Solder

Composition and Types of Solder

• Solder is composed of tin and lead, with tin concentrations ranging from 5% to 70%.
• Lead mitigates tin whisker formation.
• Common alloys for electrical soldering include 60/40Sn-Pb and 63/37Sn-Pb.
• Lead-free solders may contain tin, copper, silver, bismuth, indium, zinc, antimony, and traces of other metals.
• Lead-based solder is commonly used in electrical and electronic work, while lead-free solder is increasing in use due to regulatory requirements and health/environmental benefits.

Lead-Free Solder and Tin-Silver-Copper (Sn-Ag-Cu) Solder

• Lead-free solder is used in most consumer electronics sold in the EU and has a broad effect worldwide.
• Two-thirds of Japanese manufacturers use tin-silver-copper (Sn-Ag-Cu) solders.
• Sn-Ag-Cu solder has a reduced melting point compared to other alloys.
• Sn-Ag-Cu solder is widely used by Japanese manufacturers for reflow and wave soldering, as well as hand soldering.
• Researchers are exploring the addition of a fourth element to Sn-Ag-Cu solder for compatibility with solder sphere reflow.

Applications and Hard Solder

• Soft solder is commonly used in electronics, plumbing, and sheet metal work.
• Hard solder, or brazing, is performed using alloys with a melting point above 450°C.
• Solder wire and bars are used for hand-soldering, while jewelers use solder in thin sheets.
• Enameling solder has a high melting point to prevent joint desoldering during firing.
• Different hardness levels of solder are used in decreasing order during the manufacturing process.

Corrosion, Impurities, and Flux

• Corrosion of solder pots leads to increased dross formation.
• Impurities in solder include aluminum, antimony, arsenic, copper, and others.
• Flux is a reducing agent used to improve electrical connection and mechanical strength.
• Different types of flux, such as acid flux and rosin flux, are used in various applications.
• Flux-core solder contains embedded flux that is released as the solder melts onto the joint.

Intermetallics and Solder Joint Formation

• Intermetallic compounds are formed during solidifying of solders and their reactions with soldered surfaces.
• Intermetallics can cause mechanical reliability weakening and brittleness.
• Processes in solder joint formation involve the interaction between the substrate and molten solder, as well as solid-state growth of intermetallic compounds.
• Examples of interactions include gold and palladium dissolving in solders, and copper and nickel forming intermetallic layers.
• Different types of intermetallic compounds, such as Cu3Sn and Cu6Sn5, can form on solder-copper interfaces.

Solder Data Sources