JPS6145523A - Key switch structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pressure-sensitive key switch structure.

(Technical background of the invention and its problems) Conventionally, a key switch for a small electronic oscillator such as a small electronic calculator has generally included a fixed contact and a key switch that is provided at a distance from and facing the fixed contact and that can be operated by pressing. A contact-type key switch consisting of a fixed contact and a movable contact was used, but recently, a pressure-sensitive conductive material is provided on the key contact corresponding to the fixed contact of the above-mentioned contact-type key switch. In recent years, pressure-sensitive key switches have come into use, which are provided with conductors corresponding to the movable contacts of the above-mentioned contact key switches.

This pressure-sensitive key switch utilizes the property of pressure-sensitive conductive material, which exhibits insulating properties when no pressure is applied, and when compressed force is applied, the compressed part becomes conductive. The switch is turned on by compressing a piezoelectric material, and unlike the contact-type key switches mentioned above, this pressure-sensitive key switch does not require a space between the fixed contact and the movable contact. Therefore, if this pressure-sensitive key switch is adopted, the structure of the key switch section of a small electronic device can be simplified.

However, in the conventional pressure-sensitive key switch structure for small electronic devices, a predetermined circuit pattern is formed, key contacts are formed on the top surface of the wiring board, and sheets 1 to 1 are placed on top of the key contacts.
Because it has a structure in which pressure-sensitive conductive rubber sheets formed in a shape are stacked and a conductor facing the key contact is provided on top of the pressure-sensitive conductive rubber sheets, pressure-sensitive conductive rubber sheets are placed on the wiring board during the manufacture of electronic devices. The rubber sheet must be positioned and fixed on the chassis,
Therefore, it is troublesome to assemble the key switch, and if the pressure-sensitive conductive rubber sheet is too thin, it will be difficult to handle the pressure-sensitive conductive rubber sheet when attaching it to the wiring board. To prevent this, the pressure-sensitive conductive rubber sheet should be thickened to a certain extent (usually 0.5~ 1.0 mm) It is necessary to ensure its strength, and for this reason, the key switch part becomes quite thick, making it impossible to make the separate device thinner (Currently, small Tsumeko memorial devices that use a contact type key switch) There are ultra-thin ones with a thickness of 1 mm or less, but if the pressure-sensitive conductive rubber sheet is made to have a thickness of 0.5 to 1.0 mm to ensure its strength, this alone will cover the entire jar. The problem was that the thickness was quite thick.

[Purpose of the invention]

This invention was made in view of the above-mentioned circumstances, and its purpose is to create a pressure-sensitive type that is easy to manufacture and that is much thinner than conventional products. The objective is to provide a key switch structure that can be used to measure the

[Summary of the invention]

That is, in the present invention, a key contact is formed on a substrate surface on which a predetermined circuit pattern is formed, a pressure-sensitive conductive layer is printed on the key contact, and a pressure-sensitive conductive layer is formed on the pressure-sensitive conductive layer opposite to the key contact. By printing and forming a conductive layer that is electrically connected to the key contact through the pressure-sensitive conductive layer, a pressure-sensitive key switch can be assembled without overlaying a pressure-sensitive conductive rubber sheet on the key contact as in the conventional method. In addition, by forming the pressure-sensitive conductive N layer by printing, there is no need to ensure strength as with a separate pressure-sensitive conductive rubber sheet, and the thickness can be reduced. It is something.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings, taking a pressure-sensitive key switch of a small electronic calculator as an example.

First, to explain the configuration of the small electronic calculator, in Figs. It is a wiring board installed on the upper surface of the lower case 10a, and the lower case 10a has a flat plate shape with the upper surface recessed leaving the periphery,
As shown in FIG.
0, a display body such as a liquid crystal display panel 30, and a solar cell 4
The four parts 12, 13, and 14 which serve as relief from the 0 and 1 are formed by half-etching.

Further, the wiring board 11 is made of a flexible resin film, and is arranged on the upper surface of the lower case 10a alongside the liquid crystal display panel 30 and the solar cell 40. has been done.

This wiring board 11 has an L in which the LSI chip 20 is inserted.
An SI chip fitting opening 12a is formed on the lower surface of the wiring board 11, and as shown in FIG. 1, LSI chip connection terminals 22.22. ... are formed in an array.

This LSI chip connection terminal 22.22. 70.70 Hot-melt anisotropic conductive adhesive is placed in the array area of
is printed.

Furthermore, display panel connection terminals 33, 33. ..., a pair of battery connection terminals 44a, 44b are formed, and these display panel connection terminals 33, 33. ...and battery connection terminal 44
a.

44b is the wiring formed on the upper surface of the lower case: A50,5
o.

. . . LSI chip connection terminals 22.22.・
...is connected.

The LSI chip 20 is mounted on the wiring board 11.
The part that is fitted into the I-chip fitting opening 12a and protrudes below the wiring board 11 is inserted into the four parts 12 of the lower case 10a.
The terminals 21, 21.・
... is LS from above the anisotropic conductive adhesive 70.70
I-chip connection terminal 22.22. ...By stacking it on top and applying heat and pressure, this anisotropic conductive adhesive 70°70
LSI chip connection terminal 22.22. It is adhesively connected to... Note that the anisotropically conductive adhesive has conductivity in the film thickness direction only in the portion that is heated and pressed (the portion between the terminals).

Further, as the cross section of the liquid crystal display panel 30 is shown in FIG. Electrode substrate 31a.

The liquid crystal display panel 30 is of the TN type, with polarizing plates 34a and 34b provided on the outer surface of the panel 31b, and a reflecting plate 32 provided on the lower surface thereof.As shown in FIG. The lower part is inserted into the recess 13 of the lower case 10a, and the liquid crystal display panel 30. is the upper electrode'substrate 3
By adhering the film-like heat-seal connector 3G adhered to the terminal arrangement part 1a to the display panel connection terminal arrangement part of the wiring board 11, display panel connection terminals 33.
33. It is adhesively connected to...

The film-like heat-seal connector 36 includes the terminals 30a arranged in the terminal array portion of the liquid crystal display panel 30 and the display panel connection terminals 33, 33, 33, 33, 33, 40 of the wiring board 11 on one side of the resin film. . . . hot melt conductive adhesives 36a, 36a in a corresponding arrangement.

...is printed.

Further, the solar cell 40 is placed on the side of the wiring board 11 by inserting its lower part into the recess 14 of the lower case 10a, and the solar cell 40 has a film-like heat seal connector glued to its terminal portion. 41 to the battery connection terminal forming portion of the wiring board 11 to form a battery connection terminal 44a,
44b.

On the other hand, the upper sheet 10b is a flexible sheet made of a transparent resin sheet, and a liquid crystal display panel 30 is mounted on the lower surface of the upper sheet 10b.
The blind printing 1 leaves the display window section 15 facing the display surface of the solar cell 40 and the daylight window section 16 facing the light receiving surface of the solar cell 40.
7 (see FIG. 4), and key symbols 18, 18, . ...is printed. This top sheet 10b is attached to the lower case 1 by adhesive 19 around its periphery.
It is attached to the lower case 10a by adhering to the upper surface of the periphery of the lower case 10a.

Next, to explain the path of the pressure-sensitive key switches, in FIGS. 1 and 4, eo, so, . This pressure-sensitive key switch 60 is
A key contact 61 formed on the lower surface of the wiring board 11 facing the key code printed portion of the top sheet 11b, and a pressure-sensitive conductive layer 6 printed on the upper (lower surface) of this key contact 61.
2, and a lower conductive layer 63 printed on the top (lower surface) of the pressure-sensitive conductive layer 62 to face the key contacts 61, and each key switch 60. [30,... key contacts 61.61. As shown in FIG. 3, wirings 51, 51 . ..., LSI chip connection terminal 22.22. Details of the key signal input terminal of...
are connected to each other.

Further, the lower surface of the wiring board 11 is provided with each of the key contacts 61.
．． 61. ... part and each electronic component (LSI chip 2
0, liquid crystal display panel 30, solar cell 40) arrangement area and connection terminals for each electronic component 22.22. ..., 33.
33°..., 44a, 44b are covered with a resist film 65, and the pressure sensitive conductive layers 62, 62, .・・・
・ indicates each key contact 61, 131. . . . is formed on the resist film 65 so as to be flush with the resist film 65.

Further, the lower conductive layer 63.63 includes key contacts 6 in each row.
The pressure-sensitive conductive layer G2.62 of each key contact row is orthogonal to each key contact row so as to form a key matrix with 1.61.
The lower conductors 1163, 63 are printed on the resist film 65 so as to cover the LSI chip connection terminals 22, 22, . ... is connected to the key signal output terminal group KO.

That is, in FIG. 3, 52.52 are LSI chip connection terminals 22.22. . . . is a lower conductive layer connection wiring led out from the key signal output terminal group KO to one side edge of the lower case 10, and this wiring 52° 52 is also wired except for its terminal portions 52a and 52a. The resist film 6
Covered by 5. Further, 63a and 63a are lower conductive layers 63°6 printed and formed on the upper surface of the resist 1 film 65.
3, and the lower conductive layer 63.63 is formed by printing the ends of the leads 63a, f33a over the terminal portions 52a, 52a of the lower conductive layer connection wiring 52.52. Layer connection wiring 52.52
LSI chip connection terminals 22.22. ... is connected to the key signal output terminal group KO.

5 and 6 show the pressure-sensitive key switches 60, 60. This shows the method of forming this pressure-sensitive key switch 60°60,
... is formed as follows.

First, as shown in FIG. 5(a) and FIG. 6(a),
Each pressure-sensitive key switch 60 is mounted on the bottom surface of the wiring board 11. G
o,... key contacts 61.61. ... and connection terminals 22.22. for each electronic component. ..., 33.33.・
..., 44a.

441) including a predetermined circuit pattern (wiring 50.51.
52) is formed by screen printing with carbon ink. Note that this wiring pattern may be formed by laminating copper foil or the like over the entire lower surface of the wiring board 11 and patterning it by etching.

Next, as shown in FIG. 5(b) and FIG. 6(b),
Each key contact 61°61, .
. . , a placement area for each electronic component (LSI chip 20, liquid crystal display panel 30, solar cell 40), and connection terminals for each electronic component 22.22. ..., 33.33. ...
, 44a, 44b and the upper conductive layer connection wiring 5
2. This resist 1ll is printed to form a resist film 65 except for the terminal portions 52a and 52a at 52 (35 indicates each wiring 5 formed on the surface of the wiring board 11).
0.51.52 and these wiring 50.5
1.52 and the lead 63a of the upper conductive layer 63.83,
This resist film 15 is used to insulate between the resist film 15 and the resist film 63a, and it is sufficient if the resist film 15 has a thickness of about 30 μm.

Next, as shown in FIGS. 5(C) and 6(C), each key contact 61. which is not covered with the resist film 65.
(On top of 31, . . . , the pressure-sensitive conductive layer 6 is made flush with the resist film 65 by screen printing to a thickness of about 30 μm.)
2.62. . . . are printed and formed, and LSI chip connection terminals 22, 22. Anisotropically conductive adhesive 70.70 is printed on the array portion of .

The pressure sensitive conductive layer 62. G2. ... is a mixture of rubber materials such as silicone rubber or chloroprene rubber with thermoplastic resin, and a solvent and a tackifier added to dissolve the insulating polymer material. 1
The conductive particles mixed into the insulating polymer material are printed by mixing and dispersing microparticles (about 0μ in size), and the conductive particles mixed into the insulating polymer material are exhibits conductivity (as conductive particles are mixed into an insulating material, the resistance value of the insulating material decreases rapidly from the point where the rate of conductive particles mixed in exceeds a certain level), and the insulating material becomes It is mixed at the mixing rate just before the change from insulating to conductive. Therefore, this pressure sensitive conductive layer 62.62.
... is insulating in the unpressurized state, but when a compressive force is applied to it, the density of conductive particles in the compressed part increases and only this part becomes conductive, releasing the compressive force. The compressed part then recovers and becomes insulating again.

After this, as shown in FIG. 5(d) and FIG. 6(d), carbon ink is printed on the upper surface of the resist film 15 by screen printing to form the pressure-sensitive conductive layer 62 of each key contact row. .62 and its leads 63a, 63a are formed. At this time, lead 63
a, the end of 63-a is connected to the upper conductive layer connection wiring 52,
52 terminal parts 52a, 52a and printed on top of each other,
The upper conductive layer 63.63 is connected to the upper conductive layer connection wiring 52.5.
2 through LSI chip connection terminals 22.22. ...
Connect to the key signal output terminal group KO of the two.

Note that here, the pressure-sensitive conductive layer G2.62. . . . LSI chip connection terminals 22.22. Anisotropic conductive adhesive 70.70 is printed on the array part of...
This anisotropic conductive adhesive 70,70 may be printed after forming the upper conductive layer 63.63.

The small electronic calculator has a pressure-sensitive key switch 60.60 degrees as described above on the lower case 10a.
The wiring board 11 on which the LSI chip 20, the liquid crystal display panel 30, and the solar cell 40 are connected is held together with these electronic components, and the top sheet 11 is closely attached to the top surface of the wiring board 11 from above. The pressure-sensitive key switch 60.
GO, . . . presses the key code portion of the top sheet 10b to bend the top sheet 101) and the wiring board 11 downward, thereby compressing the pressure-sensitive conductive layer 62 and turning it on. There is.

However, in this key switch structure, the key contact 61.
61. . . . and pressure-sensitive conductive layer 62.62. . . . and the upper conductive layer G3.63 are sequentially printed on the bottom surface of the wiring board 11, and the pressure-sensitive key switch 60.60.
Compared to the conventional method in which pressure-sensitive conductive rubber sheets are aligned and polymerized, key switches can be easily formed, and small electronic calculators can therefore be assembled easily. can.

Further, in the above key switch structure, the pressure sensitive conductor 162
．． 62. Because the pressure-sensitive conductive layer 62.62 is formed by printing, there is no need to make it thick to prevent wrinkles or damage, unlike pressure-sensitive conductive rubber sheets that are handled as one component. ．． Since the key switch can be made much thinner by making ... thinner, it is possible to make a small electronic calculator thinner.

In the above embodiment, the pressure-sensitive conductive layer 63 is compressed by pressing the wiring board 11 through the top sheet 10b of the small electronic calculation system. As shown, the wiring board 11 also serves as the top sheet 10b, and the top sheet 10b is eliminated, and the wiring board 1
A key code (not shown) may be printed on the top surface of the wiring board 11 so that the wiring board 11 can be pressed directly.

In addition, in the above embodiment, the pressure sensitive key switch 60°60,
Key contacts 61.61. ... as LSI chip 2
0 key signal input terminal, upper conductive layer 63.63
is connected to the key signal output terminal of the LSI chip 20. As shown in FIG. ) 61a and 61b, one contact electrode 61a is connected to the key signal input terminal of the LSI chip 20, and the other contact electrode 61b is connected to the LSI chip 20.
This pair of contact electrodes 61
a, Glb, the pressure-sensitive conductive layer 62 and this pressure-sensitive conductive layer 6
Conductivity is established through an upper conductive layer 63 printed on top of the upper conductive layer 63 (a three-layer structure may also be used. In this case, it is not necessary to lead out the lead from the upper conductive layer 63).

Furthermore, in the above embodiment, the key switch 60.60°・
... is formed on the lower surface of the wiring board 11, and this key switch Go, 60. ... may be formed on the upper surface of the wiring board 11 as shown in FIG. (not shown), or a top sheet with a key code printed thereon may be placed on the top surface of the f@board 11. In this case, the wiring board 11 should be a hard one.

In addition, in the above embodiment, a key switch of a small electronic device N (XI) using a solar cell 40 as a power source battery was described, but the present invention provides a key switch for a small electronic calculator using a paper battery as a power source battery. It can be applied to switches, and can also be applied to key switches of small electronic devices other than small electronic calculators.

〔Effect of the invention〕

According to the present invention, although it is a pressure-sensitive key switch, it is easy to manufacture and can be made much thinner than conventional ones.

[Brief explanation of the drawing]

Figures 1 to 6 show an embodiment of this invention.
Figure 1 is a perspective view from the bottom of the wiring board that forms the pressure-sensitive key switch, Figure 2 is an external view of a small electronic calculator, Figure 3 is an exploded view of the small electronic calculator, and Figure 4 is an exploded view of the small electronic calculator. An enlarged sectional view taken along the line A-A in FIG. 2, and FIGS. 5(a) to 5(d) are plan views showing the method for forming a pressure-sensitive key switch in the order of steps;
Figure 6 Ca) and (d) are respectively shown in Figure 5 (a) to (d).
) is an enlarged sectional view of the key switch section of the device. 7 and 8 are enlarged sectional views of a pressure-sensitive key switch section showing other embodiments of the present invention, respectively. 10a...lower case, 10b...top sheet, 1
1... Wiring board, 20... LSI chip, 22...
- Sl chip connection, connection terminal, 30: liquid crystal display panel, 33: display panel connection terminal, 40: solar cell, 44a, 4413: battery connection terminal,
50.51.52...Wiring, GO...Pressure-sensitive key switch, 61...Key contact, G2...Pressure-sensitive conductive layer, 6
3... Lower conductive layer. Applicant's agent Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A key contact is formed on the board surface on which a predetermined circuit pattern is formed, and on this key contact, there is a sensation that is compressed through the key contact by a pressing operation and becomes conductive, and when the pressing force is released, it restores and becomes insulating. A piezoconductive layer is formed by printing, and a conductive layer is formed on the pressure-sensitive conductive layer, facing the key contact, and is electrically connected to the key contact through the pressure-sensitive conductive layer by compression of the pressure-sensitive conductive layer. A key switch structure characterized by being printed and formed.