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Lightweight Shielding for Circuit Board Electromagnetic Interference Control

IP.com Disclosure Number: IPCOM000039740D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Engelbrecht, JC: AUTHOR

Abstract

An arrangement is described in which electromagnetic interference (EMI) on a circuit board is controlled by shielding only the noisy components and by filtering the electrical penetrations of the shield. A combination of board-mounted shields and filters are used to control EMI that radiates from circuitry on a printed circuit board. The shields are lightweight, 0.01" copper shields soldered into a circuit board. One application is on a CRT-neck-mounted video amplifier that delivers to the CRT electron gun a 45 V swing at a 16.3 MHz pel rate. Another application is over the fast, noisy Schottky modules on a personal computer adapter card. The shields are bent up from flat, copper-sheet patterns into low-walled, 5-sided boxes. The open side of each box has solder pins spaced at 0.

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Lightweight Shielding for Circuit Board Electromagnetic Interference Control

An arrangement is described in which electromagnetic interference (EMI) on a circuit board is controlled by shielding only the noisy components and by filtering the electrical penetrations of the shield. A combination of board-mounted shields and filters are used to control EMI that radiates from circuitry on a printed circuit board. The shields are lightweight, 0.01" copper shields soldered into a circuit board. One application is on a CRT-neck-mounted video amplifier that delivers to the CRT electron gun a 45 V swing at a 16.3 MHz pel rate. Another application is over the fast, noisy Schottky modules on a personal computer adapter card. The shields are bent up from flat, copper-sheet patterns into low- walled, 5-sided boxes. The open side of each box has solder pins spaced at 0.6" intervals, and the pins are soldered into ground-plane holes on the circuit board. One shield is wave-soldered on the component side of the board, and the other shield is hand-soldered on the solder side of the board. This combination of shields completely surrounds the EMI-producing components and gives effective EMI reduction. The shields are complemented by filtering. On the video amplifier, control, CRT-biasing, and signal leads enter into the shielded area as etched traces on the board. These leads are potential escape routes for the EMI that is contained within the shields. To prevent EMI from getting out on these leads, the control and biasing signals are filtered with RC or LC filters at the walls of the shields. The signal leads are...