Castellated edges to make two boards in one?

[LoveLaika]

I'm playing around with the idea of using castellated edges to make two PCBs in one design (at least, for a very simple small design), and I was wondering if this would be the right way to go about it? The idea behind this was to make an all-in-one design for a really simple schematic rather than having two separate designs. This may not be the most elegant, but I wanted to see if the idea was feasible.

So in this schematic, I just have a simple IC with 4 connections. The idea is that on one PCB, there's a sensor with traces going to a pin header. The header connects to another PCB, which holds a connector that goes off-board. It's really straightforward, and I hope the 3D render with parts helps illustrate the idea.

To make this castellated board idea, I used holes to form the line where the PCB will be split in two. You can see that there in the image as J5. They look like copper holes, but they're non-plated through holes in KiCAD. There shouldn't be any copper associated with them despite the solder mask around them. Also, I had to play around with the net names a bit so that they'll connect through the header but they don't require traces to each other. Finally, the copper pours on the board are not tied to any net. That way, there shouldn't be any issues when the PCB is split.

What do you all think about this approach? Is it a good idea? Seems like a great idea in practice, especially since I'm not dependent on traces at the point where the boards separate. I just felt that having separate PCBs for something so simple was tedious. That way, I don't have to purchase them separately and have all boards together at once.

[Kim Christensen]

PCB houses like JLCPCB will probably treat those as two designs and charge you accordingly. Normally, the way you'd do this is by palletizing the PCBs. (Kind of what you're doing with the J5 connector anyway)

EDIT: Another way is to make a bunch of identical boards. But then you only populate certain parts to make one type and populate different parts for the other.

[JustMeHere]

Just cut the board in half with a hack saw.

[thm_w]

Non-plated means you wouldn't call them castellated edges, since you're not connecting the copper on the edge.

You can read through lots of existing threads:
https://www.eevblog.com/forum/manufacture/jlcpcb-multiple-boards-on-one-board-vs-separate-boards/
https://www.eevblog.com/forum/eda/jlcpcb-isolated-designs/
https://www.eevblog.com/forum/manufacture/is-it-my-fault-or-is-jlcpcb-overly-pedantic-when-they-say-these-are-two-designs/
https://www.eevblog.com/forum/manufacture/copying-the-same-design-a-few-times-to-get-more-boards-inside-100-mm-x-100-mm/
https://www.eevblog.com/forum/manufacture/pcb-boardhouse-that-will-allow-multiple-designs-on-one-board/
https://www.reddit.com/r/PrintedCircuitBoard/comments/crroct/manufacturing_multiple_separate_pcbs_on_a_single/

[Benta]

Silly idea.
Just make  a couple of slots in the board outline. Does the same thing.

[LoveLaika]

That would be one required step, yes.

[LoveLaika]

Thanks. I didn't think of that concern. My fab house would be OshPark, and they seem to support such practices (with a little work).

Creating modular sensors would be very handy, but you would have to imagine the use cases and sensors to interface, make sure they all work.

[LoveLaika]

Thanks for the clarification. What would be the correct definition then? I just recalled seeing this practice on OshPark's pages and thought it could be of use here.

Still, everyone here really loves JLCPCB. Running it through OshPark, they seem to charge it as one big design with the board being as wide as J5. Since it's going off the board, I'm paying for empty space. There has to be a better way to do it.

[LoveLaika]

Thanks. That's an interesting idea. I'm a bit unfamiliar with slots though. From what it seems, they look just like long, oval-shaped non-plated through-holes. Essentially, you just throw one of them onto your board to have a space between my two "boards" (in my case, replacing J5)?

[thm_w]

Thanks for the clarification. What would be the correct definition then? I just recalled seeing this practice on OshPark's pages and thought it could be of use here.

Still, everyone here really loves JLCPCB. Running it through OshPark, they seem to charge it as one big design with the board being as wide as J5. Since it's going off the board, I'm paying for empty space. There has to be a better way to do it.

Please use the Quote button.
If you are using Oshpark then its all good and you can do designs like this. Your design is fine, but will result in a few more rough edges and splinters.

To do a proper edge route + tab you'd have to move the boards apart a little, usually its ~2mm based on the cutter diameter. Might be info on their site: https://docs.oshpark.com/troubleshooting/panelized-designs/

[Benta]

Thanks. That's an interesting idea. I'm a bit unfamiliar with slots though. From what it seems, they look just like long, oval-shaped non-plated through-holes. Essentially, you just throw one of them onto your board to have a space between my two "boards" (in my case, replacing J5)?

Not quite. Slots are part of the board outline in KiCAD. Don't make them with square corners, the manufacturers' router uses a rotating vertical tool to mill them. As an example: create a 2 mm slot with semi-circular ends. Easy to manufacture.

[LoveLaika]

Thanks. That's an interesting idea. I'm a bit unfamiliar with slots though. From what it seems, they look just like long, oval-shaped non-plated through-holes. Essentially, you just throw one of them onto your board to have a space between my two "boards" (in my case, replacing J5)?

Not quite. Slots are part of the board outline in KiCAD. Don't make them with square corners, the manufacturers' router uses a rotating vertical tool to mill them. As an example: create a 2 mm slot with semi-circular ends. Easy to manufacture.

Thanks. I found this video after digging around, showing how to make slots on the Edge Cuts layer. It will be interesting to see how to incorporate this within DRC. It certainly seems more flexible than what I was doing previously.

https://odysee.com/@voltlog:b/how-to-create-high-voltage-isolation:1

[LoveLaika]

Thanks. That's an interesting idea. I'm a bit unfamiliar with slots though. From what it seems, they look just like long, oval-shaped non-plated through-holes. Essentially, you just throw one of them onto your board to have a space between my two "boards" (in my case, replacing J5)?

Not quite. Slots are part of the board outline in KiCAD. Don't make them with square corners, the manufacturers' router uses a rotating vertical tool to mill them. As an example: create a 2 mm slot with semi-circular ends. Easy to manufacture.

Would something like this be what you were mentioning? As you can see, I used the Edge Cut Layer to make a slot with rounded edges. You can see the result in the 3D viewer. Would this be the correct way to make slots?

[Benta]

Yes, that's exactly what I mean and the correct way of making slots.

[Kim Christensen]

Oshpark probably has some minimum spec for how close to the edge of the PCB you can go with the slot. Otherwise, looks good:

[LoveLaika]

Oshpark probably has some minimum spec for how close to the edge of the PCB you can go with the slot. Otherwise, looks good:

Good point. Thanks for pointing that out. I'll keep that in mind when I decide to use a slot for real.

[shapirus]

BTW does Kicad have a way of making slots without having to draw the entire outline manually? Ideally, you'd draw a path corresponding to the horizontal route of the milling bit's axis, then specify the diameter of the bit, and it would generate the respective outline from that, with proper round edges and corners etc. Maybe there's some plugin for this?

[Benta]

does Kicad have a way of making slots without having to draw the entire outline manually?

Better place to ask: forum.kicad.info

[shapirus]

Better place to ask: forum.kicad.info

Yes very likely it's a better place to ask. But it looks like a piece of shit, UI-wise, unlike a proper forum engine which is comfortable to use, so I'm not gonna bother to even register there. If someone on EEVblog knows, then cool, they'll share info, if they want, otherwise no big deal.

[Benta]

But it looks like a piece of shit, UI-wise

Wow!   

Looks are more important than content... well, happy engineering.

[shapirus]

But it looks like a piece of shit, UI-wise

Wow!   

Looks are more important than content... well, happy engineering.

Poor usability raises the justifiable threshold of the initial setup effort. This applies to everything, not just forums. The fact that whoever runs that forum chose to use some weird software looking like a 90's guestbook instead of a well-established industry-standard solution is also an indicator that it's probably better to stay away.