Device reliability testing

Figure 1. Bias pressure cooker-device reliability test, cresol-epoxy-novolac-based molding compounds.

Figure 4. Bias Pressure Cooker - Device Reliability Test LM324 Quad Op Amp, 121°C, 100% RH, and Bias...

An inherently safer control system design will, where possible, include options for on-line reliability tests and inspections. Within digital devices, this is done using watch-dog timers to assure the signals are processed. 

The selectivity inherent to TNT detection by amplified fluorescent polymers, as described in Section 4, helps to rriinirriize false-positives in land mine detection. These sensor devices respond only to nitroaromatics and similarly small, electron-deficient analytes, which are found typically only in or close to explosives and explosive devices. Field-tests to date have demonstrated that these devices are at least as reliable as trained dogs in detecting explosives that contain nitroaromatics. There is still uncertainty concerning what chemical that dogs actually detect when searching for explosives [17]. This... 

Mechanical Properties. Most of electronic IC devices are very fragile. They need strong mechanical protection from the encapsulant to retain their long-term reliability. Encapsulant must provide mechanical protection but still maintain good temperature-cycle and thermal-shock testing, which are part of the routine reliability testing of the embedding electronics. 

Rockstroh, J., Jann, O., Wilke, O. and Horn, W. (2005) Development of a reliable test method for laser printers, copiers and multifunctional devices in emission test chambers. Gefahrstoffe-Reinhaltung der Lufi, 65, 71-80. 

However, the European normalization committee is in the process of looking at the issue and is working on the EN-13648-1 Cryogenic vessels -Safety devices for protection against excessive pressure - Part 1 Safety valves for cryogenic service. The tendency is to go to a much more reliable test as described hereafter which will simulate the real process conditions to a greater degree. 

Figures 2 and 3 show that the DRAM chip perforMance has been iMproved even though the chip functionality has increased for the accelerated tests used by the seMiconductor industry. The 85 C/85X RH results are better because of a coMbination of iMproveMents in the chip design, the Manufacturing procedures and the epoxy encapsu-lent. The teMperature cycle test results, however, were priMarily improved by converting to a "low stress" epoxy encapsulant. The im-proveMent in the pressure cooker and the 125 C operating life (Figure 3) was also due to a coMbination of iMproveMents, including those in the epoxy encapsulant. These iMproveMents in device reliability are especially reMarkable when it is realized that the chip susceptibility to contaminants and stress has increased tremendously due to the 60-fold increase to functionality.

These molding compounds were also used to encapsulate electronic devices for reliability testing. In Figures 4, 5, and 6, stable bromine CEN outperformed "state-of-the-art" resins in the bias pressure cooker device test (BPC), high temperature storage device test (HTS), and the highly accelerated stress test (HAST). 

The electronics industry desires improved flame suppressant additives for microelectronic encapsulants due to bromine induced failure. Epoxy derivatives of novolacs containing meta-bromo phenol have exhibited exceptional hydrolytic and thermal stability in contrast to standard CEN resins with conventional TBBA epoxy resins. When formulated into a microelectronic encapsulant, this stable bromine epoxy novolac contributes to significant enhancements in device reliability over standard resins. The stable bromine CEN encapsulant took about 30% more time to reach 50% failure than the bias pressure cooker device test. In the high temperature storage device test, the stable bromine CEN encapsulant took about 400% more time to reach 50% failure than the standard compound. Finally, the replacement of the standard resins with stable bromine CEN does not adversely affect the desirable reactivity, mechanical, flame retardance or thermal properties of standard molding compounds. 

Mechanical shock is one of the automotive reliability tests that an accelerometer must survive. Often, these excursions are specified beyond the maximum g-range of the device. Mechanically, this shock magnitude creates the possibility of substantial proof mass movement. To maintain integrity of the mechanical structure in this environment, many accelerometers use another structural material layer to provide a stop to the proof mass that inhibits the movement. An example of an overtravel stop on a lateral accelerometer is shown in Fig. 7.1.12g. 

Acoustic waves are often used in microscopy techniques for failure analysis and reliability testing of modem devices. Although they have a quite large wavelength up to several centimeters, they can be well used for nanoscopic investigations by introduction of near-field conditions [1], e.g. with microprobes. These microprobes can be used either as an acoustic source [2,3] or as a detector [4,5] together with a comparably large acoustic transducer. 

If it can be demonstrated that an SIF device (e.g., a block valve) has dominant time-based failure mechanisms (i.e., they wear out), the random failure rate model can lead to erroneous conclusions and practices. For example, in calculating test intervals, a random model may lead to testing more frequently than actually required during the early life of the device and testing too infrequently during the later wear-out phase. Owners/operators should be aware that reliability models (e.g., Weibull) are available that divide failures into infant mortality, random, and wear-out modes. This guideline assumes failures are random. 

Bias is frequently added for testing of electronic devices, printed wiring boards, and assemblies of electronic equipment. The 85°C, 85 % RH, bias test has been the predominant one in electronics for many years [8], While it sometimes misses failure mechanisms that later occur in the field, it also finds many weak points in new products. It is especially useful for quality control of seasoned devices for which long-term reliability is known to be high if the product passes this test. There are many commercial suppliers of temperature/humidity/bias test chambers and software is widely available to automate the operation, data collection, and data interpretation. Attention to data management is mandatory when hundreds of devices are tested simultaneously. This is frequently required in electronics to obtain sufficient data to make statistically valid predictions of lifetime and failure rate under use conditions. 

C-14 Procedures for Testing of DOT Cylinder Pressure Relief Device Systems. Describes a new set of test procedures and apparatus for fire testing compressed gas cylinder safety (pressure) relief devices as required by DOT regulation, 49 CFR, Section 173.34(d). The procedures are applicable for cylinders which are less than 500 lbs. internal water volume and are designed to provide a means of testing to DOT requirements anywhere, with reliable test data and repeatable test results. Previous edition cited in 49 CFR (13 pages). 

JEDEC JESD 22-A113 Preconditioning Of Nonhermetic Surface Mount Devices Prior to Reliability Testing... 

---