Solid Wires

Solid wires consist exclusively of soldering alloy, without any internal flux. This characteristic makes them particularly suitable for processes where flux is applied separately or where maximum control over process chemistry is required. Compared to flux-cored wires, solid wires offer one less variable from a chemical point of view, allowing the operator or automatic process to select the most suitable flux for material, geometry and surface conditions. From a construction point of view, solid wires require the same dimensional precision as flux-cored wires (diameters from 0.5 to 4.0 mm), but their soldering behavior depends strictly on external flux and surface cleanliness. The 100% alloy composition guarantees maximum metallic purity and absence of fumes or flux splashes during melting, useful in controlled environments or in presence of sensitive components. The choice of external flux is crucial: in electronic processes no-clean with low residue (ROL0/ROL1) or RMA/RA for less clean PCBs are preferred; in mechanical applications high activity acid fluxes (water or alcohol-based) are used with subsequent cleaning. Solid wires integrate well in robotic systems or selective soldering, where a dedicated fluxer delivers precisely the necessary quantity, guaranteeing repeatability and reducing excesses. The most used lead-free alloys are 99.3Sn0.7Cu (tinning of conductors and contacts), SAC305 (robotic processes compliant with RoHS), SAC 0307 and 96.5Sn3.5Ag (mechanically robust joints). In some derogation areas SnPb alloys are still used, but with marginal relevance. Typical parameters include peak temperatures 10–30°C higher than equivalent SnPb, with attention to component thermal balance. Solid wires are used for automatic soldering with external flux (robots, selective soldering), controlled recharging of tin baths without introducing flux, and soft soldering of metal parts in combination with specific fluxes. Their versatility allows to standardize the alloy and modulate the flux according to substrate (copper, brass, nickel plating) and oxidative state. Alloys supplied in solid wire comply with ISO 9453 / J-STD-006 specifications; each batch is traced and accompanied by chemical analysis. Our technical support helps define the alloy-flux combination and process parameters to maximize wettability, joint appearance and reliability.