Soldering

Here we go... I have strong opinions on soldering.

Technique

Tip Loading

Load the soldering iron tip with some flux and then apply it to an area. Make sure you're using flux here as you're going to burn off all the rosin core flux while hte solder is on the iron.

Drag Tip

The mystic technique. You need a drag tip to do this (and personally, idk why you would ever use anything but a drag tip for everything you can). Drag tip soldering is actually really easy.

1. Take your IC, align it, and tack it down at the corner pins. Repeat this until it looks well aligned.

2. Feed and drag your iron tip along the pins gently, keep and eye on the feel to check if you start catching on any pins.

3. If you create any solder bridges you can usually work them out by using the iron tip like a paintbrush doing drags along the pins to distribute the excess solder.

Preheating

The contact points your solder to need to be brought up to sufficient heat at some point in the soldering process for the solder to adhere. You can put your iron tip on the components and feed solder into it. Be careful here because you can very quickly overheat your components and destroy them.

Applying Flux

There is no such thing as too much flux.

Tinning

Especially when you have filthy connections its a good idea to tin them. Apply solder to each thing before soldering them together, it'll work a lot better.

Solder and Metals

tl;dr use Kester solder. Use 63/37 if you want normal leaded solder. Use cardas quad eutectic if you want something silver-bearing.

Eutecticity

Eutectic means means a substance that is either solid or liquid and has minimal "goo" phase, where the material is soft but not melted.

Lead vs Lead-Free

Leaded solder is superior to non-leaded solder (usually). It melts at lower temperatures which helps avoid sensitive component damage as you don't have to get it quite as hot. Leaded solder is also non-dendritic, which is why the military uses it. Leaded solder also does not aerosolize lead, those are the rosin flux fumes you're seeing.

Lead-free solder is used commercially for RoHS compliance, that is the only reason. This is because when components end up in a landfill etc. They will decompose and the lead will contaminate the environment around it.

Silver Bearing Solder

I love silver bearing solder, especially when using it on silver contacts. My thinking here is that you are going to be getting incredible bonding between two mediums that share the same metal. I use cardas quad eutectic solder here. Avoid pipe solder as they are pretty purpose built for pipes and thats all.

Gold Plating

Gold plating generally sucks for HIGH POWER APPLICATIONS. Gold is an embrittling agent in solder, meaning that when you solder to it it will alloy with the solder and that alloy will be much more brittle than the original solder. Gold plating is also very very thin due to the cost involved, and therefore rubs off quickly if you have a lot of connection cycles with high force involved.

For small and typically digital connections gold is great because it is extremely non-reactive. It doesn't oxidize or anything so you don't have to worry about your connector rotting and not having enough "plug force" to scrape the oxide layer off.

Silver Plating

The military silver plates a lot of electrical connections for a reason. Silver is a fantastic conductor, isn't that expensive all things considered (you can plate it thick!), and silver oxide is still extremely conductive, and gets scraped away whenever you plug in a

Equipment

Irons

You want an iron that heats up quickly, and maintains its temperature accurately even under load. I use Metcal irons as they use a different paradigm than normal irons. normal irons heat via resistive load. Metcal irons heat via inductance. The tips actually control the iron temperature. The tip elements are made of special alloys with carefully chosen curie temperatures. This means they are inductive up to a specific temperature, at which point they become non inductive, and are thus self regulating.

You can get an old SST metcal power unit and it'll work just as good as a modern one from what I've read, possibly even better. The current MX handsets are compatible with the SST power units. This is imo the absolute best value ever, just go on ebay and grab a power unit, then add a handset and whatever tips you want.

Flux

There are a ton of different fluxes out there. They come in liquid, gel, and paste forms. Liquid fluxes are aqueous and therefore can be cleaned with simple water. Here is what you should keep track of when selecting a flux:

• is it clean or no clean i.e. do you need to wash the residue off lest it rot your stuff, is cleaning optional?
• how much can it clean (what is its activation level)

I currently use Alpha 856. I like it because of its high cleaning potential and surface tension breaking and because I have a 5 gallon jug of it. You don't NEED to clean it but I highly recommend doing so. You can do this with pretty much any electronic solvent, or very warm water. I highly recommend scrubbing it off with a toothbrush under water/solvent. If under water, scrub and rinse until there are no more bubbles.