ESP-WROOM-32 Footprint

[ralkire]

The ESP-WROOM-32 had a pinout with measurements but no dimension footprint like they did on the earlier modules. It wasn't a problem to come up with signal and power pads that surrounded the circumference of the LGA module; but the large thermal pad has been a pain. This thermal pad is attached to the exposed DAP (die attached paddle) of the ESP32 chip. This is common for QFN packages and it doesn't appear to require electrical connection. The dev kit for this module doesn't have the mating thermal pad in the gerber files. The datasheet pin out does show a thermal pad with dimensions and the physical module we bought definitely has one. The earlier datasheets showed the thermal pad at 6mm x 6mm area and the most recent datasheet, this was changed to 4mm x 4mm.
There is a discrepancy in the measurements given though. The Y dimension of the thermal pad in the datasheet of 7.3mm from bottom edge of the board to the bottom of the thermal pad doesn't match either the gerbers or physical measurement of the ESP-WROOM-32 module. We measured both the board and gerbers to be at 8.53mm. I used gerbv and altium designer to measure the gerbers. We printed footprint transparency to compare with the physical module.
The X dimension from the left edge of the PCB to the left edge of the thermal pad is 6.3mm in the datasheet. That does match the physical board but the gerbers we recently downloaded measures to be 5.5mm. I have a footprint which matches the current modules we have but not sure it will match any others we buy.
It is unclear whether a mating thermal pad is needed. The data sheet doesn't include the information needed to design to that. That is, it needs package thermal characteristics and power consumption for the CPU, peripherals and all of the radio power consumption. (not just transmit power).
It does have an onboard thermometer and probably will be worthwhile to keep an eye on it.

[philtulju]

Thanks for this information! I'm making a footprint and noticed this discrepancy as well.
Ideally, no mating thermal footprint would be required as it will make soldering the ESP-WROOM-32 module more difficult in production.
Can somebody from Espressif please weigh in on:
1) Is the current location of the thermal pad on the ESP-WROOM-32 modules going to remain the same?
2) Please confirm that the latest datasheet and hardware design guidelines drawings show the incorrect placement for the thermal pad, and what is the correct location?
3) Does there need to be a mating thermal pad on the carrier PCB? If so do you recommend that the mating pad also have thermal vias-in-pad?

Thanks!

[glitch911]

Hello,

Any update ?

From my understanding the actual datasheet is not 100% perfect between module dimensions and land pattern.
The land pattern exposed pad center is (x=8 y=10.51 from corner) and the exposed pad center on module is (x=7.5 y=10.3 from corner).