Antenna-in-Package Technology and Applications. Duixian Liu

Preface

      Rapid advances in semiconductor and packaging technologies have promoted the development of two system design concepts known as system on chip (SoC) and system‐in‐package (SiP). SoC integrates analog, digital, mixed‐signal, and radio frequency (RF) circuits on a chip by a semiconductor process, while SiP implements separately manufactured functional blocks in a package by a packaging process. SoC yields improved system reliability and functionality at a much lower system cost. However, it degrades system performance and increase system power consumption due to unavoidable compromises in every circuit type in order to use the same material and process. On the contrary, SiP enhances system performance and reduces system power consumption but results in lower system reliability and higher system cost because of functional blocks and the fabrication of the package with different materials and processes.

      Antennas are essential components for wireless systems. It is known that antennas are difficult to miniaturize, let alone integrate. Nevertheless, there have been attempts to integrate an antenna (or antennas) with other circuits in a die on a wafer using the back end of the line. An antenna realized in such a way is called an antenna on a chip (AoC) and is more suitable for terahertz applications for cost and performance reasons. In addition, there have been studies to integrate an antenna (or antennas) with a radio or radar die (or dies) into a standard surface‐mounted device using a packaging process, which has created a new trend in antenna and packaging termed antenna‐in‐package (AiP). AoC and AiP are obviously subsets of the above SoC and SiP concepts, so why do we specifically differentiate them from SoC and SiP? The reason is to highlight their unique property of radiation.

AiP technology balances performance, size, and cost, hence it has been widely adopted by chipmakers for 60‐GHz radios, augmented/virtual reality gadgets, and gesture radars. It has also found applications in 79‐GHz automotive radars, 94‐GHz phased arrays for imaging and data communications, 122‐GHz, 145‐GHz, and 160‐GHz sensors, as well as 300‐GHz wireless links. Recently, AiP technology has been under further development for millimeter‐wave (mmWave) fifth‐generation (5G) technology. Scalable large AiPs and multiple small AiPs have been successfully demonstrated in base stations, mobile phones, and networked cars at 28 GHz. We therefore believe that AiP technology will cause fundamental changes in the design of antennas for mobile communications for 5G and beyond operating in mmWave bands.

      The development of mmWave AiP technology is particularly challenging because of the associated complexity in design, fabrication, integration, and testing. This book aims to face these challenges through disseminating relevant knowledge, addressing practical engineering issues, meeting immediate demands for existing systems, and providing the antenna and packaging solutions for the latest and emerging applications.

      This book contains 11 chapters. The first five chapters lay some foundation and introduce fundamental knowledge. After the introductory chapter about how AiP technology has been developed as we know it today, several types of antennas are discussed in Chapter 2. An attempt is made to summarize the basic antennas and those antennas specifically developed for AiP technology. Emphasis is given to microstrip patch antennas and arrays, grid array antennas, Yagi–Uda antennas, and magneto‐electric dipole antennas because of their dominance in AiP technology. Performance improvement techniques of antennas for AiP technology are also described. Chapter 3 describes today's mainstream packaging solutions with either wire‐bond or flip‐chip interconnects, wafer‐level package, and fan‐out wafer‐level package. Chapter 4 focuses on the electrical, mechanical, and thermal co‐design for AiP modules. More importantly, the thermal management considerations for next‐generation heterogeneous integrated systems are reviewed in order to address the growing need for cooling the high‐power devices of future radio systems. Chapter 5 presents the design and optimization of an anechoic test facility for testing mmWave integrated antennas. This facility can be used for both probe‐based and connector‐based measurements.

The next five chapters are related to the design, fabrication, and characterization of AiPs in different materials and processes for mmWave applications. Chapter 6 discusses low‐temperature co‐fired ceramic (LTCC)‐based AiP. LTCC has unique properties for packaging mmWave circuits since it can provide a durable hermetic package with antennas, cavities, and integrated passive components. Chapter 7 illustrates how industrial organic packaging substrate technology used for classical integrated circuit (IC) packaging can support the development of innovative, efficient, and cost‐effective mmWave AiPs from 60 GHz up to 300 GHz. Chapter 8 focuses on embedded wafer‐level ball grid array (eWLB)‐based AiP. Unlike LTCC or high‐density integr (HDI), eWLB eliminates the need for a laminate substrate and replaces it with copper redistribution layers. Polymers are used for the electrical isolation between the metal layers. The metal routings are deposited by a combination of sputtering and electroplating with a thin film process. eWLB has historically been developed for mmWave automotive radar systems and therefore has naturally been used for mass production of mmWave AiPs. Chapter 9 presents surface laminar circuit (SLC)‐based AiP. Compared to LTCC, HDI, and eWLB, SLC is more suitable for fabrication of very large or dense AiPs. The chapter describes SLC materials and design guidelines, and then addresses the design challenges and solutions for 8 × 8 dual‐polarized phased arrays at 94 GHz for imaging and 28 GHz for 5G base station applications, respectively. Chapter 10 introduces different additive manufacturing technologies, methods to characterize three‐dimensional (3D)‐printed materials, a hybrid printing process by integrating 3D and inkjet printing, and a broadband 5G AiP realized with the hybrid process.

      The last chapter turns to 3D AiP for power transfer, sensor nodes, and Internet

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