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Stencil cleaning

Stencil cleaning

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I am a lay person researching the application of non-woven ... - May 30, 2006 by Bryan Hewson

Your aqueous (spray) and ultrasonic methods refer to cleanin... - May 30, 2006 by Steve Thomas

I would like to know if there is any information regarding h... - Jun 14, 2006 by

Bryan: * Most of our stencils are made from stainless steel... - Jun 14, 2006 by davef

Stencils should be cleaned frequently enough to ensure total... - Jun 14, 2006 by davef

Just to add to what dave said, the only limitation to how fr... - Jun 15, 2006 by Steve Thomas

Thanks to all for clarification - I now appreciate the diffe... - Jun 16, 2006 by

First, isn't paper a nonwoven? Maybe we start splitting hai... - Jun 16, 2006 by davef

The most common rates of in-process cleaning (under wipe) I ... - Jun 19, 2006 by Oosterhof

Ahne [?] You say, "There are almost as many ways to be su... - Jun 19, 2006 by davef

You can stop cleaning after a job when there is no more past... - Aug 16, 2006 by Oosterhof

Bryan Hewson

#41891

Stencil cleaning | 30 May, 2006

I am a lay person researching the application of non-woven material in stencil rolls either using branded material or non-branded alternatives for DEK, MPM Panasonic machines in SMT environments. I have read a number of articles referring to aqueous, ultrasound techniques as well as use of paper rather than non-woven fabric. Are these alternatives to the use of non-wovens when cleaning stencils in SMT or relating to other cleaning processes within PCB / SMT manufacturing? Any pointers would be appreciated Bryan

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Steve Thomas

#41898

Stencil cleaning | 30 May, 2006

Your aqueous (spray) and ultrasonic methods refer to cleaning of the stencil for storage between jobs.

All others would be most common as in-process cleaning methods, whether with cloth or paper products.

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Mario Berrocal

#42200

Stencil cleaning | 14 June, 2006

I would like to know if there is any information regarding how often to clean the stencil by the printer cleaning system. I am running a board with an ultra fine pithc QFP. Is there any guide available?

Regards, Mario A. Berrocal

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davef

#42202

Stencil cleaning | 14 June, 2006

Bryan: * Most of our stencils are made from stainless steel that is held by a aluminum frame, attached with epoxy with a fiber glass intermediary between the frame and the stencil. * We use stencils to print either glue [thermoset epoxy] or solder paste * Plastic stencils are almost exclusively used for glue. * Paper is used as a stencil underwipe to clean the bottom of the stencil during production as a function of printer operation. * Dedicated ultrasonic or water wash cleaners clean both sides of the stencil off-line during a stoppage of production or [as mentioned earlier] at the end of a production run.

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davef

#42203

Stencil cleaning | 14 June, 2006

Stencils should be cleaned frequently enough to ensure total removal of any bottom side residues, but not so infrequently as to allow the same residues to dry or cake on, making their removal much more difficult.

Look here: http://www.smtnet.com//forums/index.cfm?fuseaction=view_thread&CFApp=1&Thread_ID=9320&#Message37129

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Steve Thomas

#42218

Stencil cleaning | 15 June, 2006

Just to add to what dave said, the only limitation to how frequently you clean is the cost of the cleaning medium. You can wipe every board if you want to, but you'll go through material accordingly.

If you're printing 16mil pitch or smaller, cleaning every other cycle isn't out of the question but it depends on how well your stencils gasket the board (surface finish, stencil alignment), your paste rheology, etc.

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Bryan

#42234

Stencil cleaning | 16 June, 2006

Thanks to all for clarification - I now appreciate the different methodology between "in-line" & "end of run" but am still unclear as to advantages / disadvantages of paper versus non-woven material ie stencil rolls for in-line cleaning. Any info would be gratefully received. Thanks again

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davef

#42235

Stencil cleaning | 16 June, 2006

First, isn't paper a nonwoven? Maybe we start splitting hairs on whether paper is a 'fabric' or not, but what's the difference?

Second, paper versus nonwoven fabric boils down to performance and cost. We know 'paper', but it could be 'fabric' and we wouldn't know it.

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Oosterhof

#42280

Stencil cleaning | 19 June, 2006

The most common rates of in-process cleaning (under wipe) I have encountered are once per 5 to 10 prints. But this depends a on a lot of variables. More often is typically better, but more costly in under-wipe materials. (For some more info see http://www.finelinestencil.com/Products/MicroCare/index.html) Stencil cleaning after the run is finished (or temporarily interrupted) can be done many different ways and the main controlling variable is the type of flux that is used in the solder paste. Methods range from hand cleaning with alcohol, brushes and wipes to cleaning in an ultrasonic bath using water, temperature and a cleaning agent. There are almost as many ways to be successful with this as there are ways to do it wrong. Good luck.

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davef

#42285

Stencil cleaning | 19 June, 2006

Ahne [?]

You say, "There are almost as many ways to be successful with this as there are ways to do it wrong."

What do you believe are the successful and wrong was to go about cleaning stencils after the run is finished (or temporarily interrupted)?

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Oosterhof

#43352

Stencil cleaning | 16 August, 2006

You can stop cleaning after a job when there is no more paste in the apertures. Under wiping should be done with a quality cloth and should leave no paste on the underside of the stencil (assures good contact on the next print and reduces chances of solderballs) and should leave no cleaning liquid (e.g. alcohol) on the stencil.

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