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May 23, 2019 | Step-up stencil: recommendation thickness A little hard to tell without knowing your part details and behavior and your PCB design. I have seen part warping so much that will show opens joints on the sides and short in the middle at the same time. Theoretically you should have area ration of 0.66 when you design your stencil, which in your case should be 11-12mil stencil. However if the part is warping a lot or having a lot of metal volume in BGA balls, it might start shorting before the 10 mil paste height.
May 21, 2019 | Step-up stencil: recommendation thickness Hello Greg, Here are a few questions and advises that might post an answer: 1. How thick is your current stencil and what is the part that requires that thickness? 2. Can you use a carrier to keep your board straight and avoid board warpage? May be even use stiffeners? 3. If you have to print over on the large BGA go from 4 to 6mil or from 5 to 7mil stencil thickness in this area.
Sep 6, 2018 | Have any paper or data talking about "BGA Stencil design guideline for avoid bridge"? Dear davef, All of this are takling about how to improve release solder paste, Area ratio, aspect ratio...etc, but i want to learn the "When design BGA stencil which the safe air gap between solder paste in difference stencil thickness", this can help engineer design the maximum solder volume
Sep 6, 2018 | Have any paper or data talking about "BGA Stencil design guideline for avoid bridge"? I'm no expert but I think you will find the majority of discussions around BGA & good printing results focus on the PCB design and things like tented vias and pad definition. e.g https://macrofab.com/blog/bga-pad-creation-smd-nsmd/ After that, work with your stencil supplier to create a stencil
Aug 22, 2018 | Stencil life require a programmer. Maybe it can be done with excel: scan stencil (if you have barcode, or input manually), scan order (or input manually numbers) and it counts all orders. Then conditional format if the count exceeds 50 000 prints - then stencil becomes red. This is the simplest i could think of.
Mar 1, 2018 | Stencil-less printing? However the OP is talking about a machine that replaces a placement nozzle with a dispense head. This is a $20k upgrade that runs at a fraction of the speed an inline stencil printer or Mycronic dedicated dispensing machine. Essemtec offer a similar option (actually I think their options might be better). However replacing a printer is not their primary market, instead these machines are aimed at PoP, 3D assembly, glue dispensing, PiP or cases where additional paste might need to be dispensed after stencil printing. Certainly you could replace a printer for low volumes, but that won't help
Feb 16, 2018 | SMT Stencil Design Hi Ameen, Have you tried talking to your local stencil fabricator? they tend to have rule sets built up over years of experience. We are very lucky in the UK to have excellent, very knowledgeable suppliers. Also, stencil design rules are built in or options on the leading process preparation
Nov 9, 2016 | Help understanding something about stencil orientation when printing between those two long apertures is too close on the stencil anyway. I'm considering increasing the stencil thickness so I can reduce the aperture size but it needs a lot more work before I make any real decision. Anyway, thanks for your kind reply. Regards.
Sep 19, 2016 | Hi Shriram, Are you saying that there is a trace running between the pads for this 0603 capacitor? If so, this design may be causing a gasketing issue between the stencil and the PCB. The uneven height prevents the stencil from sitting flat on the PCB. This unevenness will cause a little more paste to leech out between the stencil and the PCB with the end result being mid-chip solder balls. You are correct to try a home plate aperture as a prevention. It's a cheaper alternative to redesigning the PCB.
Apr 19, 2016 | We are using Vicor SMT J-Lead VI Chip which is big component on the bottom side. The manufacturer recommends to have 6 mil stencil but the customer required 10 mil stencil. The PWB has gold contacts on both sides. We noticed some mini solder splashes or solder spot on the gold contact area on both sides of PWB randomly. Do you think it is due to the thick stencil that we using? Thank you in advance for your input.
Jan 28, 2016 | I would challenge anyone to present a legitimate cost justification on one of these machines that was not related to a very specific product/project. In other words I want to see what the advantage is $$ wise purchasing this machine over a screen printer and stencils for general paste deposition . We order 5-10 stencils a week. We have over 2000 stencils in a small footprint. We use space saver frames. The cost for this machine simply remains too high.
Sep 16, 2014 | Hi there, It looks weird how you handled the problem. Just a thought, but would you check the stencil and may be recut a new one, making sure you have the image exactly in the center and have the fiducials exactly where you want them and the frame size is exactly you want(I would start from gerber files and trace and measure everything about this stencil). To me it sounds like your stencil is on the edge of some parameters of the machine and once you go there it will reject your board. Regards, Emil
Aug 20, 2013 | I believe that Rain-X contains silicone and Nano-ProTek solution does not. I did speak with a field service guy for Nano-Protek and he told me the special coating test pen that they offer is just a sharpie with their logo on it. Thats how I test to see if my stencil coatings are still there and it has worked so far. Also, in my experience, and his, alcohol does not remove the coating. As that was my initial reason for calling. I have only noted a significant improvement to a coated stencil with some fine pitch apertures on thinner stencils (4mil) when we were experiencing insufficient solder
Mar 29, 2013 | Worked on these for many years as a Speedline FSE, now doing my own thing. You could have motion or alignment issues in the printhead. The setting in the INI could be wrong, but unlikely. Or are you just using the wrong squeegees. Without a stencil and power off mount your squeegees, remove the top cover of the print head and use the belts to lower the squeegees all the way down mechanically. Then take a stencil slide it into the machine and make sure the edge of the squeegees and lower then the bottom of the stencil.
Feb 19, 2013 | I'm not sure of the timeframe with which you have to work, but I'd consider sending the frame and mounted stencil back to DEK for repair. I'm not a huge fan of these systems, because I believe consistancy in the process is critical, and these systems leave too much up to the operator's own judgement and interpretation. (I know....training, training, training!) I understand their role, and appreciate the space saving that they can offer in stencil storage, but this solution is just not for me and my processes. (Then again, I have the luxery of working for an OEM and currently only have to worry about storage of about ten stencils)
Dec 8, 2012 | I don't know what is BOC (may be I know it by another name...), but: 1. Check placement coordinates by camera (if your mounter can do it) and tune it if they have a problems; 2. Check your stencil - it can be a mistake during stencil cutting (very small chance if you use laser cutting stencil); 3
Jul 10, 2012 | until you know if you stencil does align with the pads on the board all the fids in the world will not help you. registration is key. We do it a lot at our facility in Toronto as we have lots of measuring equipment. In cases like this. We lay the stencil over the board to check for alignment. We also measure distances from point to point using the original and edoted gerber files. We also measure from the fid to a point or points to make sure the fids are in the correct location. laying the stencil over the board on a flat workbench is pretty easy. I usually use a 40x shop scope for alignment.
Feb 3, 2012 | > Thanks very much everyone. > > I'll try out a > 5mil and see how that goes. If you are using 6mil stencil and you are saying that you need more on the 0603 parts then you might want to look at your squeege pressure. What kind of squeege blades are you using. You could be putting too much pressure on the blades to the stencil and causing the blade to dig in the aperatures. We actually use 4mil stenicl for 0603 and under. When using 6 mil stencil on 20mil pitch parts you should be causing your rework deprtment a lot of short removal steps.
Dec 9, 2011 | Stencil-PCB Alignment Mehods - Printing process didn't understand what were the techniques used to align the stencil with regard to the PCB (or to align the PCB with regard to the stencil). Which features and processes are used to make it happen? Many thanks in advance for your answers. Kind regards Alexander
Oct 13, 2011 | Ease and consistency of applying solder paste to the board is depends on the layout. With adjacent components being as close as 0.5 or 1mm from the BGA, its difficult to say the least, to position a stencil and paste the board. Applying solder paste directly to the spheres of a BGA either via a stencil or dipping it in paste (much like flux) makes life a lot easier. >>We put paste on the board at SMT to solder them on initially. Then not when they get reworked? When assembling the board, solder paste is applied to the BGA and all other SMT pads since the stencil was fabricated with those
Jul 8, 2011 | It's a $40 adder to my stencils if I have them apply it. But I've just discovered that if you have THEM add it, they add it thru a stencil and only apply it to the appertures. (My guess is they do this because it allows them to use much less material and therefore save $$) If YOU add it you can coat the entire stencil. This has enabled me to reduce squeegee pressure slightly. It does seem to work in my application. I'm just curious what others have noted.
Mar 22, 2011 | Stencil Inspection I've never done flex boards so I cant't say what tolerances you would need to maintain. Does you stencil manufacturer provide a QA data sheet with your stencils? If so I would specify to them the critical apt sizes in areas and push it back on them to show you the data when you get your screens. I
Nov 1, 2010 | 0.4 mm Pitch BGA stencil design I've searched the archives and maybe my search skills aren't up to snuff but I couldn't find much. I'm curious what people are doing for 0.4 mm pitch BGAs, assuming a type 4 paste. Pad diameter? SMD or NSMD? Stencil thickness? Aperture diameter? Using step down stencils? I've been playing
Aug 31, 2010 | If the batch cleaner is truly closed loop, then 100% of all of the process fluid (water) is captured, filtered (particulate, carbon, resin) and reused. This answer is based on a traditional closed-loop batch cleaning system with an integrated water recycler running without a defluxing chemical . In this configuration, all process water is recycled. Cost of any cleaning system is based on the following criteria: Cost of machine Cost of electricity Assemblies per load (based on size and equipment’s cleaning performance) Cycle time Filter (carbon and resin) life Filter (carbon and resin) replacement cost I do not know your assembly’s size but I will base an estimate on an average size of 4”x9”. I will also base the machine’s specifications on one that we build (others may be different). I will also make the assumption that the closed-loop recycler is integrated into the cleaning system. Finally, I
Aug 16, 2010 | Hello, i don't know if is possible to dispense paste but for reduction of cost we use a diferent type of stencils, from aluminium of 0,2 mm, purchased from a typography of newspapers. Ofcourse the pcb for what we use this stencil are simple. But this stencil is very cheap because it is already
Jun 2, 2009 | We have been doing BGA's for years now, and I would suggest updating your profile and place a thermal couple on the BGA, keep in mind the bigger the part the more heat it will need, We stencil print all of BGA's from simple bga's to complex ones, your stencil provider if they know what they ware doing will be able to work with you on the stencil thickness. (DEK Rules), I also place BGA's without solder paste. Heres the most important trick to BGA's BAKE them first, they hold more moisture than any part i have seen. Hope this helps.
Jun 1, 2009 | Stencil Design Hello there, I have a new board, fairly heavily populated with a number of FPBGA on it. The smallest has a pitch of .4mm.I have 3 questions, 1st what is the best appeture for this small pitch. 2 Will type 3 paste work or will I need type 4, and finally what will my stencil thickness be. We usually run around 5thou but I think this might even be too thick. Electroform is the way for the stencil but not sure of the thickness
Jul 28, 2008 | Your problem is being caused by to much paste being printed.Reduce apeture size on stencil. http://www.shanelo.co.za/technical_paper_about_stencil_de.htm or
Feb 18, 2008 | Inspecting a new stencil We do like Chunks says only a little bit different. Our stencil supplier e-mails us a "confirmation PDF" before processing any order. If it's a simple board, I just make sure all the apertures are there by comparing to board. If it's got a ton of apertures, I request the data they will be using for stencil manufacture, print it 1:1 on a transparency and overlay it on the board. Never had much trouble.
Feb 14, 2008 | Stencil Design Question Maybe what you could do is have the stencil contain a tightly spaced mesh or grid of openings over the ground plane areas that you need to be solder covered. Also, to help the solder flow out better, you might want to decrease the percentage of metals in your solder paste which will increase the flux volume and help the solder flow out. I've attached a image of what I'm thinking. The stencil should be pretty stable even with the mesh or grid... Steve Gregory
Dec 11, 2007 | Stencil Thicknes vs. actual solder height measurements Hi, If I were working with a 75 um thick stencil, Is there a spec. as to what the maximum value allowed on actual solder height measurements? Stencil type: Laser cut and electropolished Solder paste type: Type 4 Sn-Sb Would the measured values vary with type of components or would be a
Jun 15, 2007 | Stencil Thickness We have not processed very much 0402 size components in the past. We are finding that alot of our customers are upgrading their circuits and going with 0402 size parts. We recently processed one such circuit and odered a paste stencil 6 mil in thickness. We found that this thickness was okay in the past dealing with our mostly 0603 (and up) size components, but found that on our 0402 size parts was depositing too much paste. Does anyone know what stencil thickness would be appropiate for a 50/50 mix of 0603 and 0402 size components? Thanks
Apr 12, 2007 | Hi aj, Pete is right, there are several variables that can affect your quality when it comes to stencil design. A good idea is to have a stencil made with various designs incorporated into it. A lot of engineers like the reverse homeplate design. It provides a good area of paste to mount to without tomb-stoning, and doesn't solder ball after reflow. Depending on your application, I would think a 5 mil stencil would work well. If anything it's a starting point.
Mar 31, 2007 | Are you observing stencil design rules with regard to aspect and area ratios? For more: * IPC-7525 - Stencil Design Guidelines * A previous discussion http://www.smtnet.com/forums/Index.cfm?CFApp=1 &Message_ID=24848 * Other postings on stencil ratios in the fine SMTnet Archives can be found with SEARCH
Mar 30, 2007 | To use a mini stencil, or not to use a mini stencil. We have had issues with using the ones from Best. The holes are not always cut correctly and the edges (inside the holes) are not well defined because of the kapton material they use maybe. Plus you leave the mini stencil on the PCB under the BGA which could cause problems potentially with some
Mar 8, 2007 | If you are in the middle of a run and can't get a replacement stencil there immediately, you can always put a little kapton tape on the bottom of the stencil to mask off a portion of the DPAK pad and reduce the paste deposit. We have had to do this from time to time when the stencil guy (me) makes
Dec 15, 2006 | to be two times more than �gap-wall� volume. Stencil design is very critical thing to think about. Overprints together with stepped stencils are widely used for PIP. Calculate stencil thickness and make overprint and at least 50um step above your THT. It should work. BR, Pavel
Sep 15, 2006 | Stencil cleaners. We're all tool unless we own our own companies. Even then you're just the customer's tool then. At least every tool has a purpose. Some maybe rusty or outdated, but all have a purpose. I also agree with Kevin though, I too have never seen a stencil washer bend up a stencil. Granted, I guess
May 2, 2006 | I have experienced the exact same problem with excess solder touching the plastic component body. The solution in my case was simply to replace the stencil. I was using a reusable stencil frame that had been worn out. I replaced the stencil with a solid DC 20x20 frame and have not seen this problem
May 1, 2006 | ....am I reading this correctly? "Screen Printing" or "Stencil Printing" Screen = agree = off-contact.....it's fuzzy going back into the memory banks to the early 90's. Screen mesh and emulsion will stretch to produce the gasket affect while snapping off to release the solder for a crisp print . Stencil print. Disagree. On-contact = preferred method. Need gasket function of stencil; foil is not as elastic as mesh and do not need to snap-off because there is no mesh interfering with the solder paste.
Apr 18, 2006 | Standard for Stencil printers edges pressure Hi guys: I'm trying to get the recommended pressure for stencil edges using air compression, I'm working with I-source but they don't have any standard like IPC or something that can help me to use and decrease the replacement of stencil because of wrong setup. The pressure they recommended is 35
Dec 14, 2005 | Fine Pitch Stencil Design Aperatures are often best decided by the stencil manufacturer principally because they would know what is easiest and best for there laser cutting machines, why would i dictate to them something that would not work well for there machines. but are you really going to let a stencil maker tell you
Dec 14, 2005 | Fine Pitch Stencil Design "find yourself a good stencil manufacturer its there job really just tell them what machine you have and they should do the rest." I have to dissagree with this last statement on so many levels. There's a reason why it's called engineering. Plus, when your boss is asking for your arse cause you have 40% fallout for solder shorts, will you really have your stencil maker come in and figure it out for you?
Jun 10, 2005 | Stencil design for Right Angle LED Hi Guys..
Does anybody had experienced with designing the stencil for Right Angle LED without any dewetting problem on the LED termination? Currently our stencil opening is 1:1 and we still got so high reject due to this problem.
Pls Advise, thanks
Link: May 2, 2005 | ...when loading, unloading, and positioning the stencil, two pins drop from the print carriage - these pins are dropping ON to our adaptor, instead of in front of it, as they do with a 29" stencil. Interestingly enough, it's roughly a 5" offset, as well - the difference between our adaptor length (24 ") and the normal 29". This is all despite it being dimensioned as 24" in the stencil setup.
May 2, 2005 | ...when loading, unloading, and positioning the stencil, two pins drop from the print carriage - these pins are dropping ON to our adaptor, instead of in front of it, as they do with a 29" stencil. Interestingly enough, it's roughly a 5" offset, as well - the difference between our adaptor length (24 ") and the normal 29". This is all despite it being dimensioned as 24" in the stencil setup. Yerg.
Apr 15, 2005 | Cleaning of PCBA's Shean made some good points and offered some good starting resources. Adding to what he said, I would also mention that many times, even a no-clean flux can cause contamination that requires cleaning. Our lab has dealt with numerous cases of clients that use no clean fluxes that are not getting fully activated, and are left to react with moisture on circuit boards to create reliability issues. It is not the easiest task, but even a no-clean assembly can be cleaned if needed. Whatever the flux chemistry is, it all comes down to the amount and type of residue that is on the board, which can
Apr 14, 2005 | Cleaning of PCBA's Hi John, A primary consideration is the type of flux you are using. If it's water soluble (organic acid) then cleaning is highly recommended. Any other flux that fails the copper mirror test, we'd strongly recommend cleaning. Passing the copper mirror test though doesn't mean a flux should not be cleaned, other factors should be considered such as bulk residue and its effect on the circuit and test. Many factors contribute to why a company does clean. They basically boil down to reliability and yeild. Field failures, production yield, internal manufacturing problems related to testability
Apr 1, 2005 | A company called BEST makes a thing called Stencil Quik. It's like a stencil that sticks onto your board, you squeegee paste, place component/board and reflow. The Stencil Quik remains on the board. It prevents shorts and in your case could provide support. Take a look:
Mar 15, 2005 | stencil printing SPC Thanks for your reply. We are using EKRA E4 Inline Automatic Stencil Printer. It is Capable of Automatic stencil inspection. 2D solder coverage inspection. Fix Squeegee angle at 45 degees angle. Programmable squeegee speeds and pressure, boards snap off speeds,etc. We did very little DOE
Dec 15, 2004 | DEK/Tannlin Vectorguard stencils We have switched from IIT pro-plates to QTS stencils. lots of companies provide them. We still buy from IIT, they have been one of the best suppliers we have had. The single axes tightening just does not get it anymore with the super small parts we have to deal with and needing to rotate the stencil between an auto line and a semi-auto line due to wiper direction. The wizard system works pretty well. I assume Dek is pretty similar, just more expensive. When IIt came out with thiers, Alpha had one that was pretty much the same. I have both but the Alpha was customer supplied and equal except
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