WP616 is a zero-halogen, lead-free, water-soluble solder paste formula for both nitrogen and air reflow applications. It has a wide reflow profile window with good solderability. - WP616 is a zero-halogen, lead-free, water-soluble solder paste formula for both nitrogen and air reflow applications. WP616 provides a combination of consistent print performance at wide humidity levels, excellent solderability and ease of cleaning, while maintaining a zero-halogen flux formulation. WP616 is a stable water-soluble formula, providing consistent stencil life, tack time and print definition. WP616 is classified as ORM0 flux under IPC J-STD-004B.