Abstract
No cleaning in fine pitch printed wiring boards (PWBs) after mounting the electronic devices, possibly deteriorates insulation reliability by ion migration, because the activator of flux remains on the surface of PWBs. The relationship between the solubility of copper ion and the insulation life of PWBs was examined. The insulation life depends on the kind and the concentration of the activator in the flux. It was proved that as the value of the solubility of copper ion increases, the insulation life of PWBs shortens further. The solubility of copper ion by the activator indicates that the flux could be use or not.
