Tool and tips for good copper distribution Evenly distributed copper across layers, and choosing symmetrical buildups (stackups), are two important ways for avoiding PCB manufacturing quality issues, and problems during component assembly. We explain below why that is.
Copper thickness and planarity (within tolerances) are two important PCB quality criteria. When copper is unevenly distributed or if the layers of a multilayer PCB are not symmetrical in number or thickness above and below the horizontal centre of the PCB, the imbalance may cause mechanical instability.
This imbalance can result in bowing (curvature) and/or twisting (distortion) of the PCB because the individual components, such as the copper and glass-fibre reinforced resin in the case of FR4 material, expand and contract at different rates when heated and cooled. Heating and cooling of the PCB occurs during the pressing, etching, electroplating processes, and the application of the soldermask, as well as during the soldering of components.