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Effective Alternative To Stencil Cleaning

#5276

Effective Alternatives To Stencil Cleaning | 19 February, 2001

For smaller companies, it is difficult to justify the ~$35k cost of products in the class that you sell.

On the other side of things, sloshing boards and stencils in a plastic wash pan containing flux thinner is not a good option either. Neither is washing in an aqueous cleaner.

Please take us through the alternatives that are the middle ground.

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#5286

Effective Alternatives To Stencil Cleaning | 20 February, 2001

Hi Dave,

It sounds like you haven�t been shopping for stencil cleaners in awhile. Ultrasonic stencil cleaners start at $12,900, evaporators start at $6,800 and 440-R SMT Detergent is $19.00 per gallon. For $19,719.00 you get everything you need to clean a 29-inch stencil.

Compared to the cost of not properly cleaning a stencil, which results in misprints, stencil damage and production downtime, the cost of a new stencil cleaner sounds like a bargain.

Again, I want to recommend the article by Richard Clouthier, �Stencil Cleaning: A Decision That Could Impact Production (Improving Screen Print Yields)� found on our website: http://www.smartsonic.com . Click on the �Recommended Reading� button. After reading this article, you will discover why you can�t afford NOT to develop a good stencil cleaning process and invest in a good stencil cleaner.

Believe me folks, I don�t know who Dave is, but I want to thank him for the opportunity. Thank you Dave.

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#5287

Effective Alternatives To Stencil Cleaning | 20 February, 2001

I have a knack for asking those "set-up" questions of sales types during their presentations. It's so bad, I don't even have to pay for lunch to attend SMTA meetings. The "presenter" pays for Dave. YES!!!

I've read the Richard S. Clouthier "SMT Stencil Cleaning: A Decision That Could Impact Production" article previously and just reread it based on your suggestion. Each time I read it, I come away without a sense of the economics of the issue. It seems to be a bunch a hand waving with "this is better than that" type dialog.

Going back to the original question, regardless if we're talking ~$35k or if we're talking ~$20k; the issue remains. That's the alternative and what's the cost of ownership?

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#5294

Effective Alternatives To Stencil Cleaning | 20 February, 2001

Dave,

I think we are heading toward the same objective, but from different directions. You are asking what's the cost of ownership? However, I think a question that is just as important and one that is pertinent to your current economic picture is, �what is the cost of non ownership of a good stencil cleaner?�

You are correct, the Richard Clouthier article is a bunch of �this is better than that� type dialog. He is speaking from a stencil manufacturer�s perspective and informing the reader of what could affect the performance of his product (stencils) in an effort to help improve print yields. He does not get into the dollars and cents of each cleaning process because I think he is stressing that the economics of not properly cleaning a stencil far outweighs the economics of buying a good cleaning process by the reduction of misprints, stencil damage and production downtime and labor.

If you don�t like the Richard Clouthier article, take a look at the Nick Lester article �Surface-Mount Stencil Cleaning,� from the November �98 issue of Circuits Assembly magazine (also on our website). Mr. Lester was a past editor of Circuits Assembly and references a study that states, �51 to 72% of all solder defects are the result of screen-printing problems.� He goes on to explain how a contaminated stencil can contribute to a large portion of those solder defects.

I don�t think you will find a better cleaning process for less than the $19,719.00. You can spend more for a Smart Sonic Stencil Cleaner, but you will be buying more automation and some bells and whistles that are not necessary to obtain optimal cleanliness. Basically, all Smart Sonic Stencil Cleaners clean just as well and just as fast as the next.

The real question is, �what is it costing you in misprints, stencil damage, downtime and labor by not having a good stencil cleaning process?� Only you can do the math on that one.

Good luck.

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#5297

Effective Alternatives To Stencil Cleaning | 20 February, 2001

You�re correct, many of us recognize that problems in paste deposition are the source of the majority of SMT component defects. What would you say that the portion of the "51 to 72% of all solder defects are the result of screen-printing problems" that Mr. Lester quotes is attributable to misprints, stencil damage, downtime and labor?

Sure, the costs that can be avoided should be included in the economics of understanding ownership, along with new spending, both recurring and non-recurring.

Why am I the only one that "can do the math on what is it costing you in misprints, stencil damage, downtime and labor by not having a good stencil cleaning process?" Don't you have typical or baseline information for your customers that you can share with us? I can't believe companies are not doing evaluations to verify the proported benefits of their capital spending!!!

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#5307

Effective Alternatives To Stencil Cleaning | 21 February, 2001

Dave,

My intention was not to leave you hanging. The reason I said �only you can do the math on that one� is because everybody�s situation is different. Of the 51 � 72% of all solder defects, the portion attributed to a user of 15 mil pitch stencils and BGAs may be different from a user of 25 mil pitch stencils not placing BGAs, or long runs vs. short runs, or a printer equipped with under wipes vs. a printer without, etc. There are too many variables involved for anyone to produce a specific formula that would apply to everyone�s operation. One of the reasons we pay our field representatives the big bucks is to identify those variables so we may recommend specific solutions and justifications.

A good start would be to pull a couple of stencils out of inventory and inspect them under magnification. Since the stencils have been inventoried, I can presume they are as clean as your current process will normally achieve.

Look in the fine-pitch apertures. Do you see any solder paste contamination? Check the surface of the board-side of the stencil for contamination. Check the adhesive bonds for fatigue. Check the tension of the screen. If your current process is using hot wash solution or hot drying air >120 degrees F (49 degrees C.), check the fine-pitch apertures for shape distortion (stainless steel has a very poor memory, once it expands, it doesn�t always contract back to the same position). Check for dings and dents. A good stencil cleaning process should help reduce or eliminate all of these potential problems.

Solder paste will dry in apertures as hard as cement. If a cleaning process did not clean the solder paste when it was fresh, it is unlikely able to clean dry solder paste. The Smart Sonic process will also clean dry solder paste. I have a contract manufacturer customer that inventories hundreds of stencils. He justified the purchase of one of our systems just to remove the dry paste from all of his stencils. Buying new replacement stencils would have cost much more and would have only become contaminated again with his previous cleaning process.

Other issues to consider helping justify a better cleaning process are:

User safety � Are there any health or safety issues associated with your current process? Flammable solvents? Systems using alcohol are known to explode! Many solvents are known to cause birth defects, cancer, etc. If you can smell the solvent � you have a problem.

Cost of operation � Besides the obvious costs such as labor, chemical consumption and energy use to heat it. Does your chemistry require special storage, special transportation? Does your system require ventilation? How much conditioned air is going up the exhaust? What is the cost and effort put forth for waste disposal? Special permits?

To what liabilities is your company exposed? Are you discharging anything to drain? Hauling hazardous waste away? Does your present cleaning process contribute additional waste streams? Are employees exposed to unnecessary health or safety hazards?

I even had a customer justify a process change because his current machine was too complicated.

Please e-mail me directly with your company name, address and phone number and I would be happy to help you evaluate your current process. bill@smartsonic.com

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