Minimum slot size, Mouse bites, Arrggh!

Sketch? I can't exactly envision what you want to do. Multiple small breakaways from a long strip?

Yes, good. We have five sensor ICs on the 1.7-inch end of a 8.8-inch long, 0.45-inch-wide TH-stick PCB. The 10-parameter sensor PCB projects into the middle of a bee-hive, near the queen. At the hive wall, a thin flexible strip carries I2S signals + power past the hive's wooden supers (frame sections). A second 1.7-inch PCB piece mates the strip to a 4-wire cable to our 60-sensor bee-hive monitor (making a total of 70 sensors). The PCB sections are made and machine- assembled as one, but need to be broken apart for use.

Forgot to add sketches to my answering post. Here's the 10-parameter five sensor IC circuit-board section.

And here's the entire 10.5" long manufactured PCB.

The right 8.8-inch portion sticks into the hive. The left 1.7-inch section is broken off, and connected with MOLEX 1.25-mm spacing, 0.12mm thick Premo-Flex, past the beehive walls, to the sensor section.

One should not have to do two PCBs and two machine assemblies, when one can work, to be separated later.

If you want nice clean breaks, v-score is great. You could make a 2d array.

It won't work for mouse-bite solder connections, but you don't seem to have those.

You can snap the scores by hand, but we use this:

(My production people love to buy toys.)

1. Don't. Let the fab panelize for you. They charge per board anyway, and they get better utilization putting your boards anywhere on the panel. (If these are production quantites, you'll probably want a full custom panel, for many other reasons besides just PCB cost.)
2. 2mm width is the "everyone does this by default" size. They can rout at maximum speed with 2mm end mills.
3. Most fabs will do slots down to 1.0, even 0.6mm. This is effective for creepage between component pads, but takes more time -- it will be a cost adder particularly for long routs.
4. Mouse bites are typically 0.5mm holes, closely spaced, positioned tangential to (and inside) the board perimeter. This ensures that the broken material tends not to stick out. It is rough, of course.
5. V-score is done in a straight line, and almost always completely across the panel. (You can order partial v-score, but the tolerances on start/end position are awful -- it's basically a hand operation.) It can be done over routs, which gives the opportunity to make scored tabs -- they break off cleaner than full score (which leaves a full edge rough), and much smoother than mouse bites.

I'm fond of doing the latter -- a routed edge (often in profile, so it fits nicely into place and has smooth edges), with scored tabs so it breaks away smoothly.

Tim

Thank you Tim! This is the exact information I needed, and couldn't get from the PCB house (when it was closed).

I am a V-score fan, but the extra distances required beyond my PCB section are troublesome. Long V-scores (e.g., 10 inches) are hard to break, and using a brake or other tool, puts machine assembled parts at risk. What's more, I feel compelled to sand the broken edges.

V-score over routes, what? Cuts the trace, right? Sounds super useful, but leaves me totally confused. Hmm: rout, route?

Tim, I'm just designing a board just like this, that will snap full panels into boards that then snap into a dozen small boards each.

How do the fabs like to receive Gerbers for this? Routing and V-scores in separate layers/files? Or how? Can you share a setup you use to create these Gerbers? (I'm using Kicad)

Clifford Heath

I read that as V-score over routed slots. So you have a row of through-routed slots, and you v-score the non-routed bits (tabs) so they snap better. That sounds perfect for what I need (what I was asking about FR2 the other day)

Clifford Heath.

OK, how closely spaced? Much, much closer than my CAD system's default minimum hole-to-hole spacing, I assume?

Yeah, that's a good reason to, well -- what they do commercially is use a dual-pizza-cutter contraption to more like wedge the boards apart, rather than bend and break them. (You still want a good 100-200 mils clearance around the board edge, where components are prohibited; they aren't always careful about parts close nearby.) But otherwise, yeah, good reason to make tabs.

Yeah, "rout". Regrettable that the same word (give or take spelling, if that's even the correct spelling for this use actually..?) is used, within the same subject, for two very different things. I'm sure you know an English professor to gripe at about it. :^)

Regarding mousebites: probably like 20 mil holes, 10 mil web between holes (so, 30 mil pitch). Shouldn't be prohibited by most tools or fabs.

They may well just see that you're putting in bites or tabs, and delete yours and put in their own according to their own rules (give or take how much effort they want to spend on it, and how much you want them to check?).

Such features are indicated on a mechanical or drill drawing. Just put down some lines with arrows and a note describing what it is. So, point at one edge of the board and say "V-SCORE WITH TABS" or the like. Put some notes in regards to panelization on there, too (if you're doing the panel yourself, then something to the effect of "PANELIZATION: BUILD AS SHOWN" might clarify that).

Oh, incidentally, they may ask about thieving (unconnected copper pads, added to open areas to improve copper balance, reducing warpage). You may or may not want that on your board, but it's definitely fine on the rails.

Tim

Aren't they two different words? To route, pronounced 'ROOt' and meaning 'planning a path' and to rout, pronounced 'Rowt' meaning 'to dig up'?

Jeroen Belleman

I've put the V-score info on the dimension layer, No questions or problems. Just make the notes clear.

Cheers

In Altium, I add another layer, and explain it in a note to the PCB house. I wish Altium had separate place commands for holes and slots (they make you place and alter pads), and an official / layer setup for scoring.

What are you measuring about the hive? Temperature? Sounds?

I suspect the e-field would be interesting. Maybe plants and insects use e-fields, like fish do.

Altium uses a Region for that, or at least in "newer" versions; PCAD I don't know about. Place a region and tag it as board cutout, just that easy. :)

I make sure to add the outline of the region to the board outline layer (Keep-out Layer) just in case. Actually even better is, starting with the layout and use Tools/Convert/Create Region from Selected Objects, and setting the new region to cutout.

V-score support would be nice, kind of odd I guess that they don't. They do have flex support (kinda sorta done in a similar way, cutting the design into board regions), and AD17 and 18 or thereabouts added backdrilling and blind holes and stuff, which is nice I guess.

Tim

Aha, Place Solid Region, I never explored that, thanks!

I moved to AD18, liked the dark grey, but after fighting many issues, went back to 17 to get work done. Have installed 19, maybe will get brave, and see if they have fixed a bunch of stuff, or not.

Yes, and you also "Rowt" mobs and armies.