recommendations for soldering

[smarkoco]

Hey! I've been mainly implementing a webserver to communicate with this project over WebRTC (if interested, see https://www.cloudchop.net, and type u: "pilot", p: "tester" for credentials to see a simulation/prototype). I will now have more time to begin testing receiving the video stream into the local C++ application.

I was just wondering if you already made a stencil design for applying the solder paste before reflow oven? If not, what has been your approach to attach all components? How are you able to solder one side, and then the other side if using reflow oven?

Thanks!

[dridri]

Hello, sorry I never thought about it and mainly do it using a soldering iron and hot air station. But I have to admit that it needs some steady hands

[smarkoco]

Ah okay cool! Glad to know that's possible. I was just a little uncertain about soldering some of the tinier components like the IMU1 component, which doesn't have exposed pins once you lay it on the PCB.

So for the IMU1, would you maybe apply solder paste on each exposed PCB pad using a needle or something, and then place the IC, then slowly apply hot air with the hot air gun until it snaps into place?

Thanks!

[dridri]

My process on ICs like IMU1 is as follow :

• use low temperature soldering paste
• roughly apply it on the pads
• pre-solder it with iron to make it melt and stick to pads
• clean using isopropyl alcohol
• place the IC with a drop of soldering flux
• blow it with hot air to finally solder it
  This ICM-42605 chip is quite solid, I soldered and unsoldered some several times and they're still working

[smarkoco]

Awesome! thanks that helps a lot to clear up my confusion -- will give that a go next time I have the chance

[awright424]

My process on ICs like IMU1 is as follow :

• use low temperature soldering paste
• roughly apply it on the pads
• pre-solder it with iron to make it melt and stick to pads
• clean using isopropyl alcohol
• place the IC with a drop of soldering flux
• blow it with hot air to finally solder it
  This ICM-42605 chip is quite solid, I soldered and unsoldered some several times and they're still working

can you add pictures of the finished board minus the compute module

[smarkoco]

@awright424 here are some pics of my board so far. Just note that I'd actually recommend against soldering the header pins for the battery power line, as it will block being able to attach the CM4. I'll need to desolder that soon.

[smarkoco]

Also note that I used the wrong camera connector, and will have to desolder that as well. The one I got cannot accommodate the thick ribbon cable of the RPi cameras, so I'll actually desolder one of the display/camera connectors from the CM4 IO board to use for this drone project

[dridri]

The one on the CMIO board will not fit, to avoid cross-talk and make straight traces I chose a up-facing connector, CMIO's one is a classic down-facing

[awright424]

@awright424 here are some pics of my board so far. Just note that I'd actually recommend against soldering the header pins for the battery power line, as it will block being able to attach the CM4. I'll need to desolder that soon.

I have tried using your bom and have not been able to get it imported into mouser without seeing weird items that dont belong. Is this bom supposed to work with the bom tool?

[smarkoco]

Ahh right- I actually didn't make it with KiCAD as I should've - it's just a spreadsheet so I could keep organized and then I manually ordered each from Mouser. Sorry about the inconvenience

Yeah in the future I guess we should try to make a more official BOM (maybe with KiCAD or similar software) which could be imported automatically like you mention

[dridri]

Sorry about this, I don't know (yet) how BOM softwares work either

[smarkoco]

Also note that I used the wrong camera connector, and will have to desolder that as well. The one I got cannot accommodate the thick ribbon cable of the RPi cameras, so I'll actually desolder one of the display/camera connectors from the CM4 IO board to use for this drone project

FYI, the correct one is the one in the BOM, located HERE

My problem was that I was using too high temperature for soldering and warped the connector, which prevented proper connection to the ribbon cable. The proper temperature with hot airgun for successful soldering was 200C for 1 minute to preheat the board/component, then 30 seconds at 400-450C. I then had to use flux and cleanup pins and needed to add slightly more solder paste to ensure mechanically strong connection.

Now everything is in place and ready for testing with battery power!