Components of an electronic device which enable the device to perform its functions (e.g., internal circuitry) are often referred to as critical components. Such critical components including, for example, discrete and integrated components, are typically arranged in close configuration on a circuit board. Often it is required that the circuit board and the critical components be disposed within shielding structures to prevent unwanted electrical emissions from seeping out or in. It is also often required that the critical components be disposed below electrical circuit signals or grounding paths of the circuit board.
Also included in the circuit board are contact positions, which are necessarily connected to a variety of other structures. The contact positions are particularly useful for shielding and grounding functions and are generally formed of materials of relatively high conductivity and corrosion resistance. However, the contact positions are often required to be placed around the critical components, and thus may be difficult to access.
A printed circuit assembly may directly incorporate conductive and/or corrosion resistant materials directly into its structure in order to form the contact positions. However, such integration results in high production and replacement costs.
The present invention is directed to a device comprising a printed circuit board including a plurality of electric components mounted thereto and a shielding element for one of shielding the electric components from electric signals outside the device and shielding electric components outside the device from electric signals within the device in combination with an elastomeric gasket forming a first electrically conductive path between the shielding element and a contacting surface of the gasket and a spacer element a first surface of which contacts the printed circuit board, a second surface of the spacer element contacting the contacting surface of the gasket, the spacer element defining a second electrically conductive path between the first and second surfaces thereof to couple the first and second electrically conductive paths to electrically couple the shielding element to the printed circuit board.
The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are provided with the same reference numerals. The present invention provides a system to electrically couple contact points on a printed circuit board (“PCB”) to a secondary structure.
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The interface 240 is made from one or more materials, at least one of which is conductive. For instance, the interface may be substantially composed of a non-conductive material, such as plastic, with selected portions of the surface coated with a highly conductive material, such as gold. Those skilled in the art will understand that the coated portions may be limited to those areas which are required to conduct electricity. Specifically, all or a part of a surface of the interface 240 which contacts the conductive elastomeric gasket 220 will be coated with conductive material as will all or part of the surface of the interface 240 which contacts the PCB 260. Furthermore, one or more paths of conductive material will join these areas of electrical contact between the interface 240 and the gasket 220 and between the interface 240 and the PCB 260. Alternatively, the interface 240 may be a mass formed of one or more conductive materials. In a further exemplary embodiment, the interface 240 may be formed of one or more conductive materials with a hollow core. As would be understood by those of skill in the art, the conductive material(s) used in any of these embodiments will preferably be selected based on cost and/or desired performance criteria. For example, lead/tin, copper, gold, silver, or any other conductive material may be used.
Before the solder 250 is applied to the PCB 260 to secure the interface 240, the PCB 260 may be coated. The coating may be applied to exposed metal portions of the PCB 260, and may be any of a variety of types. For example, the coating may be organic solder preservative (“OSP”), electroless nickel/immersion gold (“ENIG”), immersion tin, immersion silver, etc. In a conventional system, the coating may serve as the electrical coupling between the PCB and the elastomeric gasket, and thus the coating would have to be highly conductive. However, according to the present invention, an electrical connection between the PCB 260 and the elastomeric gasket 220 is provided by the interface 240. Thus, it is not necessary for the coating to provide the electrical coupling, and a lower cost coating with lower conductivity, such as OSP, may be used without being cleaned. Because the OSP does not require cleaning to enhance its conductivity, a manufacturing step is eliminated and manufacturing costs are decreased.
The elastomeric gasket 220 is preferably made of silicon rubber with a highly conductive silver fill dispersed throughout. However, any compliant material may be used to form the gasket 220. Further, any highly conductive material or assembly may be used in place of the silver fill.
The contact surface 230 includes a relative degree of contact resistance. Because the interface 240 is coated with corrosion resistant material, the degree of contact resistance will not degrade significantly over time. Integrity of the contact surface 230 is also enhanced as the interface 240 increases a surface area of the PCB 260 over which electrical contact is established.
The elastomeric gasket 220 may take a variety of shapes and forms. For instance, the elastomeric gasket 220 may cover an entire surface of the structure 210. Alternatively, the gasket 220 may be formed as one or more strips distributed along a surface of the structure 210. Further, the elastomeric gasket 220 may be formed in any of a variety of shapes. For example, the gasket 220 may be substantially rectangular, conical, etc. The interface 240 eliminates the need for the elastomeric gasket 220 to be designed to extend down to the PCB 260 and contorted and maneuvered around discrete and integrated electrical components.
The structure 210 may be used for a variety of applications. For example, the structure 210 may be used to shield components of the PCB 260 from electrical emissions of other components and/or to prevent the escape of electrical emissions produced by the components of the PCB 260 to surrounding areas. Alternatively, the structure 210 may serve as a ground for circuitry disposed on the PCB 260. The structure 210 may also serve as part of a signal path. Accordingly, the structure 210 is preferably formed of sheet metal or any other conductive material possessing suitable mechanical properties.
The interface of the present invention facilitates the installation of electrical shielding, grounding, and signal contacts on conventional PCBs. Because of the highly conductive and corrosion resistant nature of the interface, the longevity and efficiency of the electrical connection between the PCB and a secondary component are significantly increased. Further, the installation is simplified and reduced in cost.
The present invention has been described with reference to the above exemplary embodiments. One skilled in the art would understand that the present invention may also be successfully implemented if modified. Accordingly, various modifications and changes may be made to the embodiments without departing from the broadest spirit and scope of the present invention as set forth in the claims that follow. The specification and drawings, accordingly, should be regarded in an illustrative rather than restrictive sense.