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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