This presentation covers the challenges associated with IC package inspection and shows how two nondestructive techniques, scanning acoustic microscopy and X-ray imaging, are being used to locate and identify a wide range of defects, particularly those in 3D packages and multilayer boards. It reviews the basic principles of scanning acoustic microscopy (SAM), X-ray imaging, and 3D X-ray tomography and the factors that affect image resolution and depth. It demonstrates the current capabilities of each method along with different approaches for improving resolution, contrast, and measurement time.

While 2.5D and 3D solutions continue to drive advancements in the electronics packaging industry, challenges persist with their reliability and qualification. In this paper, we introduce a new technique that may prove valuable for nondestructive, in-situ measurements of package and die warpage. This system allows for the powerful visualization tools of Computed Tomography to be applied to samples at elevated and cryogenic temperatures over a broad temperature range (+125C to -257C).

This paper describes a project to develop and deploy a systematic screening methodology involving computed tomography (CT) to inspect a set of electromagnetic interference (EMI) filter components for a spacecraft application. The goal was to deploy the nondestructive CT test to replace the destructive test method typically deployed for such components. The paper describes the development of test criteria, fixturing, inspection process, and data analysis, including quantitative image analysis of voids and cracks. The initial results indicated that the parts would not pass the requirements established in the test design. A waiver was written to the project clarifying that if the parts were to be used in the assembly, they should be considered as simple conductors with EMI filtering capability viewed as an added benefit rather than a guaranteed design requirement.

Reverse engineering (RE) is the only foolproof method of establishing trust and assurance in hardware. This is especially important in today's climate, where new threats are arising daily. A Printed Circuit Board (PCB) serves at the heart of virtually all electronic systems and, for that reason, a precious target amongst attackers. Therefore, it is increasingly necessary to validate and verify these hardware boards both accurately and efficiently. When discussing PCBs, the current state-of-the-art is non-destructive RE through X-ray Computed Tomography (CT); however, it remains a predominantly manual process. Our work in this paper aims at paving the way for future developments in the automation of PCB RE by presenting automatic detection of vias, a key component to every PCB design. We provide a via detection framework that utilizes the Hough circle transform for the initial detection, and is followed by an iterative false removal process developed specifically for detecting vias. We discuss the challenges of detecting vias, our proposed solution, and lastly, evaluate our methodology not only from an accuracy perspective but the insights gained through iteratively removing false-positive circles as well. We also compare our proposed methodology to an off-the-shelf implementation with minimal adjustments of Mask R-CNN; a fast object detection algorithm that, although is not optimized for our application, is a reasonable deep learning model to measure our work against. The Mask R-CNN we utilize is a network pretrained on MS COCO followed by fine tuning/training on prepared PCB via images. Finally, we evaluate our results on two datasets, one PCB designed in house and another commercial PCB, and achieve peak results of 0.886, 0.936, 0.973, for intersection over union (IoU), Dice Coefficient, and Structural Similarity Index. These results vastly outperform our tuned implementation of Mask R-CNN.

Modern 2D and 3D X-ray technologies are among the most useful non-destructive testing methods that enable the inspection of an object's internal features without cutting or disassembling the sample. This paper discusses the basic operating principle, advantages, and disadvantages of 2D and 3D X-ray based approaches for testing and failure analysis and describes how these different methods have practical application for failure analysis and dimensional metrology. The techniques discussed are radiography, classical laminography, computed tomography, and computed laminography.

Characterization of Computed Tomography X-Ray ionizing dose will be presented along with a methodology to protect space bound flight hardware from exceeding total ionizing dose (TID) budget prior to mission completion.

In this work, we introduce the use of the x-ray image as the unique fingerprint for an electronic component or printed circuit board assembly (PCBA). Unique features of the x-ray image include solder voids, cracks, part alignment, die attach porosity and voiding, die placement and alignment, and wire bonding diagram. These are just a few of the many features in the x-ray image that can be used in tandem to create a unique fingerprint for a single component or an entire PCBA. This technique can also be expanded to mechanical objects by utilizing other idiosyncratic features of the part - such as voids and porosity - to generate the x-ray image fingerprint.

In this article, we demonstrate using lock-in thermography (LIT) to perform fault isolation of leakage on a board-mounted device with rough, heterogeneous epoxy encapsulation. It is interesting to observe LIT spot shifting either on the failing unit’s reference pin or the failed pin using a different lock-in frequency. The protection diode of the reference pin is triggered by LIT and the electrical behavior should not be affected by varying lock-in frequencies (0.1 Hz to 25 Hz). The reason for the shifting hot spot is a non-uniform morphology in the epoxy encapsulation, which consists of different thicknesses and voids. This complicated epoxy encapsulation morphology results in a non-uniform heat conduction pathway when a different lock-in frequency is used. In this study, a LIT hot spot will stabilize and remain in a fixed position when the lock-in frequency is increased to greater than 5 Hz and the phase shift is directly proportional to the square-root of the lock-in frequency. This indicates that the heat conduction becomes stable under such a condition, and the phase shift value can still be used for relative depth localization. By overlaying LIT and X-ray imaging, an accurate position of the fault location in the X-Y plane can be detected. A quick and non-destructive 3D fault isolation method for complicated system level failure can be achieved in this way.

Innovative in situ X-ray metrologies for package failure analysis (FA) were developed to understand solder thermal interface materials (STIM) package process and failure mechanisms through elevated temperature. Dynamic STIM void formation mechanism and STIM bleeding-out dependency on reflow were observed. It was found that long sit time before STIM liquidus temperature helps to minimize the STIM void formation and fast cooling mitigates the STIM bleed-out risk. Our studies demonstrate that in situ metrologies offer direct guidance to packaging process optimization and accelerate root-cause identification for temperature induced package failures; therefore, it improves throughput-time for packaging technology development.

Automotive ultrasonic parking sensors were analyzed using X- ray computed tomography (XCT or microtomography), in order to determine if there were internal failures generated on the soldering process between copper wires and piezoelectric ceramic on these sensors. This paper reports the use of X-ray radiography and computer image processing for the study of internal defects. By using X-ray tomography technique, pores, cracks, holes, solder balling, insufficient solder, lead related defects, device related defects, and solder bridging may be identified (1-2). When coupled with a real time radiographic detector and image processor, X-ray technology allows instantaneous radiographic imaging and semi-automatic or totally automatic inspection. Analysis was conducted on six produced test samples showing that the application of XCT as a method of quality control of specimens produced by electronic packaging offers a wide range of possibilities to detect defects within materials. There were determined that five sensors contain internal defects on the soldered joints, between the copper wire, and the piezo electric ceramic covered with silver paint, as shown on the computed tomography. Accuracy of XCT method strongly depends on the size of the samples analyzed, but the possibility of obtaining information in 3D nondestructively shows considerable advantages of XCT method over traditional metallographic cross-sectional analysis.

The need for reverse engineering (for IP verification or for reproducibility) has reached unprecedented levels requiring not only the inspection of the circuitry but also the understanding of the packaging and interconnects. Achieving the best X-ray inspection for a particular application depends on an in-depth understanding of the X-ray system configuration, the sample configuration, and the sample preparation techniques available. This paper presents various case examples on the development of advanced X-ray inspection techniques for IC reverse engineering, along with information on the limitations of X-ray imaging, issues with 3D reconstruction, models for resolution configuration improvement, and advantages and disadvantages of advanced sample preparation techniques. It is observed that the novel X-ray inspection techniques, combined with appropriate sample prep techniques, provide the necessary resolution to achieve results necessary for current reverse engineering needs.

This paper describes how scanning acoustic microscopy can be used to inspect materials under the chamfer of electronic device packages. The technique involves the use of copper tape to locate the areas affected by the chamfer during X-ray radiography. The results are then correlated with known critical package and assembly geometries to determine how far parallel lapping should proceed to ensure that the areas of interest will become observable under acoustic microscopy without interfering with the functionality of the device.

The paper will present an approach for non-destructive localization of thermal active defects at multi chip devices combining the Lock-in Thermography and following local X-Ray inspection. In combination of both methods inner defects in inter chip connections of complex device built ups can be found in a non-destructive way before opening the device. The methods were demonstrated at defective flip chip devices with a high ohmic daisy chain with lots of chip to chip contacts. Subsequently, cross section analysis at located high ohmic contacts was performed in order to find the root cause of the failure.

Printed circuit board assembly with lead free solder is now a reality for most global electronics manufacturers. Extensive research and development has been conducted to bring lead free assembly processes to a demonstrated proficiency. Failure analysis has been an integral part of this effort and will continue to be needed to solve problems in volume production. Many failure analysis techniques can be directly applied to study lead free solder interconnects, while others may require some modification in order to provide adequate analysis results. In this paper, several of the most commonly applied techniques for solder joint failure analysis will be reviewed, including visual inspection, x-ray radiography, mechanical strength testing, dye & pry, metallography, and microscopy/photomicrography, comparing their application to lead bearing and lead free solder interconnects. Common failure modes and mechanisms will be described with examples specific to lead free solders, following PCB assembly as well as after accelerated reliability tests.

Next generation assembly/package development challenges are primarily increased interconnect complexity, density, and multi-layer/multi-stacked packages with ever shorter development time. The results of this trend present some distinct challenges for the analytical tools and techniques to support this technology roadmap. The key challenge in the analytical tools and techniques is the development of nondestructive imaging for improved time to information. The 3D X-ray Computed tomography (CT) system named “X-Tek NGI” has been co-developed by Intel and X-Tek to address this need. The current paper will discuss the configuration and several applications where this tool has been applied successfully to solve current package technology development issues and provide package construction analysis (including enabled components). This paper will discuss the details of the system configuration, examples together with the current limitations and future direction for non-destructive package failure analysis.

This article details the results of a failure analysis performed on a Qualification Unit injector for a military satellite thrusters and explains that the failure was initially detected due to a shift in performance during qualification testing. Failure analysis involved non-destructive evaluation on the injector using micro-focus X-ray and scanning electron microscopy. Serial cross-sectional metallography was then performed, with each cross-section documented by optical microscopy and SEM. The failure analysis resulted in three main conclusions: (1) the root cause of the failure was attributed to multiple detonations in or around the damaged orifice; these detonations were likely caused by fuel and/or combustion products condensing in the orifice between pulses and then igniting during a subsequent pulse; (2) multiple damage mechanisms were identified in addition to the ZOT detonations; and (3) the material and platelet manufacturing process met all design parameters.

X-ray microfocus radioscopy and computed tomography (CT) offer detailed information on the internal assembly and material condition of objects under failure analysis investigation. Using advanced systems for the acquisition of radioscopic and CT images, failure analysis investigations are improved in technical accuracy at a reduced schedule and cost over alternative approaches. A versatile microfocus radioscopic system with CT capability has been successfully implemented as a standard tool in the Boeing Defense & Space Group Failure Analysis Laboratory. Using this tool, studies of electronic, electromechanical and composite material items have been performed. Such a system can pay for itself within two years through higher productivity of the laboratory, increased laboratory value to the company and resolution of critical problems whose worth far exceeds the value of the equipment. The microfocus X-ray source provides projection magnification images that exceed the sensitivity to fine detail that can be obtained with conventional film radiography. Radioscopy, which provides real-time images on a video monitor, allows objects to be readily manipulated and oriented for optimum x-ray evaluation, or monitored during dynamic processes to check performance. Combined with an accurate manipulating stage and data acquisition system x-ray measurements can be used for CT image reconstruction. The CT image provides a cross sectional view of the interior of an object without the interference of superposition of features found in conventional radiography. Accurate dimensional measurements and material constituent identification are possible from the CT images. By taking multiple, contiguous CT slices entire three dimensional data files can be generated of objects.