Advanced QFN packaging for low cost and solution

The advanced QFN (aQFN) package is an enhanced version of conventional QFN (Quad Flat No-Lead) with multiple row terminals of featuring higher number of I/O ports. aQFN thermal and electrical performance are superior due to smaller profile, shorter interconnects. Also, the solder wettability control and board-level thermo-mechanical reliability are greatly enhanced over conventional QFN because of the higher package standoff. aQFN provides similar I/O number approaching that of a BGA-type chip-scale package (CSP) but much less cost since the expensive substrate is replaced by lead frame. aQFN turns out to be an ideal low cost solution for electrical components of portable telecommunication applications. With such advantages, the replacement of BGA-type CSP with aQFN from low pin-count up to medium high pin-count applications is therefore highly expectable, especially for handheld & PDA devices with its relative applications. In this paper, aQFN is introduced in terms of its application advantages, development, fabrication process flow, SMT process with stencil design guideline. The simulation results indicate that thermal and electrical performances of aQFN are much better than BGA-type CSP, when the same functions are to be designed in SMT process.