1. Choose the Solder Composition Lead or Lead-free is the first thing to be considered. Then, choose the right solder according to the working temperature. Generally, solders used at high temperature are available for easily accessible connections, while the ones at low temperature are for smaller and crowded connections. Next thing is to choose right solder alloy. Commonly, the most common lead free solder contains 95% tin and 5% antimony. Its smelting point is between that of 40/60 and 50/50 tin/lead solders.
2. Select Right Diameter of Pb Free Solders Select solder wires whose diameter is between 0.01 inch (0.25 mm) and 0.125 inch (3.25 mm). If the solder diameter is too small, the solder will be melted very fast, and vice versa. So, over-thin solder will result in lack of soldering, while the over-think solder will absorb too much heat and damage the welded components.
3. Select Flux Core for Lead Free Solder Choose the flux cores according to your personal style in applying flux.