Forced convective cooling of electro-optical components maintained at different temperatures on a vertically oriented printed circuit board

Forced convective heat rejection from electro-optical components maintained at different maximum operating temperatures, 60/spl deg/C and 100/spl deg/C above ambient (25/spl deg/C), on the same vertically orientated single circuit board (either FR4 or copper clad FR4) was experimentally studied. Reynolds numbers ranged from 0-20 000 in which forced ambient air was passed in the horizontal direction parallel to the plane of the board in a wind tunnel. The effect of component proximity and orientation on maximum power dissipation was explored. Observed thermal behavior patterns included an increase in power dissipation with Reynolds number, an increase in power dissipation with component spacing, and in increase in power dissipation with circuit board thermal conductivity. A significant influence of component arrangement (on the same horizontal plane versus on the same vertical plane) and relative location of the hotter component on the power dissipated was also observed and was influenced by board conduction, thermal wake interactions and/or wake shedding. Results provide placement criteria needed for designers to optimally place optical and electrical components in close proximity to each other while still achieving maximum power dissipation within given thermal management constraints.