Indium Corporation’s wafer bumping flux WS-3543 is a low-viscosity semiconductor-grade flux, specifically optimized for uniform solder bump formation across wafers up to 300mm (12 inches) in diameter. WS-3543 washes off completely, even after repeated application, reflow, and cleaning cycles, as may be seen in bump rework and after probe testing.
Indium Corporation’s wafer bumping flux WS-3543 has been used for several years to produce consistent, high-reliability joints in stacked die for 3D memory applications. The viscosity is high enough to form a film over TSV copper-pillar microbumps, yet low enough to be spun onto the wafer with a consistent thickness. As a result, uniform, oxide-free solder bumps are formed across wafers up to 300mm (12 inches) in diameter. In addition, this semiconductor-grade, water-soluble product leaves no residue after DI-water-only cleaning. This eliminates the dangers of delamination, electrical reliability concerns and underfill voiding.