Arc-ablation resistant switch contact and preparation method thereof

Abstract

An arc-ablation resistant switch contact and a preparation method thereof is disclosed. The switch contact is a complex having a plurality of layers of layered structure, wherein a first layer is a hydrophobic rubber layer, a second layer is an adhesive layer, a third layer is a sheet metal layer, a fourth layer is an adhesive layer, and a fifth layer is a metal plated layer; wherein, the fifth layer of metal plated layer is formed by dipping a complex of the first layer, the second layer, the third layer and the fourth layer in a chemical plating bath containing refractory metal elements, and depositing on surfaces of the second layer, the third layer and the fourth layer in the complex by a chemical deposition method.

Claims

1. An arc-ablation resistant switch contact, wherein the switch contact is a complex having a plurality of layers of layered structure, comprising: a first layer, which is a hydrophobic rubber layer having a thickness of 0.1-10 mm; a second layer, which is an adhesive layer having a thickness of 0-1.0 m, the adhesive layer of the second layer including a coupling agent or a metal rubber adhesion agent; a third layer, which is a sheet metal layer having a thickness of 0.01-1.0 mm; a fourth layer, which is an adhesive layer having a thickness within a range of a thickness of a monomolecular layer to an average thickness of 0.2 m, the adhesive layer of the fourth layer including a coupling agent or a metal rubber adhesion agent; and a fifth layer, which is a refractory metal plated layer having a thickness of 2*10.sup.5-0.02 mm and containing tungsten, rhenium, osmium, tantalum, molybdenum, niobium, iridium, hafnium, vanadium, chromium or zirconium alloy, wherein the fifth layer of refractory metal alloy plated layer is deposited on surfaces of the second layer, the third layer and the fourth layer in the complex or is deposited on a surface of the fourth layer in the complex.

2. The arc-ablation resistant switch contact according to claim 1, wherein the fifth layer of refractory metal alloy plated layer is chemically deposited on surfaces of the second layer, the third layer and the fourth layer in the complex or is chemically deposited on a surface of the fourth layer in the complex.

3. The arc-ablation resistant switch contact according to claim 1, wherein the fifth layer and the third layer are electrically communicated, and a resistance therebetween is less than 10 ohms.

4. The arc-ablation resistant switch contact according to claim 1, wherein the first layer is composed of a rubber material enabling a water contact angle on a rubber surface to be greater than 65 degrees.

5. The arc-ablation resistant switch contact according to claim 4, wherein the rubber material is nonpolar or weak polar rubber.

6. The arc-ablation resistant switch contact according to claim 5, wherein the rubber material is ethylene propylene diene monomer, methylvinylsiloxane gum or polymethylvinylphenylsiloxane gum.

7. The arc-ablation resistant switch contact according to claim 1, wherein the sheet metal 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, gold, or an alloy containing the elements, and the sheet metal is a single metal or composited by different metals in a layered manner.

8. The arc-ablation resistant switch contact according to claim 1, wherein the second layer and the fourth layer include a coupling agent or metal rubber adhesion agent that promotes rubber to adhere to metal, wherein a chemical composition of the second layer is identical to or different from that of the fourth layer.

9. The arc-ablation switch contact according to claim 8, wherein the coupling agent is a silane coupling agent, a titanate coupling agent, a zirconium coupling agent, or a chromium complex coupling agent, a surface water contact angle of the coupling agent after filming on the sheet metal is 10 degrees smaller than the water contact angle on the hydrophobic rubber surface.

10. The arc-ablation switch contact according to claim 9, wherein the coupling agent is an aminosilane coupling agent, an epoxy silane coupling agent, a mercapto silane coupling agent or a peroxy silane coupling agent.

11. The arc-ablation switch contact according to claim 8, wherein the metal rubber adhesion agent is heat-cured or photo-cured.

12. The arc-ablation switch contact according to claim 11, wherein the heat-cured rubber-metal adhesion agent is a carboxylic rubber type, a self-adhesive silicone rubber type or a siloxane polymer type.

13. The arc-ablation switch contact according to claim 11, wherein the photo-curable rubber-metal adhesion is of a urethane acrylate type.

14. The arc-ablation switch contact according to claim 11, wherein the surface water contact angle after curing of the rubber-metal adhesion agent is 10 degrees less than the water contact angle on the hydrophobic rubber surface.

15. The arc-ablation switch contact according to claim 1, wherein the refractory metal alloy plated layer is a metal plated layer having a melting point of higher than 1850 C., the plated layer contains a tungsten element having a weight ratio of 10-100%, a molybdenum element having a weight ratio of 0-95%, transition metal elements including iron, nickel, cobalt, copper, manganese or any combination of these element having a weight ratio of 0-70%; and the sum of the weight ratio of tungsten and that of molybdenum in the plated layer is no less than 30%.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of a sectional structure of the present invention; and

(2) FIG. 2 is a process flow diagram of a preparation method of the present invention.

(3) Wherein, in the figure: 1 refers to hydrophobic rubber layer; 2 refers to adhesive layer of rubber and metal; 3 refers to sheet metal layer; 4 refers to adhesive layer of metal and plated layer; and 5 refers to refractory metal alloy plated layer.

DETAILED DESCRIPTION

(4) The present invention will be further described in details hereunder with reference to the specific embodiments.

Embodiment 1

(5) The compositions of the plating bath were as follows: 45 g/L sodium tungstate, 20 g/L sodium molybdate, 18 g/L nickel sulphate, 28 g/L sodium hypophosphite, 20 g/L sodium acetate, 40 g/L sodium citrate, 16 g/L potassium sodium tartrate, 15 g/L sodium thiosulfate, 1 g/L sodium fluoride, 20 g/L ammonium sulfate, 0.2 g/L thiourea, 0.5 g/L sodium dodecyl sulfate, 0.1 g/L potassium iodate, and proper aqueous ammonia.

(6) A temperature for chemical plating adopted on the metal plated layer being 80 C., the time being 200 min, and a pH value of the plating bath being 8.5-9.5.

(7) Process route was as follows:

(8) As shown in FIG. 1 and FIG. 2, the products was composed of a five-layer structure: a hydrophobic rubber layer 1, an adhesive layer 2 of rubber and metal, a sheet metal layer 3, an adhesive layer 4 of metal and plated layer, a refractory metal alloy plated layer 5. The zinc-cupro-nickel sheet had a thickness of 0.1 mm, an HV hardness of 120 to 180, and a copper content of about 55% was used as the metal substrate. The reason for choosing zinc-copper-nickel alloy is that the zinc-copper-nickel alloy has excellent comprehensive mechanical properties, excellent corrosion resistance, and good hot and cold shaping property, and is suitable for manufacturing various elastic elements. The smooth zinc-cupro-nickel sheet was mechanically rolled into a sheet having fine rippers by a mechanical method, which had a crest height of 0.1 mm and a peak pitch of 0.2 mm. A basic cleaning liquid having a pH value around 9 was used to further clean and deoil the sheet under a temperature 60 C., then the sheet was washed by water, washed and deoiled by industrial alcohol, washed by 12.5% sulfuric acid solution under a temperature of 50 to 80 C. for 2 min, and washed by water. Then a nickel layer having a thickness of 2.5-5.0 m was plated on both sides of the zinc-cupro-nickel sheet having fine ripples by a chemical plating nickel plating bath containing nickel sulfate and sodium hypophosphite in a chemical plating mode. Chemical nickel plating on the metal substrate was a mature process, which would not be elaborated any more herein. The nickel-plated zinc-cupro-nickel sheet having fine ripples was cleaned up by deionized water, and blow-dried by cold air.

(9) Polymethylvinylphenylsiloxane gum (SE 4706U produced by Dow Corning Toray Co.) and dicumyl peroxide (DCP) were uniformly mixed by an open mill. The content of DCP in a rubber compound was 1.0%.

(10) The nickel-plated zinc-cupro-nickel sheet having fine ripples was dipped in a silicon polymer-containing rubber-metal adhesive agent (Megum 14135 prepared by Rohm and Haas Company, U.S.A.) for 1 min, taken out and centrifuged-dry, so that the sheet metal contacts the extremely thin adhesive agent layer.

(11) Heat vulcanization adhesion and heat vulcanization shaping were performed between the stainless steel sheet and the foregoing rubber compound under 165 C., wherein a curing time was 12 min, to form a layered composite sheet containing zinc white copper and silicone rubber and having a thickness of 1.25 mm. The composite sheet was punched into a small rounded grain having a diameter of 5 mm. The small rounded grain was cleaned for various minutes by basic cleaning liquid, washed by water, then dip into 5% hydrochloric acid for 3 min, put into 10% dilute sulfuric acid for activation for 30 s, and then cleaned, and drained off.

(12) 500 small wafers above were put into 600 mL plating bath above under a temperature of 80 C. and stirred, taken out after 200 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 layer plated with tungsten-molybdenum alloy. During the process of chemical plating, attentions should be always paid to the change of the pH value, and the pH value of the solution should be controlled by ammonia water or sodium hydroxide solution in time, so as to make the pH value within 8.5 to 9.5.

(13) Heat vulcanization adhesion and heat vulcanization shaping were performed between the small wafer containing the silicone rubber layer and plated with tungsten-molybdenum alloy and the silicone rubber. Heat vulcanization adhesion was performed between the a silicone rubber face in the small wafer and other silicone rubber, wherein one face plated with tungsten-molybdenum alloy faced outwards, so that the tungsten-molybdenum alloy layer might be contacted with a contact on a printed circuit board (PCB). After heat vulcanization shaping between the small wafer and the silicone rubber, a rubber keypad might be produced. It was this small wafer was used as a contact of a circuit switch in the rubber keypad. The contact was contacted with a gold-plated contact of the PCB, having a stable, lower contact resistance. Moreover, the small wafer plated with tungsten-molybdenum alloy had better conduction performance: after electrifying a 500 mA direct current between the small wafer made of zinc-cupro-nickel not plated with tungsten-molybdenum alloy plated layer or zinc-cupro-nickel plated with nickel and the PCB gold-plated contact, and switching about 3000 times, due to the arc-ablation during switching on or off, the contact resistance between the small wafer and the PCB gold-plated contact was significantly increased (from about 1 ohm to 100 ohm) or more, or even non-conductive condition during multiple tests); however, in the same circuit conditions, after electrifying a 500 mA direct current between the small wafer plated with tungsten-molybdenum alloy and the PCB gold-plated contact, and switching about 10000 times, the contact resistance between the small wafer and the PCB gold finger is still below 1 ohm.

Embodiment 2

(14) A stainless steel sheet having a thickness of 0.05 mm and a model of SS304 was used to replace the zinc-cupro-nickel sheet having fine ripples and plated with nickel in embodiment 1. An ethanol solution containing 2% vinyl tris-tert-butyl peroxy silane (VTPS) is sprayed on both sides of the stainless steel sheet in a spray coating method, and blow-dried for standby. The above-mentioned stainless steel sheet and the rubber compound of the silicone rubber in embodiment 1 was subject to hot embossing and shaping in a mould plated with Teflon in die cavity to form a stainless steel-silicone rubber composite sheet having a thickness of 1.0 mm. The complex sheet was punched into a cylinder having a diameter of 5 mm, and the chemical plating method in embodiment 1 was used to prepare the contact containing the refractory metal plated layer. In the prepared contacts plated with a refractory metal alloy layer, there was a good adhesive strength between the stainless steel and the silicone rubber, and between the plated layer and the stainless steel. Compared with the similar contact not plated with a plated layer, the arc-ablation resistance or service life in the contact was improved by more than one times.

Embodiment 3

(15) The stainless steel sheet in embodiment 2 was compounded with the silicone rubber containing 1% VTPS to form a complex sheet containing stainless steel and silicone rubber and having a thickness of 1.0 mm. An ethanol solution containing 2% N-(2-aminoethyl)-3-aminopropyltriethoxysilane was sprayed on the surface of stainless steel in the complex sheet, and then the complex sheet was baked under a temperature of 70 C. for 30 min. The complex sheet was punched into a cylinder having a diameter of 5 mm, and the chemical plating method in embodiment 1 was used to prepare the contact containing the refractory metal plated layer. With respect to the prepared contact plated with the refractory metal alloy layer, the plated layer was firmly adhered to stainless steel. Compared with the similar contact not plated with a plated layer, the arc-ablation resistance or service life in the contact was improved by more than one times.

(16) Those having ordinary skills in the art may also make many improvements and polish without departing from the principle of the invention, which shall all be deemed as the protection scope of the invention.