DE-BOUNCING KEYPAD AND PREPARATION METHOD THEREOF

Abstract

The present invention discloses a de-bouncing keypad and a preparation method thereof, wherein the keypad is composed of a rubber substrate and a metal contact having three layers of layered structures. A layer of tin alloy or lead alloy is plated on a surface of the metal contact by electroplating or chemical plating. The metal contact plated with the tin alloy or lead alloy has excellent contact bouncing resistance and arc-ablation resistance, and the metal contact is further composited with the rubber to shape and prepare the rubber de-bouncing keypad.

Claims

1-10. (canceled)

11. A de-bouncing keypad, comprising: a rubber substrate; and a metal contact, which is a layered complex including a first layer, a second layer, and a third layer, attached with the rubber substrate, wherein the first layer is a rubber layer having a thickness of 0.1-10 mm, wherein the second layer is a sheet metal layer having a thickness of 0.1-10 mm and containing magnesium, aluminum, titanium, chromium, manganese, ferrum, cobalt, nickel, copper, zinc, niobium, molybdenum, silver, tin, tantalum or tungsten, and wherein the third layer is a tin alloy plated layer or lead alloy plated layer having a thickness of 0.1-10 m selectively deposited onto the second layer.

12. The de-bouncing keypad according to claim 11, wherein the third layer is electroplated onto the second layer.

13. The de-bouncing keypad according to claim 11, wherein the third layer is chemically deposited onto the second layer.

14. The de-bouncing keypad according to claim 11, wherein the third layer is plated onto one or two sides of the second layer.

15. The de-bouncing keypad according to claim 11, wherein the rubber substrate is a natural rubber, styrene butadiene rubber, butadiene rubber, ethylene propylene rubber, ethylene propylene diene monomer, urethane rubber, methylvinylsiloxane gum or polymethylvinylphenylsiloxane gum.

16. The de-bouncing keypad according to claim 11, wherein the rubber substrate is an ethylene propylene diene monomer, methyl vinyl silicone rubber or polymethylvinylphenylsiloxane gum.

17. The de-bouncing keypad according to claim 11, wherein the first layer is a hydrophobic rubber enabling a water contact angle on a rubber surface to be greater than 65 degrees.

18. The de-bouncing keypad according to claim 17, wherein the hydrophobic rubber is a nonpolar or weak polar rubber.

19. The de-bouncing keypad according to claim 18, wherein the hydrophobic rubber is an ethylene propylene diene monomer, methylvinylsiloxane gum or polymethylvinylphenylsiloxane gum.

20. The de-bouncing keypad according to claim 11, wherein the second layer is a metal sheet having a convex point or a concave point, a metal sheet having a convex line or a concave line, a metal sheet having a convex surface or a concave surface, a metal sheet having a small hole with an area less than 1 mm.sup.2, a metal gauze, metal foams or a metal fiber sintered felt, wherein the metal is magnesium, aluminum, titanium, chromium, manganese, ferrum, cobalt, nickel, copper, zinc, niobium, molybdenum, silver, tin, tantalum or tungsten, or an alloy containing magnesium, aluminum, titanium, chromium, manganese, ferrum, cobalt, nickel, copper, zinc, niobium, molybdenum, silver, tin, tantalum or tungsten, and the metal sheet is a single metal or composited by different metals in a layered manner.

21. The de-bouncing keypad according to claim 20, wherein the metal sheet of the second layer is composed of a stainless steel sheet, a copper or copper alloy sheet, and a nickel or nickel alloy sheet having a thickness of 0.01-1.0 mm, and a pure nickel layer or a nickel alloy layer, a pure cobalt layer or a cobalt alloy layer, a molybdenum layer or a molybdenum alloy layer having a thickness of 0.1-10 m is plated on one side or two sides of the stainless steel sheet, the copper or copper alloy sheet, and the nickel or nickel alloy sheet; and the pure nickel layer or the nickel alloy layer, the pure cobalt layer or the cobalt alloy layer, the molybdenum or the molybdenum alloy on the stainless steel sheet, the copper or copper alloy sheet, and the nickel or nickel alloy sheet is prepared by vacuum plating, electroplating or chemical plating.

22. A method of preparing a de-bouncing keypad, the method comprising: (1) treating sheet metal, wherein the sheet metal is a stainless steel sheet, a copper or copper alloy sheet, and a nickel or nickel alloy sheet having a thickness of 0.01-1.0 mm by: using a cleaning agent and an organic solvent to deoil and clean the sheet metal, mechanically roughing a surface of the sheet metal through sand blasting and polishing, processing the sheet metal through chemical etching into concave pits or convex points having a diameter less than 1 mm, or plating a pure nickel layer or a nickel alloy layer, and a cobalt or cobalt alloy layer having a thickness of 0.1-10 m on one side or two sides of the sheet metal by electroplating or chemical plating, then using the cleaning agent and the organic solvent to deoil and clean the sheet metal obtained, (2) adhering a hydrophobic rubber to the sheet metal by: adhering a hydrophobic rubber layer onto the sheet metal plated with a prime coat or an adhesion promoter through heat vulcanization adhesion and heat vulcanization shaping, to form a layered composite sheet, or adhering the hydrophobic rubber layer with self-adhesiveness on the sheet metal plated with a prime coat or not plated with a prime coat through heat vulcanization adhesion and heat vulcanization shaping, to form a layered composite sheet, (3) cutting the layered composite sheet by separating or punching the layered composite sheet into an object, wherein the object is a cylinder comprising the hydrophobic rubber layer and the sheet metal layer having a diameter of 2-10 mm or the object has a cross section in a shape of ellipse, polygon, crisscross, star or crescent or any combinations thereof, and using a basic cleaning liquid to wash the object for about 5 min, washing the object by water, then using 5% hydrochloric acid to clean the object for about 1 min, using deionized water to clean the object, and then draining off the object; (4) preparing a plated layer by dipping the object in a chemical plating bath containing a soluble tin or lead compound and stirring to form the plated layer on a metal surface of the object by chemical plating, or putting the object into a roller for a chemical plating bath containing a soluble tin or lead compound and making the roller rotate and form a plated layer on the metal surface of the object by chemical plating; wherein the chemical plating bath contains 5-100 g/L soluble tin compound or lead compound, 5-100 g/L complexing agent, 5-100 g/L reducing agent and 2-50 g/L pH regulator, (5) cleaning and drying the plated object by taking out the plated object, using distilled water or deionized water to rinse the object, then draining the object off, and using cold air to blow-dry, or putting the object into a 70 C. constant temperature oven to dry, thus obtaining a contact with a metal surface layer plated with a tin alloy or lead alloy; (6) applying the contact obtained in step (5) to step (7) or applying the object before or after to step (7), and performing after-plating treatment on the contact plated with the tin alloy or lead alloy, wherein a method for after-plating treatment comprises applying a layer of water-soluble or an organic solvent tin alloy protective agent or a tin plated layer surface inhibitor on a surface of the tin alloy or lead alloy of the contact using a leady alkaline solution to treat the contact plated with the tin alloy to replace partial tin on the surface of the contact with lead, to form a tin lead alloy on the surface of the contact; and (7) performing heat vulcanization adhesion and heat vulcanization shaping on the metal contact and the rubber, wherein the rubber layer in the metal contact is combined with other rubber in the metal contact while shaping, and prepared into a de-bouncing rubber keypad, or preparing the plated layer firstly, then performing adhesion treatment on the sheet metal having the plated layer with the hydrophobic rubber layer, to prepare a composite sheet having the plated layer.

23. A method of preparing a de-bouncing keypad, the method comprising: (1) treating a sheet metal layer, which is a stainless steel sheet, a copper or copper alloy sheet, and a nickel or nickel alloy sheet having a thickness of 0.01-1.0 mm; either by roughing one side or two sides of the stainless steel, copper or copper alloy, nickel or nickel alloy sheet through mechanical polishing, sand blasting and chemical etching, or plating a pure nickel layer or a nickel alloy layer, a pure cobalt layer or a cobalt alloy layer, and a molybdenum layer or a molybdenum alloy layer having a thickness of 0.05-10 m through a vacuum plating, electroplating or chemical plating method, or only cleaning the sheet; (2) adhering a hydrophobic rubber layer onto the sheet metal layer plated with a prime coat or an adhesion promoter through heat vulcanization adhesion and heat vulcanization shaping, to form a composite sheet, or adhering the hydrophobic rubber with self-adhesiveness on a sheet metal layer plated with a prime coat or not plated with a prime coat through heat vulcanization adhesion and heat vulcanization shaping, to form a composite sheet; (3) dipping the composite sheet in an electroplating bath containing a soluble tin or lead compound to form a tin alloy or lead alloy plated layer on a metal surface of the composite sheet by electroplating, the electroplating bath containing 5-100 g/L soluble tin compound or lead compound, 0-100 g/L complexing agent and 10-120 g/L pH regulator; (4) applying the sheet to step (5) or applying a cylinder before or after step (5), and performing after-plating treatment on the sheet plated with the tin alloy or lead alloy, wherein a method for after-plating treatment comprises applying a layer of water-soluble or an organic solvent tin alloy protective agent or a tin plated layer surface inhibitor on a surface of the tin alloy or lead alloy of the sheet; or coating a layer of a complex of non-conductive lubricating oil, lithium-based grease or silicone having arc extinction and lubrication effects on the surface of the tin alloy or lead alloy of the sheet, wherein commercialized arc extinction grease is preferably selected; or using a leady alkaline solution to treat the sheet plated with the tin alloy to replace partial tin on the surface of the sheet with lead, to form a tin lead alloy on the surface of the sheet; (5) separating or punching the composite sheet in step (6) into a cylinder comprising a rubber layer, a sheet metal layer and a plated layer and having a diameter of 2-10 mm; and (6) taking the cylinder as a metal contact to perform heat vulcanization adhesion and heat vulcanization shaping with the rubber, wherein the rubber layer in the metal contact above is combined with other rubber in the rubber layer while shaping, and prepared into a de-bouncing rubber keypad; or, preparing the plated layer firstly, then performing adhesion treatment on the sheet metal having the plated layer with the hydrophobic rubber layer, to prepare a composite sheet having the plated layer.

24. The method of claim 23, wherein the electroplating bath or chemical plating bath for preparing the tin alloy plated layer or lead alloy plated layer contains a soluble tin compound and a soluble lead compound at the same time.

25. The method of claim 24, wherein the electroplating bath or chemical plating bath for preparing the tin alloy plated layer or the lead alloy plated layer contains 5-100 g/L stannous chloride and lead chloride, wherein a weight ratio of the stannous chloride to the lead chloride is from 1:5 to 1:100.

26. The method of claim 23, wherein the electroplating bath or chemical plating bath for preparing the tin alloy plated layer or the lead alloy plated layer contains 0.05-50 g/L brightener; the brightener is formaldehyde, acetaldehyde, 13-naphthol, 2-methyl aniline-aldehyde condensates, benzalacetone, cuminaldehyde, benzophenone, chlorobenzaldehyde, peregal, schiff base, butynediol, propiolic alcohol, 1-diethylaminoprop-2-yne, propynol ethoxylate, benzoic sulfimide, sodium benzosulfimide, sodium vinylsulfonate, sodium proparagylsulfonate, pyridine-2-hydroxypropanesulfonate inner salt, alkylphenol polyoxyethylene.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0054] FIG. 1 is a structural schematic diagram of a de-bouncing keypad according to the present invention; in the figure: 1 refers to rubber layer; 2 refers to sheet metal layer; 3 refers to tin alloy or lead alloy plated layer; 4 refers to rubber substrate; and a metal contact is composed of 1, 2 and 3;

[0055] FIG. 2 is a schematic diagram of a de-bouncing keypad switch; in the figure: 1 refers to rubber layer; 2 refers to sheet metal layer; 3 refers to tin alloy or lead alloy plated layer; 4 refers to rubber substrate; 5 refers to gold-plated contact on printed circuit board; and 6 refers to printed circuit board;

[0056] FIG. 3 is a test pattern of bouncing on an ordinary nickel-plated keypad according to the present invention; and

[0057] FIG. 4 is a test pattern of bouncing on a tin-plated keypad according to the present invention.

DETAILED DESCRIPTION

Embodiment 1

[0058] FIGS. 1 to 2 are structural schematic diagrams of the present invention, illustrating a rubber layer 1, a sheet metal layer 2, a tin alloy or lead alloy coated layer 3, a rubber substrate 4, as well as a gold-plated contact 5 on a printed circuit board and the printed circuit board 6. As shown in FIGS. 3 to 4, a bouncing trace appears on a test pattern of bouncing on an ordinary nickel-plated keypad, while no keypad bouncing appears on a tin-plated keypad of the present invention.

[0059] The sheet metal layer was prepared by stainless steel (model number is 304; and national grade No. is 0Cr18Ni9) having a thickness of 0.1 mm. The stainless steel was rolled into a sheet having fine ripples by a mechanical method, wherein a peak height of the ripples was 0.1 mm and a peak spacing was 0.2 mm. Then a basic cleaning liquid having a pH value around 9 was used to clean and deoil the sheet, then the sheet was washed by water, and further cleaned and deoiled by industrial alcohol, and blow-dried by cold air. Other methods can also be used for cleaning, deoiling and activating.

[0060] Polymethylvinylphenylsiloxane gum (for example, Elastosil R 401/60 produced by Wacker Chemie AG), vinyl tris-tert-butyl peroxy silane (VTPS) and dicumyl peroxide (DCP) were uniformly mixed by an open mill. The content of the VTPS in a rubber compound was 1%, and the content of the DCP in the rubber compound was 0.5%. VTPS was a coupling agent containing a peroxide component, which not only can crosslink silicone rubber containing vinyl but also can promote the bonding between the silicone rubber containing vinyl with metals (such as nickel, carbon steel, stainless steel, copper, or the like).

[0061] Heat vulcanization adhesion and heat vulcanization shaping were performed between the stainless steel sheet having fine rippers and the foregoing rubber compound under 165 C., wherein a curing time was 12 min, to form a layered composite sheet of stainless steel and silicone rubber having a thickness of 1.0 mm. A surface of a mold cavity of a mold for preparing the composite sheet had a Teflo coating. The existence of the Teflo coating prevented the rubber compound from being adhered to the mold during heat vulcanization. The composite sheet was punched into a small wafer having a diameter of 5 mm. The small wafer was cleaned by basic cleaning liquid, washed by water, then put into 10% dilute sulfuric acid for activation for 1 min, and then cleaned, and drained off.

[0062] Preparing a chemical plating bath having following compositions:

[0063] 8 g/L stannous chloride dihydrate, 75 g/L trisodium citrate dihydrate, 20 g/L disodium edetate dihydrate, 10 g/L sodium acetate, 0.5 g/L benzene sulfonic acid, 0.2 g/L sodium saccharin, 8 g/L titanium trichloride, and proper aqueous ammonia were added to make the pH within 8.0-9.0. The chemical plating bath was in a ready-to-use form. Titanium trichloride may be resolved by deionized water or diluted hydrochloric acid, and not added into the plating bath earlier.

[0064] 500 small wavers above were put into 300 mL plating bath above under a temperature of 80 C. and stirred continuously, taken out after 60 min, rinsed by distilled water or deionized water, drained off, and blow-dried by cold air, or put into a 70 C. constant temperature drying oven to dry, thus obtaining small wafers with a metal surface plated with a tin layer.

[0065] The small wafer containing the tin layer of the silicone rubber layer was used as a contact to perform heat vulcanization adhesion and heat vulcanization shaping with the silicone rubber, to form a rubber keypad containing the contact, as shown in FIG. 1. Heat vulcanization adhesion was performed between a silicone rubber face in the small wafer and other silicone rubber, wherein one face with a metal plated layer faced outwards, so that the metal plated layer may be contacted with other contact such as a gold-plated contact on a printed circuit board (PCB) to form an access, as shown in FIG. 2. When the contact in this keypad is contacted with other contact (such as the gold-plated contact on the PCB), a contact bouncing phenomenon will not occur substantially, or a bouncing time thereof is approaching to zero. Therefore, the keypad is a de-bouncing keypad. Our test showed that the switching times were more than 100,000 times when a current between the contacts was 50 mA, the resistance between the contacts was not increased substantially, and the switching-on performance of the contact was excellent. When the current between the contacts was 300 mA and the switching times were 30,000 times, the contact resistance between the contacts was not increased substantially and maintained within 1 ohm. Relatively, a contact bouncing phenomenon would occur when the keypad containing a stainless steel contact not plated with a tin layer was contacted with the gold-plated contact on the PCB, wherein the average bouncing time was about 10 ms; when the current between the contacts was 300 mA and the switching times were about 3000 times, the resistance between the contacts was increased remarkably, and raised to 10 ohm above.

Embodiment 2

[0066] The sheet metal used was the same as that in embodiment 1, but the sheet metal was processed by chemical plating to plate a layer of nickel having a thickness of 2.5 m on a stainless steel sheet having fine ripples. One object of nickel plating was to reduce the resistance on the surface of the sheet metal (because the electric conductivity of the nickel was greater than that of the stainless steel), and the other object was to adhere the stainless steel and a tin alloy plated layer more firmly. Then the sheet metal treated in this manner was composited with silicone rubber, then punched into small wafers, plated with a tin alloy by chemical plating, and finally prepared into a de-bouncing and arc-ablation resistant keypad.

Embodiment 3

[0067] Like embodiment 1, the small wafer containing silicone rubber and stainless steel layer was prepared, then a layer of nickel having a thickness of 2.5 m was plated on the small wafer, and then a tin alloy layer having a thickness of 2.5-5.0 m was plated on a metal surface of the small waver as shown in embodiment 1, and this plated object was used as metal contact, and then a de-bouncing arc-ablation resistant keypad was prepared.

Embodiment 4

[0068] All the processes were similar to the embodiments 1, 2 or 3, but the compositions of the chemical plating bath used were different. The compositions of the plating bath adopted in the embodiment were as follows: 15 g/L stannous chloride dihydrate, 0.3 g/L lead chloride, 75 g/L trisodium citrate dihydrate, 25/L disodium edetate dihydrate, 15 g/L nitrilotriacetic acid, 2 g/L sodium saccharin, 8 g/L titanium trichloride, and proper aqueous ammonia or 10% acetic acid are added to make the pH within 6.0-7.5. The temperature of the chemical plating was set as 60 C., and the time was set as 1 h.

[0069] The plated layer obtained using the plating bath above was a tin lead alloy plated layer. The plated layer was more stable during storage and use, and tin whisker will not grow. The keypad having such a plated layer had no contact bouncing.

Embodiment 5

[0070] Like embodiment 1, a s stainless steel sheet having fine rippers and silicone rubber were prepared into a layered composite sheet of stainless steel and silicone rubber having a thickness of 1.0 mm. 10% dilute sulfuric acid solution was used to clean the composite sheet for 3 min. Then a tin alloy plated layer having a thickness of 2.5-5.0 m was electroplated on the sheet. The plating bath and conditions used were as follows:

[0071] 50 g/L stannous mono-sulphate, 90 g/L sulfuric acid and 0.4 g/L benzalacetone. The temperature of the plating bath was controlled to be 15 C. around, and the density of a cathode current was 1.0 A/dm.sup.2.

[0072] In the plating bath, benzalacetone was a brightener. The sulfuric acid has such effects of reducing the activity of stannous ions, preventing the stannous ions from hydrolysis, improving the electrical conductivity of the plating bath and the efficiency of an anode current, etc. when the sulfuric acid was insufficient, the stannous ions were easily oxidized into quadrivalent tin.

[0073] Then the sheet plated with tin alloy was punched into small wavers having a diameter of 5 mm. The small wafer was used as a metal contact to perform heat vulcanization adhesion and heat vulcanization shaping with silicone rubber, to form a rubber keypad having a contact. The keypad prepared also had excellent de-bouncing effect and arc-ablation resistance.

Embodiment 6

[0074] A 400-mesh stainless steel plain net (the model of the stainless steel was 304) was used to replace the stainless steel sheet having fine ripples in embodiment 1, and the contact prepared using the process in embodiment 1 also had preferable de-bouncing effect and preferable arc-ablation resistance.

[0075] A mesh of the 400-mesh stainless steel net was very small, and the silicone rubber will not penetrate through the mesh of the stainless steel net when molding the stainless steel net with the silicone rubber. If a stainless steel net with a small mesh number, for instance, a stainless steel net with a mesh below 80, was selected, a technical problem that the silicone rubber penetrated through the mesh of the stainless steel net during molding will occur. Therefore, a stainless steel net with a larger mesh number needs to be adopted for preparing a switch contact having a plated layer.

Embodiment 7

[0076] A rubber keypad containing a contact plated with a tin layer was prepared like embodiments 1, 2, 3, 5 or 6. The rubber keypad was processed using a basic lead solution to replace partial tin in the tin coated layer on the surface of the contact with lead, thus forming a paper-thin tin lead alloy on the surface of the plated layer of the contact. In this way, whisker will not grow in the plated layer of the contact in the rubber keypad while the rubber keypad has de-bouncing function and arc-ablation resistance.