Advanced RF IC’s incorporate numerous components along with the CMOS circuitry. One component is a metal-insulator-metal (MIM) capacitor. Test capacitors have been stressed using accelerated voltage and temperature conditions to assess the long-term reliability. This paper describes a methodology for evaluating the MIM capacitors that have failed during reliability testing. IR microthermography was developed to detect leakage locations in areas that are not visible to optical inspection or standard emission microscopes. These areas were deprocessed to correlate the IR emission and physical defect locations. This information is utilized to understand the failures and improve the reliability.

We developed a system and a method to characterize the magnetic field induced by circuit board and electronic component, especially integrated inductor, with magnetic sensors. The different magnetic sensors are presented and several applications using this method are discussed. Particularly, in several semiconductor applications (e.g. Mobile phone), active dies are integrated with passive components. To minimize magnetic disturbance, arbitrary margin distances are used. We present a system to characterize precisely the magnetic emission to insure that the margin is sufficient and to reduce the size of the printed circuit board.

This paper discusses the issues of tin whisker growth on discrete electronic components. It presents both a critical analysis of existing published documents on tin whisker nucleation and growth and a summary of very recent experiments that provide further understanding of the potential means of whisker formation mitigation. Many of the proposed techniques for reducing the likelihood of whisker formation are inadequate, including control of the immediate underplating material, use of conformal coating, regulating the thickness of the tin coating, use of matte tin electroplating, and annealing or fusing of the tin layer. They likely reduce the incidence of nucleation or growth but do not provide guaranteed protection from lack of whisker formation. The first report of tin whiskers on electronic components dates back to 1946 [16]. Since that time whisker-related problems have been reported consistently. Today the concern is for the of increased number of whisker-related problems due to circuit geometry reductions, lower application voltages and the probability of more suppliers (rapidly) introducing pure tin plated alternatives to comply with pending Pb-free legislation.

A method to detect defects affecting laser diode radiation has been devised by imaging the induced luminescence resulting from a scanning electron beam. Electron Beam Induced Luminescence (EBIL) involves imaging the current from a sensor diode as the SEM electron beam scans across the laser diode surface. Defects preventing laser diode radiation will be shown as contrast variations in the EBIL image. This technique is similar to electron beam induced current (EBIC), reference 1, in which the electron beam provides the capability for measuring subsurface electrical and physical parameters that effect device electrical performance. However in the case of EBIL, laser diode radiation is utilized as the imaging parameter providing direct correlation between the semiconductor active layer and the resultant diode luminescence output. Alternative techniques such as Cathode Luminescence (CL), reference 2 and 5, in the scanning electron microscope (SEM) have been used for examination of semiconductor laser diodes for defects preventing radiation. However CL SEM analysis requires costly accessories, including at least an ellipsoidal mirror and a cooled photomultiplier tube sensitive to the particular laser diode output frequency. In addition the laser diode must be at the focal point of an ellipsoidal mirror, making CL SEM examination of a packaged laser diode difficult or impossible. This paper will describe the EBIL technique using several test diodes to demonstrate the ability of EBIL to image diode luminescence and defects affecting luminescent output. Deprocessing of the laser diode top electrode and EBIL operating parameters will be discussed.

High optical power is considered as the source of failures in passive optical elements. Optical connectors, in particular, have been studied because of the unavoidable exposure of their optical interfaces to environmental issues during insertion and extraction. Cleaning and insertion/extraction procedures are investigated. Evidence for burn-out, depending on the different procedures, calls for new suitable rules for handling during equipment operation and testing.

A manufacturer of computer based products in Brazil has experienced a sudden increase of failures in the LCDs (Liquid Crystal Displays) used in its products returned from field. The failures appear as dark columns. This paper describes the technique applied to find out the root cause of the failures. Conclusions pointed to a problem in the process for curing the adhesive conductive film (ACF), which provides connection of flip chip drivers to the LCD.

A failure analysis process flow development for a board mount plastic BGA multichip module is described. Both front and backside approaches are investigated. Following the probing (at both front and backside), front side chemical de-cap procedure is also developed to expose the components without disturbance. The development of this failure analysis process flow has successfully isolated defective IC dice, identified a die attach interface corrosion mechanism, and assembly related die top mechanical defects. This process can be adopted to failure analysis for other plastic BGA modules.

Among the methods for imaging failure analysis of Thin Film Transistor Liquid Crystal Display (TFT-LCD) Cell, the measurement of optical characteristics is extremely effective to identify the imaging failure type. We have evaluated time dependency of transmitted light intensity under holding condition at a single pixel level on a LCD Cell. This is defined as Optical Holding Rate (OHR). OHR characterizes the Voltage Holding Rate (VHR) of actual Cell. VHR is generally used for Liquid Crystal evaluation. This method enables us to identify which part of LCD Cell causes imaging failure, especially by measuring OHR as a function of various driving parameters. After classifying the imaging failure modes, we can investigate the failure mechanisms by structure or surface analysis. In conclusion, to measure OHR is effective to identify imaging failure type of LCD Cell.

A failure mode occasionally observed in multilayer ceramic capacitors (MLCC) is degradation of insulation resistance as the capacitor ages under temperature and electrical stress. The dielectric in MLCC can have a heterogeneous appearance when examined by optical microscope or SEM. This makes it difficult to identify features that could explain the root cause of failure or that could be used in devising inspection criteria for lot acceptance. Conventional cross sectioning in an epoxy mount leaves the sample unsuitable for examination in highvacuum equipment such as field emission scanning electron microscopy or Auger Electron Spectroscopy (AES) because epoxy outgasses and badly contaminates the high vacuum system. A novel twostep potting technique for sample preparation and inspection was developed to meet these challenges. This technique enabled us to perform electricallymonitored cross sectioning in combination with thermal inspection (infrared microscopy). Once a shorting site was identified, the sample was easily removed from the epoxy mount, allowing examination of the actual location of the short circuit in the field emission SEM (necessary to avoid sample charging). By precisely identifying the defect site, the chemistry of the defect could then be determined using electron spectroscopy and materials identification techniques [1,2,3].

In this paper, the investigation process for the failure cause of tantalum capacitors is presented. The capacitors failed during the temperature/humidity testing by reversed polarization. The failed capacitors had higher leakage current. The external visual and Xray examination didn’t show any anomalous phenomena. After cross sectioning and SEM examination, it was found that silver migration is the root cause for the failures.

Metallurgically bonded, glass-bodied DO-35 power rectifier diodes were electrically overstressed by applying forward and reverse current pulses. Forward current pulses varied from 0.1 to 3 ms with current amplitudes varying from 200 to 1000 A were applied to one group of diodes. Reverse bias current pulses in the microsecond range with amplitudes from 2 to 400 mA (above breakdown voltage) were applied to another group. A small-step cross sectioning in combination with electrical probing, light emission microscopy, liquid crystal technique, and chemical staining were used to reveal and compare damage in three groups of diodes: two overstressed groups and the third group which had failed during burn-in electrical testing. Failure mechanisms and peculiarities of damage created in these diodes and several case histories related to different types of diodes are discussed.

This paper describes a new method for the mapping of local temperatures in the active region of highpower III-V semiconductor transistors for microwave applications. The measurement technique involves scanning a focused laser beam at the surface of a chip inside its package, while the photoluminescence (PL) or the Raman spectra produced are recorded sequentially for each position of the laser beam. The local temperature is deduced either from the corresponding wavelength shift of the PL (which represents changes in the band-gap due to heating) or from Raman Stokes peak shift or from the Stokes to anti-Stokes intensity ratio (which correspond to changes in optical phonon frequencies and population respectively due to heating). Results are shown both for SiC-based field effect transistors and for bipolar type transistors (heterojunction bipolar transistors – HBTs – in the GaAs/Ga1-xInxP system). A spatial resolution of 1 µm and an accuracy in the temperature determination of ± 3 °C are demonstrated, especially for the HBTs. Finally, procedures are proposed to implement the information on local operating temperatures provided by this method into thermal resistance calculations.

We investigated the cause of the whisker/discoloration which were found in the transistor lead of stocks (package type TO-18, low power use). In process of the investigation, we estimate two corrosion models that the first model is the remnant of sulfuric acid in cracks of the nickel-phosphorus plating layer in the transistor lead, the second model is the out-gassing or the dissolved ions from the stock container and conductive mat. As the results of the investigation which includes analyses of the whisker/discoloration cross section made by FIB (Focused Ion Beam), a reproductive experiment and so on, the whisker/discoloration were the corrosion reacted between the solder (Pb-Sn) on the transistor lead and SO 4 2- ions of the stock container. We estimate that the new corrosion will not occur and grow in mounted devices because of rejecting the source of corrosion (stock containers). Further, in the worst case of the corrosion occurrence, protective coatings were applied to the mounted transistor lead, as the measure against falling away from the transistor lead.

Intermittent opens in hand-assembled electronic components have a number of expected causes. In this case the failure mechanism that was identified is of concern in certain industries, but is unexpected in the electronics business. Solder in solder pots and in flow solder systems is expected to become contaminated with the various metals and other materials that the solder contacts during use. In the analysis presented here, the solder was determined to be contaminated with mercury. This contaminated solder caused wires tinned in the solder to fracture due to liquid-metal embrittlement. Liquid-metal embrittlement (LME) is the reduction in metal ductility caused by contact with liquid metal.

This paper describes a new technique for measuring junction temperature with high accuracy in accelerated operational tests (junction temperature ≥200°C) based on the measurements of temperature dependence of gate-leakage current on a GaAs FET (gate-leakage method). The gate-leakage current on the GaAs FET is monitored in the accelerated operational tests. Then, junction temperature and thermal resistance are calculated from the temperature dependence of the gate-leakage current, especially from the temperature dependence in high temperature region. We have measured the junction temperature and the thermal resistance using this method in accelerated operational tests, and have confirmed that the junction temperature can be estimated within a range of ten degrees. The results by this method have been compared with data of simulation, and the validity has been confirmed.

Thermal properties are critical to the performance of micromachined silicon bolometers. In order to verify thermal models of the device, a means of measuring the local temperature distribution over the element is required, as it is heated by passing current through a thin film titanium meander. Because of the very low thermal mass of the membrane a non-contact method of temperature measurement is needed. Most conventional thermal imaging systems operate in the wavelength range 5-15 μm and offer poor spatial resolution but in this work an infrared microscope, operating at shorter wavelengths, was used. The microscope comprises an objective lens which focuses radiation onto a cooled (77K) cadmium mercury telluride focal plane array sensitive over the range 800 nm to 2500nm. For this application a bandpass filter centered at 2150 nm was used. Good agreement was obtained between finite element modeling of the temperature distribution, using ANSYS, and the measured data.

A specific problem in failure analysis of InGaAs/ AlGaAs laser diodes asked for a deprocessing tool able to selectively etch gold from a Ti/Pt/Au triple metal layer. Attempts made by the usual I2/KI etch confirmed the damage that it causes to the crystal stack, and non-uniform attack of gold. A new etch, indicated as Epta-Methyl-bis-diodine, has been successfully employed. Careful time control and detailed characterization of the complex metallization pattern of the devices allowed not only to properly expose the Pt layer, but also to preserve the overall electrical connection, thus maintaining the capability of both measuring the electrical characteristics at low current injection and collecting the EBIC signal from the etched device.

Cracks and other defects in ceramic materials can be difficult or impossible to examine and photograph due to the extreme lack of contrast. A method for inspecting translucent ceramics using scattered light, also known as vicinal illumination, will be described. This method has been known in the ceramics industry for quite some time, but is not well known in the testing and failure analysis community. Electronics applications include substrates, packages, multilayer capacitors, and thin film resistors. Ceramic materials are used in electronic applications as microcircuit packages and substrates which carry signals and power between microcircuits. Fine cracks in ceramic materials can result in mechanical failures, electrical failures, and loss of hermeticity. Often, fine cracks are difficult or impossible to detect using standard nondestructive inspection techniques such as visual inspection, ultrasonic inspection, or vapor crack detection. Dye penetrant inspection is usually effective, but contaminates the part, which is unacceptable for space flight hardware. One effective nondestructive inspection method of detecting cracks involves examining the way in which light scatters through the ceramic material when viewed with a standard bright field reflected light microscope. This method, termed vicinal illumination, has been used for detecting cracks during failure analyses of several part types, and screening of space flight hardware. The technique has proven effective on several different types of ceramic materials as well. A related method for use with dark field equipment has also been used to successfully locate otherwise invisible cracks.

The FM08 style fuse is specified to interrupt an overcurrent of up to 300 A in a bus of up to 125 VDC, but this applies only when its barrel is filled with air. When placed into a space-grade vacuum, the FM08 style fuse exhausts its air within a year. Then, the probability of an enduring arc is high for all ratings when the bus is above 75 VDC, and the overcurrent is large. The arc endures until something else interrupts the current. The fuse can violently eject metal vapor or other material during the sustained arcing. The evacuated FM08 does not develop a sustained arc when interrupted in a bus of 38 VDC or less, at least when there is little inductance in the circuit. This is consistent with its successful use in many spacecraft having buses in the range 24 to 36 volts.

Failure and degradation mechanisms of plastic packaged LEDs that have been subjected to high levels of moisture, current bias, and elevated temperature conditions have been investigated and analyzed. The investigation included electrical characterization and a variety of failure analysis techniques including photoluminescence (PL), electroluminescence (EL), cathodoluminescence (CL), and environmental scanning electron microscopy (ESEM). Our results highlight the usefulness of simple screening techniques to monitor the quality of newly manufactured LED packages. Our results also indicate that for AlGaAs structures, degradation of the light output and electrical performance involves a complex interaction between temperature, relative humidity at the LED surface and voltage bias.