EFFECTS OF PACKAGE ORIENTATION AND MIXED CONVECTION ON HEAT-TRANSFER FROM A PQFP

The thermal resistance of a surface-mount, plastic quad flat package ( PQFP) was measured over a range of heating powers, air velocities, and package orientations, The specific package was one developed by a Joi nt Electronic De,ice Engineering Council (JEDEC) committee for standar dized testing, The package was mounted in a low-speed wind tunnel whic h could be rotated in a vertical plane, thus changing the orientation of the package with respect to the gravity vector, Results define the limits of mixed convection for an horizontal package, and of orientati on effects for package/tunnel orientations from buoyancy-opposing to b uoyancy-assisting. For large air velocities greater than 2.5 m/s, for all tunnel orientations, the package thermal resistance shows a steep decrease, which is attributed to restarting of the surface boundary la yer on the package.