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As printed wiring boards move to thin laminate structures, there is growing interest in the use of photoimageable coatings to serve as dielectric. Shipley has developed a liquid photoimageable dielectric which combines liquid coating, imaging and plateability. This paper presents work using this material to produce electrolessly plated lines and blind vias, along with initial adhesion data. Some of the interesting properties of this material are: low dielectric constant, low moisture absorption and good compliance to stress. The material can be processed to provide a high Tg and high plated adhesion can be obtained using conventional swell and etch techniques. It can be imaged and processed using conventional printed circuit coating and imaging techniques. This material will offer a relatively low cost alternative to thin clad laminates and may find use for adding one or two layers to a conventional multilayer board or in providing surface topography for surface mount devices. The paper describes recent developments related to this dielectric and its use.

The trend towards high speed digital processing has stimulated the need for new substrate materials with superior electrical properties for multilayer printed wiring board (PWB) applications. Two important electrical substrate parameters are dielectric constant and dissipation factor. This study examines the effect of combining different resin and fibre systems for altering or possibly improving electrical performance. Resin systems studied include FR‐4, cyanate ester and polytetrafluoroethylene. Materials used for reinforcement include E‐glass, S‐glass and polytetrafluoroethylene based fibres. Results of the electrical and thermal characterisation work on the test vehicles built based on the mixed resin and fibre systems are reported.

Modern complex integrated circuits require more input/output connections and operate at faster switching speeds and higher power levels than was the case before LSI and VLSI devices. As a result, there is a need for packages with high electrical conductivity, low dielectric constant, high thermal conductivity, precise line resolution and low unit cost. Ideally, it should also be possible to include resistors and for the package to be manufactured in‐house for maximum control. Multilayer printed circuit boards, complex multilayer hybrid circuits and high temperature co‐fired ceramic packages have been used to accomplish the interconnection of complex ICs. A new technology has been developed which combines the benefits of thick film with the processing advantages of co‐fired ceramic. The thick film process begins with a bare substrate, usually 96% alumina, upon which gold, silver alloy or copper metallisation, and screen‐printable dielectric paste are applied. Processing is a series of printing and firing operations; the firing temperature is usually between 800°C and 1000°C. Interconnecting vias are typically formed by screen printing and are usually a minimum of 250 ?m (10 mil) in diameter. The high temperature co‐fired approach uses no substrate. Printing of tungsten, molybdenum or molymanganese metallisation is carried out on alumina tape dielectric. The vias are formed by mechanical punching and are typically a minimum of 200 ?m (8 mil) in diameter. A single firing is performed in a special atmosphere, usually at 1500°C. This paper describes a new materials system which consists of a tape dielectric and gold, silver and silver/palladium inner layer and via fill conductor compositions. Circuits and packages made with the system are fired in an air atmosphere in standard thick film furnaces and are compatible with other conventional thick film materials. The process for making these parts is described and critical process parameters are identified. The results of reliability testing under temperature, humidity and bias are discussed and supporting microstructural analysis is presented.

Thick film technology has been widely used in the past for medium performance packaging solutions, but has been unable to compete with thin‐film technology for high performance requirements. The problems of poor geometrical resolution, together with high dielectric constant and loss, have all contributed to the very limited adopting of thick‐film for advanced applications such as MCMs and microwave. This paper describes a new advanced ceramic based technology using thick‐film conductors and dielectric. Results showing the excellent geometrical properties which result from a combination of novel materials and processing, giving line widths down to 10 microns and via dimensions of 25 micron are presented. The novel dielectric material also provides a dielectric constant of 4, with a loss factor of 1 × 10^−4. This technology allows the fabrication of high density circuits and packages, offering many packaging solutions, including MCM, microwave, sensors and displays, all on one substrate.

The purpose of this paper is to report on fabrication procedure and present microstructure and dielectric behavior of willemite ceramic material with addition of 5% Li₂CO₃ as a sintering aid.

The samples were fabricated by ball milling of the ceramic powders, preparation of granulate and pressing and co-firing using temperature profile based on heating microscope observation. The dielectric properties of the material were measured by impedance spectroscopy (Hz-MHz), transmission method (GHz) and time domain spectroscopy (THz). The composition and microstructure of the material were investigated using X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy analysis. Ceramic powder was used to fabricate a green tape and low temperature co-fired ceramics (LTCC) multilayer structures, which in the next steps of the research were examined at the angle of cooperation with conductive pastes, strength and geometric repeatability.

The fabricated material showed low sintering temperature (920°C–960°C), low dielectric constant 6.2–6.34 and low dissipation factor at the level of 0.004–0.007. As LTCC material, willemite with 5% Li₂CO₃ addition showed good compatibility with AgPd conductive paste.

Search for new materials with low dielectric constant, applicable in LTCC technology, and development of their fabrication procedure are important tasks for the progress in modern microwave circuits.

This paper reports the characterization of a photosensitive benzocyclobutene (BCB), a low dielectric constant spin‐on polymer for use as interlayer dielectric in the microelectronics industry. Research work is divided into three main sections. First, BCB thin film characterization was done to investigate the effects of curing conditions on BCB film thickness, dielectric properties, optical properties and extent of cure. Thermal stability of BCB was then evaluated using thermogravimetric analysis (TGA) to detect weight loss during thermal curing and degradation. Finally, curing kinetics study was conducted using both differential scanning calorimetry (DSC) dynamic (American Society for Testing and Materials method) and isothermal approaches. The first study shows that determination of vitrification point during thermal curing of BCB is crucial to predict film properties. By curing to just before vitrification, lowest refractive index, hence dielectric constant, could be obtained.

The purpose of this paper on the one hand is to reduce the sintering temperature, shorten the sintering time and improve the electrical properties of the sample through the two-step flash sintering method and on the other hand is to study the effect of electric field on the phase structure, microstructure and electrical properties of the flash sintering sample.

In this paper, (Mg_1/3Ta_2/3)_0.01Ti_0.99O₂ giant dielectric ceramics were prepared by conventional sintering and two-step flash sintering, respectively. Further, the effect of electric field (600–750 V/cm) on the electrical properties of (Mg_1/3Ta_2/3)_0.01Ti_0.99O₂ giant dielectric ceramics was studied.

The results show that compared with the conventional sintering, the sintering temperature of the two-step flash sintering can be reduced by 200°C and the sintering time can be shortened by 12 times. All sintered samples were single rutile TiO₂ structure. Compared with conventional sintering, two-step flash sintering samples have finer grain size. The two-step flash sintered sample has similar dielectric properties to the conventional sintered sample. The dielectric constant of flash sintered samples decreases with the increase of electric field. When the electric field is 700 V/cm, the ceramic sample has the optimal dielectric properties, where the dielectric constant is approximately 5.5 × 10³ and the dielectric loss is about 0.18 at 1 kHz. Impedance spectroscopy analysis shows that the excellent dielectric properties are attributed to the internal barrier layer capacitance model.

This paper not only provides a new method for the preparation of co-doped TiO₂ giant dielectric ceramics but also has great potential in greatly improving efficiency and saving energy.

The trend in wireless and mobile communications for broader bandwidth microwave circuitry, coupled with high packaging density and low cost fabrication has triggered investigations of new circuit configurations and technologies that meet these requirements. We have addressed these issues through the study of multilayer microwave structures using advanced thick‐film technology. The techniques described employ several layers of metal sandwiched by thick‐film dielectric. This leads to an efficient solution for system miniaturisation. The significance of this work is that it shows the multilayer approach to microwave structures, coupled with new thick‐film technology, offers a viable and economic solution to achieve high‐density, high‐performance microwave circuits.

There has been increasing interest in the development of printable electronics to meet the growing demand for low‐cost, large‐area, miniaturized, flexible and lightweight devices. The purpose of this paper is to discuss the electronic applications of novel printable materials.

The paper addresses the utilization of polymer nanocomposites as it relates to printable and flexible technology for electronic packaging. Printable technology such as screen‐printing, ink‐jet printing, and microcontact printing provides a fully additive, non‐contacting deposition method that is suitable for flexible production.

A variety of printable nanomaterials for electronic packaging have been developed. This includes nanocapacitors and resistors as embedded passives, nanolaser materials, optical materials, etc. Materials can provide high‐capacitance densities, ranging from 5 to 25 nF/in², depending on composition, particle size, and film thickness. The electrical properties of capacitors fabricated from BaTiO₃‐epoxy nanocomposites showed a stable dielectric constant and low loss over a frequency range from 1 to 1,000 MHz. A variety of printable discrete resistors with different sheet resistances, ranging from ohm to Mohm, processed on large panels (19.5×24 inches) have been fabricated. Low‐resistivity materials, with volume resistivity in the range of 10⁻⁴‐10⁻⁶ ohm cm, depending on composition, particle size, and loading, can be used as conductive joints for high‐frequency and high‐density interconnect applications. Thermosetting polymers modified with ceramics or organics can produce low k and lower loss dielectrics. Reliability of the materials was ascertained by (Infrared; IR‐reflow), thermal cycling, pressure cooker test (PCT) and solder shock testing. The change in capacitance after 3× IR‐reflow and after 1,000 cycles of deep thermal cycling between −55°C and +125°C was within 5 per cent. Most of the materials in the test vehicle were stable after IR‐reflow, PCT, and solder shock.

The electronic applications of printable, high‐performance nanocomposite materials such as adhesives (both conductive and non‐conductive), interlayer dielectrics (low‐k, low‐loss dielectrics), embedded passives (capacitors and resistors), and circuits, etc.. are discussed. Also addressed are investigations of printable optically/magnetically active nanocomposite and polymeric materials for fabrication of devices such as inductors, embedded lasers, and optical interconnects.

A thin film printable technology was developed to manufacture large‐area microelectronics with embedded passives, Z‐interconnects and optical waveguides, etc. The overall approach lends itself to package miniaturization because multiple materials and devices can be printed in the same layer to increase functionality.

Epoxy resin (EP) is a kind of thermosetting resin, and its application is usually limited by poor toughness. In this case, a type of new flexible chain blocking hyperbranched polyester (HBP) was designed and synthesized. The purpose of this study is to enhance the toughness and dielectric properties of EP.

P-toluene sulfonic acid was used as the catalyst, with dimethy propionic acid as the branch unit and pentaerythritol as the core in the experiment. Then, n-hexanoic acid and n-caprylic acid were, respectively, put to gain HBP with a n-hexanoic acid and n-caprylic acid capped structure. The microstructure, mechanical properties, insulation properties and dielectric properties of the composite were characterized for the purpose of finding the appropriate proportion of HBP.

HBP enhanced the toughness of epoxy-cured products by interpenetrating polymer network structure between the flexible chain of HBP and the EP molecular chain. Meanwhile, HBP reduced the ε and tgδ of the epoxy anhydride-cured product by reducing the number of polar groups per unit volume of the EP through free volumes.

Yet EP is a kind of thermosetting resin, which is widely used in coating, aerospace, electronics, polymer composites and military fields, but it is usually limited by poor toughness. In a word, it is an urgent priority to develop new EP with better toughness and mechanical properties.

At present, HBP has been applied as a new kind of toughening strategy and as a modifier for EP. According to the toughening mechanism of HBP modified EP, the free volume of HBP creates a space for the EP molecule to move around when loaded. Moreover, the free volume could cause the dielectric constant of EP to diminish by reducing the content of polarizable groups. Meanwhile, the addition of HBP with flexible chains grafted to the EP could develop an interpenetrating network structure, thus further enhancing the toughness of EP