Overview:

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A leading smart city solution provider from a highly developed market engaged us to manufacture a complex 4-board PCBA module for their intelligent street lighting system—part of a larger IoT-driven urban infrastructure. The boards were multilayer, densely populated, and lacked predefined test specifications, with limited access for traditional testing. To ensure uncompromised quality, we implemented Flying Probe Testing (FPT)—a precise, fixtureless method using programmable probes to assess electrical continuity and component performance. This enabled us to achieve 97.78% test coverage, ensuring the reliability required for a mission-critical, field-deployed application. This case study showcases how adaptive test strategies can maintain engineering excellence under stringent conditions.

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Challenges:
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During the initial production phase, our team encountered several critical issues:

• Lack of Test Specifications
  The customer supplied only the Gerber files and Bill of Materials (BOM), requesting PCBA manufacturing without defining any functional or in-circuit testing criteria. This created a major gap in defect prevention and quality validation processes.
• Limited Test Point Accessibility
  The board design featured very few accessible test points, making it difficult to perform even standard in-circuit testing. This limitation constrained traditional testing methods and increased the risk of undetected defects.
• Low Initial Test Coverage
  Basic testing approaches, such as visual inspection and manual continuity checks, yielded low coverage and failed to meet the expected quality assurance benchmarks. This inadequacy raised concerns about long-term product reliability in the field.
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Solutions:

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To overcome these challenges, a structured two-phase testing strategy was developed:

• Phase 1: Outsourced MDA (Manufacturing Defect Analyzer)
  As an initial measure, MDA testing was outsourced to verify PCBA-level defects such as shorts, opens, and basic component placements. While useful, this method achieved only around 50% test coverage, primarily due to the limited number of accessible test points and the     constraints of the MDA methodology.
• Phase 2: Implementation of Flying Probe Testing (FPT)
  Recognizing the need for more robust and flexible testing, we adopted Flying Probe Testing (FPT) to dramatically improve coverage.
   
    Key benefits included:
   
  • No Need for Custom Fixtures: FPT allowed non-intrusive testing without the need for expensive or time-consuming fixture development.
  • Probing Both Components and Test Points: Enabled access to multiple nodes on the board, including areas unreachable by MDA.
  • High Test Coverage: Achieved a test coverage of 97.78%, significantly reducing the risk of undetected defects.
  • Adaptability: The dynamic probing capability allowed seamless adjustment to the board layout, facilitating faster iterations and better fault detection.
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Impact:

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The strategic implementation of FPT yielded tangible improvements across key metrics:

• Improved Defect Detection
      Enhanced test coverage led to the identification and rectification of previously undetectable issues, ensuring only high-quality boards progressed through the production cycle.
• Increased Product Quality
      The improved fault isolation and testing depth resulted in a significant uptick in board reliability, critical for a high-availability application like smart city lighting control.
• Customer Satisfaction
  By proactively addressing the lack of test specifications and introducing a sophisticated test methodology, we were able to not only meet but exceed customer expectations—strengthening our long-term relationship and establishing trust in our engineering capabilities.
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Conclusion:

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Transitioning from limited testing to Flying Probe Testing resulted in a significant enhancement in PCBA test coverage and defect detection capabilities. This proactive quality assurance approach not only met the manufacturing challenges but also elevated the end-product reliability—ultimately leading to greater operational efficiency and customer trust.

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