1. Purpose and scope
Concept work chooses the package structure. The options are many: fan-out with redistribution layers, a silicon interposer with through-silicon vias, silicon bridges embedded in a substrate or mould, an organic or redistribution layer interposer, stacks joined by micro-bumps or by hybrid bonding, and new substrate materials such as glass. Each has a different reach in interconnect density, power delivery, heat removal, size, cost and risk. The purpose of the stage is to compare them in models against the lead customer requirements, choose one, and set the targets and preliminary rules the rest of the development works to.
The second half of the stage designs the test vehicles. They are the hardware on which every module, interface and failure mechanism is measured: daisy chains for continuity and resistance, Kelvin structures, thermal test dies with heaters and sensors, stress sensors, alignment marks, and, where the drivers need it, functional dies with die-to-die links. A technology is only as well proved as its test vehicles, so their design deserves the same care as a product.
In scope: the concept comparison, modelling feasibility, package technology targets, the die-to-die interfaces to be supported, the test vehicle requirements and designs, preliminary assembly design rules, the first reliability test plan and equipment requirements. Out of scope: choosing materials and suppliers in detail and developing recipes, which follow in the next stages.
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