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Stencil Cleaning OnBoard Forum Now In Progress

#5303

Stencil Cleaning OnBoard Forum Now In Progress | 21 February, 2001

I posted a question regarding Stencil Drying in the OnBoard Forum and received some good feedback. Is there anybody in this forum that may be able to add to the information on drying stencils?

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#5313

Stencil Cleaning OnBoard Forum Now In Progress | 21 February, 2001

Sounds like you received some good advice.

Most of our stencils are used once a day [at most], so more often than not they are air dried. If we goof-up and need to reuse a stencil during a day when we have limited drying capacity, we wipe the lowest priority stencil dry and put it in the oven used to dry temporary solder mask.

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Dale Dolan

#5419

Stencil Cleaning OnBoard Forum Now In Progress | 1 March, 2001

We are currently reviewing the stencil cleaning process in house, we curently use ISOPROPYL ALCOHOL followed by a rub down with non lint wipe alls ( not good !!).As for drying the screen's, the apertures are blown out with compressed air and left to dry.The problem's being fine fibre particles remaining in apertures and no defined cleaning procedure ( one screen receives different cleaning procedure every time used ).Several different procedures mooted........one stringent universal one would be nice.

Regards,

Dale Dolan.

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#5429

Stencil Cleaning OnBoard Forum Now In Progress | 1 March, 2001

Various lint free stencil wipe suppliers take various approaches to stencil cleaning. For instance ...

Techspray Directions: Start with a dry TechClean Wipe (2358, 2361, or 2362) to remove excess solder pastes. Follow this with the 1608 Pre-Saturated Wipe to remove all pastes and contaminants.

Micro Care Hand Wipe Applications (Sheets): Cut into convenient sheets, SMT Wipes easily absorb excess solvents, dry circuit boards, clean squeegees and stencils, polish housings and cabinets, and absorb grease, oil or grime. SMT Wipes are rugged so they can be reused again and again, saving money. When defluxing surface mount boards with low-profile components, one technique is to place the SMT Wipes on top of the area to be cleaned and spray a tiny amount of solvent through the wipe. Keeping the wipe in position, use the Trigger Grip to scrub through the wipe. When the wipe is lifted away, the board will be clean and dry.

Amtech Method of Use: Isopropyl Alcohol and DI Water Clean Wipes should be used at room temperature. Do not elevate temperature above the flash point. Drying can be enhanced by using Amtech's SMT Soft Wipes or air knife.

Check with your supplier for guidance.

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DALE DOLAN

#5446

Stencil Cleaning OnBoard Forum Now In Progress | 2 March, 2001

I have read that with the advent of no clean fluxes, Isopropyl alcohol is not the best cleaning agent to use when cleaning screen's and pcb's.Is this true?..and if so what are the alternatives ?. We have just changed 90% of our products over to NO CLEAN and if this is true, this coupled with our cleaning screens/pcb's process being reviewed it is quite worrying. Thanks for your previous feedback !!

Dale.

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#5448

Stencil Cleaning OnBoard Forum Now In Progress | 2 March, 2001

I recommend that you checkout the OnBoard Forum on Stencil Cleaning. You have to enter it via the SMTnet Home Page. I tried going through the OnBoard Forum link and could not see the data. Must be a software glitch. However, there is more information there than I have seen anywhere else.

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#5449

Stencil Cleaning OnBoard Forum Now In Progress | 2 March, 2001

Hi Dale,

Care should be taken when using compressed air to dry a stencil. Just as high-pressure sprays can bend delicate land mass areas between fine-pitch apertures, so can high-pressure air. In addition, OSHA frowns on the use of high-pressuer air nozzels because the nozzel can pop off and become a projectile. Plus, any fugitive solder balls left in the apertures will become airborne.

The fastest and safest way to dry a stencil is with handheld low-pressure (<20 psi) DRY compressed air, the same quality air used to run a pick and place machine. The principle is not to "blow" the water off the stencil, the desiccated compressed air is "hungry" for moisture, just flowing the dry air across the wet stencil is like seeing alcohol evaporate. A 29-inch stencil can be dried in about 2 minutes with low-pressure dry air.

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