nRF52832 CIAA (WLCSP) BGA Routing Advice?

[oolaruu]

Hello! I am starting layout with the BGA nRF52832 in KiCAD. I've planned my GPIO usage to avoid the inner IOs, but I do need to access the 2nd row. Given the super tight spacing, how can I route this? I can't on one layer route between the IOs (0.2mm ball-to-ball), but I may be able to place a VIA directly over a ball in the 2nd row and route those signals down to a 2nd layer. Is this the recommended approach?

I'd like to use, for example, PCBWay to create this board, has anyone else routed the CIAA package and had it manufactured by PCBWay or similar online fab?

[oolaruu]

I've dug around a little and I may be able to use a micro via placed exactly underneath the ball. Speaking with a PCBWay rep, it looks like their micro VIA capabilities could give me a blind VIA to the 2nd signal layer. The size of the micro via could be 0.15mm hole + 0.0762mm ring, a 0.2262mm total. hopefully that will work??

References:

https://www.pcbway.com/advanced-pcb-capabilities.html

https://www.pcbway.com/pcb_prototype/PCB_BGA.html

https://www.pcbway.com/blog/Engineering_Technical/Reduce_Your_PCB_Costs_With_Blind_Vias_Buried_Vias__Microvias.html

https://infocenter.nordicsemi.com/index.jsp?topic=/struct_nrf52/struct/nrf52.html

[ketiljo]

It's best to use via in pad here. The actual dimensions of the via isn't important as long as you make it fit.

[oolaruu]

Thank you my friend