Wire Bonding Looping Solutions for High Density System-in-Package (SiP)

Abstract

Abstract System-in-Package (SiP) have seen a lot of growth in recent years especially in mobile devices due to its higher level of system integration, more design flexibility and smaller form factor. Two or more semiconductor die and passive components are usually present in a SiP device. Die to die bonding and increased I/O density are two common challenges associated with wire bonding in SiPs. High density SiP packages often have high I/O counts and tight wire clearance. As a result, the requirements for wire bond looping are high. To avoid wire shorts, the wire bond loops need to be well designed in order to have optimal wire clearance between various tiers of wire loops as well as neighboring loops. The formed loops need to have low wire sway after wire bonding and low wire sweep after molding. Due to the existence of multiple dies and other passive components within the same package, special wire bond loops with long flat lengths and sharp bending angles are sometimes necessary to clear the die edges and the other components. In this paper, we will review a few new wire bonding looping solutions including 3D looping design software, 3D loop clearance checking and multi-tier loop formation improvements. A robust package design is essential to improve production yield. A 3D looping design software has been developed to evaluate the robustness of various package designs from a wire looping perspective. The software is able to detect potential issues early on in the design cycle and evaluate alternatives quickly, therefore reduces the time to market and improves design robustness. A spatial 3D clearance checking tool has been developed to detect any interference between the densely populated wire loops. The tool can also detect interference between the wires and the edges of different dies. Furthermore, the wire clearance against various components in the package can also be assessed. Process engineers can leverage the clearance check tool and the 3D visualization of wires, multiple dies and components to aid wire bonding looping optimization. Multi-tier looping requires a large range of loop height and wire length capability. In order to achieve optimal looping for high density multi-tier applications, a separate wire bonding looping software has been developed to generate optimal wire bonding motion trajectories that can achieve the loop shapes designed by the 3D looping design software. An example of 6 loop tier application is developed and results are analyzed to show the wire bonding capabilities including looping height from 75um to 500um and wire length up to 5mm.