As mobile computing and telecommunication electronics arespreading fast, a demand for microelectronics packaging schemes for highdensity, fine pitch, high performance and low cost becomes even moresevere. Specifically, the conventional printed circuit board (PCB) withplated-through-hole (PTH) vias is difficult to justify its manufacturingcost as well as the packaging density requirement. To meet thischallenge, several new manufacturing schemes of high density and highperformance PCB have been recently introduced such as surface laminarcircuit (SLC), array layer inner via hole (ALIVH) and others. This newPCB fabrication process is categorized as sequential build-up (SBU) orbuild-up multilayer (BUM) using laminate-based substrates, where viaholes are filled with a conductive paste material to make reliablevertical or Z-interconnects. In this paper, a new electricallyconducting paste material to be used for via filling is introduced. Thenew conducting material consists of a conducting filler powder coatedwith a low melting point metal or alloy, a mixture of several thermosetresins, and other minor organic additives. By varying the filler contentand resin chemistry, several formulations have been produced to fill viaholes with a high aspect ratio. Via fill experiments have been performedto demonstrate void-free microstructure with good electrical continuity.Various bulk properties such as thermal, electrical and mechanical havealso been characterized to understand the material behavior during viafilling as well as the field service
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