Reworking the LLP Chip Scale Pac

　　LLP is a “Leadless Leadframe Package” – there are no leads extending beyond the package body. The contact pads are exposed and flush with the bottom of the package， providing a more compact footprint. Exposed die attach pad when soldered to the board provides a direct path for heat to transfer from the package to the PCB providing excellent thermal performance. Standard surface mount equipment can be used to assemble LLP onto the PCB. There are design guidelines and recommendations that have been established by National Semiconductor （see AN-1187 at www.national.com/an/AN/ AN-1187.pdf） to achieve high surface mount assembly yield. The rework process for LLP is similar to BGA and laminate CSP type packages where contacts are underneath the package. Commercially available equipment is used for LLP rework. Typical rework process involves： • Localized heating & device removal • Site cleaning after device removal • Application of solder paste • Component placement • Localized reflow • Inspection