Melting Temperatures and Electrical Conductivity of Lead-Free Soldering Alloys for Filler Materials

Lead-based filler metals were used for soldering for many years, but they are now being gradually replaced by lead-free materials, usually alloys. Contemporary alloys commonly contain metals such as antimony, bismuth, copper, indium, tin, zinc, silver, and gallium. Some of their properties still need to be studied in more detail. A good solder joint must create a reliable electrical connection with high conductivity, having suitable thermal properties at the same time. In addition, soldering materials must meet other requirements such as good fluidity and resistance to corrosion. Mechanical strength is usually not a top priority, except in portable or handheld devices, where the joints need to withstand impacts from drops and shocks. Pure metals are seldom used as filler materials in soldering, as alloys are generally preferred due to their broader range of beneficial properties. In this paper, we take a closer look at several key properties of the soldering alloys.