Wire-Bonding Finger Placement for FBGA Substrate Layout Design with Finger Orientation Consideration

Wire bonding is a mature packaging technique that enables chip pins to transmit signals to bonding fingers on the substrate through bonding wires. Such commodity technology is also essential in supporting the rapid development of the system in package and heterogeneous integration technologies. However, the automation tools are relatively deficient compared to other packaging techniques, resulting in tremendous manual design time and engineering effort due to numerous wire-bonding design constraints. This paper addresses the finger placement problem and serves as the first work considering the orientation constraint of fingers. The finger placement flow is divided into three stages. First, an integer linear programming (ILP) formulation is developed to allocate each net finger row. After that, we utilize mixed-integer quadratic programming (MIQP) to place the bonding fingers and consider the wire crossing constraint. Finally, the locations of the bonding finger are refined by considering both the bonding finger orientation angle and the finger spacing constraints. The final layouts generated by our integrated finger placement and substrate routing framework outperform manual designs in terms of the design time, the total wirelength, and the routing completion rate.