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EETE MAR 2015

FLEXIBLE ELECTRONICS PCB origami By Robert Huxel Design of printed circuit boards for modern electronic products is becoming ever-more complex. In the electrical domain, clock speeds and signal frequencies continue to climb; designers for whom a straightforward flow of schematic capture, followed by place-and-route, would have been sufficient, now find themselves having to invoke sophisticated signal integrity and simulation tools to ensure that their project will function as they intend. In the mechanical domain, matters are no less complex. Consumers have come to expect products that are, in each generation, smaller, and lighter than their predecessors. The product designer has to fit increased functionality into less and less space – while maintaining manufacturability, and allowing for maintenance.   Between the two lies the interface between the electrical and the mechanical spaces; in the past, this has often involved a hand-over from electrical/ electronic CAD and CAE to 3D mechanical CAD software. Worse, a single project can require multiple file transfers from electrical to mechanical EDA/ CAD, as issues are revealed and design revisions applied. Board layout (place and route) software places components according to their footprint – essentially, a 2D view. A comprehensive 3D description of all the components – not just a maximum-profile figure – is needed to ensure that when the product is assembled, there are no parts that touch or interfere with any others.  A full path from initial concept to confidence in the physical Full 3D image of the complete assembly showing the separate circuit boards and flexible interconnects. layout – that the design fits together, and that there are no components that unexpectedly clash or overlap when translated from the virtual to the real environment – has existed for some time. However, it has not always been particularly user-friendly. There is the necessity to export and import files in a suitablyreadable form, between packages; this usually also involves transferring the project to an engineer with mechanical-CAD experience. But the impediments go beyond that; for example, there is the need to source good physical models of components to generate an accurate 3D view of a PCB.  In the past, the path of least resistance has been to build early prototypes of both PCB and housings and to manually confirm (or otherwise) that one fits within the other and that no collisions occur. Among the downsides to this approach are that re-spins of either PCB or case, or both, are very likely, at considerable cost – time as well as money. Or, to avoid that hazard, designers build in margins – based on little more than experience or intuition – that result in a design which does not achieve the best-possible levels of integration.  One area in which there has been considerable progress is the availability of outlines and mechanical (software) component models. Manufacturers routinely offer such models along with the electrical parameters of their products; the major component distribution companies also maintain databases with this information. When this information arrives along with electrical data, it makes complete sense to import it together with the electrical information, into an environment that can make use of both attributes.  An integrated package that “knows about” both the electrical and mechanical environments can overcome these obstacles and give the entire team visibility of both electrical and mechanical domains, resulting in a product design that meets design targets first time and that can progress from “virtual space” to prototype and to production with no major re-designs.  One company that is meeting those challenges is Kaba, maker of access control systems. Recently Kaba has successfully completed the design of a new generation of door locks, with electronic controls that fit over 1000 components into a doormounted casing. At Kaba, Electronic Development Department Supervisor Stefan Wyss, describes how the company uses Altium Designer not only for the functional design of the circuitry, but also to develop and refine the mechanical configuration and assembly processes of its products.  One of the assemblies that Kaba has developed with Altium Designer comprises three separate circuit boards, interconnected by flexible PCBs that fold in two separate directions in order to fit into the barrel of one of the company’s locking products. In a single design environment, Stefan, and the members of his team, can not only move from the electrical design of the flex-rigid construction, into the mechanical, but can quickly see a full 3D image of the complete assembly that can be freely rotated in space to view it from any direction.  In contrast to shifting into a 3D mechanical CAD package to view geometry – or of exporting data to yet another package in the form of a file viewer - 3D exploration in Altium Designer is achieved simply with a change of viewing mode. A 3D orthographic projection reveals hidden components, with precise dimensions and positions, in a totally realistic view. Additionally, Kaba’s engineers make use of Altium Designer’s facility to animate the process of folding the PCBs into their final configurations. Because the software “understands” the mechanical parameters of the flexible connections, the animated view is also a completely realistic view of how the folding process will proceed. Kaba can verify clearances and eliminate the possibil- Robert Huxel is Technical Marketing Manager for Altium Europe GmbH - www.altium.com 40 Electronic Engineering Times Europe March 2015 www.electronics-eetimes.com


EETE MAR 2015
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