Demonstration and Comparison of Vertical Via-less Interconnects in Laminated Glass Panels from 40-170 GHz

Via-less interconnects are an interesting solution for communicating vertically across the interposer core instead of using through package vias. These interconnects could potentially reduce the cost and complexity of the fabrication of the inter-poser. In this paper, we discuss and compare the performance of wireless interconnects in glass using two different dielectric materials with the same stack-up: where one of the dielectrics is a dry film, Ajinomoto Build-up Film (ABF) GL102 and the other is a low-loss photo-imageable liquid dielectric material from JSR Corp. over a frequency range from 40-170 GHz. The stack-up is made up of 100 μm of glass (EN-A1) from AGC Inc. with 15 μm of the said dielectrics on either side of the glass. The paper characterizes the performance of the interconnects with an alignment offset from the top to the bottom layer. We use semi additive process (SAP) to form high precision redistribution layers (RDL), as compared to subtractive etching and printing techniques. As the probe pads are present on either side of the glass panel, we use L-2L de-embedding technique to extract the characteristics of a single via-less interconnect.