0201 component mass & vacuum pickup issues

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bootstrap
 
Posts: 73
Joined: Wed Jun 02, 2010 8:47 pm

0201 component mass & vacuum pickup issues

Post by bootstrap »

I am almost finished my design of an inexpensive manual pick and place device to let individual developers and startups assemble PCBs with tiny SMT components (BGAs, QFNs, 0201s~0805s, etc). I need a final few bits of information to complete the design of the vacuum pickup device.

#1: What are the masses of 0201, 0402, 0603, 0805 components? I figure the hole in the tip for tiny (0201 ~ 0805) components needs to be a blunt-end hypodermic needle with an ID somewhere between 0.10mm and 0.15mm. That's 0.01 square millimeters area, which according to my calculation means the tip could pick up about 0.004 grams for each 1psi in negative pressure at the tip. It appears reasonably good quality inexpensive pumps from china ($8 ~ $25) supposedly generate 4psi ~ 8psi according to their specifications, which would mean a 0.10mm tip could pick up components up to about 0.16 grams... at sea level at least (if that matters). My general impression is that no 0201 (or 0805) component weighs this much (a nickel coin is 5 grams), but what do I know? Do you know? If so, please reply.

#2: I have a tapped hole in the back of the vacuum pickup head where I want to screw in a vacuum fitting that has a "barb" appropriate for roughly 6.3mm ID tubing. Most of these fittings have some absurd tapered pipe fitting thread on them, which totally gross me out (probably because I'm more a machinist than a plumber). I've read many places about similar units with "straight threads" (generally UNF threads like 1/4" x 28, but also supposedly metric threads like M4, M5, M6), but I can't find any real, actual, for-sale parts. Anyone know where to find and order such things? I much prefer metal (I hate when wimpy parts break off).

#3: Anyone know where I can find air solenoids appropriate for this task? Basically I just need to toggle back and forth between "suck" and "nothing" (or slight puff or blow) each time the tip presses against a component. I figure it might be wise to have a [bag | jar | box] on both the vacuum and positive pressure side: on the vacuum side just to act as a capacitor of sorts (don't think I need this really); on the positive pressure side something that leaks a lot and thus just has a little pressure to blow the component off the tip once it is placed (again, perhaps not necessary since the component should probably "stick" somewhat to the solderpaste). General advice about these subtleties welcome.

#4: Anything I should know about what kind of tubing to get for this? I'm guessing 1/2 atmosphere isn't enough to self-pinch even modestly strong wall tubing (but probably surgical rubber tube would collapse), but again, what do I know? Any suggestions on this? I much prefer a tube that is highly flexible and inexpensive. I'll probably need a length of 24" to 72" depending on where people like to put the vacuum pump (typically about 4" x 3" x 2").

#5: For people with pick-and-place machines. Any idea how few different ID vacuum tips is sufficient to pick up everything from 0201s to 50mm square BGAs? I was guessing "maybe 2", "probably 3", "at worst 4". But again, what do I know? Not much.

#6: Who laser cuts the thickest nickel or stainless steel soldermask stencils? I think this is the best way to make component templates. They are 60mm square, and probably 0.50mm thick is sufficient.

PS: I added solidworks 3D images of my latest design in the appropriate thread.
Last edited by bootstrap on Thu Jun 23, 2011 3:59 am, edited 1 time in total.

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westfw
 
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Re: 0201 component mass & vacuum pickup issues

Post by westfw »

My general impression is that no 0201 (or 0805) component weighs this much
Well, 0805 is about 2mm*1.25mm*1.25mm (max thickness?), or .00312 cm^3. If it were made of Osmium (densest element, 22.5g/cm^3), it would weigh 0.07g. I think that makes it pretty safe to assume that no such component would weigh more than 0.16g ... :-)

bootstrap
 
Posts: 73
Joined: Wed Jun 02, 2010 8:47 pm

Re: 0201 component mass & vacuum pickup issues

Post by bootstrap »

Doh! Good point. :-)

I guess now all I need to worry about is whether there is significant loss of pressure due to the vacuum being routed through a rather long tube. I guess my intuitive sense is, this should make any difference in the ultimate vacuum level, only the rate at which the pump limited level can be achieved at the time. Given the small tips have such tiny openings, I'm thinking this is not an issue either.

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