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Underscreen cleaning cycles

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#66222

Underscreen cleaning cycles | 26 April, 2012

I was just wondering what everyone is using for a standard cleaning cycle on their screen printers? I'm sure there a study that I can do on printing but don't have the time currently. Please let me know what everyone is doing as a standard practice.

Thanks

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#66223

Underscreen cleaning cycles | 26 April, 2012

By default we clean after 10 cycles. Some boards are poorly designed and we end up doing it every 4 cycles

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#66224

Underscreen cleaning cycles | 26 April, 2012

Stencil Cleaning [AIM LeadFree] * 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. * Some applications may require cleaning after every board printed, while others may be able to clean the stencil a surprising one time per shift, or even not at all. * Regardless of how often you do clean your stencil, one sure method of determining whether or not the job is getting done is to remove the stencil and visually inspect the bottom side

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#66316

Underscreen cleaning cycles | 11 May, 2012

You may also look into a product called Nano Protek. This is an application that helps reduce your cycles and increase productivity. In some cases beter paste deposition has been recorded. Contact your stencil vendor or I can give you information.

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#66317

Underscreen cleaning cycles | 11 May, 2012

We also go with 10 cycles, adjusting from that point if needed.

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#66322

Underscreen cleaning cycles | 11 May, 2012

Regarding nano coatings : Nano coatings are susceptible to wear during the printing process and cleaning processes. As they wear they flake off and can potentially contaminate your solder. There is not a lot of independent data available on this so keep that in mind.

As far as wiping goes, we have found that there is a VAST difference in the paper technology. One that has worked very well for us is MicroCare.

We receive no monetary benefit from MicroCare.We use it and it works. That's all I got to say about that.

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#66323

Underscreen cleaning cycles | 11 May, 2012

I am not aware of the Nano protek flaking off. However I do believe it can wear off through abrasion. Unforunately there is no red light goes off when it has worn unless you have good paste inspection. Even when it wears it will not take you to a negative it will at least take you back to your acceptable level. Nano protek can be re-applied and will not adhere to itself so it only depsosits to those areas that require it. I am only familiar with Protek and coatings from Laserjob in Germany and a Japanese company. There is a material called FG coated with Nano Protek and must be cut on a fiber Diode laser. This is the most sought after stencil today. Although I am seeing an interest again in Eforms.

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#66358

Underscreen cleaning cycles | 17 May, 2012

I'm not sure why anyone would pay extra for FG (fine grain) stencils. I've run studies comparing traditional YAG laser, fiber laser, and E-form stencils with regular stainless, FG, and nickel foils. YAG is the worse and should only be used for pretty simple boards. Fiber laser and E-form were pretty much the same down to about 0.5 mm pitch. E-form had a slight edge below that, but it was a small enough difference that the extra cost isn't justified. So that leaves fiber laser as the best bang for the buck. I wasn't able to see any difference in print quality between foil types when it was cut on a fiber laser so there's no point in paying for FG, which just increases cost and reduces the pool of stencil suppliers you can use.

To the original question, I always do a "prints before wiping" study when choosing a new paste and have always been amazed how consistently it works out to 10 prints being optimal assuming an otherwise good paste and a board that's not too complex (0402's and larger, 0.5 mm pitch QFP/BGA and larger). When the apertures sizes start shrinking or I have to use a step stencil all bets are off and I perform a quick study specific to that board.

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#66359

Underscreen cleaning cycles | 17 May, 2012

there are many reasons why FG and Nano are used and many papers written on them. Nano ssems to be the topic of interest right now. I agree it is mostly for printing fine and untra fine pitch. With that comes under stencil wiping to keep the stencil onto the board and not allowing paste to lift the stencil off contact. Chrys Shea of Shea Consulting gave a great paper at SMTA INt. in Dallas. I am not sure if this is allowed but I feel it maybe quicker. If you wish to have me send you more information and papers on this matter email me at Rob@stentech.com. I am the technical Director and have been in the printing industry for 45 years most of this in Micro Electronics. I have enjoyed this forum and thank you all for your input it is great. I am undergoing medical treatment and have to bow out. Regards to all

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#66361

Underscreen cleaning cycles | 17 May, 2012

I don't have an opinion on nano coatings since I haven't tried them. Our suppliers keep pushing it so I'll eventually check it out.

The reason I zeroed in on the FG foil is because I almost fell into that trap. Several years ago I wasn't aware the suppliers were replacing their YAG lasers with fiber, so I would buy one laser cut stencil that performed about the way I was used to then the next from the same supplier would perform as well as an electroform. I couldn't figure out why. Then I bought an FG stencil based on the hype and was impressed with how it performed. What I didn't realize was that the laser type and foil type were confounded - since the FG foils only came fiber cut I didn't know whether its performance was due to the FG material, the laser type, or a combination of the two. With later stencil orders I was able to separate out the effects and see that the FG foil wasn't what gave the performance gain - it was the type of laser used to cut the stencil.

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#66362

Underscreen cleaning cycles | 17 May, 2012

Hi again quickly. Anyone need a sample let me know ..no charge. I would be evry interested in your findings and can give many references for you to talk to..customers. Scott I am working on a project with different cut parameters very time consuming but very ineteresting. We were the first with Fiber lasers over 6 years ago we now have 10. Nano I have been working for approx. 4-5 years. PHD and FG we introduced to North America 5 years ago and is now availabe to most stencil vendors. I developed the Eform Process the same time as Xerox..benn eforming since 1993. Also team leader on building lasers. email. rob@stentech.com I will help and answer any questions anyone has present customer or not. I will also be looking into these forums as I feel it gives back to our industry. Good luck with this project than you all.

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