JPH05327134A - 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:The title circuit board is provided with a base film 1, a conductor circuit 2 formed on the base film 1 surface, and a protrusion 3 of a nearly hollow circular cone type which is formed on a part of the conductor circuit 2 so as to protrude.

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 having protrusions 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 type of flexible circuit board includes a resin substrate and a metal circuit portion formed on the surface of the resin substrate, and electrically connects between the end portion (connection terminal) of the metal circuit portion and a plurality of electric components. Connected to. As a method for making such electrical connection, generally,
The method of using an insertion type connector, the method of soldering, etc. are adopted. However, in these methods, the soldering process is indispensable, so
There is a problem that a lot of equipment and labor are required to assemble 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. 3, the back surface of the resin substrate 1 of the flexible circuit board is deformed into a concave shape by using a mold, so that the surface of the resin substrate 1 is made spherical. A projection has been proposed and partly implemented (Japanese Utility Model Publication No. 59-10700) in which a projection 10 is provided and the projection 10 is crimped to a component on the other side so that electrical connection can be performed. 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 without contact failure or deformation. It is an object of the present invention to provide a flexible circuit board having a protrusion that can be electrically connected.

[0007]

In order to achieve the above object, a flexible circuit board having a protrusion of the present invention is
A resin substrate, a metal circuit portion formed on the surface of the resin substrate, and a substantially hollow conical protrusion formed on a part of the metal circuit portion are provided.

[0008]

That is, the inventors of the present invention do not cause contact failure or significantly deform when the projection provided on the surface of the flexible circuit board is pressure-bonded to the other component to make an electrical connection. To do so, a series of studies was conducted.
As a result, it was found that when the projection is formed in a spherical shape as in the conventional example, the radius of curvature of the tip becomes large, and thus the amount of deformation with respect to the stress becomes large. For this reason,
Although it has been considered to reduce the radius of curvature, if the radius of curvature of the spherical projection is reduced, the height of the projection is reduced, and there is a problem in that there are many restrictions in use. Then, as a result of further research, it was found that the radius of curvature can be made extremely small and the height of the protrusion can be sufficiently secured when the protrusion is formed in a substantially hollow conical shape. Reached In the present invention, the substantially hollow conical projection includes not only a projection in which the entire projection is formed in a hollow cone shape, but also a projection in which a part is formed in a hollow cone shape.

Although a method of increasing the thickness of the material forming the flexible circuit board can be considered in order to improve the durability of the protrusions, the flexibility of the flexible circuit board is impaired or the cost becomes high. There are many negative effects. However, in the present invention, since the durability can be improved by forming the protrusions in the substantially hollow conical shape as described above, it is not necessary to increase the thickness of the material forming the flexible circuit board, and Such an adverse effect does not occur.

Next, the present invention will be described in detail.

The flexible circuit board having protrusions of the present invention is obtained by using a resin substrate 1 and a metal circuit portion 2 formed on the resin substrate 1, as shown in FIG.

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. Most of the plastic films such as polyetherimide (PEI) film, fluorine film such as tetrafluoroethylene film, polyphenylene sulfide (PPS) film and polyparabanic acid (PPA) film are used. In particular,
A polyimide film or polyethylene terephthalate film is used, and its thickness is 0.008 to 0.2.
It is set within a range of 5 mm, preferably 0.013 to
It is set within the range of 0.125 mm.

As a material for forming the metal circuit portion 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.

As a method of integrally forming the resin substrate 1 and the material for forming the metallic circuit portion 2, a method of attaching the both through an epoxy-based, urethane-based or polyester-based adhesive, Conventionally known methods such as a method of directly forming the resin substrate 1 on the material for forming the metal circuit portion 2 or a method of directly forming the material for forming the metal circuit portion 2 on the resin substrate 1 are mentioned. ..

A protrusion 3 having a substantially hollow conical shape is formed on a part of the metal circuit portion 2. The radius of the protrusion 3 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 set within the range of 0.09 to 0.60 mm, and preferably within the range of 0.15 to 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 °. As a method of forming the protrusions 3 on the surface of the resin substrate 1, there is a method of drawing the back surface of the resin substrate 1 using a punch.

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

[0017]

1 shows an embodiment of the present invention. In the figure, 1 is a base film (resin substrate) made of a polyester film (Lumirror, manufactured by Toray) having a thickness of 25 μm, and 2 is a rolled copper foil (black treatment annealed, manufactured by Nippon Mining Co., Ltd.) having a thickness of 35 μm. It is a conductor circuit formed by etching or the like. Reference numeral 3 is a protrusion having a diameter of 1.0 mm and a height of 0.2 mm.

The flexible circuit board having the above projections can be manufactured, for example, as follows.
That is, first, a rolled copper foil is attached to a base film 1 made of a plastic insulating film such as a polyester film via an adhesive such as an epoxy type, and then,
A predetermined conductor circuit 2 is formed by performing pattern formation with a photoresist and etching. Then, a cover coat film (not shown) made of a polyester film with an adhesive is attached on the conductor circuit 2 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 portion of the base film 1 on which the conductor circuit 2 is formed is drawn from the back surface with a punch to form a projection 3 having a desired shape. This makes it possible to obtain a flexible circuit board having a desired protrusion. As shown in FIG. 2, the projections 3 of the flexible circuit board thus obtained are crimped to the conductor circuit 8 of the counterpart component 7 by using a crimping mechanism (not shown) using a spring or the like. Make electrical connections.

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

[0020]

[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, a portion of the base film on which the conductor circuit is formed is drawn from the back surface with a punch to have a diameter of 1.0 mm and a height of 0.2 m.
m, and a tilt angle of 25 ° was formed. Thereby, a flexible circuit board having a desired protrusion was obtained. As shown in FIG.
As shown in FIG. 7, the conductor circuit of the counterpart component was crimped using a crimping mechanism using a spring or the like for electrical connection.

[0021]

Specific Example 2 In the same manner as in Specific Example 1 above, a flexible circuit board having protrusions was manufactured. However, in the second specific example, the inclination angle of the protrusion is different from that in the first specific example,
That is, it was set to 35 °. Also, the diameter is 0.6 mm
The other parts are the same as those in the first specific example. The projections of the flexible circuit board thus obtained were pressure-bonded to the conductor circuit of the counterpart component in the same manner as in Specific Example 1 above for electrical connection.

[0022]

SPECIFIC EXAMPLE 3 In the same manner as in Specific Example 1 above, a flexible circuit board having protrusions was manufactured. However, in this specific example 3, the inclination angle of the protrusion 3 is set to a value different from those in the specific examples 1 and 2, that is, 15 °. The height is 0.
The length is 12 mm, and the other portions are the same as those in the specific example 1. The projections of the flexible circuit board thus obtained were pressure-bonded to the conductor circuit of the counterpart component in the same manner as in Specific Example 1 above for electrical connection.

[0023]

COMPARATIVE EXAMPLE A spherical projection 10 formed on the flexible circuit board shown in FIG. 3 has a diameter of 1.0 mm, a height of 0.2 mm, and a tip radius of curvature of 0.65 m.
It was formed so as to be m.

Using the flexible circuit boards of the specific examples 1 to 3 and the flexible circuit board of the comparative example, 2 are provided at the tips of the protrusions 3 and 10 formed on each of the flexible circuit boards.
A load of 00 g was applied, and the deformation amount (dent amount) of the tip at that time was measured. The bending strength of each of the protrusions 3 and 10 and the contact state with the counterpart component were measured by the methods described below. The results are shown in Tables 1 and 2 below.

The method for measuring the bending strength of the protrusions is as follows. That is, a load was applied to the tips of the protrusions 3 and 10, and the load when the protrusions 3 and 10 buckled (completely depressed) was measured.

The method of measuring the contact state between the protrusion and the other component is as follows. That is, the distance between the surfaces of the flexible circuit boards 1 to 3 and the flexible circuit board of the comparative example and the component 7 on the partner side is fixed to a distance such that the initial contact state is kept good, and the component on the partner side is fixed. 7 was repeated 10 times and the presence or absence of abnormal contact resistance after desorption was examined by the defective rate.

[0027]

[Table 1]

[0028]

[Table 2]

As is clear from Tables 1 and 2 above,
It can be seen that the amount of deformation is much smaller in the concrete examples 1 to 3 than in the comparative example. Further, it can be seen that the products of Examples 1 to 3 are superior in bending strength to the products of Comparative Examples and have a good contact state. In addition, although the product of Example 3 is superior to the product of Comparative Example in terms of bending strength (buckling strength), the amount of deformation is relatively large and the height is low, so that there are many restrictions in use.
Attempts to increase the height result in an unnecessarily large diameter, which is similarly limited. In this way concrete example 3
The product has less merit than the other specific examples 1 and 2.

[0030]

As described above, according to the flexible circuit board having the projection of the present invention, the projection provided on the surface of the flexible circuit board is formed in a substantially hollow conical shape, so that it is different from the counterpart component. They are in contact with each other, the surface pressure at the tip of the protrusion is high, and the strength is strong because the radius of curvature is small. 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, since the protrusions are excellent in strength as described above, the durability is improved, and it is possible to stably use the components for connecting and wiring which are repeatedly detached and attached for a long period of time.

[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 an explanatory view of a contact state between the flexible circuit board and a counterpart component.

FIG. 3 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

 1 base film 2 conductor circuit 3 protrusion

Claims (1)

[Claims] 1. A resin substrate, a metal circuit portion formed on the surface of the resin substrate, and a substantially hollow conical protrusion formed on a part of the metal circuit portion. A flexible circuit board having a protrusion.