APPARATUS AND METHOD FOR DETERMINING SURFACE IONIC CONTAMINATION LEVELS OF ELECTRONIC ASSEMBLIES SUCH AS PRINTED CIRCUIT ASSEMBLIES

摘要

A method and apparatus for determining the surface ionic contamination level on an electronic assembly utilizes deionized, heated solvent mixtures consisting essentially of water and a water miscible solvent which, when heated well above room temperature, has a vapor pressure substantially less than that of water at the same temperature. A solvent mixture is pumped from a solvent reservoir (12) by the centrifugal pump (26), heated in a heater (30) and sprayed through conduits (18), (29), (24) and (20) on said electronic assembly (14). The water miscible solvent acts quickly on the electronic assembly (14) to dissolve and to remove the non-ionic residues, thereby exposing the ionic contaminants such that they may be dissolved and removed from said assembly (14). The aqueous solution (12) flows from the enclosure (10) to a dynamic contamination measurement apparatus (34) for the determination of the ionic contamination level in the assembly (14), then returns to the solvent reservoir (12). A change in an electrical property of the mixture, such as conductivity or resistivity, due to the presence of the dissolved ionic contaminants is measured to obtain an indication of the ionic contamination level originally present in said electronic assembly (14).