As another example, NAND is manufactured on 40nm and for the foreseeable future it'll be. https://thememoryguy.com/why-3d-nand-is-stuck-at-40nm/

I’d love to be able to fab my own designs, 40nm would be awesome. Yes there are projects where you can. But they allow small area/transistor counts. Pcbway for chips would be amazing!

won't happen for such a complicated process like 40nm. The design tooling itself would cost 100s of k$.

Honestly I love that old processes are still running and old parts are still being made.

Modern SMD stuff is really rubbish for learning electronics. It's nigh impossible to hand solder because all of it is tiny af, and since it's newer it's expensive and you don't get as many attempts. Luckily there's still an immense supply of arguably completely obsolete thruhole parts that are super easy to work with, can be breadboarded and bought for basically nothing.

I respectfully disagree with what you say about SMD parts :)

SMD parts are much cheaper compared to THT in my experience. Which parts are you thinking of specifically?

I majored in CompSci but got my first job in embedded at a hardware manufacturer. IME it didn’t require many hours of practice to learn to solder e.g. 0603-parts. Around 4-5 hours of deliberate practice for me, although smaller can still be annoying.

I have slighty worse than average vision so personally need a magnifying glass or a microscope for 0402 and smaller, but I can do it and it looks pretty afterwards (says the HW techs).

I was about 5-6x slower than the HW techs at solder work and repair, so I didn’t solder something up every week/month. I can still mount a board easily with 0805s and 0603s even though it’s been a few years now.

Well there are lots of breakout/dev boards these days that do make it possible, but for something like adding an indicator LED I'd rather reach for an ol' 1/4W resistor than those ridiculously tiny SMD specks. But in general modules like the CD4051 mux, SS49E hall sensor, 74AHCT125 level shifter, etc. Cheap and super reliable stuff.

I admit I'm really crap at accurate soldering so it might be more of a me issue, but I doubt I'm entirely alone in this.

I can see what you mean. For many, it looks scary in the beginning (using tweezers etc.), but it comes quickly with practice.

It is easier than it looks IMO, though I did get some tips from our techs which likely accellerated my learning (e.g. compared to learning on your own).

With smaller (and thus lighter) parts, the surface tension helps pull the parts into place etc., so you get help on “pad-alignment”.

Hot air soldering gets more difficult though, as you risk blowing parts offboard :D

I don’t know the parts, but my experience is that everything SMD is cheaper than THT. Almost always. The hall effect sensor can likely be found cheaper in Sot23?

The only reason I ever saw for using THT parts, was the (typically) much higher power ratings.

At my previous job, a typical board with e.g. 6 layers and 500 components would have perhaps 5-10 THT parts and the rest in SMD (0805 and 0603 mostly).

YMMV and for hobbyists it doesn’t make a big difference.

SMD-soldering skills can be handy though. E.g. I’ve repaired a few of my friends’ TVs with broken backlights for pennies.

I find SMD so much easier to work with. You just drop the parts with fine tweezers after some solder paste and apply hot air. It's also much cheaper. You can also rework without trouble in my experience. Apply hot air, lift the chip with tweezers. Remember to use lot of flux.

> Remember to use lot of flux.

Agree with your post and this part especially. More flux means easier work, but more mess to clean up when done. Flux pens are practical.

I only used hot air for removing parts, but the techs who controlled it well absolutely loved it and were insanely productive.

I solder QFP by dragging a “saturated” tip across the leads and then wick up any excess solder if needed (e.g. if I bridged/shorted a few legs).

well, true, but this doesn't guarantee a node to stay in production. fabs sometimes shut down a node to use the equipment and space for another node with more demand. also, sone of these machines from 80s and 90s are simply old and it's not financially viable to buy a new machine for such a process. they typically cannibalize some of the machines for parts, or even buy old machines for parts from other fabs closing down. I believe a fan requies refreshing and investment every 15-20 years.