...
It's very likely your paste is too much on the pads. Even with hand stenciling and hand pick and place, I don't have shorts even with 0.5 mm pitch TQFP.
Usually for less crucial parts, I left the paste opening at -5% only with 0.125 mm stencil thickness.
Mr Bootstrap
you said
" An added irony is, some of those projects would be excellent components for a precision pick-and-place machine (servo controller/driver with encoder inputs and robotics vision system camera at the very least)."
You are clearly inexperienced with all aspects of this stuff- but making wild claims.... especially your belief that servos and closed loop is required. If this is from your own experience, your implementations have been flawed.
I'd suggest you go and read the following forums end to end, yes all 20 to 40 pages on eevblog
:
Neoden 4 forum
smallSMT forum
TVM 802B forum
and then go into say the DIY cnc forums and see what those guys are doing with regards to accuracy and precision and what they're using.
then go and consult all the tech manuals of all the mfrs of belts, belt drives, ballscrews, linear guideways.....
and then go and do the numbers on exactly what is required. You'll find if local datums are used and sensible motion practices are used, it is not a difficult job considering that the placement head requires no dynamic accuracy , only static.
You seem fascinated by needing closed loop and servos when the reality is, depending on the choices you make and the speed this may be entirely unnecessary (or indeed entirely necessary ) if you understand the technology rather than... guessing.
I'm actually suspect of your motives in this forum. Can you let us know if you work for a high end manufacturer?
Hi Spikee
Advanced Assembly asked me to put some local fiducials nearby the 0201s I had on JESD204 thin traces.... on a big area board
IE I had global fiducials and local fiducials- which makes alot of sense.
Saleae logic tried to do in house assembly of many 0201 components in house with a brand name 60K pick and place and dit not have good luck with that (see blog posts / their theamphour episode).
Doing 0201 reliably could be possible if the software was more advice. But it is not.
Backslash and things like that can be compensated for is software without much issue. And than you are not even using the vision as additional compensation.
Feeding / pickup issues can also be detected in hardware or in software (via vision). Did the pickup for 0201 passive not work? , just let the feeder peel another part, let the vision detect the position and pick it up.
One weird idea that came up in my head is:
Get it to scan the whole (empty) pcb and make a high detail stitched image of it. The idea of that is so real time vision positioning could be used instead of purely relying on mechanical accuracy. ... or just get it to quickly re-calibrate via fiducials every time you want to place a very small component.
Having a good camera that that can autofocus / has good resolution is key in that case.
or even fancier add more camera's to the head (for example one in each corner) and do a full (realtime) stitched image. In this way you can calibrate the offset for each part using all the fiducials on your board without doing additional movement or even loose placing speed. (assuming you can see the whole board with those four camera's (or just use ... more fiducials))
In other words if you have good vision / software you do not need super expensive fancy closed loop servo systems with glass encoders and exotic granite pnp bases.
For 0201's and 0.5mm BGA's I think you should look for something other then the Neoden4. Consider spending real money, not buying one of the cheap machines. The Neoden4 is actually pretty capable when dialed in and you figure out the software oddities etc but really doubt you'd get the results you want with it.
Thanks. Do you have a neoden4 or work with pick and place machines? I'm just curious what your reasons are for giving this advice.
I've created a number of precision mechanical systems in the past, including advanced automated telescopes that have to do some rather amazing things very precisely (I'm sure you realize the earth rotates, so both satellites and astronomical objects in the sky are constantly moving, and need to be acquired and tracked precisely if they're being photographed... sometimes for hour+ exposures). So I understand precision mechanical systems, and I've created both open-loop stepper and closed-loop servo systems before (often with DC brushed "pancake motors").
I've created a number of precision mechanical systems in the past, including advanced automated telescopes that have to do some rather amazing things very precisely (I'm sure you realize the earth rotates, so both satellites and astronomical objects in the sky are constantly moving, and need to be acquired and tracked precisely if they're being photographed... sometimes for hour+ exposures). So I understand precision mechanical systems, and I've created both open-loop stepper and closed-loop servo systems before (often with DC brushed "pancake motors").
With all that experience, you should build one.
Come and join the fun with the openPNP project, theres lots going on, and some amazing results.
Come and join the fun with the openPNP project, theres lots going on, and some amazing results.
Is that your project? If so, where are you located?
Come and join the fun with the openPNP project, theres lots going on, and some amazing results.
Is that your project? If so, where are you located?
No, its not "my" project, but im using it.. I'm in New zealand, but there are people in Europe, USA, Australia, Canada, UK...
Come and join the fun with the openPNP project, theres lots going on, and some amazing results.
Is that your project? If so, where are you located?
No, its not "my" project, but im using it.. I'm in New zealand, but there are people in Europe, USA, Australia, Canada, UK...
I assume OpenPnP is only software, correct?
If I do decide to make a pick-and-place machine, I would certainly be inclined to adopt as much open software, hardware and mechanics as possible.
With all that experience, you should build one.
I am so, so tempted to do so, partly because I need one (lame excuse), but mostly because I am finding the various aspects of pick-and-place machine operation fascinating. And as a few of my recent posts indicate, there appears to be enormous opportunities to create different configurations of pick-and-place machines to make cheaper precise [but probably not fast] units.
Frankly, if I had one or two talented partners on such a project, I'd probably buckle and go for it. I wouldn't be surprised if we could build a new pick-and-place machine from scratch for roughly the same I will probably spend on the complete production line (stencil-printer, pick-and-place, and reflow-oven). As with most projects, the problem is TIME.
One weird idea that came up in my head is:
Get it to scan the whole (empty) pcb and make a high detail stitched image of it. The idea of that is so real time vision positioning could be used instead of purely relying on mechanical accuracy. ... or just get it to quickly re-calibrate via fiducials every time you want to place a very small component.
Having a good camera that that can autofocus / has good resolution is key in that case.
In other words if you have good vision / software you do not need super expensive fancy closed loop servo systems with glass encoders and exotic granite pnp bases.
For cameras it would be good to actually use a machine vision camera as these have features that are quite nice to have in such application. Some even have the capability to do the lens correction itself. (like matlab vision can do) otherwise you might have to do that processing yourself in realtime which can probably take quite some processing time. This feature gives a corrected image where the lens curvature is gone. This can be quite useful.
I agree with glenenglish, this smells like bullshit. A seasoned linear motion engineer would start small and humble to understand his needs. A "2-3 weeks read of forums" planning is ridiculous and even more ridiculous is asking newbie questions then three sentences later reveal how the industry should do it according to your standards.
ADMIN NOTE:
As requested I have moved bootstrap's recent posts to a new thread.
ADMIN NOTE:
As requested I have moved bootstrap's recent posts to a new thread.
I don't see it. Can you provide me a link or something to help me find it? Thanks.
PS: I assume it would still be within "Manufacturing and Assembly".
PS: Found it, but this is a thread about ideas, not products. Can it remain under "Manufacturing & Assembly"?
Thanks Bob, do let us know if it works out.