Structural Failure
A mechanical separation within a multilayer ceramic capacitor occurs when tensile stresses exceed the fracture toughness of the ceramic dielectric. An mlcc ceramic flex crack represents one of the most common causes of electrical failure in surface-mount assemblies, typically occurring as a diagonal fracture from the terminal margin to the board interface. This defect often remains undetected during initial electrical testing, only to cause a short circuit after the assembly is deployed.
The brittle nature of barium titanate makes these components highly sensitive to board bending.
Stress Origin
During board separation, manual depaneling, or fixture clamping, the circuit board bends and transfers tensile strain to the solder joint and the ceramic body. This localized force initiates an mlcc ceramic flex crack at the termination boundary where the stress is most concentrated. Boards with thicker copper planes or more rigid stiffeners can exacerbate this strain by concentrating the bending forces around the capacitor terminals.
Design guidelines usually dictate the orientation of capacitors parallel to the bending axis to minimize these forces.
Mitigation Strategy
Using flexible termination materials helps absorb the mechanical energy that would otherwise damage the dielectric. An mlcc ceramic flex crack can be prevented by employing soft-termination capacitors, which utilize a conductive polymer layer in the termination band. This layer deforms under strain, protecting the ceramic core from cracking.
