Modeling and Improvement of Heat-Flow Paths Inside 3D-nand First-Level Packages With Internal Metal Structures

Rising interface speeds and compact form factors have pushednandflash solid-state drives (SSDs) toward their thermal limits. This work establishes a package-accurate thermal framework that integrates experiments, finite-element method (FEM) simulations, and a compact network model to guide first-level package (FLP) design. A detailed 3-D model of a commercialnandmodule was constructed and validated against decapsulated package measurements using an optical-fiber thermal sensor and infrared (IR) imaging, reproducing the measured saturation temperature near$80~^{\circ }$C. The calibrated model reveals two dominant heat-flow paths—upward through the epoxy molding compound (EMC) and downward through solder joints into the printed-circuit board (PCB)—with the EMC and PCB identified as primary resistance bottlenecks. To address these limits, four embedded-metal designs were proposed. Compared with the ~$80~^{\circ }$C baseline, bulk metal, exposed bulk metal, a thermal pad, and a bridged heat spreader reduced hotspot temperature to$77.0~^{\circ }$C,$75.4~^{\circ }$C,$75.7~^{\circ }$C, and$70.0~^{\circ }$C, respectively, achieving up to 12.5% improvement. Resistance trends confirm that a thermal pad mainly enhances the topside path, whereas the heat spreader enables balanced upward and downward evacuation with the most uniform heat distribution.