Nanopackaging: Nanotechnologies and Electronics Packaging

Citation

Goosey, M. (2009), "Nanopackaging: Nanotechnologies and Electronics Packaging", Microelectronics International, Vol. 26 No. 3. https://doi.org/10.1108/mi.2009.21826cae.001

Nanopackaging: Nanotechnologies and Electronics Packaging

Article Type: Book review From: Microelectronics International, Volume 26, Issue 3

Edited by James E. Morris,Springer,New York, NY,ISBN: 978-0-387-47325-3; e-ISBN: 978-0-387-47326-0

Nanotechnology is a field of applied science that is concerned with the production, manipulation and use of materials at or close to the atomic and molecular levels. A common feature of nanotechnology is that it deals with structures that have features with sizes of 100 nm or smaller, and it involves the development of materials and devices within that size range. In recent years, there has been a surge of interest in nanotechnology as it has become clear that, by operating much closer to the molecular level, it is possible to achieve things that are not possible on a coarser scale. Materials can show markedly different properties and the ability to operate at the nanometre level opens up new possibilities for a wide range of devices and applications across many industrial sectors. This is no more true than in the electronics industry where, ever since the birth of the semiconductor, there has been intense activity to make devices smaller and to build more functionality per unit area into silicon and other semiconductor materials. If one adheres to the definition that nanotechnology begins at the 100 nm mark, it can be said that the electronics industry entered the nanoworld when semiconductor manufacturers moved to the so-called 93 nm node a few years ago. Today, commercial devices are available with 65 nm technology and the industry roadmaps show that feature sizes will continue to shrink until Moore's Law really does no longer hold.

It is not only at the silicon processing level that there is a drive to reduce device size. In order to be able to use these high-density semiconductor devices, they also have to be interconnected and packaged and there is the same pressure to incorporate as much functionality into a given space as possible with packaging as there is with silicon. With its understanding of nanoscale operation and the inexorable drive to more miniaturisation, it is perhaps inevitable that the electronics industry is increasingly investigating the advantages that nanotechnology can bring to packaging and assembly, as well as to semiconductor processing. While there has been a huge amount of relatively disparate work undertaken on nanotechnology related to electronics, there is a real need for a consolidated work that covers many aspects of the potential for nanotechnology in electronics packaging and assembly. The new book Nanopackaging: Nanotechnologies and Electronics Packaging, which is edited by James E. Morris and published by Springer, provides just such a work and it provides a welcome addition to the nanotechnology literature for those in both industry and academia who are working to develop the technologies that will enable us to benefit from continued innovation in future electronics.

A review of the contents pages of Nanopackaging: Nanotechnologies and Electronics Packaging reveals that this is a very substantial work. With 23 chapters contributed by key nanotechnology experts from around the world, the book runs to an impressive 543 pages. Bearing in mind that many people working in electronics packaging will be new to the potential applications in which nanotechnology may be used and also relatively unaware of the benefits it may offer, the book sensibly begins with an introductory review chapter by the editor, James Morris. This opening chapter bridges the gap between nanotechnology and packaging by covering the potential scope for nanotechnology in this area and by providing over 100 references for further reading. There then follow three chapters that cover computer modelling in nanopackaging. The first of these, Chapter 2, is provided by Professor Chris Bailey et al. from the University of Greenwich in London. This chapter takes a high level approach to nanoscale modelling for packaging that is complimented by examples of modelling for past, present and future applications. Chapters 3 and 4, by Fan and Yuen and van der Sluis et al., respectively, both have their focus on molecular modelling techniques, especially for interfacial characterisation, with applications to carbon nanotube (CNT) thermal performance, moisture diffusion and thermal cycling and delamination failures.

The main part of the rest of the book then splits conveniently to cover nanoparticle and CNT related applications. In Chapter 5 the Editor, James Morris, contributes another chapter in which he introduces nanoparticle properties. Although relatively short, this chapter covers key aspects such as structure, electrical properties, melting point depression, sintering and mechanical and optical properties. The chapter is complimented by a comprehensive list of over 100 references. The fabrication of nanoparticles is mentioned in several chapters and Chapter 6 by Hayashi et al. concentrates on novel fabrication methods using an ecologically friendly sonochemical method.

The next three chapters cover the use of nanomaterials in passive device applications. There is a real need to enhance the dielectric, resistive, magnetic and related properties of materials used in passive devices, especially as they are increasingly being integrated into substrates as embedded components. Chapter 7, by Lu and Wong, covers the opportunities and challenges for nanoparticle high k dielectric composites. Metallic and dielectric filled composites have been of great interest in the electronics industry for many years and this chapter details the potential use of metallic and ferroelectric nanoparticulate fillers in both ceramic and polymeric matrices. Chapter 8 is by Wu and Morris and this chapter addresses nanostructured resistive materials. There is also an increasing demand for inductors and related components, especially in military, communications, automotive and portable electronics applications and Chapter 9 by Jha et al. covers the design, fabrication and packaging of nanogranular magnetic core inductors. It also gives a comprehensive review of inductor research and recent advances in the nanomaterials that are used in such high performance inductive cores.

The following three chapters have a focus on nanoparticles in conducting materials applications. Conducting and non-conducting adhesives find extensive use in electronics assembly and Chapter 10 by Lu et al. covers the nanoscale engineering of isotropically conductive adhesives. The chapter gives information on both nanoparticle additives and enhancements by surface treatments, as well as techniques such as low temperature nanosintering.

Once devices have been assembled and packaged, they are then mounted onto the next level of interconnect and this is typically a multilayer printed circuit board. With the relentless drive to higher input/output counts and smaller package dimensions, the PCB industry has also had to respond by providing much higher interconnection densities in order to be able to integrate increasing numbers of devices on a diminishing size of substrate. These demands have led to the increasing use of sequential build up technologies and the incorporation of microvias in circuit board designs. There are numerous approaches to providing these conductive pathways but, as feature sizes get smaller, the challenges continue to increase. Chapter 11 is by Das and Egitto and it covers the use of nanoparticle based conductive adhesives in microvia applications. The chapter shows how nanoparticles and nanoparticle based adhesives are attractive for use in microvia fill applications. High aspect ratio small diameter holes can be successfully filled and the nanoparticle based materials exhibit sintering at lower temperatures, resulting in higher electrical conductivity. The materials are capable of giving high performance z-axis interconnects which can be made to meet or exceed JEDEC level requirements. Chapter 12 completes this group of three focused chapters and is by Felba and Schafer. It also discusses aspects of nanomaterials technology related to PCB interconnect applications and describes progress on printable solutions and the laser sintering of nanosilver based materials.

The use of nanomaterials in soldering applications has been under investigation for a while, especially in view of the largely legislation driven migration to lead-free assembly. There has been much work undertaken to study and enhance the reliability performance of lead-free solders and the incorporation of nanoscale materials into alloys has been one such investigated approach. In Chapter 13, Amagai covers the addition of various nanoscale additives to tin-silver lead-free alloys. The addition of cobalt, nickel and platinum nanoparticles was found to have a significant impact in limiting intermetallic compound growth and thus the occurrence of mechanical failures by brittle fracture. Chapter 14 is the final chapter of the book that covers nanoparticles and in it Lall et al. detail the use of ceramic nanoparticle additives in underfill materials. A key issue with underfill materials is their relatively high thermal expansion coefficients compared to materials with which they are in contact. The addition of ceramic nanoparticles is reported to reduce the thermal expansion coefficient.

CNTs are just one type of nanoparticle but their novel and interesting properties has meant that they have been a key area of nanotechnology research. The book, therefore, not surprisingly has a significant amount of space dedicated to CNTs and their use in the area of electronics assembly and packaging. In fact Chapters 15-20 cover various aspects of CNTs and the first two (Chapters 15 and 16) are from the same research group. In Chapter 15, Yadav et al. cover the various techniques that are used to fabricate CNTs and Chapter 16 then continues with a review by Kunduru et al. of the basic properties of CNTs, their characterisation methods and potential uses. In Chapter 17, Liu and Wang discuss the use of CNTs for the thermal management of microsystems, while Chapter 18 by Cheng et al. details the use of multiwalled CNTs in the electromagnetic shielding of transceiver packaging. There is a return to the subject of soldering in Chapter 19, where Kumar et al. give information on the properties of conventional tin-lead and lead-free SAC alloy solders that have been reinforced with single wall CNTs. The chapter reports the results of studies into the impact that the CNTs have on the microstructural, mechanical, electrical, wetting and thermal properties of these composite solders. Interestingly, it was found that the addition of the CNTs reduced the thermal expansion coefficient of the solders as well as their melting points. The addition of nanotubes also significantly improved the creep rupture life of both leaded and lead-free composite alloys.

Chapter 20 is the final chapter covering CNTs and it is provided by Fielder et al. This chapter is titled “nanowires for electronics packaging” and it covers a wide range of related subject material including fabrication, materials and structures, as well as the interaction of nanowires with electromagnetic fields. There is also a discussion of future prospects and the authors provide well over 200 references. In Chapter 21 Ma et al. introduce a novel stress-engineered cantilever technique for forming free-standing interconnect wires or springs which is based on standard IC fabrication techniques. In addition to giving a detailed description of the fabrication processes for these molybdenum-chrome alloys, various applications are described including their use in non-soldered underfilled packages and sensing applications.

The penultimate Chapter is by Mallik et al. and it discusses the ever decreasing shrinkage of microelectronics features. This 22nd Chapter of the book has the title of “Flip chip packaging for nanoscale silicon logic devices: challenges and opportunities” and it is devoted to the shrinking CMOS issue. Starting with historical data, the chapter then provides an analysis of the nanometre CMOS challenges along with giving some insights into the future. Finally, Chapter 23 by Zhang brings this tour de force to a well-rounded conclusion with a top down overview of future industry directions as microelectronics moves firmly into the realm of nanoelectronics.

To summarise then, this is an impressive work that provides a substantial and relatively in depth coverage of a wide range of electronics packaging and assembly related applications for nanotechnology. Each chapter concludes with a list of references that can be used by the reader to further investigate a particular subject and the book is well produced with good quality figures and illustrations. The editor and publishers are, therefore, to be congratulated on bringing together in one place such a useful body of information relating to nanotechnology in electronics assembly and packaging. With a total of over 60 contributing authors and 23 chapters, this is clearly a very significant work and I am pleased to be able to conclude this review by rating Nanopackaging: Nanotechnologies and Electronics Packaging as “highly recommended”.

Martin Goosey