Ask the Experts
June 2, 2011 - Updated
May 31, 2011 - Originally Posted

Steam Cleaning PCB Assemblies

Are you familiar with using steam to clean circuit board assemblies? I am specifically referring to a hand-held pencil-like tool to spray steam over contaminated areas of the circuit board to remove flux residue remaining after rework.

G. N.

Expert Panel Responses

You make no reference to the type of flux you need to clean. This is very important in order for the panel to make a sound recommendation. With that said, it is important to understand that steam is usually 100 degrees Celsius. Many flux residues, OA or water soluble are designed for wash temps of @ 60C. Some of the newer water wash fluxes today clean best when exposed to 40C wash baths. If you are using a rosin or no-clean/low solids formula then the steam alone may not be effective on the complete rosin structure and other flux or thixotropic ingredients present in today's flux and solder paste formulations. Also a bit of advice for the operators of any steam appliance to remember. Steam can keep increasing in temperature as pressure increases. That is why your hand will burn quicker and more severely in steam than in boiling water. Feel free to contact me to discuss this or recommendations of other effective cleaning options.

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.

Using steam to clean PCB assemblies is not a recommended practice.

There are a number of flaws in this process, including the inconsistency of the cleaning process such as getting under a tight-fitting BGA, the inability to rinse the contamination from the circuit board, the inability of water to dissolve organic contaminates (oils and grease come to mind), the risk of damage to a component from the steam, and the slow drying time required to be sure that all the condensed water has evaporated away. In short, this is a bad, bad idea.

If you need speedy cleaning, I would strongly recommend a fast-drying, nonflammable solvent-based cleaner with a controlled dispensing system to enhance the cleaning and eliminate waste. Good solvent choices are available from MicroCare, TechSpray, Chemtronics and Miller-Stephenson.

The industry's best aerosol dispensing tools are from Miller-Stephenson and MicroCare. Check with your favorite distributors to see what they have on their shelves.

Mike Jones
Vice President
Micro Care
Mr. Jones is an electronics cleaning and stencil printing specialist. Averaging over one hundred days a year on the road, Mike visits SMT production sites and circuit board repair facilities in every corner of the globe, helping engineers and technicians work through the complex trade-offs today's demanding electronics require.

In fairness to the process, and in clear disagreement to other members of this panel, steam cleaning of assemblies is not a bad idea and is in fact a process that has been scrutinized, accepted, and adopted by the FAA, FDA, Department of Defense, and countless other companies worldwide. We have recovered countless thousands of circuit boards with this exact method. This process has been proven beyond the shadow of a doubt to be effective in removing flux and other process residues from beneath low stand-off, tight pitch style components of all types. Much like the build process itself, if all steps of the process are being properly controlled the risk of damaging the boards/components is minimal and no more than any other cleaning process. Taking all parameters in consideration on a case by case basis steaming may not be the best option but should be considered as a viable alternative. To disregard any effective cleaning method can limit your options. If you would like to see analytical data that supports this process as well as other effective cleaning options that include using aerosol type cleaners feel free to contact me and I will send you reports for free. --------------As a company that has been cleaning with a combination of saponifier and hand-held steam for about 8 years now on a regular basis I can tell you that it is a very effective method to remove all flux types and other process related contamination. The key to effective steam cleaning is the ability of the operator to use the steam wand at the correct angle and distance to basically push the residues from underneath the package body. We began recovery type cleaning for companies almost a decade ago but found it nearly impossible to remove 100% with a standard in-line cleaning system, especially under high I/O count BGA's, tight space and pitch TQFP's and the like. We have never had a customer of our come back with issues related to the steam cleaning of assemblies, be they new production or product that has been on a shelf or in the field for quite some time. If you are using a quality (see high cost ) steamer with controllers for pressure and temperature there should not be any issues with increasing temp or pressure.

Eric Camden
Lead Investigator
Foresite, Inc
Eric has been in the electronics industry for over 14 years and manages the C3 technical user group, Failure Analysis project management, Rescue Cleaning Division and is one of three Lead Investigators at Foresite.
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