Second Round Robin Evaluation of iNEMI Creep Corrosion Qualification Test
Authors: Prabjit Singh, Larry Palmer, Haley Fu, Dem Lee, Jeffrey Lee, Karlos Guo, Jane Li, Simon Lee, Geoffrey Tong and Chen Xu Company: IBM Corporation, iNEMI, iST-Integrated Service Technology, Inc., Lenovo (Beijing) Limited Corporation, The Dow Chemical Company and Nokia Date Published: 10/14/2018
Abstract: Creep corrosion on printed circuit boards (PCBs) is the corrosion of copper metallization and the creeping of the copper corrosion products across the PCB surfaces to the extent that they may electrically short circuit neighboring features on the PCBs. The paper will report the results of the second-round robin evaluation of the iNEMI creep corrosion qualification test and compare them to the first round robin test and to the recent mixed-flowing gas test results on the same iNEMI test PCBs. The modifications to and the differences in the 1st and the 2nd round robin test will be presented and discussed. The 2nd round robin test consisted of three 5-day test runs: the first 5 days at 31% relative humidity provided by MgCl2 saturated salt solution; the 2nd 5 days at 59% relative humidity provided by NaNO2 saturated salt solution; and the 3rd 5 days at 81% relative humidity provided by KCl saturated salt solution. The paper will show the round robin test results from three companies on immersion silver (ImAg), gold on electroless nickel (ENIG) and organic solderability preservative (OSP) finished PCBs soldered using organic acid (OR) and rosin (RO) fluxes. In the 1st round robin test, the ENIG finished PCBs suffered the most creep corrosion whereas in the 2nd round robin test, the ImAg finished PCBs suffered the most creep corrosion. As expected, the OSP finished PCBs suffered very little creep corrosion. The paper will also list the copper and silver corrosion rates experienced during the test runs and discuss means of better control of these corrosion rates.