Kester TSF-ULR18 is a no-clean ultra low residue tacky flux. The product was developed to support the increasing trend in high density, miniaturization, ultra-fine copper pillar and micro-ball bump flip chip IC package where the flux cleaning effectiveness to remove the residue becomes more challenging. Another segment where TSF-ULR18 is highly recommended is in the Flip Chip on Lead frame (FCOL, FCQFN, etc) package, the kind of device where flux cleaning is not required. The flux residue that may remain after reflow can interfere with subsequent underfilling or over-molding encapsulation which can possibly affect the reliability of the package. In response to this market need, Kester has developed an ultra low residue tacky flux with post reflow residue below 10% wt, incredibly 3x reduction versus traditional rosin based tacky flux. The trace amount of residue left is highly reliable and is compatible with post process materials.