JP5003113B2 - Flexible wiring board connection structure - Google Patents

Description

  The present invention relates to a connection structure and a connection method for a flexible wiring board, and more particularly to a connection structure and a connection method for a flexible substrate having a multilayer structure.

Electronic devices such as mobile phones are increasingly required to be smaller, lighter, and thinner. In order to satisfy these requirements, the key points are how many spaces are laid out in the electronic device casing and how efficiently electronic components and structural components are arranged in the spaces.

2. Description of the Related Art In recent years, electronic devices such as mobile phones are often used with flexible wiring boards that can be bent and used with the feature of flexibility and can give a limited space a degree of freedom. As a connection method between the flexible wiring board and the printed wiring board, a connector is mounted on both the flexible wiring board and the printed wiring board, and each is connected (Board to Board), or a plug-in type connector is connected to the printed wiring board. There is a method of mounting and connecting a terminal provided on a flexible wiring board by connecting, but it is necessary to mount a connector on each wiring board, and the height of the connector is required.

Recently, in order to reduce the size, weight, and thickness of electronic devices such as mobile phones, connection by thermocompression that does not require a connector has been adopted as a method of connecting a flexible wiring board and a printed wiring board. For thermocompression bonding, an anisotropic conductive film (ACF), which is a thermocompression film containing conductive particles, is sandwiched between a flexible wiring board and a printed wiring board, and the thermocompression bonding is performed from above the flexible wiring board. This is possible.

The flexible wiring board to be connected by thermocompression bonding is provided with a pattern wiring only on one side of the base material, which is a polyimide resin, and a polyimide cover film is bonded to the outside of the wiring pattern on the surface in order to insulate the outside. It is pasted with an agent. The polyimide cover film is opened as necessary for the thermocompression-bonding terminal portion of the flexible wiring board and other terminal portions. The cover film and the base material on the front surface are translucent, and the pattern on the front surface side can be confirmed from the back surface side.

In order to further reduce the size, weight, and thickness in the future, more wiring patterns are required in a narrower flexible wiring board width, and one layer cannot fit. In order to accommodate many of these wiring patterns within a predetermined flexible wiring board width, it is unavoidable to make the wiring layers multilayer. In this case, since the front surface side cannot be seen through from the back surface side of the thermocompression bonding terminal, the spread of the resin of the anisotropic conductive film cannot be visually confirmed after the thermocompression bonding, and it is necessary to check all the continuity.

In order to visually confirm the spread of the resin after thermocompression bonding, for example, the layer other than the layer having the thermocompression bonding terminal of the multilayer flexible wiring board is patterned with the same or larger area as the area including all the thermocompression bonding terminals. By providing a non-transparent area and using only a semi-transparent polyimide base material and cover film, the front side can be confirmed from the back side of the thermocompression terminal, and the spreading of the resin of the anisotropic conductive film can be confirmed visually. (For example, refer to Patent Document 1).

JP 2003-209141 A (stages 0013 to 0015, FIG. 1)

  However, in the connection structure of the conventional flexible wiring board, since there is no pattern on the other layer of the thermocompression bonding terminal portion, it is necessary to avoid that portion, and there is a problem that the wiring pattern is restricted. . In addition, there is a problem that by avoiding the wiring pattern, the area of the flexible wiring board that is avoided increases. Furthermore, since there is a region where no wiring pattern is provided, there is a problem that the electrical performance of the connection portion is deteriorated due to the influence of external noise.

  The present invention has been made in order to solve the above-described problems, and it is possible to visually confirm the spread of the resin of the anisotropic conductive film without significantly avoiding the wiring pattern. It is an object to provide a connection structure and a connection method for a flexible wiring board.

The connection structure of the flexible wiring board according to the present invention includes a printed wiring board on which an electrical component is mounted and a wiring pattern having a connecting terminal part disposed thereon, and a connection terminal part that is connected to the connection terminal part of the printed wiring board. A wiring pattern having a central portion of the connecting portion, and a thermocompression bonding of the flexible wiring substrate having at least one window portion outside the connecting terminal of the connecting portion, and the printed wiring board and the flexible wiring substrate. An anisotropic conductive film that melts and flows to electrically connect the connection terminal portion of the printed wiring board and the connection terminal portion of the flexible wiring board,
The anisotropic conductive film is provided at a position where the flow state of the end portion of the anisotropic conductive film can be confirmed through the window portion of the flexible wiring board.

According to the present invention, even in the connection of a multilayer flexible wiring board, a wiring pattern is provided by providing a window outside the connection terminal portion of the flexible wiring board within the range of the flow peripheral edge of the anisotropic conductive film. Without significantly avoiding from the connection terminal region, the spread of the resin of the anisotropic conductive film can be visually confirmed, and the reliability can be improved.

Further, the wiring pattern can be arranged without greatly avoiding from the connection terminal region, and the area of the flexible wiring board can be reduced. Furthermore, the electrical performance of the connecting portion can be improved without being affected by external noise.

Hereinafter, various embodiments of a connection structure and a connection method of a flexible wiring board according to the present invention will be described with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a plan perspective view showing the configuration of the flexible wiring board connection structure according to the first embodiment, and FIG. 2 is a cross-sectional view taken along the line II in FIG.

  As shown in FIGS. 1 and 2, a plurality of terminals 2 as connection terminal portions are arranged in parallel at a predetermined interval on the printed wiring board 1. At positions facing the terminals 2 of the printed wiring board 1, a plurality of terminals 4 serving as connection terminal portions provided in the same manner as the connection portions 3 a of the flexible wiring board 3 are disposed. The connection portion 3a between the printed wiring board 1 and the flexible wiring board 3 is connected by an anisotropic conductive film 5 in which metal particles 5b as conductive particles are uniformly dispersed in a thermosetting resin 5a as a thermocompression bonding film, The terminal 2 of the printed wiring board 1 and the terminal 4 of the connection portion 3a of the flexible wiring board 3 are electrically connected with the metal particles 5b included in the anisotropic conductive film 5 interposed therebetween.

  The flexible wiring board 3 is composed of two polyimide film layers 6. Wiring patterns 7a, 7b, and 7c are disposed on both surfaces and layers of the two polyimide film layers 6. In the connection portion 3a of the flexible wiring board 3, the wiring pattern 7a disposed on one surface includes A plurality of terminals 4 for connecting to the terminals 2 of the printed wiring board 1 are arranged in parallel. The wiring patterns 7a, 7b, 7c are connected to each other through through holes or the like (not shown).

  The connection portion 3a of the flexible wiring board 3 is provided with a window portion 8 at the position of the flow end portion of the anisotropic conductive film 5 in the vicinity of both ends outside the plurality of terminals 4 arranged in parallel, and the wiring pattern 7a. , 7b, 7c are disposed without overlapping the window portion 8. The window portion 8 is provided in such a size that the flow state of the flow end portion of the anisotropic conductive film 5 can be confirmed from the direction A through the two semi-transparent polyimide film layers 6. .

  Next, a connection method will be described. First, as shown in FIG. 3, the anisotropic conductive film 5 is attached to the inside of the window portion 8 so as to cover a part of all the terminals 4 at the connection portion 3 a of the flexible wiring board 3, and then flexible. The flexible wiring board 3 is arranged on the printed wiring board 1 so that the terminals 4 of the connecting portions 3a of the wiring board 3 are located at the terminals 2 of the printed wiring board 1 facing each other with the anisotropic conductive film 5 interposed therebetween. To do.

The flexible wiring board 3 is positioned by inserting positioning pins (not shown) provided on the printed wiring board 1 into positioning holes (not shown) provided on the flexible wiring board 3. Moreover, you may perform by the image recognition by the target mark provided on the printed wiring board 1 and the flexible wiring board 3. FIG.

  As shown in FIG. 4, the connecting portion 3a of the flexible wiring board 3 and the printed wiring board 1 sandwiching the anisotropic conductive film 5 are subjected to a desired pressure by a thermocompression bonding head 9 heated to a desired temperature from the B direction. Is heated and pressurized. In the anisotropic conductive film 5, the thermosetting resin 5 a is melted by heating and pressing with the thermocompression bonding head 9, and is in close contact with the flexible wiring board 3 and the printed wiring board 1. Further, the metal particles 5b are brought into contact and electrically connected by being sandwiched between the terminal 4 of the flexible wiring board 3 and the terminal 2 of the printed wiring board 1.

  The anisotropic conductive film 5 inside the window portion 8 spreads to the window portion 8 by melting the thermosetting resin 5a, and the flow state and the molten state of the anisotropic conductive film 5 are confirmed from the window portion 8. Is done. Since the wiring patterns 7b and 7c are provided in the region of the terminal 4 of the flexible wiring board 3, it is possible to prevent the influence of noise from the outside and to suppress the deterioration of the electrical performance of the connecting portion.

  As described above, in the first embodiment, even in the region of the terminal 4 of the flexible wiring board 3, the wiring patterns 7 b and 7 c are arranged in multiple layers, near both ends outside the plurality of terminals 4 arranged in parallel. Since the window 8 is provided at the position of the flow end of the anisotropic conductive film 5, the flow state and melting of the anisotropic conductive film can be avoided without greatly avoiding the wiring pattern from the terminal region. The state can be confirmed from the window portion, and the reliability can be improved in the adhesion of the connection portion.

  In addition, since the wiring pattern is arranged in multiple layers in the region of the terminal 4, not only the area of the flexible wiring board can be reduced, but also the electrical reliability of the connection portion is not affected by external noise. It is possible to improve the performance.

Embodiment 2. FIG.
In the flexible wiring board connection structure and connection method of the first embodiment, the case where the window portion 8 made of a transparent member is provided has been described. In the second embodiment, a case where a window portion including a punched hole is provided will be described.

  FIG. 5 is a plan perspective view showing the configuration of the flexible wiring board connection structure according to the second embodiment, and FIG. 6 is a cross-sectional view taken along the line II-II in FIG.

  As shown in FIGS. 5 and 6, in the connection portion 10 a of the flexible wiring substrate 10, the window portion 11 is a punched hole, and the anisotropic conductive film 5 melted and flowed by heating and pressurization at the time of connection. Flows out of the window portion 11 and hardens to form a rivet-like portion 5c. Other configurations are the same as those in the first embodiment, and the corresponding parts are denoted by the same reference numerals as those in FIGS. 1 and 2 and description thereof is omitted.

  As a connecting method, the connecting portion 10a of the flexible wiring board 10 with the anisotropic conductive film 5 and the printed wiring board 1 are heated to a desired temperature from the B direction as shown in FIG. 12 is heated and pressurized at a desired pressure. FIG. 8 shows a side sectional view of the window portion 11 during heating and pressurization. The thermocompression bonding head 12 is provided with a recessed portion 12 a that is larger than the opening and is not in contact with the anisotropic conductive film 5 that has flowed out. The other connection methods are the same as those in the first embodiment, and the corresponding parts are denoted by the same reference numerals as those in FIGS. 7 and 8 and the description thereof is omitted.

  The anisotropic conductive film 5 located inside the window portion 11 spreads to the window portion 11 due to melting of the thermosetting resin 5a, and flows out of the window portion 11 serving as a hole, thereby causing the anisotropic conductive film 5 to flow out. The flow state and the molten state of 5 are confirmed. Further, the anisotropic conductive film 5 that has flowed out is cured to form a rivet-like portion 5c, thereby further strengthening the connection between the connection portion 10a of the flexible wiring board 10 and the printed wiring board 1.

  As described above, in the second embodiment, the window portion 11 of the connection portion 10a of the flexible wiring board 10 is formed as a hole, and the anisotropic conductive film 5 that has flowed out is cured to form a rivet-like portion 5c. Therefore, the connection between the flexible wiring board and the printed wiring board can be further strengthened, and the reliability can be further improved in the adhesion of the connecting portion.

  In the present embodiment, a two-layer flexible wiring board is used, but the present invention is not limited to this. This is effective not only when the flexible wiring board has three or more layers but also when an opaque flexible wiring board is used.

  Moreover, in this Embodiment, although the metal particle 5b was used for the electroconductive particle disperse | distributed to the anisotropic conductive film 5, you may use a solder as the metal particle 5b. In this case, by controlling the heating temperature, the terminals 4 of the flexible wiring board and the terminals of the printed wiring board can be soldered, and the reliability can be further improved in electrical connection.

  Further, in the present embodiment, multilayer wiring patterns are arranged in the region of the terminals 4 of the flexible wiring board to suppress the influence of noise from the outside. However, the entire surface of one of the wiring patterns in the region of the terminals 4 is solid. It is more effective to provide wiring.

It is a plane perspective view which shows the structure of Embodiment 1 of the connection structure of the flexible wiring board which concerns on this invention. It is a sectional side view which shows the structure of Embodiment 1 of the connection structure of the flexible wiring board based on this invention. It is a side view which shows the connection method of Embodiment 1 of the connection structure of the flexible wiring board which concerns on this invention. It is a top view which shows the connection method of Embodiment 1 of the connection structure of the flexible wiring board which concerns on this invention. It is a plane perspective view which shows the structure of Embodiment 2 of the connection structure of the flexible wiring board which concerns on this invention. It is a sectional side view which shows the structure of Embodiment 2 of the connection structure of the flexible wiring board based on this invention. It is a side view which shows the connection method of Embodiment 2 of the connection structure of the flexible wiring board which concerns on this invention. It is a sectional side view which shows the connection method of Embodiment 2 of the connection structure of the flexible wiring board based on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printed wiring board 2 Terminal 3 Flexible wiring board 4 Terminal 5 Anisotropic conductive film 7a, 7b, 7c Wiring pattern 8 Window part 10 Flexible wiring board 11 Window part

Claims (5)

A printed wiring board on which electrical components are mounted and a wiring pattern having a connection terminal portion is disposed;
A wiring pattern having a connection terminal portion connected to the connection terminal portion of the printed wiring board in a central portion of the connection portion is disposed, and at least one window portion is provided outside the connection terminal of the connection portion. Flexible wiring board,
Anisotropy for electrically connecting the connection terminal portion of the printed wiring board and the connection terminal portion of the flexible wiring board by melting and flowing by thermocompression bonding the printed wiring board and the flexible wiring board With a conductive film,
The anisotropic conductive film is
A connection structure for a flexible wiring board, wherein the flexible wiring board is provided at a position where the flow state of the end portion of the anisotropic conductive film can be confirmed through the window portion of the flexible wiring board.   The flexible wiring board connection structure according to claim 1, wherein the window portion is made of a transparent member.   The flexible wiring board connection structure according to claim 1, wherein the window portion is formed of a punched hole.   4. The flexible wiring board connection structure according to claim 3, wherein the anisotropic conductive film is melted at the time of thermocompression bonding and flows out of the window portion, and then a part thereof is cured in a rivet shape.   The flexible wiring board connection structure according to any one of claims 1 to 4, wherein the flexible wiring board comprises a multilayer wiring board.

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