IPC International Community magazine an association member publication
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22 I-CONNECT007 MAGAZINE I MARCH 2026 F E AT U R E A RT I C L E with subtractive being more common. Copper thick- ness is the primary factor impacting tolerancing on an etched feature. The thicker the copper, the more difficult it is to control the width or the size of the etched feature. For instance, you may be able to control the width of a conductor to ±12 μm on cop- per that is less than 18 μm (half-ounce) thick, while attempting this tolerance on one- or two-ounce cop- per would be much more challenging. Remember, when you have two or more layers, you must factor in plating, as it adds to the copper thickness. But- The challenge with cumulative tolerances is meeting the dimensional requirements for items dimensioned on a drawing or specification for a flexible or rigid-flex circuit. It is critical to understand the fabrication processes and how features are de- fined when creating your tolerance requirements. Common Features to Keep in Mind Copper features These are almost always photo-defined, either through an additive or subtractive (etching) process UNDERSTANDING TOLERANCES in Flexible Circuit Design BY C H R I S C L A R K , F L E X I B L E C I RC U I T T EC H N O LO G I ES