JP2001028213A - Contact member for rubber switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a contact member for a push-button type rubber switch, which is free of influence of defective contact caused by blots of a contact of a rubber switch or a fixed contact on a printed circuit, a conductive elastic body of a contact member free from fatigue failure in repeated press contact. SOLUTION: This contact member for a rubber switch is constituted, in such a condition that a plurality of linear conductors 10 are oriented in the thickness direction of the contact member for a rubber switch 10, and at least one part of layers of the contact member 9 is provided with a conductive elastic body 8, the linear conductor 10 has almost same length as the contact member 9 and is exposed at least from one direction of the surface of the contact member, when it is pressed or not pressed. The desirable length of the exposed part of the linear conductor 10 is in the range of 3 μm to 30 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact member of a push-button type rubber switch for inputting a signal provided in an electric device or the like. More specifically, a contact member for a push-button rubber switch in which a linear conductor protrudes from the surface of the contact member when the push button is pressed, and the conductive elastic body does not directly contact the printed wiring circuit on the other side, and its manufacture About the method.

[0002]

2. Description of the Related Art Conventionally, as a push-button type rubber switch provided for inputting a signal to an audio device, a cellular phone or the like, a push-button type rubber switch having a conductive elastic body and an insulating bent portion as shown in FIG. Are known. This is because the bent portion 2 is deformed by applying a certain pressure or more to the center of the push button 1 and the conductive elastic portion 3 on the back surface thereof is brought into contact with the fixed contact portions 4 and 5 formed on the printed wiring circuit. Things.

[0003]

However, in the above-mentioned contact mechanism, dirt which hinders energization such as hand oil and adhesion of flux in a reflow process is present in the contact portion of the rubber switch or the fixed contact portion on the printed wiring circuit. In this case, there is a problem that a contact failure easily occurs.

Further, when repeatedly pressed as a button type rubber switch, the conductive elastic body in contact with the fixed contact portion on the printed wiring circuit undergoes fatigue failure, and a part of the conductive elastic body peels off and loses the current-carrying function. In other words, there is a problem in that the signal input is not released even if the pressure is released by fixing to the contact portion, thereby causing a connection failure.

The present invention solves the above-mentioned problem. Therefore, the contact portion of the rubber switch and the fixed contact portion on the printed wiring circuit are less susceptible to connection failure due to dirt. An object of the present invention is to provide a contact member for a push-button type rubber switch that is not easily damaged by fatigue.

[0006]

In order to achieve the above object, a contact member for a push-button type rubber switch of the present invention has a large number of linear conductors oriented in the thickness direction of the contact member for a rubber switch. And at least a part of the contact member is formed of a conductive elastic body, the linear conductor has a length substantially equal to the thickness of the contact member, and is a linear conductor when not pressurized or when pressurized. Is at least one of the contact member surfaces
It is configured to be exposed from a direction.

In the rubber switch contact member, it is preferable that conductive layers and insulating layers are alternately formed in the thickness direction of the contact member.

In the rubber switch contact member, it is preferable that the linear conductor penetrates or contacts the conductive elastic body constituting at least a part of the contact member.

In the rubber switch contact member, the exposed length of the linear conductor is preferably in a range of 3 μm to 30 μm.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as shown in FIG. 1, a bent portion 11 is deformed by applying a predetermined pressure or more to a central portion of a push button 12, and a conductive portion on the rear surface thereof is provided. The elastic portion 9 is brought into contact with the fixed contact portions 13 and 14 formed on the printed circuit. That is, the linear conductor 10 contacts the circuit electrodes 13 and 14, and functions as a signal input circuit via the conductive elastic body 7 through which the linear conductor 10 in the contact member penetrates.

In the above configuration, the thickness of the contact member is not limited, but the average length is desirably 2 mm or less from the viewpoint of preventing the linear conductor 10 from buckling. More preferably, the average length is 1 mm or less.

The linear conductor 10 is preferably cylindrical, and preferably has an average diameter of 50 μm or less as a linear diameter. More preferably, the average diameter is 20 μm or less.

The linear conductor 10 having the above-described structure is selected from a thin metal wire, and is preferably made of iron, nickel, stainless steel (SUS) or the like. Is preferred.

Further, the linear conductor having the above structure is characterized in that it projects from the surface of the contact member when not pressurized or when pressurized. There is no particular limitation on the protruding length of the linear conductor,
3 μm to 30 μm is desirable. More preferably, 5 μm or more
15 μm.

Further, as a manufacturing method for projecting and orienting the linear conductor into the contact member having the above structure, for example, there is the following manufacturing method.

A large number of magnetic linear conductors having substantially the same length are mixed and dispersed in a matrix liquid, and the surface is covered with an inactive soft coating, and is kept at a distance equal to or greater than the magnetic linear length. The liquid mixture is filled between two planes and held in a sheet shape, and the linear conductor is oriented in the thickness direction of the sheet by the action of a magnetic field. While maintaining the orientation, the distance between the planes is reduced until both ends of the linear body are recessed into the soft coating, and then the matrix is solidified. A large number of linear conductors slightly longer than the thickness of the sheet are oriented in the thickness direction of the sheet, and both ends of the linear conductor project from both sides of the sheet.

In addition, the matrix component having the above-mentioned constitution is sufficient to disperse the linear conductor at a temperature lower than the Curie point of the magnetic substance at any stage of a polymer, a prepolymer or a monomer. Any material having melt fluidity and forming an elastic polymer by polymerization or solidification may be used.

The conductive elastic portion 7 has a thickness of 5 μm or more in the thickness direction of the contact member, and examples of the conductive material include carbon fiber, carbon powder, and conductive metal particles.

The insulating elastic body is formed as a surface layer of the conductive elastic body, and preferably has a thickness of 5 μm or more in the thickness direction of the contact member. More preferably, 10 μm
That is all.

According to the contact member for a push-button type rubber switch of the present invention described above, a large number of linear conductors are oriented in the thickness direction, and the linear conductors extend from the contact member surface when not pressurized or when pressurized. A rubber switch contact member that is configured to protrude. Even if hand oil or flux is present at the fixed contact portion on the printed wiring circuit when the rubber switch is pressed, a linear conductive member is connected to the circuit board. Since the connection is made in such a way that the body bites into the body, it is possible to make the connection less susceptible to the connection-inhibiting substances, and it is possible to provide a rubber switch contact member having high connection reliability.

The contact member for a push-button type rubber switch has a conductive layer and an insulating layer alternately formed in a thickness direction.
The surface layer of the contact rubber is characterized by being an insulating layer,
By bringing an insulating elastic body having relatively high physical strength into contact with the circuit electrode, a direct physical load is not applied to the conductive elastic body. Deterioration of the conductive elastic body that occurs when repeatedly pressed is suppressed, and the physical durability performance is improved.

[0022]

The present invention will be described more specifically with reference to the following examples.

FIG. 1 shows a rubber key according to an embodiment of the present invention, and FIG. 2 shows a contact member according to the present invention. 3 to 7 are schematic diagrams showing a method of manufacturing the present contact member in time series.

First, a contact member which is an object of this embodiment will be described with reference to FIG. 2. An insulating elastic body 6 (for example, electrically insulating silicone rubber), a conductive elastic body 7 (for example, conductive silicone) and Insulating elastic bodies 8 (for example, electrically insulating silicone rubber) are alternately arranged in the thickness direction of the contact member, and a linear conductor 10 (for example, a ferrite type stainless steel fiber) penetrates these sheets 9. The conductor 10 protrudes from the surface of the sheet 9.

The connection of the contact member will be described with reference to FIG. 1. The contact member 9 of the present invention is adhered to the bent portion 11 of the rubber key, and a predetermined pressure or more is applied to the switch portion 12 to form on the printed wiring circuit. The fixed contact portions 13 and 14 are connected. The fixed circuit portions 13 and 14 come into contact with the linear conductor 10 in the contact rubber, and the conductive elastic body 7 in the contact member is contacted.
, The circuits of the contact portions 13 and 14 are electrically connected. In addition, the insulating elastic body 8 has a protective function of the conductive elastic body 7.

This contact member is manufactured as follows.
First, an orientation sheet of a linear conductor is prepared. Meridian 12μ
1 mm short fiber (linear conductor) obtained by cutting ferrite-type stainless steel fiber
Was added to the silicone rubber stock solution 5% by weight, mixed, and defoamed. This mixed solution was applied to two 50 μm-thick polyester films 17, 17 sandwiching a 0.5-mm-thick aluminum spacer. In between, the thickness of the liquid layer is 0.7
Injection was performed with the volume determined to be mm (FIG. 3). FIG.
In the above, reference numeral 16 denotes an inert soft body layer, which is an acrylic-styrene copolymer sheet. The upper thickness is 20 μm,
The lower thickness was 40 μm.

Next, when the mold spacing is 1.2 mm, a magnetic field is applied to a flat mold that also serves as a magnetic pole and has a magnetic field strength of 0.3 T at the mold spacing. conductor)
10 was oriented in the thickness direction of the sheet. Next, the mold interval was slightly narrowed. By this, short fiber (linear conductor)
Both ends of 10 were embedded in the inert soft body layer 16 and pierced. In this state, the temperature was heated to 60 ° C., and the mold was closed while the magnetic field was applied. afterwards,
Two hours later, the mold was opened, and the cured silicone rubber sheet sandwiched between the films was taken out. As a result, the intermediate of FIG. 4 was obtained.

Next, from the intermediate, films 17, 17
And by removing the inert soft body layers 16, 16,
An oriented sheet of the linear conductor 10 was obtained (FIG. 5). The obtained sheet had a linear conductor projecting from the surface, and an oriented sheet of a linear conductor having a projection length of 10 μm on the upper surface and 40 μm on the lower surface was obtained.

Next, a conductive silicone ink (PRK-3C, manufactured by Toray Dow Corning Co., Ltd.) was screen-printed on one surface (lower side of FIG. 5) of the alignment sheet of the linear conductor obtained above. An 80-mesh screen plate was used to apply a coating having a thickness of 10 μm to 20 μm. Then 200
The silicone ink was cured in a hot air circulating oven at ℃. After 30 minutes, the sheet was taken out of the oven to obtain a sheet shown in FIG. In FIG. 6, reference numeral 7 denotes a portion of a conductive silicone rubber layer.

Next, as shown in FIG. 7, an insulating silicone ink 8 is applied to the surface coated with the conductive silicone ink 7 by a screen printing method using a screen plate of 80 mesh.
After applying a coating having a thickness of 10 μm to 20 μm, the silicone ink was cured in a hot-air circulation oven at 150 ° C.
After 30 minutes, the sheet was taken out of the oven to obtain a sheet shown in FIG. The length of the linear conductor 10 exposed from the sheet was about 10 μm on both the upper and lower surfaces.

The obtained sheet was cut into a size required for the contact portion of the rubber switch, and was integrally molded when the bent portion 11 of the push button type rubber switch was heated and cured in a mold. Further, the same configuration can be obtained even if the bent portion 11 of the push button type rubber switch is heat-cured and then integrated with the contact member with a silicone-based one-component adhesive.

FIG. 8 shows resistance data in which the contact members of the above embodiment are mounted on a printed circuit board coated with flux.

When the contact member of the above embodiment was repeatedly pressed on a printed circuit board having two independent electrodes, the conductive elastic material was transferred between the electrodes, and it was confirmed that no leakage occurred between the fixed electrodes. It is shown in FIG.

As is clear from FIGS. 8 and 9, the product of the embodiment of the present invention is less susceptible to connection failure due to contamination of the contact portion of the rubber switch and the fixed contact portion on the printed wiring circuit than the conventional product. It was confirmed that the conductive elastic body of the contact member is a contact member for a push button type rubber switch that is hard to be broken by fatigue during repeated pressure welding.

[0035]

As described above, according to the present invention,
A large number of linear conductors are oriented in the thickness direction of the rubber switch contact member, and at least a part of the contact member is formed of a conductive elastic body, and the linear conductor is substantially equal to the thickness of the contact member. It has the same length, and the linear conductor is exposed from at least one direction of the contact member surface when not pressurized or when pressurized. It is possible to provide a contact member for a push-button type rubber switch that is hardly affected by poor connection due to contamination of the fixed contact portion and that is less likely to cause fatigue damage to the conductive elastic body of the contact member during repeated press-contacting.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a push-button type rubber switch using a contact member of the present invention.

FIG. 2 is a sectional view showing an example of a contact member for a push button type rubber switch of the present invention.

FIG. 3 is a schematic view showing a manufacturing process of the contact member of the present invention;
Sectional drawing of the process which filled the linear mold | conductor with the liquid rubber solution in the molding die space.

FIG. 4 is a cross-sectional view of a process in which the linear conductor is oriented in the thickness direction of the sheet and the rubber is cured.

FIG. 5 is a cross-sectional view of a process in which a molding die in a vertical direction is removed.

FIG. 6 is a cross-sectional view of a step of applying a conductive silicone ink to one surface of the sheet.

FIG. 7 is a cross-sectional view showing a step of forming an electrically insulating silicone rubber layer on the surface of the conductive silicone ink layer.

FIG. 8 is a diagram showing resistance value data when the contact member according to one embodiment of the present invention is pressed against a printed circuit board on which a flux is applied.

FIG. 9 shows the contact member of the present invention repeatedly press-contacted on a printed circuit board having two independent electrodes according to an embodiment of the present invention and a conventional example, and the contact member contacts between the two electrodes except for pressing. The figure which shows the insulation resistance data between two electrodes in the state without.

FIG. 10 is a sectional view of a conventional push-button rubber switch.

[Explanation of symbols]

 1,12 push button 2,11 rubber key bent part 3,7 conductive elastic part 4,5,13,14 circuit electrode of printed wiring 6,8 insulating elastic part 9 contact member 10 linear conductor 16 inert soft body Layer 17 Polyester film 18 Liquid rubber (before solidification)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masakazu Koizumi 175 Blacksmith House, Ohara-mura, Nishikamo-gun, Aichi Prefecture F-term (reference) 5F006 AA01 AZ01 AZ08 FB06 FB16 FB36 5G051 AA08 AC13 AC28

Claims (4)

[Claims] A plurality of linear conductors are oriented in a thickness direction of a rubber switch contact member, and at least a part of a layer of the contact member is formed of a conductive elastic body; Has a length substantially equal to the thickness of the contact member, and is configured such that the linear conductor is exposed from at least one direction on the surface of the contact member when not pressed or when pressed. . 2. The rubber switch contact member according to claim 1, wherein conductive layers and insulating layers are alternately formed in the thickness direction of the contact member. 3. The rubber switch contact member according to claim 1, wherein the linear conductor penetrates or contacts the conductive elastic body constituting at least a part of the contact member. 4. The exposed length of the linear conductor is 3 μm to 30 μm.
The contact member for a rubber switch according to claim 1, wherein the thickness is in a range of μm.