What footprint to use with the UFQFPN48 casing

[DBlan.4]

Hello,

In the product specification STM32WLE5xx/STM32WLE4xx, december, 2022 DS13105 Rev 12, we can find on page 137 a recommended footprint in Figure 32 for the UFQFPN48 casing.

But, we can also download the footprint of this casing in the CAD Ressources, for example link: STM32WLE5CC - Sub-GHz Wireless Microcontrollers. Arm Cortex-M4 @48 MHz with 256 Kbytes of Flash memory, 64 Kbytes of SRAM. LoRa, (G)FSK, (G)MSK, BPSK modulations. AES 256-bit. Multiprotocol System-on-Chip. - STMicroelectronics

The both footprints are not identical (pad dimensions etc...).

Why do we have 2 footprints for the UFQFPN48 casing ? Could you tell me the best footprint to use?

Thanks in advance, regards, Daniel.

[Sarra.S]

Hello @DB.7lanzat​ ?

Do you mean these two footprints :

1) 2)

I can't see any differences between the two

Same number of pads : 12 on each side

same dimensions on each side : note that the beginning and and end of dimension measurement is not the same ; the first start from the end of the pad and the 2nd one doesn't!

[DBlan.4]

The point I want to emphasize here:

In product specification :

Pad dimensions : 0.30 x 0.55 mm

Ground pad dimensions : 5.60 x 5.60 mm

In CAD ressources :  

Pad dimensions :  0.255 x 0.808 mm

Ground pad dimensions : 5.69 x 5.69 mm

So why does ST suggest 2 different footprints?

Which is better and why?

[Sarra.S · Accepted solution]

Hello again @DB.7lanzat​ 

You're right!

In fact, Ultra Librarian is responsible for the footprints, symbols and 3D models present in CAD resources.

So, you can go to Model Feedback and write your observations and it will be corrected!  

To answer your question, the footprint in the Datasheet is the most reliable!

Hope that helps!

[DBlan.4]

Thank you for your feedback, Regards, Daniel.