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July 17, 2006

Which cleaning solution do you recommend to avoid damage to relay contacts, coils and filters?

1) Which cleaning solution is recommended for the PCB assembly cleaning?

2) We have faced problems with the saponifier/water base cleaning. As the saponifier cleaning is water based cleaning due to that relay contacts & coils of the transformer & filters get damaged.

3) We use RMA flux on the assemblies.



Sunil S. Bhurake

Experts Comments

In regards to the issue of water-damage caused during cleaning of water-sensitive components, this is a fairly common problem. Indeed, aqueous cleaning has numerous problems when cleaning intricate shapes where liquids can become entrapped:

1. Size & Spacing: Aqueous solvents typically have difficulty getting into and cleaning in and around parts which are extremely small or have extremely small spaces. This can be somewhat ameliorated by additives in the water or high pressures, but these work-arounds cause problems of their own (residues, damage, higher costs).

2. Entrapment: Aqueous cleaners resist coming out of tiny spaces. Imagine the amount of water which could be trapped in a filter, or deep inside a tiny female electrical connector with 100 or more openings. In addition, if the water can get into tight spaces it can drag contamination with it, trapping both materials deep inside the spaces. Symptoms of the problem include residues and corrosion. Typical work-arounds include extra processing, such as baking the products in ovens to drive the water out of the traps.

3. Spots: Water often leaves unacceptable water spots. Common work-arounds include more additives to reduce the surface tension or enhance drying, more aggressive heating and powerful air knives. Less commonly, a final rinse in a solvent cleaner is often used.

4. Compatibility: Water cleaning often is not suitable because some components or products are sensitive to the high pressures of water cleaning, the heat of washing and/or drying, or the minor surface residues mentioned above. There are no common work-arounds which can solve compatibility problems.

5. Cleaning Effectiveness: Many common contaminates are not soluble in water, so no amount of water, pressure and heat can remove them. Common work-arounds include more additives, higher pressures, and higher temperatures.

6. Environmental Problems: Water cleaners require a great deal of water and electricity, and produce a continuous discharge of contaminated water. The most common work-around is an expensive water treatment system to be installed alongside the cleaning system iteself. Aqueous systems require hard-to-get waste water discharge permits which can entail entensive paperwork and government oversight. For more details, see FAQ 61 about water cleaning and the environment.

7. Costs: While water is usually cheaper than solvents on a per-pound basis, the costs of buying, installing and operating the machines can be far higher than a solvent-cleaning system. For more details, see FAQ 63 about water cleaning costs.

Now, you didn't note in your question the TYPE of damage you are seeing, so it could be issues 1, 2, 3, 4, or 5. The proper response is to solve the issue by getting rid of the water and the surfactants/saponifiers completely.

In this application, we frequently recommend a small vapor degreaser and Vertrel(r) solvents from DuPont. These cleaners work fast, work thoroughly, dry completely, and use far less energy than water-based cleaners. The exact "flavor" of Vertrel depends upon the materials of construction used AND the contamination. You can use Vertrel in small "jewelery cleaners" with ultrasonics for small batches or rework; and you can go all the way up to huge in-line systems that will process thousands of parts per hour.

More details are available from www.VertrelSolvents.com.

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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.

Unsealed components present issues in most cleaning processes. AVD (waterless) cleaning processes may present a solution but at a high fiscal and environmental cost.

In more common water-based cleaning systems, the application of peelable latex solder-mask on the unsealed components prevents water intrusion.

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Mike Konrad
President
Aqueous Technologies
Mr. Konrad has been in the electronic assembly equipment industry since 1985. He is founder and CEO of Aqueous Technologies Corporation, a manufacturer of automatic de-fluxing equipment, chemicals, and cleanliness testing systems.

There are many possible solutions to the problem you have identified. Let's walk through the key aspects of this question.

1. "Saponifier" is a very old fashioned term that was used to describe very early generation, rather unsophisticated cleaning products. They tended to clean well (sometimes anyway), be hard on solder joint appearance (almost all the time), be cheaply priced, and provide limited (meaning short) bath life. More modern technology has eliminated or greatly reduced the potential for these issues.

2. Compatibility is the critical issue you have raised. The aggressiveness of these old fashioned materials made them relatively effective cleaners but at a cost of being rather aggressive. That aggressiveness routinely affected solder joint appearance, but certainly could also affect many other parts of the assembly. This seems to be your situation.

While the saponifiers tend to be very hard on assemblies, situations do arise when the modern, sophisticated cleaning technologies introduced in the past 5 or so years can have an affect on some devices or components--though it is relatively rare.

3. Process optimization is always a critical step in the evolution of a cleaning operation. There are times when the process it self is the cause of the defects you have described. This optimization can be assisted by reviewing Applications Lab testing, but the rubber hits the road in the day to day operation of your process. This optimization includes evaluating process time and conditions (temperature, concentration of cleaning agent, and spray nozzle configuration and pressures).

Quite often these older technologies have been around for years, generally more than 10 years. Just think about what else in your operation today is exactly the same as it was 10 years ago? Likewise, the organizations that provide these old "mainstays" may not be able or willing to provide the field technical support after the sale. I believe this is your situation since you have asked the "industry" for help rather than your supplier.

4. Soil to cleaning solution match? There are times when the soils simply do not match up ell with the cleaning solution. This is often the case with these legacy technologies and many new lead free materials. This is easy to evaluate by reviewing industry benchmark testing.

So the what you should consider is getting some help to evaluate your current process for effectiveness and the potential for being overly aggressive due to process parameters or inherent material aggressiveness. You might also consider some of the newer technology that has improved cleaning and compatibility performance while generally reducing cost of ownership issues along the way.

Hope this helped, feel free to contact me if you would like to discuss this issue in more depth.

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Tom Forsythe
Vice President
Kyzen Corporation
Mr. Forsythe is a recognized expert in cleaning chemistries and processes. Tom has a Bachelor's in Applied Mathematics & Engineering from the US Naval Academy. He is well published in both the industry trade magazines. Tom has spent the last 14 years with Kyzen Corporation.
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