A chiplet design that achieves clean tape-out sign-off and then fails at assembly is not a yield problem. It is a workflow problem. Semiconductor Engineering surveyed the ecosystem and the consensus is precise: multi-die teams are still running a fundamentally linear design flow on a problem that is inherently iterative. Thermal, mechanical, power delivery, and signal integrity decisions at the package level all affect each other, and none of them are visible inside the single-die sign-off tools teams already know.
The coordination cost this creates is front-loaded in the wrong direction. Teams are making die-partitioning decisions early, locking in UCIe interface choices, and committing to interposer geometry without full visibility into how those choices affect thermal hotspot propagation or PDN stability across the stack. By the time a thermal-current interaction surfaces, it is after a tape-out. The Siemens EDA quote in the article is exact: "You need to understand very early on whether you're making the right decisions or not." The structural problem is that the tools that could answer that question are not part of the early-stage flow; they are sign-off tools, run late.
What changes this: a unified workflow that treats the package as the system boundary rather than as a handoff point. That is not a new idea, but the industry is now generating enough failure data from real multi-die programs to stop treating it as aspirational. Expedera's description of the NPU interface shift is a concrete signal: the AXI bus assumptions are wrong for UCIe-speed die-to-die links, and teams are redesigning IP to match. That is a workflow constraint surfacing at the IP level, which is earlier in the flow than anyone planned for.
The teams with 18-month advantage here are the ones that have already built cross-domain models connecting die implementation, package thermal, and PDN sign-off into a shared feedback loop. The teams still handing off a Cadence netlist to a packaging team via email spreadsheet are running a process that produces expensive surprises at assembly. The question is not whether to restructure the workflow; advanced packaging economics guarantee it. The question is which EDA vendors and OSAT partners build the shared tooling first.