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PCBD-June2017

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40 The PCB Design Magazine • June 2017 to 30 pF/mm 2 and be compatible with standard printed board manufacturing processes. (Note: Capacitor design guidelines for the print- able and foil dielectrics are available from the mate- rial manufacturers.) Formed Inductor Elements Formed inductors are basically current loops configured to induce a magnetic field for storing and controlling inductive energy. The inductor configuration most commonly designed into a circuit structure is the defined as a 'spiral' in- ductor. The resulting inductance of the spiral is determined by the length of the conductor in the spiral and number of turns. The spac- ing between turns is critical as well because the spacing controls the resonant frequency of the inductor. A wider spacing will typically reduce capacitance and raise the inductance frequen- cy. PCB planar spiral inductors can be used as antennae or components for forming high fre- quency matched filters in a RFID system. The sizing of inductors is dependent on several pa- rameters: • Line width • Spacing • Geometry Simple inductor elements can be integrated into the PCB circuit path on a single surface of the PCB, but more complex inductor applica- tions may require a stacked configuration with- in the multilayer circuit. Single layer copper spi- rals for example, can only reach about 10nH, however, multilayer spirals can be configured reach up to 30 nH. Additionally, utilizing a ferromagnetic ma- terial either as a core within loops of copper or positioned beneath or sandwiching a spiral in the multilayer PCB can possibly extend the in- ductor value into the 100nH range. The resistances and inductances of a formed spiral inductor can be calculated using guidance furnished in IPC-2316. Many software tools for developing the spiral inductor layout are com- mercially available. As an alternative to forming component parts, many companies are placing discrete pas- sive components within the substrate layers. In an upcoming issue, "Embedding Components, Part 3" will focus on selecting compatible com- ponents for embedding, land pattern criteria and attachment methodology. PCBDESIGN Vern Solberg is an independent technical consultant specializing in surface mount technology and microelectronics design and manufacturing technology. To read past columns or to contact the author, click here. EMBEDDING COMPONENTS, PART 2 A recent advancement in microscope imaging technology at the University of Waterloo could soon make diagnosing disease more accessible and affordable. The advancement, developed by Waterloo re- searchers Farnoud Kazemzadeh and Alexander Wong, has led to a new form of spectral light-fusion micro- scope for capturing lightfield images in full-colour. The several-hundred-dollar microscope has no lens, and uses artificial intelligence and mathemati- cal models of light to develop 3D images at a large scale. It's a process that currently requires a techni- cian to "stitch" together multiple images from tra- ditional microscope images to get the same effect, and requires a machine that costs several hundred thousand dollars. "In medicine, we know that pathology is the gold standard in helping to analyze and diagnose patients, but that standard is difficult to come by in areas that can't afford it," said Wong, an associate professor of Engineering at Waterloo and Canada Research Chair in Medical Imaging. The current spectral light-fusion microscope rep - resents the second-generation of technology that he patented last year with Kazemzadeh. The microscope captures light fields and allows for 3D images that are approximately 100 times larger than the 2D images captured by more traditional microscopes. Artificial Intelligence Imaging Research Makes Diagnosing Disease Easier

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