JPS618820A - Manufacturing method of membrane keyboard switch - 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 method for manufacturing membrane type keys and board switches with a simplified manufacturing process, and in particular to a method for manufacturing a membrane type key and a board switch, which has a simplified manufacturing process, and particularly relates to a method for manufacturing a membrane type key and a board switch with a simplified manufacturing process. The present invention relates to a method for manufacturing a keyboard switch that does not require a 100% air-tightness, and therefore has excellent airtightness, electrical conductivity, and durability.

[Technical background of the invention and its problems] As a recent trend, membrane-type keyboard switches with extremely thin and flat switch sections have been widely used in electronic desktop calculators, electronic scales, etc. There is. Although this switch does not have as much of a click feeling when pressed as compared to a mechanical switch or a rubber switch, it has the advantage that the switch part is flat and the overall structure is thin. Conventionally, the following three methods have been used to manufacture membrane type keyboard switches. (1) A conductive layer area formed on the back side of the button with numbers, letters, symbols, etc. and an electrical port formed with each desired contact point corresponding thereto.
m,=o*mci□,. Eh, E1. □Tsu.

A method of incorporating a flexible intermediate insulation sheet or spacer. (2) A spacer made of printed and hardened insulating rubber with a thickness of about 100 to 500 μm is provided on the part of the electric circuit that formed each contact part, excluding the contact part, and this is used to mark numbers, letters, symbols, etc. A method of bonding the conductive layer area formed on the back side of the button. (3) A pressure-sensitive conductive rubber sheet with a thickness of 0.5 to 1 mm is placed on the electric circuit forming each contact part, and a conductive layer is formed on the back side of the button with numbers, letters, symbols, etc. How to paste areas together.

Of these three methods, method (1) requires the longest and most complicated assembly process, and also requires high cost because the opening of the spacer must be formed accurately. Method (2) requires a shorter and simpler process than method (1), but it requires 100% of the liquid rubber for the spacer.
It has the disadvantage that it must be formed at a thickness of ~500 μm, which is extremely difficult for screen printing technology.

Method (3) uses pressure-sensitive conductive material between the upper and lower conductive contacts.
.

Since it incorporates a rubber sheet, (1)
Although it has an airtight structure unlike that obtained by method 1 (2), if a pressure-sensitive conductive rubber sheet is placed over the entire electrical circuit, there will be a lot of unnecessary material and the cost will be extremely high. Furthermore, if the sheet is placed only on the contact area, the sheet must be cut to size and must be placed accurately on the contact area, making the process extremely complicated.

[Object of the Invention] The present invention has been made to solve the above-mentioned drawbacks, and provides a membrane type keyboard that has excellent airtightness, electrical conductivity, and durability using simple processes and materials. The present invention attempts to provide a method for manufacturing a switch.

[Structure of the Invention] That is, the present invention comprises a step (A) of forming an electrode corresponding to a switch portion of a circuit board used in the following step (C) on the back side of a flexible electrically insulating substrate film, and a step ( A)
By applying a pressure-sensitive conductive paste to a position corresponding to the electrode on the electrode-forming substrate film obtained in step 1, and having the same size and shape as the electrode, or a wider area including the electrode, and curing the paste. Step of forming a pressure-sensitive conductive layer (B
) and a circuit board on which a desired electric circuit including a switch part is formed on an electrically insulating substrate or film, the pressure-sensitive conductive layer-formed substrate film that has undergone steps (A) and (B) is applied to the switch part. This method of manufacturing a membrane keyboard switch is characterized by comprising a step (C) of placing the pressure-sensitive conductive layer and the pressure-sensitive conductive layer so as to correspond to each other and fixing them together.

Examples of the flexible Q insulating substrate film used in step (A>) of the present invention include films of polyester, polyimide, polyurethane, etc. The electrode on the back surface is
It is formed by attaching a conductive metal foil to a substrate and then etching it, screen printing a conductive paste, or vapor depositing a conductive metal. Screen printing is suitable for forming the film accurately and economically. The conductive paste used for this purpose is one in which one or more of silver, copper, carbon, etc. is dispersed in a curable polymer compound.

The polymer compounds include uncured phenol resin,
Examples include epoxy resin, polyester, polyurethane, silicone resin, silicone rubber, and polyimide, but silicone rubber-based materials are preferred because they have rubber elasticity, and as the pressure-sensitive conductive paste that is coated and cured in step (B). Silicone rubber is preferred because of its ease of adhesiveness.

Next, the pressure-sensitive conductive paste used in step (B) is
Anything can be used as long as it can be cured at room temperature, by heating, or by light irradiation, but it has rubber elasticity after curing and has excellent workability, heat resistance, and durability, so it has good adhesion to the substrate. silicone, which is paste-like in its uncured state, and in which one or more conductive particles such as silver, copper, nickel, or carbon are dispersed, along with non-conductive fillers if necessary. Are suitable. In particular, those in which surface-treated conductive metal powder is dispersed in polyorganosiloxane that can be cured into a rubber-like state have excellent dispersibility. A composition in which metal powder such as powder is surface-treated with a platinum compound and then dispersed in the above polyorganosiloxane (Japanese Patent Application No. 57-2074)
15 specification) is advantageous in that the resistance value varies greatly depending on the operating pressure. This composition is fluid or thixotropic in its uncured state, and its fluidity can be adjusted by adding a solvent to make it suitable for screen printing.

The position where the pressure-sensitive conductive paste is printed on the electrode-forming substrate film is the position corresponding to the electrode on the substrate film. Its shape and dimensions are the same as or wider than the electrode portion, provided that it does not come into contact with any electrode other than the corresponding electrode. Its specific shape is circular,
It may be of any shape such as an oval, polygon, semicircle, sector, etc.

Any printing method can be used to apply the pressure-sensitive conductive paste, but it is difficult to create fine patterns accurately and over time.
) Screen printing is suitable for economical printing.

The thickness of the pressure-sensitive conductive layer formed by applying the pressure-sensitive conductive paste is suitably about 10 to 200 μm, preferably 30 to 100 μm. Although it depends on the shape and conditions, if the coating thickness is less than 10 μm, it tends to become conductive when no pressure is applied (when OFF), and when it exceeds 200 μm, it tends to become insulated when pressure is applied (when ON). Also, 2
It is difficult to form a thickness exceeding 00 μm by screen printing.

The pressure-sensitive conductive paste applied in this manner is cured at room temperature, by heating, or by light irradiation to form a pressure-sensitive conductive layer using a method and conditions suitable for the paste.

The electrically insulating substrate or film used in step (C) of the present invention includes phenol resin, epoxy resin,
Examples include laminates and molded products made of polyester, silicone resin, polyimide, etc., and they may be either plate-like or film-like, and may be either rigid or flexible. The electric circuit including the switch part is formed using silver, copper, carbon, etc.
This can be done by screen printing a conductive paste containing one or more seeds, by vapor depositing a conductive metal, or by bonding and etching conductive metal foils.

Next, the pressure-sensitive conductive layer of the substrate film formed in step (Δ) and step (B) is placed at a position corresponding to the switch part of the circuit board on which the desired electric circuit is formed on the electrically insulating substrate or film. and fix both.

By combining steps (A), (B), and (C) in this way, the method for manufacturing a keyboard switch of the present invention is provided.

[Examples of the Invention] The present invention will be described in detail with reference to Examples below, but the present invention is not limited to the Examples as long as the gist of the present invention is not impaired. In addition, in the reference examples and examples, all parts represent parts by weight.

Reference Example 1 (Manufacture of conductive metal powder treated with platinum compound) To 100 parts of nickel particles with an average particle diameter of 3 to 7 μm obtained from nickel carbonyl, 100 parts of a 1% by weight xylene solution of vinylsiloxane-coordinated platinum complex was added. was stirred and heated to reflux.

After 4 hours, the complex-treated powder was filtered and washed, and
The mixture was heated at 0° C. for 2 hours to obtain platinum-siloxane complex-treated nickel particles.

Reference Example 2 (Production of pressure-sensitive conductive silicone rubber paste) Additive silicone rubber [Toshiba Silicone Corporation'ITS
E3221] 300 parts of the platinum-siloxane complex-treated nickel particles of Reference Example 1 were premixed with 100 parts using a small blender, and then dispersed using a triple roll.
A pressure-sensitive conductive silicone rubber composition was obtained. Further, to 100 parts of this composition, a solvent [0 stone (
By adding 1.5 parts of Viallom 2S (manufactured by Co., Ltd.) to dilute the mixture, a pressure-sensitive conductive silicone rubber paste was obtained.

Example 1 As shown in FIG.
A polyester resin was screen printed, cured and dried to form an electrode 2 with a thickness of 15 μm.゛The cross section of this electrode printed substrate film is shown in Fig. 2 [Step (A)].

Next, place 2 at the position corresponding to the electrode 2 formed in step (A).
The pressure-sensitive conductive silicone rubber paste obtained in Reference Example 2 was screen-printed using a polyester screen plate having a 0.00 mesh and a layer thickness of 120 μm, and was dried by heating at a temperature of 120° C. for 30 minutes. The pressure-sensitive conductive layer 3 thus formed is
The thickness was 40 μm.

A cross section of this pressure-sensitive conductive layer printed substrate film is shown in FIG. 3 [Step (B)].

Next, the pressure-sensitive conductive layer 3 formed in step (8) is placed on the comb-shaped electrode portion 4a on the surface of the paper phenol resin printed wiring board 4 having a thickness of 2InIl, and the printed wiring board 4 and the substrate film 1 are placed in correspondence with each other. (Step C)]
The keyboard switch thus obtained has an insulation resistance of 10
0MΩ or more, continuity resistance 30Ω or less, switching load 2
511 and had excellent durability.

Example 2
1. .

As shown in FIG. 4, a conductive polyester resin containing silver particles was screen printed on the back side of a polyester substrate film 5 with a thickness of 75 μm, and was cured and dried to form an electrode 6 with a thickness of 15 μm. A cross section of this electrode printed substrate film is shown in FIG. 5 [Step (A)].

Next, in the same manner as in Example 1, a pressure-sensitive conductive silicone rubber paste was printed and dried to form a pressure-sensitive conductive layer 7. A cross section of this pressure-sensitive conductive layer printed substrate film is shown in FIG. 6 [Step (B)].

Next, the substrate film 5 formed in step (B) is placed on the film circuit board 8, which is made by printing and curing a conductive polyester resin containing silver particles on a 125 μm thick polyester film, at positions corresponding to the comb-shaped electrode portions 8a. A pressure-sensitive conductive N layer 7 was placed thereon, and the film circuit board 8 and the substrate film 5 were bonded together [Step (C)]. The thus obtained keyboard switch had an insulation resistance of 100 MΩ or more, a conduction resistance of 30Ω or less, operated with a switching load of 2511 Ω, and had excellent durability. Further, the keyboard switch of this embodiment has a total thickness of approximately 0.3 mm. It was very thin, mi.

[Effects of the Invention] The keyboard switch according to the present invention has no voids in the switch portion, has excellent airtightness, and has a very thin and flat surface. Therefore, it also has excellent electrical conductivity and durability, and the process is greatly simplified compared to conventional methods. .

[Brief explanation of the drawing]

FIG. 1 is a process diagram explaining the steps of Example 1 of the present invention.
(a) of the figure is a perspective view of the substrate film, (b) of Figure 1 is a perspective view of the substrate film on which electrodes are formed in step (A), and (C) of Figure 1 is a perspective view of the substrate film in which electrodes are formed in step (B). FIG. 1(d) is a perspective view of a printed wiring board; FIG. 1(e) is a schematic cross-sectional view showing a key switch according to Example 1; Fig. 2 is a schematic cross-sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is a schematic cross-sectional view taken along the line ■-■ shown in Fig. 1. Fig. 4 is a schematic cross-sectional view taken along the line ■-■ in Fig. 1. Process diagram explaining step 2, 4th
(a) of the figure is a perspective view of the substrate film, (b) of Figure 4 is a perspective view of the substrate film on which electrodes are formed by step (A), and (C) of Figure 4 is a perspective view of the substrate film formed by the process (B). 4(d) is a perspective view of a film circuit board, FIG. 4(e) is a schematic cross-sectional view showing a keyboard switch according to Example 2, and FIG. 5 is a perspective view of a substrate film on which a conductive layer is formed. A schematic cross-sectional view taken along the line v-v in Fig. 4, and Fig. 6 a schematic cross-sectional view taken along the line Vl-Vl in Fig. 4. 1... Substrate film, 2... Electrode, 3...・Pressure-sensitive conductive layer, 4...Circuit board (printed wiring board),
4a...Switch part of circuit board (comb-shaped electrode), 5.
...Substrate film, 6. ...Electrode, 7...Pressure-sensitive conductive layer, 8...Circuit board (film), 8a...
・Switch part of circuit board (comb-shaped electrode). Patent applicant: Toshiba Silicone Corporation Figure 1 Figure 4 Figure 2 Figure 3 Figure 1 Figure 5 Figure 6

Claims (1)

[Claims] 1. Step (A) of forming an electrode corresponding to the switch part of the circuit board used in the following step (C) on the back side of the flexible electrically insulating substrate film; A pressure-sensitive conductive paste is applied to a position corresponding to the electrode on the obtained electrode-forming substrate film and has the same size and shape as the electrode, or a wider area including the electrode, and is cured. Step (B) of forming a piezoconductive layer, and a circuit board in which a desired electric circuit including a switch portion is formed on an electrically insulating substrate or film, and a pressure-sensitive conductive layer that has undergone steps (A) and (B). A method for manufacturing a membrane keyboard switch, comprising a step (C) of placing a layer-forming substrate film so that the switch part and the pressure-sensitive conductive layer correspond to each other, and fixing them together. 2. The method for manufacturing a membrane keyboard switch according to claim 1, wherein the electrodes are formed on the back surface of the flexible electrically insulating substrate film by screen printing of a conductive paste. 3. The method for manufacturing a membrane keyboard switch according to claim 1, wherein the pressure-sensitive conductive paste is prepared by dispersing surface-treated conductive metal powder in silicone rubber. 4. The method for manufacturing a membrane keyboard switch according to claim 1, wherein the pressure-sensitive conductive paste is applied by screen printing. 5. The method for manufacturing a membrane keyboard switch according to claim 1, wherein the pressure-sensitive conductive layer has a thickness of 10 to 200 μm.