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Electronic components have a wide range of failure modes. These can be classified in various ways, such as by time or cause. Failures can be caused by excess temperature, excess current or voltage, ionizing radiation, mechanical shock, stress or impact, and many other causes. In semiconductor devices, problems in the device package may cause failures due to contamination, mechanical stress of the device, or open or short circuits. Failures most commonly occur near the beginning and near the ending of the lifetime of the parts, resulting in the bathtub curve graph of failure rates. Burn-in procedures are used to detect early failures. In semiconductor devices, parasitic structures, irrelevant for normal operation, become important in the context of failures; they can be both a source and protection against failure. Applications such as aerospace systems, life support systems, telecommunications, railway signals, and computers use great numbers of individual electronic components. Analysis of the statistical properties of failures can give guidance in designs to establish a given level of reliability. For example, power-handling ability of a resistor may be greatly derated when applied in high-altitude aircraft to obtain adequate service life. A sudden fail-open fault can cause multiple secondary failures if it is fast and the circuit contains an inductance; this causes large voltage spikes, which may exceed 500 volts. A broken metallisation on a chip may thus cause secondary overvoltage damage.〔(STFA 2001: proceedings of the 27th International Symposium for Testing and Failure Analysis ): 11–15 November 2001, Santa Clara Convention Center, Santa Clara, California, p. 267 ISBN 0-87170-746-2〕 Thermal runaway can cause sudden failures including melting, fire or explosions. ==Packaging failures== The majority of electronic parts failures are packaging-related. Packaging, as the barrier between electronic parts and the environment, is very susceptible to environmental factors. Thermal expansion produces mechanical stresses that may cause material fatigue, especially when the thermal expansion coefficients of the materials are different. Humidity and aggressive chemicals can cause corrosion of the packaging materials and leads, potentially breaking them and damaging the inside parts, leading to electrical failure. Exceeding the allowed environmental temperature range can cause overstressing of wire bonds, thus tearing the connections loose, cracking the semiconductor dies, or causing packaging cracks. Humidity and subsequent high temperature heating may also cause cracking, as may mechanical damage or shock. During encapsulation, bonding wires can be severed, shorted, or touch the chip die, usually at the edge. Dies can crack due to mechanical overstress or thermal shock; defects introduced during processing, like scribing, can develop into fractures. Lead frames may contain excessive material or burrs, causing shorts. Ionic contaminants like alkali metals and halogens can migrate from the packaging materials to the semiconductor dies, causing corrosion or parameter deterioration. Glass-metal seals commonly fail by forming radial cracks that originate at the pin-glass interface and permeate outwards; other causes include a weak oxide layer on the interface and poor formation of a glass meniscus around the pin.〔 Various gases may be present in the package cavity, either as impurities trapped during manufacturing, outgassing of the materials used, or chemical reactions, as is when the packaging material gets overheated (the products are often ionic and facilitate corrosion with delayed failure). To detect this, helium is often in the inert atmosphere inside the packaging as a tracer gas to detect leaks during testing. Carbon dioxide and hydrogen may form from organic materials, moisture is outgassed by polymers and amine-cured epoxies outgas ammonia. Formation of cracks and intermetallic growth in die attachments may lead to formation of voids and delamination, impairing heat transfer from the chip die to the substrate and heatsink and causing a thermal failure. As some semiconductors like silicon and gallium arsenide are infrared-transparent, infrared microscopy can check the integrity of die bonding and under-die structures.〔 Red phosphorus, used as a charring-promoter flame retardant, facilitates silver migration when present in packaging. It is normally coated with aluminium hydroxide; if the coating is incomplete, the phosphorus particles oxidize to the highly hygroscopic phosphorus pentoxide, which reacts with moisture to phosphoric acid. This is a corrosive electrolyte that in the presence of electric fields facilitates dissolution and migration of silver, short-circuiting adjacent packaging pins, lead frame leads, tie bars, chip mount structures, and chip pads. The silver bridge may be interrupted by thermal expansion of the package; thus, disappearance of the shorting when the chip is heated and its reappearance after cooling is an indication of this problem.〔 Delamination and thermal expansion may move the chip die relative to the packaging, deforming and possibly shorting or cracking the bonding wires.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Failure of electronic components」の詳細全文を読む スポンサード リンク
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