JP2863094B2 - Wiring board connection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of connecting a wiring board to form a through hole for connection by beam irradiation, and more particularly to a method of forming a through hole by irradiating a laser beam by superposing a plurality of flat cables. The present invention relates to a method for connecting wiring boards to be connected.

[0002]

2. Description of the Related Art Conventionally, there is a wiring board made of a resin board on which a circuit made of a conductor is mounted, which is made of a flexible resin board having flexibility, and is widely used as a so-called flexible wiring board. Such a flexible wiring board includes a flat cable having a plate-like conductor. A through hole is provided for connecting a conductor of a flexible wiring board including such a flat cable to another flexible wiring board or a conductor of a rigid wiring board, and the through hole is filled with a conductive filler to conduct. Connected.

As such a configuration, for example, Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. 236291/1990. As shown in FIG. 10, the flexible printed wiring board 54 is formed by laminating a flexible resin plate 54c, a connection pattern 54a, and a resist 54b, and through holes 55 penetrating these three layers are formed in advance. The rigid printed wiring board 57 has a connection pattern 57a and a resist 57b laminated on a rigid resin board 57c. A through hole 59 penetrating through the resist 57 and reaching the connection pattern 57a is formed in advance.

At the time of joining the two printed wiring boards 54 and 57, the flexible printed wiring board 54 is mounted on the rigid printed wiring board 57 so that the two through holes 55 and 59 are aligned. Then, the conductive paste 56 is injected into the through holes 55 and 59 while maintaining this positional relationship. Next, the conductive paste 56 is solidified to electrically connect the two connection patterns 54a and 57a.
The two printed wiring boards 54 and 57 are joined together.

[0005]

However, in the connection method having the above structure, it is necessary to provide through holes in each wiring board to be joined before executing the joining processing of the wiring boards. Therefore, prior to the joining process of filling the conductive filler, it is necessary to accurately position each through hole to be joined. Moreover, in addition to this positioning work, means for holding the positioned positions of the respective wiring boards through the process of filling the conductive filler and melting and cooling the filler is required.

Further, the conductive filler leaks out of the gap formed between the two joining members, which may cause a short circuit in the conductor circuit. This will be described with reference to FIG. 12 showing a cross section taken along the line AA in FIG. 11 showing the joint structure of the flexible printed wiring board. As shown in FIG. 12, a gap 58 is formed between the flexible printed wiring board 54 and the rigid printed wiring board 57. In such a case, the conductive filler (not shown) leaks from below the through hole 55 into the gap 58, which may cause a short circuit or the like of the circuit to cause an unexpected failure or the like.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and it is unnecessary to perform a work of positioning a through hole, and it is not necessary to perform a work of holding a wiring board through a process of filling and cooling a conductive filler. Another object of the present invention is to provide a method of connecting a wiring board in which a conductive filler does not leak from a gap between joining members.

[0008]

SUMMARY OF THE INVENTION The object of the present invention is to provide a method of connecting wiring boards, wherein at least one wiring board having at least one surface covered with through holes is connected to each other.
After laminating a plurality of wiring boards, the upper wiring board is irradiated with a beam capable of thermally melting the wiring board to reach at least the conductor of the lower wiring board together with the insulating coating and the conductor of the wiring board. To form a through-hole by melting and removing a conductive filler in the through-hole and electrically connecting between a plurality of wiring boards to achieve a connection between the wiring boards. .

Further, the above object is achieved by positioning a plurality of wiring boards with the formation of through holes. Furthermore, the above object is achieved when the beam is a laser beam.

[0010]

In the method for connecting wiring boards according to the present invention, a plurality of wiring boards are superimposed, and then a beam capable of thermally melting the wiring boards is irradiated on the upper wiring board to insulate the wiring boards. The through-hole is formed by melting and removing at least the conductor of the lower wiring board together with the coating and the conductor, and the through-hole is filled with a conductive filler to electrically connect the plurality of wiring boards. Thereby, along with the insulating coating of the wiring board and the melting and removal of the conductor, the resin of the molten insulating coating portion is
The inner wall of the conical through-hole is formed, and the peripheral portion of the gap existing between the upper and lower wiring boards is closed. Therefore, when the conductive filler is filled into the through hole, the conductive filler is prevented from leaking into the void.

Further, the resin of the molten insulating coating portion is
The lower and upper wiring boards are welded and solidified, and the upper and lower wiring boards are connected and fixed. Therefore, in the operation of filling the conductive filler into the through-hole, there is no need to adjust the positioning of the upper and lower wiring boards, and the means for holding the both wiring boards becomes unnecessary, and the working efficiency is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method for connecting wiring boards according to the present invention will be described below with reference to FIGS. FIG. 1 is an explanatory view of a method of connecting a wiring board according to the present invention, and FIG. 2 is an explanatory view of a coating fusion portion forming a through hole in FIG. In addition,
In this embodiment, a case where the present invention is applied to a flat cable will be described.

As shown in FIG. 1, a laser beam 1 is used as an irradiation beam for melting an object to be irradiated used in this embodiment. The laser beam 1 is irradiated from the side of the superposed upper flat cable 2 to melt predetermined portions of both flat cables 2 and 3 to form a through hole 4 having an arbitrary depth from the surface to the inside. .

As shown in FIG. 2, in this hot-melt processing, a through-hole 4 formed penetrates through the insulating coating 2A, the conductor 2B, and the insulating coating 2C of the upper flat cable 2, and further passes through at least the lower flat cable 3. Conductor 3D
Is processed by irradiation of the laser beam 1 so as to reach. In this case, the resin of the insulating coatings 2C and 3A thermally melted by the laser beam 1 forms the coating melting portion 7 of the through hole 4 and solidifies. However, since the inner wall formed here straddles between the upper and lower flat cables, The upper and lower flat cables 2 and 3 are connected and fixed. That is, the coating fusion portion 7 formed by thermal fusion is welded to the insulating coatings 2C and 3A and the welding surfaces 8A and 8B.

As a result, the upper flat cable 2 and the lower flat cable 3 are connected and fixed via the coating fusion portion 7. That is, since the upper and lower flat cables 2 and 3 are connected and fixed after the heat melting, subsequent position holding becomes unnecessary.

Further, a coating fusion portion 7 as an inner wall of a through hole is provided in a gap 6 existing between the upper and lower flat cables 2 and 3.
As a result, the conductive filler 5 is prevented from leaking into the gap 6 during the filling process of the conductive filler 5 after the through hole 4 is formed. Therefore, as shown in FIG. 1, the conductor 2B of the upper flat cable 2 is correctly and electrically connected to the conductor 3E of the lower flat cable 3 via the conductive filler 5, and a failure or abnormal operation due to a short circuit or the like is eliminated. Can be.

As shown in FIG. 3, in the procedure for connecting the flexible wiring board of this embodiment, first, at the start of the processing,
The flat cable 2 having the conductors 2B, 2D, 2E, 2F to be joined is moved and superposed on the flat cable 3 having the conductors 3B, 3D, 3E, 3F in the direction of arrow P, and is fixed at this position. .

Next, as shown in FIG. 4, a predetermined position is irradiated with a laser beam to melt and remove the insulating coating and the conductor of the flat cable 2 and the insulating coating of the flat cable 3. As a result, through holes are formed as shown in FIG. That is, the laser beam 1B forms a through hole 4B for connecting the conductor 2B and the conductor 3B. The laser beam 1D is applied to the conductor 2D and the conductor 3D.
The laser beam 1E forms through holes 4D, 4E and 4F for connecting the conductors 2E and 3E, and the laser beam 1F forms the conductors 2F and 3F.

In this process, the inner wall around the through holes 4B, 4D, 4E, and 4F is formed so that the insulating coating existing between the flat cable 2 and the flat cable 3 closes the gap between the flat cables 2 and 3. Form. The inner wall prevents the conductive filler from leaking into the gap when the conductive filler is filled in the through hole.

Furthermore, as a result of the molten resin of the insulating coating portion of the flat cable 2 flowing down and reaching the flat cable 3 and solidifying by welding, the flat cable 2 and the flat cable 3 are connected and fixed while maintaining this state. Therefore, it is possible to maintain accurate positions of both flat cables 2 and 3 through the subsequent process of filling the through hole with the conductive filler.

Next, a conductive filler is filled in the through holes formed as shown in FIG. The figure shows a state in which the conductive fillers 5B and 5D have already been filled in the through holes 4B and 4D, and the dispenser 10, which is a filler supply device, is filling the through holes 4E.
After the filling, a heat treatment is performed for melting and solidifying the conductive filler. In addition, filling of the conductive filler,
In addition to using the dispenser 10, it is also possible to carry out manually.

FIG. 7 is an explanatory view of laser beam irradiation by the method for connecting a flexible wiring board according to the present embodiment, as shown in FIG. In this irradiation example, the focus F of the laser beam 1 is located on the upper end surface of the flexible wiring board 22. In this case, if the output energy (peak power) of the laser beam 1 is small, the through hole H1 becomes a relatively small diameter and shallow hole. When the focal point F is at this position, the laser beam 1
When the output energy of the through hole H2 is increased, the through hole H2 has a relatively small diameter and a deep hole.

When the focal point F of the laser beam 1 is positioned above the flexible wiring board 22 as shown in FIG. The diameter is also increased. If the output energy of the laser beam 1 is small, the through hole H3 becomes a relatively large diameter and shallow hole. When the output energy of the laser beam 1 is increased at the focal point F at this position, the through hole H4
Has a relatively large diameter and a deep hole. As described above, by controlling the output energy (peak power) of the laser beam and the focal position at the time of irradiation, it is possible to obtain a through hole having an arbitrary diameter and depth.

FIG. 9 shows an example of a flat cable simultaneous multipoint drilling apparatus based on the method of connecting a flexible wiring board according to the present embodiment. The flat cable simultaneous multi-point drilling apparatus M includes one laser beam 16 and three half mirrors 15B, 15D, 1 having a transmittance of 1/3.
5E, lenses and optical fibers 12B, 12D, 12
E and emission units 11B, 11D, and 11E.
It consists of a set of irradiation mechanisms. This laser light 16
In the process of sequentially transmitting the three half mirrors 15B, 15D, and 15E, three reflected light beams 14
B, 14D and 14E. For example, the separated reflected light 14B is transmitted from the lens 13B to the optical fiber 12B.
Is transmitted to the emission unit 11B.

Each of the emission units 11B, 11D, 11
E irradiates the laser beams 1B, 1D, and 1E so as to form images at predetermined positions of the flat cable 2, respectively. Thus, the simultaneous multi-point drilling apparatus M of this embodiment
Is to simultaneously irradiate three laser beams to the flat cable at once, so that three through holes can be formed at once in the flat cable surface by the thermal melting action of each laser beam.

In the simultaneous multi-point drilling apparatus M, a single laser beam is split into a plurality of laser beams by a plurality of half mirrors, so that the productivity can be greatly improved. Therefore, the present invention is not limited to the configuration of three half mirrors, and it is possible to form more branched laser beams depending on the arrangement of the half mirrors.

Although a conductive filler has been described as an example of the conductive substance in the above description, the present invention is not limited to this, and a conductive adhesive such as solder or silver paste may be used. Further, in the above embodiment, connection of a plurality of flat cables is described, but the connection method of a wiring board of the present invention is also applied to connection of a flexible wiring board and a rigid wiring board, and a plurality of rigid wiring boards. Things.

[0028]

As described above, in the method for connecting wiring boards according to the present invention, a plurality of wiring boards are superimposed and then a beam capable of thermally melting the wiring boards is irradiated onto the upper wiring board. By melting and removing at least the conductor of the lower wiring board together with the insulating coating and the conductor of the wiring board, a through hole is formed, and a conductive filler is filled in the through hole to form a plurality of wirings. Conductive connection between the plates.

Thus, the melted resin of the insulating coating between the upper and lower wiring boards forms a wall that closes the gap existing between the upper and lower wiring boards. When the wall is filled with the conductive filler in the through hole, the conductive filler is prevented from leaking into the gap, so that a failure or accident caused by a short circuit or the like can be eliminated. Therefore, safety and reliability in connection of the wiring board can be improved.

Further, the positioning of the plurality of wiring boards is performed with the formation of the through holes. That is, the molten resin of the insulating coating between the upper and lower wiring boards is welded and solidified around the through hole. As a result, the upper and lower wiring boards are connected and fixed while maintaining this state, and the positions of the upper and lower wiring boards are accurately secured through the subsequent filling of the through holes with the conductive filler. Therefore, the holding means for the upper and lower wiring boards is not required, the connection operation is simplified, and the productivity can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a wiring board connection method according to the present invention.

FIG. 2 is an enlarged view of a coating fusion zone forming a through hole in FIG. 1;

FIG. 3 is a perspective view at the start of processing by the wiring board connection method of the present embodiment.

FIG. 4 is a perspective view showing a laser beam irradiation state following FIG. 3;

FIG. 5 is a perspective view showing a state of the formed through hole following FIG. 4;

FIG. 6 is a perspective view showing a state of filling with a conductive filler, following FIG. 5;

FIG. 7 is an explanatory view showing an example of laser beam irradiation by the wiring board connection method of the present embodiment.

FIG. 8 is an explanatory diagram showing an example of laser beam irradiation different from that of FIG. 7;

FIG. 9 is a perspective view showing a configuration example of a simultaneous multi-point drilling apparatus according to the wiring board connection method of the present embodiment.

FIG. 10 is a sectional view of a wiring board structure according to a conventional wiring board connection method.

FIG. 11 is a plan view of the wiring board structure in FIG. 10;

12 is a sectional view of the wiring board structure taken along line AA in FIG. 11;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser beam 2 upper flat cable 2A, 2C insulating coating 2B conductor 3 lower flat cable 3A, 3C insulating coating 3B, 3D, 3E conductor 4 through hole 5 conductive filler 6 void 7 coating fusion part 8A, 8B welding surface

Claims (3)

(57) [Claims] 1. A method for connecting wiring boards in which at least one surface is covered with a plurality of wiring boards provided with through holes and connected to each other, wherein the plurality of wiring boards are overlapped with each other, and then the wiring boards are heated. By irradiating the upper wiring board with a fusible beam and melting and removing at least the insulation coating and the conductor of the wiring board up to the conductor of the lower wiring board to form a through hole, the through hole is formed. A method for connecting wiring boards, comprising: filling a plurality of wiring boards with a conductive filler. 2. The method according to claim 1, wherein a plurality of wiring boards are positioned with the formation of the through holes.
The connection method of the wiring board described. 3. The method according to claim 1, wherein the beam is a laser beam.