No-clean And Water-clean Mass Reflow Processes Of 0.4 mm Pitch, 256-Pin Fine Pitch Quad Flat Packs (QFP)

Abstract

The water-clean and no-clean mass reflow processes of the 0.4 mm pitch, 28 mm body size, and 256-Pin fine pitch quad flat packs (QFP) are presented. Emphasis is placed on the fine pitch parameters such as the printed circuit board (PCB) design, solder paste selection, stencil design, printing technology, component placement, mass reflow, and cleaning. Furthermore, the cross sections of the assemblies from both processes have been thoroughly studied using scanning electron microscopy (SEM).