Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.

stencil cleaning

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stencil cleaning | 11 October, 2005

HI We start to make a product which have a 0.4 mm pitch IC and start having problems with not enough solder printed, to solve this problem we had to increase the manual cleaning, now we are cleaning the stencil every 8 printings, before we was running models with 0.5 mm pitch IC's without any problem (cleaning stencil every 15 pcb's) Do you have any recommendation about solvent to clean the stencil, right now we are cleaning with regular alcohol ? We want to reduce the printing defects and reduce the manual stencil cleaning frequency.

I will appreciate your support.

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stencil cleaning | 14 October, 2005

Your problem is not the 0.4 pitch. Your problem is the manual cleaning. Manual cleaning will only remove the solder paste from the surface of the stencil. What's more, manual cleaning will force additional contamination into the 0.4 pitch apertures causing additional blockage.

After you manually clean the stencil, I recommend inspecting the apertures under magnification. The inspection will reveal your real problem and the need of a good ultrasonic stencil cleaner.

A good reference article is "SMT Stencil Cleaning: A Decision That Could Impact Production (Improving Screen Printing Yields)" by Richard Clouthier. We keep a copy on our web site:

If you need additional assistance, please feel free to contact me.

Bill Schreiber Smart Sonic Corporation Tel: +1(818) 610-7900 E-mail: Web:

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stencil cleaning | 14 October, 2005

We encounter this kind of issue. We use stencil clean in the stencil printer and also use air to blow aperture after cleaning. We are having some luck !!

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stencil cleaning | 17 October, 2005

There are a lot of things that might affect your cleaning efficiency. Paste type (no clean or w/s?), cleaning chemistry, aperture aspect ratio (aperture width/stencil thickness), "linty" wipes, etc.

Another thing you need to look at is the frequency you print. If you print every 30 seconds you'll have a lot less paste drying in the corners than if you print once every 8 minutes.

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stencil cleaning | 21 October, 2005

1.- Clean bottom and top stencil with a cloth/alcohol at same time.Pay special attention to fine pitch locations. 2.- Clean again bottom stencil side .To prevent any residual of solder 3.- Blow air with a air gun under the stencil to remove the solder in the aperture, specially on fine pitch points.

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stencil cleaning | 22 October, 2005

Proof Of Design has a number of free documents as operations procedures:



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