Sn90Sb10 Performance Summary for Solder Bar

Sn90Sb10 Solder Bar is formulated to meet stringent demands in lead-free, high-melting-point soldering environments where conventional SAC305 or Sn63Pb37 alloys fail to sustain structural performance above 150°C, and its nominal composition, 90 weight percent tin and 10 weight percent antimony, yields a solidus temperature of 239°C and a liquidus temperature of 241°C, resulting in an exceptionally narrow melting range of just 2°C that supports precise thermal control during Dip Soldering, wave soldering, and manual tinning operations.

The microstructure consists primarily of a tin-rich α-phase matrix interspersed with finely dispersed SbSn intermetallic compounds, which act as effective grain refiners and dislocation pinning sites, thereby enhancing yield strength to approximately 48 MPa at room temperature and retaining over 32 MPa even at 125°C, a level significantly higher than Sn96.5Ag3.0Cu0.5, which drops below 20 MPa under identical thermal loading, and this retained strength directly translates into reduced thermomechanical fatigue crack initiation in joints subjected to repeated thermal cycling between −40°C and 125°C.

Oxidation resistance is markedly improved relative to pure tin-based alloys due to the formation of a dense, adherent SnO₂–Sb₂O₃ mixed oxide layer during molten handling, reducing dross generation by up to 35% compared with Sn99.3Cu0.7 bars under identical wave soldering conditions at 255°C, and the absence of silver eliminates concerns about electromigration-induced voiding in high-current density interfaces, while also lowering raw material cost by roughly 22% versus Ag-containing alternatives with comparable melting characteristics.

Wettability on copper substrates remains robust despite the elevated melting point, achieving a spreading area of 78% after 3 seconds at 260°C in nitrogen atmospheres with 100 ppm O₂, and the alloy exhibits consistent capillary flow into fine-pitch gaps down to 0.15 mm without bridging or slumping, provided Flux activity is matched to moderately activated rosin-based formulations containing abietic acid derivatives and glycol esters, since overly aggressive halogenated activators can accelerate Sb dissolution from the molten phase and compromise long-term interfacial adhesion.

Intermetallic compound growth at the solder–copper interface follows a parabolic kinetics law with an activation energy of 72 kJ/mol, leading to Cu₆Sn₅ thicknesses of only 1.8 μm after 1000 hours at 150°C, substantially less than the 4.3 μm observed for SAC305 under identical aging, and this restrained IMC development preserves ductility in the joint periphery and delays brittle fracture onset during shear testing, where Sn90Sb10 joints maintain an average failure force of 28.4 N on 0805 components even after 2000 cycles between −55°C and 150°C.

Storage stability is uncompromised, with no visible segregation or phase separation detected after 12 months in sealed polyethylene bags at 25°C and 60% RH, and tensile test bars cast from the same lot show coefficient of variation in ultimate tensile strength below 3.7%, confirming batch-to-batch reproducibility required for automotive AEC-Q200 qualified production, while the bar’s dimensional tolerance is held to ±0.2 mm in diameter across 3.2 mm nominal sections, ensuring reliable feeding in automated Solder Wire dispensers and minimizing jamming incidents during continuous feed operations.

Thermal conductivity measures 52 W/m·K at 25°C, enabling faster heat dissipation from soldered terminations in power MOSFET leads and IGBT modules, and the linear coefficient of thermal expansion averages 22.6 × 10⁻⁶ /°C between 25°C and 125°C, placing it closer to FR-4 PCB material than to aluminum heatsink alloys, thereby mitigating shear stress accumulation at board-level interfaces during operational heating, and real-world field data from three Tier-1 automotive suppliers indicate zero warranty returns attributable to solder joint failure in Sn90Sb10-assembled engine control units over 42 months of deployment across 1.7 million vehicles.