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  Printed circuit board with improved via designUSPTO Application #: 20080026602Title: Printed circuit board with improved via design Abstract: A circuit board includes an electrically conductive sheet having an insulative coating surrounding the conductive sheet, with a surface of the insulative coating around an edge of the conductive sheet having an arcuate or rounded shape. At least one electrical conductor is conformally deposited on at least the rounded insulative coating around the edge of the conductive sheet and defined via photolithographic and metallization techniques. Each electrical conductor on the insulative coating thereon around the edge of the conductive sheet conforms to the arcuate or rounded shape of the insulative coating and, therefore, has an arcuate or rounded shape. (end of abstract) Agent: Ppg Industries Inc Intellectual Property Dept - Pittsburgh, PA, US Inventors: Alan E. Wang, Kevin C. Olson USPTO Applicaton #: 20080026602 - Class: 439059000 (USPTO) Related Patent Categories: Electrical Connectors, Preformed Panel Circuit Arrangement, E.g., Pcb, Icm, Dip, Chip, Wafer, Etc., With Mating Connector Which Receives Panel Circuit Edge The Patent Description & Claims data below is from USPTO Patent Application 20080026602. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATION [0001] This application is a divisional application of U.S. patent application Ser. No. 11/442,016, filed May 26, 2006 which is a continuation-in-part of U.S. patent application Ser. No. 10/987,480, filed Nov. 11, 2004, which is incorporated herein by reference, which is a continuation-in-part of U.S. patent application Ser. No. 10/227,768, filed Aug. 26, 2002, now U.S. Pat. No. 6,844,504, which is incorporated herein by reference, which is a continuation-in-part of U.S. patent application Ser. No. 10/184,387, filed Jun. 27, 2002, now U.S. Pat. No. 6,951,707, which is incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] Presently, printed circuit boards are fabricated as part of a larger panel. Each printed circuit board can be configured in any shape, although most printed circuit boards in common use are made in rectangular shapes of standard sizes. When fabrication of a printed circuit board is complete, it is cut and separated from the larger panel, mostly by way of a machine cutting or routing process in which a channel is cut around the printed circuit board. In certain designs, the channel around the printed circuit board does not completely encircle the perimeter of the printed circuit board. Rather, tabs are left at several places around the perimeter of the printed circuit board to attach it to the larger panel until the board is singulated from the larger panel by breaking the tabs. Typically, metal planes in the printed circuit board do not extend to its edge where they would be cut by the routing process. In this way, no conductive metal is left exposed on the edges of the printed circuit board. [0003] The existing methods of cutting printed circuit boards from larger panels are unsatisfactory for high density boards because the limited dimensional stability of the printed circuit boards does not allow registration of one high density pattern to the next on the larger panel. Cut lines made around the periphery of the printed circuit board further weaken the panel material, exasperating misregistration of one pattern to the next. [0004] Electronic systems assembled onto conventional printed circuit boards rely upon thermal conduction from integrated circuits dissipating heat to the printed circuit board to remove some of the heat from the integrated circuits. For intermediate ranges of heat, up to about 2 watts per chip, conduction to the printed circuit board is sufficient to cool the integrated circuits without the need for bulky and expensive heat sinks. In high performance systems, however, as the density of the system and the percentage of the substrate covered by the integrated circuits increases, the thermal path to the printed circuit board is less efficient. At a point when the density of the system increases sufficiently, the printed circuit board is not effective as a heat sink for the integrated circuits. However, the need for effective thermal conduction from the integrated circuits to the substrate and therefrom to the ambient becomes more important as system density increases. Because of the evolution toward higher system density and larger integrated circuit coverage, means are needed for cooling the substrate in order to maintain the integrated circuits on the substrate at a safe operating temperature. [0005] In addition to thermal conduction, high performance systems increasingly require low impedance power and ground voltage supplies to run the integrated circuits at high clock speeds. Typically, the AC impedances of power and ground supplies are lowered by the use of low impedance bypass capacitors connected to the power and ground planes. On conventional printed circuit boards, capacitors are connected to power and ground planes through vias which extend through some thickness of the board, increasing the impedance of this contact and degrading performance of the system. As switching speeds increase, the problem of making low impedance connections between bypass capacitors and the power and ground planes becomes more important. [0006] It would, therefore, be desirable to overcome the above problems and others by providing a printed circuit board having one or more printed circuit board layers each of which has a conductive layer which extends to the edge thereof and which is substantially, but not completely, covered by an insulating material. The edge of the conductive layer not covered by the insulating material can be on the perimeter (or edge) of the printed circuit board layer or on the edge of a tab which is utilized to couple the board to a disposable part of a larger panel that the board is formed from during fabrication. The exposed edge of the conductive layer becomes exposed upon singulating the printed circuit board layer from each tab connected thereto or upon breaking the tab during singulation of the printed circuit board from the disposable part of the larger panel. In one embodiment, the broken end of one or more tabs terminate in a recess in the perimeter of the printed circuit board. In a second embodiment, the broken end of one or more tabs extend outward from the perimeter of the printed circuit board. [0007] The conductive plane can be formed from metal that can serve the dual purpose of conducting heat away from electrical components disposed on one or both surfaces of the printed circuit board or printed circuit board layer and for providing power or ground to the electrical components. The tab which extends outward from the edge of the second embodiment printed circuit board can be coupled to a mechanical fixture and/or an electrical fixture to provide a path for the flow of heat from the printed circuit board to externally coupled mechanical fixtures and/or to provide electrical power to the electrically conducting layer of the printed circuit board. [0008] Each printed circuit board layer can include one or more landless through-holes or vias extending all or part of the way therethrough. Each landless through-hole or via is desirably configured to facilitate the deposition of conductive material therein, the patterning and etching of said conductive material and the formation of the through-hole or via without a conductive land on each exposed end thereof. SUMMARY OF THE INVENTION [0009] The invention is a circuit board that includes an electrically conductive sheet coated with an insulative coating that forms an insulating top layer covering one surface of the conductive sheet, an insulating bottom layer covering another surface of the conductive sheet and an insulating edge layer covering an edge of the conductive sheet, and a first electrical conductor on one of the top and bottom layers and on at least part of the insulating edge layer. The insulating edge layer and the portion of the first electrical conductor thereon each have an arcuate or rounded outline or shape. The portion of the first electrical conductor on the insulating edge layer is electrically isolated from the edge of the conductive sheet by the insulating edge layer. [0010] The first electrical conductor can also be on the other layer of the circuit board. The portions of the first electrical conductor on the top and bottom layers of the circuit board are electrically connected by the portion of the first electrical conductor on the insulating edge layer. [0011] The combination of the portion of the first electrical conductor and the insulating edge layer it overlays can be in a notch defined in the edge of the electrically conductive sheet. [0012] The circuit board can include a second electrical conductor on the top and bottom layers of the circuit board that are electrically connected by a portion of the second electrical conductor on the insulating edge layer which can be in the notch in electrical isolation from the portion of the first electrical conductor in the notch. [0013] The insulative coating can be initially electrodeposited and thereafter heated until it flows thereby forming the insulating edge layer having the arcuate or rounded shape. [0014] The circuit board can further include a copper layer disposed between the electrically conductive sheet and the insulative coating. [0015] The invention is also a method of forming a circuit board comprising: (a) providing an electrically conductive sheet having top and bottom surfaces and an edge desirably perpendicular thereto; (b) conformally coating the top and bottom surfaces and the edge of the electrically conductive sheet with an insulating material; (c) exposing the conformally coated insulating material to an elevated temperature such that the insulating material at least partially melts and flows around the edge of the electrically conductive sheet whereupon, upon removal of the elevated temperature, the insulating material around the edge of the electrically conductive sheet has an arcuate or rounded shape or outline; and (d) following step (c), forming a first conductor on the insulating material with at least a portion of the first conductor on the insulating material around the edge of the electrically conductive sheet, whereupon said portion of the first conductor has an arcuate or rounded shape or outline. [0016] The first conductor can also be formed on the insulating material overlaying at least one of the top and bottom surfaces of the electrically conductive sheet. [0017] The portion of the first conductor and the insulating material it overlays can be in a notch formed in a side of the electrically conductive sheet. [0018] Step (d) can include forming a second conductor on the insulating material with at least a portion of the second conductor overlaying the insulating material in the notch, whereupon the portion of the second conductor has an arcuate or rounded shape or outline. The portion of the second conductor in the notch can be electrically isolated from said portion of the first conductor in the notch. [0019] Step (b) can include electrodepositing the insulating material. [0020] The portion of the first conductor electrically connects other portions of the first conductor on the insulating material overlaying the top and bottom surfaces of the electrically conductive sheet. [0021] The invention is also a circuit board that comprises an electrically conductive sheet including an insulating edge layer covering an edge of the conductive sheet, and an electrical conductor on the insulating edge layer. The insulating edge layer and the electrical conductor thereon have an arcuate or rounded shape or outline. Continue reading... Full patent description for Printed circuit board with improved via design Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Printed circuit board with improved via design patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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