Surface-mount soldering trouble: what am I doing wrong? - Page 1
Forum section: electronics / beginners

author: exscape
author_rank: Contributor
timestamp: August 12, 2012, 07:13:25 pm
content: First off, I've watched the EEVBlog soldering tutorials, of course, as well as quite a few other videos... but I'm still stuck!I have and use:* A 48 W temp-controlled soldering station - cheap, but it should do* The above set to ~370 C (~700 F), most of the time* 60/40 solder, 0.7 mm - I've had it for many years, though* A rosin flux pen* Solder wick w/ fluxThe tip I've been using recently look something likethis- there's no proper chisel tip for my iron, so that's the closest I could get.Okay, so on to the problem. There might be multiple, but one is that I find the solder "sticky". Despite flux, it bridges a VERY easily, even on SOIC-pitch pins (i.e. fairly large). Those bridges are pretty easy to remove (with the soldering iron tip, or solder wick if really needed), though. On finer-pitch devices, the results are, frankly, shit. I simply can't seem to solder one, at all.In addition to the bridging, the solder also tends to "follow" the iron when I lift it out, causing spiky joints here and there.One thing is most likely worth noting: all the practice soldering I've been doing has been on OLD boards (1995 or so), where I've "desoldered" brute force with a hot air gun. The results aren't great, as you'll see.Here are a few pictures... embarrasing (bad alignment, tons of flux residue, bad joints etc):In the first picture, note the "spiky" blob of solder connected to the second pin. It simply follows the iron when I lift it.I can certainly do a bit better than the BQFP there, but the solder prefers to stay the way it looks there. ... and the bent leg happened while desoldering. Yes, it's ugly, but the board is garbage either way!I can think of a few possible reasons:1) Old, dirty boards2) The "desoldering" process isn't exactly something I'd do on a board I care about - the entire area around the IC gets very hot, which might cause problems.3) Incorrect soldering iron temperature for SMD work - I haven't tried lower (or higher) recently4) Old solder (it looks brown-ish here and there on the roll)Any advice?

author: 8086
author_rank: Super Contributor
timestamp: August 12, 2012, 07:43:03 pm
content: As for the "sticky" solder problem, remember to apply heat before applying solder. You tend to get this problem when all the flux has evaporated. Also remember to clean and tin your tip often.Where you have bridges just use the wick to soak it up.Your boards could probably use a clean if they are quite oxidised, given their age.

author: exscape
author_rank: Contributor
timestamp: August 12, 2012, 07:49:16 pm
content: Quote from: 8086 on August 12, 2012, 07:43:03 pmProblem is, the only way to get rid of them is to wick up virtually *all* the solder, so that not enough remains. Remove less and the bridges stay.I'll do another try tomorrow (it's 10 PM here now), and make sure I have proper contact with both the pins AND the pad. I realized that I might've been sloppy there.

author: IanB
author_rank: Super Contributor
timestamp: August 12, 2012, 08:00:23 pm
content: The solder gets "sticky" when it forms a thin layer of oxide in its surface ("scum" or "dross"). This is a sign of too little flux. For SMT soldering ample flux is a key thing. In many SMT soldering videos the area to be soldered is flooded with liquid flux before applying the iron.If your solder is old, the flux may have dried out and become less active. You might consider some fresh solder and see if that also improves things.

author: TerminalJack505
author_rank: Super Contributor
timestamp: August 12, 2012, 08:03:04 pm
content: I would start by focusing on the tip. Apply some solder and see if the solder takes to the tip or not. If not, and you're sure your temperature is what you say it is, then clean the tip with a wet sponge and reapply solder, clean, reapply solder. Repeat until the tip wets. (You might use some flux from your pen to help with the cleaning process.) You won't be able to get heat from the tip to the board and pins until your tip takes the solder.Once your tip is prepared, I would focus on the board and parts. Clean the board with ISO alcohol. If the board is oxidized then you might want to tin the pads before soldering. Use plenty of flux when tinning and soldering.By the way the footprints on your board make hand soldering trickier than necessary. They were likely made for reflow soldering. Footprints made for hand soldering will usually extent the foot print a little beyond the pin. This makes getting the tip on the pad easier. A professional would likely drag solder those. That might be a little too challenging for you, however.

author: jahonen
author_rank: Super Contributor
timestamp: August 12, 2012, 08:05:11 pm
content: 0.7 mm solder is way too thick at least for smaller things making it difficult to dose it properly, try something like 0.3 mm or so.Regards,Janne

author: krenzo
author_rank: Regular Contributor
timestamp: August 12, 2012, 08:08:47 pm
content: Try this technique:See how much flux he uses in this video? Take your flux pen and rub it on the pins until you can see a definite layer of flux on the board. Then, run your tip back and forth to spread the solder out and remove any bridges. If you used enough flux, it will make the solder flow easier and keep it from bridging. When your flux is gone, you will start to see the solder act "sticky."

author: nanofrog
author_rank: Super Contributor
timestamp: August 12, 2012, 08:10:22 pm
content: Quote from: exscape on August 12, 2012, 07:13:25 pmLinking it might help with the particulars, as someone here may have the same unit.Quote from: exscape on August 12, 2012, 07:13:25 pmSo long as it's good quality, this shouldn't be a problem (unless the flux is useless <wick, pen, or solder core>, or the solder is highly oxidized). I have some solder that's more than 20yrs old that still works very well.Not had the best experience with the Chinese made solder wick (labeled as GOOT), but it may have been a bad batch. But I've gone back to name brands for wick (MG Chemicals). Pens, I go for Kester, and solder either Kester (285 or 44) or Multicore (502 series). All RMA or RA (Kester 44).Quote from: exscape on August 12, 2012, 07:13:25 pmLooks like it's a Hakko 900M clone to me at the iron end at least. Personally, I have trouble with this shape as well vs. a chisel for general purpose work, so mine is barely used in comparison (specialty use for me).IF this is the case, there are more tip geometries available (example of a set:http://www.ebay.com/itm/10-Solder-Soldering-Iron-Tip-for-Hakko-Station-900M-933-/251103701489?pt=LH_DefaultDomain_0&hash=item3a76f269f1). This is where the link to your iron would help though, as someone else may know for certain if this is the case.Quote from: exscape on August 12, 2012, 07:13:25 pmPotential issues I see:1. Clean the old boards before working on them if they need it prior to working on them.2. Use a smaller diameter solder.3. Iron might be a bit cold (assuming its not oxidation; real temp at tip may be colder than what the iron is set for).4. Might also be insufficient amount of flux, so try using a bit more (oxidized joints).5. Clean the tip more often (try between every joint, then 2, ... until you figure out the best results for what you're working with). Rework on older boards can require even more frequent cleaning than new boards and parts.Hope this helps.

author: T4P
author_rank: Super Contributor
timestamp: August 12, 2012, 11:25:24 pm
content: That goot belongs to a goot RX-701/711 series soldering stationBut he just says "Looks something like that"Well i guess his station must be a Weller Clone (Zhongdi) or a Weller or even one of those tiny soldering station with a sponge on the top

author: David Aurora
author_rank: Frequent Contributor
timestamp: August 12, 2012, 11:46:08 pm
content: Hang on, you desoldered with a hot air gun, but you're resoldering with an iron and a roll of solder? Why don't you just get some solder paste and use hot air?

author: RCMR
author_rank: Frequent Contributor
timestamp: August 13, 2012, 01:54:01 am
content: I think I run my iron colder than that because the problem is often that you lose the flux too quickly with higher temps and, once the flux is gone, your solder *will* bridge pins/lands and act like snot.Of course you ought to be using a decent solder in the first place -- one that has adequate flux.If you're using el-cheapo solder with minimal flux in the core and your iron is too hot so that what little flux there is simply turns into smoke within the first second or two -- you will not be happy.Good solder, an iron that's only "hot enough" and good technique are the secrets.A flux-pen can be used if things still turn to custard.

author: JuKu
author_rank: Frequent Contributor
timestamp: August 13, 2012, 06:01:31 am
content: The tip: It might be too big. Unless you have the drag soldering technique mastered, you want to use a small round tip to solder each leg separately, something like the top one in the eBay link The drag technique is actually somewhat difficult, unless you get a concave tip - and I believe the Pace patent is still valid, and Pace knows how to make money on it. (With a genuine Pace that is the easiest way to put down an IC.)The tip might also be old and worn. Unless it takes solder really nice, you are going to have trouble. Your local electronics shop can sell you a tip refreshener, a small jar with hard stuff in it. You press a hot tip in it. You'll get back a nasty smell and a tinned tip like new. But even that only goes so far, at some point you want to trash the tip anyway. As you can see, tip should cost less than 1$ a piece.The materials: Your solder is too thick for modern IC's. You'll end up using too much and can't really avoid it, nobody has the technique to melt just enough from 0.7mm. The flux might be bad also, but that hard to tell without seeing.Your iron might not be as hot as you think, but I guess it is one of the above. I use 360C, but I've done soldering over 30 years, I can make a good joint in the 3 to 5 sec the flux stays good at that hot. I like to work fast, but I would recommend 330 or so for a beginner. If you set the temperature at 330 on your iron, do you get 280 (way too low) or 380 (way too hot)? When you have experience in soldering, you'll know if your iron runs hot, cold or about right from the setting. Without experience or the special temp meter, you just don't know. Which get to my last point:Experience: Like many other skills, soldering is not really that hard, once you know how it is done. But it is might be hard to learn by yourself and with trial and error. Go to your local hackerspace meeting or to a friend and ask somebody to show you how to solder an IC. If you don't know anybody, YouTube might do, but I'd much prefer hands-on show-and-tell. And then, practice.PS: Old IC legs might be oxidized, and then soldering is very difficult to anybody. Just for fun, when you go to buy the tip refreshener, buy a couple of new IC's too, just to experiment. If you tell them you want solder practice and want to buy the cheapest per pin they have, you might get some from trash for free. At the very least, find relatively new scrap boards to take IC off and do clean the legs before trying to solder the IC back.

author: amyk
author_rank: Super Contributor
timestamp: August 13, 2012, 07:13:43 am
content: Quote from: David Aurora on August 12, 2012, 11:46:08 pmI'll agree with this. It's much easier to work with SMD using hot air, and through-hole using a regular iron.What you're doing wrong... is not using hot air.

author: JuKu
author_rank: Frequent Contributor
timestamp: August 13, 2012, 09:08:39 am
content: But do note, that a brute force hot air gun (the type you use for stripping paint) is a different thing than a hot air soldering equipment. I've used the paint stripping type to salvage parts from old boards (heat from the bottom until parts fall off, open the window:-) ), but it is not a good idea to use something like that to mount parts.If he has an old iron, and is just learning to solder SMD, he is unlikely to have a real hot air soldering station. More likely, he has a plain hot air gun, just as he said.

author: amyk
author_rank: Super Contributor
timestamp: August 13, 2012, 10:12:52 am
content: You can get adecent hot air stationfor not much more than the cost of a temperature controlled iron, so that's what I'd recommend getting if you really want to work with SMD.

author: exscape
author_rank: Contributor
timestamp: August 13, 2012, 11:45:06 am
content: Wow, tons of info here, thanks!I figured I would reply after giving it another go, but the replies are piling up a little too fast. I don't want to abandon the thread... so I'll just answer the questions here. Rest assured that I've read and considered each post, though.Quote from: nanofrog on August 12, 2012, 08:10:22 pmI looked up the solder I have: it's Multicore M7 (and, as said, 60/40 0.7 mm), with 5-core Ersin flux. Haven't heard of that before... but according to searches it's meant for "telecommunications and electronics work".I also looked around a bit on buying thinner solder, and ended up with three choices for reasonable prices: Multicore 370 (3% rosin activated, 60/40) C400 (2% no-clean, 63/37) and C502 (3% no-clean, 63/37). They cost virtually the same... If there's a measurable difference, which should I prefer? I assume one with 3% flux, so the decision is 60/40 RA vs 63/37 no-clean.63/37 is supposed to be better of course, but is the no-clean a disadvantage?Quote from: nanofrog on August 12, 2012, 08:10:22 pmThe reason I didn't link is that I don't have a link in English. It's this one:http://www.kjell.com/sortiment/el/verktyg/lodning/lodstationer/analog-lodstation-48w-p40065You'd be hard pressed to find anything cheaper with temperature control.Here are the extra tips:http://www.kjell.com/sortiment/el/verktyg/lodning/lodspetsar/lodspetsar-p40070I just noticed now that the 3rd one looks like a rounded(?) chisel tip... I'll give it a try.Quote from: David Aurora on August 12, 2012, 11:46:08 pmJuKu hit the nail on the head. I didn't call it "brute force" for nothing. It's one of these (roughly, not the exact model):http://www.asia.ru/images/target/photo/50586154/Hot_Air_Gun.jpgI wouldn't use that on anything I intend to work!Hot air is looking pretty good, I'll keep looking into that. What do I need past the rework station? Solder paste, I would assume... Anything else?

author: KTP
author_rank: Frequent Contributor
timestamp: August 13, 2012, 12:09:14 pm
content: all you need is small diameter solder (much smaller than .7mm), a flux pen, and a small tip on your iron.A stereo microscope would help greatly but not required.I have used the above to solder TSSOP and MSOP parts...quite a bit finer pitch than what you are doing...with no problem. If I used .7mm I would have no success at all.

author: T4P
author_rank: Super Contributor
timestamp: August 13, 2012, 01:53:01 pm
content: Slightly different from what i was anticipating ... turns out to be a weller/weller cloneThat's actually not temperature regulated, it's POWER REGULATED!God that's a bummer for yaAll you need is Kester 58 NoClean Flux Code 245 .4mm ...Solder wick, Kester 186 Flux Pen and a 1.2mm/1.6mm chisel or a small conical tipANDDD please, get the Atten 858D before you want to buy a proper soldering station ( well you can do with Hakko 936 clones ... ) it will do you VERY well for soldering SMD and some solder paste (Cheap ones on dealextreme.com ...)If you want to buy a 936 clonehttp://www.aliexpress.com/product-fm/524720490-free-shipping-ESD-safe-220V-HAKKO-936-Soldering-Station-907-soldering-handle-A1321-heating-element-HAKKO936-wholesalers.htmland these tips :900M-T-3CM900M-T-3C900M-T-K900M-T-I900M-T-1.2D/1.6D

author: nanofrog
author_rank: Super Contributor
timestamp: August 13, 2012, 06:26:15 pm
content: AsT4Pindicated, it's a Weller clone, not a Hakko clone, and it's not a proper temperature controlled iron (essentially just a stick iron and a dimmer switch; no thermocouple in the iron).I'd get a proper temperature controlled iron, possibly a Chinese Hot Air Station (some of these also offer a temperature controlled iron + Hot Air). As per the order if you get separates, that's up to you. I'd get the iron first if the combo unit isn't possible due to budget reasons, and learn to drag solder.Also, get smaller diameter solder wire of good quality.Example of a hot air + iron combo unit:http://www.aliexpress.com/product-gs/601986477-yaxun-852-hot-air-gun-and-soldering-2-in-1-SMD-rework-station-wholesalers.html. The iron is a Hakko clone, so there are plenty of tip shapes available, and are inexpensive as well.

author: T4P
author_rank: Super Contributor
timestamp: August 13, 2012, 06:43:47 pm
content: http://www.aliexpress.com/product-fm/507208842-3155-DHL-free-shipping-110V-or-220V-Saike-898D-Hot-Air-Rework-Station-Hot-Air-Gun-wholesalers.htmlhttp://www.aliexpress.com/product-fm/540580977-Free-Shipping-110V-220V-Saike-898D-Hot-Air-Rework-Station-Hot-Air-Gun-BGA-De-Soldering-wholesalers.html

author: exscape
author_rank: Contributor
timestamp: August 13, 2012, 06:53:08 pm
content: Quote from: T4P on August 13, 2012, 06:43:47 pmHmm, looks pretty good. I take it the iron accepts Hakko tips, by the looks of it?Are those two the exact same thing from different sellers, though? Only one of them actually mention the soldering ironin text(the one for $43, though with shipping the price is about the same for me).

author: T4P
author_rank: Super Contributor
timestamp: August 14, 2012, 01:19:15 am
content: The site's to china what ebay is to usPick whichever you likeQuote from: exscape on August 13, 2012, 06:53:08 pmYeah.

author: Michael Weston
author_rank: Contributor
timestamp: August 14, 2012, 08:43:31 am
content: Quote from: amyk on August 13, 2012, 10:12:52 amWhile I agree a hot air solder rework station is the best tool for exscape's work, I do not necessarily think jumping to the hot air rework station immediately is the best action for exscape now because there is valuable experience to be gained from overcoming the soldering challenges.I would not recommend getting the Atten 858D+ hot air solder rework station for 2 reasons:The somewhat loud, whiny fan in the handle might be uncomfortable for exscape to tolerate.When I recently searched for a hot air solder rework station to buy, Atten was not the best quality station. I think this is demonstrated in Dave's review of the Atten 858D+ at 9 minutes and 17 seconds when he takes the handle apart, revealing the fan housing, and he points out the blower fan was intentionally damaged at the factory for an unknown purpose. If the Atten 858D+ was indeed a high quality product, the fan would be proper without any modification. Instead of the Atten 858D+, I would suggest a nicedigital hot air solder rework station from SRA Soldering Products. Or, if exscape wants to stay with a soldering iron for now,SRA Soldering Products' temperature controlled, ESD-safe soldering stationsare quite nice. Every time I did business with SRA Soldering Products, I had an excellent experience that included professional, knowledgeable, polite and friendly customer service; very prompt order processing, very good packing, prompt delivery, and all the products arrived as described on the web site and in brand new condition. I had many questions before my purchases at SRA Soldering Products, and all were answered fully and immediately.

author: T4P
author_rank: Super Contributor
timestamp: August 14, 2012, 08:54:56 am
content: I do not know what you are on about .the 858D is fairly decent and i had one that wasn't whinyAfter all they sell AOYUE's which is pretty comparable and air pumps used in 850-types are harder to find than say a 24V fan of the size we needof course the 898D+ is great, it's an all in one(Shipping the 850-types are far more expensive and the 858D's have a true digital loop not some station that has been cloned right out of a Hakko 850B)

author: amyk
author_rank: Super Contributor
timestamp: August 15, 2012, 10:09:03 am
content: The holes in the fan were probably ground-off mounting lugs that otherwise wouldn't fit. And as the video shows, they're not really detrimental to performance since hot air still comes out the tip like it's supposed to. Could it have been designed better? Probably. Does it matter in actual use? Probably not.

author: T4P
author_rank: Super Contributor
timestamp: August 15, 2012, 11:49:04 am
content: Quote from: amyk on August 15, 2012, 10:09:03 amExactly. But i've only seen this in atten ...

author: baljemmett
author_rank: Unknown
timestamp: August 15, 2012, 03:19:53 pm
content: Quote from: amyk on August 15, 2012, 10:09:03 amI bought one recently (I needed to do one job which was probably going to be unsuccessful, so I wasn't going to spend real money on it!) -- took the machine apart just to check it out, after some of the comments here about build quality, earthing etc.. Looks like I got a good one -- no ground-off bits on the fan cage, power switch and grounding connected properly. Dunno whether quality's improved overall or if it's just luck of the draw, but anyway. A data point.