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Introduction to Radio Frequency and Microwave Microelectronic Packaging

Abstract:

Electronic packaging at radio frequency (RF) and microwave frequency has become an important part of engineering development for a wide variety of products. Mobile phones, for instance, contain a multitude components such as processors, RF amplifiers, antennas, and passive components into a compact and robust form factor. The processors and amplifiers can dissipate significant heat, which requires proper heat transfer design. In addition, the high-speed digital signal lines, microwave transmission lines, and interconnects must be designed to maintain the integrity of the signal. The antennas in mobile phones are often integrated into the case or circuit boards and radiate not only away from the phone but also into the phone circuits. This means that sensitive circuits in the phone must be designed to minimize coupling of the phone’s wireless signals that can cause undesirable effects such as oscillations or resonances in the circuits. Passive components must be carefully chosen and implemented because their physical size is a significant fraction of a wavelength at the operating frequency. As a result, the passive components may no longer function as ideal capacitors, inductors, or resistors. Rather, they may have distributed effects that must be taken into account to achieve desired performance. For these reasons, and others, the task of electronic packaging is widely recognized as a critically important task for development of products operating at microwave and millimeter-wave frequencies.

This chapter is concerned with providing an introduction to the main issues and concerns encountered in developing products at radio and microwave frequencies. The focus is on presenting fundamental principles in three of the most important areas. This first is distributed effects. As mentioned earlier, as the frequency of operation of a circuit increases, the size of the circuit itself and/or its components becomean appreciable fraction of a wavelength. The result is that special care must be taken in detailed design. The second area is transmission lines, which are used to carry RF and microwave signals from one point in a circuit or system to a different point. Basic transmission line concepts are introduced, such as line impedance, propagation constant, group delay, and dispersion. The third is materials. There are a few important material characteristics that are particularly important when developing products at these frequencies, such as dielectric constant, dielectric loss tangent, coefficient of thermal expansion, and thermal conductivity. These material param- eters are introduced and simple examples are given. These topics are addressed in detail in following chapters, but this chapter introduces these ideas and provides the fundamental concepts that the following chapters build upon.