Failure electronic devices

One of tlte principal applications of the normal distribution in reliability calculations and liazard and risk analysis is tlte distribution of lime to failure due to wearout. Suppose, for example, tliat a production lot of a certain electronic device is especially designed to withstand liigh temperatures and intense vibrations lias just come off the assembly line. A sample of 25 devices from tlie lot is tested under tlie specified heal and vibration conditions. Time to failure, in hours, is recorded for each of the 25 devices. Application of Eqs. (19.10.1) and... 

These examples indicate that it is necessary to keep the possible effect of point defects on bulk and mechanical properties in mind. Although less definitive than electronic and optical properties, they may make the difference in the success or failure of device operation. 

Leakage. By far the majority of implanted electronic devices fail due to mechanisms of the second type (i.e. leakage). In a poorly encapsulated implant, this failure mode can cause rapid deterioration in a matter of days, hours, or even minutes. As the size of the implant designs are reduced, the risk of this type of failure is greatly Increased because due to the small dimensions involved, the time for fluid entry into the package becomes very short. 

Figure 15.13 illustrates the hydrolytic stability of various polymeric materials, determined by a hardness measurement after exposure to high-RH aging. A period of 30 days in the 100°C, 95 percent RH test environment corresponds approximately to a period from 2 to 4 years in a hot, humid climate such as that of southeast Asia. The hydrolytic stability of urethane potting compounds was not believed to be a problem until it resulted in the failure of many potted electronic devices that were noticed first during the military action in Vietnam in the 1960s. 

The reliabilities of electronic devices are also degraded at high temperatures so that the failure of a part and thus the particular eqviipment becomes more frequent. The hydraulic materials or fluids generate pressures at elevated temperatures and may also cause a failvure of the equipment. 

Power-traosistors that are commonly used in electronic devices consume large amount of electric power. The failure rate of electronic components increases almost exponentially with operating temperature, As a rule of thumb, the failure rate-lof electronic components is halved for each 10°C reduction in the junction operating temperature. Therefore, the operating temperature of electronic components is kept below a safe level to minimize the risk of failure. 

Finned surfaces of various shapes, called heat sinks, are frequently used in the cooling of electronic devices. Energy dissipated by these devices is transferred to the heat sinks by conduction and from the heat sinks to tlie ambient air by natural or forced convection, depending on the power dissipation requirements. Natural convection is the preferred mode of heat tiansfer since it involves no moving parts, like the electronic components themselves. However, in (he natural convection mode, the components are more likely to run at a higher temperature and thus undennine reliability. A properly selected heat sink may considerably lower the operation temperature of the components and thus reduce the risk of failure. 

Mass spectrometry has become more useful In the support of electronic development and manufacturing processes. Fourier transform mass spectrometry, the latest advance in this analytical method, Is another step forward in versatility, sensitivity and reproducibility in analytical characterization, qualification and quantification of raw materials and contaminants as used in electronic devices. A review will be provided of basic instrument hardware and interfacing, significant operating parameters and limitations, and special inlet systems. Emphasis will be placed on material evaluation, process control and failure analysis. Data handling will be reviewed using appropriate examples encountered in material and failure analysis. 

U. Wagner, J. Franz, M. Schweiker, W. Bernhard, R. Muller-Fiedler, B. Michel, O. Paul, Mechanical reliability of MEMS structures under shock load, Proc. 11th European Symposium on Reliability of Electron Devices, Failure Physics and Analysis (2001) 657-662. 

In dry-heat sterilization, the parts are exposed for 2-3 hours at 165°C-170 °C. Dry-heat exposure is the least effective sterilization method and most likely to degrade materials and electronic devices. Although adhesives may have been cured at 165 °C prior to hermetic packaging, the additional temperature exposure within the sealed package can result in further outgassing of moisture and corrosive volatiles causing electrical failures. Outgassing is worse if the adhesive had been cured at a temperature below 165 °C. 

Pacemakers are among the most reliable electronic devices ever built device survival probabilities of 99.9% (excluding normal battery depletion) at 10 years are not unheard of. But despite intensive quality assurance efforts by manufacturers, the devices do remain subject to occasional failures the annual pacemaker replacement rate due to generator malfunction has been estimated at roughly one per 1000 devices implanted, a marked improvement in reliability since the early 1980s (Maisel et al. 2006 Maisel 2006). There have been multiple major advisories and recalls issued by the FDA regarding pacing leads, with more of these because of problems with the lead insulation than with the lead conductor. 

A failure rate is typically represented by the lower case Greek letter lambda (X). A failure rate has units of inverse time. In the design of electronic devices, it is a common practice to use units of "failures per billion (10 ) hours." This unit is known as FIT for Failure unlT. For example, a particular integrated circuit will experience seven failures per billion operating hours at twenty-five degrees C and, thus, has a faUure rate of seven FlTs. It is also common to use units of "faUuies per million hours" or "failures per year."... 

A FMEDA is a systematic detailed procedure that is an extension of the classic FMEA procedure developed and proven decades ago. The technique was first developed for electronic devices and recently extended to mechanical and electro-mechanical devices (Ref. 5). This analysis for hardware devices provides the required failure data needed for SIF verification. 

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