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Article
Publication date: 1 April 1987

J. Balde and G. Messner

Low dielectric constant printed circuit board materials are becoming available. There are four or more materials that can produce boards with a dielectric constant of 28…

Abstract

Low dielectric constant printed circuit board materials are becoming available. There are four or more materials that can produce boards with a dielectric constant of 28. This paper will discuss the electrical and system advantages of having a lower dielectric constant, and the advantages and disadvantages of each of the principal new materials. In particular, the use of lower dielectric to increase circuit density will be stressed, rather than the more usual expectation that the lower dielectric constant will be used to increase propagation velocity or reduce capacitance. The increase in circuit density will reduce the size of boards, and achieve the reduction in propagation delay even though the capacitance and characteristic impedance are unchanged.

Details

Circuit World, vol. 14 no. 1
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 1 February 1986

S. Gazit

The increasing use of high switching speed systems in both microwave electronics and high speed logic devices has created the need for printed circuit boards which are…

Abstract

The increasing use of high switching speed systems in both microwave electronics and high speed logic devices has created the need for printed circuit boards which are based on low dielectric constant and low loss materials. In addition, these circuit materials must be capable of withstanding elevated temperatures typical of hostile service environments and of board fabrication processes. Such low dielectric constant rigid boards are commercially available from a few sources. However, there is a growing demand for low dielectric constant flexible printed circuit boards for interconnecting rigid boards or in rigid/flex applications where high speed, fast rise times, controlled impedance and low crosstalk are important. A new family of thin laminates which are suitable for fabrication of flexible low dielectric constant printed circuit boards have been developed by Rogers Corporation. These circuit materials are called ROhyphen;2500 laminates and offer flexible interconnections in high speed electronic systems. RO‐2500 circuit materials are based on microglass reinforced fluorocarbon composites and have a typical dielectric constant of 25. The transmission line properties of these materials have been evaluated by the IPC‐FC‐201 test method. The results indicated that these circuit materials improve the propagation velocity by about 10% and the rise time by about 30% when compared with the same geometry, polyimide film based, flexible PCs in stripline constructions. Also, dimensional stability of these laminates after etch and heat ageing is improved over that of the standard flex circuit materials based on polyimide film. RO‐2500 laminate properties have been evaluated by the IPC‐TM‐650 test methods, which are widely accepted by the flexible PCB industry.

Details

Circuit World, vol. 12 no. 3
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 7 August 2017

Beata Synkiewicz, Dorota Szwagierczak and Jan Kulawik

The paper aims to report on fabrication procedure and present microstructure and dielectric behavior of multilayer porous low-temperature cofired ceramic (LTCC) structures…

Abstract

Purpose

The paper aims to report on fabrication procedure and present microstructure and dielectric behavior of multilayer porous low-temperature cofired ceramic (LTCC) structures based on glass-cordierite and glass-alumina.

Design/methodology/approach

The LTCC structures were created as multi-layered composites with dense external layers and inner layers with intentionally introduced porosity. Two preparation methods were applied – subsequent casting of both kinds of slurries and conventional isostatic lamination of dried green tapes arranged in the designed order. Optical microscope observations were carried out to analyze the microstructure of green and fired multilayer structures and pore concentration. To evaluate the adhesion strength of the composite layers, pull test was performed. Dielectric behavior of the composites was studied in the frequency range 50 kHz-2 MHz.

Findings

The fabricated porous LTCC structures showed dielectric constant of 3-5.6. The lowest dielectric constant was attained for glass-cordierite composite made by the conventional tape casting/lamination/firing method from slurry with 50 per cent graphite content. The samples prepared using multiple casting were of worse quality than those fabricated in conventional process, contained irregular porosity, showed tendency for deformation and delamination and exhibited a higher dielectric constant.

Originality/value

Search for new low dielectric constant materials applicable in LTCC technology and new methods of their fabrication is an important task for development of modern microwave circuits.

Details

Microelectronics International, vol. 34 no. 3
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 1 February 1994

K. Laursen, D. Hertling, N. Berry, S.A. Bidstrup, P. Kohl and G. Arroz

Multichip modules provide short chip‐to‐chip interconnects in order to take advantage of the high speeds available in integrated circuits. One multichip approach utilises…

Abstract

Multichip modules provide short chip‐to‐chip interconnects in order to take advantage of the high speeds available in integrated circuits. One multichip approach utilises layers of embedded microstrip. In order to achieve the highest possible speed, it is necessary to use metals and dielectrics which have low relative dielectric constants and low loss. Polymer and polyimide dielectric materials hold great promise in MCM applications; however, their high frequency characteristics are often not well known. Since thin film dielectric properties may differ from the bulk properties, it is important to be able to determine the dielectric properties using on‐wafer measurement techniques rather than more conventional techniques. This paper focuses on some of the techniques available and discusses the advantages and shortcomings of different techniques for measuring dielectric properties.

Details

Microelectronics International, vol. 11 no. 2
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 1 March 2004

Swapan K. Bhattacharya, P. Markondeya Raj, Devarajan Balaraman, Hitesh Windlass and Rao R. Tummala

This paper addresses materials and processes for printed wiring board compatible embedded capacitors using polymer/ceramic nanocomposites and hydrothermal barium titanate…

Abstract

This paper addresses materials and processes for printed wiring board compatible embedded capacitors using polymer/ceramic nanocomposites and hydrothermal barium titanate. Polymers allow low temperature fabrication appropriate to the board (MCM‐L) technology. The lower dielectric constants of the commercially available polymers can be greatly compensated by incorporating higher permittivity ceramic fillers. Materials requirements for higher capacitance density (>30 nF/cm2) have been addressed through implementation of a novel low‐temperature processable hydrothermal barium titanate film on a patterned titanium foil laminated to the PWB. Application of hydrothermal grown barium titanate is currently being evaluated using a multi‐layer system‐on‐package demonstration.

Details

Circuit World, vol. 30 no. 1
Type: Research Article
ISSN: 0305-6120

Keywords

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Article
Publication date: 8 February 2011

Thomas Apeldorn, F. Wolff‐Fabris and V. Altstädt

The purpose of this paper is to investigate and present the properties of a new substrate material based on thermoplastic polymers (so‐called LuVo Board) for…

Abstract

Purpose

The purpose of this paper is to investigate and present the properties of a new substrate material based on thermoplastic polymers (so‐called LuVo Board) for high‐frequency applications.

Design/methodology/approach

The thermal, mechanical and electrical properties of a new thermoplastic substrate are investigated and compared to conventional substrates for printed circuit board (PCB) applications.

Findings

The new LuVo Board exhibits similar properties to commercially available high‐performance substrates. The main advantage of the LuVo Board is a reduction of manufacturing costs in comparison to conventional substrates, as a highly automated manufacturing process can be employed. Moreover, the LuVo Board exhibits some further advantages: the material is inherently flame resistant and can be thermally shaped after the assembly process.

Originality/value

This paper presents an entirely new thermoplastic substrate, which can be employed in high‐frequency applications. In comparison to standard materials, a further advantage of the thermoplastic substrate is lower production costs.

Details

Circuit World, vol. 37 no. 1
Type: Research Article
ISSN: 0305-6120

Keywords

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Article
Publication date: 1 August 2016

Beata Synkiewicz

This paper aims to present a method for the reduction of dielectric constant of low-temperature co-fired ceramics (LTCC) substrates with the use of controlled internal porosity.

Abstract

Purpose

This paper aims to present a method for the reduction of dielectric constant of low-temperature co-fired ceramics (LTCC) substrates with the use of controlled internal porosity.

Design/methodology/approach

A glass-ceramic green tape with addition of graphite as a pore former was developed. The green tapes were laminated and then sintered into multilayer structures with porous interior and thin external dense layers. Microstructure of green and fired structures was studied using optical and scanning microscopy. The behavior of the samples during heating was examined in a heating microscope. Impedance spectroscopy was applied for investigation of dielectric properties of the fabricated substrates.

Findings

Microstructure and dielectric properties of the fabricated LTCC structures were compared with the characteristics for non-porous samples with the similar composition. Introduction of 50 Wt.% admixture of graphite in the internal layers of the LTCC substrate was found to result in decrease in dielectric constant value down to about 3. Application of non-porous outer layers improved mechanical strength of the structure and smoothness of its surface, allowing screen printing of conductive pastes on both sides of the substrate.

Practical implications

The rapid growth of the wireless communication industry has created a great demand for the development of new and improved materials and devices operating properly at high frequencies. The fabricated materials can be useful for substrates of microwave devices.

Originality/value

The paper presents an innovative method of dielectric constant decrease of substrate materials. Getting insight into the phenomena responsible for formation of pores is crucial for designing materials for microwave electronics.

Details

Microelectronics International, vol. 33 no. 3
Type: Research Article
ISSN: 1356-5362

Keywords

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Article
Publication date: 22 November 2011

Christopher J. Caisse, John Coonrod and Allen F. Horn

The purpose of this paper is to quantify the effects of thermal conductivity (TC), dielectric constant and dissipation factor (DF) of circuit laminates on the temperature…

Abstract

Purpose

The purpose of this paper is to quantify the effects of thermal conductivity (TC), dielectric constant and dissipation factor (DF) of circuit laminates on the temperature rise with active components and RF trace heating.

Design/methodology/approach

Temperature rise measurements were made on surface mounted chip resistors (to simulate active components) at various dissipated power levels, with and without “via farms”. The RF heating temperature rise of 50 ohm microstrip transmission lines on 0.5 mm laminates was also measured by the same method.

Findings

The chip resistor temperature rise correlated with the independently measured TC of the laminate materials. The use of a “via farm” substantially reduced the temperature rise in all materials, but the higher TC laminates still conferred a measurable advantage. The trace temperature rise due to RF heating correlated with both TC and DF.

Research limitations/implications

It was shown that the one‐dimensional heat transfer model does not accurately calculate the temperature rise due to significant in‐plane heat spreading, particularly with lower TC materials.

Originality/value

This paper details how temperature rise of both active components and 50 ohm transmission lines is affected by the thermal and electrical properties of the circuit laminate.

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Article
Publication date: 1 March 1995

P.D. Knudsen, R.L. Brainard and K.T. Schell

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…

Abstract

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.

Details

Circuit World, vol. 21 no. 3
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 1 March 1991

M.F. Blackshaw, L.H. Lee and R. Burt

The trend towards high speed digital processing has stimulated the need for new substrate materials with superior electrical properties for multilayer printed wiring board…

Abstract

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.

Details

Circuit World, vol. 17 no. 4
Type: Research Article
ISSN: 0305-6120

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