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The drive for smaller size and thickness has created new package assembly process challenges. Stacked die packages are increasing in interest due to the resultant smaller package and increased functionality. The requirements for a stacked package is a thinner wafer that enables more die to be stacked in a package. The die are bonded using Die Attach Film (DAF) that is laminated on the back of a wafer prior to singulation. The singulation of DAF laminated wafers with wafer thickness

Materials and processes currently used for 1st level interconnects are reviewed, and possible options for achieving significant reductions in temperatures to which the processor is exposed during packaging are considered. While the low melting point tin-bismuth alloys that are being introduced to board level assembly are potential candidates for 1st level interconnect, it has yet to be confirmed that other properties of these alloys are consistent with the requirements of materials needed to make fine pitch connections in close proximity to the processor. Of particular concern is the possibility of alpha emissions, microstructural stability, susceptibility to electromigration, whisker growth, and the possibility of polymorphic transformation of the tin phase at the cryogenic temperatures to which some processors might be exposed. For high frequency circuitry the inductance and the capacitance properties of the interconnect material also have to be taken into account. Consideration has to be given to whether the low melting point indium alloys that are used in the attachment of IR Focal Plane Arrays could be used for 1st level interconnects. Where the mechanical properties of low melting point alloys might not be sufficient to cope with possible service conditions, there are methods for forming a bond that is substantially comprised of intermetallic compounds at temperatures lower than the process temperatures required for reflow of conventional lead-free solders.

It is eagerly required to prevent external stress type Sn whisker generated from Sn plating film on connecter joints because it causes short circuits. We evaluated a variety of Sn plating films using various current waves and conducted external stress type whisker test. The results showed that Sn plating film using periodic reverse (PR) current was most effective to suppress the whisker growth. We analyzed the plating films by XRD to investigate the mechanism of the whisker suppression. The plating film using PR current had large numbers of Sn crystal orientations than other current waves. We believe that controlling Sn crystal orientations is a key factor to suppress Sn whisker growth.

One of the hardly predictable issues in the case of solder joints are tin whiskers. Tin whiskers are electrically conductive crystals that spontaneously grow on a surface. This article deals with tin whiskers growth on the three types of metallization (pure tin, SnCu1 and SnCu3 solder alloy) of the copper substrate. Two stressing factors were considered in the experiment – temperature ageing (three temperature conditions were chosen: 20 °C, 50 °C and 80 °C) and mechanical stress via bend of wire before and after the soldering process. The incidence of whiskers on the surfaces was observed by confocal microscopy. The results show that the major influence on whiskers incidence has two factors, mechanical stress followed by the influence of temperature. Whereas the other factor – copper content in used materials showed a minor influence on whiskers incidence.

Tactile sensing can provide sufficient cues concerning the geometry and texture of the contact in unknown environments. This paper proposes a semi-flexible triboelectric bionic whisker sensor (TBWS) as a novel scheme for robotic tactile perception. To be specific, it comprises power generation units (38mm in length, 18mm in width, and 10mm in thickness), octagonal plate, carbon fiber shaft (300mm in length, 1.5mm in diameter), shape memory alloy, and supporting parts. The octagonal plate hit the power generation units resulted from the carbon fiber shaft subjected to the external force, allowing to gene rate signals from the principle of via triboelectric and electrostatic induction. One another feature of the proposed sensors is that it is inspired by the structure of rat whisker follicles characterized by complex higher-order dynamics. Experimental result shows that TBWS can help robots accomplish autonomous work in complex environments. There is no doubt that the invention of sensor TBWS provides a new direction for robots’ future research.

This paper presents a flow-structure interaction simulation-aided morphology optimization of harbor seal whisker, for generating a whisker-like structure which could possibly perform better in minimizing vortex-induced vibrations (VIVs) when subjected to steady flows. We also propose a whisker-inspired flow sensor design which features a 3D printed polymer model of the optimized seal whisker mounted on a 3D-printed double cantilevered sensor base consisting of graphene nanoplatelets piezoresistors at the hinges. The designed flow sensor’s performance in sensing the flow velocity and its sensitivity to the external force are demonstrated by computational fluid dynamics simulations and proof-of-concept experiments, respectively.

Mammals use whiskers to sense their surrounding environments. By whisking over an object to transduce tactile signals (forces or moments) to mechanoreceptors at the snout, then transmitting this data to the somatosensory cortex in the brain, they can extract features such as contact distance, texture and shape of the object. In this study, we propose a morphological computation method to localize the contact position/locate the contacted object by investigating the induced strain, measured by a strain gauge representing sensory nerves, along the length of a whisker. To accomplish this task, an artificial tapered whisker sensor was made from a soft material (silicon rubber) to provide flexibility, sensitivity and more importantly adaptability. The first part of this paper introduces an analytical model of the proposed whisker based on elastic linear beam theory, and describes the unique correlations among the strain, contact distance, and whisker movements. The second part of this paper analyzes differences between the analytical model and a practical model to ascertain the optimum sensing conditions and any similarities in tactile behavior among the proposed whisker and a biological one. Our final goal is to give an idea of simple soft whisker-like sensory system which can be integrated in an autonomous robot.

Perceptual sensors play a crucial role in the next generation of robots due to their potential application in agriculture, biomedicine and industry fields. In this field, with dependence on visual, auditory and tactile techniques, sensors are utilized to intelligently assess their environment. Here, this study investigates a bio-inspired whisker sensor with self-power capability based on triboelectric nanogenerators (TENG) for building an robotic perceptual system. The whisker sensor is composed of cylindrical structure house (52mm in height and 10mm in diameter), a PTFE pellet fixed to the spring-fixed base, four copper (Cu) films attached symmetrically to inner of house, and memory alloys (50mm in length). Generally, the displacement of the whisker rod causes the change in voltage in four direction because of generated tensile. From experiments to data analysis and modeling, the sensor is characterized by simple structure, convenient fabrication, high sensitivity and self power supply without external power supply. Thus, this 3D printable self-powered whisker sensor should be applicable to a wide range of automaton applications.

An important question in Sn whisker research concerns the role of lateral Sn diffusion in the film to the whisker root, providing the feedstock for whisker growth. In an elegant tracer experiment on diffusion in Sn films, Woodrow (2006) observed lateral atomic Sn diffusion over distances of hundreds and thousands of microns through Sn grain boundaries during whisker growth. In this work, we examine the effect of limiting the lateral extent of the Sn feedstock available during whiskering by employing extremely thin, micron-sized patterned Sn deposits, and compare to whisker growth from an comparatively large, essentially infinite (1cm x 1cm) thin Sn film. A series of metal, mesh grids of varying sizes were used as masks to define the area of sputtered tin deposited on Si substrates. The defined areas were primarily in the form of squares, with sizes ranging from7.5μm x 7.5μm to 153μm x 153μm. Sample areas also included 2 circles, with radii of 1μm and 4μm, and a rectangular strip with dimensions 46μm x 3000μm. A thickness of ~500A of sputtered Sn was deposited on each specimen. The samples were subsequently incubated for 34 days under three incubation conditions: 23oC (isothermal); 100oC (isothermal); and thermal cycling over -40oC

This article discusses the failure of connectors used in car navigation equipment due to tin whisker growth. Comparative and analysis of the tin whisker growth at the contact position of the classic case connector. Based on the test results, the specific measures to control the growth of tin whisker of such products are obtained.

Spontaneous growth of tin whiskers have been a threat in electronic devices for several decades. The growth behaviors of tin whiskers on a Sn-Al coating was investigated in this paper. A polycrystalline 100 μm thick Sn coating was fabricated on a Al substrate by reflow soldering. The coating was confirmed as a hypereutectic Sn-Al coating. The microstructure of Sn-Al coating consisted of primary α-Al phases and Sn-Al eutectic phases. Tin whiskers was found showing a fast growth rate on the Sn-Al coating. The grains of the Sn-Al coating showed random orientations which was different from the coating fabricated by electroplate. Tin whiskers preferred to grow on the Sn grain with (001) plane in Z direction. Grain boundaries were not found at the whisker root indicating that lattice diffusion should be response for the growth of the whisker.

In this study, the whisker growth from SAC0307-Mn07 solder alloy was investigated. To get fast information, an ultra-thin film was vacuum evaporated from the examined solder alloy onto Cu substrates. The evaporated layer was $\sim 100 - 150$ nm thick in average with the same grain size. The layers were kept at room temperature for 28 days. Whisker growth was monitored by scanning electron microscope with some days frequency, and the layer structure under the whisker was examined on focused ion beam cuts. The large mechanical stress on the Sn layer due to the intermetallic layer growth initiated the whisker growth right after the layer deposition. However, it stopped after 2 weeks since the intermetallic grains consumed the ultra-thin Sn layer. The whisker density was extremely high $(\sim 24 \, 000 pcs./mm^{2}$). Most of the whiskers were the short nodule and hillock type, which does not mean risk in microelectronics. Therefore, the alloying of Mn into the high Sn content solder alloys have a positive effect on the reliability of the solder joints.

This study proposes an out-of-plane electronic whisker (e-whisker) array that integrates a three-dimension whisker structure using polydimethylsiloxane (PDMS) and nanocarbon-based strain sensors. The strain sensor is fabricated by a laser-induced graphene from polyimide film and transfer process from polyimide to the PDMS. Fundamental characteristics of an out-of-plane electronic whisker such as sensitivity and response time are studied as well as the demonstration of e-whisker array. By considering the device structure, multiple directional force detection is realized for the first time. Based on the properties of the sensors, simple and low-cost three-dimensional device fabrication process works well for the e-whisker application.

This work presents the design, modeling, and fabrication of a whisker-like sensor capable of measuring the whisker’s angular displacement as well as the applied moments at the base of the whisker. The sensor takes advantage of readily accessible and low-cost 3D magnetic sensors to transduce whisker deflections, and a planar serpentine spring structure at the whisker base is used to provide a mechanical suspension for the whisker to rotate. The sensor prototype was characterized, calibrated, and compared with analytical models of the spring system and the magnetic field. The prototype showed a moment sensing range of 1.1N·mm when deflected up to 19.7°. The sensitivity of the sensor was 0.38°/LSB for the angular displacement sensing, and 0.021 Nmm/LSB for the moment sensing. A fully integrated system is demonstrated to display real-time information from the whisker on a graphical interface.

Low-temperature soldering using Sn-3.5Ag-8In-0.5Bi solder, Sn-8Zn-3Bi solder, 42Sn-58Bi eutectic solder cause the tin whisker growth on the tin plating in the testing for tin whisker. Especially, the tin whisker on the tin plating of MLCC (multi-layer ceramic capacitor) mounted by Sn-3.5Ag-8In-0.5Bi solder grew up fast, and its length became $160 \mu \mathrm{m}$ at 8000 h in 30°60%RH. But the mechanism of the whisker growth was unknown. We suggest a new mechanism of whisker growth related to the shape of ternmination and reflow temperature.

It has been demonstrated that biological whisker sensing system has excellent capacity to achieve the pattern recognition, and whisker sensor based robot tactile perception has caused widespread concern. However, most of current existed whisker sensors are too large in size, and are difficult to be integrated into a small robot. In this paper, we proposed a MEMS based biomimetic whisker sensor inspired by rats, which integrates four sensing units on a square silicon wafer with a side length of 6.8mm and makes it possible to be installed on a small robot with similar size to a real rat. Our sensor measure the bending moment at the root of the whisker based on the piezoresistive effect. We have explored the range of functions that whisker arrays can serve on and it is shown that our whisker sensor can determine obstacle distance, and is also capable of gathering surface information including shape and texture.

Picosun is undertaking a research programme, funded by the European Space Agency, in collaboration with Oy Poltronic Ab and Loughborough University, to evaluate conformal coatings made with atomic layer deposition (ALD) as a method of mitigating the growth of tin whiskers and for corrosion protection. ALD is a mature, key enabling technology in modern IC industries, and it is also utilised for corrosion protection in various special applications. As such, ALD is an interesting option for the protection of assembled electronic circuit boards and modules when extremely thin, practically massless, reworkable, transparent and inert coatings are needed, especially in specific high-end applications. The results show that the ALD process can significantly reduce tin whisker growth and thus offers considerable potential as a reworkable whisker mitigation strategy. The latest output of these, started in 2015 (Phase 1) and 2018 (Phase 2), are presented.

An influence of a magnetic impurity distribution on the AC transport of charge carriers in silicon whiskers doped with boron and nickel at low temperatures was investigated. The concentration of Ni impurities obtained from impedance and magnetization data was shown to coincide and equal to 3×1017 cm−3. The obtained hysteresis of the whisker magnetization was used to design multifunctional sensor as well as storage device.

Whisker growth from metal surfaces of electrical connectors and other components has shown itself to create reliability issues. If a whisker grows in a location that bridges between two conducting surfaces not previously electrically connected, a short can occur, resulting in faulting components. The current passing through the whisker will cause its temperature to rise due to Joule Heating. This can eventually cause the whisker to melt, which can than disconnect the short circuit. Therefore whisker shorts are limited by this melting current. Previous works have examined the coupled electro-thermal model of a solid whisker conductor, but most neglect the convection of heat into air, which dissipates some of the heat, reducing the temperature rise of the whisker. This work examines the influence of convection on the melting of a shorted whisker. This is done using a finite difference model that considers the temperature dependent conductivities when solving the coupled one-dimensional heat and electrical conduction equations. Since there exists a variety of metals capable of whiskering, various metal whiskers will be modeled here for comparison purposes.

The article deals with the studies of strain influence of n-type GaSb whiskers magnetoresistance at low temperatures 4.2 – 60 K The crossover from WAL to WL occurs under the compressive strain at 4.2 K The field dependency of the whiskers magnetoresistance was used for design of sensor of magnetic field induction in the range 1-11 T.

Tin-based lead-free solders susceptible to grow tin whiskers, which can cause in short circuit and threaten the reliability of electronic devices. Herein, the influence Cu or Ni micro-nanocones（MNCs）has on the Sn whisker formation were studied. From the results, we found that after the insertion of Ni MNCs, the growth of Sn whisker was mitigated effectively for thin Sn coating with 1 μm thickness but no suppression effect was found for Sn coating with 3 μm thickness. For Cu MNCs, the number of tin whiskers increased but its length was reduced. The investigate method and the mechanism of suppression proposed here are benefit to the prevention and control of Sn whiskers.

This paper presents a strategy to measure static or quasi-static magnetic field by using a RTD-Fluxgate magnetometer and a bimorph artificial whisker used as actuator. The movable architecture of measurement has been conceived for localization of magnetic dipoles in an angular range of about 8° with a suitable sinusoidal voltage used to drive the bimorph material. In order to address this task first, we characterized the flexible bimorph actuator able to move the magnetic sensor, than we investigated the possibility to detect localized magnetic sources by using the performance of a novel configuration of flexible RTD-Fluxgate. The system has been analytically modeled and an experimental campaign, in order to demonstrate the proposed principle, has been performed obtaining very interesting results.

The Sn thin film on Cu substrate has high Sn whisker growth susceptibility because of the intensive Cu 6 Sn 5 intermetallic formation at the Sn-Cu interface. In this study, the whisker development on vacuum evaporated Sn thin film deposited on Cu substrates was investigated, starting directly from the Sn deposition. The aim was to obtain more information about the whiskering behavior of Sn thin film in the early stage of the life cycle. For the study, 99.99% pure tin was vacuum evaporated onto Cu substrates. Two different Cu substrates were applied with different surface roughness to investigate the effect of surface roughness on the whisker development. The average thickness of the evaporated Sn layer was ~2 μ m. Samples were stored at room temperature for 10 weeks. Whisker development was observed by scanning electron microscope. It was found that the large compressive stress in the Sn layer because of the intermetallic formation initiates the whisker development even after 1 day of the Sn layer deposition. Almost only filament type whiskers were detected. The characteristics of the whisker density showed exponential saturation up to 10 days of the study, while the length of the whiskers was growing further still the end of the study. It was also found that the surface roughness of the Cu substrate affects the rate of whisker growth.

In this study, a single-step additive manufacturing approach to fabricate an array of bio-inspired soft whisker-like sensors is presented. Each whisker is a damped oscillator system that is tuned to a different resonant frequency whose response is characterized through experimentation in an air medium. A 3 × 1 polymer based whisker-array is used to distinguish individual frequency components in mixed-frequency signals, achieving a form of “mechanical Fourier transform”

Tin whiskers are small, hair-like structures that can form naturally from the surface of tin components. While the mechanisms by which tin whiskers form are poorly understood, their potential effects are well documented: they can cause short circuits and arcs within electrical devices, damage micro-electromechanical systems (MEMS), and interfere with the operation of optical and RF components. As automotive systems become increasingly reliant on integrated electronics, the potential for reduced functionality or damage resulting from tin whisker formation increases; however, because the factors that contribute to whisker growth are still debated, design practices, testing standards, and mitigation processes to address tin whiskers have not matured. We discuss potential contributors to tin whisker growth, failure mechanisms that may be induced by whiskers, current testing standards and processes, and mitigation strategies, with a particular focus on the automotive industry.

This paper is an introduction of heat resistant joint material only using base metals (Cu and Sn) mainly for power semiconductors’ assembly. By sophisticated control of Cu-Sn Intermetallic Compound (IMC) forming procedure, the joint region after sintering has IMC skeleton structure to provide robust and stable joint characteristics. The key components of the developed material are fine particles of Cu source and IMC source. The IMC source contains 8wt% Cu and 92wt% Sn. Remelting point of the joint material (preform-sheet and paste) can be above the sintering temperature. Even using Sn rich component (IMC source), the evaluation indicated no whisker in joint area after TCT 1,000cycles (−55~+175°C) and no allotropic transformation of Sn (between α-phase and β-phase). The joint test using IGBT, SiC and GaN, we confirmed the joint structure keeps its initial condition even after 1,000 cycles TCT without critical cracks/delamination/voids. The joint material is not only for power semiconductor die attach but also for MEMS device encapsulation.

We have developed a heat resistant joint paste by Cu-Sn IMCC (Intermetallic Compound Composite) for thin joint thickness. The developed IMCC paste contains only IMCC fine particles as a metal composite. Re-melting point of the paste can be above the sintering temperature. For example, 320C remelting point was observed by 280C sintering. The paste is adoptable for heat resistant joint. The paste also indicated there is no whisker in joint area after TCT 1,000cycles (-55~+175C). When the joint thickness to be thin, voids in the joint region becomes conspicuous. There are two root causes to form voids. The first is non-uniform interaction between joint material and objects (joint targets). The second is gas void. For the paste, we chose a simple composition using only IMC source (fine particles which already contains IMC micro-colonies in them) as a metal component to provide moderate and uniform interaction with joint targets. To eliminate gas voids, two-stage sintering process was adopted. The first sintering (pre-sintering) is to evaporate all volatiles from the paste and to make appropriate interconnection with the substrate keeping the paste shape convex and providing enough joint strength for subsequent cleaning treatments. The second sintering (main-sintering) is for the device joint to the paste without voids. For making thin joint thickness around 30μm, weak pressure onto the device (~0.7MPa) is effective. Test sample with Si die (700μm thick, 6mm width) with Ni/Au finished backside metal was mounted on to Cu substrate. The joint region is almost filled by grown IMC layers. The thickness of the joint region is 30μm for entire joint region without voids.

In this paper, a specially designed method for inspecting and categorizing whiskers in press-fit systems was established. Effect of PTH final hole diameter and pin coating thickness on whisker growth was evaluated. It was found that PTH final hole diameter showed more significant effect on whisker growth than pin coating thickness. The smaller the hole was, the more and longer whiskers grow in the press-fit system. However, thicker coating on pins introduced more scratched residue on annular rings and also could increase the chance of short circuit failure. The tin coating thickness on pins for telecom/datacom applications is recommended to between 0.5 μm and 2.5 μm.

Tin whiskers continue to be a major concern in electronics assembly. This paper will firstly give an explanation of tin whiskers and their formation. Secondly, it will summarize their potential risks and mitigation techniques. A description of Failure Modes and Effects Analysis (FMEA) as a technique to assess tin whisker risk, for a given technology, will be then be discussed.This paper will conclude with a discussion of tin whisker reliability strategies for consumer and mission critical products. At the end of the presentation, attendees will have all of the basic relevant information to develop an effective tin whisker strategy.

High thermal conductive adhesive sheet whose dielectric constant (Dk) is 5.0 was developed. To obtain low Dk. low Dk matrix polyimide resin whose Dk is 2.6 was designed to decrease Dk as much as possible. To obtain high thermal conductivity, h-BN sphere shaped filler was used as a main heat thermal conductive filler. The h-BN sphere shaped filler shows high thermal conductivity (40W/mK) as bulk filler and low Dk (4.0). High thermal conductive adhesive was obtained by mixing the h-BN cohesive filler into the low Dk polyimide matrix resinIn addition, to make heat path in the high thermal conductive adhesive to z-direction, AlN whisker was oriented to z-direction in the thermal conductive adhesive. We successfully developed novel method to disperse AlN whiskers to z-direction preferably. By utilizing the alignment method, thermal conductivity of the materials increased drastically.As a result, the heat conductive sheet shows the heat conductivity of 15W/mK with low dielectric constant. In addition, the sheet shows excellent break down voltage. The adhesive sheet is suitable for Thermal Interface Material (TIM) for high voltage power modules.

This paper retrieves the parameters of the refined compact model of planar diode with anode pin in a form of air bridge with whisker. The model gives an opportunity to simulate amplitude, phase, and noise characteristics in SHF, EHF, and THz frequency ranges.

This work considers the behavior of a metallic whisker as it is causing a short circuit. This is achieved by using a coupled electro-thermo-mechanical numerical model (i.e. multiphysics finite elements). The shorted current passing through the whisker will cause it to heat and the temperature to rise. The temperature rise can cause the whisker to soften and stresses to grow. Eventually this could cause the whisker to melt or fail, which in turn breaks the short circuit. This work examines at what conditions this will occur for typical whiskers consisting of tin. The model is able to include temperature dependent properties such as resistivity and strength, which is difficult to accomplish in closed-form analysis. Based on the finite element model and existing theory, equations are also provided to make predictions of the maximum current that can be withstood by a typical whisker before its demise.

Rats rely heavily on tactile information from their whiskers to acquire information about their surroundings. A whisker has no sensors along its length. Instead, mechanical deformation of the whisker is sensed via receptors at its base. The present study introduces a micro-sensor developed specifically to imitate the sensing of biological rat whiskers. The sensor responds to bending moments resulting from touch and/or airflow in two axes. The sensor was designed based on analytical models from cantilever beam theory, and the models were validated with finite-element analysis. Sensors were then fabricated using micro-milled molds and integrated into an Arduino-based circuit for simple signal acquisition. The present work begins to develop the technology to allow investigation of important engineering aspects of the rat vibrissal system at Ix scale. In addition to its potential use in novel engineering applications, the sensor could aid neuroscientists in their understanding of the rat vibrissal-trigeminal pathway.

In this paper a bio-inspired tactile whisker sensor made by 3D printing is discussed. Whisker inspired sensors were printed using flexible dielectric and conductive thermoplastic poly-urethane (TPU). The conductive TPU is used for strain-gauges facilitating resistive read-out. A single whisker sensor contains two strain-gauges allowing to determine both the force acting on the whisker as well as the contact point on the whisker. To the best of our knowledge this is the first work on 3D multimaterial printed, flexible, whisker inspired tactile sensors.

Perception of changes in the environment is essential for any robot to successfully navigate through its surroundings. Ongoing research on soft sensors is primarily directed to measuring strains. However, less work aims to provide position and navigation feedback. In this study, we present the design and fabrication of soft resistive sensors embedded into whisker follicles and the simple synthesis of a conductive composite by mixing 99% silver powder and a soft elastomer. Whisker follicles can be tuned to detect a specific frequency. These kind sensors are a simple, robust and straightforward method to detect changes in the environment. The performance is compared to bend sensors commercially available. Finally, a frequency detection experiment is presented to show the capabilities of the sensor.

Pre-plated leadframe (PPF) is an evolved technology to plate Nickel (Ni) — Palladium (Pd)-Gold (Au) or Gold Alloy on copper, with a typical plating thickness

In this study, a series of factors that may affect whisker growth on electroplated tin coatings under high external pressure were studied by an indentation method, including storage time, coating thickness, loading and ball diameter. The indentation test results showed that longer storage time, thicker coating (< 3 μm), heavier loading and smaller inert ball could accelerate whisker growth. In addition, the insertion force, retention force and whisker behavior of compliant press-fit pins inserted into the same design of plated through holes with three different types of final finishes (Immersion tin, ENIG and OSP) were investigated.

Due to restrictions on lead usage often resulting in the use of pure tin deposits, coupled with global miniaturization, the unpredictable risks of Sn whisker growth rises, especially in highly stressed coating applications. The ability to prevent whisker growth is particularly important for the growing implementations of solderless press-fit pin connections, where although very beneficial, produce high stress gradient conditions on the compliant pin's coating, leading to higher risks of whisker induced failures. Therefore, TE Connectivity has developed a new production level tin-whisker free technology through the application of an electroplated Bismuth (Bi) based deposit (LITESURF), tailored for reliable press-fit pin connections with the ability to accommodate for further miniaturization trends. In this work we discuss the properties of LITESURF plating and its universal use in various PCBs (iSn, iAg and OSP) along with how it is a promising tin alternative for press-fit applications, which can reduce the risk of whisker growth related failures by orders of magnitude.

The hybrid material of PI (with SiC whisker, SiC particle, AlN particle, and diamond particle) is proposed to satisfy the requirement of higher thermal conductivity for the high density package system. The thermal conductivity of the proposed hybrid materials with a moderate amount of doping can be improved to about 6–12 times. The hybrid films are fabricated by mechanical ball-milling process, high speed mechanical stirring and spin-coating process. When the redistribution layer with the improved thermal conductivity (from 0.15 W/m.K to 1.5 W/m.K), the maximal temperature of the Si interposer reduced by 0.89 °C– 3.47 °C (2.50%–4.41%) and maximal thermal gradient decreased by 84.36% when the power density of the chip is among 2 W/m.K–8 W/m.K. And the tensile stress of sy was reduced from −201 MPa to 189 MPa.

Morphological structure has a decisive influence on the microwave absorbing properties of three-dimensional (3D) nano zinc oxide whisker (ZnOw) material. However, due to the complexity of the microstructure, it is still a difficult challenge to develop a fast and accurate optimization method for this kind of nanostructured material. Hence, as an attempt, we enhance the generality of our optimization method, which is based on the effective electromagnetic parameters, by using the imitative prismatic stand volume formula in the radius expression of the equivalent spherical particle. Then, the morphological structure of a nanostructured ZnOw composite is optimized to obtain desired microwave absorbing properties. The results demonstrate that on the one hand the absorbing properties can be further improved by morphology design without changing the existing macroscopic structure; on the other hand a more general approach can be adapted to the fast development of such interesting nanostructured material.

Whisker growth from Sn coatings is a serious reliability concern in electronic packages particularly when the required service life is over a decade e.g in aerospace and defense applications. Until recently whisker growth from tin coatings was mitigated by the addition of a small amount of Pb. However current requirements for lead-free electronics preclude using Pb as an additive requiring an alternate approach to whisker mitigation. Here we present the results of In-alloying on whisker growth from 1 pm and 3 pm thick electroplated Sn films and demonstrate that when 5–10% indium is incorporated throughout the thickness of the Sn films whisker growth is completely eliminated. The reasons behind this mitigation are experimentally explored using X-ray diffraction (XRD) and finite element analysis (FEA). XRD is used to elucidate the role of Cu-In intermetallic formation. FEA is used to investigate the role of In-incorporation in the surface-oxide as revealed by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Based on the analyses it is inferred that the observed mitigation due to In addition occurs due to a multitude of factors including reduction of the driving force for whisker growth due to incorporation of In in the native Sn-oxide film and the formation of Cu-In intermetallics at the substrate-coating interface.