High-temperature Electronic Packaging Research Articles

Facile synthesis of Cu-Sn nanoparticle film and its bonding mechanism for power electronic packaging

The Cu-Sn full intermetallic compound is a promising high-temperature electronic packaging material, while its preparation is usually time-consuming. In this work, a novel dual-beam laser co-deposition method was proposed to prepare Cu-Sn nanoparticle film for power electronic packaging with high bonding efficiency. Various Cu-Sn contents were prepared to reveal the bonding mechanism of the full intermetallic compound structure. The results show that joints with a Cu content ranging from 20 wt% to 80 wt% could form full intermetallic compounds within 2 min with the shear strength reaching 120 MPa. Specifically, Cu6Sn5, 'island-like' Cu3Sn, and sintered Cu generated successively in the bondline center with the increasing Cu content. All failures occurred within the bondline indicating a higher interface bonding quality, while the 'island-like' Cu3Sn enhanced the shear strength. This die attach process is compatible with current commercial SiC die attach process with lower material cost as well as high efficiency, enabling the Cu-Sn nanoparticle film to be a promising material for high-reliability power electronic packaging.

Bonding with brazing alloys as high-temperature interconnection filler through self-propagating exothermic reaction

There has been growing interest in wide bandgap (WBG) semiconductors including SiC and GaN due to the increasing demands for electronic devices serving at high temperatures. However, to maximise the potential capacity of WBG devices, new high-temperature interconnection materials and processes are indispensable as the current existing Sn-based solder alloys and bonding processes developed for Si devices are unable to meet the reliability requirements. In the present work, reactive brazing alloys including Cu-15Ag-5P and Incusil (Ag-27.25Cu-12.5In-1.25Ti) with melting points above 600°C have been utilized as the interconnection materials which offer excellent properties under high operation temperature. The self-propagating exothermic reaction (SPER) was applied for the bonding process via an intense rapid local heating and cooling at a millisecond scale. The strong Cu/Cu-15Ag-5P/Cu and Cu/Incusil/Cu sandwich bonded structures have been created with the assistance of SPER, where the nanofoil was applied from the outside of stacked structures as an external heat source and the bonding process was conducted in the ambient atmosphere without using flux. It has been found that the P element in Cu-15Ag-P alloy has the self-flux effect, which is beneficial for the ultra-fast interfacial reaction process. The experiments where the nanofoil was placed inside of stacked structures between two sheets of brazing alloys have also been conducted, which exhibited the well-bonded interface microstructures between nanofoil and brazing alloys. The outlook on the design for practicality and industrial uses for SPER-assisted bonding with brazing alloys has also been discussed, as a potential viable assembly route for the high-temperature and high-power electronics packaging.

Pt/HTCC Alumina based Electronic Packaging System and Integration Processes for High Temperature Harsh Environment Applications

Electronic devices capable of operation at 500°C are required for long term Venus surface missions, as well as for in situ monitoring and control of next generation aeronautical engines. High temperature sensors and electronics can also find many applications in military, and energy and automobile industries. Various silicon carbide (SiC) sensors and electronic devices have been developed for operation at 500 °C, and a compatible packaging system is needed for long term test and deployment of these high temperature devices. High temperature co-fired ceramics (HTCC) alumina with platinum (Pt) conductor was proposed for high temperature electronic packaging. A prototype Pt/HTCC alumina packaging system including chip-level package and circuit board has been briefly reported previously for long-term electrical testing of SiC integrated circuits at 500 °C, and brief testing at much higher temperatures. HTCC alumina is an excellent dielectric material with acceptable dielectric constant and low dielectric loss over wide temperature and frequency ranges. Pt is chemically noble and can be co-fired with HTCC alumina in air ambient producing a viable electronic packaging material system for high temperature applications. This paper presents a more detailed description of this packaging system including prototype low power packages and circuit boards based on HTCC alumina and Pt metallization for 500°C and other harsh environment applications. The key technical considerations for chip-level packaging and circuit board assembly, including materials and processes for 500 °C durable wire-bonding and SiC die attach, and integration of multi-chip circuit boards, are presented. Experimental test results of this packaging approach applied to SiC integrated circuits at 500 °C and 700°C are discussed as well.

Microstructure and mechanical properties of electroplated Ni-Sn TLP bonded joints with different bonding and aging times

Much attention has been drawn to the Ni Sn transient liquid phase (TLP) bonded joints for high-temperature electronic packaging applications since their inception. A comparative study of Ni Sn TLP bonded joints with different interlayers was conducted. The evolution of microstructure and mechanical properties of joints with different bonding times was also investigated. In addition, the high-temperature (300 °C) thermal reliability of the Ni Sn TLP bonding joints was explored with aging times from 0 h to 100 h. The results show that the electroplated Ni Sn TLP bonding joint exhibited a slightly higher average shear strength than when using a Sn foil and Sn 96.5 Ag 3.5 paste. Also, the average shear strength of the electroplated Ni Sn TLP bonded joints was greatly improved as the bonding time increased from 0.5 h to 5 h, while there was a continuous decrease in the average shear strength with the aging time from 4 h to 100 h. During the aging, the Ni/Ni 3 Sn 2 interface was the preferential site for the nucleation of the newly formed Ni 3 Sn 2 intermetallic compounds (IMCs). Furthermore, the cross-sectional microstructure of the shear fractured joints after aging from 4 h to 100 h indicates that the shear fractures propagated through both the Ni 3 Sn 4 IMCs and the Ni 3 Sn 2 /Ni 3 Sn 4 interface. • Joints using electroplated Sn were stronger than that using Sn foil or solder paste. • The average shear strength of joints increased with bonding time from 0.5 h to 5 h. • Prolonged aging time (from 4 h to 100 h) deteriorated the shear strength of joints. • Ni/Ni 3 Sn 2 interface was the preferential site for nucleation of Ni 3 Sn 2 during aging. • Aged joints shear fractured through both Ni 3 Sn 4 IMCs and Ni 3 Sn 2 /Ni 3 Sn 4 interface.

Anisotropic highly conductive joints utilizing Cu-solder microcomposite structure for high-temperature electronics packaging

The miniaturization of power conversion systems requires high-power density operation of power modules, causing the heat-density increase. Therefore, it is essential to develop bonding technology to realize highly thermally conductive and reliable high-temperature joints. In this study, we propose a novel anisotropic microcomposite (AMC) joint that integrates a lotus-type porous Cu (LPC) sheet and Sn-based solder for high-temperature electronic applications. The AMC joint was successfully fabricated by infiltrating the molten solder into the unidirectional pores of the LPC sheet during a simple reflow process. Steady-state thermal conductivity measurements for a uniquely designed specimen revealed its equivalent thermal conductivity (142.4 W/m·K), 2.5 times higher than the solder. Finite element simulations supported its excellent thermal performance by investigating the heat flux distribution and thermal conductivity prediction that utilize a three-dimensional image-based constructed model. In addition, the aging test at 200 °C for 1008 h clarified a stable shear strength of over 46 MPa. This indicates a reliable mechanical performance at 200 °C, which is only 20 °C below the melting point of the solder. These experimental and numerical studies proved the potential of the novel joint as a high-temperature electronics joint and offered possible mechanisms for its thermal and mechanical property enhancement.

Bismaleimide/Phenolic/Epoxy Ternary Resin System for Molding Compounds in High-Temperature Electronic Packaging Applications

Development of a new packaging material with superior high-temperature stability is becoming increasingly crucial in high-power and high-density electronics industry. In this study, we employed bis(3-ethyl-5-methyl-4-maleimidephenyl)methane (BMI), para-xylene phenolic resin (PF), and triphenylmethane novolac epoxy resin (EP) as matrix resins to develop high-temperature-stable BPE ternary resin molding compounds for power device packaging. BMI was first melt-blended with PF to obtain the premix with a reduced softening point for meeting the requirement of melt-kneading process. 2-Ethyl-4-methylimidazole with a dosage of 2 wt % of the ternary resins, could effectively promote the curing reaction, making the molding process of BPE molding compounds be compatible with that of the existing epoxy molding compounds (EMC). The introduction of BMI component could enhance the chain rigidity and heat resistance of cured resins. When the BMI content was more than 70 wt % of the ternary resins, the cured BPE molding compounds exhibited the glass transition temperature and initial decomposing temperature larger than 250 and 400 °C, respectively, indicating a much superior thermal performance to that of the cured EMC. Moreover, the flexural performance and the adhesion strength with copper at 260 °C, high-temperature aging resistance, dielectric properties, and thermal conductivity of the cured BPE molding compounds were also improved compared with those of the cured EMC. This study provides a promising strategy for preparing heat-resistant electronic packaging molding compounds.

Microstructure evolution and mechanical properties changes during the formation of full Cu41Sn11 joint in high-temperature electronic packaging

In this study, Cu/Sn/Cu structure under a pressure of 1.5 N was soldered at 390–450 °C. Then, microstructure evolution and changes in mechanical properties of solder joint during the formation of full Cu41Sn11 joint were systematically analyzed. Experimental results showed that Cu6Sn5 and Cu3Sn were observed in the interfacial region at 420 °C in the early stage of soldering. The Cu/Sn/Cu structure completely transformed into Cu/Cu3Sn/Cu at 1 h. With the further progress of the interfacial reaction, Cu41Sn11 appeared and grew at the expense of Cu3Sn. Eventually, the full Cu41Sn11 joint was formed at 10 h. The growth of Cu41Sn11 was controlled by volume-diffusion. Moreover, diffusion activation energy of Cu41Sn11 was about 108.19 kJ/mol. The shear strength of full Cu3Sn joints was 45 MPa, while that of the solder joints with 25, 50, 75 and 100% Cu41Sn11 was 50, 52.2, 59 and 64.5 MPa, respectively. For full Cu3Sn and full Cu41Sn11 joints, respectively, the fracture occurred partly within intermetallic compounds (IMCs) layers and partly along the Cu/IMC interface. However, for the joints composed of Cu3Sn and Cu41Sn11, all fractures occurred in the IMCs layer. Besides, all IMCs joints were brittle fracture, and the fracture of Cu3Sn was mainly intergranular, while the fracture that occurred in Cu41Sn11 was mainly transgranular.

Ultrasonically enhanced flux-less bonding with Zn-5Al alloy under ambient condition for high-temperature electronics interconnects

Zn-5Al eutectic alloy is a promising Pb-free solder suitable for high-temperature electronics packaging. However, the soldering with Zn-5Al alloy is undermined by its poor oxidation resistance and wettability in ambient atmosphere, which also demands significant time to complete if transient liquid phase soldering (TLPS) is required. In this work, the TLPS assisted by ultrasonic vibration (USV) under ambient condition without flux has been performed to enhance and accelerate interfacial reactions between Zn-5Al and Cu or Ni substrate. It has been found that the resultant full intermetallic compounds (IMCs) joints with uniform microstructure can be formed within 1 min and 3 min on Cu and Ni substrate, respectively, without flux or protective inert gases. The IMCs resulted from the interfacial reactions have been identified after the completion of TLPS process. For the ultrasonic-assisted TLPS (U-TLPS) of Zn-5Al onto Cu substrate, the joints consist of three IMC layers, CuZn, Cu5Zn8, and CuZn with the residual oxide fragments remained at the central line inside of IMC Cu5Zn8, where Al is rich likely due to the segregation of element Al during the TLPS process. For the U-TLPS of Zn-5Al onto Ni substrate, three IMC layers, Ni5Zn21, NiAl and Ni5Zn21 IMC were also observed, with the porous Ni5Zn21 IMC layers present in adjacent to the Ni substrate. Both residual oxide fragments in the Zn-5Al/Cu joints and porous Ni5Zn21 IMC in the Zn-5Al/Ni joints could potentially deteriorate mechanical integrity of the joints, which is yet to be understood.

Nano Ag sintering on Cu substrate assisted by self-assembled monolayers for high-temperature electronics packaging

Sintering of nano Ag paste on bare Cu has attracted more interests recently for high-temperature electronics packaging, which offers the advantages of high reliability, cost-effective and direct bonding process. However, the current bonding methods normally need a protective atmosphere or metallization on Cu substrate to avoid oxidation. In this study, self-assembled monolayers (SAMs) were deposited on Cu substrate to suppress oxidation prior to nano Ag sintering. Thermal-compression bonding process of Cu/nano Ag/Cu joints was conducted and analysed with and without SAMs treatment. The cross-sectional characterization and shear tests were conducted to evaluate the influence of SAMs treatment. When SAMs applied, shear strength of 12.72 MPa has been achieved in the ambient atmosphere, which is much higher than the value without SAMs treatment (3.77 MPa). It has been identified that the shear mode changed from the interfaces of sintered nano Ag/Cu to inside of sintered nano Ag due to the applied SAMs. This technological approach provides a tangible and cost-effective method for high-temperature electronics packaging.

Application of Alumina-Based Ceramic Paste for High-Temperature Electronics Packaging

Abstract Alumina-based die-attach and encapsulation for high-temperature (300–500 °C) electronic packaging were investigated. The alumina paste material comprises aluminum dihydric phosphate as a binder and alumina powder as a filler with embedded nano-aluminum nitride and nanosilica powders to promote its curing process, reduce its curing tension, and increase its bond shear strength. The chip-to-substrate bond strength was enhanced and met the MIL-STD-883 2019.9 requirements for die-attach assembly. Its encapsulation property was improved with fewer cracks compared to similar commercial ceramic encapsulants. The die-attach material and encapsulation properties tested at 500 °C showed no defect or additional cracks. Thermal aging and thermal cycling were carried out on the samples. X-ray photo-electron spectroscopy (XPS) analysis revealed a higher oxygen bonding percentage for the 10% nanosilica ceramic sample than the samples with no nanosilica. XRD peak broadening is largest for the 10% nanosilica ceramic, which indicated smaller crystallite sizes. The smaller crystallite size for the 10% nanosilica sample introduces a larger microstrain to the alumina crystal structure. FTIR revealed the presence of alumina-silicate bonds on these samples with the largest amount present in the 10% nanosilica samples. Si-O and Al-O bonds were observed from FTIR on nanosilica samples especially the higher than 10% nanosilica samples. SEM and energy dispersive X-ray (EDX) results showed a uniform bond line for the 10% sample and uniform material distribution.

Laser-Assisted Sintering of Silver Nanoparticle Paste for Bonding of Silicon to DBC for High-Temperature Electronics Packaging

This article presents the development of a laser-assisted sintering method of a silver nanoparticle paste for bonding of a silicon chip to a direct bonded copper (DBC) substrate for high-temperature electronics packaging applications. The effects of the bonding parameters such as laser power, bonding pressure, and time on shear strength were studied. For comparison, samples using hotplate bonding were also produced and studied. Shear strength, cross section, and fracture surface analysis were carried out in reliability studies. The results show that shear strength of 10 MPa can be achieved at the bonding pressure of 3 MPa, laser power of 70 W, and a very short irradiation time of 1 min. The shear strength reached 20 MPa when the irradiation time was increased to 5 min. The research indicates that the shear strength can be improved by increasing the bonding pressure, laser power, and hence the sintering temperature and the irradiation time. The laser-assisted method with a short irradiation time of 5 min can produce the same level of shear strength as compared with the hotplate-based approach requiring a sintering time of tens of minutes. With the ability of fast and localized heating effect, the laser-assisted sintering method can improve the manufacturing efficiency for packaging of high-temperature electronics and sensors.

Study on Microstructure and Shear Property of Cu/In-xCu/Cu Transient Liquid Phase Bonding Joints

Transient liquid phase (TLP) bonding is a promising interconnection technology for high-temperature electronic packaging. In this paper, the effect of Cu particles on the microstructure and shear property of Cu/In-xCu/Cu TLP joints was investigated. The results show that Cu/In-xCu/Cu joint is mainly composed of an In and Cu11In9 phase after bonded for 60 min. A small amount of Cu2In phase forms at the interface of Cu/Cu11In9 with bonding time exceeding 300 min. The bonding efficiency and shear property of In-Cu mixed particle solder joint are superior to that of the In foil solder joint, because the bonding time was reduced and the shear strength of the solder joint was improved. The phase composition of Cu11In9 and Cu2In in the joint increased, the porosity decreased and the shear strength increased with increasing Cu content. When the Cu content of the In-xCu solder was 45 wt.%, the shear strength of the Cu/In-45Cu/Cu joint reached the peak value of 15.7 MPa.

Ag–Sn Transient Liquid Phase Bonding for High Temperature Electronic Packaging: Effect of Ag Content

Transient liquid phase (TLP) bonding is a promising solution for high temperature (HT) electronic devices as high-quality bonds can be formed at a temperature much lower than the melting point of the resulted joint. In this work, Ag-rich Ag–Sn TLP bonding was evaluated as a potential die attach solution for HT (250 °C) electronic applications. The influence of varying the Ag content on the mechanical strength of the Ag–Sn TLP joint was investigated through room temperature (RT) and HT shear tests. The study was complemented with X-ray imaging of any void formation, and scanning electron microscope (SEM)/energy-dispersive X-ray spectroscopy (EDX) spectra for composition and morphology analysis. It is shown that the Ag-rich joint comprises Ag and Ag3Sn intermetallic compound (IMC), and no obvious void was observed. The shear strengths of the joints measured at both RT and 250 °C have satisfied the requirement for HT applications. In addition, the fractured surfaces after the shear test showed that the failure of Ag-rich joints occurred mostly in the Ag3Sn IMC region. Furthermore, the shear strength improved with increasing Ag content (up to 81.5 at.%) in the bond.

Fabrication of high-strength Cu–Cu joint by low-temperature sintering micron–nano Cu composite paste

To solve the problems of high cost of nano-metal paste and high porosity of die-attach layer, a novel and cost-effective micro–nano Cu composite paste was prepared and demonstrated for fabricating the high-strength Cu–Cu joint at low sintering temperature. The microstructures and bonding properties of Cu–Cu joints were systematically investigated by adjusting the mass ratio of nano- to micron particles and sintering parameters. Consequently, the Cu–Cu joints sintered at 250 °C display the high shear strength of 45.6 MPa, and the die-attach layers yield the low resistivity of 5.44 µΩ cm and the low porosity of 2.67%. Furthermore, the Cu–Cu joints still present the high shear strength of 41.5 MPa at the low sintering temperature of 225 °C for 5 min. Therefore, the micro–nano Cu composite paste has a huge potential as a low-cost die-attach material for high-temperature electronic packaging.

High-Temperature Electronics Packaging for Simulated Venus Condition

Abstract An electronic packaging technology that survives the simulated Venusian surface temperature of 465°C and 96 bar pressure in carbon dioxide (CO2) and nitrogen environments, without the corrosive trace gases, was developed. Alumina ceramic substrates and gold conductors on alumina were evaluated for electrical and mechanical performance. The most promising die-attach materials are thick-film gold and alumina-based ceramic pastes. Alumina, sapphire, silicon, and silicon carbide dies were attached to the alumina substrates using these die-attach materials and exposed to 96 bar pressure in a CO2 environment at 465°C for 244 h. The ceramic die-attach material showed consistent shear strengths before and after the test. An alumina ceramic encapsulation material was also evaluated for thermomechanical stability. The devices on the packaging substrates were encapsulated by a ceramic encapsulation with no significant increase in cracks and voids after the Venusian simulator test. Wire pull strength tests were conducted on the gold bond wire to evaluate mechanical durability before and after the Venusian simulator exposure. The average gold bond wire pull strengths before and after exposure were 5.78 g-F and 4 g-F for 1-mil gold bond wires, respectively, meeting the minimum MIL-STD-885 2011.9 standard. The overall wire bond daisy chain resistance change was .47% after the Venus simulator test, indicating a promising wire bond integrity. A titanium package was fabricated to house the ceramic packaging substrate and a two-level metalized feedthrough was fabricated to provide electrical interfaces to the package.

Arresting high-temperature microstructural evolution inside sintered silver

The surface oxidation of internal pore surfaces of nano-scale sintered silver has increased stability for high temperature applications. Operating temperatures of up to 400 °C have resulted in no or minimal changes in microstructure. By contrast, it is known that the microstructure of untreated pressure-less sintered silver continuously evolves at temperatures above 200 °C, grain and pore growth resulting in microstructure coarsening and increased susceptibility to fatigue. Oxidation of the internal pore surfaces has been shown to freeze the microstructure when the contact metallization is also silver or chemically inert. Samples exhibited no change in microstructure either through continuous observation through glass, or after cross sectioning. The tested specimens under high temperature storage resisted grain growth for more than 1000 h at 300 °C. The oxidising treatment can be performed via many different routes. For example, exposure to steam, or even by dipping in water for 10 min followed by immediate high temperature exposure and the effectiveness of these varying treatments is assessed. In this work we explore the mechanism that causes stabilization and explore the hypothesis that oxidation prevents grain boundary movements by arresting the fast migration of atoms along the internal pore surfaces. Analysis of the surface structure of the sintered silver by X-ray photoelectron spectroscopy shows presence of silver oxide (Ag2O) and computer simulation of grain boundary movements confirm the presence of a barrier to atomic movement on the internal silver surfaces. These findings are very promising for potential applications of sintered silver as a die attach material for High Temperature electronics packaging.

Microstructure evolution and mechanical properties of Cu/Sn/Ag TLP-bonded joint during thermal aging

Low-temperature transient liquid phase (TLP) bonding is a promising joining technology for high-temperature electronic devices packaging. However, the effect of thermal aging on the joint microstructure and performance has been rarely studied so far. In this paper, the relationship between microstructural evolution and mechanical property was developed for the Cu/Sn/Ag TLP-bonded joint during 350 °C aging. Experimental results show that an interfacial reaction occurs between the intermetallic compounds (IMCs) of Cu3Sn and Ag3Sn, which induces that a great amount of Cu3Sn particles or wedges embed into the Ag-Sn phase layer. The reaction process is controlled by a volume diffusion of Cu elements from the Cu substrate, and capable of promoting the transformation from Ag3Sn into Ag(Sn) solid solution. Cu41Sn11 phase can be formed at the expense of Cu3Sn and Cu, of which transformation process is completely achieved after aging for 480 h, and the Cu(Sn) solid solution intimately contacts with the opposite Ag(Sn) solid solution in many areas after aging for 960 h. The joint mechanical property initially declines due to the formation of Cu41Sn11 phase and Cu-Sn IMCs grain coarsening, and then increases because of the complete depletion of Cu3Sn and substantial precipitation of Cu(Sn) solid solution. After aging for nearly 1000 h, the joint still maintains a high shear strength of >40 MPa, indicating an excellent thermal reliability.

Effect of powders on microstructures and mechanical properties for Sn–Ag transient liquid phase bonding in air

Transient liquid phase (TLP) bonding is a promising interconnection technology for high-temperature electronic packaging; however, the development is seriously limited by the long bonding time. Mixed powders with different melting points have been employed as interlayer to reduce the bonding time, but some problems still remain, such as void and undesirable property. In this paper, Cu–Cu substrates were bonded by using Sn–Ag mixed powders for a short time in air, and then the mechanism of void formation was studied, followed by a discussion of the effects of Ag/Sn proportion and powder size on the microstructures and mechanical properties of the joint. After bonded at 260 °C for just 10 min, the liquid Sn in solder paste is totally consumed, and the joint has a high shear strength of 39.5 MPa. The Ag/Sn proportion is vital to joint performance. Sn70Ag joint has the highest shear strength of 72.3 MPa, which is much more excellent than those in other studies due to the denser microstructures with fewer voids. The size of SnAgCu powders affects void size in the joint, and the size of Ag powders has a significant effect on the reaction process, suggesting that too large powders are not preferable. Moreover, the oxidation of small Sn powders should be given to sufficient attention. Finally, TLP bonding with mixed powders has an advantage over foil-based TLP bonding in terms of bonding efficiency and mechanical properties, as the bonding time is much shorter and the shear strength is much higher, which is related to the size and distribution of voids.

Low-pressure solid-state bonding technology using fine-grained silver foils for high-temperature electronics

A solid-state bonding technique using fine-grained silver (Ag) foils is presented. The Ag foils are manufactured using many runs of cold rolling and subsequent annealing processes to achieve the favorable microstructure. X-ray diffraction and pole figure measurement are performed to examine the crystal structure and grain orientations. Si chips are bonded to bare Cu substrates using the Ag foil as the bonding medium at 300 °C in 0.1 torr vacuum assisted by 6.9 MPa static pressure, which is much lower than that used in conventional thermal compression bonding. Cross sections prepared by focus ion beam show clear bonding interfaces with only a few voids smaller than 100 nm. The bonded structures do not crack after cooling down to room temperature, indicating that the ductile Ag layer is able to manage the strain induced by the large coefficient of thermal expansion mismatch between Si and Cu. The average shear strength of as-bonded samples is 29 MPa. High-temperature storage tests are conducted, and slight increase in strength can be observed after 300 °C aging. Fracture analyses show that the breakage occurs within the Ag foil rather than on the bonding interface. Transmission electron microscopy and energy-dispersive spectroscopy (TEM/EDX) are conducted for Ag/Cu interface after 200-h aging, and the result shows that slight diffusion proceeds during the aging. Since Ag has the highest electrical and thermal conductivities among metals, therefore the bonded structures reported in this paper probably represent the best possible design for high-temperature and high-power electronic packaging applications.

An Advanced Extreme-Environment Wireless Telemetry System for Turbine Blade Instrumentation

As advanced natural gas power generation systems evolve, the thrust for increased efficiencies and reduced emissions results in increasingly harsh conditions inside the turbine environment. These high temperatures, pressures, and corrosive atmospheres result in accelerated rates of degradation, leading to failure of turbine materials and components. Wolfspeed, A Cree Company, Siemens Energy, and Siemens Corporate Technology, in collaboration with the Department of Energy (DOE)'s National Energy Technology Laboratory, are developing a reliable and long-term monitoring capability in the turbine hot gas path in the form of novel ceramic-based thermocouples and wide bandgap instrumentation electronics that will contribute to the overall reliability of gas turbines. When equipped with better monitoring and controls, power plants can operate with increased fuel-burning efficiency, improved process dynamics and gas concentrations, and increased overall longevity of the power plant components. This will result in increased turbine availability and a reduction in outages and maintenance costs. The technology being developed in this program is based on advanced techniques and innovations in nearly every aspect of high-temperature electronics, including materials, semiconductor devices, subcomponents, electronic packaging, and system integration. The environment in which this wireless system must operate has continuous centrifugal loads with a gravitation force on the order of 16,000 times the force of gravity (16,000 g) and temperatures exceeding 400°C. This article will specifically discuss the background and motivation for the high-temperature instrumentation system and will explain the high-level electrical system, the construction of the instrumentation package, the techniques used for integration onto rotating components, as well as the wireless power and data transmission systems. In addition to the electrical and mechanical design, this article will also discuss results from laboratory bench testing as well as heated spin rig testing. Finally, this article will highlight the future direction of the instrumentation system evolution, with a final objective of insertion into Siemens natural gas turbine power plants.