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70 PCB007 MAGAZINE I AUGUST 2025 4. Adaptive Cavity Routing This represents the pinnacle of precision, employing a closed-loop feedback system: • Measure surface by touch probe: Establishes the starting reference • Routing: Performs an initial routing pass • Measure depth with a with a touch probe: The probe measures the depth achieved after the pass • Final routing if necessary: If the measured depth deviates from the target, the machine performs a final, adaptive routing pass to achieve the specified depth. This process ensures unparalleled accuracy. Laser Cases: When Mechanical Routing Reaches Its Limits While mechanical depth routing offers immense capabilities, there are instances where its limitations require laser technology for skiving processes. These cases often arise when dealing with materials that are difficult to machine mechanically, when the required feature size and precision exceed mechani- cal capabilities, or when thermal impact needs to be minimized. Lasers, particularly high-end ones such as PICO-green, are perfect for tasks like remov- ing thin coatings from copper pads or accessing contact pads with minimal damage. A PICO-green laser can ablate microns with minimal impact on the next layer. This non-contact, highly precise, and localized energy delivery ensures minimal thermal impact on the surrounding material, preserving the integrity of sensitive copper pads and fine-line structures. Laser skiving provides superior control and cleanliness compared to mechanical methods for specific applications. Summary The ability to perform highly accurate depth rout- ing is fundamental for producing today's complex PCB designs, including rigid-flex boards, PCBs with embedded components, and those requiring inte- grated heat sinks. Several machine features play a crucial role in ensuring depth routing accuracy. These include the previously discussed functions and capabilities, as well as clamped spindles that enhance tool stability, linear drives that enable pre- cise and rapid movement, and adjustable valves that allow for accurate pressure control of the pressure foot, among other factors. The strategic combination and correct use of these machine functions (or mix of functions), together with proper routing tools, suitable backup materials, and the expert work of a skilled process engineer, make it possible to produce the most intricate and demand- ing PCB designs. These advanced capabilities are essential for meeting the complex requirements of modern electronics, ensuring superior performance, reliability, and miniaturization. PCB007 Kurt Palmer is president of Schmoll America. To read past columns, click here. D R I V I N G I N N OVAT I O N F i g u re 1 0 : L a s e r s k i v i n g s a m p l e. ▼