Hint No. 2: Treat the panel as a full PCB. You can improve assembly and test time by extending the PCB connections onto the panel. I was working on an analog circuit that had a fairly compact form factor. This circuit was to go into a small housing; also it was to be held in place by soldered connections that were added after insertion into the housing. If there was any need for rework it would be cumbersome to remove the board from the housing, so we wanted to test the board before final assembly. There was another issue as well. Each device had to be warmed up for several minutes prior to final calibration.
We decided to test the boards whilst still in the panel. We brought the traces out onto the panel to a flat cable header so that all of the modules could be powered simultaneously. Then we perform a rough calibration sequentially on each module. Once this sequence is complete, we return to the first module -- which has been quietly warming up -- and perform the fine calibration on this module, and then repeat for the remaining modules. This saves a lot of time. The spin off from this is that now a lot of our product panels use the same header, which means we can use the same bed-of-nails and design the test electronics to connect via the flat cable connection. The original panel can be seen in Figure 4.
Figure 4. Eight boards interconnected and brought out to the flat ribbon connector location on the left. No connector is really needed since the pins will be picked up by the contacts on the bed of nails, although this was originally installed before the bed of nails had been produced.
(Click here to see a larger, more detailed image.)
Hint No. 3: Standardizing the external connections on the panel will allow for standard fixtures for testing, thereby saving development time, development costs, and storage costs. One cautionary note -- we use the same CAD software (originally PCAD and now Altium) that we use for the PCB itself to create the panel. Some CAD software may not like to connect identical PCBs. This is because there may be connectivity issues due to the fact that the connections have the same identifiers. There are ways around this, such as manually drawing the connection with a line rather than a trace.
Although I am not intimately connected to the PCB manufacturing process, and may therefore have misrepresented certain aspects, I hope I have managed to give you some ideas on how to think outside the board. Good luck with your endeavors and -- of course -- please share any additional ideas in the comments below.