Separate the package from the board problem
List the signals and supply connections that actually reach the PCB. Memory integrated within a package creates different board routing needs from external memory devices. Do not infer the required layer count from compute performance or a product category.
Build a preliminary escape map including power pins, grounds and reserved package areas. Compare at least one simpler via arrangement with the intended HDI arrangement. Record what becomes possible with each extra buildup step instead of treating more layers as an automatic margin.
Allocate power distribution space early
Intel's board power guidance emphasizes the role of local bypassing and decoupling in meeting transient demand. For an accelerator layout, the practical task is to coordinate regulator position, capacitors, power copper and package escape before routing closes those options.
Review the entire current path, including connectors, plane changes and return connections. If a compact placement forces an indirect power path, compare it with a slightly larger placement using realistic operating modes rather than a board area target alone.
Make cooling part of placement review
Overlay heatsink keepouts, retention hardware, component heights and service access on the PCB. Confirm whether components on the opposite side compete with the support mechanism. Include the expected assembly order; an excellent thermal arrangement is not useful if it prevents installing or inspecting another critical part.
- Identify memory and host links with constrained routing budgets.
- Reserve measurement points for rail behavior and sequencing.
- Check power paths around mounting and package keepouts.
- Record operating loads used for thermal and interface testing.
Design a staged bring-up path
Define a sequence that verifies basic rails, control and recovery access before stressing compute and high speed interfaces. Include a way to distinguish a firmware startup issue from a board connection or power problem. Dense boards benefit from deliberately placed diagnostic access.
Archive the final construction and measurement configuration with the first article results. When increasing workload or changing cooling, review whether the original board validation covered the new conditions instead of assuming that software changes cannot affect hardware margins.
Adjacent-layer access, one connection at a time
Dielectric · geometry + material
Core or build-up dielectric
Illustrative only. Copper thickness, dielectric construction and via spans require a reviewed stackup.
Common questions
Does an AI accelerator automatically need any-layer HDI?
No. The external package connections, memory arrangement and channel requirements determine the board architecture. A package escape study provides better evidence than the AI label.
Should routing be completed before power integrity review?
Review them together. Signal escape can consume space needed for decoupling and current paths, making late corrections expensive or requiring a new stackup.
References & further reading
Method & assumptions · General design guidance. Validate the proposed construction and acceptance criteria for your project.