JPH0231874B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of connecting a printed circuit board and a flexible circuit board.

[Conventional technology]

2. Description of the Related Art Not only electronic devices for home use but also various devices for in-vehicle use are required to be more and more multi-functional, smaller, and less expensive. Under these circumstances, the number of switches and displays on the front operation panel tends to increase, so it is common to use a flexible board for the connection between the panel side circuit board and the device body side circuit board. Become. In this case, if a connector is used to connect the flexible board and the circuit board (printed board), it is not only difficult to downsize, but also expensive. Therefore, a simple soldering method is often used.

FIG. 4 shows an example of this type of board connection method, in which numeral 1 represents an electronic device housing, and 2 represents its front panel. The front part of this device consists of a front decorative plate 2 and a front board (printed circuit board) 3, and the board has LEDs (light emitting diodes) 31 for various indicators and switches 3.
2 is installed. 4 is a main body board (printed board), which is connected to the front board 3 by a wide flexible board 5. In addition, a display LED array 33 is attached to the front substrate 3, but since the number of wires on the flexible substrate 5 is insufficient for connection between it and the main substrate 4, another flexible substrate 6 is used.

These two flexible substrates 5 and 6 are combined into one
When soldering a printed circuit board 4, conventionally the connection portion is as shown in FIG. 4b. The figure is a bottom view of a, and numeral 41 indicates various chip parts soldered to the conductive pattern (not shown) of the board 4. The flexible substrates 5 and 6 have a plurality of soldering lands 5 along the edges of their surfaces (outer surfaces).
1,61 are arranged in one row. 42 and 43 are soldering lands arranged on the surface (outer surface) of the main substrate 4 at pitches corresponding to the lands 51 and 61. Note that the wiring patterns connected to these lands are omitted in the drawing. FIGS. 4c and 4d are partially enlarged views, and numeral 7 indicates a soldering portion on the lands 51 and 42.

[Problem that the invention seeks to solve]

In the above structure, the land 42 of the substrate 4 is the fourth
As shown in Figure a, the minimum dimensions of pattern pitch a and pattern width b are restricted from the viewpoint of manufacturing technology or from the viewpoint of avoiding solder bridges, so there is a limit to the number of arrangements. Therefore, if the total number of lands on the flexible substrates 5 and 6 exceeds the maximum number of lands 42 arranged, lands 43 in a different column from the lands 42 are required.

By the way, the main board 4 and the flexible board 5,
When soldering chip part 6,
Since this is after the first components have been mounted, soldering is performed with the back cover 11 of the casing 1 attached as shown in FIG. 4B in order to protect these components. However, if the back cover 11 completely covers the board connection part, soldering cannot be performed, so a minimum notch 12 is formed in the back cover 11. and,
This notch 12 is closed by the lower cover part 21 of the front decorative plate 2 during assembly.

In an electronic device having such a housing structure, the notch 1
If the area (A x B) of 2 is large, the area of the bottom cover part 21 that closes it will also be large, and if the front decorative plate 2 is made of a resin material, the disadvantage is that distortion will occur in the integrally molded bottom cover part 21. There is. The present invention attempts to improve this point.

[Means for solving problems]

The present invention provides a board connection method for connecting a printed circuit board and a flexible board by soldering, in which a rectangular window or protrusion is provided at the connecting portion of the flexible board so that the soldering lands are connected to each other at least on the long sides of each board. formed to face each other,
Further, the present invention is characterized in that soldering lands are formed in a corresponding pattern on the printed circuit board side so as to be exposed from the flexible substrate, and the corresponding lands on both boards are soldered.

[Effect]

If a window or a protrusion is formed at the connecting portion of the flexible substrate and a soldering land is formed at the periphery of the window or protrusion, connection (soldering) between the two substrates can be made at a shallow position from the end of the printed circuit board. As a result, the notch of the back cover of the device that covers the component mounting surface of the printed circuit board can be made shallow, and the area of the bottom cover that covers the notch is small, resulting in a structure that is less susceptible to distortion. This will be explained in detail below with reference to illustrated embodiments.

〔Example〕

FIG. 1 shows an embodiment of the present invention, in which a is a bottom view in a connected state and b is a bottom view before connection. Boards 4, 5
have the same relationship as in FIG. 4, but 6 is included in 5. A rectangular window (square hole) 52 is formed in the wide flexible substrate 5, and two rows of lands 51a and 51b are further formed around the window. The above-mentioned land 51 is located on the main board 4 side.
Two rows of lands 42a, 42 corresponding to a, 51b
b is the window 52 when the flexible substrates 5 are overlapped.
It is formed so that it is exposed from the inside. On the other hand, since the narrow flexible substrate 6 in FIG. 4 allows terminal arrangement, it is included in the flexible substrate 5, and corresponding lands are provided at 51a and 51b.

With such a land structure, the area (A×B) of the cutout portion 12 of the device back cover 11 can be made smaller than that in FIG. 4. As a result, the area of the lower cover portion 21 (FIG. 4) can be reduced, resulting in a structure that is less prone to distortion.

2 and 3 are other embodiments of the present invention. In the example shown in FIG. 2, one land 51a on the flexible substrate 5 side is arranged along the periphery of the window 52, the other land 51b is arranged along the tip 53, and the land 42a on the main substrate 4 side is arranged along the edge of the window 52. It is exposed through the window 52, and 42b corresponds to the land 51b at the tip 53.

In the example shown in FIG. 3, a protrusion 54 is formed at the tip of the flexible substrate 5, and lands 51a and 5 are formed on both sides of the protrusion 54.
1b are arranged, and the land 4 on the main board 4 side
2a and 42b are also arranged outside the protrusion 54 along this line. In this embodiment as well, the area of the connection location can be reduced.

In any of the examples, lands may be arranged around the entire circumference of the window 52 or the protrusion 54 to form a loop shape.

〔Effect of the invention〕

As described above, according to the present invention, since the soldering lands of the flexible board can be arranged in at least two rows, the area of the connection part with the printed circuit board can be reduced, and the cost and size of the connection part by soldering can be reduced. Of course, since the area of the lower surface cover portion of the front decorative plate that covers the component mounting surface of the printed circuit board can be reduced, distortion can be reduced, and furthermore, there are advantages such as an improvement in the degree of freedom in terms of design. In addition, since the lands are formed to face each other on at least the long sides of the rectangular window or protrusion, the number of lands can be increased and the connection strength at the connection part of the flexible substrate can be improved. This makes positioning during soldering easy. Furthermore, since the land on the main board side is exposed from the flexible board, soldering work becomes easier.

[Brief explanation of drawings]

1 to 3 are plan views showing different embodiments of the present invention, and FIG. 4 is an explanatory diagram showing an example of a conventional board connection method. In the figure, 4 is a printed circuit board, 42a, 42b are soldering lands, 5, 6 are flexible boards, 51a, 51b, 61 are soldering lands, 52 is a window, 54 is a protrusion, and 7 is a soldering part. be.

Claims (1)

[Claims] 1. In a board connection method in which a printed circuit board and a flexible board are connected by soldering, a rectangular window or protrusion is provided in the connection part of the flexible board, and soldering lands are made to face each other at least on each long side. 1. A method for connecting a board, comprising forming a soldering land in a corresponding pattern on the printed board side so as to expose it from the flexible board, and soldering between corresponding lands on both boards.