How do I connect the underside pads on the Teensy 4.0 to a solder pad on a PCB with the same dimensions?

[Chonky Planky]

I plan on using the underside pads for a micro-sd card and I'm wondering if I can just solder them together using solder paste. I saw that there are capacitors on the underside of the Teensy 4.0 and I thought they might become a problem for soldering the pads directly, any solutions? I'm trying to make my pcb as small as possible so I can't really use expansion boards.

 

[MichaelMeissner]

Before the Teensy 4.1 was released, there were a lot of people making PCBs to bring out the SD card and other pins:

• OSH park PCB of trainer4edu's PCB without USB host
• OSH park PCB of trainer4edu's PCB with USB host
• Trainer4edu's board description
• Blackketter's PCB
• Blackketter's github repository for the PCB

The trainer4edu boards are nice, because pins 24-33 are at the same position in the PCB as the Teensy 4.1. I have used the trainer4edu PCB with Teensy 4.0 and later substituted an official Teensy 4.1, and it worked as long as I only used pins 0..33, and for the SPI1 bus, I used pin 1 for MISO1 and not pin 39.

The big thing is you have a hole cut in the PCB where the Teensy 4.0 capacitors and such are located. Assuming you have the hole in the appropriate spot, then you can put the PCB directly under the Teensy 4.0 and make a solder bridge between the boards.

Note, the SD pins are laid out with 2mm pitch instead of 2.54mm pitch, so you will need to adjust to the smaller area.