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Freshman in SMT industry needing advice

My company is relatively small but we have a SMT line. Howev... - Mar 04, 2004 by

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Robert

#27476

Freshman in SMT industry needing advice | 4 March, 2004

My company is relatively small but we have a SMT line. However, we don't have a stencil cleaner so I resort to a spray bottle of denatured alcohol, wiping it with a cloth and then using a toothbrush to brush the apertures. Finally another wipe down and the stencil is clean. Or is it? This is probably scandalous in the industry. I'm looking into a cleaning machine but I can't justify spending $10k+. I've looked into SMarT Sonic. I'm sure there are other companies. Help?

Second, I've began running double-sided PCB. My process is running the backside first because it's the least and smallest components. After they've gone through the oven, I run the frontside. Mind you, I'm using the same heat profile for both runs. What is the proper procedure for a dual sided board? Using Kester Easy Profile 256.

Lastly, I've got components that I suspect may be thermally shocked because I've exceeded the component manufacturer's specs but can't change the profile because other components require a longer soaking/reflowing. I'm using Kester Standard profile so the board takes about 5 minutes to run through the oven.

Thank you for helping out. Even though I've been doing this for 2 years, I'm still very green and could soak up some knowledge or advice.

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#27479

Freshman in SMT industry needing advice | 4 March, 2004

I know that many smaller companies clean their stencils the same way you do. If you get good results cleaning your stencils this way then I would say stick with the alcohol/wipe method. Take your stencil and put it under a microscope.If the aperture walls are clean and there is no residue left on the foil, then you are good to go. Another thing you can do is take a good high pressure air nozzle and blow through the apertures after you have wiped your stencil down.

As far as the double sided reflow goes, it is pretty standard to run the same profile for both sides. However, you need to run a profile on both sides to confirm that you are meeting your paste specs.

You say that you "suspect" that you have thermally shocked components. The only way to know for a fact is by running a thermal profile. Something sounds weird there. A longer soak will not shock a component. A rapid rise and a high peak temperature will.

Hope this help a little.

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Robert

#27482

Freshman in SMT industry needing advice | 4 March, 2004

Another question... I use 500gm jars of Kester 256. After a job is complete the used solder is collected and put back into the jar. Generally while a job is run, the jar and used paste could be left out/open for up to 4 hours. A piece of seran wrap is used to keep air and moisture out. The next day it would be used again for another job. After a couple of jobs, I notice the paste doesn't flow as smooth when I stir it. But the paste has been open for no more than mayber 4-5 days and always closed and sealed when not in use. Should I just throw this into cost of business and not reuse paste that has already been used? It's just so expensive to throw away...

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#27483

Freshman in SMT industry needing advice | 4 March, 2004

Try buying your paste in 500g pyles cartridges .You can use these cartridges in a standard caulking gun. Also.. have your paste vendor supply you with some empty jars.(They will usually do this free of charge)

Whenever you run a job, dispense paste from the cartridge onto the stencil. When you are done with the job, scoop the paste up and put it in a clean empty jar. The next time you use that particular jar you want to make sure that you dispense paste from the *cartridge* when low on your stencil. This method insures that you are always adding fresh paste, and not mixing old with old.

Did I explain that clearly ?

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#27484

Freshman in SMT industry needing advice | 4 March, 2004

I agree with above but would like to add:

1. You may want to try something like Bioact SC-10 wipes to clean your stencils. If what your using works good stick with it. Ultrasonic cleaners are expensive, take up room and my experience has not been good trying to clean epoxy. (we clean those by hand still)

2. Do go with the cartridges. Depending on paste type, you may only want to use "used" paste on jobs with no fine pitch parts where release is not so much an issue.

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Ken

#27489

Freshman in SMT industry needing advice | 4 March, 2004

There is a japanese company that makes a ultrasonic hand-held stencil cleaner. I demo'd it for a day and it was fantastic! It even cleaned epoxy stencils. Can't recall the price...but it should be much much less than the smart sonic and other "machines". Plus it can use water, alcohol, zestron or kyzen. Vaporizing alcohol (from a spray bottle)can be dangerous from a health perspective and is HIGHLY FLAMABLE.

Thermal shock occures on rapid heat-up cycles AND / OR rapid cooling cycles....

In the world of profiling there is only one rule: You can not control what you do not measure. Profile that puppy!

As far as the solder paste goes: Here is what I recommend: 1. Never reuse solder paste. You can not control the rheology of used paste and you can not control the performance. 2. I bet your mixing the solder in the 500gram jars. Hope your not scraping plastic bits into the solder? 3. Solder is cheap. What do your defects cost?

Fitness-for-use criteria is subjective on solder paste. When using used paste you will find reducing solder related defects is like tryig to hit a moving target. Your DPMO probably will roller-coaster as a function of when you have new or used solder. This is a practice I immediately stopped (with huge opposition) at my current company. Essentially, I chose to assume increased consumables costs in exchange for consistency in defect levels. Once the defects "plateaued" then you can begin to actually problem solve. There is NO comparison to the cost of solder paste vs the cost of defects.

Good luck

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Roger

#27490

Freshman in SMT industry needing advice | 4 March, 2004

Hi Robert,

We've been using a SmartSonic cleaning system for years. We place a lot of 0402's and FBGA components. The system cleans those apertures very effectively. The chemistry used in the cleaning solution is very safe and environmentally friendly, and when you hook the system up to an evaporator the amount of waste generated is minimal. I hope this helps.

We also use the same oven profile for our single and double sided products.

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Mike Konrad

#27497

Freshman in SMT industry needing advice | 4 March, 2004

There are several companies that manufacturer stencil cleaning systems.

They include:

Aqueous Technologies www.aqueoustech.com

Smartsonic www.smartsonic.com

EMC www.emcgti.com

PMR www.pmrsystems.com

JNJ www.jnj-industries.com

UnitDesign www.unitdesign.com

As Ken mentioned, that Japanese company that makes a �hand-held� stencil cleaner is SAWA (www.seikausa.com). Maybe its just be, but strapping an ultrasonic transducer to my wrist and dragging it across a stencil covered in lead paste and cleaning chemicals is not high on my to-do list.

All of the above companies make decent stencil cleaning systems. Many have cleaners less than $ 7K. What ever brand you go with will be a great improvement over hand-cleaning stencils. Hand cleaning stencils subjects the stencil to potential damage, the operator to potential lead poisoning, and increases your awareness of OSHA and EPA.

Mike Konrad Aqueous Technologies www.aqueoustech.com konrad@aqueoustech.com

(909) 944-7771 ext 29

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Ken

#27499

Freshman in SMT industry needing advice | 4 March, 2004

I have an Aqueous Technologies stencil cleaner and I can see many SAWA advantages over the "larger" machines.

1. Floor space savings 2. Chemical cost (up to 30 dollars a gallon) 3. Hand ultra sonic cleaning could never destroy the webbing and bond. 4. Removing a stencil from a dunk tank exposes you to the same chemicals as the sawa. 5. Sawa has only one switch (on and off). Ultrasonic machins tend to have many switches and we all know how operators like to fiddle with knobs and dials!

As far as lead poisoning he may have a lead free process? What does the maintenance guy deal with when he has to change the filters and pull the solids bin? Yuk!

What ever you buy, request a users list with at least 3 OEM and 3 CM's. Find out what they think.

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#27503

Freshman in SMT industry needing advice | 5 March, 2004

That hand held cleaner is 10K+. I have used one before. It works OK on paste, but doesn't do a thing for epoxy.

10 grand buys a lot of wipes and elbow grease.

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#27505

Freshman in SMT industry needing advice | 5 March, 2004

We use a SAWA to clean our stencils and it performs quite well on solder paste but not so great with epoxy. Operators find the machine very easy to use and like mentioned before it takes up minimal space and has a lower intial and operating cost.

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#27514

Freshman in SMT industry needing advice | 5 March, 2004

We also use a SAWA. Works great. Easy to use. Small footprint. Easy to implement into our process. Nothing "strapped" to my operators as previously stated. Evaluated several units under 10K. Some were very good, some not so good. SAWA matched our needs best. Work yourself up a comparison matrix and pick the one that suits your production needs best.

Not connected with or receive any compensation from SAWA.

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#27535

Freshman in SMT industry needing advice | 8 March, 2004

New Stencil Cleaning machine on the scene. Saw it at APEX 04, manufactured in West Viginia.

http://www.pressureproducts.com/SPPC_Hm.htm

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Robert

#27541

Freshman in SMT industry needing advice | 8 March, 2004

In the printing process... Do any of you change your print profile regularly? Let's say you just opened a fresh jar of paste and you're on your 50th print. Do you slow the squeegee speed or change anything on your existing profile? I just add more paste and hope that I don't get any misprints.

Thanks to everyone who's posted some very good advice on this thread.

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pdeuel

#27546

Freshman in SMT industry needing advice | 8 March, 2004

We had problems with paste drying out when opened for more than a couple of days. We solved this problem by ordering paste in 250 gram quanities. This is about a third of a jar in the same size container.

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#27573

Freshman in SMT industry needing advice | 9 March, 2004

There is an article on our web site by Richard Clouthier, �SMT Stencil Cleaning: A Decision That Could Impact Production.� He talks about how high pressure sprays can damage the delicate land mass areas between fine-pitch apertures. High pressure air can cause the same damage. In addition, OSHA doesn�t like the idea of solder paste becoming airborne. Mr. Clouthier makes several points about stencil-cleaning that I do not see as part of this thread. A copy of the article can be found at: http://www.smartsonic.com/article.html

Best regards, Bill Schreiber Smart Sonic Corporation www.smartsonic.com Tel: 1(800) 806-440R

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Primus

#27689

Freshman in SMT industry needing advice | 20 March, 2004

The BioAct SC-10 wipes work great, but I've noticed some contamination in our solder joints after I began using them on the stencils. After cleaning the paste off the stencil with the wipes, I started spraying the stencil down with isoproponal and blow drying. This introduced a different contamination, so I stopped blow drying and started wiping the stencil dry. The oil from the lubricator in the air lines was the second cause, because now there's no contamination at all and the apperature walls are cleaner than ever. I stopped using the toothbrush because over time our quadpack stencils were begining to scratch up. Our stencils are roughly 20" square (I never measured them but they fit a DEK) and it takes me about 5 minutes to clean up after about 100 cycles in 4 hours. We've looked into cleaning machines but maintanance doesn't want anything more to need to fix, and one we looked at took 10 minutes to do a lousy job.

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charlie

#27697

Freshman in SMT industry needing advice | 21 March, 2004

if u buy the machine for that,we can supply the roll for you,it is would be grateful if u interested in.

MR charlie shenzhen comofaje co. ltd. www.comofaje.en.alibaba.com www.comofaje.com tel:86-755-28091635 fax:28091645 mobile:013714778363 mail:sales@comofaje.com

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starbillias

#27698

Freshman in SMT industry needing advice | 21 March, 2004

Hello Robert, I have a used EMC Global Technologies Spirit 30 IPA Stencil Cleaner For Sale. This is in mint condition and I am only asking $4,250. Feel free to contact me with more questions. Thanks Regards, Bill 978-790-2774 wladakos@comcast.net

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#27751

Freshman in SMT industry needing advice | 26 March, 2004

I'm keen to find out more about the SAWA cleaner. What type of solvent is being used. Does anyone use water or any other enviromentaly friendly agent. Is the result with glue stencils good.Is this a messy machine to use. Any feedback would be good. I would like to see the back of our old dinosaur cleaner.

Thanks, Alan.

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RDR

#27759

Freshman in SMT industry needing advice | 26 March, 2004

Looks like all of your questions are answered above

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#27805

Freshman in SMT industry needing advice | 29 March, 2004

It should be noted that some of the main reasons to change from manual cleaning to automated stencil cleaning are: � Manual cleaning is not consistent � quality is totally in the operators hands � Contamination left on the stencil and in the apertures from manual cleaning will cause paste transfer issues, insufficients, bridging and/or solder balling. � Manual cleaning causes dings, dents, screen tension problems that lead to co-planarity, misregistration, misprint and stencil replacement problems. � Manual cleaning can be hazardous to the user � exposure to lead, solvents, fire hazards, odors, etc.

The Sawa handheld cleaner does not eliminate any of these issues. In fact, the Sawa unit may augment the problem or introduce other concerns.

I had an opportunity to demo a Sawa unit about a year ago. Some problems with the Sawa concept include:

� Must still preclean the stencil manually with wipes. (More wipes for disposal) � Must place an electrical appliance into a liquid. Kind of like blow-drying your hair in a bathtub. Electricity and liquids don�t mix! � If stencil became dinged, dented and stretched from cleaning with a cloth. What amount of additional damage can be expected by replacing the cloth with a heavy metal transducer? � IPA is flammable. The transducer and generator are electrical. An electrical spark or arc can cause serious injury to anyone in the area, especially the one with his hand in the alcohol! Sawa warns that the transducer becomes hot after 20 seconds of use or if there is not enough solvent in the sponge. IPA has a very low flash point! There is a warning on the alcohol container to keep it away from heat! It appears that their transducer is not compatible with alcohol. Yet, they recommend using alcohol. � Alcohol is a VOC. � The stencil must be placed on one of the disposable sponges provided by Sawa. Sawa notes that one reason for poor cleaning is a �dirty sponge.� The sponge must therefore be changed often at a cost of $4.00 ea. How does one dispose of a lead/alcohol contaminated sponge? � Sawa�s brochure states �After cleaning with the Sawa Cleaner remove the stencil from the tray and wipe the top and bottom of the stencil with a clean, wet SMT wipe (more wipes for disposal) to remove any remaining solder balls or adhesive.� If you have to clean the stencil before and after using the Sawa Cleaner, what exactly does the Sawa Cleaner do? It is common knowledge that hand wiping just pushes solder balls back into apertures and vias. Therefore, it can be expected that any �remaining solder balls or adhesive� left on the stencil after Sawa cleaning will be placed back into the apertures and/or vias. � Must clean transducer head after each use. If not, solder will dry on the head and scratch and scrape the stencil during the next use. This can cause significant damage to fine-pitch apertures. � Sawa does not provide any chemistry. When the system fails, they can always blame the chemistry used. � The Sawa system is not recommended for cleaning misprinted PCBs, pallets, squeegees, oven radiators or other tooling. � The Sawa system is not an ultrasonic stencil cleaner, but rather just another tool to be used manually.

Sawa also has an automatic machine available. While I have not used the automatic machine, I have seen it while I was in Japan and can tell you that it does not contain the odors of the chemical in use. Vapors of whatever chemical is used can be detected 20 feet away. I guess if your clean water washable solder paste, it might not be so bad.

Needless to say, my experience with Sawa was not a good one. I would recommend sticking with a traditional ultrasonic stencil cleaner with a good chemistry.

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Michelle Ogihara

#30648

Freshman in SMT industry needing advice | 22 September, 2004

As many people have participated in this email string, including competitors and customers of Sawa, I would like to respond to especially one rather detailed email expressing concerns with this stencil cleaning system. Also, this teaches me to keep an eye out for such discussions so that I may speak out on a more timely basis.

Found on smtnet message board: Author kerrynhijacker dated march2004 "The Sawa handheld cleaner does not eliminate any of these issues. In fact, the Sawa unit may augment the problem or introduce other concerns." Response: The Sawa Corporation has sold over 3,000 stencil cleaners worldwide. It is the leading stencil cleaner supplier in Japan and throughout Asia. There are many satisfied users including U.S. customers who find the system most effective for stencil cleaning, attractively priced and environmentally-friendly. The overall low costs include savings due to low volume solvent usage, no plumbing, permit or installation of solder catcher costs and no or low liquid waste disposal concerns.

"I had an opportunity to demo a Sawa unit about a year ago. Some problems with the Sawa concept include: �EMust still preclean the stencil manually with wipes. (More wipes for disposal)"

Response: Most stencil cleaner suppliers recommend that excess solder paste be removed so that the remaining paste does not contaminate the solvent with excess solder balls. This will also enable the solvent to hold a longer lifespan in the cleaner. For the Sawa cleaner, the key is the capability of removing solder spheres from fine-pitch apertures and BGA apertures which is far more of a difficulty than surface removal of paste off of the stencil.

"�EMust place an electrical appliance into a liquid. Kind of like blow-drying your hair in a bathtub. Electricity and liquids don't mix!" Response: A foam sponge underneath the stencil is soaked with solvent only to the extent of keeping moist and allowing the solder balls to be wicked into it after being dislodged by the ultrasonic energy of the cleaning head placed lightly on top of the stencil which is also sprayed(not drenched) with solvent. The ultrasonic head is never immersed fully in liquid and the transducers are well protected in the event that more liquid solvent is applied.

"�EIf stencil became dinged, dented and stretched from cleaning with a cloth. What amount of additional damage can be expected by replacing the cloth with a heavy metal transducer?"

Response: As with all types of operation, one must be careful and use common sense in handling equipment. The Sawa cleaner is no acception to this rule. However, we have a special cart with a pulley to assist in holding up the cleaning head for ease of cleaning should the customer request such an option.

"�EIPA is flammable. The transducer and generator are electrical. An electrical spark or arc can cause serious injury to anyone in the area, especially the one with his hand in the alcohol! Sawa warns that the transducer becomes hot after 20 seconds of use or if there is not enough solvent in the sponge. IPA has a very low flash point! There is a warning on the alcohol container to keep it away from heat! It appears that their transducer is not compatible with alcohol. Yet, they recommend using alcohol."

Response: Again, we suggest using common sense here. Because the Sawa cleaner is very effective in removing solder balls from fine-pitch apertures quickly and with little effort, even IPA may be utilized for some solder paste chemistries. However, we do not suggest that it is the recommended solvent. The Sawa cleaner may be safely used with any solvent heeding the guidelines that the manufacturer recommends. There is a 20-second safety timer on the cleaning system as a preventive measure to help remind the user not to run the ultrasonic cleaning head dry. As with all ultrasonic systems, the Sawa cleaner should also be used in conjunction with a liquid solvent. The ultrasonic energy may be reapplied by simply stepping on the foot pedal. As the cleaning process will be accomplished within one to two minutes on a stencil, typically, the length of time for the cleaner to overheat is not a concern.

"�EAlcohol is a VOC." Response: Yes, that's correct.

"�EThe stencil must be placed on one of the disposable sponges provided by Sawa. Sawa notes that one reason for poor cleaning is a dirty sponge.�EThe sponge must therefore be changed often at a cost of $4.00 ea. How does one dispose of a lead/alcohol contaminated sponge?" Response: The foam sponge is simply the polyurethane type often used for packing. If the customer has an abundance of this foam available from their shipping department and it is clean, it can be used at no extra cost. The foam sponge wickes in solder spheres from the apertures of the stencil. The balls are captured and often fall deep within the sponge allowing the surface to be reused once again. In addition, the foam may be re-used numerous times by simply rotating the clean areas underneath the apertures as needed. Because the sponge requires little solvent(though it should be moist at the time of cleaning), it will evaporate to some extent due to the porous nature of the sponge. Waste disposal would be the same as with cleaning wipes, gloves and other paper product wastes that contain lead.

"�ESawa's brochure states after cleaning with the Sawa Cleaner remove the stencil from the tray and wipe the top and bottom of the stencil with a clean, wet SMT wipe (more wipes for disposal) to remove any remaining solder balls or adhesive.�EIf you have to clean the stencil before and after using the Sawa Cleaner, what exactly does the Sawa Cleaner do? It is common knowledge that hand wiping just pushes solder balls back into apertures and vias. Therefore, it can be expected that any remaining solder balls or adhesive�Eleft on the stencil after Sawa cleaning will be placed back into the apertures and/or vias." Response: As Sawa recommends to clean the excess paste from both the surface and bottom of the stencil before running the cleaning head, there should be very few excess balls on the stencil. Most of it will be wicked into the sponge from the apertures. This last step may or may not take place depending on how well the initial cleaning with wipes has been conducted.

"�EMust clean transducer head after each use. If not, solder will dry on the head and scratch and scrape the stencil during the next use. This can cause significant damage to fine-pitch apertures." Response: All equipment requires some type of maintenance. There is not much else required of the Sawa cleaning system so a quick wipe of the cleaning head taking a few seconds after usage is not much to ask for.

"�ESawa does not provide any chemistry. When the system fails, they can always blame the chemistry used."

Response: Sawa does not provide chemistry for the cleaners which allows the company to be unbiased in terms of recommendations. And, yes, there is a recommended solvent list by Sawa. However, it is the user's choice as the Sawa Cleaner is effective with most solvents recommended for cleaning by the solder paste manufacturer.

"�EThe Sawa system is not recommended for cleaning misprinted PCBs, pallets, squeegees, oven radiators or other tooling."

Response: Sawa has several models in the ultrasonic cleaning system line including those that can handle stencils, ICT pins, misprinted PCBs, pallets, squeegess and other tooling. If the customer is interested in a multiple task use cleaning system, Sawa has a solution.

"�EThe Sawa system is not an ultrasonic stencil cleaner, but rather just another tool to be used manually."

Response: The Sawa cleaner is definitely a system utilizing ultrasonic transducers. Specifications can be provided by emailing the contact below.

"Sawa also has an automatic machine available. While I have not used the automatic machine, I have seen it while I was in Japan and can tell you that it does not contain the odors of the chemical in use. Vapors of whatever chemical is used can be detected 20 feet away. I guess if your clean water washable solder paste, it might not be so bad."

Response: Sawa has many models of the automatic and semi-automatic cleaners available. We will have to take your word for it that the smell came from vapors emitted though this is generally not a complaint from Sawa users.

"Needless to say, my experience with Sawa was not a good one. I would recommend sticking with a traditional ultrasonic stencil cleaner with a good chemistry."

Response: In closing, even within this thread of discussion, there have been many words of support and satisfaction by Sawa Ultrasonic Stencil Cleaner users. Each experience may be different due to a number of factors including the type of paste used, the type of solvent used and the correct operation of the cleaning system as recommended by the manufacturer. Another common factor that may determine outcome of the system demonstration is the cleaning of older stencils that due to the previous poor cleaning methods utilized, often have solder balls that have cured on to the stencil and can be detected with(or sometimes even without!) a microscope. Sawa has had success even in some of these very difficult circumstances by utilizing the direct contact ultrasonic energy with a good solvent.

All in all, I would be happy to discuss the above with anyone interested in finding out more about the Sawa cleaners or still has issues/questions with how this system works.

Best regards,

Michelle Ogihara Seika Machinery, Inc. Sales Agent in North/South America for the Sawa Ultrasonic Stencil Cleaners www.seikausa.com michelle@seikausa.com

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