Chiplet3D: Pin- and Thermal-Aware 3D Chiplet Floorplanning via Convolution-Embedded MILP

By Shuo Ren, Libo Shen, Yaohui Han, Rongliang Fu, Junying Huang, Bei Yu, Tsung-Yi Ho

Abstract

As traditional Moore's Law scaling slows down, 3D-ICs stack multiple active dies vertically to sustain performance scaling. However, this vertical stacking traps heat inside, making temperature a design concern. Although we can fix thermal issues at different design steps, floorplanning is the earliest and most cost-effective stage to solve it. Previous methods handle this by assuming wires connect to block centers and estimating temperature through simplistic power-based calculations, but these assumptions mislead their wirelength optimization and leave hotspots unresolved. To address these limitations, we present Chiplet3D, a pin- and thermal-aware floorplanner for two-die 3D-ICs. To achieve pin-awareness, it supports all four rotations and two flips, measuring wirelength from exact pin locations so the solver can flip or rotate blocks to pull connected pins closer. On the thermal side, Chiplet3D replaces the inaccurate power-based metrics of prior work with a fast, coarse convolution field embedded directly in a mixed-integer linear program (MILP) to accurately track the true 3D heat spread. We evaluate Chiplet3D on the ICCAD'24 ATPlace benchmarks, validating every temperature with a golden 3D-ICE simulation. Chiplet3D reduces wirelength by 39%--43% on average (and up to 62% in the best case), while lowering peak temperatures by up to 45.9∘C and reducing thermal non-uniformity by up to 56% compared to the SOTA baselines. Overall, these results demonstrate that by co-optimizing pin alignment and thermal fields, Chiplet3D establishes a stronger Pareto frontier between thermal-aware layout and interconnect efficiency.

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