JP3003918B2 - Flexible printed circuit board connection structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure between a flexible printed board and a circuit board.

[0002]

2. Description of the Related Art A land portion of a wiring pattern formed on a circuit board and a land portion of a wiring pattern formed on a flexible printed board having elasticity are formed by a thermocompression bonding method.
Alternatively, the connection is made by any of the manual soldering methods. First, connection by a thermocompression bonding method will be described. FIG.
3A, the circuit board 41 includes a base 41a made of an insulator, a conductive layer 41b formed on the base 41a, a conductive layer 41b, and an overcoat 41c that covers the base 41a from above. The conductive layer 41b is formed to have an appropriate pattern shape, and an end of the pattern has a land portion 42 having an area larger than other portions.
It has become. The land part 42 has an overcoat 41c.
And is exposed to the outside.

A flexible printed board 43 is connected to a land 42 of the circuit board 41 by solder 45. The flexible printed board 43 includes an under-insulating layer 43a, a conductive layer 43b formed on the lower end surface side of the under-insulating layer 43a, and an over-insulating layer 43c covering the lower end surface side of the conductive layer 43b. The conductive layer 43b is formed to have an appropriate pattern shape, and the end of the pattern is a land portion 47 having an area larger than other portions. The land portion 47 is also not covered with the overcoat 43c, and is exposed to the outside.

[0004] The circuit board 41 and the flexible printed circuit board 43 are formed on the side of the overcoat 41 c and the over insulating layer 43.
The c side faces each other, and the land portion 42 and the land portion 47 are overlapped with the solder 45 interposed therebetween. In such a form, the flexible printed circuit board 43
By applying heat from the base 43a side, the solder 45 is melted, the land 42 and the land 47 are electrically connected, and the circuit board 41 and the flexible board 43 are connected and fixed. Incidentally, FIG. 6A shows an example in which the flexible substrate 43 is connected in the middle of the circuit board 41, and FIG. 6B shows the case where the flexible substrate 43 is connected in the edge portion of the circuit board 41. An example is shown.

[0005] Next, connection by a manual soldering method will be described. In FIG. 7, the circuit board 51 includes a base 51.
a, insulating layer 51b and insulating layer 5 formed on base 51a
1b, and an overcoat 51d that covers the conductive layer 51c, the conductive layer 51c, and the insulating layer 51b from above. The conductive layer 51c is formed so as to have an appropriate pattern shape. At the end of the pattern, a land portion 52 having a larger area than other portions and formed at an edge of the circuit board 51 is formed. Have been. The land portion 52 is not covered with the overcoat 51d and is exposed to the outside.

[0006] A flexible printed board 53 is mounted on the circuit board 51. The flexible printed board 53 includes an under-insulating layer 53a, a conductor layer 53b formed on the upper surface of the under-insulating layer 53a, and an over-insulating layer 53c covering the conductor layer 53b except for the terminal portions 54 exposed to the outside. I have. The conductor layer 53b is formed to have an appropriate pattern shape.

[0007] The terminal portion 54 is a flexible printed circuit board 5.
3 and is disposed at a position close to the land 52 of the circuit board 51. After that, the land portion 5 of the circuit board 51 is
2, the solder 55 is applied and welded, and the conductor layer 53b of the flexible printed board 53 and the conductor layer 5 of the circuit board 51 are
1c is electrically connected, and the flexible printed board 53 is fixed to the circuit board 51. A portion of the flexible printed board 53 extends outside the circuit board 51 to form an extension 53e.

As shown in FIGS. 9A and 9B, a through hole 53d is formed in the flexible printed circuit board 53, and a land 57 is formed on the entire edge of the through hole 53c. Solder 55 is applied to the entire inner edge of the
In this case, since the diameter of the through hole 53d is small, the solder 55 is rounded due to surface tension, and the solder 55 does not reach the land 52 located on the lower side. There is a risk of damage.

[0009]

The connection structure of the thermocompression bonding method shown in FIG. 6 has a problem that a large-scale facility is required and the cost rises, and the connection portion cannot be confirmed after the connection. .

Further, in the manual soldering method shown in FIG.
There is an advantage that a large-scale facility is not required, and a connection portion between the land portion 52 of the circuit board 51 and the land portion 57 of the flexible printed board 53 can be easily confirmed. But,
Normally, the flexible printed circuit board is used to derive power to a portion separated by a predetermined distance from the circuit board, and thus has an extension 53e that is not joined to the circuit board. However, when stress F is applied to the extension 53e due to vibration or the like, a crack C is generated in the solder 55, and the conductor layer 53b
There is a possibility that poor conduction may occur between the conductive layer and the conductive layer 51c.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. The connection portion can be easily confirmed, and even if a stress is applied to the extending portion of the flexible printed circuit board, the solder cracks. It is an object of the present invention to provide a connection structure for a flexible printed circuit board, which does not cause a conduction failure due to the occurrence of a problem.

[0012]

SUMMARY OF THE INVENTION The present invention relates to a connection structure of a flexible printed circuit board in which terminals of a flexible printed circuit board are connected to lands formed on a circuit board by soldering. Are formed on one side of the through hole formed in the intermediate portion of the flexible printed board and on the opposite side of the extended portion of the flexible printed board that does not overlap with the circuit board. The shape of the terminal portion may be an arc shape, a V shape, or a U shape.

[0013]

The terminal portion of the flexible printed circuit board which is connected to the circuit board by soldering is formed on the side opposite to the extending portion of the through hole. Therefore, stress or stress due to vibration or the like is not directly applied.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a connection structure for a flexible printed circuit board according to the present invention will be described below with reference to the drawings. In FIG. 1, a circuit board 1 has a substantially circular shape, and a wiring pattern of an appropriate shape is formed on an upper end surface thereof. One end of the wiring pattern is gathered at a portion on the outer peripheral side of the circuit board 1. The flexible printed circuit board 3 is superimposed on the portion where one end of the wiring pattern is collected. A through hole 6 is formed in a portion of the flexible printed board 3 that overlaps with the circuit board 1, and an end of the wiring pattern is provided on the outer periphery of the through hole 6. The end of the wiring pattern of the flexible printed circuit board 3 and the end of the wiring pattern of the circuit board 1 are overlapped and electrically connected by the solder 5 provided through the through hole 6.
Further, the flexible printed board 3 is connected and fixed to the circuit board 1 by the solder 5.

Next, the connection between the flexible printed board 3 and the circuit board 1 will be described in detail. 2, 3 and 4, a circuit board 1 is a base 1 made of an insulator.
1, a wiring pattern 12 formed on an upper end surface of a base 11,
It is composed of a wiring pattern 12 and an overcoat 13 covering the base 11. One end of the wiring pattern 12 is a land 2, which is not covered with the overcoat 13 and is exposed to the outside.

A flexible printed board 3 is overlaid on the circuit board 1. The flexible printed circuit board 3 has an extension 3 extending outside without overlapping with the circuit board 1.
a. In addition, the flexible printed circuit board 3
Comprises an undercoat 14, a wiring pattern 15 formed on the upper surface of the undercoat 14, an overcoat 16 covering the undercoat 14 and the wiring pattern 15. 1 is a cross-sectional view of a portion where the wiring pattern 15 is not provided. On the flexible printed circuit board 3, a through-hole 6 composed of a small-diameter semicircular portion and a large-diameter semicircular portion is formed. One end of the wiring pattern 15 is disposed so as to surround the outer periphery of the small-diameter semicircular portion of the through hole 6 to form a land portion 7. The U-shaped portion of the land portion 7 disposed at the edge of the small-diameter semicircle portion serves as the terminal portion 4. The terminal portion 4 is arranged at the edge of the through hole 6 on the opposite side to the extension 3a.

The flexible printed board 3 is laminated on the circuit board 1 such that the land 2 is located inside the through hole 6, and the solder 5 is applied from the terminal 4 to the land 2. Being connected.

According to the connection structure of the flexible printed circuit board 3 having the above configuration, the terminal portion 4 of the wiring pattern 15 of the flexible printed circuit board 3 is connected to the extending portion 3a of the through hole 6 of the flexible printed circuit board 3. Since it is formed on the opposite side and is connected to the land portion 2 of the circuit board 1 by soldering, even if a stress F as shown in FIG. Thus, the solder 5 does not directly affect the solder 5, and the solder 5 does not crack. Therefore, the wiring pattern 15 of the flexible printed board 3 and the wiring pattern 1 of the circuit board 1
2 can be eliminated. Also, the through holes 6
Since the connection portion is formed only on one side, the connection state can be confirmed by the through hole 6, and the reliability of the connection is improved. Further, the through hole 6 enables soldering connection not only at the end of the flexible printed circuit board 3 but also at an intermediate portion thereof, so that the degree of freedom of the wiring pattern 15 formed on the flexible printed circuit board 3 can be improved. Further, there is an advantage that the cost can be suppressed because equipment such as a thermocompression bonding method is not required, and since the terminal portion 4 has an arc shape, solder is easily collected and soldering is easy.

The shape of the terminal portion 4 of the through hole 6 on the flexible printed board 3 is not particularly limited. Any shape may be used as long as the position is on the side opposite to the extension 3a of the through hole 6. For example, as shown in FIG. 5A, when the land portion 2 of the circuit board 1 has a square shape,
May be square, and the shape of the terminal portion 4 may be U-shaped. Alternatively, as shown in FIG. 5B, when the shape of the land portion 2 of the circuit board 1 is elliptical, the shape of the portion of the through hole 6 opposite to the extension 3a is V-shaped. The shape of the end 4 may be V-shaped in accordance with.

[0020]

According to the present invention, the terminal portion of the flexible printed circuit board is formed on one side of the through hole formed in the intermediate portion of the flexible printed circuit board, and the terminal portion is formed of the flexible printed circuit board. Is formed on the opposite side of the extended portion of the flexible printed circuit board, even if stress is applied to the extended portion of the flexible printed circuit board, the effect of this stress does not affect the solder, eliminating cracks in the solder. In addition, it is possible to prevent poor conduction of the wiring pattern. Also,
It is also possible to confirm the connection state between the wiring patterns from the through holes.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a connection structure of a flexible printed circuit board according to the present invention.

FIG. 2 is an enlarged perspective view showing a main part of the above.

FIG. 3 is an enlarged sectional view showing a main part of the above.

FIG. 4 is an exploded perspective view showing the essential parts of the above in an enlarged manner.

FIG. 5 is an enlarged plan view showing a main part of another embodiment of the connection structure of the flexible printed circuit board according to the present invention.

FIG. 6 is a sectional view showing an example of a conventional connection structure of a flexible printed circuit board.

FIG. 7 is a sectional view showing another example of a conventional connection structure of a flexible printed circuit board.

FIG. 8 is a sectional view of the same.

9A and 9B show an example of a conventional connection structure of a flexible printed circuit board, wherein FIG. 9A is a perspective view and FIG. 9B is a cross-sectional view.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Circuit board 2 Land part 3 Flexible printed board 4 Terminal part 5 Solder 6 Through-hole

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-58-48492 (JP, A) JP-A-2-15092 (JP, A) JP-A 3-102755 (JP, U) JP-A 59-48 54974 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H05K 1/14

Claims (2)

(57) [Claims] 1. A connection structure of a flexible printed board in which terminals of a flexible printed board are connected to lands formed on the circuit board by solder, wherein the flexible printed board does not overlap with the circuit board.
There has extending portion, the terminal portion of the flexible printed circuit board, on one side of the through hole drilled in the middle portion of the flexible printed circuit board, or
And a connection structure for a flexible printed circuit board, which is formed on a side opposite to the extension . 2. The flexible printed circuit board connection structure according to claim 1, wherein the shape of the terminal portion is an arc shape, a V shape, or a U shape.