Solder Paste Stencilling - This really sucks!
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- เผยแพร่เมื่อ 29 ก.ย. 2021
- Applying solder-paste is THE most important step in the PCB manufacturing process... So why is it so hard to work worth stencils? Why does one have to invest in $20k + stencil machines to be able to reliably align and flatten a stencil perfectly on a panel????
This really sucks!
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The non-transferring of paste correctly is indeed THE most frustrating part of manual stenciling. Have many bad boards to prove it. So much time is wasted in rework. This is a great project! thanks for sharing.
Impeccable timing. About to tackle this exact issue and can now spend the weekend making a vacuum attachment.
I saw your tweet, I thought it looked like a vacuum attachment, then I thought "what do I know". Glad you found a working solution for your problem Seon.
Well, it's still a WIP - but so far it's looking really promising :)
A great tip, *especially* the part about 3D printing alignment jigs! Brilliant to use the vacuum too: I’ve done the same for contact-printing film negatives with extremely fine detail on them, but I’m not sure I would have thought to extend it to solder stencils on my own…
I did something simillar for my one off frameless stencils. I 3d printed an air bed that fits my boards and has a lip the same height as the board around the board edge. I put channels in my boards to allow suction at the middle of the stencil. I use a mini pump for fishtanks, the kind they have for sucking air out of over the back syphon overflow boxes.
Actually really cool idea. I do by the tape flap method with boards around it as a jig. Works alright but this looks good for tighter pitch stuff
I like this idea Seon. So simple and effective.
Cheers Michael! I hope you are well :)
Mother of invention! This is killer for non-framed stencils. Consider a bleeder valve for aligning then close for paste. You just saved hundreds of dollars for makers who are considering stencil printer, now they just need some PLA. I thought your part turntable was clever but this tops it. Well done. Thanks.
Cheers mate! It's still a WIP... but in time I'll refine it for both framed and non-framed user and I'll keep everyone updated on my progress.
okay now that's a cool solution. Not that I've encountered it yet but still pretty cool.
This is why I go frameless on small boards and use the tape flap. A stencil that is much larger than a board will have a warp. A small stencil will sit completely on the board with no outside pressures from a frame.
Ha I was just playing with a vacuum forming machine for the same thing! Nice solution
Please let me know if you make any progress with something that isn't run off a Vac. Though I am aiming for a DIY solution, and everyone has a vac somewhere :)
That's pretty cool. Does the vacuum bleed the paste under the stencil at all?
You can probably do that. It depends on the strength. My vacuum cleaner is adjustable and i have not had that problem yet. But if the suction is two high, i guess you could atleast pull the flux out of the paste if you leave it for some time.
Nope! Not with my initial tests. I'll show more soon once I've printed the next revision that has a way for me to clamp down the base to the stencil printer.
I was more thinking about if it pulled through a via. But I've tested pulling vacuum on pcb by using cheap barometers with an ABS housing over it with O-rings. The via's are the things to look out for. So if they are tented on the opposite side if there is a via in pad I don't think there would be an issue for pulling paste through.
Hey Seon -- I have to admire you doing this pioneering exploration and sharing it with us! I'm a little concerned that the suction would suck excess solder paste through the stencil, especially if there are through-holes or slots in or between the boards of the panel. So I'll be interested to hear what you observe in that regard. Also -- might there be a role for magnets to hold down the stencil -- rather like the flex plates for 3D printer beds? I wondered if the magnets would attract the stainless steel stencils, but I tried a couple here and they do seem susceptible to magnets.
I'll have more to show over the next few weeks :) Yes the stencils are a tiny bit magnetic... def not enough to be useful for anything I don't think, but maybe?
@@UnexpectedMaker hmm i forgot that tin is magnetically susceptible, so magnets sufficiently strong to hold the stencil might disrupt the solder paste.
Nice, I have worked with vacuum test gear that pulls PCB's down onto the bed of nails and this is a great implementation, The company who made the gear is called ' Wayne Kerr ' no joke, it was named after the actor John Wayne and actress Deborah Kerr as the two guys who founded the company were big fan's ! I look forward to your further refinements....cheers.
Wow, what an unfortunate name !!!! hahhaha
Maybe you can get one of those variable speed vacuums, lower noise if it docent need to run at full speed.
A top tip working with "vacuum" When you get closer to the final solution, add a pressure sensor to measure what level of vacuum you achieve. Suitable for repeatability and simply do not trust only your eyes and fingers. Cheers.
Seems a excellent solution that is most probably a great improvement over the present manual method.
Only immediately ppssible issue is sucking paste sideways between stencil and pcb, may remain no issue.
Probably mainly at outer boundary or regions of drilled holes of the panel. Especially if any residual burs are left from routing, drilling or V groove , or even micro height lift of stencil from text print/ resist layer. So careful control neede on amount of vaccum versus minimum needed to ensure flat holding effect.
Next issue is effect on e vaccum is off and the stencil lifts away due to any bowing or misalign of stencil frame or bowing of pcb, if adhesion of paste is imperfect, to same effect as former non flat stencil, retaining paste in stencil holes.. Though should be no worse than complete lifting of stencil to remove the panel
Yup, lots of further experimentation required.. this is definitely just a WIP for now, so I'll definitely follow up with working examples once I iron out a few challenges - like keeping the unit locked to that miss-aligned metal plate ;)
Seon, If you make sure the panel has holes or cut outs between the individual boards would the suction on the the stencil be better?
Brilliant Seon, thanks for sharing, gonna think about this for my pasting setup. A milled block would be something I would purchase if available rather than 3D printing one..
Cheers mate! If only I had a CNC ;)
I may tackle giving this a try on my cnc. Literally came here after having the exact issue you experienced!
Really cool!
Well that just sucks!
Nice work with the design.
wow I always assumed stencil frames were like screenprinting and it pulled it down hard against the pcb, but yeah I suppose they are not flexible enough and wont stretch but bow instead..
Been doing this for years; I just assumed it was industry standard. The first engineering company i worked for did screen printing of dials upstairs, so whenever i had to solder paste a board i just went upstairs and just threw it on a vacuum table and stenciled the board, i do like the board jig though.
Same been doing this years by hand. The place I worked brought in silk screen printer guys to train us up. Leart alot but mostly cleaning the stencil between uses for fine pitch work used to be key.
Hi, Seon! Excellent setup, thanks for sharing! Do you have some sort of filter to prevent solder paste from getting sucked into the vacuum cleaner, or is it not really a concern because hardly any paste would be sucked in?
No paste should be sucked in... it's transferred directly to the pads and once the stencil is lifted, the vac pressure drops right off as the holes for the stencil are uncovered. If you have excess paste that would go into the vac, then you are applying WAAAY too must paste anyway..... ;)
@@UnexpectedMaker So you don't use paste-in-hole at all for your USB connectors?
@@KeanM Yes I do, but there is no holes under the USB connectors.. so no paste gets sucked through... and once the stencil is lifted even a tiny bit, the vac pressure drops heaps as it exposes all of the holes that hold the stencil down. So combo of Vac off, and stencil lift means no paste is sucked anywhere.
@@UnexpectedMaker I expected as much, and the simple solution is just a little forethought in alignment (and/or some hole blocking). I just thought it weird you didn't mention it.
I cut about 8mins of stuff from this video to keep it short-ish. I also didn't mention it's fixed height, where the top panel holder has cutouts for the different thickness panels, so I'll never have to adjust the stencil height when moving between 0.8mm, 1mm, 1.2mm and 1.6mm PCBs ;)
I'll make more videos about this as I progress the design.
I suspect the thumbs down came from a specific pick and place manufacturer that we all know well.
hahaha, nah, prob from Neoden cause I complained about their holes being non-uniform :)
@@UnexpectedMaker I was surprised to hear about the hole spacing uniformity. Leads me to think it's cast with a machining final step.
Have you had any thoughts on the "open" nature of the project? Still to be decided?
Why can't you make an array of neodymium magnets embed into the plastic base so that it will hold the stencil in place without any air gap?
Because a stencil is not magnetic?
is there any possibility of paste being sucked in by the vacuum and smearing on the PCB
You definitely don't want vias in pads here!
My pet hate is watching people spread paste over their stencil like they were painting a wall i.e. going over and over and in various directions.....all the time pushing more and more paste down and under the stencil with each subsequent swipe......aarrgghhh! what a mess.
If set up correctly and with a wide enough spreader, then one swipe across the board is all it will need.
PS. Have never tried a vacuum table, looks great!
Yes, ideally it should be a single swipe, but that's often hard to do... but with a stencil that's sucked to the PCB like this, multiple passes because less of an issue ;)
I have been using this method myself the last year six months and it works pretty good, however, it's not perfect. The problem I have is that the vacuum finds it way to the stencil cutouts, which means it will suck out the solder paste from the holes. My solution is frameless and I adjust the vacuum so it's as low as possible without the stencil moving around. I have managed to get some flawless solder paste applications, however, now when I just purchased some new solder paste, the viscosity dramatically decreased and the sucking of solder paste from the cutouts got very apparent. Have you had any experience with this problem? Any solutions?
Somewhere I can purchase one of these?
But isn't a bit of leakage in the vacuum table a good thing? Bad for the vacuum pressure but non shop vacuums use the suction airflow for cooling the motor...
That is actually Genius
seems to me like a vacuum table and a frameless stencil with alignment pins might be a winner here? just pop it on over the pins and you're done. no clue how accurate the manus get those pins tho.
That would work for one offs, but not for production runs... production needs a slot in, paste, remove, repeat process that doesn't require any alignment changes between. But lots of possibilities here!
Nice work! I should probably make some videos to about mine :)
Yes you should! I've been telling you that for months!
@@UnexpectedMaker I can think it's years now. Haha
Can you make a mini shed outside your garage to house the vacuum, then run a PVC pipe to your bench? Then say: Alexa, this sucks!
HAHAHA
You should get a Yamaha YCP10, does this automaticall. It's a little bigger though. :)
Yeah, and 3000x more expensive :)
brilliant !
nice improvement. But why vacuum cannot enter the office in a silent way ...
I'm proto-typing... who cares how loud it is right now :)
Could see immediately with that overlapping frame that arrangement would flex the stencil in all directions in use, good idea with the vac, but would look to support the frame as well, in fact from the vide it is obvious that the bottom pattern is moving well, none of the arrangement is stiff enough. On the design side why are you going to ever smaller component sizes, design for manufacture just as important as design for functionality, can you really not keep component sizes to a sensible size for self build, why stress your processes more than necessary or are your boards really that densely populated?
Yes, one of my new boards is THAT densely populated and space constrained. I'd REALLY prefer to stay at 0402, which all of my boards use, but you gotta put your VDDA decoupling next to the VDDA pin ;)
Neoden wants $600-$1000 for that stencil frame holder. Is that right?
Well I want one
This really sucks...
Indeed!
Have you spoken to Christo from @Burgduino?! ;)
Nice :-)
Cheers mate!
Those panels are stainless steel ... can't you use Magnets? or electro-Magnets? ... no need for such complex machined parts for the vacuuming. Just an idea.
Wait and see :)
The stencil is not "that" magnetic... I stuck 10 magnets there and it would not hold the stencil in place, though Marius is working on something with magnets for non-framed stencils.
You still deal with CHINA? -----Ok.