hckrnws
Almost 30 years old. Old good times without BGAs and modern barely visible components. While some basics are still applicable the modern problems are not covered at all.
Provided you have good eyesight and steady hands, I've mostly found what happens as you get smaller is:
- Heating becomes easier. There's no large sinks to take the heat away. It's also easier to overheat things.
- You need finer tweezers, and don't drop them because if you do the tips will bend.
- The solder's surface tension does more of the work. It feels a lot more like sticking together things with tiny droplets of glue. Having the correct amount of solder in the right place is critical.
- Solder and flux become two separate things you have to care about individually
- It is easier to burn yourself
- learning how to brace your hand against something in a way that gives you very fine control. One reason soldering with an iron can be difficult is because your hand is so far away from the tip, like trying to write with a pen held by the end.
When I started my first job a coworker encouraged me to learn how to solder SMDs and do "microsoldering". Like most people I thought I was going to need high precision and a much steadier hand. Probably like most people that learned I was impressed at how quick I picked it up. I think the hardest thing was learning about part "tombstoning" but that's not that difficult to deal with. I'm not going to say it is easier than soldering through-hole components, but I think for most people the mental barrier is much higher than the actual barrier.
I now highly recommend learning it to anyone doing electronics. It's well worth the (small) time investment and makes things a lot easier, opening lots of doors. Even for a hobbyist you immediately get benefits. Everything becomes more compact, 2 sided boards are much more usable, and, of course, it opens up a lot of repairability (and recycling. Are you really a hobbyist if you aren't desoldering and reclaiming parts?).
Agree that SMD hand assembly is easier than it looks, at least down to 0603 imperial. If I can wait the week for boards to arrive, I’ll often skip the breadboard step and go straight to a proto PCB, especially since most parts aren’t available in throughhole without waiting on dev boards anyway.
When you hand someone a board with 0603s on it that you hand-assembled, it seems like magic to people who stop to think about it.
> Are you really a hobbyist if you aren't desoldering and reclaiming parts?
Fun memory from who-knows-how-many years ago:
While installing a Playstation mod chip, I accidentally dislodged a nearby surface mount resistor, pulling off one of its metal contacts in the process. (Is that what happens when you overheat them?) I didn't think that was fixable, and since it was Sunday, the local electronics shop was closed. I ended up disassembling an old junk digital camera that hadn't yet been taken to the e-waste recycling drop, and finding inside it a resistor that seemed close enough to maybe work. The transplant was a success, and the Playstation ran great thereafter. Very satisfying.
I recently got rid of a lot of components that I have salvaged and hoarded over the years. If I need a doodad for something I'll just buy it. I'm done storing all this junk I will never use
One reason soldering with an iron can be difficult is because your hand is so far away from the tip, like trying to write with a pen held by the end.
Newer irons, especially for SMD work, have gotten smaller and the grip-to-tip distance also shrunk; here's a good visual comparison:
https://www.eevblog.com/forum/reviews/grip-to-tip-distance-o...
It's worth noting that the longest one there is already much shorter than the classic mid-century unregulated irons, and all of those can be held like a pencil.
> The solder's surface tension does more of the work. It feels a lot more like sticking together things with tiny droplets of glue. Having the correct amount of solder in the right place is critical.
I believe this is why I have an easier time hand-soldering BGA than QF[np]: I can't screw up solder amount/evenness.
What tools do you use for BGA soldering? I’ve seen people (well, dosdude1) using board preheaters and hot air stations, but I could never justify the expense for the amount of board rework I actually do.
Hot plate, flux pen, hot air gun.
Important caveat: The downside to this is you can't inspect it (without an x-ray machine), and if you screw up, you're going to need a new chip (Re-balling does not look approachable/time-efficient)
How are you burning yourself? I've only ever worked with one person who burned himself soldering when working on a SMT PCBs, and it was while desoldering a through-hole connector, when a desoldering station was long past its cleaning interval and it dripped some solder onto a metal ring he was wearing. This was a guy who would lick a soldering iron to see if it was hot and touch the molten solder in the wave solder machine. The Leidenfrost effect goes a long way.
An easy one is heat transferring through an SMD component to your tweezers, while trying to gently remove it from a heavy ground plane.
I don't think that modern boards are really repairable at all beyond component replacement- 4+ layer stackups being the big reason. If there's a way to do anything to those boards besides total replacement I'd be super interested to know.
The techniques here are also way beyond basics I think- like, you look at most guides for repair and it's "idk just solder some bodge wires on there, here's what a good joint should look like"
Andrew Zonenberg posted a Twitter thread a year or two ago where he fixed a missing PCB trace some layers down a PCB, with a stereo microscope, precision mill and very steady hands.
Edit: here's the thread. It's a 6 layer PCB with a short on L5 that needs to be fixed from the L1 side.
10/10 read
For boards with a bunch of layers and BGA/LGA packages, that have internal manufacturing errors or damage (e.g from overflexing), repairs can be untenable.
If the parts all have pads on their perimeter, then a jumper wire can replace internal traces. If the pads are underneath the part, and the trace is only internal, than a jumper may not be feasible, unless the damage happens from the surface in, in which case each layer can be jumpered at the damage.
Mostly when things fail it's not a trace, it's components
It's great for working on vintage equipment, stuff that might need (and warrant) that kind of repair. Less so if you run a cell phone repair shop.
There are a surprising number of Indian cell phone repair shops with YouTube channels that do feats of soldering, like repairing torn flex cables… I bow down at their craft. If I ever get a sabbatical I’ll go to India and ask to be an apprentice.
It started getting really annoying earlier with PGA, to be honest.
Missing: how to solder a wire to the thermal pad on the bottom side of an IC. Assume there are components on the back side.
If it's QFN, you're probably best deadbugging it and jumpering all of the pins individually, but first make sure that you need the connection. QFP wireframes all have a center pad, whether or not it's electrically connected to the die or needed for thermal dissipation.
If it's an SO package, e.g. SSOP, TSOP, etc., Desolder the IC, add the jumper wire, bend the pins down enough to account for the thickness of the jumper wire, and resolder the IC.
Either way, make sure you have enough thermal mass connected to it for thermal dissipation. If there's components on the opposite side of the PCB, it's probably not much.
Isn't it just ground? If not, can you drill a corner of the chip? Most of chip material is just plastic.
I have a problem of dismounting brittle SATA ports, maybe I just need more preheating but they are sitting really tight in the board.
SATA ports are often rated for only tens to hundreds of cycles, so they're often made out of fallapartium.
If you're replacing one, it's easiest to cut all of the plastic off first, then desolder the contacts one at a time. Sometimes you can even pull the plastic off, without damaging it. It's usually necessary to preheat the board.
Things like that are often the only through-hole components on a PCB.
I like to melt the original solder one contact or area at a time, add a little bit of fresh flux-containing solder if needed, and as soon as it gets to the consistency of mercury, vacuum it clean out with a good soldersucker.
Watch the PACE videos as well, they’re on YouTube and they also cover how to remove conformal coating and using different tools.
Beautiful illustrations!
Crafted by Rajat
Source Code