JP4056521B2 - Manufacturing method of pushbutton switch member - Google Patents

Description

  The present invention relates to a method for manufacturing a member for a push button switch used in an electronic device, a portable terminal, and an automotive part, and more particularly to a method for manufacturing a member for a push button switch having a reverse hook-shaped portion that generates a click feeling. .

  Conventionally, switch parts of electronic devices that are required to be light and thin, such as mobile terminals, have a click feeling generated by a metal or resin disc spring (reverse hook-shaped spring member) in order to obtain a reliable click feeling with a minimum thickness. A pushbutton switch member used as a member is used. FIG. 7 shows a push button switch member 60 conventionally used in a thin mobile phone. The push button switch member 60 is incorporated in the casing as a separate part from the key top member 61 and the metal disc spring 63. That is, the metal disc spring 63 is arranged so that the reverse saddle-shaped portion of the metal disc spring 63 corresponds to the hole portion of the holey PET sheet 65 with adhesive arranged on the fixed substrate 64, and And is covered with a disc spring fixing sheet 66, and is separate from the key top member 61. The key top member 61 is used in an overlapping manner on the metal disc spring 63. It is configured.

  In this case, the positional deviation of the two parts occurs due to the assembling tolerance at the time of assembling and the dimensional tolerance of the parts, and the pressing force transmitter 62 which is a protrusion provided on the bottom surface of the key top member 61 is In some cases, the center portion is not pressed and a click feeling is poor.

In view of this, the present applicant proposed in Japanese Patent Application No. 10-364919 a method of assembling and fixing a dome-shaped metal disc spring directly to the pressing force transmitter of the key top member using an adhesive. Measures against misalignment are performed (see Patent Document 1).
Another patent document discloses a switch mechanism in which a conductive rubber is interposed on the inner surface of a disc spring (see Patent Document 2).
There are the following.

Japanese Unexamined Patent Publication No. 2000-188035 (paragraph [0007], FIG. 1) Japanese Utility Model Publication No. 05-043436 CD-ROM (paragraph [0019], FIG. 3)

  Although the above-mentioned proposal can prevent misalignment of the key top member and the metal disc spring for generating a click feeling, the metal disc spring is extremely hard when used as a member for generating a click feeling. When pressed from above, there is a characteristic of making point contact with the contact of the fixed substrate. For this reason, there has been a problem in that, when a component is assembled, if there is a minute foreign matter mixed in or attached to the movable contact portion formed on the metal disc spring, contact failure occurs. Specific examples of the foreign matter include powder at the time of cutting a fixed substrate made of glass epoxy or the like, or dust or sand that enters from the outside. In many cases, the size is 0.1 mm or less, and even if attention is paid to the installation environment, it is difficult to determine with the naked eye.

  Therefore, recently, as shown in FIG. 8, the conductive contact 67 is printed on the polyester sheet 65, and the polyester sheet 65 and the spacer 68 are integrated and fixed on the fixing substrate 64 with an adhesive film. See examples of arranging the key top member 61 and examples of additionally incorporating an anisotropic conductive elastic sheet including a fiber structure on the inner surface of the metal disc spring or the fixed substrate side at the expense of the click feeling required for the pushbutton switch. It is supposed to be.

  In any case, it is not enough as a pushbutton switch member because it increases the number of assembly steps, reduces the input recognition function (click feeling) as a pushbutton switch, and adversely affects the thinning of parts. Met.

  An object of the present invention is to provide a method for manufacturing a member for a pushbutton switch using a reverse saddle-shaped member that is thin and lightweight, does not impair a good click feeling, and does not easily cause poor conduction due to minute foreign matter.

The present invention has been made to solve the above-mentioned problems, and the manufacturing method of the member for a push button switch according to claim 1 is characterized in that the tip of the pressing force transmitter projecting downward from the bottom surface of the key top portion is pressed. A method of manufacturing a member for a push button switch in which a reverse saddle-shaped spring member that generates a click feeling by deformation thereof is bonded and integrated with an adhesive,
First, an uncured conductive rubber elastic body is supplied to the center of the inner surface of the reverse saddle spring member,
The tip portion is formed into a substantially convex shape having the same curved surface as the curved surface of the reverse saddle-shaped spring member, and the tip portion is made to have the reverse saddle-like spring member using one or more fine protrusions on the surface. And is pressed with a predetermined pressure to cure the uncured conductive rubber elastic body, to form a conductive rubber elastic body layer in a predetermined range on the inner surface of the reverse saddle-shaped spring member,
Subsequently, an adhesive is applied to the tip of the pressing force transmitter to bond the apex of the reverse saddle spring member.

  The invention according to claim 2 is characterized in that the conductive rubber elastic body layer is formed with a predetermined thickness over the entire surface centering on a central portion of the reverse saddle-shaped spring member. It is a manufacturing method of the member for pushbutton switches of Claim 1.

  According to the method for manufacturing a member for a pushbutton switch according to the present invention, the switch structure is simplified, the conductive rubber elastic body layer is uniformly applied, and the switch structure is thin and lightweight, but the click feeling is impaired. In addition, there is an effect that it is possible to provide a method for manufacturing a member for a push button switch in which a conduction failure due to a minute foreign matter is unlikely to occur.

  Hereinafter, with reference to the drawings, a related switch structure will be described as a first embodiment of a method for manufacturing a pushbutton switch member according to the present invention. 1A and 1B show a first embodiment of a push button switch member according to the present invention, in which FIG. 1A is a longitudinal sectional view and FIG. 1B is a bottom view. As shown in the drawing, the push button switch member 10 has a key top portion 11, and the tip of the pressing force transmitter 12 provided below the bottom surface of the key top portion 11 is not pressed. Further, a metal disc spring (reverse hook-like spring member) 13 that generates a click feeling due to the deformation is bonded by a conductive adhesive 14. Further, a predetermined range of the inner central portion of the metal disc spring 13, that is, in terms of diameter, at least 8% of the diameter of the metal disc spring 13, and preferably a thickness of 0.037˜ A 0.15 mm conductive rubber elastic body layer 15 is formed.

  The metal disc spring 13 is provided with a through hole 13 a having a diameter of 5% to 20% of the diameter of the metal disc spring 13 at the center thereof, and a conductive rubber formed on the inner surface of the metal disc spring 13. The elastic body layer 15 and the conductive adhesive 14 applied to the pressing force transmitter 12 communicate with each other through the through hole 13a. This is generated when the metal disc spring 13 is bonded to the pressing force transmitter 12.

  This manufacturing method will be described. First, a conductive adhesive 14 in which conductive particles are blended with a silicone rubber elastic body is applied to the tip of the pressing force transmitter 12. Next, the apex of the metal disc spring 13 is positioned and brought into contact with the tip. Subsequently, as shown in FIG. 4, the tip 40 a is formed in a substantially convex shape having the same curved surface as the dome-shaped curved surface of the metal disc spring 13, and a plurality of, preferably 0.2 mm in diameter on the surface, preferably A tip 40a of a jig 40 having three (number shown) or four fine projections 41 is fitted to the inner surface of the metal disc spring 13 and pressed with a predetermined pressure. As a result, a part of the conductive adhesive 14 applied to the distal end portion of the pressing force transmitter 12 flows out from the through hole 13a in the central portion of the metal disc spring 13 to the inner surface, and the conductive rubber elastic layer 15 Formed as.

  The jig 40 is made of aluminum or SUS, and a Teflon coat is applied to the front end portion 40a and the surface in the vicinity thereof. The pressure for pressing the metal disc spring 13 is 500 gr, the temperature at that time is 100 ° C., and the pressing time is 30 sec. When the height t of the fine protrusions 41 is set to 0.04 mm, for example, the thickness of the conductive rubber elastic body layer 15 is also formed to 0.04 mm (40 μm). If the height t of the fine protrusion 41 is set in the range of 0.037 to 0.15 mm, the thickness of the conductive rubber elastic body layer 15 can also be set in the range of 0.037 to 0.15 mm. In this case, the place where the fine protrusion 41 is provided is other than the central portion of the tip of the jig 40. Strictly speaking, the setting of the height t of the fine protrusion 41 is performed in consideration of the shrinkage associated with the thermosetting of the conductive rubber elastic body layer 15. The reason why the thickness of the conductive rubber elastic layer 15 is in the range of 0.037 to 0.15 mm will be described later.

  Next, the manufacturing method of the member for a pushbutton switch of the present invention will be described as a second embodiment by first showing the switch structure. FIG. 2 shows a second embodiment, where (a) is a longitudinal sectional view and (b) is a bottom view. As shown in the figure, the push button switch member 20 has a key top portion 21, and the distal end portion of the pressing force transmitter 22 projecting from the bottom surface of the key top portion 21 is pressed. A metal disc spring (reverse hook-shaped spring member) 23 that generates a click feeling due to the deformation is bonded by an adhesive 24. In addition, a predetermined range of the central portion of the inner surface (inner surface) of the metal disc spring 23, that is, a diameter of 0.037 mm to 0.15 mm in the range of at least 8% of the diameter of the metal disc spring 23. A rubber elastic body layer 25 is formed. This push button switch member 20 is different from the first embodiment in that a through hole is not provided in the central portion of the metal disc spring 23.

  A manufacturing method according to an embodiment of the present invention will be described. First, a liquid conductive rubber elastic body is supplied to the center of the inner surface of the metal disc spring 23, and then the tip 50a is the same as the dome-shaped curved surface of the metal disc spring 23 as shown in FIG. Using a jig 50 which is formed in a curved convex shape and has fine protrusions 51 on the surface, the tip 50a is fitted to the inner surface of the metal disc spring 23 and pressed with a predetermined pressure. Thereby, the conductive rubber elastic body layer 25 is formed in a predetermined range on the inner surface of the metal disc spring 23. Next, an adhesive 24 is applied to the tip of the pressing force transmitter 22, and the apex of the metal disc spring 23 is positioned and bonded. The jig 50 in this case is also made of aluminum or SUS, and the tip portion 50a and the surface in the vicinity thereof are coated with Teflon. The pressure for pressing the metal disc spring 23 is 500 gr, the temperature at that time is 100 ° C., and the pressing time is 30 sec. Also in this case, when the height t of the fine protrusion 41 is set to 0.04 mm, for example, the thickness of the conductive rubber elastic body layer 15 is also formed to 0.04 mm (40 μm). If the height t of the fine protrusion 41 is set in the range of 0.037 to 0.15 mm, the thickness of the conductive rubber elastic body layer 15 can also be set in the range of 0.037 to 0.15 mm.

  In the pushbutton switch member 20 of the second embodiment, the range of the conductive rubber elastic body layer 25 formed on the inner surface of the metal disc spring 23 is the center of the metal disc spring 23 as shown in FIG. Although it is in a certain range (at least 8% or more of the diameter of the metal disc spring 23), the amount of the conductive rubber elastic body to be supplied is increased, and as shown in FIG. May be formed. In this way, when the key top portion 21 is pressed to deform the metal disc spring 23, the fixed contact surface of the fixed substrate with which the hem portion of the metal disc spring 23 abuts is slid slightly. If the conductive rubber elastic body layer 25 is formed over the entire inner surface of the metal disc spring 23 in this way, the conductive rubber elastic body layer 25 itself contacts the fixed contact surface. Because it slides in close contact, it is hard to be damaged.

  In order to give the conductive rubber elastic body to the surface of the metal disc spring 13 (23), technical techniques such as printing, painting, and transfer are conceivable, but the size of the foreign matter that cannot be visually confirmed is 0.1 mm or less. The foreign material must have a thickness that allows it to surely sink into the conductive rubber elastic layer 15 (25) and to be electrically connected to the fixed substrate, and the click feeling that is a basic required characteristic of the metal disc spring 13 (23). While ensuring a load value of 180 gr to 280 gr and exhibiting an effect on foreign matters, and further, the conductive rubber elastic body is uniformly applied to the inverted saddle-shaped curved surface of the metal disc spring 13 Is required.

  Next, as a result of verification, it has been found that the thickness of the conductive rubber elastic body 15 (25) that does not impair conduction with respect to a foreign object of 0.1 mm or less may be 0.037 mm to 0.05 mm. It has been found that 0.04 mm is preferable. In addition, when it is set as the range which does not impair electrical conduction with respect to the foreign material having a size of 0.1 mm or less, which is a premise, the thickness is not particularly limited as long as it is 0.037 mm or more. This will impair the click feeling of the disc spring. Therefore, the thickness is preferably 0.04 mm as described above.

  Next, the thickness of the conductive rubber elastic body 15 (25) is set to 0.04 mm, the diameter of the metal disc spring 13 (23) is changed to 3, 4, and 5 mm, and the height of the dome-shaped portion that does not impair the click feeling. Table 1 shows the results of the verification.

From Table 1, it can be seen that the height of the reverse saddle-shaped portion can be realized at 0.19 mm to 0.35 mm, and preferably 0.22 mm that showed the best click feeling. The click feeling will be described. When the key top portion is pushed down, as shown in FIG. 6, the load gradually increases with the stroke change, but reaches a predetermined stroke point S1, and has a reverse saddle shape. The part suddenly reverses and deforms downward. Immediately after the reverse saddle-shaped portion suddenly reversely deforms downward, the load is reduced even if the stroke increases. Further, when the stroke S2 is reached and the movable contact provided in the reverse saddle-shaped portion comes into contact with the fixed contact provided below, the deformation of the reverse saddle-shaped portion ends, and when the stroke is subsequently increased, Only the load increases rapidly without deformation. The click rate, which is said to be an indicator of good click feeling, is (F1-F2) / F1 × 100 (%)
(However, F1: Load at stroke S1, F2: Load at stroke S2)
It is expressed. Here, the good click feeling is defined as a case where the numerical value of the above formula is 30% or more.

  As described above, in this embodiment, verification was performed in the range of 180 to 280 gr, which is a general value of the maximum load requirement in the switch device, and in the range of the metal disc spring diameter from 4 mm to 6 mm. When the disc spring diameter is 6 mm or more and the maximum load is 280 gr or more, the thickness of the conductive rubber elastic body provided on the inner surface of the metal disc spring can be increased with a change in the height of the dome-shaped portion where a click feeling can be obtained. In that case, if necessary, the height t of the fine protrusions of the jigs 40 and 50 is changed to 0.037 to 0.15 mm, and the thickness of the conductive rubber elastic body layer 15 is set to 0.037 mm to 0.15 mm. You can do it.

  Next, the thickness of the conductive rubber elastic layer 15 (25) is set to 0.04 mm, the diameter of the foreign matter is changed from 0.04 mm to 0.150 mm, the key top member 11 (21) is pushed in, and the metal disc spring is pressed. Table 2 shows the results of verifying the time to turn on compared to the case of only the case.

  As can be seen from Table 2, compared to the case where the conductive rubber elastic body layer 15 (25) is provided, the reaction time is longer when only the metal disc spring 13 (23) is used, and the foreign matter diameter is 0.09 mm. The contact could not be turned on. When the conductive rubber elastic layer 15 (25) was provided, it was found that the contact point was turned on even when the diameter of the foreign material was 0.09 mm.

  Now, the reason why the thickness of the conductive rubber elastic layer 15 (25) is set in the range of 0.037 mm to 0.15 mm will be described here. First, regarding the lower limit of 0.037 mm, from Table 2, when only a metal disc spring is used, conduction is not obtained when the diameter of the foreign object is 0.09 mm, and on when the diameter of the foreign object is 0.063 mm. Although it takes time to do, it turns on, so this is considered to be almost the limit point. Therefore, if the maximum diameter of a foreign object that cannot be seen is 0.1 mm, the height of the portion protruding to the outside is set to 0.063 mm when this is buried in the conductive rubber elastic layer 15 (25). Indicates that the thickness of the conductive rubber elastic layer 15 (25) may be 0.037 mm (0.1−0.063 = 0.037 mm).

  Next, the upper limit of 0.15 mm will be described. As the thickness of the conductive rubber elastic body 15 (25) swings in the thicker direction, a better result is obtained in terms of measures against foreign matters, but in terms of generating a clear click feeling, which is a basic performance as a switch. Since the stroke is reduced, it is not preferable. In general, a metal Belleville spring has a cross-sectional shape in which a gentle hemisphere is placed on the upper base of a substantially trapezoidal shape, with a stroke of 0.18 mm to 0.7 mm, many 0.2 mm. To 0.35 mm. In order not to impair the click feeling even at this 0.35 mm stroke, it is understood that 0.35-0.2 = 0.15 mm is obtained by subtracting the minimum stroke of 0.2 mm that does not impair the click feeling. . Therefore, the conductive rubber elastic body layer necessary for satisfying the effect on all foreign matters having a diameter of 0.1 mm or less is 0.03 mm to 0.15 mm. In addition, the foreign material exceeding 0.1 mm can be removed by visual inspection in the manufacturing / assembly process.

  Next, the results of measuring the contact resistance values are shown in Table 3.

As can be seen from Table 3, it is obvious that the resistance value is lower when only the metal disc spring 13 (23) is used, but this is not a particularly problematic difference. 15 (25) is also shown to be sufficient as a contact member. As a contact resistance value of the conductive rubber elastic body layer 15 (25), if it is 50Ω or less, there is no problem, and a desired elastic body can be selected in relation to the elastic modulus and the resistance value.
However, when verifying with the aim of increasing the conductivity and decreasing the resistance value, adding conductive carbon particles or metal particles to the rubber elastic body excessively will not only affect the contact life from the physical strength, but also contact points. There is also the possibility of causing a short circuit between the contacts due to powder.
It can be within 10% to 45% of the number of material parts of the rubber elastic body raw material, and more preferably within the range of 15% to 35%.

Stainless steel disc spring made of SUS301 with a thickness of 0.05 mm in a reverse bowl shape is formed into a reverse bowl shape with a reverse bowl shape part diameter of 5 mm, a reverse bowl part height of 0.26 mm, and a maximum load of 230 gr. Mold.
KE-3490 conductive RTV adhesive (manufactured by Shin-Etsu Chemical Co., Ltd.) is supplied to the inner surface of the reverse hook-shaped part in an amount of 0.15 gr. (See FIG. 5) After heating to 100 ° C., pressure is formed on the inner surface of the metal disc spring at 500 gr for 30 seconds. The pushbutton switch member 20 was obtained by bonding and fixing the metal disc spring obtained here to the pressing force transmitter.

The metal disc spring is made of stainless steel 0.05 mm thick made of SUS301 in a reverse saddle shape with a reverse die shape with a reverse saddle shape part diameter of 5 mm, reverse saddle shape part height of 0.28 mm, and a maximum load of 250 gr. Is molded. At this time, a 0.7 mm through hole is provided in the center of the metal disc spring.
5 parts of carbon-based conductive particles and 10 parts of silver particles are blended and fixed in a silicone-based adhesive Super X (manufactured by Cemedine Co., Ltd.) used when the pressing force transmitter and a metal disc spring are bonded and fixed.
At that time, after the conductive adhesive discharged from the center part of the metal disc spring was heated to 100 ° C. (see FIG. 4), the aluminum cylindrical jig whose tip shape was processed in the same manner as the inverted saddle-like shape and processed with Teflon Then, a member 10 for a push button switch provided with a conductive rubber elastic body layer cured by press forming at 500 gr for 30 seconds on the inner surface of the metal disc spring was obtained.

  In the above-described embodiment and examples, the metal disc spring 12 (23) made of SUS or the like is used as the inverted saddle-like member referred to in the present invention. Etc. can also be used.

1A and 1B show a first embodiment related to a method for manufacturing a member for a push button switch according to the present invention, in which FIG. 2nd Embodiment concerning the manufacturing method of the member for pushbutton switches of this invention is shown, (a) is a longitudinal cross-sectional view of the member for pushbutton switches, (b) is the bottom view. The modification of the member for pushbutton switches of 2nd Embodiment is shown, (a) is the longitudinal cross-sectional view, (b) is the bottom view. The jig | tool and manufacturing method when manufacturing the member for pushbutton switches which concern on 1st Embodiment are shown, (a) is a top view of a jig | tool, (b) is a side view, (c) is a conductive rubber elastic body It is a figure which shows the shaping | molding method of a layer. The jig | tool and manufacturing method when manufacturing the member for pushbutton switches concerning 2nd Embodiment are shown, (a) is a top view of a jig | tool, (b) is a side view, (c) is a conductive rubber elastic body FIG. 4D shows a layer forming method, in which (d) shows a state in which a metal disc spring is bonded to a pressing force transmitter of a key top member. It is a switch characteristic curve which shows the relationship between a pressing load and a stroke. It is a longitudinal cross-sectional view of the conventional member for pushbutton switches. Similarly, it is a longitudinal cross-sectional view of the conventional member for pushbutton switches.

Explanation of symbols

10, 20 Pushbutton switch member 11, 21 Key top member 12, 22 Pressing force transmitter 13, 23 Metal disc spring (reverse saddle spring member)
14 Conductive adhesive 15, 25 Conductive rubber elastic layer 24 Adhesive 40, 50 Jig 41, 51 Fine protrusion

Claims (2)

A pushbutton switch member in which a reverse saddle-shaped spring member that generates a click feeling due to deformation thereof is bonded and integrated with an adhesive at the tip of a pressing force transmitter projecting downward from the bottom surface of the key top portion. A manufacturing method comprising:
First, an uncured conductive rubber elastic body is supplied to the center of the inner surface of the reverse saddle spring member,
The tip portion is formed into a substantially convex shape having the same curved surface as the curved surface of the reverse saddle-shaped spring member, and the tip portion is made to have the reverse saddle-like spring member using one or more fine protrusions on the surface. And is pressed with a predetermined pressure to cure the uncured conductive rubber elastic body, to form a conductive rubber elastic body layer in a predetermined range on the inner surface of the reverse saddle-shaped spring member,
Then, the manufacturing method of the member for pushbutton switches characterized by apply | coating an adhesive agent to the front-end | tip part of the said pressing force transmission element, and adhere | attaching the vertex of the said reverse saddle-like spring member.   2. The member for a push button switch according to claim 1, wherein the conductive rubber elastic body layer is formed with a predetermined thickness over the entire surface centering on a central portion of the reverse saddle-shaped spring member. Method.

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