Comment on Request for comments: USB C "trigger board"
JDavis@lemmy.world 1 week ago
I’ll also jump in, mirroring some of what jeinzi said, and providing some of my own thoughts. I agree that both what you originally had, and what you have now should work.
Your schematic should read left-to-right with the flow of current. I don’t believe a wire is necessary, though I do see how it could be beneficial. The only thing I would change is flipping Q1 so that VOUT is on the right side of the schematic instead of being on the left as it is now. I had to do a double take to figure out what was going on there.
I also tend to prefer global labels, especially with a single page schematic like this, as they’re a little easier to read than the standard net labels.
On to layout, I’m a “Route Power, pour ground everywhere else” kinda guy. Remove islands, but I then via stitch all my grounds together. This is most useful for higher layer count boards and stuff dealing with RF. This shouldn’t see any of that, so it’s less of an issue. I rather dislike the setup with the 5 separate planes/pours on this board. I forked your repo and quickly threw together how I personally would route it, assuming I:
- Couldn’t use different components (0603 or really 0402 for the passives) (different PMOS package)
- Couldn’t change the outline (Okay, I lied here. Please round your corners. Right click -> shape modification -> fillet [or chamfer]. Makes the board feel so much more premium, and gets rid of those awful sharp corners.)
- Couldn’t change the placements of the USB Connector and Terminal block.
Hopefully that’s somewhat useful and doesn’t feel like I’m stomping on toes.
Some additional ancient knowledge. Try to avoid sharp angles when laying out traces. I see that you’ve got a lot of those, especially near the jumpers. The old wisdom is that acid from the etch can get stuck in the corner and slowly eat away at the trace. The honest reality is that this is not a problem anymore, but it is still generally recommended to avoid sharp corners. Especially when you’ve got the space to do so.
Re assembly. I think this is all doable by hand with a nice soldering iron and maybe a light pair of hobby magnifiers at worst. I strongly prefer “bevel” style tips. TS-BC2 for TS100/pinecil. You could also go with solder paste and either a hot air gun or a hot plate. If you get low melt solder paste (138C), you can even use an old clothing iron if you’ve got a way to hold it upright.
This is really scattered, so let me know if you’ve got any questions or if there’s anything I missed.
eutampieri@feddit.it 1 week ago
Wow, thanks! You’re not stepping on anyone’s toes. I’m a computer science guy that sometimes likes to dabble with electronics.
I haven’t looked at your PCB yet but I will considering merging this.
Also, how do I solder underneath the CH224K?
JDavis@lemmy.world 6 days ago
Ooh it does have a thermal pad…
In that case, I think you’re on the solder paste train. Get it in a syringe, and use a small lure lock dispensing needle/tip to put a dab (about the size of the pad) on each pad. If dabs are touching a little bit, its okay, but if your board is absolutely covered in paste, you’ll likely have problems.
Then with a pair of tweezers (I like the ifixit 45° ones), you can carefully position each component so its legs touch down into the paste.
Once all the components are on, you need to reflow it. A hot plate works, a clothing iron could work, you could even fill a junk/scrap pan (That will NEVER see food again) with sand and use the stove to heat the pan, removing it from the heat, and pulling the board with beefier tweezers once the paste has melted and wetted all the pads and pins.
Since solder paste is just a bunch of tiny metal balls suspended in flux, so have a fume extraction plan. When it all melts, there will be some smoke/fumes from the flux that travel upward. Try not to breathe those in. A little bit won’t kill you, but it is an occupational health hazard.
eutampieri@feddit.it 6 days ago
Thanks! I will look into this!