Electrical contacting on aluminium busbar - Page 1
Forum section: electronics / projects

author: damien22
author_rank: Contributor
timestamp: February 27, 2019, 07:14:53 am
content: Hi There,Posting here after Months of unsuccessful research and I hope there gonna be some smart guys with good idea.In a equipment I'm building, I need to carry large current to many PCBs. To do so, I've planned to use busbar. Those busbar have a length of 1.3 meter and are 7x8mm to which the PCB are screwed with M4 screws and the current goes trough it.Now there are two issues, one is the electrical contact, because of the oxidation of the material which is an issue for the electrical contact and another is the strength of the material to avoid the bar to be bend during manufacturing.We are trying to use Aluminium for this, but raw aluminium cannot be directly connected due to the oxide layer.We have looked a lot to do surface treatment such as plating or coating but it seems impossible to find anybody that can do that on bars that are 1.3 meter long and I cannot split them unfortunately.The solution we are looking at currently is to use inserts. As the insert a pressed fit or screwed on the aluminium, it breaks the oxide layer and then stay in place. We know of some companies doing so using ARCAP inserts.However, one of the issue, is that there isn't much space to allow much bigger hole size (M4 on 7mm wide bars), as the insert would need to be at least 2mm thick on M4 would mean a hole ~6mm, leaving only 0.5mm of material.Then I found Helicoil inserts which have the advantage of not needing a much larger hole size and that would mechanically fit.https://blog.baysupply.com/common-uses-for-helical-inserts-and-why-you-need-themHowever, there are very little information about using this for contacting on aluminium as an insert. The best information I found is"This makes tangless inserts particularly vital to automotive and electrical applications".Question being, is there anyone having experience with that, perhaps have recommendation or other ideas to contact those busbars, help would be very much appreciated.The equipment is for indoor and lab.Thanks

author: beanflying
author_rank: Super Contributor
timestamp: February 27, 2019, 09:47:45 am
content: Ok I will bite.First question is what Current? and also what Voltage (AC or DC) and are you running one or two bars for a Ground/Neutral?What are your reasons for not using a Copper Alloy (Brass) of some sort and what are the reasons for your tight dimensional constraints?Also will you be supporting the busbar along the length or have you or does it need to be self supporting which from your description seems your choice?What weight does it need to support?Reason for the questions is we are not clairvoyants

author: coromonadalix
author_rank: Super Contributor
timestamp: February 27, 2019, 09:55:02 am
content: In my shop we discarded / ditched the aluminum bars and gone to copper ones ..... master electricians at our shop recommended this over aluminum ??They said aluminum strech and expand over time, problematics for contacts / wiring / screwing .... at they require checking time to time for eveything connected to them, but they did not talk about oxidation ??We replaced bars in our pcb oven, and pick and place machines power distribution circuits , (they are not American made) we have around 6 kw 347vac of power passing thru them ... not as long as your 1.3 meter, but thicker (around 3/4 inch, maybe 1 inch thick) but we dont have any pcb's connected directly on them, all wiring.You surely have some master electrician(s) in your country who could give you more insights ?? Do's and Dont

author: damien22
author_rank: Contributor
timestamp: February 27, 2019, 09:57:45 am
content: Hi Beanflying.We tried brass, the problem is that the manufacturer (we tried 2) are not able to process the bar without bending it, by handling I suppose.Also there are questions, as brass also oxidize, what would be the long term impact. I had somehow divergent input about this and also couldn't find much solid information about that. Brass also have about half conductivity of aluminium.The bars, once installed are supported and there is not much mechanical stress, so there is no issues on that side.There are several voltages rails, ranging from 15V to 90V DC. The current is up to 120A at the extremity of the GND busbar but this is a pulsed current of about 500ms every 15 seconds, not continuous.For the size constrain, the width of the bars are constrained by the PCB design and space available, for the length is due to the system design. No chance to change those unfortunately.

author: damien22
author_rank: Contributor
timestamp: February 27, 2019, 10:05:07 am
content: Hi coromonadalix,We also thought of copper but as being very soft material, the bending issue we already have with brass would only be worse. Copper also oxidize and usually those are treated when used on electrical installation.On electrical installation, and EV for example, more and more copper (or other material) plated aluminium busbar are being used as it's cheaper and lighter. We cannot do so because ours are too long.Unfortunately electricians weren't of help as usually in electrical installation you use either copper or copper plated aluminium busbar which you can have stock.

author: wraper
author_rank: Unknown
timestamp: February 27, 2019, 10:05:40 am
content: Brass is fine. Aluminium and copper mixed together do not behave well. They are dissimilar metals which cause galvanic corrosion, especially if moisture is present.

author: beanflying
author_rank: Super Contributor
timestamp: February 27, 2019, 10:20:27 am
content: Not all Brass is the same. Mild surface oxidation over time on most Copper Alloys is very minor compared to the horror that is Aluminium.There is some oddballs such as what is generically called Gunmetal and also Marine Grade Bronze it's mechanical properties are similar to mild steel. We used it a heap in the Pump industry including pumping raw seawater so it handles corrosion really well. Also used for Marine Propellers.Have a look through this Datasheet for a start for some light readinghttps://www.copper.org/applications/marine/cuni/alloys/pub-206-copper-alloys-for-marine-environments.pdf

author: coromonadalix
author_rank: Super Contributor
timestamp: February 27, 2019, 10:24:50 am
content: oh forgot to sayWith the copper bus bars, we have everything connected to it made in copper, terminal blocs / screws blocs / distributions posts, even the bolts are in copper ... they were screwed with torque wrenchs.

author: beanflying
author_rank: Super Contributor
timestamp: February 27, 2019, 10:28:55 am
content: The only problem with pure copper is it will be to flexible given the dimensions and span required. It really should have some mid span supports if it can added. Then Copper could be reconsidered.

author: damien22
author_rank: Contributor
timestamp: February 27, 2019, 10:51:11 am
content: I had a look at the bronze but electrical conductivity is too low, we would have to increase the size.I'll have a second look at using pure copper, if we can find a supplier able not to bend them...

author: dmills
author_rank: Super Contributor
timestamp: February 27, 2019, 11:08:47 am
content: For this I would absolutely be going with copper bars, ally is just a pain in the arse for electrical connections (It can be done, but **EVERYTHING** has to be perfect or it fails high resistance after a while).A 1.3M long copper busbar is a perfectly standard requirement, and it would not need to be anything like 56mm^2 CSA for 120A in copper (More like 20mm^2 probably, but you might want more for mechanical reasons).Be a little careful of the brasses, and especially things like ally-bronze, they tend to be surprisingly resistive.Any non ferrous stockholder will be able to supply raw copper bar in 1.3M lengths, no problem at all.I would note that copper is a bugger to tap, clearance holes and bolted connections will make everyones life easier, or do the helicoil thing. Current should mostly be transferred by the contact between the face of the bar and the face of the lug anyway, the bolt should not normally be a major current path, a disk spring is useful here to take up thermal expansion and prevent loosening in the long term.Regards, Dan.

author: damien22
author_rank: Contributor
timestamp: February 27, 2019, 11:20:36 am
content: Thanks for the input dmills.In my region seems very difficult to get unfortunately.Would stainless helicoil thing be a good solution ? Unfortunately we cannot bolt as the bar lay flat on an insulator to which they are fixed and on the other side the PCB are mounted.The PCB does contact with the bars so most of the current would go through there.

author: MagicSmoker
author_rank: Super Contributor
timestamp: February 27, 2019, 11:30:49 am
content: Plate the aluminum bus bars with nickel; problem solved.

author: wraper
author_rank: Unknown
timestamp: February 27, 2019, 11:35:13 am
content: Quote from: MagicSmoker on February 27, 2019, 11:30:49 amNothing solved. It's easier, cheaper and much better to just not use aluminium.

author: damien22
author_rank: Contributor
timestamp: February 27, 2019, 11:42:30 am
content: QuoteAs discussed, we couldn't find any supplier that can do this sort of plating beyond 1m length

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 27, 2019, 12:00:39 pm
content: When I used to service welders, they often used aluminium busbars and windings in the transformers.These busbars would pass up to 2000A at 50-80v or so at full output on the larger machines.To make terminations, standard practice was to sand the aluminium with fine grit emery paper, then immediately smear it with a good amount of jointing compound then attach the lug with a bolt as usual and torque to spec.I never had a burnt termination doing that.Before I started working there and made the other techs do the joints the same way, there were a number of joint failures after extended use due to the oxide layer and dissimilar metals etc.

author: damien22
author_rank: Contributor
timestamp: February 27, 2019, 12:08:47 pm
content: QuoteWhat can of join compound were you using ?Had the idea of similar process, by threading the holes a bit smaller, adding grease and then when putting the screw it would break the oxide layer and the grease would avoid oxidation but I don't know how well that would go over time...

author: MagicSmoker
author_rank: Super Contributor
timestamp: February 27, 2019, 12:16:50 pm
content: Quote from: damien22 on February 27, 2019, 11:42:30 amI was able to get large aluminum bus plates for a locomotive drive system (>1m x 1m) nickel plated at a local shop for a very reasonable price and this isn't even a particularly big city; surely there is someone not too far away who can handle something larger than 1.3m... Electroless nickel is one of the most common surface treatments for a wide variety of materials, after all.Despite wraper's opinion - which does not seem to be informed by actual experience - no alternative comes anywhere close to cost vs. ampacity of aluminum, even factoring in the nickel plating of the latter. Copper is anywhere from 4-8x more expensive than aluminum on an ampacity basis and this comparison only gets worse if you need the bus bar to be thicker/bigger than is strictly necessary for mechanical reasons, rather than ampacity. No brass or bronze should even be considered unless this is a marine application and you have, shall we say, an unrestricted budget.Pre-posting edit - saw TERRA Operative's comment and while threading aluminum and making connections to it directly is possible if the surface is prepped well, that last bit - relying on the competence of assembly technicians now and service techs later - is often the main argument against using bare aluminum. The type of anti-oxidation grease most commonly used in the US is "NoAlOx" which is basically a suspension of zinc particles in silicone dielectric grease. Probably something similar is available over there.

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 27, 2019, 12:26:45 pm
content: I can't remember the brand of grease we used beyond it being a slightly green/brownish grey and being in a tall squeeze bottle with a red lid..... (10 years ago is too long for my brain to remember those details....)Also, for a bit of clarification, we didn't thread into the aluminium busbar, we used nuts and bolts (and washers and spring washers) with through-holes to enable us to really torque down the lug without tearing out weaker aluminium threads.

author: damien22
author_rank: Contributor
timestamp: February 27, 2019, 12:58:54 pm
content: QuoteAs I understand its more special for aluminium as you need to have some special treatment before hand to remove the oxide layer otherwise the plating will not hold over time.Quotehttps://www.pfonline.com/articles/adhesion-of-electroless-nickel-deposits-to-aluminum-alloysand only very specialized companies does it as far as I understand.

author: ConKbot
author_rank: Super Contributor
timestamp: February 27, 2019, 01:12:16 pm
content: I don't know if it gets used for bus bars or not, but Alodine or Iridite coatings can be used on aluminum for a conductive corrosion resistant surface. I've seen it used on surfaces that were for electrical shielding and grounding purposes, not as a bus-bar conductor so they may not be suitable. They are chromate conversion coatings, so hexavalent and trivalent chromium processes exist, with the former most definitely not being RoHS.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: February 27, 2019, 01:35:14 pm
content: Two-ish questions:1. Why is the brass or copper so easily bent? Both are available in hardness grades; dead-soft would be annoying (gummy) to machine anyway. Full hard is pretty springy.1a. Why is the shop bending them at all? Clearly they're a bad shop that can't follow directions (you did put a flatness spec on the drawing, right?..) and don't deserve your money, find another that will.2. Why does it matter if it's slightly bent? You have frequent mounting brackets to secure this long span of metal, right..?Regarding 2, it seems pretty common to use flat stock for bus bars, which will be even more flexible, which is fine because it's secured frequently, to account for flex, vibration and so on.You may be just as well off using a more conventional approach -- #0 cable or thereabouts (or the metric equivalent, rather), with crimp lugs and bolted connections. If you need a lot of drop connections, this isn't going to be very convenient, but it is just fine for a 1.3m length.The other conventional approach would be a terminal block, then routing individual connections with thinner cable of lengths, say, 0.2 to 1.6m or whatever. Instead of a multi-drop bus, you have a star connection.Tim

author: damien22
author_rank: Contributor
timestamp: February 27, 2019, 01:46:53 pm
content: QuoteI agree, but unfortunately have little control over that. Tried 2 suppliers and both same result with the second being slightly better. The problem is that it's down to the operator, and even if a set is good for a particular supplier, maybe next one won't be and that can go into production hell. We'll check for higher strength brass but I don't have much hope.For the cable approach, there are 120 boards, each requiring 3 voltage rails + GND. That would need almost 500 large section cable and would be a real mess and pain to mount. The busbare also act as the support for the boards.

author: coppercone2
author_rank: Super Contributor
timestamp: February 27, 2019, 01:55:01 pm
content: read about the oxide growth on aluminum to get an idea of whats going on. finishing101.com has some insight (linked directly in one of my previous posts).When I read that I wanted to no longer ever use aluminum and just pay the piper at 10x cost. fuck it.Not an option? its infrastructure essential to the function of a modern society!!!its a train they are in service for like 70+ years sometimes, look at cuba or Switzerland. Why are you going cheap for that? people actually like trains. Its not a going obsolete in 2 years equipment. Transportation isimportant.How much does a damn bus bar cost in the scheme of a fucking train even if you consider a order of magnitude cost increase?MTA is already going to fuck it up with unknown unpredictable means, don't make it worse. Train fires suck. They can burn in tunnels etc.

author: MagicSmoker
author_rank: Super Contributor
timestamp: February 27, 2019, 02:08:08 pm
content: Quote from: coppercone2 on February 27, 2019, 01:55:01 pmI guess you are directing this tirade at me? Economics wasn't a factor at all in *my* decision to use aluminum for the bus plates, rather, it almost entirely due to mechanical reasons. But I'm sure that article you read on finishing101.com has made you an expert now so...

author: Siwastaja
author_rank: Super Contributor
timestamp: February 27, 2019, 02:31:39 pm
content: Yeah, aluminium alloys are great for the mechanical sturdiness - low weight - low cost combo (as you could guess from the fact aeroplanes are made from it).Almost all large-scale electrical power transmission is based on aluminium wiring and yes, even bus bars. It's a solved problem, although you need to know what you are doing and to have the process right to avoid quality issues. Copper is easier for the rest of us, but if you need to combine electricity transfer to mechanical support, aluminium's pretty high on the list!

author: coppercone2
author_rank: Super Contributor
timestamp: February 27, 2019, 03:58:06 pm
content: Nah what made me weary is reading about it and seeing someyhing one bees dick from a full structure fire because of aluminum wiring. The oxide growth is insidious.I feel bad for ypur train man, burning choo choo

author: TomS_
author_rank: Frequent Contributor
timestamp: February 27, 2019, 04:12:23 pm
content: Quote from: TERRA Operative on February 27, 2019, 12:26:45 pmTry searching for "NO-OX-ID".

author: duak
author_rank: Super Contributor
timestamp: February 27, 2019, 05:30:48 pm
content: I would recommend Alodine. This is a chemical conversion process that leaves chromate on the aluminium surface that prevents the oxide layer from forming. It was developed for the aircraft industry and is widely used. We could get pieces done in Vancouver, Canada (an industrial backwater) over 40 years ago.I see there is a Swiss company that might be helpful:https://www.bwb-group.com/en/Procedures_overview/Surface-treatments-for-aircraft.phpThere are also dielectric greases and oils available to the electrical industry here that are applied to the contact areas before mechanical bonding. These exclude air from the joint to prevent oxidation.Cheers,

author: damien22
author_rank: Contributor
timestamp: March 01, 2019, 12:08:36 pm
content: We will investigate all the solution proposed, many thanks for the feedback!

author: David Hess
author_rank: Super Contributor
timestamp: March 01, 2019, 11:47:55 pm
content: Quote from: damien22 on February 27, 2019, 11:20:36 amHelicoils would prevent the threads from bring ripped out of the relatively soft aluminum or copper but I have never heard of them being used for conductivity.QuoteBe careful about crushing the printed circuit board material.Quote from: coppercone2 on February 27, 2019, 01:55:01 pmDuring World War 2, the copper bus bars from the substations and power houses along the Columbia river were replaced with silver bus bars and armed guards were assigned to protect them until they could be replaced with copper again.

author: Gregg
author_rank: Super Contributor
timestamp: March 02, 2019, 06:39:47 pm
content: Aluminum bus bar is used extensively in large mains switchgear and even home breaker panels because it is cheap and light weight. There are thousands of variations of alloy, conductivity and hardness available and a designer needs to choose wisely. Most of the large current aluminum bus bars I have seen are tin plated at the factory to minimize the problems with connection conductivity. There is nothing inherently wrong with properly designed and implemented aluminum bus bar installations; it is the branch circuit wiring that causes many of the aluminum wiring related problems and copper clad aluminum is just as bad.Quality commercial and industrial aluminum bus bar systems use bolted connections and are designed so that expansion and contraction will not stress the connections. If you can't easily get a nut on the back side of your bus bar, look for PEM nuts or press fit nuts similar to these:https://www.ebay.com/i/173438526393Helicoils are great for some purposes, but I personally don't think they are suitable for bus bar application. In any case, as already mentioned, the bolt should not be considered as a conductor.

author: kony
author_rank: Regular Contributor
timestamp: March 02, 2019, 09:59:55 pm
content: Stock material in -T6 temper if it is some 60xx alloy or in -H18 if you go after highest conductivity (EN AW 1050), electroless nickel per ISO 4257 (at least 15um, ~10% P content) and fuck it. There is nothing nonstandard at it, even for aluminium alloys, and any good plating shop serving electronics industry will be capable of that. Don't forget to keep the bolted connections under preload, prefferably not just by the screw torque, but by some other means as well - best case disk spring washers. Especially if there is PCB pads in the stack-up of the fastener, the common laminates will creep badly over time!Alodine or other conversion passivation is wrong here, so are dissimilar metals inserts.Also be VERY wary of tin plating on busbars (regardless of base metals) - whiskers are a big deal here and can turn your gear into big plasma ball in short few years.

author: MagicSmoker
author_rank: Super Contributor
timestamp: March 03, 2019, 12:32:50 am
content: Quote from: kony on March 02, 2019, 09:59:55 pmFinally someone gets it!The type of lock washer most commonly used in the US for high-reliability bus bar applications is called "Belleville." It is a conical in cross-section with radial ribbing or teeth; I'm not sure how popular Belleville washers are in the EU, though, so Nord-Lok are an excellent - albeit more expensive - alternative. I also agree that directly threading the bus bar - even with Helicoil inserts - is not ideal, but it can work just fine for small small ring terminals such as #6 (M3) through #10 (M5); once you go past 1/4" (M6), though, you really can't generate enough clamping force with threads in aluminum (unless the bus bar is unusually thick). I also agree that alodine is not an appropriate choice of surface finish as it's effectively an insulator.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 03, 2019, 04:02:23 am
content: Ahh-- not quite!Conical washers are indeed springy. They're perfect for this: a short-throw, high-force spring.Nord-Lock aren't conical or domed, as far as I know. So they don't take up any spring force. They do prevent unscrewing -- very important in high vibration (especially high shear) applications, but only useful when the bolt and base metal can be relied upon to not creep or stretch. They're also rather expensive AFAIK, so are best reserved for these cases when they're needed.There's also wave washers, though they tend to be softer than cone washers.Split washers, by the way, are literally no good at all: as a spring, they crush at even less tension than wave washers do, and in tests, they perform as well,or poorer,than plain old flat washers! Which is often worse than no washer at all, because they add another friction surface and can make the joint easier to move.FR-4 can creep or flow under pressure, too (especially at high temperature). If you're making high current bolted connections to PCB, consider using spring washers there, too!Tim

author: Mechatrommer
author_rank: Super Contributor
timestamp: March 03, 2019, 06:02:43 am
content: Quote from: damien22 on February 27, 2019, 07:14:53 ami think you over complicating things. i think oxidation will only form on exposed part, if there will be oxidation on the contact, it means you've made not a good contact so you may revise your assembly technique. if bending is an issue, why dont use thick wire and find suitable tap to it? people have done bolt nut tap with no issue at much larger current, i think its the de facto standard... if you really concern, just solder them, problem fixed... now where's that high voltage nutter? why dont he chime in to give some good and practical advice, safety-wise advice, rather than keep breaking somethings

author: MagicSmoker
author_rank: Super Contributor
timestamp: March 03, 2019, 12:13:44 pm
content: Quote from: T3sl4co1l on March 03, 2019, 04:02:23 amNord-Locks develop tension in the bolt through cam action. More specifically, by interlocking wedges on opposing washer faces with the wedges arranged such that unscrewing the bolt increases the tension on it (at least for the first few degrees of rotation). However, you are correct that they aren't recommended for materials which will experience significant creep after tightening. So, soft metals like unhardened copper or aluminum, especially if they are less thick than the bolt diameter. Also not recommended for cost-sensitive applications, as they are, indeed, bloody expensive. I only used them for the 1/2" bolt holes on dual-hole 4/0 compression lugs; a case where, contrary to the Mythbuster's mantra, failure was not an option.Quote from: T3sl4co1l on March 03, 2019, 04:02:23 amAlso true, at least for bolts under, say, #10 (M5) in diameter. Split-ring lockwashers can be okay for non-critical use on 1/4" (M6) or larger bolts. I tend to prefer internal tooth lockwashers for general purpose application, myself.Quote from: T3sl4co1l on March 03, 2019, 04:02:23 amVery, very true! In fact, I don't think any kind of washer can accommodate the amount of creep a PCB will experience even at temperatures well below the glass transition. Either use a screw terminal standoff (e.g. - Keystone Electronics 7787) or a soldered-in male quick-disconnect (e.g. - Keystone Electronics 1287) for high/moderate current wire to board terminations, respectively.

author: David Hess
author_rank: Super Contributor
timestamp: March 03, 2019, 03:52:04 pm
content: Quote from: MagicSmoker on March 03, 2019, 12:32:50 amI would love to use Belleville washers more for power transistor mounting but pricing and availability has always been a problem.Quote from: T3sl4co1l on March 03, 2019, 04:02:23 amWhen it matters, I end up stacking wave washers to get enough force.

author: coppercone2
author_rank: Super Contributor
timestamp: March 03, 2019, 05:58:41 pm
content: how about lockwire?I have been meaning to get lockwire pliers.Pretty sure you can modify hex insert bolts to accommodate lockwire too. What I am thinking is to drill a small hole in the busbar, braze on a peg with a hole in it, then lockwire the washer to the peg.

author: OM222O
author_rank: Frequent Contributor
timestamp: March 03, 2019, 07:53:45 pm
content: why are you trying to manufacture the bars with such weird dimensions? usually for longer runs, you would use a plate shape rather than a square (6x7 is almost a square) and you can make runs like this without a problem using copper:this also gives you a lot more width for your connections. as you mentioned, you're struggling with a single M4 screw! I suggest using 10 screws in parallel next to each other per PCB as it provides a lot better contact with the PCB as well as the bus bar, makes it easier to manufacture the bars and is also safer in case one of the screws fails or isn't making proper contact, as well as reducing the load to 12A per screw rather than 120! there would be a ton of voltage drop and heating of the screw with 120A passing through it and it won't last long at all! just make sure to use a washer on both sides which ensures there is good grip and you will be fine. I attached an example of the PCB which you might want to use:Obviously make the thick copper zones (light blue) on both sides for a more even distribution and also add some vias for stitching just to be on the safe side.One single M4 screw is a terrible idea and you will have lots of issues with it.Also if you make your plates out of copper, you can add plenty of flux and burn it with a torch to get rid of the oxidization but I'm not sure if the same can be done for aluminium. copper also oxidizes a lot more slowly than aluminium (a few days compared to a few minutes!).If you can, drill the holes in the positions with a smaller bit, let's say M2.5 instead of M4 so you have the correct positions. then just before installing the PCB, drill and tap the holes to the correct dimension. This way you can make sure there is no oxidization during installation. I'm not an electrician but this issue has already been solved by othersI hope this answer helps.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 03, 2019, 08:00:11 pm
content: Lockwire serves the same purpose as Nord-Lock but with cheaper materials and way more manual labor (and possibly less retention torque, depending on the stretchiness and ultimate tensile limit of the wire, and give or take how long the wire is to the tie point?).Quote from: David Hess on March 03, 2019, 03:52:04 pmThat never made sense to me... they can potentially be produced in a single stroke like any other washer. Is it just a quantity thing -- they're expensive because no one wants them because they're expensive?...The ridged ones I can see being more expensive or specialty, I guess, but still.'Spose this is a good situation to shop China...QuoteIndeed, wave washers add in parallel when stacked.(They add in series if you can keep them aligned peak-to-peak rather than peak-to-trough, but that would be hard without keying.)Belleville also add in parallel when stacked in nested-cups direction, or in series when stacked oppositely, rim-to-rim.Series meaning, more displacement but the same force; parallel, more force but same displacement.Tim

author: dmills
author_rank: Super Contributor
timestamp: March 03, 2019, 08:54:05 pm
content: Belleville is a trade name for a type of "Disk Spring" that may be more readily available under that name.I tend to keep a box of M3/4/5 on the general mechanical bits shelf, they are useful.FR4 flows, a lot, so directly bolted connections are not a great idea, but you can get press fit inserts from the likes of Erni and Wurth that make heavy current bolted connections to PCBs a far more viable thing.Regards, Dan.

author: coppercone2
author_rank: Super Contributor
timestamp: March 03, 2019, 11:25:37 pm
content: don't you want to drill a hole and solder in a insert to a PCB?

author: damien22
author_rank: Contributor
timestamp: March 05, 2019, 04:39:15 am
content: We are currently looking to have tin plated or zinc plated aluminium busbar, waiting for feedback from some suppliers.Here is a picture of how it looks like and also explains the dimensional constraints.http://imgur.com/a/bWYE9omhttps://imgur.com/a/bWYE9om(image tag not working ?)

author: David Hess
author_rank: Super Contributor
timestamp: March 05, 2019, 08:02:02 pm
content: Quote from: T3sl4co1l on March 03, 2019, 08:00:11 pmI have always assumed it is a quantity issue. Wave washers have more applications than Belleville washers and people use split washers in place of both even when they should not.

author: langwadt
author_rank: Super Contributor
timestamp: March 05, 2019, 08:11:59 pm
content: Quote from: David Hess on March 05, 2019, 08:02:02 pmrandom hit from google,https://www.amazon.com/Belleville-Washer-Stainless-Steel-Pack/dp/B01J2XR93G$8 for 100 M4 washers isn't what I'd call expensive

author: David Hess
author_rank: Super Contributor
timestamp: March 05, 2019, 08:27:35 pm
content: Quote from: langwadt on March 05, 2019, 08:11:59 pmOh, they can be found *now* but go back 20 or even 10 years and it was a problem. The same thing from McMaster Carr is 10 times the price.And them someone in the field loses the washer during a repair and cannot find a replacement at even the local industrial hardware store.

author: tooki
author_rank: Super Contributor
timestamp: March 05, 2019, 09:32:12 pm
content: Quote from: damien22 on February 27, 2019, 07:14:53 amSurely, with all the heavy electrical industry here in Switzerland, this is a problem that's been solved over and over domestically. There must be some industry groups that you could meet up with and talk about it with, including finding a supplier. It seems absurd to me that, in a country known expressly for precision manufacturing, that you can't get what you need made.

author: tooki
author_rank: Super Contributor
timestamp: March 05, 2019, 09:35:34 pm
content: Quote from: coppercone2 on February 27, 2019, 01:55:01 pmBruh… take it down a notch, mmkay?

author: tooki
author_rank: Super Contributor
timestamp: March 05, 2019, 09:36:48 pm
content: Quote from: MagicSmoker on March 03, 2019, 12:32:50 amJust a little bit of nationalist pedantry: Switzerland (where the OP is) is in Europe, but is not part of the EU.

author: MagicSmoker
author_rank: Super Contributor
timestamp: March 06, 2019, 12:28:04 am
content: Quote from: tooki on March 05, 2019, 09:36:48 pmYou know how us 'Murican's are... can barely identify whether Canada is to the north and Mexico is to the south, so everything across the big pond is just one big mess.

author: tooki
author_rank: Super Contributor
timestamp: March 06, 2019, 03:44:38 am
content: Quote from: MagicSmoker on March 06, 2019, 12:28:04 amHahahaha yep. Being American myself, when I'm back in the States visiting, you can't imagine how many times I get asked "Oh, you live in Switzerland! Neat! How's your Swedish?"And of course I know the stories from the pre-Web days, when mail-order meant calling up the company on the phone, where people in New Mexico would try to order something (from a US vendor) and be told "oh, sorry, we don't ship abroad"…And then of course one neighboring country (to Switzerland) is Austria, where the people have to explain to some Americans that no, they don't have kangaroos and Crocodile Dundee in Vienna…

author: damien22
author_rank: Contributor
timestamp: March 06, 2019, 04:07:09 am
content: Exactly

author: duak
author_rank: Super Contributor
timestamp: March 07, 2019, 06:10:43 am
content: A few have replied that Alodine is not appropriate as it is an insulator. This is true if the Alodining is Class 1A for maximum corrosion protection. However, it is not true for Class 3. Please see the first page of MIL-DTL-5541F athttps://www.chemical-supermarket.com/files/Henkel%20Alodine%20Conversion%20Coatings/Spec,%20MIL-DTL-5541F.pdfI have a few sample pieces over 20 years old and it is indeed conductive with little or no contact pressure. I mentioned it because it is used in aircraft and the vendor is most likely used to dealing with unusually sized pieces of aluminium.Cheers,

author: tooki
author_rank: Super Contributor
timestamp: March 07, 2019, 12:02:32 pm
content: Quote from: tooki on March 06, 2019, 03:44:38 amYou know how you mention something, and then it pops up on its own? I just came across this yesterday, after I commented the above: apparently this is such a big problem with New Mexico that the state's travel magazine has been writing about it for years!https://www.newmexico.org/nmmagazine/heart-of-nm/one-of-our-50-is-missing/

author: MagicSmoker
author_rank: Super Contributor
timestamp: March 07, 2019, 12:18:39 pm
content: Quote from: tooki on March 06, 2019, 03:44:38 amHah, even I know the correct question to ask is, "How's your Swiss?"(I kid!)Quote from: duak on March 07, 2019, 06:10:43 amInteresting. I knew there were two options for Alodine, but I thought the distinction was between whether exceptionally nasty hexavalent chromium was used, or slightly less nasty trivalent; I had no idea there was a process specifically for maintaining conductivity, so thanks to you for learning me something new.

author: damien22
author_rank: Contributor
timestamp: April 02, 2019, 08:36:23 am
content: For the Feedback, we had a try a Tin coating on aluminum and that seems to be the winner.