Decapsulation of silver wire bonded packages with known techniques often results in damaged silver wires. The chemical properties of silver and silver compounds make silver bond wire inherently susceptible to etching damage by acid, conventional plasma, and oxygen-based Microwave Induced Plasma (MIP). In this paper we solve this problem by developing a specific decapsulation chemistry, based on a hydrogen-containing MIP, for artifact-free decapsulation of silver wire bonded packages.

Accurate root cause determination of integrated circuit devices necessitates the preservation of evidence during failure analysis. Identifying the cause of systemic defects requires capturing physical evidence provided by very few customer returns. Each piece of physical evidence is valuable due to the scarcity of returns in most cases less than 1 ppm. Harvesting infrequent physical evidence requires that each attempt to decapsulate a fail unit has a high probability of retaining the material that caused the defect. A measured method that retains the critical evidence is the fastest way to solve a defect driven systemic failure mechanism because one gathers the evidence more efficiently. This paper presents two case studies of improved evidence gathering using halogen-free microwave induced plasma (MIP) decapsulation during the root cause investigations. This relatively new method of decapsulation enabled us to preserve evidence, including any changes to the metal and die surface structures along with the presence of contaminants or by-products of failure mechanisms.

When it comes to complex system-in-package (SiP) with a wide spectrum of materials and packaging structures integrated into a single module, decapsulation and the following failure analysis become extremely complex. Previous work published by the authors' group has demonstrated that a halogen-free microwave induced plasma (MIP) system has great advantage compared to the conventional techniques mentioned before. This paper explores the applicability of the halogen-free MIP on the most complex SiP module decapsulation. Applications in special structures in SiP include 3D stacked-die, gallium arsenide, surface acoustic wave (SAW) and bulk acoustic wave filters, and copper re-distribution layer. The halogen-free MIP decapsulation process can expose and preserve all the dies and passive components as well as the original failure sites, which proves to be key to ensuring a high success rate in SiP failure analysis.

Disk splats are usually observed when the deposition temperature exceeds the transition temperature, whereas thick oxide layer will reduce the adhesion resulting from high deposition temperature. In present study, single molybdenum splats were sprayed onto polished molybdenum substrates with different preheating processes to clarify the effect of surface oxidation on the splat formation. Three preheating processes included heating the substrate to 350 °C, 550 °C, and cooling the substrate from 550 °C to 350 °C, which were performed in argon atmosphere. The chemistry and compositions of substrate surface was examined by XPS. The cross sections of splats were prepared by focus-ion-beam (FIB), and then characterized by SEM. Nearly disc-shaped splat with small fingers in the periphery was observed on the substrate preheated to 350 °C. Perfect disc-shape splat was deposited at 550 °C. Flower-shaped splat exhibited a central core and discrete periphery detached by some voids on the substrate preheated to 350 °C (cooling down from 550 °C). The results of peeling off splats by carbon tape and morphology of FIB sampled cross-sections indicated that no effective bonding formed in the splat-substrate interface for the substrate ever heated to 550 °C, due to the increasing content of MoO 3 on preheated molybdenum surface.

Ni20Cr splats were sprayed onto polished substrates at different preheating temperatures in an argon atmosphere by Low Pressure Plasma Spray to reveal the dominating factor on the effective interface bonding formation. The splat morphology, microstructure and splat-substrate interface bonding were characterized by SEM and EBSD. The interface for examination of typical splats was prepared by FIB. Disk splats were obtained on AISI 304 stainless steel substrates preheated to temperatures of 100 °C (cooling from 350 °C), 350 and 550 °C. Moreover, typical distinct two-zone microstructure feature was observed on the splat surface by SEM and EBSD, including central coarse grain and marginal fine grain. When the preheating temperature was higher than 350 °C, effective bonding formed only in the entire central coarse zone, whereas no effective bonding was observed in the fine grain zone. By using glass, copper, nickel and 304 SS as substrates, it was found that increasing thermal conductivity of metallic substrates has little effect on splat diameter and morphology and however decreased the area fraction of central coarse grain zone. It was revealed that the melt/substrate interface temperature plays a crucial role on the interface bonding formation.

This study investigates the feasibility of using solution precursor plasma sprayed (SPPS) zinc oxide to fabricate NO 2 gas sensors. In the experiments, thin ZnO layers were deposited on Al 2 O 3 substrates that had been printed with interdigitated gold electrodes. FE-SEM images show that the as-sprayed films are highly porous and nanostructured as desired. Diffuse reflectance measurements reveal that significant absorption occurs in the visible light range. In gas sensing tests, the SPPS ZnO films were responsive to concentrations of NO 2 gas down to 0.4 ppm. The performance is attributed to the porous nanostructure and the presence of oxygen vacancies, or mid-bandgap defects, as confirmed by XPS analysis.

In this study, stainless steel splats were deposited on preheated stainless steel substrates with oxide scales of different thickness in inert low-pressure plasma spay (LPPS) conditions to examine the effect of in-situ oxidation of prior splats on the morphology and bonding of subsequently formed splats. Splat-substrate interface cross-sections were prepared by focus-ion-beam milling. Splat morphology and bonding state with the substrate were characterized by SEM. The results show that with oxide films up to 35 nm thick, disk-type splats are deposited that bond well to the substrate except in the periphery region. As oxide films become thicker (100 nm) and present a surface with micro-scale roughness, splats take on a finger-like shape with poor bonding at the interface.

Aluminum-titanium powder mixtures were deposited on γ-TiAl alloy substrates by cold spraying then heat treated for 5 h at 600, 650, and 700 °C. SEM and XRD examination showed that the treatment caused Al to diffuse into the substrate where it reacted with Ti, resulting in changes in microstructure. The diffusion of Al left pores in the fringes of the TiAl 3 phase, increasing the porosity of the coatings. A surplus of Al remained in the coatings after heat treatment at 600-650 °C, but at 700 °C, all Al was consumed, contributing to the formation of a continuous TiAl 3 layer.

Formation of voids is inevitable in plasma sprayed coatings, and the role of voids on coating properties has long been established. In fact, the void content within coatings is often adjusted by manipulating the process parameters to obtain coatings with desirable performance. Quantification of voids via image analysis allows the determination of not only the void content within a coating, but also the spatial distribution of the voids. Void content in plasma sprayed neodymium iron boron (Nd-Fe-B) coatings was varied from 1.8 to 8.2% by changing the standoff distance (SOD). Spatial distribution parameters, including near-neighbor distance (d min ), nearest-neighbor distance (d mean ), and nearest-neighbor angle (θ n ), were determined via the Dirichlet tessellation method. Coefficient of variation (COV) values of d min and d mean allow the determination of inhomogeneity and degree of clustering of the voids within a coating. The θ n values show the anisotropy behavior of the voids within plasma sprayed coatings. The influence of void content and its spatial distribution within the coatings on the microhardness and elastic modulus of the coatings was determined.

La 2 (Zr 0.7 Ce 0.3 ) 2 O 7 (LZ7C3) ceramic was prepared by solid state reaction method at 1400 °C for 12h using La 2 O 3 , ZrO 2 , and CeO 2 as starting reactants. The phase composition and microstructures were studied by XRD and SEM technology. The thermal conductivity and linear thermal expansion coefficient were investigated by laser-flash method and pushing-rod method respectively. XRD results revealed that LZ7C3 is a mixture of pyrochlore and fluorite, and the pyrochlore is the main phase which is a small solid solution of La 2 Ce 2 O 7 (LC) in La 2 Zr 2 O 7 (LZ). The thermal conductivity of LZ7C3 decrease gradually with the increase in temperature until 1200°C, and the value is 0.79 W⋅m -1 ⋅K -1 , which is almost 50% lower than that of LZ. The linear thermal expansion coefficient which is 11.6 × 10 -6 K -1 at 1200°C is larger than that of LZ. These results show that LZ7C3 ceramic material can be explored as a novel prospective candidate material for use in new thermal barrier coating systems in the future.

The deposition behavior of particles during cold spraying is determined by plastic deformation of both substrate and impinging spray particles. In this paper, the in-situ heating and subsequent softening of the local substrate were examined to reveal their influence on the deposition behavior of spray particles and the microstructure and property of the cold-sprayed 316L stainless steel and copper coatings. Results show that the temperature of the substrate surface, where the spray gas stream and high velocity particles were projected on, increased to 300°C when the gas temperature was 500°C. Such effect is referred to as the in-situ substrate heating. The in-situ heating of the substrate surface was enhanced with the decrease in the gun nozzle traverse speed. With the decrease of nozzle traverse speed from 100 to 20 mm/s, the relative deposition efficiency significantly increased and the porosity of cold-sprayed 316L coatings decreased from 5.6% to 2.5%, and the micro-hardness of the coatings increased from 283 Hv to 351 Hv. The influence of the nozzle traverse speed on the microstructure and property of cold-sprayed coatings is discussed based on the influence of the in-situ heating and softening effect of substrate surface on its deformation behavior and particle deposition upon the impact of spray particles. The in-situ substrate surface heating is proposed as an essential processing parameter as a function of gun traverse speed during cold spraying.

Thermal spray coatings are comprised of millions of heated particles that are driven at high velocity to impact against a substrate; thereby building up to form a consolidated coating. Thus, investigating single solidified droplets contributes to fundamental understanding of coating evolution and their properties. In this study, Scanning Electron Microscopy (SEM) studied the splat morphology of flame sprayed ethylene methacrylic acid (EMAA) with respect to the stand-off distance when deposited onto glass and mild steel substrates. A splat shape transition from a “splash” to a “disc shape” was observed. The morphology of EMAA droplets can be described as a ‘splash splat’ when sprayed onto mild steel at room temperature, whereas a 35 cm stand-off distance produced a disk-shaped splat when the polymer was deposited onto a glass substrate.

Cold spray is a material deposition process that uses a high pressure, high velocity gas jet for the deformation and bonding of particles. However, deposition of brittle or hard materials such as ceramics has not been successful: unless they are co-deposited with a ductile matrix material. This paper examines the WC particle size and its influence on the deposition of Co-based cermets. Micro- and nano-structured powders with similar Co content were employed. Varying the WC particle size influenced significantly the deposition efficiency of the coating process. Micrometer-structured WC-Co feedstocks did not permit coating build up when processed under comparable or elevated thermal spray parameters used for the nanostructured WC-Co feedstocks. In addition, micrometer-structured WC-Co coatings exhibited a conjoint erosion and deposition effect on the surface. Fine WC particles (<1 μm) were observed near to the substrate interface and larger WC particles (1-2 μm) in the vicinity of the coating surface. These observations indicate the existence of a critical WC particle size for deposition by the cold spray method and that the size criteria arises due to the formation and cohesion mechanisms within the coating layer.

Ti and Ti alloys can be applied to the steels as a protective coating in view of its excellent resistance to corrosive environment. Cold spraying as a new surface engineering technique has potential advantages in Ti coating manufacturing in comparison with conventional thermal spraying techniques. Ti coatings were prepared on a carbon steel substrate by cold spraying via controlling the process condition variables concluding carrying gas, temperature and pressure. The microstructure of coatings was observed by SEM. Potentiodynamic polarization experiments were performed to understand the corrosion behavior of the coatings. The SEM examination showed that the coatings become more compact with increase of molecular weight, pressure and temperature of carrier gas. Potentiodynamic polarization technique was used to measure the corrosion and electrochemical property of coatings deposited under different process conditions and surface conditions. The polarization curves indicated that the coatings which had lower porosity had lower corrosion current. The polishing treatment peeled the rough outer layer including the small pores as well as decreasing of the actual surface area of the coating, leading to the considerable improvement of corrosion resistance.

High temperature titanium alloys are considered as good candidate materials for many aerospace applications. In order to increase the usable temperatures and oxidation resistance of titanium alloys, plasma spraying thermal barrier coatings on the titanium alloys is considered as an effective method. The effect of plasma spraying process on microstructure and microhardness of the titanium alloy was investigated by scanning electron microscope, energy dispersion analytical X-ray spectroscopy and microhardness test. The results show that the microstructure of the titanium alloy inside the substrate keeps unchanged after plasma spraying, and no interaction and atomic diffusion happen evidently at the bond coat/substrate interface. However there exists a thin layer of plastic deformation zone in the substrate beneath the bond coat/substrate interface after plasma spraying. The residual stresses are induced inside the titanium alloy due to the thermal expansion mismatch and the temperature gradient inside the substrate during plasma spraying, and lead to generating microcracks in the surface beneath the bond coat/substrate interface and the increase of microhardness in the substrate.

In order to develop protective coatings for sink rolls in continuous hot-dip galvanizing, a sprayed MoB/CoCr cermet coating was formed on a 316L stainless steel by the HVOF spraying process and its durability in the molten 55%Al-Zn- 1.5%Si bath (923 k) has been investigated by SEM and EDS. The immersion test revealed that the MoB/CoCr coating has much higher durability (640 hours) in 55%Al-Zn-1.5%Si bath than the conventional sprayed coatings (120 hours), such as WC-Co, WC/Co/Cr and ceramics. It was found that the failure of MoB/CoCr coating is mainly caused by the mismatch of coefficient of thermal expansion (CTE) between the top coating and the substrate. The failure procedure is that first crack is generated because of heat stress, then the crack proceeds and causes scaled delamination, at the same time molten Al-Zn will enter into cracks and/or Al-Zn reaches the undercoat and/or substrate, finally molten Al-Zn dissolves the substrate.

Thermal spray coatings of new MoB/CoCr cermets were developed. The mechanical behavior of HVOF-sprayed MoB/CoCr novel composite coatings was evaluated via Vickers microhardness. Microstructure of the coatings on 316L stainless steel substrates, as well as powders, were studied with optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD). X-ray microanalysis of the coatings was carried out using energy dispersive X-ray spectrometer (EDS) attached to the SEM. The distributions of microhardness values of the coatings were analyzed via Weibull statistic. Weibull analysis revealed a bimodal distribution of Vickers microhardness values. Such distribution was attributed to the presence of melted and unmelted phases in the resultant coating produced from the microstructured powder feedstock. The excellent mechanical properties of the coating are due to the MoB/CoCr powder, which results in the formation of complex ternary transition metal boride hard particles that exhibit exceptional mechanical properties.

Mechanical properties of micro/nanoscale structures are necessary to design reliable ceramic coatings. Micro/nanomechanical characterizations of novel nanocomposite coatings (NCCs) and micron composite coatings (MCCs) have been studied. Hardness, elastic modulus and creep resistance of these materials were measured by means of nanoindentation. It is found that the nanocomposite coatings exhibit higher hardness, elastic modulus and creep resistance as compared to the micron composite coatings. The nanoindentation tests used in this study can be satisfied to evaluate the mechanical properties of micro/nanoscale structures of ceramic coatings

This paper gives an account of pin-on-disc low stress abrasive wear and erosion wear tests on the specimens made by oxy-acetylene flame spray-fusing technology to explores the effect of WC content on the wear resistance of oxy-acetylene flame spray-fusing overlays. In the test, Ni60, NiWC25 and NiWC35 three kinds of various WC content Ni-base self-fluxing alloys were used as the typical wear resistance materials compared with 16Mn material and high Cr cast iron arc surfacing overlay. In pin-on-disc wear tests, SiC, Al 2 O 3 and SiO 2 different abrasive were used, and in erosion wear tests 30° and 90° erosion wear tests were performed. This paper also analyzed the wear mechanisms of spray-fusing overlays that possess different WC content by means of hardness tests and overlay's structure analysis. The results show that WC content influences the wear resistance of spray-fusing overlays greatly, but in various wear type and conditions, its effect's degree and tendency are quite different.

Focused Ion Beam (FIB) technique has been widely used to directly modify device functionality by adding ion-induced conductive lines and cutting signal traces with chemical enhance etching. However, in this work, FIB technique is employed to add a 15 ohm resistor to a RF circuit to solve its oscillation problem. After the modification, the oscillation problem is solved and the performance of the RF device is improved significantly. The successful FIB application of adding a defined resistor to modify a circuit is reported in this paper for the first time.