Designing a PCB for modules with hidden pads

Community PCB Design
1

I’d really like to design a PCB around this module, which is built around the Nordic Semiconductor nRF52840: https://www.raytac.com/product/ins.php?index_id=24

SparkFun uses it on their nRF52840 MicroMod.

All of the contacts are on the underside of the module. They’re 0.4mm x 0.8mm, on 0.8mm centers.

Am I basically stuck doing reflow with either a hot-plate or an oven?

I’ve seen boards that connect to hidden pads on modules using vias. Do you think a similar approach might work here, or might the 0.4mm pad width be too small to allow solder to flow through to contact the module?

I’m already aware of boards like the Arduino Nano 33 BLE ( https://store.arduino.cc/usa/nano-33-ble ) which uses a different module built around the same chip. That would be great – except for the fact that they don’t expose nearly enough pins for my project.

If I could buy the thing pre-soldered to a breakout board that exposed all of the pads on vias or castellated holes, I’d be thrilled.

2

If you have a reflow oven, that would be the way to go but if not, it’s not a deal breaker.

I would imagine you’re going to have trouble getting solder to flow down the vias consistently on every pad while trying to solder by hand. I think you’d be a lot better off using no-clean solder paste and a hot plate. You would need to experiment with the temperature and how long to let it cook though since you can’t see when the solder melts.