October 16, 2017
De-ionized (DI) water is plain water that has been purified to remove contaminants such as metals and salts (ions). When DI water is used in ultrasonic cleaning systems it can improve cleaning performance, depending on the parts to be cleaned and the nature of the contaminants to be removed. Such increased cleaning performance is especially important for delicate parts that can’t tolerate detergents. For these cleaning applications, using slightly heated DI water makes the ultrasonic cleaning process more effective than when using plain water.
When to Use DI Water
While ultrasonic cleaning systems will work with plain water, adding a mild detergent can often speed up the cleaning action. Delicate parts such as semiconductor wafers, printed circuit boards and some medical devices might be damaged by using detergents, so in these applications cleaning with DI water is recommended. The DI water helps the ultrasonic bubbles clean rapidly, even in the absence of detergents.
For stubborn grease and oil contamination, DI water is not effective in speeding up the cleaning process. Instead, a mild detergent or solvent specific to the particular contaminant is needed. Sometimes using a solvent that attacks the dirt but doesn’t harm the part to be cleaned can be found. For other types of cleaning, the use of DI water throughout the cleaning process is beneficial.
When an ultrasonic cleaning system has removed dirt from the parts to be cleaned, the cleaning solution is drained away but the parts often still have to be rinsed to finish the cleaning process. Normal water has dissolved minerals and other impurities so that rinsing can leave a deposit. After the parts are dry, they may have spots or films left over from the evaporated water. If this is not acceptable, DI water can be used for rinsing. Since it contains no impurities, dried parts and components will be completely clean and free of spots.
How DI Water Helps Clean
DI water helps ultrasonic systems clean parts and components in two ways. DI water without any additives has no impurities and therefore acts like a sponge. Once the microscopic bubbles generated by the ultrasonic cleaning system have dislodged tiny particles, the DI water quickly absorbs any dissolved substances. Normal water already contains impurities and therefore doesn’t absorb contaminants to the same extent.
A second way in which DI water helps ultrasonic systems clean quickly applies when mild detergents are added to the system. When normal water is used, the detergent first absorbs the impurities in the water before going on to help clean away dirt. With DI water, there are no impurities to reduce the effectiveness of the detergent and all of the cleaning power goes to absorb contaminants removed from the parts to be cleaned.
As a result, the use of DI water can improve the effectiveness of ultrasonic cleaning systems in general. It speeds up cleaning for applications that can’t use detergents and helps systems clean when detergents are required. In both cases, rinsing with DI water will remove any remaining impurities.
How Kaijo Can Help
Kaijo has over 65 years of experience with ultrasonic technology and can help with specific customer applications. The company will provide free consultation and advice on using ultrasonic cleaning systems and can help determine whether the use of DI water is effective in each customer’s application. As well as giving expert advice, Kaijo can follow up with concrete proposals drawn from its extensive line of ultrasonic cleaning systems and components. In addition to guidance on DI water, customers can get advice on which systems will work best for them, what ultrasonic frequencies to use for their cleaning applications and how to best configure their systems.