I've done rigid-flex PCB designs a number of times in the past but it was long enough ago that I cannot remember how I solved this issue. My design has three sections - the main board, the flex, and a daughter board. The flex obviously connects the two rigid boards. The problem is that I cannot seem to place tracks across where the split lines are defined, meaning using the interactive routing tool I can't run traces from the main board over the flex to the daughter board. When I place a trace and move it so that it crosses the line, the error I see is this:
Altium clearly thinks that just because I go from a rigid section to a flex section, that I am going outside the board outline (which is not true). I have no idea what the poly region is, and I do not see anything on the "Multilayer" layer indicating a poly region.
My board stackup is shown below:
I have tried running tracks on all of the four layers and all of them behave the same way.
How does one draw tracks across different sections of a rigid-flex design? My guess is the problem has something to do with the stackup but I can't place my finger on it.
I am using Altium Designer 18.1.7.