What Are The HDI Board Risks for Radar Modules

•Solution - DFM review and impedance verification confirmed the stack-up and routing were compatible with HDI PCB fabrication.

•Transition - The HDI multilayer structure supported reliable RF routing without requiring changes to the original PCB layout.

•Result - The radar module PCB moved smoothly from prototype fabrication into stable automotive PCBA production.

One of KnownPCB customers which is automotive electronics manufacturer was developing a radar sensing module as part of a broader ADAS platform. The internal electronics were applied on a dense HDI multilayer PCB integrating the radar transceiver IC, processor, memory, and supporting power management circuitry within a tightly constrained board outline.

After completing the initial PCB layout, the client's engineering team shared the PCB fabrication data with KnownPCB to review manufacturability before prototype production. During this HDI PCB DFM review, we paid particular attention to the RF routing layers that is used by the radar front-end.

Automotive radar systems operate in the millimeter-wave frequency range , where maintaining stable impedance along RF signal paths is critical for system performance. Manufacturing analysis showed that variations in dielectric thickness, copper profile, and lamination parameters during HDI board fabrication could introduce impedance variation across RF traces. While the design itself met electrical requirements, ensuring consistent RF characteristics across fabrication panels became an important consideration before moving forward with production.

The factors should be involved:

1. Dielectric Material Consistency

2. Copper Profile & Etch Factor

3. Lamination & Registration (Layer-to-Layer Registration, Scaling)

4.  Surface Finish Impact: Thickness of immersion silver