As a BMS design expert, I understand that in automotive ADAS and EV power systems, PCBs are not just carriers for components but lifelines for the safe transmission of high voltage, high current, and high-speed signals. Any minor electrical defect can lead to catastrophic consequences. Therefore, rigorous testing and validation are critical throughout the manufacturing and assembly process. Among these, Flying Probe Test stands out as a core technology for ensuring the automotive-grade reliability of these complex PCBs, thanks to its unparalleled flexibility and diagnostic depth.

DFM/DFT/DFA Review: Ensuring Efficient Execution of Flying Probe Test from the Source

Introducing Design for Manufacturability (DFM), Design for Testability (DFT), and Design for Assembly (DFA) reviews during the design phase is the cornerstone of successfully implementing any testing strategy. A thorough DFM/DFT/DFA review ensures that all critical networks have accessible test points, avoiding issues where probes cannot reach due to structural obstructions or insufficient spacing. This not only paves the way for subsequent Flying Probe Test but also significantly improves the pass rate of First Article Inspection (FAI). Neglecting this step often leads to discovering issues late in production, resulting in costly rework or even redesigns-unacceptable in the tight development cycles of automotive projects.

Busbars/Copper Bars and Heavy Copper: Optimization and Validation of High-Current Paths

EV power PCBs, such as inverters and onboard chargers, need to handle currents of hundreds of amps. This requires the use of heavy copper PCB technology and often integrates Busbars or copper bars to create low-impedance, high-current-capacity paths. However, the integrity of these thick copper layers and the reliability of connection points are blind spots for traditional testing methods. Here, Flying Probe Test demonstrates its unique advantage: it can precisely measure resistances as low as milliohms, verifying the robustness of Press-fit terminal connections to the PCB and ensuring no abnormal temperature rise under high-current surges. This is a critical step in guaranteeing the quality of the entire SMT assembly process.

Electrical Connection Testing Under Complex Thermal Structures: MCPCB and Cold Plate Integration

To address thermal challenges caused by high power density, Metal Core PCBs (MCPCB) and integrated designs with heat spreaders and cold plates have become mainstream. These complex mechanical-electrical hybrid structures introduce new testing difficulties. Flying probe test probes can flexibly move under software control, precisely accessing test points surrounded by heat fins or complex structures. Performing thorough electrical testing before potting/encapsulation is critical, as repairs become impossible afterward. HILPCB ensures 100% electrical performance compliance for every complex thermal PCB before sealing through advanced flying probe test equipment.

Case Study: ADAS Radar Front-End Board (BGA/QFN + Microwave Traces)

• Challenges: Bottom solder joints, micro-vias/blind vias, RF trace impedance constraints
• Methods: X-Ray (voids/bridging) + FPT (resistance/polarity/power rails) + FCT (RF functionality)
• Criteria: BGA void rate ≤10% (example), power ripple/noise meets front-end budget
• Results: First-article FPT full coverage, engineering change cycle <24h, FAI passed on first attempt

Case Study: EV Inverter Power Board (Heavy Copper/Busbar/High Voltage)

• Challenges: mΩ-level current paths, press-fit/busbar connections, pre-potting withstand voltage
• Methods: FPT 4-wire method (mΩ precision) + Hipot (1-3 kV example) + AOI/X-Ray (solder quality)
• Criteria: Connection point ΔR within limits, leakage current compliance, hotspot temperature rise below thermal model threshold
• Results: 100% electrical verification before sealing, transition to ICT for higher throughput in mass production

Synergistic Collaboration Between Flying Probe Test and Optical/X-Ray Inspection

A single testing method cannot achieve the zero-defect goal for automotive-grade products. A comprehensive quality control system requires the collaborative use of multiple technologies such as Flying Probe Test and SPI/AOI/X-Ray inspection.

• SPI (Solder Paste Inspection): Checks solder paste printing quality before SMT placement.
• AOI (Automated Optical Inspection): Inspects component placement accuracy, solder joint appearance, and other surface defects.
• X-Ray Inspection: Detects hidden defects such as voids and bridging in bottom solder joints of BGA, QFN, etc.
• Flying Probe Test: Conducts final electrical functional verification after the above inspections to detect issues like open circuits, short circuits, and incorrect component values.

This "inside-and-out" strategy, combined with rigorous DFM/DFT/DFA review, ensures comprehensive quality monitoring from materials to finished products.

From First Article to Mass Production: The Evolving Roles of FAI and Flying Probe Test

First Article Inspection (FAI) is a critical milestone for verifying production process stability and product compliance. During prototyping and small-batch production phases, Flying Probe Test is the optimal choice for executing the electrical testing portion of FAI, as it eliminates the need for expensive test fixtures and enables rapid response to design changes. HILPCB's Small Batch Assembly leverages this advantage of flying probe testing to help customers iterate products quickly. As projects transition to mass production, data accumulated from flying probe tests can guide more efficient ICT (In-Circuit Test) fixture design, achieving the best balance between cost and efficiency.

FPT / ICT / FCT: When to Use, Cost vs. Efficiency

Dimension	FPT (Flying Probe)	ICT (In-Circuit Test)	FCT (Functional Test)
Initial Investment	Low (No fixtures)	High (Fixtures/Development)	Medium (Tooling/Fixtures)
Change Response	Fast (Suitable for prototypes/small batches)	Slow (Adapted after mass production stabilization)	Medium (Script/Process updates)
Coverage	Connectivity/Components/Partial functions	Connectivity/Components (Fast)	System functions/Interfaces
Mass Production Efficiency	Medium (Optimizable through parallelization)	High (Fixture-based)	Medium (Per test case)

Get PCB Quote ## Reliability Assurance in Extreme Environments: Potting and High-Voltage Isolation Testing

Automotive electronics must remain stable under harsh conditions of vibration, humidity, and temperature cycling. The potting/encapsulation process, which involves completely encasing the PCBA with materials like epoxy resin, provides ultimate physical and environmental protection. However, this also means the testing window is closed. Therefore, the final electrical verification before potting is critical. Flying probe testing not only detects common open/short circuits but also performs high-voltage isolation testing (Hipot Test), ensuring sufficient insulation clearance between high-voltage networks and low-voltage control circuits, as well as between the chassis ground, to prevent arc breakdown under high voltage. This precise verification of safety boundaries is the fundamental guarantee for the safe operation of EV power systems.

Measurement and Judgment Criteria: From "Testable" to "Judgable"

Item	Typical Target/Threshold	Method	Notes
High-current path resistance	mΩ level (±1 mΩ accuracy example)	Four-wire Kelvin measurement (FPT fixture/probe)	Busbar/Thick Copper/Crimping Point Thermal Rise Related
BGA Void Rate	≤10% (Example, depends on package/specification)	X-Ray Calculated Void Area Ratio	Electrothermal Reliability Sensitive
Withstand Voltage Leakage	μA Level (Voltage/Creepage/Clearance Related)	Hipot (e.g., DC 1-3 kV, Example)	Set Based on IEC/Corporate Standards
Sampling Frequency	100% for First Article, Gradually Relaxed from Pilot to Mass Production	SPC + Risk Grading	Linked to DFM/DFT Maturity

Note: Indicators are common practice examples. Final criteria should follow applicable automotive/customer specifications (e.g., ISO 26262, IPC-9252, IPC-A-610 Class 3, IATF 16949) and design constraints.

Typical Process: From DFM to Pre-Potting Validation

1. DFM/DFT/DFA Review (Including Flying Probe Accessibility/Four-Wire Measurement Points)
2. SMT/THT + SPI/AOI/X-Ray (Appearance and Hidden Defect Screening)
3. FPT (Continuity/Components/Critical Functions + High-Current Four-Wire Method)
4. Hipot/Partial Discharge Screening (Depends on High Voltage Level/Safety Regulations)
5. Pre-Potting Verification of Critical Electrical Points and Sampling
6. FCT + Aging + Sampling Retest (ICT Introduced in Mass Production for Efficiency)

Frequently Asked Questions (FAQ)

• Is the flying probe too slow?: Fast coverage for prototypes/small batches, no fixture development required; can collaborate with ICT for efficiency in mass production.
• Can testing proceed without test points?: Some networks can be replaced with fixtures/probes, but DFT预留 (DFT预留 remains as is, assuming it's a term) is recommended.
• Relationship with ICT/FCT?: FPT focuses on "structure/connectivity + local functionality", ICT is highly efficient, and FCT verifies system-level functionality
• When to switch to fixtures?: Transition to ICT/FCT fixture-based testing when the version is stable and production volume increases, based on cycle time/cost evaluation

In summary, in the high-standard field of automotive ADAS and EV power PCBs, Flying probe test has transcended the scope of traditional testing tools to become a critical bridge connecting design, manufacturing, and final reliability. It works closely with processes such as DFM/DFT/DFA review, SPI/AOI/X-Ray inspection, and First Article Inspection (FAI), collectively forming a robust quality assurance system. By deploying advanced verification methods like Flying probe test at every key manufacturing milestone, we can confidently deliver high-performance electronic products capable of withstanding extreme automotive environments and ensuring driving safety.

Related links

• heavy copper PCB
• Metal Core PCBs (MCPCB)
• Small Batch Assembly