Help! Unable to desolder through hole pins. - Page 1
Forum section: electronics / beginners

author: Ensan
author_rank: Newbie
timestamp: November 29, 2021, 05:49:52 am
content: So I'm trying todesoldersome 6pin through holes and no matter how much I crank the heat up (tried from 320C to 480C) & used a lot of flux,they just don't seem to take on solder or even melt.- The solder melts easily on the iron tip even on low 300C, but when the iron is on the pin and with extra paste flux they just don't take on.I have tried:1. Solder sucker 2. Solder wick 3.Heat Gun to warm the area a bit then use iron. 4. Narrow and wide tips to cover more surface area.- Nothing seems to work, I was barely able to kind of scrab off the surface of one of them but there is still some in the whole which I cant get to melt.Image of the problem:- Rework station is: Saike 952D 480C max temp.Any ideas are much appreciated, thanks <3

author: james_s
author_rank: Super Contributor
timestamp: November 29, 2021, 05:57:58 am
content: Looks like you've got a huge ground plane there that is sucking the heat right back out. You'll probably have to preheat the board, around 100C will usually do it. Either a heat gun or a halogen lamp can be used lacking access to a proper rework preheater.

author: WattsThat
author_rank: Frequent Contributor
timestamp: November 29, 2021, 06:14:38 am
content: Yes, there is probably a lot of copper there but tip temperature is only one factor in soldering, others are the wattage of the iron and the thermal mass of the tip. If it’s one of those little 1/32” conical tips typical of those Chinese soldering stations, that’s the problem.In all likelihood, not enough iron wattage and not enough tip mass. An 80W Pace with a 1/4” chisel thermodrive tip would have that job over and done in about 5-10 seconds.

author: andy3055
author_rank: Super Contributor
timestamp: November 29, 2021, 06:26:51 am
content: Use a de soldering gun. Some thing like this:https://www.ebay.com/itm/203714942418?epid=8016088138&hash=item2f6e5b55d2:g:AIUAAOSw6W9hnguP

author: Ensan
author_rank: Newbie
timestamp: November 29, 2021, 06:36:54 am
content: Quote from: WattsThat on November 29, 2021, 06:14:38 amMine is 60W unfortunately, although I did switch to a more broad tip and it was slightly better but still not enough.3C is the one I use as seen here:

author: IDEngineer
author_rank: Super Contributor
timestamp: November 29, 2021, 06:38:08 am
content: Agreed on the desoldering gun. Hakko makes a great one. You want plenty of wattage for exactly this situation, interchangeable tips for different pin/wire diameters, and a self contained vacuum pump so you don't have to connect to a compressor. Single best soldering tool I own, and the one thing my son threatened to take with him to college. Expensive and totally worth it, wish I hadn't waited all those years. This is a great excuse to buy one. Do it today.

author: Ensan
author_rank: Newbie
timestamp: November 29, 2021, 06:40:01 am
content: Quote from: james_s on November 29, 2021, 05:57:58 amThanks, can I achieve this with air gun pointing at the pin area while I try to desolder? my station comes with this gun holder so I can make use of that for passive heating.

author: Ensan
author_rank: Newbie
timestamp: November 29, 2021, 06:41:45 am
content: Quote from: IDEngineer on November 29, 2021, 06:38:08 amAs much as I would want that, leaving in a 3rd world country to on 100$ salary doesn't help at allBut it really seems like that's the best tool for the job.

author: james_s
author_rank: Super Contributor
timestamp: November 29, 2021, 06:51:36 am
content: Quote from: Ensan on November 29, 2021, 06:40:01 amYes that looks like it should work nicely. If you are replacing a damaged connector you might also cut the pins off of the old one if you can and then heat them and remove individually rather than trying to desolder the whole thing and pull it out at once.

author: WattsThat
author_rank: Frequent Contributor
timestamp: November 29, 2021, 07:15:25 am
content: The connector certainly appears damaged in the first photo, nice big burned area.The approach I use when connector replacement is the goal is to pull the pins out one by one with needle nose pliers and then remove the solder from the hole. Trying to do this in one step is very difficult without a proper desoldering tool, a soldering iron with a solder sucker or braid is just an exercise in frustration compared with dedicated desoldering station.

author: Psi
author_rank: Super Contributor
timestamp: November 29, 2021, 07:50:09 am
content: Put the tip on the joint then add LOTS of extra solder, ball that thing up really huge. Like 4mm wide(The solder ball will make for a much better thermal connection between the iron tip and the PCB.)Now run that ball up and down the pins.

author: m k
author_rank: Super Contributor
timestamp: November 29, 2021, 11:49:30 am
content: Quote from: WattsThat on November 29, 2021, 07:15:25 amThis is the right way.First pin then tin.The pin is not nesessary coming out with one try.Some are pretty tightly placed.Finally it can drop out by it self.

author: Ian.M
author_rank: Super Contributor
timestamp: November 29, 2021, 01:13:00 pm
content: ChipQuik Low Melting Point Alloy. Its <expletive> $expensive$, but when you absolutely *MUST* save the board and conventional desoldering with preheat or even hacking up the part or connector isn't getting the component leg free, it can save your day. They show its application to SMD removal, but it also helps with tough through holes, *if* you can get enough of it down the hole to mix with the existing solder. Its less effective for through hole than for SMD of course, but it certainly beats refilling the hole with ordinary solder in an attempt to get better thermal transfer to get a clean 'suck'. Its also very helpful if you've got a clean 'suck' but the pin corners are still stuck.

author: CaptDon
author_rank: Super Contributor
timestamp: November 29, 2021, 01:44:19 pm
content: I have used a 'Third hand' vise to hold the board, then after applying some fresh solder it helps to have a pencil iron of 40 to 60 watts applied to the pin on the top side while using a Pace or Hacko heated vacuum solder sucker on the bottom side. Also, as another poster has said, cut the connector apart, use big heat to heat the board and pin from the bottom, pull the pin out with needle nose pliers, then go about cleaning out the hole. This is a learned skill and after about a year or two of doing this work every day you will get really good at it. As good and resourceful as I am, there were women in the rework area of our company who could make me look like a clumsy child when it came to board reworking!!!

author: Ian.M
author_rank: Super Contributor
timestamp: November 29, 2021, 02:14:13 pm
content: There are also 'desoldering needles', which are mounted stainless thin wall tubes, similar to hypodermic needles, but unsharpened. In theory, you are meant to use them from the solder side of the board, selecting one that will fit between the pin and the side of the hole by pushing it down over the pin while you keep the joint molten with the iron, till its through the board, then let it cool and remove the needle leaving the pin free, but that only works properly if there is plenty of clearance between the pin and the hole. Wiggle them fractionally as the ex-joint cools so solder shrinkage doesn't trap them. Also they are rather fragile so don't attempt to straighten pins with them, or push or pull too hard if they are jamming in the hole, and if you find them useful, get a spare set. You'll find them on Ebay, Amazon, and the usual far east eBazars.However they wont help the O.P. get the pins of his connector out of the holes as its obvious there is very little or no clearance at the corners. Where they will help is clearing the holes of residual solder, preparing them for a new connector. Stainless steel has relatively poor thermal conductivity, and as they are thin walled, wont rob the heat from the work as much as any other metal probe, so if you are reasonably lucky and one of the sizes is a good close sliding fit in the hole, you can get the hole cleaned out with less effort than most other methods.

author: LaryPant
author_rank: Contributor
timestamp: November 30, 2021, 05:39:42 pm
content: The board appears to have been soldered in a factory with (most likely) lead-free solder, which has a considerably higher melting point than leaded-solder, which most people use for hand soldering.Try adding leaded-solder to the joints - don't be afraid to use a lot - this will lower the melting point and make it easier to remove.I and many others I know have had great success with this method.I hope it helps,Lary

author: DavidAlfa
author_rank: Super Contributor
timestamp: December 02, 2021, 06:10:57 am
content: Are you trying to remove that huge connector? I can feel the pain!If you are going to replace it, my advice is to carefully cut the pins with cutting pliers, so you can take each one easily by applying heat and pulling.Use a lower melting point solder, indium or gallium based, they work great for that.But clean the holes well after that, those alloys are pretty weak, I wouldn't use them for a heavy duty connector like that.A small hot air like that won't do much. This might sound strange, but works great:Preheat the over to 180ºC. When it reaches the temperature, turn it off and wait 3 minutes to let the temperature normalize, so the heaters aren't glowing red and things like that.Put he board in, wait 10 minutes.Take the board out and wrap it with some fabric, old cotton clothes or anything similar to prevent it from cooling down quickly, exposing only the connector area.The solder will flow much better while it's hot... do the job quickly!

author: Ensan
author_rank: Newbie
timestamp: December 02, 2021, 09:22:35 am
content: I did cut the pliers and was able to remove the pins but not all the solder in the holes. For some reason the solder wick just wont absorb it and they don't stay molten enough for the sucker to suck it.Your method sounds like it would have been easier, but I feel like I'm not experienced enough to execute it properly :_)

author: Ian.M
author_rank: Super Contributor
timestamp: December 02, 2021, 01:09:29 pm
content: Yes, once you've partially sucked the holes there isn't enough copper CSA to conduct heat down the hole to melt the remaining solder which may be heatsinked by too much copper on an inner layer. At this point your best chance of saving the board is preheating the board + using ChipQuik to get molten solder/ChipQuik all the way through the hole, sucking it, then wiping off any residual ChipQuik from the pads with a dry Q-tip (the preheat should keep it molten), and from inside the hole with a close fitting wooden plunger (sand down a cocktail stick or bamboo skewer).For board preheating, well you've got that hot air tool, so you could improvise a hot air preheater customized to the connector footprint using thin aluminum sheet (cut up a foil baking tray), folding over tabs to lock seams and using Kapton tape to reinforce and secure it, possibly using corrugated cardboard for external insulation. Another option is an electric griddle on a simmerstat to turn it down below its usual min. cooking temperature, with heavy corrugated cardboard to protect you from the hot edge of the griddle, or do as I did and build an IR preheater using a MR16 12V 50W Halogen spotlight bulb, a dimmable 12V 'transformer' and a dimmer, all out of my junk box:https://www.eevblog.com/forum/manufacture/small-bottom-heater-for-rework-and-reflow/msg3427730/#msg3427730N.B. DavidAlfa's suggestion of a low melting point Indium or Gallium alloy in place of ChipQuik could also work, but high Indium alloys are even more <beeping> expensive than ChipQuik, and Gallium is notorious for dissolving other metals. Copper is somewhat resistant to it but if the hole plating was damaged while removing the pin it may make the damage worse.N.B.2 You can reuse used ChipQuik for less critical desoldering tasks, so clean out your sucker first, so you can save the dross and re-melt it into a slug for reuse.

author: andy3055
author_rank: Super Contributor
timestamp: December 02, 2021, 02:53:16 pm
content: Quote from: Ensan on December 02, 2021, 09:22:35 amIf you don't have a de-soldering gun, heat each hole from one side while using the solder puller from the other side. It is not that hard to do if you can hold securely by some means. A 60 watt iron will do just fine. I have used much lower wattage irons and has been able to clean similar boards/holes. Make sure to use some new solder and some flux.

author: zzattack
author_rank: Regular Contributor
timestamp: December 02, 2021, 04:24:38 pm
content: Most tips have been given by now: first exchange as much leaded or 20 year old solder for fresh 63/37 to get the melting point down. In extreme cases, bringing in overpriced low-melt chip quick solder can make the difference.Another tip: hang the board over the edge of your desk, use your hot-air station from below and after a few seconds use your iron + wick from above. After seeing the ease with which Alex from northridgefix removes (admittedly, usually small) leftovers from connectors I've begun to adopt this method and won't look back.

author: Ian.M
author_rank: Super Contributor
timestamp: December 02, 2021, 07:35:44 pm
content: The advantage of ChipQuik is you can keep it molten with mild preheat at well under 100 deg C so can take as long as you need to do the job right without cooking the board, which is probably already severely thermally stressed. The disadvantages of ChipQuick are price, availability, and unlike Sn63Pb37, you *MUST* clean as much residue as possible off the pads and out of the hole to avoid potential embrittlement due to Bismuth segregation at grain boundaries.Whichever you choose to use, use plenty of a good electronics grade gel or paste flux!

author: IDEngineer
author_rank: Super Contributor
timestamp: December 02, 2021, 08:06:46 pm
content: We're all dancing around the fundamental problem here: He needs a HUGE heat source. Big components, soldered to ground planes, are giant heat sinks. By the time any standard iron gets all that metal hot enough, that heat will have conducted away and seriously compromised the rest of the board.Heck, as ugly as they are, even a soldering GUN (like you'd use to fix a metal bucket!) is a more appropriate choice here. He simply must have something with enough heat capacity to get the joint hot - FAST - instead of monkeying around with solder chemistries and other tricks. I'm a fan of tricky moves but this is a heat sinking problem, not a chemistry problem.

author: m k
author_rank: Super Contributor
timestamp: December 03, 2021, 10:17:39 am
content: Quote from: Ensan on December 02, 2021, 09:22:35 amIs the sucker here a manual tin sucker?If so then heat it from up and suck from down side.Don't block the hole with the soldering iron.Side here is not the board but how you place it.You can also try tapping but it seems that for that those holes might be too small.There you tap the board from down to up so that molten tin drops out.The hole wont become empty but possibly clear enough for the connector.Blowing is as equally possible as is sucking.You just need to make a suitable nozzle, put there some side holes also for extra air.Then just heat the hole from down and blow from up.Sides are again how you place the board.Key here is a full and truly molten hole.When new tin drops in it's all molten.Those desoldering needles may feel uncomfortable but you can use any material that can take the heat.There you should place the board so that component side is up.Then heat from down and push the stuff down from up.Use wood if you're affraid that the stuff gets stuck, you have some hard ones there.Possible leftovers will flatten when new connector is soldered in or you can cut them away.Don't pull the stuff back, leave it for later when tin is hardened.When you put the new connector in don't let it partially drop out.On the other hand, you have a practice so...

author: Xenon
author_rank: Contributor
timestamp: December 03, 2021, 10:49:23 am
content: When I run into a problem like this, I use the soldering and desoldering iron combined.First I try to add some fresh solder. Doesn't need to flow nicely, a blob is fine.Then I apply the soldering iron (large tip) on the pin at component side, and the desoldering iron at bottom side. Both at maximum temperature setting for an extra boost as the temperature will drop quickly.After some seconds I have always been able to suck out (most of) the solder.But of course, not everybody owns a good desoldering iron. I worked with a hand pump for a long time before I could finally get hold of a used Weller.

author: rcbuck
author_rank: Frequent Contributor
timestamp: December 03, 2021, 08:25:01 pm
content: I have a Weller 8200-N 100W/140W soldering iron that I bought in 1962 that I use for these cases. Once the connector is off the board, I use the iron and solder wick to remove all excess solder from the holes. The key to the wick working is to cover it with solder flux. It usually takes about 8-10 seconds to clear each hole. You will easily see when the wick starts to absorb the copper.

author: armandine2
author_rank: Frequent Contributor
timestamp: December 03, 2021, 08:48:46 pm
content: to deconstruct the other posts (expert) Adamant IT has a beginner's technique

author: Vovk_Z
author_rank: Super Contributor
timestamp: December 05, 2021, 05:43:57 am
content: It seems to me that Saike 952D is not powerful enough plus tip is not best for this purpose.Something like T12 usually works better. I use my T12 station with different PC motherboards and it works MUCH better then "usual" cheap Lukey 702 etc.

author: aargee
author_rank: Frequent Contributor
timestamp: December 05, 2021, 08:06:23 am
content: Depending on the board geometry, I have had success using a solder pot. The solder pot’s thermal mass is enormous, it is quick and the connector just pulls off with a pair of pliers.Of course it depends on surrounding components and how careful you are.

author: m k
author_rank: Super Contributor
timestamp: December 05, 2021, 12:54:14 pm
content: Back in the though hole era every hardcore module repair center had an adjustable solder wave size chip replacement device.

author: Vovk_Z
author_rank: Super Contributor
timestamp: December 07, 2021, 06:29:05 pm
content: As it seen from photo of tips, Saike 952D is not good for soldering large planes.T12-type solder stations do much better with this.