JPS5945164B2 - pushbutton switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pushbutton switch or keyboard switch used in electronic devices such as electronic desktop calculators and touch-type electronic tuners.

Conventionally, in order to make electronic desktop calculators thinner and more compact, movable contacts made of sheet-like contact metal or elastic conductors such as conductive plastic are pressed against pushbuttons made of insulators, etc. Various pushbutton key switches have been developed. There is also a type in which a protruding key part is provided on the upper part of the movable conductive rubber contact and an insulating coating is provided on the protruding key part. As an example, US Pat. No. 3,699,294 is shown in FIG. Here, A indicates the assembled product, and 口 indicates its parts.
In the figure, reference numeral 1 denotes a printed circuit board, on the upper surface of which a fixed contact 2 and its circuit pattern are provided, and a terminal 9 in contact with the above is fixed on the lower side.

A spacer 3 made of an insulating plate placed above the printed circuit board 1 is provided with a window corresponding to the fixed contact 2f1C. Reference numeral 4 denotes a movable elastic conductive contact plate made of a mixture of silicone rubber and carbon powder, which has a movable contact portion 5 corresponding to the fixed contact 2VC as a lower protrusion, the upper part of which is provided with 6 push-button protrusions, and its surface is insulated. It is coated.

7 is a cover plate that also serves as a display plate, and has a push button protrusion 6V
C-fitting window 8 etc. b: Provided.

Then, the circuit board 1, the spacer 3, the movable elastic conductive contact plate 4, and the cover plate 7 are mutually positioned, overlapped, and fixed to form a keyboard switch. In this switch, the movable elastic conductive contact plate 4 made of conductive rubber is made of a mixture of carbon or precious metal powder and rubber-based resin, etc., which reduces flexibility and elastic modulus and improves compressibility. There is a sponge inside to increase the effective contact area and reduce contact resistance. Conductive rubber contacts with microscopic cavities are used. It is desirable for the pushbutton to have the feel of a snap switch, so the switch operation part or movable contact part has a hemispherical elastic thin part and is made of plastic such as mylar or polycarbonate, or silicone rubber, which has excellent pressure characteristics. Keyboard switches with a tactile feel have also been developed. For example, in foreign countries, U.S. Pat.
Inventions such as No. 9586 were also made in Japan in 1986-377.
65, Publication No. 51-8703, Japanese Patent Publication No. 52-71658
and 52-67775, etc.

However, conventional switch boards use a printed circuit board, and the fixed contacts are plated with gold on the copper foil contact pattern, which increases the cost. Therefore, if silver plating is used instead, the cost will be considerably lower, but it will be damaged by sulfide gas. Contact failure BS occurs due to the formed silver sulfide film, and insulation failure due to silver migration occurs in humidity.

As a countermeasure to this problem, a method of coating the copper foil contact pattern with carbo resin was proposed in Japanese Utility Model Application Publication No. 49-37765. This is difficult to manufacture, and therefore it is difficult to coat it with carbon resin, and it is especially difficult to completely coat the sides. Furthermore, when the surrounding conditions are severe, an insulating film is likely to form on the copper layer at the interface with the carbon layer, increasing contact resistance. Furthermore, forming a carbon resin layer on copper foil has weak mutual adhesion.
There are problems such as it becomes even more difficult to coat the switch with a low-resistance carbon resin containing a small amount of resin component in order to lower the contact resistance. The present invention improves the above-mentioned drawbacks of the structure of the conventional fixed contact portion, reduces insulation failure due to silver migration and increase in contact resistance due to silver sulfidation, and provides a highly reliable and low-cost keyboard switch. is intended to provide.

Further, the present invention provides a keyboard switch in which the pushbutton knobs are separate, making it easy to insert them into the board, and making it easy to change the number and arrangement of pushbuttons, thereby simplifying parts production and assembly. The purpose is to

In the present invention, for example, six switch units are arranged in series to form a set of keyswitches.

Here, by overlapping each of the six switch parts excluding the knob, it is possible to easily assemble six VC switch units into one unit, and also connect these six key switches in parallel or in series. It is also possible to arbitrarily increase the number of unit switches by arranging them. Also, the details will be explained later on BZ, pushbutton knob 3 that drives the switch.
0 is independent from each other and has a structure that is attached individually, so 1
It is also easy to arbitrarily reduce the number of knobs attached to the six switch units. Embodiments of the present invention will be described in detail below with reference to the drawings.

1 to 5 are drawings showing an embodiment of the present invention, in which FIG. 1A is an assembled perspective view with a part cut away, the same opening is a front view of the same mounted on a panel board, FIG. 2A, Both marks t are a plan view of the embodiment of the main body board, Figures C and 2 are enlarged cross-sectional explanatory views of the fixed contact pattern of the main body board, Figure 3 is a movable contact plate, A is a plan view, mark t is a side view, and C is a side view of the main body board. FIG. 4 is a partially cutaway perspective view of the press button, and FIG. 5 is a perspective view of the electrode terminal. As shown in FIG. 2, the main body board 10 (hereinafter simply referred to as the board) is a rectangular heat-resistant insulating board such as a Bakelite laminate, with fixed contact patterns '11, 1 on one side.
2, 12', etc. are provided on the surface of each switch unit corresponding to the switch design.

Also, six switch units are connected in series here. As an example, in FIG. 2A, a common electrode pattern 12 is shown in which two individual conductive electrode patterns 11 are connected. Further, in the opening of FIG. 2, an electrode pattern in which one side is a common electrode is shown as 12'. Then, the details will be explained later by insulating each other corresponding to the short-circuiting carbon rubber elastic movable contacts 25 provided on the movable contact plate 20, and connecting the pair of fixed contact parts 15 facing each other with a certain narrow interval between them. There are 6 sets. (Hereinafter, the part of the board with a narrow gap between both fixed contacts 15, 15 will be referred to as the insulation gap 15a.) Fixed contact patterns 11, 12,
Terminal holes 13 are provided at equal intervals corresponding to terminal holes 12', etc., and eyelet fixing portions 43 of external terminals 40, which will be described later, are inserted into the terminal holes 13 and crimped to secure the conductive connection. However, due to the circuit nature of the set, the terminal holes 13 are rarely all used as terminal holes. In this example, the details will be explained later.
As an example, the elastic movable contact plate 20 that is fixed to the substrate 10 is provided in a staggered pattern around the lower fixing surface VCl, or serves as a positioning hole that engages with the caulking protrusion 23VC. Here, the positioning hole that engages with the positioning protrusion of the movable contact plate 20 may be provided separately from the terminal hole 13. Here, on both sides of the board 10 are terminal positioning grooves 14 that engage with positioning protrusions 44 of terminals 40 made of metal plates, which will be described later, and snap pin positioning grooves that engage with snap pin mounting legs 36 of pushbuttons 30, which will be described in detail later. An engagement groove 16 and a set of positioning grooves 17 that engage with the projections 27 at both ends of the movable contact plate 20 at both ends in the longitudinal direction are provided. The fixed contact patterns 11, 12, 12' of the board 10 shown in FIG. External terminal 4 that is fixed
It consists of a terminal electrode part 13a around the terminal hole that makes electrical contact with 0, and a conductive connection part 13b therebetween. Here, the switch fixed contact patterns are generally required to have low respective resistance and contact resistance, high reliability of electrical connection, and sufficiently high insulation between the contact patterns. FIG. 3 shows the movable contact plate 20.

The movable contact plate 20VC made of a continuous piece of elastic rubber is integrally provided with a movable contact portion 29 corresponding to each pair of fixed contacts, and each movable contact portion 29 is provided at the center of each switch portion of the board. The base portion 26 that is in close contact with the fixed contact portions 15, 15 has its central portion opened downward, and the substrate 1
A space portion 22a corresponding to the fixed contact portion 15 of 0 is formed,
On the upper side of the base 26, there is a relatively thin dome-shaped elastic skirt portion 22 that performs a continuous snap-button operation, and a relatively thick platform protrusion portion 21 as the central upper end of the upper end of the elastic skirt portion 22. has been established. A downward contact protrusion 24 is provided at the inner lower part of the table-like protrusion 22, and a carbon rubber elastic contact 25 is fixed to the lower tip of the protrusion 24 to make switch contact with the fixed contact 15 of the board. . The movable contact plate 20 also includes a somewhat thin flexible connecting portion 28 that connects the base portions 26 of the movable contact portions 29, and relief grooves 28 that engage with the head portions 41 of the external terminals 40 on both sides thereof. One pair of each are provided on the bottom surface. Here, the central switch unit section is provided with two downwardly projecting positioning protrusions 23 that engage with the terminal holes 13 of the board 10. The positioning protrusion 23 may have a sufficient length so that it can be fixed to the substrate 10 by thermocompression bonding or ultrasonic compression bonding, or a snub-in hook may be attached to its tip. Also, a pair of lower protrusions 27 are provided at both ends in the longitudinal direction to engage with the grooves 17 of the substrate 10.
has been established. Furthermore, although the present invention is provided with a pushbutton 30, the pushbutton 30 is not specially used, and a knob protrusion or the like is directly attached to the upper side of the table-like protrusion 21 of the movable contact portion 29, as shown in the opening in FIG. It may be fixed. FIG. 4 shows a pushbutton 30 made of an insulating and elastic plastic, with an operating knob 31 at the upper end that engages with a hole in the cabinet of the set and protrudes outward to form an operating section, followed by a shoulder 32. The main body portion 33 has a flat plate shape.

A pair of elastic plate-shaped mounting legs 36 for fixing a snub-in are suspended from the lower portions of both side surfaces of the main body portion 33 and are engaged with a pair of engagement grooves 16 on both sides of the base plate 10. Each mounting leg 36 has a vertical slit 38 at its lower center end, and a pair of supporting legs 36a at the bottom of the mounting leg 36 has protruding claws 37 for locking and fixing provided on the outer side of each lower end. Further, the lower surface of the recess 34 on the lower side of the push-button main body 33 comes into contact with the platform-like protrusion 21 of the movable contact plate 20 while being biased downward to some extent. By pushing down the operating knob 31 of the pushbutton 30, the platform-like protrusion 21 of the movable contact portion 29 of the movable contact plate 20 is pressed down.
, the elastic skirt portion 22 is bent downward to perform a snubbing operation.

The elastic movable contact 25 made of carbon-based conductive rubber has concentric double-row elastic contact rings 25a, 25 on the bottom surface.
It has a port and makes bridge contact with a pair of fixed contact portions 15 of the substrate 10 on a wide surface to make an electrical connection. FIG. 5 shows the substrate 10
Terminal hole 1 of conductive fixed electrode pattern 11, 12, 12'
An external terminal 40 made of a metal plate with an eyelet fixing portion 43 protruding downward for engagement with 3VC is shown.

The terminal 40 includes a contact plate portion 41 , an engagement positioning protrusion 44 that engages with the groove 14 of the substrate 10 , an external terminal portion 42 , and a narrow tip terminal portion 45 located between the external terminal portion 42 and its shoulder.
An elastic bend 46 or the like for inserting a snubbin that is fixed to a terminal hole of a printed board to be engaged is provided at the terminal hole. Second
As shown in FIGS.
First, a relatively thin layer of about 3 μm high-resistance carbon resin resistance paint with a high resin content is applied as a base layer A on an insulating substrate.

This base layer A increases the adhesive strength with the substrate, and when a silver resin conductive layer B is provided as an intermediate layer to be described below, it prevents insulation deterioration and other failures due to well-known silver migration. Next, a silver resin conductor layer B is applied on the base layer A as a conductive intermediate layer. Here, as an exception, silver resin conductor layer B
is a case where high contact resistance between contacts is acceptable (approximately 1k0)
In some cases, it may be omitted, as shown on the right side of Figure 2 C and Figure 2 B, but if low contact resistance between contacts is required (approximately 50 Ω), it is shown on the left side of Figure 2 C. A silver resin conductor layer B is provided including the contact portion 15 as shown in FIG. In the case between the above two (approximately 500Ω), the B layer is provided only in the conductive connection portion 13b excluding the contact portion. Here, the terminal electrode part 13a is connected to the external terminal 40 when there is sufficient space between the electrodes.
It is better to expose the silver resin conductor layer B in order to reduce the contact resistance between the two. The thickness of the silver layer is usually 10 μm or less, and it can easily be made even thinner. Next, a low-resistance carbon resin is coated on the fixed contact portion 15, except for the insulation gap 15a between the fixed contacts, as the uppermost layer c. Although the contact resistance here is somewhat higher than that of gold contacts, it has the same level of reliability as the highest grade contacts such as gold. In other words, copper contacts oxidize in the air, resulting in high contact resistance and cannot be used as contacts unless the surface is coated with gold or silver. It is well known that the contact resistance of normally used silver contacts becomes high in sulfide gas, and that silver contacts are susceptible to breakdowns such as insulation deterioration due to migration etc. in high humidity environments. For convenience of the process, if the uppermost layer C is coated on the conductive connection part 13b, excluding the terminal electrode part 13a, troubles caused by silver migration and sulfurization in this part can be reduced. The fixed electrode patterns 11, 12, 12' include the fixed contact portion 15, the terminal electrode portion 13a, and the conductive connection portion 13b, and are made by overlapping the carbon resin layer A1, the silver resin layer B, and the low resistance carbon resin layer C in a desired pattern. After coating, heat treatment and baking are performed, so the process is simple, the adhesive strength of the coating film is strong, and the cost is low. Here, it is an enlarged sectional explanatory view of the fixed contact pattern of the main body board. As shown in Figure 2C, the silver resin conductive layer B is sufficiently bordered with a high-resistance carbon resin layer A on the lower side and a low-resistance carbon resin layer C on the upper side to completely cover the top, bottom and sides. There is. If platinum or gold plating is applied to the conventional printed circuit copper foil etched pattern fixed electrode, problems caused by insulation deterioration due to migration and formation of an insulating film on the contact surface such as sulfurization, which are problems with silver plating, will be avoided. However, platinum-based metals cause the formation of an organic film, and gold-based metals cause mutual diffusion, etc. To improve reliability, a considerable number of man-hours such as thickening and multilayering are required, which also increases costs. It gets expensive. In addition, high-cost special products such as glass fiber-containing epoxy boards are used for the main body board, etc., to prevent migration of silver from silver contacts.
: Required. Since the present invention does not have the above-mentioned drawbacks, it is possible to use a Bakelite laminate which is low in cost and has excellent mechanical strength characteristics, although the migration characteristics of silver are poor. Here, in order to accurately provide a narrow insulation gap 15a between a pair of mutually insulated contact parts 15 that come into contact with the movable contact 25 of the fixed contact pattern, it is necessary to use carbon resin which requires a somewhat thick film thickness. This is a difficult technique when printing with conductive paint or other materials. Therefore, as shown in Figure 2, the insulation gap 15a between the fixed contacts 15, 15 must be
By providing slits or sufficiently deep recesses 15a/ instead of the slits, conductive paint does not adhere to these parts during a conductive printing process such as a screen method, so that it is possible to easily and accurately obtain the desired fixed contact pattern 15 that is insulated from each other. ing.
This also becomes more advantageous as the contact pattern becomes multilayered and thicker. Further, if the slit 15a' is formed between the fixed contacts 15 and has a sufficient length, the reliability of the insulation between the fixed contacts 15 and 15 will be very high. As described above, in the present invention, a relatively thin high-resistance carbon resin resistance paint with a high resin content is applied as a base layer A on an insulating substrate as a pair of contact patterns on the surface of the insulating substrate. A silver resin conductor layer B is applied as a conductive intermediate layer, and a low resistance carbon resin is applied as an uppermost layer C.

Therefore, (1) the intermediate conductive layer B is made of silver resin, the base layer A is made of carbon resin, and the top layer C is also made of carbon resin.
The middle conductive layer B completely covers the top, bottom and sides.
This prevents insulation deterioration between the fixed electrodes 15 and other failures due to silver migration.

(2) Therefore, as the main body substrate, it is possible to use a Bakelite laminate, etc., which has low silver migration properties, excellent electrical and mechanical performance, and is inexpensive.

(3) Furthermore, the high-resistance carbon resin layer A of the base layer has a high adhesive strength due to its large resin component, thereby increasing the adhesive strength between the substrate and the electrode portion.

(4) Also, since the lowermost carbon resin layer A, the silver resin intermediate layer B, and the upper low-resistance carbon resin layer CbZ are bonded to each other by their respective resin components, their mutual adhesion strength is strong.

(5) The uppermost layer generally has a small amount of resin and adhesion strength b: the adhesive strength of the weak low-resistance graphite carbon resin layer C is high, and because of the low-resistance carbon resin layer C, the contact resistance of the switch is low, and sulfide gas oxidation There is no deterioration of the contact due to gas etc., and the performance and reliability of the contact can be improved.

(6) The thickness of the silver resin-based intermediate conductive layer B is usually 10μ or less, unlike the case of silver foil for printed circuits, which is about 30μ, and it is easily possible to make it even thinner.
The difference in thickness between the conductive layer B and the substrate can be reduced, the uppermost carbon resin layer C can be easily printed, and the narrow insulating gap 15a between the electrodes and the dimensional accuracy of the electrodes as a whole are improved.

(7) Here, in a keyboard switch in which a carbon layer is formed on a pair of fixed copper foil electrodes as shown in Utility Model Application Publication No. 49-37765, the copper foil layer is usually thick at about 30μ, and thin. It is difficult to coat the copper layer at the interface between the copper layer and the carbon layer when the surrounding conditions are harsh. When a carbon resin layer is formed on a copper foil, the mutual adhesive force is weak.

In order to lower the contact resistance of the switch, it becomes even more difficult to coat it with low-resistance carbon resin, which has a small amount of resin components. On the other hand, in the present invention, the silver resin conductor layer B is usually 10 μm or less and can be made even thinner, so it is easily possible to completely cover it with the carbon resin layer.

Silver resin layer B has higher stability of contact resistance than copper layer,
Lower carbon resin layer A, silver resin layer B, and upper low-resistance carbon resin layer Cb: They are connected by their respective resin components and have higher adhesive strength. Furthermore, in the present invention, the thickness of the main body substrate is reduced because an insulating plate is used. Also, the engaging parts for attaching the push button are the engaging grooves (recesses) 1 on both sides of the board.
6, the structure is small and simple, and since it is manufactured by punching, the processing is easy and the cost is low. To attach the pushbutton 30 and the board 10, open the pair of elastic mounting legs 36 of the pushbutton outward and insert the pushbutton into the pair of grooves 16 on the side of the board that engage the mounting legs 36VC. It is easy to insert without any effort. Further, since the protruding claw portion 37 for locking and fixing the mounting leg 36 is provided outward, the structure of the molding die is simple and molding is easy. In addition, the pushbutton knobs are individual and easy to insert into the board, so by changing the number and arrangement of pushbuttons to be inserted, you can easily use (switch) a keypad switch with multiple switch units. can be easily changed.

[Brief explanation of the drawing]

Figures 1 to 5 are drawings showing embodiments of the present invention.
Figure A is an assembled perspective view with a part cut away, the same opening is a front view of the same mounted on the panel board, Figure 2 A and Figure 2 are both a plan view of the embodiment of the main body board, and Figures C and 2 are the main body board. An enlarged cross-sectional explanatory diagram of the fixed contact pattern, Figure 3 is a movable contact plate, and A is a plan view.
The opening is a side view, C is an enlarged sectional view at the center, FIG. 4 is a partially cutaway perspective view of the press button, and FIG. 5 is a perspective view of an electrode terminal. FIG. 6 shows a conventional example of a push-button switch using elastic plastic movable contacts. 10: Main board, 11, 12,
12': Fixed contact pattern, 13: Terminal hole, 15: Fixed contact part, 15a: Insulating gap between one set of fixed contacts, 20:
Movable contact plate, 22: Elastic skirt portion, 25: Carbon rubber elastic movable contact, 29: Movable contact portion, 30 Two push buttons, 31: Operating knob portion, 36: Mounting leg, 36a: Support leg portion, 37b: Insertion Tapered part, 38: Slit, 40:
External terminal.

Claims (1)

[Claims] 1. A plurality of pairs of fixed contacts 15, 15 facing each other in close proximity are provided on the upper surface of the main body substrate 10 made of an insulating material, corresponding to each switch unit, and a pair of fixed contacts 15 is provided on the upper part. 15
, 15, a pair of fixed contacts 1 provided on a main body substrate 10 are provided.
5 and 15 are high-resistance carbon resin layer A as a base layer,
Thereon, a highly conductive silver resin conductor layer B as an intermediate layer,
Furthermore, there is a low resistance carbon resin layer C as a surface layer.
The silver resin conductor layer B is sufficiently bordered and covered with a high resistance carbon resin layer A as a base layer and a low resistance carbon resin layer C as a surface layer, and the elastic movable contact 25 is attached to the substrate 10. The trapezoidal protrusion of the dome-shaped elastic skirt portion 22 of the movable contact portion 29 is integrally formed on the movable contact plate 20 made of a single piece of elastic rubber fixed to the surface of the movable contact portion 29 corresponding to each pair of fixed contacts. The movable contact 25 is fixed to the inner surface of the lower part of the portion 21, and when the movable contact portion 29 is pressed down by the table-shaped projection portion 21, the movable contact 25 is connected to the pair of fixed contacts 15,
A pushbutton switch that short-circuits between 15 and 15. 2. Each movable contact part 29 of the movable contact plate 20 includes a box-shaped base part 26 having a lower opening space 22a corresponding to the pair of fixed contacts 15, 15 on the upper surface of the board 10, and the lower surface of the base part 26 has a pair of The upper surface of the base 26 has a dome shape which is deformed so that the lower inner surface of the platform protrusion 21 engages with the fixed contacts 15, 15 of the base 26. The elastic skirt portion 22 is made to protrude upward;
A plurality of terminal holes 13 of the board 10 are provided on the lower surface of the movable contact plate 20.
A few positioning protrusions 23 are protruded to engage with the base plate, and an elastic movable contact 25 made of carbon rubber is fixed to the inner surface of the lower part of the platform protrusion 21 of the skirt portion 22 to short-circuit a pair of fixed contacts 15, 15. A pushbutton switch according to claim 1. 3 A plurality of pairs of fixed contacts 15, 15 facing each other in close proximity are provided on the upper surface of the main body board 10 made of an insulating material, corresponding to each switch unit, and a pair of fixed contacts 15, 15 are provided on the upper part. In a pushbutton switch in which a plurality of elastic movable contacts 25 made of conductive rubber are disposed, which are simultaneously melted and short-circuited between both contacts, a width is provided on the board between a pair of fixed contacts 15, 15 provided on the main board 10. Narrow slit or recess 15
'a, and a pair of fixed contacts 1 provided on the main body board 10.
5 and 15 are high-resistance carbon resin layer A as a base layer,
Thereon, a highly conductive silver resin conductor layer B as an intermediate layer,
Furthermore, there is a low resistance carbon resin layer C as a surface layer.
The silver resin conductor layer B is sufficiently bordered and covered with a high resistance carbon resin layer A as a base layer and a low resistance carbon resin layer C as a surface layer, and the elastic movable contact 25 is attached to a substrate. The dome-shaped elastic skirt portion 22 of the movable contact portion 29 is integrally formed on the movable contact plate 20 made of a piece of elastic rubber fixed to the surface of the movable contact portion 29 corresponding to each pair of fixed contacts. A movable contact portion 29 fixed to the lower inner surface of the protrusion 21 and formed by the trapezoidal protrusion 21
When the movable contact 25 is pressed down, the pair of fixed contacts 15
A push-button switch that makes short-circuit contact between , and 15. 4. Each movable contact part 29 of the movable contact plate 20 includes a box-shaped base part 26 having a lower opening space 22d corresponding to the pair of fixed contacts 15, 15 on the upper surface of the board 10, and the lower surface of the base part 26 has a pair of The upper surface of the base 26 is deformed so that the inner surface of the lower part of the platform protrusion 21 engages with the fixed contacts 15, 15 of the substrate 10. The elastic skirt portion 22 is made to protrude upward;
A plurality of terminal holes 13 of the board 10 are provided on the lower surface of the movable contact plate 20.
A few positioning protrusions 23 are protruded to engage with the base plate, and an elastic movable contact 25 made of carbon rubber is fixed to the inner surface of the lower part of the platform protrusion 21 of the skirt portion 22 to short-circuit a pair of fixed contacts 15, 15. A pushbutton switch according to claim 3.