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30 DESIGN007 MAGAZINE I JULY 2021 Size constraints, functional requirements, and environmental factors can make selecting PCB thickness difficult. Here we will examine best practices for choosing board thickness that results in quality, highly functional PCBs. It's Not Always as Easy as 1.57 mm Industry standard or your design tool's default board thickness are great places to start, but designers increasingly must con- sider using a custom board thickness. ere are several factors to consider as you deter- mine if a commonly used thickness will work. How thick does the board need to be to work? How thin must it be to fit into the device? What are its function and operating environ- ment? inner boards offer more flexibility and are preferable if keeping the device weight lower is a priority. icker is better if durability is an issue, because thick PCBs are less brittle and won't break as easily. ey also weigh more, run hotter, and will not work for many applications or assembly types. To determine thickness, you must consider how functional requirements will impact the number of layers you'll need, as well as what signal and via types are needed. e board's operating envi- ronment is an equally impor- tant consideration. Is your board going into a wearable or handheld device that operates in a regulated environment or is it part of a Mars rover? When your manufacturer receives a design, they can evaluate it before production to ensure its manufacturabil- ity and functionality, but very seldom are manufacturers made aware of how the board will eventually be used. It's unlikely they'll be able to judge whether a board, as designed, is too thick or too thin for the device it goes into or the envi- ronment in which it operates. The Board Thickness Challenge Connect the Dots by Matt Stevenson, SUNSTONE CIRCUITS