I have two 5 meter neopixel strips that I would like to solder together end-to-end. However, I’m worried about damaging the strips. I’ll have to take off the connectors that are soldered on at the moment.
Any advice on how to get the job done without burning something up? Is a 30w soldering iron OK?
Lots of good tips online. You want to melt solder onto the pads, but not heat the pads “too much” either, as they might lift. You might want to practice a bit first.
For the small pads on strips, a lower wattage iron shouldn’t be a big deal.
Having a clean (non-oxidized) tip is always an advantage. I like to keep a lump of solder on the tip of my iron when I’m not using it (hot or cold), then clean it and apply a little fresh solder right before I use it.
I’ve noticed that some strips are composed of 1-m or 0.5m lengths that are lapped a bit, with the upper layer cut across the pad at the midline, and overlaid at the midline of the underlayer. Maybe have a look at your strip and look for those, and see if you can emulate that technique!
Good news about practice (as scruffy mentioned) is if you mess it up, you’re usually out only a pixel (maybe 3 on 12V strips?)
I think I have some short pieces I cut off the ends of my old rgb strips. They would make great soldering practice. There’s no way I put them in the trash. I just need to find them…
When I install LED strips I always use a temperature controlled soldering iron, that way you get just the right amount of heat and no more. The only problem is when the installation is outside and its cold, as gust of wind can play havoc with the temperature. And a solder sucker is a must. I find that desoldering braid a bit hit and miss. Nothing beats a good solder sucker.
The solder should be as thin as is possible but still have the flux built in. That way you get a nice quick solder joint. Definitely practice. I also use an illuminated angle poise style magnifying glass.
I also recommend an iron that allows you to adjust the temperature. Not only is temperature regulation important, but adjusting it for the job can make things so much easier. Cheap irons can get REALLY hot and destroy LED strips, and hot irons will evaporate the flux much faster making the solder dry and hard to work.
The iron I’d recommend for general use is the Hakko 888D. It’s reasonably priced and is an excellent iron.
I was hoping you would recommend a dual station hot air/iron. I’m looking for one that doesn’t break the bank.
My first air rework station has since been discontinued, but it is excellent and still works great to this day. It is very similar to this more expensive model:
The key difference from many of the cheaper air stations that I see today in that the air pump is in the box, and there is a wider tube that feeds air to the handle. The cheap ones I see use fans in the handle and in my limited experience, aren’t quite as good.
In the only dual station I’ve owned the soldering iron half was terrible. It was about $75. It would still beat a completely uncontrollable iron, but the iron quality was so low we now have a Hakko sitting next to it. Still, the air side is usable. Cheap irons will waste your time, destroy your boards, and cause nothing but frustration.
I see cheap hot air rework stations, the kind with fans in the handle, for $40 and up. If you want a low cost workable setup, I would pair one of those with the Hakko. That still puts it in the $150 range with both.
What solder are people using/prefer? I’d like to go lead-free. I work with led strips a lot, stranded wire, solid core wire, and some pcb work(adding headers to esp32 dev boards) and some perf board prototyping. I’m used to using flux-cored.
Ya’ll should know I’m a big proponent of lead-free solder. 
I will say that I have had BAD lead free solder, unusable stuff! And I got it from SparkFun, which is usually quite trustworthy. That was ages ago, and hopefully they don’t carry it anymore. The big lesson there is that the solder matters and it’s worth trying alternatives.
These days I use Kester #48 flux core solder (the tin, silver, copper formulation). You can get it in various thicknesses, but they tend to be about $70-100 a spool. Unless you are doing manufacturing, it will last a decade for hobby work.
I looked around, and its really hard to shop for this stuff on Amazon. I found it easier to navigate the Kester site for #48 and get a part number, then search for that.
https://www.amazon.com/Kester-24-7068-1405-Content-Activated-Sn96-5Ag3Cu0-5/dp/B08JN83ZM8/
Perhaps I should sell this in smaller inexpensive amounts and make it easier for people to get.
I also recommend taking a look at ventilation or air filtration. The smoke from any soldering work is an irritant and breathing it should be avoided.
I am sad @wizard that I can only like your reply once. Making Kester available in smaller sizes would be HUGE! I have heard many people lament on how sad it is that they don’t do it themselves. I would LOVE to see it in 8oz, 4oz, and 2 oz. Or even 8oz and 4 oz, or just 8oz 
I would like to try a couple different Kester formulations… but there is non way I am buying a pound at $70-100 only to find out I don’t like it. And I was indeed aware of your views on leaded solder. I like how you laid it out there. In fact that is why I am asking this question. I am tossing my “tons” of leaded solder because of what you said.
My understanding is that it is a specialty solder alloy with a higher temperature (melting point is 227C) compared to the silver containing solder (melting point of 217C) and may be more difficult to use, but would have desirable properties depending on the application (perhaps bonding to different metals better, or where the silver content is undesirable). For general use I would use the Sn96.5Ag03Cu.5 stuff also called SAC305.
Of course your iron is going to be hotter than the melting point. I generally have it set to 350-400C, often defaulting to the 700F/371C that the Hakko defaults to. Too hot and the flux will be gone before it can do any good. I turn it up a bit when I want to go fast or have very large metal things to solder to, such as massive ground planes and thick copper wire. The idea is that I’m getting it to melting temp faster, not reaching those high temperatures at the solder joint.
On the topic, I have also used some Chip Quick bismuth based solders with a very low working temperature (melting point of 138C), lower than leaded solder (183C). These are great for working with temperature sensitive parts, like surface mount LEDs, especially for prototyping/hobby work. The downside is that it oxidizes like crazy and doesn’t “flow” quite right. When using hot air with a paste, it will often leave little solder balls instead of coalescing into larger blobs, and these have to be cleaned off, or scooted into pads/pins with an iron.
Additional reading material:
Whiskers!?!? I never even knew it was an issue. lol I am such a newb.
Is the default Hakko temperature of 750 okay for soldering the strips or should it be cooler?
FWIW I ususally use 660-700 and have good results.
