Query on Nordic NRF52805 Footprint

[Jovin Basil]

I am looking for technical support on Nordic Chip NRF52805 chip recommended footprint – BGA pad size.

 

Based on the application note on WLCSP Package guidelines from Nordic, it recommends for NSMD – 0.9 x UBM Pad Size which will be 155um * 0.9 =  ~0.14mm.

 

The datasheet recommends pad size range from min 0.197mm -max 0.257mm.

 

I have checked the Nordic forum (link attached below) where it says 0.14~0.2mm should be enough and anything above would be risky.

https://devzone.nordicsemi.com/f/nordic-q-a/11290/wlcsp-footprint-inconsistency

 

Can you provide a clarification on what would be the ideal pad size to be provided.

[Marjeris Romero]

Hi,

Based on the application note on WLCSP Package guidelines from Nordic, it recommends for NSMD – 0.9 x UBM Pad Size which will be 155um * 0.9 =  ~0.14mm.

The general recommendations are for NSMD: UBM pad size * 0.9

The UBM is the underbump metallurgy pad size, see Figure 3 in the application note on WLCSP Handling Guidelines. It varies from chip to chip, take note that the UBM pad size in Table 2 of the is for nRF51422 and nRF51822 WLCSP packages.

Instead you should take a look at the reference files for the nRF52805 to determine the proper footprint, see here.

For nRF52804 we recommended a copper pad diameter of 0.194mm.

Best regards,

Marjeris