The rapid growth of new-energy intelligent vehicles and high-level autonomous driving keeps driving the iteration of the vehicle Electrical/Electronic Architecture (EEA). As the computing core for smart cockpit and autonomous driving, the Domain Control Unit (DCU) processes massive real-time data traffic. It imposes stringent automotive-grade requirements on matching PCBs: high-speed transmission, high-density interconnection, superior flatness, high-temperature resistance, CAF immunity, and long-term reliability.

1. Evolution of Domain Controller Architecture & PCB Design Trends

The vehicle EEA is evolving from distributed ECUs toward domain-centralized and central-computing architectures. Cockpit‑ADAS integration has become the mainstream technical route, divided into four phases: separated cockpit and ADAS domains, Cockpit‑ADAS Fusion 1.0 multi-board solution, Cockpit‑ADAS Fusion 2.0 single-board solution, and Cockpit‑ADAS Fusion 3.0 single-chip solution.

- Cockpit‑ADAS Fusion 1.0: Independent multi-board PCBs interconnected via Ethernet;

- Cockpit‑ADAS Fusion 2.0: Single-board PCB solution with SoC integrated on one PCB, interconnected via high-speed PCIe;

- Cockpit‑ADAS Fusion 3.0: Highly integrated single-chip solution, with PCBs evolving toward advanced HDI.

As ADAS computing power continues to rise, the computing capability of L2~L4 ADAS domain controllers is scaling from dozens of TOPS to thousands of TOPS. DCU PCBs are shifting from conventional multilayer boards (MLB) to High-Density Interconnect (HDI) boards. The pitch of mainstream main BGA packages shrinks to 0.65 mm, 0.5 mm and even 0.4 mm. Typical stackups adopted include advanced HDI structures such as 1+2+1, 2+4+2, 3+4+3 and 4+2+4. Fine line widths, small aperture vias and precise impedance control have become standard requirements.

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> Juehui Weiye Circuit supplies cockpit domain PCBs, ADAS domain PCBs and integrated cockpit‑ADAS HDI domain controller boards. Our products support Qualcomm SoC platforms and customized fabrication for corresponding stackups, line/space rules and BGA pitches.

2. Signal Integrity (SI) Control for DCU High-Speed PCBs

Data interfaces for advanced ADAS have upgraded from PCIe 3.0 (8 Gbps) to PCIe 4.0 (16 Gbps) and PCIe 5.0 (32 Gbps). L4/L5 autonomous driving platforms are already conducting pre-research for PCIe 6.0 (64 Gbps). High-speed signal loss and consistent impedance are top-priority indicators for domain controller PCBs.

2.1 Automotive-Grade High-Speed Substrate Selection

Core evaluation metrics for high-speed materials: Glass Transition Temperature (Tg), Coefficient of Thermal Expansion (CTE), Dielectric Constant (Dk), Dissipation Factor (Df), CAF migration resistance, halogen-free formulation and high thermal resistance.

The mainstream automotive substrate grades in the industry are M2 / M4 / M6 / M7. Low-Df materials deliver excellent insertion loss performance at 28 GHz, satisfying high-speed link requirements for L3 and above ADAS systems. All mass-production substrates pass repeated 260°C lead-free reflow thermal validation and 85°C / 85% RH biased HTHG CAF reliability testing.

✅ Juehui Weiye Circuit Material Selection Principle:

We match substrates according to the customer’s ADAS autonomy level and interface speed, instead of blindly specifying premium-grade materials. We balance insertion loss, fabrication yield and cost, and provide substrate comparison reports and measured insertion loss curves.

2.2 Fine Trace & Differential Impedance Control

High-level HDI domain controller PCBs widely adopt 0.35 mm BGA pitch, with differential line/space of 38~40 μm and differential impedance of 75 Ω / 85 Ω ±10%.

We master two mature process routes: the subtractive (Tenting) process and the Modified Semi-Additive Process (mSAP):

- Subtractive process: Stable and mature for high-volume production; controllable etch factor and impedance deviation;

- mSAP: Optimized for ultra-fine traces, delivering superior line width uniformity and tighter impedance consistency.

Combined with LDI (Laser Direct Imaging) and laser microvia annular alignment targets, our process eliminates registration deviation introduced by multiple lamination cycles and sequential laser drilling, enabling stable fabrication of 40 μm laser microvias.

3. Manufacturing Process & Quality Control for High-Level ADAS DCU PCBs

3.1 Local High Flatness Control within BGA Zones

Large-format, fine-pitch BGAs impose strict warpage requirements on PCBs. For ADAS domain controller PCBs, the flatness deviation within BGA areas must be ≤100 μm; premium projects require ≤60 μm. Flatness deviation directly causes SMT cold joints and functional failure.

Key factors affecting flatness: substrate Tg, storage modulus, Z-axis CTE, resin flowability and residual lamination stress.

Juehui process optimization solutions:

1. Symmetrical stackup design, with interlayer copper area ratio difference strictly controlled below 5%;

2. Optimized lamination temperature profile with extended dwell time for full resin cross-linking;

3. Extended cooling segment for gradual release of thermal stress after lamination;

4. Tg-point bake after routing and drilling to eliminate mechanical stress;

5. Full-process warpage inspection via Shadow Moiré method, monitoring flatness variation across a wide temperature range of 30~260°C.

3.2 Reliability Scheme for High-Density Buried & Blind Vias

Dense buried and blind vias represent a core challenge for HDI domain boards. With via-to-via spacing below 100 μm, regions with concentrated blind and buried vias are prone to resin delamination, via cracking and via blowout after repeated lamination.

To address “via blowout and copper foil delamination” when CO₂ laser drilling RTF copper paired with high-speed resin systems, Juehui optimizes laser parameters: reduced single-pulse energy, elevated pulse frequency and spot overlap compensation. Combined with vacuum pre-treatment of prepreg, the risk of delamination around blind vias is effectively reduced.

Resin desmear and plasma descum are applied in dense buried-via zones to mitigate stress concentration at via edges, meeting reliability requirements for 20 cycles of lead-free reflow soldering.

3.3 Plating Crack Control (TCT Thermal Cycle Reliability)

Automotive DCUs must pass thousands of Thermal Cycle Test (TCT) cycles from -40°C to 160°C, with resistance change limited to ≤5%. Plating cracks at via barrels or trace corners are prohibited.

Plating cracks mostly occur at through-hole corners and dense via arrays, strongly correlated with CTE matching of laminates, TOC contamination in plating chemistry and copper grain quality.

Juehui countermeasures: Prioritize high-Tg, low Z-CTE substrates; control TOC impurities within plating baths; tune parameters of Vertical Continuous Plating (VCP) to improve plating ductility. We also compare TCT cycle test data of different substrates to recommend the optimal crack-resistant material combination for customers.

3.4 CAF (Conductive Anodic Filament) Reliability Assurance for Thick-Copper Thin-Dielectric Structures

High-computing SoC domain boards carry large instantaneous current. Power and ground planes often use 70 μm thick copper with dielectric thickness reduced below 80 μm. This thin-dielectric + thick-copper structure is highly susceptible to CAF ionic migration and insulation failure under prolonged high-humidity and high-bias conditions.

Stackup simulation is used to predict resin filling risks. We control prepreg resin content and glass fabric impregnation rate, and verify resin filling integrity via microsection inspection to avoid interlayer voids. We support 1000-hour CAF validation at 85°C / 85% RH with 100 V bias, ensuring stable insulation under high-voltage humid environments.

4. Juehui Weiye Circuit | Summary of Capabilities for Automotive ADAS Domain Controller PCBs

✅ Product Scope: Advanced HDI DCU boards, cockpit domain PCBs, ADAS domain PCBs, integrated cockpit‑ADAS single boards, high-speed automotive PCBs

✅ Process Capability: HDI stackups including 1+2+1, 2+4+2, 3+4+3, 4+2+4; subtractive + mSAP semi-additive process; LDI laser microvias; precise differential impedance control

✅ Material Portfolio: Full series of M2/M4/M6/M7 automotive halogen-free high-speed low-Df laminates, compatible with RTF and HVLP ultra-low-profile copper foils

✅ Reliability Validation: Moiré warpage scanning, insertion loss testing, TCT thermal cycling, biased HTHG CAF testing, repeated reflow thermal resistance verification

✅ Supported Platforms: Mainstream Qualcomm automotive SoC domain controller solutions. Fast DFM evaluation available based on customer-provided stackup and BGA parameters.

> With the rapid iteration of autonomous driving, PCB serves as the cornerstone for stable domain controller hardware. Juehui Weiye Circuit continues to deepen expertise in automotive HDI high-speed PCB processes. Adhering to automotive-grade reliability standards, we help ADAS customers shorten hardware validation cycles and achieve stable mass production of domain controller motherboards.

> For ADAS domain controller PCB prototyping, DFM reviews or high-speed substrate selection consultation, welcome to contact our technical team.