Multichip packaging in QFPs by PBO-multilayer high density interconnect

Further development of the HDP market will be determined primarily by the cost and availability of high density packaging alternatives such as multichip packages (MCP), fine pitch surface mount devices (SMD with pitch <0.5 mm), chip scale packages (CSP, including flip chip) or chip on board (COB). With high end PCB and special assembly processes required, fine pitch SMD, CSP or COB cause higher system board assembly cost, although they appear relatively cheap as a component. MCPs, due to higher functionality, are more expensive as a component, but reduce system board assembly cost because fewer components with less solder pads are to be mounted on PCBs of reduced complexity. This contribution reports on an MCP using a new high density interconnect (HDI) substrate technology for multichip packaging with thin QFP. The HDI uses the new polybenzoxazol (PBO) as a dielectric. PBO, developed and patented by SIEMENS AG, Germany, has several interesting features, ranging from outstanding electrical performance with easy processability to excellent adhesion properties to molding compounds, metals and ceramics. Deposited as a multilayer with sputtered signal layers and a plated bond layer on top of a thin ceramic plate, this HDI enables standard backend assembly lines for QFPs to perform highly efficient multichip packaging. The qualification results with a telecommunications application show that this type of MCP using PBO-HDI is ready for mass production.