Seemingly impossible board cutout for USB Micro-B receptacle - Page 1
Forum section: electronics / projects

author: Aleksolder
author_rank: Contributor
timestamp: September 05, 2014, 02:44:44 am
content: When these arrrived, I noticed that they need a board edge cutout, and lo, it does show in the datasheet (in the attached excerpt the edge is labeled "PWB edge").How is it possible to make such a board cutout? The cutting tools rotate, so square edges are not possible.The part is a USB Micro B receptacle, Hirose ZX62WRD-B-5PC.

author: TerraHertz
author_rank: Super Contributor
timestamp: September 05, 2014, 03:06:27 am
content: Mass produced boards are punched out using custom machine tools, not routed. The punch tooling can have any shape they want.So, this connector is intended to be unusable for anything not mass produced.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: September 05, 2014, 03:14:57 am
content: Quote from: TerraHertz on September 05, 2014, 03:06:27 amBah, maybe, but just shoot some non-plated drill hits in the corners so when they route it'll have an inside radius.

author: Aleksolder
author_rank: Contributor
timestamp: September 05, 2014, 03:37:39 am
content: TerraHertz: I didn't know, thanks. My boards will be mass-produced, but not so mass-produced as that.Alex: I did think of that, but the tolerances look very tight. To stay 0.35mm from the nearest pad on this part, the corner drills would have to be 0.6mm, making the router bit 0.3mm, not very feasible.

author: DanielS
author_rank: Frequent Contributor
timestamp: September 05, 2014, 04:04:27 am
content: You can finish the cut-outs with a thin grinding wheel or anything else of the sort that can do plunge-cuts from the PCB edge to square the cut-outs off.

author: ConKbot
author_rank: Super Contributor
timestamp: September 05, 2014, 05:31:41 am
content: How thick of a board? Are there any PCB fabs that do laser routing? I'm not even sure how well FR-4 would laser cut with all the glass content in it though.

author: Aleksolder
author_rank: Contributor
timestamp: September 05, 2014, 05:39:42 am
content: DanielS: sure, manual touch-up for one-off, but not for thousands. In fact, for a prototype, I've already ground off the bumps on the receptacle to make it fit a prototype board that did not have the cutouts, works fine.ConKbot: 0.6mm. I was looking for a laser engraver to make Mylar stencils, and apparently the commonly available lasers won't go through glass nor fiberglass. And if possible, it sounds specialized, which would greatly narrow my selection of fabs. Can't hurt to ask, though.

author: David Hess
author_rank: Super Contributor
timestamp: September 06, 2014, 02:36:23 am
content: A notcher would cut it just fine. This was how old printed circuit board connector fingers were keyed and the relief cut out.

author: Aleksolder
author_rank: Contributor
timestamp: September 06, 2014, 02:53:17 am
content: Very interesting, I looked it up, great tool. I don't think I'd trust my Shenzen fab to get this right, though, even if it's a tool they have. I will look into it next time I'm visit them, though.

author: andy_silicon
author_rank: Regular Contributor
timestamp: September 06, 2014, 04:11:06 am
content: How about the square hole drill/mill bit ?http://youtu.be/rI-15fovYEY

author: Paul Moir
author_rank: Frequent Contributor
timestamp: September 06, 2014, 04:43:06 am
content: Well you could stack a bunch of boards on end and run a standard endmill though it.(Rant: things designed with square inside cutout corners like that are a design fail. Even though mass produced boards are stamped out, someone has to make the tooling, and square corners like that needlessly drives up cost.)

author: marshallh
author_rank: Unknown
timestamp: September 07, 2014, 03:20:42 am
content: oshpark can mill 20mil slots. so it's routable.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 07, 2014, 05:31:14 pm
content: What are the slots actually for? Take a look at an actual connector and see if you can get the required clearance with a sensible sized router

author: DanielS
author_rank: Frequent Contributor
timestamp: September 07, 2014, 05:48:49 pm
content: Quote from: Aleksolder on September 05, 2014, 05:39:42 amYou can use a table saw with two blades and the right spacer thickness in-between, put a stack of boards together (might want to have tooling holes for alignment rods which may double as stack clamps) and run the stack through. That would work fairly well for 100+ boards at a time once the jig is properly setup.You could do a similar thing with a router table: put a router with a bit just the right size at just the right height, stack your boards, run them through.