The 4-14 IPC Standards Committee recently created a revision to the IPC4552 specification for Electroless Nickel/Immersion Gold (ENIG) finished Printed Circuit Boards (PCB). Revision A brings a more comprehensive evaluation of metal layer thicknesses measurement, composition and introduces, for the first time, a quality aspect for nickel corrosion which has been historically connected to a defect called black line nickel or black pad. The introduction of these revisions will ensure a higher level of quality for conforming ENIG deposits but it will also present some challenges in achieving and consistently delivering the required level of quality from PCB fabrication. IPC4552 Revision A requires that the PCB fabricator demonstrate capability in measuring and maintaining electroless nickel thickness and composition. The reduced minimum gold thickness and newly introduced maximum gold thickness specifications challenge not only measurement systems but also process control to comply with statistical restrictions on conforming ENIG product. The PCB Fabricator will also have new responsibility to establish control of the electroless nickel corrosion levels within given acceptability guidelines.
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