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High current connector options for PCB

High current connector options for PCB

(OP)
Hi All,

I am looking for an alternative to these cable lugs
On my current PCB design I am using 10 of these in a row (rating of 30V DC with max 50A)

Unfortunately these lugs makes if very hard to design an enclosure and I came across the 'Powerpole PP75' connectors from Anderson Power.

Has anyone experience using them? I am in particular interested in the usage of the 'BusBar' type (rightmost pair):
Can they be directly screwed into the PCB?

Markus

RE: High current connector options for PCB

This type of connector is popular for battery connectors on small commercial UPS designs. It's a decent connector but the mating force required is likely to be too high for a standard PCB to withstand. I guess you could use a much thicker laminate and provide a lot of mechanical support local to the connector area, although I'm still not convinced it is a good solution.

RE: High current connector options for PCB

Any time a bus connection is made, you should assume there will be mechanical strengthening elements designed into the surrounding area of PCB. PCBs are not designed to handle the mechanical forces, that's the job of the case and support it's attached to.

Does this need to be quickly removed (either by the user or repair technician), or is this a more semi-permanent job? If it's the latter, the lugs are "okay", but I wouldn't trust them long-term due to heat cycling potentially causing loosening (though you can always use Loctite, or similar). If the former, plenty of solutions out there... look at computer servers, for example. Another would be hot-swap power supplies. Fat traces, often PCB-based, and connectors that allow for easy insertion yet high current.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: High current connector options for PCB

Do you really need 50A or is that just the rating of that block?

RE: High current connector options for PCB

"...you should assume..."

And that is the root of so many problems! smile

RE: High current connector options for PCB

Anderson power..
TE Rapid Lock/Crown Line/
or these http://www.te.com/catalog/cinf/en/c/11410/1204
Harting Han-Fast
Amphenol Radsok
Molex Extreme BBC
FCI Barklip

and more..

More details on the intended use will help.. like one time or serviceable/multiple insertion.. wire or bus bar?,etc...

RE: High current connector options for PCB

(OP)
@ScottyUK: Anderson Power is also offering the PCB mount type but that is only rated for 25A

@MacGyverS2000: the purpose is more a 'semi-permanent job'. Ideally this is setup once and never unplugged.

@mcgyvr: I really need 50A at 24VDC - at least this is what I want my unit to be rated for.

RE: High current connector options for PCB

50A is getting close to the point where you'd build up the high current circuits using (mechanical) bus bars, and the PCB would be like a daughter card holding only the low current circuitry. Maybe 50A is still within the range of PCB current carrying capabilities, but you're getting close. I'm not sure where the transition point is; somebody on here will know.

If you look inside really high current power supplies, you'll see a lot of bus bar construction, with a little PCB off in the corner.

RE: High current connector options for PCB

(OP)
I am using 2oz copper on both sides of the board and I was told that is OK - can someone confirm that?

RE: High current connector options for PCB

Note.

Same URL: "The original graphs that this tool is based on (published in IPC-D-275) only cover up to 35 Amps..."

RE: High current connector options for PCB

VE, it would take 5oz copper to get down to 33(ish)mm traces.

Some of the better shops will do 4oz, but frankly, I think that's irrelevant. You are working at 50A, which means busbar.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: High current connector options for PCB

Actually, there are PCB places that specialize only in heavy copper plating, even up to 40 Oz. I am presently using a 10 Oz double sided that also contains SMT caps and resistors (nothing smaller than 1206). This PCB carries 70+ amps and forms the backbone of a 1800 Watt full-bridge converter, 24 volt input. Attachment to it is swaged-and-soldered 5/16 hex standoffs for #10 screws.

mcgyvr listed some connector series. I can add to this:
Hirose DF 60 series, listed as rated for 40 Amps, but designed for 12 to 8 AWG wire to PCB.
Molex Mini-Fit Sr. family rated 50 Amp.

RE: High current connector options for PCB

(OP)
@VE1BLL: thanks for the link, I measured 11mm in parallel on both sides: 22mm with 2oz.

@Comcokid: can you share the information about the place you use for the high Oz copper?

Also can someone recommend places that have experience with bus-bars?

RE: High current connector options for PCB

Comco,

Do those places actually etch/plate? Seems like at that thickness, it would be laser-cut (or mechanical) copper shim glued to a substrate.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: High current connector options for PCB

I run "high currents" (up to 100A+) in circuit board traces all the time.. Most of my boards are 3 or 4oz clad plated up to 4 or 5oz or so after through hole plating with nice wide traces (1" W double sided or so as needed)
Many PCB houses can "plate" up to 10oz total thickness (but they must be UL approved to do so also)..
I also include thermal reliefs to aid in soldering,etc... As well as thermal vias to help spread the heat out between each side/plane..

We attach 8 AWG wire to PCB's all the time too but like the OP I had trouble finding an off the shelf terminal that fit our needs (and most importantly budget..whats out there is high dollar).. So we just make our own and have enough volume to justify it.. (which doesn't take much as you don't need to get it approved if used in your products only and when compared to whats out there already you can save quite a bit in the long run)

For bus bar attachments to PCB's I prefer to use PCB pem studs and leave a nice "pad" on the PCB to land the bus bar surface on.. Works great.. Sometimes I even use a pattern of vias spread far enough around the pem studs through hole radially to ensure that the plane to plane integrity is not compromised. I've also simply used "swage" standoffs in the PCB and attach a terminal/bus bar to that.


RE: High current connector options for PCB

Interest discussion here!

mcgyvr; Are you saying you use various swagged/soldered standoffs (very short I imagine) then screw down essentially just flat copper with holes drilled to match the standoff placement? In other words home-fabbed busbar?

Keith Cress
kcress - http://www.flaminsystems.com

RE: High current connector options for PCB

I will post info on vendors who do heavy plated PCBs when I get to work on Monday.

I have seen designs where heavy currents were handled on a PCB by leaving the mask off the trace, manually soldering a tin plated bus wire down the trace. If you look at far east made DC/AC inverters, they tend to leave the mask off the trace so during wave solder a thick solder buildup is made on the trace. Commercial grade inverters tend to use bus bars that are vertical to the PCB that solder-in at the high-currnet places.

SolarTrap - who makes the screw lug you are using?

RE: High current connector options for PCB

Using solder buildup for high-current applications is bad bad bad. It would certainly never pass a UL/CE approval. There's no consistency in thickness, you can't guarantee a specific thickness, it has a higher resistance to current flow, etc.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: High current connector options for PCB

I once saw in some magazine, the vertical, with leg pins, off-the-shelf, busbar being advertized. Of course when I finally needed some I couldn't remember the detail of who made it. All I can ever seem to find now is custom made-to-order only, shocking price busbar.

Keith Cress
kcress - http://www.flaminsystems.com

RE: High current connector options for PCB

Those type of bus bars are also sometimes described as PCB or Board Stiffeners. Or more precisely, I have seen some being described as both.

RE: High current connector options for PCB

Quote (itsmoked)

mcgyvr; Are you saying you use various swagged/soldered standoffs (very short I imagine) then screw down essentially just flat copper with holes drilled to match the standoff placement? In other words home-fabbed busbar?

Yes we have done that for certain products and never had a problem with it. In the past we would actually solder the tin plated standoff to the pcb pad after swaging to ensure it wouldn't loosen but after some extensive testing (lots of thermal cycling,etc...) we determined that really wasn't needed.
We typically use that connection just to tie the bus bar to the board from maybe an input connector or something like that.
We aren't using the bus bar to improve the current rating of the trace (but it obviously does help some as its a great heatsink).. Its more of just a way to transition from bus bar to PCB.. And the only reason we use the standoffs vs directly bolting the bar to the PCB is because of other pins/protrusions in that area so we don't have a flat plane to bolt to.

RE: High current connector options for PCB

Most interesting mcgyvr, thanks for that!

I had no idea so many of us run mammoth currents on our circuit boards. You folks are fearless.

I've seen hottub control boards with big traces. Comcokid is doing inverters. Scotty mentioned UPSs.

What other kinds of products are needing these big trace currents?

Keith Cress
kcress - http://www.flaminsystems.com

RE: High current connector options for PCB

I'm DC power distribution.
I've never run into a problem where the "trace heating" is the problem. Its obviously always the other "heat generating" devices on the board that give me the worst headaches..
Not to mention our products are placed in high ambients (65-70deg C) and couple that with people always wanting higher density and lower cost..And all our products rely on natural convection only.. I've gotten pretty creative/out of the norm lately.. :)

With most of the world reducing power requirements.. we go the opposite way.

RE: High current connector options for PCB

As promised, here is a list of heavy copper PCB vendors I have. The list is about 2 years old. The key words for a Google search is "PCB" and "extreme copper".

www.upe-inc.com (up to 200 oz)
www.asapcb.com (up to 10 oz)
http://www.epectec.com/pcb/extreme-copper/ (up to 40 oz)
http://www.bestpcbs.com/products/heavy-copper-pcb.... (up to 200 oz)
www.saturnelectronics.com (up to 20 oz)

www.methode.com They did list up to 200 oz, but I couldn't find a recent link at their website. However, they do have connectors for up to 200 amps that might be suitable for the OP question.

Some of these vendors example PCBs capable of carrying up to 1000 amps.

RE: High current connector options for PCB

(OP)
@mcgyvr: 'thermal reliefs to aid in soldering,etc... As well as thermal vias to help spread the heat' -- I looked this up in wikipedia but I am not really clear how it looks like. Do you have a good picture? Also, are your high current boards all UL certified?

@MacGyverS2000: I need UL approval for my board, so solder buildup is a no-go, right? What are the UL certifies looking for when they inspect a board in terms of routing and copper thickness?

@Comcokid: Thanks for the list of links - I might have to get quotes from them now. The lugs I am showing are sold here: http://lugsdirect.com/PCBsolderable-lugs.htm

RE: High current connector options for PCB

For UL, you will need to meet the requirements for track spacing (to prevent arc-over) and track thickness (to carry the current level desired within a specified level of heat rise).

Here is an example of thermal relief on a pad:


I've never tried doing such a thing with heavy copper, but the overall premise is the same. Note: Thermal relief defeats the purpose of heavy copper if the pad you're relieving will be carrying heavy current... you can't do the latter if you're including the former.




Dan - Owner
http://www.Hi-TecDesigns.com

RE: High current connector options for PCB

I copied the above image from Google... and I just noticed the pad/via without thermal relief really should be completely surrounded/touching the plane (red touching gray) to make sense of what we're discussing. Otherwise, it's just a regular via.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: High current connector options for PCB

http://www.synqor.com/documents/appnotes/appnt_the...

A "thermal via" is just a regular "via" but its intended purpose is to help transfer heat to the other plane and not intended (but it does) to pass electrical signals (if using double sided boards,etc.. where the copper plane on the other side is in the same net as the top side)

RE: High current connector options for PCB

Wait, I thought we were talking about thermal relief vias, not thermal vias. Two different animals with different goals.

Dan - Owner
http://www.Hi-TecDesigns.com

RE: High current connector options for PCB

mcgvr mentions both in his posting, which is probably where the confusion comes from.

Note that with thick copper, thermal reliefs will still suck a lot of heat away from a soldering iron, so a really hot one is probably needed to get a good joint

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RE: High current connector options for PCB

The trick with thermal reliefs is finding the "spoke width" that works best for each application.. Not too thin to where it can't carry the required currents without negative effects and not too thick to where its sucking the heat away too fast as IRstuff mentioned..

RE: High current connector options for PCB

Earlier in this post I mentioned I use a double sided 10oz board with SMT. This board also has some thru-hole radial electrolytics. For electrolytics that have a lead making plane connection both under the part and on the solder side, I use a thermal relief on the plane under the part. On the solder side I have found it most effective skip the thermal relief, and to put a rectangular mask opening the width of the solder tip being used to solder. The rectangular mask opening is 0.2" x 0.1" so a Metcal STTC-117 tip (0.2" wide) can solder the part.

Extreme copper PCBs require extreme soldering irons, like Metcal. The thermal relief under the part makes it possible to melt the solder under the part from the solder side. You really have to think carefully about the heat flow for assembly and rework. If you don't, you can easily create an un-solderable and un-reworkable PCB.

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