Hi. I’m getting a small run of PCBs done. My “main” board is L-shaped, resulting in wasted space. I have a tiny related board that can use that wasted space, plus I made another design that could also use some of the remaining space. The thing is, that neither of these designs are worth spending extra cash so I’m trying to work within the production house’s limits regarding “multiple-project” designs.
I think I’ve figured out the best use of space… but seperating them is going to be the only issue. I want to have a single V-score horizontally as shown, but it presents one of two problems:
#1) If the v-score is too easy to break, then the upper part of my “L” won’t do its job - which is just a single mounting hole. So is a v-scored PCB so easy to break that it will likely come apart with handling and/or light pressure from the screw?
#2) If the v-score is too difficult to break - by hand - then I’m going to have headaches just getting the things apart.
I have ZERO experience with v-scored panels that are still attached. Since I need that “L” intact, I can’t ask the production house to do the de-panelization for me. I tried searching youtube to see if I could find a video of someone breaking one apart by hand and all I saw was pneumatic machines doing it, which made me think problem #2 is likely.
I’m not sure if I was clear on the shape. In the pic attached above, the lower part plus the top right section form the “L”. That is all one board, but because the production house can’t stop the v-score part way across, it will be scored as well. That’s OK electrically since there’s no traces or components (or anything but a mounting hole) in that upper right section… I’m just not sure if its OK physically. The other 5 sections are separate individual boards.
One more thing I didn’t mention… the boards will NOT be populated with components prior to snapping them apart. I realize strain on parts is an issue so I plan to depanelize first, then load the boards.
If so, you just specify a route around the edge of the L-shaped board that isn’t quite continuous - like a perforation that has a lot more gap than connecting material.
That’s tab-routing, correct? They can do either (or both) tab routing and v-scoring. I went with v-scoring because it seemed easier to draw and I thought it would produce cleaner results once de-panelized. Plus I’ve never been able to find any sort of specifications on how exactly to do a tab-route. Spacing between boards? How long are the tabs? How many holes? What sized holes? Hole spacing? That sort of things.
They are all probably questions that the manufacturer would be used to answering. It depends what they use, but you can go with the smallest bit they have, because you are going all the way through the material.
Tabs are up to you, but if you have a 5mm tab every 50mm or so I think that’s be appropriate.
Yep you need to do a little bit of cleaning up if you are going for a professional look. Seems worth it to me in comparison to a v-score through the tab, which I’d always be thinking was just about to fail
V-scores vary so much you really can’t depend on them for any structural purpose. They are intended to let you break the PCB, after all. Just use tab routing for the small boards, leave your L intact. It’ll actually be cleaner than V score, except for the spots there were tabs.
I’ve come to the same conclusion. In fact, I just finished designing for tab-route. The reason I was shying away from it was I could not find anything via Google that showed me how to design for tab routing. The PCB manufacturer just told me “minimum 40 mils” but that basically said nothing. I still didn’t know how many or what sized holes to drill… how wide the tabs should be, etc. I eventually searched for the term “breakaway” and had better luck. For anyone interested, [I came across this thread which at least showed one guy’s measurements.
You may want to put tabs in connecting the ‘fingers’ on the board. That way there’s a little extra material in place to keep everything together until you’re ready to snap it apart. (Mainly so it doesn’t break up while in the machines being routed.)
Either way, you probably want to contact your fab house and see if they’re happy with the design. DFM is a complicated beast, and they may have additional suggestions specific to their manufacturing line.
I didn’t think the “fingers” needed them because every “specification” I’ve seen says to put them every 5cm or so, and the fingers there are only 2cm in length.
Anyway, the manufacturer wasn’t very forthcoming at first, but once I actually submitted the order… NOW they have loads of suggestions (yeesh)
I had to increase the spacing between the “fingers”. They wanted me to increase the holes in the tabs from 0.46mm to 0.8, which meant having 3 holes instead of 5. Other than that, they say its fine.
yeah, will do! I still haven’t gotten my order confirmation (placed it yesterday) so presumably Monday will be “Day 1” of 8… so I probably won’t see them until about the 2nd week of December.
So I got my boards in a few days ago… I forgot to update this post right away.
They look great in white! Although, I don’t think I’ll use white again for hand-soldered boards… even after thorough cleaning, the rosin flux residues leave a yellowish stain that look disturbingly similar to a sweaty man’s arm-pit stains on his white t-shirt. Even no-clean flux leaves a bit of a stain.
pcbcart did a fantastic job I think. Certainly on par with goldphoenix and it was considerably cheaper. They got them to me ahead of schedule and they were packaged perfectly.
My tab-routing described above worked perfectly for my needs. They break off very easily. If you need it to stay together during assembly, then I’d say they break off too easily. I always intended to seperate them prior to hand-assembly, so its perfect for me. When I say “too easily” I don’t mean they just fall off on their own or anything. They’ll stand up to a little handling even. But it doesn’t take much pressure to break it. I’d say just about the same amount of effort that it takes to break a kit-kat bar
Hopefully this thread helps someone down the road! Thanks for everyone’s input.
s_mack:
pcbcart did a fantastic job I think. Certainly on par with goldphoenix and it was considerably cheaper. They got them to me ahead of schedule and they were packaged perfectly.
Interesting. If you don’t mind me asking, what kind of price did you get at pcbcart? I have just placed my first professional pcb order via DorkboxPDX and I haven’t looked at pcbcart for a quote yet.
s_mack:
My tab-routing described above worked perfectly for my needs. They break off very easily. If you need it to stay together during assembly, then I’d say they break off too easily. I always intended to seperate them prior to hand-assembly, so its perfect for me. When I say “too easily” I don’t mean they just fall off on their own or anything. They’ll stand up to a little handling even. But it doesn’t take much pressure to break it. I’d say just about the same amount of effort that it takes to break a kit-kat bar
You know, they **are** talking of changing the SI base unit of force from newtons to "kit-kat bar breaks"... :D
I too am a satisfied customer of PCBcart. If you are interested in only a few boards, Dorkbot will be the way to go. IF you’re interested in a large quantity of the same board, PCBcart will be cheaper by far. I don’t know where the cross-over point is…
colinb:
You know, they are talking of changing the SI base unit of force from newtons to “kit-kat bar breaks”…
Yeah, I’m always up with the latest in ISO trends.
colinb:
If you don’t mind me asking, what kind of price did you get at pcbcart? I have just placed my first professional pcb order via DorkboxPDX and I haven’t looked at pcbcart for a quote yet.
I never heard of DorkboxPDX. The cheapest I found up till now was Gold Phoenix who charges 110 for 155Sq In. In my case, I was well over 155sq In so they quoted me $400 (and sounded like they were doing me a favor). That was still cheaper than any other source I found except pcbcart, which came out to just under $300 including fast shipping. That was for 100 boards at 4.47 x 2.14 inches. White solder mask, black silk screen (everything else standard)
OK, I just looked up DorkboxPDX. Its $5 per square inch. That’s great for really small orders. But in my case, for example, that would have cost me $4782.90
s_mack:
I never heard of DorkboxPDX. The cheapest I found up till now was Gold Phoenix who charges 110 for 155Sq In. In my case, I was well over 155sq In so they quoted me $400 (and sounded like they were doing me a favor). That was still cheaper than any other source I found except pcbcart, which came out to just under $300 including fast shipping. That was for 100 boards at 4.47 x 2.14 inches. White solder mask, black silk screen (everything else standard)
DorkbotPDX is an electronics club’s PCB batching service. The PCBs are sent out to Gold Phoenix for production.
It looks like 100 * 4.47 in * 2.14 in = 956.58 in^2, so $300 / 956.58 in^2 ~= $0.32 / in^2, a fantastic price.
s_mack:
OK, I just looked up DorkboxPDX. Its $5 per square inch. That’s great for really small orders. But in my case, for example, that would have cost me $4782.90
Actually not quite that much since you get three copies of your board for that $5/in^2 price. Thus it ends up costing about $1626 at $1.67/in^2 but there is no setup fee, shipping, or any other overhead so it sounds like a big win for smaller board/lower quantites. On the other hand, you can’t get your special solder mask and silk screen colors with DorkbotPDX, and pcbcart obviously is tremendously cheaper for the volume you’re doing, while also giving you full control of the special features you need.
pcbcart’s setup and shipping fees are among the most reasonable I’ve seen. I wouldn’t call 100 pcs “high volume” by any means, and they were the cheapest (by far) that I found for that mid-low volume. I have no idea how they stack up for high volume. For really low volume… the setup fee undoubtedly makes them more expensive than batch services.
