An implantable medical device with a ceramic enclosure has a novel multi-layered ceramic feedthrough substrate in place of a prior art glass-to-metal feedthrough substrate, leading to lower costs and a higher feedthrough density. Use in a metal enclosure is also disclosed.

Implantable ceramic enclosure for pacing, neurological, and other medical applications in the human body

A microelectromechanical (MEM) switch is fabricated inexpensively by using processing steps which are standard for fabricating multiple metal layer integrated circuits, such as CMOS. The exact steps may be adjusted to be compatible with the process of a particular foundry, resulting in a device which is both low cost and readily integrable with other circuits. The processing steps include making contacts for the MEM switch from metal plugs which are ordinarily used as vias to connect metal layers which are separated by a dielectric layer. Such contact vias are formed on either side of a sacrificial metallization area, and then the interconnect metallization is removed from between the contact vias, leaving them separated. Dielectric surrounding the contacts is etched back so that they protrude toward each other. Thus, when the contacts are moved toward each other by actuating the MEM switch, they connect firmly without obstruction. Tungsten is typically used to form vias in CMOS processes, and it makes an excellent contact material, but other via metals may also be employed as contacts. Interconnect metallization may be employed for other structural and interconnect needs of the MEM switch, and is preferably standard for the foundry and process used. Various metals and dielectric materials may be used to create the switches, but in a preferred embodiment the interconnect metal layers are aluminum and the dielectric material is SiO2, materials which are fully compatible with standard four-layer CMOS fabrication processes.

CMOS-compatible MEM switches and method of making

Optimized lightweight, compact and high temperature sustaining shielding materials for neutron and gamma radiation were developed by genetic algorithms (GA) combined with the Monte Carlo N-Particle (MCNP) code. A series of samples were designed according to the method. Deep penetration tests by the MCNP code were completed. The results show that the designed samples have more advantages related to the radiation shielding effects in comparison with PB202 and KRAFTON-XP3, especially the Cakes with multi-layers structures of the Fe-interlayer-Pb have excellent performance. Taking into account the ratios designed of components among elements in the material, the manufacturing process of polymer with nano-TiO2 was studied experimentally by differential scanning calorimetry (DSC). Several samples have been tested. The attenuation experiments on the samples were carried out using tandem electrostatic accelerator neutron source, spontaneous fission neutron source of 252Cf and gamma-rays source of 60Co. The experimental results verify the correctness of optimal design and craft. The Cakes are quite suitable for applications in the practices of nuclear science and technology.

Study on Composite Material for Shielding Mixed Neutron and $\gamma$ -Rays

An integrated digital circuit is protected from reverse engineering by fabricating all transistors of like conductivity with a common size and geometric layout, providing a common layout for different logic cells, connecting doped circuit elements of like conductivity with electrically conductive doped implants in the substrate rather than metalized interconnections, and providing non-functional apparent interconnections that are interrupted by non-discernable channel stops so that all cells falsely appear to have a common interconnection scheme. The camouflage is enhanced by providing a uniform pattern of metal leads over the transistor array, with a uniform pattern of heavily doped implant taps from the transistors for connection to the leads; undesired tap-lead connections are blocked by channel stops.

Digital circuit with transistor geometry and channel stops providing camouflage against reverse engineering

The thermomechanical properties of epoxy filled with two different types of silica nanofillers: spherical nanoparticles and nanofibers were investigated as a function of silica nanofiller aspect ratio and concentration. Results indicated that at room temperature and at 8.74% silica nanofiber concentration (by volume) the thermal conductivity of epoxy increased twofold and coefficient of thermal expansion (CET) decreased by ∼40%. Silica nanofiber filled epoxy showed 1.4 times greater CET and 1.5 times greater thermal conductivity compared to spherical nanoparticle filled epoxy. The significant changes observed in thermomechanical properties of silica nanofiber filled epoxy were attributed to its high aspect ratio by constraining the polymer matrix as well as reducing the phonon scattering due to the formation of a continuous fiber network within the matrix. In addition to being electrically insulating, the improved properties of silica nanofiber filled epoxy make it an extremely attractive material as underfill and encapsulant in advanced electronic packaging industry.

Engineering the coefficient of thermal expansion and thermal conductivity of polymers filled with high aspect ratio silica nanofibers

Adhesives are widely used in the manufacture and assembly of electronic circuits and products. Generally, electronics design engineers and manufacturing engineers are not well versed in adhesives, while adhesion chemists have a limited knowledge of electronics. This book bridges these knowledge gaps and is useful to both groups. This book includes chapters covering types of adhesive, the chemistry on which they are based, and their properties, applications, processes, specifications, and reliability. Coverage of toxicity, environmental impacts and the regulatory framework make this book particularly important for engineers and managers alike. The third edition has been updated throughout and includes new sections on nanomaterials, environmental impacts and new environmentally friendly 'green' adhesives. Information about regulations and compliance has been brought fully up-to-date. As well as providing full coverage of standard adhesive types, Licari explores the most recent developments in fields such as: tamper-proof adhesives for electronic security devices; bio-compatible adhesives for implantable medical devices; electrically conductive adhesives to replace toxic tin-lead solders in printed circuit assembly - as required by regulatory regimes, e.g. the EU's Restriction of Hazardous Substances Directive or RoHS (compliance is required for all products placed on the European market); and, nano-fillers in adhesives, used to increase the thermal conductivity of current adhesives for cooling electronic devices. A complete guide for the electronics industry to adhesive types, their properties and applications - this book is an essential reference for a wide range of specialists including electrical engineers, adhesion chemists and other engineering professionals. It provides specifications of adhesives for particular uses and outlines the processes for application and curing - coverage that is of particular benefit to design engineers, who are charged with creating the interface between the adhesive material and the microelectronic device. It discusses the respective advantages and limitations of different adhesives for varying applications, thereby addressing reliability issues before they occur and offering useful information to both design engineers and Quality Assurance personnel.

Adhesives Technology for Electronic Applications: Materials, Processing, Reliability

A microelectronic device is rendered resistant to reverse engineering by encapsulating it in a dual layer encapsulant. The inner layer is compatible with the operation of the device, and has a greater resistance to chemical attack then does the device. The outer layer includes a filler of barium sulfate and gadolinium oxide, to absorb X-rays and N-rays respectively, is more resistant to chemical attack than the inner layer, and includes a groove around its periphery, to preferentially allow chemical attack radially. A full chemical attack damages the device beyond usable inspection, but a partial chemical attack is insufficient to remove X-ray and N-ray concealment.

Reverse-engineering resistant encapsulant for microelectric device

A monometallic batch process for forming beam leads of a preferred metal such as aluminum or gold. The process is applied to a wafer of finished microelectronic devices already having metal contact pads of the same preferred metal. Where aluminum is the desired metal, high deposition rates are used to minimize aluminum oxide contamination. High yield is achieved by forming the beam leads to have an elevated cantilevered configuration, by deep scribing of the wafer and, when desired, by providing an energy absorbing cushion to reduce the effect of collisions between chip edges and beam leads.

Batch process providing beam leads for microelectronic devices having metallized contact pads

Publisher Summary This chapter discusses various aspects of chemistry, formulation, and properties of adhesives. Epoxy adhesives are the most widely used and most versatile of the polymer types and they combine numerous desirable properties including adhesive strength, thermal stability, reparability, dielectric properties, and retention of the properties under high thermomechanical stresses and environmental exposures such as humidity. Epoxy adhesives are widely used in electronics assembly and packaging and formed by polymerizing epoxy resins having one or more terminal glycidyl ether groups with a variety of curing agents, hardeners, or catalysts. Primary amines react rapidly with epoxy resins, even at room temperature, by opening up the epoxy ring and forming a secondary amine structure. Silicone adhesives, coatings, and encapsulants have been used from the inception of electronics and their formulations have improved steadily with each new generation of microelectronic assemblies. Moisture-cured silicones are used in many applications including sealing lids and housings, assembling components onto circuit boards, for chip-scale spacers and die attachment.

Chemistry, Formulation, and Properties of Adhesives

A composition for forming a boundary lubricant for metal and ceramic wear surfaces consisting of transition element complexes, including those of the higher molecular weight carboxylic acids such as the long chain fatty acids (C x H 2x +1 COOH; x = 8, 9, 10, . . . 29). The transition elements used here are metals such as Cr, Mn, Fe, Co, Ni or Al that can form coordination complexes. Exemplary metal complexes are chromium stearate and chromium behenate. An exemplary complex may be prepared by (1) reducing chromium trioxide by a reducing alcohol in a low molecular weight organic acid to produce chromium acetate; then 2 hydrating and olating the chromium acetate. A solution containing a maximum concentration of about 11 weight percent of the transition metal complex in a solvent such as trichloroethylene is applied as a thin layer onto a wear surface, then the layer is heated for 1-4 hours at a temperature at or above 70°C and, within the approximate range 70°-160°C. The transition metal complex chemically adheres to the wear surface, and is cross-linked by the heat treatment, to form an anchored, polymerized array of molecules that provides a hydrophobic, durable, boundary lubricant having a low coefficient of friction. The transition metal complex solution may be applied to non-porous wear surfaces or, alternatively, may be impregnated into chrome oxide coatings or other porous refractory coatings on wear surfaces to form a porosity-filling boundary lubricant thereon. The lubricant decreases the clearance required between porous bearing surfaces, decreases the formation of corrosion cells, and lowers the coefficient of friction. The preferred amount of fatty acid or organic polyacid that can be stably incorporated into a complex chromium soap for use as a porosity-filling lubricant, that is, the optimum fatty acid mol/chromium gm-atom ratio, is approximately 1-1.2/1.

James J. Licari

Papers

Adhesives Technology for Electronic Applications: Materials, Processing, Reliability

Reverse-engineering resistant encapsulant for microelectric device

Batch process providing beam leads for microelectronic devices having metallized contact pads

Chemistry, Formulation, and Properties of Adhesives

Composition for boundary lubricant and method