ULTRA-FLAT AND ALMOST NO PROFILE ED-COPPER FOILS FOR HIGH SPEED DIGITAL PCBS AND CHIP SCALE PACKAGING

摘要

Copper surface roughness has become a significant factor influencing conductor loss in high speed PCBs, particularly as they move above the 10 GHz range and for etching very narrow pitch in CSP applications. A new type of ED copper foil has been developed that achieves very smooth surfaces. Specific ultra-flat and arsenic free treatments with highest density and uniformity are being applied on such topographies. This significant increase of the active contact surface is providing secure bond strength to a large number of proprietary low and very low loss resin systems. The reduction of the foil's treatment profile has essential advantages since insertion loss is improved and therefore allowing new opportunities in the antenna and high speed arena. Advantages of ultrathin functional copper foils down to 1μm thickness for highest pitch definitions are described. Such new ultrathin functional foils have almost no profile roughness. Combined with a thin Primer Coating, they are designed for L/S < 15/15μm, as well as for embedding techniques of passive and active devices. The combination of both, flat functional foil's topography and a very thin 4μm Primer Coating layer ensures high adhesion and thermal reliability on filled, low CTE and high TG resins used in CSP applications. They allow new concepts for coreless build up and can be combined with CO_2 laser direct drilling for via formation in the thin functional copper layer.