The Kester 2331-ZX flux pen is designed for leaded and lead-free rework of conventional and surface mount circuit board assemblies. 2331-ZX Flux Pen is an innovation in organic acid water soluble flux chemistry for soldering circuit board assemblies. This unique, neutral pH chemistry flux provides the best ionic cleanliness of any organic watersoluble flux available to the electronics industry. This popular flux has been used for soldering critical assemblies in the telecommunications, computer and other industries. No offensive odors will be emitted during soldering. - 2331-ZX Flux Pen will not create excessive foaming in standard water cleaning systems. 2331-ZX Flux Pen has good soldering properties for improved productivity without sacrificing reliability of the assembly. This flux does not attack properly cured solder masks or FR-4 epoxy-glass laminate. 2331-ZX Flux Pen is not detrimental to the surface insulation resistance of the soldered assembly. Use of this flux minimizes cleaning costs while complying with environmental regulations.