Early SMT all use water washing process, now only part of the medical, military, aerospace and other high reliability requirements and high cleanliness requirements of the product use water washing process. The solder joints under the water cleaning process have higher solder creep because there is no flux residue, so the products have high reliability and long service life!
The most famous water washing machine is the United States of America's ELECTROVERT, under the SPEEDLINE sub-brand. Now there are a large number of domestic alternative products.