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Radio frequency identification (RFID) tags with anisotropically conductive joints (ACAs) are used in different applications where the environmental conditions may impair their reliability. Thus the effects of different environmental stresses on reliability need to be investigated. The effects of high temperature and humidity may change the performance of the tags. More- over, the effects of constantly varying temperature and humidity conditions may be even more harmful. In this study, the effects of changing humidity conditions on the performance of a passive ultra high frequency (UHF) RFID tag with ACA joints were studied. The tags were tested in a humidity cycling test where humidity varied from 85%RH to 10% RH, and temperature from 85°C to 25°C. Tags with four different sets of bonding parameters were tested. Significant differences in the reliability between the tags with different bonding parameters were observed. The results were also compared with results from a corresponding constant humidity test where the humidity was 85%RH, and the temperature 85°C. The tags had different failure times, modes, and mechanisms in these two tests. Furthermore, the effects of bonding parameters on the reliability were different in these tests. According to this study, it is important to investigate the effects of changing humidity, when the reliability in different environments is investigated, but the constant humidity test cannot be replaced with the faster humidity cycling test.