Z-axis Interconnections for Next Generation Packaging

摘要

In this paper, the use of electrically conducting adhesives(ECA) to form z-axis interconnections for next generationpackaging is discussed. In particular, current efforts related toZ-axis interconnections for device level fabrication,integration, and electrical performance are highlighted. A fewoptimized ECAs were used for hole fill applications tofabricate Z-axis interconnections in laminates. Conductivejoints were formed during composite lamination using theECA. Around 5,000 to 200,000 through holes in the joiningcores, formed by laser or mechanical drilling, and havingdiameters ranging from 50 μm to 750 μm, were filled with anoptimized conducting adhesive. The adhesive-filled joiningcores/layers were laminated with circuitized subcomposites toproduce a composite structure. As a case study, a variety of zaxisinterconnect constructions for a flip-chip plastic ball gridarray package, rigid-flex, rigid-rigid, package-interposerpackage(PIP), RF structures, and PWBs were fabricated andevaluated at both the subcomposite and composite levels tounderstand structural and electrical integrity. Electrically, Sparametermeasurements showed very low loss at multigigahertzfrequencies. The losses were low enough to supporttypical SERDES up to 15 Gbps over 750 mm. The presentprocess allows fabrication of z-interconnect conductive jointshaving diameters in the range of 55 to 500 μm. The processesand materials used to achieve smaller feature dimensions,satisfy stringent registration requirements, and achieve robustelectrical interconnections are discussed.