A visualization-based approach for bump-pad/IO-ball placement and routing in flip-chip/BGA technology

The routing problem in area array integrated circuit (IC) packaging has become an extremely complex problem in the realm of high I/O count IC packages. With the advent of flip-chip and ball grid array (BGA) technology to meet the current demands of smaller size and high wiring densities, the routing problem lies in the core of electronic design automation process. In this paper, we describe an intuitive computer visualization-based approach for placement and routing of bonding pads that would result in low manufacturing costs and smaller component size compared to conventional approaches. This novel approach is an extension of "balls shifted as needed" method for I/O ball placement in BGA package enabling single-layer board-level routing for any I/O count. The I/O ball/pad layout and routing designs along with results are presented for two routing layers with the inclusion of vias in the design. This routing scheme is shown to be easily extensible to accommodate more practical multilayer routing and can be incorporated in current electronic design automation (EDA) computer-aided design (CAD) tools to offer an integrated routing solution for area array chip-package-board codesign. The results show that different trace routing patterns lead to different area requirements for same number of I/Os. This has led to the formulation of new design paradigms which are presented in the paper for smaller component size.