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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Blocking stencil apertures (on purpose)


K

#24320

Blocking stencil apertures (on purpose) | 28 April, 2003

I've got a set of apertures on a stencil that I would like to "plug" or block off. In the past we've done this with Kapton tape, but since this location is close to a fine pitch component, the thickness of the tape prevents good gasketing at the fine pitch location causing bridges.

I am curious if others out there have used some type of adhesive to plug the apertures temporarily & what adhesive they've used. I would like the option of being able to remove the adhesive with a solvent at a later date if needed.

Ideas?

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#24372

Blocking stencil apertures (on purpose) | 30 April, 2003

Morris

Why do want to do this [keep solder from pads]?

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#24373

Blocking stencil apertures (on purpose) | 1 May, 2003

Why not fill the apertures with paste and let the paste dry-out? We have found that a hammer and chisel are very effective for removing dried paste.

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#24374

Blocking stencil apertures (on purpose) | 1 May, 2003

we have used board mask that we let dry. It's tricky to get it flat with no spikes, but after a few tries you'll get it. I like the guys recommendation to try paste and let it dry. we have that problem when the operators do not clean the stencil properly, so I know it'll work.

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#24375

Blocking stencil apertures (on purpose) | 1 May, 2003

ehess

Why do YOU want to block apertures to keep solder from pads?

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K

#24380

Blocking stencil apertures (on purpose) | 1 May, 2003

Dave: After the stencil was made with apertures for a connector on this PCB, it was discovered that the connector would have to be handsoldered after SMT reflow.

If the solder deposits are left to reflow on the pads, it makes it difficult for the operators to handsolder the connector on later and keep the connector level, since they cannot reflow all the connector leads at one time. (it's a long connector)

We've used Kapton tape to mask off the apertures on the underside of the stencil, but the thickness of the tape creates a gasketing problem on a nearby fine pitch part.

kelly

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k_h

#24382

Blocking stencil apertures (on purpose) | 1 May, 2003

If Kapton tape doesn't work, I would recommend eating a few hundred bucks and ordering a new stencil. I think your asking for more trouble trying to plug the apertures with dried paste, glue, or anything else. It will dislodge sooner or later and probably just cause other printing problems.

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