JPH05327138A - Flexible circuit board having protrusion - Google Patents

Abstract

PURPOSE:To obtain a flexible circuit board which can be easily treated at the time of contact bonding work and enables stable electric contact with parts for a long term which parts is repeatedly detached. CONSTITUTION:This circuit board is provided with a base film 1 and a conductor circuit 2 formed on the base film 1 surface. A through hole 1a is formed in the base film 1 corresponding with a specified portion of the conductor circuit 2. The part of the conductor circuit 2 corresponding with the through hole 1a is formed to be a hollow protruding part 3. A plating part 4 is formed on the rear of the hollow protruding part 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible circuit board used for wiring electric and electronic circuits.

[0002]

2. Description of the Related Art Flexible circuit boards are widely used for wiring electric and electronic circuits. This kind of flexible circuit board includes a resin substrate and a metal circuit formed on the surface of the resin substrate, and electrically connects between an end portion (connection terminal) of the metal circuit and a plurality of electric components. To be done. As a method of making such an electrical connection, a method of using an insertion type connector, a method of soldering, etc. are generally adopted. However, with these methods,
Since the soldering process is indispensable in both cases, there arises a problem that a lot of equipment and labor are required for assembling the circuit. Moreover, the flexible circuit board has a problem that the use of an expensive polyimide film is unavoidable because the material constituting the flexible circuit board is required to have high heat resistance against the heat added in the soldering step. is doing.

Therefore, in order to solve the above problem, as shown in FIG. 6, the back surface of the resin substrate 1 of the flexible circuit board made of a laminate of the resin substrate 1 and the metal circuit 2 is metalized by using a mold. By projecting a predetermined portion of the manufactured circuit 2 and deforming it into a concave shape, a spherical projection 10 is provided on the surface of the resin substrate 1, and the projection 10 is crimped to a counterpart component for electrical connection. Such a thing is proposed and implemented in part (Japanese Utility Model Publication No. 59-10700). According to this method, since the soldering step can be omitted, a lot of equipment and labor are not required for assembling the circuit. Moreover, since high heat resistance is no longer required, various plastic films other than the polyimide film can be used as the material forming the flexible circuit board.

[0004]

However, in the electrical connection by the spherical projection 10, when the projection 10 is crimped to the counterpart component by a mechanism using a spring or the like, the projection 10 and the counterpart There is a problem that the above parts come into surface contact with each other, and the surface pressure at the tips of the protrusions 10 becomes low, resulting in poor contact. Further, in order to prevent the contact failure, when the protrusion 10 is pressure-bonded to a counterpart component with an excessive force, the protrusion 10 is largely deformed and its height becomes low, so that the electrical contact is prevented. The problem arises that the resistance is abnormally increased. For this reason, it is necessary to handle the flexible circuit board with caution when crimping.
The reality is that it requires more effort than necessary.

A flexible circuit board of this type is
It is also used for connecting and wiring parts that are repeatedly attached and detached by taking advantage of the connection method by crimping, but in this case, there is a problem in durability against the attachment and detachment work.

The present invention has been made in view of the above circumstances, and it is easy to handle during crimping work, and stable and long-term electrical operation is possible even for parts that are repeatedly detached and attached without contact failure or deformation. It is an object of the present invention to provide a flexible circuit board that can be electrically connected.

[0007]

In order to achieve the above object, a flexible circuit board of the present invention comprises a resin board,
A metal circuit formed on the substrate surface of the resin substrate, a through hole is formed in the resin substrate corresponding to a predetermined portion of the metal circuit, and the metal circuit portion corresponding to the through hole is hollow. The hollow protrusion is formed in the protrusion, and the reinforcing filler is filled in the hollow protrusion.

[0008]

That is, in the flexible circuit board of the present invention, a through hole is formed in the resin substrate corresponding to a predetermined portion of the metal circuit, and the metal circuit portion corresponding to the through hole is formed in the hollow protrusion. A reinforcing filler is filled inside the hollow protrusion. As described above, in the flexible circuit board of the present invention, since the hollow protrusions are reinforced with the reinforcing filler, the strength thereof can be increased and the durability can be greatly improved. Therefore, when crimping or the like to the counterpart component by a mechanism using a spring or the like, a contact failure or a large deformation does not occur, and the circuit is easy to handle during assembly. Moreover, since the durability of the hollow protrusion is improved as described above, it can be stably used for a long period of time even for connection and wiring of components that are repeatedly detached and attached.

Next, the present invention will be described in detail.

The flexible circuit board of the present invention is obtained by using a resin board 1, a metal circuit 2 formed on the resin board 1 and a reinforcing filler 4, as shown in FIG. 1, for example.

The resin substrate 1 is not particularly limited as long as it has an electric insulating property such as an insulating film. For example, a polyimide film, a polyethylene terephthalate film, a polyethylene film, a polyethylene naphthalate (PEN) film. Almost all plastic films such as fluorine film such as polyetherimide (PEI) film and tetrafluoroethylene film, polyphenylene sulfide (PPS) film and polyparabanic acid (PPA) film are used.
In particular, a polyimide film or a polyethylene terephthalate film is preferably used and its thickness is 0.0
It is set within the range of 08 to 0.25 mm, preferably within the range of 0.013 to 0.125 mm.

As the material for forming the metal circuit 2, for example, various metals such as gold, silver, copper, nickel, cobalt and alloys thereof are used. In particular, a copper foil is used, and its thickness is set within the range of 0.008 to 0.140 mm, preferably within the range of 0.018 to 0.070 mm.

A through hole 1a is formed in the resin substrate 1 corresponding to a predetermined portion of the metal circuit 2, and a portion of the metal circuit 2 corresponding to the through hole 1a is formed in the hollow protrusion 3. The hollow protrusion 3 is formed in various shapes such as a spherical shape and a conical shape. When the hollow protrusion 3 is formed in a spherical shape, its radius is set within a range of 0.15 to 1.00 mm, and preferably within a range of 0.25 to 0.50 mm. The height is 0.09-0.60 mm.
Set within the range of 0.15 to 0.30 mm
It is set within the range of. Also, the radius of curvature of the tip is 0.2
It is set within the range of 8 to 1.84 mm, preferably 0.4
It is set within the range of 6 to 0.92 mm.

As a method of integrally forming the resin substrate 1 and the material for forming the metal circuit 2, a method of adhering the resin substrate 1 and the metal circuit 2 through an adhesive such as an epoxy type, urethane type, polyester type, or the above resin is used. A conventionally known method such as a method of directly forming a film on the substrate 1 for forming the metal circuit 2 or a method of directly forming a film for forming the metal circuit 2 on the resin substrate 1 can be used. Here, before the film is attached, or after the film is attached or after the film is formed, the through hole 1a is formed at a location on the film where the hollow protrusion 3 is to be formed, by machining, chemical etching or the like. At this time, the shape of the through hole 1a depends on the shape of the hollow protrusion 3 to be processed.

As a method of forming the hollow protrusion 3 in the portion of the metal circuit 2 corresponding to the through hole 1a formed in the resin substrate 1, a method of drawing the back surface of the resin substrate 1 using a punch or the like is used. Can be given.

A reinforcing filler 4 is filled inside the hollow protrusion 3 formed as described above. Examples of the method of filling the reinforcing filler 4 include a method of plating the back surface of the hollow protrusion 3 with nickel or the like, a method of screen-printing a plastic such as an epoxy resin by potting, or the like.

Next, an embodiment of the present invention will be described.

[0018]

1 shows an embodiment of the present invention. In the figure, 1 is a base film (resin substrate) made of a polyethylene terephthalate film (Lumirror, manufactured by Toray) having a thickness of 50 μm, and 2 is rolled copper foil (black treatment annealed, manufactured by Nippon Mining Co., Ltd.) having a thickness of 35 μm. And a conductor circuit formed by etching or the like. 3 is a spherical hollow protrusion having a diameter of 1.0 mm,
The height is 0.3 mm and the radius of curvature of the tip is 0.92 mm. 4 is a nickel plating part.

The flexible circuit board can be manufactured, for example, as follows. That is, first, as shown in FIG. 2, a base film 1 made of a plastic insulating film such as a polyethylene terephthalate film coated with a polyester adhesive has a diameter of 1.2 mm in advance at a place where the hollow protrusion 3 is to be formed. Round hole 1
a is provided by die processing. The base film 1 having the round holes 1a formed therein and a rolled copper foil having a thickness of 35 μm are attached to each other to form a flexible circuit board material. After that, pattern formation by a photoresist and etching are performed to form a predetermined conductor circuit 2. And this conductor circuit 2
A cover coat film (not shown) made of a polyester film with an adhesive is attached to the top to form an insulating layer. When forming the insulating layer, the end portion (connection terminal) of the conductor circuit 3 is not covered with the insulating layer and is exposed at the end portion of the base film 1. Next, a hollow projection 3 having a desired shape is formed in the portion of the base film 1 where the round hole 1a is formed by drawing from the back surface with a punch. Then, nickel is adhered to the back surface side of the hollow protrusion 3 by electroplating to a thickness of about 10 μm to form the nickel-plated portion 4. Thereby, a desired flexible circuit board can be obtained. The hollow protrusion 3 of the flexible circuit board thus obtained is attached to the conductor circuit 12 of the counterpart component 11 by using a crimping mechanism (not shown) using a spring or the like, as shown in FIG. Press to make electrical connection.

In the flexible circuit board thus obtained, since the nickel plated portion 4 is provided on the back surface of the hollow protruding portion 3, the strength of the hollow protruding portion 3 is increased and the durability is greatly improved. Therefore, when crimping to the other component by a mechanism using a spring, contact failure may occur,
It will not be significantly deformed and will be easy to handle when assembling the circuit. Moreover, as described above, the hollow protrusion 3
Since the durability of is improved, it can be stably used for a long period of time for connecting and wiring parts that are repeatedly detached and attached.

FIG. 4 shows another embodiment of the present invention. In this embodiment, a conical hollow projection 5 is formed instead of the spherical hollow projection of the above embodiment. The radius of the hollow protrusion 5 is 0.15 to 1.00 mm.
Set within the range of, preferably 0.25 to 0.50 mm
It is set within the range of. The height is 0.09 ~
It is set within the range of 0.60 mm, preferably 0.15 to
It is set within the range of 0.30 mm. The inclination angle θ of the conical shape is set within the range of 15 to 60 °, and preferably within the range of 20 to 40 °. The other parts are the same as those in the above-described embodiment, and the same parts are denoted by the same part numbers. Such a flexible circuit board can be manufactured in the same manner as in the above embodiment. However, in this embodiment, the hollow protrusion 5 is formed in a conical shape.

The flexible circuit board thus obtained has the same effect as that of the above-mentioned embodiment, and the hollow protrusion 5 is formed in a conical shape. The surface pressure at the tip of the protrusion is higher than that of the spherical protrusion of the above-described embodiment, and the strength is strong because the radius of curvature is small. Therefore, it becomes easier to handle the circuit when assembling, as compared with the above embodiment. Moreover, it can be stably used for a long period of time even for connection and wiring of parts that are repeatedly detached and attached.

FIG. 5 shows still another embodiment of the present invention. In this embodiment, an epoxy resin 8 is filled as a reinforcing filler by screen printing and potting inside the protrusion 7 formed by drawing with a punch. The other parts are the same as those in the above embodiment, and the same parts are denoted by the same reference numerals.

Next, specific examples will be described together with comparative examples.

[0025]

[Specific Example 1] First, a rolled copper foil having a thickness of 35 μm is attached to a base film made of a polyester film having a thickness of 25 μm via an epoxy adhesive, and thereafter, pattern formation by a photoresist and etching treatment are performed. A predetermined conductor circuit was formed. Then, a cover coat film made of a polyester film with an adhesive was stuck on the conductor circuit to form an insulating layer. When forming this insulating layer, do not cover the end of the conductor circuit with the insulating layer.
Exposed to the edge of the base film. Next, the portion of the base film on which the conductor circuit was formed was drawn from the back surface with a punch to have a diameter of 1.0 mm and a height of 0.3 m.
m, and a spherical hollow protrusion having a radius of curvature of 0.92 mm at its tip was formed. Then, nickel was deposited on the back surface of the hollow protrusion by electroplating to a thickness of about 10 μm to form a nickel-plated portion. As a result, a desired flexible circuit board was obtained. As shown in FIG. 3, the projection of the flexible circuit board thus obtained was crimped to the conductor circuit of the counterpart component by using a crimping mechanism using a spring or the like for electrical connection.

[0026]

Specific Example 2 A flexible circuit board was manufactured in the same manner as in Specific Example 1 above. However, in this specific example 2, the radius of curvature of the tip of the protrusion is set to a value different from that in the specific example 1, that is, 1.33 mm. Also, diameter 1.0m
m and height 0.2 mm. In the same manner as in Specific Example 1 above, the projections of the flexible circuit board thus obtained were pressure-bonded to the conductor circuits of the mating parts for electrical connection.

[0027]

Specific Example 3 A flexible circuit board was manufactured in the same manner as in Specific Example 1 above. However, in this specific example 3, the radius of curvature of the tip of the protrusion is different from those in the specific examples 1 and 2,
That is, it was set to 0.62 mm. Also, the diameter is 0.6
The height was set to 7 mm and the height was set to 0.2 mm. The projecting portion of the flexible circuit board thus obtained is used in the concrete example 1 described above.
In the same manner as above, the conductor circuit of the other component was crimped and electrically connected.

[0028]

Concrete Example 4 The flexible circuit board shown in FIG. 4 was manufactured in the same manner as in Concrete Example 1 above. However, in this Specific Example 4, the projection is formed in a conical shape. The diameter of this protrusion is set to 1.0 mm and its height is set to 0.
It was set to 2 mm. Other than that is the same as the above-mentioned specific example 1. In the same manner as in Specific Example 1 above, the projections of the flexible circuit board thus obtained were pressure-bonded to the conductor circuits of the mating parts for electrical connection.

[0029]

Specific Example 5 The flexible circuit board shown in FIG. 5 was manufactured in the same manner as in Specific Example 1 above. However, in this specific example 5, an epoxy resin is filled by screen printing and potting into the inside of the protrusion formed by punching. Other than that is the same as the above-mentioned specific example 1. In the same manner as in Specific Example 1 above, the projections of the flexible circuit board thus obtained were pressure-bonded to the conductor circuits of the mating parts for electrical connection.

[0030]

Comparative Example A spherical projection 10 formed on the flexible circuit board shown in FIG. 6 has a diameter of 1.0 mm, a height of 0.3 mm, and a radius of curvature of 0.92 at its tip.
It was formed to have a size of mm.

Using the flexible circuit boards of the specific examples 1 to 5 and the flexible circuit board of the comparative example, the protrusions 3, 5, 6, 7, formed on each of the flexible circuit boards described above.
A load of 200 g was applied to the tip of No. 10, and the deformation amount (dent amount) of the tip at that time was measured. Further, the bending strength of each of the protrusions 3, 5, 6, 7, and 10 and the contact state with the counterpart component were measured by the method described below. The results are shown in Tables 1 and 2 below.

The method for measuring the bending strength of the above-mentioned protrusion is as follows:
It is as follows. That is, a load was applied to the tips of the protrusions, and the load when the protrusions buckled (completely recessed) was measured.

The method of measuring the contact state between the above-mentioned protrusion and the other component is as follows. That is, after the minimum value of the distance between the surface of the flexible circuit board and the counterpart component is set to a distance such that the initial contact state is kept good, and the counterpart component is repeatedly attached and detached 10 times. The presence or absence of abnormal contact resistance was examined by the defect rate.

[0034]

[Table 1]

[0035]

[Table 2]

As is clear from Tables 1 and 2 above,
It can be seen that the deformation amount of the concrete examples 1 to 5 is much smaller than that of the comparative example. Further, it can be seen that the products of Examples 1 to 5 are superior in bending strength to the products of Comparative Examples and have a good contact state.

[0037]

As described above, in the flexible circuit board of the present invention, a through hole is formed in the resin substrate corresponding to a predetermined portion of the metal circuit, and the metal circuit portion corresponding to the through hole is hollow. The hollow protrusion is formed on the protrusion, and the reinforcing filler is filled in the hollow protrusion. As described above, in the flexible circuit board of the present invention, since the hollow protrusions are reinforced with the reinforcing filler, the strength thereof can be increased and the durability can be greatly improved. Therefore, when crimping or the like to a component on the other side by a mechanism using a spring or the like, there is no contact failure or large deformation,
It is easy to handle when assembling the circuit. Moreover,
Since the durability of the hollow protrusion is improved as described above,
It will also be possible to use it stably for a long period of time for connecting and wiring parts that are repeatedly attached and detached.

[Brief description of drawings]

FIG. 1 is a sectional view of a flexible circuit board showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a manufacturing process of the flexible circuit board.

FIG. 3 is an explanatory diagram of a contact state between the flexible circuit board and a counterpart component.

FIG. 4 is a sectional view showing another embodiment of the present invention.

FIG. 5 is a sectional view showing still another embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

 1 Base film 2 Conductor circuit 3 Hollow protrusion 4 Plating part

Claims (1)

[Claims] 1. A resin substrate and a metal circuit formed on a substrate surface of the resin substrate, wherein a through hole is formed in a resin substrate corresponding to a predetermined portion of the metal circuit, and the through hole is formed in the through hole. A flexible circuit board, wherein a corresponding metal circuit portion is formed in a hollow protrusion, and a reinforcing filler is filled inside the hollow protrusion.