JP2007250765A - Land structure of printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a land structure of a printed wiring board which is capable of preventing a gap from occurring in the mounting position of an LED when the LED is mounted on the printed wiring board by soldering. <P>SOLUTION: The land 9 of a printed wiring board has a configuration in which a part of a conductor 4 is made to appear from an opening 8 provided to an insulating layer formed on the surface of the conductor 4. The LED is connected to the land 9 through solder. The land 9 is equipped with an electrode mount 10 where the electrode 51 of the LED is mounted, and the electrode mount 10 is configured in such a manner in which it extends along the periphery 52a of the mounting surface 52 of an electrode 51. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a land structure of a printed wiring board to which an electronic component, in particular, an LED (Light Emitting Diode) is connected via solder.

  In general, in a liquid crystal display device with a built-in liquid crystal display panel in which liquid crystal is filled between a pair of transparent substrates and an electric field is selectively applied to the liquid crystal to display information such as characters and figures, A backlight LED (light emitting diode) for irradiating the liquid crystal display panel with light is provided. Further, the LED for backlight is provided in a liquid crystal display device and mounted on a printed wiring board connected to the liquid crystal display panel in response to a recent demand for miniaturization of the device.

In general, the LED is mounted on the printed wiring board by soldering the electrode of the LED to a land portion provided at a predetermined position of the printed wiring board. More specifically, for example, in a land structure of a printed wiring board including a base material and a conductor provided on the base material, a part of the conductor is exposed from an insulating layer provided on the conductor. In addition to forming a land portion, the LED electrode is soldered to a rectangular electrode mounting portion of the land portion, and the LED is mounted on a printed wiring board (for example, Patent Documents). 1).
JP 2005-136077 A

  In general, as shown in FIG. 6, in the electrode 51 of the LED 50 for backlight, a portion of the surface mounted on the electrode mounting portion of the land portion formed on the printed wiring board (hereinafter referred to as “mounted surface”). ) 52 has a substantially L-shape, but in the land structure described in Patent Document 1, the electrode mounting portion has a rectangular shape as described above. Thus, when the shape of the mounting surface 52 of the electrode 51 and the shape of the electrode mounting portion are different, the solder flowing in the electrode mounting portion 61 of the land portion 60 is solidified as shown in FIG. Of the electrode mounting portion 61 moves to a portion 61a where the mounting surface 52 of the electrode 51 is not mounted. If it does so, the electrode 51 of LED50 on solder will also move to the above-mentioned part 61a in which the to-be-mounted surface 52 is not mounted. Therefore, when the electrode 51 of the LED 50 is connected to the land portion 60 by soldering and the LED 50 is mounted on the printed wiring board, the electrode 51 of the LED 50 is placed outside the electrode mounting portion 61 as shown in FIG. There is a problem that the mounting position of the LED 50 is displaced, and the mounting accuracy of the LED 50 is lowered.

  Accordingly, the present invention has been made in view of the above-described problems, and a print that can prevent a deviation in the mounting position of the LED when the LED is mounted on the printed wiring board by soldering. An object is to provide a land structure of a wiring board.

  In order to achieve the above object, the invention according to claim 1 includes a conductor provided on a base material and an insulating layer provided on the surface of the conductor, and a part of the conductor is formed in the insulating layer. In a land structure of a printed wiring board having an LED connected to the land portion through solder, the land portion is an electrode of the LED. The electrode mounting portion has a shape along the outer periphery of the mounting surface of the electrode.

  According to this configuration, when the solder flowing through the electrode mounting portion of the land portion solidifies, the solder stays in the region of the electrode mounting portion having a shape along the outer periphery of the electrode mounting surface, and the electrode mounting portion Therefore, the movement of the electrode on the solder is prevented, and the electrode remains in the region of the electrode mounting portion. Therefore, when the LED electrode is connected to the land portion by soldering and the LED is mounted on the printed wiring board, it is possible to prevent the LED mounting position from being displaced. Accuracy will be improved.

  The invention according to claim 2 is the land structure of the printed wiring board according to claim 1, wherein the land structure has a plurality of wiring patterns formed of a conductor and connected to the electrode mounting portion, and the plurality of wiring patterns The electrode mounting portion is drawn toward the outside of the opening.

  According to the configuration, even if a crack occurs in a part of a plurality of wiring patterns at the boundary between the opening and the land formed in the insulating layer, the other wiring pattern in which no crack is generated Thus, it is possible to ensure electrical connection between the LED and the printed wiring board.

  The invention according to claim 3 is the land structure of the printed wiring board according to claim 1 or 2, wherein the outer periphery of the electrode mounting portion is arranged outside the outer periphery of the electrode mounting surface. It is characterized by being. According to this configuration, when connecting the electrode of the LED to the land portion by soldering in the electrode mounting portion of the land portion, it is possible to secure the area of the connecting portion by solder.

  The land structure of the printed wiring board according to any one of claims 1 to 3 of the present invention is such that the LED electrode is connected to the land portion by soldering, and the LED is mounted on the printed wiring board. At this time, it has the characteristic that the mounting accuracy of the LED is excellent. Therefore, as in the invention according to claim 4, the printed wiring board land structure according to any one of claims 1 to 3, wherein the electrode mounting surface has a substantially L-shape, It is preferably used when a backlight LED for irradiating light onto a liquid crystal display panel is mounted. According to this configuration, the liquid crystal display panel can be appropriately irradiated with light by the backlight LED.

  According to the present invention, when the LED electrode is mounted on the printed wiring board by connecting the electrode of the LED to the land portion of the printed wiring board by soldering, it is possible to prevent the mounting position of the LED from being displaced. Thus, the mounting accuracy of the LED is improved.

  Hereinafter, a preferred embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing a schematic configuration of a printed wiring board according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a state where LEDs are mounted on the printed wiring board shown in FIG. 3 is a plan view showing a land structure of the printed wiring board according to the embodiment of the present invention, and FIG. 4 is a plan view showing a state where LEDs are mounted on the land structure of the printed wiring board shown in FIG. FIG. FIG. 5 is a partially enlarged view of FIG. In the present embodiment, a land structure of a printed wiring board on which a backlight LED for irradiating light to a liquid crystal display panel built in the liquid crystal display device is mounted will be described as an example.

  The printed wiring board 1 is obtained by forming a conductor 4 with a predetermined pattern on a base material 2 formed of a flexible resin film with an adhesive layer 3 interposed therebetween. Further, a coverlay film 5 that is an insulating layer is provided on the surface of the conductor 4 so as to cover the conductor 4. The cover lay film 5 is composed of an adhesive layer 6 laminated on the conductor 4 and a resin film 7 laminated thereon so as to cover the conductor 4.

  As shown in FIGS. 1 and 3, the cover lay film 5 has an opening 8 for exposing a part of the conductor 4. In this embodiment, a part of the conductor 4 is formed. The land portion 9 is formed by exposing through the opening 8 formed in the coverlay film 5. The land portion 9 is formed with an electrode mounting portion 10 on which the electrode 51 provided on the main body 53 of the LED 50 for backlight is mounted.

  Then, as shown in FIG. 2, in the electrode mounting portion 10 of the land portion 9, the electrode 51 of the LED 50 is connected to the land portion 9 via the solder 11, thereby electrically connecting the LED 50 and the printed wiring board 1. The LED 50 is mounted on the printed wiring board 1.

  As the resin film 7 constituting the base material 2 and the coverlay film 5, a resin material having excellent flexibility is used. Examples of the resin material include polyamide resin, polyimide resin, polyamideimide resin, Any general-purpose resin for printed wiring boards, such as a polyester resin, can be used. Of these resins, it is preferable to have high heat resistance in addition to flexibility, particularly considering resistance to molten solder, and examples of such resins include polyamide resins, polyimide resins, and polyamides. An imide resin is preferably used.

  The adhesive constituting the adhesive layers 3 and 6 is preferably an adhesive having excellent flexibility and heat resistance. Examples of such an adhesive include nylon, epoxy resin, butyral resin, and acrylic resin. And various resin adhesives. Further, as the metal foil constituting the conductor 4, a copper foil is preferably used. Moreover, the electrode 51 of LED50 is comprised by copper, silver, lead, or these alloys, for example. As the solder 11, for example, a solder paste containing 95 wt% or more of tin can be suitably used. In consideration of the environment, it is preferable to use a solder paste containing no lead.

  Here, the present embodiment is characterized in that the electrode mounting portion 10 of the land portion 9 has a shape along the outer periphery 52 a of the mounting surface 52 of the electrode 51 of the LED 50. More specifically, as shown in FIG. 4, the electrode mounting portion 10 of the land portion 9 has substantially the same shape as the mounting surface 52 of the electrode 51 of the LED 50, that is, the outer periphery of the mounting surface 52 of the electrode 51. It is characterized in that it has a substantially L-shape along 52a.

  With such a configuration, when the solder 11 flowing through the electrode mounting portion 10 of the land portion 9 is solidified, the solder 11 has an electrode along the outer periphery 52 a of the mounting surface 52 of the electrode 51. Since it is possible to effectively prevent the solder 11 from moving outside the electrode mounting portion 10 while remaining in the region of the mounting portion 10, the movement of the electrode 51 on the solder 11 is prevented. It stays in the region of the electrode mounting portion 10. Accordingly, when the LED 51 is mounted on the printed wiring board 1 by connecting the electrode 51 of the LED 50 to the land portion 9 by soldering, it is possible to prevent the mounting position of the LED 50 from being displaced, The mounting accuracy of the LED 50 is improved. As a result, the liquid crystal display panel (not shown) can be appropriately irradiated with light by the backlight LED 50.

  That is, when mounting the LED 50 on the printed wiring board 1, first, the solder 11 is provided on the land portion 9, and the electrode 51 of the LED 50 is mounted on the electrode mounting portion 10 of the land portion 9 via the solder 11. Put. Next, the solder 11 is melted by heat treatment. At this time, the melted solder 11 flows on the land portion 9, but the electrode mounting portion 10 of the land portion 9 has substantially the same shape as the mounting surface 52 of the electrode 51 of the LED 50 (that is, substantially L-shaped). Therefore, the electrode 51 of the LED 50 on the solder 11 does not move out of the electrode mounting portion 10 and remains mounted on the electrode mounting portion 10 as shown in FIG.

  Next, the molten solder flowing through the electrode mounting portion 10 of the land portion 9 is solidified to connect the electrode 51 of the LED 50 to the land portion 9. At this time, the electrode mounting portion 10 of the land portion 9 is connected to the electrode 50 of the LED 50. Therefore, it is possible to effectively prevent the solder 11 in the electrode mounting portion 10 from moving outside the electrode mounting portion 10 because the mounting surface 52 has substantially the same shape (that is, substantially L-shaped). it can. Therefore, the electrode 51 of the LED 50 on the solder 11 shown in FIG. 4 can be kept mounted on the electrode mounting portion 10. Therefore, it is possible to prevent the deviation of the mounting position of the LED 50.

  Further, in the land structure of the present embodiment, as shown in FIG. 5, the land structure includes a plurality of wiring patterns 20 to 22 formed of the conductor 4 and connected to the electrode mounting portion 10. From the electrode mounting part 10, it is set as the structure pulled out toward the outer side of the opening part 8 of the coverlay film 5 (namely, toward the direction of arrow X, Y, Z in a figure).

  In general, after the LED 50 is mounted, cracks are likely to occur in the wiring pattern formed by the conductor at the boundary portion between the opening 8 and the land portion 9 of the coverlay film 5, but as described above, the electrode mounting portion 10 By pulling out the connected wiring patterns 20 to 22 from the electrode mounting portion 10 toward the outside of the opening 8 of the coverlay film 5, the boundary portion between the opening 8 and the land portion 9 of the coverlay film 5 In other wiring patterns 21 and 22 where no crack is generated even if a crack occurs in a part of the wiring patterns 20 to 22, for example, the wiring pattern 20, the LED 50 and the printed wiring board 1 It is possible to ensure electrical connection.

  In addition, this invention is not limited to the said embodiment, A various design change is possible based on the meaning of this invention, and they are not excluded from the scope of the present invention.

  For example, as shown in FIG. 5, the electrode mounting portion 10 of the land portion 9 is shaped along the outer periphery 52 a of the mounting surface 52 of the electrode 51, and the outer periphery 10 a of the electrode mounting portion 10 is It is good also as a structure arrange | positioned outside the outer periphery 52a of the mounting surface 52. FIG. With such a configuration, when the electrode 51 of the LED 50 is connected to the land portion 9 by soldering in the electrode mounting portion 10 of the land portion 9, the area of the connection portion by the solder 11 can be ensured. . At this time, the outer periphery 10a of the electrode mounting portion 10 is mounted so that the distance D between the outer periphery 10a of the electrode mounting portion 10 and the outer periphery 52a of the mounting surface 52 of the electrode 51 is 0.1 mm or less. It is preferable to arrange the outer surface 52a of the surface 52 outside.

  Moreover, in the said embodiment, although demonstrated using LED50 for backlights as an example as an electronic component mounted in the printed wiring board 1, the land structure of the printed wiring board 1 of this invention has a chip capacitor, a chip | tip. Also when mounting electronic components such as resistors and connectors on the printed wiring board 1, it can be suitably used.

  As an application example of the present invention, there is a land structure of a printed wiring board in which LEDs are connected via solder.

It is sectional drawing which shows schematic structure of the printed wiring board in embodiment of this invention. It is sectional drawing which shows the state which mounted LED in the printed wiring board shown in FIG. It is a top view which shows the land structure of the printed wiring board which concerns on embodiment of this invention. It is a top view which shows the state which mounted LED in the land structure of the printed wiring board shown in FIG. It is the elements on larger scale of FIG. It is the schematic for demonstrating the shape of the electrode of LED for backlights. It is a top view which shows the land structure of the conventional printed wiring board. It is a top view which shows the land structure of the conventional printed wiring board.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Printed wiring board, 2 ... Base material, 4 ... Conductor, 5 ... Coverlay film (insulating layer), 8 ... Opening part, 9 ... Land part, 10 ... Electrode mounting part, 10a ... Outer periphery of electrode mounting part, 11 DESCRIPTION OF SYMBOLS: Solder, 20 ... Wiring pattern, 21 ... Wiring pattern, 22 ... Wiring pattern, 50 ... LED, 51 ... Electrode, 52 ... Electrode mounting surface, 52a ... Periphery of electrode mounting surface, D ... Electrode mounting portion Distance between the outer circumference and the outer circumference of the electrode mounting surface

Claims (4)

A land portion formed by exposing a part of the conductor from an opening formed in the insulating layer, comprising a conductor provided on the substrate and an insulating layer provided on the surface of the conductor In the land structure of the printed wiring board in which the LED is connected to the land portion through the solder of the printed wiring board having
The land portion includes an electrode mounting portion on which the electrode of the LED is mounted, and the electrode mounting portion has a shape along an outer periphery of a mounting surface of the electrode. Construction.   A plurality of wiring patterns are formed by the conductor and connected to the electrode mounting portion, and the plurality of wiring patterns are led out from the electrode mounting portion toward the outside of the opening. The land structure of the printed wiring board according to claim 1.   The land structure of the printed wiring board according to claim 1, wherein an outer periphery of the electrode mounting portion is disposed outside an outer periphery of a mounting surface of the electrode.   The mounting surface of the electrode has a substantially L shape, and the LED is an LED for a backlight that irradiates light to a liquid crystal display panel. Land structure of the printed wiring board described.

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