Ball Grid Array package for automotive application: strong link between design and 3D modeling

High speed signals, design density, many power domains, product miniaturization and integration require high level of electrical, thermal and thermo-mechanical performances on each system component (IC-PKG-PCB). Ball Grid Array (BGA) package, thanks to design flexibility and wide substrate technology portfolio, is today a key part, highly challenging, of complex systems. This package is largely used also in automotive domain mainly for high-pin-count devices and in combination with Flip Chip (FC) technology for a direct and short device-to-substrate connection. In this work we describe design techniques and 3D modeling activity done to improve Power Integrity (PI), Signal Integrity (SI), thermal and thermo-mechanical behaviors of a complex FC-BGA automotive product using Cu pillar bumps and 4LY substrate as starting point. More than one thousand bumps and five hundred balls are the boundary conditions of the package connectivity. Step by step all design improvements are described: substrate stack-up modification, power and ground layers new sequence, device positioning analysis, SMD capacitors choice, placement and connection, vias number increase and pwr-to-gnd coupling maximization, top metal parasitics reduction by fan-in routing optimization on device area, planes integrity and layout improvement. Electrical, thermal and thermo-mechanical simulations, as fundamental part of design activity and performed through validated flows, demonstrate the improvement achieved. The strong link between design and modeling is today essential for first package success and, predicting 'by design' potential issues and weaknesses, helps to reduce overall cost and development cycle time.