In nearly every circumstance, hot water (120-150F) will be better than room temperature water (70-80F) in terms of removing residues from soldering processes. While the surface tension concern that you mention is one aspect in this equation, the fact that solubility of most organic materials is better in hotter water is another strong case for going with hotter water.

The greater solubility of organic materials in hotter water generally means that you will have better luck removing residues in hot water than room temperature water.

Brian Smith General Manager - Electronic Assembly Americas, DEK International Mr. Smith has been supporting customers in the electronics assembly industry since 1994. His expertise is focused on solder paste printing and reducing soldering defects. He holds a BS in Chemical Engineering and an MBA in Marketing. He has authored several papers in trade magazines and at industry conferences. He is an SMTA Certified Process Engineer.

The answer is "It depends"...

Hot water will dissolve residues more quickly than cold water. In a time-critical process step, hot water will be more efficient from a through-put standpoint.

Also, materials will typically be more soluble in hot water than in cold. So, cleaner and faster with hot water, in general..And, yes, hot water will have a lower surface tension.

Jim Williams Chairman, 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.

I would strongly recommend heated DI water as some wetting agents used in fluxes will Gel if hit with cold water instead of heated. Also heating the water will aid drying times considerably. Recommend 45-50C water.

I'm not too sure about heating water to make it more searching for low standoff components but adding a small amount of Saponifier/cleaning agent will help with this considerably and neutralise any activators present.

Greg York Technical Sales Manager, BLT Circuit Services Ltd Greg York has twenty two years of service in Electronics industry. York has installed over 350 Lead Free Lines in Europe with Solder and flux systems as well as Technical Support on SMT lines and trouble shooting.

Surface tension of water can be reduced and its solvency can be increased by increasing its temperature. Hot rinse water has better capability of creeping underneath components and rinsing off potentially re-deposited contaminants faster from the wash cycle.

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".

You can get decent results but not equally good results. The rinse will be more active and do a better job in a shorter period of time. The old rule of thumb, double the activity for every 10 degree C rise in Temp applies here.

You have to find your own sweet spot however. Perhaps some SIR testing at different temps is in order if you really want to find that sweet spot for your operation.

Daniel (Baer) Feinberg Vice President, Fein-Line Associates Mr. Feinberg is a forty-four year industry veteran and a former President of Morton Electronic Materials (Dynachem). Feinberg presently owns Fein-Line Associates, a management consulting and market research company.

Heating the final rinse water is a waste of energy and is not needed in most modern inline cleaners. If the wash, chemical isolation and power rinse sections did their jobs, the flux and cleaning chemistry are gone. The purpose of the final rinse is to dilute soiled rinse water before stripping the water in the dryer; not to clean the boards.

Steve Stach President, Austin American Technology Founder and President of AAT. Steve holds numerous patents and has authored numerous research papers and articles in cleaning and soldering. Steve is a founding member of the Central Texas Electronics Association and is a past Director of IMAPS. Steve is active on several IPC cleaning committees.