In a similar vein, I discovered and have started using the Tag-Connect TC2030-USB to program/troubleshoot my boards. While it's technically/originally intended as a way to do JTAG debugging, I am completely enamored with the ability to drop a footprint on my PCB and be able to connect to it without having to place a relatively expensive connector (or a connector at all) that I don't necessarily want users interacting with.
They're fine for one guy using them on the bench but they are a nightmare for mass production. The 50-mil pitch is annoying to make work with a bed-of-nails fixture, the clips are fundamentally incompatible with production lines, either robot or human, the parts are expensive, and the cycle life is not there.
I have had one too many arguments with firmware people who think these things are sufficient for production that I am just done with them by now. There are other ways to do it.
Just put normal test pads next to the tag connect, a bit more spaced out. A bed of nails in the production line connects to that, the tag connect can be used for bench development.
I've been doing a cheap DIY version of Tag-Connect for some STM32 projects (6-pin debug). I just put the holes for a pin header near the edge of the board, and use a pogo clip to connect [0]. (These are readily available on AliExpress in various sizes.)
Doesn't it require ENIG? I wanted edge connector for my pcb project but it adds $20 to the price of pcb, that's just too much. Anyone knows card edge alternative? I'm thinking pin header but that's not very user friendly. Edge card can be inserted blindly even if you don't see the connector, pin header would probably just bend irl.
I've found 0.8mm to make much more reliable connections, since the specification says that the tongue should be 0.7mm. 0.6mm will disconnect if the cable is angled in any way.
i wonder how often you can plug/replug the connector in this case. how will the pcb material hold up? with my press-fit or clip-fit (is that a term?) 3d prints, ive noticed that 20 cycles can be sufficient to induce substantial 'loosening'.
It’s likely in the order of 10-30, especially with something like ENIG as a finish. If you wanted more cycles, you’d want to switch to a hard gold finish which would likely increase the cost substantially.
This is truly only for a debug port, not anything else.
That's cool but I am not sure how a customer of mine would feel if I shipped a board to them like that. (I could see trying it on a project for myself, though.)
The problem with USB-C connectors for hobby projects is that they are ass to solder by hand—I’m still looking for one that would use a larger pitch by shorting the four USB pin pairs for either orientation. If you’re shipping something to a customer, I think it’s fair to assume that you don’t really have that problem :)
They're also ass to make PCBs for. The second you need 2oz or higher you start to really push the limits of what most prototype shops can do.
This is a pretty standard 2.0 receptacle, you've only got 0.2mm between pads if you follow their footprint (literally the limit for soldermask bridges on 2oz at JLCPCB): https://gct.co/download?type=PDFDrawing&name=USB4105.pdf
Get a hot air gun: it'll make your life way easier. You can tin the pads with a soldering iron, put the connector on and squirt some flux on the leads, and then just blow hot air until it reflows into place.
What do you do if the structural through-holes already have solder in them, that wick doesn’t seem to get? I’ve been trying to put a new USB C port onto my switch for quite a while now. (Now that I think about it, I can probably just shorten the prongs on the port and add solder after for structural strength).
How would tinning those tiny pads not create a massive bridge between them? Does the bridge somehow go away in the reflow phase? (Not familiar with reflow at all)
Do you find the 6-pin charge-only Type-C connectors too small? Or the 16-pin 2.0-only ones? They seem reasonably hand-solder-friendly but I admit I've been fortunate enough to have the factory handling them for me.
Yeah, I find the 16-pin ones a little beyond my skill. They also feel silly—why can’t I have one with just six pins for D±, VBUS, GND, and CC1/2? I guess I could have a factory make a bunch of modules like that for me, but it definitely feels like a thing that should already exist.
(There are passive A-to-C adapters, so I see no reason why I couldn’t short pin pairs like that.)
In a similar vein, I discovered and have started using the Tag-Connect TC2030-USB to program/troubleshoot my boards. While it's technically/originally intended as a way to do JTAG debugging, I am completely enamored with the ability to drop a footprint on my PCB and be able to connect to it without having to place a relatively expensive connector (or a connector at all) that I don't necessarily want users interacting with.
https://www.tag-connect.com/solutions-target-devices/usb-ser...
They have FTDI versions as well, for those who want the full USB boot/reset treatment.
Also, they have another connector for attaching to castellated edges. I think it's just so clever.
Maybe you like this - "paw connect", a whimsical version of the footprint for this connector:
https://github.com/LeoDJ/Paw-Connect
They're fine for one guy using them on the bench but they are a nightmare for mass production. The 50-mil pitch is annoying to make work with a bed-of-nails fixture, the clips are fundamentally incompatible with production lines, either robot or human, the parts are expensive, and the cycle life is not there.
I have had one too many arguments with firmware people who think these things are sufficient for production that I am just done with them by now. There are other ways to do it.
Out of curiosity what are the other ways?
Just put normal test pads next to the tag connect, a bit more spaced out. A bed of nails in the production line connects to that, the tag connect can be used for bench development.
I've been doing a cheap DIY version of Tag-Connect for some STM32 projects (6-pin debug). I just put the holes for a pin header near the edge of the board, and use a pogo clip to connect [0]. (These are readily available on AliExpress in various sizes.)
[0] https://www.adafruit.com/product/5433
I do exactly the same on my boards and use that same clip.
I had good experience with carefully spaced holes in PCB and a 50 mil header, see https://jacdac.github.io/jacdac-docs/ddk/firmware/jac-connec...
I just use ordinary straight pin headers and stagered via holes. The board just has vias and the cable just has a plain pin header not even pogo pins.
Same, enamored and I’m not even the EE. Elegant, no cost on the product side, and I don’t have to take the board out of the case to access it.
Doesn't it require ENIG? I wanted edge connector for my pcb project but it adds $20 to the price of pcb, that's just too much. Anyone knows card edge alternative? I'm thinking pin header but that's not very user friendly. Edge card can be inserted blindly even if you don't see the connector, pin header would probably just bend irl.
What PCB thickness is optimal? The USB-C tongue on a shieldless part I use is ~0.7mm, which is a pretty thin PCB.
They say "use 0.6 mmm"
https://x.com/AnasYMalas/status/1982060711670067350
That is a very thin PCB. For anyone reading this, 1.6mm is standard.
I've found 0.8mm to make much more reliable connections, since the specification says that the tongue should be 0.7mm. 0.6mm will disconnect if the cable is angled in any way.
+copper+ENIG is going to make that 0.7mm
i wonder how often you can plug/replug the connector in this case. how will the pcb material hold up? with my press-fit or clip-fit (is that a term?) 3d prints, ive noticed that 20 cycles can be sufficient to induce substantial 'loosening'.
It’s likely in the order of 10-30, especially with something like ENIG as a finish. If you wanted more cycles, you’d want to switch to a hard gold finish which would likely increase the cost substantially.
This is truly only for a debug port, not anything else.
Plug an OTG cable in and connect to that, so you don't repeat plug-unplug?
What about the force transferred by the connector wiggling? I think You'd need a very good mechanical design on the case to make it all work.
I don't think it's intended for thousands of mating cycles. It's a "free" standard programming/debugging/recovery/configuration interface.
That's cool but I am not sure how a customer of mine would feel if I shipped a board to them like that. (I could see trying it on a project for myself, though.)
The problem with USB-C connectors for hobby projects is that they are ass to solder by hand—I’m still looking for one that would use a larger pitch by shorting the four USB pin pairs for either orientation. If you’re shipping something to a customer, I think it’s fair to assume that you don’t really have that problem :)
They're also ass to make PCBs for. The second you need 2oz or higher you start to really push the limits of what most prototype shops can do.
This is a pretty standard 2.0 receptacle, you've only got 0.2mm between pads if you follow their footprint (literally the limit for soldermask bridges on 2oz at JLCPCB): https://gct.co/download?type=PDFDrawing&name=USB4105.pdf
Get a hot air gun: it'll make your life way easier. You can tin the pads with a soldering iron, put the connector on and squirt some flux on the leads, and then just blow hot air until it reflows into place.
What do you do if the structural through-holes already have solder in them, that wick doesn’t seem to get? I’ve been trying to put a new USB C port onto my switch for quite a while now. (Now that I think about it, I can probably just shorten the prongs on the port and add solder after for structural strength).
A desoldering pump (manual model, $10 or so for a decent one) is very suitable for removing solder from through-holes, if that is the main issue.
How would tinning those tiny pads not create a massive bridge between them? Does the bridge somehow go away in the reflow phase? (Not familiar with reflow at all)
Yes, the surface tension of melted solder pulls the solder to just the pad areas (assuming you don’t have far too much)
Using with a little flux while tinning usually prevents the pads from bridging
Do you find the 6-pin charge-only Type-C connectors too small? Or the 16-pin 2.0-only ones? They seem reasonably hand-solder-friendly but I admit I've been fortunate enough to have the factory handling them for me.
Yeah, I find the 16-pin ones a little beyond my skill. They also feel silly—why can’t I have one with just six pins for D±, VBUS, GND, and CC1/2? I guess I could have a factory make a bunch of modules like that for me, but it definitely feels like a thing that should already exist.
(There are passive A-to-C adapters, so I see no reason why I couldn’t short pin pairs like that.)
Very clever packaging of a connector
If you're interested in other PCB edge connectors, here's an HDMI one I designed:
https://forum.kicad.info/t/hdmi-pcb-edge-connector-for-raspb...