JP2003051648A - Flexible printed board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible printed board, in which disconnection of a leading wire can be prevented, by reducing the tension applied to the lead wire from a component land in forming surface mounting component land of a small- sized component in a multilayer FPC (flexible printed circuit). SOLUTION: In the multilayer FPC for mounting the surface mounting component 11, when the lead wire 13a from a conductor land 12 for mounting a component is not covered with a surface coverlay film 14, either/both a conductor 24 on the rear surface of the wire 13a or/and a coverlay film 25 on the rear surface of the wire 13a is/are removed. By so doing, even if the multilayer FPC is bent, absence of either/both the conductor 24 or/and the film 25 reduces the tension 29 applied to the wire 13a, and the disconnection of the wire tends not to occur.

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a flexible printed circuit board on which electronic components or electronic circuit components are mounted, and more particularly to a conductor from a conductor land for mounting a surface mount component. The present invention relates to a flexible printed circuit board for preventing breakage of a lead line when the line lead line is not covered with a coverlay film. 2. Description of the Related Art With the miniaturization of electronic products, miniaturization of electric circuit boards has been promoted, and components mounted on the boards also tend to be miniaturized. FIGS. 6 and 7 show mounting lands for electronic components on a conventional flexible printed circuit board (hereinafter, referred to as FPC). FIG. 6 shows mounting lands for components of a normally used size (normal size components), and FIG. 7 shows mounting lands for components of smaller size (small size components). Here, the normal size part is a part size of 1.6.
It refers to a surface mount component of about mm × 0.8 mm (hereinafter, 1608 size) or more. Also, the small-sized component refers to a small surface-mounted component having a component size of 1.0 mm × 0.5 mm (hereinafter, 1005 size) or 0.6 mm × 0.3 mm (hereinafter, 0603 size). I have. In FIG. 6, when a component 1 of a normal size is mounted as a component to be mounted, conductive lands (hereinafter, component lands) 2 formed on a base material to have a large area for component mounting are provided.
2 and conductor lines 3 and 3 respectively connected thereto, and a cover lay film 4 having a cover lay opening 4a exposes the mounted component 1 and a part of the component lands 2 and 2 and the component lands 2 and 3. , 2 are pressed. Furthermore, between the component lands 2 and 2, a mounted component 1 of a normal size having electrodes (not shown) at both ends is soldered. That is, it is designed such that part of the component lands 2 and 2 and the conductor lines 3 and 3 are held down by the cover lay film 4 so that the component lands 2 and 2 and the conductor lines 3 and 3 do not come off from the base material. [0005] In mounting normal size components as shown in FIG.
The shape is such that the component land 2 is covered with the coverlay film 4 on at least one of the four sides of the component land 2 on which the component 1 is mounted. In this case, since the periphery of the component land 2 is relatively widely covered by the cover lay film 4, even if the FPC is bent and bending stress is applied to the component land 2, the conductors of the component land portions 2 and 2 are not easily disconnected. However, in mounting small-sized components having small component dimensions, if a land shape in which the periphery of the component land is covered with a cover lay film as in the case of the normal size component described above (FIG. 6), a cover for the component land is used. The influence of the sticking of the ray film becomes remarkable, and the land shape becomes unbalanced, so that phenomena such as component inversion and non-connection occur at the time of component mounting. [0007] In order to prevent this, when mounting small-sized components, as shown in FIG.
Is made larger than the component land 12 so that all four sides of the component land 12 are exposed. In FIG. 7, when a small-sized component 11 is mounted as a mounted component, component lands 12, 12 for component mounting and conductor lines 13, 13 respectively connected to the component lands 12 are arranged on a base material. Also coverlay opening 14a
Are formed on the component lands 12, 12 for component mounting and the conductor lines 1 connected thereto.
3 and 13 are attached in a state where the lead wires 13a and 13a are exposed. Further, between the component lands 12, 12, a small-sized mounting component 11 having electrode portions (not shown) at both ends is soldered. As a result, the mounting component 11 and the component lands 12, 12 are opened from the coverlay opening 14a.
And a lead wire 13a which is a part of the conductor line 13, 13,
13a is exposed to the outside. [0009] However, in the case of FIG.
The lead line 13a from the component land 12 is connected by a thin conductor pattern. For this reason, when the FPC is a multilayer FPC having the conductor pattern 24 and the coverlay film 25 on the back surface side of the mounting surface of the component 11 as shown in FIG. A tension 29 is applied to the outermost lead wire 13a.
As a result, the lead wire 13a is easily broken because it is not protected by the cover lay film. In FIG. 8, reference numeral 22 denotes a front surface conductor pattern (including the conductor line 13), 23 denotes a base material, 24 denotes a back surface conductor pattern, 25 denotes a back cover lay film,
Reference numeral 6 denotes solder for fixing the component 11. Normally, as shown in FIG. 9, the bent part 32 of the FPC 31 and the part 11 are separated from each other, and are arranged so as not to apply bending stress as close to the part land as possible.
The bending stress is applied to the parts lands in the vicinity of the parts lands even if the FPC is formed or handled during the process.
There is a possibility that the lead wire 13a is disconnected at the portion 27 as shown in FIG. In order to prevent disconnection of the lead wire 13a,
There is also a method of attaching a reinforcing plate to the back surface, but this increases the cost. Further, as shown in FIG.
There is a method in which a reinforcing conductor 15 is left around a to make the FPC hard to bend. However, there may be a case where a conductor that can sufficiently reinforce the space cannot be left. In view of the above-mentioned problems, the present invention reduces the tension applied to a lead line from a component land when forming a surface-mounted component land of a small-sized component having a size of 1005 or less in a multilayer FPC. An object of the present invention is to provide a flexible printed circuit board capable of preventing disconnection of a lead wire. A flexible printed circuit board according to the present invention is a multi-layered flexible printed circuit board on which a surface mount component is mounted, wherein a lead from a conductor land for mounting the component is a coverlay film. When not covered, the conductor on the back surface of the lead wire and / or the coverlay film on the back surface of the lead wire are removed. As described above, even if the multilayer FPC is bent by removing both or one of the conductor and the coverlay film directly behind the mounting surface of the lead wire,
Since there is no conductor on the back surface of the lead wire and / or either of the cover lay film, the tension applied to the lead wire becomes small, and the wire is hardly broken. Embodiments of the present invention will be described with reference to the drawings. [First Embodiment] FIG. 1 is a back view and a front view of a flexible printed circuit (FPC) according to a first embodiment of the present invention. FIG. 1A is a rear view, and FIG. 1B is a front view. FIG. 2 is a cross-sectional view taken along line AA of FIG. In these figures, the FPC includes a component 11 mounted on the surface of the FPC, component lands 12 and 12 on which electrode portions (not shown) of the component 11 are mounted, and component lands 12 and 12. From the conductor line 13,
13, a surface coverlay film 14, a surface conductor pattern 22 (including the conductor line 13), and a base film 2 serving as a base material.
3, a back conductor pattern 24 formed on the back side of the base film 23, a back cover lay film 25, and solder 26 for fixing the electrode portion of the component 11 to the component land 12. Each component 14, 2
In some cases, an adhesive for connecting 2, 23, 24, and 25 to each other is provided, but is omitted in the drawings. As shown in FIGS. 1 (b) and 2, component lands 12, 12 for soldering the electrodes of the component 11 are formed on the surface of the FPC by removing the surface cover lay film 14. Further, the lead lines 13a, 13a from the component lands 12, 12 are also formed on the surface coverlay film 14.
The surface conductor pattern 22 connected to the lead wires 13a, 13a is covered with the surface cover lay film 14 without being covered with the lead wire 13a. On the other hand, on the back surface of the FPC, FIG.
As shown in FIG. 2, the back conductor pattern 24 and the back cover lay film 25 are removed from a portion 28 (and 17) located directly behind the lead wire 13a. FIG. 3 shows a state in which the FPC is bent by the lead wire 13a from the unbent state in FIG.
Since there is no conductor 24 and no coverlay 25 in the portion 28 located directly behind the leader line 13a, the tension 29 applied to the apex 27 of the bent portion is reduced, and the leader line 13a is less likely to break. [Second Embodiment] FIG. 4 shows a second embodiment of the present invention.
3 shows a cross-sectional view when the FPC is bent according to the embodiment. The same parts as those in FIG. 3 are denoted by the same reference numerals. FIG. 4 shows an example in which the back coverlay film 25 is removed from the portion 28 (and 17) located directly behind the lead line 13a. Back conductor pattern 2
4 is not removed, so that the effect of preventing disconnection is inferior to that of the first embodiment. However, if the back conductor 24 cannot be removed for the purpose of shielding or the like, the coverlay film 25
The method of FIG. 4 in which only the conductor 24 is removed and only the conductor 24 is removed is effective in preventing disconnection. [Third Embodiment] FIG. 5 shows a third embodiment of the present invention.
3 shows a cross-sectional view when the FPC is bent according to the embodiment. The same parts as those in FIG. 3 are denoted by the same reference numerals. FIG. 5 shows an example in which the back conductor pattern 24 is removed from a portion 28 located directly behind the lead line 13a. Since the back cover lay film 25 is not removed, the effect of preventing disconnection is inferior to that of the first embodiment. However, if the back cover lay film 25 cannot be removed for any purpose, only the conductor 24 is removed and the cover lay film is removed. The method shown in FIG. As described above, according to the present invention, when a surface-mounted component land of a small-sized component is formed in a multi-layer FPC, the conductor pattern and the cover lay on the back surface of the lead wire from the component land are formed. By removing both or one of the films, the tension applied to the lead wire can be reduced, and disconnection can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a back view and a front view of an FPC according to a first embodiment of the present invention. FIG. 2 is an FPC sectional view in the first embodiment of FIG. 1; FIG. 3 is a cross-sectional view when the FPC in FIG. 2 is bent. FIG. 4 is a cross-sectional view at the time of FPC bending according to a second embodiment of the present invention. FIG. 5 is a cross-sectional view at the time of FPC bending according to a third embodiment of the present invention. FIG. 6 is a plan view showing an example of a conventional component land of a normal size component having a size of 1608 or more. FIG. 7 is a plan view showing an example of a component land of a conventional small-sized component having a size of 1005 or less. 8 is an FPC cross-sectional view of the example small component part land of FIG. 7 when the lead wire is disconnected. FIG. 9 is a perspective view showing the positional relationship between FPC bending and component positions. FIG. 10 is a plan view showing a conventional example of preventing lead wire disconnection in a component land example of a small-sized component. [Description of Signs] 11 ... Mounted part 12 ... Conductor land (part land) 13 ... Conductor line 14 ... Surface coverlay film 14a ... Coverlay opening 22 ... Surface conductor pattern 23 ... Base film (base material) 24 ... Backside conductor pattern 25 ... Back coverlay film

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Sayuri Watanabe             2-43-2 Hatagaya, Shibuya-ku, Tokyo Ori             Inside of Opus Optical Co., Ltd. F term (reference) 5E314 BB05 BB12 CC15 FF06 FF11                       GG12                 5E336 AA04 AA16 BB02 BB03 BB12                       BC23 BC34 CC31 CC32 GG14                       GG16                 5E338 AA02 AA03 AA12 BB71 BB75                       CC07 CC10 CD33 EE27 EE28

Claims (1)

Claims: 1. In a multilayer flexible printed circuit board on which a surface mount component is mounted, if the lead wire from the conductor land for mounting the component is not covered with a coverlay film, the drawer is provided. A flexible printed circuit board, wherein a conductor on the back surface of the wire and / or a coverlay film on the back surface of the lead wire are removed.