Passive Integration (Download Full Report And Abstract)
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Joined: Dec 2008
22-02-2009, 01:35 AM
Miniaturization has been a key contributor to advances in electronic technology. Certainly, miniaturization has been made possible mostly through remarkable breakthroughs in reducing the size of active components. But as integrated circuits get smaller and more complex, there is an increasing need to also reduce the space required for the supporting passive components. If any of the electronic devices such as cellphone, camcorder, computer, or other consumer electronics system is opened, one or two circuit boards on which are mounted a few integrated circuits and dozens and dozens of tiny discrete devices-resistors, capacitors, inductors etc can be seen. It is those so-called passive devices that dominate the boardâ„¢s real estate.
Many electronics applications have serious space considerations that are pressuring manufacturers to reduce component size. Much of the motivation for this has come from military and aerospace needs, but today's miniaturization demands are more likely to come from other market segments including telecommunications (cellular phones), computers (laptops), instrumentation (handheld devices), and medical electronics (pacemakers). Such applications continue to drive size reduction in components for commercial uses as well as for applications with very high reliability requirements, such as lifesaving medical equipment. However, simply reducing the case size of a part is not always the most effective way to miniaturize. Consequently, passive component manufacturers have begun to combine discrete components into volumetric-efficient multielement packages. By combining discrete passive components into multielement packages, designers can save more board space than by simply reducing the size of the components themselves.
Passive integration suggests that if the passives were so small and flat, then they could be inserted between layers of the circuit board itself, rather than taking space on top of it. The electronic devices could be thinner and sleeker than they are today, or they could contain more electronics, or if it is a phone can have much larger batteries and therefore longer talk time and brighter color screens. The same goes for almost every device from PDAs to portable DVD players.
The integrated passives would be a part of the circuit board itself, formed when the board was, so odds are good that their overall cost could eventually be less than what manufacturers pay today to buy and solder on discrete devices. Speaking of solder, eliminating it is another advantage of integration, because bad solder joints are one of the most common reasons electronic gear fails. Less solder also means less harm from lead waste.
The list of advantages goes on: putting the passives "underground" leaves more room on the surface of the board for ICs, which means more design flexibility. And there are electrical benefits, too. Because current travels along a different path in integrated capacitors than in surface-mounted components, integrated capacitors can be made freer of the trace amounts of the inductance, called parasitic inductance, that plagues any capacitor and limits usefulness in high-frequency circuits. Finally, because the components are custom-made when the board is, the resistors, capacitors, and inductors can be sized to any desired value, rather than being chosen from a manufacturer's list of available parts.
Advantages like these point to a potentially huge shift for the electronics industry. Over a trillion passive components were bonded to boards last year, according to the National Electronics Manufacturing Initiative's road map. These devices are minuscule, and that makes putting them in place a chore. The smallest discrete passives today measure 0.50 mm by 0.25 mm; spread on a sheet of paper, they'd look like ground pepper. Such compact components are difficult to handle and attach, even for automated assembly equipment. And though the total cost of each partâ€including capital, assembly, and the prorated cost of the underlying boardâ€is less than two cents on average, collectively the impact of integrated passives on system cost, reliability, and, most of all, size, could be enormous.
But for these passives to make a big dent in the US $18-billion-a-year market for discrete passive components, makers of circuit boards will have to reposition themselves as purveyors of passive electronic networks. It's starting to happen, but slowly. Such manufacturers as Gould, Shipley, Ohmega, MacDermid, DuPont, Oak-Mitsui, 3M, and Sanmina all market products and processes for integrating resistors directly into printed-circuit boards, using at least four different technologies; and for integrating capacitors, using at least five. These sizable companies have all poured tens of millions of dollars in R&D funds into proving the concept. In the meantime, several other companies, including California Micro Devices Corp. and AVX Corphave been working on an alternative approach to integrating passives. They are selling arrays and networks of miniaturized passive devices in single IC-like packages.
In a sense, the situation with passive components today is a lot like that of active devices 40 years ago, when Intel, Fairchild, and others had just introduced ICs that combined active devices like transistors and diodes on a single substrate. But don't expect Moore's Law to apply to passives. These components cannot be scaled down into the submicron realm occupied by active devices. The reason, of course, is that passive components have to handle signals whose amplitude cannot be reduced arbitrarilyâ€say, microwave signals going to a cellphone antenna or inputs for analog-to-digital conversion. Despite this fundamental limit, passive integration will make for much more miniaturization.
NEED FOR PASSIVE INTEGRATION
Passive components refer to such kind of electrical components that cannot generate power. Typical components are resistors, capacitors and inductors. The primary functions of passive components are to manage buses, bias, decouple Ics, by-pass, filter, tune, convert, and sense and protect. It is a huge, multi-billion business, supporting the various electronic products in automotive, telecommunications, computer and consumer industries, both for digital and analog-digital applications. There are a large number of passive components that are used in consumer electronic products such as VCRs, camcorders, television tuners, and other communication devices. Most of the passive components nowadays are discrete surface mount passive components that directly mount on the surface of the printed circuit board. It is called as discrete passive component-a singular component enclosed in a single case that must be mounted to an interconnecting substrate. Passive components are commonly referred to as glue components since they glue integrated circuits together to make the system.
Surface mount technology was starting to take deep root in our industry in early 80â„¢s and is fully developed till today. In the early days, surface mount components were many times more expensive than through hole components and new surface mount assembly equipment costs were off the charts. As time went on, the cost of the components, assembly equipment and all of the other infrastructure came down, today it is less expensive to build a surface mount assembly than a through hole assembly. However, the faster bus speeds required new technology. PCB traces have always had transmission line characteristics and are more sensitive at subnano-second rise times. The package lead inductance and line capacitance have greater impact on signal integrity. The integrated circuit industry is achieving faster speeds by shrinking technology; it follows that the passive solution must also shrink. In addition to these, the need to drive out every cent of costs, miniaturization, improved product reliability and the passive to active ratios have caused to seriously consider much higher levels of passive integration than in the past. Then comes the idea of integral passives.
Integral passives are noted as passive components embedded within or on the surface of a substrate. These are distinguished from discrete chips and also from integrated(multiple passive functionality within a single package).It is a part of the printed circuit board using some type of material to make resistors, capacitors or inductors. The requirement for integral resistors, capacitors and inductors are:
A primary requirement for integral resistors is that they be size competitive with the chip resistor. It dictates that the largest dimension be of the order of 1.0mm.Cost considerations dictate that trimming should not be required to obtain a 5%-10% tolerance. The range of values used,from one ohm to one mega-ohm dictates that if that range was implemented there would be insufficient numbers in the tails of the value distribution to justify integrating the full range
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