This article presents two case histories that shed light on the role of gold in lead-free solder joint failures and the damage mechanisms involved. One of the failures, a brittle fracture of the solder joint, is attributed to the synergistic effects of voids, intermetallic compounds, and CTE mismatch. The investigation of the other failure revealed evidence of tin-whisker formation. As the author explains, the growth of tin whiskers is due to compressive stress in the tin solder material caused by diffusion of end-cap metals (Ni and Cu) and the formation of Sn-Ni-Au intermetallics. In both cases, the failures can be prevented by limiting the thickness of gold on all components.

This article presents a method for determining the integrity of solder joints made from mixed and lead-free solders. It discusses the procedures involved in sample preparation and testing and explains how to interpret the results, particularly the effect intermetallic formation, cracking, and voiding.

Failures of interest in this article usually occur on single-sided, non-plated-through-hole circuit boards. Evidence of failure may be as subtle as crazing (a pattern of small surface cracks) of solder-joint surfaces or as catastrophic as burning of the circuit board. Over time, crazing coalesces into circumferential cracks in the solder joint, and these cracks deepen until catastrophic failure occurs.

A detailed analysis based on FIB etching and SEM image capture was conducted on a flip-chip solder joint deep inside a tablet PC. 3D views reconstructed from SEM images show what appears to be a copper pillar with a solder cap connected to a copper trace on the substrate. The investigators believe the joint was formed by thermal compression bonding with a preapplied underfill. The analysis also revealed the presence of voids and intermetallic compounds along with signs of filler entrapment.

In this case study, the author describes the investigation of a defective DC-DC converter retrieved from an aircraft following the report of abnormal system behavior. Electrical testing, local probing, X-ray imaging, and cross-sectional analysis led to the discovery of cracks on several pins and in some of the solder material. The cracks were caused by different rates of thermal expansion and were remedied with the help of thermomechanical analysis, EBSD imaging, and phase map comparisons for thick and thin solder joints.

IBM engineers recently conducted a study to better understand and control the reliability of copper pillar solder joints in 2.5-D packages. Here they describe their approach and the results they obtained. They explain how they created test samples to evaluate different solder compositions, pillar geometries, and thermal histories and assess their effect on microstructure, precipitate morphology, intermetallic layer thickness, and shear strength. They also present thermal cycling test results comparing the performance of silicon and glass interposers.

This article is the first in a two-part series analyzing solder connection failures between BGA packages and PCB assemblies. Part I examines failures attributed to oxygen intrusion during reflow, underetched solder resist, and solder paste printing problems. In the latter case, X-ray inspection revealed no abnormalities other than a variation in ball size. To get to the root cause, the corpus of the BGA was progressively ground away, leaving only the balls and an unobstructed view of the PCB surface. A description of the process, supported by detailed images, is included in the article. In Part II, scheduled for the May 2017 issue of EDFA, the author delves deeper into the analysis of voids and presents an alternate FA approach that involves grinding away much of the PCB.

This is the second article in a two-part series investigating solder connection failures associated with BGA packages. Part I, in the February 2017 issue of EDFA, examines various cases of open and short circuit failures, discusses the formation of voids, and explains how to reveal important clues by grinding away the BGA package. Part II continues the analysis of voids and focuses in on failures due to circuit board faults. In such cases, the board is ground away from the backside, stopping just short of the first inner copper layer. The alignment of the two uppermost copper layers, the integrity of microvias, and other potential problems are then examined using polarized light which readily passes through the remaining resin and fibers. As the examples in the article show, this approach can reveal a wide range of manufacturing defects in PCBs.

Plasma focused ion beam (PFIB) systems can generate ion beams with much higher current and are therefore able to remove larger volumes of material at much faster rates while still maintaining precise control of the beam and its milling action. This article explains how the improved performance of PFIB is leading to new applications in delayering, deprocessing, and site-specific failure analysis.

There is a little known failure mechanism that affects dc coils, particularly those used in low-side-switched circuits. This mechanism involves electrolytic transport of copper from the winding in conjunction with chemical corrosion. For this phenomenon to occur, several conditions must exist simultaneously. This article discusses the conditions under which such failures occur and explains how to minimize their effects if not prevent them.

This article provides a summary of the ISTFA 2013 Panel Discussion on failure analysis and reliability challenges in photovoltaic systems.

This article reviews the basic failure modes of surface-mount tantalum capacitors and the methods used to determine the cause. It discusses the factors that contribute to leakage, shorts, opens, and high series resistance, the characteristics of each failure mode, and the best approaches for failure analysis.

Four panel members participated in the ISTFA 2014 Panel Discussion on the importance of correctly determining the cause of failure in electronic devices and systems designated for use in space, downhole drilling, and other such applications. Reliability of these components is critical because they cannot be easily replaced and malfunctions can be catastrophic. The panelists presented several methods for analyzing failures in integrated electrical systems and identifying the root cause.

This article, the first of a two-part series, investigates the causes of failure in electromechanical relays. In Part I, the author examines contact-related failures due to the buildup of nonconductive particles and films and the effects of arcing and wear. Part II, scheduled for the May 2018 issue of EDFA , presents examples of failures caused by nitrous gases, phosphoric acid crystals, and wax. It also examines a case involving a sealed relay that popped open during operation.

Electronic components and assemblies are subjected to temperature variations at every stage of life, resulting in the buildup of internal stress. This article explains how such stress contributes to failures and introduces a measurement technique that allows users to visualize stress distributions and assess their effects on lifetime and reliability. Application examples illustrating the capabilities of the new topography and deformation measurement approach are also presented.

Although plastic-encapsulated packaging dominates most of the IC industry, deprocessing and reliability testing continue to be a problem, particularly in industries making the switch from hermetically sealed ceramic packages. This article discusses the challenges designers and failure analysts face in the military and aerospace electronics industry stemming from the use of plastic packages. It provides examples of the types of failures encountered and describes the procedures used to detect and identify them.

This article explains why it has become necessary for equipment builders to analyze passive component failures and how the findings should be reported to manufacturers. It describes the general approach and steps involved in analyzing passive component failures and the methods and equipment used. It also explains how an actual failure involving a microwave switch was resolved.

This article explains how the failure of a high-voltage capacitor led to the discovery of an unusual defect. Testing showed that the capacitor shorted due to silver migration, which investigators believe was facilitated by voids in the dielectric that had been present from the time of manufacture. Through some combination of time, electric potential, trapped humidity, and elevated operating temperature, plate material migrated into the voids, creating a short path that led to the failure. Using acoustic images as a guide, the failed capacitor was cross-sectioned, allowing investigators to examine the voids more closely and thereby confirm their theory.

Modified Talbot X-ray interferometry provides three contrast modes simultaneously: absorption, phase, and dark field/scattering. This article describes the powerful new imaging technique and shows how it is used to characterize various types of defects in advanced semiconductor packages.

Tin whiskers are single-crystal filaments that can grow from tin-plated copper or nickel components. This article discusses the effect of plating thickness, composition, and grain size on tin whisker formation and explains how to assess damage potential based on microanalysis, whisker length distribution models, and metal vapor arc risk factors. The authors also present and analyze several examples of failures caused by tin whisker formation in space systems.