Copper Wrap Plate as specified in IPC 6012B table 3-2, is a requirement developed to enhance reliability for PCB's designed with via structures that require planarization and surface capping. PCB's built without wrap plating are more prone to failures associated with separation between the interconnection of the barrel copper to the surface copper. The improvement in reliability is a function of the copper wrap thickness, which supports the difference in IPC requirements for Class II and Class III programs. The general rule is "the thicker the wrap plating the better the reliability." The increase in copper thickness, associated with wrap plating, however competes with the ability for PCB fabricators to manufacture products with high density and fine features. The general rule for manufacturing fine features is "the thinner the copper the better the manufacturability."The technology developed by DDI Corp. called FLAT-WRAP? offers a copper wrap solution that does not require buildup of copper on the external surface of a filled plated hole. This allows the improvement in reliability without sacrificing the ability to manufacture designs with high density and/or fine features. This technology also facilitates, in process nondestructive copper thickness measurements and ensures consistency of copper wrap thickness across the entire board surface. In this technology, the external surface copper thickness of filled plated holes will control the copper wrap thickness. In Printed Circuit Board designs requiring multiple copper wraps, the benefits of this technology are even more evident.This article examines the current process problems with copper wrap plate and discusses the benefits provided by the new technology with respect to manufacturing and reliability.
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