Meaning
Threshold value of the product of current density and conductor length below which electromigration-induced damage does not occur in a metallic interconnect. Designers use the blech critical product to create short interconnects that are theoretically immune to failure from atomic migration. Material values are a property of the metal and the surrounding dielectric encapsulation.
Mechanical Equilibrium
Pressure gradients build up within the metal when atoms accumulate at the anode and leave the cathode. This internal stress creates a force that pushes atoms in the opposite direction of the electron flow. If the conductor length is below the calculated limit, the two forces reach a steady state.
Design Specification
Engineering teams in the Chinese integrated circuit sector apply this principle to reduce the size of redundant wiring. Optimization of the metal layout allows for higher current densities without compromising the twenty year service life mandated for industrial controllers. Documentation for the Ministry of Science and Technology often highlights the use of these limits to justify the density of a new chip architecture.
Physical Limit
Effectiveness of the immunity vanishes if the dielectric shell around the metal trace cracks or yields under pressure. Damage to the surrounding structure removes the containing force.
