Many experts in the electronics assembly world will cringe when they hear about a manufacturer hand-washing their boards with soap and (gasp!) water. The first point to bring up here is that boards should never need to be washed. This is a clear indication that you are somehow bringing dirt into the process, whether through alcohol, brushes, or something else the boards are coming in contact with.
Know Your Water Grade
There are three grades of water that you can use to clean the boards; tap water, distilled water, and deionized (DI) water. For this type of precision cleaning you should never use tap or distilled water, which themselves contain contaminants that can affect your boards. If you must clean your boards with water, the only choice is deionized water.
Deionized water is measured by the water’s resistance to electric current. 50kOHM is standard and can be purchased easily and at a relatively low cost. 1 megaohm is really the minimum required for this type of precision cleaning. In high-precision manufacturing, such as semiconductors, 20 megaohms is the industry standard. Obviously cost and availability are both big factors. As you increase the pureness of your water, it also becomes more difficult to handle.
One option is a sealed, closed-loop system which purifies the water, performs the cleaning task, and then recycles the water. However, this type of system is costly and can result in a slow through-put. Given these restrictions when using water in the cleaning process, more and more manufacturers are switching to cleaning with solvents. The ideal solvent is strong enough to remove the contamination, while still mild enough to not damage any components on the board.
GoKimco has a complete line of solvents, ideal for finding this healthy balance for cleaning your boards.