Tool/software:
Hello,
we have a device in full production. It has been produced for more than three years now. More than 100.000 units. Unfortunately, we changed to a new PCB manufacturer. During the technical questions before PCB production, the PCB manufacturer noticed that we had a very large area without any copper in the coil area and he added copper. Just under the coil.
Now the circuit is not working any more. At first we thought that the extra copper under the coild coul have change its inductance. But measuring it, the change looks negligible: 11.23 uH to 11.31uH.
We tried to sniff the Qi communication with the Qi Avid and we logged a error we do not understand "Internal failure"
Looking at the VRECT pin we see something like this:
It looks that with the new PCB the system is much more sensitive to relative position of TX - RX while with the correct PCB the system was quite insensitive to inaccurate positioning.
We thought the FOD could have a role and we increased the FOD resistence to reduce the FOD detection sensitivity, but nothing changed. When you find the perfect position the system works and the operating frequency is 135 KHz as it as always been.
Of course, the easy solution is to go back to the right PCB, but we have 7.500 pieces assembled with that one and we would really like to recover them. Any suggestion what we could try to change? What is the effect of the copper under the coil?
Thank you very much for your help.
Andrea
