Solder is essentially a wire of metal with a “low” melting point, meaning it can be melted with a soldering iron. In electronics, solder is usually a mixture of tin and lead. Tin has a lower melting point than lead, so the higher the tin content, the lower the melting point. The most common lead-based solder you’ll find in electronics stores is 60Sn/40Pb (60% tin, 40% lead). You might also see some other variations, such as 63Sn/37Pb.
Molten metal is not to be trifled with, as it’s somewhat like water: its surface tension is particularly important. If it can’t find something to “stick” to, molten metal will clump together. This is why solder mask prevents jumper wire formation and why you see surface mount soldering techniques. Generally, metal tends to stick to metal, but not to oily or oxidized metal. Simply being exposed to air will cause our components and circuit boards to oxidize, and they will also accumulate dirt during operation. The solution is to clean the components and circuit boards first. This is the role of flux cores in soldering. Flux cores have a lower melting point than solder and can be applied to the area to be soldered. Flux cleans the surface, and if the surface isn’t too dirty, it’s sufficient to form a strong solder joint.
Solder Cores
There are two common types of solder cores: acidic solder cores and rosin solder cores. Acidic solder cores are used for piping systems and should never be used for electronic components. You should keep this in mind, but generally, they are usually available in the electronic components section of an electronics store; it’s not recommended to buy them in the piping section of a home improvement store. Generally, for hobbyists, as long as components are kept clean and not left to stand for extended periods, solder cores are unnecessary. However, if you need soldering, it’s best to choose rosin solder cores. The only reason you, as a hobbyist, wouldn’t use solder with a solder core is that you know perfectly well why you don’t need solder. However, if you have some solder without a solder core on hand, you can safely use it for hobby purposes.
Lead-Free Solder
For hobbyists, this is basically all they need to know, but it’s worthwhile to understand lead-free solder, as it’s moving in that direction. The EU now requires almost all commercially available electronics to use lead-free components, including solder. This trend is spreading, and while you can still find leaded solder, this can be confusing. The purpose of lead-free solder is exactly the same as leaded solder: it’s an upgrade to a more environmentally friendly product. The problem is that lead is highly toxic, so other metals are now used instead, but these metals are not as effective as lead in controlling melting points. Generally, hobbyists can use lead-free and leaded solder interchangeably, but lead-free solder is slightly more difficult to work with because it doesn’t flow as easily as leaded solder and its melting point is not as low. This won’t prevent you from successfully soldering, and generally, for hobbyists, lead-free and leaded solder are almost interchangeable.
