Package Substrate Research Articles

Glass Platform for Co-Packaged Optics

Placing the electrical and photonic chiplets in a single package leads to significant power reduction. Chiplets are connected by fine-line electrical routing over a length of a few millimeters and optical interconnects in the package connect photonic chips with optical fibers for off-package communication. A packaging substrate made of glass with optical waveguides, through glass vias and electrical redistribution layers inside a single-sided cavity enables lower-cost assembly. A single-sided 50 µm deep cavity was etched in glass, and electrical copper lines with 5 µm in height and width were deposited on the floor of the cavity. Ion-exchange (IOX) waveguides with propagation loss of <0.1 dB/cm were fabricated below the glass surface. For flip-chip assembly of photonic chips and optical coupling with the IOX waveguides at the top surface of the glass, all electrical interconnects were located inside the cavity. Photonic chips with silicon nitride waveguides were optically coupled to glass waveguides with a minimum loss of 0.5 dB, achieved by fiducial-aligned flip-chip photonic assembly. A low-profile fiber connector with height of 4.4 mm connects the integrated ion-exchanged waveguides with the optical fibers. Average connector loss of 0.83 dB was demonstrated with physical contact between fibers and IOX glass waveguides.

β-Ga2O3: ultralow-loss and low-permittivity dielectric ceramic for high-frequency packaging substrate

The β-Ga2O3 ceramic exhibits excellent dielectric properties with a Q × f of 133 140 GHz and εr of 9.57. A sub-6 GHz patch antenna was designed and fabricated using a Ga2O3 ceramic substrate, showing great potential for high-frequency applications.

Active Agents Incorporated in Polymeric Substrates to Enhance Antibacterial and Antioxidant Properties in Food Packaging Applications

Active packaging has played a significant role in consumers’ health and green environment over the years. Synthetic polymers, such as poly(ethylene terephthalate) (PET), polyethylene (PE), polypropylene (PP), polystyrene, poly(vinyl chloride) (PVC), polycarbonate (PC), poly(lactic acid) (PLA), etc., and naturally derived ones, such as cellulose, starch, chitosan, etc., are extensively used as packaging materials due to their broad range of desired properties (transparence, processability, gas barrier properties, mechanical strength, etc.). In recent years, the food packaging field has been challenged to deliver food products free from microbes that cause health hazards. However, most of the used polymers lack such properties. Owing to this, active agents such as antimicrobial agents and antioxidants have been broadly used as potential additives in food packaging substrates, to increase the shelf life, the quality and the safety of food products. Both synthetic active agents, such as Ag, Cu, ZnO, TiO2, nanoclays, and natural active agents, such as essential oils, catechin, curcumin, tannin, gallic acid, etc., exhibit a broad spectrum of antimicrobial and antioxidant effects, while restricting the growth of harmful microbes. Various bulk processing techniques have been developed over the years to produce appropriate food packaging products and to add active agents on polymer matrices or on their surface. Among these techniques, extrusion molding is the most used method for mass production of food packaging with incorporated active agents into polymer substrates, while injection molding, thermoforming, blow molding, electrospinning, etc., are used to a lower extent. This review intends to study the antimicrobial and antioxidant effects of various active agents incorporated into polymeric substrates and their bulk processing technologies involved in the field of food packaging.

All-Silicon Packaging Technology for Fiber Bragg Gratings and Its Application in Tilt Sensor

A fiber Bragg grating (FBG) sensor includes three main parts, an FBG, a sensor substrate, and a packaging material. The most commonly used packaging material is epoxy resin adhesive, which is prone to aging and failure, which further affects the performance and life of a sensor. This research provides an innovative approach that enables all-silicon sensor fabrication, where the substrate and packaging material are prepared by silicon glass, which is consistent with silicon optical fiber. In the packaging process, there are three main bottleneck problems, which are considered in this study: 1) highly elastic processing of glass used in the sensor elastic element; 2) thermal fixation between the silicon packaging material and substrate; and 3) selecting appropriate FBG parameters and fixing methods. In the proposed approach, an elastic glass cantilever beam and an FBG are packaged with molten glass powder. The proposed approach is verified by tests, and the test results show that the packaged FBG has good package quality and sensing performance. The theoretical analysis of the wavelength drift phenomenon during the packaging is presented. Finally, the introduced packaging method is applied to the fabrication of an FBG tilt sensor. The sensor shell, cantilever beam, temperature compensation beam, mass block, and other components are designed and made of silicon glass. The sensing principle and performance tests of the tilt sensor have been described in detail. The tilt sensor shows good linearity and repeatability. The presented packaging technology shows good applicability and has promising applications in the fabrication of high-performance FBG sensors.

Wafer-Scale Room-Temperature Bonding of Smooth Au/Ti-Based Getter Layer for Vacuum Packaging.

This study demonstrates room-temperature bonding using a getter layer for the vacuum packaging of microsystems. A thick Ti layer covered with an Au layer is utilized as a getter layer because it can absorb gas molecules in the package. Additionally, smooth Au surfaces can form direct bonds for hermetic sealing at room temperature. Direct bonding using a getter layer can simplify the vacuum packaging process; however, typical getter layers are rough in bonding formation. This study demonstrates two fabrication techniques for smooth getter layers. In the first approach, the Au/Ti layer is bonded to an Au layer on a smooth SiO2 template, and the Au/SiO2 interface is mechanically exfoliated. Although the root-mean-square roughness was reduced from 2.00 to 0.98 nm, the surface was still extremely rough for direct bonding. In the second approach, an Au/Ti/Au multilayer on a smooth SiO2 template is bonded with a packaging substrate, and the Au/SiO2 interface is exfoliated. The transferred Au/Ti/Au getter layer has a smooth surface with the root-mean-square roughness of 0.54 nm and could form wafer-scale direct bonding at room temperature. We believe that the second approach would allow a simple packaging process using direct bonding of the getter layer.

Low-Temperature Direct Bonding of 3D-IC Packages and Power IC Modules Using Ag Nanotwinned Thin Films

Ag has the lowest stacking fault energy of all metals, which allows twin formation to occur more easily. The (111)-preferred orientation Ag nanotwinned films is fabricated by either sputtering or evaporation method exhibit columnar Ag grains grown vertically on Si substrates. Ag nanotwinned films have a (111)-preferred orientation with a density about 98% and diffusivity that is 2 to 5 orders of magnitude higher than those of (100) and (110) surfaces. Low temperature direct bonding with (111)-oriented Ag nanotwins films is proposed to fulfil the requirements for wafer-on-wafer (WoW), chip-on-wafer (CoW), and chip-on-wafer-on-substrate (CoWoS) advanced 3D-IC packaging, with the process temperature drastically reduced to 100°C. Such an innovative bonding method also provides a promising solution for die attachment of Si chips with DBC-ceramic substrates for power module packaging.

The Adhesion of Protective Coatings to Novel Trivalent Cr Metal / Cr Oxide Coatings Used for Packaging Applications

When manufacturing canned goods, the aim is to create a shelf-stable product that will keep for anywhere between one and five years (under ambient storage conditions). It is for this reason that steel, which offers desirable mechanical properties, is often used. However, steel is known to undergo corrosion thus impacting final product quality. It is therefore common for packaging substrate materials to have a protective metallic coating which is further coated with a lacquer to shield both the substrate material from the cans contents and vice-versa.One example of a coated packaging product is Electrolytic Chromium Coated Steel (ECCS) which is typically used for lacquered applications [1]. This chrome coating is deposited from a chromic acid bath containing Cr (VI) and results in a steel substrate covered in a bi-layer chromium metal (~20 nm) /chromium (hydr)oxide (~7 nm) layer. This substrate is then overcoated with lacquer which is usually epoxy based.Once the can is lacquered and filled, a retort process is used to pressure cook its contents. This is undertaken at 121 °C at a pressure of 1 bar for 90 minutes. This retort process has proven to be detrimental to the adhesion of protective lacquers applied to the substrate material which serve to prevent corrosion caused by the cans contents [2,3]. At elevated temperatures and pressures, the lacquers exhibit porosity which creates an ion pathway for the cans chemical contents to migrate through the coating and interact with the substrate. This interaction initiates localised corrosion on the surface causing de-adhesion of the lacquers through localised anodic metal dissolution.However, both Cr (VI) and Bisphenol-A, a chemical commonly added to epoxy lacquers to enhance thermal and chemical stability, have been identified as substances of concern by REACH - a regulation associated with the restriction of chemicals that are harmful to human health. Thus, a dual issue exists of finding a suitable substrate replacement for ECCS and investigating the adhesion of lacquers to this substrate. Coatings made with Trivalent Chromium Coating Technology (TCCT®) are currently being developed as a potential replacement for ECCS. TCCT® production has developed to consist of a two-electrolyte process. Various issues including coating in-homogeneity have previously been reported [4]. Additionally, lacquers to which Bisphenol-A have not intentionally been added (BPANI) have been manufactured.To ensure that TCCT® substrates are successful, it is important that they perform comparably to existing products such as ECCS. For this reason, a range of TCCT® substrates varying in Cr (III) oxide coating weight (1.8 mg.m-2 to 23.35 mg.m2) have been experimentally analysed for their lacquer adhesion (both epoxy-phenolic and BPANI) in simulated industrial retort conditions, using scratch testing. They have also been analysed for their surface electrochemical activity utilising the scanning vibrating electrode technique (SVET) which is a technique designed to spatially resolve areas of dissimilar electrochemical activity.A Cr (III) oxide coating weight of approximately 8-10 mg.m2 was found to be critical to the adhesion of the lacquers. In addition, the SVET scans illustrated a pronounced rate of increase in anodic activity on the substrates coated with smaller amounts of Cr (III) oxide. Indeed, higher coating weights exhibited a lower total anodic and cathodic activity alluding to the insulating and inert nature of Cr (III) oxide.[1] B. Boelen, H. den Hartog, H. van der Weijde, Product performance of polymer coated packaging steel, study of the mechanism of defect growth in cans, Prog. Org. Coatings. 50 (2004) 40–46. https://doi.org/10.1016/J.PORGCOAT.2003.09.011.[2] A. Allman, E. Jewell, A. de Vooys, R. Hayes, Inter-layer Adhesion Performance of Steel Packaging Materials for Food Cans Under Retort Conditions, J. Packag. Technol. Res. 2 (2018) 115–124. https://doi.org/10.1007/s41783-018-0033-6.[3] A. Allman, E. Jewell, A. Vooys, R. Hayes, H.N. McMurray, E. Jewell, R. Hayes, Food packaging simulant failure mechanisms in next generation steel packaging, Packag. Technol. Sci. 32 (2019) 1–15. https://doi.org/10.1002/pts.2448.[4] A. Allman, J. Whiteside, E. Jewell, C. Griffiths, N. McMurray, A. de Vooys, Surface modification of Cr(III) packaging substrates for enhanced adhesion via citric acid processing, Surfaces and Interfaces. 20 (2020) 100545. https://doi.org/10.1016/J.SURFIN.2020.100545.

(Invited) Tutorial on Semiconductor Advanced Packaging

In this lecture semiconductor advanced packaging is defined. The kinds of advanced packaging are ranked based on their interconnect density and electrical performance and are grouped into 2D, 2.1D, 2.3D, 2.5D, and 3D IC integration, which will be presented and discussed. Key enabling technologies such as flip chip and fan-out will be briefly mentioned. The trends and challenges (opportunities) of advanced packaging will be discussed. Also, in this lecture, chiplet design and heterogeneous integration packaging are defined. The chiplet design and heterogeneous integration packaging such as those given by Xilinx, AMD, Intel, TSMC, and Samsung will be presented and discussed. The lateral communication between chiplets such as the silicon bridges embedded in organic build-up package substrate (Intel’s EMIB and IBM’s DBHi) and fan-out epoxy molding compound (Applied Materials’ chip-first face-up, Unimicron’s chip-first face-down, TSMC’s LSI, SPIL’s FO-EB, ASE’s sFOCoS, IME’s EFI, and Amkor’s S-Connect Fan-Out Interposer) as well as flexible bridges will be presented. Key enabling technologies such as thermocompression bonding and hybrid bonding will be briefly mentioned. The trends and challenges (opportunities) of chiplet design and heterogeneous integration packaging will be discussed.

Promotion of High-Speed Copper-Filling Performance for Interconnections with Increasing Aspect-Ratio Using Compound Additives.

Interconnections are essential for integrating the packaging substrate, and defect-free copper-filling can further improve the reliability in through holes (THs). The coating properties and filling processes are mainly dominated by the interplays among additives in the direct current electroplating. The acidic copper sulfate electroplating solution contained three typical convection-dependent additives and chloride ions (Cl−). The THs with aspect ratios (ARs) of 6.25, 5, and 4.17 (thickness of 500 μm) were selected as the study subjects. The effects of Cl− and ARs on the interactions among the additives were investigated in detail using electrochemical measurements, which were verified by the THs filling experiments. The additive compounds present a convection enhanced inhibition effect and cathodic polarization, leading to a copper filling capacity increase with ARs and the amelioration of copper compactness and corrosion resistance. The defect-free copper filling of THs and a uniform mirror bright surface circuit can be achieved simultaneously using compound additives at a relatively high speed.

Non‐leaching antimicrobial cellulose‐based membrane for food packaging: Effect on food‐borne bacteria, probiotic bacteria, and spoilage of Karish cheese

Hydroxyethyl cellulose (HEC) was grafted with a synthesized monomer, 1-butyl-3-vinylimidazolium bromide (BVIm)[Br], and methyl acrylate (MA) to obtain antimicrobial membranes for food packaging. The film elasticity increased by increasing BVIm[Br] content while the stress strength values were 3.03 of HEC-MA, 2.01 of HEC-MA-BVIm[Br]-I, and 0.86 of HEC-MA-BVIm[Br]-II. Minimum inhibitory concentrations (MIC) and minimum cidal concentrations (MCC) values of the (BVIm)[Br] monomer were about 30 and 46 mg/ml for gram-negative bacteria 80 and 60 mg/ml for gram-positive bacteria. Films retarded the spoilage of Karish cheese without negative effects on lactic acid and probiotic bacteria. Samples with a protein content of 14% with very low fat (0.5%) and ash content (3.6%) make this cheese a good candidate for low-calorie diets. Free radical activities of ABTS and DPPH solutions were suppressed for all HEC-grafted substrates. HEC-grafted films do not impair the starter organisms as panelists liked the treated cheese with acceptable taste and smell. Novelty impact statement Non-leaching polymeric coatings have been employed to provide antimicrobial substrates for food packaging. Hydroxyethyl cellulose (HEC) was grafted with a synthesized monomer, 1-butyl-3-vinylimidazolium bromide (BVIm)[Br], and methyl acrylate (MA) to preserve Karish cheese without a negative impact on lactic acid and probiotic bacteria. Sensory panelists liked the coated cheese samples with acceptable taste and smell.

Characterization of Optical Redistribution Loss Developed for Co-Packaged Optics

We previously proposed a new package substrate called active optical package (AOP) substrate to realize co-packaged optics. An optical redistribution technology on silicon photonics dies was developed to fabricate the AOP substrate. It is composed of a polymer waveguide, with a mirror-based optical coupling between the polymer and silicon waveguides. The fabricated optical redistribution loss was characterized in this study. An average loss of approximately 4 dB and wavelength dependent loss of ±1 dB were observed for the wavelength range of 1460–1600 nm. It was shown that the low wavelength-dependent optical redistribution was available owing to the broadband characteristics of mirror-based optical coupling and polymer waveguide.

Smart, Self-cleaning coating Based Ultra-Hydrophobic Copolymer Nano-composites

Ultra-hydrophobic (UH) surfaces have gained a great attention due to the high potential for tremendous applications. Simplified preparation technique was used with low-cost value to produce UH nano-composites coating. Copolymer nano-composites have numerous advantages as a flexible coating through the huge covering volume/area. The molecular weight of prepared copolymer was defined with gel permeation chromatography. UH coating films were investigated with differential scanning calorimetry, dynamic laser scattering, transmission electron microscopy, atomic force microscope, and dielectrically study. The contact angle of UH coating film and surface area were measured. Copolymer coating with 9% loaded ratio of nanocomposite given 132° contact angel with excellent nano particle size, and surface area. The zeta potential results indicated to perfect stability of ecofriendly emulsified coating. The main aim of research was verified the ability of prepared copolymer nano-composites as a UH self-cleaning coating film on different applications especially solar panel and packaging substrates.

Topology for Substrate Routing in Semiconductor Package Design

In this work, we propose a new signal routing method for solving routing problems that occur in the design process of semiconductor package substrates. Our work uses a topological transformation of the layers of the package substrate in order to simplify the routing problem into a problem of connecting points on a circle with non-intersecting straight line segments. The circle, which we call the Circular Frame, is a polygonal schema, which is originally used in topology to study the topological structure of 2-manifolds. We show through experiments that our new routing method based on the Circular Frame competes with certain grid-based routing algorithms.

The Atmospheric Corrosion of Trivalent Cr Metal / Cr Oxide Coatings for Packaging Steels

The superior mechanical properties associated with steel mean that it is heavily utilized in many industries including automotive, and construction (1). Although steel offers desirable mechanical properties such as toughness and tensile strength, it is known to corrode, this having cost implications and raising safety concerns, for instance within the food packaging industry. Thus, steel is often used in conjunction with a coating as a preventative measure for corrosion.Within the food packaging industry, steel is often coated with a thin (~20 nm thick) chromium metal-chromium oxide coating, the product being referred to as electro chromium coated steel (ECCS), which is produced during a continuous electrodeposition process whereby a low carbon steel strip passes through baths of chromic acid electrolyte containing hexavalent chromium, Cr(VI). The final coating consists of two distinct layers; a 20-110 mg.m-2 chromium underlayer and a 2-20 mg.m-2 native (hydr)oxide outer layer (2). REACH, a regulation associated with the restriction of chemicals that are harmful to human health and the environment, have made a legislation that has imposed a restriction on the use of Cr(VI) due to its carcinogenic nature (3). This impact has resulted in the drive of the steel packaging industry to find a suitable, non-toxic replacement for ECCS.Coatings made with Trivalent Chromium Coatings Technology (TCCT®) are currently being developed as a potential replacement for ECCS. TCCT® production has developed to consist of a two-electrolyte process involving an aqueous solution of Cr(III) sulphate, sodium sulphate, sodium formate and sulphuric acid leading to the formation/application of a bilayer coating. Various issues including coating inhomogeneity have previously been reported (4).Due to the low coating weights involved, packaging products such as ECCS and TCCT® are also used in conjunction with an organic coating. Thus, they could be susceptible to various modes of organic coating failure including corrosion-driven cathodic delamination, whereby a coating becomes physically separated from the underlying substrate, a key failure process that affects organically coated metal products in high humidity, such as those experienced during storage in the packaging industry. Cathodic delamination occurs when an electrolyte comes into contact with the metallic substrate at a flaw in the organic coating at which anodic metal dissolution occurs. This is coupled to the cathodic oxygen reduction reaction which takes place at the delamination front. The hydroxide ions produced during the cathodic reduction of oxygen, or a reaction intermediate, disturb the bonds between the substrate and coating leading to adhesion failure and delamination of the coating (5).To ensure that new products such as TCCT® are successfully incorporated into the market it is important that they are comparable in performance to existing products. For example, TCCT® must provide sufficient delamination resistance. The scanning kelvin probe (SKP) is a technique which measures corrosion potential under a thin electrolyte film and organic coatings, which can be used to create a surface potential map (6).This study makes use of the SKP to investigate the rate of cathodic delamination as a function of TCCT® Cr(III) oxide (varying from 1.8 mg.m-2 to 23.35 mg.m-2). The results will help to determine the minimum satisfactory chromium oxide coating weight needed for commercial TCCT®.It was found that higher Cr(III) oxide coating weights had a positive effect on inhibiting cathodic delamination, confirming the mechanism. The results were explained using complementary electrochemical data including OCP measurements as well as potentiodynamic polarisation which showed that higher TCCT® Cr(III) oxide coating weights were acting to supress the cathodic reaction.The results also highlighted that a TCCT® Cr(III) oxide coating weight of around 7 mg.m-2 is sufficient with regards to resisting cathodic delamination completely. This work has determined that the Cr(III) oxide coating weight value is very important with regards to improving coating coverage and resisting cathodic delamination.References Singh MK. Application of Steel in Automotive Industry Application of Steel in Automotive Industry. Int J Emerg Technol Adv Eng. 2016;6(7):2250–459.Wijenberg J, Steegh M, Penning JP, Portegies Zwart I. Wo 2014/079909 2014.Petry T, Knowles R, Meads R. An analysis of the proposed REACH regulation. 2007;44(2006):24–32.Allman A, Whiteside J, Jewell E, Griffiths C, McMurray N, de Vooys A. Surface modification of Cr(III) packaging substrates for enhanced adhesion via citric acid processing. Surfaces and Interfaces. 2020 1;20:100545.Øystein O, Knudsen AF. Corrosion Control Through Organic Coatings. Second. Schweitzer PA, editor. New York: Taylor & Francis; 2017.Stratmann M, Streckel H, Feser R. A new technique able to measure directly the delamination of organic polymer films. Corros Sci. 1991;32(4):467–70.

Electroless Ni–B sealing on nanoporous anodic aluminum oxide pattern: deposition and evaluation of its characteristic properties

Suitable coatings on electronic packaging substrates are generally preferred to surround the internal components, protect them from adverse conditions, and improve heat-dissipating performance. Such coatings are developed using different deposition techniques to attain a cosmetic appearance on a single sheet, preferably aluminium alloys. These coatings have to overcome certain challenges, including heat dissipation and mechanical robustness. In this study, a nickel–boron (NiB) binary alloy was sealed and deposited on an already developed nanoporous anodic aluminium oxide (AAO) pattern using an electroless deposition method. The performance is studied with respect to different deposition times. The resulting NiB layer has a nano nodular-like morphology with a 0.95-μm layer thickness. The structural analysis shows a mixture of amorphous and crystalline nature with sharp Ni peaks (111), (220), including the crystallite size of 377 nm. Compared with the bare Al substrate, the 1-hr NiB sealing on AAO has a significant reduction in thermal resistance (Rth) to 29.65%, a rise in junction temperature (Tj) to 27.36%, and improved bulk thermal conductivity (k) to 50.1%. In addition, this binary NiB exhibits a roughness of 0.89 μm, an indentation hardness of 2560 MPa, and a scratch hardness of 8764 MPa. Results show enhanced properties of the AAO sealed binary NiB coating as a feasible option for packaging substrates.

Urethane-Foam-Embedded Silicon Pressure Sensors including Stress-Concentration Packaging Structure for Driver Posture Monitoring.

We propose urethane-foam-embedded silicon pressure sensors, including a stress-concentration packaging structure, for integration into a car seat to monitor the driver’s cognitive state, posture, and driving behavior. The technical challenges of embedding silicon pressure sensors in urethane foam are low sensitivity due to stress dispersion of the urethane foam and non-linear sensor response caused by the non-uniform deformation of the foam. Thus, the proposed package structure includes a cover to concentrate the force applied over the urethane foam and frame to eliminate this non-linear stress because the outer edge of the cover receives large non-linear stress concentration caused by the geometric non-linearity of the uneven height of the sensor package and ground substrate. With this package structure, the pressure sensitivity of the sensors ranges from 0 to 10 kPa. The sensors also have high linearity with a root mean squared error of 0.049 N in the linear regression of the relationship between applied pressure and sensor output, and the optimal frame width is more than 2 mm. Finally, a prototype 3 × 3 sensor array included in the proposed package structure detects body movements, which will enable the development of sensor-integrated car seats.

Structure and sintering behavior of BaO–SrO–B2O3–SiO2 sealing glass for Al2O3 ceramic substrates

BaO–SrO–B2O3–SiO2 sealing glass for Al2O3 ceramic substrates was prepared and the effect of B2O3 on its structure, sintering behavior, and properties was studied. Owing to the fluxing action of B2O3, the glass transition temperature, sintering temperature, and crystallization temperature of the sealing glass were decreased with increasing B2O3. With an increase in the B2O3/SiO2 ratio, the average bridge oxygen number of the glass network first increased and then decreased, and the boron abnormality phenomenon was detected at a B2O3/SiO2 ratio of 0.55, at which the polymerization degree of the glass network was maximized. Furthermore, the precipitation of BaAl2Si2O8 crystals was promoted and the crystallinity of the sealing glass was increased, inhibiting sintering densification and weakening the material. The sealing glass with a B2O3/SiO2 ratio of 0.55 sintered at 800 °C for 10 min showed the best properties: a thermal expansion coefficient of 7.89 × 10−6 K−1, flexural strength of 114.28 MPa, Vickers hardness of 622.98 HV, dielectric constant of 12.14, and a dielectric loss value of 4.11 × 10−3. After the sealing glass was co-sintered with the Al2O3 ceramic substrate, the interface was tightly bonded. This indicates the great potential applicability of BaO–SrO–B2O3–SiO2 sealing glass for Al2O3 ceramic substrate packaging.

Microstructural evolution, fracture behavior and bonding mechanisms study of copper sintering on bare DBC substrate for SiC power electronics packaging

Robust bonding of Cu quasi-nanoparticles sintering for Ag coated chip and bare copper substrate was achieved. The effect of temperature, pressure and time on the sintering bonding strength and microstructural evolution was deeply studied. 36.5 MPa shear strength was achieved when applied 5 MPa pressure. By increasing to 30 MPa, it shows the best die shear strength of 116 MPa, accomplished with a sintering temperature of 250 °C for 3 min. Temperature also influenced the shear strength a lot. Between 210 °C and 230 °C can already provide strength over 30 MPa. When increased to 270 °C, the strength was extremely enhanced to over 120 MPa. Inspection on the fracture behaviors and cross-section of sheared off samples was conducted by SEM, EDS, and XRD. It is found that low bonding performance is due to both of the incomplete burnt out of organics and incomplete Cu QNPs sintering. In addition, high bonding is account for the positive effect of pressure and temperature on promoting the necking growth, sintering networking formation, pores isolation and brittle-ductile fracture transformation. The recommended sintering profile is 250 °C, 3 min, 20 MPa. Finally, the feasibility for SiC MOSFET power electronics DA was verified by testing its static characteristics at both room temperature and 150 °C.

Self-Assembled Vector Curvature Sensor Based on Vernier Effect

A novel fiber Fabry-Perot interferometer (FPI) vector curvature sensor based on Vernier effect is proposed and demonstrated. The triangular-distributed sensing structure is fabricated by self-assembly of FPI and single-mode fiber (SMF). When the device is bent in any orientation, a direction-dependent wavelength shift of the interference pattern is produced because the sensing fiber always deviates from the neutral plane. In order to overcome the trade-off between high sensitivity and large dynamic range, we connect the reference fiber and the sensing fiber to produce the Vernier effect. Without affecting the measurement range of the sensing structure, the sensitivity of the self-assembled sensor based on Vernier effect is amplified by 5 times and 3.6 times respectively by using different FPIs as sensing arm. The experimental results show that the sensing structure has good stability and repeatability. Compared with the substrate packaging, the fiber FPI sensing structure based on self-assembly can realize miniaturization, which is conducive to the application of the sensor in medical detection and artificial intelligence.

Analysis of a Novel Resistive Film Absorber for Suppression of Electromagnetic Radiation in System-in-Packages

This paper presents a new method to suppress the electromagnetic radiation between the heatsink and packaging substrate in the system-in-package by using a resistance film absorber. The proposed absorber is designed with the indium tin oxide sputtered on both sides of the glass substrate, and the top layer adopts the combination of Jerusalem cross-shaped, ring-shaped, and L-shaped resistive film to expand the bandwidth. The unit size of the absorber is 0.14 λ L × 0.14 λ L and the thickness is 0.049 λ L . It has an absorptivity of more than 90% in the frequency range of 21 GHz to 55 GHz with polarization insensitivity, and angular stability. Moreover, the radiated electric field from the chip package at 3 m is significantly reduced when employing the proposed absorber, and the maximum suppression of the electric field reaches 18 dB. Finally, the measurement results are carried out to verify the simulation results. Both simulation and experiment results demonstrate that the proposed absorber has excellent radiation suppression, which can be properly applied to electromagnetic interference suppression of the printed circuit board.