A design engineer told me our PCB prototypes would be completed soon and then he would have his assembler "run a panel". Does anyone know what that means?
Like Olin said.
Making a layout of the PCBs on a panel is called a panelization. In most cases V-cuts will be made between PCBs, so they can easily be separated by bending the panel. Care must be taken with high components (e.g. connectors) close to the edges, that they don't prevent the bending.
Alternatively a panel may be milled so that the PCBs are only connected at a few points. These connections are perforated so that they are also easily separateble. Milling is more expensive but may be required for the PCB; they are more precise than V-cuts, and also if your boards isn't rectangular you'll have to mill the edges.
A panel will at least have a couple of edges on opposite sides where the PCB manufacturer will place fiducials.
These are small marks, as copper circles, which are used by the pick-and-place machine as reference points to know where the parts should be placed. Here there are just 4 fiducials on the edges, but I've seen them as two rows at the top and bottom of the panel.
Panels will often have a number of identical PCBs, but you can make a panelization of different PCBs:
PC boards are fabricated whole "panels" at a time. These are bigger than most ordinary boards, so ususally you tile several end boards onto a panel. The panels are all the same size to fit whatever machines that production line is set up with. All the etching, plating, drilling, and silkscreening operations happen on whole panels.
For some production purposes, you buy whole panels of your boards from the board house. The individual boards tiled onto a panel might be partially routed apart by the board house with "mouse bites", or V scored. For high volume production, it's more efficient to do pick and place on a entire panel of boards. These are then broken apart only at the last possible moment. Sometimes even parts of the final board testing is done when they are still in panels.
Panels vary in size depending on the machines the board house uses, but somewhere around a square with 24 inches on a side is to be expected.