JP6780955B2 - Light source unit and lamp - Google Patents

Description

The present invention relates to a light source unit including a semiconductor light emitting element such as an LED (light emitting diode), and more particularly to a light source unit having an improved circuit board on which an LED is mounted and a lamp having the light source unit.

In a lamp using an LED as a light source, a circuit board for supporting the LED in the lamp and at the same time supplying power to the LED is provided. As this circuit board, a rigid substrate having high mechanical strength but low flexibility and a flexible substrate having excellent flexibility are provided. In recent years, a flexible substrate with a high degree of freedom in arranging a light source in the lamp has been adopted due to the variety of lamp designs corresponding to the shape of the vehicle body.

This flexible substrate is an FPC (flexible printed circuit board) composed of a base film made of a flexible resin having a copper foil pattern formed on its surface and a cover film attached to the surface of the base film to cover the copper foil pattern. It is configured as a circuit board). In this FPC, the land portion provided in the copper foil pattern is exposed in the opening provided in the cover film, and the LED is mounted on the exposed land portion. For example, Patent Document 1 is an example of a display device using an LED, but a technique of mounting an LED on a land provided in an FPC is described.

By the way, when mounting an LED on an FPC, it is required to mount the LED in a state of being accurately positioned at a predetermined position with respect to the FPC. In the case of a rigid substrate, lands are formed on the copper foil pattern by printing technology using photoresist (photolithography technology), so the position accuracy of the lands is high, and LEDs must be mounted with high accuracy by the self-alignment method. Is possible.

On the other hand, since the FPC has a structure in which the cover film is attached to the surface of the base film as described above, a part of the copper foil pattern is exposed to the opening provided in the cover film as in Patent Document 1 to expose the cover film. The part is composed as a land. At this time, the LED is positioned by using the opening of the cover film. However, the sticking tolerance of the cover film is about ± 0.3 mm, which is larger than the printing tolerance of ± 0.1 mm of the rigid substrate. Therefore, the position accuracy of the LED mounted on the FPC is low.

Japanese Unexamined Patent Publication No. 2-189803 Japanese Unexamined Patent Publication No. 2005-2860099

Therefore, it is conceivable to make the land of the copper foil pattern formed on the base film into a structure capable of self-alignment at the time of reflow. For example, in Patent Document 2, a slit or a resist located just outside a desirable position of a mounting component (LED) is formed on a land. The slits and resists constrain the flow of solder during reflow and enable self-alignment of LEDs.

However, the technique of Patent Document 2 is applied to a rigid substrate, and cannot be directly applied to an FPC in which a cover film is present. As described above, in FPC having a large attachment tolerance of the cover film, a part of the cover film may cover a part of the land, and the slit or resist of Patent Document 2 may be covered by the cover film. In such a case, the self-alignment function is lost, and the LED cannot be mounted with high position accuracy.

An object of the present invention is to provide a light source unit and a lamp that can mount a light emitting element with high position accuracy even in a lamp that uses an FPC as a circuit board on which the light emitting element is mounted.

The present invention is a light source unit including a circuit board in which a cover member is attached to a base member provided with a conductive layer so as to cover a part of the conductive layer, and a light emitting element mounted on the circuit board. Is provided with a land portion on which a light emitting element is mounted and a wiring portion electrically connected to the land portion, terminals provided on the light emitting element are connected to the land portion with a brazing material, and the land portion has a positioning edge. It is formed . The positioning edge is arranged in the connection region between the land portion and the wiring portion, and is composed of one side of a square or rectangular window from which a part of the conductive layer is removed.

In the present invention, the cover member is provided with an opening that exposes the land portion. Further, a positioning edge is exposed in the opening of the cover member. Further, it is preferable that the window provided in the conductive layer is formed to have a size at least equal to or larger than the formation tolerance of the cover member, and is arranged at a position where the edge portion of the opening crosses the connection region.

According to the present invention, the positioning edge provided on the conductive layer allows the light emitting element to be mounted on the land portion with high position accuracy by the self-alignment action at the time of reflow. Since the land portion or the positioning edge is exposed in the opening of the cover member, even if the cover member is displaced, the self-alignment action at the time of reflow can be ensured and the light emitting element can be mounted with high position accuracy.

Cross-sectional view of the embodiment of the present invention. An exploded perspective view of a part of the light source unit. (A) is a perspective view of the LED module viewed from the rear surface, and (b) is a horizontal sectional view of the LED module. Top view of the main part of the copper foil pattern. The cross-sectional view along the VV line of FIG. 4 in the state where the LED is mounted. The figure explaining the self-alignment operation by the edge of a land. A schematic plan view showing the relationship between the sticking tolerance of the cover film and the positioning edge. (A) is a plan view showing the flow state of solder in the embodiment, and (b) is a plan view showing the flow state of solder in Patent Document 2. The schematic plan view which shows the modification of the positioning edge.

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic configuration of an embodiment in which the present invention is applied to a light source unit of an automobile lamp. The lamp housing 1 is composed of a container-shaped lamp body 11 having an open front surface and a translucent front cover 12 attached to the front opening of the lamp body 11. A light source unit 2 and a reflector 3 are contained in the lamp housing 1, and the light emitted by the light source unit 2 is reflected by the reflector 3 and is transmitted through the front cover 12 and emitted as illumination light.

The light source unit 2 includes a circuit board 4 made of an FPC having flexibility in the plate thickness direction, and an LED module 5 mounted on the circuit board 4. The circuit board (hereinafter referred to as FPC) 4 is supported in the lamp housing 1 by a fixing member 6 fixed to the lamp body 1. The fixing member 6 is formed by injection molding of resin, and is bent and formed in a stepped shape having a plurality of steps, here, three steps of flat portions 61 toward the front-rear direction of the automobile lamp, in a portion not shown in the figure. It is fixed to the lamp body 11.

Three LED modules 5 are arranged here in the number corresponding to the number of bending stages of the FPC 4, and each LED module 5 corresponds to each flat portion 61 of the fixing member 6. It is mounted on the front surface of each area 4a of the FPC 4. As a result, the three LED modules 5 are mounted side by side in the horizontal and horizontal directions when viewed from the front of the lamp at different positions in the front-rear direction of the lamp. Further, a metal plate 7 having high heat conductivity such as aluminum is integrally provided on the back surface of each region 4a of the FPC 4, and the FPC 4 is fixed to the fixing member 6 via the metal plate 7. There is. The metal plate 7 also functions as a heat sink for each LED module 5.

The FPC 4 is provided with a connector 8 electrically connected to a wiring portion 47 described later at one end 4b, and the connector 8 is arranged at a position facing the connector opening 11a provided in the lamp body 11. A power connector (not shown) connected to the vehicle-mounted battery can be fitted to the connector 8, so that the power from the power connector is supplied to the FPC 4 via the connector 8. It has become. Further, a lighting circuit (not shown) is constructed in the FPC 4, and the LED module 5 is made to emit light by the lighting circuit.

FIG. 2 is an exploded perspective view of a part of the light source unit 2, and FIGS. 3A and 3B are a perspective view of the LED module 5 viewed from the rear surface and a horizontal sectional view thereof. As shown in these figures, the LED module 5 has a configuration in which an LED chip 52 is mounted on a lead frame 51 made of a metal plate and sealed with a package 50 made of an insulating material such as resin or ceramic. The lead frame forms a cathode terminal 53, an anode terminal 54, and a heat dissipation terminal 55, and these terminals are exposed on the back surface of the package 51 in a state of being arranged in parallel. The cathode terminal 53 and the heat dissipation terminal 54 are integrated, and the LED chip 52 is mounted on the surface of the heat dissipation terminal. Further, the LED chip 52 and the anode terminal 54 are electrically connected by a bonding wire 57. The portion of the package 50 on the surface side facing the LED chip 52 is formed as a lens 56 by a translucent member.

The FPC 4 has a base film 41 made of a flexible resin such as polyimide, and a conductive layer pattern in which a conductive layer is formed in a required pattern on the surface of the base film 41, in which a copper foil is required. The copper foil pattern 42 formed in the pattern is formed. The copper foil pattern 42, which will be described in detail later, is composed of a land portion 46 for mounting the LED module 5 and a wiring portion 47 for electrically connecting the land portion 46 to the lighting circuit described above. ..

A cover film 48 made of a flexible resin such as polyimide is attached to the surface of the base film 41. The cover film 48 has a land opening 48a partially opened, and a part of the copper foil pattern 42, that is, a part of the land portion 46 and a part of the wiring portion 47 are excluded in a region other than the land opening 48a. The area is insulated and coated.

FIG. 4 is a plan view of a main part of the copper foil pattern 42 of the FPC 4. The land portion 46 is composed of a cathode land 43, an anode land 44, and a heat radiation land 45 corresponding to the cathode terminal 53, the anode terminal 54, and the heat radiation terminal 55 of the LED 5, respectively. That is, each land 43 to 45 is configured as a rectangular pattern having a vertical side and a horizontal side having substantially the same dimensions as the terminals 53 to 55, and the region indicated by the alternate long and short dash line in FIG. 4 is configured as the land portion 46. There is. The land portion 46 has a dimension equal to or slightly larger than the vertical and horizontal dimensions of the LED module 5. Here, in the following description, the vertical / horizontal and horizontal directions are based on FIG. 4, the vertical direction is the vertical direction, and the horizontal direction is the horizontal direction. The vertical side is a side extending in the vertical direction, and the horizontal side is a side extending in the horizontal direction.

The cathode land 43 is connected to a part of the wiring portion 47a of the wiring portion 47 at a vertical side portion opposite to the heat radiation land 45. The wiring portion 47a is bent 180 degrees from the vertical side of the cathode land 43, and then has a required distance from the upper and lower horizontal sides of the cathode land 43, the heat radiation land 45, and the anode land 44. It has a laterally extended portion 47b. As a result, a gap d is formed between the upper and lower horizontal sides of the lands 43 to 45 and the wiring portion 47b.

Therefore, in this gap d, each lateral side of the cathode land 43, the heat radiation land 45, and the anode land 44 appears as an edge e1, and this edge e1 is regarded as a positioning edge of these lands 43 to 45. The gap dimension of the gap d in which the positioning edge e1 is exposed, that is, the gap dimension in the vertical direction is set to be substantially equal to or slightly larger than the sticking tolerance of the cover film 48.

An edge window 43a for exposing a part of the edge e2 on the vertical side of the cathode land 43 in the boundary region between the cathode land 43 and the wiring portion 47a connected to the vertical side portion of the cathode land 43. Is formed. The edge window 43a is configured as a square or rectangular opening from which a part of the copper foil pattern 42 is removed, and here, two edge windows 43a are separated from each other along the vertical side of the cathode land 43 at predetermined intervals. It is opened in the state of being closed.

By providing the edge window 43, the right vertical side of the edge window 43a appears as the positioning edge e2 of the vertical side of the cathode land 43. The vertical side dimension of the edge window 43a is arbitrary, but it is formed so as to have a width dimension that does not hinder the flow of solder at the connection portion between the cathode land 43 and the wiring portion 47a due to the formation of the edge window 43a. Is preferable. Further, the size of the side surface of the edge window 43a is a size substantially equal to or slightly larger than the sticking tolerance of the cover film 48.

The anode land 44 is connected to a part 47c of the wiring portion 47 on a vertical side opposite to the heat radiation land 45. The wiring portion 47c extends from the anode land 44 in the lateral direction. An edge window 44a for displaying a part of the edge e3 on the vertical side of the anode land 44 is formed in the boundary region between the anode land 44 and the wiring portion 47c. The edge window 44a has the same configuration as the edge window 43a of the cathode land 43.

By providing the edge window 44a, the left vertical side of the edge window 44a appears as the positioning edge e3 of the vertical side of the anode land 44. The dimensions of the vertical side and the horizontal side of the edge window 44a are also the same as those of the edge window 43a of the cathode land 43. In particular, although the description using the reference numeral is omitted in the edge window 43a, the dimension s of the lateral side of the edge window 44a is substantially equal to the attachment tolerance of the cover film 48, which is the same as the lateral dimension of the edge window 43a. Or it is a size slightly larger than that.

The cover film 48 has a land opening 48a as described above. As shown by the alternate long and short dash line in FIG. 4, the land opening 48a is formed as a square or rectangular opening having a vertical side dimension and a horizontal side dimension slightly larger than the vertical and horizontal dimensions of the land portion 46. The vertical and horizontal dimensions are obtained by adding the sticking tolerance of the cover film 48 to the vertical and horizontal dimensions of the land portion 46.

In the FPC 4 having the above configuration, for example, a copper foil is formed on the entire surface of the base film 41, and this copper foil is selectively etched by a photolithography technique using a photoresist, and copper having a land portion 46 and a wiring portion 47 is provided. The foil pattern 42 is formed. With this photolithography technique, the copper foil pattern 42 can be formed with high positional accuracy with respect to the base film 41. On the other hand, as the cover film 48, a land opening 48a opened by molding, punching, or the like is attached to the surface of the base film 41 with an adhesive or the like. As a result, an FPC 4 in which a part of the land portion 46 and the wiring portion 47 of the copper foil pattern 42 is exposed to the land opening 48a and the other region is covered with the cover film 48 is obtained.

FIG. 5 is a cross-sectional view taken along the line VV of FIG. 4 in a state where the LED module 5 is mounted on the FPC 4. Since the cross-sectional structure of the LED module 5 is as shown in FIG. 3B, the illustration is omitted here. In order to mount the LED module 5 on the FPC 4, a metal brazing material, here creamy solder (solder) H, is applied to the surface of the base film 41 exposed in the land opening 48a. Then, the LED module 5 is placed in the land opening 48a. At this time, the cathode terminal 53, the anode terminal 54, and the heat radiation terminal 55 of the LED module 5 are positioned corresponding to the cathode land 43, the anode land 44, and the heat radiation land 45 of the FPC 4, respectively. Then, by performing reflow to melt the solder H, as shown in FIG. 5, the terminals 53 to 55 of the LED module 5 are soldered to the lands 43 to 45 of the corresponding FPC 4.

At this time, as shown in a partially enlarged view in FIGS. 6A and 6B, the LED module 5 may be displaced with respect to, for example, the land (anode land) 44. In this case, as shown in FIG. 6C, surface tension is generated in the molten solder H, and the surface tension causes the solder H to flow so as to collect on the surface of the land 44. Due to the flow of the solder H, the LED module 5 is moved in the horizontal direction, that is, the vertical side of the anode terminal 54 is moved to the position of the positioning edge e3 on the vertical side of the anode land 44 exposed in the edge window 44a. The same applies to the cathode terminal 53 and the cathode land 43. As a result, the LED module 5 is positioned laterally with respect to the land portion 46 with high accuracy, and mounting by self-alignment is realized.

Further, although not shown, when the LED module 5 is mounted on the FPC 4 in a vertically displaced state, the lateral sides of the cathode terminal 53 and the anode terminal 54 are present due to the gap d during solder reflow. It is moved to the position of the positioning edge e1 on each side of the cathode land 43 and the anode land 44. As a result, the LED module 5 is mounted at an accurate position with respect to the land portion 46 by self-alignment. This self-alignment is also performed by moving between the heat dissipation terminal 55 and the heat dissipation terminal 55 by soldering on the heat dissipation land 45.

Here, when the LED module 5 is mounted on the land portion 46, the LED module 5 is mounted in the land opening 48a of the cover film 48, so that the mounting position of the LED module 5 with respect to the land portion 46 has an error due to the sticking tolerance. There is concern that it will occur. For example, as shown in FIG. 7A, when the cover film 48 is attached to the base film 41 in a state where the cover film 48 is displaced in the lateral direction (left direction) at the maximum attachment tolerance, the LED module 5 is displaced by this attachment tolerance. May be installed.

However, in this embodiment, since the lateral dimensions s of the edge windows 43a and 44a are formed to have substantially the dimensions of the attachment tolerance, even if the cover film 48 is attached in a misaligned manner, it is inside the land opening 48a. Is sure to expose a part of the edge windows 43a and 44a, that is, the positioning edges e2 and e3 on the vertical side of any of the lands. Therefore, if the above-mentioned reflow is performed, the terminals 53 and 54 of the LED module 5 are self-aligned with respect to the corresponding lands 43 and 44.

When the cover film 48 is attached in a state of being displaced in the vertical direction (upward direction) at the maximum attachment tolerance as shown in FIG. 7B, the dimension of the gap d described above is formed to be substantially the dimension of the attachment tolerance. Therefore, the positioning edge e1 on the side of any of the lands 43 to 45 forming the gap d is always exposed in the land opening 48a. Therefore, if the above-mentioned reflow is performed, the terminals 53 to 55 of the LED module 5 are self-aligned with respect to the corresponding lands 43 to 45.

As described above, according to the FPC 4 of this embodiment, the LED module 5 can be reliably mounted at a predetermined position of the land portion 46 regardless of the attachment tolerance of the cover film 48, and the position accuracy is high with respect to the FPC 4. LED module 5 can be mounted. Incidentally, in the technique of Patent Document 2, since the slit provided in the land is narrow, when the cover film is misaligned within the range of the sticking tolerance, the slit is covered by the cover film, and at the time of reflow. Self-alignment cannot be ensured.

Further, in the FPC 4 of this embodiment, even when the edge windows 43a and 44a are opened, the dimensions of the edge windows 43a and 44a are adjusted so as not to suppress the flow of solder at the connection portion between the land portion 46 and the wiring portion 47. By setting, the solder melted at the time of reflow flows between the land portion 46 and the wiring portion 47, and the self-alignment described above can be promoted.

On the other hand, when the solder flows in this way, as shown in FIG. 8A, even if a sticking tolerance occurs, the entire edge window 43a is not exposed in the window 48a. Therefore, the range of solder flow (arrows in the figure) is suppressed within the area of the connection portion between the land portion 46 and the wiring portion 47 indicated by ◯ in the figure. As a result, the entire area of the surface of each of the terminals 43 to 45 of the LED module 5 becomes wet with solder and is covered with solder. Therefore, in the state after the LED module 5 is mounted, rusting on the surfaces of the terminals 43 to 45 can be prevented, and treatment such as rust-preventive plating becomes unnecessary.

Incidentally, in the technique of Patent Document 2, as shown in FIG. 8B, if the length of the slit S is not set appropriately, the flow of solder between the land portion 46 and the wiring portion 47 (arrow in the figure). ) Cannot be secured, and suitable self-alignment cannot be expected. In FIG. 8B, the same reference numerals are given to the portions equivalent to those in the embodiment. Further, in the technique of Patent Document 2, when the length of the slit S is short, the amount of solder H flowing from the land portion 46 to the wiring portion 47 becomes large, and each terminal 43 is in a state after the LED module 5 is mounted. There may be a portion of the surface of ~ 45 where the solder does not get wet, and rust may occur at this portion. Therefore, treatment such as rust-preventive plating is required for each terminal 43 to 45, which is disadvantageous in terms of manufacturing man-hours and cost.

In the present invention, the edge window for revealing the positioning edge of the land portion does not necessarily have to be a rectangular opening, and a part of the vertical sides of the cathode land 43 and the anode land 44 is exposed as the positioning edges e2 and e3. Any configuration may be used. 9 (a) to 9 (c) are views showing a modified example of the edge window and the gap of the embodiment, and the same reference numerals are given to the portions corresponding to the embodiment.

Although detailed description of these modifications will be omitted, in each case, a copper foil pattern is formed in which the wiring portion is connected to the cathode land and the anode land and the positioning edge is exposed at least a part of the vertical side of each land. Is forming. As a result, lateral self-alignment is performed during reflow. Further, in some modifications, the pattern configuration is such that the positioning edge appears at least a part of the horizontal side of the cathode land, the anode land, or the heat radiation land, so that self-alignment is performed even in the vertical direction at the time of reflow. As can be seen from these modifications, what forms the positioning edge of the land portion in the present invention is not limited to the gap and the edge window described in the embodiment, but a void having an arbitrary shape, that is, a conductive layer. It can be configured by removing it into an arbitrary shape.

The circuit board in the present invention is applied to an FPC having a configuration in which a cover film is attached to a base film. A cover member is attached to the base member, and a land portion is exposed in an opening provided in the cover member to expose a light emitting element. As long as it is a circuit board having a configuration in which the above is mounted, it does not necessarily have to be a circuit board configured as an FPC. Alternatively, the present invention is also applied to a circuit board having a structure in which an insulating liquid material is applied to the surface of a base film using a pattern mask or the like and solidified by high-temperature drying or ultraviolet irradiation to form a layered cover member. be able to. In this case, the above-mentioned sticking tolerance should be read as the coating tolerance.

The light emitting element in the present invention is not limited to the LED module, as long as it is a light emitting element having a configuration in which the land portion formed by the conductive layer of the circuit board is surface-mounted by reflow using a brazing material or the like. It may be another light emitting element including an LD (laser diode).

The specific pattern shape of the land portion and the wiring portion according to the present invention is not limited to the configuration of the embodiment, and may be formed as the land portion and the wiring portion having an arbitrary configuration.

1 Lamp housing 2 Light source unit 3 Reflector 4 FPC (circuit board)
5 LED module (light emitting element)
6 Fixing member 7 Metal plate 8 Connector 41 Base film 42 Copper foil pattern 43 Cathode land 43a Edge window 44 Anode land 44a Edge window 45 Heat dissipation land 46 Land part 47 Wiring part 48 Cover film 48a Land opening 50 Package 51 Lead frame 52 LED chip 53 Cathode terminal 54 Anode terminal 55 Heat dissipation terminal e1 to e3 Positioning edge

Claims (6)

A light source unit including a circuit board provided with a film-like or layered cover member so as to cover a part of the conductive layer on a base member provided with the conductive layer, and a light emitting element mounted on the circuit board. The conductive layer includes a land portion on which a light emitting element is mounted and a wiring portion electrically connected to the land portion, and terminals provided on the light emitting element are connected to the land portion by a brazing material. Is formed with a positioning edge, which is arranged in a connection region between the land portion and the wiring portion, and is composed of one side of a square or rectangular window from which a part of the conductive layer is removed. a light source unit, characterized in that that. The light source unit according to claim 1 , wherein the cover member has an opening for exposing the land portion. The light source unit according to claim 2 , wherein the positioning edge is exposed in the opening of the cover member. The light source unit according to claim 2 or 3 , wherein the edge of the opening is arranged at a position across the connection area. The light source unit according to any one of claims 1 to 4 , wherein the window has a size equal to or larger than the formation tolerance of the cover member. A lamp comprising the light source unit according to any one of claims 1 to 5 .

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