aQFN Footprint Blind Vias

RE: aQFN Footprint Blind Vias

JONATHAN LL — Wed, 20 Apr 2022 15:11:34 GMT

[quote user=""] Just wanted to make sure I fully understood why blind vias were being used before I deviated from the reference design.[/quote]

Due to manufactures have limitations and prefers standard layouts to have micro via aspect ratio 1x1(usually), through hole vias needs to be larger due to the fact that they are drilled and need to be caped. Capping of small through hole is often not recommend do to trapping air in the via, this can cause expiation wit temp and atmosphere pressure changes.

Manufacturer limitations or etiquette you could say is part of the reason. So contact the manufacturer and see if it will be cheaper, might not.

Regards,
Jonathan

RE: aQFN Footprint Blind Vias

juztin_m — Wed, 20 Apr 2022 14:41:20 GMT

Hi Jonathan,

Thanks for the reply. The plan is to use vias-in pad for just a few of the pads on the inner row of the aQFN footprint. In the reference design, they are blind vias, but I was hoping to make them through-hole to potentially reduce cost. I don't have any issues with them interfering with objects on the other layers.

They will have the same pad diameter and hole diameter as the blind vias in the reference design, still capped, but will be through-hole. Just wanted to make sure there wouldn't be a problem with that.

Justin

RE: aQFN Footprint Blind Vias

JONATHAN LL — Wed, 20 Apr 2022 14:03:00 GMT

Hi,

Note: just want to inform you that we do HW reviews, so you can request a review of the design here on Devzone. Simply create a new case, include the schematic and layout files, PDF/GERBER or Altium files and we will provide feedback.

Is the plan to use only some of the pins with through-hole or all?

Using blind VIAS does not innfetere with all other layers, so for example if the centre pad grounding is poor and it is disrupted by through-hole vias that cut of the centre pad from the rest of the ground plane.

So, we always recommend that you follow the latest ref design we have: nRF52833 SoC - Downloads - nordicsemi.com

Regards,
Jonathan