Layers and Stackup

[MattHorton]

Is there any reason not to use a 2-layer board for the nRF9160? Is a 2-layer or 4-layer board recommended? My current board is just 2-layer and I haven't had any issues with it but I wanted to check to see if anyone else has any input.

[Andreas]

Hi,

 

nRF9160 needs a (mostly) solid ground plane, if you can keep your bottom layer free from components and trace routing it should be fine to use a 2-layer board. Feel free to submit it here if you want an evaluation, you can make a private ticket if you do not want anyone but Nordic support engineers to see your design.

 

Best regards,

Andreas

[awneil]

Andreas said:

nRF9160 needs a (mostly) solid ground plane

This applies to pretty much any radio device!

Also, it is typical of radio devices that will take very high peak currents - so you also need to ensure that your power connections are good and solid. A power plane is a good way to achieve this.

Hence we end up with 4 layers as a common practice ...

[Andreas]

Hi,

awneil said:

This applies to pretty much any radio device!

This is very true, thanks for correcting.

One thing is to have good enough grounding that the radio and its sensitive modules onboard work as they should, but the ground plane (total over all layers) effectively acts as half the antenna, thus a poor ground plane will also affect wireless range negatively.

 

Best regards,

Andreas

[awneil]

Andreas said:

thanks for correcting

Not really a correction - just emphasising that it's not something specific to nRF9160 or Nordic.

MattHorton the point being that RF design is a specialist area - so, if you need to ask this question, there are probably other issues waiting to bite you.

If this is for a commercial product, you should consider getting an expert involved...

https://devzone.nordicsemi.com/f/nordic-q-a/48284/nrf52832-wlcsp-ciaa-rf-do-not-work/191537#191537

[MattHorton]

Thanks guys! I've designed boards with Quectel, uBlox, and Telit modems before no problem. They all end up being 4-layer with dedicated signal/power/ground planes. The quick turnaround for the 2 layer is why I started with it this time. I'll revise it for the usual 4 layer and send in a copy for review.

It's a shame I didn't see any modules for the 9160 on the third-party modules page. We have the thingy91 and 9160 dev kit and have our application working fine on those and my first ed 9160 breakout. I've used Spinnaker as our CM in the past and done PTCRB certification so the process and overhead for making a module isn't too insane but if there's already an economical 9160 module I'd rather use that than design and certify a new board.