Copper plating nickel covered brass contacts

[Buriedcode]

I have about 50 power connectors to solder, two terminal, 7.5mm pitch, with what appears to be nickel plated brass pins (non magnetic, shiney, brassy under plating when filed/sanded).

I am unable to get any replacement/equivalent for these so I'm stuck with them, and whilst I can get them to take solder, its a task - requires higher temperature, by which time the plastic housing becomes soft, its generally an unpleasant experience all round. I had a similar problem with those cheap test-hooks from fleabay - but those were most likely steel.  If I was just soldering a handful of these I'd suck it up, but 50 is a daunting and depressing prospect. 

They have no thread, or any kind of crimp termination, just a terminal similar to the bottom of a winding post shown here on the right:


So, as I have the time, I'm thinking of using a handful of the surplus connectors to test out plating them to see if it improves solderability:  copper plating, and/or tin plating.

Does anyone have experience with this?  I don't see it as being that problematic - nickel is often used as a strike before copper plating on many metals, so copper -> nickel should be fairly straight forward.  I also don't really need a thick plating at all, its just something to allow the solder to wet.  It's a lot of hassle for a few connections, but might be a handy setup to keep for future problems/projects.

[andy3055]

Get some lugs like attached.

[thm_w]

What soldering iron and what flux are you using? A better iron can heat solder on the surface faster, meaning potentially less part heating.

Electroless tin is available, but only works on copper.
Probably tin or tin-lead electroplating is the best, but I'm not sure what chemicals are needed to prep the nickel https://www.aotco.com/metal-finishing-processes/tin-lead-electroplating/

Photo of connectors?

[Buriedcode]

Get some lugs like attached.

I'm not sure how to attach those to a secure connection for >3A.

What soldering iron and what flux are you using? A better iron can heat solder on the surface faster, meaning potentially less part heating.

Just standard RMA, I'm hesitant to use anything more agressive as it would require cleaning afterwards.

Electroless tin is available, but only works on copper.

I do have some immersive tin crystlas that I once used for DIY PCB's, but as you pointed out, they're meant for copper, and as its electroless, has probably quite specific chemistry that may not work on nickel.  And even then I'd still ahve to activate thenickel surface regardless

Photo of connectors?

Attached, you can see one terminal I went at it with a file just to see the base metal, looks like brass to me.

[thm_w]

Yeah looks like brass.

What soldering iron and tip? The tip should be large enough to completely cover the end flat portion when pressed up against the terminal.

[andy3055]

I misread the original post and suggested those lugs.

If, as you say those pins are brass,  rosin cored solder should work on them. If the plating is tough, use a sand paper and roughen the surface.

[jpanhalt]

Nickel can be soldered with ordinary Kester #44 flux and 63/37 solder.  Done it with nickel strips to make NiCd battery packs many times.

Never tried LF, if that is what you are using.

[macboy]

I agree with jpanhalt, Kester 44 flux cored solder works wonders in many situations where lesser flux does not cut it. Even though it is technically RA, it usually doesn't need to be cleaned. I'd also try a pan scrubber (scotch brite etc.) or brass wool to scuff up the surface of the lugs before soldering. Sometimes it helps to just break that surface oxide so that the solder can begin to wet the metal.

Definitely pre-tin the lugs before soldering the wires, to reduce the total amount of heat needed to tin the lugs. After it has cooled completely, you can more easily solder the wires to the lugs.

Sometimes when soldering to pins in plastic housings like this, I will insert the mating connector beforehand, to help hold the pins in place when/if the housing softens due to heat.

[tooki]

When dealing with connectors melting, assuming the metal can wet properly (let’s assume for the moment that it can), the problem is actually that it’s being heated for too long, and not that the temperature of the iron is too hot. Consequently, but somewhat paradoxically, the solution is to get more heat into the contact in less time. The best way to accomplish this is to use a larger soldering iron tip, the second is to increase the iron temperature. Using a low temperature to try to be gentle on the connector actually results in it taking too long, causing precisely the damage one seeks to avoid.

Also make sure your wire is pre-tinned, and additionally pre-tinning the terminal can also be an option.

Now, assuming the issue is not heat, but solderability problems due to oxidation, what I’d recommend is either a rubber ink eraser (I love the pencil style ones, like Faber-Castell’s Perfection 7058 B), or ultrafine grit wet-dry sandpaper (fabric backing, with the finest grit). If the oxidation isn’t too severe, then a more active flux, like others have suggested, might suffice.

[Buriedcode]

Righty, sorry for the late reply, several projects on at the moment - I should be grateful for the surplus of work.

Yeah looks like brass.

What soldering iron and tip? The tip should be large enough to completely cover the end flat portion when pressed up against the terminal.

I have a 60W iron with a large 3mm chisel tip - pretty beefy, or at least the beefiest I have.  This works just fine for tin plated large screw terminals of a similar size/mass.  I do indeed use the flat side butted up against the end of ther terminal - furthest from the plastic housing to minimise potential melting, along with a small blob of solder to provide the best thermal contact.  Again, for similar tin plated terminals this works well, I can tin the terminals in about a second - but for these its more like 6-7.  Temp was set to 400C (350 took way too long).  By which time the poor flux had all burned away.

Nickel can be soldered with ordinary Kester #44 flux and 63/37 solder.  Done it with nickel strips to make NiCd battery packs many times.

Never tried LF, if that is what you are using.

I'm using SAC305, but have some higher temp LF.  I am not using any special kind of flux.  I have seen flux specifically for nickel surfaces: https://termopasty.pl/en/produkty/ag-soldering-acid/  And a youtube video of a guy using it points out its pretty noxious and must be thoroughly cleaned afterwards.  It's an option of course, but I'll probably have to do the soldering (well, just using this to tin the contacts) in a better ventilated workshop.

What I've done - before I get into any kind of plating, is try and sand the contacts with 400-800 grit.  This is enough to get the brass to shine through but cannot get to the part where the diameter of the contact narrows.  So when soldering, the solder won't wety to this part, and forms a small amount of black - which I'm guessing is nickel oxide - crud that forms a void under the joint.  It's really rather messy, so I'm sacrificing a few of these connectors to test.

Re: "Pre-tinning".  Thats what I'm trying to do.  Once solder is on the contact, its obviously going to be easy, but getting the solder to wet is tough.  As I said the only way I have managed this is both by sanding the metal - not really ideal for 50+ of these things - and then using a higher temp iron + far too long dwell time which is only going to risk damaging the housing.

I agree with jpanhalt, Kester 44 flux cored solder works wonders in many situations where lesser flux does not cut it.

I'll see if I can pick some up.  If it isn't has potent as the one I linked above it'll be handy to have on the shelf for just this sort of thing.
Edit: it seems I can get "sample" amounts of kester 44 Sn63 Pb37, and/or LF (SAC305) with flux 285.  Are both fluxes compatible with nickel?

Sometimes when soldering to pins in plastic housings like this, I will insert the mating connector beforehand, to help hold the pins in place when/if the housing softens due to heat.

Yes, I do that.  I learned I had to do that for some cheaper DC sockets I used a while back.  The plug that goes into these sockets doesn't sit neatly (I've glued shims to one to use it as the "holder"), but it grips the pins with enough force to hold them in place, and probably will prevent me from pushing or pulling the pins out of a melted housing. So far, none of the pins have moved on the 3 connectors I've done.

Whilst I mentioned plating in the original post, I had a thought - I need to solder to this, and considered plating something over it (additive) but what about deplating (subtractive)?  Stripping nickel chemically is going to require fairly harsh acids, but electrochemically?  Might be workrth sacrificing a couple more to test if I can pull the nickel plating off the brass using nothing more than an electrolyte and a few volts.  Time isn't really a concern, and these are quite small, so I could do them in batches of 10 in a tiny (de)plating bath.

[MikeK]

I would be using my big pistol-grip Weller (>100W) for this.  In another thread I saw IanM improved soldering on some micro-grabber tabs by dipping in copper sulfate for a few seconds.

[thm_w]

I have a 60W iron with a large 3mm chisel tip - pretty beefy, or at least the beefiest I have.  This works just fine for tin plated large screw terminals of a similar size/mass.  I do indeed use the flat side butted up against the end of ther terminal - furthest from the plastic housing to minimise potential melting, along with a small blob of solder to provide the best thermal contact.  Again, for similar tin plated terminals this works well, I can tin the terminals in about a second - but for these its more like 6-7.  Temp was set to 400C (350 took way too long).  By which time the poor flux had all burned away.

Watt rating doesn't mean too much in terms of iron performance. Additionally, if its a poor quality tip, it will be even slower to respond to load.
3mm should be OK, but if I were you I would have a 5mm on hand in case you ever need it.

Of course, if it works well for all your other tasks, and this is the only difficult one, well, it might be fine.

Watch this coin comparison from SDG for an example:
https://youtu.be/TGaTJmuy21U?t=1088

I would be using my big pistol-grip Weller (>100W) for this.  In another thread I saw IanM improved soldering on some micro-grabber tabs by dipping in copper sulfate for a few seconds.

Could be worth a try https://www.sciencesource.com/archive/Image/Nickel-Reacting-With-Copper-Sulfate-SS2603127.html

[Buriedcode]

... In another thread I saw IanM improved soldering on some micro-grabber tabs by dipping in copper sulfate for a few seconds.

I believe that was copper chloride.  The spring steel he was plating too would self plate in sulpahte, but without adhesion, the chloride probably activated the surface of the steel and allowed it to plate.  Similar to a woods nickel strike, copper chloride can be used to plate copper onto "difficult" metals.

[mawyatt]

One could use a very "aggressive" flux and tin all the terminals, and clean them IPA. Then use a "normal" flux and solder to attach the wire.

Best,

[Cerebus]

Perhaps turn the problem on its head.

You said "requires higher temperature, by which time the plastic housing becomes soft". I've fixed that problem before by cooling the plastic. It just needed something as simple as wrapping as much of the plastic part as possible with wet paper towel (making sure to include the part where the metal and plastic join). Messy, not elegant, but it got the job done.

That solution of course requires that your part is situated where you can afford to have water slopping about and that you have enough room between the "bit to be soldered" and "bit to be kept as cool as I can".

I've never had any difficulty soldering clean nickel plating, just knock-on effects like you're experiencing. I have found that cleaning the terminal first (scotchbrite is ideal) and wiping some liquid flux on before starting helped (just a standard Multicore flux pen). Actual soldering: just standard Multicore (loctite) rosin core flux and a suitable sized soldering iron bit on a 40W or higher iron and the confidence/patience to wait for everything to get hot enough for the flux to do its work and the joint to wet out.

[Buriedcode]

Well, just an update.  Got some Kester 44, and it worked beautifully.    Each contact took around 2 seconds to solder, and it wetted so easily I didn't bother just tinning the second contact before soldering the wire, just do it all in one.

I also tried it on some DC barrel sockets that have always given some grief when soldering - even when using large mass tip, took a few seconds to "take" at least some solder - and that pretty much instantly wetted.

The stuff I have is leaded, so I'll have to pick up some SAC305 with 44 in it for work, but I'm completely sold.  I didn't realise there were fluxes that could do nickel without requiring extensive cleaning afterwards.

One could use a very "aggressive" flux and tin all the terminals, and clean them IPA. Then use a "normal" flux and solder to attach the wire.

Best,

That was my backup plan if this 44 stuff didn't work.  Just tinning the joints using the harsh stuff then cleaning.

Perhaps turn the problem on its head.

You said "requires higher temperature, by which time the plastic housing becomes soft". I've fixed that problem before by cooling the plastic. It just needed something as simple as wrapping as much of the plastic part as possible with wet paper towel (making sure to include the part where the metal and plastic join). Messy, not elegant, but it got the job done.

That solution of course requires that your part is situated where you can afford to have water slopping about and that you have enough room between the "bit to be soldered" and "bit to be kept as cool as I can".

The sockets - like IEC figure 8 sockets - have a recess which I suppose could have water flowing into/out of it, but soldering near running water, it all sounds like a massive hassle.  Thankfully, with the decent flux I can solder the terminal before the other end of the pin is too hot to touch, let alone melt plastic.  I still use a custom moulded plug to hold the pins more or less in place whilst soldering jsut incase.

Thanks folks.  I was almost looking forward to trying out plating as I haven't done it in years (had limited success with plating copper over solder years back) but it's an expensive experiement to try, not to mention messy.

[Kleinstein]

An important part with plating is cleaning the surface. So if the "nickle" (maybe zinc ?) surface does not solder well, it may as well not plate well.

[Buriedcode]

An important part with plating is cleaning the surface. So if the "nickle" (maybe zinc ?) surface does not solder well, it may as well not plate well.

I emailed a couple of plating companies that sell "kits", and whilst of course they want to sell their products, all suggested some form of activator (that removes protective oxides and sometimes etches the surface).  Some can clean and activate at the same time.  From what I remember of my brief experiments years ago it wasn't just an important part, getting the surface clean and activated was probably the most difficult bit. Definately more hassle than its worth.