Common electronic component failures in PCB

Common electronic component failures in PCB

Component failures happen due to mechanical, thermal, environmental, thermal, electrical, packaging, and aging factors. It is essential to know all the details about these causes.

1.Mechanical failure

Mechanical failure in a circuit board includes elastic and plastic deformation, fatigue fracture initiation and propagation, brittle fracture, warpage, and creep and creep fracture.

2.Elastic and plastic deformation

Deformation is simply the distortion that can change the shape and size of an object. It is of two types: elastic and plastic. Elastic deformation is temporary and goes away after the removal of external forces that cause stress and alteration. However, plastic deformation is permanent and retains the distortion even after removing external forces that generate stress. PCBs comprise copper foil, resin, glass cloth, and other materials having different chemical and physical characteristics. Pressing these board materials together sometimes results in deformation. Apart from this, mechanical cutting (V-scoring), wet chemical processes, and high temperature also induce deformation.

3.Brittle fracture

Brittle fracture is the type of failure that occurs suddenly with a rapid cracking of equipment under stress. In such situations, the material shows no sign of degradation or breakage. In circuit boards, this type of failure happens at the soldered joints. These fractures develop due to tensile stresses occurring in the components during assembly, testing, and transport. Additionally, these fractures exist because of exposure to shocks, vibrations, and thermal excursions.

Vibrations are adverse to populated boards, especially in class 3 products.

4.Warpage

Warpage is the twisting or bending of the device which deviates from the original shape because of heat and moisture. PCB warping changes the profile of the board during the reflow soldering cycle. The reasons for the warpage include unbalanced layers during board design, thermal expansion during the soldering (because of different material properties), and weight of components, heat sinks, or shields.

5.Creep

A creep is a time-dependent deformation resulting from an increase in temperature and constant pressure. The failure resulting from creep is known as creep fracture. Surface finishes generate creep corrosion. As per the RoHS directive, the electronics industry has to focus on lead-free surface finishes. One cost-effective option is immersion silver, but it is more likely to cause creep. ENIG (electroless nickel immersion gold) and OSP (organic solderability preservative) possess a low risk of creep. In a harsh atmosphere, creep failure is a growing hazard. Nowadays, researchers are investigating advanced lead-free finishes to mitigate this risk.

6.Fatigue

Fatigue is the initiation and development of cracks in a material as a result of cyclic loading. In populated boards, solder fatigue is a critical failure. Inconsistent CTE is the fundamental cause of solder fatigue. CTE determines the contraction and expansion of the material during temperature deviations. Soldering low-CTE components to low-CTE boards and high-CTE components to high-CTE boards is a good practice. If it is mismatching, solder fatigues eventually form because of thermal and diurnal effects.

7.Thermal failure

Thermal failure occurs when the component is heated above its critical temperatures, such as the glass transition temperature (Tg), melting point, or flashpoint. Tg is the temperature at which the base material changes from rigid to elastic state. Substrates decide the Tg value of the circuit board. If the operating temperature exceeds the Tg, it will result in thermal failure leading to component burning.

8.Environmental failure

Environmental failure results from the entry of foreign objects, moisture, dust, power surges, and exposure to heat.

9.Electrical stress failure

The causes of electrical stress failure include electrostatic discharge (ESD), surface breakdown, dielectric failure, overvoltage, and surface trapping.

10.ESD

Extreme electrical stress causes ESD that results in catastrophic failure, permanent parameter variation, and hidden damage. This might occur because of high current density, high electric field gradient, and localized heat formation. PCB assemblies are susceptible to ESD when they come in contact with any charge-carrying object. Depending on the electromotive force between the two and their distance from each other, ESD is most likely to occur when the two are in close proximity.

11.Dielectric failure

Dielectric failure describes an electric breakdown within a solid insulator placed between two conductors. It is often associated with the puncture or decomposition of the insulation material. Any material will fracture or puncture at some point when exposed to a high voltage gradient. Material (thickness and quality of sample) and environmental (temperature and humidity) factors influence this level.

12.Conductive anodic filaments

Boards may develop conductive anodic filaments (CAFs) along the fibers of the composite material. During the via plating, metal is injected into an exposed surface, where it migrates due to ions, moisture, and electrical potential. Poor glass-resin bonding and PCB drilling damage are the contributors to such failures. Due to thermal expansion differences of fibers and matrix, the bond weakens after soldering. Lead-free solders require a higher soldering temperature which increases the probability of CAFs.

13.Packaging failure

Packaging is often the cause of breakdowns in many electronic parts. It acts as a barrier between electronic components and environmental influences. Thermal expansion results in mechanical stresses that damage materials. Aggressive chemicals and humidity may cause corrosion. Excessive thermal stress can overstress wire bonds, causing the connections to loosen, chips to crack, or packaging to break. The effects of humidity and subsequent high-temperature heating may also cause cracks leading to mechanical damage. Bonding wires can be cut and shorted during encapsulation.

14.Aging failure

Each component has a limited operational life. If it operates beyond this point, the possibility of breakdown due to mechanical fatigue will increase. Through a component lifecycle, its availability advances along various stages. The cycle ends when the component’s production stops. As a result, parts sourced during this end-of-life (EOL) stage may be outdated and do not meet the latest performance specifications. Thus causing them to fail prematurely.

Know more:What is electronic component failure?