Fiber Optic Module Grounding

Application

Ever-increasing bandwidth demand has driven systems containing fiber-optic modules to operate at increasingly higher frequencies. Fiber-optic modules operating at these high frequencies generate EMI and heat, both of which must be controlled.

Summary

One North American systems OEM solved the problems of excess heat and EMI by using GORE-SHIELD™ SMT RF grounding pads. The initial design relied on I/O grounding pins to ground the fiber-optic module to the PCB. A conductive fabric/foam composite was also tried, but proved too difficult to install. The OEM then added GORE-SHIELD SMT RF grounding pads to the PCB. GORE-SHIELD SMT RF grounding pads are thermally conductive, and so this manufacturer also saw an opportunity to improve the heat dissipation from the fiber-optic module through the circuit board.

Results

When the fiber-optic module was installed to the board, an EMI seal was formed around the perimeter of the module case. This design change reduced emissions to acceptable levels. The manufacturer also reduced production costs because the GORE-SHIELD SMT RF grounding pads could be installed on the PCB using existing high-speed, automated production equipment. Also, by adding a few additional SMT pads to the PCB near the center of the module case, the OEM was able to eliminate a separate thermal pad from the assembly without sacrificing thermal performance.