Improved protoboard/perfboard for direct SOIC mounting - Page 1
Forum section: electronics / general

author: electronic_eel
author_rank: Regular Contributor
timestamp: January 06, 2018, 09:59:33 pm
content: Hi,over the last few months (pcb order & shipment cycles) I developed my take on protoboard or perfboard. My main goal was being able to directly mount common smd packages like SOIC without additional adapters and also to allow more dense packaging by using 1.27mm pitch.I keep the regular 2.54mm raster for THT parts, but put 1.27mm raster smd pads in between. The smd pads have a funky spiked layout to help the solder form bridges when wanted. I found that this makes it more easy to "draw" traces with solder. After a few iterations I think I got the dimensions of these spikes right now for optimal control of the solder flow. Of course you still need a bit more care while soldering and I recommend a smaller tip for your soldering iron (1,2mm chisel, JBC C245-906 is what I use).Now it works as planned and I'd like to share the results:I know that there were some others improving protoboard. Here are the ones I know of:https://www.eevblog.com/forum/crowd-funded-projects/perf/https://www.eevblog.com/forum/crowd-funded-projects/perf-the-perfboard-reinvented-**kickstarter-launch**/http://www.elecfreaks.com/2362.htmlBut as far as I know, nobody offers one with a focus on direct smd mounting.Also I don't want any money for this. The idea is that you can order it for yourself from the pcb manufacturer of your choice. Ordering smallquantities of 10x10cm pcbs has become so dirt cheap that buying regular, one sided protoboard from a local reseller is more expensive by piecefor me than ordering these custom made boards from China.There are no patents or any other crazy stuff for this, the KiCAD sources and some gerber zips ready for ordering are all on github:https://github.com/electroniceel/protoboardHappy prototyping!

author: AF6LJ
author_rank: Unknown
timestamp: January 11, 2018, 02:12:32 pm
content: This is Way Cool.

author: Howardlong
author_rank: Super Contributor
timestamp: January 11, 2018, 02:28:21 pm
content: I like the TSSOP breakouts to 1.27mm.Another product I use extensively nowadays are the Busboard 0.05" square matrix boards: 0.8mm thick with solid ground plane on the underside and unplated holes on a 0.2" square grid.The ground plane makes it reasonable for use with higher speed stuff.

author: plazma
author_rank: Frequent Contributor
timestamp: January 11, 2018, 02:28:42 pm
content: I have used 1.27mm pitch perf boards from Aliexpress. Great for SOIC and 0603.5pcs/lot 6 X 8CM spacing 1.27 universal board ,thickness 1.6mm sided HASL PCB test boardhttp://s.aliexpress.com/nUrI3aqy

author: electronic_eel
author_rank: Regular Contributor
timestamp: January 11, 2018, 08:28:53 pm
content: The Busboard 50x50mil SMT looks good if you really only want to use SMT parts and want to profit from the groundplane. I often mix and match more complex circuitry on a breakout board (say, a microcontroller on something like a blue pill board, reference design from the manufacturer or similar) with my own circuit. To allow that I kept the 2.54mm THT grid.But I know that the groundplane is necessary for some designs. I already thought about using a 4 layer board (prices for them from China came down recently too) to add a ground and power plane. But I couldn't come up with a satisfying design without needing advanced and still expensive stuff like 0.1mm holes to fit it into my raster. Does anybody have an idea for a design to make that work?The linked Aliexpress offering is a regular 1.27mm grid protoboard with all holes plated through. I don't like that because then you can't use the other side of the board to cross different tracks. This is something I used on all my prototypes I've done with my protoboard yet and something I value very much over traditional protoboard.

author: electronic_eel
author_rank: Regular Contributor
timestamp: January 11, 2018, 08:41:15 pm
content: I got a notice that JLCPCB is refusing to manufacture the layout with the breakouts because of the half-cut holes:https://github.com/electroniceel/protoboard/issues/2Now I don't know if they always refuse this or if this was just a overzealous operator on a bad day.Was someone able to have the protoboard-6x4-breakout.zip design produced by JLCPCB/EasyEDA?When you log into their interface and go to "Order history", you can see the status of your order. I think it says "in production", "manufacturing" or similar when it has passed their scrutiny test. It would be nice to get feedback so I can properly inform others about this issue.

author: janoc
author_rank: Super Contributor
timestamp: January 11, 2018, 09:08:35 pm
content: I have the boards "in production" right now, both the 6x4 and 10x5 ones.JLCPCB contacted me twice to "verify and confirm that I want to proceed" and something about "adjustments" but they didn't tell me neither what is wrong/to be verified nor what should I adjust, despite me explicitly asking about it. I have even asked whether it was about the SC70 breakouts (including sending them a picture of the board from your Github) because I have seen the README. No answer, so no idea.I have finally told them to go ahead with the boards as they are in your Gerbers, we will see how it turns out. Can't complain too much for that price.I guess English communication isn't their forte (still better than my Mandarin, though!)

author: ataradov
author_rank: Super Contributor
timestamp: January 11, 2018, 09:12:11 pm
content: Quote from: electronic_eel on January 11, 2018, 08:41:15 pmNope. Those half cut holes are called castellated vias, and most manufacturers will either refuse to do them, or charge extra. They are hell for milling bits. It is an interrupted cut with different materials. And mills must be sharp to have a nice edge without spreading copper all over the place.

author: janoc
author_rank: Super Contributor
timestamp: January 11, 2018, 09:22:23 pm
content: Quote from: ataradov on January 11, 2018, 09:12:11 pmI agree, but we will see. So far they didn't charge me anything extra.The milling shouldn't be all that different from milling slots - you need a sharp bit for FR4 anyway and a good milling machine won't have a big problem with it. Only if they use a very thin bit which could break on the hole edges with a too high feed rate. However, I don't think there is a reason for that here - there was an ample width for the routing, so they could use a larger bit.Now not all vendors do slots neither but that would be another story.

author: ataradov
author_rank: Super Contributor
timestamp: January 11, 2018, 09:26:21 pm
content: Quote from: janoc on January 11, 2018, 09:22:23 pmit is very different because of copper in the cut. It is the same reason why manufacturers don;t let you have copper close to the edge of the board. At the speeds they cut FR4, copper gums up the mill. You need different speed and feed for cutting the mixed material, which is sub-optimal.

author: janoc
author_rank: Super Contributor
timestamp: January 11, 2018, 09:28:46 pm
content: Quote from: ataradov on January 11, 2018, 09:26:21 pmTrue, but hardly unmanageable. If they support through-plated slots (or cutting slots in general - many are in copper pours too!), they will have the same problem so they will have to have a procedure for it in place.JLCPCB is not a cheap, hobbyist grade fab (despite the low prices), from what I know they are one of the largest board fabs there.

author: electronic_eel
author_rank: Regular Contributor
timestamp: January 11, 2018, 09:35:19 pm
content: Quote from: janoc on January 11, 2018, 09:28:46 pmNo, that's different. Because plated through slots will be milled before plating. The castellated holes will be cut afterwards with the rest of the outline.I know of the difficulties of cutting copper and castellated holes. But this technique has become quite popular in the last years, so most manufacturers support it some way or the other.

author: Howardlong
author_rank: Super Contributor
timestamp: January 12, 2018, 08:29:22 pm
content: Regarding the groundplane and the Busboards, you’re not precluded from using DIP parts, they just dance a bit above the board unless you choose to shorten the pins. I leave them as-is, if I blow up the part I can snip it off more easily. More likely though with a microcontroller I use a socket for a DIP part anyway.It depnds what you’re doing, most of my stuff is mixed signal, including RF, so a decent ground plane is pretty much essential. The same will also apply to many SMPS designs.I agree it’s not a simple thing to apply in a generic fashion. Schmartboards do it with their breakouts, it’s quite a compromise, but better than nothing.

author: electronic_eel
author_rank: Regular Contributor
timestamp: January 12, 2018, 09:32:55 pm
content: Quote from: Howardlong on January 12, 2018, 08:29:22 pmI see. Since a lot of prototype manufacturers now allow sending a separate NPTH Excellon file, I could create an alternative layout with a solid ground plane on bottom, non plated-through holes in 2.54mm grid and the layout as it is on top. That would allow using this alternative layout for designs that require a proper ground plane.Or do you have an idea how to modify the layout to allow using a 4 layer board with internal ground and power? Maybe tapping to ground or power by scratching off soldermask somewhere. But I couldn't come up with a layout yet that didn't require 0.1mm holes or blind vias, both stuff which is still pretty expensive.

author: janoc
author_rank: Super Contributor
timestamp: January 18, 2018, 07:58:36 pm
content: OK, an update on the JLCPCB results.I have got my box of 20 boards today (ordered 9th Jan, arrived today by DHL, not bad, considering the e-mail ping-pong at the start - normally they are faster).The board quality if overall OK, but the castellations are definitely at the limit of the process they are using for these cheap boards.They did route through the holes, as specified, no problem. However, it is not very clean, there are pieces of copper and FR4 hanging in places. So I am not sure whether the breakouts will be usable, the SC70 ones have also silkscreen across the area where the chip is supposed to goThat will make soldering there interesting. Not sure whether that's a mistake they made or the gerbers are like that (didn't check).But hey, for $10 for all 20 boards delivered, I am not going to complain!Sorry for the poor image quality, don't have a camera for my good microscope so had to make do with a cheap USB one. The boards are green, the purple/bluish tint is because of my camera/LED light.

author: ataradov
author_rank: Super Contributor
timestamp: January 18, 2018, 08:09:14 pm
content: Yes, this is exactly what happens if you use the same feeds and speeds as for normal boards, without taking into account that you are machining copper and have interrupted cut.

author: janoc
author_rank: Super Contributor
timestamp: January 18, 2018, 08:33:45 pm
content: Quote from: ataradov on January 18, 2018, 08:09:14 pmWell, frankly, to me it looks more like they had a dull milling bit to begin with because even the FR4 alone is torn up and chewed, not just the copper.But as I have said before - hard to complain for the price and for something they aren't normally offering.

author: electronic_eel
author_rank: Regular Contributor
timestamp: January 18, 2018, 10:27:29 pm
content: Thanks for the feedback with the photos.Quote from: janoc on January 18, 2018, 07:58:36 pmThe ones I got from Elecrow looked a bit better, but they look still usable to me. Just use a bit of sandpaper on the sides to get rid of the remaining copper.Quote from: janoc on January 18, 2018, 07:58:36 pmIt was designed like this. The Silkscreen isn't on the pads, just between the two sides of the ic. Looks like their silkscreen is a bit thicker than usual, but don't think this will be a problem.

author: janoc
author_rank: Super Contributor
timestamp: January 18, 2018, 11:57:26 pm
content: Quote from: electronic_eel on January 18, 2018, 10:27:29 pmYeah, I guess no biggie, just have to make sure to really clean that up well - the hanging copper causing shorts could be a real pain.Quote from: electronic_eel on January 18, 2018, 10:27:29 pmI am afraid that if I put a chip on that footprint it won't sit flat and will be difficult to solder it on. In the worst case I will need to scrape it off there. I think it looks so thick because it is a very short line so the ink has pooled there. If you look at the other examples in the pictures, their normal silkscreen isn't that thick.I wouldn't have personally put silkscreen inside of the footprint, though, only maybe an orientation mark outside. It is probably something you may want change for the future revisions, along with the castellations - breakout with normal holes is completely fine, even if it takes more space on the protoboard and needs wires/pins soldered in the holes.

author: Kean
author_rank: Unknown
timestamp: January 19, 2018, 12:02:08 am
content: Castellations do require special processing as mentioned earlier, so without them optimising for that (and you paying extra) this is what you'll get.http://docs.oshpark.com/tips+tricks/castellation/Seems pretty good for the price.

author: janoc
author_rank: Super Contributor
timestamp: January 19, 2018, 12:09:29 am
content: Quote from: Kean on January 19, 2018, 12:02:08 amYeah, certainly not complaining. $10 for 20 sets of protoboards? Gimme any time. I have actually explicitly told them to go ahead even if it won't be perfect, fully expecting the breakouts on the side to be a write-off. This is a lot better than I have expected.Just @electronic_eel may want to revise his (otherwise pretty good) files for the future to avoid these issues.

author: electronic_eel
author_rank: Regular Contributor
timestamp: July 21, 2019, 03:27:07 pm
content: I created a new variant with a near-solid GND plane on the bottom side:Plated-through holes in 2.54mm rasterThe holes have a minimal annular ring of 0.15mmAround the ring is another 0.15mm spaceAfter that the GND plane beginsA hole just soldered on the top is not automatically connected to the GND plane because of the 0.15mm spaceJust put a blob of solder on the bottom to connect a hole to the GND planeSources and ready-to-order gerbers as always athttps://github.com/electroniceel/protoboard.