Circuit boards are manufactured by forming a substrate with a dielectric surface, laminating a metal foil and a peelable film to the substrate, and forming holes in the substrate through the peelable film and foil. A filler material with an organic base may be filled with electroconductive particles or dielectric thermoconductive particles. The filler material is deposited onto a sacrificial carrier and the filler material is heated to at least partially cure it. The filler material is laminated onto the peelable film with sufficient heat and pressure to force the filler material to fill the holes. For thermoconductive filler the holes are filled sufficient for electrical connection through the holes. The peelable layer, sacrificial carrier and filler material remaining therebetween are peeled off the copper foil. The filler material is abraded to the level of the foil and is then copper plated. The copper is patterned to form a wiring layer. A permanent dielectric photoresist layer is formed over the wiring layer and via holes are formed through the photoimagable dielectric over pads and conductors of the wiring layer. Holes are formed through the substrate and the photoimagable dielectric, walls of the via holes, and walls of the through holes are copper plated. The copper plating on the photoimagable dielectric is patterned to form an exterior wiring layer which is covered by solder resist with windows over lands around the through holes and surface mount connection pads of the exterior wiring layer to form a high density circuitized substrate. Surface mount components and/or pin in hole components are attached to the circuitized substrate with solder joints between terminals of the components and the lands and/or connection pads to form a high density circuit board assembly. One or more of the circuit board assemblies are mounted in an enclosure with a power supply, CPU, RAM, and I/O means to form an improved information handling system with increased performance due to shorter signal flight times due to the high component density.