An alternative technique that also works well is to heat up your board a bit first and then dab a little bit of solder paste onto the pads. When the paste contacts the pad, the heat sort of melts the solder a bit more and it flows onto the pad. This results in less solder spilling over the edges.
@@kazdean I'm assuming the idea of solder paste is to avoid using an iron? I'm a noob at this, so forgive my ignorance. Honestly, I don't want to be soldering smc (at this time I wouldn't have the skill), but I do have an air-fryer 😉
@@Dazza_Doo solder paste is great for mass production using a stencil and a reflow oven, its a waste of time and effort for single pcb assembly. Only wankers use it for single boards or components, it's the look at me "I'm special using solder paste" factor.
Your video really helped me! I just converted a toaster oven into a reflow oven, and I did a few small tests with no components (just solder paste) and as you said, trying to spread the paste on the pads was just moving it around. After watching your video I thinned down a little paste with some isopropanol and dabbed it on and it worked perfectly! My first board looked like it came out of a factory. Thanks so much for posting this - the other tutorials I've seen just show how to apply the solder paste - none of them talked about how they thinned it down.
Good to hear Stephen! Normally you should not have to thin down paste, but when it is old, or not the best quality it can help to get those nice solder joint!
Thanks for this ... it works very well because the connections don't get overwhelmed with solder. Its true, you wouldn't need to do this if you had a solder mask and reflow oven. I have neither and it works a charm.
Excellent! Thanks for the tip. I liked the detailed view of the microscope. It perfectly shows how you're letting the mix with all the solder balls flow onto the pads.
You're welcome Marcel! A microscope is pretty handy for this. Although not necessary. One of those jewelers loupes also works. Only more difficult to film ;)
@@DustinWatts Thats amazing technique for diy soldering. Can you please tell me which microscope you are using. Its quality looks amazing, and i am in need of one such. Thanks for your content
@@deepak_00 In this video I used the Eakins HD microscope. There screen, so hou have to have separate screen to sre what you are doing. If you want a good microscope with a screen: Try this one: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Typ87TGNsy8.html It also has a really good quality and Has a screen. Since I have this one. I use it all the time instead of the Eakins. Plus, It also has HDMI out.
You are a very patient man... I have some custom designed and professionally made PCBs sitting in my shelf for over six months but I dont have patience to sit down and solder all the components. Hopefully if I see a dozen more videos on RU-vid of ppl soldering QFN packages, maybe that will get me all excited again :)
I just bought a bottle of solder paste already mixed. Brush it on with the enclosed brush, heat it and it sucks into the components perfectly. Super quick and easy.
You can use Propylene Glycol (PG), known to be also in vaping liquids, to make your solderpaste more liquid. It just disappears nearly without any residues when heatied up. I can only recommend this, as it works really well. ❤ that!
The great thing about putting QFN parts down on those breakout boards, is that it's really easy to electrically check for bridges. This is more difficult in-circuit, unless you design your board with loads of test points
Great tool tutorial. It's fascinating how the solder takes shape as you heat it. I was going to ask if applicator tools could be made from a syringe but that was answered. I've been watching people artifice tools and it seems something could be made using needles or pins inserted into a handle. Thank you. I like your setup with the microscope. It answers some questions.
If thats a No Clean flux or RMA please clean it off, if the chip runs at 90c or more the flux will become an acid and eat away at the copper. Also remember flux moves away from heat (Ice flow effect) taking oxides with it, it also crystallises at around 380c rendering it useless. One other thing to remember is the ramp up temp, component data sheets will states this, normally 2deg C per second, so avoid using an iron (internal component damage). Thanks for the video, Michael
I assume that cleaning a board after soldering is something we all do so I did not mention it in my video. But you are right! When you are done with you board, clean off the flux. Even if you just use a the "normal" soldering iron, clean your board folks! :D Thanks for reminding us again, Michael!
wow that's really cool. and a bit complicated due to the size. But this helped me further understand "heat" is always the worst enemy of solid state components. The low melting point of the solder paste.
You are correct. When it comes to heat (which you have to use otherwise you can solder). More heat for a shorter amount of time, is better than less heat for a longer time. Less time is better then less heat. All within reason off course :)
From the vid I thought your reflow time was rather short - if you check (some) FTDI datasheets they have a desired heat profile. I try to do this by pre-heating the board for a minute with my hot air gun, then come in closer and flow the individual components.
I use a heated plate (thermo controlled) for melting the paste. If you heat the PCB a little, the paste will stick. If you keep the syringe a bit warm (eg by keeping it near the heating plate), the paste will flow out easily.
You can also use solder wick to remove excess solder. It is actually nearly impossible to remove too much solder this way from this kind of solder joint.
A "tip" when you want to remove just a little solder: Add fresh solder to the tip, wipe it clean, quickly apply it to the joint before it oxidizes. The tip will take up just a little of the solder. That is what Dustin did at 10:26 when you hear him say "clean it" and then wiped the tip across the row of solder joints.
I do not use this method often, I use stencils most of the time. But for reworking a component I do use the "dragging" part of this method. I usually have my iron set to 350 degrees Celsius. That is fine if you drag quickly. You could go for a lower/safer temperature if you prefer. I have had no issues with 350C and a quick pass.
138 °C solder paste or tin is only intended for removing components. By adding it to the already existing solder, a reduced soldering temperature is obtained and thus the removal of the component becomes easier. 138°C tin or paste must not be used to make new solders! All such low temperature solder must be carefully removed before permanent soldering. Permanent soldering either standard for lead solder with 60/40 tin or lead-free.😊
This is the first I have heard of this. And I dont't think this is true. 138°C LT solderpaste is used for stenceling a lot. Brands like Chipquick sell them and I have used them a lot myself. The profile calls off course for a peak of higher then 138°C (out of the top of my head is it 165°C). Which is used for manufacturing and not only for re-work. I'd like to get a source for you information because I believe you are wrong.
Thank you for sharing. I have a 0.4mm pitch TDFN-10 package I need to solder. There was no other package option for the chip. I never did solder paste soldering, I'll try it today
@@DustinWatts thank you Dustin. You won't believe what happened. There was no footprint drawing at the end of the datasheet. So I checked Analog Devices TDFN-10 Package. I made the PCB footprint: pitch was 0.4mm I got the PCB. I saw it'll be tight. Very tight. I didn't fit. I lost my mind, didn't know where I made the mistake. I printed the Footprint 1:1 scale on paper. I was Bigger than my footprint. Then I went back to the datasheet. There was a link around the middle to the technical drawing of the footprint with....0.5mm pitch and bigger pads. Daaamn. There is a 0.4 and 0.5mm pitch TDFN package. Shiiiit. it was like 6 years since I screwed up a footprint. Pay attention everyone
@@GaborGubicza Aaaw that sucks. But yeah always check the footprint of the part you are ordering. Sometimes, as you now have experienced, there are different pitches per part. Also some parts maybe be wider or something else is different. Always check the partnumber and then recheck de datasheet. Still in you case not a real big disaster, just some extra work.
Without a microscope and with my old eyes, surface mount stuff is 50/50 guesswork. If I can get one pin soldered down solid, I flow solder over all the other pins then use solder braid to try to fix it. As you can guess, I try to avoid SMD stuff whenever I can :D
From my point of view that's a perfectly acceptable technique :) When I prototype, I like to get the biggest package I can. Unfortunately sometimes the biggest package is still very small!
Interesting technique. Appears to work very well. Is there a downside to just dumping a load of the flux from the syringe into the pot of flux and mixing it up en masse?
I think you meant dumping the flux in the solderpaste? Well... there is already flux in the solderpaste. Basically, solderpaste is nothing more than little solder balls floating around in flux. However, if the solder paste is too dry, adding some flux and stirring it can "freshen it up". But for this technique I would do it in small batches, because it is a bit more flux then you actually need when you do it normally with a stencil for example. So the downside would be that you would have a jar of solderpaste that is too fluid for normal use.
Would tinning the pads with solder (from a wire solder), adding flux and reflowing work? I *feels* to me you'd have better control on the amount of solder per pad
Sure that would work! There are more and better ways to get a QFN chip soldered. This absolutely not a tutorial. What al lot of commenters missed is that this is my response to the question "I have solderpsate and a PCB. Like a breakout board. Nothing more, how would you do it using the paste?" Personally I almost never do it like this. I get a stencil for my own boards. And if I want a QFN on an breakout board I go through al my designs an hope I have that footprint on a stencil somewhere :D And as the number of boards grow so do the numbers of stencils and the chances I find the right one. The just some Kapton tape and I can use the stencil :) Also there are stencils available for all sorts of foot prints. You can just buy the one that has the one you need on it.
@@DustinWatts I thought the comment made sense because even if someone says "I have solder paste and a PCB", it's pretty likely they also have solder wire. Even if they don't, they should probably buy some as they'll need it at some point (whereas I kinda understand the will to avoid buying a stencil you'll use once). But thanks for the very thorough answer!
First of all don't put too much paste (i over did it a little) But with and QFN with an e-pad (ground pad on the bottom you ill never know unless you have x-ray machine. How ever you can check every pin with GND. To see if there is continuity. And fixing it, I would start over.
Bridges around a QFN chip are the easiest to fix in my opinion. Just run your soldering iron tip along the side of the chip. It is even more easy if you add some flux :)
I've seen some videos on that. I usually order a stencil when I order boards. This was more on how I do it when I have small footprints and no stencil.
An easier way is to bump the pads on the PCB using ordinary soldering wire anda soldering iron. Make sure that the ground in the middle does not get to much solder (to much and the chip will be lifted). Then put the chip on and heat it up. When the solder have melted you put some flux around the chip and it will "snap" into place with very little risk of getting bridges between the pins.
Hi there Dustin, I recently got into using solder paste since I used flux with solder wire with soldering iron. How do you determine the amount of solder paste you need to apply to get an even amount whilst at the same time minimizing short circuits/bridges? How do you know if you have not created shorts under the pads of the QFN when soldering? Very good job on the soldering and excetellent explanation. Mateusz
Hi Mateusz! To check for shorts you can use a multimeter on continuity mode. That should give you a good idea. On professional assembly lines they use an x-ray machine to check underneath the chip, which unfortunately most of us don't have ;) Determining how much solder paste you need can be tricky. I have found that most bridges form on the outside so you can spot them. A better practice is to use a stencil, this will ensure you have the correct amount on each pad. A standard stencil has a thickness of .125mm and the cutouts are just a bit smaller than the actual pad. So if you get in the ballpark of that volume you are ok. Most of the time though, you can get away with using a lot more and not have bridges. It is however also something that you will get a "feel" for when doing it more often.
Nowadays I have so many stencils laying around that I have almost every footprint somewhere on a stencil. So for mission critical applications I do not want to hand solder I just use a taped off stencil. Leaving only the component I need. But for a quick job this method is still valid :)
The solder paste is getting too dry, when it is old. Mixing it with flux gel was my rescue, too. The syringes are not great, it helps to have this contraption, that pushed more equally, because it has a thread. I use it for flux and for solder paste. The cooles diy method of soldering SMD is a hot plate. I have a big one (20cm x 20cm), but that‘s an overkill. 10cm x 10cm is usually sufficient.
Problem with solder paste is it has a shelf life of about 6 months and needs to be kept in a fridge. So it's not really economical if you don't get through it in time. So adding extra flux I suppose extends it life, as the metals can't really go off. They might oxidize which might hinder flowing.
I'm thinking of buying a paste from Chip Quik which is advertised as thermally stable. Meaning you can store it outside a fridge. That should mean it wouldn't go off as quick.
@@DustinWatts my view is always buy solder and flux from well known distributors, so you can see the MSDS sheet. Which ChipQuik product did you look at I can't find one on their website with a long shelf life but i did not look too hard. but for Part Number: SMD291SNL250T3 www.chipquik.com/store/product_info.php?products_id=520001 Shelf Life Refrigerated >6 months, unrefrigerated >2 months ? is that not the greater then symbol '>' so if you don't refrigerate it it will last greater then 2 months. 12 months is greater than 2 so how long does it last :) maybe they need an "up to" symbol.
That's definitely what one might call a low temperature solder. Pure tin and very cheap unleaded solder is around 230°C Unleaded standard electronics solder with silver and additives like SAC various grades is around 220°C Leaded solder old style 60-40 like used in the 70s is is 195°C thereabouts. It's still useful because it can lower the melting point of unleaded solder to ease desoldering more efficiently than newer grades. Leaded solder eutectic which is more modern is 183°C, this is what you get as a high quality rework solder, obviously it's not used in manufacturing except in fields which demand high reliability and high vibration resilience. My absolute favourite is sn62pb36ag02 it's magic, it never fails. 136°C that's a tin bismuth low temperature solder. It's a little on the brittle side i think.
You might think it is brittle, but I have used it in some projects for my self and after years still have good connections. My favourite solder paste atm is the TS391LT which is Sn42/Bi57.6/Ag0.4. But the fact that is can be stored at room temperature is great. And after reflow I get some pretty nice connections and it cleans very well!
Nice demonstration Dustin. I see others mentioning the shelf life of solder paste. But your application is likely also a good way to make use of older solder paste, given my understanding that the shelf life issue is related to the flux going off / drying out. By mixing in some flux with the paste that you intend to immediately use, you can rejuvinate older paste. But only when you are going to use the mixture straight away. :)
You are welcome. Since this video is doing pretty good, I might make a version 2 of this video. Even better I hope! But I am glad you are helped by this video!
Try using a hot plate instead. You will probably avoid having any bridges at all. In a first stage you apply the paste to hot PCB and it should adhere to the pads only, and in a second stage you place all the components in place and re-heat it to solder the components to the board. As long as there is enough paste, it should be easier to do without any rework. If you get good results, please make another video and share your experience. The stencils aren’t cheap, and that should help with lowering the cost. Another alternative is to try to make stencils with plastic sheets cut with a laser. Tools like KiCAD can provide the drawing on the pads, and once cut, the plastic sheets should be good for a few rounds. Having a laser is no longer a luxury. It’s actually such a versatile tool that it pays for itself. It’s quiet, doesn’t produce the same mess as a milling machine, you don’t break bits, and as long as you take the necessary care, it’s quite safe as well.
I agree there are way better way. Once is what you just said. The context of this video was how to to it with nothing but paste and a heatgun. I was more a "how would you do it"-like video then an actual tutorial. I can make one. I thing there is some real demand for something like that.
And mine was just a suggestion as well. There are options out there, and plenty of creative people. Keep the ideas coming, it’s always interesting to watch.
@@DustinWatts maybe one day I will be fortunate enough to be able to see a comunal science club. No politics, no bullshit, no state. Just people who love science and want to learn and have fun together. Until then, I’ll watch videos and make my own stuff.
@@Ferreira019760 I think creators on RU-vid are doing this quite well. Lot's of people who create just because to love t create and ope other people learn from it. At least that is how approach my channel....
Nice method sir. I will try a mix myself along with a hot plate to assist in the solder attracting itself to the pads. I have a laser solder gun on order to. And am looking into a full optical camera microscope with laser attachment and a CNC joystick operated mechanical robotic arm to fight my Parkinson's disease. I'll use a micro vacuum tipped hyperdermic needle to grab and release chips as needed. These shaky hands really stink. It'l be about $5000 bucks to get around them.
Absolutely. There are way better ways of applying solder paste to a board. This was a response to someone and not a "how to" video :) Ow, and I agree if there are other things already on the board in the neighbourhood you don't want to affect, use the accessories!
Unfortunately yes. It i a cheap brreakout PCB. Although a lot of board houses also don't do soldermask when the gap is to small. It will cost you extra.
Hi! I use the Eakins microscope with Sony IMX290 (IMX307 is a upgrade) sensor: s.click.aliexpress.com/e/_DklhMDt My soldering iron is the TS100: s.click.aliexpress.com/e/_DmGxfsF The iron tip is the TS-I or TL-ILS: s.click.aliexpress.com/e/_DkbLNHN And the Hot air gun is an 858D style: s.click.aliexpress.com/e/_DFJEB9N Hope this helps!
Been using that method for years (making the paste runny) -- HOWERVER don't make it too runny, otherwise it doesn't tack enough, and you'll get tomstoning when doing small passives. There's a "just" kind of consistency that is a bit gloopy and stick to the pad when you touch it, but doesn't 'run' off.
@@DustinWatts You could also experiment with some (a little!) solder paste mixed with quite a bit of *plumber* flux... make a mix of that, coat a copper surface with like 1mm of the thing, and pass your soldering iron in the gloop to 'paint' the copper.... magic tinning! I'm fairly sure I invented this one. I used that for years to tin DIY copper etched PCBs, however these days, it's a lot quicker to hit F5 on the JLPCB 'progres' page than making my own pcbs :-) ;-)
@mikedenmark7854 Technically yes. But you can check the pins from the outside you you can rule those out. And the pad underneath of the chip is ground (usually for heat dissipation), so if nothing shorts to ground you can rule out a short to underneath the chip. And of course, don't put heaps of solder paste on. A little is enough.
@@DustinWatts I have tried it with a stencil Advantages in repairs 1. In conjusted less place it puts at ease 2. As solder paste is minimum and solder to the right place minimum chances of bridging Minimum time
This was made with the Eakins HDMI Microscope with SONY IMX290 sensor. I did a review of it a while back on my channel: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-b3sHHVctGyU.html
I like handy things :D I think you mean for applying the solder paste? For 2$ it is definitely worth a shot :D In fact, there is already one in my shopping cart on Ali :P Thanks for the tip!
@@DustinWatts They are very handy, the smallest I have is 0.15mm (red), the largest is 0.45mm (black). The smallest I almost never use, same with the largest. Mine are aliexpress bergeon copies.
@@wombatau I'll order all colours and see what works the best for me. They are cheap so worth actually giving them all a try. Btw, I always use stencils. This was just a reaction to some one who asked what can I do when I have no stencil, no syringe, or anything, just paste and a board.
@@DustinWatts Awesome 👍 I don’t know if it helps also, but sharing because when I learned it, it kinda blew my mind. A bit of a secret watchmaker trick with tweezers and tiny parts is they dress their tweezers with a stone, as in, make them a perfect surface and also rough it up a bit. That’s how they do such fine work without gears and springs pinging off into oblivion. I learned it whilst trying to learn how to fix a couple of watches and a clock. The clock works great. The watch.. well.. one of them I fixed works pretty good, but the other one I sent a jewel into space. I then learned about dressing the tweezers.
@@wombatau I always feel amazed if I learn about something that is intended to use for something totally different, works perfect for what I need it for! A example, I use dentist tools for some electronic application. Works like a charm!
This is Really good,I've been thinking about working whit solder paste,I work on turntables,I do tonearm rewiring ,RCA replacement,pcb boards replacement etc,this will work for me Really good,what's the best solder paste brand to work whit ? Great vid thanks !
Your are welcome! Nowadays I use Chipquik TS391LT. But the cheaper Mechanic solder paste is also really good! For example the Mechanic XGZ and XGSP series are pretty good.
@@DustinWatts OK cool, wanted to make sure I hadn’t missed something. I’m gonna have to try this. I think the manufacturer of the solder paste we use (chipquik) sells the exact same fluxes that are in the paste as gel fluxes.
From own experience and seeing lots of such Video IMHO bridging is caused by to much solder. If you are frugal with it it does not matter if you lay a string across pads if it is narrow enough. During reflow it will retract back to the pads and break up over the solder stop due to the surface tension. I smeared once the paste all over the pads of a qfn. But using a 0.1 mm thick stencil the quantity was small. At the end it reflowed relay beautifully.
For regular use it is. Sometimes paste is a bit dry or when you need it to be a bit more liquid you can add some extra flux. This trick I use when I do not have a nice way of applying it. But generally when you have solder paste, the flux in there should be sufficient.
It would worth a try to make the solder paster more fluid and immerse the chip pins into it. Then all the pins would get enough solder paste and those won't be contacted at all ( compared as it would in case of more solder paste than using a wire).
If you have to press really hard on your flux syringe and still barely getting anything, just get a thicker needle. The higher viscosity the thicker needle you need
I usually set it to 400 degrees, but with very low airflow and a distance of 10cm from the board. Going in small circles until the solder starts reflowing.
To see those you have to have x-ray eyes. But pushing down on the ship when the solder is still molten, will usually push excess solder to the outside, which you can then clean up with a soldering iron....
You should use more flux when you clear the bridges. It will be way more easy for you. And also to not wander if the middle pin is soldered - when the chip is settled press it to the board it will push out all excess solder out and with enough flux it will guarantee that there will be no bridges under the chip. Continue pressing until solder hardens. Clean the outside bridges adding more flux. Last step - cleanup the flux.
Flux is your friend you are right! Pushing on chips when soldering them is something I rarely do. You have the possibility to create a short between the EP (ground pad) and a pin. I usually let them just float on the solder.
@@DustinWatts Yes you are right about the short that might happen, but if you use more flux it just won't happen, because the solder will be pushed outside of the chip. And yes, there will be some solder blobs on the legs of the IC, but again with more flux and soldering iron you will clean them easily.
Why would you use 400° when the low melt literally says 138 on it...now that the board has hit high temp already, any future repairs have a higher chance of damaging it from multiple heating and cooling.
Because the airflow is very low the board never reaches 400 degrees. I'll do a followup video with a thermocouple so you can see the actual temperature of the board.
First make sure all the pads are nice and clean, use some IPA (99% pure alcohol). While using your heat gun, try to take longer. Start higher (about 10cm/4") with your heat gun and heat up the surroundings as well (try not to melt things :P). Make little circles and go slowly lower and take your time to melt every little ball. It might take while. Don't rush... It could also be that your solderpaste is a bit dry. Then you could try to mix in some flux. Good luck!
@@DustinWatts I already mixed mine with flux to thin it! I did preheat to 100c for a minute but maybe it wasn't enough (although my readings are probably inaccurate as the PCB is reflective) maybe i'll try cleaning my boards first with IPA
@@ameliabuns4058 I think that will also help. Just for reference: My settings on my heatgun are 400° but with an airflow of 1 and a bit. So high temperature and minimal airflow.
indeed...why am i messing with this paste...nice for production runs+stencil but kinda tired of hot air and then needing to rework it anyway with an iron/wick
