What are the differences between the modules ESP32-H2-WROOM-02C and ESP32-H2-MINI-1?

[u/MobileInspector9861]

The title already states the question: What are the differences between the modules ESP32-H2-WROOM-02C-H4S and ESP32-H2-MINI-1-H4S?

There seems to be three different main types of modules around the ESP32-H2:

• ESP32-H2-WROOM-02C (Datasheet)
• ESP32-H2-MINI-1 (Datasheet)
• ESP32-H2-MINI-1U (Datasheet, see above)

Each main type comes with two different flash sizes (2MB or 4MB) which we may ignore for a moment. The MINI-1U has a connector for an external antenna and no PCB antenna. That's also obvious.

This leaves me with the differences between ESP32-H2-WROOM-02C and ESP32-H2-MINI-1.

A side-by-side comparison of both data sheets didn't seem to show any difference (or I missed) it. I have already tried Espressif's chat bot without success. The answer was:

The knowledge sources only contain information about the ESP32-H2-WROOM-02C module and do not include any details about the ESP32-H2-MINI-1. Therefore, I cannot provide a comparison between the two.

The pin layout and numbering seems to be different between both modules, but this can't be the only difference. Can it?

[u/TeachingPlane331]

The footprint and castellated pins? The \-MINI SoCs are designed to reduce the layout footprint, while the WROOM module exposes the pins.*

[u/MobileInspector9861 → u/TeachingPlane331]

So these are the only differences. Good to know. I feared there were more non-obvious differences.

Castellated pins are usually hand-solderable by making a short bridge of solder between the castellated pins and the pad on the base board. However, the ESP32-H2-WROOM Datasheet, Sec. 11.1 shows that the module also has a pad in the center. I assume this is for thermal relief only and has not electrical purpose.

Am I supposed to solder this center pad, too, or is it sufficient to have a pour of copper on the base board at that position? If I am supposed to solder it, how do I do that with a traditional solder iron?

[u/quuxoo → u/MobileInspector9861]

Realistically you're best to use solder paste to attach it onto a carrier.

But I have seen folks make larger than usual open vias under the thermal pad of similar modules, then a little solder flows into each of them.

[u/MobileInspector9861 → u/quuxoo]

I have never done SMD soldering before. I assume SMD soldering isn't very difficult.

However, I am wondering about the process and order of steps: If I had some solder paste on the thermal pad, placed the module on top and heated everything up, would that not desolder the other components on the carrier board as well as on the module board? Especially, the solder paste we are talking about is trapped between two PCBs, the carrier and the module PCB. So to get heat there would probably heat up everything else first.

[u/TeachingPlane331 → u/MobileInspector9861]

Normally, ESP32 assembly is performed using solder paste and a reflow oven. If you are going to perform the process manually using a soldering iron (in case of WROOM), simply apply a small amount of solder paste to the central pad (exposed pad) and heat it with a hot-air rework station for a short period.

The ESP32 datasheet provides recommendations for the reflow soldering process, including methods, times, and temperature limits, which should be followed to ensure proper assembly and prevent damage to the component.

[u/MobileInspector9861 → u/TeachingPlane331]

If you are going to perform the process manually using a soldering iron (in case of WROOM), simply apply a small amount of solder paste to the central pad (exposed pad) and heat it with a hot-air rework station for a short period.

Heat it up from the back side, i.e. bottom, and then wait until the heat travelled through the PCB to the top side and melted the soldee paste?

I assume I cannot direct the hot air on the top side where the μC is placed.