Influences on the Mechanical Strength of Inkjet-Printed, Ag-Nanoparticle-Based Interconnects of Fine-Pitch Components

This study analyses the main influences on mechanical joint stability of surface mount components connected to a printed circuit board (PCB) using inkjet-printed silver nanoparticle-inks (nAg-joints). In previous publications, we presented a novel approach by using such inks as a connective medium for fine pitch components of sizes 0201 to 008004. In separate experiments we expand on the original research by evaluating the influence that printing and mounting accuracy, as well as sintering parameters in convection sintering have on nAg-joints. Furthermore, we analyse the effect of PCB surface metallization on joint strength and examine the use of near infrared light (NIR) sintering as an alternative sintering method. Optimization in convection sintering parameters with electroless nickel immersion gold (ENIG) surface finish on both PCB and SMD-LEDs yielded a peak median shear resistance of 3.48 MPa. Change in PCB surface metallization from ENIG to immersion silver (IAg), resulted in a peak median shear resistance of 1.85 MPa. The combination NIR and IAg led to the highest shear resistance of 9.43 MPa for components with Sn surface, while ENIG components were measured at 1.82 MPa. Furthermore, the proposed process chain has been utilized in hybrid manufacturing, combining stencil and ink jet printing in one module. While this study proves that adequate mechanical stability can be achieved using the proposed process, further evaluation is needed regarding material combinations, material distribution and heat transfer in optically inaccessible nAg-joints.