Reliability evaluation of plastic encapsulated parts

This work compares the failure rates of several families of plastic encapsulated microcircuits (PEMs) using both field and test data (test data are converted to device failure rates for field conditions using common acceleration equations) and Mil-Hdbk-217 calculations. Calculated failure rates are obtained from the Mil-Hdbk-217F for both plastic encapsulated and ceramic hermetic class-B microcircuits. Comparisons show that the results from Mil-Hdbk-217 are misleading and that the US military and Government part-selection methods should not be burdened by this -217 methodology     

Plastic encapsulated microcircuit reliability predicition: why?

Reliability prediction models for microcircuits have been a function of steady-state temperature. Failure rates generated from accelerated temperature tests were extrapolated to predict system reliability at system use temperatures. This is now known to be completely inaccurate. Attempts are now being made to predict the reliability of plastic encapsulated microcircuits (PEMs) based on accelerated temperature/humidity testing. Failure rates generated due to corrosion failure mechanisms at these high stress levels are then extrapolated and used to predict system reliability at used temperature/humidity conditions.This paper discusses the fallacy of this approach. A new concept for the assurance of PEM corrosion resistance is proposed. It will be shown that today's best commercial practice suppliers have already addressed the design, materials, and processing issues of molded packaged microcircuits, and corrosion is no longer a mechanism of concern to the user.     

Why use PEMs in military equipment: users'' response

Since the early 1980s, with significant improvement in plastic packaging of microcircuits, accelerated environmental testing has indicated continuous reliability improvements. These data have been generated by independent researchers, Universities, users and suppliers. The question which still remains concerns their use in high reliability applications for extended periods in harsh environments. Such applications would be in the military, automotive, and commercial airline markets. This report is the result of responses to a survey directed at military equipment developers. Its goal was to determine advantages and disadvantages in the use of commercial plastic encapsulated microcircuits (PEMs) versus the use of MIL approved microcircuits as received by the equipment manufacturer. Responses, however, impacted all three markets, not only military.     

Plastic-encapsulated microcircuit reliability andcost-effectiveness study

This study evaluates the reliability and cost-effectiveness of using commercial plastic-encapsulated microcircuits (PEM) in a typical military system, with a view to increasing their acceptability in military applications. The cost comparison indicates an average 6-fold decrease in cost when commercial devices are used. Assurance testing did not reveal any special problems with commercial parts. Thus, if commercial PEM were proven to be sufficiently reliable for an intended military application, large cost savings would be gained by using them instead of hermetic packages. The 4.5 sigma enhanced inspection program and the process-control methods suggested here would enhance the manufacturing yield of the PLGR (precision lightweight global positioning system receiver) by encouraging improvements in the manufacturing process while simultaneously cutting the cost of a 100% rescreen to qualify the final product. Neither the requirements assurance tests (including the step-stress test-analyze-and-fix test), nor the reliability demonstration test, nor the operational test, showed more failures than are typical for any new development, and no problems unique to PEM were observed. Thus, the use of PEM did not lead to any special problems that caused PLGR-use specifications to be violated. Complete failure analysis of the isolated parts is in progress, and the results will help to understand the specific reliability issues involved with the use of PEM in military systems. These issues can then be addressed to improve the acceptability of such devices in future military applications     

Qualification of plastic encapsulated microcircuits (PEM) for avionicsBased on ``Plastic Encapsulated Microcircuits (PEM) Qualification Testing'''', by J. A. Scalise, which appeared in the Proceedings of the 46th Electronic Components and Technology Conference, Orlando, FL, U.S.A., 28–31 May 1996, pp. 392–397. © 1996 IEEE.

Microcircuit package qualification testing is used to establish the reliability of integrated circuit processes and devices as they relate to part packaging. This paper presents the results of package qualification tests conducted on plastic encapsulated microcircuits (PEMs) and plastic discrete devices (diodes, transistors) used in avionics applications. Highly accelerated stress test (HAST) and temperature cycle (TC) test results, including part failure mechanisms and associated failure rates, are provided. A variety of plastic package styles and integrated circuit functions have been tested. Examples of package styles tested include small outline (SO), plastic leaded chip carrier (PLCC), thin small outline package (TSOP), plastic quad flat package (PQFP) and plastic dual-in-line (PDIP).Manufacturers' devices have been evaluated and various plastic compounds have been compared to determine which provide optimum reliability. The testing showed that package qualification performance of PEMs is affected by type of compound, passivation (including die coat) and die size. HAST failures are caused by moisture penetration of the package while temperature cycle failures result from coefficient of thermal expansion (CTE) mismatch effects.     

Radiation testing of semiconductor devices for space electronics

Radiation effects testing, part selection, and hardness assurance for application to electronic components in the natural space environment are discussed. The emphasis is on semiconductor devices, primarily silicon microcircuits, which are used in the greatest quantity and which, in most cases, are the most sensitive. After a summary of the natural space radiation environment and the effects of radiation on semiconductor devices, laboratory simulation of space radiation and extrapolation to space are covered. Radiation testing is performed to understand failure mechanisms, to characterize the radiation response of specific devices, and to provide data for lot acceptance. Part selection and hardness assurance are discussed by contrasting the traditional approach with the unique aspects of space systems. Some recommendations are made for treating the more complex aspects of space system microcircuit hardness assurance     

An infrared scanning technique for the determination of temperature profiles in microcircuits

Circuit reliability and performance, particularly in high-density microcircuits, are affected by temperature. Therefore, a knowledge of the heat transfer paths and temperature distribution are of prime importance in topological design for efficient circuit performance. The method of thermal profiling described uses infrared scanning. The method is direct, rapid, and nondestructive, and the temperature profile is unaffected by the measurement. The effects of heat sinks, heat sources, and unusual geometrical patterns are automatically taken into account. The "heart" of the infrared scanning system is a photosensitive element of single-crystal indium antimonide with a long wave cutoff near 6 microns. The system has successfully determined isothermal patterns from 55°C to >250°C in thin-film tantalum microcircuits having linewidth patterns as small as 2 mils. Isothermal patterns of various geometries are shown to illustrate how the area and shape of resistors affect the thermal pattern and the temperature of the hottest part. Life data correlating the temperatures at the hottest parts with operating stability of thin-film resistive networks is presented. Through the correlation of temperature profiles with storage life tests, the potential exists for greatly reducing the amount of costly life testing of microcircuits for every new bias condition and circuit. Although emphasis is placed on thin-film microcircuits, a thermal profile of a solid silicon microcircuit is presented to indicate usefulness of the infrared scanning technique for temperature profiling of other types of microsystems.     

Microprocessor and LSI Microcircuit Reliability-Prediction Model

This paper discusses the development of an improved failure-rate prediction method which can be used to assess the reliability of complex and new-technology microcircuits, especially memories, microprocessors, and their support devices. The prediction models are similar to those presented in MIL-HDBK-217C with several modifications to reflect the variation of reliability sensitive parameters and to discriminate against the device design and usage attributes which contribute to known failure mechanisms. A comparison of the failure rate predictions calculated using MIL-HDBK-217C and the actual failure rates for LSI random logic and memory devices did not indicate a reasonable correlation. An analysis of the 217C models revealed that the lack of correlation was attributable to the generic consolidation of model parameters, which ultimately reduced model sensitivity to several critical reliability factors. The model accuracy was greatly improved, without substantially increasing model complexity, by separating some generic parameters into sets of more detailed parameters. The major model revisions included: ? Complexity factors oriented toward major device function and technology categories ? Development of temperature factors for each device technology, in both hermetic and nonhermetic packages ? Introduction of an additive package failure-rate factor based upon package type and number of functional pins ? Introduction of a voltage derating stress factor for CMOS devices with maximum recommended operating supply voltage greater than 12 volts ? Introduction of a ROM and PROM programming technique factor to reflect the influence of the programming mechanism used in these devices.     

MOEMS chip-level optical fiber interconnect

A package design, fabrication process, and assembly process to hermetically seal the microstructure area of a microoptoelectromechanical system (MOEMS) at the chip level is presented and evaluated. The packaged chip is fabricated using the Bosch deep reactive ion etching (DRIE) process on silicon on insulator (SOI) substrates. The packaging structures are formed during the batch fabrication of the MOEMS device. A hermetic seal is formed via an indium solder ring around the perimeter of the MOEMS chip that span channels etched in the silicon for optical fibers. The seal is made between the device chip, metallized optical fibers, and a cap chip with a fluxless soldering process. The integrity of the package is evaluated through die shear, fiber pull, and highly accelerated life testing (HALT).     

Accelerated temperature testing of transistors does not cause excess flicker noise

Electrical noise measurement analysis has been applied in reliability screening of semiconductor devices. Normally it is expected that during accelerated testing reactions increase in composition of device materials causes early failures through the process of defect production. An increase in defects is further expected to result in an increase in the noise of semiconductor devices. Accelerated temperature testing of sample of indegenous NPN transistors was done and noise was measured after certain durations of test time. No appreciable change was observed in the noise level (mainly flicker or 1/noise) even though the devices reached the stage of complete failure. This indicates that defects produced by accelerated temperature testing are not noise generators. X-ray radiography and SEM analysis study has been done for completely failed devices.     

基于加速性能退化试验的板级可靠性评估

传统的可靠性评估方法一般基于失效寿命数据,而目前对于高可靠长寿命的电子产品,很难通过加速试验获得其失效寿命时间。为解决这一矛盾,将性能退化理论引入到传统可靠性评估中,提出了基于失效数据及加速性能退化的可靠性评估的新方法。应用某型雷达24V/2A稳压电源板加速性能退化试验进行验证,结果表明该方法用于高可靠长寿命电子装备的可靠性评估是正确有效的。     

Applications of fracture mechanics to quantitative accelerated life testing of plastic encapsulated microelectronics

Accelerated testing must address the failure mechanisms active within the devices undergoing tests in order to assess lifetimes in a meaningful way. The assumption of constant temperature, thermally activated lifetime, based upon the Arrhenius assumptions, does not always provide the necessary understanding to interpret accelerated tests in microelectronics. Plastic encapsulants, dielectric polymers, and underfill materials are subject to delamination and cracking with thermal cycling. Crack propagation during use environment exposure, drives the potential for failure of microelectronic devices and is therefore a necessary focal point in qualification and life testing. This paper reviews the available research in the application of fracture mechanics to this class of problems in microelectronics including relevant test data. In addition, useful acceleration factor models are derived for polymer crack propagation based on principles of linear elastic fracture mechanics. Further, a simple approach to estimating the minimum temperature cycling ranges, necessary to propagate a crack, is also presented. Finally, a methodology of applying acceleration factors to develop testing plans is shown, with an example in spaceflight for a cubesat in low Earth orbit. Overall, this is a paper that shows a useful and appropriate process for creating physics of failure based life testing for delamination and cracking failures in microelectronic polymers in a temperature cycling environment.     

Conformal Hermetic Sealing of Wireless Microelectronic Implantable Chiplets by Multilayered Atomic Layer Deposition (ALD)

A hermetic sealing method of sub‐millimeter‐sized microelectronic chiplets for wireless body implants is presented by ultrathin and electromagnetically transparent atomic layer deposition (ALD) coatings. Fully 3D conformal encapsulation of wirelessly powered microdevices is demonstrated both with and without opening windows for electrophysiological measurements. The chiplets embedding custom application‐specific integrated circuits (ASICs) with radio frequency (RF) transmitters are encapsulated by a stack of alternating layers of hafnium oxide and silicon dioxide to maximize impermeability of water and ionic penetration while minimizing the volume of the packaging material. The hermeticity of the devices is characterized through accelerated aging tests in saline at T = 87 °C, while continued functionality is monitored via evaluation of backscattered RF signals (near 1 GHz) to ascertain possible degradation and electronic failure. Earliest failures of wirelessly functional devices occur after more than 180 d of immersion at 87 °C. Wireless devices having opening windows through the ALD envelope show no signs of degradation for >100 d. This implies an equivalent lifetime >10 years at T = 37 °C. This approach is readily scalable to high throughput batch processing of hundreds of microchiplets, offering a methodology for hermetic packaging of microscale biomedical chronic implants.     

A Reliability Evaluation of Plastic Packaged Semiconductor Components

Qualification testing programs have been developed for assessing the reliability of commercial grade discrete semiconductors for use in office business machines. These programs include accelerated stresses of high temperature storage (HTS) and high temperature reverse bias (HTRB) for 1000 hours, and a sequence test of thermal cycle and thermal shock followed by storage at 85°C and 85% RH (85/85) for 1000 hours. Both hermetic and plastic encapsulated parts have been tested more than 15 million part hours. HTRB and 85/85 are about twice as effective as HTS in identifying potentially unreliable parts. Plastic packaged semiconductors are inherently capable of withstanding 85/85 for 1000 hours without parameter degradation. The value of qualification testing against the 85/85 environment is demonstrated by the observed correlation of machine failure rates in the field with the relative humidity in the use environment. The observed failure rate of plastic parts is not more than 3.2 times that of hermetic parts. Plastic parts are capable of reliable operation, but the marked differences in reliability between different vendors and between different part types from the same vendor require increased process and materials control in order to achieve the potential of which plastic parts are capable.     

Reliability assessment of a MEMS microphone under mixed flowing gas environment and shock impact loading

In this work the reliability of a Micro-Electro-Mechanical Systems (MEMS) microphone is studied through two accelerated life tests, mixed flowing gas (MFG) testing and shock impact testing. The objective is to identify the associated failure mechanisms and improve the reliability of MEMS devices. Failure analyses are carried out by using various tools, such as optical microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS). Finite element analysis is also conducted to study the complex contact behaviors among the MEMS elements during shock impact testing. The predicted failure sites are in agreement with the experimental findings.     

气密性平行缝焊技术与工艺

气密性封焊的产品因其杰出的可靠性被广泛应用于军事应用。与储能焊、激光焊相比,平行缝焊具有可靠性高、密封性能优越、运行成本低及生产率高等特点,是微电子器件最常用的气密性封装方法之一。主要阐述了气密性平行缝焊技术与工艺,并对焊接工艺参数进行了详细分析,同时给出了气密性检测要求及针对性措施。     

The P-channel refractory metal self-registered MOSFET

In this paper p-channel self-registered Mo gate MOSFET fabrication techniques are described and tested. Excellent p-channel devices resulted. Device characteristics including junction characteristics, threshold, stability, effective channel mobilities, and Si-SiO2interface studies are examined and compared with theoretical predictions. Simple processing steps yielded FETs whose threshold is predictably controlled by the intrinsic properties of Mo and the Si-SiO2system. Effective mobility theory matches the data at low fields, but at high fields theory predicts values that are too low. Similarly constructed integrated circuits are T²L compatible with excellent threshold reproducibility and exhibit stability during accelerated temperature-bias life testing.     

Design and development of high-frequency thermoacoustic engines for thermal management in microelectronics

Thermoacoustic heat engines provide a practical solution to the problem of heat management in microcircuits where they can be used to pump heat or produce spot cooling of specific circuit elements. There are basically two types of thermoacoustic engines, a prime mover where heat is converted to acoustic energy, and a heat pump or cooler where sound can pump heat up a temperature gradient. Such devices are relatively simple, they can be efficient, and they are readily adaptable to microcircuit interfacing. Since this type of engines is usually operated in a resonant mode, the operating frequency determines its size. The devices presented here are pumped at frequencies ranging from 4 to 24 kHz. They have been developed for interfacing with microcircuits as heat pumps or spot coolers. Results of their performance are presented and suggestions for further improvements are discussed.     

Accelerated lifetime test of RF-MEMS switches under ESD stress

This paper presents the results of a study on issues of reliability and accelerated life testing for radio frequency micro-electromechanical system (RF-MEMS) capacitive devices. A human-body-model electrostatic discharge tester has been used to induce charging by operating at stress levels much higher than would be expected in normal use. Temperature ranges from 300 K to 330 K allows the understanding of physical mechanisms that may be responsible for the device’s reliability.