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Complex Design and Test Requirements

Client Background

A Silicon Valley autonomous driving startup was developing a next-generation LiDAR (Light Detection and Ranging) system requiring unprecedented integration of high-speed digital, analog, and RF circuitry on a single 14-layer rigid-flex PCB. The system demanded millimeter-wave signal integrity at 77 GHz, tight impedance control (±5% for differential pairs), and extensive functional testing under extreme environmental conditions—all within an aggressive 18-week development timeline.

The Challenge

The client faced three interlocking challenges that threatened their product launch:

  • Design Complexity – The 14-layer rigid-flex PCB combined high-speed digital (25 Gbps SerDes), precision analog (16-bit ADC), and RF (77 GHz radar) circuits on the same board. Signal isolation, crosstalk mitigation, and impedance matching across mixed technologies required advanced simulation and layout expertise.

  • Test Rigor – The system required validation across a wide range of operating conditions: temperature cycling (-40°C to +125°C), vibration (20 Grms), and humidity (95% RH non-condensing). Traditional functional testing was insufficient—full parametric characterization was required.

  • Regulatory Compliance – Automotive-grade certification (AEC-Q100/200) demanded documented traceability for every component and process, with zero defects permissible in safety-critical functions.

With no prior manufacturing experience and a fragmented supply chain of specialized design houses, the client needed a single partner capable of managing the entire NPI lifecycle—from design optimization to certified production.

Our Approach

Weller’s engineering and test teams implemented a comprehensive design-for-test (DFT) and validation framework tailored to the complexity of the LiDAR system:

  • Collaborative Design Optimization – Our engineers embedded with the client’s design team during schematic and layout phases, performing:
    • Electromagnetic simulation (HFSS) for RF sections to optimize trace geometry for 77 GHz signals
    • Signal integrity analysis (HyperLynx) for high-speed digital lanes to minimize jitter and crosstalk
    • Power integrity modeling to ensure stable 1.8V and 3.3V rails under dynamic loads
    • DFM/DFA reviews to optimize panel utilization and assembly yield
  • Custom Test Architecture – We developed an integrated test strategy covering all critical parameters:
    • In-circuit test (ICT) for 100% component-level verification
    • Flying probe for high-density areas inaccessible by bed-of-nails fixtures
    • Boundary scan (JTAG) for testing interconnects between BGAs and FPGAs
    • Custom functional test with environmental chamber integration for temperature cycling and vibration characterization
  • Controlled Manufacturing Process – Production was performed under strict process controls:
    • Rigid-flex lamination with ±0.05 mm layer registration
    • Backdrilling to remove signal stubs on 25 Gbps lanes
    • ENIG surface finish (IPC-4552) for fine-pitch BGA compatibility
    • 100% X-Ray inspection for BGA solder joint integrity
  • Traceability & Compliance – A comprehensive quality management system was implemented:
    • Batch-level traceability for all components
    • In-process inspection records correlated with final test data
    • Environmental test logs for temperature, humidity, and vibration profiles
    • Full documentation package for AEC-Q100/200 submission

Result

The integrated design and test approach delivered the performance and reliability required for autonomous vehicle deployment:

Metric

Requirement

Achieved

Impedance Control (Differential)

±10%

 ±5%

RF Signal Loss @ 77 GHz

<2.5 dB/ft

<1.8 dB/ft

Test Coverage

95%

99.2%

First Pass Yield

 >85%

93.7%

Temperature Cycling

500 cycles

1,000 cycles

AEC-Q Compliance

Pending

Certified

The client completed their NPI phase in 16 weeks—two weeks ahead of schedule—and successfully scaled to production volume of 5,000 units per month within the first quarter. The integrated test architecture reduced diagnostic time for field returns by 70%, enabling rapid root cause analysis and continuous improvement.

Conclusion

This project demonstrates that mastering complex design and test requirements requires more than advanced equipment—it demands a deeply integrated approach spanning design optimization, controlled manufacturing, and comprehensive test architecture. By embedding engineering expertise early, developing custom test solutions, and maintaining rigorous process controls, Weller enabled our customer to bring a safety-critical autonomous system to market with confidence.

For OEMs developing high-performance electronics in automotive, aerospace, or telecommunications, an integrated design-to-test partnership is essential to managing complexity without compromising reliability.

Cross-section comparison of EMI shielding methods for rigid-flex PCB: conductive silver paste coating, sputtered copper layer, and stamped metal shield can with via stitching to ground plane

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