This year the printed wiring board (PWB) industry has been given the obligatory shake-up. While struggling to eliminate warehouses of excess inventory, many companies have focused on new technologies that will help differentiate them from their competitors. Two areas of technology seeing growing investment throughout the electronics industry are embedded components and optoelectronics.
Tasked with providing designs offering greater functionality and increased speed through these emerging technologies, designers may suddenly find themselves facing an array of questions.
The emergence of embedded passives in the design of telecommunications, avionics and high-speed systems offers an alternative route to increasing the functionality of circuits through the reduction of overall number of discrete surface components, thereby freeing up precious PWB real estate for IC packages.
The utilization of embedded capacitors and resistors offers tremendous potential for high frequency, high density and-eventually-low cost applications. These new devices will usher in a new generation of materials with enhanced dielectric constants and thicknesses, but what challenges are posed for the designer and the fabricator? What are some of the thermal considerations (such as stability under thermal cycling) for resistors that are fired onto copper foils and subsequently embedded into PWBs? The need for a standard covering mechanical, electrical and thermal properties becomes readily apparent.
If you haven't witnessed the barrage of information on optoelectronics that is sweeping over the PWB industry at the moment, there's a good chance you've been soaking up the sun somewhere away from civilization.
Encouraged by the Internet's appetite for increased data flow rates (bandwidth), the union of electronics and optical components offers to permanently reshape the face of PWBs. Because optical transmissions do not emit electromagnetic waves, relying instead on transmission of light through a glass fiber core, they are immune to many of the pitfalls that can affect electrical signals traveling down copper paths. The technology holds much promise for industry segments such as telecommunications and RF, and for products such as missile guidance, high-speed optical data links, digital medical imaging systems and airborne communications links.
If that alone isn't enough to raise interest among designers, then simply marvel at the numbers. One optical signal has the capacity to carry 10 million times more information than an electronic signal traveling through copper. Dr. Ken Gilleo of Cookson Electronics, one of the chief proponents of optoelectronics, relayed the mind-numbing comparisons: The amount of information that can be transferred through 4 oz. of fiber optics would require roughly 33 tons of copper to achieve the same results.
As with any emerging technology, design hurdles abound. Thermal behavior such as the thermal expansion among two optical elements on an FR-4 board will differ markedly from that of copper paths. Optoelectronics requires extreme location accuracy of parts mounted on substrates. Will there be a need for a local fiducial for every part on the PWB as opposed to global fiducials? As optoelectronics pushes boards to higher frequencies, at what point will FR-4 dielectrics need to be discarded in favor of lower loss materials?
Show me the Way
The need for standardization has already been vocalized. During the recent IPC International Conference on Optoelectronics in Toronto, Canada, more than 150 attendees from the United States and Canada heard discussions regarding the key factors in the cost reduction of this new technology, one of them being the adoption of standards.
IPC will begin these standardization efforts at the IPC Annual Meeting, which takes place Oct. 9-13, 2001, at the Rosen Centre Hotel in Orlando, FL. There, attendees will be able to take in paper sessions on embedded passive components, as well as a panel discussion on optoelectronics. Each day after the paper session, a full day of standards development meetings will be held to pick up where the sessions left off and offer designers the opportunity to assemble the building blocks of design, material and performance standards for embedded and optoelectronics technologies.
For more information regarding the upcoming IPC Annual Meeting, visit IPC's Web site: www.ipc.org.
John Perry is a technical project manager at IPC. He can be reached at 847-790-5318, or e-mail firstname.lastname@example.org.
© 2001 CMP Media LLC.
9/1/01, Issue # 1809, page 46.
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