Contamination happens long before the product enters the cleanroom; critical cleaning often happens long before the product enters the cleanroom. Critical cleaning may involve aqueous, solvent, or non-chemical cleaning agents. A cleanroom can minimize re-contamination, but the most sophisticated cleanroom or controlled environment may not correct a contaminated product.
Clearly defining the cleaning steps is important, but they have to be the correct steps, at the correct point in the build process. Identify, then qualify/validate and monitor the critical cleaning steps; you will achieve a quality product.
From: Tipping Point” Cleaning