GROUND wire won't tin... Not a noob question. - Page 1
Forum section: electronics / beginners

author: CheekyRobot
author_rank: Contributor
timestamp: February 03, 2019, 05:56:54 pm
content: Okay, this is driving me crazy. I've been soldering for about 40 years, got plenty of skills and experience all the way down to SMD soldering with a microscope.... so why the question about soldering a stupid wire?I'm repairing a splice for my external CCTV camera cable. The British weather took its toll.Pair of double-insulated wires. One a twin pair for 12v power, the other coax for the video.I cut away about 20cm from each end to avoid any oxidation / moisture etc, stripped the insulation nicely. Red +ve wire tins like a treat, core signal wire on the video cable tins like a treat. Straight away, no problems.BUT: Can I get the ground on the video or the black ground on the power to tin? No sir. Solder just rolls off both.Flux you say? Sure, I used flux. Proper leaded flux cored solder, plenty of heat, cleaned the wire, scraped it with a blade, tried mucking about with some offcuts.Nope, the wire isn't lacquered. Checked a sample with a meter.The ground wire on the power DOES look slightly darker than the +ve, but I've never had problems with a little oxidation before, bit of flux, abrasion no worries, even with the mankiest bits of wire.So... what gives?If I'd had trouble with ALL the 4 wires here then I'd be happy, they ought to oxidise equally...It's almost like the fudamental CHEMISTRY of the copper has changed... but that's just silly.

author: james_s
author_rank: Super Contributor
timestamp: February 03, 2019, 05:59:50 pm
content: It's not aluminum is it? With copper prices where they are I've been seeing more and more CCA wire.I've also on a few occasions had insulation on certain wires react with the copper and make them very difficult to solder. You could try using some find sandpaper or something to clean off the wire.

author: CheekyRobot
author_rank: Contributor
timestamp: February 03, 2019, 06:02:57 pm
content: I did wonder if it was aluminium. I did try sanding it and it looked kind of silvery.BUT.... would they make one of the pair of wires copper and the other ALU?How come it's just ONE of the wires in the pair I can't solder?Doesn't make sense.

author: ArthurDent
author_rank: Super Contributor
timestamp: February 03, 2019, 06:09:19 pm
content: I've had this problem and it is an oxide. On stranded wire you can try using an xacto knife to scrape each strand so it looks a bright copper color. It is a PITA and if replacing the wire is an option, go for it.

author: RoGeorge
author_rank: Super Contributor
timestamp: February 03, 2019, 06:15:52 pm
content: If it's Aluminium wire, it can still be soldered under a drop of oil. First, scratch the Al wire until it's shiny, then make the soldering under a big drop of oil. Some are using car engine (unused) oil, but I tried soldering Al foil kept under a big drop of cooking oil, and it worked. The solder nicely wet the Al foil like it was Copper.If you use the oil trick, either use an old soldering tip, or if you use a good one, cover it in Al foil before diving the heated tip under oil. After soldering under oil, the tip will be very, very hard to clean, will become almost unusable.The idea with the oil, is that Al will oxidize almost instantly when heated. The drop of oil will keep the Oxygen away from the Al wire.There is also special "flux" for Al soldering, but I never tested such flux.

author: james_s
author_rank: Super Contributor
timestamp: February 03, 2019, 07:15:51 pm
content: It's possible that both wires are copper plated aluminum and one color of insulation contains compounds that have attacked the copper while the other is still plated.

author: CheekyRobot
author_rank: Contributor
timestamp: February 03, 2019, 07:23:56 pm
content: Quote from: RoGeorge on February 03, 2019, 06:15:52 pmI never knew that! I'll give it a go with an offcut.

author: CheekyRobot
author_rank: Contributor
timestamp: February 03, 2019, 07:25:21 pm
content: Quote from: james_s on February 03, 2019, 07:15:51 pmHmmmm... I like that explanation a lot! Cheers.

author: saike
author_rank: Regular Contributor
timestamp: February 03, 2019, 07:26:05 pm
content: This is a problem on some of the heat resistant wiring in lamps I have to repair sometimes. The core which comes out to a much cooler part of the lamp seems more like stainless steel than copper. It can be soldered with stainless flux and plenty of heat but it still does not flow as well as a normal soldered wire joint.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: February 03, 2019, 10:04:06 pm
content: A while back there was an issue with cheap chinese ethernet cables made of aluminium condoctors which did not meet spec.When that became known it became common to weigh rolls of Ethnet cable, as aluminium is a lot lighter than copper.The next step was Ethernet cables with 2 wire pairs of aluminum,and two wire pairs of steel.But steel is easily detected with a magnet.I don't know what happened next.Sometimes stainless steel is used for conductors in headphone cables.It's low current and resistance don't matter much and the stainless has much less fatigue due to repetitive bending compared to copper.I also had a roll of copper wire once which had some kind of oil embedded and it even oozed out as a dark purpelish almost black fluid. That stuff was also hard to solder and I simply disposed of it.

author: vealmike
author_rank: Regular Contributor
timestamp: February 04, 2019, 11:53:39 am
content: https://en.wikipedia.org/wiki/Tinsel_wire?The stuffs impossible to solder, the nylon melts and coats the copper before the solder wets it.

author: pwlps
author_rank: Frequent Contributor
timestamp: February 04, 2019, 02:16:37 pm
content: I had a similar problem several times when trying to repair broken headphone wires. These were thin stranded wire coated with varnish, no way to solder with a standard organic flux. Strands were so thin that when I tried to scrape off the varnish with a blade they usually ended up breaking. Then I found this trick on a radioamateur site (I forgot were it was) : I put a big drop of lemon juiceon the wire then tried to scrape off the varnish gently with a hot soldering iron tip, repeating it several times the varnish eventually went off. This worked at least with with copper wires, however on another occasion the wire was made of something else (some alloy or stainless steel, I don't know) and the lemon juice wasn't quite enough to have the tin stick to the wire, then instead of lemon I have used a diluted orthophosphoric acid (used as flux for stainless steel soldering and that I borrowed from our mechanical workshop).

author: IDEngineer
author_rank: Super Contributor
timestamp: February 04, 2019, 07:05:23 pm
content: We see this in small BLDC motor wires once in a while. Often generous application of flux - rather than just relying on what is in the solder's core - gets the job done. I love all the other, more exotic ideas in this thread but I'd try the simple ideas too... whatever works!

author: CheekyRobot
author_rank: Contributor
timestamp: February 07, 2019, 10:42:19 pm
content: Well, in the end I soldered the compliant wires.... and then twisted the others together and packed it all up with a goodly amount of duct tape.Video signal looks good and crisp. This may end up being an annual event though....but... twist and tape... I just feel DIRTY now

author: viperidae
author_rank: Frequent Contributor
timestamp: February 07, 2019, 11:24:15 pm
content: Instead of twist and tape, you could crimp it...

author: james_s
author_rank: Super Contributor
timestamp: February 08, 2019, 04:33:05 am
content: I hate duct tape, it's one of those products that does a whole bunch of things poorly and almost nothing very well, for everything it gets used for there is a better product out there. It leaves a nasty sticky mess all over everything.

author: Psi
author_rank: Super Contributor
timestamp: February 08, 2019, 08:36:13 am
content: I've seen CAT5 cable with copper plated aluminum wire that will tin once.If you try again the copper comes off and you will never get solder to stick again.

author: bd139
author_rank: Super Contributor
timestamp: February 08, 2019, 10:40:09 am
content: Coke Zero works as flux on that shit. Smells awful though.

author: Rerouter
author_rank: Super Contributor
timestamp: February 08, 2019, 11:47:43 am
content: Aluminium can be soldered, you just need the flux to cover a decent area, the flux is wanting to rip the oxide off, you just need to make sure it cannot reform, and solder will take.I've soldered steel and aluminium many times just by going overkill on the rosin flux, once its changed translucent and spread, scrape the base metal through the flux with a pick, then bring in the solder and it will bite at the scrape marks and spread, You will however see a very odd mix of colors on the surface of the flux, it looks like a grey mud on aged aluminium.You will have to be prepared to get that joint hotter than a normal copper joint. Up to a certain point the flux gets more aggressive at higher temperatures.Also never use plumbers flux, sure the acid helps, but aluminium leaves some voiding in the alloy, and still forms skins of partial oxide unless you give it a silly amount of time to dissolve in the lead, so you get trapped little droplets of acid.