Learning to solder electronics

The green circled one is a perfect solder joint. The yellow one has a bit too much solder, but its still fine. It was heated enough for the solder to flow around the connections of the work. The red one could be better. It looks like you had a good solder joint when you put that resistor on, but then later it looks like you came back with a solder covered wire to run the connection over to the contact on the right. The fact I'm not seeing deformation of the resistor solder joint when the wire was attached makes me think you might have a cold solder joint there at the resistor for the wire.

Honestly, for this simple circuit all your solder joints are at least passable if not perfect. I doubt this board would ever be in circumstances that any of these solder joints would fail.

A few other things that I've learned over decades of soldering:

• Soldering is the act of heating the work not the solder. When the work is hot enough, the solder will melt and flow over the connection.
• Good soldering is moving the heat into the work as efficiently as possible with the shortest time so as to not damage the board or the components. If you place a "dry" iron tip against the work a shockingly small surface area will actually be in contact with the work to transfer heat. Instead "wet" the iron it with just a tiny bit of solder. It will liquefy instantly and sit as a small liquid ball on the tip of your iron. That ball of liquid solder will squish around whatever shape you're applying the tip to providing an excellent thermal bridge to move the heat into the work.
• All soldering irons have a "heat battery". Here's a bunch of them I circled in green:

Typically inside that section is not only the heating element but a dense piece of material. Usually ceramic but sometimes metals. They all perform the same function. When the heating element heats up, heat is drawn off the element into the dense material in the iron. When you place the tip of the iron on the work, most of the heat is draining from that dense material, and only a bit from the heating element itself.

The consequence to this is that if you're soldering lots of small points back-to-back, or a very large contact just once, you can drain all the usable heat out of the iron and still not bring the work up to the right temperature for solder to flow right. If solder starts acting weird and plastic like after you've solder a bunch of points, simply set the iron back on its rest and wait for a minute or so for the iron to fill its heat battery back up. After that you'll see the solder behaving how you expect.

Wonderful day! Looks not bad, but doesn't look perfect, sorry. Yet, there's progress it seems!
Generally:

1. Clean both platforms for the join, and the soldering iron;
2. If the solder does not come with flux, apply a proper flux to the both ends (flux must be compatible with the metal);
3. Heat and apply a solder to the first fluxed end;
4. Heat and apply a solder to the second fluxed end;
5. Heat and join to ends together;

I've been into electronics for almost two decades, and I relatively recently noticed the following video that you may find interesting. It is more modern than books and quickly summarizes the principles to be researched manually further if required (e.g. in books):
- Do This Before You Solder Anything

I believe it mostly comes with practicing, and experiments with an iron that has a temperature indicator should support it.

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Flux. Flux. Flux. Flux. Flux.

Your joints look like mine when I don't have any flux.

Get yourself a couple liquid flux pens, some paste flux, solder braid, and a squirt bottle of rubbing alcohol to clean up.

Flux is about 75% of a clean, perfect solder joint. Get the flux right and everything else gets easy.

Learn what "wetting" means. Compare a drop of water falling on waxed paper vs on a paper towel. The water drop does not "wet" the waxed paper; it just beads up on the surface. Solder does exactly the same thing.

If the substrate is not hot, or if it is dirty, or has an oxide layer on it, the solder will not "wet" the substrate. Flux cleans the surface and removes the oxide layer, so that solder will wet the hot substrate.

You want to look at the shape the solder pool takes at the very edges. If the solder beads up, forming a convex, ball shape, it didn't wet the surface; it's a "cold" joint that may fail. If it forms a concave, "dished" shape, it wetted the surfaces, and has formed a strong joint.

The trick is to get all parts of the joint hot at the same time, without overheating anything. Flux and a well tinned ("wetted") iron make that easier.

Flux is your friend. Do not be scared to use it. I like RMA-218 myself.

Solder does have flux inside of it, but having separate flux gives you much more control over where the flux goes, and it will do a relatively better job at cleaning oxidation from your pads and leads, leading to a better joint.

Needs more heat.

If the circular holes are heated enough, the solder wil flow and distribute evenly over them. You'll need patience if your soldering iron is old or slow.

But, it is easier to heat those holes using flux since it give a direct connection.

Lovely first solder job! Get some flux paste to help it bead if you ever need. Should copy me, get a bunch of USB-C PD boards and make yourself a quick-charge station

Temp controlled irons make it a breeze if you can afford it (they can be a bit pricey). Check locally on fb marketplace, craigslist or secondhand electronic component stores if theres one near you for an older model as they'll last you for life. I personally picked up a Hakko FX-888D years ago and the quality is great (Japanese).

A hot air station is nice but the biggest help with small electronics is magnification, your hands will be a lot steadier once you see better. I think the control loop in our brain can handle small movement a lot better once the feedback is bigger. Once i see the tip of the iron under the microscope i can solder miniature smd stuff without shaking at all.

Good tweezers are a must. And a iron with intigrated heaters in the tip like the cheap t12 stations from ebay works a lot better than the stations with tips and heater separated. A nice project is this:
https://github.com/wagiminator/ATmega-Soldering-Station

You can get t12 handles and tips for cheap on aliexpress.

Also the cheap hot air stations are fine but i would check the temps with a thermocouple when setting it up the first time they may not be calibrated correctly.

Get lead solder, if you wash your hands and dont eat the solder its fine, it will flow better and doesnt need the high temps of unleaded solder.

Flux also is really important, you can mix your own with rosin and ethanol for cheap but you can only clean it with ethanol so be aware that its very sticky. If you have questions please ask, its always nice if people learn to repair stuff :)

Definitely do some reading/research on proper iron and tip care. You can burn through tips really quickly if you don't know what you're doing.

It’s an incredibly rewarding skill to learn, but in my experience a hot air station is just as, if not more useful than a good soldering iron. For tiny components hot air and a pair of tweezers is far easier for me, plus it opens up being able to swap ICs of various kinds to expand your skill set further. I also occasionally use mine combined with a really small iron tip to remove solder from stubborn through-holes.

However, keep in mind that soldering is only half of the skill. The other half is electronics troubleshooting, so taking the time to learn about that will absolutely be worth your time. Poking around with a multimeter to find a hidden short rather than just relying on a visual inspection can mean the difference between wasted time and a successful repair. Being able to measure voltages and currents to verify that a circuit is doing what it’s supposed to be doing is essential.

Can you try making a raspberry pi next? Gotta aim big

I've been soldering occasionally for years and years, and always thought I was pretty shit at it. But then I got an actual quality soldering iron.

Which do you use?

I learnt that blu tack or the like is nice to hold stuff in place. It sticks well and is easy to remove. Way easier to adjust than a third hand.

Also: when a hole is filled with solder but it shouldn't be: wooden tooth picks and heat to the solder.

Wider soldering tip: more heat, more stable temperature.

I am happy to see someone also struggling with soldering and the helpful comments are actually helpful! Online comments always just seem to go "heat up both sides and voila!" and it never goes the way it should :(

voultar on youtube has some great confidence building tipa too. even though he does more advanced stuff

Nice work!!

Keep going, get a reflow station and try some smd solder kits. Get all the solder kits you like, try chisel tips with your iron. Try to etch your own pcb.