Can I apply a "Water-Clean" process to BGA packages?
BGA-cleaning has proven to be well within the capabilities of most aqueous or semi-aqueous systems. Generally, no special steps must be taken to insure cleaning beyond those typically practiced in the SMT factory. If specific problems occur, surfactants can be used to induce better water penetration and flow.
The only factor unique to BGA cleaning is insuring dryness. Because of the many close spaces, water tends to become trapped beneath the package. In some instances, a factory-standard drying profile does not completely evaporate all the water. In this case, the water can react with the solder balls as it dries, resulting in precipitate formation. These precipitates can act as humidity bridges for short formation between biased points.
To determine if a drying profile is adequate, simply blow compressed air under one edge of the package upon exiting the cleaner. A spray of water indicates that more effective drying is required. If this is necessary, increase the drying temperature or slow down the passage through the drying zone (or combine these techniques). Once a satisfactory setup is achieved, it is usually not necessary to monitor this on more than an occasional basis.