Addressing Flux Dip Challenges for 3D Integrated Large Die, Ultra-fine Pitch Interconnect

Abstract The requirement for closely coupled, highly integrated circuits in the semiconductor industry has spawned alternative packaging innovations such as 2.5D/3D integration. The incredible potential of this alternative comes with great challenges, not the least of which is the unprecedented reduction in package interconnection pitch. Market acceptance of new fine-pitch microelectronic products is strongly dependent upon the development of flawless assembly processes that align with the traditional Moore-like expectation of higher performance without cost penalty. One such process is the application of flux to the interconnect surfaces in order to achieve effective joining. Insufficient flux quantity or flux activity can impede the formation of solid, reliable joints, while excessive quantities or activity can cause solder bridging or difficulties with downstream operations such as residue cleaning or underfill reinforcement. This delicate balance, already complex for traditional chip joining, is furth...