Flight Control Core Board (HDI) PCBA

8-Layer 2+N+2 HDI Stack-Up with Laser Microvias — IPC-6012 Class 3 / DO-254

Product Overview

The Flight Control Core Board with HDI (High-Density Interconnect) technology represents Superb Automation's most compact and advanced flight controller solution. Built on an 8-layer 2+N+2 HDI stack-up with laser-drilled microvias and buried capacitance layers, this board achieves component densities previously unattainable with conventional PCB fabrication. The HDI architecture allows the integration of a dual-core ARM Cortex-M7 processor running at 480 MHz, dual IMU redundancy (ICM-42688-P and BMI088), and an onboard digital barometer — all within a footprint of just 20 × 20 mm. The microvia structure reduces parasitic inductance by up to 40% compared to through-hole vias, significantly improving signal integrity at the high edge rates demanded by modern MEMS sensors. All fabrication and assembly meet IPC-6012 Class 3 requirements.

The board employs two build-up layers on each side of a 4-layer rigid core. All BGA escape routing utilizes 0.1 mm laser-drilled blind microvias filled with electrolytic copper, enabling the fine-pitch (0.4 mm) BGA packaging of the STM32H743 microcontroller. The inner layers incorporate embedded distributed capacitance planes that reduce PDN impedance across a broad frequency spectrum, eliminating numerous discrete decoupling capacitors and freeing valuable board real estate. Impedance control is maintained at 50 Ω ±10% for single-ended signals and 100 Ω ±10% for differential pairs throughout all layers.

Key Specifications

HDI PCB Manufacturing Challenges

Fabricating the 2+N+2 HDI stack-up demands sequential lamination with precise layer-to-layer registration tolerances under ±50 µm. Laser-drilled microvias at 0.1 mm diameter require controlled pulse energy and clean debris removal to ensure reliable copper filling by electrolytic plating. The buried capacitance layers are formed from ultra-thin (12 µm) high-Dk laminate, demanding tight thickness control across the panel to maintain consistent distributed capacitance values. Each build-up cycle is followed by automated optical inspection of via formation, and the completed board undergoes 3D X-ray inspection to verify via fill integrity across all layers per IPC-6012 Class 3 void criteria.

Test Strategy

Flying probe testing verifies all net connectivity with 10 µm probe positioning accuracy to access the fine-pitch BGA escape routes. Boundary scan (JTAG) validates interconnects between the MCU and peripheral sensors through the microvia chains. Functional testing includes rate-table calibration of both IMUs simultaneously, verifying cross-sensor agreement within specified tolerance bands. Each board undergoes thermal cycling from -40 °C to +85 °C with continuous sensor output monitoring to validate via reliability under thermal stress.

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