1. Field of the Invention
The present invention relates to a movable contact unit used for a control panel and the like of various electronic apparatuses, and the invention also relates to a method of manufacturing the same.
2. Background Art
With the recent trend of reduction in sizes and thickness of various electronic apparatuses, there is a continuous increase in number of portable and easy-to-carry apparatuses such as mobile phones, and this trend has been pushing ahead with development of such panel switches as featuring low profile with capability of yielding good tactile responses to actuations for use as control panels and the like of these apparatuses. A large number of the movable contact units now being employed are the type that uses movable contacts of dome-like shape formed of conductive metal plates having elasticity since they can provide reliable electrical contacts.
Referring now to
Sectioned views among these drawings are enlarged dimensionally only in one direction along their thickness for the purpose of making the structures easily comprehensible.
Movable contact unit 4 is pasted with adhesive layer 2 in a removable manner onto a surface of a release layer formed on an upper surface of insulative separator 5 made of PET or the like material. This prevents corrosion of movable contacts 3, and keeps adhesive layer 2 on the underside of base film 1 from accidentally adhering to other parts and collecting undesirable objects during transportation and storage.
In
Movable contact units 4 of the above structure placed on the upper surface of separator 5 are manufactured in the following manner.
First, a required number of downwardly opened dome-like movable contacts 3 are fixed in their respective positions by adhering upper center surfaces thereof to adhesive layer 2 formed on the underside of base film 1.
Next, the entire surface of movable contact unit 4 is adhered to belt-like separator 5 made of an insulation film by using adhesive layer 2 on the underside of base film 1 in a manner to sandwich movable contacts 3, as shown in a sectioned view of
Work-in-process item 6 is then placed with base film 1 side up and separator 5 side down on top of rubber sheet 8 of about 1 mm thickness laid on press table 7 made of a metallic material such as iron.
Press die 9 heated by a heater (not shown) and positioned above base film 1 is then moved down to heat and press (hereinafter described as “hot press”) work-in-process item 6 from the upper side of base film 1.
Press die 9 used here is so formed that a number of portions 9A corresponding to movable contacts 3 are hollowed to avert hot pressing upon areas occupied by movable contacts 3. Flat face 9B thus shaped is capable of pressing the entire surface of work-in-process item 6 except where movable contacts 3 are disposed.
The hot press is carried out under the conditions of 80 to 130° C. in temperature and 0.1 to 0.3 MPa in pressure for 1 to 3 seconds, to complete the manufacturing process of movable contact unit 4 affixed to separator 5.
The hot press carried out in the above manner can bring base film 1 into close adhesion to movable contacts 3 along the dome-like shape, while also preventing base film 1 from coming off separator 5 in areas around the outer rims of movable contacts 3. This method ensures flat surface portions of a sufficient area between adjoining movable contacts 3 for adhesion with separator 5 even when movable contacts 3 are arranged closely with respect to one another. Accordingly, this method achieves consistency of the fixing positions of movable contacts 3 as well as steadiness of adhesion by way of increasing an overall area of adhering surface when movable contact unit 4 is bonded to a wiring board.
A plurality of movable contact units 4 adhered in this manner are arranged at regular intervals on belt-like separator 5, as shown in the perspective view of conventional movable contact units 4 in
Switch 15 constructed as above is used for a portable information-handling device requiring a low-profile structure such as a mobile phone, for example. When this is the case, the switch is placed inside an enclosure case in a manner that the movable contacts are located behind dial buttons and the like, and connected to a control circuit so that the control circuit detects and executes communication control and the like tasks when the dial buttons are pushed.
In the structure discussed above, when a certain amount of pressing force is applied to movable contact 3 from the upper surface of base film 1, movable contact 3 elastically deforms downward into an inverse shape with a tactile click, and the lower center portion of movable contact 3 comes in contact with center stationary contact 12A. This establishes an electrical continuity between center stationary contact 12A and outer stationary contact 12B via movable contact 3.
When the pressing force is removed thereafter from the upper surface of base film 1, movable contact 3 elastically deforms upward into the original shape by its own elastic restoring force. This results in separation of the lower center portion of movable contact 3 from center stationary contact 12A to resume the electrically open state between center stationary contact 12A and outer stationary contact 12B.
In this conventional movable contact unit and the manufacturing method, base film 1 can be processed by the hot press to deform it along the dome-like shape down to the rims of movable contacts 3 since both base film 1 and separator 5 are formed of film materials such as PET. On the other hand, however, there occurs a small extent of deformation in any of base film 1 and separator 5.
An extent of the deformation is not so significant for each set of movable contact unit 4 that it hardly causes any problems in the process of manufacturing when only one set of movable contact unit 4 is adhered onto separator 5. When a plurality of movable contact units 4 are adhered onto separator 5, however, even a small deformation developed in separator 5 can accumulate. As a result, there emerges a substantial deviation in positions of pilot holes 5A used as the reference in a process of forwarding separator 5 from the press table after the hot press, thereby giving rise to a problem of decreasing productivity of movable contact units 4.
There is also a drawback with the above configuration wherein the plurality of movable contact units 4 are disposed at regular intervals on the belt-like separator 5, that a positional correction needs to be repeated frequently due to a cumulative increase in the positional deviation of pilot holes 5A when movable contact units 4 are mounted continuously onto wiring boards 11. This poses another problem of decreasing the efficiency of producing electronic apparatuses.
The present invention addresses the above problems of the conventional art, and provides a movable contact unit and a manufacturing method thereof, which is contrived to reduce deformation attributed to hot press, as compared to the ordinary movable contact unit manufactured by the conventional method, so as to improve an efficiency of manufacturing an electronic apparatus.
The movable contact unit of the present invention comprises a base film, an adhesive layer formed on the underside of the base film, and a downwardly opened dome-like movable contact adhesively fixed to the adhesive layer, wherein the base film has a press-on portion of a circular shape formed by hot press around a peripheral part, or a base of a convex-shaped portion retaining the movable contact, and the base film is in close adhesion with the movable contact from a dome-like top portion down to an outer rim thereof.
By virtue of this structure, the deformation attributed to the hot press becomes smaller as compared to the movable contact unit manufactured by the conventional method. It can thus improve an efficiency of manufacturing the movable contact unit as well as an efficiency of manufacturing an electronic apparatus equipped with a switch comprised of the movable contact unit bonded to a wiring board.
A method of manufacturing a movable contact unit of the present invention comprises a first step of fixing a movable contact of a downwardly opened dome-like shape made of a conductive metal plate having elasticity by adhering an upper center surface thereof to an adhesive layer formed on the underside of a base film, a second step of adhering an upper surface of a separator onto the adhesive layer in a manner to sandwich the movable contact between them, and a third step of hot-pressing in a circular shape the periphery of the movable contact from above the base film to form a convex-shaped portion in an area of the base film corresponding to the movable contact in a manner to fit along the dome-like shape of the movable contact, and to make a peripheral area, or a base of the convex-shaped portion pressed circularly into close adhesion to the separator with the adhesive layer.
Accordingly, the structure can improve the efficiency of manufacturing the movable contact unit as well as the efficiency of manufacturing the electronic apparatus equipped with a switch comprised of the movable contact unit bonded to a wiring board.
Description is provided hereinafter of an exemplary embodiment of the present invention with reference to
Base film 21 is hot-pressed at areas around peripheral parts, or bases of convex-shaped portions retaining movable contacts 23 individually. Base film 21 is in close adhesion with movable contacts 23 from dome-like top portions down to outer rims thereof, and press-on portions 28 are thus formed by being hot-pressed in generally a circular shape around the peripheral parts, or the bases of the convex-shaped portions retaining movable contacts 23.
In
Movable contact units 24 of this structure placed on separator 25 are manufactured in the following manner.
First, a required number of downwardly opened dome-like movable contacts 23 are fixed in their respective positions by adhering upper center surfaces thereof to adhesive layer 22 formed on the underside of base film 21. Next, an entire surface of movable contact unit 24 is adhered to belt-like separator 25 made of an insulation film by using adhesive layer 22 on the underside of base film 21 in a manner to sandwich movable contacts 23, as shown in a sectioned view of
Work-in-process item 26 is then placed with base film 21 side up and separator 25 side down on top of rubber sheet 8 of about 1 mm thickness laid over press table 7 made of a metal material such as iron.
Press die 27 heated by a heater (not shown) and positioned above base film 21 is then moved down to hot press work-in-process item 26 from the upper side of base film 21.
Press die 27 used here has a number of flat faces 27A for pressing in generally a circular shape around the peripheral parts of movable contacts 23, and this hot press is carried out under the conditions of 80 to 130° C. in temperature and 0.1 to 0.3 MPa in pressure for 1 to 3 seconds.
The hot press carried out in this manner can bring base film 21 into close adhesion to movable contacts 23 along their dome-like shape. At the same time, the hot press also produces press-on portions 28 of generally the circular shape (refer to
In addition, the present invention reduces an overall area of surfaces where the hot press is applied on base film 21 since base film 21 is pressed and affixed closely to separator 25 only around the bases of the convex-shaped portions covering the peripheries of movable contacts 23 in a manner to form press-on portions 28 of generally the circular shape. The invention can thus alleviate to a satisfiable degree the deformation of base film 21 and separator 25 attributed to the hot press as compared to the conventional method since there is hardly any deformation to develop in other areas that are not hot-pressed.
A plurality of movable contact unit 24 adhered in this manner are arranged at regular intervals on belt-like separator 25, as shown in the perspective view of movable contact units 24 in
When the plurality of movable contact units 24 are bonded one after another onto wiring boards 11, there are not any deformations developed by the hot press in separator 25 except in the areas corresponding to press-on portions 28 of base films 21. It thus becomes possible to continuously bond movable contact units 24 to wiring boards 11 without making correction of their positions since there is no positional deviation between them even when pilot holes 25A are used as the reference for setting the bonding positions.
Switch 30 of the above structure is assembled within an enclosure case of an electronic apparatus such as a mobile phone in a manner so that movable contacts 23 are located behind dial buttons and the like, and connected to a control circuit. The control circuit detects and executes controlling tasks of the electronic apparatus when the dial buttons are pushed.
In this exemplary embodiment, what has been described is a typical configuration, in which belt-like separator 25 carrying a plurality of movable contact units 24 is used in the process of bonding movable contact units 24 continuously onto wiring boards 11 as illustrated in
In addition, what has been described in this exemplary embodiment is an example, in which adhesive layer 22 on the underside of base film 21 is formed over the entire surface of base film 21. However, base film 21 may have certain areas in press-on portions 28 around the surfaces fixing movable contacts 23 where adhesive layer 22 is not provided in a manner to form passages communicating with the outer rims of adjoining movable contacts 23. This structure achieves movable contact unit 24 having an outstanding click response when being pressed since it allows the air under any of dome-like movable contacts 23 being pressed to escape through the areas not provided with adhesive layer 22 toward adjoining movable contacts 23.
According to this exemplary embodiment, as discussed above, movable contact unit 24 comprises base film 21 made of an insulation film, adhesive layer 22 formed on the underside of base film 21, and downwardly opened dome-like movable contact 23 adhesively fixed to adhesive layer 22, wherein movable contact unit 24 is hot-pressed around the peripheral part of movable contact 23 to make base film 21 in close adhesion with the dome-like shape of movable contact 23, and to form the press-on portion of generally circular shape around the peripheral part of movable contact 23, or the base of the convex-shaped portion of base film 21. The present invention thus enables reduction of the deformation attributed to the process of hot press as compared to the movable contact unit manufactured by the conventional method, thereby providing the novel movable contact unit and the manufacturing method thereof that achieves improvement of the efficiency of manufacturing movable contact units as well as the productivity of electronic apparatuses.
Number | Date | Country | Kind |
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2007-325566 | Dec 2007 | JP | national |
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6593537 | Teruyama et al. | Jul 2003 | B2 |
6604278 | Sera et al. | Aug 2003 | B2 |
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1371110 | Sep 2002 | CN |
8-306261 | Nov 1996 | JP |
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Number | Date | Country | |
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20090152090 A1 | Jun 2009 | US |