Do I need better soldering iron for non-Leaded solder? - Page 1
Forum section: electronics / general

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 19, 2018, 12:32:35 pm
content: I'm trying to de-solder the output caps of a computer PSU. I'm having a hard time de-soldering non-leaded solder. I'm using flux, I keep adding 60/40 solder to dilute the factory stuff, trying to use a pump, and using solder wick. And it's taking a lot longer than I bet it should. The traces are big I guess but still.I'm using a cheapo $40 solder station w/ temp control I think it was 40W but IDR. It supposedly goes up to 450C. And I'm putting the dail over 400C, almost max. And in no time the tip gets oxidized, so I'm always trying to clean it, dip it in flux, and tinning it.I swear it took me 20min to remove 3 caps (made a bit harder since it was hard to grasp them)

author: coppercone2
author_rank: Super Contributor
timestamp: September 19, 2018, 12:40:00 pm
content: throw flux on the joint to desolder and soak the solder braid in flux and use the yellow nasty sticky flux rather then the clear low residue one. You need stronger shit for old non leaded joints. Also you can put solder on your braid then press the braid against the joint then the solder iron against the braid to start the wicking process.Doing this may help. You can put a big glob of solder down. Your tip should not oxidize that fast though.I recommend you melt a big glob of solder on top, melt the whole joint, and use a solder sucker though. If its being a bitch you can melt it and use a duster-spray/compressed air in a tiny nozzel like the straw to blow the solder inwards, but you get little spikes of solder that go all over the place. With really big caps you can yank on them a bit with no consequence they seem to be built pretty tough, I have seen them shot out of black powder guns before lol. You can like melt one joint, pull on it a tiny bit to move it up, then do it on the other joint, and kinda walk it out. When its almost walked out you add more solder to actually fill the joint so you have thermal transfer and you keep walking it. In the end you might get a tiny little connection that you can just rip off,basically the strength of electrical solder tensile is roughly 6000 pounds per square inch.So if you have6000=640mm2x=0.1mmso a little 0.1mm bond has a tensile strength of less then 1 pound. I would not worry too much about ripping it a bit when its almost done and you have some pissant contact between the capacitor and a VIA for instance (fucking super annoying).

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 19, 2018, 12:49:54 pm
content: Yeah I'm using a jar of flux thats like thick honey. I dip the solder wick in there with heat.I'm going to try some more today. I took a lot of stuff off another PSU and that took forever too. If it was anything truly temperature sensitive I would have fried it for sure.I'm using a chisel tip and a more rounded 1. And I'm cutting off lengths of the wick, so I'm not heating the whole thing.

author: coppercone2
author_rank: Super Contributor
timestamp: September 19, 2018, 12:52:08 pm
content: melt the whole thing and use a sucker or walk em out or try blowing in there with strong compressed air when molten but be sure to expect that little globs of solder will fly on things and possibly short out your circuit and be annoying/sharp.wick freaking sucks ass for through hole parts that use a VIA anyway. IMO its a SMD thing or for cleaning solder attachment points etc.If its a single sided connection on the bottom of the PCB with no VIA then the wick is decent, If its top soldered under the part the wick is less useful and with heavy copper via's wick is just pretty horrible (my extent is 90W irons from hakko/weller)

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 19, 2018, 01:06:11 pm
content: Ok I'll try more solder. This is just 1-sided PCB, thankfully no solder on the top.I have a brand new tip here I can try. The other 2 work fine enough for 60/40, but I'm pretty new to soldering, I probably cooked them too long last year.I have an old old 100W or 120W Weller here, but that's big and bulky and the tip is huge.I have a 858D hotair station. That worked on this type of solder before. I took out an 18-pin sister PCB. But I burned the main PCB doing it.

author: coppercone2
author_rank: Super Contributor
timestamp: September 19, 2018, 01:15:33 pm
content: you should use the bigger soldering iron if you trust its temperature control for larger joints so you don't stress the smaller one out, its good practice.

author: sn4k3
author_rank: Frequent Contributor
timestamp: September 19, 2018, 07:18:30 pm
content: The most dificult caps to remove are from desktop motherboards, the tiny via they use and small join is hell to remove even with hot air and 400ºc and board deformation i have a bad time to remove them

author: mmagin
author_rank: Frequent Contributor
timestamp: September 19, 2018, 08:00:15 pm
content: From my limited experience with lead-free solder, I would mention that at the higher temperatures, it's easier to burn traditional rosin flux into a mess that's hard to get off your iron tip. I'd definitely suggest a more modern no-clean flux if dealing with lead-free temperatures.

author: coppercone2
author_rank: Super Contributor
timestamp: September 19, 2018, 09:40:13 pm
content: I find those fluxes don't clean old components for crap. I only got decent result from the clear ones on pristine parts. If it was something ancient I needed to use the sticky amber one. The results with the clear one were downright frustrating.Kester 186 works great on old crap like removing components from ancient consumer PCB. 951 was a fail at this, but it works very well for clean new parts on fresh PCB, at least the one I have. I try to use the 951 when possible because its much less of a pain in the ass to clean, the 186 if spilled is completely disgusting. I have had moments of extreme frustration when I just used the 'latest and greatest 951' that 186 made disappear.It is possible I got cut stuff from eBay though.I just meant avoiding using 951 for this job. My 186 is still very liquidy despite being amber.. maybe your flux is actually your problem.. I did use the thick-gel kester kind from a syringe before, but for small rework on commercial PCB.. but never with real old heavy stuff.You are using something different then I thought. I like this for old stock and desoldering:https://www.kester.com/products/product/186-soldering-fluxand this one for nice new partshttps://www.kester.com/products/product/951-soldering-fluxAlso, if you want to try (but I am starting to think heat is your problem) you can use a small wire brush lol

author: Bassman59
author_rank: Super Contributor
timestamp: September 23, 2018, 10:30:22 pm
content: Quote from: lordvader88 on September 19, 2018, 12:32:35 pmAvoid soldering kit that measures its output in power instead of temperature.I bet your tip gets cold the instant it's put on the work and cannot get hot enough to actually be of use.This means spending more than $40. Get a Metcal. You won't be sorry.

author: lordvader88
author_rank: Frequent Contributor
timestamp: September 24, 2018, 01:31:22 am
content: The traces and overall mass off it all is huge, so yeah it's that more than the flux.3 thing on my list is good flux tho like Kester stuff thanks, and also, some low-temp Bismuth alloy solder.And time to start reading about a nicer solder station

author: Ian.M
author_rank: Super Contributor
timestamp: September 24, 2018, 03:06:42 am
content: If you are dealing with massive traces or ground planes without thermal relief round the pads, you *NEED* the largest possible (parallel sided) hoof bit in your iron to get enough heat transfer. A tapered bit just doesn't have enough copper CSA to get the heat to the joint effectively. If you are having to turn up the temperature excessively the iron has insufficient wattage and you might as well be using a non-controlled soldering gun, which will probably do less damage than 'cooking' the joint with an under-powered temperature controlled iron.

author: macboy
author_rank: Super Contributor
timestamp: September 26, 2018, 12:25:55 am
content: I agree with Ian, you don't need a higher tip temperature or more flux. You need better heat transfer. If the tip is heavily oxidized, too small, or doesn't fit well over the heating element then heat just can't move into the joint effectively. With a single sided board there is no excuse for not being able to reflow those joints; there is something wrong with the heat transfer.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 26, 2018, 02:51:05 am
content: Get a soldering gun for big connections.

author: Sceptre
author_rank: Regular Contributor
timestamp: September 28, 2018, 02:09:11 am
content: Quote from: NiHaoMike on September 26, 2018, 02:51:05 amAgreed. Also:1. Preheat the board on a hotplate or in an oven to, say, 150C.2. If you buy a Metcal, get tips "Optimised for thermal performance", i.e. stubby. The STTC tips end in P, the SxVs in A.

author: seanspotatobusiness
author_rank: Regular Contributor
timestamp: September 28, 2018, 03:17:10 am
content: Quote from: lordvader88 on September 19, 2018, 12:32:35 pmWould it be possible to heat both pads/leads at the same time and remove the capacitors without sucking up the solder?

author: Nusa
author_rank: Super Contributor
timestamp: September 28, 2018, 03:31:39 am
content: Since you've got a hotair station, turn it down to maybe 200C and preheat the whole area on the trace side. Having a pre-heated board will reduce the required contact time for the soldering iron a lot.But if you're going to do heavy traces a lot, the proper solution is to get a better soldering iron.

author: Shock
author_rank: Super Contributor
timestamp: September 29, 2018, 03:51:16 am
content: For old dry joints adding leaded solder can assist if your process is not totally lead free. It will bring down the soldering temp required, plus you can additional flux if needed. Doing this allows the solder to flow into the joint a little and makes removal easier.As for the iron it's about tip geometry and the irons ability to keep dumping heat fast enough to allow for quick removal and avoid causing damage by prolonged heating. I used to use a separate high wattage iron specifically for quick removals with an iron.I load up one side of a large tip with solder to make a good thermal bridge and it takes about 3-4 seconds to heat two pins through and then you just gently pull the cap out. Once you know the right temps and timing it's very easy. Not proper technique still but low risk when you're good at it. For large caps or wide spaced pins you can alternate pins a few times and rock/walk them out. If it takes longer than a few seconds you're doing it wrong.This is a Pace 6.35mm tip I was testing on a few boards. The Pace ADS200 can provide up to 120W power if required and can easily handle difficult ground planes. This is the best of both worlds for me as I can use fine tips and huge tips.A desoldering iron is going to be the best tool at the end of the day. I'd use hot air as a last choice for through hole as it's time consuming and carries a greater risk of damage than a powerful iron. The idea with anything is practice on junk boards till you get good.