Footprint for a ESP32-S3-WROOM-1-N16R8 Microcontroller-with-antenna? - Page 1
Forum section: electronics / general

author: makebit
author_rank: Unknown
timestamp: October 11, 2025, 06:36:47 pm
content: Hi,I'm obviously not giving away any secrets here about PCB layout of an ESP32-S3-WROOM-1-N16R8microcontroller with built-in antenna. Since its an offTheShelf chip.The attached shows how ours is layed out.ESP32-S3-WROOM-1-N16R8 datasheet...https://www.espressif.com/sites/default/files/documentation/esp32-s3-wroom-1_wroom-1u_datasheet_en.pdfPage 46 of the datasheet shows an area meant to be left clear for the antenna. I am not sure why theycall it "antenna area" since the antenna is inside the chip?Anyway, page 46 of the datasheet also shows 9 separate ground pads, but we have done these as shown with just one big copper pad.Will this be OK?Page 43 of the datasheet appears to show a "pcb trace antenna" above the chip. Surely this shouldn't be there as theantenna is in the chip? Page 9 of the datasheet shows the antenna being inside the ESP32-S3-WROOM-1-N16R8Anyway, do you think our footprint is OK?

author: pastaclub
author_rank: Regular Contributor
timestamp: October 11, 2025, 09:07:31 pm
content: The antenna is not in the chip. It's on the PCB (that's why it's called PCB antenna). It's on the PCB of the module though, maybe that is what you meant.The PCB antenna should ideally hang free (not overlapping the carrier board). If not possible, at least keep any traces and ground planes away from it.The ground pad is split for better paste application using a stencil, I assume. If you have one large opening in the stencil and the board, stencil and squeegee are not perfectly flat, you get too little or too much paste. That's less likely to happen with multiple smaller openings. Another reason is the vias. You don't want to apply paste into them which will drop out on the other side during reflow.

author: makebit
author_rank: Unknown
timestamp: October 11, 2025, 09:52:24 pm
content: Thanks but page 9 of the above datasheet clearly shows the antenna outside the chip for the "1" and inside it for the "1U".The datasheet gives no recomended antenna and they would if the "1" version had a "pcb antenna".Mind you i see what you mean because the following does show a "pcb antenna" but doesnt show to which pins it shoudl connect to on the ESP32-S3-WROOM-1-N16R8.https://docs.espressif.com/projects/esp-thread-br/en/latest/hardware_platforms.htmlWould you say the footprint on page 46 intends there to be a full ground plane but with solder mask openings for that "9 pad" square thing?...otherwise what are those vias in the "9 pad square" thing connecting to.?The Espressif forum won't register me, so i cant ask there.

author: tooki
author_rank: Super Contributor
timestamp: October 11, 2025, 10:23:52 pm
content: Quote from: makebit on October 11, 2025, 09:52:24 pmFirst of all, the WROOM isnot a chip. It’s amodule, which is what pastaclub tried explaining to you already. The module contains the chip as well as all the basic support components.Page 9 of the datasheet shows this: the dotted line shows the module, and right in the center is the chip, surrounded by the crystal, flash memory, and RF matching circuitry. The antenna is NEVER part of the CHIP, but it is part of some MODULES.Second, page 9 of the datasheet clearly shows that it is the -1 that has the integrated PCB antenna, and that the -U1 has the connector for the external antenna. That’s exactly the opposite of what you said. Remember, we are talking about MODULES, not the chips used in the modules!

author: makebit
author_rank: Unknown
timestamp: October 11, 2025, 11:16:03 pm
content: Thanks, I take it you mean the thing is a module, and it contains chips.The following shows the ESP32-S3-WROOM-1-N16R8 with an external antenna....we are wonderingif there is a layout example for this antenna, and to which pins we must connect it toon the module?https://docs.espressif.com/projects/esp-thread-br/en/latest/hardware_platforms.html

author: pastaclub
author_rank: Regular Contributor
timestamp: October 12, 2025, 09:37:34 am
content: There are two versions of the module. One has a PCB antenna on the module, the other has an SMA connector. Look at the pictures on the first page of the datasheet.The one with SMA connector is meant to have an external antenna connected using a cable to the SMA connector, not a trace to a castellated hole. If you don't want an external antenna, you can choose the version with PCB antenna. In neither case do you have to layout an antenna on the PCB or route traces to an antenna. Just in case of the PCB antenna, keep that area free of copper.

author: makebit
author_rank: Unknown
timestamp: October 12, 2025, 11:35:44 am
content: Thanks i see, the ESP32-S3-WROOM-1-N16R8 actually comes with the PCB antenna attached to it, thanks.Do you think the following is the only correct way to lay out the ESP32-S3-WROOM-1-N16R8?https://dl.espressif.com/dl/schematics/PCB_ESP32-S3-DevKitC-1_V1.1_20220429.pdf...it shows the ground pins of the ESP32-S3-WROOM-1-N16R8 (pins 1 and 40) are connected to the top layer ground plane with no thermal vias...this suggests that a really lowimpedance ground connection is needed?Also the ESP32-S3-WROOM-1-N16R8 has a ground pad which is made up of 9 solder mask defined pads all together.One of the ESP32-S3-WROOM-1-N16R8 App notes says that you dont even need to connect this "9_pad" ground pad...but just as lomng as it doesnt overheat.This sounds really bizarre...i mean, the ESP32-S3-WROOM-1-N16R8 doesnt really dissipate much power anyway......so why add the thermal ground pad at all?The above link shows the centre ground pad "group" being connected to the top layer ground plane with no thermal reliefs at all.....surely this would be nearly impossible to properly solder?.......i mean, if soldering that works, then there would never be ever a need for thermal reliefs in the whole of electronics?

author: gamalot
author_rank: Super Contributor
timestamp: October 12, 2025, 12:17:27 pm
content: Quote from: pastaclub on October 12, 2025, 09:37:34 amThat's not an SMA connector, it's way smaller. Many manufacturers make compatible versions, but they go by different names like U.FL or IPEX.

author: tooki
author_rank: Super Contributor
timestamp: October 12, 2025, 07:51:47 pm
content: Quote from: makebit on October 11, 2025, 11:16:03 pmCan you use more specific words than “thing”?Quote from: makebit on October 11, 2025, 11:16:03 pmNo. It. Doesn’t!!The PCB antenna is PART OF THE MODULE.Look, I’ve attached photos of a -1 and a -1U module. The -1 (black background) has the PCB antenna. The -1U (white background) has a U.FL antenna connector.The module is a little circuit board, and underneath the metal can is the actual ESP32-S3 chip, as well as all the other parts I mentioned before: the crystal, the flash memory, and basic support components.Quote from: makebit on October 11, 2025, 11:16:03 pmThe PCB antenna is part of the module PCB; you don’t connect to it.The entire point of the ESP32 modules is that the RF design is testedand certifiedso you don’t have to do that, which is difficult and expensive.Espressif does document how do work with the bare chips if you want to (using the module design as the example:https://docs.espressif.com/projects/esp-hardware-design-guidelines/en/latest/esp32s3/pcb-layout-design.html#fig-pcb-layout-example) but for hobbyists and small manufacturers, the modules are a MUCH better idea.

author: tooki
author_rank: Super Contributor
timestamp: October 12, 2025, 08:14:21 pm
content: Quote from: makebit on October 12, 2025, 11:35:44 amObviously it is not the only way, since the module datasheet has a whole section on PCB layout with various examples of what to do and not do.Quote from: makebit on October 12, 2025, 11:35:44 amI think you’rereallyconfused about terminology: a “via” is a small plated hole through the board. A “thermal via” is simply a via placed for thermal reasons. I suspect what you’re thinking of is athermal relief, where you separate a pad from a copper pour and then connect it only through some thin spokes. That’s done to prevent issues when soldering. (For through-hole parts, to ensure solder flows well; for SMD, it’s mostly done to prevent small chip components from “tombstoning” when one pad melts much sooner than the other. A large copper pour takes longer to heat than a small pad.)In this case, the module is so big that there is no way thermal reliefs would make any difference, so you just leave them out. They didn’t use thermal reliefs on any of the SMD pads, but did use them on the through-hole pads.

author: tggzzz
author_rank: Super Contributor
timestamp: October 13, 2025, 10:36:47 am
content: Caution.It is believed that makebit==Treez/Faringdon/ocset/zenerbjt etc etc