Abstract
Investigation of Ionic Migration (IM) in printed wiring board with narrow spacing between Cu conductors (<50μm) has been described, and an effect of epoxy resin coating on IM also has been investigated. An endurance test was carried out in a chamber controlled at 85°C, 85%RH and 20V. As the result, the insulating resistance remained 107Ω over the test period of 1000hr, however, deposits between the conductors were observed on the surface of all specimens by an optical microscope. From the results of observation of the deposit and element analysis by EPMA, it is clear that epoxy coating is not effective and the growth of deposits accelerates under narrow spacing condition (20μm). Furthermore, we have to be careful to interface treatment between conductors and substrates because Ni, which is one of elements composed of bonding layer, was detected in the deposits. It is revealed that the obtained results are very useful for the insulation reliability of the fine and high-density wiring.
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