I sent a customer 200 chips for one production batch.
Usually I will program them before sending them, but due to time shortage we agreed they program them after building the board. We did incorporate a JTAG connector in the design, and my customer have reprogrammed before for testing and other purposes. So I know the interface works, so does my customer.
After building those boards close to 30 of them were not programmable! The ususal things were tried to make sure it was not their JtagII, it's flex cable or anything like that.
I got 3 of those boards sent to me. I removed the AtMega16 chips (DIP) using a desoldering pump and put them on "my" (identical) board that has a ZIF socket. No programming possible. The Xtal oscillator runs. I tried programming the chips using ISP on STK500 and same result.
At the same failure rate we'll end up with over 100 dead boards before christmas, so any suggestions are very welcome.
The chips are:ATMEGA16L 8PU 0835K.
Lot info on bottom side: 8G4736-35565O 1-P0835 83