Abstract
The soldering flux residue with the cracked surface adsorbs moisture on the surface of its own, and this moisture adsorption causes following problems: insulation deterioration by ionic migration, dielectric breakdown, and so forth. As a general rule, for the insulator with the cracked surface, to quantify the surface hygroscopicity (the property of the moisture adsorption on the surface) is the decisive and effective factor in evaluating the electrical reliability of that. However, few reports regarding this issue have been published; therefore we have tackled it. In consequence, measuring the dielectric loss tangent of the insulator in damp offers a quantitative evaluation method for characterizing the surface hygroscopicity associated with the insulation reliability. And we applied this measurement to the flux residue with the cracked surface. As a result, we obtained a valuable piece of information to forecast the occurrence of ionic migration for the flux residue.
