PCBA and ESP32 module

I’m going to have a board manufactured with an ESP32 module that has castellated pads. Layout seems simple enough as the same or similar footprints are in the library. The current revision of my design uses the official dev kit (ie breakout board).

I’ve researched the strapping pins and am pretty sure I’ll get that correct. Most are already pulled correctly internally and I have the ESP-PROG programmer working with the dev kit which takes care of the rest. What do I need to be aware regarding having the ESP32 module soldered to the main PCB in an oven? It seems to me this can be tricky. I use PCBWay mainly for PCBA. Thanks.

I have an ESP32 project on my desk with Two different Dev-Kit Brands of them (HilTego and Xiuxin)…

Regarding your question:

I recommend placing Pin-Headers on the PCB so it will be easy to remove/install ESP32 boards. It’s frustrating to unsolder a board with many pins and/or throw away an otherwise good PCB…

Note: different brands of the Dev-Kit have differing quantities and arrangements of Pins (Pin count, Row-Spacing and Pin Numbering… You might consider that…

I’m already using pin headers and the official dev kit on the current board revision. The dev kit costs 3x what the module does. The module will be exactly the same one that is used on the dev kit. I don’t need the regulator, buttons, leds etc as all that is taken care of by the ESP-PROG programming device. What do I need to know before asking asking PCBWay to solder a castellated module to a PCB? Things get lost in translation so it useful to know what to ask first.

So, a “devkit” in this context is Breadboard breakout PCB?


For automated assembly, every touch by human fingers cost you extra. And thus availability in pre-packaged rolls of tape is almost mandatory. On those breadboard modules the ESP32 module is already added fully automatic. The castellated PCB is designed for it, so it can be done.

But they’re not “standard parts”, and not every PCB assembly factory may want to do it for you. So contact them in advance. They may want you to use a particular module variant, or have other advise.

@paulvdh 's comments are valid.

Re: your cost: The ‘espressif’ chip cost is only about $3 less than a full Dev-Kit board…
I pay about $10 for them. Sure, you may want to use the Chip without the rest of the hardware and can access other pins that are not routed on the Dev-Kit.

But, for my money, I’d stick with the Dev-Kit.

REe: Castellated PCB: Link to useful info

As an alternative, you can also solder the castellated modules yourself. Either with hot air or a big tip to put in some heat. with some proper tools (inclusive stereo microscope) and experience you can probably do it in less then a minute.
A bit of pre-heating also helps.

When you use a soldering iron, then longer pads also help, and always use enough flux. You can never have enough flux. There are plenty of SMT soldering tutorials on youtube.

[Edit] (again)
Just had a short peek at Aliexpress. They have the castellated modules for around EUR3.
Would there be fake versions of those? It’s already a very low budget thing from China…

And bigger numbers don’t help much. I aw a reel of 650 for EUR1800.

What sort of numbers are you thinking about?

This is going to be a mass production board for my client. Purchasing chips from Amazon/Aliexpress is not an option. Nor is soldering the modules myself.

The devkit breakout:


And the module:


Arghh I just noticed that the lastest version (E) of the devkit are out of stock. At least with trace antenna. The very next revision is still going to use the devkit. I think I can substitute the D version.
I have one to try. They have some of the modules (E) but more of the previous version (D). Supply chain is killing me. I could sub with a wrover but there is no advantage and they are more expensive.

I’m not sure what exactly you’re asking. I just had a PCB made by JLCPCB with an ESP32-WROOM-32 on it. I just placed the footprint and they put the module on.

If this is for mass production, you might be better off with a naked chip and replicating the components of the module on your board. Maybe you can find a schematic of a Sonoff Dual R3 or a Shelly Plus 1.

Make sure you have plenty of capacity for the ESP32’s power supply, they are notoriously picky about keeping the voltage up during current spikes.

Do you need anything other than a footprint? I just paste the pads and solder it (ESP-12, but same deal) on with hot air. I don’t see why the PCBA couldn’t do the same. The modules come on tape and should very P&P friendly (though a bit large).

Thanks for all the replies. I’ve seen this done on lots of commercial boards (with ESP and other modules) so I know its possible. Really my question is about the solder reflow profile. I’ve had about a dozen surface mount boards made in the last 2 years using PCBWay and never once have they asked me about conflicting solder reflow profiles. Do they even check the profile for the parts I specify or just use a standard? I really wonder.

Hand soldering / hot air… I suck at it. I had some breakout boards made with just the footprint and I botched all three :frowning: The ground pad underneath is hard to solder.

As for cost in Canada the module costs about $5 depending on ram/antenna combo whereas the devkit costs about $15. Thats 3 times the cost. Now I am not making 100K but rather 100. Still thats $1000 my client doesn’t need to spend.

Using Aliexpress etc I don’t know what I am getting. Its great for dev/experimenting and one/two offs, but if I can’t buy it on Digikey/Mouser etc its not okay for production.

Building up the ESP32 from bare chips (ie CPU, ram. antenna etc) can’t be justified to my client. Spending the dev money on this would be insane. RF certification I don’t even want to think about.

Lastly, supply chain is imploding. I bet there is a container full of Espressif product sitting off the port of Los Angeles right now. Latest shipment by DHL from PCBWay was on hold for 5 days in Shenzen and is still on hold for 4+ days in Hong Kong.

The ground pad really is difficult. I have soldered manually with iron maybe some hundreds of pretty much similar RN2483 which doesn’t have that kind of center pad. If the large gnd pad must be soldered, it certainly makes it very difficult, I don’t know how I would do it. Hot air with solder paste could work if there are no components in the other side of the board, but the one I did had the whole design in the other side and the module covered the bottom.

I really know nothing about soldering profiles, but I wonder how they can actually be taken care of at all. Can anyone choose their components according to their soldering profiles? The assembly house must use some compromise and this must be true for almost every design. It’s their job, not yours.

What about LCSC? They seem to have plenty of ESP32-WROOM-32E(16MB). And they are already in China, so maybe they could ship directly to your assembly house? Especially with the supply chain issues, it seems wasteful to send parts from China to North America, just to send them back to China again.

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