Miniaturized PCBs at the Intersection of Form and Function
July 17, 2017
In recent years, we’ve seen a proliferation of new electronics applications requiring smaller packages, new form factors, lower power consumption and increased functionality including embedded signal processing, sensors, imaging interfaces and power management components – all integrated within tight dimensions and sometimes even flexible substrates. This trend is posing numerous challenges to conventional PCB technologies. Where previously flat-surface, rigid PCBs were the mainstay, the emergence of smart watches, IoT devices and other compact systems have spurred the development of advanced new miniaturized PCBs designed to fit the contours of ever-shrinking package sizes. This new generation of PCBs barely resembles the generation that preceded it, and designers have struggled to adapt.
These trends have influenced designers to stress production technologies to thinner conductions lines, high-speed signal transmission lines, difficult impedance controls and via-placement practices, as well as modified substrates and increased reliance on embedded devices. This imposes numerous constraints related to the design of the PCB, with significant implications for system reliability, functionality, power management and the overall success of the design project.
Myriad design challenges
Battery life is of course a critical consideration for the new generation of compact electronic devices, and this affects the PCB design in myriad ways. Designers need to be mindful of signal loss and propagation issues that will result in shortened battery life, and focus increased attention on signal integrity, power management, and EMI issues. Signal integrity issues can be particularly pronounced for flexible PCBs, where impedance control may be strained in instances where high-speed signals are skewed due to the flexing of the PCB.
Additional passive devices like resistors, capacitors, and inductors will be needed to counter the aforementioned signal and interference challenges, and the lack of available package space will typically require these devices to be embedded in the PCB. But embedding passive devices in PCBs is not a mature, developed capability, and can lead to functionality issues – perhaps the device won’t hold power, or reliability isn’t as hoped – and numerous restrictions are imposed on the design flow.
Increasing the functionality of compact electronic devices often entails employing near-field RF communications – yet another function that needs to be embedded in the PCB design. In conventional electronics, RF components are housed in rugged, rigid and higher-cost materials, with ample space to reside. Compact devices require the use of thinner and more flexible materials however, pressuring designers to stray outside mainstream PCB design principles. Copper traces need to be formed with much greater precision, and the distances between lines are much narrower. The placement of vias between PCB layers is also affected, impacting the size and positioning of these interconnects, and alternative materials may need to be substituted to strengthen these vias in instances where the surrounding PCB layers don’t employ the glass-fiber composition of conventional rigid PCBs.
Innovations in miniaturized PCB manufacturing
To meet the key challenges inherent to new generations of compact electronic devices, laser direct imaging (DI) systems are increasingly being employed by PCB manufacturers to form very thin conductors with 10-micron feature size. The ideal DI solution should provide a balance of high registration accuracy and optimal quality even at high production speeds. A suitably high depth of focus should ensure favorable results on PCB topography changes, with precision line uniformity. These systems provide a low-cost alternative to front-end lithography, and with continued innovation in solder mask positioning technology, the embedded electronics industry will soon be poised to achieve sub-10 micron lines.
In parallel, advanced UV laser drilling systems can be employed to drill small vias through a wide range of materials of varying thinness and strength, including ABF, polyimide, ceramic, resin, mold compounds, metal and solder resist, with no residue or damage to the bottom of the via and no undercut, with registration accuracy down to 6 microns.
Designed to streamline the manufacturing processes for today’s electronic devices as they become thinner, smaller, flexible and with higher functionality, these systems allow manufacturers of miniaturized PCBs to increase their manufacturing precision and quality, while improving their production throughput.
On the business side, investments in these production systems should ultimately improve PCB suppliers’ aggregate yield and therefore improve their profits. Many production shops have avoided producing high-functioning devices with miniaturized PCBs due to yield management concerns. The new generation of PCB inspection, imaging and laser drilling systems reduces yield risks considerably. At the same time, these systems accommodate smaller dimensions and newer PCB materials with repair capabilities that will keep yield at acceptable levels even under the stringent constraints imposed by continued PCB miniaturization.
Author: Gil Tidhar, Co-head, Global Product Organization (GPO), Orbotech
Published by: Embedded.com
Cautionary Statement Regarding Forward-Looking Statements
Some of the matters discussed in this website (including in press releases, webcasts, presentations, posts and other places) are projections or other forward-looking statements within the meaning of the U.S. Private Securities Litigation Reform Act of 1995. These statements relate to, among other things, future prospects, developments and business strategies and involve certain risks and uncertainties. The words “anticipate,” “believe,” “could,” “will,” “plan,” “expect” and “would” and similar terms and phrases, including references to assumptions, have been used in this website to identify forward-looking statements. These statements are only predictions and actual events or results may differ materially. We refer you to the documents KLA files from time to time with the Securities and Exchange Commission, specifically, KLA’s most recent Form 10-K and Form 10-Q. These documents contain important factors that could cause the actual results to differ materially from those contained in projections and other forward-looking statements including, among others, volatility and cyclicality in the semiconductor equipment industry and other industries in which KLA and its subsidiaries operate, potential fluctuations in operating results and stock price, international trade and economic conditions, the ability to compete successfully worldwide, management of technological change and customer requirements, fluctuations in product mix within and among divisions, the timing and strength of product and service offerings by KLA and its subsidiaries and its and their competitors, intellectual property obsolescence and infringement, and factors associated with key employees, key suppliers, acquisitions, and litigation. Additional factors impacting the business of KLA and its subsidiaries include integration between KLA and its acquired companies, ability to achieve synergies and other benefits of acquisitions in the timeframe anticipated, if at all,
KLA and its subsidiaries assume no obligation to update the information in this website (including press releases, webcasts, presentations, posts and other places) to reflect new information, future events or otherwise, except as required by law.
This site is provided by KLA Corporation (or its subsidiaries) on an "as is" basis. None of KLA and its subsidiaries make any representations or warranties of any kind, express or implied, as to the operation of the site, or the accuracy or completeness of the information, content, materials, pricing, services, or products included on this site. Product specifications and prices are subject to change without notice, and products may be discontinued without notice. None of KLA and its subsidiaries will be liable for any damages of any kind arising from the use of this site, or the material that is provided on this site, including but not limited to direct, indirect, special, incidental, punitive, or consequential damages.