How do they wind coils with ridiculous gages like 56AWG? - Page 1
Forum section: electronics / projects

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 15, 2023, 01:05:15 am
content: I'm trying to figure out one step in the manufacturing of floppy drive R/W heads. At least the older ones I am looking at.I know no one makes those, but someone is still making ridiculously small and fine coils for teeny-tiny earbuds, etcI mean just in general. The wire is so fine just yanking it a bit too much it breaks. Soldering it is another mystery, solder dissolves copper. I managed with much bigger headphone wire but even that was tough.How do you wind something this fine let's say on a 1mm diameter coil? Or remove the enamel on the ends?What terms should I google for?

author: amyk
author_rank: Super Contributor
timestamp: June 15, 2023, 01:34:02 am
content: Look for "fine wire winding" machinery.https://azonicproductsinc.com/products/wire-tensioning-devices/model-3535-ultrafine-tensioner-awg-45-to-56-wire-52533641https://audemars.com/micro-coils-manufacturing/

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 15, 2023, 01:59:26 am
content: Thanks. I know this guy managed 60 years agohttps://pasadenahistory.org/collections/micromotor/so it's not impossible... But there isn't much detail about how he did it.

author: Ian.M
author_rank: Super Contributor
timestamp: June 15, 2023, 02:02:09 am
content: As long as the winder is designed with the known tensile strength of the wire in mind, I don't see any problems. Stripping the wire can be done chemically, and soldering it just needs a solder alloy with a composition that has a near-saturation copper concentration in it so it has very little tendency to dissolve the wire.

author: Circlotron
author_rank: Super Contributor
timestamp: June 15, 2023, 02:16:58 am
content: A related issue - I used to work in a SMPS lab where we had reels of various diameter winding wire. To make sure of what we chose when winding up a prototype we would use a pair of calipers to measure the wire diameter and then subtract 0.1mm to allow for the thickness of the insulation coating. This worked great for wire of 0.25mm upward, but what about say 56AWG like the OP mentions? The insulation thickness would account for a much greater percentage of the overall diameter, and therefore going to a thinner wire would have less and less usefulness. Are there different insulation thicknesses on very fine wires?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 15, 2023, 02:39:43 am
content: Quote from: Ian.M on June 15, 2023, 02:02:09 amFor sure, if someone showed me the tools I can learn. I'm just fixated right now on how these floppy heads were made. Because in my ... let's say enthusiastic ignorance, I feel with enough knowledge I can take the defective coils out of the head (it's just goop in there, it's not potted) and ... somehow, magically get a new coil in there. No I don't know how to get the coil off from a closed loop of ferrite... one step at a time.Quote from: Circlotron on June 15, 2023, 02:16:58 amI found a video of a guy who bought a spool of AWG56 and I think the micrometer squashes the wire and you can't get a reliable reading. In any case the manufacturer of the fine wire can't even measure it, the dimensional chart says dimensions are "theoretical".https://youtu.be/pn8ufOdbJ5M

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: June 15, 2023, 02:43:58 am
content: I remember meeting the CEO of a UK company that made 2-to-4 wire transformers (called "hybrids").These were used in telephone line interfaces. The company had problems using fine enough wire.I advised him to check out Japanese manufacturers of low-power 48 V telecom relays. At the time,not every relay OEM offered these, because the wire needed was too thin, and the normal manufacturingprocess would result in too low a yield. Judging by their pricing at the time, Japanese OEMs like Takamisawahad mastered the necessary art, and we used these by the boatload.

author: iMo
author_rank: Super Contributor
timestamp: June 15, 2023, 07:01:28 am
content: FYI - 2 weeks back I was repairing an 1MegaOhm wire-wound resistor, the wire invisible with a naked eye - see below the shot with a piece of the wire wound on a matchstick (the control line is 0.076mm wide).I spent 3 hours with it and the resistor works again (but it is by 8kOhm lower)

author: MisterHeadache
author_rank: Regular Contributor
timestamp: June 15, 2023, 03:32:55 pm
content: Constant control on wire tension is a must. My experience is limited to no smaller than 42 gauge, which we wound onto sensors and coil bobbins for automotive sensors using Marsilli industrial machines. The terminations were wound into a structure called a 'skein', which essentially is the wire wrapped around itself several times to make a blob thick enough for subsequent soldering or resistance welding. But even so, the transition from the skein to the single strand was always a weak point and prone to breaking.

author: coppercone2
author_rank: Super Contributor
timestamp: June 15, 2023, 05:24:11 pm
content: for soldering wire of small gauge you need a solder alloy that has the wire material in it so there is less tendency to dissolve.I.e. copper bearing solder. It will protect plating too. Same idea as silver bearing solder for tektronix metalized silver ceramics.As to what % you need, I have no idea.My procedure would be this:1) clean wire (not sure how, maybe molten KOH, wear goggles + safety shield + long gloves + apron .. nasty work)2) strain relief the wire with a silicone or q-dope drop after its positioned correctly for the solder joint3) allow for full cure4) perform solder joint with correct metal bearing solder and flux4) don't touch nothingYou don't want to be bending or positioning the wire or anything during soldering IMO. It needs to be laid correctly then just submerged. And I would say you should make sure not to over heat it, so the rosin does not burn too much, so you can flow clean it, and possibly use a brush (not a tissue) to agitate it a little.

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 15, 2023, 05:27:40 pm
content: Using a Sn-Cu alloy should help a bit, as the tin has already "relieved" some of its affinity for copper.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 15, 2023, 06:24:38 pm
content: Once you have equipped and trained yourself to work at these gauges welding might be easier than soldering. Thing of it like wire bonding on ICs

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 15, 2023, 07:50:55 pm
content: I've contacted the Swiss company. I'm pretty sure there's not much that can be done to revive these dead old heads, but if this company can wind me a few test coils for fun, who knows?Thanks all!

author: Ian.M
author_rank: Super Contributor
timestamp: June 15, 2023, 10:15:33 pm
content: Seehttps://www.eevblog.com/forum/projects/soldering-ultrafine-wire/Apparently Sn60/Pb/Cu2 solder will reduce the rate that 54AWG copper wire immersed in molten solder dissolves at, sufficiently that it will last over a minute, so you can expect negligible wire thickness loss at the surface of a normally made solder joint.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 15, 2023, 10:22:04 pm
content: The smallest wire I have wound with a Swiss made winding machine was 0.008 mm.It is more a question of good quality tentioners.If all is set correctly this is not a challenge anymore.

author: Bud
author_rank: Super Contributor
timestamp: June 15, 2023, 11:05:49 pm
content: Now, how do they make such thin wires

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 15, 2023, 11:40:29 pm
content: Quote from: Bud on June 15, 2023, 11:05:49 pmVery carefully.

author: coppercone2
author_rank: Super Contributor
timestamp: June 16, 2023, 12:05:05 am
content: you need swiss people to make a smaller version

author: MathWizard
author_rank: Super Contributor
timestamp: June 16, 2023, 01:51:51 am
content: No wonder I've found it hard to solder headphone wires. Not only is there something like cotton wound in for strength. And the wire is enamelled and burns onto the wire so it's hard to wet. And now I see the wire also could be dissolving a bit.

author: Ian.M
author_rank: Super Contributor
timestamp: June 16, 2023, 03:25:46 am
content: https://www.eevblog.com/forum/beginners/tips-for-soldering-in-ear-earphone-wires/

author: Edwin G. Pettis
author_rank: Frequent Contributor
timestamp: June 16, 2023, 06:26:35 pm
content: Copper being a relatively 'soft' element is limited to how small a wire can be drawn out to, 56 AWG is approaching the physical limit of drawing it out. However, the 1 Megohm resistor mentioned was not made with cooper wire, at the very least it was Manganin and more likely an Evanohm alloy. Evanohm has been drawn down to as small as 0,000,4" (0,010,16mm) for many years, I have wound resistors with 0,000,7" (0,017,78mm) wire and it is not easy. The wire will break at the slightest jolt to it and it is a lot tougher than copper or copper alloy. Yes the wire is difficult to 'see', the lighting must be aimed exactly in order to 'see' the wire, preferably with a darker background for contrast. There has been several manufacturers in the US over the years that made this fine wire, no need for the Swiss' fine capabilities though.Depending on the size of the bobbin, the 1 Meg resistor was wound with wire <0,000,9" and some of the smaller ones used 0,000,4" wire. Note that the wire sizes quoted here are the actual diameter of the resistance wire and not the finished size with enamel coating on it.I do not know all of the finer details of making very fine wire but diamond dies are used with progressively smaller holes in them. As a nod to the difficulty of drawing out these fine wires, the last quote I got on 0,000,7" Evanohm wire was $18,000/pound and that was a few years back!

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: June 16, 2023, 06:53:16 pm
content: It looks like the wire in the floppy head is nowhere near 56AWG, looks more like 39AWG AFAICT. But winding a coil is the least of the problems...Thanks all, I guess I'll try to find local coil winders if they exist. Not that I want anything right now but in case I make a breakthrough in how to swap coils in a head.I know it's likely not possible but whatever.