Desoldering smd: braid or hot air station?  - Page 1
Forum section: electronics / beginners

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 14, 2021, 08:48:53 pm
content: I stole some old electronic boards to do some desoldering tests (smd component).I have both the desoldering braid and a Chinese hot air station: the hot air station I took it on purpose to unsolder smd...But today's tests disappointed meTwo pin smd: according to my theory, a hot air temperature of 300 °, a low speed, use a small round nozzle and rotate over the smd .. would have been enough and it would have unsoldered easily. Actually I had to set 400 °, and many times pushing the smd the pads of the board were also detached ...With the braid, on the other hand, I can quite well unsolder the two-pin smd. Maybe today I learned that to unsolder a two pin smd you don't need a hot air station?Maybe old electronic boards have solders that are difficult to unsolder?Which procedure is best for unsoldering two pin smd?I'm a disaster...Charlotte

author: John B
author_rank: Frequent Contributor
timestamp: July 14, 2021, 09:23:52 pm
content: I use a Quick 861DW and have never had issues desoldering components. Desolder braid can't get rid of the surface film of solder and therefore the component will still have a pretty strong connection to the pad, more than enough to rip it off. I use a fine nozzle and don't spread the heat around too much. The solder should visibly change when it melts, then the chip will lift off easily.

author: hugo
author_rank: Regular Contributor
timestamp: July 14, 2021, 10:21:51 pm
content: You do not need a hot air station for desoldering:

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 14, 2021, 10:33:13 pm
content: Quote from: hugo on July 14, 2021, 10:21:51 pmoh yes, but I would like to avoid using flux for desoldering; and then I have to learn how to unsolder with hot airthanks

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 14, 2021, 10:38:47 pm
content: Quote from: John B on July 14, 2021, 09:23:52 pmI paid 5 times less for my station. Yes true, with the braid there is a surface film but in the tests I have not even detached a pitch with the braid. While with the air I detached many pitches. Maybe I was pushing the component too hard with a tip while heating ...However in the tests with 380 ° .. after 10 seconds the tin did not melt ...But with such a long time, there is no risk of causing damage to pitches or neighboring parts?I'm confusedMaybe there is some trick I don't know ..thanks

author: Howardlong
author_rank: Super Contributor
timestamp: July 14, 2021, 10:56:40 pm
content: Depends on how many layers & power planes: they will sink away heat. If one of the pads is on a flood fill, on a thermal via, or a thermal relief on a flood, it'll take longer too.I usually use soldering tweezers for 2 pad SMDs, but you can use hot air. I run mine at 350C and full speed, but it's usually used for removing medium sized QFNs & QFPs rather than small smds. The first time I use it in a session, it takes a few tens of seconds extra for the hot air iron to warm its own thermal mass compared to using it soon afterwards.Yes, you will need braid too, to clean up afterwards.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 14, 2021, 11:06:27 pm
content: Quote from: Howardlong on July 14, 2021, 10:56:40 pmOk so anyway for the two-pin smd (medium size) it still takes a few tens of seconds to unsolder (I was convinced that it would unsolder in 3-4 seconds).Air flow then I will set it high (scale 1-10, I thought 2-3 was enough). Of course the track is excellent for cleaning up the pitches.Maybe my mistake is to force with a small crowbar while I'm warming .. that's why in the tests I detached many pitches ..thanks

author: timenutgoblin
author_rank: Regular Contributor
timestamp: July 14, 2021, 11:48:16 pm
content: I have had success desoldering and reusing SMD parts including resistors, capacitors, sot-23 packages and SOIC packages using either a soldering iron or hot air station. Sometimes the SMD parts are glued or cemented to the PCB which makes them stubborn to remove. Heat can be used to break the surface tension between the SMD part and the glue/cement. Sometimes the PCB has a heavy ground plane which can act as a heatsink which may require preheating. The only force that is holding an SMD part to a PCB is surface tension. There is surface tension in the glue/cement if used and solder regardless of whether it is melted or not. I recommend using tweezers to lift the SMD part up off the PCB when the SMD part is ready to be removed.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 15, 2021, 12:43:00 am
content: Quote from: timenutgoblin on July 14, 2021, 11:48:16 pmHowever, if I unsalt a smd (2 pin) generally then you change it; so it doesn't matter if it breaks, the important thing is not to lift the pitches; tweezers ok, but don't overdo it to pull ahead of time. Today I made this mistake, and I raised many pitches ...thanks

author: twospoons
author_rank: Frequent Contributor
timestamp: July 15, 2021, 03:27:38 am
content: I find hot air + hot plate to be the best, especially for larger chips, or boards with big copper planes. 120C-150C preheat with the hot plate, then 350C air. The preheat means to don't have to sit there roasting a chip for 3 minutes to get it to melt - usually only takes 10-20 secs of hot air to push the joints past melt temp.Same setup is good for soldering SMT too - paste, place and reflow in one hit.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 15, 2021, 06:29:32 am
content: Quote from: twospoons on July 15, 2021, 03:27:38 amin the test yesterday I used the adapter with 3mm round end, I was about 1 centimeter away from the smd, 380 degrees. But I saw that the tin did not turn liquid. Maybe this board is very old and the tin could be difficult to unsolder, maybe I try with other boards ...

author: Berni
author_rank: Super Contributor
timestamp: July 15, 2021, 07:04:35 am
content: Hot air works great when you use it right.Hotplate helps with large boards with lots of copper mass, but for most cases its not needed.You want to use a big nozzle of >= 5mm and plenty of air flow at temperatures of 320 to 400°C depending on the difficulty of the job. Do NOT point at the chip, all this does is cook the IC. You move the hot air around the board in a circle (something like 5 cm in diameter) this preheats the surrounding area to keep it from pulling so much heat, then narrow down on the chip and start moving in circles around the chip to heat up the board in that area. Once it is ready to go move the hot air gun farther away from the board and start pointing directly at the chip. Going farther away reduces the temperature, since at this point you just want to keep it molten for long enough to do your thing, if the solder grabs again just come a bit closer again.Also wrapping the rest of the PCB in aluminum foil helps a lot. This is because it prevents the board from radiating heat away on the bottom side. Foil or kapton tape can also be used to protect any sensitive plastic connectors that might be right next to the chip you are working on.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 15, 2021, 09:44:35 am
content: Quote from: Berni on July 15, 2021, 07:04:35 amthanks Bernias for the heating plate, i don't understand what could help in desoldering for example a two pin smd.Regarding your analysis, I agree, but I am not considering the desoldering of multi-pin ICs, for those I have square adapters of different sizes suitable for the case.I was talking about desoldering a simple two-pin smd (type 1206) with hot air. However from what you wrote, I started to understand some of my mistakes: I have to use higher temperatures also for smd (I had set 300 ° as the smd balance them even at 280 ° ..); air desoldering takes time, and does not resolve in a few seconds; maybe a 3mm nozzle is too smallWith next tests I hope to do better

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 15, 2021, 09:48:13 am
content: Quote from: Shock on July 15, 2021, 08:33:22 amI didn't understand well (I'm not good in English ..); so are you saying that before desoldering I could use some flux on the soldered pins of the smd? Does this help melt the solder tin better? I have both a water flux and a chip quik..thanks

author: Berni
author_rank: Super Contributor
timestamp: July 15, 2021, 10:35:44 am
content: Quote from: CharlotteSwiss on July 15, 2021, 09:44:35 amFor just simple resistors and capacitors all you need is a soldering iron.Set the soldering iron to a much higher temperature than you normally use for soldering, such as 360°C. heat up one pad and add a big blob of solder on it, do the same to the other pad too, then start quickly alternating the iron between the two pads. Eventually one pad stays hot enough for you to get to the other one and you can use the soldering iron tip to push the capacitor off the pads and lift the iron up, the capacitor will typically stick to the irons tip and you can just flick it off onto the table. Fast and easy.The adding of solder to the capacitors pins will leave flux there anyway. This flux helps make a nice clean ball on the pin so its welcome anyway. You just need something for cleaning flux from the board. There are PCB cleaning sprays out there (such as Kontakt Chemie PCChttp://www.kontaktchemie.com/koc/KOCproductdetail.csp?division=&product=KONTAKT%20PCC&ilang=all&plang=all) or just get some Isopropanol Alcohol (IPA) or pure Ethanol and a brush to scrub your board (or google some of the diy flux cleaner recopies online). You just put the stuff on, scrub a bit and then while it off with a paper towel, you can use compressed air to get the cleaner out from under chips and connectors (or just blowing with your mouth helps, just don't spit on your board). Flux is easy to clean with the right tools. Same cleaners are also good for cleaning any other gunk or crap off circuit boards. Even just using dish soap and water works fine for cleaning PCBs, just make sure to dry it off really well in that case (hair drier or an oven at 120°C)

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 15, 2021, 11:18:10 am
content: Quote from: Berni on July 15, 2021, 10:35:44 amthanks Berni; with the soldering iron I used the braid, but I had also heard about this method that you wrote; new welding brings flux and facilitates. To clean I have always used Isopropanol Alcohol and I am fine. As I specified, with the soldering iron I already get good results in desoldering two-pin smd; but to make sense of the money wasted on the hot air station, I wanted to learn how to use that to unsolder two-pin smd too. An alternative, just to learn a new thing.Tonight I go to the workshop and do more tests with hot air. Yes, I love spending evenings among the electronic components. I'll let you know if I've been able to improve

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 15, 2021, 02:12:25 pm
content: Quote from: Shock on July 15, 2021, 01:32:36 pmthanks, tomorrow i will watch the video

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 15, 2021, 04:34:00 pm
content: In light of the new advice, I did other two-pin smd desoldering tests: temperature 380-400 (better 400), air flow at maximum, instead of the pliers I used a tweezers of the pointed ones, simply holding it pointed at the smd without pushing: I unsoldered about 30 smd, no ruined pitch. The problem was the low temperature, calculating that if I set 380 ° on the air station, I believe that after 1 cm from the terminal it is much less ... I have not tried with 350 °, I imagine that in any case after many tens of seconds even so it will desolder. The riddle could be: 390 ° and 10-20 seconds better, or 360 ° and 30-40 seconds?Come on tonight it was already much better, happy.

author: Berni
author_rank: Super Contributor
timestamp: July 15, 2021, 05:01:09 pm
content: Yeah hot air temperature is not the same as soldering iron temperature.You get different results with the same temperature if you just change the nozzle size, airflow, distance...etc. The hotter you go the faster you can get the job done, but it means you have to be more alert to back off the distance when it does melt or you risk burning the PCB.But still the quickly alternating between the ends is the fastest way to get resistors and capacitors off, takes like 3 seconds. The benefit of hot air comes in with components with more pins or tricky components with pins under it such as LGA packages, inductors with bottom pads etc... Anyone that is working often with SMD components should have a hot air station. It makes dealing with chips sooooo much easier and you can pick up a perfectly good hot air station for $40 from china. No need to spend lots of money on some fancy one.EDIT:Oh and about desoldering braid, its not really all that good at actual desoldering (i use a pump or hot air for that), but that does not make it useless. The stuff is excellent at sucking up excess solder. If you hand solder a fine pitch SSOP, TQFP etc and short the pins, the braid is great at sucking that solder bridge out of there while still leaving enough solder to keep the pin soldered. It is also good at cleaning up footprints after removing a chip. If you just removed a chip and want nice clean flat pads on the PCB to hand solder a new one, then running some hot desoldering braid over those pads cleans them up as good as new. Same for cleaning up that ChipQuik low melting point solder after using it (You MUST clean it since the alloys with regular solder and turns its mechanical properties into crap)

author: twospoons
author_rank: Frequent Contributor
timestamp: July 16, 2021, 05:50:06 am
content: If you really want to go fast with 2-pin smd then two fine tip soldering irons works great. With one in each hand you can melt both joints and lift the smd away.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 16, 2021, 06:00:34 am
content: Quote from: twospoons on July 16, 2021, 05:50:06 amRapid? no no, I'm very slowinteresting suggestion, thanks

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 16, 2021, 06:12:53 am
content: Quote from: Berni on July 15, 2021, 05:01:09 pmin the tests last night I did not burn any adjacent component or the pcb. With hot air, however, 3 seconds I could not unsolder anything ... the fastest to detach were smd resistors (very small size), but certainly more than 3 seconds.Tonight I dreamed of this technique to unsolder 2-pin smd: soldering iron and braid to remove the bulk of the small soldered duw ... and then hot air (a not high temperature might be enough) to detach the smd from the pcb, it should come off in a moment..thanks

author: Berni
author_rank: Super Contributor
timestamp: July 16, 2021, 08:17:58 am
content: Hot air is slow because it needs to heat up the board to solder melting temperature, since the pin is soldered to the board it will be at a similar temperature as the board. Less solder will not help since the board has many times more thermal mass than the little bit of solder.The reason why just quickly alternating between the 2 pins with a soldering iron is so much faster (those 3 seconds) is because the soldering iron directly touches the pad, so the only thing limiting heat transfer is the thermal conductivity of the soldering iron tip and the solder itself. The board is not thermally conductive enough to overcome that and sink away heat. Only thing faster than this is using two soldering irons (as suggested by twospoons) to grab the component between the irons and lift it off while heating both sides, this brings the desoldering time down to 1 second. But it takes more setup to grab a 2nd soldering iron and warm it up, so i only use this method when i have a lot of 2 pin components to remove, like for example i placed the wrong value resistor in 20 places on a board)Hot air is rarely the tool of choice for working with just simple 2 pin passive components. The one time where hot air is a better choice than a soldering iron is when working with very small parts such as 0201 or perhaps 0402. Since they are literally as big as a grain of salt makes it difficult to accurately poke with a huge soldering iron, so using hot air and tweezers tends to work better (of course under a microscope, even if you have good eye sight).

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 16, 2021, 12:55:20 pm
content: Quote from: Berni on July 16, 2021, 08:17:58 amOk I misunderstood, I thought 3 seconds was referring to the hot air, not the soldering iron.In the test on small smd (I think 0402) it is quite fast even with the air and pushing gently to the side with the tweezers, they come off immediately. For the terminal I think the smallest is better (for smd), mine is 3mm round: so I don't heat up adjacent areas too much.After these tips I could say that for smd 2 pin it is better to use the soldering iron (air maybe for the smaller ones); while for smd> 2 pin better to use hot air to desolder.When i have time i will continue my tests also with smd> 2pin .. and then i will try the soldering with smd air(but I have already seen that it is enough to hold the smd on the tinned pads with tweezers, heat with air and ok it soldering)thanks

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 19, 2021, 07:13:09 pm
content: found the deception for which I could not unsolder the 2 pin smd using the hot air station: I used the small terminal (3 mm), I did some tests by detecting the air temperature, and with this terminal if you are going to 1 centimeter from the weld, the air has a temperature of 80 ° lower than that set on the station.While using a terminal of at least 5mm, and remaining about 5 mm from the soldering, the detected temperature is about the set one; in fact tonight I tried to unsolder with the 5mm terminal and I can unsolder in a range of 300-380 ° (better 380 °, it comes off immediately in about 2 seconds ..)Great

author: richard.cs
author_rank: Super Contributor
timestamp: July 19, 2021, 07:21:58 pm
content: Quote from: twospoons on July 16, 2021, 05:50:06 amThis is my preferred technique for 2-pin, and sometimes 3 or 4 pin if you can get the irons in at the right angle. It's very quick, maybe 2-3 seconds to remove a component Anything with more pins I use hot air.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 19, 2021, 08:04:47 pm
content: Ok two soldering irons, but now that I understand which terminal to use and the right temperature, I have seen that in less than 2 seconds the smallest smd (2 pins) are desoldered, while for the medium-large ones (always 2 pins) in about 3 seconds slip away which is a pleasure ..

author: tautech
author_rank: Super Contributor
timestamp: July 20, 2021, 11:56:03 pm
content: Quote from: CharlotteSwiss on July 19, 2021, 08:04:47 pmIf you are using a Hakko type iron get some K style tips for removal of SMD passives:https://www.hakko.com/english/products/hakko_fx838_tips.html

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 21, 2021, 12:19:31 am
content: I use Ersa not Hakko; however i have a tip about how the K, i will do some tests

author: tautech
author_rank: Super Contributor
timestamp: July 21, 2021, 01:57:41 am
content: Many SMD PCB's are not laid out with rework in mind and even simple rework often requires hot air but as you have discovered the PB free muck solder is not always easy to work with.In cases of rework on modern PCB's the addition of some lead based solder can make rework life much easier.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 21, 2021, 06:05:17 am
content: yes of course, I already had to add 60/40 solder to then facilitate the desoldering

author: perieanuo
author_rank: Frequent Contributor
timestamp: July 21, 2021, 06:18:02 am
content: hi,that's no arguing here, hotair is the way to go, just learn the technique and the gotcha's.desoldering with braid, hammer or other medieval methods it's a jokewhat do you do if a bga chip arrives on you bench, stretch the braid underneath?one of my old bosses from a french R&D company that r&q-eed and prototyped + manufactured electronic modules desoldered with braid and 1kg soldering material wasted per chip, when he hit BGA he came to me and said "ok, pierre, let's do it your way" (hotair desoldering, of course). later, you will add heating plate for tough worksso, learn the good way, no some gizmos that will make you finally a bad image as a pro (even a beginner will eventually became a pro, right? that's the idea, to progress, not to find cheezy methods)regards, pierre

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 21, 2021, 10:05:18 am
content: ok,for multi-pin components (IC ...) there is no discussion about the use of hot air ONLY; in this topic I wanted to understand if it was better the air or the braid for SMD with TWO pins: after testing I realized by myself that it is better to use hot air also for SMD with two pins. For THT components I think it is better to solder and sucking pumpMy 2 cents

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 28, 2021, 08:37:16 pm
content: tonight i did some two pin smd soldering tests (2mm long); I did not use flux (even if I still have it), tip 0,8 mm (I also used flat tip 1,6mm, but better with the 0,8 one), soldering temperature 280 ° but I preferred 300 °.As a method I put a little tin on the tip and soldered 1 pin ok, then the second pin with the wire: I thought it was more difficult, solders came out quite well.

author: jpanhalt
author_rank: Super Contributor
timestamp: July 28, 2021, 09:08:32 pm
content: Whenever I do something like that, after the additional pin(s) are soldered, I remelt the original to relieve an stress I may have introduced.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 28, 2021, 09:43:05 pm
content: I too would have thought of having to solder the first pin again; but after testing I saw that even with a small amount of solder on the tip to solder the first pin, the solder on it looked goodPerhaps the same pond could be heated again; adding more tin would be too much

author: jpanhalt
author_rank: Super Contributor
timestamp: July 28, 2021, 09:59:00 pm
content: I am not referring to what the joint looks like. A good looking solder joint may actually apply more stress as it is stronger. There are many articles about the adverse effects of stress on solder joints and components.Assume you have an SOIC-8 component, you solder one pin, then align the other pins a little bit better with a little twist. You have added stress to that first pin. Even two-lead components (e.g., SMD capacitors) can suffer that. It only takes a second to relieve that potential stress.Anyway, it's what I do. In fact, my first joint usually needs a little more solder, as I depend on a little tinning for the "soldering" that holds it in place. My hands today are nowhere near as steady as they once were. So, the second hand in most cases isn't to apply solder, but to hold the component in place while I heat that first joint.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 28, 2021, 10:15:31 pm
content: thanks for the contribution, now I understand: I want to clarify that when I soldering the first pin (I was referring to two-pin smd), I keep it pretty still .. even a few moments after soldering, so in theory it should not suffer any strees. I then did traction tests on the component, nothing to do, it didn't come off at all in the world

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 29, 2021, 11:21:12 am
content: One of the doubts I have about the soldering of multi-pin smd is: use the technique by dragging the soldering iron, or better to solder with hot air? Maybe the answer could come from the pin spacing of the component, I don't know .. I'll have to experiment

author: Berni
author_rank: Super Contributor
timestamp: July 29, 2021, 11:30:36 am
content: Both work well.I tend to prefer drag soldering since to use hot air you need to fist tin the pads really well beforehand. So if im running around the footprint with a soldering iron i might as well just solder the thing then and there. Shorts are easily solved with some extra flux or desoldering braid.But i do tend to prefer hot air for QFNs. They are usually pretty small, so easy to heat up the area, and they often have heat dissipation power pads under them

author: tautech
author_rank: Super Contributor
timestamp: July 29, 2021, 11:52:10 am
content: Just find what works best for you with the gear you have on hand.Interesting alternative method:More ideas here:https://www.eevblog.com/forum/beginners/so-surface-mount-it-is/

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 29, 2021, 12:48:25 pm
content: thanks for the links, TautBerni... true what you say, but it scares me enough to have to remove all the bridges that are created with the dragging of the tip. However with the gun I have unsoldered many SMD multi pin, as soon as I can I will play to figure out which method could be easier for me.thanks

author: Berni
author_rank: Super Contributor
timestamp: July 30, 2021, 05:07:07 am
content: I don't even care about the bridges when drag soldering, in fact i try to leave some bridges because that means there is enough solder, so that i know all the pins got soldered properly.It's easier to just not care and fix the shorted pins later, rather than be super careful not to short any in the first place. The process for getting rid of the shorts is so simply add some flux and drag the soldering iron along again with a dry tip. This tends to grab any solder bridges and pull the along until the end of the row of pins, leaving you with just a short on the last 2 to 5 pins. This then easily gets sucked away by placing some desoldering braid on top, pressing down a soldering iron on top to heat it up and lifting it away as soon as it starts wicking up solder. Sometimes it pulls away too much solder leaving the last few pins looking a bit dry. In that case i just add a tiny bit of solder to the iron and go back to touch them up slightly(sometimes also adding a bit more flux). At the end i use some PCB cleaner spray to clean off the flux residue.I only do the careful pin by pin method on the larger chips like SOIC

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 30, 2021, 09:59:51 am
content: ok, in august i will do some tests on soldering of smd IC; i will try both pin to pin, drag, hot air ...So if I understand correctly, ONLY soic components are suitable for using the pin to pin method?Maybe we need to evaluate the distance between two adjacent pins I guess ..thanks

author: Berni
author_rank: Super Contributor
timestamp: July 30, 2021, 10:15:17 am
content: Not that anything smaller than SOIC (1.27mm pitch) is unsuitable, but more that the level of skill to do it reliably quickly goes up. I need to do it under a microscope to properly see what i am doing and it is pretty slow. Also SOIC chips tend to have a fairly low number of pins, usually somewhere between 8 and 16 pins, the largest ones tend to get to 28 pins, so the speed does not matter as much.But when you get to something like a 160pin TQFP with 0.5mm pitch its going to take a while to do it one pin at a time. So it makes the speed gain of drag soldering much more of a advantage. I might still do it pin by pin on a small 8 pin TSOP chip, since the cleanup effort afterwards is higher with drag soldering.For the fastest ways of soldering and desoldering tiny chips the best sources are youtube channels that repair electronics. The ones that have been doing this on a daily basis for the past few years have found all the best ways of soldering stuff.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: July 30, 2021, 10:44:12 am
content: ok thanks Berni, i will do various tests on multi pins and see what will be the best option for me: i don't care about speed, but the best way to do a clean job without damage.I have to look for a table with all types of existing smd ICs, it might be useful to know which chips are on the market and their pin sizes.For chips with 100 closely spaced pins, I can't even imagine how it could be possible to do pin to pin .. maybe with a tin nullity on the tip without wire ...

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 04, 2021, 09:41:45 am
content: I was training to solder 2 pin smd (also 1.2mm wide measure); with the 0.8mm tip I saw that I can weld, while with the 0.5 mm tip I had big problems, it is difficult to heat the soldering area.I think this 0.5 mm tip should only be used for micro smd 0.5 mm wide and that's it, no other use maybe ...My procedure is to put some solder on the tip, place the smd and solder one pin ... then solder the other pin with the wire.But watching this video (from 7.30)https://youtu.be/fYInlAmPnGo?t=451use another method: put the drop on the pitch, then drag the smd into position and ok, I knew this technique too. But the thing that amazes me is that when the welding has already been done, it puts flux on the welds and heats up.Does this procedure make sense?

author: Terry Bites
author_rank: Super Contributor
timestamp: August 04, 2021, 11:30:42 am
content: Braid aka solder wick and flux. It sometimes helps to put some new solder on top of the old solder to get a hot puddle going for the wick.Tales from the solderwick chronicles.

author: Berni
author_rank: Super Contributor
timestamp: August 04, 2021, 11:38:21 am
content: Well how else would you solder a 2 pin component? Tinning one pin and sticking it on while its hot is the only way i know of doing it.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 04, 2021, 01:50:44 pm
content: Quote from: Terry Bites on August 04, 2021, 11:30:42 amthanks TerryI solved the problem of desoldering, I can both with braid and with hot air; first for testing I unsoldered 50 smd without problems and without ruining any pitch (without disturbing the flux)

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 04, 2021, 01:56:52 pm
content: Quote from: Berni on August 04, 2021, 11:38:21 amInstead of tinning the pitch, put tin on the tip; I think it's the same thing, the component is already in place and there is no need to fix it .. but the two procedures could be equivalent.My doubt in the procedure of the video was not the positioning or the welding ... but the fact that after having welded it puts flux on the welds and heats them, it seems bizarre to me, but obviously there will be a reason.Meanwhile I did other tests this time with smd width 1.6 mm using the 1.6 mm flat tip. So I can easily solder even without flux and they come out pretty well

author: Berni
author_rank: Super Contributor
timestamp: August 04, 2021, 04:24:21 pm
content: Ah the flux. Well adding some flux and heating it up again is a easy way of fixing ugly looking joints. If you move and reheat a joint too much it gets crusty and ugly looking, but adding a bit of flux and melting it again turns it back into a nice shiny smooth joint because the flux eats away all the crud, letting the solder flow freely into the shape it wants.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 04, 2021, 05:23:35 pm
content: Thanks Berni, OK now I got it; I would say that adding flux after soldering is ONLY to be done when soldering looks bad, normally we can do without.I have already become a better woman with the soldering iron in my hand: up to smd width 0.8 mm I can weld, with the smaller ones I have not yet tried, but perhaps soldering paste and air would be more suitable ...

author: Howardlong
author_rank: Super Contributor
timestamp: August 08, 2021, 11:25:18 am
content: Quote from: CharlotteSwiss on August 04, 2021, 01:56:52 pmIf I am understanding correctly, you're advocating applying solder to the iron's tip and then applying it to the pad and part? It so, this is fraught with difficulty, because the flux in the solder will have evaporated by the time you apply it to the pad and/or part.QuoteThe reason is that any previous flux, either from the solder itself or explicitly applied, will have already evaporated or deactivated.The only problem with the video is the amount of time the tip's on the joint: it's far too long. It should be a straight in and out procedure, half a second or so, unless you're soldering thermal pads.Furthermore, with ceramic caps in particular, you risk cracking them with too much thermal stress. Worse still, that failure mode is often intermittent.QuoteI think you may be over analysing the tip size. I only use two tip sizes for soldering, a 0.2mm conical 40W cartridge bit for most SMD connections, and a 2.4mm x 0.8mm chisel for joints with higher thermal mass on an 80W temperature controlled iron. Both are dialled in at 350 deg C.For soldering QFPs, it's as in the video.For QFNs or other devices with power pads underneath, I lightly tin all the pads, removing excess solder with braid, apply flux, hold the device over the pads with tweezers and reflow with hot air. Once the solder has melted on all of the pads, you should be able to slightly nudge the part with the tweezers and see it snap into place due to the surface tension of the solder.For desoldering small SMDs, I use a tweezer iron with a selection of different sized 2x40W cartridge bit sets which manage everything from 008004 to SOIC8. Sure, you can fight with a normal iron with a larger tip, but if you're going to be doing it quite a bit, tweezers are the way to go. Hot air is also an option, but for small SMDs, I much prefer tweezer irons.For desoldering larger SMDs like QFPs, QFNs, BGAs and power devices, I use hot air, and then clean up all the pads with braid.The only time I use paste is with a stencil, and typically that's when I'm assembling a final preproduction batch or doing a respin. Otherwise I tend to manually hand solder each part especially if it's only a small board with a under a couple of hundred parts.To remove excess flux I use an aerosol flux cleaner with a brush attachment for most use cases. For high impedance and ultra low power stuff, I use an ultrasonic bath with detergent followed by a couple of rinses in deionised water.A good iron and bits will last many years: the Wellers I use are 15 years old and see daily use. The bits, if treated well, will also last years. The chisel bit is exactly the same one that came with the iron all that time ago, and before I switched to cartridge bits about three years ago, the 0.2mm conical traditional bit I used was also still going strong after well over a decade.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 08, 2021, 01:14:54 pm
content: Quote from: Howardlong on August 08, 2021, 11:25:18 amthanks for your excellent contributionyou got it right, I put a small drop of tin on the tip and then solder the first pin; But first I put some flux on the pitch and pin ..However, even by stagnating the pitch and then approaching the component at a later time .. and re-melting the pond, the flux will have vanished ...In my opinion the two procedures are the same, in both cases it should be fluxed before carrying out the welding.Timing to carry out the soldering on ONE pin of the smd: do you maintain that the tip support must last only 0.5 seconds in total? Isn't that too little?If we talk about soldering with tip and wire, I heat the area for 1 second .. then we have almost 1 second to bring the wire closer and melt it .. and then important still 1 second more so that the tin is well arranged. Total about 3 seconds (note: I use a low temperature for SMD, 280 °)I'm still learning about tin soldering:.THT desoldering with pump I succeed well.SMD desoldering with hot air is good for me.THT soldering with iron ok.two pin SMD soldering with iron okNow I am experimenting with soldering of SMD IC, and from some timid tests I have begun to understand that:.with a fairly wide Pitch I can solder in the traditional way (pin to pin).with very narrow pitches I have two possibilities: (solder paste I am not interested in for now)1) drag welding2) hot air welding (first, however, I have to tin the pitches with the soldering iron)For now I have tried only a 14 pin smd IC with 1.27mm pitch: I have tinned the 14 pitches (easy), I have placed the IC on top and held with tweezers (not easy operation, the pond on the pitches does not help ..); I heated with air to 300 °, after a few seconds I saw the pond melt and the 14 feet that slowly drowned .. it came out well! (in trying again, however, I struggled, maybe it's not that easy)The experiments on IC smd soldering continue...

author: tooki
author_rank: Super Contributor
timestamp: August 08, 2021, 01:35:24 pm
content: Charlotte, you are again using various terms incorrectly, which makes me suspect you've misunderstood what other people mean when you read their posts. So here are the correct meanings (in correct English; nobody needs to reply that their native language uses them differently, nor what the incorrect use by nonnative speakers is):soldering: joining two metal objects by melting adifferentmetal (the solder), which melts at a lower temperature, between them. Soldering is a comparatively low temperature process. This is what we use in electronic circuits.(There also exists "hard soldering", which is still soldering, but with higher temperatures. It's used in things like plumbing and sheet metal roofs, but not in electronics.)"Welding" is not an acceptable term for soldering.welding: joining two objects by melting them directly and/or joining themwith the same material.Soldering is not welding. None of this discussion has ANYTHING to do with welding.solder: the alloy used to solder two things together."Tin" is not an acceptable term for solder.("Solder wire" is solder in wire form, essentially a metal tube with a flux filling. "Solder paste" is powdered solder suspended in flux gel or paste.)tin (verb only):applying fresh solder to a soldering iron tip. (Proper tinning procedure is to wipe the iron clean, then apply solder to the tip. If the old solder on the tip was very oxidized, it can be helpful to repeat the process to ensure the old, overcooked solder is really gone.)applying a small amount solder to a pad, wire (especially stranded wire), or component terminal in preparation for soldering it to another object.joint: the connection point where objects are soldered together. (This word applies both before and after the soldering process is completed.)fillet: the solder in a soldered joint. (Like in the sentence "In a THT joint, the solder fillet should be concave.")pitch: the repeating distance between pin or pad centers. So "0.5mm pitch" means thecentersof the pins are 0.5mm apart. The pins, necessarily, will be narrower than that.pad(or land): the metal area on a PCB to which a component pin/terminal is soldered."Pitch" is not an acceptable term for a pad.flux: a chemical that removes oxides. In electronics soldering, flux comes from two sources: 1. a flux core inside the solder wire. 2. separate flux, like liquid, gel, or paste. ("Tacky" flux means a gel or paste that has a sticky texture, which can be great for holding down an IC when hand-soldering it.)Now that this is clear, some points:Quote from: CharlotteSwiss on July 29, 2021, 12:48:25 pmBridges aren't a big problem when drag soldering,as long as you use a good flux. (And periodically re-tin your soldering iron tip well, to "rinse" it of overcooked solder.) I recommend a gel flux — my favorite is ChipQuik's SMD291NL, which smells like toasted hazelnuts during use instead of like burning acid.Quote from: CharlotteSwiss on August 04, 2021, 01:56:52 pmIt's similar but not the same: the solder on the iron tip will oxidize the entire time it's on the tip, since it stays hot. The solder on the pad isn't kept hot as long, so it won't oxidize as much.Oxidation leads to bridging, dags (spikes formed when pulling away the soldering iron tip), dull surfaces, and difficulty in solder flow.Flux doesn't remain active forever.Traditional rosin fluxes have two temperature ranges before burning:inactive (cold) <-> active (hot) -> burnt (hotter).Modern no-clean fluxes have three temperature ranges before burning:inactive (cold) -> activated (hot) -> deactivated/neutralized (hotter) -> burnt (even hotter)The soldering iron temperature is hotter than the temperature needed to burn the flux,so it's only active for a brief moment before it gets too hot, deactivates, and burns up as smoke. So when you apply solder wire directly to the tip,allthe flux from the flux core gets destroyed a moment after it's applied.This is why in traditional hand soldering, the rule is to always apply the solder wire to the joint, not the tip: the flux in the core melts a fraction of a second sooner than the solder itself, flowing across the joint just before the molten solder follows. When you try and carry solder to the joint on the iron tip, there is no flux.The exception, somewhat, is joining solder to solder: when both objects to be joined (like a pad and component terminal, or two wires) are already freshly tinned, you can often get away with reflowing without added flux. But for this to be successful, oxidation must be kept at a minimum: the tinning processes had to be quick and properly fluxed, and the iron tip must be freshly tinned without oxidized solder. It won't work if the iron is dirty with old solder, and it won't work on tinned objects that have sat around for a while, as their surfaces will oxidize.By adding flux, you give the entire "system" a way to eliminate the oxidation, resulting in a good joint.Side note about no-clean fluxes in hand soldering: The flux in solder wire always reaches a temperature high enough to deactivate it, so residues do not need to be removed. But when you add additional flux liquid, gel, or paste, parts of the board may get hot enough to activate the flux, but not hot enough to deactivate it (they do not deactivate by cooling off!!), meaning that residues can be corrosive. So it is important to remove these residues in hand soldering. Rosin fluxes, on the other hand, become inactive once they cool down. However, some rosin gels and pastes have ingredients that make them behave a bit like no-clean, so I recommend cleaning those residues, too. Liquid rosin is usually fine, as long as it is able to dry quickly.Quote from: CharlotteSwiss on August 04, 2021, 05:23:35 pmNot in drag soldering. Flux ismandatoryfor this method, or any other reflow method, because you aren't applying solder wire (and thus its flux core) to the joint. Flux gel/paste is ideal for reflow soldering because it allows the terminals to remain "flooded" in flux, so that as you drag the iron across, there is always flux present.When doing 2-terminal components (like chip resistors), I normally use liquid flux. The explanation above tells you why.(I typically tin one pad of each component's footprint, for the entire board at once. Then I brush flux onto all the pads, both the tinned ones and the blank ones, then freshly tin the iron tip, then go in and remelt the solder on a pad and push in the component. I do that for the whole board, then look at the board from the side and make sure the components are laying flat. Any that are not, I brush on flux, then hold the component down with tweezers or a wood stick, and reheat the joint so it lays flat. Once they're all flat, I go back and solder the second side of each component.)

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 08, 2021, 01:59:46 pm
content: thanks tooki, in fact you had already suggested that I am wrong the terms; I am well aware of what the various terms are, the problem is the translator who sometimes confuses / mistakes the terms! Anyway yes, my fault!I haven't done the drag test yet, but I'll try it in the next few days; the flux I had taken is exactly what you indicated (perhaps you had recommended it to me when I took it); I'll try with the small concave tip, we'll see ..So for the pointing of the first pin of the SMD, it is ALWAYS better to tin the pad and then bring the component and tip closer to solder it; so better to avoid the drop of tin on the tip then?Classic soldering with tip and wire: if, however, the wire I support it only at the joint and not at the tip, it takes enough time for the wire to melt ... for this reason I support it between the tip and the joint, but I understand that it would be better not to rest the thread on the tip ..For the final cleaning no problem, I always use isopropyl alcohol and a toothbrush, the board is cleanWe can therefore state that: every time a solder melts with the tip to fix it (so we do not use the wire), we must first apply some flux

author: tooki
author_rank: Super Contributor
timestamp: August 08, 2021, 02:03:42 pm
content: Quote from: CharlotteSwiss on August 08, 2021, 01:14:54 pmFor leaded or lead-free solder? For leaded, that's on the slightly low side, and for lead-free, that's almost certainly too low. I generally set 300C for leaded and 320C for lead-free on my Ersa, but big joints or very small soldering iron tips (which have poorer heat transfer) can require higher temperature settings.A temperature that is too low can actuallyincreasedamage, if it means you have to dwell on the joint too long. This is a classic mistake with, for example, connectors. Intuitively, you think "well, the plastic will melt, so I'd better stay with a lower temperature". But the mass of the contact sucks the heat away and solder won't take, so you have to keep heating. Meanwhile, the plastic is going gooey. With a higher soldering iron temperature, the contact gets hot enough to solder quickly, before the plastic has time to get hot.Similarly, PCB pads behave the same way: brief high temperatures are better than prolonged lower temperatures. A pad that is heated for 30 seconds (even at, say, just 260C) ismuchmore likely to lift than a pad heated to 340C for three seconds.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 08, 2021, 02:35:48 pm
content: I only use lead wire for now.I used my Ersa like this (before reading your message): THT in general, about 320-340 °SMD (for now only two pins): 280-300 °Let's say that THT always balances them at 330 ° (it could be good); here is perhaps better that I raise the temperature for the SMD, no more 280 but better 300-320 ° ....(I thought the smd could be damaged).Obviously, by raising the temperature the contact times of the tip decrease ...For the IC that I have yet to experiment, the soldering iron will use about 300 °, while the air I saw that 300 ° could be fine (with air I have to cover all the extra area, otherwise bye bye plastics .. )

author: tooki
author_rank: Super Contributor
timestamp: August 08, 2021, 05:06:51 pm
content: Quote from: CharlotteSwiss on August 08, 2021, 01:59:46 pmQuote from: CharlotteSwiss on August 08, 2021, 01:59:46 pmCould be, I may have suggested it!Quote from: CharlotteSwiss on August 08, 2021, 01:59:46 pmI wouldn't go so far as to say ALWAYS without exceptions, but as a general rule, yes.Drag soldering is exactly such an exception (with the concave tip being designed specifically for this technique), but the flux becomes absolutely mandatory.Quote from: CharlotteSwiss on August 08, 2021, 01:59:46 pmYou only want to feed the solder wire onto the joint itself, not onto the tip. However, what is usually helpful is to have a small pillow of solder on the tip to act as a thermal bridge. It will shape itself to the component leg and the pad, providing much better, faster heat transfer than a tip that's completely "dry". This way, the joint itself heats up much faster, allowing the solder wire to melt on it quickly. With time, you'll get a feel for this. (And yes, if you begin to heat a joint and then realize the pillow is missing, you can feed atinyamount of solder wire onto the tip to create the pillow, then proceed with feeding the solder onto the joint itself.)Quote from: CharlotteSwiss on August 08, 2021, 01:59:46 pmFYI, not all fluxes (especially no-clean ones) come off with isopropyl. (And even the ones that do, it's usually a bit slower and uses up more solvent.) Commercial flux removers are much better. Here in Switzerland, where isopropyl costs nearly as much as flux remover, it really makes sense to use the flux remover. (The cheapest one I've found here is Distrelec's house brand,RND 605-00128. It's about 12 francs for a 400ml can, which is only slightly more than the 26 francs you pay for a liter of IPA at the pharmacy. I suspect it's actually made by Electrolube.)Quote from: CharlotteSwiss on August 08, 2021, 01:59:46 pmYes, basically.

author: tooki
author_rank: Super Contributor
timestamp: August 08, 2021, 05:13:51 pm
content: Quote from: CharlotteSwiss on August 08, 2021, 02:35:48 pmFor leaded solder, 280-300C will be fine, then.Hot air temperatures are nowhere near as exact, since even just the distance from the board makes a huge difference in temperature. I usually use a temp of around 270-300C, with a large nozzle, high air flow, and longer distance, to preheat the bottom of the board. Once the board is properly preheated, I'll use 320-340C with a smaller nozzle, low air flow, and short distance from the top to reflow the components. Preheating is especially important for multilayer boards, heavy/large components (like large inductors), and components with thermal pads on the bottom. Also for delicate parts like connectors, which you want to expose to only minimal direct heat.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 08, 2021, 10:16:29 pm
content: tooki:QuoteI will use the procedure of tinning the pad then; but perhaps then, before approaching the component, it would be better to use the flux on the tin plating done previously ...Quoteok of course, in reality I always tin the tip before a weld, but only slightly .. I will do some tests without placing the wire on the joint ..Quotein fact I usually use water flux, it does not dirty very much indeed almost nothing ... The other one I struggle more, but it comes away(I took isopropyl, because I also use it in MTB maintenance)Quoteyes, but for THT I prefer to solder at 320-330 °; with SMD ok then I keep a good range 280-300 (in the tests done at 280 °, I must say that the welds came out well and fast)QuoteWith hot air welding I have just started ... so I am at a level below zero; However, I immediately realized that small nozzles heated very little. I will only use this solder exclusively for IC with many pin (and pitch close) or just to do a rework of the component to revive the contacts, so it will happen to me a few times, but it does not matter, I will experiment to learnI would also add that soldering with hot air only makes sense for a rework, or it would make sense using solder paste; adding solder to each pad (and then heating to solder the component) doesn't seem like a logical job...thanks

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 20, 2021, 10:56:51 pm
content: ok, i tried soldering an smd IC (32 pin, pitch 1.27), this is the second or third time i try soldering an IC. To start I wanted to try soldering one pin at a time in the traditional way. I must say that I thought worse, I welded it without creating any bridge.The welds of the upper side in the photo, I made them with a 0.8 tip (320 °), but often it didn't weld immediately, or it was cold ball .. maybe with a 0.8 tip I would have had to raise the temperature more I guess ...While the welds below in the photo, I made them with the 1.2 flat tip, temperature 280 ° (I wanted to try to weld on purpose with this low temperature), but it certainly went better, the tin melted immediately and welded the pin well; maybe I should remove the wire first and maybe pour less tin, but it seems to me that for being one of the first times did not go badly.Note: I used a soft water-based flux (I didn't bother with the better performing one).Now I would like to understand if with a lower picht it is still possible to solder pin to pin, and if it will be necessary to do the drag instead ...

author: tooki
author_rank: Super Contributor
timestamp: August 21, 2021, 06:48:49 pm
content: You talk about drag soldering as if it were this hugely difficult task only to be done if nothing else is possible. It’s actually my favorite type of hand soldering, to me the question is “can I drag solder this?” I don’t understand why you would want to solder pin by pin on anything that can be drag soldered.And yes, solder paste is definitely the way to go for hot air.

author: thinkfat
author_rank: Unknown
timestamp: August 21, 2021, 06:54:44 pm
content: If you have a proper paste for hot air and a good method to dispense it, then, yes. I find myself often just tinning the pads, adding flux, placing the component in the bed of flux and then using hot air to reflow. Especially for QFN this is my go-to method. But also for QFP.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 21, 2021, 09:10:01 pm
content: Quote from: tooki on August 21, 2021, 06:48:49 pmit was just a pin to pin test, just to understand if I was capable, I thought worse; obvious that my intent will be to solder these IC with drag, as soon as I have time I try (but I think it will be time to use the classic flux ..), for now with two-pin smd and IC pin to pin not I still used it.With solder paste it would be too easy, my final test with the ICs will be to tin all the pins with wire and then solder with hot air

author: jmelson
author_rank: Super Contributor
timestamp: August 21, 2021, 09:10:38 pm
content: The chip photo looks quite good! If in doubt, while under the microscope, poke the leads gently sideways with the point of an X-acto knife. If the lead moves, it wasn't soldered well. If it doesn't move, the soldering was fine. I routinely do down to 0.4mm lead pitch witht this sort of technique. The 0.4 are difficult, 0.5 is easier, 0.65 mm is quite easy.Jon

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 21, 2021, 09:14:17 pm
content: Quote from: thinkfat on August 21, 2021, 06:54:44 pmThe paste makes the job easier, but I am a traditionalist, I believe that soldering is with tip and wire

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 21, 2021, 09:19:47 pm
content: Quote from: jmelson on August 21, 2021, 09:10:38 pmYes, especially with the tip of 1.2 (lower welds in the photo) to be a beginner I was not bad (I want to say, without using classic flux, but a water flux, maybe just water really).Let's say that I succeeded in the 1.27 pitch measure, lower I don't know; 0.5 seems to me already a close measure, if I have not misunderstood the pin to pin balance?Thanks for the advice on testing the tightness of the welds, I could use the tip of my pointed tweezers

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 21, 2021, 09:40:17 pm
content: Quote from: Shock on August 21, 2021, 09:26:23 pmyes in fact I have problems using the fine tips (in my case 0.8 mm), because it often seems that they do not heat well .. certainly raising the temperature will be better with these fine tips, I could also use 330 °; with the 1.2 flat tip even at 280 ° I saw it stagnate well.Yes, I spilled too much solder, all pins are solder-free, and it shouldn't be. But they are so small that it is not easy, maybe even my 0,56 thread is too big for these jobs I think ...

author: tooki
author_rank: Super Contributor
timestamp: August 22, 2021, 12:11:34 am
content: Quote from: Shock on August 21, 2021, 09:26:23 pmShe has now made clear that she uses uncorrected machine translations and doesn’t care about the correct terminology that has been explained repeatedly to her. Don’t waste your time, I wasted enough for all of us.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 22, 2021, 09:34:08 am
content: Quote from: Shock on August 21, 2021, 11:40:29 pmThank you Shockusing the tip of 1.2 I did not put it flat in front of the pin, but laterally (perpendicular to the IC), by doing so there is no problem with touching other pins. Of course I would have liked to use the 0.5 tip, but I have seen that it hardly melts the tin in a short time. Yes, with the small tips I have (0.8 and 0.5) I have to improve the technique.To unsolder IC I use hot air, it's very easy (I just have to cover adjacent plastic parts with insulation, if there are any.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 22, 2021, 09:42:11 am
content: Quote from: Shock on August 22, 2021, 05:04:32 amSo do the pins have a concave part that accommodates the solder? I have to zoom in with the lens and check; one thing that I did not understand when I placed the chip above the pads, is why the legs reached the END of the pad in width, soldering can only take place on the sides and not in front of the pin---------------------------------------------Off topic:English yes / English no / translator: not all people in the world are lucky enough to speak English, so if we want to converse on a worldwide forum we have to use the translator; if the translator is wrong, I can also re-bind 100 times, but I will not be able to understand the error.I believe that the important thing is not to discriminate against people for the language they speak!

author: tautech
author_rank: Super Contributor
timestamp: August 22, 2021, 09:48:27 am
content: Quote from: CharlotteSwiss on August 22, 2021, 09:42:11 amNo.Imagine L represents the end of a IC pin and the pad junction.Add solder and it should look a little like a C with the concave part all of solder.With a wide pad the sides also represent a C.

author: thinkfat
author_rank: Unknown
timestamp: August 22, 2021, 09:51:42 am
content: Quote from: CharlotteSwiss on August 21, 2021, 09:14:17 pmI would not say it is easier. I use paste mostly for passives or larger pad pitch components, because it is faster to solder many parts at the same time. It's also cleaner as it leaves less flux residue on the PCB.However, for fine pitch parts like TSSOP or anything at or below 0.5mm pad pitch it is quite difficult to apply the right amount of paste if you don't use a stencil. It's almost always too much, leading to bridged pads and requiring a touch up with more flux and braid. It's easier and faster to drag solder those parts.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 22, 2021, 09:55:03 am
content: Quote from: tautech on August 22, 2021, 09:48:27 ami did not understand the example, but i will try to enlarge the pins of an IC so i understand better

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 22, 2021, 09:58:23 am
content: Quote from: thinkfat on August 22, 2021, 09:51:42 amok thanks, now I understand: I thought soldering paste was used for very narrow pitches, but this operation is not easy.

author: tautech
author_rank: Super Contributor
timestamp: August 22, 2021, 10:04:03 am
content: Quote from: CharlotteSwiss on August 22, 2021, 09:55:03 amYes do that.For SMD it is not necessary for any solder to be on top of the pin.Only the underneath from wicking and the sides and end need solder for a perfect joint.Have a study of a commercially built PCB and you will see just how little solder is needed to make a perfect joint.

author: jpanhalt
author_rank: Super Contributor
timestamp: August 22, 2021, 10:16:40 am
content: Quote from: CharlotteSwiss on August 22, 2021, 09:58:23 amSoldering paste is used for small parts and narrow pitches. That is, you use it with a stencil. (Or, automated machinery.)As a suggestion, if you plan to add solder paste manually by dabbing it on, there is an easy way to get accurate, sub-microliter depositions with liquids. We used a flat bottom pin of a specific diameter. A 1-mm diameter, flat bottom pin will deposit quite reproducibly 0.1 ul of a typical culture broth. I have never tried it with solder paste 'cause I use a a stencil; however, for paste, I might try a slightly tapered pin or thinner needle and a very slightly thinned paste. I am not proposing this as a tried method, just extrapolating from years of experience dispensing sub-microliter amounts of various culture broths and cell suspensions.

author: Electro Fan
author_rank: Super Contributor
timestamp: August 22, 2021, 04:03:49 pm
content: tooki, this is really articulate and nicely formatted. You have provided very clear and precise definitions and very helpful distinctions and explanations. Thanks for taking the time to write your post below.Quote from: tooki on August 08, 2021, 01:35:24 pm

author: Electro Fan
author_rank: Super Contributor
timestamp: August 22, 2021, 04:10:22 pm
content: Shock, Excellent video on SMD removal you posted below. Thx!Quote from: Shock on August 21, 2021, 11:40:29 pm

author: Electro Fan
author_rank: Super Contributor
timestamp: August 22, 2021, 04:17:14 pm
content: Shock, this is another great video you posted below. Very helpful info. Thanks againQuote from: Shock on August 22, 2021, 02:17:23 pm

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: August 22, 2021, 07:14:29 pm
content: Quote from: CharlotteSwiss on July 14, 2021, 08:48:53 pmWith the solder I use I can it takes about a minute for hot air to loosen the solder.If your ripping off pads its either way too hot or your pushing too hard.Solder can vary a lot. I bought in some cheap Chinese solder and my iron could barely melt it !I did try soldering with it but it just left big blobs. Then couldn't de-solder device as solder wouldn't melt.So binned it and got some from a reputable dealer.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 23, 2021, 09:42:24 am
content: Quote from: tautech on August 22, 2021, 10:04:03 amyes I have seen the soldering of the commercial IC, the soldering is not in relief, the trick is not to melt too much tin .. indeed I have seen in the tests, that the residual tin layer on the pad and the tin veil on the tip, would almost be enough to solder the pin

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 23, 2021, 09:44:21 am
content: Quote from: jpanhalt on August 22, 2021, 10:16:40 amthanks for the suggestion, in the meantime, however, I don't want to use solder paste, but I focus only on soldering with wire; then maybe in the future ..

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 23, 2021, 09:51:46 am
content: Quote from: Shock on August 22, 2021, 02:17:23 pmthanks for the video I will watch it well and calmly; now I understand how the soldering quality on the IC pins should be; maybe the thing I don't have very clear is where I should be with the tip. With two-pin smd it is obvious that I am in front of the pin ... but with the legs of the IC in front there is little space, in what I soldered for testing, the pins reached almost to the end of the pad ... Then maybe the trick it would be to not rest the wire on the tip, perhaps it could melt less tin; Isn't 350 ° too much? it also depends on the size of the tip: 350 ° with tip 1.2 heat a lot, but if I use the tip 0.8 they heat much less .. thanks

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 23, 2021, 09:54:22 am
content: Quote from: nigelwright7557 on August 22, 2021, 07:14:29 pmWith the solder I use I can it takes about a minute for hot air to loosen the solder.If your ripping off pads its either way too hot or your pushing too hard.Solder can vary a lot. I bought in some cheap Chinese solder and my iron could barely melt it !I did try soldering with it but it just left big blobs. Then couldn't de-solder device as solder wouldn't melt.So binned it and got some from a reputable dealer.thanks: I passed the IC desoldering speech, the problem was that by heating with the air, in the meantime I pushed the smd too hard and the pads would rise .. Then I discovered that I have to be patient and when I see the IC float, it comes off without force and the pads remain immaculate

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 23, 2021, 10:45:28 pm
content: Or solder the pins again and then desolder ... it almost always works

author: tooki
author_rank: Super Contributor
timestamp: August 24, 2021, 10:02:35 pm
content: Quote from: CharlotteSwiss on August 22, 2021, 09:42:11 amMy reply is going to be somewhat controversial, I think, but… despite the fact that Idon’tbelieve in discriminating by language as such, I don’t think it’s right to try and discuss complex things (where terminology matters) on a public forum via machine translation. Why? Because as a forum user, you have a certain responsibilitytowards the other users.One of the biggest responsibilities and signs of respect is to not waste other people’s time. And while I love to help, at some point, it shifts to just being a waste of time if the responses go nowhere. If you cannot communicate effectively (in either direction), then the result is what’s happened here, going in circles of misunderstandings. Machine translations simply are not good enough.I know there are tons of great forums in other languages. I’m certain there are tons and tons of amazing resources in Chinese and Japanese, for example, which makes them completely unavailable to me. That sucks. But I’m not going to on a Japanese forum and use google translate to post questions that the others have trouble understanding, with replies I will have trouble understanding. It’s not respectful of their time and effort.

author: tooki
author_rank: Super Contributor
timestamp: August 24, 2021, 10:27:48 pm
content: <off topic>Quote from: Electro Fan on August 22, 2021, 04:03:49 pmThe (former) professional technical writer in me came out, I think!In a previous career, I wrote the style guides for our public-facing communication. Not only does a style guide make one’s own writing more consistent (and provide a place to look for when you think “how did I word that nicely a year ago?”), but allows for multiple authors to produce texts that have a single “voice” and won’t confuse readers with inconsistencies. For example, that being at a software company, we established the exact verbiage used for describing how to navigate UIs, for example, to “select” and “clear” a checkbox, not “check” it (could mean to place a checkmark, or just to verify it), not “click” it (since you may not know its state, so the outcome of a click is not guaranteed). And that you list information in the order it is needed (like “On the File menu, click Save As, select where you want to save the file, enter a file name, and then click Save.” and not “Click Save As on the File menu, then click Save after selecting a folder and entering a file name.”)And yes, giving counterexamples of what not to do is just as important as giving examples of what to do.Terminology is a fascinating area (and yes, it’s even something some people specialize in!), and IMHO a spectacularly useful one, since establishing a clear, unambiguous vocabulary for a given discussion can make communication dramatically more productive.Unfortunately, if (like in this thread) not every participant in the discussion is able and willing to commit to a shared vocabulary, then it can be for nought.</off topic>

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 26, 2021, 10:41:12 am
content: Quote from: Shock on August 22, 2021, 02:17:23 pmabove in the messages I was advised that it was better to put a drop of tin on the pads and not on the tip to give the smd the first soldering; but in the video he does exactly as I saidt, that is, he has the pond on the tip ... So maybe everyone does as he prefers?watch the video to the exact minute:https://youtu.be/EW9Y8rDm4kE?t=87Also interesting on the narrow 100 pin IC, it does not drag solder, but does 1/2 pin at a time going from the inside out with the tip, the result looks good. But maybe in this case, the hardest thing will be to check if each of the 100 pins is actually soldered well!https://youtu.be/EW9Y8rDm4kE?t=904

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 26, 2021, 12:55:30 pm
content: Quote from: Shock on August 26, 2021, 12:30:28 pmthanks shock very kind (and do not discriminate to those who do not speak excellent English). In fact, I had said it, putting the tin on the tip, it would be appropriate to put the flux on the pad / pin. However, I can very well use the drop of tin on the pad, it's easy .. (but then I'll do this solder again anyway)It remains for me to try only the soldering by dragging, but I will do as in the video, like brushing from the inside out, 1/2 pin at a time (for this job, however, I will not use the water flux, but the classic one).

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 26, 2021, 08:07:10 pm
content: Quote from: Shock on August 26, 2021, 03:34:50 pmit has been said that not having command of the English language, it would be better not to write in the forum. In my house it's called discrimination.But that's not a problem for me

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 26, 2021, 08:10:51 pm
content: Quote from: Shock on August 26, 2021, 04:09:21 pmI had purposely taken the concave tip to do the drag, I'll try to try with that and get my bones. Meanwhile, I saw that it is excellent (the concave one) also for cleaning the pads, without using the braid.Thanks for new video

author: thinkfat
author_rank: Unknown
timestamp: August 27, 2021, 08:56:10 am
content: Quote from: CharlotteSwiss on August 26, 2021, 08:07:10 pmStill, it's a fact (at least today) that you won't get very far in this domain if you don't have at least some knowledge of English. Tomorrow, it may be Mandarin, though.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: August 27, 2021, 10:12:55 am
content: I read it and understand English without a translator, but I struggle to speak / write it without it. This does not limit me in electronics.I just pointed out that I don't distinguish between people who speak English or not, for me they are all the same here on the forum.

author: thinkfat
author_rank: Unknown
timestamp: August 27, 2021, 10:46:11 am
content: Quote from: CharlotteSwiss on August 27, 2021, 10:12:55 amI wasn't questioning thatI feel similar. If one values their own time/persona so highly that they cannot be arsed to put a little effort into understanding a question that is unclear at first sight because the writer was struggling with the language barrier - yeah nah.

author: tooki
author_rank: Super Contributor
timestamp: August 28, 2021, 08:22:42 am
content: Quote from: thinkfat on August 27, 2021, 10:46:11 amMy frustration was that I put atonof effort into both understanding and replying (not just in this thread, but also other threads of hers), only to get back responses that appeared to completely ignore the responses I had put so much effort into. To accuse me of being lazy completely ignores the tons of time I put into this user.Had she said from the beginning “I am writing via machine translation”, that would have provided critical context into whether the continued errors were due to not understanding, not caring, or simply errors produced by the translation service.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: September 04, 2021, 10:21:31 pm
content: With the test of soldering an IC with pitch 1.27 pin to pin I had been successful; today I wanted to try to solder an IC with pitch 0.80 and I wanted to try the 0.50 tip again: with this tip I can't solder, it's as if it doesn't heat up enough (note that I have set 350 °!).So I tried with the tip 0,8 and let's say that I soldered it pin to pin, even if I still put too much tin.I then moved on to the next step, try to solder an IC by dragging the tip: for the occasion I then tried the quality flux (ChipQuik) for the first time, I put it on the whole row of pins, but here's the surprise : the tin remained attached to the tip and did not go on the pin / pad, as if the flux layer acted as an insulator.In short, as a first test using this flux, I didn't understand much. I need to watch some videos and try again...

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: September 05, 2021, 10:23:14 am
content: watching some videos, maybe I found the best solution: it was here in the EEV houseTonight I try to solder an IC (1.27 pitch) with the technique you can see from the 9.55 minute of the video...that the devil assists mehttps://youtu.be/hoLf8gvvXXU?t=597

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: September 05, 2021, 09:13:10 pm
content: Following the EEV video above, using the same technique (in the video it uses a flat tip, I used the concave tip), I was able to solder an IC with pitch 0.80.Now I could see how the ChipQuik flux does its job, helping in soldering; but especially where there is a need to touch up some badly soldered pins, prevent the tin from creating bridges between adjacent pins.My concave tip measures 3.2 mm, I would say maybe too big (maybe I would have done better to take the 1.6mm one), more than anything else if there was another smd close to the pins it would be difficult to pass ...It is then difficult to evaluate well if the pins are soldered with sufficient tin or not, if in doubt, in addition to plugging above the soldering points as in the video, I went over all the pins by dragging the tip from the body of the IC towards the terminal part of the pins; however, this has also drawn tin in the peripheral areas.Anyway, I then tensioned all the pins with tweezers, and they turned out to be pretty firm (except one that was broken earlier).One thing I have noticed with this flux is that the solders are bright / bright silver, very good.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: September 06, 2021, 09:36:23 am
content: thanks Thinkfatit is only a first test with pitch 0.80, I can and will certainly improve

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: September 11, 2021, 02:00:48 am
content: I have had trouble with some solders and SMD.I bought some cheapo stuff and the iron would hardly melt it !So bought in some better solder and that was much better.Pads coming away is either cheap pcb's or solder with too high melting point or just being too rough.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: September 11, 2021, 10:58:54 pm
content: in fact there are solders that melt first and others that are more stubborn; however, if the component is lifted only when the tin is well melted, while still heating, the pads do not rise

author: thinkfat
author_rank: Unknown
timestamp: September 12, 2021, 06:09:05 am
content: Yes, but if you need excessive heat to melt the solder, pads might come of anyway.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: September 12, 2021, 11:20:38 pm
content: you are right, in fact in the tests by heating some IC pitch 0.80, the pad were unglued exclusively for the heat. It should also be said that they would have done their job anyway by soldering a new IC on it

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: October 17, 2021, 12:34:08 pm
content: Quote from: John B on July 14, 2021, 09:23:52 pmI use this fact when soldering TQFP's.I drag solder all the pins then if any shorts I use braid to remove it.This tends to remove a lot of the solder but the solder behind and along the side of the pins is left intact.

author: tooki
author_rank: Super Contributor
timestamp: October 17, 2021, 03:11:33 pm
content: Quote from: nigelwright7557 on October 17, 2021, 12:34:08 pmNext time, try this: apply flux to the bridge. Thoroughly re-tin your iron, so that it’s free from “overcooked” solder, wipe off the excess, then quickly go back and remelt the bridge. That’ll usually take care of it.

author: perieanuo
author_rank: Frequent Contributor
timestamp: October 18, 2021, 07:23:57 am
content: Quote from: CharlotteSwiss on July 14, 2021, 08:48:53 pmhi,i see you're a frequent contributor here hence my surprise you ask thisno doubt, hotair is the best one (just gotta work your hand), they do it in industrial manufacturing (but not like most of us, they heat from 2 sides, so for difficult jobs you'll need some heating plate)is you need to rise over 400C you got a technique problem or tooo cheap soldering hotair station.we start from what device manufacturer says about soldering time and temp and if we just respect this, it'll work 100%standard reflow profiles like one from maxim shows temp peaks like 220C and total time ~270 secs, so that's the correct approach imho, otherwise overcooking the devices result in less device lifethe braid is better to use it to clean after removing the part

author: thinkfat
author_rank: Unknown
timestamp: October 18, 2021, 08:12:03 am
content: Quote from: perieanuo on October 18, 2021, 07:23:57 amYou see, some frequent contributors don't know yet how to handle SMD repairs, and some other frequent contributors ignore 5 pages of conversation, adding redundant information.

author: CharlotteSwiss
author_rank: Frequent Contributor
timestamp: October 18, 2021, 11:02:28 pm
content: Quote from: perieanuo on October 18, 2021, 07:23:57 amhi, are you telling me that I should heat at 220 ° for 270 seconds to desolder? I could try ... However, the message you quoted was at the beginning of my journey, then by choosing a nozzle with a more suitable diameter I was able to easily unsolder the smd. Thanks

author: nigelwright7557
author_rank: Frequent Contributor
timestamp: January 10, 2022, 01:11:02 am
content: I always use hot air station.Braid wont pick up solder from behind the pins.