The climate resistance of electronic PCBs is normally characterised by measuring the specific surface resistance (SIR – surface insulation resistance). Evaluating these test results does allow the conclusion that an electronic circuit established with the selected materials and processes does not have sufficient climate stability but the results do not allow for conclusions to be drawn about the reason why the SIR value has fallen below the acceptance criterion.
This article discusses how and to what extent measuring the ionic contamination using ion chromatography enables the SIR values obtained to be interpreted. As the surface resistance is influenced significantly by the hygroscopy of ionic substances and contamination, knowledge of the composition of the ion balance with regard to the hygroscopy and electrophoretic creeping ability enables a conclusion regarding the cause of the resistance reduction to be drawn.
Dr. Helmut Schweigart
Head of Reliability & Surfaces, ZESTRON EUROPE
Dr. Helmut Schweigart obtained his doctorate for research into the reliability of electronic sub-assemblies, and he has been employed at ZESTRON Europe since the early days of the company. He is now Head of Reliability & Surfaces Team. He is also a member of the Board of Management at GfKORR (Gesellschaft für Korrosionsschutz – a company specialising in corrosion inhibitors) as well as an active member of GUS (Gesellschaft für Umweltsimulation – an environmental simulation company) and of the IPC. He has already published numerous technical articles.
Dr. Markus Meier
Senior Technology Analyst, ZESTRON EUROPE
After his study of chemistry at the Technical University Munich, Markus Meier worked among others on the ageing of cement and earned a PhD on the topic crystallization of cement-hydrate-phases under microgravity conditions. He is experienced in the areas interfacial chemistry and surface analytics. He is part of the Reliability & Surfaces Team in which he is responsible for the coordination of research projects as well as the organization of technology coachings. He has already published numerous technical articles.