0
\$\begingroup\$

I am building my first PCB ever with an ESP32. I want the PCB to be built by JLCPCB (or similar) and I am not sure what to do with the Pad39

I read these opinions:

  1. Do not add vias in pad, and if you do put more solder paste in those pads (for example this post)
  2. JLCPCB can do vias in PAD (example link - but does not mention smt assembly)
  3. Official documentation says that Pad39 does not need to be solder at all
  4. Official schematics solders it and add vias to IT

Official docs (link to page 24):

Soldering EPAD Pin 39 to the ground of the base board is not a must, however, it can optimize thermal performance. If you choose to solder it, please apply the correct amount of soldering paste.

Official Esp32 DevKit Layout (I overlapped the layers) (documents link)

enter image description here

Do I need to do anything If I add vias before sending to JLCPCB/PcbWay? Would it be better if I add the vias outside to the pad? For example:

enter image description here enter image description here

My full schematics and layout: link

\$\endgroup\$

1 Answer 1

2
\$\begingroup\$

You can safely do without the vias - indeed you can do without the exposed pad entirely. This is confirmed by Espressif in this thread:

If the pad is soldered then it should be soldered to Ground. If soldered then the ESP32 will run a little cooler due to heat sinking into the main board. However, this is not necessary for adequate thermal performance (for example, all the current generation development boards with ESP-WROOM32 have a solid solder mask layer under the thermal pad.)

I can also confirm this from personal experience: the module runs cool (within a few degrees C of ambient) even without the pad. Incidentally, this makes it easily hand-solderable for DIY without a hot air gun or reflow oven.

\$\endgroup\$
9
  • \$\begingroup\$ Note the ESP32 can get rather toasty running both cores at 240MHz and doing lots of WiFi. \$\endgroup\$
    – Kartman
    Feb 7, 2022 at 0:51
  • \$\begingroup\$ @Kartman Can you define "rather toasty" and give some detail on your application where you've seen this? It is not normal. Thorough review of the ESP32 forums confirms this. \$\endgroup\$
    – TypeIA
    Feb 7, 2022 at 6:32
  • \$\begingroup\$ @Kartman Also remember all current dev kits leave off the exposed pad (this is easy to verify). This fact together with the official manufacturer advice I linked is a solid basis for an answer, so I'd ask you to reconsider your DV. \$\endgroup\$
    – TypeIA
    Feb 7, 2022 at 6:41
  • \$\begingroup\$ Depends on how well the chip is heatsinked, but the chip will pull over 0.5W when transmitting. That equates to over 50C temp rise. Run a streaming camera and see how toasty it gets. \$\endgroup\$
    – Kartman
    Feb 7, 2022 at 6:53
  • \$\begingroup\$ @Kartman We're talking about the ESP32 module here, not the standalone chip. That 0.5 W is about right but is dissipated into the ground plane of the huge (by SMT standards) module. (The ESP32 IC itself is thermally soldered to the pad [pin 49] on the modules.) \$\endgroup\$
    – TypeIA
    Feb 7, 2022 at 7:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.