Yesterday we discussed water jet angle variation, but how do you know how this experimentation actually effects cleaning? A UV traceable flux may be just the ticket. The UV responsive material that is added to a flux will also remain after reflow in the residue. This is what lets you know how much flux residue is left after washing, or if the cleaning process was adequate. Simple steps include:
1) Assemble your flip chip with a UV traceable flux
2) After reflow, wash the residue with one set of cleaning parameters
3) Remove the flip chip and observe the bumps under an ultraviolet light.
4) Repeat these steps with different cleaning parameters and determine which works best for you.