Best way to mass de-solder electronic components (through hole and smd) - Page 1
Forum section: electronics / general

author: jastreb
author_rank: Contributor
timestamp: September 02, 2019, 05:29:15 am
content: HI everyone,I have amassed a massive pile of all kinds of PCBs full of good stuff and I would love to be able to desolder some of them and put in my parts bins for playing around with. I spent all weekend trying to desolder components off a single PSU. I now have burnt fingers from holding/pulling on components while heating the legs with an iron. I tried two different irons an even a desoldering station (one of those s-998 things from aliexpress which died in 10 mins). 220$ down the gurgler. Also used 3 different types of manual solder suckers and braid but was all just not working too well and really slow.So been searching, and seen people using heat guns, to blow torches to dipping board in a molten lead bath.... Can anyone give me a suggestion that they have tried and works rather well. I don't mind putting in the effort but what I have tried so far just does not work.Yes I know the components salvaged may not be in best state or damaged but I would still like to do it. Thank you for your time.

author: amyk
author_rank: Super Contributor
timestamp: September 02, 2019, 05:40:17 am
content: Quote from: jastreb on September 02, 2019, 05:29:15 amProbably the fastest way, best done outdoors or in an area with good ventilation. Search "solder pot" for more info.

author: kripton2035
author_rank: Super Contributor
timestamp: September 02, 2019, 05:55:05 am
content: I've had success with a heat gun to mass-desoldier some pcb once in a while. it's ok to desoldier passive components or relays or triacs or transistors, but not for delicate IC's

author: John B
author_rank: Frequent Contributor
timestamp: September 02, 2019, 06:52:48 am
content: If the purpose is to acquire parts for use, you should ask how well you value your time and whether that time is better spent learning or designing. Most components can be acquired so cheaply in bulk, there's no reason to spend time desoldering things, unless they are a rare and expensive part. I'm thinking expensive voltage references, really big electrolytic caps, relays etc. But not resistors, regular caps etc.

author: Jeroen3
author_rank: Super Contributor
timestamp: September 02, 2019, 07:10:19 am
content: I've took a bunch of lem sensors from a board by pausing the bath solder machine. If you have a machine like that, you could use it.

author: Ian.M
author_rank: Super Contributor
timestamp: September 02, 2019, 07:23:13 am
content: Quote from: John B on September 02, 2019, 06:52:48 am+1.You also have to consider wear&tear on tools and useage of consumables to have *any* chance of coming out ahead on part salvaging.Scrap boards are best kept intact, each labelled with the make & model of what it was out of and the fault if known. Then you can salvage parts as you need them and have much more confidence that you'll get a good part. Also, when looking for a part by specifications rather than part number, you can look for it in sections of the circuit that run at appropriate voltage & current levels, so you don't waste your time looking up part numbers of totally inappropriate parts. You can also get a quick check on the pinout, by comparing what it connects to, again saving time with databooks/datasheets rejecting inappropriate parts.Also, sometimes I've even gone at a scrap board with a hacksaw, salvaging a whole section of its circuit for reuse. e.g. chopping a corner off a scrap TV main PCB to get the audio amp complete with heatsink, surrounding passives etc., and setting it up with a wallwart, a volume pot and some input jacks as a bench monitor amp.When a board is getting a bit too stripped, then, and only then you cherry pick any remaining nice parts you are short of before sh-tcanning it.

author: digsys
author_rank: Unknown
timestamp: September 02, 2019, 07:56:23 am
content: Depending on IF you want to save the board, and IF there are components on the bottom side you want to save - an old "trick" we did years ago was to hold the board upside down and pass a low flame butane torch over the components, 1 at a time, while shaking / or tapping the board at the same time.It didn't work well on DIL ICs that were "jammed in", but they were easily removed with Weller DIL solder tips - from DIL4 0.3" to DIL 48 0.6" plus a few other shapes.In cases where the boards were severely "starved" of solder / or lead-free, we'd wipe all the pins with a flux first, just a paint brush. Just an idea.

author: Psi
author_rank: Super Contributor
timestamp: September 02, 2019, 08:26:09 am
content: A blow torch on the back side of a multilayer PCB gets through-hole parts to let go quick. You can just grab them and pull them out.It ruins the PCB obviously, and you have to watch the toxic fumes from burning pcb.So its use is limited.

author: Shock
author_rank: Super Contributor
timestamp: September 02, 2019, 08:55:06 am
content: I have a hot air rework station, a vacuum desoldering iron, soldering tweezers and soldering irons for component removal (which is essentially a part of rework).It's actually more time efficient to leave everything on the PCB but electrolytics are fairly fast to remove and you will use them for repairs more than resistors. Once you have a good selection you can just leave everything else on the PCB. As a rule you only ever should salvage a high quality brands. Only exception perhaps some of the more expensive (larger) middle tier brands but please don't desolder Chinese crapacitors, it's just pointless.If you have a soldering station that has large mass tips (5mm shown in image) they are the most efficient for a few small electrolytic caps in one swoop but only if a suitable pin pitch. Vaccuum desoldering is the most efficient way for bulk through hole especially vintage ICs which are way faster. Hot air for anything surface mounted that you cannot remove with an iron or tweezers.After this photo was taken I removed two low profile Nichicon caps from a quality power supply PCB that were about $40 each.

author: jastreb
author_rank: Contributor
timestamp: September 02, 2019, 10:36:29 am
content: Wow, so many responses already. Thank you all for taking the time to give me your thoughts. I appreciate it. Might have to try afew of the methods myself. Probably heat gun first as I don't have a solder pot or blow torch.One question, some of the caps I was removing got rather hot. I assume this will have a very detrimental effect on their lifespan if not damage them right away. Would I be right in that assumption? These were electrolytic.Thank you all again .

author: digsys
author_rank: Unknown
timestamp: September 02, 2019, 11:45:03 am
content: They give you their max lifetime temp rating on them - 85C or 105C are the most common. Naturally the 105C ones are much better grade and dearer.A cap spec'd as 105C for 2000hrs, for example, will run at that temp for that many hrs. MUCH longer at lower temps. They'll likely go 2x for a very short time

author: nctnico
author_rank: Super Contributor
timestamp: September 02, 2019, 12:00:19 pm
content: A heat gun works very well but you have to do this in a well ventilated room and even then it isn't particulary healthy. The trick is to use the high setting to pre-heat the board and then use the lower setting to heat the solder over the melting temperature. Tap the board onto a hard surface on one side and all the components will fall off (unless they have been glued down).

author: Psi
author_rank: Super Contributor
timestamp: September 02, 2019, 12:46:08 pm
content: Another option is putting the PCB into a toaster/reflow oven.Once its up to temp you can open the door and remove any part with tweezers very easily.Since the entire board is up to temp it takes some time with door open to cool down enough for the solder to re-solidify.So you have some time. 30sec or so.

author: Red Squirrel
author_rank: Super Contributor
timestamp: September 02, 2019, 06:59:59 pm
content: I've used heat gun for big heavy components. Trickier for the small components though especially if the pins were prebent to hold component in before soldering.Desolder guns are probably the best bet if you will do this a lot though but they are not cheap. I've tried those plastic solder sucker things that look like syringes but I could never get it to work properly. I think it would be better if the tip was made of metal as I could put it right into the molten solder then release the trigger but don't want to do that with plastic.

author: Buriedcode
author_rank: Super Contributor
timestamp: September 02, 2019, 08:59:31 pm
content: I used to use a heat gun (one of the worst ways to do any hot air, as it was 2kW, without temperature regulation) for getting parts of larger boards - think monitor/TV and main PCB's purely because I didn't want to scrap a lot of consumer electronics, without at least collecting a biscuit tin of bits. I have probably used about 5% of what I got, so arguably not worth it.With that method, you get a lot of parts off, TH and SMD alike but... given the sheer power and widely varying temperature, by the time you've got most of the board up to the point where solder melts, some parts will be so hot the plastic of connectors melts, IC's become damaged etc... Crude, somewhat fun (yeah I'm like that) but not particularly helpful. It's a case of trial and error, medium setting, and play with the distance.If space isn't a problem, then I would leave them on the boards, and remove then as and when you need the parts... perhaps just removing "large" parts that make storage awkward, like massive heatsinks Components are safer mounted on the board, and you don't spend a lot of time desoldering stuff you won't ever use.I'll also add to the "its not really worth it", especially for passives. With caps and resistors sometimes literally 10 a penny, and logic IC's still stupid cheap, it's not something one does to save money. Very few IC's have any resale value, and those that do, are usually very vintage and can be easily damaged when removing. Also the ones that are most prototype friendly - through hole - can be hard to desolder in bulk, because of friction of the pins in the holes.With allll that said... I'll confess I did spend a few hours years ago stripping damaged/scrap laptop motherboards, and ended up with some small plastic boxes of SMD caps, logic, PSU IC's, and MOSFETs and regularly use those parts for my own projects, where I can deal with the possibility the part is damaged. I only cost me a few hours, no money, and takes up about 30x15x10cm space total for storage. Cut up, levelled and cleaned the bare PCB's to make coasters.

author: MosherIV
author_rank: Super Contributor
timestamp: September 02, 2019, 09:03:26 pm
content: A really cheap is to use a cheap electric hot air paint stripper.As others have suggested, put the board upside down, heat sections of the board and tap when the solder has turned moltern.It will destroy the pcb, tracks will peal off.If you are quick, the pcb heats up faster than the caps.However, is it worth salveging caps or resistors?

author: jastreb
author_rank: Contributor
timestamp: September 02, 2019, 11:57:05 pm
content: Some very good advice. I have made a list of things to try and your tips. I will report back if anyone is interested what I found to be best for me as time progresses.Just to answer some of your questions:1. I have LOTS and LOTS of top quality data centre boards and power supplies that I have salvaged from going to ewaste through my work. Looking at a sample, you will not find a sign of any cheap caps or as Dave would say "Long Hung Low"components. Having said that the board build quality is also top notch and that has the effect (I feel) to make the components that much harder to de-solder. I tried on weekend some cheap board I had which I think came out of a home PC power supply and was relatively easy to desolder.2. Even though I said what I said in 1, I agree, components are cheap these days. However, its having it whenever you need it that is the issue. If I want it in a couple of days, I would have to pay postage which doe's not make those components so cheap anymore if I want just 1 diode for example. Alternative is I buy it from ebay or aliexpress, potentially get a fake, and wait 1.5months for something to "maybe" arrive.3. I have OCD to a point. I like to be meticulous, I organise the parts and store them in a grid with each grid location pointing to records in a database that point to octopartlinks and datasheets. So when I need something I can easily find it if I have it in my used parts list, or a suitable alternative. Having the parts on boards saves time but when you need something you need to take them out of storage (my roof right now) and then try and find a component that may be suitable. So what I save in de-soldering I waste in searching for a component when I do need one. And then possibly not even find one.4. I don't mind the time spent. I find it relaxing and satisfactory. I guess I am just feeding my OCD and that releases endorphins that I find pleasant lol. I do not enjoy the burnt fingers so that is why I am here asking for your advice.Please don't judge me. People are different. I am I would say at a novice level even though I am middle aged. Always had the passion and love for electronics but only recently did I finally get the opportunity to create a little corner workshop in my garage and finally start enjoying it.Thank you all again.

author: Shock
author_rank: Super Contributor
timestamp: September 03, 2019, 02:30:15 am
content: Some boards have a conformal coating on them. You can either scrape this off especially if thick or burn though it with your iron if easy by adding a little extra solder (which tends to help in desoldering in general). Make sure you keep your iron tip clean and add fresh solder to the tip regularly though.Regarding habitually desoldering, cataloging and storing used components, it's unhealthy from a mental perspective. It's repetitive and pointless work to store anything more than a few to save a little money. Not that I'm much of a psychologist but humans have a tendency to horde which is an innate survival instinct.If you get bored it's far more practical to learn more about electronics than compulsive desoldering and by repairing the odd thing or designing and selling a small project perhaps even a small income can be made. Noone wants to stop you from learning to desolder but at the same time electronics tends to bring out obsessive compulsive behavior so you should try to limit it where you can.

author: Ian.M
author_rank: Super Contributor
timestamp: September 03, 2019, 11:28:41 am
content: Yes. *DON'T* become the guy that collected this lot:https://www.eevblog.com/forum/blog/eevblog-737-world_s-biggest-collection-of-electronics-components/or if you do and you have a family that isn't into electronics, make an agreement in advance with your local hacker space or radio ham group that in exchange for a sizeable donation to their groups funds, available immediately in the event of your death, they will come and clear all your electronic junk and *TRY* to keep as much as is practical out of eWaste. Payment on full clearance of course.If you don't have a family and your executor isn't a close friend, donate your pile of equipment and junk to the radio hams or hackerspace in your will with the condition that they must remove what they want within one month of the date of bequest.Do check in advance that the group you are proposing to leave your junk to accepts donations from peoples estates.

author: ElektroQuark
author_rank: Unknown
timestamp: September 03, 2019, 06:13:45 pm
content: If you heat the PCB with a hot air gun and tap them, components will fall down and a rain of melted solder too BEWARE, you could buirn yourself and the components will be soaked in solidified solder. It's far beter to take the need components one by one with the gun and some pliers.

author: jastreb
author_rank: Contributor
timestamp: September 04, 2019, 03:15:59 am
content: Quote from: Ian.M on September 03, 2019, 11:28:41 amI have seen that video and I so admire that guy. I will never reach the level he did though. The rest of your post is depressing me. All those parts neatly stored and catalogued to be trashed by my wife and kids. NOOOOOO!!!!

author: jastreb
author_rank: Contributor
timestamp: September 04, 2019, 03:18:56 am
content: So last night a took a heat gun to a PCB for the first time. I was heating the back side of the board. It took a lot more time than I thought it would to get any parts off, and even then I had to bang the crap of the board for the parts to come off. My biggest issue with this method was the fumes. Usually its pretty windy where I live but yesterday afternoon it was dead still so this might not be as much of an issue if I do it in a breeze.I will try gas torch next.

author: digsys
author_rank: Unknown
timestamp: September 04, 2019, 03:58:56 am
content: LOL @ "bang the c@p". Well, you can work out from the various replies, that it may not be an easy task, and will vary a lot between PCB manufacturers / solder / mask etcOne sure fire method, even though it it slower, is to use one of those alligator clip / component clip stands - PCB upside down, clip on to the component you want to remove, apply a bit of flux to the pins - then heat only that part and pull gently while doing so. Slower, but solves most the issues. Good luck

author: jastreb
author_rank: Contributor
timestamp: October 02, 2019, 04:44:42 am
content: UPDATE: tried a solder pot. Melted some lead all the way to the top and then while being very careful, i put the circuit boards on top of the melted lead. My summary after a few hours of doing this is that it is better than a heating gun but it is not without all its issues:PROS: quicker than heating gun, I think the parts undergo much less stress, can control the temperature much more finely than with heating gunCONS: a bit dangerous, does not work well with boards that have parts on both sides, more dangerous, still a lot of fumes but being able to control temp helps with this. Also my pot only has a 50mm diameter so any parts i can not submerge all the pins in solder pot at once I can not remove.I am thinking of making my own pot with a larger surface area but it needs to have fine temp control.

author: Cyberdragon
author_rank: Super Contributor
timestamp: October 03, 2019, 02:36:44 pm
content: Quote from: Red Squirrel on September 02, 2019, 06:59:59 pmYou ARE supposed to touch the tip directly to the joint, it's high-temp plasic just like the iron. If you don't get it right up next to the solder it won't do anything.

author: Analog
author_rank: Contributor
timestamp: October 04, 2019, 12:36:51 pm
content: You need to preheat the board and then apply local heat to remove the part. The board was assembled this way and it works for disassembly too.

author: digsys
author_rank: Unknown
timestamp: October 04, 2019, 12:49:26 pm
content: Quote from: jastrebThinking back to when we had a wave soldering station ... you could make something similar using that methodology.You only need a few mm of flowing solder in a large rectangular pan, of pretty much any size. Keep the level low enough as not to seep over the pcb topside. Apply a few degrees of tilt for solder flow, switching each time you end the flow. Maybe a brush roller tin? Even has the catchments.