Plated board edge routing - Page 1
Forum section: electronics / projects

author: rs20
author_rank: Super Contributor
timestamp: September 03, 2013, 11:11:29 am
content: So, I was developing a board which had a few "plated through-slots" (think plated through-holes, except slots), and then I was thinking, hey, what if I made the slot a bit longer, combined three of them, and then defined my board outline to cut right though the centrelines of the slots? Well, this happened: (see attachments)I think it looks awesome, almost as if there's a block of solid silver integrated into the side of the PCB. I've used it as a convenient place to attach ground alligator clips during testing, although of course you only need copper on the top and bottom for that, having it around the edges is kinda pointless. But cool looking. I don't think I'm exaggerating when I say that this may be one of the greatest leaps in electrical engineering in all of human history.What does everyone think? Crazy/pointless? Crazy/cool? Maybe evenuseful for something?? Here are some thoughts I had on why this might be useful (mostlyat leasthalf joking):Have a high frequence trace running near the edge of the board and you're trying to stop the EMI from escaping using ground via stitching? Just plate the edge and trap the HF properly!Taking this to the extreme, have you ever wanted to integrate coaxial cable right into your PCB? Just place your trace on an inner layer, and surround the trace with ground planes above and below, and long plated slots either side. Win!Want a mains wire coming loose and touching the side of the board to be more likely to contact earth to trip an RCD/fuse? Plate the edge!A battery/switch contact where you don't care about its long term reliability/corrosion resistance? Plate the edge!It looks cool.

author: EEVblog
author_rank: Unknown
timestamp: September 03, 2013, 11:40:05 am
content: PCB fabs will usually charge more for properly plated board edges like this, but you can do it the poor mans way by defining the route path in the middle of existing plated holes. That's common for PCB modules that are flush SMD PCB mounted for example.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 03, 2013, 11:46:24 am
content: You need to specify that the edges are plated - typically you supply two routing layers - one for plated, done at the same time as drilling before the plating process, and nonplated, done as the final step of manufacture.There may be an additional charge for the edge plating depending on the manufacturing process, i.e. whether they can drill & rout on the same machine.

author: rs20
author_rank: Super Contributor
timestamp: September 03, 2013, 12:02:11 pm
content: Quote from: EEVblog on September 03, 2013, 11:40:05 amSo the thing is, the board in the photos above didn't attract any extra charge, because I didn't say or request anything special -- I just set the route path right through the plated slots. I guess the trick that I'mabusingpulling here is that any fab that supports plated though slots (which aren't all that unusual?) already support routing, albeit very brief little routs. I'm using circuitlabs in NZ (notjustbecause Dave chose it for some of his projects, but because I was born in Auckland, and knew about it before (I knew) he did!)Now of course, you can't get your entire circumference plated this way, because your board would just fall out of the panel before it even got to the plating bath. But getting 50% or more of your circumference plated for free shouldn't be a problem because it doesn't require any special attention from the PCB fab -- or does it? Or do they charge you extra regardless? I'm looking at this from a purely theoretical point of view, loving this real-world reality input from you guysI guess another realization I just had is thatanyarbitrary-shaped/sized internal cutout can be plated this way, too. Again, can't think why this is useful.Quote from: EEVblog on September 03, 2013, 11:40:05 amAh yeah, great point,like this bluetooth audio module, eh?

author: EEVblog
author_rank: Unknown
timestamp: September 03, 2013, 12:13:13 pm
content: Quote from: rs20 on September 03, 2013, 12:02:11 pmNo, not unusual, it's a very common and widely used technique.Some fabs don't like doing it and will flag it during gerber checking, but generally I've found most houses will do it without much fuss. Sometimes it's just a matter of making it clear that's what you want. They may often do it with the caveat that they can't guarantee the result. e.g. the plate though may rip out during routing (as partially shown in your photo)QuoteDepends entirely upon the house and their manufacturing process and in-house rules.Not all fab houses manufacture boards in the same way and with the same steps.Some will charge extra for plated slots (or none at all on shared panels sometimes for example).Some won't do plated slots longer than a certain length.Some will remove plating on holes that overlap the edge (without telling you).If you want your entire board egde plated (common to find on RF boards for example), then you normally specify this as a separate step on your design drawing or notes.QuoteOnce again - "it depends". Some fabs won't do unusual shaped plated shapes without extra cost.QuoteYep, that's what I meant.

author: free_electron
author_rank: Super Contributor
timestamp: September 03, 2013, 01:56:44 pm
content: Rf people have been doing this for a long time. You can create captured coaxes in a pcb. Hp (agilent) did this on many a pcb for their rf stuff..Not a new trick. You can actually plate the entire circumference of the board, without gaps. They use a special jig to gold the pcb during plating. You need 2 or 4 sacrifical holes in the board. They clip a plastic stud in those. These holes will not be plated.True castellations (like on that bluetooth module) are done a different way. Castellation is the name for that kind of side plated pad. Looks like the turrets on a castle...Drill the holes , or mill the flats where plated wall is needed.Apply electroless copper. This is molecular levelMill through the holes.The molecular film can not be ripped off by the mill like the finished copper could be.Now electroplate.Process as usualThere are limits to what can be done for castellations as it is determined by the smallest mill diameter availalble. This gives you the interstitial