USB footprint/part question - cheap Chinese connectors. - Page 1
Forum section: electronics / general

author: phil from seattle
author_rank: Super Contributor
timestamp: January 23, 2018, 07:26:01 pm
content: I found a cheap source of USB connectors. Footprint drawing below. It's lacking in one key detail (pad length for the 5 pins) but that's not my question as I can make a reasonably good guess on that.The two boss holes are incredibly close to the pads and even the most aggressive and optimistic (i.e. probably unreasonable) DRC rules fail the check. If I ignore the error and send the board to OSHPark, it passes their tests. Note that I've moved the smd pads back (from the center of the connector) because the actual pins on the part are farther back. Also the bosses have a diam of .45 mm (+/- .05mm) and the drawing calls out .8 mm holes but this overlap with pads (VBUS and GND) so I reduced the holes to .6mm. I've monkeyed with footprint layout. There's no copper getting cut by the drill. Overall, this feel like I'm hacking rather than designing.I'll probably get the board made but wanted to get some feedback before I give it a try. If it doesn't work out I'll just junk these parts but, at $0.10 each, it would be great if they can be made to work.Any thoughts or guidance appreciated.

author: ebastler
author_rank: Super Contributor
timestamp: January 24, 2018, 07:45:14 am
content: How do you intend to use these parts? If it's just for a one-off, or a few units you will hand-build, I would probably remove the boss holes from the footprint, cut off the plastic pins from the jacks, and carefully position them manually for soldering.If you intend to produce a larger batch, and connectors with more generous tolerances are available, I would ditch the 10 cent parts. Why risk wasting a whole batch of PCBs in case the tolerances don't work out, just to save a few dollars on the connectors?

author: phil from seattle
author_rank: Super Contributor
timestamp: January 24, 2018, 05:38:42 pm
content: Thanks for replying!Not a production run but stock parts for projects. Some times I'll build up to 10 copies. maybe 30-50 boards a year. So, over time it adds up. The JAE connector I usually use is > $1.00 in small quantities so it's a pretty significant differential. I'm not so worried about the tolerances of the parts but the vendors abilities to manufacture PCBs with the footprint. I'm about ready to send off a test board so we'll see. I think I'm going to give ALLPCB a try with this. If they can do it, it's a pretty safe bet the others can.Good point about cutting off the bosses though the connection to be PCB will be pretty weak and will require good placing to get it straight for reflow (I doubt it will self-center).By the way, this isn't the first time I've found parts that have spacing issues like this. A number of them are from reputable manufacturers so it's an issue that goes well beyond cheap Chinese parts. My guess is most designers know what their board fab is capable of and just ignore the DRC errors.

author: Monkeh
author_rank: Super Contributor
timestamp: January 27, 2018, 04:32:30 pm
content: I can't say as to the manufacturability of that part, but for a durable micro socket which isn't too expensive (at least over here) and is manufacturable, I use one by the part number of 10103592-0001LF. It requires some plated slots, but it has the bonus of being sturdy andthe right bloody way upwhen on top of the board.For whatever reason over here they're about half the price of most.

author: josip
author_rank: Regular Contributor
timestamp: March 04, 2018, 09:06:01 am
content: I am using the same connectors, and holes for plastic pins are larger (on drawings and eagle lib examples that can be found on web) than they should be. Also, all pads in my custom lib are rounded (there is no sharp edges) so it helps also to put elements closer.