I would like to do the routing of the stm32wle5jbi6 chip that comes in a tiny UFBGA73 package. Please see the datasheet here: https://www.mouser.de/datasheet/2/389/dm00648230-1799409.pdf The dimensions are provided on p128 and p129.
I'd like to send the PCB for manufacturing to pcbway.com and they have a minimum trace width and spacing of 4mil: https://www.pcbway.com/capabilities.html But they recommend 6mil for both trace width and spacing.
I see that the size of the solder mask (tstop layer) might be the problem. I cannot do any routing in the chip. What do you think about just reducing the size of the soldermask, what is the minimum distance it should have to the cream layer? Can I eventually not use it at all?