IEC 62396-2:2012 aims to provide guidance related to the testing of microelectronic devices for purposes of measuring their susceptibility to single event effects (SEE) induced by atmospheric neutrons. Since the testing can be performed in a number of different ways, using different kinds of radiation sources, it also shows how the test data can be used to estimate the SEE rate of devices and boards due to atmospheric neutrons at aircraft altitudes. Although developed for the avionics industry, this process may be applied by other industrial sectors. This first edition includes the following significant technical changes with respect to the technical specification IEC/TS 62396-2: - additional information on heavy ion data, neutron and proton data and thermal neutron data; - updates with regard to neutron sources: additional radiation simulators; - addition of the Anita spallation neutron source; - additional information on whole system and equipment testing; - comparison between accelerator based neutron sources.