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Thermal-mechanical Reliability of Sintered Nano-Ag Bond Pads Printed by Aerosol Jet

Additive manufacturing has been extensively studied as a promising candidate for complete or partial replacement of traditional photolithography methods. The focus of this paper is on redistribution layers (RDLs) fabricated by aerosol jet (AJ) printing. Nanoparticle silver ink was deposited directly on silicon chips to form the conductive layer, while dielectric ink was used for the passivation layer. As a comparison, chips with copper RDLs, which had the same layout, were prepared using conventional photolithography. After assembling this chip-scale package (CSP) onto a PCB through common SMT processes, the reliability of such assembly under thermal cycling and thermal shock loads was tested. The number of cycles to failure of these samples was monitored in real time through a daisy chain structure. Cross-sectional investigations were performed after tests for failure analysis. Testing results revealed that the adhesion between the printed PI layer and the wafer might be the weakest link in the printed structure.