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Improve the Reliability of PCBs With Vibration Fatigue Analysis

Key Takeaways

  • Vibration is a significant failure mode in the electronics industry. 

  • The effect of vibrations and temperature affect the operating lifetime of the circuit. 

  • Vibration fatigue analysis informs the designer about the dynamic characteristics of the PCB.

 Vibration fatigue analysis

Structural integrity is of great importance when it comes to the reliability of electronics. For example, consider airborne electronic circuit boards, which may be subjected to extreme vibrations and thermal exposure. Even under the worst vibrational conditions, these electronic circuits must operate without failure. To ensure this, vibration fatigue analysis is performed on the circuit under consideration. If the circuit withstands the vibration load under vibration fatigue analysis, it is an indication of the reliability of the electronic circuit. 

Vibration Loading

Vibration in a PCB can be a significant threat to its reliability. Vibration is one kind of mechanical loading that adversely affects components as well as the rest of the PCB. The vibration motion refers to the oscillation of the PCB and its components. The vibration can be random or periodic.

Vibration is a significant failure mode in the electronics industry and is common in the electronic circuit boards present in aerospace, automotive, and military applications. Most commonly, vibrations damage interconnect structures in printed circuit boards and subsequently lead to short circuits or no connections.

Random Vibrations in Electronics Circuits

Electronic circuits are used in various environments such as space, healthcare, the military, etc. In these applications, circuits are subjected to vibrations and high temperatures, which affect their endurance or operating lifetime. Generally, the lifetime of components in a printed circuit board are cut in half by vibrations. Surface-mounted components are potential victims of mechanical loading or vibration. The leads of the surface-mounted components experience vibration-induced stress and generally undergo vertical pull.

When subjected to vibrations and temperature, the durability of sensitive components and interconnections in printed circuit boards is compromised. Interconnections can bend or twist, causing damage to sensitive components under vibrational conditions. Usually, the vibrations develop flexural stress at the solder joints and lead wires in PCBs.

Vibrations introduce dynamic loading on the printed circuit board, leading to the premature failure of sensitive components. In printed circuit boards, concurrent vibrations result in solder interconnect damages. There is vertical displacement of the components under the vibration effect. Stress introduced on the interconnect materials, such as solder, substrate, or wires, has an adverse effect on the reliability of printed circuit boards.

Common damages induced by vibration include:

  1. Cracking of solder joints

  2. Twisting, bending, and breaking of component leads

  3. Connection damages 

  4. Screw loosening

The Need for Vibration Fatigue Analysis

In applications prone to mechanical loading, electronic systems are intended to function without getting affected by fatigue. Considering the time and money invested in electronic circuitry, most designs are equipped to handle dynamic environments. When encountering fatigue-related problems, especially temperature, shock, and vibration, an extensive amount of redesign might be needed.

Vibration failures in PCBs can be prevented by understanding the nature of vibration. Vibration fatigue analysis is a method used for understanding the impact of mechanical vibrations on PCBs. Through vibration fatigue analysis, it is possible to identify the modes of vibration. The specific patterns of vibration are called modes of vibration, and depending on the mode, the shape of the vibration also varies.

Vibration fatigue analysis can help the circuit designer find the characteristic frequency of oscillation and boundary conditions. The response of the PCB to random vibrations can be predetermined by performing vibration fatigue analysis. Dynamic displacements and stress can be evaluated with vibration fatigue analysis as well. Altogether, vibration fatigue analysis informs the designer about the dynamic characteristics of the PCB.

Advantages of Vibration Fatigue Analysis

The operating frequency of the PCB resonating with the frequency of oscillation can damage the PCB due to the large amplitudes of oscillations. It is necessary to eliminate the resonance conditions by either changing the natural frequency of oscillation or the external excitation frequency. As the external excitation frequency is not in the control of the designer, it is better to change the natural frequency – which depends on the mass and stiffness of the PCB.

With the help of vibration fatigue analysis, a designer can determine and change the natural frequency of oscillation by changing either mass or stiffness. The time to failure of the PCB can be obtained by conducting a vibration fatigue analysis, which will inform the designer about the vibration-withstanding capabilities of the PCB and the vibration peak threshold that can be overcome without damage.

Cadence’s suite of design and analysis tools can help you deliver the most reliable layouts for critical applications that can withstand vibrations and shocks. Cadence tools help to eliminate the need for costly vibration testing on hardware prototypes in mission-critical applications.

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