November_EDFA_Digital

ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 20 NO. 4 22 Failure signature/ malfunction Cracks in ceramic capacitors (cercaps) and filters, all kinds of electronics Stitchbond cracks, all kinds of electronics, also in car keys ESD impacts with EOS failure signature, often in engine control electronics

Table 1 Summary of important early life failures in automotive electronics

Root causes

Why no t=0 failure?

Remarks

PCB assembly/support/layout, PCB punching and/or pressing, mechanical bending or torsion stress, vibration, mechanical shock PCB layout, small overlap pin/mold compound, bending stress, also due to neighboring push button switches, vibration, out-of-spec soldering, dirt at bonding capillary, heel cracks, mold pressing, curing, non-application- suitable package types Charge generation within isolated mounted sensors joined into rubber pipes with strongly whirled air or liquid streaming. Discharge via cable into electronic systems Voltage spikes from E-motors with commutators with non-capacitor- suppressed carbon contacts; new servo motors show fat or profiled carbon contacts, still not unground to the commutator shape, thus creating high interference pulses Insufficient sealing against humidity ingress and condensation water, lifetime reduction by intrinsic pre-damage, dendrite formation, electrolytic corrosion by residue voltage in off-mode Non-suppressed commutators, shorts by relieved metal punching burrs, electrostatic charging of plastic bearings Corrosive gases within the tire, enclosed humidity/water in the tire, outgassing of battery cells, RF transmission disturbed or damaged (in sensor receiver) by car radiotelephone without radio interfe- rence suppression (latent) ESD by mounting, dry front shield cleaning, attaching or removing of vignettes

Post cracking; time-delayed protrusion of metal, needs up to months to complete short Only when sub-µ-movement of pin starts, intermittent contact or open follows later

See also tutorial/paper Gert Vogel, ESREF 2015

Frequently also intermittent, temperature, or pressure-dependent contact behavior

Charging generation suddenly and thresholdwise, not linear, in priority at high rpm.

No further failures after repair, due to dust/dirt at the rubber pipes, making them electrical dissipative; Hall sensors in motors/ gears often affected Voltage pulses become smaller when the carbon contacts are ground to the collector shape Intrinsic pre-damages are frequently not considered in binning (reverse bias leakage) very tolerant RBL-specifications

ESD-like defects with EOS failure signature in electronics, controlling servo motors (e.g., seat adjustment, window lifter)

Not every pulse destroys electronics immediately, but a continuous shower of pulses is capable of it

LED failures

Humidity ingress through plastic needs some time before root cause mechanisms start

E-motors with integrated electronics

Failure mechanism appearance by change

Tire pressure sensor failure

Long-term chemical reactions, formation of microclimates, time delay by potting, radiotelephone not continuously used and at variable ERP

Additional acceleration of failure evidence by thermal and mechani- cal add-on stressors

Rain sensors

Both t=0 and delayed failures possible (latent EDS)

Malfunction is frequent- ly not realized imme- diately by the user

ABOUT THE AUTHOR

After studying technical physics in Munich, Peter Jacob began his professional work in 1981 as a failure analysis expert at the IBM semiconductor plant in Böblingen, until 1992. After a short period at Hitachi Scientific Instruments, where he was responsible for electron microscopy configura- tions and customer training, he joined ETH Zurich/EMPA as a senior expert for failure analysis on micro- and power-electronics, from device to system level. Parallel to this work, he joined Swatch Group‒EM Microelectronic Marin as a principal FA engineer in 1995. Jacob has authored more than 60 contributed and invited papers, including two ESREF Best Papers and an ISTFA outstanding poster award. He volunteers in the German ESD Forum, EDFAS, and Eufanet. In 2007, he was appointed as

an Honorary Professor of the Technical University in Munich and in 2010 he received the International Barkhausen Award from the Technical University of Dresden. In 2016, he was appointed to head the Swiss Electronics & Reliability Center at EMPA Dübendorf.

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