Correcting a soldering mistake - Page 1
Forum section: electronics / beginners

author: IamSynthetiC
author_rank: Regular Contributor
timestamp: September 21, 2020, 04:36:11 pm
content: GreetingsI tried to solder a HV5222PG-G (QFP-44 Package) and i made a huge mistake both when soldering and when tried to correct it (Images bellow)For some reason the wick does not absorb the solder, even after adding flux. Am i making some rookie mistake ? and what do you normaly do in such a situation ?Thanks in advance

author: DuPe
author_rank: Regular Contributor
timestamp: September 21, 2020, 04:43:41 pm
content: I am sure just adding sticky flux and reheat will solve that issue

author: Ian.M
author_rank: Super Contributor
timestamp: September 21, 2020, 04:49:50 pm
content: It looks like grossly inadequate heat transfer to the work.What iron are you using, what bit is in it, and what temperature is it set to?Post a good closeup photo of the bit.What flux are you using?Also, if you take a short length of fresh desolder braid, place it on a piece of cardboard and try to tin the end with solder, using ordinary flux core solder wire and your iron on whatever setting you usually use for soldering wires, what happens?

author: alsetalokin4017
author_rank: Super Contributor
timestamp: September 21, 2020, 05:27:43 pm
content: Add flux, use a hotter iron, add more solder to the blob first, add flux to your solder wick.

author: Jwillis
author_rank: Super Contributor
timestamp: September 21, 2020, 05:31:52 pm
content: I agree with what Ian is saying and would like to add that some solder wick does not have flux added or has very little. So don't be afraid to use more flux when using solder wick . A good liquid flux is best for surface mount because clean up is much easier. Also using to low a watt soldering iron can transfer excess heat into the component causing damage before melting the solder. High watt soldering irons keep the heat more localize to the point where the solder is being made.

author: Renate
author_rank: Super Contributor
timestamp: September 21, 2020, 09:26:32 pm
content: It looks like there is not enough heat transfering and you're just abrading the top layer off.Don't get too aggressive mashing that around, you may lift a pad.My favorite hint:Take an old soldering tip and saw the end off, file it so that the end is about 1/8" round.You can tin it if it will take it, but not absolutely necessary.Use the soldering iron held vertically over the solder braid.Prepping the braid helps.Tin the end of it, then trim it so just a whiff of solder is on the end.

author: tkamiya
author_rank: Super Contributor
timestamp: September 21, 2020, 11:48:47 pm
content: Are you using good quality wick? Cheap kind won't work well no matter how much flux you add. Been there, done that. SOLDER-WICKS brand works well. They are expensive. But worth it.It also looks like alloy is contaminated. I would add some fresh solder, fresh flux, then wick it off with a good wick.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 22, 2020, 05:06:04 am
content: When I worked in Broadcasting, the "gospel" was:-De-solder completely, clean the pads, then redo the soldering from the beginning.

author: Jeroen3
author_rank: Super Contributor
timestamp: September 22, 2020, 06:55:30 am
content: Use the right amount of flux.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 22, 2020, 07:14:33 am
content: Quote from: vk6zgo on September 22, 2020, 05:06:04 amthe gospel is incomplete. for full IC replacement it is correct. but in this case, some of the posts will complete the gospel... the problem is not the amount of flux (the wrong type of flux? maybe) we can use very little flux to get the job done. but the main problem is lack of heat to melt the excess solder.

author: Psi
author_rank: Super Contributor
timestamp: September 22, 2020, 08:27:26 am
content: I agree with what others have said.There is something wrong with your setup/equipment/technique.But it's hard to know which it is.Pretty sure it will be one of these..- Iron temp too low- Soldering iron tip is worn out and solder is not wetting to it, or maybe it is, but only in one tiny area.- The solder you're using is wrong type. (make sure it's intended for electronics)- Not enough flux (make sure it's intended for electronics)- The end of the soldering iron tip is too tiny, (i've seen people try to use the most ultra-fine iron tips to solder SOICs and they never get anywhere because you just cannot get enough heat transfer)- Your solder wick could be fake/counterfeit and solder will just not stick to it no matter what you do. (Maybe they used copper plated steel)

author: NivagSwerdna
author_rank: Super Contributor
timestamp: September 22, 2020, 08:51:56 am
content: Firstly I am a huge fan of the HV5222 and friendsWhat you have done is OK so far but you need to flood it with liquid or gel flux and reheat and by dragging gently across a d away it should come good.Watch a Louis Rossman repair video to get an idea.Flux and heat is like magic

author: Ian.M
author_rank: Super Contributor
timestamp: September 22, 2020, 09:47:01 am
content: *GOOD* flux +heat is like magic. However there are plenty of crappy fake fluxes out there on Ebay and other direct to customer marketplaces, a significant proportion of which are useless or even worse than no flux at all, and there are even plumbing fluxes that will destroy your board in months or even weeks, so lets wait for the O.P to say what they are using.Louis Rossman is so liberal with flux because 'time is money'. He's also frequently working with water-damaged corroded parts and boards where he cannot afford to take any chances when trying to get a joint to whatever slim sliver of sound metal may remain in the track or pin. He's operating a commercial repair shop in NY, paying NY rent and overheads, and has a swept frequency ultrasonic cleaner to clean up the horrible mess of gel flux residue he leaves behind wherever he works like the slime trail behind a slug!Without the time pressure (or the ultrasonic cleaner), you'd be better advised to use quite a bit less flux. A pool of flux sitting on top of a TQFP or QFN isn't doing anyone any good except the flux manufacturer! As long as the whole joint is under a small pool of gel flux, any more isn't doing anything useful.

author: IamSynthetiC
author_rank: Regular Contributor
timestamp: September 22, 2020, 12:31:40 pm
content: Thank you all for your replies.For my soldering iron i am using a brand new JBC CD-2SQE with a wedge-type tip (largest one i have), i noticed the lack of heat transfer and i turned the temp up to 400C with little change. I also own a cheepo YIHUA 8786D soldering iron-Hot-air-station,should i try using them both at the same time ?As for my wick and solder, i am using some cheep chinese solder with i hate as it melts wierdly, and Stanol wick. I have watched many videos on soldering and desoldering (Louis Rossman's Videos aswell) and i can tell with great certainty my solder does not behave the same, no matter the flux.As for flux, i have a case of solid flux and a bottle of liquid for smd. They both seem legitimate and work at times.My primary suspect is the solder for obvious reasons (picture below), i will order another one.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: September 22, 2020, 12:42:39 pm
content: I use... Sn62PbAg2 - 0,35mm 100g, EDSYNI really don't like thick stuff for anything apart from connectors...Treat yourself to some proper solder.I never have my soldering iron set for more than 350C, that HV5222 should be easy.

author: Renate
author_rank: Super Contributor
timestamp: September 22, 2020, 12:54:57 pm
content: That's the problem with your solder! It doesn't have flux, it has "flus".It's also kind of large at 0.8 mm.I use 0.5 mm (0.020") and NivagSwerdna just quoted 0.35 mm.It can be difficult to drive sufficient heat through the larger sizes of solder wick.That's one reason I recommended using a sawed-off used soldering tip.You don't have to worry about setting the heat too high and burning the tip.And it really can't be beat for heat transfer.

author: Ian.M
author_rank: Super Contributor
timestamp: September 22, 2020, 01:03:07 pm
content: Hmm. Something is sucking heat out of those joints faster than your iron can heat them. 400 deg C is already a bit on the high side for normal work with Sn60/Pb40 solder, so it isn't a settings error. If you've got it, an image of the top and bottom copper layers of the PCB layout round that chip would be helpful.How large is the wedge tip? I'm assuming that its bright and freshly tinned, with no black spots across the whole face of the bit. If it isn't wider than the desolder braid you haven't got a snowflake's chance in hell of doing anything useful with it.Personally, I use 1.2mm Sn60/Pb40 solder for all except very fine SMD work (for which I go down to 0.5mm solder or even 0.3mm solder), but to do fine work well with thick solder you need quick reactions, excellent fine motor control and a very steady hand. Most users do better on fine work with significantly thinner solder.Its hard to determine if solder is the correct alloy without an accurately calibrated heatsource to determine its melting point. Neither of your irons are likely to be closely calibrated, but if you try melting some of the solder on a freshly cleaned bit with both of them, then turn down the temperature till the solder on the bit gets (and stays) 'mushy' you should be able to do a rough check. Testing the solder blob with a wooden toothpick is the easiest way of checking its state. Sn60/Pb40 solder should go from fully solid to fully liquid over the range 183 - 190 deg C so if you are seeing a much wider or higher temperature range with both your irons, odds are the solder's fake.Also, you can take a 1" square of plain copper clad PCB, and clean it with scouring powder and a little dish detergent till its bright copper with absolutely no fingerprints or other tarnish, then rinse it first with water and then with IPA, taking care to only hold it by the edges and only touch the copper surface with a clean brush or wipe, dry it thoroughly on kitchen paper and immediately (before it has a chance to tarnish) melting a 1/2" length of your solder on it using your hot air tool with an orbiting motion. If the solder is any good and has usable flux, it will melt and wet the copper. If its got good flux, it will spread over a significant area without you poking or otherwise disturbing it. If it melts and balls up, failing to wet the copper, the flux it it is not doing its job so must be fake.I would suggest replacing the solder from a reputable European supplier e.g.TMEor any of the major international first world based component distributors, rather than local shops that may be having supply chain integrity problems or Ebay, Amazon and the various Chinese direct to consumer marketplace websites, which are full of fakes.Meanwhile, your board should be saveable with lots of flux and hot air reflow, picking up excess solder with one of your soldering irons with the largest bit you have, freshly wiped and set at a temperature only a little above your solder's melting point, without using any braid.Don't try to use the braid unless you've got a bit at least 50% wider than it. If so, you can try it with extra flux, and the very tip of the braid tinned with solder, then cut back till the solder in the braid is less than the bit width to provide initial good thermal contact between the bit and the joint through the braid. You *MUST* keep cutting back the solder-loaded braid as you work, only leaving a couple of mm with solder at the end for good thermal contact to the next joint.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 22, 2020, 01:10:32 pm
content: Since you've got a hot air station...A very common way to rework such chips is to screen the surrounding areas with aluminum foil and kapton tape, so only your IC is exposed, and then heat it with hot air untill the solder melts.Another way is to use your hot air to pre-heat the board upto 100C to 150C or so, and then use the soldering iron to add more local heat.Also:Some wicks are just wicked and won't work at all.Have you had luck with using this same wick on other components?Maybe you can get some old PCB's from somewhere to practice your (de-) soldering skills.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: September 22, 2020, 01:15:33 pm
content: Make sure the iron tip is tinned, bright and clean. The little solder on it should transfer to the wick when you use it. Going in dry will get you nowhere, even with the iron cranked up way past where it should be (which burns flux and causes the tip to oxidize that much faster). Immersing everything in flux can still help (a poor liquid is better than awful air, at heat transfer) but not as good as proper solder.If that's a multilayer board, you may also want to preheat, or use a hot air machine. Yes, both can be used at the same time. Have an assistant hold it (or get some hands-free clamps).Tim

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 22, 2020, 02:48:46 pm
content: Quote from: IamSynthetiC on September 22, 2020, 12:31:40 pmtry it on another pcb that is simpler and easier, with those flux and wick... if they work on another board, then your supply is not the problem. some pcb like graphic cards or power electronics have very large heatsink copper clad inside laminate that it sucks heat from your soldering iron before it can melt anything. preheat the pcb with hot air is one solution. but if your supply is not working properly on simple board than i will be surprised...as i think i'm the one here with crappiest supply. ps: i keep solder blobs recovered from previous work/rework and sometime collected and remelted from solder sucker tank. that i reuse for various purposes, mainly to desolder ICs, and to add where a point/joint needs very large amount of solder such as large battery tabs or connecting thick wires, or probably one day to make fishing line weight (yes i have few kilos of melted tin here sitting for many many years, although its very unlikely) those blobs have depleted (zero) flux, but i can make them live again by just adding fluxes, so in worst condition that you got a crap solder is still not an excuse in the presence of a flux supply, ymmv.

author: lukego
author_rank: Frequent Contributor
timestamp: September 22, 2020, 03:04:57 pm
content: Sorry to pipe in without much new to say but I love this kind of troubleshooting!I'd agree that the problem is probably a dirty oxidized tip not transferring enough heat and/or flux that doesn't work very well. You should be able to easily melt solder onto the tip and see it spread out nicely, otherwise the tip needs cleaning with flux (from fresh solder, or from brass cleaning-wire ball in the stand, or just dispense some flux and poke the iron into that followed by fresh solder.) Repeat cleaning until the tip takes the solder well.Or backup plan as others have said just put on PLENTY of flux and heat the joints with hot air. If the flux is any good the problem will fix itself. Maybe need to add a little extra solder with the iron but guessing not.

author: Psi
author_rank: Super Contributor
timestamp: September 25, 2020, 09:26:02 am
content: I think you probably have shit solder or a bad iron tip.Bad/fake iron tips absolutely exist and make it a nightmare to solder anything. The solder just wont stick to them or flow correctly.Can you put some fresh solder on your iron tip and then post a close up photo of the tip?You could do an iron temp solder melt test. To get a rough idea if your iron temp scale is accurate.- With a cold iron, set temp as low as it will go and turn it on.- Place some solder over the tip so it's resting on the end.- Now keep moving the temp up in steps of 10deg C every 20 seconds and tell us at what temp the solder first melts.

author: IamSynthetiC
author_rank: Regular Contributor
timestamp: October 01, 2020, 04:45:47 pm
content: Hi again, sorry i took so long to reply, i was waiting on some new solder and was consolidating my results and answers.I followed most of the advice, cleaning my tip thoroughly, using plenty of flux, and adding extra heat with the hot-air. Most of the solder came off, but a layer remained stuck on the "floor" of the PCB rendering the board useless.My new solder (EDSYN 0.35mm Sn62Pb36Ag2 arrived today and i immediately tested it on a spare PCB with many smd components. The differences where night and day. Low melting temp (200C), clean and effortless desoldering with wick and it was easier to stick on the tip.I managed to solder some packages ranging from 0201-1208, TSSOP-8&16, and some wierd QFN variants. I'll try to solder the original IC on a brand new board tommorow when the sun is up.Someone also asked for a photo of the PCB layout, so here it is. (big chuncky ground planes sucking up heat all around)Thanks again

author: NivagSwerdna
author_rank: Super Contributor
timestamp: October 01, 2020, 05:04:43 pm
content: Quote from: IamSynthetiC on October 01, 2020, 04:45:47 pm

author: Psi
author_rank: Super Contributor
timestamp: October 02, 2020, 09:42:28 am
content: Yep, 3 things that should always be purchased form legit sources- Solder Wire/Paste- Solder Wick- Iron tipsBut i'm glad you sorted out your problem

author: Ian.M
author_rank: Super Contributor
timestamp: October 02, 2020, 09:55:36 am
content: Quote from: IamSynthetiC on October 01, 2020, 04:45:47 pmIf the bad board hasn't been cooked to death, try flooding the QFN footprint with the good solder. You can probably dilute the remaining bad solder to the point you can brush most of it off and clean up the rest with desolder braid and extra flux.Rigging some sort of preheater under the board will be a massive help. Even an electric hotplate set really low (well below the melting point of solder) with a thick corrugated cardboard safety screen with a cutout for the board so you don't burn yourself on it would be a massive help as if you can get the whole board up to around 120 deg C, heat loss from the solder joint into the ground plane will be approx half what it would be with the board at room temperature.

author: IamSynthetiC
author_rank: Regular Contributor
timestamp: October 07, 2020, 10:48:03 am
content: It has been a while so I though I'd give an update.Problem 1- Bad solder. My old solder was terrible but cheap and got the job done (mostly), and as I don't solder often, I decided to bear the inconvenience, and use it all before buying another. Now, having bought a new quality solder (aswell as other quality consumables), i can say with great certainty i am not going back to that horrible mess of a solder.Disaster 2- This was a board of my design that i ordered though JLCPCB. I am in no way a professional, and that goes to show when i decided to use a solid ground planedirectlyconnected to each pin (not spoked). Therefore when soldering, the ground plane sucked all the heat. Proving a lot of you right. Using the hot air along the soldering iron helps, but soldering is still difficult, especially when it comes to the VQFN packages with their heatpad connected directly to ground.This board was intended to be a mere prototype, so I am not too unhappy with the partial soldering I managed to do. The important things are sitting happily on the board and are ready to be meddled with.The things I took away from this are:Buy good quality consumablesPreheating is your friendGood PCB Design#Don'tBeAnIdiotThank youallfor help

author: Psi
author_rank: Super Contributor
timestamp: October 07, 2020, 11:53:37 am
content: On rare cases using bad solder can damage the iron tip.Another useful thing to know.Don't be tempted to use your iron tip to melt plastic. Some types of plastic will permanently ruin your iron tip, even with one exposure.(If you must do it dedicate an old iron tip for plastic use)

author: NivagSwerdna
author_rank: Super Contributor
timestamp: October 07, 2020, 02:07:50 pm
content: Quote from: IamSynthetiC on October 07, 2020, 10:48:03 amI looked at the screenshot of the PCB layout earlier in the thread and around the driver IC it looks fine... there really isn't much in the way of copper mass there. Thermal reliefs will help but I'm not sure you are seeing that hugely. For the under the chip pads which are via stitched to a mass of copper then you will likely need to hot air pre-heat it first before adding the chip.Maybe you need a cheapo thermocouple from fleaBay to check you temps...? Perhaps your soldering iron is running too cold.