Effect of Water Absorption Temperature on Space Charge Profiles in Paper/phenol-resin Composites for Printed Circuit Boards

Abstract

More and more electronics are intended for use in adverse environments at high temperatures with high humidity. The spatial distributions of internal charge carriers, mainly due to ionic impurities that appear in hot and humid environments, are considered to affect the reliability of bulk insulation. Therefore, the authors examined space charge behavior inside paper/phenol‐resin composites for printed circuit boards under DC voltages, focusing on the effect of the water absorption temperature. Both the sample weight and thickness were increased monotonically by immersion in water with an increase in the water temperature from 24 to 85 , indicating that the water absorption by the sample was temperature dependent. In the early periods of water absorption (up to 10 hours), the electric field decreased near the two electrodes and increased in the other regions. Furthermore, heterocharge formation was observed near the cathode as the water absorption progressed, becoming more significant at higher water temperatures. Ion chromatography analyses detected numerous ions such as Na+, $NH_{4}^{+}$ and Cl‐ from the water, in which the sample had been immersed for 100 hours at various temperatures. It is highly possible that these ions are responsible for the heterocharge formation. 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 173(2): 1–7, 2010; Published online in Wiley InterScience (http://www.interscience.wiley.com). DOI 10.1002/eej.20992

Generation mechanism of electrochemical migration in printed wiring board insulation

“…On the other hand, to achieve further integration of circuits, a build‐up PWB and a PWB with embedded passive electronic parts and semiconductor modules have been developed and they are at the beginning stage of practical use [5–7]. Since these PWBs have complicated multilayered wiring of conductors, their insulating properties are important not only along the surface direction but also along the thickness direction [8–12]. On this point, a reliable nondestructive method of detecting growth of migration in the thickness direction is required.…”