Accelerated Incoming Thermal Soak Verification Procedure for Sensor Lots
Accelerated incoming thermal soak verification exposes latent transducer parameter drift within 48 hours, enabling quantitative C=0 lot rejection before production integration.
Passivation Cracking
Formation Breach
Structural fractures in the protective thin film layer on the surface of a semiconductor. Passivation cracking often occurs due to the mismatch in thermal expansion between the dielectric film and the underlying metal or silicon. These cracks create a path for moisture and contaminants to reach the active circuitry.
Stress Source
Mechanical pressure from the molding compound or the wire bonding process can trigger the defect. Passivation cracking is more likely in large dies or in chips with complex topographies. During temperature cycling, the shifting layers exert force on the brittle passivation.
This can lead to electrical leakage or short circuits.
Reliability Impact
Open paths to the silicon surface allow ions to migrate and cause corrosion. Passivation cracking can lead to the gradual degradation of the transistor performance over time. This failure mode is often identified using scanning electron microscopy after the chip has been decapsulated.
Verification of the crack depth is essential for determining the risk to the device.
Design Rule
Engineers use rounded corners and stress relief structures to prevent the initiation of fractures. The thickness and material of the layer are optimized to balance protection against mechanical flexibility. Passivation cracking can be minimized by selecting molding compounds with lower shrinkage rates.
Proper design ensures the long term survival of the integrated circuit.