ES2367631T3 - EMI METAL AND PLASTIC SCREEN IN COMBINATION. - Google Patents

Abstract

Screen (10) EMI presenting at least one compartment (11) that can be mounted on or on top of a printed circuit board (72) to enclose the circuitry (74, 76) of an electronic device, said screen comprising: a first element (12) formed of a thin metal sheet; and a second element (14) formed of an electrically conductive composite material comprising a mixture of a polymeric component and an electrically conductive particulate charge component, wherein the second element is attached to the first element so as to form a screen of a single piece, and has at least one wall (30a-d) that extends from the first element and which together with the first element defines at least a part of said compartment.

Description

Background of the invention

The present invention relates generally to electromagnetic interference (EMI) screens, such as housings, housings or parts thereof such as covers, or plate-level screens such as single compartment covers or multiple compartments or "covers", for cell phone apparatus, that is to say mobiles, telecommunication base stations, and other electronic devices, and particularly to a screen having a thin metal base part to which a wall part formed by a conductive plastic or other material is attached polymeric that can be molded or otherwise formed in a plurality of ways.

The generation of electromagnetic radiation within the set of electrical circuits of the equipment assists the operation of electronic devices such as televisions, radios, computers, medical instruments, commercial machines, communications equipment, and the like. As detailed in US Patent Nos. 5,202,536; No. 5,142,101; No. 5,105,056; No. 5,028,739; No. 4,952,448; and No. 4,857,668, such radiation often develops as a field or as transient oscillations within the radio frequency band of the electromagnetic spectrum, that is, between about 10 KHz and 10 GHz, and is called "electromagnetic interference" or "EMI ”Since it is known to interfere with the operation of other nearby electronic devices.

To mitigate the effects of EMI, a shield can be used that has the ability to absorb and / or reflect EMI energy both to confine EMI energy within a source device and to isolate that device or other "target" devices from other source devices. Said shielding is intended as a barrier that is interposed between the source device and other devices, and is normally configured as a grounded and electrically conductive housing enclosing the device, or as a "sheath" covering a discrete component or assembly of device components. The housing or sheath may be formed of a metal such as steel, aluminum or magnesium, or alternatively, of a plastic or other polymeric material that is charged to be electrically conductive, as described in US Patent Nos. 5,397,608; No. 5,366,664; No. 5,213,889; No. 5,137,766; No. 5,019,450; No. 4,973,514; No. 4,816,184; No. 4,664,971; and No. 4,559,262, and in WO 02/43456 and 02/02686, or which may be provided with a conductive coating generally applied across the interior surfaces of the housing.

The coating may be an electrically conductive paint, a molded elastomeric layer, conductively charged, a transfer or laminated metal film material, or a layer of flame-sprayed or other deposited metal. A conductive joint can be used to provide electrical continuity between the coating layers applied to the various matching housing parts.

Such housings, covers, and procedures are further described in legally assigned US Patent Nos. 6,348,654 and 5,566,055, US 20030015334, and WO 02/093997 and 02/093996, and in US Patent Nos. 6,431,884 ; No. 6,256,878; No. 6,090,728; No. 5,847,317; No. 5,811,050; No. 5,571,991; No. 5,475,919; No. 5,473,111; No. 5,442,153; No. 5,397,857; No. 5,180,639; No. 5,170,009; No. 5,150,282; No. 5,047,260; and No. 4,714,623, WO 02/43456; 01/97583; 00/29635; 99/43191; 99/40769; 98/54942; 98/47340; and 97/26782, EP 1 148 774; 0 936 045; and 0 940 068, and DE 19728839, and in the following publications of the Chomerics Division of Parker Hannifin Corporation (Woburn, MA): "CHO-SHIELD® Conductive Compounds;" "CHOSHIELD® EMI Shielding Covers," Technical Bulletin 22, (nineteen ninety six); "CHO-SEE SHIELDTM EMI Shielding Plastic Cover with Molded Conductive Elastomeric Gasket," (1999); “CHO-SHIELD® 2052 Conductive Coating,” Technical Bulletin 48, (2000); “CHOSHIELD® 2054 Conductive Coating,” preliminary product datasheet, (2000); and “CHO-SHIELD® 2056 High Performance Conductive Coating,” preliminary product datasheet.

Japanese patent application No. JP19970133170 discloses a structure for a high frequency screen housing that can reduce the number of joined elements and have a sufficient shielding effect.

International patent application WO 0243456 discloses an electromagnetic radiation interference attenuation screen for an electronic circuit component. The screen includes a body formed from an electronically and thermally conductive material.

From the above, it can be seen that many different types of materials and constructions have been used in the production of EMI screens. As can be expected, each of these materials and constructions show certain inherent advantages and disadvantages. For example, stamped aluminum screen constructions are well known and can be manufactured by presenting a very thin wall, that is, z axis, thicknesses of 0.2 mm or less, but they are relatively expensive and difficult to manufacture profitably in the complex forms that may be required for certain applications. Likewise, conductively loaded plastics can be economically molded or otherwise formed in a variety of complex shapes, but generally cannot be used in screening applications where very thin wall thicknesses are required in certain sections of the screen.

As electronic devices such as mobile phone devices continue to proliferate, it is believed that additional EMI screening options and options for device housings and other enclosures could be well received by the electronic products industry.

Broad Exposure of the Invention

The present invention relates generally to electromagnetic interference (EMI) screens, such as housings, housings, or parts thereof such as covers or plate-level displays such as single compartment covers or multiple compartments or "covers" , for cell phone devices, ie mobile phones, telecommunication base stations, and other electronic devices. More particularly, the invention relates to a screen having a thin metal base section to which a wall section formed by a conductively charged plastic or other polymeric composite material that can be molded or otherwise formed into a wall is attached. plurality of forms.

In an illustrative embodiment, the screen is configured as a cover at the plate or case level for an electronic device, and has multiple compartments to shield the device circuitry. In this regard, the wall section is configured to define the multiple compartments, and can be molded, such as by molding with inserts, onto the base section to form a one-piece screen. The screen can be attached to the plate, such as with an end surface of the wall section that is in contact with a grounding track formed on the plate, using fasteners, clamps, or other mechanical means. Alternatively, the screen can be welded or glued to the plate. An electrically conductive coating or elastomeric joint can also be interposed between the screen wall section and the plate to improve the electrical contact between them.

Advantageously, the screen of the invention allows a more economical construction compared to metal stamping, while offering the designer the ability to manufacture screens that have complex shapes but still offer the thinnest z-axis profiles that can be achieved through use of metal sheets. These and other advantages will be readily apparent to those skilled in the art from the description contained herein.

Brief description of the drawings

For a better understanding of the nature and objectives of the invention, reference should be made to the following detailed description from the accompanying drawings, in which:

Figure 1 is an exploded perspective view of a representative EMI metal and plastic combination screen according to the present invention;

Figure 2 is a bottom view of the screen of Figure 1;

Figure 3 is a cross-sectional view of the screen of Figure 1 taken through line 3-3 of Figure 2;

Figure 4 is a somewhat schematic cross-sectional view of an insert molding process for manufacturing the screen of Figure 1;

Figure 5 is an exploded overall view showing a representative printed circuit board (PCB) shielding application for the screen of Figure 1; Y

Figure 6 is an enlarged view of a cross section of Figure 4 showing the contact surface between the screen and the PCB in improved detail.

The drawings will be described further in connection with the following detailed description of the invention.

Detailed description of the invention

Certain terminology may be used in the following description for convenience and not in a limiting manner. For example, the expressions "forward" and "backward", "frontal" and "rearward", "right" and "left", "upper" and "lower", "upper part" and "lower part" and " right ”and“ left ”designate directions in the drawings to which reference is made, referring to the expressions“ inward ”,“ internal ”,“ internal ”or“ on board ”and“ outwardly ”,“ external ” , "Outside" or "out of plate", respectively, to the directions towards and away from the center of the element to which reference is made, referring to the terms "radial" or "vertical" and "axial" or "horizontal", respectively , to the directions or planes perpendicular and parallel to the longitudinal central axis of the element to which reference is made. Terminology of similar importance apart from the terms specifically mentioned above, should also be considered as terms that are used for convenience and not limiting.

In the figures, reference may be made herein to elements that present an alphanumeric designation collectively or alternatively, as will be apparent from the context, by only the numerical part of the designation. In addition, the constituent parts of various elements in the figures can be designated with separate reference numbers that should be appreciated that refer to that constituent part of the element and not to the element as a whole. General references, together with references to spaces, surfaces, dimensions and extensions can be designated with arrows or underlines.

In the context of the following discussion, the precepts of the present invention are described in relation to the construction of a multi-compartment metal and plastic combination cover or "sheath" that can be mounted on or above a PCB to enclose various sections. of PCB circuitry that can itself be housed with the screen inside a housing, housing, or other enclosure of an electronic device such as a cell phone device, that is mobile, or another electronic device such as an apparatus of personal communication services (PCS), PCMCIA card, global positioning system (GPS), radio receiver, personal digital assistant (PDA), laptop or desktop personal computer (PC), wireless telephone device, router or server network, medical electronic device, modem, wireless communication base station, telemetry device, os component telematic system, or the like. As used herein, the term "EMI display" should be understood to include, and for use interchangeably with, electromagnetic compatibility (EMC), surface ground connection, crown shielding, interference interference shielding. radio frequency (RFI), and antistatic discharge protection, ie electrostatic (ESD).

It should be appreciated, however, that the screen may alternatively be configured as a single compartment cover, or as another cover or housing of the device, or configured to mount on or come into contact with another part of the device that may be another screen, a part of cover or housing, or a spacer joint or other structure. Aspects of the present invention may also be useful in other EMI shielding applications, such as indoor or outdoor equipment cabinets. The use within such other applications and in such other configurations should therefore be considered to be expressly within the scope of the present invention.

Referring then to the figures in which the corresponding reference characters are used to designate corresponding elements in all of the various views with reference to the equivalent elements with main or sequential alphanumeric designations, an exemplary EMI screen according to the present invention is generally shown in 10 in the various views of Figures 1 to 3 presenting one or more compartments, one of which is designated in 11, to enclose the circuitry of an electronic device. In a basic construction, the screen 10 includes a first element or section, 12, and a second element or coupling section, 14, which joins the first section 12, and which is configured to divide the screen 10 into one or more compartments 11. Each of the compartments 11 can be used to house components, circuits or separate areas of the circuitry of the device in order to electromagnetically isolate them from other components, circuits or zones of this type from the circuitry.

Depending on the requirements of the particular application involved, the first section 12 may be generally flat, and in the illustrative embodiment of Figures 1 to 3 it has an outer surface, 20, and an inner surface, 22. The first section 12 it can be stamped, stamped, or otherwise formed in a variety of ways, so that it can be defined by an outer margin, 24, and otherwise it can be provided as a thin metal sheet having a z-axis thickness, to which reference is made in t1 in the cross-sectional view of Figure 3, of, for example, not greater than about 10 thousand (0.25 mm), and normally between about 3 and 5 thousand (0.075-0.125 mm) or less. Although the first section 12 is shown in generally flat Figures 1 to 3, the section may be alternately contoured or otherwise not flat as the application requires. Typically, the first section 12 may be formed of a sheet of an aluminum metal or aluminum alloy. Alternatively, a sheet of another metal, such as zinc, magnesium, or steel,

or a combination or alloy thereof may be substituted or used in combination with the aluminum or aluminum alloy material.

The second section 14 joins the first element, and has one or more walls, designating a group of adjacent walls in 30a-d, which extend, either generally perpendicularly as shown or alternatively, at an angle, from the inner surface 22 of the first section 12. As shown for walls 30a-d, each group of this type of adjacent walls 30, together with the surface 22 of the first element 12 can define a compartment separated from the compartments 11 It should be appreciated that, as used herein, the term "wall" may refer to an exterior wall or part thereof, as referenced in 30a and 30b, and / or to an interior wall or part thereof, such as any of the walls 30c or 30d. Normally, each of the walls 30 may have a z-axis thickness, referred to in t2 in the cross-sectional view of Figure 3, which may be the same or different, and that otherwise may be between approximately 3 and 10 thousand (0.075-0.254 mm).

As can be seen more clearly with a continuous reference to the cross-sectional view of Figure 3, each of the walls 30 extends between a first end surface, referred to in 32 for the adjacent wall 30b to the inner surface 22 of the first section, and a second distal end surface, referred to in 34 for wall 30b. The first end surfaces 32, which, as shown, can generally be adjacent so that the contact surface, referred to in 36, which is thus defined as a whole is generally flat. Alternatively, as it may depend on the contour of the first section 12, the first end surfaces may end non-flat. Likewise, the second end surfaces 34 may end to define a contact surface, 38, which is generally flat as shown or, instead, not flat. The second end surface, which can be used, for example, to come into contact with the grounding path of a PCB, can generally be flat as shown or, alternatively, round, toothed, flanged, of decreasing or shaped section of another way.

The second section 14 can be additionally formed with features, such as the through corner holes referred to in 40a-d, for joining using screws or other screen fasteners to a PCB or other part of the device. The through holes 40 may be configured in other ways such as for pins or for threaded metal with heat application or other insertion parts. Similarly, the second section 14 may be formed with features for a pressure adjustment or other interference adjustment or mechanical engagement with another part of the device. A flange (not shown) can also be provided extending outwardly from the end surfaces 34 around all or a portion of the outer perimeter, referred to in 42, of the screen 10 defined by the outer walls of the same.

As will be described in greater detail hereinbelow, the second section 14 may be molded or otherwise formed into one or more pieces of an electrically conductive composite material that may be the same or different in each piece. Such material can be formulated, as can be described in greater detail in US Patent Nos. 5,397,608; No. 5,366,664; No. 5,213,889; No. 5,137,766; No. 5,019,450; No. 4,973,514; No. 4,816,184; No. 4,664,971; and No. 4,559,262, and in WO 02/43456 and 02/02686, as a combination or other mixture of a resin, plastic, an elastomeric component or another or another polymer component, and an electrically conductive particle charge component .

The polymer component, which by itself can be a combination or other mixture, can be a thermoplastic

or hardened plastic, and specifically can be selected based on one or more of operating temperature, hardness, chemical compatibility, elasticity, adaptability, compression-deflection, compression properties, flexibility, resilience after deformation, modulus, tensile strength , elongation, stress-strain, flammability, or other chemical or physical property. Depending on the application, suitable materials may include, in particular, polyurethanes, silicones, fluorosilicones, polycarbonates, ethylene vinyl acetates (EVA), acrylonitrile-butadiene-styrenes (ABS), polysulfones, acrylic compounds, polyvinyl chlorides (PVC) ), poly (phenylene ethers), polystyrenes, polyamides, nylon, polyolefins, poly (ether ether ketones), polyimides, polyetherimides, poly (butylene terephthalates), poly (ethylene terephthalates), fluoropolymers, polyesters, acetals, polymers liquid crystal, poly (methyl acrylates), poly (phenylene oxides), polystyrenes, epoxy resins, phenolic resins, chlorosulfonates, polybutadienes, buna-N, butyls, neoprenes, nitriles, polyisoprenes, natural rubbers, and copolymer rubbers such as styrene-isoprene-styrenes (SIS), styrenebutadiene-styrenes (SBS), ethylene-propylene (EPR), ethylene-propylene-diene (EPDM) monomers, nitrilobutadiene (NBR), and styrene-butadiene (SB R), and copolymers and combinations thereof. Any of the above materials can be used without foaming or, if required by application, blown or chemically or physically treated to provide an open or closed cell foam.

The polymer component may generally form a binder or other continuous or matrix phase within the material in which the charge can be dispersed into electrically conductive particles as a discrete phase. The charge is generally included within the binder in a proportion sufficient to provide the level of electrical conductivity desired for the intended application. For most applications, a mass or volume resistivity not exceeding approximately 1,000 Ω-cm, and / or a surface resistance not exceeding approximately 1000 Ω / sq. Would be considered acceptable, and would be transferred to a load grade which can generally be between about 5 and 95% by weight, based on the total volume or weight, as may be the case with the compound.

In general, the charge may be of any form, or combination of shapes, and may be broadly referred to herein as "particulate material," which should be understood to include solid or hollow spheres and microspheres, elastomeric balloons, flakes, platelets, fibers. , rods, irregularly shaped particles, which can be crushed or ground, or fine filaments, and powders. For many applications, the particle size or charge distribution, which can be a diameter, imputed diameter, length, or other dimension of the particulate material will normally be between about 0.01 thousand (0.25 µm) and about 10 thousand (250 µm) for powders, and between about 0.004 inches (0.1 mm) and about 1 inch (25 mm) for fibers.

Suitable electrically conductive charges include: non-metals such as carbon, graphite, and inherently, that is, intrinsically conductive polymers; noble and non-noble metals such as gold, silver, nickel, copper, tin, aluminum, and nickel; noble or non-noble metals metallized, plated, coated with metal, or noble and non-noble metals coated otherwise such as gold or copper plated with silver, nickel, or aluminum, and tin or copper plated with nickel, silver, bismuth, indium , and lead; non-noble or non-noble metal coated metals such as gold, silver and / or nickel plated or graphite coated, that is, gold-plated nickel-coated graphite, glass, ceramics, plastics, elastomers, and mica; metals and nonmetallic coated metals; and combinations and mixtures thereof. The electrically conductive load can be specifically selected depending on one or more of conductivity, resin demand, hardness, chemical compatibility, such as with the polymer component, and cost. In the case of a coating, the coating can be formed of one or more layers of the same material, or layers of different materials.

Additional fillers and additives may be included in the formulation of the material depending on the requirements of the particular intended application. Such fillers and additives, which may be functional or inert, may include wetting or surfactants, pigments, dispersants, dyes, and other dyes, opacifying agents, foaming or antifoaming agents, antistatic agents, coupling agents such as titanates, extender oils chain, tackifiers, flow modifiers, pigments, lubricants such as molybdenum disulfide (MoS2), silanes, peroxides, film reinforcing polymers and other agents, stabilizers, emulsifiers, antioxidants, thickeners and / or flame retardants and other fillers such as aluminum trihydrate, antimony trioxide, salts and metal oxides, intercalated graphite particles, phosphate esters, decabromodiphenyl oxide, borates, phosphates, halogenated compounds, glass, silica, which can be pyrogenic or crystalline, silicates, mica, ceramics, and polymer or glass microspheres. Typically, these fillers and additives are combined or otherwise mixed with the formulation or with the polymer component thereof, and may comprise between about 0.05 and 80% or more in total volume of the formulation.

The formulation for the electrically conductive composite material of the second section 14 may be composed in a conventional mixing apparatus such as a mixing of the polymer and filler components, and any additional filler or additive. Alternatively, and as may be further described in US Patent Nos. 5,397,608; No. 5,366,664; No. 5,213,889; No. 5,137,766; No. 5,019,450; No. 4,973,514; No. 4,816,184; No. 4,664,971; and No. 4,559,262, and in WO 02/43456 and 02/02686, the material may be provided in the form of granules having a core of graphite or carbon fibers coated with nickel, or other conductive fibers, which are introduced in rows or otherwise coated or embedded within an outer coating of the polymer component that may be a thermoplastic. Such granules can be injection molded to form the second section 14.

For example, the granules described above, or another compound of the electrically conductive composite material, can be used in an insert molding process both to form the second section 14 and to join the section to the first section 12. A process of drawing is schematically illustrated. this type at 50 in the view of figure 4. In such a procedure, the stamping or other form of the first section 12 can be placed inside a cavity, 52, defined between or formed inside one of a pair of mold halves, 54a-b, defining the rest of the cavity 52 the configuration of the second section 14. With the mold halves 54 closed, such as along the joint line shown in 56, The compound of the composite material can be introduced under pressure or otherwise into the rest of the cavity. With cooling or other hardening or curing of the material, such as polymerization, crosslinking, additional crosslinking

or polymerization, vulcanization, drying, or other chemical or physical process, the mold halves 54 can be opened and the finished or substantially finished screen 10 thus formed can be released therefrom.

Advantageously, by means of such insert molding or other procedure, the second section 14 of the screen 10 can be molded or glued or otherwise joined to the first section 12 in a single operation. In this regard, and referring again to the various views of Figures 1 to 3, it can be seen, particularly in the cross-sectional view of 3, that the second section can be attached to the first section 12 along the surface of contact 36. Although it is envisaged that the respective sections 12 and 14 may be constructed as separate parts that are mechanically fastened or interferentially engaged or otherwise, or glued together or otherwise bonded, sections 12 and 14 are shown in the illustrative embodiment that is self-adhering or stuck. Such bonding can be by mechanical forces, fusion or chemical bonding, and / or electrostatic forces, of van der Waals, or other forces of valence or attraction, since they can depend on the composition and compatibility of the metallic and plastic materials that they form sections 12 and 14. To facilitate such bonding, such as increasing the surface area between the sections, or developing additional mechanical or interlocking hooks, the metal sheet of the first section 12 can be stamped, cut or otherwise formed since they have one or more openings, referring to one of which in imaginary line at 60 in Figures 3 and 4, for the flow through it of the composite material of the second section 14. The metal sheet of the first section 12 it can also be manufactured by presenting fingers, flanges, or other features in which the material of the second section 14 can flow inside or around it.

With regard again to Figure 5, reference is generally made in 70 to an assembly incorporating the screen 10 of the invention in the exploded view of the figure. For illustration purposes, assembly 70 is shown to include a PCB, 72, which may be a component or module of an electronic device. As shown, various electronic components, referring to one of which in 74, or another set of circuits can be mounted on the PCB 72, and can be grouped into different circuits, referring to one of which in 76, so which may be delineated by the pattern of a ground track, referred to in imaginary line at 78. The screen 10 can be attached or otherwise connected to the PCB 72 by means, for example, of the screws 80 housed through the holes 82 of the PCB and inside the through holes 40 of the second section 14. Alternatively, the screen 10 can be attached or otherwise connected to the PCB 72 by other mechanical means, such as a clamp, or by gluing with a metal weld

or with an adhesive that can be electrically conductive, or a two-sided tape.

As it joins the PCB 72, the contact surface 38, or a part thereof, may be in alignment and in electrical contact with the ground track 78 to thereby isolate one or more, or each, of circuits 76 of other circuits 76 or of other components within the device, or of other devices. In this regard, by referring to the enlarged view of a cross section of the complete assembly 70 shown in 90 in Figure 6, the electrical contact between the contact surface 38 and the ground track 78 or another part of the device can be improved by means of a separate layer, 92, of a conductive material electrically interposed between the contact surface and the track. Depending on the requirements of the application, said layer 82 may be provided to extend continuously or discontinuously between all or a portion of the contact surface surfaces 38 and 78, and additionally it may provide an environmental seal between them. The layer 92 can be the solder or the adhesive that can be used to glue the screen 10 to the PCB 72, or the layer can be another coating such as a metal or a metal-loaded paint that can be applied to one or both of the contact surfaces 38 and 78 such as by flame or wire-arc spraying, immersion, painting, screen printing or transfer printing, dispensing, extrusion, coating, metallization, lamination, non-electrolytic or electrolytic plating, vacuum or chemical deposition in vapor phase, evaporation, cathodic deposition, plasma coating, or the like.

Alternatively, the layer may be an electronically conductive joint or joint-like material. In this regard, such material can be provided in the form of a joint having a flexible core element that provides void filling capabilities, in which the core element can be charged, sheathed, or coated with an electrically conductive element. The flexible core element, which can be foamed or non-foamed, solid or tubular, can usually be molded, extruded, punched, or otherwise formed from an elastomeric thermoplastic material such as polyolefin, polyvinyl chloride, or a combination of prolipropylene-EPDM or a thermoplastic or thermosetting rubber such as butadiene, styrene-butadiene, nitrile, chlorosulfonate, neoprene, urethane, silicone or fluorosilicone.

Conductive materials for loading, sheathing or cladding include metal or metal plated particles, textile materials, meshes and fibers. Preferred materials include copper, nickel, silver, aluminum, tin or an alloy such as Monel, including fibers and preferred textile materials, natural and synthetic fibers such as cotton, wool, silk, cellulose, polyester, polyamide, nylon, polyimide. Other particles and conductive fibers such as carbon, graphite, plated glass, or a conductive polymer material can be substituted. The gasket, alternatively, may be provided to be of a knitted wire construction, of metal in its entirety, or such as an overmolded or in situ formed (FIS) bead of an electrically conductive urethane or curable silicone composition. As for an FIS construction, the composition can be distributed in a fluid state on one or the other of surfaces 38 and 78, and subsequently cured or foamed in situ by the application of heat or with atmospheric humidity, UV radiation, or other sources of Energy.

The means for attaching the gasket or gasket material to one or other of the surfaces 38 and 78 includes pressure sensitive adhesive tapes or other layers (not shown), which can be charged to be electrically conductive, interposing between the surface and the board. Alternatively, mechanical joining means such as clamps, fasteners, or a groove tongue or other interference fit can be used. In the case of an overmolded or FIS construction, the joint can be self-bonded by chemical, mechanical, or other surface adhesive. EMI screen joints and their manufacturing and use procedures are further described in US Patent Nos. 6,121,545; No. 6,096,413; No. 5,910,524; No. 5,882,729; No. 5,731,541; No. 5,641,438; No. 5,603,514; No. 5,578,790; No. 5,566,055; No. 5,524,908; No. 5,522,602; No. 5,512,709; No. 5,438,423; No. 5,202,536; No. 5,142,101; No. 5,115,104; No. 5,107,070; No. 5,105,056; No. 5,068,493; No. 5,028,739; No. 5,008,485; No. 4,988,550; No. 4,968,854; No. 4,952,448; No. 4,857,668; and 3 No. 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, volume 47, No. 19, p. 74-77 (August 7, 1975).

Since it is anticipated that certain changes may be introduced in the present invention without departing from the precepts implied herein, it is intended that the entire object contained in the above description should be interpreted as illustrative and not in a limiting sense. All references that include any priority document mentioned herein are expressly incorporated by reference.

Claims (38)

1. EMI screen (10) presenting at least one compartment (11) that can be mounted on or above a printed circuit board (72) to enclose the circuitry (74, 76) of an electronic device, said device comprising screen: a first element (12) formed of a thin metal sheet; Y a second element (14) formed of an electrically conductive composite material comprising a mixture of a polymer component and an electrically conductive particle loading component, wherein the second element is attached to the first element so that it forms a screen of a single piece, and has at least one wall (30a-d) that extends from the first element and which together with the first element defines at least a part of said compartment.

2.

Screen according to claim 1, wherein the polymer component comprises one or more thermosetting or thermoplastic polymers or copolymers, or a combination thereof.

3.

Screen according to claim 1, wherein the polymer component is selected from the group consisting of epoxy resins, phenolic resins, poly (ether ether ketones), polyimides, polyolefins, polyetherimides, poly (butylene terephthalates), poly (terephthalates of ethylene), nylon, polyamides, fluoropolymers, polysulfones, polyesters, homo and copolymers of acetal, liquid crystal polymers, polyacrylic compounds, poly (methyl acrylates), poly (ester and ether urethanes), polyurethanes, acrylonitrile-butadiene-styrene, polyvinyl chlorides, poly (phenylene ethers), poly (phenylene oxides), polystyrenes, polycarbonates, and copolymers and combinations thereof.

Four.

Screen according to claim 1, wherein the screen shows an EMI shielding efficiency of at least about 60 dB substantially over a frequency range between about 10 MHz and about 10 GHz.

5.

Screen according to claim 1, wherein the composite material has a volume resistivity not exceeding approximately 1,000 Ω-cm.

6.

Screen according to claim 1, wherein the composite material comprises between about 5 and 95% by weight of the loading component.

7.

Screen according to claim 1, wherein the metal sheet has a thickness not exceeding approximately 10 mil (0.125 mm).

8.

Screen according to claim 1, wherein the wall of the second element has a thickness of between about 3 and 10 thousand (0.075-0.254 mm).

9.

Screen according to claim 1, wherein the second element is self-attached to the first element.

10.

Screen according to claim 1, wherein the sheet is formed of aluminum, zinc, magnesium, steel, or a combination or alloy thereof.

eleven.

Screen according to claim 1, wherein the wall extends from the first element towards an end surface, the end surface being able to be arranged in a part of the device.

12.

Screen according to claim 11, further comprising an electrically conductive gasket or layer disposed on the end surface.

13.

Screen according to claim 12, wherein the electrically conductive layer comprises a metal or a resin charged with electrically conductive particulate materials.

14.

Screen according to claim 12, wherein the joint comprises an elastomeric resin loaded with electrically conductive particulate materials.

fifteen.

Screen according to claim 12, wherein the joint or layer is self-adhering on the end surface.

16.

Screen according to claim 1, wherein the electrically conductive particle charge component comprises electrically conductive fibers.

17.

Screen according to claim 16, wherein the electrically conductive fibers are selected from the group consisting of: graphite, carbon, inherently conductive polymer, and metal fibers; the metallic or non-metallic fibers having an electrically conductive coating; and mixtures and combinations thereof.

18.

Screen according to claim 17, wherein the electrically conductive coating comprises one or more layers of carbon, graphite, or one or more inherently conductive polymers or metals, or a combination thereof.

19.

Screen according to claim 16, wherein the fibers have an average length of between about 0.004 and 1 inch (0.1-25 mm).

twenty.

Screen according to claim 1, wherein the compartment is housed on the circuitry of the device.

twenty-one.

Assembly according to claim 20, wherein the polymer component comprises one or more thermosetting or thermoplastic polymers or copolymers, or a combination thereof.

22

The assembly according to claim 20, wherein the polymer component is selected from the group consisting of epoxy resins, phenolic resins, poly (ether ether ketones), polyimides, polyolefins, polyetherimides, poly (butylene terephthalates), poly (terephthalates of ethylene), nylon, polyamides, fluoropolymers, polysulfones, polyesters, homo and copolymers of acetal, liquid crystal polymers, polyacrylic compounds, poly (methyl acrylates), poly (ester and ether urethanes), polyurethanes, acrylonitrile-butadiene-styrene, polyvinyl chlorides, poly (phenylene ethers), poly (phenylene oxides), polystyrenes, polycarbonates, and copolymers and combinations thereof.

2. 3.

The assembly according to claim 20, wherein the screen shows an EMI shielding efficiency of at least about 60 dB substantially over a frequency range between about 10 MHz and about 10 GHz.

24.

Assembly according to claim 20, wherein the composite material has a volume resistivity not exceeding approximately 1,000 Ω-cm.

25.

Assembly according to claim 20, wherein the composite material comprises between about 5 and 95% by weight of the filler component.

26.

Assembly according to claim 20, wherein the metal sheet has a thickness not exceeding approximately 10 mil (0.125 mm).

27.

Assembly according to claim 20, wherein the wall of the second element has a thickness of between about 3 and 10 inches (0.075-0.254 mm).

28.

Assembly according to claim 20, wherein the second element is self-attached to the first element.

29.

Assembly according to claim 20, wherein the sheet is formed of aluminum, zinc, magnesium, steel, or a combination or alloy thereof.

30

Assembly according to claim 20, wherein the wall extends from the first element towards an end surface, the end surface being arranged on a part of the device that together with the compartment encloses the circuit assembly.

31.

Assembly according to claim 30, further comprising an electrically interposed gasket or conductive layer between the end surface and the part of the device.

32

Assembly according to claim 31, wherein the electrically conductive layer comprises a metal or a resin charged with electrically conductive particulate materials.

33.

Assembly according to claim 31, wherein the joint comprises an elastomeric resin charged with electrically conductive particulate materials.

3. 4.

Assembly according to claim 31, wherein the joint or layer is self-adhering on the end surface.

35

The assembly according to claim 20, wherein the electrically conductive particle charge component comprises electrically conductive fibers.

36.

Assembly according to claim 35, wherein the electrically conductive fibers are selected from the group consisting of: graphite, carbon, inherently conductive polymer, and metal fibers; metallic or non-metallic fibers having an electrically conductive coating; and mixtures and combinations thereof.

37.

Assembly according to claim 36, wherein the electrically conductive coating comprises one or more layers of carbon, graphite, or one or more inherently conductive polymers or metals, or a combination thereof.

38.

The assembly according to claim 35, wherein the fibers have an average length between about 0.004 and 1 inch (0.1-25 mm).