The effect of sintering profile and printed layer variations with inkjet-printed large-area applications

Inkjet-printed conductors with large areas and increased layer thickness may cause challenges with the materials applied. The possibly required increased sintering energy can result in exceeding the heat tolerance of the substrate and cracks in the conductor surface can be formed. The advantages of inkjet print technology can be applied to reduce these challenges by limiting the ink usage by varying the conductor thickness locally or even removing the parts of material from the layout. In this paper, large-area RF applications are studied in terms of varying conductive ink usage and sintering profile. An antenna type with high current density areas is used as a demonstrator of an application requiring larger uniform printed area. The paper shows the advantages of limited local printing on additional layers compared to printing full layers. Two different sintering profiles are applied to differently printed antenna versions fabricated for 868 MHz and 2.4 GHz frequencies. It is shown, that with less sintering energy, the antennas with only local additions perform better than antennas with fully printed antennas with more ink. With longer sintering process time, the local antenna and the fully printed antenna behave equally in terms of total efficiency.