I'm taking an assembly of three boards to a small production run. There's a main board (n=25) and a satellite sensor board (n=100). The sensor board connects to an adapter board, which simply connects the sensor to the main board through an 8-conductor FFC.
The main board is a USB device, reading signals from a variety of sensors through a harness as well as the FFC, and sending the signals as an HID. I'm thinking about the QC (and have been for a while). The contract assemblers would like to know that the components they're working with are good, of course. Since there's only 25 main boards, I thought testing each one for enumeration on a PC and making sure the signals from the test harness come through isn't that unreasonable -- I figure 2 minutes per unit, max.
For the sensor board, I figure on providing a kitted test platform to test the sensor, with maybe an led bar display. Twenty seconds a unit, max.
The issue is the ZIF FFC connection between boards. I'm using these connectors I'd like to hold down this testing, as I think it will be slow and fairly tedious. I'm thinking about spot-checking about 3-5 units, and going for visual inspection of the solder on the connectors for all the rest (they're fairly large pitch).
Does this make sense? Does it make more sense, with respect to the FFC's, to test the first few off the run then a random sample?
I've had zero problems with the hand-populated prototypes, which have really been run through the mill. I'm using a very reputable local board assembly plant that routinely constructs to mil-spec.