Rosin core solder is the correct type of solder to use when constructing an electronic circuit board. Constructionists should not use acid core solder, as this is intended for plumbing.
Solder is used to join two metals. It has a lower melting point than the metals being connected, allowing it to melt when heated by a soldering iron. Solder comes in different forms, including pellets, bars, paste and wire. Solder wire is the most popular, and it comes in various diameters. The .75 millimeter to 1.0 millimeter wire is the best, according to Science Buddies. Thinner wire should be used for smaller joints.