Types of soldering wires
When you solder, it is important to buy a good soldering wire. Some of the soldering wires can damage electronics, especially a PCB. When you have black flecks on PCB, it damages components and prevents a current flow properly. Also, it prevents current flow between thicker wires. So which one to use?
It would help if you bought soldering wires only from the trusted sellers and manufacturers. Avoid cheap wire from unknown manufacturers. There is a different ratio between tin and lead, like 63/37, 60/40, 62/38, etc. They will not be the same for everybody. Some of them melt faster than others. If you are new to soldering, you can buy a small quantity of soldering wire and try each of them to find a proper one for you. There is also a lead-free soldering wire (RHoS).
Lead-free soldering wires are commonly used in fabrics to prevent poisoning from heavy metal toxic. The main difference between lead-free and tin-lead wires is in melting temperature. Tin-lead wires have a melting temperature of around 370ºF, and it is easier to work with them. Lead-free wires are better for health, but they need a bigger temperature to get melted. Professionals often use wire with a small Cu ratio. Cu ratio is often 2%, and it is used because copper allows better connections with components. Wires with Cu take good critics, and you can try them if you are curious.
Which one is the best soldering wire
It is almost impossible to find the best soldering wire because everyone has his way of soldering. I can only recommend you one of them, like this one (Low Residue Core Solder). It is designed for electronic assembly. This wire provides the soldering performance of an activated rosin flux and the clean visual appearance of a low residue flux. This wire does not drain a fume, and it is easy to use. It came in a big package 1 pound weight. It makes good connections, and it is one of the best wires on the market.