You are welcome! :)

Yes! Good tip!

if you are going to that effort, just add regular solder to the pads with an iron, flux paste will keep it from bridging

@@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.

@@kazdean 🤣👌 I better get pumping

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!

Excellent! That was the last puzzle piece -- isopropanol! Thank you.

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 ;)

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 :)

Glad it works for you as well as it does for me! :)

Once you start you wont stop! :)

Thank you! There are a lot of better options, but in a pinch.... this could work you 😀

You are welcome! Hope the transistor tester comes out good!:)

Thanks Riesmoos! I like the Eakins microscope as well. I bought the FTDI from Mouser, so it better be genuine! :)

You are very welcome! Have fun with al those beautiful QFN IC's out there! :D

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.

Indeed it is. That's why I usually order a stencil when designing a board with QFN chip.

I now look pretty stupid as I typed that comment just before you did that check in the video!

You are welcome @Dee C!

You are welcome! Glad it helped you in some way!

Thanks for the tip. Never used it or heard of it, but I'll try it sometime.

You are welcome. But there a way better ways of doing things!

You are welcome Ted!

Yes... I do still need a heat plate. I use a soldering over now which makes things easier and leaves me with beautiful joints.

You are welcome Carlos!

You are welcome Dragan! Have fun with small IC's ;-)

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 :)

Absolutely a viable way! This by no means the best way. It was to show one of my commenters one way to use paste without a stencil.

Thanks!

Sure... the microscope is an Eakins microscope with Sony IMX290 sensor.

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.

Thanks Luis!

Off course following the temperature profile of you paste will yield better results :)

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!

@@NicksStuff Lol true. Use the wire.

Your are welcome Drex!

Thank you! Hope it helps you in some way!

Yes also a valid technique ;)

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 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!

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.

@@DustinWatts Good point! I never use stencils so for me that wouldn't be an issue. But true, would be a shame to have to have two tubs. Cheers!

With solder all over the place!

Can you translate? 😁

You are welcome Bobby!

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!

I don't think so. I do not see any advantages and it may even increase the change of bridges....

@@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

You are welcome!

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.

I heard you... I fixed it right away!

I noticed :)

You are absolutely right! Do not make the viscosity too low!

@@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 :-) ;-)

@@buserror The days of me etching PCB's are waaaaay behind me indeed ;)

You are welcome Dan!

There is something very relaxing about watching solder reflow... :)

You are welcome!

Getting a hotplate is still on my wishlist. I am actually waiting for the bigger version of the Miniware MHP30 hotplate.

My first thought is that this is sarcasm... but I do enjoy some good sarcasm! :)

@@DustinWatts looking back I didn’t mean it as sarcasm.

You can get stencils that cheap?

Just simple cheap flux.

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!

In this case I think I had it at around 350 degrees Celsius.

@@DustinWatts Thank you bro.

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.

Season to taste!

Very inspiring! Is there somewhere we could follow your project?

Good luck Daniel! Let me know how it turns out!

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.

Are you speculating on this or have you actually tried it?

SevenDeMagnus I am not aware of any ‚liquid solder‘ existing.

I agree. If you can afford it definitely go with a stencil, it will make your life so much easier!

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!

Correct, but then it could be that you get to much paste out if your pad is a tiny one.

This was made with the Eakins HDMI Microscope with SONY IMX290 sensor. I did a review of it a while back on my channel: ukposts.info/have/v-deo/mmOkfH6Nmqp42ok.html

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.

Thanks Digicool Things! Indeed.. letting this mixture sit for a while won't work as good. Mix it and use it! :)

I absolutely do! I more or less mixed up my words there :)

@@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.

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.

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.

@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.

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

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....

Thanks!

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.

Why I soldered the chip to the board? This is a break outboard, so it gives me access to all the pins of the tiny chip.

5 days? That is a lot of pins! :)

It starts out like that... but after some practice. It is not that bad!

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.

Thanks for that! :)

I absolutely do ;)

Perfect! Whatever works best for you, right? :)

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 Got it,Hey thanks for replying, I'll check it out ! Have a good one!

I've gotten so many comments about my misuse if the word viscous, I will never forget it :D

But once you get the hang of it... a whole new world of IC's opens up to you!

If you think that’s bad, try fine-pitch BGA. Many of them are so small that you can’t route them out on standard prototype PCB processes (JLCPCB, PCB way, SEEDstudio, etc) without violating the trace/space limits.

I know... I corrected myself in the comments. I used the word wrong :)

Isn't that exactly what I did?

Yes it is. This was more a video if you insist using solderpaste but do not have a stencil :D

I find that using wick on such small pads doesn't work well for me.

I agree. There are much better ways to solder the chip on the video to the board. This video was just about how you could do it without a stencil, with paste, and without a syringe.