The performance of multilayer directional couplers using a range of different thick-film dielectrics has been investigated. The properties of multilayer coupled lines are examined using their coupled-mode parameters. It is found that the optimum performance of multilayer directional couplers is largely affected by the thick-film dielectric used. A practical design strategy for multilayer directional couplers is developed, which overcomes the problem of excessive computation that is normally associated with the optimization of multilayer circuit designs. The methodology has been verified through the design and measurement of wide bandwidth 2 dB and 3 dB directional couplers that were fabricated using multilayer thick-film technology.

In this paper we present new measured loss tangent data for commercially available substrates, and these data are supported by simulations that show how practical variations in loss tangent affect the performance of microwave interconnections and devices. The paper reviews the measurement techniques that are currently available to measure the dielectric constant and loss tangent of substrate materials, and includes a new variation on an existing method that enables substrate parameters to be more easily measured but retains high accuracy. Simulations have been performed on microstrip lines fabricated on 10mil thick substrates using gold conductors to show the relative contributions of conductor and dielectric loss to the total line loss over the frequency range 0‐40GHz. Included in these simulations are the effects of conductor surface roughness. The simulated data are related to measured line microstrip line loss data over the frequency range 50MHz‐40GHz. The measured values, for an etched gold line on alumina, vary from 0.0045dB/mm at 50MHz to 0.04dB/mm at 40GHz.

A novel octave band DC block (2.5 -10.5GHz) and a broadband 3dB directional coupler (3-8GHz) have been designed, fabricated and tested using a new multilayer format. The multiple layers of thick-film dielectric and metal were printed on an alumina base and an etching technique used to form the final conductor pattern. The tight coupling required between the coupled lines was realized by overlapping these lines in a multilayer structure. Very good agreement was obtained between measured and simulated data. The results demonstrate that multilayer thick-film techniques provide an efficient method of achieving small size, low cost components having good microwave performance. In particular, the new multilayer approach has been shown to overcome the problem of fabricating very small gaps between coupled lines in a traditional single layer structure.

A new LTCC technology is described which offers excellent performance for the fabrication of millimetre-wave planar microwave circuits. The technology provides significant commercial benefits in terms of cost and suitability for high volume production when compared with alternative processes yielding the same microwave performance. Measurement data show a 50 /spl Omega/ line loss of 0.03 dB/mm at 40 GHz on the LTCC material, which is comparable with that obtained with etched lines on 99.6% microwave quality alumina.

Microwave applications at frequencies in excess of 1 Ghz, such as wireless devices, are well suited to ceramic construction. Other circuit fabrication technologies do not exhibit the same balance of low loss, precise geometries, cost and reliability. In addition, ceramic technology has the ability to provide greatly enhanced functionality by integrating buried passive components. A further requirement stems from the increasing use of flip-chip technologies, which provide compact assemblies with good microwave characteristics suitable for volume production. Many alternative technologies fail to provide the appropriate interconnect density and, in the case of polymer circuits, require an expensive under fill process. This article describes a new low loss low temperature cofired ceramic (LTCC) technology that, when combined with a photo-patterned thick-film technology, offers outstanding interconnect density and microwave performance. The ability to combine the efficiency of cofired ceramic with multiple out photo processing leads to low cost systems solutions involving multichip module with cofired substrate (MCM-C) technology. Data are presented to show the outstanding performance available both as microstrip lines and other circuit components, extending the application of LTCC into the 30 GHz and higher range of frequencies.

‘Soldering and Cleaning in Electronics’ international conference, including an exposition, took place in Brno on 12–13 October 1993. The conference was organised by SMT‐Info, together with the ISHM‐Czech and Slovak Chapter. The purpose of this common action was to bring together the professionals in surface mount technology and thick film technology. In the framework of the conference, in which 130 home and foreign delegates participated, the annual meeting of the ISHM‐Czech and Slovak Chapter took place.

The conference and exhibition got off to a good start with an official reception by the Mayor of Bournemouth on Tuesday evening where attendees could relax and chat—a pleasant way to meet old friends and to make new acquaintances.