Design News, March 2013

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All of the circuit layers are laminated into a complete package using an epoxy-based substrate, such as FR4 or polyimide. Boards incorporating heavy copper circuits are produced in exactly the same way, albeit with specialized etching and plating techniques, such as high-speed/step plating and differential etching. Historically, heavy copper features were formed entirely by etching thick copper clad laminated board material, causing uneven trace sidewalls and unacceptable undercutting. Advances in plating technology have allowed heavy copper features to be formed with a combination of plating and etching, resulting in straight sidewalls and negligible undercut. Plating of a heavy copper circuit enables the board fabricator to increase the amount of copper thickness in plated holes and via sidewalls. It's now possible to mix heavy copper with standard features on a single board, we refer to this as PowerLink. Advantages include reduced layer count, low impedance power distribution, smaller footprints, and potential cost savings. Normally, high-current/high-power circuits and their control circuits were produced separately on separate boards. Heavy copper plating makes it possible to integrate high-current circuits and control circuits to realize a highly dense yet simple board structure. The heavy copper features can be seamlessly connected to standard circuits. Heavy copper and standard features can be placed with minimal restriction provided the designer and fabricator discuss manufacturing tolerances and abilities prior to final design (see Figure 2). hand. Let's try to answer both of these questions together. When current flows along a trace, there is an I2R (power loss) that results in localized heating. The trace cools by conduction (into neighboring materials) and convection (into the environment). Therefore, to find the maximum current a THE PERFECTIONIST Current Carrying Capacity and Temperature Rise How much current can a copper circuit safely carry? This is a question often voiced by designers who wish to incorporate heavy copper circuits into their project. This question is usually answered with another question: How much heat rise can your project withstand? This question is posed because heat rise and current flow go hand-in- FOR DYNAMIC PRECISION APPLICATIONS: OUR METAL BELLOWS COUPLING. RW-AMERICA.COM Design News | December 2012 | www.d esign n RW_America_Feb2013_Ad_revised.indd 1 –M5– THE COUPLING. 2/22/13 10:16 AM

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