Source: https://patents.google.com/patent/US6763576?oq=6%2C907%2C387
Timestamp: 2018-03-18 16:51:38
Document Index: 581337375

Matched Legal Cases: ['arts 16', 'arts 16', 'art 16', 'art 16', 'arts 16', 'arts 16']

US6763576B2 - Manufacture of electronics enclosure having a metallized shielding layer - Google Patents
Manufacture of electronics enclosure having a metallized shielding layer
US6763576B2
US6763576B2 US10137229 US13722902A US6763576B2 US 6763576 B2 US6763576 B2 US 6763576B2 US 10137229 US10137229 US 10137229 US 13722902 A US13722902 A US 13722902A US 6763576 B2 US6763576 B2 US 6763576B2
US10137229
US20020166682A1 (en )
George R. Watchko
Matthew T. Gagnon
Walter H. Dolbier, Jr.
To attenuate EMI effects, shielding having the capability of absorbing and/or reflecting EMI energy may be employed both to confine the EMI energy within a source device, and to insulate that device or other “target” devices from other source devices. Such shielding is provided as a barrier which is interposed between the source and the other devices, and typically is configured as an electrically conductive and grounded housing which encloses the device. The housing may be formed of a metal such as steel, aluminum, or magnesium, or alternatively, of a plastic or other polymeric material which is loaded with a metal or other electrically-conductive filler or which is provided with a metal or other conductive layer fastened, over-molded, spray painted, dip coated, clad, electrolessly or electrolytically plated, thermal or vacuum metallized, or otherwise generally applied or deposited across the interior surfaces of the housing. The conductive layer may be an electrically-conductive paint, a conductively-filled, molded elastomeric layer, a metal foil laminate, transfer, or liner, a metal plating, or a flame, arc, or other thermally-sprayed metal. A conductive gasket may be used to provide electrical continuity between the coating layers applied to the various mating housing parts. Such housings and methods are further described in commonly-assigned U.S. Pat. No. 5,566,055, in DE 19728839, U.S. Pat. Nos. 5,847,317; 5,811,050; 5,442,153; 5,180,639; 5,170,009; 5,150,282; 5,047,260; 4,714,623; and WO 00/29635; 99/43191; 99/40769; 98/54942; 98/47340; 97/26782, and in the following publications of the Chomerics Division of Parker Hannifin Corporation (Woburn, Mass.): “CHO-SHIELD® Conductive Compounds;” “CHO-SHIELD® EMI Shielding Covers,” Technical Bulletin 22, (1996); “CHO-VER SHIELD™ EMI Shielding Plastic Cover with Molded Conductive Elastomeric Gasket,” (1999); “CHO-SHIELD® 2052 Conductive Coating,” Technical Bulletin 48, (2000); “CHO-SHIELD® 2054 Conductive Coating,” Preliminary Product Data Sheet, (2000); and “CHO-SHIELD® 2056 High Performance Conductive Coating,” Preliminary Product Data Sheet.
One thermal spray process known as “flame spraying” or “metallizing” employs a combustion flame to spray metals and other materials in powder, wire, or rod form onto a metal, plastic, or ceramic substrate. A mixture of a fuel gas such as acetylene, kerosene, propylene, or hydrogen, and an oxygen-containing gas (oxy-fuel) are flowed through a nozzle and ignited within a combustion chamber or at the nozzle tip. The material to be sprayed, which typically is zinc, steel, bronze, molybdenum, aluminum, nickel, or aluminum, but which may be a ceramic, cermet, or a thermoplastic, is metered into the flame where it is heated, and is then atomized using compressed air or another gas to form a fine, molten spray which is propelled to the surface of the substrate. The droplets solidify upon contact with the substrate to form a coating. In a wire spray technique, the feedstock comprises a metal rod or wire which is passed axially or tangentially into the center of the flame front. In a powder spray variation, a metal powder is injected axially into the flame front by means of a carrier gas or by a gravity feed.
Another thermal spray process known as “plasma spraying” utilizes a high-velocity gas plasma to spray a powdered or other particulate material onto a substrate. To form the plasma, a gas such as argon, nitrogen, hydrogen, or helium, is flowed through the nozzle of a plasma spray gun having an anode and cathode. A potential difference is applied to develop an arc between the electrodes. Resistive heating by the arc causes the gas to ionized into a high-temperature, e.g., 10,000° C. or higher, plasma stream. The powder or other particulate to be sprayed is entrained in the plasma and accelerated towards the substrate at a high velocity which may exceed Mach 1.
In another thermal spray technique known as “arc spray” which is further described in U.S. Pat. Nos. 3,546,415 and 4,668,852, two consumable solid or composite wires are employed as electrodes. An electric arc developed in an “arc zone” between the tips of the wires causes the wires to heat and melt. As the wires melt, the arc is maintained between the tips by the continuous feed of the wires. The molten metal at the wire tips is atomized by a one or more streams of compressed air or another gas, and is accelerated by the gas to a substrate. The molten particles impacting the substrate rapidly solidify to form a coating. Alternatively, the arc spay technique may use non-consumable electrodes and instead, with metallized material being introduced into the arc zone as a powder. Conventional arc spray coatings are known to be generally dense and free of oxide.
The present invention is directed to an electromagnetic interference (EMI) shielded enclosure, such as a case, housing, or a part thereof such as a cover, for mobile telephone handsets and other electronic devices. More particularly, the invention relates to an electrically-conductive, metallic or “metallized” coating layer for such enclosures which is conformally applied by means of a thermal spray process to an interior surface of a metal or plastic enclosure or enclosure part, such coating layer providing EMI shielding and also corrosion protection.
FIG. 3 is a cross-section view of the enclosure part of FIG. 2 taken through line 3—3 of FIG. 2; and
For the purposes of the discourse to follow, the precepts of the present invention are described in connection with the application of the metallized shielding layer involved as sprayed on the interior surface of a front or back cover part of a housing, case, or other enclosure for a handheld electronic communication device such as a mobile, i.e., cellular, telephone. For the purposes hereof, the term “EMI shielding” should be understood to include, and to be used interchangeably with, electromagnetic compatibility (EMC), surface grounding, corona shielding, radio frequency interference (RFI) shielding, and anti-static, i.e., electro-static discharge (ESD) protection. In view of the discourse to follow, however, it will be appreciated that aspects of the present invention may find utility in other applications, such as for other electronic devices, including indoor or outdoor cabinets, requiring both EMI shielding. Use within those such other applications therefore should be considered to be expressly within the scope of the present invention.
As the plastic material forming the enclosure parts 16 will generally be non-electrically conductive, or in the case of metal parts 16 covered with a non-conductive paint or otherwise requiring an electrically-conductive, corrosion-resistant surface, shielding layer 14 is provided, as may be seen with additional reference to FIG. 2 wherein enclosure part 16 a is shown in enhanced detail and to the magnified cross-sectional view thereof of FIG. 3, as an adherent, electrically-conductive film or other coating or the like which is applied as an EMI shielding layer to cover at least a portion of one or both of the interior surfaces 18 a-b of the corresponding enclosure part 16 a-b. For most applications, shielding layer 14 will have a film thickness, referenced at “t” in FIG. 3, of between about 1-100 mils (0.025-2.5 mm), with the enclosure parts 16 a-b having a thickness, referenced at “T” in FIG. 3 of between about 0.020-0.250 inch (0.05-1 cm).
In an illustrative embodiment, metallized shielding layer 14 is thermally-sprayed, such as by means of standard arc wire equipment, onto at least a portion of and, typically, substantiality the entirety of the interior surfaces 18 and interface surfaces 40 and 42 of the parts 16 a-b. For corrosion resistance, layer 14 may be formed of tin, nickel, or an alloy thereof. Typically, the composition of layer 14 may comprise between about 80-95% by weight of tin or nickel, with the balance being between about 5-20% by weight of or more of zinc, copper, or aluminum. Trace amounts of other metals, elements, and organic or inorganic compounds also may be present. A preferred material for layer 14 is a tin-based Babbit metal comprising about 85% tin and about 14% zinc, the balance being trace metals, elements, or compounds. Such material is both economical and provides a corrosion-resistant coating on surface 18. By “corrosion-resistant,” it is meant that the shielding layer 14 is more corrosion resistant than the zinc flame sprayed coatings heretofore known in the art. In this regard, layer 14 typically will exhibit a less than about 5-15% increase in surface resistance upon exposure to a salt-fog environment for about 48 hours at about 35° C. Layer 14 similarly will be observed to exhibit substantially no increase in surface resistance following a thermal cycling of at least about 5 cycles at −40° C. to 85° C. with a dwell time of about two hours at each of the upper and lower temperature limits.
Advantageously, as thermally-sprayed in accordance with the present invention, shielding layer 14 is self-adherent to interior surface 18 as being bonded thereto. Such bond principally will be by way of mechanical forces, but additionally may include fusion or chemical bonding, and/or electrostatic, van der Waals, or other valance or attractive forces depending upon the composition and the compatibility of the metal or plastic material forming surface 18 and the metal material forming the metallized layer 14. Typically, layer 14 will be observed to have an assigned rating of about “5,” i.e., substantially no coating pickoff, as determined on a scale of 0B-5B in accordance with ASTM Test Method D3359-97, “Standard Test Methods for Measuring Adhesion by Tape Test,” in which the adhesion of coatings is assessed by applying and removing pressure-sensitive tape over cross-hatch cuts made in the coating.
Means of securing gasket 50 to the layer portion 62 include pressure-sensitive adhesive tapes or other layers (not shown), which may be filled to be electrically conductive, interposed between the layer 14 portion 62 and the gasket. Alternatively, mechanical means of attachment such as clips, fasteners, or a tough-in-groove or other interference fit may be employed. In the case of an over-molded or FIP construction, the gasket 50 may be self-bonded by chemical, mechanical, or other adhesive forces to the layer 14 portion 62. EMI shielding gaskets and their methods of manufacture and use are further described in U.S. Pat. Nos. 6,121,545; 6,096,413; 5,910,524; 5,882,729; 5,731,541; 5,641,438; 5,603,514; 5,578,790; 5,566,055; 5,524,908; 5,522,602; 5,512,709; 5,438,423; 5,202,536; 5,142,101; 5,115,104; 5,107,070; 5,105,056; 5,068,493; 5,028,739; 5,008,485; 4,988,550; 4,968,854; 4,952,448; 4,857,668; and 3,758,123, and in WO 96/22672 and 98/54942; Japanese Patent Publication (Kokai) No. 7177/1993; DE 19728839, and Severinsen, J., “Gaskets That Block EMI,” Machine Design, Vol. 47, No. 19, pp. 74-77 (Aug. 7, 1975).
1. A method of EMI shielding a part of an enclosure for housing circuitry in an electronic device, the enclosure part having an exterior surface and an opposing interior surface, and said method comprising the steps of:
(a) providing a feed material comprising tin, nickel, or an alloy thereof;
(b) heating said feed material of step (a) into a molten state;
(c) atomizing said feed material of step (b) while in said molten state;
(d) spraying the atomized feed material of step (c) while in said molten state on at least a portion of the interior surface of the enclosure part to form a conformal coating of said metal thereon; and
(e) solidifying said coating of step (d) to form an electrically-conductive, corrosion-resistant, self-adherent EMI shielding layer on said portion of said interior surface.
2. The method of claim 1 wherein said housing part is formed of a metal.
said feed material is atomized in step (c) and by a gas stream passed with said feed material through said arc zone; and
said feed material is sprayed in step (d) by entrainment within said gas stream.
said atomized feed material is prayed in step (d) on substantially the entirety of the interior surface of the enclosure part; and
said coating is solidified in step (d) to form said shielding layer on substantially the entirety of the interior surface of the enclosure part.
said interior surface of the enclosure part has a structure formed therein;
said atomized feed material is prayed in step (d) on said structure; and
said coating solidified in step (d) conforms to said structure.
15. The method of claim 1 wherein said interior surface of the enclosure part defines an interface surface with another part of the device, said atomized feed material is prayed in step (d) on said interface surface, and said coating is solidified in step (d) to form said shielding layer on said interface surface, said method further comprising the additional step of:
(f) disposing an electrically-conductive gasket on said enclosure part, said gasket being supported on the shielding layer formed on said interface surface and being compressible therebetween and said another part of the device.
16. The method of claim 15 wherein said gasket of step (f) comprises of a blend of a elastomeric resin and an electrically-conductive filler.
20. The method of claim 1 wherein said coating layer of step (e) has an adhesion on the interior surface of the enclosure part of about 5B as rated in accordance with ASTM Test Method D3359-97, “Standard Test Methods for Measuring Adhesion by Tape Test.”
exposing the interior surface of the enclosure part to a plasma comprising one or more ionized gases.
22. The method of claim 21 wherein the interior surface of the enclosure part is etched by said exposure to said plasma.
US10137229 2001-05-10 2002-05-01 Manufacture of electronics enclosure having a metallized shielding layer Active 2023-02-18 US6763576B2 (en)
US28992001 true 2001-05-10 2001-05-10
US10137229 US6763576B2 (en) 2001-05-10 2002-05-01 Manufacture of electronics enclosure having a metallized shielding layer
US10287490 US6965071B2 (en) 2001-05-10 2002-11-01 Thermal-sprayed metallic conformal coatings used as heat spreaders
US10287490 Continuation-In-Part US6965071B2 (en) 2001-05-10 2002-11-01 Thermal-sprayed metallic conformal coatings used as heat spreaders
US20020166682A1 true US20020166682A1 (en) 2002-11-14
US6763576B2 true US6763576B2 (en) 2004-07-20
ID=23113733
US10137229 Active 2023-02-18 US6763576B2 (en) 2001-05-10 2002-05-01 Manufacture of electronics enclosure having a metallized shielding layer
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Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:LEE, GEORGE A.;REEL/FRAME:012863/0579
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SAUER, JAMES J.;REEL/FRAME:012863/0836
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WATCHKO, GEORGE R.;FLAHERTY, BRIAN F.;GAGNON, MATTHEW T.;AND OTHERS;REEL/FRAME:012751/0735