploded perspective view of the light emitting device of the embodiment.

Fig. 3 is a schematic view showing a case where the wiring substrate of the embodiment is formed in a flat plate state.

Fig. 4 is a schematic perspective view showing a state of being rolled into a truncated cone shape in a state where the surface mount type LED is mounted on the wiring substrate of the embodiment.

Fig. 5 is a schematic view showing a relationship between respective dimensions of the wiring substrate which is wound in a truncated cone shape in this embodiment.

Fig. 6 is a graph showing a relationship between a curvature of the wiring substrate and a mounting density in the present embodiment.

Fig. 7 is a graph showing a relationship between a curvature of a wiring substrate and a mounting density in another embodiment of the present invention.

Description of the symbols

100: light emitting device, 1: wiring substrate, 2: pad, 21: electrode pad, 22: heat dissipation pad, 3: a surface-mount LED.

Detailed Description

A light emitting device 100 according to an embodiment of the present invention will be described with reference to the drawings. As shown in fig. 1 and 2, in the ring-shaped light emitting device 100 of the present embodiment, a large number of Surface Mount (SMD) LEDs 3 are mounted on the inner surface of the wiring substrate 1, and the wiring substrate 1 is rolled into a truncated cone shape and has flexibility. The wiring board 1 which is rolled into the truncated cone shape is housed inside a substantially annular case 4.

The cartridge 4 includes: a base member 41 having a through hole H in a central portion thereof, on which an outer surface of the wiring substrate 1 rounded in a truncated cone shape is placed; and a substantially thin cylindrical cover member 42 that sandwiches the wiring board 1 and is attached to the base member 41. For example, when the light emitting device 100 is used for inspection, the through-hole H is used for visual observation or for imaging an inspection object.

As shown in fig. 3 (a), the wiring board 1 is formed in a partially circular band shape in a flat plate state before being rolled, and a large number of surface mount LEDs 3 are fixed by soldering to the surface as the inner side surface in a state of being rolled and bent into a truncated cone shape. In the present embodiment, the surface-mounted LEDs 3 are arranged on the wiring board 1 in a flat plate shape on the inner circumferential side and the outer circumferential side having different radii, and two rows of the surface-mounted LEDs 3 are formed in parallel. Therefore, in the wiring substrate 1 in a flat plate state, a plurality of sets of pads 2 are provided in a row along the circumferential direction with a radius r from the center point₁，r₂(r₁≤r₂) Part (c) of (a).

As shown in the enlarged partial view of fig. 3 (b), each set of lands 2 is formed of 3 rectangular strip-shaped copper foils extending in the radial direction on the flat wiring board 1. Here, focusing on the group 1 pads 2, two narrow copper foil tapes at the outer side are the electrode pads 21 on which the electrode portions of the surface-mount LED3 are mounted, and a wide copper foil tape at the center is the heat dissipation pad 22. In the present embodiment, for example, a solder paste is applied to the two electrode pads 21 and the heat dissipation pad 22 located outside of the 1-group pad 2. The surface-mount LED3 is mounted on the pad 2 to which the solder paste is applied, and fixed by reflow soldering.

Next, a range of the mounting density of the surface-mount LEDs 3 on the wiring substrate 1 of the light emitting device 100 with respect to the circumferential direction will be described. Here, the circumferential direction refers to a direction in which the wiring substrate 1 is bent or rounded. In the present embodiment, a range that can be realized as the light emitting device 100 is defined by using, as variables, y, which is a ratio of the total length s of the lands 2 to the length L of the arc of the portion of the wiring substrate 1 that is rounded in a truncated conical shape and in which the surface mount LEDs 3 are arrayed in the circumferential direction, and the curvature x of the portion of the wiring substrate in the circumferential direction where the surface mount LEDs 3 are provided.

In the following description, as shown in fig. 3, a distance from a center point CP to a center in a radial direction of a pad 2 provided on a wiring substrate 1 in a flat plate state is defined as a radius r. Further, a curvature radius 1/x which is a reciprocal of the curvature x is defined by a normal line to the curved surface of the wiring substrate 1 in a rounded state (see fig. 5).

From the geometrical relationship, the center point CP of the wiring substrate 1 in the flat state shown in fig. 3 (a) corresponds to the virtual apex a when the wiring substrate 1 in the state of being rolled into a truncated cone shape shown in fig. 5 is present on the apex side, and the radius r is the length of the generatrix from the virtual apex a to the point B. When an intersection point that is perpendicular to the center axis CA from the point B is denoted by C, the length of the line segment BC is equal to the radius of a circle having a circumference L that is the same as the length L of the arc of the circular arc at the portion of the flat wiring substrate 1 that has the radius r from the center point CP. That is, when the central angle of the partially annular wiring substrate 1 formed in a flat state is θ (rad), the arc length L is calculated as L ═ r θ. Thus, the length of the line segment BC is expressed in terms of L/2 pi ═ r θ/2 pi.

As shown in fig. 5, when a point D is defined as a point where a line perpendicular to the surface of the wiring substrate 1 from the point B intersects the central axis CA, the radius of curvature 1/x is equal to the length of the BD. For example, the length of the BD is determined by using a triangle ABC having a shape similar to that of the triangle ADB. That is, the radius of curvature 1/x ═ r θ/√ (4 π/√ g) is expressed using the radius r and the center angle θ, which are parameters of the wiring substrate 1 in a flat state²-θ²). According to this formula, the curvature x of the portion where the pad 2 or the row of the surface-mount LED3 is formed on the wiring substrate 1 which is rolled into a truncated cone shape can be obtained.

Further, s is calculated as the sum of the widths of the pads 2 along the direction of the arc shown by the two-dot chain line in fig. 3. For example, the width of the electrode pad 21 in the circumferential direction is s₁S represents a circumferential width of the heat dissipation pad 22₂When the number of sets of the pads 2 is n, s is equal to n (2 s)₁+s₂) And (4) showing. Since the same number of surface-mount LEDs 3 as the number of groups of pads 2 are mounted, the circumference of the surface-mount LED3 increases when y increases by s/LThe smaller the separation distance, the higher the mounting density in the circumferential direction.

In the case where the horizontal axis is the curvature x (1/mm) and the vertical axis is the mounting density, i.e., y, is s/L (%) as shown in the graph of fig. 6, the mounting density of the surface-mounted LEDs 3 in the circumferential direction is set so as to be within the region indicated by oblique lines in the present embodiment. Further, the radius r of the inner side of the flat-plate-shaped wiring substrate 1 is r₁And the radius r of the outer side is r₂Each column of the corresponding pad 2 is also set to be included in the hatched area.

Specifically, the oblique line area is an area which simultaneously satisfies y is less than or equal to-24.8 x +1.63, y is less than or equal to 0.72 and is less than or equal to 0.005. This region is actually created by actually changing the combination of the ratio y of the total width s in the circumferential direction of the pad 2 to the curvature x and the arc length L, and is set as a result that no trouble occurs even when the wiring substrate 1 is bent and rounded. This point is produced without actually causing any trouble and is shown by a general example of a triangle.

The mounting density when the surface-mount LEDs 3 are arranged on the wiring substrate 1 in the circumferential direction is adjusted so as to be included in the region indicated by the oblique lines, so that cracks are not generated in the solder or the wiring substrate 1 is not cracked in the wiring substrate 1 that is curved by being rounded into a truncated cone shape.

In addition, if the luminance is within this region, the luminance can be achieved to be equal to or higher than that of the ring-shaped light emitting device 100 using the shell-type LED.

In addition, within the range of the oblique lines shown in fig. 6, it is possible to obtain the effect of improving the mounting density of the surface mount LEDs 3 and suppressing the occurrence of defects in various manufacturing methods such as the case where the wiring substrate 1 is rounded after the surface mount LED3 is mounted on the wiring substrate 1, or the case where the surface mount LED3 is mounted after the wiring substrate 1 is rounded.

Other embodiments will be described.

In the above embodiment, the wiring substrate is rolled into a truncated cone shape, but the present invention can be applied to an example in which a flexible wiring substrate formed into a linear strip shape is rolled into a cylindrical shape such that end edges thereof are butted against each other. When the wiring substrate is rolled into a cylindrical shape, the radius of curvature 1/x in the circumferential direction of the pad and the surface-mount LED array coincides with the radius of the cylinder formed by the wiring substrate. Therefore, the mounting density that can be configured as a light emitting device can be set for each curvature x. The wiring board may be bent to form a partial truncated cone shape corresponding to 1/4 cycles or 1/2 cycles of the truncated cone shape in the above embodiment, for example. For example, two wiring boards of partial truncated cone shape rounded by 1/2 cycles may be used to form 1 truncated cone shape. Similarly, the wiring board may be rolled into a partial cylindrical shape or may be rolled into a semi-cylindrical shape.

The ratio of the sum of the lengths of the pads in the circumferential direction to the length L of the arc, s, may be counted as pads for the entire portion when all the rear surfaces of the surface-mount LEDs are soldered. The heat dissipation pad may be fixed by a heat conductive adhesive without welding. In the present invention, the mounting density of the surface-mount LED is evaluated by the ratio y of the total number s of the lands to the length L of the arc of the portion of the land or the surface-mount LED arranged in a row in the circumferential direction on the wiring substrate to be rounded. Therefore, regardless of the type of the pad and the method of fixing, the range of the wiring board and the range of the surface-mount LED fixed thereto can be evaluated, and the mountable range can be defined (for example, in the case where the surface-mount LED is not fixed by soldering by being brought into contact with the heat radiation pad via the heat radiation oil, the sum s is not included). The method of fixing the surface-mount LED to the wiring board is not limited to solder, and may be fixed with a conductive adhesive, for example.

The light emitting device according to the above-described embodiment is an example, and the number of rows of the surface-mount LED array may be only 1 row, or may be a plurality of rows of 3 or more, and in the case of a plurality of rows, at least 1 row may satisfy the relationship shown in fig. 6 and the relationship shown in fig. 7 described later. The shape of the wiring board is not limited to the partial circular shape shown in the above embodiment, and the central angle may be any of various angles such as an obtuse angle, an acute angle, and 180 degrees. In the present invention, the surface-mount LEDs arranged in the circumferential direction need not be mounted in the entirety for 1 cycle, and may be mounted on at least a part thereof.

The extending direction of the pad with respect to the wiring board is not limited to the direction shown in the above-described embodiment, and for example, the pad may extend in the circumferential direction on the wiring board formed in a partial circular ring shape.

The light irradiation device of the present invention is not limited to the example in which the surface mount type LEDs are mounted at the mounting density shown in the above embodiment. Specifically, when the horizontal axis is the curvature x (1/mm) and the vertical axis is the mounting density, that is, y is s/L (%), the curvature x and the mounting density y may be within a range that satisfies the relationship between the curvature x and the mounting density y in the region indicated by oblique lines in the graph of fig. 7. Specifically, the inventors of the present invention have made extensive studies and, as a result, have found for the first time that a surface-mount LED can be mounted with predetermined reliability on a curved surface in a region represented by y ≦ 1.04x +1.80, 0.35 ≦ y ≦ 0.745, and 0.005 ≦ x ≦ 0.109. That is, the effect of the present invention can be enjoyed when at least a part of the surface mount LEDs arranged on a plane including a bent portion on the wiring substrate after bending satisfy the surface mount density in the relationship shown in fig. 6 and 7.

Other combinations and modifications of the various embodiments can be made without departing from the spirit of the present invention.

Industrial applicability of the invention

According to the present invention, it is possible to provide a light emitting device which improves the mounting density of surface mount LEDs to the utmost, realizes high luminance, and is less likely to cause defects.