Silver wire problem soldering - Page 1
Forum section: electronics / general

author: aldopopp
author_rank: Newbie
timestamp: July 26, 2022, 08:54:02 am
content: New to the forum, so sorry if i break any rules.At work we have these medical application wires that need to be soldered on a board ( that will be inside an enclosure to separate it form tissue and whatever, anywasys the product is really in the very early stages of concept). They are very thin silver wires inside of a silicone sleeve, coworker tried soldering them on the pads of the pcb (insulation has definetely been stripped entirely from the stranded conductors) but to no avail, applying flux does not help, even staying for a long time with the iron on them does not help, tried different temps but to no avail.I tried my research skills on google and the forum and found an old post speaking about silver plated wire, i also know it is widely used for connections on a breadbord style pcb but can't imagine why its not working for this case, maybe the conductors are too thin and solder can't get inside through capillarity?Is the manufacturer applying maybe something that is keeping the solder from sticking to the wire? ( it is custom made for us from a partner specialized in medical wires)I tried applyiong isopropyil alcohol to clean the wire but nothing changed. Even heated it up to 550 degrees in case it had something like enamel around it but also that did not change anything...As a last resort , I tried opening up the wire a little bit, making it more into a brush at the tip but it still would not take the solder.Any tips or advice on how to proceed?(right now we are crimping some very thin wire termination, think about the back of a mil spec micro connector, and soldering the crimped section, that takes solder with no issue, on the board)

author: Ian.M
author_rank: Super Contributor
timestamp: July 26, 2022, 10:04:32 am
content: How certain are you that the wire is real silver or real silver-plated? Unless its extremely tarnished (dark brown or black) silver generally solders extremely easily.Also what solder alloy and flux are you using?

author: andy3055
author_rank: Super Contributor
timestamp: July 26, 2022, 10:38:15 am
content: If it is a medical application, it may be stainless steel. Best to check with your supplier for the composition.

author: SeanB
author_rank: Super Contributor
timestamp: July 26, 2022, 11:15:06 am
content: Yes likely either stainless steel or aluminium, easy enough to ttell by heating the wire with a flame, aluminium will melt. For stainless steel you need a silver loaded solder with acid flux, which is a common enough solder paste for things like stainless steel mesh brazing, but you need a very high temperature to activate the flux and melt the silver solder, so your solution of crimping a brass header onto it then soldering that will work. Otherwise you will need a separate step, outside the manufacturing area because of the corrosive fumes, to prepare the wire ends to take the silver solder, and then a thorough wash, preferably 3 steps of ultrasonic, in some flux remover, isopropyl alcohol and then DI water, to clean the prepared wires for soldering, or you risk corrosion of the wires.

author: aldopopp
author_rank: Newbie
timestamp: July 26, 2022, 11:27:30 am
content: Quote from: Ian.M on July 26, 2022, 10:04:32 amWe are definetely sure it is indeed silver. Will ask again for confirmationQuote from: Ian.M on July 26, 2022, 10:04:32 amUsing the attached image solder type, which looks like has been acquired by locktite as locktite products turn up while looking for it.

author: aldopopp
author_rank: Newbie
timestamp: July 26, 2022, 11:28:52 am
content: @andy @sean will check with my coworker and confirm

author: SMTech
author_rank: Frequent Contributor
timestamp: July 26, 2022, 02:53:29 pm
content: Quote from: aldopopp on July 26, 2022, 11:27:30 amHenkel added Multicore & Loctite to its portfolio ages ago and variously used those brands on solder products by region or whim.This year Henkel solder its rosin and solder business to Harima, but to my understanding has kept solder wire. That said plenty of people are struggling to find their favorite Loctite/Multicore solder pastes and our solder wire of choice (96SC Ecosol) is also currently showing an ETA of August with multiple suppliers, so either way the sale seems to have caused some disruption/confusion.Your wire certainly seems to be "Multicore" but I can't translate LBL 591 into anything (neither flux nor alloy), however their labels are terrible, they may have written something on the other side of the reel or just be being unhelpful. Some lead free solder wires are quite tricky to use, some fluxes are whimpy but it does sound like it is your wire in this instance, either its old and tarnished or not what you think it is.

author: TimFox
author_rank: Super Contributor
timestamp: July 26, 2022, 03:23:50 pm
content: Teflon-insulated copper wire (solid or stranded) is almost always silver plated (since tin would melt during the application of the insulation), and I have never had a problem soldering to it with normal electronic solders.(The only non-silver teflon-insulated wire I have seen is unplated copper, which is less common that silver plated.)

author: Stray Electron
author_rank: Super Contributor
timestamp: July 27, 2022, 02:26:43 am
content: Quote from: TimFox on July 26, 2022, 03:23:50 pmThis, over and over again! I have mountains of silver plated teflon insulated wire that I got directly from at a large US defense contractor when I worked there (with full MIL-SPEC documentation I might add) and it is VERY solderable. Either the stuff you have isn't silver plated wire or you're using some kind of junk solder. I use either 2% or 3% silver loaded Kester brand lead/tin solder for just about everything that I do (yes I hoarded about 40 pounds of it when it was still available) but I have used standard 60/40 and 67/33 alloy solder (Multicore and Alpha brand IIRC) and never had ANY problems soldering silver plated wire. I use only the flux that comes in the solder, I've never used added flux of any type for silver plated wire.FYI I've been told that all teflon insulated wire MUST be silver plated or else the gasses from the Teflon will attack the copper. I assume that it true because I have never seen unplated copper wire with Teflon insulation.

author: tooki
author_rank: Super Contributor
timestamp: July 29, 2022, 02:58:49 pm
content: Quote from: aldopopp on July 26, 2022, 11:27:30 amThat image doesn’t show what kind of solder it is. That’s the back label with the manufacturer’s general information. The front label is the one that matters. But just read what your roll actually says and type it in.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 29, 2022, 05:24:40 pm
content: Quote from: Stray Electron on July 27, 2022, 02:26:43 amI have a few scraps of some nice "mineral filled PTFE" (probably M22579?) which is nickel plated: mildly magnetic, and a right bitch to tin (it can indeed be tinned, but needs great patience).Anyway, that's Teflon; stuff just in a siliconesleeve, sounds like it could be anything. I suppose titanium isn't even out of the realm of possibility, or nitinol, which are even less solderable than stainless and aluminum. Aluminum should be the silvery-est looking of the possibilities though.The more likely case I would think, for actual silver wires, is dissolving in excess solder, because it's highly soluble at that scale (a few percent at soldering temperatures). The trick in that case is to heat the joint for the shortest time possible; making a well flowed joint can be a challenge.Tim

author: Ian.M
author_rank: Super Contributor
timestamp: July 29, 2022, 05:46:19 pm
content: Quote from: T3sl4co1l on July 29, 2022, 05:24:40 pmOr use one of the solder alloys that already contain >2% Ag.

author: TimFox
author_rank: Super Contributor
timestamp: July 29, 2022, 08:24:08 pm
content: Quote from: T3sl4co1l on July 29, 2022, 05:24:40 pmI once obtained some high-temperature wire that was nickel plated, and it was almost impossible to solder.I wouldn't think medical wire would be nickel plated, but it is "silvery" in appearance.

author: 13hm13
author_rank: Frequent Contributor
timestamp: March 13, 2023, 06:33:41 am
content: Something like this is used in audio earphones quite a bit, especially in the higher-end audio models.For example:https://www.aliexpress.us/item/2255800651290793.htmlIt can be very difficult strip the plastic lamination -- the inside wound strands are very fragile. And will easily snap unless one isverygentle. Also, the stands are "sliver"-coated but that coating is NON-CONDUCTIVE. The silver is just a pretty paint for bling factor.To solder (tin) the actual Cu part, one must take soldering iron to 890F (476 C), the max my Hakko can do. And work a blob of solder until it sticks (tins).I also let the hot solder burn off the lamination as that was the what I found easiest. Final clean up with Q-tip and acetone.Some of the most challenging soldering I've done to date!

author: BradC
author_rank: Super Contributor
timestamp: March 13, 2023, 06:42:22 am
content: Quote from: TimFox on July 29, 2022, 08:24:08 pmI encountered some nickel plated steel I needed to solder to a fragile connector. I ended up "tinning" it with a 45% silver alloy, fluoride based brazing flux and the oxy torch. The tinned end then soldered nicely to the connector with standard leaded solder.

author: 13hm13
author_rank: Frequent Contributor
timestamp: March 13, 2023, 09:09:16 am
content: Note the DMM reads OL ("open", infinite ohms ) for + and - clips on either ends of bare "silver" stands . These are bare stands -- stripped from inside the clear plastic sheath we are used to handling -- from the Fiio FH7 iem cable shown.https://postimg.cc/R3SRW2nk