Dual Sourced Low Tier Commercial Sensor Supply Exposure
Dual-sourcing low-tier commercial sensors introduces baseline offset drift, thermal hysteresis, and ASIC filtering divergence that increase total landed product cost.
Bond-Wire Fatigue
Interconnect Degradation
Structural weakening of internal electrical connections occurs when repeated mechanical or thermal loading cycles exceed the elastic limit of the conductive material. This process, known as bond-wire fatigue, typically results in cracks forming at the heel of the wedge or ball bond. Microscopic fractures propagate through the gold or aluminum wire under the influence of vibration or temperature fluctuations.
The electrical resistance of the joint increases gradually until a total open circuit occurs.
Thermal Stress
Differences in the coefficient of thermal expansion between the silicon die and the ceramic or plastic package lead to recurring strain on the delicate wire loops. As the device powers up and down, bond-wire fatigue accelerates due to the expansion and contraction of these dissimilar materials. This cycle is particularly aggressive in automotive or industrial environments where rapid temperature swings are common.
Engineers mitigate this by optimizing the loop height and wire geometry.
Failure Mechanism
Metallurgical changes at the interface between the wire and the bond pad create localized brittleness. When bond-wire fatigue progresses, the crack growth follows the grain boundaries of the metal.
Fatigue Life
The number of cycles a connection survives depends on the amplitude of the applied stress and the ductility of the chosen wire alloy. Once bond-wire fatigue initiates, the remaining operational life of the sensor package drops rapidly. Qualification testing uses accelerated power cycling to estimate the reliability of the interconnects over a ten year service period.
Durable designs utilize heavier gauge wires or ribbon bonding to extend the duration of the assembly.