ASK AN ENGINEER is LIVE now! Click here to watch our weekly show with LADYADA!

Re: super-cheap pick-and-place device with ~1 mil accuracy

by bootstrap on Tue Jun 28, 2011 2:37 pm

Rob_ski wrote:http://www.solder.net/stencilquik/default.asp
http://www.solder.net/stiknpeel.asp

There are tutorials on the website explaining how to use them. I've placed 10 or so BGA's using those having an X-Ray of each one taken after reflow. Each one has come back near perfect.
Although I have a 5 zone convection reflow oven. I imagine this could be reflowed with a heat plate and an air gun

I was confusing my Mils with mm


Yeah, I looked into those stickons, and I assume they do work (looks like they should). Unfortunately, for a PCB like mine that has a few (7) BGA components on it, the cost of those 7 stickers is more than the cost of the assembly house to assemble the PCB. So yeah, it does let you "assemble at home", but it isn't cost effective. It is potentially "time effective", assuming you order the stickers long before your bare PCBs arrive. Last time I checked they cost $7 each, assuming you don't accidentally mess any of them up. That's $50 per PCB for my PCB, and more for PCBs with more BGAs. And that still doesn't solve the same problem with QFN components (unless maybe they now have QFN equivalents... don't know).

My goal was to find a cheap and permanent solution that works for all mini-pitch, hidden-contact components. That's what my device is. I'm sure the stickers make more sense for some people, like if they only make a couple/few PCBs per decade. For others, not so much. In my case I need to make 25 of my larger PCBs (with 7 BGAs and lots of QFN-like components) to prototype larger systems and to provide [development] samples to others. So for me, even this one project justifies the manual place device and a reasonable reflow oven.
bootstrap
 
Posts: 72
Joined: Wed Jun 02, 2010 7:47 pm
Location: phobos

Re: super-cheap pick-and-place device with ~1 mil accuracy

by Rob_ski on Wed Jun 29, 2011 2:26 pm

You mentioned having problems with the nozzle head size. Have you considered making a slightly larger round nozzle with a solid end then perforating the tip so that one nozzle can handle smaller 0402 0201 sizes. If you were concentrating on QFP, QFN and BGA's in your design then the tip would have to be perfectly flat. Most larger nozzles I see for that have a metal tip and a rubber grommet around it to act as a seal. For QFP, QFN, BGA's the tip would have to be perfectly flat otherwise. You wouldn't have to worry about striking the part too hard and deforming the tip. You also might want to consider spring loading the nozzle tip so that if it does go too far on the Z axis the spring will take up the difference with out damaging the part, the board or the nozzle.
Rob_ski
 
Posts: 3
Joined: Fri Jun 24, 2011 5:36 pm

Re: super-cheap pick-and-place device with ~1 mil accuracy

by bootstrap on Wed Jun 29, 2011 5:26 pm

Rob_ski wrote:You mentioned having problems with the nozzle head size. Have you considered making a slightly larger round nozzle with a solid end then perforating the tip so that one nozzle can handle smaller 0402 0201 sizes. If you were concentrating on QFP, QFN and BGA's in your design then the tip would have to be perfectly flat. Most larger nozzles I see for that have a metal tip and a rubber grommet around it to act as a seal. For QFP, QFN, BGA's the tip would have to be perfectly flat otherwise. You wouldn't have to worry about striking the part too hard and deforming the tip. You also might want to consider spring loading the nozzle tip so that if it does go too far on the Z axis the spring will take up the difference with out damaging the part, the board or the nozzle.


Yes, we're planning to make a single nozzle head with the smallest central hole (for the size of hypodermic needle that has an ID of about 0.10mm). To make the larger 2 or 3 sizes, we'll just drill that hole out to the larger size appropriate for shrink fitting larger hypodermic needles (at least 0.50mm and 4.00mm).

We can make the ends totally flat, that's not difficult. However, I think it is better to also have a silicone rubber tube around the OD of the needle, sticking just a tiny distance further down than the end of the needle (maybe 0.25mm ~ 0.50mm). That should make the vacuum seal more secure and reilable. My only worry is whether we can find small enough ID silicone rubber tubing. Maybe we can figure out a way to start with solid silicon rubber rod and put the holes in ourselves. That might work.

In our design, the "spring loading" of the tip is those two thin spring steel plates that hold the rather large, long "vacuum pickup bar" to the linear rods that slide through the vertical axis linear bearings. The harder the tip presses against the component, the more those "compliance plates" bend. That is also how the device knows to switch the solenoid to turn on the vaccum. There will be a tiny [pushbutton] limit-switch just above the top end of that "vacuum pickup bar". When the compliance plates bend just a little ways due to pressure against the component, that will switch the solenoid between "negative pressure (vacuum to pick up component from template)" and "positive pressure (puff of exhaust air to detach component onto PCB)".

I do worry that even with these compliance plates, someone could push too hard and bend the smallest of the hypodermic needles when trying to pickup or place 0201s for example. I guess I'll find out when I test it.
bootstrap
 
Posts: 72
Joined: Wed Jun 02, 2010 7:47 pm
Location: phobos

Re: super-cheap pick-and-place device with ~1 mil accuracy

by MadmanLighting on Mon Jul 30, 2012 11:08 am

I've been following this thread for a while and am very interested in the result.

I have a home based electronics company that could use one of these machines, even if its not good enough to place BGAs and other parts needing less than 1 mil accuracy since I use nothing smaller than an 0603 part, having found anything smaller too difficult to reflow at home.

Please, continue your work! If you really can make such a machine, or a kit for such, for about $1k and its reliable enough to leave it running all day long, you've got a sale.

Thanks,

-John Cook

President
Madman Lighting Inc
MadmanLighting
 
Posts: 1
Joined: Mon Jul 30, 2012 11:02 am

Re: super-cheap pick-and-place device with ~1 mil accuracy

by mgregg on Thu Jan 24, 2013 2:05 pm

Hey bootstrap,

I know it's been several years, but have you made any progress on that pick-n-place machine you were working on?

Do you have the solidworks files for your design? I'd like to look at them. Maybe I could contribute something to the project.

Michael-
mgregg
 
Posts: 1
Joined: Tue Jul 24, 2012 1:17 pm

Re: super-cheap pick-and-place device with ~1 mil accuracy

by burdij on Mon Mar 04, 2013 9:35 am

I would be interested to know the status of this project also. I am currently working on a placer head add-on for the Shapeoke CNC platform (http://www.shapeoko.com). I was thinking of using EMC2 software (now called LinuxCNC) as the controlling software. I would like to use, as much as possible, the hardware components of that platform and Open Source software. A preliminary head design puts the parts cost at around $500 (could be way off on that, does require some CNC machining operations) so the total package for both the CNC basics and head at around $1000. It appears the accuracy would be about +- 5 mils or +- 0.125 mm. That should be able to get a 0402 size part aligned well enough on a pad so that solder surface tension will finish the job.
burdij
 
Posts: 1
Joined: Mon Mar 04, 2013 9:13 am