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==Printed circuit board failures==
[[File:PCB corrosion.jpg|thumb|right|Severe PCB corrosion from a leaky PCB mounted Ni-Cd battery]]
[[Printed circuit board]]s (PCBs) are vulnerable to environmental influences; for example, the traces are corrosion-prone and may be improperly etched leaving partial shorts, while the [[via (electronics)|vias]] may be insufficiently plated through or filled with solder. The traces may crack under mechanical loads, often resulting in unreliable PCB operation. Residues of solder flux may facilitate corrosion; those of other materials on PCBs can cause electrical leaks. Polar covalent compounds can attract moisture like [[antistatic agent]]s, forming a thin layer of conductive moisture between the traces; ionic compounds like [[chloride]]s tend to facilitate corrosion. Alkali metal ions may migrate through plastic packaging and influence the functioning of semiconductors. [[Chlorinated hydrocarbon]] residues may [[hydrolysis|hydrolyze]] and release corrosive chlorides; these are problems that occur after years. Polar molecules may dissipate high-frequency energy, causing parasitic [[dielectric loss]]es.
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