Define the radio architecture before the stackup

Identify the bands, antenna arrangement and location of the RF front end. A carrier for a packaged modem has a different design boundary from a board containing the transceiver and antenna array. Record exactly which interfaces the selected module supplier exposes and which matching or keepout requirements remain on the carrier.

Analog Devices' discussion of compact 5G massive MIMO front ends illustrates the value of integration. For a PCB designer, however, fewer discrete parts does not remove the need to understand the remaining thermal and RF interfaces.

Route from a complete interface inventory

Create separate budgets for host data, radio control, clocks and antenna paths. Use the selected modem and connector documentation for each. Avoid assigning a universal high speed rule to every connection simply because the product uses 5G.

In a dense module, compare alternative package orientations before adding buildup layers. A rotation that simplifies host escape may complicate RF access or cooling, so assess the route, power and mechanical overlays together.

Plan for active radio loading

Evaluate power delivery during the intended transmit and processing modes. Provide practical measurement access near the load and describe the supply source used during testing. An apparently adequate bench supply can mask or introduce behavior that will differ from the installed battery or host rail.

  • Reserve antenna connectors and cable bend space.
  • Map heat flow from active devices to the enclosure or heatsink.
  • Check shielding attachment against routing and rework access.
  • Define the host's maximum intended data and power operating modes.

Make changes visible to the RF review

Track the RF artwork, material construction and enclosure revision with each prototype result. Proposed copper additions, changes in dielectric thickness or shield locations deserve review when they alter the modeled environment. Do not classify a change as cosmetic solely because its netlist is unchanged.

For procurement, separate mandatory requirements from candidate alternatives. A supplier can then evaluate a specific construction rather than guessing whether a named material, exact thickness or generic performance statement takes precedence.

DESIGN NOTE / SCHEMATIC

Adjacent-layer access, one connection at a time

Signal copper

Dielectric · geometry + material

Reference copper

Core or build-up dielectric

Signal copper

Illustrative only. Copper thickness, dielectric construction and via spans require a reviewed stackup.

Real smartphone circuit board illustrating compact component placement
Illustrative compact electronics example; not a product-specific manufacturing sample. © Raimond Spekking / CC BY-SA 4.0. Credits & license.

Common questions

Does a carrier for a 5G module require any-layer HDI?

Not necessarily. Connector escape and host interface routing may fit a simpler board. Use an escape study and the module's integration requirements to decide.

Are all 5G PCB paths millimeter wave paths?

No. The board can include several types of radio, digital and power connections. Identify the actual signals and architecture instead of applying one RF assumption everywhere.

References & further reading

Method & assumptions · General design guidance. Validate the proposed construction and acceptance criteria for your project.