Soldering just plain copper has gone away. Now, there are many different surface finishes that we, as an industry, solder to. This includes Organic Solderability Preservative (OSP) copper, immersion silver (ImAg), immersion tin (ImSn) and Electroless Nickel / Immersion Gold (ENIG).
Each one of these surfaces has its own benefits and downfalls, as well as their own set of requirements to solder to them properly, with the best looking, highest tensile strength and lowest voiding solder joint possible. This list does not include the other surfaces, usually on components, that we must solder to. Such as bright tin, matte tin, Hot Air Solder Leveling (HASL), pure nickel, etc…
We will talk about OSP, ImAg, ImSn and ENIG, and discuss their strengths, weaknesses and how to solder to them. This includes discussions on relative shelf life, history of use, what to look for and special reflow needs.