Hybrid Microcircuits Research Articles

Qualification Methodology for the Double Side Printed Substrate for Hybrid Microcircuits Application

Hybrid Microcircuits (HMCs) are always preferred over discrete versions due to small size, less weight, better performance and high reliability for space applications. Double side printed substrates realized using Thick film screen printing and Printed Through Hole (PTH) processes are being used in HMCs in order to achieve further miniaturization. This article details the newly developed innovative Thick film process technology involving drilling of holes and filling the through hole with gold conductive paste to connect the front and rear side of conductor patterns on an alumina substrate. The biggest challenge in the realization of double side printed substrates is creating multiple via holes and filling them with conductor paste. In addition, the limited ability to achieve substrate integration and uniformity pose additional challenges that require optimization of process parameters. A comprehensive test plan created to qualify this innovative method in terms of quality and reliability suitable for the aerospace industry is also presented.

Tests and Analysis of Storage Life Extension of Hybrid Microcircuits for Aerospace Applications: A Case Study

Hybrid Microcircuits (HMCs) which bring about miniaturization with better performance and reliability are ideally suited for specific application where low volume requirement needed for aerospace missions. A large number of HMCs for varied applications are used in aerospace industry. HMCs generally use passive components and interconnections in thick film form, and active devices (MOSFETs, Transistor and Diode dice) and monolithic ICs (as bare chips) bonded to a substrate and are employed to carry out multiple functions. The die and other chip components utilized in making HMCs necessitated usage of hermetic sealing. The resulting HMCs consisting of multiple components are used as standalone EEE component. A general guideline of using HMCs for 9 years and re-screening after 3 years result in lot of constraint on resources and not viable in present scenario. The study conducted to find out the criticality and testing methodology for the extension of usable storage period. Comprehensive test plan consisting of variety of HMCs having varied processes, materials, density and various tests conducted as per the plan. This article details the various plans, choice of HMCs, testing results and analysis for the basis of extending the usable storage period of the HMCs for aerospace industry.

Fusing Current Characterization of AU Wire Bonds for Hybrid Microcircuits in Aerospace Environment

Wire bonding is one of the major as well as critical processes in the realization of Hybrid microcircuits (HMCs), Microwave Integrated Circuits (MICs) and Monolithic Microwave Integrated Circuits (MMIC) where fine gold or aluminum wires are used. Selection of fine wires in wire bonding depends upon the requirement of current carrying capability of the circuit and process feasibility. This article details the experimental study and analysis of wire bonds having various diameter, length as well as thermal effects. The effect of substrate also investigated taking into Alumina (96% and 99.6%) and Aluminium Nitride apart from effect of metallisation methodology encompassing sputtering and thick film screen-printed gold.

Dice Selection in Hybrid Microcircuits For Aerospace Applications

Hybrid Microcircuits which bring about miniaturization with better performance and reliability are ideally suited for application specific low volume production requirement of space missions. A large number of HMCs are used in every spacecraft. HMCs generally use passive components and interconnections in thick film form, and active devices (MOSFETs, Transistor and Diode dice) and monolithic ICs (as bare chips) bonded to a substrate. Environmental radiation threat to ICs and other active circuitry is one of the major causes of failures in HMCs. The ionizing radiation present in the Van Allen Belt penetrates the satellite resulting in the excitation of electrons in the semiconductor valence band to conduction band in the active circuit and can be trapped. Secondary photon radiation, which are generated due to slowing down of high energy particles also strike interior of the spacecraft. The total interaction of various charged particles and photons to the internal circuitry of HMC depends on mass, charge state, kinetic energy of the striking photon as well as on the mass, charge and density of the die structure internal to HMC. The MOS die is prone to failure due to total ionization dose as well as single event effects which in turn may cause HMC failure. HMCs for space applications are mostly characterized with die passivation and hermetically sealed packages for its inherent advantages. In spite of the advantages offered by hermetic sealing like reliability, radiation shielding, out gassing etc, the radiation hardened dice are preferred for realization of HMCs for space systems. A feasibility study is carried out for using MIL and Commercial grade dice in HMCs without compromising on reliability aspects. The layout design, die attachment process, testing and extensive qualification become important in HMC apart from hermetic sealing so as to avoid catastrophic failure. This article details the radiation phenomena and its effects on dice used in HMCs. The advantages of hermetically sealed packages and use of MIL/Commercial grade dice in HMCs along with various mitigation techniques to have reliable circuit meeting the desired performance in space environment are also presented.

Mechanical Properties and Interface Microstructure of SAC305 Solder Joints Made to an Ag-Pd-Pt Thick Film Metallization: Part 1—Processing Effects

Abstract The processibility was document for interconnections made between the 96.5Sn-3.0Ag-0.5Cu (wt.%, abbreviated SAC305) Pb-free solder and an Ag-Pd-Pt thick film conductor on an alumina substrate. The Sheppard’s hook pull test was used to assess the solder joint strength. Microanalysis techniques documented the corresponding microstructures. Excellent solderability was observed across the process parameters defined by the soldering temperatures of 240–290°C and soldering times of 15–120 s. Molten SAC305 solder dissolved the Ag-Pd-Pt thick film, leading to the precipitation of Ag (trace of Pd) and (Pd, Pt)xSny intermetallic compound (IMC) particles upon solidification. The mechanical strengths of the solder joints were excellent (10–15 N) and remained largely insensitive to the processing conditions. The failure mode was ductile fracture in the solder. These findings confirmed that the SAC305 solder/Ag-Pd-Pt thick film interconnection system had the necessary process window for use in high reliability, hybrid microcircuit (HMC) applications.

Mechanical Properties and Interface Microstructure of SAC305 Solder Joints Made to a Ag-Pd-Pt Thick Film Metallization: Part 2—Isothermal Aging Effects

Abstract The performance and reliability were documented for solder joints made between the 96.5Sn-3.0Ag-0.5Cu (wt.%, abbreviated SAC305) Pb-free solder and a Ag-Pd-Pt thick film conductor on an alumina substrate. The Sheppard’s hook pull test was used to assess the solder joint strength. The Part 1 study confirmed that the solder joint fabrication process had a wide process window. The current study determined that the SAC305 solder joints maintained that robustness after accelerated aging at temperatures of 70–205°C and time durations of 5–200 d. Short-term aging of 5–10 d caused a peak in the pull strength peak that resulted from precipitation hardening by Ag-Pd and (Pd, Pt)xSny intermetallic compound (IMC) particles. The pull strengths did not decrease significantly after longer aging times at 70°C and 100°C; those conditions were accelerations of typical service lifetimes. Longer aging times at temperatures of 135–205°C resulted in a gradual, albeit not catastrophic, strength decrease when the precipitation hardening mechanism was lost to dissolution of the particle phases and their reprecipitation at the solder/alumina interface. The failure modes were ductile fracture in the solder except for the most severe aging conditions. These findings confirmed that the SAC305 solder/Ag-Pd-Pt thick film interconnections have excellent long-term reliability for hybrid microcircuit and high-temperature electronics applications.

Advanced Materials and Processes for realisation of High Power Hybrids for Space Applications

This paper describes about an advanced material used in the realisation of Power Hybrid and its qualification which involves various new processes. This Power Hybrid is realised using hybrid microcircuit (HMC) technology. A new material capable of dissipating high power, and handling high current is selected and used for realising Power Hybrid which is realised for space applications. Choice of material plays a very important role in high power and high current applications, in order to keep the device temperatures well within the safe operating limits. An advanced material, namely direct bonded copper which satisfies both thermal and current requirements, has been chosen for this application. As this material is used for the first time in HMCs, process optimisation and qualification activities have been carried out. HMC package which is used for the realisation of this Power Hybrid is also custom made with the new materials and also undergoes qualification processes. Using this advanced material and new type of package, four new processes are successfully qualified and implemented in a Power Hybrid which is a part of satellite power subsystem.

Analysis of low isolation problem in HMC using Ishikawa model: A case study

Electronics systems for space application always demand higher performance, weight saving and volume diminution etc. without sacrificing their reliability. As part of this stringent requirement, a few circuit blocks which are repeatedly used in various inertial systems are being realized in Hybrid Micro Circuits (HMCs). Recently, a few batches of HMCs fabricated by a specific vendor showed low electrical isolation between the HMC package body and other functional pins at ambient temperature. However, the electrical isolation values were found to be normal at elevated temperatures. The low electrical isolation was causing leakage current between pins or package body to other pins. This makes the performance of the HMCs unpredictable during its operational period.In this paper, study and analysis conducted with respect to the low electrical isolation observed in HMCs are discussed. Root cause of the problem was analyzed by conducting methodical and systematic tests based on a formulated Ishikawa model. The major tests conducted in this analysis include external visual inspection, isolation measurements, Scanning Electron Microscopy (SEM), leak tests, Residual Gas Analysis (RGA), internal visual inspection etc. Based on the test results, root cause of the isolation problem was narrowed down to process related, which was one of the primary causes as stipulated in Ishikawa model. The real cause of the problem was the formation of ammonium hydroxide inside the HMC due to the presence of ammonia and moisture. The defective HMCs showed very large quantity of these conducting residues inside the HMCs during the RGA test. These residues emanated from the epoxy material used to attach the alumina substrate in the HMC. These faulty HMCs have not undergone vacuum baking properly before being sealed due to faulty functioning of the chamber. Hence residual gases and moisture could not be outgassed completely before sealing. Internal visual inspection of the HMCs revealed spill over of substrate attach epoxy to the Glass To Metal Seal (GTMS) thereby bridging the package pin and HMC body. Ammonium hydroxide present in this bridged epoxy was causing the low electrical isolation at ambient condition. The electrical isolation that resulted from the ammonium hydroxide is quantified and the results were found comparable with the measured values. At elevated temperatures, the ammonium hydroxide again decomposes to ammonia and water vapor and loses its conductivity and the isolation values become normal.

Design and Development of Detector Simulator for Total Ionized Dose and ground checkout system of radiation monitoring instrument

Abstract This Paper describes the simulator development for the Total Ionizing Dose (TID) measurement of radiation monitoring instrument. The TID Detector (UDOS001-micro dosimeter) is a compact hybrid microcircuit which directly measures Total Ionizing Dose absorbed by an internal silicon test mass. The developed detector simulator, simulates the equivalent Total Ionized Dose absorbed from the space radiation and Ground checkout simulator receive the data from Radiation monitoring Instrument through UART and process it for the functional verification of the Radiation monitoring Instrument, which is discussed in the paper.

On the Loading of Slime Mold Physarum polycephalum with Microparticles for Unconventional Computing Application

The plasmodium of Physarum polycephalum is a large single cell visible with the naked eye. The plasmodium realizes a pattern of protoplasmic veins which span sites of sources of nutrients, producing efficient network structures like cycles and Steiner minimum trees. Besides, the plasmodium can embed different chemicals; therefore, it should be possible to program the plasmodium to realize deterministic adaptive network and spatial distribution of nanoscale and microscale materials. The transported particles can be used for the modification of the physical properties of the system (electrical, optical, magnetic) facilitating the readout of the information, processed by the slime mold. Experiments with polystyrene microparticles and MnCO3 microparticles demonstrate that the plasmodium of Physarum can propagate nanoscale objects using a number of distinct mechanisms. The results of our experiments could be employed in the field of the unconventional computing and bio-computing application devices, using Physarum network as scaffolds for the development of hybrid nanocircuits and microcircuits and devices.

Test Method of Current Leakage for Dielectric Paste

A test method of current leakage for dielectric paste was proposed by simulating the application processes of dielectric paste for manufacturing the dielectric layer in the multilayer thick film hybrid microcircuit. That is, by screen printing and sintering processes, the sliver conducting layer was fabricated on the surface of glass substrate, and then dielectric layer, finally the glass substrate sample with conducting layer and dielectric layer was dipped in 5 Wt% NaCl aqueous solution. The conductive line was soldered on the silver conducting layer to form the test circuit, and powered with 5 volts direct power, the current in the test circuit was taken as the current leakage of the dielectric paste. The method may be used to evaluate the current leakage of dielectric paste.

An analysis of the radiation behavior of pulse voltage stabilizers

A typical structure of modern hybrid microcircuits of pulse voltage stabilizers (PVSs) is analyzed. Experiential studies of dose and single-event local ionization effects in basic units of modern pulse voltage stabilizers are performed. The model of pulse voltage stabilizers for analyzing single-event effects is proposed, and its experimental verification is fulfilled. The most radiation-sensitive basic units of pulse voltage stabilizers are revealed. Recommendations for increasing their radiation resistance are given.

Design of an FPGA-based electronic flow regulator (EFR) for spacecraft propulsion system

This paper describes a scheme for electronically regulating the flow of propellant to the thruster from a high-pressure storage tank used in spacecraft application. Precise flow delivery of propellant to thrusters ensures propulsion system operation at best efficiency by maximizing the propellant and power utilization for the mission. The proposed field programmable gate array (FPGA) based electronic flow regulator (EFR) is used to ensure precise flow of propellant to the thrusters from a high-pressure storage tank used in spacecraft application. This paper presents hardware and software design of electronic flow regulator and implementation of the regulation logic onto an FPGA. Motivation for proposed FPGA-based electronic flow regulation is on the disadvantages of conventional approach of using analog circuits. Digital flow regulation overcomes the analog equivalent as digital circuits are highly flexible, are not much affected due to noise, accurate performance is repeatable, interface is easier to computers, storing facilities are possible and finally failure rate of digital circuits is less. FPGA has certain advantages over ASIC and microprocessor/micro-controller that motivated us to opt for FPGA-based electronic flow regulator. Also the control algorithm being software, it is well modifiable without changing the hardware. This scheme is simple enough to adopt for a wide range of applications, where the flow is to be regulated for efficient operation. The proposed scheme is based on a space-qualified re-configurable field programmable gate arrays (FPGA) and hybrid micro circuit (HMC). A graphical user interface (GUI) based application software is also developed for debugging, monitoring and controlling the electronic flow regulator from PC COM port.

‘Lead Free’ thick film thermistors: a study of variation in glass frit concentration and organics composition

There is a need to develop environment friendly electronic materials due to worldwide constraint for the use of hazardous chemicals such as lead, cadmium which are the main constituents of the electronic components. Considering such need, the work on lead free thick film thermistors has been initiated. Thick film materials have been proved to possess economical processing and functional advantage over other technologies and quick turnaround production of hybrid microcircuits. Thick film thermistors are different from the conventional thermistors (bulk) not only by the preparation process but also in composition, transport properties etc. In this paper, we have specifically focused on the influence of glass frit content and organic composition on the properties of lead free spinel based NTC thermistors. We noted that the glass frit concentration is responsible for the change in physical as well as electrical properties of the thick film thermistor. However, the type of organic vehicle (i.e., composition) did not show any adverse effect on microstructure and electrical properties of the thermistor.

Fast IR spectrograph (0.5–3.0 μm) based on a hybrid 1 × 384 InAs module

A design and parameters of the IR spectrograph based on an MS2004I monochromator-spectrograph and a hybrid microcircuit of a one-dimensional 1 × 384 InAs focal plane array for registration of fast processes (the registration time from 0.2 ms) are presented. The obtained spectral resolution is 0.3 nm/element at a wavelength of 1.7 μm. The wavelength range registered in a fixed position of the diffraction grating at this wavelength is 118 nm.

LTCC Microsystems and Microsystem Packaging and Integration Applications

Low Temperature Cofired Ceramic (LTCC) has proven to be an enabling medium for microsystem technologies, because of its desirable electrical, physical, and chemical properties coupled with its capability for rapid prototyping and scalable manufacturing of components. LTCC is viewed as an extension of hybrid microcircuits, and in that function it enables development, testing, and deployment of silicon microsystems. However, its versatility has allowed it to succeed as a microsystem medium in its own right, with applications in non-microelectronic meso-scale devices and in a range of sensor devices. Applications include silicon microfluidic ‘chip-and-wire’ systems and fluid grid array (FGA)/microfluidic multichip modules using embedded channels in LTCC, and cofired electro-mechanical systems with moving parts. Both the microfluidic and mechanical system applications are enabled by sacrificial volume materials (SVM), which serve to create and maintain cavities and separation gaps during the lamination and cofiring process. SVMs consisting of thermally fugitive or partially inert materials are easily incorporated. Screeding is an incorporation technique we describe that improves uniformity and eliminates processing steps. Recognizing the premium on devices that are cofired rather than assembled, we report on functional-as-released and functional-as-fired moving parts, including an impeller that has been exercised over thirty million cycles, and a cofired pressure sensor that requires only pressure source and electrical connections. Additional applications for cofired transparent windows, some as small as an optical fiber, are also described. The applications described help pave the way for widespread application of LTCC to biomedical, control, analysis, characterization, and radio frequency (RF) functions for macro-meso-microsystems.

Synthesis and characterization of CaRuO3 and SrRuO3 for resistor paste application

Resistors are used in Hybrid Micro Circuits (HMC) are essentially cermet composites consisting of an intimate mixture of an insulating phase (the glass binder or glass frit) and suitable conducting phase, the relative proportions of which to a greater degree, determine the nominal resistivity of the resultant resistor paste. In this paper, we report resistor pastes formulated by using ruthenium based perovskites of Ca and Sr. Though the ruthenates of alkaline earth elements (Ca and Sr) have high metallic conductivity (28–300 μΩ cm) and have been extensively used in superconducting and ferroelectric systems, their usage in thick film resistor pastes has rarely been reported. Ca and Sr ruthenates were prepared by air—heating the physical admixtures of respective carbonates of Ca/Sr and RuO2 at three different temperatures, viz., 500, 800 and 900°C. In each case, heating was carried out for 15 h. The resultant powders were characterized by TGA/DTA, SEM-EDX and XRD techniques. The solid-state reactions were found to occur between 700–800°C. But the powder, thus obtained, contained certain amount of carbonate and hence the powders were heated again at 900°C for 15 h to eliminate detrimental effect of carbonate in resistor paste. The microstructural studies of powders revealed that the average particle size is around 200–400 nm. The resistor paste was formulated by using powder admixtures heated at two different temperatures, viz., 800 and 900°C. In this paper, we are presenting the preliminary account on synthesis and physico-chemcial, electrical and microstructural properties of powders and fired TFRs.

Oxide Materials for Development of Integrated Gas Sensors—A Comprehensive Review

ABSTRACT In the recent past a great deal of research efforts were directed toward the development of miniaturized gas-sensing devices, particularly for toxic gas detection and for pollution monitoring. Though various techniques are available for gas detection, solid state metal oxides offer a wide spectrum of materials and their sensitivities for different gaseous species, making it a better choice over other options. In this article a critical parameter analysis of different metal oxides that are known to be sensitive to various gaseous species are thoroughly examined. This includes phase of the oxide, sensing gaseous species, operating temperature range, and physical form of the material for the development of integrated gas sensors. The oxides that are covered in this study include oxides of aluminum, bismuth, cadmium, cerium, chromium, cobalt, copper, gallium, indium, iron, manganese, molybdenum, nickel, niobium, ruthenium, tantalum, tin, titanium, tungsten, vanadium, zinc, zirconium, and the mixed or multi-component metal oxides. They cover gases such as CO, CO2, CH4, C2H5OH, C3H8, H2, H2S, NH3, NO, NO2, O2, O3, SO2, acetone, dimethylamine (DMA), humidity, liquid petroleum gas (LPG), petrol, trimethylamine (TMA), smoke, and many others. Both doped and undoped oxides are analyzed for the compatibility with silicon processing conditions and hybrid microcircuit fabrication techniques. In silicon processing conditions, they are further analyzed for the suitability for simple silicon surfaces, silicon-on-insulator (SOI) surfaces, and micromachined silicon geometries for different operating temperatures. Discussion on gas-sensing properties of each material and its applications are described in the text in alphabetical order of the elemental oxides. Further, the gas-sensing properties like sensitivity, detection limits, operating temperature, and so on are summarized in tables along with relevant references. The figures incorporated in the present review are primarily based on discussions and data in tables. However, these figures provide a qualitative comparison and present a pictorial view to examine suitability of a material for a particular application. From the known parameters, the present study clearly indicates the suitability of certain materials and the gases that they cover for the development of integrated micro gas sensors. A clear picture has been brought out for the development of silicon-based processing technology. Various parameters are discussed for the selection of these materials, to examine their suitability and practical problems that are being associated. Etching of these metal oxides and the reliability of devices are also discussed.

Hybrid Micro Circuits

Hybrid microcircuits (HMCs) are playing important roles in various electronic fields such as military, space, medical, computer, automotive, instrumentation, industry and consumer electronics etc. The strength of hybrid microelectronics is the ability to choose and mix different technologies to best meet the requirements of the application. The early hybrid microcircuits generally combined discrete transistors, diodes, capacitors and resistors to produce analog or digital circuits. But with the latest developments in microelectronics industry, the hybrid microelectronics has grown combining ICs, LSI & VLSI functions, GaAs devices, single and multiple chips, optical and superconductor chips on single monolithic ceramic substrate. For performing complex electrical functions, three-dimensional (3-D) integration is now made possible to produce advanced multi-chip and multi-layer hybrids known as multi chip modules (MCMs). High frequency, high power, higher reliability, size, weight, thermal performance, low cost and design to product turn around time are the important factors, which preferably decide the use of hybrid microelectronics. The present note introduces hybrid microcircuits, technologies for hybrid manufacturing, advanced hybrid technologies, advantages and various applications areas for hybrid microcircuits.

Excess lateral photo-response caused by technological and constructive defects in the IR-sensitive hybrid microcircuits

IR probe technique is applied to recognize and study some technological and constructive defects producing excess photo-response in the IR-sensitive (InAs CID line array or FPA)-(Si multiplexer) hybrid microcircuits. The ways to reduce extra signal intensity are discussed.