Soldering SMD IC's - Page 1
Forum section: electronics / projects

author: NMNeil
author_rank: Contributor
timestamp: October 21, 2017, 11:02:52 pm
content: A few month ago I was forced into the unknown territory of SMD. This was because the IC I wanted to use was only available in SMD. I watched Dave's video on soldering SMD parts and it looked easy. After a few weeks of misaligned components, burned fingers, and copious amounts of genuine Anglo Saxon cursing I thought “There must be a better way”, and I may have found it.I don’t claim any originality and would like other forum members to try this and if possible photograph or video it because my camera’s not up to the job.Starting with this flux;which has the consistency and adhesion properties of treacle, I used a toothpick and smeared a layer onto the copper pads, no tinning, just the flux. The SMD IC was then put in place and, just like anything in treacle, it stuck. Turn the board upside down and it doesn't move.Now the good part. With a toothpick holding the IC to the board touch your soldering iron to your regular rosin cored solder. Of course the flux will burn off but it doesn't matter because there is plenty of flux on the board and under the legs of the IC. Now touch the solder to the IC leg, count to 2 and your done. The result is pretty close to a perfect commercial soldering job.The inspiration to try it this way came from watching a Purdy craftsman silver solder the rib between the barrels of a shotgun. They put the flux in first and then add the silver solder.Just want to share.

author: ebclr
author_rank: Super Contributor
timestamp: October 22, 2017, 12:28:12 am
content: The tip is the biggest secret on SMD soldering by hand.I'm having excellent results with T12-BCM2,

author: mrpackethead
author_rank: Super Contributor
timestamp: October 22, 2017, 12:48:59 am
content: You'll find flux available in syringe form with a dispensing needle. Even easier.

author: NMNeil
author_rank: Contributor
timestamp: October 22, 2017, 01:02:18 am
content: The secret is having one hand to hold the IC in place and the other to use the soldering iron, no trying to feed solder onto the tip of the iron while trying to stop the IC moving.

author: nanofrog
author_rank: Super Contributor
timestamp: October 22, 2017, 01:55:38 am
content: Quote from: NMNeil on October 22, 2017, 01:02:18 amA couple of alternatives would be:Use a tip designed specifically for drag soldering (i.e. has a well/spoon/hollow in the face of a hoof/bevel that holds a ball of solder).Tack opposite corners to be sure it stays in place, then drag solder with whatever tip shape that'll do the job such as a regular hoof/bevel or knife. This way your other handisfree to feed solder if needed.Others as well that don't require an iron at all (i.e. solder paste + hot air, reflow oven, or even an electric skillet).

author: Simon
author_rank: Unknown
timestamp: October 22, 2017, 07:10:23 pm
content: You can never have too much flux, Essentially you need to hold the part down and solder being confident that the joint will happen easily, you have guaranteed that with the flux. Really you will soon be replacing the flux with solder paste and then just hot air it and then once you have fully converted to SMD you might even get stencils and one of those little infrared ovens if you get fed up with the hot air soldering iron and blowing bits around.....

author: technix
author_rank: Super Contributor
timestamp: October 22, 2017, 07:17:05 pm
content: Quote from: Simon on October 22, 2017, 07:10:23 pmIron and hot air are still useful when reworking though.

author: Simon
author_rank: Unknown
timestamp: October 22, 2017, 07:44:41 pm
content: yes, hot air is the only way of removing a chip and usually one gets a hot air iron before going the whole oven route so still has it for reworking.

author: mrpackethead
author_rank: Super Contributor
timestamp: October 22, 2017, 11:14:46 pm
content: Hot air is'nt the only way.You can use somethign like QuikCHip Low Melt..You can sometimes just use good old solder wick.In all cases, use lots of flux. The biggest issue is overheating where you can lift tracks off pcbs.

author: NMNeil
author_rank: Contributor
timestamp: October 23, 2017, 12:55:28 pm
content: Funny, I joined this forum because I had the strange belief that it was to help newbies and established makers, how wrong I was.I found what I though was a better. inexpensive way of doing something and posted my findings. I thought this may help someone struggling with SMD soldering, but all I got was "No you need to do it this way" or "No you need to buy a hot air gun, solder paste etc".No one has actually tried using my method meaning that nobody on the forum is prepared to try anything new, only pass negative comments.I have learned a lot from this forum, not just from a technical standpoint but also an insight into the human attitude of, "I've always done it this way so it's the only way".So I would ask the administrators to close this thread now that I know that the forum members have closed minds and are of the opinion that if you have an idea you should keep it to yourself.Armed with that knowledge I will now just stay in the background and keep quiet.

author: technix
author_rank: Super Contributor
timestamp: October 23, 2017, 01:57:33 pm
content: Quote from: NMNeil on October 23, 2017, 12:55:28 pmSad to see this...Your soldering technique is fairly similar to mine, kind of a variant of the "drag soldering" technique.People mention hot air station and IR ovens because with just a soldering iron you can lock yourself out of some SMD package styles - the biggest offender is BGA and CSP, both of which requires hot air or an oven to solder, since they have pins on the bottom of the chip; and things like QFN or any package with an exposed pad beneath it doesn't make life easier. And a lot of modern chips are only available in those inconvenient packages.I have been designing circuits for a while now, both as a hobby and as a job. There have been a few cases where my ideal chip is only available in BGA, locking me out of an idea since even with a hot air gun I am not exactly comfortable with soldering BGA myself. You can make a read at my quests of a single-board computer that runs Linux and can solder using an iron - I have to use a decade-old platform and compromise features, simply because nobody makes either the processor or the memory chips, often both, in easy packages like QFP, SOIC or SSOP anymore. Most ARM chips are BGA only, Allwinner A13 requires memory that is only available in BGA, and this leaves me with only Allwinner V3s, Microchip AT91SAM9260 and NXP i.MX233, the first being an all-in-one solution which is not flexible at all, and the latter two being based on decade-old ARM926EJ-S architecture.

author: imidis
author_rank: Frequent Contributor
timestamp: October 23, 2017, 02:05:39 pm
content: I wouldn't read into it too much honesltly. I have a hot air station and I find I don't tend to use it much for soldering SMDs, desoldering yes for sure, but not soldering for me. I solder pen some flux down, get some solder on my tip and go to town -works for me. I say people should do what they find works for them on what they are comfortable with. And what works for what they are doing.These test pads are pretty tiny and that method works.(soldered USB and IR) USB is 4 pads the GPIO side of the H3 chip.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: October 23, 2017, 02:07:44 pm
content: Quote from: NMNeil on October 23, 2017, 12:55:28 pmThis is the interweb... and this forum is no exception... people will express their opinions and experiences... personally I use a flux pen.Your technique sounds good. FWIW I think Louis Rossman;s YouTube SMD videos are worth a watch... he uses floods of flux (although the microscope probably makes it look more flood than it might actually be).

author: Buriedcode
author_rank: Super Contributor
timestamp: October 23, 2017, 02:57:16 pm
content: Quote from: NMNeil on October 23, 2017, 12:55:28 pmWell you are correct in that some will state "their method" and can get quite defensive if someone points out another way - acting almost like they've been told they're doing it all wrong, but you are doing the sameWhilst there are many videos of how to do SMD, and claimed 'methods' there really aren't that many ways to do it - I can count them on one hand (hand, hot-air, oven, flood). What you described is called 'tacking' pins - often diagonal ones - of an IC to hold it place, freeing up a hand to feed the solder. With flux on the pads you can put a tiny blob of solder on your iron, even long enough to let it oxidize, and when touching the pad it will *still* flow because the flux is working its magic, so no need to have three hands. After that, one can go pin-by-pin, or drag soldering, which is basically the same deal when you have flux on the pads. I don't know if its a 'standard' technique, but its not new.I realize I have just described your method, but it is one I feel is very common...I mean, how else do people do it? having a clamp to hold the IC in place must be a nightmare to set up. The idea that soldering is some mysterious skill is silly.. its mostly experience/knowledge about tips, temps, and fluxes, the actual act of soldering most parts (sans BGA) is pretty straight forward. Not trying to bash people here, if you're proud of your work, good for you, but it hardly takes 'years' to achieve acceptable results. (That said, I have seen some horrifying soldering the in Automotive sector by people doing it for decades).As many have mentioned, flux is your friend. Perhaps the flux in cored solder is still enough for basic TH stuff, for SMD flux is a must, and makes soldering a breeze,muchharder to develop solder bridges. It seems you have just discovered this. Congrats, you'll never look back!

author: Simon
author_rank: Unknown
timestamp: October 23, 2017, 05:24:08 pm
content: Quote from: NMNeil on October 23, 2017, 12:55:28 pmWell I'm very sorry that you happened to stumble across one method many use and was not treated as a messiah. As you are clearly starting out in SMD we tried to offer further advice, if you don't want it then so be it.

author: Old Don
author_rank: Regular Contributor
timestamp: October 23, 2017, 06:50:16 pm
content: You can also use something like Chip Quik SMDLTLFP which is a solder paste. No need to hand hold a piece of solder while touching an iron to the SMD.

author: Mr. Scram
author_rank: Super Contributor
timestamp: October 23, 2017, 06:59:40 pm
content: Quote from: NMNeil on October 22, 2017, 01:02:18 amJust make sure to fixate the IC first. Tin two pads on opposing sides of the IC, hold the part on, and reheat both pads one by one. Your part is now fixated. You can start soldering elsewhere without a chance of things moving about.

author: jmelson
author_rank: Super Contributor
timestamp: October 23, 2017, 07:51:04 pm
content: Quote from: Mr. Scram on October 23, 2017, 06:59:40 pmYup, that's my system, too, for ICs. I've been doing this for about 20 years. For low-density stuff like SOIC (.050" spacing) I use wire solder. For higher density stuff, sometimes I use solder paste.Jon

author: technix
author_rank: Super Contributor
timestamp: October 24, 2017, 07:59:30 am
content: Quote from: jmelson on October 23, 2017, 07:51:04 pmI have been usbig wire solder down to 0.5mm TQFP...

author: mrpackethead
author_rank: Super Contributor
timestamp: October 24, 2017, 09:19:16 am
content: I'll do .4mm QFP with .7mm solder. Does'nt really make much difference, when you are using a concave soldering iron bit. Its a great tool for this job.

author: wasyoungonce
author_rank: Frequent Contributor
timestamp: October 24, 2017, 09:56:33 am
content: Quote from: NMNeil on October 21, 2017, 11:02:52 pmThanks but no thanks...poor advice. I've done SMD and IC replacements on myriad of PCBs from Military Avionics to Iphone. Sorry you need solder on pin for a start.Yes lots of flux is nice but hey its the solder that forms the electrical joint not the flux. You didn't mention this for "pin 1". Then pin 2...hell no...once pin 1 tacked...check alignment then do diagonal opposite pin or rework pin 1. Obvious reasons why...then...what solder you didn't mention any! Then later you mention silver solder....sorry you lost me. Silver Solder...lets hope its a typo. No mention of wait to cool between joints. No inspection post cleaning!Sigh...look I don't want to rain on your parade but to many what ever method works for them but sadly this is not good at all.To those novices in SMDs...as said, this is not good advice it misses basics. Prepare clean pad surfaces, use flux appropriate to your solder type (ideal solder for high density ICs is probably .56mm or less, depends upon tips used), small amount on a iron tip tack 1st pin, wait to cool, then diagonal opposite (usually use a fine tip and if low density IC then maybe continue allowing cooling) remember iron tip fresh solder and tip "cleanliness is close to godliness"!If a high density IC and close pin spacing drag tip mentioned is then ideal method. Hot air is ok for rework but generally overheats everything with normal solder before you get acceptable results. I've never used LMP unless chipquik to remove SMDs.Then when done clean inspect inspect and some more. Be critical. Re-work ...you gonna need more flux and fresh solder.Of course everyone does it differently and no one ,method is perfect, but the basics:Clean solder with kimwipe and PCB cleaner...solder oxidises rapidly with air and all that will be part of the join. Do this every 10 mins or less YMMV.Clean iron tips, brass wool and wet sponge (which also helps to case harden the tip as well as wipe it).Clean tip every join.....fresh solder...unless drag solder.Clean pads, use lots of flux. Use flux appropriate to solder. Look I'm old skool...I still luv rosin cored and rosin flux 63/37 Kester or 60/$40. Yes I know and have used no clean solder and lead free...but...I always go back. "I luv the small of rosin flux in the morning"!Allow joints & IC to cool between joints.Use antistatic procedures...lastlyLook at the IC legs...I've seen a few with oxides on the legs which doesn't clean off unless scraped..I have no cure for this on SMD but use hexacon lead cleaner for thru hole parts.

author: nanofrog
author_rank: Super Contributor
timestamp: October 24, 2017, 10:08:25 am
content: Quote from: wasyoungonce on October 24, 2017, 09:56:33 amAn abrasive ink eraser might help followed by RA.

author: Old Don
author_rank: Regular Contributor
timestamp: October 24, 2017, 06:36:21 pm
content: Petty much what wasyoungonce said.Paste rosin flux can be your friend holding SMD's in place and can act as your 3rd hand at times. Liquid flux works well for keeping air away while you solder but it is near useless for keeping IC's from moving around on you. Sometimes holding the solder, the iron and pressing on a chip seems impossible unless you stick a chip with rosin flux. Clean up sucks so use as little as possible.I won't use an eraser unless you know the IC can withstand static, but then again I haven't tried it so it might be safe.

author: KL27x
author_rank: Super Contributor
timestamp: October 25, 2017, 04:41:40 am
content: QuoteFor DIP, I usually tack at most one pin. Hold chip with tweezers, align and tack the top right pin, torque the chip slightly as necessary to align the rest of the pins, and zip up the bottom row of pins left to right. Then after moving the board to the next part, finally let go of the IC with the tweezers. I finish zipping the other side when it's time to rotate the board (I find it super betterer to tilt my microsope to see at a forward and down angle. If you like to look straight down, you can solder both sides, no problem, I suppose, and you get the same view on either row.)QuoteI'm not sure why you would need flux to hold the IC wherever you happened to drop it on the board. When I'm actually first lining up the IC/component to the pads, my solder iron is in my other hand, already, tinned and ready to go. Liquid flux keeps the parts from moving if you bump the board while handling it, which is all I ask of it. Why bother lining up a part, then letting go and putting down the tweezers, then soldering it? Sounds to me like, just a guess, maybe you are old school and are applying super thin solderwire to the joint(s) with your left hand while iron in the right? The flux allows you to NOT do it like this.The main difference between the paste and liquid fluxes, AFAIC, is the method of application. And a puck of paste flux is handy perhaps for dipping the end of a row of pin headers or wire-ends into. I used to keep a puck of paste rosin flux, but I ended up binning it. I rarely found much need for it.My latest tip/trick for heavy volume work is for thin boards and FPC. I used to put the boards/panels onto a big piece of FR-4 to protect my workbench from heat. What I like to do, now, is to fix the FR-4 in place on the bench and move the board over it, so (under microscope which doesn't move) the soldering is always taking place over the same spot on the plate. The plate will store a surprising amount of heat, acting like a preheater. This is especially handy when you find you are low on flux on a QFP on the followup (I like to touch them with iron after hot air). Rather than squirting large amount of liquid flux over the chip to get a little bit to dribble into the "crack," I will take a dab of dried up rosin flux on a tiny chisel and wipe it over the leads, more precisely, and the residual heat will melt it.

author: technix
author_rank: Super Contributor
timestamp: October 25, 2017, 05:14:07 am
content: For this “place chip first, solder with Iron next unassisted” method some of those wave soldering glue may help.

author: mrpackethead
author_rank: Super Contributor
timestamp: October 25, 2017, 07:18:01 am
content: Quote from: Old Don on October 24, 2017, 06:36:21 pmone reason really like a concave 'hoof' tip on my iron is htat it holds a pool of solder, so, i can put some solder on it, then hold my part with tweezers and tack the first pins down. It was a 'aaah' moment when i first got one.. Its also awesome for drag soldering, as the surface tension in the 'pool' on the tip drags the solder along.. Of course you need to use flux with this method, as the flux that is in teh solder, will be long gone by the time you are actually soldering.

author: tooki
author_rank: Super Contributor
timestamp: October 25, 2017, 02:50:03 pm
content: Quote from: NMNeil on October 23, 2017, 12:55:28 pmThe tone on this forum tends to be a bit rough around the edges (sometimes maddeningly so), don’t take it personally. It isn’t you. And of course the usual rules of the internet apply: everyone has an opinion, and is gonna state it.Quote from: NMNeil on October 23, 2017, 12:55:28 pmI use this method. I like using a tacky flux to hold the components in place until I can tack down one corner, check/adjust alignment, and then continue the rest of the pins. (The tacky flux makes it easier to make small corrections IMHO, since small movements are damped a bit.)It works really well for SMD discrete components, like chip resistors and LEDs. I assembled two LED clocks that each have 105 discrete LEDs on them, using just this approach. My paste flux came in a syringe, so I put a fine needle on it and dispensed a thin line of flux across the pads for a row of LEDs. Then I laid down the row of LEDs with tweezers, and then went in to solder, using the tweezers to adjust position as needed.I mean, using a paste to hold SMD components isn’t a weird concept... solder paste does the same thing! If others prefer liquid flux, fine, that’s cool too.As for the comments about what was omitted (cleaning, etc)... that’s scope creep. You addressed one single section of the assembly process, and did it just fine if you ask me.

author: Buriedcode
author_rank: Super Contributor
timestamp: October 25, 2017, 05:09:27 pm
content: Quote from: NMNeil on October 23, 2017, 12:55:28 pmI skipped over this in my previous reply, but it seems others have just stated 'how they do it' without actually keeping the thread on topic. How do you know 'nobody has tried' "your method" ? Also, how do you think others hand solder SMD IC's? My point is, there isn't myriad ways of doing it, and "your method" is pretty much how most (I've seen) do it.The fact you've discovered this by yourself has clearly excited you and you wished to share - that is of course welcome, but I think the coarse replies were a combination of folks saying "so what? isn't that how everyone does it?" and "I have a better method" type attitudes. Neither of which are particularly helpful but.... to be fair, what did you expect?Again, I don't really understand people talking about "methods" or "techniques", it implies there is some elaborate secret sauce, or wacky weird technique to soldering SMD IC's - there isn't. Sure results can vary, from shocking cold solder joints to beautiful shiny fillets, but there aren't distinct completely different approaches to hand soldering. I - like I assume most here - learned to do it just by doing it. These days, its even easier as there are hundreds of forum posts, tutorials, and youtube videos to help out beginners, although that can actually be detrimental since people spend more time reading, less time practicing.If you have any other "methods" or techniques you wish to share, I'm sure someone will appreciate it, but perhaps ask if its common place rather than assuming you discovered it.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 25, 2017, 05:54:59 pm
content: Quote from: Buriedcode on October 25, 2017, 05:09:27 pmWhat coarse replies? I didn't see even a slightest hint of such a tone in any of the replies, just normal everyday discussion on topic, then the OP suddenly losing his mind completely randomly. After that, sure, some slight "coarseness" ensued, unsurprisingly.Maybe he was dissatisfied in the totally neutral, almost boring discussion and was expecting to be treated like some kind of reincarnation of Jesus Christ and Albert Einstein combined?These kind of touchy, randomly exploding people come and go on the forums, post a message, threw a tantrum totally out of nowhere, promise to never come back; and usually come back. They are irrelevant people; ignore list features are specifically designed to take care of these things.