EEVblog

Dave shows you how easy it is to do surface mount SMD reflow soldering with a solder paste stencil and a hot air gun:
astore.amazon.c...
Hints and tips for quick and easy component placement, solder paste application, and reflow soldering using cheap easy to get tools.
Forum Topic: www.eevblog.com...
EEVblog Main Web Site:
www.eevblog.com
EEVblog Amazon Store:
astore.amazon.c...
Donations:
www.eevblog.com...
Projects:
www.eevblog.com...
Electronics Info Wiki:
www.eevblog.com...

[@michaelmolter6180]

I make "free" stencils for almost all of my SMD projects. The lab I work in has a cheap, hobby-level, laser cutter that I use. I cut open aluminum cans, sand of the inner plastic layer, spray paint the can, laser off the part of the spray-paint mask that I want to have solder on, and then etch the aluminum in standard PCB etchant. It takes a half hour tops.

[@sigmundurjohansen7166]

Would like to see a video of that :)

[@MrMWPro]

or you can pay like 5$ at jlcpcb

[@Minecraftmike5089]

@@MrMWPro the can method can be done in 30 minutes, i don't think jlcpcb will beat that

[@freezedream]

I know this is 4 years old, but this method sounds amazing. I was looking into using Al cans but thought I had to do toner transfer. What type of paint? Just standard gloss spray? What type of etchant do you use for Al? I thought it needed to be something like HCl/H2O2. I guess even just NaOH should work.

[@michaelmolter6180]

freezedream This was a while ago before JLCPCB had really become as popular as it is now. PCBs were really expensive back then ($50+) so I was making those using a similar process on copper circuit board material. I just used off the shelf matt black spray paint. It was a chemistry lab, so we had easy access to diluted HCl solutions. A little bit of Baquacil pool oxidizer (concentrated H2O2, but much cheaper) really sped up the reaction. I remember it always being a bit of a balance between using up your HCl or oxidizer and having to add a bit more to keep the bubbles etching.

[@ZsomborZsombibi]

After 6 years, your adventures are still actual and give help to others.

[@jwiegley]

Dave, I know this video is well over a year old now but I wanted to add that in a pinch I find an old credit card makes a good squeegee for my stainless steel stencils. Has a good sharp edge, is very stiff while able to give some bend under high pressure and doesn't scratch the stencil.

[@BenjaminGoose]

Never seen this done before, pretty amazing the way the solder melts and reforms into an efficient shape.

[@henrikaleksandernilsen6388]

I was told a story about a group of people soldering LEDs on boards for emergency exit signs. Someone screwed up on which way the LEDs go and placed it the wrong way, and everyone trusted that guy so they put them on the way he did. And no one paid attention, because they were busy talking about weekends and wife and kids and stuff. And it wasn't until the next day they realized that they have to throw away all the 5000 boards because the LEDs were put on the wrong way!

[@cam3oh]

Did you know that not all LEDs are put on with the same orientation? I discovered this when soldering on some various coloured LEDs some wouldn't turn on. I dismounted the non-working ones and tested with a DMU. Mind blown.

[@magnuswootton7368]

electricity goes backwards.

[@dr_jaymz]

A place i worked had done huge capacitors backwards. They didn't spot that until it was powered. That woke up the dead.

[@m.t-thoughts8919]

@@dr_jaymz 🤣

[@cesaru3619]

@@dr_jaymz hah whta dvmb4sses, kaboom!

[@jerryschroeder3878]

Thank you. I didn't know anything about reflow soldering other than the Gigabyte motherboard tour. This vid takes the mystery out of it and leaves no questions unanswered.

[@ynzeselders4184]

if you apply the past in multiple passes it goes under the stencil edges and it ends up next to the pads, if you do it in one pass you get nice sharp edges. Might not be a big deal in some cases but when using IC's with very close pin spacing shorts will form between them.

[@NathanSweet]

I don't find this to be the case when the stencil is taped down firmly and a metal putty knife is used. The main thing that leads to smeared paste is the stencil lifting slightly. Keeping it pressed down the whole time helps.

[@EEVblog]

The titanium Centurion, or "Black" AMEX Card works the best!

[@CyrusEpion]

The paste issue you had with it not sticking onto the pads when wiping is due to the paste either being too warm or not kneaded enough. Knead it on an aluminum plate to where it becomes the consistency of peanut butter, for a few mins till it's very smooth, then apply it. But like you touched on, the paste should re-flow once in the oven too. Been an SMT Operator producing class 3 PCB's for a few years now, and always see this issue whenever someone doesn't prep the paste. It's awesome to see people producing PCB's right at home. Feel free to ask any other questions, love teaching and passing info to people who like to learn.

[@NathanSweet]

With a syringe you can't mix the paste. I never buy syringes.

[@CyrusEpion]

@@NathanSweet Yeah that's true.. Plus whenever ordering paste online it's impossible to get it shipped cold. Warm SMT paste means the flux and solder balls will separate. Gotta mix it and when not using it, stick it in the fridge.

[@michaelpiotrowicz6100]

Thanks Dave, your video collection needs to be held by the National Library.

[@catharperfect7036]

The solder mask working along with the hot air is so satisfying.

[@Joru666]

This video is even more interesting than usual because I got the same hot air tool. Never did a stencil work nor did a whole board with reflow, just some single ICs. Thanks Dave.

[@ScramblerUSA]

I'd like to say this once again - it's a good practice to preheat the board from the bottom. In Russia we even used an iron sometimes (yes, the one your wife uses to iron the clothes). Just put it upside down, place the board on it and enjoy. Soldering is much easier in this case, because board doesn't take so much heat anymore. And the chance to overheat your chips is also much less now. Well, iron is weird, it's better to use IR heater.

[@krist370]

You can use old credit card or similar plastic or metal sheet to apply stencil paste. Also a thin squeegee from local hardware show will do job perfectly. It is important that edge is smooth and material isn't to flexible. I work with smd every day at my job. For printing stencil we use LPKF stencil printer for bigger series of boards, but for prototypes I just make frame like this one on video and I attach metal mask with some tape on one side to create sort of hinge.

[@CAXRAMEDIA]

A dramatic and emotional soldering video 😂 I want to cry happily to see it. we like your video. thank you for sharing

[@EEVblog]

Correct. It's also why the paste should be kept in the fridge, so the solder balls don't all fall out of being suspended in the paste.

[@SE45CX]

According to IPC general recommendations the stencil should have rounded corners to optimize for maximum release when the stencil is removed from the board. And it is very important to have about 50% of the size pad size for the solder paste opening in larger thermal pads, especially under the components. Please use IPC recommendation solder paste layer when you're using stencils.

[@dimauniverse3174]

-.- tool

[@superdau]

The flux is included in the solder paste. AFAIK that's the main reason for the shelflife and the time parts can be placed after applying the paste. The solvent of the contained flux will evaporate and the paste will go hard.

[@stefan7231]

Whenever I'm soldering LED's, mostly in monitor backlight boards, I heat the borad from below so the solder melts before the temperature gets to the LED's.

[@morelenmir]

MANY thanks indeed for this - definitely one of my favourite of all your videos. There is something of doing a jigsaw, or building a lego kit about this surface mount reflow stuff. Please do more!

[@memphetic]

For those who are looking for where to get stencils made, you can get great mylar stencils from Polulu for very small run projects or prototypes, then you can get stainless steel laser cut ones from QuickStencil when you're ready to move up. Good luck!! Also, look into building a reflow toaster! Super cheap and extremely effective!

[@EEVblog]

I usually don't shake doing this stuff. It's the combination of the camera angles with the tripod in the way etc and having to stand up doing it reaching further than normal, and also talking at the same time.

[@Jenny_Digital]

Just a quick note too all those keen on getting a reflow oven. I bought a cheapie from China and found it to be crap beyond use even. It was the T962 (not the A version). Get a good one, modify a toaster or whatever you need to do but don't get a T962 because you will have wasted your money. In the end the 858D+ I bought served me best. Cheers Dave by the way.

[@EEVblog]

I've done a tutorial on SMD hand soldering

[@envisionelec]

For the folks in the US, I found a couple tools that work very well for stenciling. The spreader is a Hyde 4” Flexible Joint Knife. It's got the right amount of "spring" to apply constant pressure and has a sharp edge. I use a Techni-Tool Spatula Part #: 758SO0026 to apply the paste evenly. I've assembled hundreds of boards using these two tools and they're as good as new.

[@timothymasters4687]

It seems you use two tools. One for spreading (Hyde 4) and One for smoothing paste evenly (Techni-Tool Spatula....). Is this a correct interpretation of your recommendation?

[@Johnnii360]

Thank you, you show me to solder SMD parts. I finished my qualification as Industrial Electrician, Subject Area: Machines and System last Friday. The problem is SMD solder wasn't a part of content in the qualification, so I must catch up on myself. This video bring me a little bit closer to the SMD solder technique. :)

[@EEVblog]

Yes. The syringe is the only type available at my local Jaycar store.

[@AxelWerner]

just opened up a post on the beginners section on eevblog to discuss this further. you can see the surface resistance/conductivity there.

[@EEVblog]

Nothing, I just took out some extra dialog, it did work first go. I posted a preview of a longer version of this video on Twitter at first, it was 40min and probably has the extra dialog. This final edited version is 31min, so many more cuts.

[@sdevane75]

Brilliant. Great to see how this is done from start to finish!

[@EEVblog]

The heat gun can also be a very ham-fisted tool, as can an uncontrolled or mis-used toaster oven.

[@EEVblog]

If you don't keep it in the fridge then the solder balls that are suspended in the flux paste will all settle and gunk up. You can try remixing it though.

[@memphetic]

Absolutely - that's how I started out. It's pretty convenient to just pop them in, push a button, then out pops a properly reflowed part at a specified temperature profile. Just like baking cookies ^_^

[@jan.tichavsky]

Very nice video quality, I can see the individual microballs of solder!

[@bearwolffish]

This was gold for pitfalls to avoid.

[@onjofilms]

One trick for shaky hands is to use one of those pano-vise. Clamp in your solder iron, tighten the nut just enough to move the iron with a little effort. Very stable.

[@electronichome1153]

Still very good! Even in 2021. Thanks Dave!

[@mariushmedias]

The solder paste has liquid flux in it, a lot of it actually. So no, no flux needed. In fact, the gradual increase of temperature, besides giving time to the pcb to warm up gradually and not crack or bend or whatnot, is also chosen in such as way as to give time to the flux to work on the surfaces for a few seconds before it boils/evaporates and the solder actually reaches the temperature needed to make the connections.

[@clifforddicarlo9178]

Makes one long for the days of soldering vacuum tube-based circuits, Dave!

[@Appvpro]

Awesome ... thanks answered alot of my questions on solder masks

[@yuppiehi]

I can't speak for the solder paste itself. But, things like glues, drugs and many other substances are designed to be maintained with consistent environmental conditions, in order to preserve and extend the potency of the substances. If the manufacturer said keep it under room temperature, first you have to define what room temperature is. Also, room temperature can change back and forth throught the days and weeks, which weakens substances. A fridge provides a consistent environment.

[@kay486]

near the end of the video, you can see that U1 has not the middle right pin soldered well

[@EEVblog]

Well yeah, it's just an example. Wasn't a PITA, but yeah, could be just as quick by hand.

[@DDICyber]

you can also use magnets to hold the stencil on place i used with reballing of cell phone chips it works greet i have under the boards also a plate for the magnets greets mmtpc

[@EEVblog]

A toaster oven is much better than a frying pan, much better controlled temp over the whole board volume. I'd rather use a hot air gun than a frying pan.

[@Vermilicious]

Now that was satisfying to watch, despite the spatula. You don't have to be in contact with the solder paste. Couldn't see any smoke either, like from regular soldering. I wouldn't be surprised if this becomes the preferred way of soldering, if it isn't already - even for hobbyists. I reckon you would need a bit more paste for through-hole components though.

[@davisfoster1321]

The other poster is incorrect. It is because they spin the silicon to help form it, which naturally creates the circular shape, It is then sliced for use in wafers.

[@roryevans5032]

I think that the issue with dragged solder paste is that your spatula is too soft. It's bending quite a lot so the trailing edge is very flat on the paste, and that increased surface area is dragging the solder away from the trailing edge of the mask.

[@abpccpba]

Good show nice work. A basic suggestion on hand placement. You would do better if you used both hands when placing parts. If you get some sharp pointed wood like the bamboo kabob sticks. Here is the basic move; keep the stick in none tweezers hand. Place the part with the stick near it. Set down the part and simultaneously put the point on top of the part to hold it down which will help with the shaking hand from moving the part. Release the tweezers and then the stick. It will take time to get.

[@CreatureOTNight]

Cooking with EEVblog and todays show "Reflowing".

[@jeremysaise]

Personally I would have put the extra boards top and bottom tape them down then align the stencil tape the stencil down. Use a metal ruler hold it a 60 degrees. Put. A bead of paste along the top edge and pull down holding the ruler at 60 degrees it should give an even print. Btw I work for a company that makes a 3d solder paste inspection system so I have a little bit of experience with it :)

[@grantfielder]

You should do a tutorial about the mounting and removal of surface mount electrolytic capacitors, great video btw :)

[@JeffDM]

Dave did all that, then said he'd normally use his favorite iron & wire solder for this board? I'd think that's more hassle than the stencil & reflow method.

[@SE45CX]

But for the thermal pad under a QFN part it might be the only way for a DIY solution. However I would do a very tiny bit of solder paste on that pad rather than using a stencil. An example of such a device is the ADCLK925 which is only available in such a package.

[@larsclausen3586]

Use the sticky part of a post-it to hold the smd parts easier to pick up with tweezers

[@zytechnology]

The WF24 Chip looks like it could use a little more love :) Thanks for the nice Video :)

[@mosfet500]

Dave, Thanks for the video. A couple of things. The reason the spatula doesn't work is that it is too flexible and it bends down into the stencil hole. A rigid spreader is best. The best way to do your heating is to have a hotplate of some type under the board. What you're doing here may look good but the life of the parts might be marginalized and might have a short life in service. Not one of your best videos.

[@RelaxingASMR]

Interesting video. Great quality. Would love to know which camera you used?

[@HeliEye]

Neat and interesting Idea. I've always hand solder these tiny pitch chips, QFN's mainly. I just pre-tin pads, remove excess solder with home made silver plated desolder braid, place and align chip, spray contacts with SK10 solder flux, then run iron/solder down a whole row at a time. use the same silver plated braid on the soldered area to tidy up. result looks like a reflow job ;-) #Note: I don't use Toy soldering irons for this type of work, I use a Metcal MX5000 workstation. Steve

[@pepe6666]

damn dave this was a really great video. ive only just figured out what this wave soldering stuff was and i was looking for a start to end video and well look at this. solder mask and stuff makes more sense now.

[@nicholasbrown8384]

I can always count on you for these things!

[@EEVblog]

No need to build/hack a reflow toaster, an off-the-shelf manual one will do for starters, just control it manually and be careful.

[@TheRealUberSteve]

Just posted some internal photos of the cheapy YH-992DA on the forum for anyone that's interested. ("YH-992DA Hot Air Rework Teardown" under Product Reviews, Photos, and Discussion)

[@simonspeaker]

Proskit made one suction pickup tools that works with 1xAAA battery and works like a real charm ! ive been using it for a year and its awesome! its Pro'sKit MS-B126 and its 20$

[@nyang8888]

The model that served you the best, the 858D+, is also made in China, and it is a "cheapie" too, in case anyone wonders.

[@NilsO78]

If you would like to improve your reflow process: simply buy a cheap pizza oven and a "reflow oven controller", which will control the temperature inside that oven by directly adjusting the power supply!

[@Dexter101x]

Thanks to all these videos, I am really interested in restarting my very old hobby.....#madscientist ensues

[@m.t-thoughts8919]

I just love reflow slodering, even if I need to do some extra research on how much heat, I can put on the board till I fuck up a part.

[@microphonixvirtualstudio1634]

Generally, if you can read the lettering, pin#1 is the lower left corner pin.

[@johnekare8376]

I’m not sure this would be needlessly complicated for only a marginal gain but: if your stencil is made of a thin steel sheet, maybe you could use magnets underneath the PCB to secure it in place and get multiple anchor points spread over the whole surface?

[@koldenrjk]

I assume you had the stencil made? For prototyping that can be quite expensive. I'd like to avoid that high cost ($125) each time. For production its worth it. Good video - thanks much.

[@dedasdude]

DAVE! since the spatula is rubber, it will curve into the gaps in the stencil and hence digs out some of the paste. best to use a credit card!

[@envisionelec]

You can scrape the remainder off the stencil and reuse.

[@kewlbns69]

a few questions about this: how, if necessary, do you clean your stencils? is it good practice to do so? also if so how often should it be done?

[@ales_xy]

I buyed Elme mat recently and it seems to be very similar to 3M top quality mats. It's made from two rubber materials, top layer is not conductive, thermally and mechanically resistant, bottom layer is conductive. I tested thermal resistance with soldering iron set to 300C for a few seconds and the only effect was discolouring the blue rubber. Maybe it was caused by flux from solder wire. It's only cosmetic issue, but beige seems to be natural color, so that variant should not have this problem.

[@Oekelmania]

Ok, when I ignore the self-praising Parts ;) I am suprised how good it works. I own an Reflow-Oven and never thought it could be done with such a windy tool like the hot-air-pistole. Nevertheless I think you should not work on SMD if you had to pull them on the board by Hand. At minimum a "half-automated" System would speed it up a lot. Last Remark: Temp. is not the only critical part on the parts. Even the quantity of getting up-heated and cool-downs are critical. Take a look at some datasheets. They tell you a nb. ob 2-3 times. I do not belive that this is possible with the hot-gun and you have to repair/replace many parts. Didn't you?

[@JordanEdmundsEECS]

Awesome video, ready to do my own!

[@MacoveiVlad]

Guess the problem with that squeegee is with the way rubber bends inside the cutouts, essentially creating a convex scraper inside the cutout based on the pressure you apply.

[@bcsupport]

2:30 Dave did a magic trick !

[@dalenassar9152]

They should really have a -standard- male/female "centering dimple pair" on the PCB / SMD component as an aid in centering. Of course, the male dimple would be something like 'clip-off' type for the parts that don't have this feature.

[@myronww]

You can make a really cool vacuum pickup tool by getting a fish tank pump and reversing the value so it will suck instead of blow.

[@huxleypig5007]

Great stuff, thanks mate! Bit of a sus edit just before the plug in tho!

[@siliconwitch]

It seems these hot air guns go by many names. I have pretty much the same one by a company called W.E.P. Model is 876D. Looks exactly the same except has a soldering iron too.

[@phomann]

Nice video. A couple of points. The solder your using is a lot less viscous than paste designed to stencils. Also for an applicator, use plastic spatulas designed for plastering, body filling etc. To see how I do paste application have a look at my projects at homanndesigns Cheers, Peter

[@gglovato]

and what about using a regular kitchen gas oven with temp control?, turn it on, set it to 250, leave it 2 mins, done!(and you can put muffins as well!)

[@pikuorguk]

15:53 - The DaveCo Pick & Place machine goes into full speed

[@ameliabuns4058]

I love how you used a cheap crap hot air gun :) Not everyone can afford fancy tools! tho i'm really tempted to make a DIY oven for reflowing, or a simple hot plate, but AC scares me... i'm more of a low-voltage microcontroller type of gal

[@williamsmith455]

A plastic credit-card type card makes a much better spatula than that cake spatula. I guess you noticed there was a lot of wasted paste on your stencil. The paste isn't cheap and it also has lead in it, in your case.

[@XPLOREanXPLODE]

Great video! Very informative, gonna try SMD soldering in the next time :)

[@EEVblog]

Components are designed to survive reflow soldering temperatures, it's usually in the datasheet. Traditional hand soldering is subject to ham-fisted humans with plummers irons, so it gets that bad rep.

[@ElectronicsPubVideos]

Dave! BAD SOLDER JOINT on the middle pin of one of those WF24 chips!

[@atamasuzu]

i'm using my AMEX to apply solder paste, seems to work better than MasterCard.

[@Agent24Electronics]

Dave, I read somewhere that solder paste can be refreshed by running the container of paste through an ultrasonic jewellry cleaner. I think the idea was that it re-mixes the flux components. Have you heard of this before or tried it?

[@satipsrl5207]

Very good idea thank you......

[@MrPaddy1000111]

The visual identifier on those LED's was the one angled corner I think?

[@EEVblog]

The flux is built into the solder paste.

[@slavenbukva3286]

If you want to apply solder paste correct way then use metal squeegee. And dont smear it in like oil painting, do it in one stroke.

[@andrewwhite1793]

A stencil is not absolutely necessary if you have hot air reflow. Just a little dab on each pad and don't worry about bridges as surface tension will sort it out. This even works on chips with completely hidden pads..

[@fumil4489]

Thank you for such a good video with practicable details!

[@teknoman117]

I'm about to try an 0.4mm TQFN job with a stencil in the next few days, wish me luck...

[@kamranbaniensan]

Hi Dave, I love your program, relay useful for every one ,please keep going and make more and more video Thank's and have good job

[@mekbots7607]

YOU ARE AMAZING ,MATE