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The most difficult part about smd soldering is when you buy an expensive micro chip that you waited for months and it falls from the table into the void to never be seen again

Hi I work for an electronics assembly company and I think I can help out with your smt assembly process. The main issue I saw in your technique was the paste application, you should try to get the stencil much flatter, you can't have tape laying under the stencil as it raises the edge. You should try to lay a line of paste then uses a squeegee or credit card to swipe the paste in one clean motion, additional passes would cause unwanted squeeze through. When you finish you should check and see no excess paste between qfn pads, if you get this right the reflow will work with pretty much any of your techniques with no shorts. Personally, when I'm home assembling boards I preheat the boards to around 200c which you could do with the sand, then I let it soak for around 60 seconds and then finally reflow the solder with a hot air station, world's perfectly for me everytime. Happy soldering :D

Entertaining and informative, as always. Before changing employment to R&D in a new company, I did 5 years of SMD reflow and rework, a few tips for a possible revisit video. 1. Hot air blower only does tent to melt some plastics due to how long it takes the board to heat up, when building or reworking I always used a heat plate to heat the board from below, much less time was needed with the hot air blower to make connections, I also found that touching up connections worked best with blower and iron, iron alone often would not be able to heat the Solder enough without help from hot air. 2. I have not tried sand yet but I imagine it would be a lot more effective if a glass pan lid was place over the pan to retain air heat around the board, I've also seen this done with sand. 3. For all methods, a good single pass with paste is best. Ensure stencil is in the correct place and apply a good amount of paste along one side, them with firm, slow and even pressure, hold spatula/bank card at an angle and make one pass and lift stencil. You should find nice Solder deposits with fine vertical edges. When making more than one pass the stencil lifts then catches the edge of existing Solder and pushes it away from the pad, this happened with your USB-C. 4. Missing mechanical connection sderon USB-C, a few tiny blobs of paste applied with tooth pic or iron soldered afterwards, the 4 tabs each side of the USB need to be soldered to the board, they are for mechanical strength, not electrical. With out these all insertion, removal and any cable movement stresses are all applied to the pads and will break in a short time. If you have made it to the end of this, thank you for reading, I love your videos, I hope this information is seen as useful and not plain criticism.

*Fun fact* : Scott uses "Recently" as the first word in about 99.9% of the videos 😂

About a month late GreatScott!. I bought the same hot air station to repair my Nintendo switch motherboard with (eventually) positive results (my nintendo switch now functions again)! A note on your use of the hot air station, make sure to heat up the board from a distance for a few minutes so that the entire pcb is warm (it makes reflowing the solder much easier) and then go in close with the hot air gun. Also, you can shield the usb type c port with capton tape to reduce the likelihood of melting the connector. Great first try, would recommend the hot air station for anyone doing re-work/repair and the reflow oven for new pcbs (not everyone wants to reflow all components at once during a repair job). Also, as noted by a few other commentors, there was too much solder paste on the board for all operations.

Little tip for better stencil printing: Spread the solderpaste next to the holes and use a PCB with a good straight edge (holding it 70 degrees to the stencil in pushing direction) to push the solderpaste to the other side. Don't do it more than once and you will get perfect solder joints. Trust me. I'm working at a electronics company. We printing and do smd pick and place thousands of pcbs per week. Sometimes we need to do prototypes with stencil too and I am better in printing with the stencil as the printer designed for that. If you need, I can do a video how I would do it. Sadly I can't show it with a stencil at home because I don't have a project right now.

Whoa, thanks for those high magnification shots of the solder paste. I'd never seen the actual particles of solder so clearly before. Neat!

I enjoy your videos! Looking at your soldering process, I see room for improvements in a few places. 1) your stencil might have been too thick for the size of features you were trying to print. See if you can order one closer to .100mm. The thickness of the stencil is how you control how much paste gets deposited. 2) your solder paste shows "T3" (type 3) which tells me the size of the solder balls. Those are also on the large size for your project. Try to find a T4 or T4.5 and you'll probably have better luck. 3) not sure if this contributed to your issues, but pay attention to the shelf life and storage conditions of your solder paste. Keep it refrigerated until a few hours before you are ready to use it then let it warm up to room temp. Unrefrigerated, some types of solder paste are trash in only 2 weeks. If kept under 6°C, you can get 6 to 12 months tops. 4) try upgrading your squeegee to a razor blade or a glass microscope slide. Credit cards can actually get abraided by the apertures in the stencil and leave tiny plastic slices behind 5) always get stencils with frames. That's makes the release much cleaner than a with a flimsy piece of steel. Best of luck!

People who dislike these videos... Why????? Its literally FREE information made to HELP you.

3:02 I would recomand fix the stencil better, so it don't lift up from the pcb. You will get much sharper outlines (than 3:23) because there is less solder paste on the pad and much more important it don't get under the stancil. Otherwise you will get some problems with smaller ICs or when our solder paste get a bit older. (Some of your problems in this video also come from it i would say) For T962A there some (pricey) upgrade kits like from estechnical. But it is only sensible if the reflow oven is used more often. Works just fine for me for prototyping or pre-series PCBs.

In my youth I was involved in the hobby of lapidary. I heated stones to change their colors, or to speed up epoxy cure times. When I used sand, it would get in the epoxy and looked bad. I ended up using table salt. If it got on the epoxy, it would dissolve in water. I suppose in the case of electronics, if one were to use salt, it would require very careful cleaning after cool down.

Nice video GreatScott! I had surprisingly good results using a really simple heat gun, first heating the board up a bit from afar and then coming in closer. I did use a technique mentioned in other comments, making sure I had cleanly applied solder paste to reduce touch-ups.

Thanks for your video on this. Two tips however! One, you can save money on the stencil by using a solder paste from a tube. It's possible to apply by hand without a sencil. Two, you can skip the sand and reflow right on the pan! With an infrared stovetop that lets you skip the pan too and go right on the glass.

Great man. Love watching your videos. Everytime I learn something new

When you pick up a 0402 resistor with tweezers and it infront of your eyes vanish by opening a smal black hole and forever never to be seen again.

Hey GreatScott! Thanks for this Video. Right now I get started with smd components and this video helped me a lot. I never heard about the resoldering technique with the pan. I think I will try it out soon. Keep this good quality up. Greetings from Bavaria.

It will also help you a lot when using a multiple thicknesses one. In German it is called Stuffenschablone. It helps to distribute different quantities of solder paste. That's why QFN, MLP and BGA packages require one. KSG or Siebtronic are one of the companies that do that. Happy soldering! Looking forward for your next video :)

I love it! I grew my love for electronics with your videos 😃

Hey just one thing. I am a micro soldering technician and when you are doing rework on smd chips, you don’t leave the paste on the pcb, you place the solder paste on the chip and you heat it up, and then add flux and place it on the pcb. Also for connectors and caps or resistors you add the solder on the pcb and melt it. The add the component and reflow with flux. It makes the perfect job.

Some tips for you guys who attempt the first method, use the card to apply solder into the stencil diagonally from the holes, and try to go over only once, this way there won't be any excess solder, so less to none soldering iron action. Also if you are afraid of overheating components use Bismuth based solder, which is more expensive but solidifies at 160 degrees.

I worked with that reflow oven on my ex job. You had to use program 8(old software), that was test program for reflow. You have to press more on stencil to avoid shorts after reflow. Also, you can use syringe with solder paste and reflow station, works great!

"Where MLP stands for Micro Leadframe Package" Scott while writing the script: "Totally not My Little Pony or anything"

I have used a regular, big, hot air gun, but, unlike the hot air source you used, it heats a big area...place the PCB inside a box that is about 3-4 do the size of the PCB, held on some kind of platform, or, hung from wires that go through mounting holes, or simply wrap around the board...then, you use the hot air gun, blowing across the bottom and top of the board alternately, until you see the reflow... The box keeps the hot air circulating around the whole board, so that you are not heating individual parts of the board too much... combined with the stencil, this works really well. Thanks for the video, & Ein gutes Neues Jahr!

A few years ago my colleague and I built a soldering oven from an open source project at instructables. Since then, we have soldered and repaired many devices with it. Sometimes we even desolder components using this device.

Vielen Dank für die immer wieder lehrreichen Videos. Liebe Grüsse aus der Schweiz - bleib gesund und bis zum nächsten Mal

I use a standard cooking oven. Preheat to 475 F. Insert board for 3 minutes. Very professional results with no component failures after 20+ boards done so far.

I keep loving Great Scott

GreatScott getting us through quarantine tho :)

THANKS A LOT for those free 2 PREMIUN months and for such a greats vids Scott... BLESS 👈🏾🎩!!!

I do my soldering with an IR preheating station and a reflow heat gun. Preheat your boards slowly up to like 200-225C and then use the heat gun at about 15-20C above the reflow temp of your paste, and they should reflow within seconds, giving little time for any damage to nearby components. This is especially useful with large boards because I can leave them on the IR preheater and slowly bring them back down to temp so they don't warp.

lots of helpful comments on here, I personally preheat board and then use hot air gun for reflow. stencils are a right pain especially for reballing, reading that it works much better in single pass is helpful, thank you community :)

Super useful tips :) thank you. The sand method looks promising if you can be careful about it. One definitely wouldn't want to spill oven baked sand in their home.

I love the visuals of this video :)

For the hot air method try heating the board underneath to protect sensitive chips or components with plastic. Takes longer than direct heating but it works well

You are the great Scott , great video👍👍👍👍

I have the T962 and it was interesting seeing you following the exact same upgrades I did a few years ago! One tip when using the T962, you need to keep the board off the tray - I just use some spare FR4 board - the metal tray acts as a heat sink and prevents the air blower getting air underneath the board. Great video! 😃

usually, when I'm doing SMD, I use a hot air gun almost exclusively. I typically use MG Chemicals flux and a 60/40 solder blend. I usually tin the pads with as much solder as they can hold with my trusty TS-100, and the components as well (if they are large enough). and usually, the flux lets the solder flow enough that the connections are solid. It does require a little extra cleanup with 70% isopropyl alcohol and a toothbrush, but I think it turns out better than most of my attempts with solder paste.

Regarding T-962A, you’ll probably want to do the cold-junction compensation mod - otherwise all the temp ramps come in low. At least that’s what happened on mine. I also added a second fan on the opposite side which also helped to keep the controller cool.

Something important to consider when using stencils is the effect of parallax. At those sizes it becomes an issue, and I could clearly see the paste misalignment in the video due to this. Luckily the soldermask on the PCB gives you tolerance to this.

Hi scott, great video! Can you do a video on reflowing double-sided pcb's? Thanks.

I really want to make projects everytime you upload latest video Engr. GreatScott!

Haven't finished video yet, but 3:23 the way he said beautiful I just loved it

One recommendation to add on to what others have said. You might get better results lifting the PCB off the tray of the IR oven. I use a few strips of PCB to do this (left over tooling edges that have been broken off, etc) and get better performance. However larger boards, it has some hot and cold spots

Nothing beats hot air gun when you want precision soldering. My recent findings on a qfn 20 with irregular shape taught me that you need to observe the paste when it reflow and move the chip around a bit or even remove it and put it back in order to avoid shorts and misalignments...

Another Great video BIG-GS

2nd(sand) method i like Nice video👍

GreatScott, Is that a DIY usb c pd board? I've been wanting to make one for my projects! :)

I worked in the communications industry years ago, R&D didn't do their R properly and they had the SMT department stuff 1000s of boards, suddenly a leadless chip similar to yours started failing on every board. R&D couldn't figure it out, they never failed on their test boards. Me and the lead re-worked developed a method to remove and replace the chip manually. We would apply solder to every pad including the centre ground. we would then heat the board from the bottom and allow the solder to melt and place the chip on top, never failed, and placed a perfect IC every time. These chips never failed so R&D said it was a batch of bad ICs so they had 1000's more stuffed and they failed. It took the lead re-worker and our supervisor who had no more training than a hobbyist to read the data sheet and discover that the IC had a max heat threshold of 250C and the board stuffer oven got much much hotter than that. The method me and the lead re-worker developed became the standard procedure for installing the IC.

Several years back I looked into this and found that you can use low temperature solder paste for this. (Other people have also done this.) Bismuth solder is generally low temp and can be found in lead free version. Its so low temp you could probably get by with a hair dryer or heat shrink gun. You can also get industrial hot air guns for low price but these will likely damage the PCB if not careful. One problem with Bismuth solder is that it is low temp, in particular when certain blends come into contact with lead. Assuming my memory is correct, Bismuth solder will melt lower than lead free which melts higher than leaded. This will generally stay around 138 degrees Celsius, however when lead is present it can go to around 95. I would check this, but the point is you can get around 5cc (15g) of paste for 11 dollars and a heat source for around 14. Which makes this pretty low cost, and does not risk losing a pan. You can still damage the PCB but you would have to try a little harder to do. General recommendation is to warm the board up slowly, apply the high temp, followed by a slow cool down. This is to prevent thermal shock which can happen due to thermal expansion/contraction. Heat can also cause layer separation if not careful or using certain kinds. Note: boards will be hot as they act like thermal capacitors, for example concert in the blistering sun. You can also use the surface tension of molt solder to help test/ensure reflow and part placement. (Be at a point where you are calm, steady, rested and patient. It can save you money and time!) The sand approach is interesting, compared to the hot plate method. Hot air still works best for lead free or normal temp solder, which you would want for linear regulators which produce heat and operate over 95 degrees Celsius. The oven will likely always win due to the ability to follow profile. However hot plate may work for some compared to hot air. I have yet to master hot air, and can be a serious challenge depending for certain PCBs. I would recommend starting with low temp unless your design can't. The idea of super heating Teflon is not recommended either. Note I am far from an expert on this. Remember to read all disclaimers, datasheets, material/hazard information, etc. fctsolder.com/products/low-temperature-solder-paste/ www.sparkfun.com/products/10326 www.digikey.com/product-detail/en/chip-quik-inc/NC191LT15/315-NC191LT15-ND/11480396

Very nice! I didn't know you could buy reflow ovens so cheap

Muy buenos vídeos, saludos desde Argentina

Thanks for the vid! How thick of a layer of sand do you recommend for that method?

Again, another awesome video! Thanks!!

For what it's worth, SeanHodgins has some videos about using solder paste with stencils. He really stresses using as little as possible. If you used less, you might not need to touch up your joints at all.

Well,the trick of using hot air is similar to reflow smd, u can't put the handle close to components at the very beginning. u need to get a little bit far and let the rosin in the paste to melt and just like reflow curves. Then after warming up for about half to a minute, u can put ur hot air handle close to the board for about 5 to 10s and ur components will be well soldered. I 've tried hot air for many boards and they all look pretty decent. The key is to simulate the reflow curves and don't haste. Components are more tough than we expected.

Iam still learning more how soldier smd but your opinion and tips really are helpful Thank you soo much ❤️❤️❤️

You might have a better reflow in the over if you elevate the PCB on stand-offs. The slots in the tray look like they may be screw slots. Try to get the smallest contact area you can between the PCB and the top of the stand offs and give that a try.

I think you put way more paste on the pads with that stencil, and thats why you had to remove a bunch of solder after reflow. You could also try applying the paste with a syringe with a small flat end needle. Also you could use additional flux, it helps the solder stick to the surfaces, and can also help with dividing the joints, so it will be less likely to form solder bridges. AMtech makes very good flux that requires little to no cleanup after reflow, you can also go Louis Rossman with it and use a liter of it for one chip :D Great video BTW, greetings from Hungary!

Thank you, Scott 👍

well presented - THANK YOU old git, UK

At my faculty we have a big oven with some oil that boils at the melting point of the soldering paste. Of course it is very expensive, but is very interesting and it has a very good profile that is calibrated and you can see the process through a window :D

Nice! I'm still waiting for the SMD reflow hotplate I ordered from aliexpress over a month ago to even be shipped! I'm pretty close to just cancelling it and ordering another from a different vendor. The reflow oven looks nice, but I've only got a tiny apartment so I have no idea where I'd keep it. Not to mention it's a bout twice the cost of the hotplate, even before you add the cost of shipping! So I think the hotplate is a good compromise.

to unsolder the SMD LEDs I used a 50 W armored resistor and I powered it until it developed all its power. Resting the printed circuit on the resistance, after a short time the solder melted allowing me to remove the led and replace it. For small printed circuits you can use the same method: it is equivalent to the sand method but to me the solder has melted very well ... for large circuits you can add resistors on metal plates. I also removed integrated circuits like yours without problems. Since it was disassembly for me, I did not worry too much about the temperature reached, but the LEDs once disassembled still worked perfectly. By doing some tests you can get to the right temperature without risk for semiconductors. see you soon

It's cool to see that you can also do this at home potentially easy. I've choose the easier way and ordered it with all parts placed and soldered from jlcpcb. It's a little bit more work with the lists you need to send them but if there are more components it seems more efficient😅 and is also not much more expensive 😉

Congratulations, with one video you just convinced me to switch to SMT.

Finally a new sponsor :D

Sand??? I don't like sand. It's coarse and rough and irritating and it gets everywhere. Sorry, I couldn't resist! 😂 Stay safe there! 🖖😊

I have same oven, great little thing. Been planning to update firmware for a while but havent gotten around to it.

Great video! Thank you!

When soldering with hot air I usually remove the nozzle and increase flow to get wider coverage, and more energy through without blowing components out of place. Not sure if it is recommended, but it works.

Exelent explanation

Very interesting, I expected oven method to be more reliable, but it seems that some rework was required. If I need to pull out my soldering station anyway then I might skip the oven part altogether. Thanks!

Awesome work

Thank you so much for your verry great explanation. Sir, It will be verry helpfull to us, if you make for us a video about solder mask, all about this task please sir.

We really need to get you some good tweezers. A set of SMD precision tweezers is like $6. And as comments below said, that's about 2x the solder paste that should be on that board. Also, I never run my reflow heat gun higher than 225°C. It takes 8-10 seconds to warm up part of the board. Thanks for doing these videos.

Thanks! Interesting and useful.

Look into silkscreen printing, it uses basically the same processes we already use to develop circuit boards but you remove some of the plastic material that allows for making tshirts... It also makes GREAT pcb stencils that don't last very long (not as durable as a piece of stainless steel) but are cheap and can be made in just a few hours, using the same printing systems that we already use for pcb etching.

Your video is great and very informative. The only thing I would suggest would be to use a small syringe to apply the solder paste. Some brands already sell the paste in the syringe, it makes your life easier and you can control the amount of paste applied in smaller solder pads. Keep up the good work!

Thanks for great and detail demonstration on PCB reflow. But do you mind to share how to define the proper thickness of the stencil choosen? Different component (caps / relay / IC ) should have different pin and HW spec. How can you to do that?

Fantastic video (as always). Just a quick mention that iron is pronounced without the ‘r’ sound similar to ION. :)

Great video, thanks!

Hey Scott, I would recommend trying out a knife tip (like the hakko T18-K) for soldering QFN packages. I load the tip with some solder on both sides, apply a generous amount of flux and drage the tip across the edge and it solders nicely. The dragging action wicks out excess solder. Only thing to consider is you will have to hold longer if there is ground pads to allow heat transfer.

Something we use when doing hot air to reflow solder is something called a "hot air bath". We put it under the board and it heats up the PCB to around 150C, or hot enough to activate the flux. We can then go in with the hot air at the proper temperature and reflow the solder paste. Also, for anyone who has trouble with tweezers because of their shaking hands, if you hold your tweezers like chopsticks and place your fingers against the table, you will find the shaking stops. Use your work surface to stabilize your hands. If you get this down you will become a master in no time. And finally, the 3 ulitimate rules of soldering (especially SMD): 1. More Heat 2. Less Solder 3. Flux is Magic

I did not know about the sand layer method. interesting ;-)

Wow I never thought about that sand method before. I wonder if it would work well with reflowing PCBs that have components on top and underneath.. or maybe it'll make a mess. Any thoughts?

Thus, I enjoyed thee video!

I used to reflow my friend's graphics cards with my kitchen oven, poor's man solution I guess, but it worked, I used to put small balls of aluminim foil in the bottom to keep it separated from the tray :D

Great scott is great

I use my normal owen to reflow, works very well

I already have a Hot Air station, the problem of overheating I did see solved to some extend is to use kepton tape. I did not try that at this time. I also have a Hot Plate that i am going to try soon, only disadvantage is that I don't have a stencil.

I'm an SMT machine operator, and make PCBs of various kinds and functions. I work with stencils and paste almost every day (although on an industrial scale). First of all, at the 3:20 mark "...we get an even distribution of the paste all over our solder pads in a very precise way. BEAUTIFUL!!" It made me laugh, simply because I would fail a board for a single solder bridge or excessive paste. If I could offer a few suggestions. Use less paste. With the pastes, less is more. Barely any of it is supposed to be applied at any one time. Lay the stencil flat on the surface of the PCB before applying a thin layer of paste, no tape or any other objects between the stencil and the board. As other have pointed out, use a smooth, flat object such as a credit or gift card and a thin line of paste on one side of the stencil, then one smooth motion keeping the card edge flat against the stencil. Lift the stencil straight off the PCB. Great video. I really like all of them so far. I'm a new follower.

I would be curious what you think of building a reflow oven. I have done that using an old toaster oven, an arduino with a temp sensor inside the oven, and a relay. Turn the oven to hot, no timer, hit start on the arduino and it ran. There are some really good arduino sketches out there for DIY reflow.

Very interesting, thanks!

With the cheap reflow oven, it would be interesting to compare the temperatures the oven gives to temperatures taken with a thermocouple and temperature meter, before and after reprogramming. I'm wondering if the factory does some kind of calibration on the oven temperature that gets wiped when you flash the new software.

There will be a point when the "See you next time!" will explode in a big earrape. I like it!!!!

Please make a video on making your own RF transmitter and reciever as I am a beginner.

buying an oven, reprogramming it, using it - I love it

Thank You!!

Manual soak, NICE (I sometimes do the same thing to make sure the pizza gets cooked through). Now that you know what the thing thinks the temperature of reflow is, you need to hold it there until you see the reflow you want then set the program for that. DO NOT FORGET TO ALLOW SUFFICIENT RAMPDOWN TIME SO THAT YOUR SOLDER JOINTS/COMPONENT PLACEMENT DOES NOT DISTORT FROM OVERLY RAPID COOLING OF MATERIALS WITH NON MATCHING RATES OF EXPANSION/CONTRACTION WHICH WILL DISTURB YOUR SOLDER JOINTS POTENTIALLY CREATING MULTIPLE WEAK OR FAILED JOINTS.