Have you ever seen soldering this close? [video] | Hacker News Reader

Have you ever seen soldering this close? [video]

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601 pointszdw118 comments

A nice video, though it missed one of the most interesting aspects of BGA packages: their ability to self-centre during soldering. If the misalignment is less extreme than in the video, surface tension will pull the BGA package into alignment. Here is an example

https://www.youtube.com/watch?v=dz7ltWBDm7U

Notice how in the second part of the video, once the solder has melted, the body of the BGA moves so it is correctly centred over the PCB pads. This is happening by itself, without an external influence pushing the chip into position.

Surface tension for the win.

In the extreme misalignment example they also did not use flux so I guess they were purposefully showing what NOT soldered looks like. They did show how the solder flows in the "too much solder paste" example.

This is true for most surface mount packages, the surface tension of the solder will usually center the parts in their pads during reflow.

This. In my experience QFN-like packages self center better than comparable BGAs, it’s just that BGAs in general are big so they are easy to line up.

Small BGAs can be hell to hand solder.

I find SOICs to be by far the most forgiving; off by anything less than half the pitch and it tends to jump into place.

In fact, the force of self centering is more a problem for small 0402 parts!!!!

The force is so strong, it can 'Tombstone' the piece during reflow. This is partially why 0402 is used rather than the more electrically convenient 0204. It's easier to tombstone on the long edge.

-------

Also, if you don't care about tombstoning but need the better parasitics of a 0204 capacitor or the better heat capacities of a 0204 resistor, try them out!!

And if it doesn't work on all pads, you may need an X-ray to figure it out.

Live by the balls; die by the balls.

Most of my soldering errors are from incorrect amount of solder, so, BGA tends to work better than other footprints.

In BGA soldering, the concept of partial alignment doesn’t really happen. Here’s why: In a 2D plane (which is the PCB), only two points are needed to define alignment. If two solder balls are aligned with their pads, surface tension in the reflow process ensures the entire BGA package aligns with the rest of the pads automatically.

Surface tension acts on all the solder balls, pulling the package into place along both the X and Y axes. So once the first few balls are in place, the whole thing “snaps” into alignment. Misaligning only some pads while others are perfectly aligned isn’t possible unless something’s seriously wrong, like a warped board or damaged package.

It’s an all-or-nothing situation—either everything aligns, or nothing does.

> Misaligning only some pads while others are perfectly aligned isn’t possible

It's possible when your pcb-making process is on the odge of what designer wanted. Some pads on some boards may be not perfectly aligned in such cases. Or the board was heated not enough or in too short time and not all balls melted properly. Or it cracked under stresses because designer put too much vias in one place near the chip.

> It’s an all-or-nothing situation—either everything aligns, or nothing does.

In theory, practice and theory agrees. In practice, it sometimes does not.

I believe you forgot to quote "unless something’s seriously wrong". Your counter examples seem to describe exactly that: something going seriously wrong.

No wonder computers are binary.

I've heard of head-in-pillow defects where the solder may touch but fails to wet the pad on the chip or board. BGA probably makes it almost impossible to nudge a leg to check for mechanically solid connections. I don't know if bad joints from the factory are a problem in practice, or they usually only crack in use.

The failure mode that I worry about and would need X-ray to detect is that temporary misalignment will merge/bridge some of the solder balls.

I like to "wiggle" the chip with tweezers (under hot air) to see surface tension in action and judge whether the balls have all melted, but a tiny bit too much wiggle causes that problem.

Indeed, the only common issue we have on BGA rework is bridged balls. If it's on the edge and it's a larger BGA, we can often wick it out with desoldering braid, cut up some fine solder wire, push it under, and "reball" it in-place. If it's on an inner row you're removing the BGA.

you have to have the right amount of solder on 100% of the pads for this to work correctly though

Do you? I'd imagine you can have too little on some of the pads, such that the melted material doesn't make contact.

As long as others pads have enough they'd pull the BGA into place, and at that point those pads would make contact and complete the solder.

As someone who doesn't solder or really do much with hardware at all, this answers a longtime question of mine. I always wondered how people got all their stuff aligned perfectly ;)

Yup, when we rework BGA boards it's sufficient to go off the silkscreen outline of the package, if the board has one.

Also the cool-down BGA effect they showed is a lead-free thing, you don't see that on leaded solder balls unless something is wrong.

That microscope is amazing. Commenters debate whether it costs 30k or more around 100k so it is further out of reach for most hobbyist.

A few years ago I had quite a lot of fun with one of those cheap $30 wireless USB microscopes with up to 1000x magnification that connects to some app. My family and I always came up with new ideas about what we should look at next. Incredible fun. Unfortunately it broke down rather quickly. But it opened up the world much more than traditional backlight microscopes I am used to. They are basically “just” specialized cameras with bright flash lights.

I wonder if prices have come down a bit and if there are good options out there for such a portable microscope that doesn’t break so quickly. Better quality and magnification in the $200 range?

I am using 1500€ Amscope for soldering tasks. It does not have such amazing magnification. Such magnification is also not needed for daily work. But it replaced 10k Olympus device from a decade ago. Optical devices got radically cheaper in last 20 years. SMD rework is not possible without them.

Such amazing scope is built in into 70k professional SMD rework station I use sometimes for complex repairs. Replacing RAM and processor chips is easy, but slow. Honestly I don’t think, that the scope in video is extraordinary expensive. Definitively cheaper than my old Olympus gear.

I bought this microscope that has HDMI port for connecting monitor. Cost me little over 100€. Has no lag. Quality worse than what in video but better than some I see on youtube that also lags. This microscope is not perfect but capable to do smd soldering.

https://a.aliexpress.com/_EIRqaY9

I believe that's a Keyence microscope, and yes, way outside the scope of a hobbyist! They have a range of microscopes for this kind of thing. Some are also able to perform accurate dimensional measurements (sort of like the old optical comparators machinists used to use but far better). They're typically used for incoming inspection in manufacturing processes.

Strange Parts did a great video about, "A boy and his microscope..."[0]

We bought the same one 6(?!) years ago and still use it every day. It was ~$900 back then, looks like it's $230 now[1].

I had a really hard time spending that much back then, but it is easily the most valuable tool in our PCB engineering & assembly shop.

[0] https://www.strangeparts.com/a-boy-and-his-microscope-a-love...

[1] https://www.aliexpress.us/item/2251832694057535.html?gateway...

Shipping $80. AmScope are similarly priced and sold directly on eBay.

I bought one of those pore cleaners when I had some pores and quickly realized it was a microscope camera basically, so removed the pore thingy tip and started using it as such (which seems to be the same as you from the description). It was so interesting to explore all sort of stuff! From checking a small cut I got in my head, moles and other parts of my skin, to electronics, different kinds of fabrics, woods, etc.

The microscope is from Keyence. An entry level model I believe. I have access to one with 3 lenses on an automated turret. They’re excellent for inspection and make for a ton of fun when you have anything small and interesting to look at.

They don’t have an API which is a big miss from my perspective. Every inspection requires a human operator to drive the thing.

How much does this thing cost? What ballpark are talking about?

This is, by far, the best video on soldering I have ever seen. Soldering by hand is a dying art...My dad had a car radio repair shop - when radios were repairable (Delco: https://en.wikipedia.org/wiki/Delco_Electronics) - taught me how...like riding a bicycle, you never forget...

I respectfully disagree, and say that hand soldering is not a dying art. If you’re working on boards on the regular you probably have a soldering iron and use it often.

Yeah I agree, I solder parts like those in the video by hand (even occasionally BGAs with hot air)

Yeah, hand-soldering as the means of mass production of consumer electronics devices has (mostly) died out, but the people who actually build and test things, or the people who fix consumer electronics devices, still usually do a lot of soldering.

It's also a necessary skill in a lot of technical hobbies. Modular synthesis by means of DIY modules, the whole mechanical keyboard thing, electric guitar maintenance...

Id definitely disagree about hand soldering being a dying art! There are lots of other great techniques, but hand soldering is still vital to developing hardware. Any hardware company worth it's salt has at least a couple rework technicians that are absolute wizards with soldering.

Also stuff like reflow solder is/can still be done by hand! Its a common thing to do if you need to touch up or modify a PCB and dont want to reflow the whole thing/damage any components

Soldering by hand is a dying art...

I'm not sure. Back in the day we avoided SMD like the plague and it had a reputation of being unapproachable. THT parts were highly sought after and I would even say that a good deal of the success of AVR was because they offered THT versions of their µs long after most others had stopped. Some of us even engaged in the uphill battle of lead-free soldering only to be disillusioned.

We thought hand soldering will die with THT but it didn't.

I see a young generation that has mostly overcome these hurdles. With their young steady hands, sharp eyes, high-lead solder, small temperature controlled irons and other modern equipment they just go about. I envy them.

I actually prefer lead-free solder because its more aggressive flux and higher soldering temperature.

This allows burning away and tinning enameled wire with the soldering tip.

Though there are only two lead-free solders that qualify. I use the Felder Ultra-Clear EL Sn100Ni+. The other one is the Amasan BF32-3.

I suspect tip oxidation is an issue with leadfree? Or isnt it?

At what temperatures you solder mentioned leadfree?

Oxidation is a big problem with the harsh no-clean fluxes in many cheap lead-free solder wires. Switching to a rosin flux (RMA or RA) name brand solder should fix that (did for me.)

Metcal have a great big doc on tip care that covers this.

Tip life is inevitably worse with lead-free solder. Using a brass wool cleaner rather than a wet sponge will help prolong tip life, as will the regular use of a suitable tinning/cleaning paste (e.g. Hakko FS-100 or JBC TT-A). Keep the tip wetted with solder as much as possible - a completely "clean" tip will oxidise much faster than one with a protective layer of solder.

The correct tip temperature for any hand soldering operation is the lowest temperature that will allow the joint to be completed in two to five seconds. In practice, that depends on a host of variables - the composition of the solder alloy, the properties and calibration of your iron, the thermal mass of the joint etc. A usual rule of thumb is the melting point of the solder plus 150°C, but your mileage will vary.

High lead solder? Are you sure about that?

For what it's worth, I took the time to learn leadless soldering specifically so that I could teach my kids. I like to introduce them to safe hobbies (that why they all went skydiving before their 10th birthday, too).

Leaded solder is safe to use if you wash your hands afterwards. Leaded solder - particularly 63/37 eutectic solder - is much more forgiving of poor technique. Lead-free isn't a massive inconvenience if you know what you're doing, but it can be absolutely infuriating for novices.

What about breathing the fumes? Also, doesn't (long-term) exposure to the fumes severely affect skin? I remember the folks soldering a lot of things for the Gemini and Apollo programs had very wrinkly, obviously damaged skin on their faces.

There is no lead in the solder fumes. If anything, lead-free solder is substanially worse, since the flux used for lead-free solder is a lot... harsher. Either way, this can be largely fixed by a small fume fan.

Thank you. In fact, I drive a small horizontal quadcopter propeller with a 3.7v LiPo while soldering to pull the fumes away.

Maybe it’s just me but I find SMT easier and faster to prototype with than THT. Apply paste, place all components on the board with tweezers, reflow, done. With THT I have to bend / cut the legs of most components, and solder each point individually.

As for “high lead solder” - you won’t buy it in Europe. We had to learn using lead free for rework and you know what - it’s not much different, assuming you have high quality equipment.

As for “high lead solder” - you won’t buy it in Europe. We had to learn using lead free for rework and you know what - it’s not much different, assuming you have high quality equipment.

That's bollocks. You can buy leaded solder in Europe just fine. You only need to worry about lead-free if you want to sell a commercial product.

You can’t in Poland if you don’t own a resistered business. I tried and nope, they won’t sell it to individuals.

But thanks for letting me know, maybe it was just a local problem of the particular store, but a EU policy.

I have a roll of 38% lead solder on my desk which I bought last year from Leroy Merlin in Portugal, so you can definitely buy it in Europe.

Any idea where I can buy some from Germany? Reichelt stopped to sell it and I did not have chance to stock up

Nowadays I don't bother with Reichelt or Conrad and just get must of my stuff from Mouser. They offer leaded solder in all kinds of forms. I have to say that I have not tried out if they will actually deliver it to Germany though.

If you can do your joints on first try, lead free solder is exactly as "difficult" as leaded solder. I never notice the difference except when I have to remove it.

Yeah that's true if you have a reflow oven and avoid 0402 and below. Ovens aren't cheap or small though.

Can't you modify a toaster oven to make a usable reflow oven?

>Some of us even engaged in the uphill battle of lead-free soldering only to be disillusioned.

I've never had any trouble using lead-free solder for through-hole or SMT (and I don't have any expensive or sophisticated equipment).

What’s strange is that the larger SMD packages are far simpler to solder than THT ones are. Give me an 0805 or SOP any day over a THT package.

I guess the real driver towards hobbyists using SMD is cheap and fast PCB design. You can’t really do stripboard or wire wrap with SMD packages.

> Soldering by hand is a dying art...

Let me tell you that I'm holding up the flag. Very poorly and with shaky hands, but I'm trying to hold it up... :-D

That’s something that is so obvious under a microscope. My hands are pretty shaky, under a microscope it looks like there’s an earthquake going on.

Actually I have, and you can too! All you need is a stereo microscope - even a cheap, sub-$100 will do :)

Now that being said, I would have never been able to record such a high quality video! The depth of field in particular is really amazing :)

Link to decent soldering scopes? Looking for one since I need to solder/desolder ICs. Been using T15 or whatever tips, they are great because of how varied they are.

I’ve owned this one for about 10 years and have never felt limited by it: https://a.co/d/c3z7JMf

I've had that same one for a long time, and am pretty happy with it. But I would recommend shopping around and watching some reviews. Things may have changed.

One thing to consider is the light. I was never happy with the light on this scope, and instead use a different flexible desk lamp. Most of the ones mounted to the scope have pretty short stems, and can't be positioned to shine from the front, or very low to the side.

I've got the SM-4 7-45x, with LED ring light, 0.7x Barlow, rubber eye cups, and double-arm boom stand. Basically this[1] with some extra accessories. Works excellently, the newer design allows mounting the ring light easily (there's a grove it sits in).

[1] https://amscope.com/products/c-sm-4ntp-64s?variant=414205946...

The goto for most people is getting an AmScope on your budget range.

There are other options, but they tend to be less budget friendly, more targeted to professionals than DIYers.

Practically all hobbyists and phone repairers use the same style of generic stereo zoom microscope, loosely based on the Meiji EMZ-5. AmScope will sell you one starting at around $400, or you can buy direct from China if you want to save a few bucks. Less expensive models with fixed magnification are available, but I can't recommend them.

https://amscope.com/collections/stereo-microscopes-zoom-powe...

https://eakinsmicscopestore.aliexpress.com/store/3200040/pag...

With 10x eyepieces and a 0.5x auxiliary objective, these scopes provide a very useful range of 3.5x-22.5x magnification and a comfortable working distance. At the minimum 3.5x magnification, the standard widefield 10x eyepieces give a field of view of about 50mm.

They are available in various bundles with a wide variety of stands and accessories; the essential accessories are a ring light and a 0.5x Barlow lens. I would recommend the biggest, heaviest boom stand you can reasonably fit on your desk, because any instability in the stand will be greatly magnified in your vision.

The key to using these microscopes successfully is to adjust the parfocal, which will allow you to adjust the zoom without having to refocus.

https://www.youtube.com/watch?v=R00KyVGRMpc

The preferred industrial option is the Vision Engineering Mantis, which uses very clever projection technology to provide a stereoscopic image without eyepieces. The ergonomics are dramatically better than a conventional stereo microscope, but you'll be lucky to find a used model on eBay for less than $1000. A big investment for a hobbyist, but worth every penny if you've got back or neck problems.

https://www.visioneng.com/products/eyepiece-less-stereo-micr...

Solid post.

Just curious as I'm not into electronics but what is the name of the device where you put the PCB to be heated up? Is it expensive? What are the basic tools to perform full soldering of all components in a PCB? Seems like today you can buy all these tiny resistors, capacitors, chips, etc and pretty much do your own boards at home, right? Any suggestions on all these basic tools to have a relatively decent but not expensive lab setup?

Reflow oven

It's quite feasible to do reflow soldering by applying solder paste with a stencil and then using a cheap toaster oven. However, the lack of a precisely controlled temperature profile makes it less repeatable and reliable than the industrial process. I've done it successfully a few times but generally had to touch up one or two components with a hot air station or soldering iron.

Here's a SparkFun blog post: https://www.sparkfun.com/news/3319

- simple boards can be made by first transferring your PCB design to a copper-plated board using toner transfer or UV exposure, then etching the rest of the copper away using an etchant solution (if you're willing; takes some elbow grease and dangerous chemicals). Or you can get a cheap fab-house to manufacture and ship you something (like 7-14 days, a few tens of bucks per batch)

- simple boards you can probably solder with a cheapo (~50-100$) soldering system, or a solder-paste+hot air machine setup

- components you can get for very cheap from LCSC, aliexpress or at okay prices but good reliability from digikey, mouser etc.

You'll also need stuff like multimeter, ocsilloscope, logic analyzers, etc for debugging your boards but you'll know when you need them, and there are cheap-enough options available up to the point when you start doing advanced stuff and you know what you need.

> Seems like today you can buy all these tiny resistors, capacitors, chips, etc and pretty much do your own boards at home, right?

The "starter kit" I would suggest is:

- temperature controlled soldering iron. This is worth the premium over "dumb" irons, especially for leadfree solder. People have different opinions about brands, but try Hakko or Weller. Start with a small chisel tip

- solder paste is a more advanced substance, and is perishable and should be kept in the fridge. Stick to a reel of thin solder to get started

- flux pen is surprisingly useful

- resistors are cheap enough that you can just buy all of them: https://www.aliexpress.com/item/4001321720241.html

- ICs you should stick to Digikey or other local supplier and NOT aliexpress

- PCBs: services like JLPCB will make these and ship them to you

- desk lamp. Possibly one with a magnifier.

- some people will get serious about fume extraction; personally I quite like the smell of flux and just leave a window open. Be careful with airflow in case you blow away smaller components

- solder braid: annoying, doesn't work well. Try a solder sucker

- advanced but extremely useful tool: solder tweezers

- hot air gun and/or oven: again a more advanced tool, but critical for certain parts. Avoid those parts.

Solder wick: can really work if you have decent quality wick, either rosin-impregnated or add flux when using. Also I've found it really helps to add some fresh solder to whatever you want to desolder, before using wick. I learned that from watching the YouTube channel "Learn Electronics Repair".

For most SMT repairs, we use a pair of these hot air guns[0] and one or two Hakko Omnivises[1].

A 3/4" copper pipe elbow JB Welded on one of them turns it into a 90 degree bottom-board heater and other is waved by hand over the top of the board.

Nearby parts can be protected with a little Kapton tape or other heat resistant shielding.

[0] https://www.amazon.com/gp/product/B0752Z4165

[1] https://www.amazon.com/gp/product/B000B61IHW

That is really cool! I haven't tried hot plates because I didn't really have faith that solder would actually pull the component down and align it. I think this video might have improved that faith :-)

Using a hotplate is like driving with one eye closed. Sure you’ll get there, but your accuracy will suffer!

Though I’ve had many a SOICs magically realign on the hot plate — they were pretty forgiving — it’s not worth it to run without proper temperature profiling, even if it’s from a hacked toaster oven :)

To counter the sibbling comment: I've assembled many dozens of boards on a hotplate with no complaints. Watching them reflow with a stereo microscope (AmScope SM4) over the hot plate is fun. I've never worried about temperature profiles; I've just started it from cold on the maximum setting and turned it off when all the solder has melted.

* The hot plate I used was the "Presto 07211 Liddle Griddle", which worked well. https://www.amazon.com/gp/aw/d/B00006IUWL

Watching how forgiving solder can be, and me still being bad at it is blowing my mind right now.

could it be that you are using lead-free solder? that's almost impossible to use without precise temperature control and it's the most common source of annoyance in recent years with hobby soldering

I had that problem for an embarrassing number of years because I didn't know what flux was.

Today, I won't even plug in the iron if I can't find my flux first.

I respectfully disagree. I'm a mediocre hobbyist at best, I have cheap gear and use exclusively lead free solder/solderpaste without problems. The trick is to just use a lot of flux. I have a flux pen for hand soldering, and solderpaste usually has enough flux in it.

The hate for lead-free is wild.

Hey kids - don't listen to the old geezers (though I'm one too). Get lead-free and figure it out. It's really just about getting in reps, and caring about the results.

In my personal experience, leaded is maybe 5% easier.

If you're doing hobby level work, it is definitely not worth having lead around getting into and onto your other stuff and possibly being licked by kids or pets or whatever, and turning your projects into hazmat.

Moar flux.

Really. Just add more flux than you think it could possibly need. The biggest failure mode I've seen with solder of all kinds is not enough flux.

This Amtech no-clean is really gooey[0], but pretty useful for rework.

This Kester water-soluble is incredible, but needs to be washed[1].

If you need to hand-clean PCBs, a small photography developing tub and a sonicare (or similar) toothbrush is a game changer.

[0] https://www.amazon.com/gp/product/B09Y7N6QHF

[1] https://www.amazon.com/gp/product/B00DEDB5CM

It's super cool how they generated the 3D model on the fly, I'd love to spend some time playing with the microscope they used in the video.

I followed the link in the description and it brought me to the microscope product page. I clicked "price" and it had a page that told me to enter my business email for a quote lol.

You know it’s expensive when they won’t even tell you the price.

Reddit says around $70k: https://www.reddit.com/r/microscopy/comments/nqo4qy/keyence_...

We had them at a fab. About $85k + accessories at the time (~ 7 years ago).

Nicest light microscope I've ever used.

Whatever you do, DO NOT enter your email and absolutely do not give them your phone number. Keyence famously will not leave you alone. They’re very aggressive.

Yeah, I confirm! They're infamous for that!

https://www.govsci.com/product-detail/Keyence--Corp/VHX-7000... $45k US

Sure! Us olds routinely use microscopes. New things sure are small and you can’t solder it if you can’t see it.

I'm also shocked at how seeing hand-shake up close (via a microscope) tends to diminish the amplitude.

I'm old, and drink too much coffee most days, but I can hand-solder down to 0402 with my microscope.

Best money I ever spent was a cheap, stereo soldering microscope.

Applying paste when you have a stencil is easy but I recently tried fixing the FPC connector on a Nintendo Switch and hand-applying solder paste is messier than hand soldering.

Yes! It's ridiculously difficult to hand-apply solder paste without a stencil.

We use a pointy dental tool for larger pads and acupuncture needles for the teeny-tiny's.

I'd love to learn about better ways though, anyone else got tips for applying solder paste before a repair gets reflowed?

Not usually but just today I made a foray into surface mount soldering to mount a 2mm^2 8-pin package onto a breakout board. I'd planned to manually cut a breakout board but underestimated just how damn small it would be. Luckily a friend with a laser engraver volunteered to help and we managed to zap some breakout boards. I manually added paste (after a few false starts I used a needle like a fountain pen to dip into a blob of paste and dab it onto the traces) and reflowed it in a toaster oven. :D

Solder paste under the microscope: https://i.imgur.com/IiTKmrS.jpeg

Closeup of reflowed solder, maybe a bit janky but it went better than expected: https://i.imgur.com/9wbV8nc.png

Finished test board hooked up and working: https://i.imgur.com/xZduEUt.png

I have watched way too much Steztix Fix on YouTube - it’s kind of addicting to watch people fix things). On that channel,he manages to fix all sorts of things with commodity tools, including a cheap microscope, hot air rework station, and soldering iron. He isn’t doing any BGA soldering, but there are YouTubers who reball BGAs (that looks frustrating).

I love that channel. If you like that look up MyMateVince too and JoeyDoesTech. Super good.

Can also recommend stezstixfix - lots of humour and he’s not massively technical so it’s in to hear his thought process as he puzzles out the problem.

Yes, and I've seen closer even on YouTube recently. https://youtu.be/RuVS7MsQk4Y?si=diQB07jBvv5rK8lZ

The isometric view camera is neat though!

Can someone list here high quality solder one can buy in aliexpress that is easy to work with? (primarily) Lead based.

Asking as a hobbyist for soldering wires (think arduino) and sometimes pcb smd components. After a while when learning I realized that to solder, flux and solder makes a big difference... low quality solder and flux is just miserable.

"High quality" and "can buy on aliexpress" huh. I'd drop the latter requirement.

Kester rosin core is available everywhere including Amazon and is excellent quality. 60/40 works nicely, #44 too.

I was hooking to see an example of a cold soldier joint. (Applying soldier directly from the iron without heating the pin)

Yeah - me too!

FWIW, We got a training class from a grumpy guru a couple years ago, and "cold joint" was his most despised phrase.

He insisted we call them "dry joints," because that's what they actually were.

Now, whenever I hear (or read, or say) the terrible phrase, I can't help but think of the old guy, "No! it's dry!"

Reminds me of my physics PhD, where I would solder SMA microwave connectors to PCBs under the microscope. It was really satisfying to apply the solder, put the connector and watch it bond on the hot plate. Bonding chips was similarly satisfying and had to be done with even larger magnification.

Anyone here know why solder paste isn't made of finer particles?

What are the tradeoffs on particle size?

They make it in a variety of particle sizes. For certain pitch devices (usually under 0.4mm) you need to switch to finer particle sizes (Type 5 typically is used for the small stuff).

See:

https://fctsolder.com/solder-paste-type-3-vs-type-4-vs-type-...

The finer the solder particles, the greater the ratio of surface oxide to actual solder. Oxidized solder consumes some of the flux's reducing effect.

I've heard this 'oxide layer' argument before (usually in regards to recycling swarf) and I don't buy it. Typically these oxide layers are measured in nanometers, something a few hundred microns across isn't going to lose an appreciable amount from a tens-of-nanometers-thick layer.

There are a few reasons. Smaller ball size means more surface area. When the paste flows, the surface tension of the solder makes it cling to the part and pad, and moves the part to align with the pad. With more surface area, you can start to get solder that clings to itself, making solder balls outside of the pad, called balling. This wastes solder and makes conductive components that are effectively contamination, they now have to be cleaned off, you can't let them remain to roll around and potentially make a short. I had issues with smaller balls clinging to stencils; i think the price is also higher.

I think there is a rule of thumb for choosing solder ball size, and it was something along the line of 5-8 balls should fit in the width of the smallest solder aperture. This will give good performance according to the component size without too much balling or other flow issues.

Really cool camera and very nice set of soldering "demos", including without flux.

They have used microscope to record it.

Why downvote? It is true. Have you seen the description in the youtube? It says - Microscope used in this video is Keyence VHX-7000N https://www.keyence.eu/yt-kib-vhx-0924

What kind of heating element did the author use? I have some heat guns but it's pretty easy to burn the PCB when attempting a reflow or other operation.

If you find this awesome, you should work on manufacturing. there are lots of great manufacturing technology startups happening right now

could you elaborate on that. I'd love to explore this area!

I'm wondering how common is damage to soldering connections in extreme temperatures and/or vibrations? Fascinating video btw!

I have to do 0402 by hand to fix some old stuff this week. it's going.... let's just say that it's going

I sure haven’t

Yes.

Dupe of https://news.ycombinator.com/item?id=41545215

Reply on news.ycombinator.com