Ask the Experts
September 9, 2010 - Updated
September 7, 2010 - Originally Posted

Abrupt Decrease in DI Water Resistivity

All of a sudden we noticed an abrupt decrease in the resistivity of our DI water cleaning system. There we no unusual changes in our process, or the products we routinely clean. Can you point us in a direction to investigate?

E. V.

Expert Panel Responses

If a solvent or water based cleaning agent is currently used in the wash process, those could be the reason. If there is an equipment failure, then there could be the cross contamination of the dragged out or evaporated chemistry with the rinse water that is normally going back to the treatment system. If only pure water is being used in the process, too much flux accumulation can also cross contaminate the rinse water and block the DI-water beds. We would need more information on the machine set up, cleaning media, and the type of flux used in this cleaning process. Please contact Zestron, so that our technical team could assist you.

Umut Tosun
Application Technology Manager
Zestron America
Mr. Tosun has published numerous technical articles. As an active member of the SMTA and IPC organizations, Mr. Tosun has presented a variety of papers and studies on topics such as "Lead-Free Cleaning" and "Climatic Reliability".

An abrupt change as you described will be hard to nail down without more specifics on your wash process. The two major points to help me assist you are;
  • Do you run your washer in a total closed loop process using only DI water?
  • Is there chemistry in the wash and you only re-circulate or polish the Rinse water?
You state there is no change in your process or products currently being cleaned so now I believe the focus needs to be upstream of the wash process. An issue that could affect the life of the DI beds is your incoming water supply. Has there been any a facility or water main construction in your neighborhood? Moving or purging water lines in addition to an alternate source of water supplied by your POTW (common during the summer months) can adversely affect the columns life with an in put of solids in the tap water supply. However by far the most common issue I have seen in my experience is there is no scheduled replacement plan in place with the DI equipment supplier. The DI columns are put in place by someone outside your department of responsibility and when asked "When was the last time these were replaced?" You may be surprised with the answer you hear. If you wish to consult more on this please do not hesitate to contact me.

Charlie Pitarys
Technical Expert Sales Support
Kyzen Corporation
Charlie Pitarys has over thirty years of industry experience and has been with KYZEN for twenty-one years. Charlie is a former Marine and a retired Sargent First Class in the Army Reserves. His previous employers include Hollis and Electrovert. Charlie continues to use his expertise on cleaning processes and machine mechanics to help KYZEN customers and partners improve their cleaning operations.

Without more info this is a hard one. I would immediately suspect either equipment malfunction (detectors) or more than likely, some trace contamination getting into the water supply. Any contact with aluminum, copper, or iron surfaces? I would also run an ion analysis of the water to try and pinpoint specific contributors to this problem.

Jim Williams
Polyonics, Inc.
Jim Willimas is a PhD Chemist in Polymers and Materials Science. He specialize in printing, cleaning, inks, and coatings used in electronics manufacturng operations. Williams has more than 30 years experience.
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