JP3017142B2 - Repair method for broken circuit of printed wiring board - 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 repairing a broken circuit, and more particularly to a method of repairing a broken circuit of a printed wiring board.

[0002]

2. Description of the Related Art Conventionally, circuit breakage in such a printed wiring board is one of the most common defects in the manufacturing process of a printed wiring board, and moreover, it is one of many defects. This defect is also a factor that greatly reduces the yield of printed wiring boards in manufacturing.

[0003] A circuit breakage defect generated in the manufacturing process of a printed wiring board is caused by superimposing a repair wire on the circuit break, flowing a large current instantaneously through the welded portion, and melting the repair wire due to a rise in temperature due to the electrical resistance of the repair wire. Then, the repair wire is welded to the circuit break.

However, in this technique, the circuit disconnection repair section has a structure in which a repair wire is superimposed on the original circuit, which is not desirable from the viewpoint of a recent demand for thinner printed wiring boards. In addition, there is a problem of reflection of electric signals due to a change in circuit board thickness in the circuit disconnection repair section, and as the speed of electric signals increases, smoothing of the circuit thickness of the circuit disconnection repair section is strongly required. It has become so.

A method for repairing a smooth disconnection is disclosed in Japanese Patent Laid-Open No. 5-13931.
Has been proposed. The technique will be described with reference to FIG. FIG. 5 is a plan view showing a state in which a high-frequency current is applied to the wire 1 for wire breakage repair, in which a brazing material is applied so as to cover the wire breakage portion on the wire breakage circuit 2, and the wire 2 is welded. 6A to 6C are cross-sectional views of the printed wiring board shown in the order of steps for explaining the repair method.

First, as shown in FIG. 6 (a), on the broken circuit 2 on the printed wiring board 4, the same width as the circuit width will be formed, and one side will be composed of Ag 15%, P5%, and Cu 80%. A wire 1b for repairing disconnection, such as an alloy wire harder than the applied copper, is placed.

Next, as shown in FIG. 6B, a pressure is applied from above the wire 1b for disconnection repair. Next, after the broken wire 1b is mounted on the broken circuit 2, the circuit 2 that has been broken by pressurization and high-frequency current is electrically welded to the broken repair wire 1b to form an adhesive portion 9, and at the same time, a printed wiring board is formed. 4 to form a press-fit circuit portion 10. At this time, the melting point of the brazing material is about 800 ° C.
Since the temperature is sufficiently higher than the glass transition temperature, the thermosetting resin constituting the printed wiring board 4 is softened, and a part of the disconnected circuit 2 is buried in the printed wiring board 4 and
The bonding portion 9 is bonded to the wire 1b for disconnection repair (FIG. 6).
(C)).

[0008]

In the above-described conventional method for repairing a broken circuit, a wire for repairing a broken wire, which is harder than copper, is pressed into a printed wiring board by pressure and the surface height after repair of the broken wire is reduced as much as possible. And However, when press-fitting into the inside of the printed wiring board, a local pressing force is applied to the broken circuit itself, cracks are generated in the circuit, and problems are liable to occur in the conduction resistance. Is pressed into the inside of the printed wiring board, the resin thickness under the circuit in the repair section becomes thin, and there is a risk of occurrence of insulation failure with the inner layer circuit.

Further, even if the circuit has a thick copper body, even if the disconnection repair is performed by the above method, it is not sufficiently pressed into the printed wiring board, and the circuit disconnection repair portion becomes higher than the peripheral circuit as in the above-mentioned prior art. . Therefore, when the surface mount component is mounted on the printed wiring board, the surface mount component tilts due to the convex shape of the repaired part, and its lead cannot be soldered to the pad of the printed wiring board, guaranteeing connection reliability after soldering There is a disadvantage that it is difficult to do.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a method for repairing a broken circuit of a printed wiring board which can smooth the surface of the repaired portion without impairing the connection reliability after the repair. It is in.

[0011]

SUMMARY OF THE INVENTION A method for repairing a broken circuit of a printed wiring board according to the present invention is a method for repairing a broken circuit in a broken circuit of a printed wiring board and an insulating resin around the broken circuit at a height substantially equal to the height of the broken circuit. Coating and curing; cutting the circuit at both ends of the circuit disconnection portion and the insulating resin at the circuit disconnection portion; forming a shape matching the groove shape of the cut portion of the circuit disconnection portion and soldering at both ends. Forming a wire for repairing disconnection with a material applied thereto, a step of setting the wire for repair of disconnection to the cut portion, and heating and melting the brazing material of the wire for repair of disconnection set to the cut portion by laser. And welding the wire for repairing the disconnection to the disconnected circuit via the brazing material so as to have the same height as the disconnected circuit.

In the present invention, the cut portion of the circuit break portion has a groove shape surrounded by an insulating resin in a width direction and a cut surface (circuit break surface) of the broken circuit in a length direction. Since the cut portion has the same shape as the wire for repairing the disconnection, there is an effect that the position of the wire for repairing the disconnection can be easily adjusted. In addition, since the wire for repairing the disconnection can be welded to the broken circuit with a laser under a low pressure, there is no problem of conduction resistance due to the occurrence of circuit cracks after repair as before, and there is no insulation failure with the inner layer circuit and the disconnection The reliability of the repair is guaranteed, and the surface after the disconnection repair can be repaired smoothly.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a wire for repairing a disconnection 1 used in a method for repairing a disconnection of a circuit according to a first embodiment of the present invention. The thickness and width of the wire for repairing the disconnection are prepared in accordance with the thickness and the width of the circuit conductor of the printed wiring board to be repaired. For example, in the case of a circuit break having a circuit width of 100 μm and a circuit conductor thickness of 45 μm, the wire for repairing disconnection 1 has the same width and thickness as the circuit, and the brazing material 3 is applied to both ends of the copper wire. The length is 1mm, 1mm, 2mm, 3mm ...
The end face on which the brazing material 3 is formed is inclined at an angle of 30 to 60 degrees with respect to the upper surface of the wire 1 for disconnection repair. If this angle exceeds 60 °, the brazing material will flow too much downward during laser welding, and if it is less than 30 °, the length of the wire for repairing breakage will be too long, which is not preferable. For processing of the wire 1 for disconnection repair, after processing a copper plate into a band shape in accordance with the conductor thickness and the circuit width of the required circuit, cut both ends at an angle of 30 ° to 60 ° to the corresponding length,
It is made by applying brazing material to both ends.

FIGS. 2A to 2C are cross-sectional views of a main part of the printed wiring board for explaining the order of steps for repairing circuit breakage according to the first embodiment of the present invention. FIG. 4 is a cross-sectional view of a main part of a printed wiring board for explaining the above. As shown in FIG. 2A, the circuit 2 on the printed wiring board 4 includes
Exists. The shape (the cross-sectional shape of the circuit at both ends) of the broken circuit portion has various sizes and shapes depending on the broken circuit.

First, as shown in FIG. 2B, an insulating resin 6 is applied to the circuit disconnection portion 5 and its periphery at a height substantially equal to the height of the surface of the circuit 2 and cured. As the insulating resin 6, an ultraviolet curable or thermosetting resin such as an epoxy resin can be used. The insulating resin 6 fills the circuit disconnection portion 5. Next, the circuit breakage portion is cut into the same shape as that of the wire breakage repair wire 1 by a high-precision rotary drill (not shown) (FIG. 2C). As a result of this cutting, a groove 7 having the same shape as the wire 1 for disconnection repair surrounded by the insulating resin 6 in the width direction of the circuit disconnection portion and surrounded by the circuit disconnection surface 8 in the length direction is formed. The groove 7 is preferably processed to a length of 1 mm in accordance with the wire 1 for disconnection repair.

Next, as shown in FIG. 2D, the wire 1 for disconnection repair is set in alignment with the circuit disconnection surface 8 of the groove 7. Since the size and shape are the same, and the periphery of the groove 7 is surrounded by an insulating resin (not shown), the wire 1 for disconnection repair can be easily set by being placed on the circuit disconnection surface 8. it can.

Next, as shown in FIG. 2 (e), the brazing material 3 of the wire 1 for disconnection repair is heated from above using a carbon dioxide laser to a temperature at which the brazing material 3 can be melted. The broken wire 1 is welded to the broken circuit 2 so as to have the same height as the broken circuit 2. As the brazing material 3, generally used Ag 15%, P 5% and Cu 80% can be used, and the brazing material 3 is applied in a thickness of 10 to 20 μm. When this brazing material is applied to the wire 1 for disconnection repair, the brazing temperature is 7
Since the temperature is between 05 ° C. and 815 ° C., the laser heat is controlled so that the temperature becomes between 800 ° C. and 900 ° C. By welding in this manner, the bonded circuit can be bonded without damaging the broken circuit and without changing the resin thickness under the repaired portion. Further, as described above, even when a printed circuit board having a large circuit conductor thickness is repaired, the circuit height after the repair is equal to or less than the peripheral circuit height, and no trouble such as inclination of the surface mount component occurs.

FIGS. 3 (a) and 3 (b) are a sectional view and a plan view of a wire rod 1a for repairing disconnection used in a second embodiment of the present invention. As shown in FIG. 3, the wire 1a for disconnection repair is the first wire.
Similarly to the embodiment, for example, in the case of disconnection of a circuit having a printed circuit board having a circuit width of 100 μm and a circuit conductor thickness of 45 μm, the disconnection repair wire 1a is made of copper having the same width and the same thickness as the circuit of the printed wiring board. The brazing material 3 is applied to the surface of the copper material. The brazing material 3 may be provided on the entire surface of the copper material.

The length of the wire 1a for repairing the disconnection is processed at a constant length of 1 mm, 2 mm, 3 mm... In 1 mm steps, and the end face 9 of the wire 1a for repairing the disconnection has a stepped cross section. And the plane is semicircular. The angle of the slope of the stepped end surface 9 is preferably 45 ° to 90 °.

The wire for repairing the disconnection is formed by processing a copper plate into a band shape in accordance with the thickness of the circuit conductor and the width of the circuit, and then cutting the end surface into a semicircular shape so as to be suitable for the length of the circuit break portion. Cut the cross section stepwise. Then, the stepped surface of the copper plate is formed by coating a brazing material.

FIGS. 4 (a) to 4 (c) are cross-sectional views of a main part of a printed wiring board for explaining the order of steps for repairing circuit disconnection according to the second embodiment of the present invention. How to cut circuit breaks,
The setting of the wire for repairing the disconnection and the welding method are the same as those in the first embodiment. As shown in FIG. 4A, a circuit break 5 exists in the circuit 2 on the printed wiring board 4.

First, as shown in FIG. 4B, an insulating resin 6 is applied to the circuit disconnection portion 5 and its periphery at a height substantially equal to the height of the surface of the circuit 2 in the same manner as in the first embodiment, and cured. I do. The insulating resin is in a state of being filled in the circuit disconnection portion 5.

Next, after the circuit breakage portion is cut into the same shape as the shape of the wire breakage repair wire 1a by a high-precision rotary drill (not shown), the wire breakage repair wire 1a is aligned with the circuit breakage surface 8a of the groove 7. Set (FIG. 4 (c)). The width direction of the groove is surrounded by the insulating resin 6 and the length direction is surrounded by the circuit disconnection surface 8a, so that the position of the disconnection repair wire 1a on the circuit disconnection surface 8a can be easily adjusted.

Then, as shown in FIG. 4 (d), the wire 1a for disconnection repair is heated to a temperature at which the brazing material 3 is melted by laser heat from the wire 1a for disconnection repair so that the wire 2a has the same height as the circuit 2 in which the wire 1a for disconnection repair has been disconnected. Is welded to the disconnected circuit 2.

In the second embodiment, since the both ends of the wire for repairing disconnection are formed in a semicircular shape, the wire at the time of welding is more easily fixed than in the first embodiment. There is an advantage that the thermal stress after the mounting of the welded joint can be alleviated and the connection reliability of the welded joint can be improved.

[0027]

The first effect of the present invention is that the circuit disconnection portion is cut and shaped so as to match the shape of the disconnection repair wire, and the position of the disconnection repair wire to the circuit disconnection portion can be easily adjusted.
The circuit height of the circuit disconnection repair section after the circuit disconnection repair can be made equal to the original circuit. A second effect of the present invention is that the connection reliability of the circuit disconnection repaired part can be improved because the circuit disconnection can be repaired at a low pressure by laser welding.

A third effect of the present invention is that even if a brazing material flows out during laser welding of a wire for repairing a disconnection, the cut portion having a groove shape formed after covering the disconnected portion of the circuit with an insulating resin. Therefore, since the flow of the brazing material can be stopped, a short circuit with an adjacent circuit can be prevented, and the reliability of welding can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a wire for repairing disconnection used in a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of a printed wiring board for explaining a repair process sequence of circuit disconnection using the disconnection repair wire of FIG. 1;

FIGS. 3A and 3B are cross-sectional views of a wire for repairing disconnection used in a second embodiment of the present invention, and FIG.

FIG. 4 is a cross-sectional view of a main part of the printed wiring board for explaining a repair process order of a circuit disconnection using the disconnection repair wire of FIG. 3;

FIG. 5 is a plan view of a circuit disconnection portion in a printed wiring board for explaining a conventional example.

FIG. 6 is a cross-sectional view of a main part of a printed wiring board for explaining a repair process sequence in a conventional circuit disconnection repair method.

[Explanation of symbols]

 1, 1a, 1b Disconnection repair wire 2 Disconnected circuit 3 Brazing material 4 Printed wiring board 5 Circuit disconnection 6 Insulating resin 7 Groove 8, 8a Circuit disconnection surface 9 Adhesion 10 Press-fit circuit

Claims (5)

(57) [Claims] A step of applying and curing an insulating resin substantially equal to the height of the broken circuit of the broken circuit of the printed wiring board and the periphery thereof, and the steps of: A step of cutting the insulating resin of the circuit disconnection portion, a step of forming a wire for repairing a disconnection having a shape conforming to the groove shape of the cut portion of the circuit disconnection portion, and applying a brazing material at both ends; A step of setting a wire to the cutting portion, and heating and melting the brazing material of the disconnection repair wire set in the cutting portion by a laser, so that the disconnection repair wire has the same height as the broken circuit. Welding the circuit to the disconnected circuit via the brazing material as described above. 2. The method according to claim 1, wherein the insulating resin is an ultraviolet-curing or thermosetting epoxy resin. 3. A wire rod in which the wire for repairing a disconnection is sloped so that both end surfaces of a rectangular parallelepiped copper plate has a trapezoidal cross-sectional shape in the longitudinal direction of the upper surface, and a brazing material is applied to the end surface. 3. The method for repairing a broken circuit of a printed wiring board according to claim 1 or 2. 4. The method according to claim 1, wherein an angle between an end face of the wire for repairing disconnection and an upper surface of the wire for repairing disconnection is 30 ° to 60 °. 5. Both ends of a rectangular parallelepiped copper plate having a stepwise longitudinal cross-sectional shape and a semicircular planar shape are formed as the wire for repairing disconnection, and a brazing material is applied to the end surface or the entire surface. 3. The method for repairing a broken circuit of a printed wiring board according to claim 1, wherein the wire is used.