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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Peelable Masking

amejia

#34169

Peelable Masking | 10 May, 2005

I currently use Chemask CM8 Peelable Masking which currently takes 30 - 60 minutes to cure. Does anyone know of another solder masking which cures in less time at room temperature. I know that curing times decrease using an oven, but that is not an option right now. Any help would be greatly appreciated.

Thanks, Al

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RDR

#34171

Peelable Masking | 10 May, 2005

Capton tape, 0 cure time

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amejia

#34172

Peelable Masking | 10 May, 2005

The holes on the circuit board which need to be covered are very small and it is more time consuming to cut to size and place with kapton tape. Thanks for the feedback.

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RDR

#34173

Peelable Masking | 10 May, 2005

You can buy pre-made dots if that helps, they usually come in sizes from 1/8" on up. I have use a lot of temporary masks and no of none of them that cures quickly. I am sure that you know the thinner it is applied the quicker it cures. Have you explored the use of a wave fixture to mask these locations?

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amejia

#34174

Peelable Masking | 10 May, 2005

We actually did try dots, 1/8" to be exact. We found that they were hard to peel off using just your fingers. Also, the manufacturer punched the dots too deep and ended up going through the backing on many of them. However, using tweezers, it didn't seem like it was too bad, but the production cell leader said it was too difficult. So, that's why I was hoping to find some peelable masking with less of a curing time then Chemtronics CM8.

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#34176

Peelable Masking | 10 May, 2005

For dots this size I have applied a thin coat of Chemtronics CM8, let set 10 mins then waved. The preheaters finished the cure before the board reached the wave. You just have to drill into the heads of who applies the mask that thinner is better!

Jerry

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RDR

#34177

Peelable Masking | 10 May, 2005

Of course when it gets too thin it becomes difficult to remove! D^%#$'d if you do, D!@#'d if you don't. I agree with Jerry we also run the stuff semi wet when we have to. Do you have the possibility of getting these masked prior to assembly like the day/week before?

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#34180

Peelable Masking | 10 May, 2005

Consider: * Changing your temporary solder resist [TSR] to a light cure. * Contracting with your board fabricator to apply the TSR. * Gaining better thickness control of your application process by silk screening the current TSR. * Forcing more air circulation over the current TSR, recognizing that heat curing is not an option at this time.

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#34187

Peelable Masking | 11 May, 2005

One of my co-workers told me he worked at a place that used a UV cure mask. They screen printed the mask then UV cured it. Then they assembled the baords. He doesn't remember the brand of the mask.

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amejia

#34197

Peelable Masking | 11 May, 2005

The problem is that we don't use a wave solder machine. Our process right now is that we mask the holes, let it sit at room temperature until it dries, then conformal coat the boards with Humiseal. And, we cannot have the boards ready the day before because unfortunately right now, as soon as the boards come from SMT, the work cell does the procedure I mentioned above and preps the boards to go into our units. Once we get a better supply of boards, we will be able to mask them and coat them a day before. This is why we are looking for something that doesn't take so long to cure, and we are not using an oven.

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Frank56

#34208

Peelable Masking | 12 May, 2005

Hi Amejia, Do you can try my silly idea by using some connector header with plastic holder type cut and preparation by number of pin same as number of hole you want to mask and insert thru the pcb hole before you coat or may be you can use some type of electrical wire will do the same job. the plastic pin holder or electric wire insulator will be protection land surface for solder fillet area.

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#34210

Peelable Masking | 12 May, 2005

Amejia, If your application is strictly conformal coating and no heat is applied to the board, the product seal and peel would be the solution see link http://www.interfluxusa.com/misc.html This product solidifies immediately on cooling The only draw back is that you need a hotmelt-dispensing unit.

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amejia

#34216

Peelable Masking | 12 May, 2005

Hi Patrick,

I checked out the link and I think that just might be crazy enough to work. I'll have to research it a little bit more, but I think this would be the answer. Thanks a lot to everyone for all your help and suggestions.

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