Structural Integrity
Copper transition geometry at the entry point of an interlayer interconnect determines the local distribution of thermal expansion forces. A microvia knee stress tensor defines the mathematical relationship between the vertical barrel strain and the horizontal pad deformation during cycling. This calculation identifies the specific vector forces that promote crack propagation at the transition region between the land and the plated copper.
Mechanical fatigue in high density interconnects originates where the wall thickness changes abruptly under thermal load.
Boundary Condition
Plated copper thickness at the corner determines the magnitude of the force applied to the resin interface. A microvia knee stress tensor relies on finite element analysis to map the plastic deformation limit of the conductive path. Designers utilize this measurement to verify that the electroplating process achieves sufficient ductility to withstand repeated thermal expansion cycles without structural failure.
Copper deposition consistency directly affects the uniformity of these internal loads during board operation.
Deformation Gradient
Thermal gradients across the multilayer stack induce differential expansion between the resin dielectric and the metallic interconnect. The microvia knee stress tensor computes the localized strain gradients occurring at the neck of the structure when temperatures shift between environmental extremes. Analysis of these vectors reveals that sharper transition geometries accelerate the onset of fatigue cracking compared to contoured plating profiles.
Proper application of these calculations prevents premature loss of electrical continuity in rigid-flex or high performance circuit applications.
