JP2017028034A - Connection structure between flexible substrates for led element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connection structure 10 between flexible substrates for LED element capable of interconnecting a plurality of flexible substrates 1, while holding a high luminous efficiency, by avoiding reduction in the luminous efficiency due to existence of a connector terminal 4, that is conventionally a component indispensable for connection of a plurality of flexible substrates 1, when they are used while being connected.SOLUTION: A flexible substrate 1 is formed by laminating a metal wiring part 12 and an isolating layer 13 sequentially on a film substrate 11. The metal wiring part 12 consists of an LED mounting wiring 121 coated with the isolating layer 13, and an inter-substrate connection wiring 122 not coated with the isolating layer 13 but exposed, and the inter-substrate connection wirings 122 of a plurality of flexible substrates 1 are interconnected by a conductive material 3 in the connection structure 10 between flexible substrates.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a connection structure between flexible substrates for LED elements.

  In recent years, various LED display devices such as a liquid crystal display using an LED element as a backlight light source and a dot matrix display device that displays information such as desired characters and symbols by selectively emitting light from the LED element have been rapidly used. Is popular. In these LED display devices, in order to mount the LED element as a light source, circuit boards for various LED elements each including a support substrate and a wiring portion are usually used.

  Conventionally, a rigid board in which an LED element is mounted on a rigid board made of a glass epoxy plate or the like has been widely used as a circuit board for an LED element. However, in recent years, LED display devices have become larger and display screens have become more diversified. In recent years, a flexible substrate in which a metal circuit is formed on a flexible substrate film such as a resin sheet has been developed (see Patent Document 1). ). Since flexible substrates have higher design freedom and higher productivity than rigid substrates, further expansion is expected in the future.

  Here, in order to further increase the degree of freedom in designing the flexible substrate, a usage mode in which a plurality of flexible substrates are connected to each other to constitute circuit boards of various sizes and shapes can be considered. As a specific example of such a multi-substrate connection type flexible substrate, one in which flexible substrates that can be connected in parallel with each other via connector terminals are connected and used has been proposed (Patent Document 2).

JP 2012-59867 A Japanese Patent Laid-Open No. 2002-232009

  However, in the flexible substrate described in Patent Document 2, it is assumed that their interconnection is configured by a structure via connector terminals. Here, conventionally, the connector terminal 4 (see FIG. 5) disposed between the flexible substrates has a thickness of about 1 mm or more, generally at least about 5 mm, ordinarily about 20 mm even if it has a special specification. It was a thing. When a plurality of flexible boards are connected to form a single board, a part of the light emitted from the LED elements arranged in the vicinity of the connecting portion between the connected flexible boards is blocked by this connector terminal. As a result, the luminous efficiency is lowered.

  In the present invention, in order to maximize the degree of freedom in designing a flexible substrate, when a plurality of flexible substrates are connected and used, the presence of connector terminals, which has been an indispensable component for connecting them, has been heretofore known. It aims at providing the connection structure between the flexible substrates for LED elements which can connect the some flexible substrate mutually, avoiding the reduction | decrease of the luminous efficiency resulting from it, and maintaining high luminous efficiency.

  As a result of extensive research, the present inventors have covered the metal wiring portion of the flexible substrate for the LED element with the insulating layer except for the region where the metal wiring constituting the metal wiring portion is mounted. By adopting a structure comprising a wiring portion for LED mounting and a wiring portion for inter-substrate connection that is exposed without being covered with an insulating layer, a part from the end of the metal wiring constituting the metal wiring portion, The present inventors have found that they can be connected without using a connector terminal and have completed the present invention. Specifically, the present invention provides the following.

  (1) A flexible substrate connection structure for an LED element, wherein the flexible substrate is formed by sequentially laminating a metal wiring portion and an insulating layer on a film substrate, and the metal wiring portion includes an LED element. An LED mounting wiring portion that is a portion covered with the insulating layer except for a region for mounting, and an inter-substrate connecting wiring portion that is an exposed portion that is not covered with the insulating layer, A connection structure between flexible substrates in which the inter-substrate connection wiring portion of one flexible substrate and the inter-substrate connection wiring portion of another flexible substrate are connected by a conductive material.

  (2) The inter-substrate connection wiring portion is folded back to the back surface side that is the surface opposite to the LED element mounting surface of the flexible substrate, and the inter-substrate connection wiring portions are connected to each other on the back surface side. The connection structure between flexible substrates according to (1), which is connected by a conductive material.

  (3) The connection structure between flexible substrates according to (1) or (2), wherein the conductive material is an anisotropic conductive film.

  (4) In the inter-substrate connecting wiring portion, the metal wiring portion is arranged with a narrower pitch than in the LED mounting wiring portion, and the film substrate is connected to the inter-substrate connection. Between the flexible substrates according to any one of (1) to (3), wherein the width of the portion where the wiring portion for wiring is laminated is smaller than the width of the portion where the wiring portion for LED mounting is laminated Connection structure.

  (5) A multi-connection type flexible substrate for LED elements, in which a plurality of flexible substrates are connected by the connection structure between flexible substrates according to any one of (1) to (4).

  (6) An LED display device in which an LED element is mounted on the multi-connection flexible substrate according to (5).

  According to the present invention, in order to maximize the degree of freedom in designing a flexible substrate, when connecting and using a plurality of flexible substrates, the connector terminals, which have been indispensable constituent elements for connecting them, have been conventionally used. It is possible to provide a connection structure between flexible substrates for LED elements capable of connecting a plurality of flexible substrates to each other while maintaining high luminous efficiency while avoiding reduction in luminous efficiency due to the presence.

It is a top view with which it uses for description of the connection structure between the flexible substrates for LED elements of this invention. It is a fragmentary sectional view with which it uses for description of the layer structure of the connection structure between the flexible substrates for LED elements of FIG. It is a fragmentary sectional view with which it uses for description of the layer structure of other embodiment of the connection structure between the flexible substrates for LED elements. It is a top view which shows typically the circuit structure of the flexible substrate for LED elements which can be connected by the connection structure between the flexible substrates for LED elements of this invention. It is a top view which shows typically the usage condition by which the LED element is implemented by the flexible substrate for LED elements which can be connected by the connection structure between the flexible substrates for LED elements of this invention. It is a fragmentary sectional view with which it uses for description of the layer structure of the connection structure between the flexible substrates for conventional LED elements.

  Hereinafter, a flexible substrate that can constitute a connection structure between flexible substrates for LED elements of the present invention, a connection structure between flexible substrates for LED elements of the present invention, and a plurality of flexible substrates are connected by the connection structure. Embodiments of a flexible substrate (referred to as a “multi-connection type flexible substrate” in this specification) and an LED display device in which LED elements are mounted on the multi-connection type flexible substrate will be sequentially described. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

<Flexible substrate>
As shown in FIGS. 1, 4, and 5, the flexible substrate 1 is a circuit substrate in which a metal wiring part 12 is formed on the surface of a flexible film substrate 11.

[Basic configuration]
As shown in FIGS. 2 and 4, the flexible substrate 1 has a metal wiring portion 12 formed on the surface of the film substrate 11 by conductive metal wiring made of metal foil or the like. The metal wiring part 12 has a desired pattern corresponding to the arrangement of the LED elements, and is generally fixed on the film substrate 11 via an adhesive layer (not shown). The metal wiring part 12 is an inter-board connection wiring that constitutes the connection structure 10 between the flexible boards of the present invention, which is a connection structure between the LED mounting wiring part 121 constituting the LED element mounting area and another flexible board. Part 122.

  As shown in FIGS. 4 and 5, regarding the planar shape of the entire flexible substrate 1, the width of the portion where the inter-substrate connection wiring portion 122 is laminated (inter-substrate connection portion 112) is the same as the LED mounting wiring portion 121. It is preferably formed narrower than the width of the stacked portion (LED mounting portion 111). The board-to-board connecting wiring part 122 formed in the narrow board-to-board connecting part 112 is also arranged at a narrower pitch than the LED mounting wiring part 121 formed in the LED mounting part 111 in the same manner. Is preferred.

  Further, as shown in FIG. 5, an insulating layer 13 made of thermosetting ink or the like is formed on the mounting surface side of the LED element on the film substrate 11. The insulating layer 13 covers a portion of the surface of the film substrate 11 excluding the region for mounting the LED element 2 and the inter-substrate connection wiring portion 122, mainly for the purpose of improving the migration resistance of the flexible substrate 1. Formed. As the thermosetting ink, a known ink can be suitably used as long as the thermosetting temperature is about 100 ° C. or less. Specifically, as a representative example of an ink that can preferably use an insulating ink having a polyester resin, an epoxy resin, an epoxy resin and a phenol resin, an epoxy acrylate resin, a silicone resin, or the like as a base resin, respectively. Can be mentioned. Of these, polyester-based thermosetting insulating ink is particularly preferable as a material for forming the insulating layer 13 of the flexible substrate 1 because of its excellent flexibility. The insulating layer 13 can be formed with an insulating thermosetting ink by a known method such as screen printing.

  In addition, the flexible substrate 1 includes a reflection layer for improving the light use efficiency or various optical film layers (not shown) such as a black layer for the purpose of improving display contrast. It may be further laminated on the substrate. The optical film layer is laminated as a member for improving the optical characteristics of the LED device using the flexible substrate 1. The optical film layer may be a reflective film that exhibits reflective performance for improving the illumination effect, or may be a black or dark film that contributes to improving the contrast in order to improve the display effect. Further, in the flexible substrate 1, by providing the insulating layer 13 with these optical functions, it is possible to ensure the necessary optical functions without installing an optical film layer.

  Bonding between the metal wiring portion 12 and the LED element 2 in the flexible substrate 1 can be performed by either a reflow method through a solder layer or a laser method.

  The flexible substrate of the present invention has, for example, a multilayer circuit board in which metal wiring portions are respectively formed on both surfaces of the film substrate 11 and are electrically connected through through holes penetrating the film substrate 11. It may be. By using such a multilayer circuit board as the flexible substrate, the multi-connection type flexible substrate according to the present invention can be preferably used in an LED dot matrix display device.

[Film substrate]
The material of the film substrate 11 is not particularly limited, but is preferably a thermoplastic resin. The film substrate 11 is required to have high heat resistance and insulation. Preferable examples of such material resins include polyimide (PI), polyethylene naphthalate (PEN), amorphous polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyetherimide, fluororesin, A liquid crystal polymer etc. can be mentioned. Among these, polyethylene naphthalate (PEN) whose heat resistance and dimensional stability are improved by performing a heat resistance improvement treatment such as an annealing treatment can be particularly preferably used. In addition, polyethylene terephthalate (PET) whose flame retardancy is improved by addition of a flame retardant inorganic filler or the like can also be selected as a material resin for the resin base.

Further, the film substrate 11 is required to be a resin having high insulating properties. In general, the film substrate 11 has a volume resistivity of preferably 10 ¹⁴ Ω · cm or more, and more preferably 10 ¹⁸ Ω · cm or more.

  The thickness of the film substrate 11 is not particularly limited, but is about 10 μm to 500 μm, preferably 50 μm to 250 μm, from the viewpoint of heat resistance and insulation, and balance of manufacturing costs. Preferably there is. Also, the thickness is preferably within the above-mentioned thickness range from the viewpoint of maintaining good productivity when manufacturing by the roll-to-roll method.

[Metal wiring section]
The metal wiring portion 12 is a wiring pattern made of a metal wiring formed of a conductive material such as a metal foil on at least one surface of the film substrate 11 in the flexible substrate 1. The arrangement of the metal wiring portion 12 is not limited to a specific arrangement as long as the LED element 2 can be mounted in a desired arrangement such as a matrix shape. However, in the flexible substrate 1, it is an essential requirement that the metal wiring portion is configured to include two portions of the LED mounting wiring portion 121 and the inter-substrate connecting wiring portion 122.

  The LED mounting wiring portion 121 is a portion of the metal wiring portion 12 that is formed on the LED mounting portion 111 that occupies the main portion of the film substrate 11, and is used to join the LED element 2 to the metal wiring in a conductive manner. The insulating layer 13 is covered except for the LED mounting area required for the above.

  The inter-substrate connection wiring portion 122 is a portion of the metal wiring portion 12 that is formed on the inter-substrate connection portion 112 that occupies a portion near the end of the film substrate 11, and the metal wiring is covered with the insulating layer 13. It is exposed without being.

  As shown in FIG. 2, the flexible substrate 1 forms the flexible substrate connection structure 10 by connecting the inter-substrate connection wiring portions 122 of the individual flexible substrates 1 with the conductive material 3 in a conductive manner. Can do.

  Further, as shown in FIGS. 4 and 5, in the flexible substrate 1, the metal wiring is arranged at a narrower pitch in the inter-substrate connecting wiring portion 122 than in the LED mounting wiring portion 121. preferable. Further, the film substrate 11 is more preferably formed so that the width of the inter-substrate connecting portion 112 is smaller than the width of the LED mounting portion 111.

  Examples of the material of the metal wiring constituting the metal wiring part 12 include metal foils such as aluminum, gold, silver, and copper. The thickness of the metal wiring portion 12 may be appropriately set according to the magnitude of the withstand current required for the flexible substrate 1 and is not particularly limited, but examples include a thickness of 10 μm to 50 μm. If the thickness of the metal wiring portion 12 is less than the above lower limit value, the influence of the thermal contraction of the substrate is large, and the warp after the processing is likely to increase during the solder reflow processing. Therefore, the thickness of the metal wiring portion 12 is 10 μm or more. Preferably there is. On the other hand, when the thickness is 50 μm or less, preferable flexibility of the flexible substrate 1 can be maintained, and a reduction in handling property due to an increase in weight can be prevented.

[Method for manufacturing flexible substrate]
About the manufacturing method of the flexible substrate 1, it can be based on the manufacturing method of a conventionally well-known electronic substrate. For example, it can be manufactured by a conventional method in which the metal wiring part 12 is formed on each surface of the film substrate by an etching process involving chemical treatment.

<Connection structure between flexible boards>
As shown in FIG. 2, the connection structure 10 between the flexible boards of the present invention is such that the plurality of flexible boards 1 are electrically connected to each other between the board connecting wiring parts 122 without the connector terminals 4 (see FIG. 5). In this structure, the conductive material 3 is connected by conduction. Here, the “connector terminal” in the present specification refers to a connector terminal described in Patent Document 2 that can be exemplified as a representative specific example, and in particular, the connection structure between flexible substrates on the upper surface of the form. When forming, it shall mean the member which consists of a fixed shape including the part which protrudes on a flexible substrate at the height of at least 1 mm or more in the thickness direction of the said flexible substrate. The connection structure 10 between flexible boards of the present invention is characterized in that it does not include such a “connector terminal” as a constituent feature. Further, since the structure 10 does not include such a “connector terminal”, the connection structure 10 between the flexible substrates completely protrudes the member for holding the connection to the mounting surface side of the LED element of the flexible substrate 1. The structure can be eliminated.

  In the connection structure 10 between the flexible substrates, the inter-substrate connection wiring portion 122 in the plurality of flexible substrates 1 is in close contact with the film substrate 11, and as shown in FIG. It is preferable that the inter-substrate connecting wiring portions 122 are connected to each other by the conductive material 3 on the back surface side that is the surface opposite to the back surface.

  Another embodiment of the connection structure between flexible substrates of the present invention is a connection structure 10A between flexible substrates shown in FIG. In the connection structure 10A between the flexible substrates, one of the plurality of flexible substrates 1 to be connected is folded back to the back side in the same manner as the connection structure 10 between the flexible substrates. In the other flexible substrate, the inter-substrate connecting wiring portion 122A is not folded back, and the inter-substrate connecting wiring portion 122 is folded on the surface of the inter-substrate connecting wiring portion 122A by the conductive material 3. It is connected so that it can conduct.

  For example, when the metal wiring part 12 is formed on both surfaces of the film substrate 11 such as a flexible substrate for a dot matrix display device, the metal wiring on the back side is not bent as described above. A part of the portion 12 is formed as the inter-substrate connecting wiring portion 122, and these are electrically connected to the back surface side of the film substrate 11 by the conductive material 3, thereby forming the flexible substrate connecting structure 10 of the present invention. be able to.

  An anisotropic conductive film (ACF) can be preferably used as the conductive material 3 for conducting between the inter-substrate connection wiring portions 122. ACF is a film formed by mixing fine metal particles having conductivity with thermosetting resin into a film shape, and has been used for mounting parts such as semiconductors on printed boards. Is. The structure of the conductive particles is generally a sphere having a diameter of about 3 to 5 μm in which a nickel layer, a gold plating layer, and an insulating layer are stacked on the outermost side from the inside.

  A specific method of configuring the connection structure 10 between the flexible substrates by connecting the inter-substrate connection wiring portions 122 of the plurality of flexible substrates 1 through the ACF is as follows. First, as shown in FIG. 2, the ACF is arranged at a position where both wiring portions can be conducted between the inter-substrate connecting wiring portions 122 to be connected. Then, the ACF is crimped to the inter-substrate connecting wiring part 122 while applying heat with a heater or the like. By this thermocompression treatment, pressure is applied only to the film portion where the convex portion made of the metal wiring constituting the inter-substrate connecting wiring portion 122 is applied to the ACF, and the particles dispersed in the ACF are overlapped while contacting. The plating layers of the particles in the ACF attract each other to autonomously form a conductive path. On the other hand, since the particles in the film part where no pressure is applied retain the insulating property, the insulation between the electrodes arranged side by side is maintained. In this way, anisotropy is formed in the ACF so as to maintain conductivity in the vertical direction and insulation in the horizontal direction. Thereby, even if the pitch between the metal wirings in the horizontal direction is small in the inter-substrate connecting wiring part 122, the inter-substrate connecting wiring parts 122 can be connected to each other without causing a short circuit.

<Multi-connection type flexible substrate and LED display device using the same>
The multi-connection type flexible substrate 100 for LED elements can be comprised by connecting the some flexible substrate 1 with the connection structure 10 between the flexible substrates mentioned above. In addition, the LED element 2 is mounted on the multi-connection type flexible substrate 100, and further combined with various display screens such as a liquid crystal display panel as necessary. An LED display device using a connection type flexible substrate can be configured.

  As the LED element 2 constituting the LED display device by being mounted on the multi-connection type flexible substrate 100, a light-emitting element utilizing light emission at a PN junction where a P-type semiconductor and an N-type semiconductor are joined is preferably used. Can be used. The LED element 2 can be bonded to the metal wiring portion 12 by a known solder bonding process such as a reflow method or a laser method.

  According to the flexible substrate 1 of the present invention described above and the LED display device using the same, the following effects can be obtained.

  (1) The connection structure 10 between the flexible boards is used as an inter-board connection wiring section 122 that is a part of the metal wiring section 12 of the flexible board 1 that is exposed without being covered with the insulating layer 13. Are connected by the conductive material 3, so that the plurality of flexible boards 1 are connected without the connector terminals 4 (see FIG. 5). Thereby, when connecting the plurality of flexible boards 1, the presence of the connector terminal, which has been an indispensable structure in the past, is unnecessary, and the reduction in light emission efficiency due to the presence of the connector terminal can be avoided. Therefore, when connecting and using a plurality of flexible boards, it is possible to fully enjoy the various merits of the connection structure related to the high degree of freedom of design while preventing the decrease in light emission efficiency caused by the connection. Can do.

  (2) In the connection structure 10 between the flexible boards in (1), the inter-board connection wiring portion 122 is further folded back to the back surface side that is the surface opposite to the mounting surface of the LED element 2 in the flexible substrate 1. Thus, the inter-substrate connecting wiring parts 122 are connected to each other by the conductive material 3 on the back surface side. According to this, the protrusion of the member for connection and the component part in the mounting surface side of the LED element 2 of the flexible substrate 1 with connection can be eliminated completely. Therefore, the effect of avoiding the reduction of the issue efficiency produced by the invention of (1) can be expressed at a higher level with higher accuracy.

  (3) The conductive material 3 was formed of an anisotropic conductive film. Thereby, the connection structure 10 between flexible substrates can be formed by preventing the short circuit in the wiring part 122 for a connection between board | substrates by simple process.

  (4) Regarding the shape of the flexible substrate 1, the width of the portion where the inter-substrate connection wiring portion 122 is disposed is narrower than the width of the portion where the LED mounting wiring portion 121 is disposed. Thereby, the size of the connection structure 10 between flexible substrates can be reduced. In addition, the presence of the notch portion formed with the narrowing of the connecting portion makes it easy to visually distinguish the LED mounting wiring portion 121 and the inter-substrate connecting wiring portion 122 in the flexible substrate 1 before bending. Become. The LED mounting wiring part 121 can be bent more easily and with high accuracy. Therefore, it can contribute to the improvement of productivity of the connection structure between flexible substrates.

  (5) A multi-connection type flexible substrate 100 for an LED element in which a plurality of flexible substrates 1 are connected by the connection structure 10 between flexible substrates according to any one of (1) to (4). This multi-connection type flexible substrate 100 can be used as a multi-connection type flexible substrate for LED elements that is extremely excellent in both high luminous efficiency and freedom of design.

  (6) An LED display device in which the LED element 2 is mounted on the multi-connection type flexible substrate 100 for an LED element described in (5). According to this, the LED display device which can enjoy the effect of invention of (5) under various installation conditions can be obtained.

  As described above, according to the present invention, it is possible to avoid a decrease in issuance efficiency due to the connection of a plurality of flexible boards, and to ensure the preferable characteristics originally intended for a multi-connection type flexible board, such as freedom of design and high productivity. A multi-connection type flexible substrate that can be developed in an LED and an LED display device using the same can be obtained

DESCRIPTION OF SYMBOLS 1 Flexible substrate 11 Film substrate 111 LED mounting part 112 Inter-board connection part 12 Metal wiring part 121 LED mounting wiring part 122 Inter-board connection wiring part 13 Insulating layer 2 LED element 3 Conductive material 4 Connector terminal 10 Between flexible boards Connection structure 100 Multi-connection type flexible substrate

Claims (6)

A flexible substrate connection structure for LED elements,
In the flexible substrate, a metal wiring part and an insulating layer are sequentially laminated on a film substrate,
The metal wiring portion is an LED mounting wiring portion that is a portion covered with the insulating layer except for a region for mounting an LED element, and a portion that is exposed without being covered with the insulating layer. And a wiring part for inter-board connection,
A connection structure between flexible substrates in which the inter-substrate connection wiring portion of one flexible substrate and the inter-substrate connection wiring portion of another flexible substrate are connected by a conductive material.   The inter-substrate connecting wiring portion is folded back to the back surface side opposite to the LED element mounting surface of the flexible substrate, and the inter-substrate connecting wiring portions are connected to the conductive material on the back surface side. The connection structure between the flexible substrates according to claim 1, wherein the connection structures are connected with each other.   The connection structure between flexible substrates according to claim 1, wherein the conductive material is an anisotropic conductive film. The metal wiring portion has metal wiring arranged at a narrower pitch in the inter-substrate connection wiring portion than in the LED mounting wiring portion,
4. The film substrate according to claim 1, wherein the width of the portion where the inter-substrate connection wiring portion is laminated is smaller than the width of the portion where the LED mounting wiring portion is laminated. 5. A connection structure between flexible substrates according to any one of the above.   A multi-connection type flexible substrate for an LED element, wherein a plurality of flexible substrates are connected by the connection structure between flexible substrates according to claim 1.   An LED display device comprising an LED element mounted on the multi-connection flexible substrate according to claim 5.

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