Placement of integrated circuits

[Luc]

The machine looks pretty interesting. I am ready to buy! But, there is not much information about the placement of integrated circuits. I would like to know what could be achieved, minimum pitch and the maximum size for: SOIC, TSOP, TSSOP, QFN, BGA, FBGA, TFBGA, QFP... Could you place other type of SMC like small FCC connectors or surface mount USB connector.

[JuKu]

Short answer: At the moment, unless parts come on tape or are relatively low precision (SOIC), the machine cannot reliably place them.

Long answer: The key words being at the moment. Technically, the problem is locating the part. The machine knows very well where the pickup needle and camera image is, but that is only half of the problem, we also need to know precisely where the parts are. From tape, the video processing can measure the tape holes with good results. For loose parts, it does not work so well. SOICs are fine, smaller pitch parts are not. I do see this as the biggest shortcoming of the machine, and I intend to do something about it.

1: The trivial solution is to find more robust part recognition algorithm(s). I'm looking into that also, but it is unsure if and when a suitable solution can be found. Like with all new inventions, we'll know we have it only when we have it, not sooner. In the meanwhile:

2: A jig based IC placement: You would place a corner of some sort on the table, and place the parts at that corner. With a table of part sizes, the machine now knows where the part is and can place them accurately.

3: Manually assisted placement: Machine takes a picture of the part, picks it up and places the image as close as the real position that it can; the user fine-tunes the placement manually. I have done some work towards this. Obviously the snapshot image quality needs enhancement, but this image tells the idea:


Both the latter methods require some operator assistance, but I don't se this a big shortcoming. After all, this is intended as a prototype building machine, not a big deal if you have to assist it on a few parts? Both 2 and 3 are relatively straight forward to implement, adding these shouldn't take very long.

[JuKu]

I will implement this as soon as I can. Also, the same idea works for BGAs and other chips wih pads on the underside, using the up looking camera.

[Luc]

I am not an expert at vision and placement algorithm, but here is one solution I am thinking about.
1. Fix pièces of metal, wood or plastic to form a corner
2. Place the part carefully on the corner
3. Assuming the machine knows the position of the corner and the part, it should be able to precisely compute the center to pick the part
4. Since the machine picked up a perfectly centered part with exact rotation angle, it should be able to place it
- the placement could be manually assisted
Does this make sense?
Here is a link to an image:
[Moderator edit: Right click the link and open in another tab/window. The link below does not allow coming back here with a back button.]
https://truck.it/p/WO3DAblcAP

[JuKu]

Yes, this very much makes sense, and should be easy to implement as well.

[Spikee]

I am not an expert at vision and placement algorithm, but here is one solution I am thinking about.
1. Fix pièces of metal, wood or plastic to form a corner
2. Place the part carefully on the corner
3. Assuming the machine knows the position of the corner and the part, it should be able to precisely compute the center to pick the part
4. Since the machine picked up a perfectly centered part with exact rotation angle, it should be able to place it
https://truck.it/p/WO3DAblcAP

This is basically how pick and place trays work
like this:

[JuKu]

That - or smaller versions of it - look something that would be very useful to have. Can we buy something like this somewhere?

[Spikee]

here (picture):
http://hothotsmtmachine.com/e_products/ ... 50-44.html

A free one:


Or 3d print one yourself:
http://hackaday.com/2014/06/12/3d-print ... e-machine/

The off the shelf ones might be quite expensive.
It is a easy job for someone with a cnc machine to make a couple out of aluminium for a reasonably low price.
or just laser cut two pieces of material and put it on top of each-other.

Random china tray on neoden pnp:


another random one:


If there is any specific design you want / like than i can 3D print or mill one out of alu.

[metRo_]

here (picture):
http://hothotsmtmachine.com/e_products/ ... 50-44.html
A free one:

I bought 3 atmega328p from Mouser or some samples directly from atmel that comes on one of this but I threw away it :s

[Spikee]

here (picture):
http://hothotsmtmachine.com/e_products/ ... 50-44.html
A free one:

I bought 3 atmega328p from Mouser or some samples directly from atmel that comes on one of this but I threw away it :s

If you email mouser they will probably trow a bunch of those things in for free.