Comparison of sintering methodologies for 3D printed high-density interconnects (2.3 µm L/S) on organic substrates for high-performance computing applications

Abstract

High performance computational demands are pushing for rapid technological advancements in the field of electronics and packaging. The high-density organic interposer has emerged as a cost-effective alternative to the conventional silicon interposer. Using redistribution layers (RDLs) can help in optimization of heterogenous packages, while providing significant benefits to signal integrity. The challenge, however, lies in dimensional limitations imposed by the rough organic substrate on established fabrication approaches for the RDLs. This paper explores the use of additive manufacturing as an alternative technique to fabricate high-density interconnects on the non-conductive organic substrate. Printing of interconnects with line/space of 2.3/2.5 µm using silver inks is demonstrated directly on organic substrates coated with a dielectric film. Sintering of the nanoparticle ink is a critical step to obtaining high-resolution conductive patterns. Given the low glass transition temperatures of the substrate and the dielectric film, we investigate photonic curing as an alternative sintering technology for the printed structures and compare it to the conventional thermal oven curing method. Resistivity values obtained are almost twice that of the thermal oven cure for the ink used. A final comparison is made where single step photonic curing was observed to produce a lower resistivity value as compared to a combination of thermal and photonic curing for connector widths < 5 µm.