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UltraSonic cleaning machine

Michael F.

#21680

UltraSonic cleaning machine | 22 September, 2002

We are about to purchas a new cleaning machine for stencils & miss print and we are considering an ultrasonic one. Can someone light this point for me? What are the advantages / disadvantages of this method? How it effect the components and their solder joints? Thanks, Michael.

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#21682

UltraSonic cleaning machine | 22 September, 2002

To get started, search the fine SMTnet Archives for discussion on stencil cleaners.

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Michael F.

#21688

UltraSonic cleaning machine | 23 September, 2002

Dave,

I'm looking for some advice or direction in regards with assembled PCB miss print and how it influent on the components.

Michael

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#21689

UltraSonic cleaning machine | 23 September, 2002

#21700

UltraSonic cleaning machine | 23 September, 2002

Michael, If you do not find the information you are looking for in the archives, call me and I happy to discuss this with you and fax you some articles on the subject. The answer to your question is too involved to reply via the forum.

Regards, Bill Schreiber Smart Sonic Corporation Tel: 1(800) 806-440R Fax: 1(818) 610-7909 E-mail: bill@smartsonic.com

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#21701

UltraSonic cleaning machine | 23 September, 2002

Isn't this a blatant violation of rules? Couldn't Bill have e-mailed a response directly to the poster? I'm not sure if acts like this frustrate users that actually are the people who work in this industry but it definately frustrates suppliers who try to play by the rules. But...there are many suppliers who can satisfy your requirements. There are benefits in using both ultrasonic and spray-in-air technologies. Try using the Industrial Directory in SMTNet. Or wait around until other suppliers get free advertising, even when they do sponsor and have been asked to cool it.

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Brian Doyle

#21702

UltraSonic cleaning machine | 23 September, 2002

Actually I didn't really think it was that blatant. He has something that could solve the problem of the original poster. Instead of putting his company's brochure on the forum he just left it up to the original poster to make the next contact.

Perhaps he should have just contacted the user directly, that works too. I see your point, if we had EVERY company in the database come in and let a user know that they can contact them for help it might get a little messy. There's really no perfect solution.

I've seen (and removed) somre really blatant and out of place advertising recently. This didn't strike me as one of them.

This is a commercial forum. Basically its a user from one company soliciting help from users at other companies.

I always want users to contact us about threads that they feel violate the board rules. We review them and then take action if necessary. Use info@smtnet.com or bpdoyle@smtnet.com .

Lets not drive the companies away from this site. They can add a lot to the forum. We are also aware the adverse affects that over commercialization can have on the forum. Our track record shows that we take these things seriously.

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CAL

#21743

UltraSonic cleaning machine | 25 September, 2002

Michael- Please when concidering you U-sonic machine, keep in mind possible chemistries Petroferm, Kyzen, Aqueous technologies, and Zestron products. All are good products and all need to be evaluated with your stencils. Depending on your component type and Solderpaste type will determine the proper Chemistries.

Some times people tend to look at the capitol equipment side (cause of the $) and tend not to do there home work on contributing products.

If you need the key contact people at these companies to assist you in your chemistries...feel free to contact me at cal_driscoll@manncorp.com.

Cal

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#21745

UltraSonic cleaning machine | 25 September, 2002

I don't think 'this a blatant violation of rules' as such. I think it is a blantant disrespect of the principle of free and open communication that is the corner stone of interenet forums and a slap in the face of everyone that wants to learn more about this business.

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Matt2138

#21746

UltraSonic cleaning machine | 25 September, 2002

UltraSonic cleaners do a good job of cleaning both stencils and misprint PCBs. Make sure the frequency that the machine comes set to is ok to use with both stencils and misprint PCBs. If you are a CM make sure your customers are ok with using the ultra sonic cleaner. Some ultra sonic manufactures lock you into their chemistry and if you don't use it you may void some part of the cleaning warranty. Make sure the manufacture is flexible in chemisty being used, what may work for one paste may not work on another. Look at cycle times as well, some seem to have a short cycle time because they only show a wash time and then you must take the stencil out and dry it by hand. There are fully automatic cleaners out there. As what RobF. had said there are other methods of cleaning stencils besides ultra sonic. If you would like to talk about these you may contact me using my email address and we can discuss this info off line.

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#21754

UltraSonic cleaning machine | 25 September, 2002

#21755

UltraSonic cleaning machine | 25 September, 2002

Hello Dave, I hope that electronic slap didn�t hurt too much.

Robf,

I am sorry that you did not agree with my initial response, but the answer is very detailed and most of the support material I have is only in paper format so I need to either snail mail or fax it to Michael F (or any other interested party). If I had e-mailed my response directly to the poster, Dave�s face would have been slapped even harder because of the lack of �free and open communication that is the corner stone of internet forums.� So Dave, do you want to be the rock or the hard spot on this one?

However, in self-defense, I will describe the general guidelines and reference my sources. If you have access to a good library, I guess you may be able to find them. The material is about 40 pages, so the time and effort that I was originally willing to put forth on the copy/fax machine will now be allocated to the following:

Here goes. Ultrasonics (u/s) originally got a bad rap back in the 1950s when Westinghouse developed the process for the U.S. Air Force. At that time, the technology used very low frequencies (20 kHz - the lower the u/s frequency, the more aggressive the cleaning action) and very high power or power density (200 watts/gallon). This early technology was tested for cleaning PCBs with devastating results. The PCBs of that era were very fragile with weak wire bonds and the u/s technology was very strong and uncontrollable, so the two technologies were not compatible. As a result, the U.S. Military Specified that Ultrasonics should not be used for cleaning PCBs.

Since then, u/s has developed into the most controllable precision cleaning process available. Virtually every parameter can be managed. The frequency, the amplitude of the sonic wave, the power input (density), the bath temperature, the chemistry, the exposure time, use of multiple �sweep� frequencies, positioning and movement of parts are all controlled with today�s technology.

Today�s surface mount PCBs are more durable than the through-hole technology of the 50�s, so research by the EMPF laboratory, GEC Marconi, Smart Sonic and others have revealed that the two technologies are now very compatible for many PCB cleaning applications.

For most, ultrasonic technology is a mysterious science. Because the cleaning activity (cavitation) is microscopic, it is difficult to discern one system from another. Simply put, however, ultrasonic cavitation is the formation of tiny vapor bubbles, caused by pressure changes in a liquid cleaning media that collapse to form vacuum pockets throughout the bath. These collapsing vacuum pockets serve to �pull� contamination away from solid surfaces. So, ultrasonics is basically a �pulling action�.

Ultrasonic frequencies vary from 20 � 400 kHz. Power input to the bath is measured in watts of energy and vary depending on the cleaning task. Low frequency/High watt systems are usually designed to clean durable parts with difficult contaminants like rebuilt carburetors or aircraft wheel housings. High frequency/Low watt systems are usually designed for cleaning delicate parts with mild contaminants like disk drives and optics. An analogy can be made that the frequency is similar to the bristles of a brush. The lower the frequency, the stronger and larger the bristles. The wattage is similar to the force applied to the brush. The more watts, the more force applied to the brush.

This is one reason care should be taken when evaluating an ultrasonic cleaning system for they can vary tremendously. The wrong frequency or power could be devastating to misprinted PCBs.

Most ultrasonic systems designed for cleaning solder paste and adhesive use 40 kHz �sweep� frequency generators. �Sweep� frequency meaning that the ultrasonic generator will alternate within a tight range of frequencies (say 38 � 42 kHz) to prevent cavitation from concentrating in any one area of the bath. Lower frequencies could damage stencils and PCBs. Higher frequencies will not be able to form large enough vacuum pockets to effectively pull away the contaminants. The input power (watts), however, may vary tremendously from one supplier to another. This is also a good way to determine if an ultrasonic supplier is expert in PCB applications or just supplying generic ultrasonic equipment.

If cleaning tooling alone, high wattage systems may have an advantage (strong brush with lots of force). Unfortunately, if misprinted PCBs are to be cleaned in the same machine, the excessive power wattage could be detrimental.

It is important to work with the chemistry and machine supplier simultaneously. The chemistry will play an important role in determining the wattage necessary to properly clean all desired applications. Generic ultrasonic stencil cleaners that propose their machine may be used with any chemistry must power their machines to help compensate for inferior chemistries (more power is not always better when cleaning misprinted PCBs). When a machine is designed for use with a specific chemistry, the power can be tailored to safely clean tooling and PCBs. Guidelines for proper frequency, power and cleaning cycles of an ultrasonic system designed for cleaning misprinted PCBs are: �the ultrasonic frequency should be 40 kHz using a �sweep� frequency technology �the power input (density) to the bath should be less than 11 watts per liter or 42 watts per gallon (total watts of ultrasonic generator / total liters (gallons) of cleaning solution in bath). In general, the lower the power required to clean effectively, the better. �the ultrasonic wash cycle should be less than 10 minutes

References:

1. Robins, M., �Solutions for PCB Cleaning,� Electronic Packaging and Production, August 2000, pp. 42 - 49 2. Clouthier, R., �Improving Screen Print Yields,� Electronic Packaging & Production, July 1996, pp. 32- 36 3. Lester, N.J., �Surface-Mount Stencil Cleaning,� Circuits Assembly, November 1998, pp. 56 � 60 4. Bivins, B., �Cleaning Solutions for Stencils and Misprints,� Proceedings of the 1999 NEPCON West Conference, pp. 94-97 5. Seto, P., and Loew, N., �Stencil Cleaning,� SMT, May 2001, pp.66 � 72 6. Richards, B., Burton, P., and Footner, P., �Does Ultrasonic Cleaning of PCBs Cause Component Problems: An Appraisal,� IPC Technical Review, June 1990, pp.15 � 27 7. Vuono, B., and Crawford, T., �Ultrasonic Cleaning of Military PWAs,� EMPF TS0040, April 1991 8. Kenyon, W.G., �Ultrasonic Cleaning Acceptance Accelerates,� SMT, May 1995, pp. 21 9. Hymes, L, �Defluxing with Ultrasonics,� Circuits Assembly, September 1999, pp. 80-81 10. Hutchins, C.L., Equipping for the Cleanup, SMT, November 1992, pp 11-12 11. Mil-Std-2000A (Superseding Mil-Std-2000) February 14, 1991 12. Schreiber, B., �SMD Adhesive Cleaning,� Proceedings of the 2002 APEX Conference, pp. S27.3.1 � S27.3.6 13. Schreiber, W., �Environmentally Certified Technologies: A Case Study,� SMT, July 1999

Anyone interested in copies of these articles may still contact me rather than researching the technical libraries.

Regards, Bill Schreiber Smart Sonic Corporation

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Randy V

#21764

UltraSonic cleaning machine | 26 September, 2002

There are allot of issue to washing that need to be considered before you purchase a washer. But to answer your question regarding ultrasonic cleaning:

1. Ultrasonics with the correct frequency will not damage most components. Washing in general can damage parts but this has a lot to do with the chemistry. Stay away from Solvents. 2. Ultrasonics will clean solder paste from stencils and boards at ambient temperature. 3. Ultrasonics will have a tough time cleaning no-clean flux residues and adhesives from boards. Heating the chemistry to 120 degrees F. will help. 4. With any washer you need a good filter system that can filter the wash chemistry (circulation system) especially if your cleaning adhesive from boards and stencils. Five micron or less filters final filters should be used with 25 micron as your first filter. 5. Drying is an issue with any washer and takes up as much or more time than washing if it�s not automatic. 6. DI water should be used for mixing any aqueous chemistry and for rinsing. 7. An open bath ultrasonic system is a safety concern. Operators have to wear safety shields and gloves. 8. An eye wash station with running water must be installed near the washer (any washer). 9. Evaporative waste systems can cost allot to operate and are considered to be treating hazardous waste by some states. A good filter system with duel lead removal beds will work for many areas.

General: Most companies will let you try out a system in your plant if you are serious about buying a system. I would recommend getting a good spray washer and a good ultrasonic washer installed and run some tests in your facility. AAT, Electrovert, Smart Sonic, etc. have been around for some time. Do not skimp on price as you pay for what you get. Note: On any washer in line filtration is critical and the pump used must be able to handle solder paste. I used duel Cuno housings for inline filtration with 5 filters per housing to keep solder paste from entering the wands and nozzles. If your using your washer a few times a day you can get buy with smaller housings. Call the pump manufacturer yourself to make sure it can handle solder paste as few can and some manufacturers do not use the correct pump. Plumbing is also critical and you cannot go wrong with stainless steel. Stay away from systems that use plastic as they will leak.

I personally prefer a good self-contained spray washer but a good one is hard to find and they are expensive. I had three washers custom built per my specifications and they work great but costs 85K each. I also have an ultrasonic system that is used mainly for cleaning printer blades. Look around before you buy anything.

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