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I’ve used 1/8" chisel tips and conical chisel tips for doing hot iron reflow. All the work I do is hot air removal and hot iron installation on older gear, but can even do newer stuff, but I put it all down or back with leaded solder.
For flux I prefer the GC Chemicals liquid rosin flux that comes in a bottle with a brush. Flux is key to keeping everything from bridging.
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I always use the cheap charlies DIY method:
Works great. I used craft paper to help direct the hot air where I wanted it and avoid desoldering surrounding parts.And I didn’t use as much paste as this video, which helps keeps the joints nice and clean.
The embossing tool runs about $18 at hobby lobby.
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That’s a ridiculously-sized iron for the work he’s doing.
SMT work is where the Metcal really shines. Use the STTC-140 cartridge, .035 solder or smaller, and be liberal with the flux to avoid bridges (as Raymond already mentioned).
If you’ve got a bunch to do, use solder paste, a stencil, and a cheap non-stick electric griddle to reflow all at once. Works great for BGA, too!
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Really? It isn’t much larger at the tip than the pads. When I started SMD soldering I used the ultra fine tips. They ended up being more hassle than they were worth. I tend to use a smaller flat tip, but when I say smaller it is a bit wider than 1/8 of an inch so not too tiny. To each their own I guess.
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It’s a matter of dexterity, and I do a lot of it for work and hobby. If I were teaching someone to solder SMD at DMS, I’d use the Metcals exclusively.
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I use a 1/8" chisel tip with a small ball of solder on it and drag it gently across the joints. Works like magic with the flux.
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+1 to Raymond’s drag method.
+1 on the metcal. You need to bring the whole joint to temp quickly, by dumping in just the right bolus of heat.
What the guy in the video was doing wrong was heating up the joint and feeding solder in, as if it were a through hole part, or a terminal on a freestanding switch. That will result in uneven heating, longer heating times, inconsistent joints, and damaged components, such as SMT ceramic caps which can delaminate. Don’t emulate that technique. Liquid solder is a much better heat conductor with much better surface area than air and dry metal. Use the already melted solder to heat the joint to flowing temp.
I use
- a 1.8mm 700 deg. tip (such as metcal P/N STTC-137). Works great for through-hole and SMT, unless you are going smaller than 0603. Then a 1mm tip. The idea is to have sufficient surface area to hold melted solder.
- water-soluble flux, then I wash the board when I’m done with hot water and a toothbrush, until there are no more suds. RMA medium can be OK, but require more vigorous cleaning. Medium solids. Avoid no-clean fluxes.
- 63/37 eutectic solder. Just no need to bother with anything else. 1mm or greater solder. Whatever you use for through hole. You are putting it on the tip anyway, so no need to try to match the pad size. The flux core is only for cleaning the tip here, it will sizzle away before it gets near the joint, and you will wipe it off, so no matter what kind of flux. Still, I avoid no-clean.
- Various size solder wick, but 2mm is pretty general purpose. Sometimes 1mm is better to avoid overheating tiny pads. Get chem-wick, or similar. If you have no-name or really old wick, wet the tip of the wick with flux .
- cheap tweezers. I have expensive tweezers, but I always reach for the cheap ones. Keep the good ones for truly small parts.
- Head band/magnifier. I like this the megaview by Vision USA. More expensive than the cheap models, but solid, and flips up out of the way. I’ve used the cheap ones. They don’t last, and tend to flop down and get in your way. I got the one with the glasses-style band, but I think they only make the full headband model now.
- I have a binocular microscope, but I consider it optional. I use it for inspection, not for soldering. Again, I don’t get down to the really tiny sizes.
- Hot tweezers with a variety of tips are really, really desirable for removing parts.
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Guys, there are many ways that work. I personally use a one that is a mix of the above approaches.
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Looks fun, but takes way, way longer than just soldering the part.
If you’re doing several boards and get into a rhythm placing the paste, then the parts all at once, then using an oven, you may save time. Hot air is great for leadless parts and BGA though. And for removing parts when a hot tweezer isn’t an option.
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I would add that a board pre-heater makes things much easier. If you get the board to around 100C, the iron or hot air only has to raise the temp by 200-300C instead of 300-400C.
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Thanks for the tip on the headband magnifier. I’ve been looking for one that doesn’t make me curse when using it.
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Yes, I’ve tried quite a few. I have the “glasses” style over the headband style, but I can’t find that anymore. But I am sure the headband works fine. I like that you can see around the edges to grab stuff.
Plus, although my wife has yet to admit it, this is the only magnifier that you can forget to take off, wear around the house, and still look cool.
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I just opened my headband magnifier. This is the one I got, with LED lighting. As someone with aging (59) eyes, the additional illumination is really helpful. In fact, this morning when trying it out I wasn’t able to read the marking on a really small QFN chip. But after turning on the LED and aiming it, the marking was easily readable.
Megaview LED Loupe - Includes 4 interchangeable lenses 2.0x, 2.5x, 3.0x, & Monocular 4.0x.
https://visionusasupplies.com/megaview-led-loupe-includes-4-interchangeable-lenses-20x-25x-30x-monocular-40x-pr_id-2344
Thanks again for your recommendation, else I would not have likely have found this. It will be immediately useful, as I’m debugging a board with FG676 FPGA and 0402 resistors.
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Nice. Looks solid–probably stays on better than the glasses-style. I hope it does you well.
I’m in the same boat–It’s always on my head when I’m in the lab.
I finally turned up my model. I have the Megaview Compact, sold by American Jewelry supply, and by some international sellers. They also have another model, Megaview Compact III (MG3), which I think is the same but more expensive, with a fancy case.
This model doesn’t have built in lights, but I had to put in LED bars and targetable LED lamps at every bench.
I should have listed those as basic kit as well.
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The other night I finished a small board with a couple different types of SMD components on it. I used the Hakko iron in the lab with the small chisel tip. The biggest challenge I faced was keeping the components on the pads. I think the only one that went on straight was a SOC-16. The second challenge I faced was finding the Components are I managed to drop while trying to place them. Let’s see, there was a LED, a resistor, and capacitor. Luckily I managed to find them. Now to see if it works.
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After putting down some flux and wetting the iron with solder, touch the tip to one pad. Use the tweezers to position the part in place, and reflow the pad with solder on it. Then, close the tweezers and use them to push directly down on the part, and reflow the pad again. Now the part is aligned and flush. Touch the solder-wetted iron to the other pad, until a fillet forms.
For SOIC, same thing, except you’ll be tacking down pins on opposites of a diagonal, making sure the chip is flat, then dragging solder along all the pins.
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Tweezers…I bet that works much better than trying to position and hold it with a pick. Thanks.
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This is a very pertinent thread. I did not even realize how pertinent it was and how pertinent it is becoming looking forward as our PCB processing improve and the pads, traces, balls, connectors, not to mention process geometries, all shrink in size.
So it is such an item of interest, that I am going to propose an improvement. I think that the improvement is not only necessary, but can be something we embrace and drive right here at DMS. I noticed the problem was getting bad in the lab here in Dallas, I was inspired to try to do something about it here in Dallas, and I think that a great place to test the usefulness of any possible solution could happen, well, right here in Dallas.
Check out this thread and throw in your two cents…