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PCB Failure Causes: 5 Design Pitfalls & Solutions

Introduction

Recognizing the root causes of PCB failure is crucial to upholding the dependability and durability of electronic devices. From thermal stress to mechanical strain, each aspect poses distinct challenges that may undermine the effectiveness of printed circuit boards. This article investigates five primary contributors to PCB failure and proposes practical solutions for prevention and mitigation.

Preview of 5 PCB Failure Causes:

  1. Thermal Stress: We’ll examine how excessive heat impacts PCB integrity, leading to solder joint failures, delamination, and component degradation.
  2. Moisture and Contamination: Discover how exposure to moisture and contaminants can trigger corrosion, electrical shorts, and material degradation in PCB assemblies.
  3. Component Defects: Learn about the risks associated with poor-quality or counterfeit components and explore strategies for ensuring component quality and authenticity.
  4. Overvoltage or Voltage Spikes: Explore the consequences of voltage surges on PCBs and discover protective measures against overvoltage conditions.
  5. Mechanical Stress: Understand the implications of mechanical shocks, vibrations, and flexing on PCB reliability and uncover design considerations for minimizing mechanical stress.

By dissecting each of these factors and providing actionable insights, we aim to empower PCB designers and manufacturers with the knowledge and tools necessary to enhance the robustness and performance of their electronic systems.


1. Thermal Stress

A thermal image of a PCB illustrating thermal causes of PCB failure

The significance of thermal stress on PCB integrity cannot be overstated, as it is among the critical causes of PCB failure. Excessive heat triggers a cascade of reliability issues and failure modes within PCBs. When subjected to elevated temperatures, PCB materials, including substrates and solder joints, undergo thermal expansion, inducing mechanical stress and deformation. This, in turn, escalates the risk of delamination, solder joint fatigue, and component detachment. Moreover, prolonged exposure to high temperatures accelerates material degradation, significantly reducing the overall lifespan of the PCB.

Examples of thermal stress-related failures include solder joint fatigue, delamination, and component damage. Solder joints undergo fatigue from repeated thermal cycling, leading to cracks and eventual electrical open circuits. Differential thermal expansion between PCB layers can result in delamination, compromising the board’s structural integrity. Additionally, excessive heat can exceed the maximum operating temperatures of electronic components, leading to degradation or failure.

By effectively managing thermal stress, PCB designers can mitigate the risks associated with excessive heat and enhance the overall performance and longevity of electronic systems. Incorporating appropriate thermal management techniques, such as heat sinks, proper ventilation, and material selection, is essential for safeguarding PCB integrity and reliability in demanding applications.

To mitigate thermal stress, several strategies can be employed:

  • Heat Sinks and Thermal Pads: Implementing heat sinks and thermal pads helps dissipate heat away from critical components, reducing the risk of thermal damage.
  • Proper Ventilation and Airflow: Ensure adequate ventilation and airflow within electronic enclosures to prevent heat buildup and maintain components at optimal operating temperatures.
  • Thermal Design Considerations: Incorporate thermal design considerations into PCB layout and enclosure design, distributing heat-generating components evenly and providing sufficient clearance for airflow.
  • Heat Dissipation Techniques: Utilize techniques such as copper pour, vias, and thermal vias to enhance heat dissipation across the PCB surface and through the layers.
  • Material Selection: To minimize thermal stresses and improve reliability, choose PCB materials with high thermal conductivity and low coefficient of thermal expansion (CTE).
  • Temperature Monitoring and Regulation: Implement temperature monitoring and regulation systems using temperature sensors and thermal management algorithms to prevent PCBs from operating beyond their thermal limits.

Effectively managing thermal stress is crucial for ensuring the reliability and longevity of PCB assemblies, particularly in applications exposed to high temperatures or thermal cycling. By employing appropriate thermal management strategies, designers can mitigate the risks associated with excessive heat and enhance the overall performance of electronic systems.


2. Moisture and Contamination

    A PCB with damage from moisture and contamination during manufacturing.

    Moisture and contaminants pose significant risks to PCBs, compromising their electrical performance and reliability. Exposure to moisture leads to water absorption by PCB materials, causing electrical shorts, corrosion, and insulation degradation. Additionally, contaminants, including dust, dirt, oils, and chemicals, exacerbate these issues by promoting corrosion, interfering with electrical connections, and causing insulation breakdown.

    Common sources of moisture and contamination include environmental exposure, handling and assembly processes, and improper packaging and storage. Environmental exposure during storage, transportation, and operation exposes PCBs to ambient moisture and airborne contaminants. Improper handling practices during assembly, such as bare-hand contact or inadequate cleanliness of assembly tools, introduce contaminants onto the PCB surface. Inadequate packaging materials or storage conditions expose PCBs to moisture and contaminants during long-term storage or shipping.

    By implementing preventive measures and best practices for moisture protection, such as encapsulation, proper handling procedures, and the use of moisture-resistant materials, PCB designers and manufacturers can effectively safeguard PCBs against the detrimental effects of moisture and contaminants, ensuring long-term reliability and performance in diverse operating environments. These strategies mitigate the risks associated with moisture ingress and contamination, addressing critical aspects of the causes of PCB failure and enhancing overall product quality and longevity.

    To safeguard against moisture and contamination, preventive measures and best practices can be implemented:

    • Encapsulation and Conformal Coating: Apply protective coatings such as epoxy or silicone encapsulants and conformal coatings to seal the PCB, preventing moisture ingress and enhancing insulation and mechanical protection.
    • Hermetic Sealing: Consider hermetically sealed enclosures or packages for applications requiring stringent moisture protection, completely isolating the PCB from the external environment.
    • Desiccant Packs and Humidity Control: Include desiccant packs or humidity control devices within electronic enclosures to absorb moisture and maintain low humidity levels, preventing moisture buildup.
    • PCB Design Considerations: Design PCBs with moisture-resistant materials and structures to minimize moisture absorption and enhance reliability, utilizing moisture-resistant substrates, solder mask materials, and surface finishes.
    • Proper Handling and Storage: Implement proper handling and storage procedures to minimize the risk of moisture and contamination. Use antistatic packaging and storage containers, and avoid exposure to humid or corrosive environments.

    By implementing these preventive measures and best practices, designers and manufacturers can safeguard PCBs against the detrimental effects of moisture and contaminants, ensuring long-term reliability and performance in diverse operating environments.


    3. Component Defects

    An illustration of the causes of PCB failure related to component defects

    Component defects are among the significant causes of PCB failure, posing substantial risks to both reliability and functionality. These defects can manifest in various forms, including premature failure, erratic behavior, and safety hazards. They stem from multiple factors, such as substandard materials, manufacturing defects, and inadequate quality control processes. Poor-quality components often deviate from specifications, display inconsistent performance, or are vulnerable to environmental stressors, thereby compromising the overall reliability and performance of the PCB assembly.

    Addressing these causes of PCB failure requires robust quality assurance processes, supplier verification, and material traceability throughout the supply chain. By implementing these strategies, PCB designers and manufacturers can mitigate the risks associated with component defects, ensuring the integrity and longevity of electronic systems in diverse applications. This proactive approach enhances product quality and reliability, safeguarding against potential failures and optimizing overall performance.

    To identify counterfeit components, several methods can be employed:

    • Supplier Verification: Verify the credibility and reputation of component suppliers through thorough research, reviews, and certifications. Established distributors with a track record of quality assurance are less likely to distribute counterfeit components.
    • Physical Inspection: Conduct visual inspections of components to check for signs of counterfeit or substandard quality, such as discrepancies in labeling, packaging, markings, and overall appearance.
    • Component Testing: Perform electrical and functional testing of components to validate their performance and authenticity, utilizing testing equipment and techniques to assess key parameters like electrical characteristics, reliability, and consistency.
    • Certifications and Documentation: Request certificates of compliance, authenticity, and traceability from component suppliers. Authentic components are typically accompanied by comprehensive documentation, including datasheets, manufacturer information, and batch/lot numbers.

    Strategies for ensuring component quality and authenticity involve:

    • Authorized Distribution Channels: Source components from authorized distributors and manufacturer’s representatives to ensure authenticity and traceability, as authorized channels adhere to strict quality control standards and provide genuine components with reliable documentation.
    • Quality Assurance Processes: Implement robust quality assurance processes and procedures throughout the supply chain, conducting incoming inspections and quality audits to detect and prevent the use of counterfeit or substandard components.
    • Material Traceability: Maintain comprehensive records of component sourcing, procurement, and usage to establish material traceability and accountability. This will enable effective identification and mitigation of counterfeit components while ensuring compliance with regulatory requirements.
    • Collaboration and Information Sharing: Collaborate with industry associations, government agencies, and stakeholders to exchange information and best practices for combating counterfeit components. Participate in initiatives aimed at raising awareness and enhancing supply chain security.

    By implementing these strategies for ensuring component quality and authenticity, PCB designers and manufacturers can effectively mitigate the risks associated with poor-quality components, safeguarding the reliability and performance of electronic systems. This comprehensive approach ensures that printed circuit boards (PCBs) operate optimally and remain resilient against potential malfunctions.


    4. Overvoltage or Voltage Spikes

    A PCB with damage from overvoltage or voltage spikes

    Voltage surges, whether transient spikes or sustained overvoltage conditions, are significant threats among the causes of PCB failure, compromising both functionality and performance. These surges precipitate various consequences, including component damage, insulation breakdown, and data corruption.

    Causes and sources of overvoltage and voltage spikes include:

    • Power Supply Issues: Fluctuations in the power grid, such as voltage transients, sags, and swells, introduce overvoltage conditions into electronic systems. Power surges resulting from lightning strikes, switching events, or utility faults are common sources of voltage spikes.
    • Switching Inductive Loads: Switching inductive loads like motors, relays, and solenoids generate voltage spikes due to the inductive kickback effect. Rapid changes in current flow through inductive components induce high-voltage spikes, which propagate through the circuit and affect neighboring components.
    • Electrostatic Discharge (ESD): ESD events from static electricity discharge between objects produce voltage spikes with high peak currents and short durations. Human body ESD and equipment ESD are significant sources of transient voltage spikes in electronic systems.

    To protect against overvoltage and voltage spikes, various methods and devices can be employed:

    • Voltage Regulators: Utilize voltage regulators such as linear or switching regulators to stabilize the supply voltage and maintain it within safe operating limits. Voltage regulators regulate the output voltage regardless of input voltage variations, providing protection against overvoltage conditions.
    • Transient Voltage Suppressors (TVS): Install TVS diodes or transient voltage suppression devices to clamp transient voltage spikes and divert excess energy away from sensitive components. TVS devices respond rapidly to voltage transients, shunting excessive voltage to ground and limiting the voltage across protected circuits.
    • Varistors: Incorporate metal-oxide varistors (MOVs) or voltage-dependent resistors (VDRs) to absorb transient voltage spikes and limit overvoltage conditions. Varistors exhibit nonlinear resistance characteristics, rapidly decreasing resistance with increasing voltage, to protect against voltage surges.
    • Fuse Protection: Include fuses or circuit breakers in the power supply path to interrupt excessive current flow during overvoltage events. Fuses provide overcurrent protection by opening the circuit when the current exceeds a predetermined threshold, preventing damage to downstream components.

    By implementing these protection methods and devices, including surge protection mechanisms, PCB designers can effectively mitigate the risks associated with overvoltage and voltage spikes. This proactive approach ensures the reliability and robustness of electronic systems in the face of transient voltage events, safeguarding against potential damage and downtime.


    5. Mechanical Stress

    A PCB subjected to mechanical stress indicating a cause of PCB failure

    Mechanical stress, a critical contributor to the causes of PCB failure, poses a substantial threat to reliability and performance. It can instigate various failure mechanisms and lead to performance degradation, compromising the assembly’s integrity.

    Under mechanical stress, PCBs and their components are vulnerable to physical damage, structural deformation, or electrical discontinuities. These consequences include:

    • Cracked Traces and Pads: Excessive bending or flexing of the PCB can lead to cracks in copper traces and solder pads, disrupting electrical continuity and causing circuit malfunction.
    • Solder Joint Fatigue: Mechanical vibrations and thermal cycling can induce fatigue in solder joints, resulting in cracks and eventual failure of electrical connections.
    • Component Displacement: Shock or vibration events may dislodge surface-mounted components or lead to component tilt, affecting their electrical performance and solder joint integrity.
    • Board Warping: Uneven mechanical loading or thermal expansion mismatch can cause the PCB to warp or bow, leading to stress concentration and potential damage to components and traces.

    Common scenarios leading to mechanical stress include:

    • Handling and Installation: Rough handling during transportation, assembly, or installation can subject PCBs to mechanical shock, impact, and bending, leading to stress-induced damage.
    • Environmental Conditions: Exposure to temperature extremes, humidity variations, and mechanical vibrations in harsh environments, such as automotive, aerospace, and industrial applications, can exacerbate mechanical stress on PCB assemblies.
    • Constrained Movement: Mounting or enclosures that restrict the natural movement of the PCB, such as tight clearances, inadequate support, or rigid fixturing, can induce mechanical stress and strain on the assembly.
    • Connector Mating and De-mating: Repeated mating and de-mating of connectors can impose mechanical forces on the PCB, leading to wear and tear on connector pins, pads, and vias.

    To minimize the impact of mechanical stress on PCB reliability, various design considerations and structural enhancements can be incorporated:

    • Component Placement and Orientation: Optimize component placement and orientation to minimize mechanical stress concentrations and improve the PCB’s mechanical robustness. Position critical components away from high-stress areas, such as board edges or mounting holes.
    • Flexibility and Compliance: Design PCBs with sufficient flexibility and compliance to accommodate mechanical deflection and thermal expansion without inducing excessive stress on components and traces. Incorporate flex-rigid designs, flexible substrates, or compliant mounting techniques to enhance mechanical resilience.
    • Mounting and Support Structures: Use reinforced mounting holes, stiffeners, and support structures to distribute mechanical loads evenly and provide adequate support for the PCB. Ensure mounting hardware, such as screws, standoffs, and spacers, are properly sized and tightened to avoid overconstraint.
    • Shock Absorption and Damping: Integrate shock-absorbing materials, such as elastomers or foam padding, between the PCB and its mounting surface to dampen mechanical vibrations and attenuate shock loads.
    • Conformal Coating and Encapsulation: Apply conformal coatings or encapsulants to PCBs to provide mechanical protection against environmental factors and enhance structural integrity. Conformal coatings offer a barrier against moisture, dust, and contaminants while providing a protective layer against mechanical stress.

    By incorporating these design considerations and structural enhancements, including mechanical stress-relief features and reinforced mounting structures, PCB designers can effectively minimize the impact of mechanical stress on PCB reliability. This comprehensive approach ensures robust performance and longevity in demanding applications, safeguarding against potential failures and enhancing the overall resilience of printed circuit boards (PCBs).


    Conclusion

    In conclusion, addressing the common causes of PCB failure, including thermal stress, moisture and contamination, component defects, overvoltage or voltage spikes, and mechanical stress, is essential for ensuring the reliability and performance of electronic devices. Throughout this article, we’ve explored strategies for prevention and mitigation to enhance the robustness of printed circuit board (PCB) assemblies.

    Various measures can be taken by designers and manufacturers to mitigate the risks associated with each cause of failure, from implementing thermal management techniques to safeguarding against moisture ingress and addressing component defects. Additionally, protecting against voltage surges and minimizing mechanical stress are crucial aspects of optimizing PCB design and reliability.

    By understanding the importance of these preventive measures and best practices, PCB professionals can effectively mitigate the likelihood of failure and prolong the lifespan of electronic systems. As the electronics industry continues to evolve, staying informed and adopting best practices are essential for navigating the complexities of PCB reliability with confidence.

    Let’s commit to a culture of excellence in PCB design and manufacturing, where reliability, durability, and performance are paramount. Together, we can build a future where electronic systems thrive, delivering value and functionality to users worldwide.

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