It's 5 in the morning, and I figured I would post some more production videos. One thing that a lot of new PCB designers omit are fiducials on their PCBs. These are essential for more complex designs, since they allow for the machines to establish a known good reference point(s) so that accurate pick and placing can happen.
A lot of times, contract manufacturers will add these fiducials to your design if they are procuring the PCBs used in your design.
It is very common for these fiducials to be circular in shape. These are OK, but for finer-pitched components (0.5mm pitch for example) we have had some trouble with them (being off by 1 or 2 mils is a problem). We try to compensate for this error by iterating with fine offsets of the placement. They can also be problematic if the board has a HASL finish. HASL finish is not perfectly flat, and therefore the machine vision can see a non-uniform shape. Round fiducials can really only be used reliably on ENIG or silver-immersion finished boards.
We have found a cross shape to be much more accurate. The cross is simply two 8 mil traces that are 60 mil long. The solder mask is pulled back approximately 20 mil around the cross. For this design, we put three of them on the board. Below is a video showing our Samsung using them on board load to set all of the panel image reference points. It finds 5 sets of three - there are five images (or badges) per panel.
Another very useful thing that we use fiducials for is to establish the origin (i.e. coordinate 0,0) of the PCB. We do this in Altium before we export the pick and place file that tells the machine where components go. This makes the machine setup much easier, and much more accurate since the machine is going to very accurately determine the fiducial position. So the origin fiducial performs a double-duty - it helps the machine establish how the board is positioned in the machine and it sets the panel image (or individual PCB in the panel) origin.
Once the fiducials are found, the machine takes off placing components. There are much faster machines than ours, but the Samsung isn't too shabby.