Quantification of cleanliness beneath surface mounted devices positions on printed wiring and assembled with aggressive flux and total immersion cleaning: SOTs, passive chip discrete resistors and capacitors.

This memorandum reports on the results of an investigative program that addressed cleanliness of printed wiring surfaces beneath surface mounted passive chip discretes and SOTs. The surface mounted devices were wave solder assembled. Two printed wiring assemblies were examined containing high solder joint count (35-47 solder joints/square inch). The objective of this study was to determine the cleanliness attainable and the cleaning efficiency employing a number of assembly processes. The processes examined were: Water soluble flux/total immersion cleaning (water) - Synthetic activated flux/total immersion cleaning (Freon TMS) - Rosin flux/total immersion cleaning (Freon TMS) - Rosin flux/total immersion cleaning (water-detergent) - Rosin flux/underbrush solvent cleaning (1,1,1 Trichloroethane).