Compact SMD power connection - Page 1
Forum section: electronics / beginners

author: anvoice
author_rank: Frequent Contributor
timestamp: June 18, 2025, 07:35:15 am
content: I have a project that I was thinking of using an XT30PW-M connector for, but realized it's about a third of my board size in both dimensions, a bit too much I think. The nice thing about the XT30 is it handles 30A continuous current based on hands-on tests, and I will need to push a fair bit of current for controlling a brush-less motor. Is there a good alternative connector that is fairly compact? I was looking at the HB-9500 barrier terminal block, but that has a pitch of 9.5mm and I would prefer to fit 5 of these to a side (the board will likely be a 32mm square). Can't seem to find something that performs similarly with a pitch of 5-6mm.

author: mtwieg
author_rank: Frequent Contributor
timestamp: June 18, 2025, 12:50:56 pm
content: High current, SMD, and compact... if you try for all three then I think you'll have issues with pads getting ripped off the board.30A through one wire means AWG 10 wire. I don't believe you'll find any connector that accepts AWG 10 wire with a pitch below 7mm.How much current does each wire actually need to carry (long-term RMS)? Would it be ok to break each circuit into multiple smaller wires in parallel?

author: anvoice
author_rank: Frequent Contributor
timestamp: June 18, 2025, 09:01:25 pm
content: Quote from: mtwieg on June 18, 2025, 12:50:56 pmI erred in the title: it should be PCB-mount, not SMD. So through-hole is perfectly fine. I am looking at a little over 16A peak current (BLDC motor with DRV8316 driver, each phase I believe peaks at 8A, 2 phases active at once, plus mcu and small power draw components). The 30A was just a reference to what the XT30 can do, not necessarily a requirement. Also, the PCB will likely be 32x32mm with 3.2mm holes in the corners (on a square 28-29mm to a side). Then I need to fit 5 contact points for power (Vbatt or 24V and GND) and the A, B, and C phases to a single side.

author: mtwieg
author_rank: Frequent Contributor
timestamp: June 19, 2025, 12:23:55 pm
content: Ah ok, then this is a lot more reasonable.I'm betting you can find something within the Mini-fit family which will work. For example the"MINI-FIT PLUS HCS"parts advertise current ratings up to 13A per contact (depending on the wire gauge and number of contacts in the housing, see table 4.3 for details). For example you could use39303035(13.8mm wide) for the three BLDC connections, and26013114(5.4mm wide) for the DC power. Should leave you room to spare.

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 19, 2025, 02:47:58 pm
content: You can use one of Fast-On variant, like 4.8 mm or 6.3 mm (or even 9.3 mm one).Like this726386-2TE CONNECTIVITYIt can be 90 degree angled too.928814-1TE CONNECTIVITY 90degi'm not sure it is smaller than XT30 (I guess it is a bit larger), but just another possibility for high currents.I used them a lot until XT30/XT60 became popular.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 19, 2025, 03:15:10 pm
content: Quote from: Vovk_Z on June 19, 2025, 02:47:58 pmAnd if you look really hard you can find right-angle the other way round - surprising how uncommon this type ishttps://www.digikey.co.uk/en/products/detail/te-connectivity-amp-connectors/62166-1/294408

author: anvoice
author_rank: Frequent Contributor
timestamp: June 20, 2025, 06:13:24 am
content: Quote from: mtwieg on June 19, 2025, 12:23:55 pmNot sure adding pins and housings for the pins is the most efficient solution... I was hoping for some type of screw terminal as I really need that 16A (13 is a bit low). The idea is to place pads with holes that could accommodate either a connector or wires soldered directly. The challenge is finding a type of screw terminal with the right pitch and current rating.Quote from: Vovk_Z on June 19, 2025, 02:47:58 pmThose look curious, but how does one connect wires to those? Also a shame that there is no isolation between connectors if I were to go that route, I like that barrier blocks or screw terminals have the plastic to prevent possible shorts should something go mildly awry.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 20, 2025, 08:11:00 am
content: Quote from: anvoice on June 20, 2025, 06:13:24 amFor screw terminals there is always this style, available in a range of sizeshttps://www.toby.co.uk/pcb-hardware/spade-screw-terminals/pcb-1-valcon-low-profile-34mm-pcb-screw-terminal/

author: tooki
author_rank: Super Contributor
timestamp: June 20, 2025, 10:24:26 am
content: Quote from: mikeselectricstuff on June 19, 2025, 03:15:10 pmThat isn’t a through-hole part: it’s intended to be screwed or riveted to a PCB, producing the same orientation as the one in the very first link above.

author: mtwieg
author_rank: Frequent Contributor
timestamp: June 20, 2025, 11:09:40 am
content: Quote from: anvoice on June 20, 2025, 06:13:24 amEh, I typically prefer cable assemblies over individual wire connections to prevent mixing up polarities.If you want 16A rated contacts for the DC supply, you could step up to something likemega-fit(8.35mm wide for a 1x2 header). Not sure if you have a height restriction though...If you really want highest power density without soldering directly to the board, then quick disconnect/faston terminals are probably your best option, as Vovk_Z suggested.QuoteYou crimp each wire into a female terminal. You can get female terminals with full insulation,like this. The insulation does add substantial bulk though. For that terminal its "thickness" is about 4.3mm, but that should be compact enough for your board.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 20, 2025, 11:27:26 am
content: Quote from: tooki on June 20, 2025, 10:24:26 amDidn't notice that - they can be used as a through-hole, but the depth in the hole isn't well defined.This style is surprisingly rare, the only other one I could fine was thishttps://www.toby.co.uk/pcb-hardware/spade-screw-terminals/pc1l-valcon-right-angle18mm-diameter-screw-hole-pcb-spade-terminal/

author: tooki
author_rank: Super Contributor
timestamp: June 20, 2025, 11:59:19 am
content: Quote from: mikeselectricstuff on June 20, 2025, 11:27:26 amTo me it’s not surprising why they’re rare: fastons can take a lot of force to mate, especially the first time, so inserting one in that way makes it really easy to just bend the thing backwards, since only the thickness of the two pins is there to resist bending. On the more common right-angle ones, the insertion force is well-bolstered.

author: anvoice
author_rank: Frequent Contributor
timestamp: June 25, 2025, 07:09:11 am
content: Well, after scouring the web and Digikey, I'm still stuck. I found 5mm pitch connectors which carry 20A max, but not 4mm pitch ones (these seem to top out at 10A). Not sure what to do aside from soldering the wires to the PCB. The 5mm pitch ones encroach significantly on the hole spacing.I could make the PCB a little larger, but was hoping it doesn't come to that.

author: Simmed
author_rank: Frequent Contributor
timestamp: June 25, 2025, 07:44:32 am
content: card edge ?https://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/1888946-1/4021557there is a odd 1https://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/2351970-1/12349777the pdf is on this pagehttps://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/2338718-1/10294580looks like 25A max (per pin ?)https://www.te.com/en/product-2351970-1.html

author: anvoice
author_rank: Frequent Contributor
timestamp: June 25, 2025, 08:03:25 am
content: Quote from: Simmed on June 25, 2025, 07:44:32 amLooks nice, but there's a catch: If using 2.54mm pitch positions, I won't be able to solder the wires on directly if necessary (spacing too small). This could be preferable for the motor phase connections, for example, if they don't need to be disconnected. I was hoping to have the choice to use terminals or leave them off and solder directly to the pads. Apologies for not clarifying that earlier.There are some copper terminal blocks that could do the job, but the only ones small enough for the job are flat-bottom (i.e. no pin that goes through the PCB). That's probably asking to get the pad ripped off.

author: Simmed
author_rank: Frequent Contributor
timestamp: June 25, 2025, 08:08:51 am
content: Quote from: anvoice on June 25, 2025, 08:03:25 amthe power type is about 9mm wide, not normal 2.54mm pitchits an odd 1its about the same size as the faston 9.3mm

author: anvoice
author_rank: Frequent Contributor
timestamp: June 25, 2025, 08:13:39 am
content: To be honest, I don't understand that one completely, If it has one position (and is 9mm wide) I definitely can't fit 5 of those. If it has 3 positions and is 9mm wide, that's pretty good, but I can't see where the pins meet the actual pads...

author: mtwieg
author_rank: Frequent Contributor
timestamp: June 25, 2025, 08:16:03 pm
content: Quote from: anvoice on June 25, 2025, 07:09:11 amWait, so suddenly you require 4mm pitch? I'm confused.What's wrong with the faston/quick disconnect terminals?Here, you can even getfive tabs in one assembly, each rated for 15A, total length is 23.1mm.

author: anvoice
author_rank: Frequent Contributor
timestamp: June 25, 2025, 10:30:11 pm
content: I reread my initial post and that's where the confusion stems from. Indeed, I later realized I need 4mm: 5mm pitch plus several mm for the sides of the housing means I can't actually fit a 5mm pitch connector between the holes. I'm attaching a preliminary picture of the PCB to illustrate (the footprint on the very top is a has 5mm pitch between holes). The max allowed length of all 5 connections is about 20mm: otherwise the screws won't fit. Apologies for not noticing this sooner, I honestly thought I'd be fine with 5mm before.That one looks nearly perfect. The only issues are length (by 3.1mm) and the 15A rating: assuming the motor draws close to that (should top out at 16A), that leaves barely any breathing room for the electronics on the board.I know I'm asking for a lot in a compact connector, but I wanted to explore all the options before having to forget the removable connectors, change the board size, or try to stagger the connectors.

author: thm_w
author_rank: Super Contributor
timestamp: June 25, 2025, 11:46:46 pm
content: Does the board actually need to be that small? Who defined it?Motor has been tested and will actually draw 8A?You can consider doing what most ESC boards do: solder the wires straight to the board and then have a XT30 on the end of that short wire segment.https://rotorvillage.ca/esc-s-speed-controller-s/OPs other thread is here for reference:https://www.eevblog.com/forum/projects/bldc-driver/

author: anvoice
author_rank: Frequent Contributor
timestamp: June 26, 2025, 03:29:36 am
content: Quote from: thm_w on June 25, 2025, 11:46:46 pmIt's not a strict requirement, but a very strong preference of mine. The idea is to use the board for various sized motors, and the smaller it is, the better the chances it will fit a smaller motor properly. It's also the size of an Odrive micro, which I wanted to emulate for compatibility (if that ever becomes a need).I just noticed yet another mistake: the DRV8316 has a peak total current of 8A (continuous 3A), not per phase current as I thought for some reason. This essentially limits its use case to smaller motors. Although it's moot now, the biggest motor I was planning to use is rated for 11.2A stall torque, which means the DRV8316 is not the right fit for it.To conclude: I need a screw terminal with a current rating of 10A, not 20A. I'll now get to finding a properly specced part. As far as my biggest motor goes, I'll probably need to design yet another controller with discrete FETs for it. It'll be easier to make and certainly easier to program with the experience from the current project.Edit: KF350 is a nice fit for my board. A total length of 16.5mm, close to ideal, and carries 10A current, which should (unfortunately) be plenty.

author: mtwieg
author_rank: Frequent Contributor
timestamp: June 26, 2025, 01:16:11 pm
content: Quote from: anvoice on June 25, 2025, 10:30:11 pmYeah I don't think you'll find anything reasonable with a 4mm pitch (unless you're willing to use some ultra fancy samtec parts).My suggestion from reply #3 still applies though.Quote from: anvoice on June 26, 2025, 03:29:36 amReally? Where do you see this?AFAIK the part has no hard limit on output current, it all comes down to thermal management. But yeah if your board is small and you don't have some sort of heat spreader then your achievable output current might be less than 8A total.

author: thm_w
author_rank: Super Contributor
timestamp: June 26, 2025, 11:12:53 pm
content: I would just copy what odrive micro has done then10A rated connector OQ0532510000G

author: anvoice
author_rank: Frequent Contributor
timestamp: June 27, 2025, 10:24:55 am
content: You're right, it's the perfect size. I'll incorporate it into the PCB.